WO2008145797A1 - Device for determining the porosity of thin films and use thereof - Google Patents

Device for determining the porosity of thin films and use thereof Download PDF

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Publication number
WO2008145797A1
WO2008145797A1 PCT/ES2008/070099 ES2008070099W WO2008145797A1 WO 2008145797 A1 WO2008145797 A1 WO 2008145797A1 ES 2008070099 W ES2008070099 W ES 2008070099W WO 2008145797 A1 WO2008145797 A1 WO 2008145797A1
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porosity
adsorption
temperature
quartz
thin sheets
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PCT/ES2008/070099
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Spanish (es)
French (fr)
Inventor
Angel Barranco Quero
Ana Borras Martos
Juan Ramón SANCHEZ VALENCIA
Agustín Rodriguez Gonzalez-Elipe
Juan Pedro Espinos Manzorro
Francisco Yubero Valencia
José COTRINO BAUTISTA
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Consejo Superior De Investigaciones Cientificas
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Publication of WO2008145797A1 publication Critical patent/WO2008145797A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
    • G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
    • G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
    • G01N2015/0866—Sorption

Definitions

  • the present invention has diverse applications, in fields such as optics and optoelectronics. It can be used in the measure of porosity for all types of thin layers and coatings with applications in optics (anti-reflective systems, in lenses, mirrors, polarizers, etc.), protective layers (against corrosion, abrasion, improvement of wear resistance , UV protection, etc.), coatings to improve the aesthetic appearance and with decorative applications (metallized in jewelry, sanitation or coating of construction materials among others), layers and membranes used as biocompatible coatings and nanoparticles with applications in biomedicine (in which porosity is essential to control its biocompatibility), thin sheets, supported membranes and nanostructured materials used as gas sensors, irradiation, in solar cells, nanotubes and nanowires used as part of electronic devices, materials of important applications in microelectronics and other functional layers for application Energy ones among others.
  • the supported membranes are used to limit the passage of certain components in fluid mixtures, favoring the passage of others in order to separate them.
  • a broad set of membranes are based on the restriction of the diffusion of these components through pores, so it is critical to define their size, shape and distribution.
  • these supported membranes in the range of thicknesses referred to here, are deposited on highly porous substrates to modify the filtration capacity of these.
  • Nanostructured materials are materials defined by the reduction of one of its characteristic lengths to the range of 100 nm, among which ultrafine sheets, nanoparticles, nanotubes, nanofibers or nanowires can be found, provided that they can be deposited on a flat substrate.
  • Chemical deposition from vapor phase (CVD) that can also be assisted by plasma, by ions, by laser, etc.
  • Physical deposition from the vapor phase such as sputtering, evaporation, ion-assisted, molecular beams, etc.
  • the ellipsometry technique has been used to show changes in the refractive index of the layer as a function of the partial pressure of a condensable gas or vapor at room temperature (for example water, toluene , etc.)
  • a condensable gas or vapor at room temperature for example water, toluene , etc.
  • This procedure has several limitations, the first of which is that the layers that can be used cannot disperse the light (they have to be transparent) and the second one, which, as it has been used to date, does not allow the elimination of water or other gases / vapors that are in the pores due to the exposure of the layer to the atmosphere.
  • the presence of Pre-adsorbed gases / vapors conditions the results obtained in experiments of this type using ellipsometry as a measurement technique (A. Borras, A. Barranco, AR Gonzalez-Elipe, "Design and control of porosity in oxide thin films grown by PECVD" , J. Mater. Sci. 41, 2006, 5220).
  • An additional disadvantage of this method is the high cost of the equipment to be used and its complexity when interpreting the data required by the dedication of highly specialized personnel.
  • quartz sensor commonly known as a quartz scale or quartz oscillator, on which the layer to be investigated is deposited
  • MR Baklanov KP. Mogilnikov, VG Polovinkin and FN Dultsev, "Determination of pore size distribution in thin films by ellipsometric porosimetry ", J. Vac. Sci. Technol. B 18, 2000, 1385; Dultsev FN., MR Baklanov," Nondestructive determination of pore size distribution in thin films deposited on solid substrates ", Electrochem Sol. Stat. Lett 24, 1999, 192).
  • This system is based on the measurement of the frequency of vibration of a quartz crystal in the form of a small sheet with gold contacts. This vibration frequency is characteristic of quartz and varies if some type of material is deposited or accumulated on the surface thereof. This procedure is used almost systematically to control the growth of thin layers by evaporation methods or the like.
  • this method has two fundamental limitations, the first of which is that it performs the adsorption / desorption experiment on layers that may have pre-adsorbed gases / vapors in its pores and, by Therefore, it will not give faithful information about the actual porosity of the samples.
  • the second which does not control the temperature of the enclosure where the experiment is carried out, a fact that alters the results by not controlling the phenomena of adsorption-desorption in the walls of the vapor enclosure that is dosed.
  • the lack of an efficient and controlled system for heating the sample also prevents successive adsorption / desorption characterizations with several different vapors.
  • the object of the present invention constitutes a device, hereinafter device of the invention, and its use to determine the porosity of thin sheets, nanostructured materials and supported membranes, comprising the following elements (detailed in Figure 1): one or more Quartz oscillators, a vacuum chamber, a system to maintain the walls of the chamber at a temperature higher than that of adsorption / desorption, temperature meters, pressure meters, a system to initially heat the sample, a system to maintain constant the temperature of the quartz sensor or sensors, a vacuum system, a set of opening and closing valves to dose the steam and a computer system.
  • elements detailed in Figure 1: one or more Quartz oscillators, a vacuum chamber, a system to maintain the walls of the chamber at a temperature higher than that of adsorption / desorption, temperature meters, pressure meters, a system to initially heat the sample, a system to maintain constant the temperature of the quartz sensor or sensors, a vacuum system, a set of opening and closing valves to dose the steam and a computer system.
  • the device of the invention presents technical solutions that allow to overcome the restrictions of the existing methods to date.
  • the heating of the walls of the vacuum chamber to a temperature higher than that which the adsorption / desorption is being carried out avoids the oscillations in the measure due to unwanted adsorption / desorption processes from the walls of the vacuum chamber of the steam used for the measurement.
  • the possibility of heating the sample initially allows the removal of condensates from vapors (pre-adsorbed gases / vapors) that they may exist in it because it has been exposed to the atmosphere.
  • This allows to overcome the inconveniences detected when, either the ellipsometry technique or the quartz oscillator, are used without considering that there may be vapor condensates in the pores (pre-adsorbed gases / vapors) prior to the adsorption / desorption measures.
  • This possibility also opens the way to perform successive tests with several vapors (sequential adsorption / desorption) on the same sample, since by preheating the sample we ensure that no gases / vapors are left pre-adsorbed therein.
  • the device of the invention also, unlike what happens with traditional methods such as ellipsometry, has no limitation as to the type of gases with which isotherms can be determined, being able to be used for organic vapors or other condensable liquids at room temperature Even tests with liquids of different polarity can be performed sequentially. Otherwise it would be necessary to change the sample every time one wanted to change steam, with the consequent reproducibility problems that this might imply.
  • Another important feature of the device of the invention is that it allows the use of more than one quartz scale and, consequently, the realization of more than one adsorption / desorption isotherm simultaneously to determine the porosity of the samples.
  • the device allows measurements "in situ" of optical properties of the samples and even modify these properties while performing the test with treatments of the sample that require vacuum or controlled pressures such as irradiation, plasma treatment, etc. .
  • This possibility is supported by the fact that the experiment is carried out in a vacuum chamber that allows the incorporation of all types of accessories. For example, it is possible to change the hydrophilic / hydrophobic character of certain materials by lighting or by plasma treatment. These changes must bring together a modification of the adsorption properties Io that would be verified by measuring the corresponding isotherms by means of the quartz sensor.
  • Another object of the present invention is the use of the device described above for the determination of the porosity of thin sheets, nanostructured materials and supported membranes, as well as for the determination of adsorption / desorption isotherms of said materials.
  • the device can be used to determine the percentage of meso and micropores (sizes larger and smaller than 20 nm) of the analyzed samples. This requires the evaluation of experimental isotherms through appropriate calculation methods. For this purpose, the adsorption / desorption isotherm is used, and the percentage of each of them can be established from the corresponding calculations.
  • Figure 1 Elements comprising the device of the invention.
  • Figure 2. Water vapor adsorption / desorption isotherms on a TiO 2 sheet 439 nm thick with and without prior heating of the sample. The volume of water vapor adsorbed measured in cm 3 is plotted against the relationship between the pressure at a given time and the initial pressure.
  • Figure 3 Water vapor adsorption / desorption isotherms on a TIO 2 sheet of 496 nm thickness. The steam volume of adsorbed water measured in cm 3 against the relationship between the pressure at a given time and the initial pressure.
  • the object of the present invention constitutes a device capable of determining the porosity of thin sheets, nanostructured materials and supported membranes and comprising the following elements:
  • quartz oscillators commonly called quartz scales or quartz sensors, on which the layer whose porosity is to be measured is deposited and which allows to determine the amount of gas adsorbed by variations in the oscillation frequency.
  • quartz sensors there may be one or more quartz sensors within the vacuum chamber which allows the measurement of the porosity of several samples simultaneously.
  • a vacuum chamber constructed of a material resistant to vacuum conditions, such as, for example, and without limiting the scope of the present invention, stainless steel sealed by means of copper seals or other similar vacuum closing systems.
  • quartz oscillator s
  • the quartz oscillator connected to the outside by means of a gland to allow the passage of cooling water and electrical contacts for the measurement of the oscillation frequency.
  • a heating system for heating the walls of the chamber so as to maintain a temperature higher than that of the realization of adsorption / desorption which without limiting the scope of the present invention can be a heating belt.
  • the heating of the walls of the vacuum chamber prevents random oscillations of the measurement of the quartz balance due to unwanted adsorption / desorption processes of the steam used for the measurement of the adsorption / desorption isotherms on the walls of the chamber of emptiness. 4.
  • Temperature meters, one of them applied to the quartz sensor which improves the control of the experimental conditions, preventing that during the initial heating of the sample the temperature of the quartz sensor rises above 130 0 C Io that it could cause irreversible damage.
  • This temperature meter is connected to the outside of the vacuum chamber through passages that allow the corresponding electrical signal to be taken to a suitable controller. Another meter applied to the walls of the vacuum chamber measures the temperature of these and, together with the temperature control system described in point 7, allows the temperature of the latter to be kept constant and therefore also that of the sample.
  • the temperature meters and without limiting the scope of the invention can be of the thermocouple type or the like.
  • One or more pressure gauges This pressure meter in a particular embodiment of the invention, is based on the capacitance measurement and whose range depends on the type of steam used to measure the isotherms. The most common is the measurement of water vapor isotherms, in which the range of pressures to be controlled ranges from very low values of the order of 10 ⁇ 2 torr to the pressure of the water vapor at room temperature, around a few tens of torr. This range could be extended if the liquid water used to provide the steam that is sent to the chamber where the quartz oscillator is located is heated. Pressure gauges that can be used are universal gauges.
  • a system for controlling the temperature of the sensor or quartz sensors to keep its temperature constant throughout the experiment may be composed of a water circuit, a Peltier to achieve even finer control of the temperature of the quartz scale, a temperature meter (described in point 4 ) and a temperature controller.
  • the isotherms are generally determined at room temperature, but with this temperature control system they could even be determined below this. These systems are connected to the outside by means of suitable pasamuros.
  • a vacuum system coupled to the vacuum chamber and which, without limiting the scope of the present invention, may be composed of a rotary and a turbomolecular pump although there are other possible methods of making vacuum based on diffuser pumps, pumps " roots “or ionic (LI Maissel, R. Glang," Handbook of thin film technology ", Mcgraw-Hill Book Company New York 1970).
  • the use of the combination of a rotary and a turbomolecular pump have the advantage of its speed, its reasonable cost and, above all, the possibility of pumping significant amounts of gases / vapors, reaching low limits.
  • a set of opening and closing valves that define a set of small volumes that, filled with steam from the enclosure where the liquid isotherm is to be measured, expand to the main chamber where the quartz scale is. This way and after successive opening and closing processes, the vapor pressure in the vacuum chamber where the quartz sensor is gradually can be varied.
  • the valves used must be watertight against the vacuum and respond in open and close positions to external electrical or pneumatic impulses.
  • the control over the valves that regulate the vapor pressure in the vacuum chamber can be carried out by means of a control program of electronic devices that, without limiting the scope of the present invention, can be carried out in a Labview environment. 10.
  • a computer system that, through the appropriate ports and interfaces, controls both the measuring equipment (pressure meters, quartz balance electronics) and orders the valve opening / closing processes that allow the automatic operation of the system .
  • the layer whose porosity is intended to be determined is placed on the head of the quartz sensor integrated within the vacuum chamber. From the measurement of the frequency change in the oscillator through the coupled quartz sensor, the amount of deposited or adsorbed / desorbed material can be known.
  • Another object of the present invention is the use of the device just described for the determination of the porosity of thin sheets, nanostructured materials and supported membranes, as well as for the determination of adsorption / desorption isotherms of said materials.
  • the device of the invention can additionally include software, which, based on the results obtained in the different adsorption / desorption isotherms, provides direct information on the amount of adsorbed / desorbed material, the total pore volume, the proportion thereof which are micropores or mesopores and, in the latter case, the distribution of pores according to sizes.
  • Df is the thickness of the layer in Amstrongs.
  • N q is the frequency constant for the quartz crystal.
  • D q is the density of quartz in gm / cm 3 ⁇ : is the constant Pi, 3.141592653
  • Df is the density of the material in gm / cm 3
  • Z is a characteristic factor of the material related to its density and its mechanical properties.
  • F q is the frequency of the quartz sensor before depositing the material.
  • F c is the frequency of the quartz sensor after depositing the material.
  • the calculation of the porosity and the size distribution is based on the application of different thermodynamic and classical physicochemical equations, such as the Kelvin equation to determine the pore size:
  • V L is the molar volume of the liquid from which the vapor is formed
  • R is the constant 8.30107 ergK “1 moles " 1
  • T is the temperature in K at which the measurement is made and: it is the surface tension of the liquid r m : it is the average radius of the pore.
  • the "tplot" representation of the measurement of the isotherm consists in drawing the adsorbed volume values measured with the quartz sensor against the thickness of the equivalent layer that would be adsorbed on a flat, compact and homogeneous surface. From the “tplot” curves, the volume and size of micropores and the volume of mesopores can be deduced as a difference from the total pore volume.
  • the equivalent thickness depends on the value of the partial vapor pressure according to the following equation:
  • t is the thickness of the equivalent layer.
  • HPi, HP2 and HP3 constants that depend on the adsorbed vapor.
  • the pore size distribution is calculated from the experimental data, applying the two previous equations and the Pierce method (SJ. Gregg, K. S. W. Sing, "Adsorption, Surface Area and Porosity", Academy Press London, 1982).
  • This device may contain one or several quartz sensors Io that allows to determine the adsorption / desorption isotherms and therefore the porosity of several samples simultaneously.
  • the device of the invention allows not only measurements of several samples simultaneously but also adsorption / desorption can be performed sequentially, using different liquids and even using liquids of different polarity. For example, successive water and toluene isotherms could be made. Given the different size of these two molecules and their different polar character, the phenomenology of Ia adsorption of each of them would be different by providing complementary information on the pore structure of the material.
  • this device is not only limited to the determination of adsorption / desorption isotherms, and therefore to the measure of the porosity of said thin sheets, nanostructured materials and supported membranes, but also the device of the invention is compatible with
  • Example 1 Measurement of the porosity of a thin sheet of 439 nm
  • the porosity of a T ⁇ O2 layer prepared by means of a chemical deposition technique from plasma assisted vapor phase (PECVD) is measured.
  • the 439 nm thick sheet is placed on a quartz scale (13 mm in diameter) coupled to the oscillator system (Instruments Sycon) with Nor-Cal Products measuring electronics.
  • the quartz sensor is located in a 3 L volume stainless steel vacuum chamber, sealed by CF seals with 1/4 "and 1/8" Swagelok copper joints.
  • the enclosure is closed and empty.
  • the vacuum system consists of an Edwards rotary with a capacity of 6 m 3 / h and a turbomolecular pump of
  • the pressure inside the chamber is measured with a pressure gauge Capacitance Balzers, 0.2 to 10 torr, Pfeiffer (all range, capable of measuring between 10 ⁇ 7 to 103 torr).
  • the sample is heated by irradiation with a halogen lamp of 12 V and 100 W to a temperature above 100 0 C, to eliminate the gases pre-absorbed in the layers.
  • a control system formed by 120 W Peltier (Amidata), dc (Tech) power supply for the Peltier, TEMPATRON tc4800 temperature controllers, 100 W heating bands (Caburn) and K-type thermocouples (Amidata).
  • the cooling is carried out by means of water at room temperature through the stainless steel circuit coupled by Swagelok 1/8 "racorer ⁇ a keeping the temperature at 18 0 C.
  • a pyrex bulb (Caburn) where the liquid is placed.
  • This bulb is coupled to a manual open / close valve system (Withey) by means of stainless steel pipes and fittings (Swagelok).
  • This system is connected either to the chamber where the quartz scale is located or directly to the vacuum system, all through CF (Caburn) joints sealed with copper joints.
  • the connection allows dosing increasing pressures of water vapor in the chamber.
  • it is sought to be able to degas the liquid water of the bulb before the adsorption experiment by successive freezing / evacuation processes.
  • T ⁇ O2 layers prepared by means of the chemical deposition technique from plasma-assisted vapor phase (PECVD) are synthesized by appropriate changes in the preparation protocols, layers with completely different porosities can be obtained, although their index of refraction is similar.
  • a T ⁇ O2 sheet is also used, this time of thickness 496 nm.
  • the device used to carry out the determination of the adsorption / desorption isotherms and the experimental measurement conditions are identical to those indicated in example 1.
  • Figure 3 shows the adsorption / desorption isotherm of the TYPE 2 layer of 496 nm. As can be seen in this case, the adsorption isotherm and the desorption is almost coincident. This behavior is typical of samples with micropores, where there is no contribution of large pores. In this case the adsorption / desorption process is completely reversible, with no hysteresis or residual adsorption observed.

Abstract

The invention relates to a device which can be used to determine the adsorption/desorption isotherms and porosity in thin films, supported membranes and directly supported nanostructured materials. For this purpose, the adsorption and desorption isotherms of the sample are determined and subsequently used to determine the type of porosity of the sample, as well as the pore volume and pore size distribution thereof, using solid surface thermodynamic and physicochemical concepts.

Description

DISPOSITIVO PARA LA DETERMINACIÓN DE LA POROSIDAD DE LÁMINAS DELGADAS Y SU UTILIZACIÓN DEVICE FOR THE DETERMINATION OF THE POROSITY OF THIN SHEETS AND ITS USE
SECTOR DE LA TÉCNICA La presente invención tiene aplicaciones diversas, en campos como por ejemplo Ia óptica y Ia optoelectrónica. Puede utilizarse en Ia medida de porosidad para todo tipo de capas delgadas y recubrimientos con aplicaciones en óptica (sistemas antirreflectantes, en lentes, espejos, polarizadores, etc.), capas de protección (contra Ia corrosión, abrasión, mejora de Ia resistencia al desgaste, protección UV, etc.), recubrimientos para mejorar el aspecto estético y con aplicaciones decorativas (metalizado en joyería, saneamientos o recubrimiento de materiales para Ia construcción entre otras), capas y membranas utilizadas como recubrimientos biocompatibles y nanopartículas con aplicaciones en biomedicina (en las que Ia porosidad es esencial para controlar su biocompatibilidad), láminas delgadas, membranas soportadas y materiales nanoestructurados utilizados como sensores de gases, de irradiación, en células solares, nanotubos y nanocables utilizados como parte de dispositivos electrónicos, materiales de importantes aplicaciones en microelectrónica y otras capas funcionales para aplicaciones energéticas entre otras.SECTOR OF THE TECHNIQUE The present invention has diverse applications, in fields such as optics and optoelectronics. It can be used in the measure of porosity for all types of thin layers and coatings with applications in optics (anti-reflective systems, in lenses, mirrors, polarizers, etc.), protective layers (against corrosion, abrasion, improvement of wear resistance , UV protection, etc.), coatings to improve the aesthetic appearance and with decorative applications (metallized in jewelry, sanitation or coating of construction materials among others), layers and membranes used as biocompatible coatings and nanoparticles with applications in biomedicine (in which porosity is essential to control its biocompatibility), thin sheets, supported membranes and nanostructured materials used as gas sensors, irradiation, in solar cells, nanotubes and nanowires used as part of electronic devices, materials of important applications in microelectronics and other functional layers for application Energy ones among others.
ESTADO DE LA TÉCNICASTATE OF THE TECHNIQUE
Una característica de difícil determinación cuando se trabaja con láminas delgadas, membranas y materiales definidos por longitudes características en el rango de los micro o nanómetros, es su porosidad.A characteristic of difficult determination when working with thin sheets, membranes and materials defined by characteristic lengths in the range of micro or nanometers, is their porosity.
Dentro del concepto de lámina delgada o recubrimiento se engloban todos los materiales soportados sobre sustratos tridimensionales o planos en los que sus características están determinadas por los fenómenos de superficie, que predominan sobre los de volumen. El espesor de estas láminas se encuentra en el rango comprendido entre las decenas de nanómetros y varias mieras. El límite superior de tamaño viene impuesto por Ia estabilidad mecánica de Ia capa y por su propia definición ya que las características o propiedades consideradas dependen de Ia relación superficie/volumen del material.Within the concept of thin sheet or coating all materials supported on three-dimensional or flat substrates are included in which their characteristics are determined by surface phenomena, which predominate over those of volume. The thickness of these sheets is in the range between tens of nanometers and several microns. The upper limit of size is imposed by the mechanical stability of the layer and by its own definition since the characteristics or properties considered depend on the surface / volume ratio of the material.
Las membranas soportadas se utilizan para limitar el paso de ciertos componentes en mezclas de fluidos, favoreciendo el paso de otros con el objetivo de separarlos. Un conjunto amplio de membranas se basan en Ia restricción de Ia difusión de esos componentes a través de poros, por Io que resulta crítica Ia definición del tamaño, forma y distribución de los mismos. En ocasiones, estas membranas soportadas, en el rango de espesores al que aquí nos referimos, se depositan sobre sustratos de gran porosidad para modificar Ia capacidad de filtración de éstos.The supported membranes are used to limit the passage of certain components in fluid mixtures, favoring the passage of others in order to separate them. A broad set of membranes are based on the restriction of the diffusion of these components through pores, so it is critical to define their size, shape and distribution. Sometimes, these supported membranes, in the range of thicknesses referred to here, are deposited on highly porous substrates to modify the filtration capacity of these.
Los materiales nanoestructurados, son materiales definidos por Ia reducción de una de sus longitudes características al rango de los 100 nm, entre los que se pueden encontrar láminas ultrafinas, nanopartículas, nanotubos, nanofibras o nanocables, siempre que puedan depositarse sobre un sustrato plano.Nanostructured materials are materials defined by the reduction of one of its characteristic lengths to the range of 100 nm, among which ultrafine sheets, nanoparticles, nanotubes, nanofibers or nanowires can be found, provided that they can be deposited on a flat substrate.
Existen numerosas técnicas diferentes para Ia fabricación de estos materiales basadas en procesos físico-químicos, como:There are numerous different techniques for the manufacture of these materials based on physical-chemical processes, such as:
Deposición química desde fase vapor (CVD) que puede además estar asistida por plasma, por iones, por láser, etc. • Deposición física desde fase vapor, como pulverización catódica, evaporación, asistida por iones, por haces moleculares, etc. • Deposición desde disoluciones: sol-gel y electroquímica.Chemical deposition from vapor phase (CVD) that can also be assisted by plasma, by ions, by laser, etc. • Physical deposition from the vapor phase, such as sputtering, evaporation, ion-assisted, molecular beams, etc. • Deposition from solutions: sol-gel and electrochemistry.
O bien se puede obtener este tipo de materiales a partir del tratamiento de superficies con láser, plasmas, mediante implantación, etc. El grado de porosidad de Ia lámina y el tipo de porosidad (mesoporos, microporos, etc.) determina una gran variedad de propiedades de las mismas que influyen sobre las aplicaciones de estas.Or you can obtain this type of materials from the treatment of surfaces with lasers, plasmas, by implantation, etc. The degree of porosity of the sheet and the type of porosity (mesopores, micropores, etc.) determines a great variety of properties thereof that influence their applications.
En el caso de materiales en forma de polvo Ia determinación de su porosidad se fundamenta en el análisis de isotermas de adsorción de gases (N2, Ar, Kr) según procedimientos muy bien establecidos basados en Ia denominada ecuación BET (SJ. Gregg, K. S. W. Sing, "Adsorption, Surface Área and Porosity", Academic Press, London, 1982). Este tipo de métodos no es aplicable a las láminas delgadas por problemas de sensibilidad. En una lámina delgada de espesores por ejemplo de una miera, Ia cantidad de material a investigar es pequeño y los sistemas BET tradicionales no pueden detectar fenómenos de adsorción que se puedan relacionar con Ia porosidad real de las capas.In the case of materials in powder form, the determination of their porosity is based on the analysis of gas adsorption isotherms (N 2 , Ar, Kr) according to very well established procedures based on the so-called BET equation (SJ. Gregg, KSW Sing, "Adsorption, Surface Area and Porosity", Academic Press, London, 1982). This type of methods is not Applicable to thin sheets due to sensitivity problems. In a thin sheet of thicknesses, for example of a mill, the amount of material to be investigated is small and traditional BET systems cannot detect adsorption phenomena that can be related to the actual porosity of the layers.
En el caso de las láminas delgadas de uso en óptica se ha utilizado Ia técnica de elipsometría para evidenciar cambios en el índice de refracción de Ia capa en función de Ia presión parcial de un gas o vapor condensable a temperatura ambiente (por ejemplo agua, tolueno, etc.) (A. Brunet-Bruneau, A. Bourgeois, A. V. Jousseaume, N. Rochat, S. Fisson, B. Demarets and J. Rivory "An in situ study of mesostructured CTAB-silica film formation using infrared ellipsometry: evolution of water contení", Thin Sol. Films, 455, 2004, 366; A. Ruud Balkenende, F. K. de Theije and J. C. Koen Kriege, "Controlling dielectric and optical properties of ordered mesoporous organosilicate films", Adv. Mater. 15, 2003, 139; A. Alvarez- Herrero, H. Guerrero, E. Bernabeu and D. Levy, "Analysis of nanostructured porous films by measurement of adsorption isotherms with optical fiber and ellipsometry", Appl. Optics 41 , 2002, 6692). Con este procedimiento se han medido isotermas de adsorción/desorción de las que es posible obtener información sobre Ia porosidad y estructura de los poros de las capas. Sin embargo, con este método no se pueden realizar procesos secuenciales de adsorción de un mismo vapor o de varios vapores, sencillamente porque no se suele calentar las muestras tras Ia primera adsorción para eliminar el primer vapor adsorbido en Ia muestra.In the case of thin sheets for use in optics, the ellipsometry technique has been used to show changes in the refractive index of the layer as a function of the partial pressure of a condensable gas or vapor at room temperature (for example water, toluene , etc.) (A. Brunet-Bruneau, A. Bourgeois, AV Jousseaume, N. Rochat, S. Fisson, B. Demarets and J. Rivory "An in situ study of mesostructured CTAB-silica film formation using infrared ellipsometry: evolution of water contení ", Thin Sol. Films, 455, 2004, 366; A. Ruud Balkenende, FK de Theije and JC Koen Kriege," Controlling dielectric and optical properties of ordered mesoporous organosilicate films ", Adv. Mater. 15, 2003, 139; A. Alvarez-Herrero, H. Guerrero, E. Bernabeu and D. Levy, "Analysis of nanostructured porous films by measurement of adsorption isotherms with optical fiber and ellipsometry", Appl. Optics 41, 2002, 6692). With this procedure, adsorption / desorption isotherms have been measured from which it is possible to obtain information on the porosity and structure of the pores of the layers. However, with this method, sequential processes of adsorption of the same steam or of several vapors cannot be carried out, simply because the samples are not usually heated after the first adsorption to eliminate the first vapor adsorbed in the sample.
Es asimismo frecuente en este tipo de estudios no realizar el ciclo completo de adsorción/desorción, debido fundamentalmente a que se requiere un sistema relativamente complejo de evacuación controlada de los vapores para poder llevar acabo el proceso de desorción.It is also common in these types of studies not to perform the complete adsorption / desorption cycle, mainly because a relatively complex system of controlled evacuation of the vapors is required to carry out the desorption process.
Este procedimiento presenta varias limitaciones, Ia primera de ellas es que las capas que pueden emplearse no pueden dispersar Ia luz (tienen que ser transparentes) y Ia segunda que, tal y como se ha utilizado hasta Ia fecha, no permite eliminar el agua u otros gases/vapores que se encuentren en los poros debido a Ia exposición de Ia capa a Ia atmósfera. La presencia de gases/vapores pre-adsorbidos condiciona los resultados obtenidos en experimentos de este tipo utilizando Ia elipsometría como técnica de medida (A. Borras, A. Barranco, A. R. Gonzalez-Elipe, "Design and control of porosity in oxide thin films grown by PECVD", J. Mater. Sci. 41 , 2006, 5220). Una desventaja adicional de este método es el alto coste de los equipos a utilizar y su complejidad a Ia hora de interpretar los datos que exige Ia dedicación de personal muy especializado.This procedure has several limitations, the first of which is that the layers that can be used cannot disperse the light (they have to be transparent) and the second one, which, as it has been used to date, does not allow the elimination of water or other gases / vapors that are in the pores due to the exposure of the layer to the atmosphere. The presence of Pre-adsorbed gases / vapors conditions the results obtained in experiments of this type using ellipsometry as a measurement technique (A. Borras, A. Barranco, AR Gonzalez-Elipe, "Design and control of porosity in oxide thin films grown by PECVD" , J. Mater. Sci. 41, 2006, 5220). An additional disadvantage of this method is the high cost of the equipment to be used and its complexity when interpreting the data required by the dedication of highly specialized personnel.
Otro método alternativo utilizado en Ia literatura científica es un sensor de cuarzo, conocido comúnmente como balanza de cuarzo u oscilador de cuarzo, sobre el que se deposita Ia capa a investigar (M. R. Baklanov, KP. Mogilnikov, V.G. Polovinkin and F. N. Dultsev, "Determination of pore size distribution in thin films by ellipsometric porosimetry", J. Vac. Sci. Technol. B 18, 2000, 1385; Dultsev FN., M. R. Baklanov, "Nondestructive determination of pore size distribution in thin films deposited on solid substrates", Electrochem Sol. Stat. Lett 24, 1999, 192). Este sistema se fundamenta en Ia medida de Ia frecuencia de vibración de un cristal de cuarzo en forma de pequeña lámina con contactos de oro. Esta frecuencia de vibración es característica del cuarzo y varía si sobre Ia superficie del mismo se deposita o acumula algún tipo de material. Este procedimiento se usa de forma casi sistemática para controlar el crecimiento de capas delgadas por métodos de evaporación o similares.Another alternative method used in the scientific literature is a quartz sensor, commonly known as a quartz scale or quartz oscillator, on which the layer to be investigated is deposited (MR Baklanov, KP. Mogilnikov, VG Polovinkin and FN Dultsev, "Determination of pore size distribution in thin films by ellipsometric porosimetry ", J. Vac. Sci. Technol. B 18, 2000, 1385; Dultsev FN., MR Baklanov," Nondestructive determination of pore size distribution in thin films deposited on solid substrates ", Electrochem Sol. Stat. Lett 24, 1999, 192). This system is based on the measurement of the frequency of vibration of a quartz crystal in the form of a small sheet with gold contacts. This vibration frequency is characteristic of quartz and varies if some type of material is deposited or accumulated on the surface thereof. This procedure is used almost systematically to control the growth of thin layers by evaporation methods or the like.
Sin embargo, este método tal y como ha sido planteado hasta Ia fecha, presenta dos limitaciones fundamentales, Ia primera de ellas es que realiza el experimento de adsorción/desorción sobre capas que pueden tener gases/vapores pre-adsorbidos en sus poros y, por Io tanto, no dará una información fiel sobre Ia porosidad real de las muestras. La segunda, que no controla Ia temperatura del recinto donde se realiza el experimento, un hecho que altera los resultados al no controlar los fenómenos de adsorción-desorción en las paredes del recinto del vapor que se dosifica. La carencia de un sistema eficaz y controlado para calentar Ia muestra impide también que se puedan hacer caracterizaciones sucesivas de adsorción/desorción con varios vapores diferentes. DESCRIPCIÓN BREVEHowever, this method, as it has been proposed to date, has two fundamental limitations, the first of which is that it performs the adsorption / desorption experiment on layers that may have pre-adsorbed gases / vapors in its pores and, by Therefore, it will not give faithful information about the actual porosity of the samples. The second, which does not control the temperature of the enclosure where the experiment is carried out, a fact that alters the results by not controlling the phenomena of adsorption-desorption in the walls of the vapor enclosure that is dosed. The lack of an efficient and controlled system for heating the sample also prevents successive adsorption / desorption characterizations with several different vapors. BRIEF DESCRIPTION
Constituye el objeto de Ia presente invención un dispositivo, en adelante dispositivo de Ia invención, y su uso para determinar Ia porosidad de láminas delgadas, materiales nanoestructurados y membranas soportadas, que comprende los siguientes elementos (detallados en Ia Figura 1 ): uno o varios osciladores de cuarzo, una cámara de vacío, un sistema para mantener las paredes de Ia cámara a una temperatura superior a Ia de Ia adsorción/desorción, medidores de temperatura, medidores de presión, un sistema para calentar Ia muestra inicialmente, un sistema para mantener constante Ia temperatura del sensor o sensores de cuarzo, un sistema de vacío, un conjunto de válvulas de apertura y cierre para dosificar el vapor y un sistema informático.The object of the present invention constitutes a device, hereinafter device of the invention, and its use to determine the porosity of thin sheets, nanostructured materials and supported membranes, comprising the following elements (detailed in Figure 1): one or more Quartz oscillators, a vacuum chamber, a system to maintain the walls of the chamber at a temperature higher than that of adsorption / desorption, temperature meters, pressure meters, a system to initially heat the sample, a system to maintain constant the temperature of the quartz sensor or sensors, a vacuum system, a set of opening and closing valves to dose the steam and a computer system.
Cuando Ia muestra porosa colocada sobre el sensor de cuarzo se expone de manera controlada a presiones crecientes (adsorción) de un vapor (agua, tolueno, etc.) o de desorción (si se disminuye sistemáticamente Ia presión desde el máximo de saturación), se obtienen medidas de Ia frecuencia de vibración de Ia lámina de cuarzo en función de Ia cantidad de vapor de agua adsorbida en los poros de Ia capa depositada, Io que permite construir una isoterma de adsorción. Al disminuir Ia presión el vapor de agua, esta se desorbe por Io que se obtiene Ia isoterma de desorción. A partir de Ia evaluación de esas isotermas de adsorción/desorción se puede estimar el tipo de porosidad, volumen de poros y Ia distribución de tamaño de poros (porcentaje de meso y microporos) de Ia muestra.When the porous sample placed on the quartz sensor is exposed in a controlled manner to increasing pressures (adsorption) of a vapor (water, toluene, etc.) or of desorption (if the pressure is systematically decreased from the maximum saturation), Obtain measurements of the frequency of vibration of the quartz sheet as a function of the amount of water vapor adsorbed in the pores of the deposited layer, which allows the construction of an adsorption isotherm. When the water vapor decreases, it is desorbed by what is obtained by the desorption isotherm. Based on the evaluation of these adsorption / desorption isotherms, the type of porosity, pore volume and pore size distribution (percentage of meso and micropores) of the sample can be estimated.
El dispositivo de Ia invención presenta soluciones técnicas que permiten superar las restricciones de los métodos existentes hasta Ia fecha. Así, el calentamiento de las paredes de Ia cámara de vacío a una temperatura superior a Ia que se está realizando Ia adsorción/desorción, evita las oscilaciones en Ia medida debido a procesos de adsorción/desorción no deseados desde las paredes de Ia cámara de vacío del vapor usado para Ia medida.The device of the invention presents technical solutions that allow to overcome the restrictions of the existing methods to date. Thus, the heating of the walls of the vacuum chamber to a temperature higher than that which the adsorption / desorption is being carried out, avoids the oscillations in the measure due to unwanted adsorption / desorption processes from the walls of the vacuum chamber of the steam used for the measurement.
Asimismo, Ia posibilidad de calentar Ia muestra inicialmente permite eliminar los condensados de vapores (gases/vapores pre-adsorbidos) que pueden existir en ella debido a que ésta ha estado expuesta a Ia atmósfera. Ello permite superar los inconvenientes detectados cuando, bien Ia técnica de elipsometría o Ia del oscilador de cuarzo, se utilizan sin considerar que puede haber condensados de vapor en los poros (gases/vapores pre-adsorbidos) previamente a las medidas de adsorción/desorción. Esta posibilidad abre asimismo Ia vía para realizar ensayos sucesivos con varios vapores (adsorciones/desorciones secuenciales) sobre Ia misma muestra, ya que al calentar previamente Ia muestra nos aseguramos de que no queden gases/vapores pre-adsorbidos en Ia misma. El dispositivo de Ia invención además, a diferencia de Io que ocurre con los métodos tradicionales como Ia elipsometría, no presenta limitación en cuanto al tipo de gases con los que pueden determinarse las isotermas, pudiéndose utilizar para vapores orgánicos u otros líquidos condensables a temperatura ambiente, incluso pueden realizarse secuencialmente ensayos con líquidos de diferente polaridad. En caso contrario sería necesario cambiar Ia muestra cada vez que se quisiera cambiar de vapor, con los consiguientes problemas de reproducibilidad que ello pudiera implicar.Likewise, the possibility of heating the sample initially allows the removal of condensates from vapors (pre-adsorbed gases / vapors) that they may exist in it because it has been exposed to the atmosphere. This allows to overcome the inconveniences detected when, either the ellipsometry technique or the quartz oscillator, are used without considering that there may be vapor condensates in the pores (pre-adsorbed gases / vapors) prior to the adsorption / desorption measures. This possibility also opens the way to perform successive tests with several vapors (sequential adsorption / desorption) on the same sample, since by preheating the sample we ensure that no gases / vapors are left pre-adsorbed therein. The device of the invention also, unlike what happens with traditional methods such as ellipsometry, has no limitation as to the type of gases with which isotherms can be determined, being able to be used for organic vapors or other condensable liquids at room temperature Even tests with liquids of different polarity can be performed sequentially. Otherwise it would be necessary to change the sample every time one wanted to change steam, with the consequent reproducibility problems that this might imply.
Otra característica importante del dispositivo de Ia invención es que permite Ia utilización de más de una balanza de cuarzo y, por consiguiente, Ia realización de más de una isoterma de adsorción/desorción simultáneamente para determinar Ia porosidad de las muestras.Another important feature of the device of the invention is that it allows the use of more than one quartz scale and, consequently, the realization of more than one adsorption / desorption isotherm simultaneously to determine the porosity of the samples.
Además, el dispositivo permite realizar medidas "in situ" de propiedades ópticas de las muestras e, incluso, modificar estas propiedades mientras se realiza el ensayo con tratamientos de Ia muestra que requieran vacío o presiones controladas como por ejemplo irradiación, tratamiento con plasmas, etc. Esta posibilidad se sustenta por el hecho de que el experimento se lleva a cabo en una cámara de vacío que permite Ia incorporación de todo tipo de accesorios. Por ejemplo, es posible cambiar el carácter hidrofílico/hidrofóbico de ciertos materiales mediante iluminación o mediante tratamiento con plasmas. Estos cambios deben llevar unidos una modificación de las propiedades de adsorción Io que se verificaría midiendo las isotermas correspondientes mediante el sensor de cuarzo. La posibilidad de hacer todos los experimentos "in situ" es esencial ya que, en caso contrario, habría que exponer Ia muestra al aire modificando en consecuencia sus propiedades superficiales y de adsorción y, en el caso de medir su porosidad sin un calentamiento previo de Ia muestra, los resultados obtenidos no contemplarán Ia porosidad real de Ia muestra.In addition, the device allows measurements "in situ" of optical properties of the samples and even modify these properties while performing the test with treatments of the sample that require vacuum or controlled pressures such as irradiation, plasma treatment, etc. . This possibility is supported by the fact that the experiment is carried out in a vacuum chamber that allows the incorporation of all types of accessories. For example, it is possible to change the hydrophilic / hydrophobic character of certain materials by lighting or by plasma treatment. These changes must bring together a modification of the adsorption properties Io that would be verified by measuring the corresponding isotherms by means of the quartz sensor. The possibility of doing all "in situ" experiments is essential since, otherwise, the sample should be exposed to air, modifying its surface and adsorption properties accordingly and, in the case of measuring its porosity without prior heating of the sample, the results obtained will not contemplate the real porosity of the sample.
Otro objeto de Ia presente invención Io constituye Ia utilización del dispositivo descrito anteriormente para Ia determinación de Ia porosidad de láminas delgadas, materiales nanoestructurados y membranas soportadas, así como para Ia determinación de isotermas de adsorción/desorción de dichos materiales.Another object of the present invention is the use of the device described above for the determination of the porosity of thin sheets, nanostructured materials and supported membranes, as well as for the determination of adsorption / desorption isotherms of said materials.
Asimismo, el dispositivo puede ser utilizado para determinar el porcentaje de meso y microporos (tamaños mayores y menores de 20 nm) de las muestras analizadas. Ello requiere Ia evaluación de las isotermas experimentales mediante métodos de cálculo adecuados. Para este propósito se utiliza Ia isoterma de adsorción/desorción, pudiéndose establecer el porcentaje de cada uno de ellos a partir de los cálculos correspondientes.Also, the device can be used to determine the percentage of meso and micropores (sizes larger and smaller than 20 nm) of the analyzed samples. This requires the evaluation of experimental isotherms through appropriate calculation methods. For this purpose, the adsorption / desorption isotherm is used, and the percentage of each of them can be established from the corresponding calculations.
BREVE DESCRIPCIÓN DE LAS FIGURASBRIEF DESCRIPTION OF THE FIGURES
Figura 1. Elementos que comprende el dispositivo de Ia invención. 1- oscilador de cuarzo, 2-cámara de vacío, 3-sistema de calefacción de Ia cámara de vacío, 4-Medidores de temperatura, 5-medidores de presión, 6- sistema para calentar Ia muestra inicialmente, 7- sistema de control de Ia temperatura del sensor de cuarzo, 8- sistema de vacío, 9- conjunto de válvulas de apertura y cierre, 10- sistema informático. Figura 2. Isotermas de adsorción/desorción de vapor de agua sobre una lámina de TiO2 de 439 nm de espesor con y sin calentamiento previo de Ia muestra. Se representa el volumen de vapor de agua adsorbido medido en cm3 frente a Ia relación entre Ia presión en un momento dado y Ia presión inicial. Figura 3. Isotermas de adsorción/desorción de vapor de agua sobre una lámina de TÍO2 de 496 nm de espesor. Se representa el volumen de vapor de agua adsorbido medido en cm3 frente a Ia relación entre Ia presión en un momento dado y Ia presión inicial.Figure 1. Elements comprising the device of the invention. 1- quartz oscillator, 2-vacuum chamber, 3-vacuum chamber heating system, 4-temperature meters, 5-pressure meters, 6- system to initially heat the sample, 7- control system The temperature of the quartz sensor, 8- vacuum system, 9- set of opening and closing valves, 10- computer system. Figure 2. Water vapor adsorption / desorption isotherms on a TiO 2 sheet 439 nm thick with and without prior heating of the sample. The volume of water vapor adsorbed measured in cm 3 is plotted against the relationship between the pressure at a given time and the initial pressure. Figure 3. Water vapor adsorption / desorption isotherms on a TIO 2 sheet of 496 nm thickness. The steam volume of adsorbed water measured in cm 3 against the relationship between the pressure at a given time and the initial pressure.
DESCRIPCIÓN DETALLADA Constituye el objeto de Ia presente invención un dispositivo capaz de determinar Ia porosidad de láminas delgadas, materiales nanoestructurados y membranas soportadas y que comprende los siguientes elementos:DETAILED DESCRIPTION The object of the present invention constitutes a device capable of determining the porosity of thin sheets, nanostructured materials and supported membranes and comprising the following elements:
1. Uno o varios osciladores de cuarzo, comúnmente denominados balanzas de cuarzo o sensores de cuarzo, sobre el que se deposita Ia capa cuya porosidad se quiere medir y que permite determinar Ia cantidad de gas adsorbido mediante las variaciones en Ia frecuencia de oscilación. Formando parte del dispositivo de Ia invención puede haber uno o más sensores de cuarzo dentro de Ia cámara de vacío Io que permite Ia medida de Ia porosidad de varias muestras simultáneamente.1. One or several quartz oscillators, commonly called quartz scales or quartz sensors, on which the layer whose porosity is to be measured is deposited and which allows to determine the amount of gas adsorbed by variations in the oscillation frequency. As part of the device of the invention there may be one or more quartz sensors within the vacuum chamber which allows the measurement of the porosity of several samples simultaneously.
2. Una cámara de vacío construida en un material resistente a las condiciones de vacío, como por ejemplo, y sin que limite el alcance de Ia presente invención, acero inoxidable sellado mediante juntas de cobre o de otros sistemas de cierre vacío similares. Dentro de esta cámara se encuentran el/los oscilador/es de cuarzo conectados con el exterior mediante un pasamuros para permitir el paso de agua de refrigeración y contactos eléctricos para Ia medida de Ia frecuencia de oscilación.2. A vacuum chamber constructed of a material resistant to vacuum conditions, such as, for example, and without limiting the scope of the present invention, stainless steel sealed by means of copper seals or other similar vacuum closing systems. Within this chamber are the quartz oscillator (s) connected to the outside by means of a gland to allow the passage of cooling water and electrical contacts for the measurement of the oscillation frequency.
3. Un sistema de calefacción para calentar las paredes de Ia cámara de forma que mantengan una temperatura superior a Ia de realización de Ia adsorción/desorción, que sin que limite el alcance de Ia presente invención puede ser una cinta calefactora. El calentamiento de las paredes de Ia cámara de vacío evita las oscilaciones aleatorias de Ia medida de Ia balanza de cuarzo debidas a procesos de adsorción/desorción no deseados del vapor usado para Ia medida de las isotermas de adsorción/desorción en las paredes de Ia cámara de vacío. 4. Medidores de temperatura, uno de ellos aplicado al sensor de cuarzo, Io que mejora el control de las condiciones experimentales, evitando que durante el calentamiento inicial de Ia muestra Ia temperatura del sensor de cuarzo, suba por encima de los 130 0C Io que Ie podría ocasionarle daños irreversibles. Este medidor de temperatura, se conecta con el exterior de Ia cámara de vacío a través de pasamuros que permiten llevar Ia señal eléctrica correspondiente a un controlador adecuado. Otro medidor aplicado a las paredes de Ia cámara de vacío mide Ia temperatura de estas y junto con el sistema de control de Ia temperatura descrito en el punto 7 permite mantener constante Ia temperatura de éste y por tanto también Ia de Ia muestra Los medidores de temperatura y sin que limite el alcance de Ia invención pueden ser del tipo termopar o similares.3. A heating system for heating the walls of the chamber so as to maintain a temperature higher than that of the realization of adsorption / desorption, which without limiting the scope of the present invention can be a heating belt. The heating of the walls of the vacuum chamber prevents random oscillations of the measurement of the quartz balance due to unwanted adsorption / desorption processes of the steam used for the measurement of the adsorption / desorption isotherms on the walls of the chamber of emptiness. 4. Temperature meters, one of them applied to the quartz sensor, which improves the control of the experimental conditions, preventing that during the initial heating of the sample the temperature of the quartz sensor rises above 130 0 C Io that it could cause irreversible damage. This temperature meter is connected to the outside of the vacuum chamber through passages that allow the corresponding electrical signal to be taken to a suitable controller. Another meter applied to the walls of the vacuum chamber measures the temperature of these and, together with the temperature control system described in point 7, allows the temperature of the latter to be kept constant and therefore also that of the sample The temperature meters and without limiting the scope of the invention can be of the thermocouple type or the like.
5. Uno o varios medidores de presión. Este medidor de presión en una realización particular de Ia invención, está basado en Ia medida de capacitancia y cuyo rango depende del tipo de vapor utilizado para medir las isotermas. Lo más usual es Ia medida de isotermas de vapor de agua, en las que el rango de presiones a controlar oscila entre valores muy bajos del orden de 10~2 torr hasta Ia presión del vapor de agua a temperatura ambiente, alrededor de algunas decenas de torr. Este rango podría ampliarse si se calienta el agua líquida usada para proporcionar el vapor que se hace llegar a Ia cámara donde se sitúa el oscilador de cuarzo. Los medidores de presión susceptibles de ser empleados son medidores universales. La utilización de estos medidores basados en Ia capacitancia frente a otros basados en otros principios (piranis, pennings, cátodo frío, etc.) simplifica su uso ya que sirven para todo tipo de gases y su respuesta no depende del gas/vapor cuya presión quiere medirse (L. I. Maissel, R. Glang; Handbook of thin film technology; Mcgraw-Hill book company New York 1970). En caso de usar otra opción, se tendría más limitación en el rango de presiones y sería necesario realizar calibraciones para cada tipo de gas/vapor. 6. Un sistema para calentar Ia muestra inicialmente (generalmente hasta una temperatura superior a 100 0C) para desorber el agua u otros gases (gases/vapores pre-adsorbidos) presentes en los poros debido a Ia exposición de Ia muestra a Ia atmósfera. Este sistema, sin que limite el alcance de Ia presente invención, puede consistir en una lámpara halógena conectada con el exterior por medio de un pasamuros eléctrico que permita alimentarla desde el exterior.5. One or more pressure gauges. This pressure meter in a particular embodiment of the invention, is based on the capacitance measurement and whose range depends on the type of steam used to measure the isotherms. The most common is the measurement of water vapor isotherms, in which the range of pressures to be controlled ranges from very low values of the order of 10 ~ 2 torr to the pressure of the water vapor at room temperature, around a few tens of torr. This range could be extended if the liquid water used to provide the steam that is sent to the chamber where the quartz oscillator is located is heated. Pressure gauges that can be used are universal gauges. The use of these meters based on capacitance compared to others based on other principles (pyranis, pennings, cold cathode, etc.) simplifies their use since they serve all types of gases and their response does not depend on the gas / steam whose pressure you want measured (LI Maissel, R. Glang; Handbook of thin film technology; Mcgraw-Hill book company New York 1970). If another option is used, there would be more limitation in the pressure range and it would be necessary to perform calibrations for each type of gas / steam. 6. A system to heat the initial sample (generally to a temperature above 100 0 C) to desorb water or other gases (gases / vapors pre-adsorbed) present in the pores due to the exposure of the sample to the atmosphere. This system, without limiting the scope of the present invention, can consist of a halogen lamp connected to the outside by means of an electric cable gland that allows it to be fed from the outside.
7. Un sistema de control de Ia temperatura del sensor o sensores de cuarzo para mantener constante su temperatura durante todo el experimento. En una realización particular de Ia invención, este sistema de control, puede estar compuesto por un circuito de agua, un Peltier para conseguir un control aun más fino de Ia temperatura de Ia balanza de cuarzo, un medidor de temperatura (descrito en el punto 4) y un controlador de temperatura. Las isotermas generalmente se determinan a temperatura ambiente, pero con este sistema de control de Ia temperatura incluso podrían determinarse por debajo de esta. Estos sistemas se conectan con el exterior mediante pasamuros adecuados.7. A system for controlling the temperature of the sensor or quartz sensors to keep its temperature constant throughout the experiment. In a particular embodiment of the invention, this control system may be composed of a water circuit, a Peltier to achieve even finer control of the temperature of the quartz scale, a temperature meter (described in point 4 ) and a temperature controller. The isotherms are generally determined at room temperature, but with this temperature control system they could even be determined below this. These systems are connected to the outside by means of suitable pasamuros.
8. Un sistema de vacío acoplado a Ia cámara de vacío y que, sin que limite el alcance de Ia presente invención, puede estar compuesto por una rotatoria y una bomba turbomolecular aunque existen otros posibles métodos de hacer vacío basados en bombas difusoras, bombas "roots" o iónicas (L. I. Maissel, R. Glang, "Handbook of thin film technology", Mcgraw-Hill Book Company New York 1970). El uso de Ia combinación de una rotatoria y una bomba turbomolecular tienen Ia ventaja de su rapidez, su costo razonable y, sobre todo, Ia posibilidad de bombear cantidades importantes de gases/vapores, alcanzándose vacíos límites bajos.8. A vacuum system coupled to the vacuum chamber and which, without limiting the scope of the present invention, may be composed of a rotary and a turbomolecular pump although there are other possible methods of making vacuum based on diffuser pumps, pumps " roots "or ionic (LI Maissel, R. Glang," Handbook of thin film technology ", Mcgraw-Hill Book Company New York 1970). The use of the combination of a rotary and a turbomolecular pump have the advantage of its speed, its reasonable cost and, above all, the possibility of pumping significant amounts of gases / vapors, reaching low limits.
9. Un conjunto de válvulas de apertura y cierre que definen un conjunto de pequeños volúmenes que, llenos del vapor procedente del recinto donde está el líquido cuya isoterma quiere medirse, se expansionan a Ia cámara principal donde está Ia balanza de cuarzo. De esta manera y tras procesos de apertura y cierre sucesivos se puede ir variando paulatinamente Ia presión del vapor en Ia cámara de vacío donde está el sensor de cuarzo. Las válvulas utilizadas deben ser herméticas frente al vacío y responder en posiciones de apertura y cierre a impulsos eléctricos o neumáticos exteriores. El control sobre las válvulas que regulan Ia presión de vapor en Ia cámara de vacío se puede realizar mediante un programa de control de dispositivos electrónicos que, sin que limite el alcance de Ia presente invención, puede estar realizado en entorno Labview. 10. Un sistema informático que a través de los puertos e interfaces adecuados, controla tanto los equipos de medida (medidores de presión, electrónica de Ia balanza de cuarzo) como ordena los procesos de apertura/cierre de válvulas que permiten Ia operación automática del sistema. La capa cuya porosidad se pretende determinar se coloca sobre Ia cabeza del sensor de cuarzo integrado dentro de Ia cámara de vacío. De Ia medida en el cambio de frecuencia en el oscilador a través del sensor de cuarzo acoplado se puede conocer Ia cantidad de material depositado o adsorbido/desorbido. Otro objeto de Ia presente invención Io constituye Ia utilización del dispositivo que acaba de describirse para Ia determinación de Ia porosidad de láminas delgadas, materiales nanoestructurados y membranas soportadas, así como para Ia determinación de isotermas de adsorción/desorción de dichos materiales. El dispositivo de Ia invención puede incluir adicionalmente un software, que a partir de los resultados obtenidos en las distintas isotermas de adsorción/desorción, proporciona información directa sobre Ia cantidad de material adsorbido/desorbido, el volumen total de poros, Ia proporción de los mismos que son microporos o mesoporos y, en este último caso, Ia distribución de poros según tamaños.9. A set of opening and closing valves that define a set of small volumes that, filled with steam from the enclosure where the liquid isotherm is to be measured, expand to the main chamber where the quartz scale is. This way and after successive opening and closing processes, the vapor pressure in the vacuum chamber where the quartz sensor is gradually can be varied. The valves used must be watertight against the vacuum and respond in open and close positions to external electrical or pneumatic impulses. The control over the valves that regulate the vapor pressure in the vacuum chamber can be carried out by means of a control program of electronic devices that, without limiting the scope of the present invention, can be carried out in a Labview environment. 10. A computer system that, through the appropriate ports and interfaces, controls both the measuring equipment (pressure meters, quartz balance electronics) and orders the valve opening / closing processes that allow the automatic operation of the system . The layer whose porosity is intended to be determined is placed on the head of the quartz sensor integrated within the vacuum chamber. From the measurement of the frequency change in the oscillator through the coupled quartz sensor, the amount of deposited or adsorbed / desorbed material can be known. Another object of the present invention is the use of the device just described for the determination of the porosity of thin sheets, nanostructured materials and supported membranes, as well as for the determination of adsorption / desorption isotherms of said materials. The device of the invention can additionally include software, which, based on the results obtained in the different adsorption / desorption isotherms, provides direct information on the amount of adsorbed / desorbed material, the total pore volume, the proportion thereof which are micropores or mesopores and, in the latter case, the distribution of pores according to sizes.
La determinación de Ia cantidad de material adsorbido se determina a través de Ia siguiente relación: πx (F -Fc) d V , = x ArcTan Z x Tan π x Df x Z xFr F 1The determination of the amount of adsorbed material is determined through the following relationship: πx (F -F c ) d V, = x ArcTan Z x Tan π x D f x Z xF r F 1
Donde:Where:
Df: es el espesor de Ia capa en Amstrongs.Df: is the thickness of the layer in Amstrongs.
Nq: es Ia constante de frecuencia para el cristal de cuarzo.N q : is the frequency constant for the quartz crystal.
Dq: es Ia densidad del cuarzo en gm/cm3 π: es Ia constante Pi, 3.141592653D q : is the density of quartz in gm / cm 3 π: is the constant Pi, 3.141592653
Df: es Ia densidad del material en gm/cm3 Df: is the density of the material in gm / cm 3
Z: es un factor característico del material relacionado con su densidad y con sus propiedades mecánicas.Z: is a characteristic factor of the material related to its density and its mechanical properties.
Fq: es Ia frecuencia del sensor de cuarzo antes de depositar el material. Fc: es Ia frecuencia del sensor de cuarzo después de depositar el material.F q : is the frequency of the quartz sensor before depositing the material. F c : is the frequency of the quartz sensor after depositing the material.
El calculo de Ia porosidad y Ia distribución de tamaños se basa en Ia aplicación de distintas ecuaciones de termodinámica y fisicoquímica clásica, como Ia ecuación de Kelvin para determinar el tamaño de poro:The calculation of the porosity and the size distribution is based on the application of different thermodynamic and classical physicochemical equations, such as the Kelvin equation to determine the pore size:
P0 RT rm P 0 RT r m
Donde: p/po: presión parcial de vapor. VL: es el volumen molar del líquido del que se forma el vaporWhere: p / po: partial vapor pressure. V L : is the molar volume of the liquid from which the vapor is formed
R: es Ia constante 8.30107 ergK"1 moles"1 R: is the constant 8.30107 ergK "1 moles " 1
T: es Ia temperatura en K a Ia que se realiza Ia medida y: es Ia tensión superficial del líquido rm: es el radio medio del poro. La representación "tplot" de Ia medida de Ia isoterma, consiste en dibujar los valores de volumen adsorbido medidos con el sensor de cuarzo frente al espesor de Ia capa equivalente que se adsorbería sobre una superficie plana, compacta y homogénea. De las curvas "tplot" se puede deducir el volumen y tamaño de microporos y el volumen de mesoporos como diferencia respecto del volumen de poros totales El espesor equivalente depende del valor de Ia presión parcial de vapor según Ia siguiente ecuación:T: is the temperature in K at which the measurement is made and: it is the surface tension of the liquid r m : it is the average radius of the pore. The "tplot" representation of the measurement of the isotherm consists in drawing the adsorbed volume values measured with the quartz sensor against the thickness of the equivalent layer that would be adsorbed on a flat, compact and homogeneous surface. From the "tplot" curves, the volume and size of micropores and the volume of mesopores can be deduced as a difference from the total pore volume. The equivalent thickness depends on the value of the partial vapor pressure according to the following equation:
Figure imgf000015_0001
Figure imgf000015_0001
Donde: t: es el espesor de Ia capa equivalente.Where: t: is the thickness of the equivalent layer.
HPi, HP2 y HP3: constantes que dependen del vapor adsorbido.HPi, HP2 and HP3: constants that depend on the adsorbed vapor.
La distribución de tamaño de poro se calcula a partir de los datos experimentales, aplicando las dos ecuaciones anteriores y el método de Pierce (SJ. Gregg, K. S. W. Sing, "Adsorption, Surface Área and Porosity", Academia Press London, 1982).The pore size distribution is calculated from the experimental data, applying the two previous equations and the Pierce method (SJ. Gregg, K. S. W. Sing, "Adsorption, Surface Area and Porosity", Academy Press London, 1982).
Este dispositivo puede contener uno o vario sensores de cuarzo Io que permite determinar las isotermas de adsorción/desorción y por Io tanto Ia porosidad de varias muestras simultáneamente.This device may contain one or several quartz sensors Io that allows to determine the adsorption / desorption isotherms and therefore the porosity of several samples simultaneously.
Además, el dispositivo de Ia invención permite no solo realizar medidas de varias muestras simultáneamente sino que además se pueden realizar adsorciones/desorciones secuencialmente, empleando diferentes líquidos e incluso empleando líquidos de diferente polaridad. Por ejemplo, se podrían hacer isotermas sucesivas de agua y de tolueno. Dado el distinto tamaño de estas dos moléculas y de su diferente carácter polar, Ia fenomenología de Ia adsorción de cada una de ellas sería diferente proporcionando información complementaria sobre Ia estructura de poros del material.In addition, the device of the invention allows not only measurements of several samples simultaneously but also adsorption / desorption can be performed sequentially, using different liquids and even using liquids of different polarity. For example, successive water and toluene isotherms could be made. Given the different size of these two molecules and their different polar character, the phenomenology of Ia adsorption of each of them would be different by providing complementary information on the pore structure of the material.
El uso de este dispositivo no solo se limita a Ia determinación de las isotermas de adsorción/desorción, y por tanto a Ia medida de Ia porosidad de dichas láminas delgadas, materiales nanoestructurados y membranas soportadas, sino que además el dispositivo de Ia invención es compatible conThe use of this device is not only limited to the determination of adsorption / desorption isotherms, and therefore to the measure of the porosity of said thin sheets, nanostructured materials and supported membranes, but also the device of the invention is compatible with
Ia realización simultánea de medidas de diversas propiedades ópticas de las muestras e incluso con Ia realización de tratamientos en estas láminas delgadas materiales nanoestructurados y membranas soportadas que modifiquen sus propiedades, como por ejemplo Ia irradiación, plasmas, etc.The simultaneous realization of measurements of various optical properties of the samples and even with the realization of treatments in these thin sheets nanostructured materials and supported membranes that modify their properties, such as irradiation, plasmas, etc.
EJEMPLO DE REALIZACIÓN DE LA INVENCIÓNEXAMPLE OF EMBODIMENT OF THE INVENTION
Ejemplo 1. Medida de Ia porosidad de una lámina delgada de 439 nmExample 1. Measurement of the porosity of a thin sheet of 439 nm
Como ejemplo de Ia invención se mide Ia porosidad de una capa de TΪO2 preparada mediante una técnica de deposición química desde fase vapor asistida por plasmas (PECVD) .As an example of the invention, the porosity of a TΪO2 layer prepared by means of a chemical deposition technique from plasma assisted vapor phase (PECVD) is measured.
Para ello en primer lugar se determinan las isotermas de adsorción de vapor de agua a 18 0C con presiones de saturación en torno a 15 torr.For this first adsorption isotherms of water vapor at 18 0 C are determined saturation pressures around 15 torr.
La lámina de 439 nm de espesor, se coloca sobre una balanza de cuarzo (13 mm de diámetro) acoplada al sistema oscilador (Instruments Sycon) con electrónica de medida Nor-Cal Products. El sensor de cuarzo se encuentra en una cámara de vacío de acero inoxidable de 3 L de volumen, sellada mediante cierres CF con juntas de cobre y racorería Swagelok de 1/4" y 1/8".The 439 nm thick sheet is placed on a quartz scale (13 mm in diameter) coupled to the oscillator system (Instruments Sycon) with Nor-Cal Products measuring electronics. The quartz sensor is located in a 3 L volume stainless steel vacuum chamber, sealed by CF seals with 1/4 "and 1/8" Swagelok copper joints.
Se cierra el recinto y se realiza vacío. El sistema de vacío está formado por una rotatoria Edwards de capacidad 6 m3/h y una bomba turbomolecular deThe enclosure is closed and empty. The vacuum system consists of an Edwards rotary with a capacity of 6 m 3 / h and a turbomolecular pump of
Alcatel de capacidad 100 L/s. La presión en el interior de Ia cámara se mide con un medidor de presión Capacitancia Balzers, 0.2 a 10 torr, Pfeiffer (todo rango, capaz de medir entre 10~7 hasta 103 torr).Alcatel capacity 100 L / s. The pressure inside the chamber is measured with a pressure gauge Capacitance Balzers, 0.2 to 10 torr, Pfeiffer (all range, capable of measuring between 10 ~ 7 to 103 torr).
Se calienta Ia muestra por irradiación con una lámpara halógena de 12 V y 100 W hasta una temperatura superior a 100 0C, para eliminar los gases pre- adsorbidos en las capas. Simultáneamente se calientan las paredes de Ia cámara de vacío con un sistema de control formado por Peltier de 120 W (Amidata), fuente de alimentación d.c. (Tech) para el Peltier, controladores de temperatura TEMPATRON tc4800, cintas calefactores de 100 W (Caburn) y termopares tipo K (Amidata).The sample is heated by irradiation with a halogen lamp of 12 V and 100 W to a temperature above 100 0 C, to eliminate the gases pre-absorbed in the layers. Simultaneously the walls of the vacuum chamber are heated with a control system formed by 120 W Peltier (Amidata), dc (Tech) power supply for the Peltier, TEMPATRON tc4800 temperature controllers, 100 W heating bands (Caburn) and K-type thermocouples (Amidata).
Una vez realizado el calentamiento inicial de Ia muestra, y tras eliminar los gases pre-adsorbidos, se procede a Ia refrigeración mediante agua a temperatura ambiente a través del circuito de acero inoxidable acoplado mediante racorería Swagelok 1/8" manteniendo Ia temperatura en 18 0C.Once the initial heating of the sample has been carried out, and after eliminating the pre-adsorbed gases, the cooling is carried out by means of water at room temperature through the stainless steel circuit coupled by Swagelok 1/8 "racorería keeping the temperature at 18 0 C.
Se introduce entonces vapor de agua mediante un sistema hermético formado por un bulbo de pirex (Caburn) donde se coloca el líquido. Este bulbo está acoplado a un sistema de válvulas abre/cierra manual (Withey) por medio de tubos y racorería de acero inoxidable (Swagelok). Este sistema se conecta o bien con Ia cámara de donde está Ia balanza de cuarzo o directamente al sistema de vacío, todo ello a través de uniones CF (Caburn) selladas con juntas de cobre. En el primer caso, Ia conexión permite dosificar presiones crecientes de vapor de agua en Ia cámara. En el segundo, se persigue poder desgasificar el agua líquida del bulbo antes del experimento de adsorción mediante procesos de congelación/evacuación sucesivos.Water vapor is then introduced through an airtight system formed by a pyrex bulb (Caburn) where the liquid is placed. This bulb is coupled to a manual open / close valve system (Withey) by means of stainless steel pipes and fittings (Swagelok). This system is connected either to the chamber where the quartz scale is located or directly to the vacuum system, all through CF (Caburn) joints sealed with copper joints. In the first case, the connection allows dosing increasing pressures of water vapor in the chamber. In the second, it is sought to be able to degas the liquid water of the bulb before the adsorption experiment by successive freezing / evacuation processes.
Con el sistema de válvulas electrónicas abre/cierra Danfoss para tubo de 1/4" Swagelok trabajando a 220 V, 50 Hz y 9 Wat se dosifica una primera cantidad de vapor de agua se deja estabilizar el sistema, se mide Ia presión con el medidor de presión y se registra el cambio en Ia medida del sensor de cuarzo. El programa informático para el control de las válvulas está realizado en entorno Labview.With the Danfoss electronic valve system opens / closes for 1/4 "Swagelok tube working at 220 V, 50 Hz and 9 Watts, a first quantity of water vapor is dosed and the system is stabilized, the pressure is measured with the meter of pressure and the change in the measurement of the quartz sensor is recorded.The computer program for the control of the valves is carried out in Labview environment.
Se repite esta operación tantas veces como sea necesario hasta completar el ciclo de "adsorción". Una vez alcanzada Ia saturación, se puede empezar el proceso de desorción. Para ello, utilizando el sistema de válvulas del sistema, se van retirando cantidades crecientes del vapor de agua de Ia cámara donde está Ia balanza de cuarzo, concluyendo con abrir completamente esta cámara al vacío. Para cada presión de vapor de agua en Ia cámara se mide Ia respuesta de Ia balanza de cuarzo, representándose los datos en Ia misma gráfica (rama de desorción). En Ia Figura 2 representado con círculos se muestra Ia isoterma de adsorción/desorción correspondiente a Ia capa de TÍO2 de 439 nm medida con vapor de agua a 18 0C. Se observa que, en este caso, tras Ia desorción queda un cierto volumen de poros que no se desocupa (proceso de histéresis acompañado con adsorción residual) ya que no se llega hasta el punto inicial en que comienza Ia adsorción.This operation is repeated as many times as necessary until the "adsorption" cycle is completed. Once saturation is reached, the desorption process can be started. To do this, using the system of valves in the system, increasing amounts of water vapor are removed from the chamber where the quartz scale is, concluding with completely opening this chamber under vacuum. For each water vapor pressure in the chamber, the response of the quartz scale is measured, the data being plotted in the same graph (desorption branch). Figure 2 represented with circles shows the adsorption / desorption isotherm corresponding to the TIO2 layer of 439 nm measured with water vapor at 18 0 C. It is observed that, in this case, after the desorption a certain volume of pores that are not vacated (hysteresis process accompanied by residual adsorption) since it does not reach the initial point at which the adsorption begins.
Para poner de manifiesto que, efectivamente, existe esa adsorción residual, en esta misma figura (Figura 2) se representa una segunda isoterma de adsorción/desorción pero en este caso no se realiza ningún proceso de calentamiento inicial de Ia muestra para vaciar sus poros. Cuando se hace una segunda isoterma a partir de ese punto se obtienen las curvas definidas por cuadrados en Ia Figura 2. Esta segunda isoterma es Ia que se obtendría si Ia muestra no se hubiera calentado previamente con Ia lámpara halógena. Es evidente que tal proceder hubiera dado lugar a errores significativos en Ia determinación de Ia porosidad quedando de manifiesto que Ia posibilidad de eliminar por calentamiento el agua irreversiblemente adsorbida en los poros es uno de los elementos singulares del dispositivo de Ia invención que Io diferencia de otros ensayos semejantes descritos en Ia literatura científica.To show that, in fact, this residual adsorption exists, in this same figure (Figure 2) a second adsorption / desorption isotherm is represented but in this case no initial heating process of the sample is performed to empty its pores. When a second isotherm is made from that point, the curves defined by squares are obtained in Figure 2. This second isotherm is the one that would be obtained if the sample had not been previously heated with the halogen lamp. It is evident that such proceeding would have resulted in significant errors in the determination of the porosity, making it clear that the possibility of eliminating the irreversibly adsorbed water in the pores by heating is one of the unique elements of the device of the invention that differentiates it from others. Similar essays described in the scientific literature.
Ejemplo 2. Medida de Ia porosidad de una lámina delgada de 496 nmExample 2. Measurement of the porosity of a thin sheet of 496 nm
Cuando se sintetizan las capas de TΪO2 preparadas mediante Ia técnica de deposición química desde fase vapor asistida por plasmas (PECVD) mediante cambios apropiados en los protocolos de preparación se pueden obtener capas con porosidades completamente diferentes, pese a que su índice de refracción sea semejante.When the TΪO2 layers prepared by means of the chemical deposition technique from plasma-assisted vapor phase (PECVD) are synthesized by appropriate changes in the preparation protocols, layers with completely different porosities can be obtained, although their index of refraction is similar.
En este segundo ejemplo, se emplea también una lámina de TΪO2, esta de vez de espesor 496 nm. El dispositivo empleado para llevar a cabo Ia determinación de las isotermas de adsorción/desorción y las condiciones experimentales de medida son idénticas a las señaladas en el ejemplo 1. En Ia Figura 3 se presenta Ia isoterma de adsorción/desorción de Ia capa de TÍO2 de 496 nm. Como puede verse en este caso Ia isoterma de adsorción y Ia de desorción casi coinciden. Este comportamiento es típico de muestras con microporos, donde no hay contribución de poros de gran tamaño. En este caso el proceso de adsorción/desorción es completamente reversible, no observándose ni histéresis ni adsorción residual alguna. In this second example, a TΪO2 sheet is also used, this time of thickness 496 nm. The device used to carry out the determination of the adsorption / desorption isotherms and the experimental measurement conditions are identical to those indicated in example 1. Figure 3 shows the adsorption / desorption isotherm of the TYPE 2 layer of 496 nm. As can be seen in this case, the adsorption isotherm and the desorption is almost coincident. This behavior is typical of samples with micropores, where there is no contribution of large pores. In this case the adsorption / desorption process is completely reversible, with no hysteresis or residual adsorption observed.

Claims

REIVINDICACIONES
1. Dispositivo para Ia determinación de Ia porosidad de láminas delgadas caracterizado porque comprende los siguientes elementos: uno o más osciladores de cuarzo, una cámara de vacío, un sistema de calefacción de Ia cámara de vacío, varios medidores de temperatura, uno o varios medidores de presión, un sistema para calentar Ia muestra inicialmente, un sistema de control de Ia temperatura del sensor de cuarzo, un sistema de vacío, un conjunto de válvulas de apertura y cierre y un sistema informático. 1. Device for determining the porosity of thin sheets characterized in that it comprises the following elements: one or more quartz oscillators, a vacuum chamber, a vacuum chamber heating system, several temperature meters, one or several meters of pressure, a system to heat the sample initially, a control system of the temperature of the quartz sensor, a vacuum system, a set of opening and closing valves and a computer system.
2. Dispositivo según Ia reivindicación 1 caracterizado porque puede comprender más de un sensor de cuarzo Io que permite medir Ia porosidad de más de una muestra simultáneamente.2. Device according to claim 1, characterized in that it can comprise more than one quartz sensor which allows measuring the porosity of more than one sample simultaneously.
3. Dispositivo de acuerdo con las reivindicaciones 1 y 2, caracterizado porque el/los osciladores de cuarzo se encuentran en el interior de Ia cámara de vacío.3. Device according to claims 1 and 2, characterized in that the quartz oscillators are inside the vacuum chamber.
4. Dispositivo según las reivindicaciones 1-3 caracterizado porque las paredes de Ia cámara de vacío pueden calentarse a una temperatura superior a Ia que se realiza Ia adsorción para evitar procesos de adsorción/desorción del vapor en ellas, mediante un sistema de calefacción de Ia cámara de vacío, preferentemente mediante una cinta calefactora.4. Device according to claims 1-3 characterized in that the walls of the vacuum chamber can be heated to a temperature higher than that adsorption is performed to avoid processes of adsorption / desorption of steam therein, by means of a heating system of Ia vacuum chamber, preferably by means of a heating tape.
5. Dispositivo de acuerdo con las reivindicaciones 1-3 caracterizado porque puede calentarse inicialmente Ia muestra para eliminar gases/vapores pre-adsorbidos en los poros de esta, mediante un sistema de calentamiento apropiado, preferentemente mediante una lámpara halógena.5. Device according to claims 1-3 characterized in that the sample can be initially heated to remove pre-adsorbed gases / vapors in the pores thereof, by means of an appropriate heating system, preferably by means of a halogen lamp.
6. Dispositivo de acuerdo con las reivindicaciones 1-3, caracterizado porque mantiene constante Ia temperatura de Ia muestra y del sensor de cuarzo mediante un sistema de control de Ia temperatura del sensor de cuarzo que preferentemente incluye un circuito de agua, un Peltier y un medidor de temperatura. 6. Device according to claims 1-3, characterized in that it maintains constant the temperature of the sample and the quartz sensor by means of a control system of the temperature of the quartz sensor that preferably includes a water circuit, a Peltier and a temperature meter
7. Dispositivo según Ia reivindicación 1 , caracterizado porque comprende adicionalmente un software que correlaciona las medidas de las isotermas de adsorción/desorción con el tipo de porosidad de ésta, el volumen de poros y Ia distribución de tamaño de poros. 7. Device according to claim 1, characterized in that it additionally comprises software that correlates the measurements of the adsorption / desorption isotherms with the type of porosity thereof, the pore volume and the pore size distribution.
8. Uso del dispositivo según las reivindicaciones 1-7 para determinar las isotermas de adsorción/desorción de láminas delgadas, materiales nanoestructurados y membranas soportadas a temperaturas incluso por debajo de Ia temperatura ambiente.8. Use of the device according to claims 1-7 to determine the adsorption / desorption isotherms of thin sheets, nanostructured materials and membranes supported at temperatures even below room temperature.
9. Uso de un dispositivo según las reivindicaciones 1-7 para Ia determinación de Ia porosidad de laminas delgadas, materiales nanoestructurados y membranas soportadas.9. Use of a device according to claims 1-7 for the determination of the porosity of thin sheets, nanostructured materials and supported membranes.
10. Uso del dispositivo según las reivindicaciones 1-7 para determinar el tipo de porosidad, volumen de poros y Ia distribución de tamaño de poros (porcentaje de macro y microporos) de las láminas delgadas, materiales nanoestructurados y membranas soportadas.10. Use of the device according to claims 1-7 to determine the type of porosity, pore volume and the pore size distribution (percentage of macro and micropores) of the thin sheets, nanostructured materials and supported membranes.
11. Uso de un dispositivo según las reivindicaciones 1-7 para hacer medidas simultáneas a Ia determinación de Ia porosidad de diversas propiedades ópticas de las láminas delgadas, materiales nanoestructurados y membranas soportadas. 11. Use of a device according to claims 1-7 to make simultaneous measurements to the determination of the porosity of various optical properties of thin sheets, nanostructured materials and supported membranes.
12. Uso de un dispositivo según las reivindicaciones 1-7 para realizar tratamientos de las láminas delgadas, materiales nanoestructurados y membranas soportadas, que modifiquen sus propiedades, preferentemente mediante irradiación o tratamiento con plasmas.12. Use of a device according to claims 1-7 to perform treatments of thin sheets, nanostructured materials and supported membranes, which modify their properties, preferably by irradiation or plasma treatment.
13. Uso de un dispositivo según las reivindicaciones 1-7 para Ia determinación de las isotermas de adsorción/desorción y Ia porosidad de láminas delgadas, materiales nanoestructurados y membranas soportadas, empleando varios líquidos secuencialmente.13. Use of a device according to claims 1-7 for the determination of adsorption / desorption isotherms and the porosity of thin sheets, nanostructured materials and supported membranes, using several liquids sequentially.
14. Uso de un dispositivo según Ia reivindicación 13 caracterizado porque dichos líquidos pueden poseer diferente polaridad. 14. Use of a device according to claim 13 characterized in that said liquids can have different polarity.
PCT/ES2008/070099 2007-05-28 2008-05-26 Device for determining the porosity of thin films and use thereof WO2008145797A1 (en)

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