Method of gas-permeable membrane production and gas-permeable membrane

FIELD: technological processes.

SUBSTANCE: invention concerns selective membrane production for molecular gas mix filtering and can be applied in compact fuel cells. Method of gas-permeable membrane production includes vacuum sputtering of a metal displaying chemical stability in concentrated hydrogen fluoride solutions in anode polarisation conditions onto monocrystalline silicon plate in closed pattern, and further double-side electrochemical etching of the plate area limited by the mentioned closed pattern. Etching process is performed until its spontaneous cease determined by break of time function curve of anode current on the plate surface not covered by sputtered metal.

EFFECT: increased thickness homogeneity of solid monocrystalline filtering silicon layer, improved membrane durability at higher gas permeability.

31 cl, 9 dwg, 2 ex

 

The invention relates to the manufacture of selective membranes for molecular filtration of gas mixtures with the release of the hydrogen gas and helium and, in particular, may find use in a compact fuel cell, namely to clean and uniform supply of hydrogen to the catalyst on the anode side of portable fuel cells use hydrogen.

There are two fundamentally different types of gas-permeable membranes, namely: a microporous membrane with dimensions of through pores larger than the diffusing related molecules, and solid, amorphous or polycrystalline membrane, atomic structure characterized by the presence of voids with dimensions sufficient for the introduction of solid phase or only atomic hydrogen (close-Packed crystalline structure of metals), or molecular hydrogen and light monatomic gases such as helium and neon (zeolites, quartz glass). The parameters of the selectivity of the transmission of light gases by membranes of the first type are small in numerical terms range from one to hundreds. In the second case, a partial selective transmittance with respect to the gas molecules, which can dissolve in the solid phase, is determined only by the presence of extended defects in the structure of the filtering layer of the membrane, form the through their channels, - cracks, capillary holes, dislocations, block and intergranular boundaries. Therefore, the best material for the manufacture of filter layers of gas-permeable membranes could be defect-free monocrystalline film that is not used for this purpose up to the present time. An important advantage of single-crystal films must be practical independence selectivity bandwidth gases from the thickness of the films. Thus, when using single-crystal materials, you can increase the absolute permeability of the membranes without loss of quality separation of gas mixtures only by reducing the thickness of the solid filter layer. This, in turn, allows you to extend the range of materials suitable for practical use in the construction of vasoselective membranes.

A known method of manufacturing a filter element (see US patent No. 6328876, IPC C25F 3/12 published 11.12.2001,), including the formation of through holes with a diameter of 1-2 nm to 50 nm in the semiconductor plates with simultaneous electrochemical etching in solutions of hydrofluoric acid and light plates light.

The filter element is obtained in a known manner, is a plate of porous silicon, which is a through hole that does not allow them to use the VAT as filters for the selective extraction of light gases (hydrogen and helium) from gas mixtures.

A known method of manufacturing ultra-thin semiconductor membranes (see US patent No. 4952446, IPC H01L 21/306, published 28.08.1990, including the creation of the ion implantation of low energy thin partially disturbed areas on one side of the semiconductor wafer, followed by etching the wafer from the reverse side to the implanted layer.

The known method provides for receiving layers of continuous monocrystalline silicon of a thickness of from 150 nm to 1 μm with heterogeneity in thickness within 10% when the diameter of the layer is from 15 to 100 microns.

In the specified range of thickness of the solid silicon layers cannot be used as a gas-permeable membranes regardless of the size of the gas molecules. It should also be noted that the mechanical strength of the membranes of this type will be small, even in comparison with the strength of the porous layers of silicon of a thickness exceeding 100 μm.

A known method of obtaining a gas-permeable membrane (see claim US No. 20040033180, IPC B01J 8/00, published 19.02.2004, by forming on the surface of the porous substrate film, the resulting gas-phase reaction in a sealed vessel by heating the silicon source and an aqueous solution of alkali or alkaline solution of a source of aluminum without mixing.

There is a method allows to obtain a gas-permeable membrane with a homogeneous size is m long. A disadvantage of the known method of obtaining a gas-permeable membrane is the necessity of using ready-made porous substrate and sophisticated equipment, including temperature-controlled reactor high pressure block evaporation organosilicon compounds and a mechanical input device and rotation of the substrate.

Known gas-permeable membrane obtained as described above is composed of a porous substrate on which is deposited a film based on a zeolite having pores of from 0.02 to 2.00 μm when the porosity of the substrate 10 to 60%.

Known gas-permeable membrane is not continuous and does not provide a high selectivity for the separation of gases.

A method of obtaining a composite gas separation module (see claim US No. 20040237779, IPC B01D 53/22, published 02.12.2004 g)includes applying by chemical vapor deposition on a porous substrate of the intermediate porous layer and the subsequent deposition on it of a continuous layer of palladium, acting vasoselective membrane.

The disadvantages of this method are its multi-stage, complexity and long duration of operations in time

Known composite gas separation module, obtained as described above, includes a porous substrate made of stainless steel or alloys containing x is ω Nickel, the intermediate porous metal layer of palladium or palladium and metal 1B group and a continuous layer of palladium (˜20 μm), perform the function vasoselective membrane.

A disadvantage of the known composite gas separation module is its rapid degradation when used in conditions of significant temperature fluctuations. Moreover, the discontinuity of the filtering layer of palladium comes from even a single cooling in a hydrogen-containing atmosphere to a temperature T<150-180°C.

A method of obtaining a composite gas separation module (see claim US No. 20040237780, IPC B01D 53/22, published 02.12.2004 g), including the application by sequential chemical vapor deposition on a porous substrate intermediate porous combined metal layer in the form of three layers of palladium, separated by two layers of metal element 1B group (copper or silver), application in several stages in the intermediate layer is thicker (˜10 μm) layer of palladium, mechanical grinding formed surface and the subsequent application of a continuous layer of palladium.

The disadvantages of this method are its multi-stage, complexity and long duration of operations in time.

A known design of a composite gas separation module, poluchennogo is described above. The module consists of a porous metal substrate, covering the intermediate porous metal layer and a solid metal membrane selectively permeable to hydrogen, lying on the intermediate porous layer. The intermediate porous layer is made up of three layers of palladium, separated by two layers of metal element 1B group (copper or silver), on top of which bears more than a thick (˜10 μm) layer of palladium on the polished surface of which is coated with a continuous layer of palladium or its alloy (˜20 μm), perform the function vasoselective membrane. The obtained composite module operated at temperatures to 350÷500°and has a high selectivity bandwidth of hydrogen.

A disadvantage of the known composite gas separation module is its rapid degradation when used in conditions of significant temperature fluctuations. Moreover, the discontinuity of the filtering layers of palladium and its alloys come from even a single cooling in a hydrogen-containing atmosphere to a temperature T<150-180°C. it is Known that the dissolution of hydrogen in metals is accompanied by the dissociation of molecules and the formation of solid solutions, in which atomic hydrogen is chemically associated with the atoms of the crystal lattice of the metal. With a sharp decrease in temperature of the feast upon the aqueous solid solution of hydrogen in palladium begins the evolution of precipitates hybrid phase, what causes internal stresses, leading to the formation of cracks in the filtration membrane layer. In addition, to the destruction of the palladium layer of the composite membrane can lead to deformation caused by differences in coefficients of thermal expansion of the layer and the material of the porous substrate.

A method of obtaining vodorodopronitsaemosti oxide membrane (see US patent No. 5453298, IPC B01D 71/02, published 26.09.1995,), including the formation within the porous glass or ceramic substrate, a continuous layer of oxide formed by filing reagents from opposite sides of the substrate. As reagents can be halides of silicon, boron, aluminum and titanium; CHLOROSILANES or chloralosane. The precipitation product is in the process of hydrolysis reagent water vapor at temperatures of from 100 to 800°depending on the composition of the resulting oxide. The resulting structures are subjected to long-term (from 5 to 15 days) high-temperature annealing in an atmosphere of wet nitrogen, providing a sintering the deposited oxide material of the porous substrate and the formation of a continuous filter layer.

The disadvantages of this method include the complexity of hardware design and duration of operations required to achieve the desired result. Also available is the industry receive solid films inside the microporous substrate is limited to the original pore sizes.

Vodorodopronitsaemosti oxide membrane obtained as described above, consists of microporous (pore size from 2.5 to 12 nm) glass or ceramic (aluminum oxide) substrate, made in the form of a tube. Inside the porous substrate is formed by a continuous layer of oxide in the form of a continuous filter layer. Selectivity bandwidth hydrogen such membrane in relation to nitrogen varies from hundred to several thousand at operating temperatures from 800 to 450°C.

In known vodorodopronitsaemosti oxide membrane, the possibility of obtaining a solid films inside the microporous substrate is limited to the original pore sizes. Therefore, high selectivity bandwidth hydrogen such membranes can only be achieved if the small size of pores in the substrate and, accordingly, with its high initial resistance to the gas stream, which may exceed the resistance of the solid filter layer.

The known method of forming membranes in single-crystal silicon substrate (see patent RU No. 2099813, IPC H02L 21/308 published 20.12.1997, including the protective coating on the silicon surface, the opening in the protective coating Windows, the formation through the Windows on the outside side of the porous silicon substrate to a predetermined depth by anodic treatment in a solution of hydrofluoric acid and Alenia porous silicon etching in alkaline solution. Before removing the porous silicon non-working side of the substrate protects chemically resistant coating, and on the working side of the substrate in the layer of monocrystalline silicon create holes to porous silicon, through which remove the porous silicon to a predetermined depth by etching in alkaline solution, optionally containing ethylene glycol. In the known method, the etching is carried out with one hand before approaching the front to the working surface of the plate at a specified distance, and then through a specially created on the working side of the membrane window selective chemical etching to remove part of the porous layer, leaving a loose membrane. The remaining part of the porous layer serves as a reinforcing element in the design. In the described method it is assumed that the mask is a layer of organic photoresist or chemically resistant lacquer, and electrochemical etching is carried out in an aqueous solution of hydrofluoric acid, not causing swelling and peeling of the organic mask layer.

The obtained porous layers are characterized by considerable heterogeneity density by volume, and the front of their progress is not smooth. The last fact is significant heterogeneity in the thickness of the membranes, which layer thicknesses ˜10 µm can reach 30%.

zwesten method of etching silicon wafers (see the US patent No. 6284670, IPC H01L 21/306, published, 04.09.2001) for the manufacture of diaphragms used in pressure sensors, including anisotropic etching part of the silicon wafer through a mask, followed by anodic oxidation and isotropic etching.

The known method provides for receiving layers of continuous monocrystalline silicon is a relatively large thickness is 10 μm or more.

Manufactured in a known manner the layer due to the large thickness has no gas permeability.

A known method of manufacturing a filter permeable membranes made of polycrystalline silicon (see US patent No. 5919364, IPC B01D 63/00, published 06.07.1999, including the fabrication on a substrate covered with a film of SiO2, frame made of silicon nitride with a thickness of about 1 μm with multiple through holes, which are grown permeable membrane made of polycrystalline silicon of a thickness of less than 300 nm; Department of the frame with the filter layer from the substrate is provided by etching the oxide layer by HF molecules penetrating through the film of polycrystalline silicon.

Obtained in a known manner, the filter includes a reinforcing frame, which is formed of a filtering membrane layer.

In the known method as the material of the filter layer is selected polycrystalline silicon, which has a through hole RA is the mayor of the order of 10 nm, due to the distance between the grains, which does not allow to use this filter for the selective extraction of light gases (hydrogen and helium) from gas mixtures.

A known method of obtaining a gas-permeable membrane (see PCT application no WO 9905344, IPC B01J 8/00, published 04.02.1999 year), including unilateral electrochemical etching one side is fixed in the holder monocrystalline wafer of semiconductor AndIVwith the doping level of 1017-10191/cm3while lighting the light the other side of the plate for forming a layer of porous material.

Made known method gas-permeable porous membrane has a size of through pores, greatly exceeding the size of the diffusing related molecules, resulting in the selective transmission of light gases such membrane is extremely low, including at room temperature.

Known gas-permeable membrane obtained as described above (see US patent No. 6328876, IPC C25F 3.12 published 11.12.2001,), comprising a layer of porous silicon formed from the original monocrystalline wafer of semiconductor AndIVwith the doping level of 1017-10191/cm3by one-sided electrochemical etching, while the porous layer is enclosed in a frame of the above-mentioned monolithic mo is kristallicheskogo semiconductor And IVmade in the form of a closed loop.

Known gas-permeable membrane is strong enough, but has a very low selectivity transmittance of light gases, including at room temperature.

The closest to the essential features of the claimed method is a method of manufacturing a gas-permeable membrane adopted for the prototype (see Aveil, MOV, Sgornick, Neverhow, Aigebra, Dashkeev, Gradescience, Vpoly. - "10 nm semiconductor membrane for the purification of gases of light metals". - Sat. proc. ninth int. seminar "Russian technologies for industry" Alternative energy sources and energy saving problems, S.-Petersburg, 30.05-1.06 2005, p.11-12). Prototype method includes bilateral electrochemical etching of single-crystal plate of the connection AndIIIBVn-type conductivity or of semiconductor AndIVwith bandgap E≥1,0 eV and the doping level of 1017-10201/cm3while installing the modes mentioned etching for the formation of homogeneous porous layers, and the etching process leading up to the moment of its spontaneous termination and formation of a solid separation layer of fixed thickness, which is determined by the kink in the curve of the time dependence of the anode current at a given part of the square plate.

The closest to the essential features of the claimed gas-permeable membrane is gas-permeable membrane obtained above. The membrane includes nanoscale semiconductor layer located between the layers of porous material, which are formed by the known method of the prototype from the original single-crystal plate of the connection AndIIIBVn-type conductivity or of semiconductor AndIVwith bandgap E≥1,0 eV and the doping level of 1017-10201/cm3.

Porous layers such membranes are formed by the system through pores with a size of 10-20 nm and have a porosity of 60-70%. The resistance of these layers, the gas flow is much less than the resistance of porous Vycor glass and multilayer ceramics of Al2O3used as substrates in selective membranes filter layers of thin solid films of SiO2. The permeability obtained by the method of the prototype silicon membranes with 20 nm continuous layer more than an order of magnitude greater than the permeability of the hydrogen-best of membranes with 10 nm filter layer of SiO2while the indicator of the selectivity of gas separation, determined by CO2for silicon membranes at least three times higher.

One of the disadvantages of membranes of this type is insufficient IU anochezca strength, determined by the strength of a porous material with a total thickness comprising 100-200 μm. The disadvantages should also be considered violations of the homogeneity of the thickness of the filtering layer in the manufacture of plane-parallel plates membranes with a diameter of about 0.7 cm and more. This is due to the manifestation of edge effects during electrochemical etching, causing an increased etching rate at the periphery of the field of interaction with the electrolyte and as a consequence of the concavity of the fronts of steam formation and incomplete connection at the completion of the process. The result is a drop in the effective permeability of gases per unit area of the membrane.

The objective of the proposed technical solution was to develop such a method which would ensure the creation of a gas-permeable membrane with increased structural strength. The problem is solved by a group of inventions constituting a single General inventive concept.

In terms of how the task is solved in that a method of manufacturing a gas-permeable membrane includes applying a vacuum coating at least one surface of a monocrystalline silicon wafer at least one closed loop of at least one metal, is chemically stable in concentrated solutions of fluoride-hydrogen acid in the conditions of the anode is polarized, and subsequent bilateral electrochemical etching area of the plate bounded by the loop, with the set the etching for the formation of homogeneous porous layers, and the etching process leading up to the moment of spontaneous termination of a square plate that is not covered deposited metal.

The deposition of metal by vacuum deposition can be paired with each other closed contours that form the grid.

In the closed circuit can cause the metal of the platinum sub-groups, such as platinum, palladium or gold sublayer solicitousness metal.

As solicitousness metal can be applied chromium, titanium, tungsten, molybdenum, niobium, vanadium, tantalum.

In the part of the device, the task is solved in that the gas-permeable membrane includes at least one cell containing a nanoscale layer of continuous monocrystalline silicon, located between the layers of homogeneous porous monocrystalline silicon, enclosed in a frame made of monolithic single-crystal silicon, made in the form of a closed loop.

The cell membrane can be formed by bilateral electrochemical etching of isolated plot of the original single crystal silicon plate modes, providing the formation of agnor the bottom of the porous layer, until his spontaneous termination within the isolated section of a silicon wafer.

The membrane can be formed from multiple cells by the above-mentioned bilateral electrochemical etching isolated from other areas of the original monocrystalline silicon wafers

If the membrane contains multiple cells, they can be placed in it regularly.

One or two sides of the frame can be covered with a layer of metal, which may be in the form of a grid.

Applied to the frame of the cell layer can be made of metal of the platinum sub-groups, such as platinum Pt, palladium Pd.

Applied to the frame of the cell layer can be made of gold Au sublayer solicitousness metal.

As solicitousness metal can be deposited chrome Cr, titanium Ti, tungsten W, molybdenum Mo, niobium Nb, vanadium V, tantalum TA, Nickel Ni.

Nanoscale layer of continuous monocrystalline silicon may have a thickness equal to 10-20 nm.

Layers of uniformly porous silicon in the cell may have a porosity of 60-70% and a pore size of 10-20 nm.

In the present invention for hardening of the membrane asked to leave the walls of monolithic silicon in the porous layer. To do this, before manufacture of the porous membrane on a silicon substrate (with one or two sides) n what are the metal loop, the role of the mask, which does not etch silicon.

A metal mask on a silicon (Si) substrate must withstand for a long time extreme conditions of electrochemical etching in fluoride electrolyte. For this purpose suitable noble metals: Pt, Pd, Au. Best Pt or Pd, however, due to the high cost of these materials, it is preferable to use a cheaper gold. For good adhesion (adhesion) Au with Si must be applied to the metal sublayer, which provides high adhesion to Si, due to its ability to restore the Si film, the natural oxide SiO2(which reduces the requirements to the quality of the processing surface of the wafer before deposition) and chemically interact with the silicon, forming a continuous layer of silicides. As a sublayer can be applied W, Mo and Cr, Ti, Nb, TA, V, Ni.

The inventive method allows for the mechanical reinforcement of the gas-permeable membrane, to improve the uniformity in thickness of the filtering layer of continuous monocrystalline silicon by leveling edge effects when reducing the size of "Windows" and reduce series resistance in the region of convergence of the fronts of steam formation; get distributed electrical contact to regions of silicon involved in the electrochemical reactions is x steam formation.

In the result, it is possible, in particular, to establish on the basis of the inventive gas-permeable membrane, the anode of the hydrogen fuel cell.

The claimed technical solution is illustrated by drawings, where:

figure 1 shows a schematic diagram of the installation for etching a silicon wafer according to the present method;

figure 2 schematically shows a perspective view of the gas-permeable membrane-prototype;

figure 3 schematically depicts a perspective view of the inventive gas-permeable membrane with a single cell;

figure 4 shows the inventive gas-permeable membrane with a single cell in cross section;

figure 5 shows a top view of the gas-permeable membrane with multiple square cells;

figure 6 shows the section a-a gas-permeable membrane is depicted in figure 5 one-way loop of metal;

figure 7 shows the cross section a-a gas-permeable membrane is depicted in figure 5 two-way circuit metal;

on Fig shows a top view of the gas-permeable membrane with a few round cells;

figure 9 shows a top view of the gas-permeable membrane with multiple tetrahedral and octahedral cells.

Installation for etching a silicon wafer 1 by the present method (see figure 1) consists of a PTFE vessel 2 with the electrolyte solution 3, in which RA is mesena original monocrystalline silicon wafer 1, on two sides of which the contour of the applied metal layer 4. From two opposite sides of the plate 1 is set to a platinum cathode 5. The plate 1 is connected with the positive pole of the power source (not shown).

Manufactured by the method of the prototype gas-permeable membrane (see figure 2) consists of two porous layers 6, between which is enclosed nanoscale semiconductor layer 7.

The inventive gas-permeable membrane with a single cell (see figure 3, figure 4) consists of two porous layers 6, nano-filtration layer 7 of continuous monocrystalline silicon, prisoners in the frame 8 of the monolithic single-crystal silicon, made in the form of a closed loop, covered on one surface 9 (see figure 5, 6) or two surfaces 9, 10 (see Fig.7) layer 4 at least one of metal, is chemically stable in concentrated solutions of fluoride-hydrogen acid under conditions of anodic polarization. The membrane may include a few square cells (see figure 5). The cells may be round (see Fig), tetrahedral and octahedral (see Fig.9) and any other forms. Multiple cells it is advisable to formulate in the case of a square membrane, because when the electrochemical etching is increased, the etching rate at the periphery of the field of interaction with the electrolyte and the AK consequence the concavity of the fronts of steam formation, incomplete connection when the process is complete.

The inventive method of manufacturing gas-permeable membrane is as follows. On one or two surfaces of the monocrystalline silicon wafer 1 by thermal spraying in vacuum through a mask put a layer 4 of metal (platinum or palladium), given a closed circuit. When using gold previously, given a closed circuit is applied sublayer solicitousness metal, which can cause chromium, titanium, tungsten, molybdenum, niobium, vanadium, tantalum (see state Diagrams dual-metal systems. Handbook, volume 3, book 1, edited by Nepljueva. - M.: Mashinostroenie, 2001; p-T-x phase Diagram of the double metal systems: Issues, ed. in 2 books. Book 1/ Levinsky Y. - M.: metallurgy, 1990. 400 C.). Application of metal can be paired with each other closed contours that form the grid. The grid may be square, round, hexagonal or any other shape of the cell. Carry out the known process of bilateral electrochemical etching plate 1 until spontaneous termination of the electrochemical process. Etching occurred on portions of the original plate 1 that is not covered by the metal layer 4. The pores on the outside part of the plate 1 ve grow cicalino from the surface, also the distribution of pores along the surface of the under layer 4 at a distance of approximately 0.6-0.7 depending on the depth of the porous layer 6. The onset of spontaneous termination of electrochemical process with the formation of a continuous separating layer 7 fixed thickness is determined by the kink in the curve of the time dependence of the anode current. Hence, when the total thickness of the plate Si 200 microns minimum width of the metal layer 4 deposited on the contour (the width of the metal mesh)shall be not less than 200 μm. The maximum linear dimension of a single cell fabricated on the silicon wafer thickness of about 200 microns with a concentration of charge carriers R˜10191/cm3should not exceed 2 mm Fraction of the area of the layer 7 in relation to the area of the cells formed by the layer 4 applied on the contour of the metal on the original surface of the plate 1, is estimated as the ratio of the magnitude of the current downturn to its value at the break point of the current curve.

Example 1. Manufacturer of gas-permeable membrane containing regularly spaced isolated cells from porous silicon with integrated solid nano-filtration layers.

The source material was square (20×20 mm2) silicon single-crystal plate of p-type conductivity with the concentration of the second carrier 5· 1019cm-3. The plate thickness was 210 μm. The silicon wafer was pre-oxidized, removing the oxide in HF, put the metal sublayer (Cr) with a thickness of 20 nm by thermal spraying in vacuum through a mask, annealed plate in vacuum at a temperature of 350°, struck gold by thermal spraying in vacuum through the same mask and annealed plate in vacuum. As a result, the silicon wafer was formed acid-resistant metal mesh with regularly spaced 144 Windows size 1×1 mm2. Anodic treatment, the plates were held at room temperature in a mixture of ethanol with hydrofluoric acid[HF]=40%) in a volume ratio of 1:1. The process of steam formation is conducted in potentiostatic mode with an initial value of the current density of 70 mA/cm2(7 a/m2) until formation of a continuous separating layer of fixed thickness, which was recorded as a break on the curve time dependence of the anode current.

After fabrication of the structure obtained was tested for mechanical strength using a classic cross three-point bending. Experiments have shown that the critical voltage of the destruction of the plates with cellular membranes manufactured by the present method, was $ 61.3±5 MPa, which is more than 12 times higher than the critical stress fracture panotopoulos silicon wafer of the same size and thickness.

The obtained porous membrane (when the total area of the plate equal to 4 cm2) is characterized by the following parameters: permeability to hydrogen at 20° - 4,6·10-11·mol-1PA-1and at 100° - 2,1·10-10·mol-1PA-1; permeability for helium at 20° - 1,6·10-11·mol-1PA-1and at 100° - 2,2·10-10·mol-1PA-1.

Example 2. Was made membrane of silicon, consisting of two porous layers separated by a continuous single-crystal layer with a minimum thickness of 10÷15 nm.

In the same way as in example 1, the starting material was square (20×20 mm2) silicon single-crystal plate of p-type conductivity with a carrier concentration of 5·1019cm-3, which was formed by the cell size 17×17 mm2. The silicon wafer was pre-oxidized, removing the oxide in HF, inflicted platinum thermal spraying in vacuum through a mask and annealed plate in vacuum. Anodic treatment of the plates was carried out as in example 1. The onset of spontaneous termination of the electrochemical process and the formation of a solid separation stationary layer thickness was determined by the kink in the curve of the time dependence of the anode current. The fraction of the area of this word is in relation to the area of Windows was estimated as the ratio of the magnitude of the current downturn to its value at the break point of the current curve.

Critical stress fracture of a plate with a membrane obtained by the above method, amounted to 44.1 MPa.

The resulting membrane with the same total area of the plate equal to 4 cm2, characterized by the following parameters: permeability to hydrogen at 20° - 9,9·10-12·mol-1PA-1and at 100° - 4,5·10-11·mol-1PA-1; permeability for helium at 20°to 3.5·10-12·mol c-1PA-1and at 100° - 4,8·10-11·mol-1PA-1.

Indicators selectivity bandwidth of hydrogen relative to the argon and oxygen in the temperature range from 20°to 150°respectively (9÷7)·103and (4÷3)·104and does not substantially change depending on the selected configuration of the membrane skeleton.

As can be seen from the above data, the gas-permeable membrane made by the claimed method has greater resistance to mechanical damage during Assembly and operation of the filters, especially when used in fuel cells (and therefore longer service life of the fuel element).

1. A method of manufacturing a gas-permeable membrane, including the application of vacuum coating at least one surface of a monocrystalline silicon wafer for men is our least one closed loop of at least one metal, chemically stable in concentrated solutions of hydrofluoric acid in the conditions of anodic polarization, and the subsequent bilateral electrochemical etching mentioned limited contour plot mentioned plate, this set the modes mentioned etching for the formation of homogeneous porous layers, and the etching process leading up to the moment of its spontaneous termination, determined by the kink in the curve of the time dependence of the anode current on the square plate is not closed mentioned sprayed metal.

2. The method according to claim 1, characterized in that the said application of at least one metal carry out paired with each other closed contours that form the grid.

3. The method according to claim 1, characterized in that at least one closed circuit is applied to the metal of the platinum group.

4. The method according to claim 3, characterized in that at least one closed circuit is applied platinum.

5. The method according to claim 3, characterized in that at least one closed circuit is applied palladium.

6. The method according to claim 1, characterized in that at least one closed circuit is applied gold sublayer solicitousness metal.

7. The method according to claim 6, characterized in that as solicitousness metal put chrome.

8. The method according to the .6, characterized in that as solicitousness metal is applied titanium.

9. The method according to claim 6, characterized in that as solicitousness metal is applied tungsten.

10. The method according to claim 6, characterized in that as solicitousness metal is applied molybdenum.

11. The method according to claim 6, characterized in that as solicitousness metal put niobium.

12. The method according to claim 6, characterized in that as solicitousness metal put vanadium.

13. The method according to claim 6, characterized in that as solicitousness metal put tantalum.

14. The method according to claim 6, characterized in that as solicitousness metal put a Nickel.

15. Gas-permeable membrane comprising at least one cell in the form of nano-sized layer of continuous monocrystalline silicon, which is located between the layers of uniformly porous monocrystalline silicon embedded in the skeleton of the monolithic single-crystal silicon, made in the form of a closed loop, is covered at least on one surface with a layer of at least one metal, is chemically stable in concentrated solutions of fluoride-hydrogen acid under conditions of anodic polarization.

16. The membrane 15, characterized in that the said cells are located in it regularly.

17. The membrane 15,characterized in that the metal layer is made in the form of a grid.

18. The membrane 15, characterized in that the said layer is made of a metal of the platinum group.

19. The membrane p, characterized in that the metal of the platinum sub-groups used in platinum.

20. The membrane p, characterized in that the quality of the metal of the platinum sub-groups used palladium.

21. The membrane 15, characterized in that the said layer is made of gold sublayer solicitousness metal.

22. The membrane according to item 21, wherein as solicitousness metal deposited chromium.

23. The membrane according to item 21, wherein as solicitousness metal deposited titanium.

24. The membrane according to item 21, wherein as solicitousness metal deposited tungsten.

25. The membrane according to item 21, wherein as solicitousness metal deposited molybdenum.

26. The module according to item 21, wherein as solicitousness metal deposited niobium.

27. The membrane according to item 21, wherein as solicitousness metal deposited vanadium.

28. The membrane according to item 21, wherein as solicitousness metal deposited tantalum.

29. The membrane according to item 21, wherein as solicitousness metal deposited Nickel.

30. The membrane 15, distinguish what the lasting themes these nanoscale layer of continuous monocrystalline silicon has a thickness equal to 10-20 nm.

31. The membrane 15, characterized in that the said layers of uniformly porous silicon in the above-mentioned cell have a porosity of 60-70% and a pore size of 10-20 nm.



 

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FIELD: technology for producing semi-penetrable membranes for molecular filtration of gas flows and for division of reaction spaces in chemical reactors.

SUBSTANCE: method for producing gas-penetrable membrane includes two-sided electro-chemical etching of monocrystalline plate made of composition AIIIBV of n conductivity type or of semiconductor AIV with width of forbidden zone E≥1,0 electron volts and alloying level 1017-1020 1/cm3. Modes of aforementioned etching are set, providing for generation of simultaneously porous layers, while etching process is performed until moment of spontaneous stopping of electro-chemical process and generation of solid separating layer of stationary thickness on given part of plate area, determined using sharp bend on the curve of temporal dependence of anode current.

EFFECT: gas membrane, produced in accordance to method, has increased penetrability for molecules of light gases and increased selectivity characteristics at room temperature.

2 cl, 3 dwg, 3 ex

The invention relates to a process for electrochemical treatment of semiconductor wafers and can be used to create silicon substrates with surfaces that are applicable as emitters ions in analytical instruments, in particular the mass-spectrometers

The invention relates to electronic equipment, namely the processes of electrochemical processing of semiconductor wafers, in particular to the operations of electropolishing and thinning of the plates, the formation of anodic oxide films or layers of porous silicon (forming a porous silicon includes several simultaneously occurring processes: electrochemical etching and polishing and anodic oxidation)

FIELD: technology for producing semi-penetrable membranes for molecular filtration of gas flows and for division of reaction spaces in chemical reactors.

SUBSTANCE: method for producing gas-penetrable membrane includes two-sided electro-chemical etching of monocrystalline plate made of composition AIIIBV of n conductivity type or of semiconductor AIV with width of forbidden zone E≥1,0 electron volts and alloying level 1017-1020 1/cm3. Modes of aforementioned etching are set, providing for generation of simultaneously porous layers, while etching process is performed until moment of spontaneous stopping of electro-chemical process and generation of solid separating layer of stationary thickness on given part of plate area, determined using sharp bend on the curve of temporal dependence of anode current.

EFFECT: gas membrane, produced in accordance to method, has increased penetrability for molecules of light gases and increased selectivity characteristics at room temperature.

2 cl, 3 dwg, 3 ex

The invention relates to the field of electronic technology and can be used to obtain fluorescent screens and indicators

FIELD: technological processes, filters.

SUBSTANCE: invention is related to the field of materials production with preset porosity, which may be used in production of membranes. In method of pores size reduction in surface layer of porous body, which contains of non-organic oxide, the surface of porous body is scanned with laser radiation with laser radiation intensity density from 25 kW/cm2 to 200 kW/cm2 with scanning rate from 10 mm/hr to 5,000 mm/hr and additional heating is performed up to temperature of 200-1,200 °C. Suggested invention allows to reduce pores in surface layer of porous body with preservation of its structure and phase composition, and also size of pores in body thickness, which provides possibility to produce highly efficient oxygen-conducting membranes on its base.

EFFECT: provision of possibility to produce highly efficient oxygen-conducting membranes.

2 cl, 4 dwg, 8 ex

FIELD: mechanics; filtration.

SUBSTANCE: invention relates to the field of production and application of membrane filters made from inorganic materials and may be used in various industrial branches for purifying and concentrating solutions, processing waste waters, purifying potable water and service water, etc. The membrane has a ceramic substrate and a conducting membrane layer. The latter is a carbon selective layer produced by applying a polymer-graphite mix onto the ceramic substrate with subsequent drying and furnacing with no oxygen in the 600 to 1400 °C temperature range. The solution is forced through the membrane obtained and between the electrodes. The conducting membrane layer makes one of the electrodes. The proposed invention allows increasing the separation efficiency along with power savings in the process of separation.

EFFECT: increase in separation selectivity along with power savings in the process of separation.

5 cl, 7 ex

FIELD: chemistry; processing of hydrocarbon material to synthesis gas.

SUBSTANCE: porous ceramic catalytical module represents the product of exothermic finely dispersed nickel-aluminium mixture exposed to vibration compaction and to sintering. The said product contains: nickel 55.93-96.31 Wt%; aluminium 3.69-44.07 Wt%. Porous ceramic catalytical module may contain up to 20 Wt% (based on the module weight) of titanium carbide as well as catalytic coating including following groups: La and MgO, or Ce and MgO, or La, Ce and MgO, or ZrO2, Y2O3 and MgO, or Pt and MgO, or W2O5 and MgO in quantity 0,002-6 Wt% based on the module weight synthesis gas is produced by conversion of methane and carbon dioxide mixture on porous ceramic catalytical module in filtration mode The process conditions are as follows: temperature 450-700°C, pressure 1-10 atm, rate of CH4-CO2 mixture delivery to catalytical module 500-5000 l/dm3*hr.

EFFECT: inventions permit to carry out the process at lower temperatures.

5 cl, 37 dwg

FIELD: inorganic chemistry, possible use for producing materials for filtration and membrane division of liquid and gaseous substances which contain zeolite layer on a substrate.

SUBSTANCE: method for producing zeolite layers on substrates includes selection or manufacture of porous substrate, precipitation of dispersion with zeolite crystals on the porous substrate, which crystals may be used as centers of crystallization of zeolite layer, reaction mixture is prepared for synthesis of zeolite in the layer, movement of substrate to position of contact with reaction mixture and hydro-thermal crystallization with creation of zeolite layer on a substrate, according to which as the substrate, the structure is used which contains gradient-porous layer of oxide ceramics on macro-porous substrate, produced by application of dry metal oxide powder onto macro-porous substrate, transformation of oxide layer to gel, transformation of gel to sol, and following plating of particles in surface-adjacent layer with an additional ceramic oxide layer.

EFFECT: ensured production of high quality membranes, which contain a zeolite layer without usage of organic structure-guiding agents.

5 cl, 3 tbl, 1 dwg

FIELD: separation of gases.

SUBSTANCE: device comprises inorganic diaphragm provided with separating member and porous substrate. The separating member of the diaphragm has dried porous layer of sol made of solidified elastomer based on silicon.

EFFECT: enhanced efficiency and expanded functional capabilities.

31 cl, 9 dwg, 1 tbl, 3 ex

FIELD: chemical industry; petrochemical industry; other industries; methods of production of the inorganic gradient-porous material with the clad layer.

SUBSTANCE: the invention is pertaining to the of the inorganic chemistry and the production process of the cellular materials including the materials with the adjustable nanoporous structure. The method of production of the composition gradient-porous material provides for formation of the inorganic gel directly on the surfaces of the macroporous substrate, drying and the thermal treatment. At that on the surface of the substrate apply the uniform layer of the dry powder of the metal oxide of the metal selected from group: titanium oxide, zirconium oxide, aluminum oxide, silicon oxide and exercise formation of the gel out of the applied oxide by humidification of the layer surface by the electrolyte solution having the clotting properties in the given system, and conduct drying. Then, at least, once repeat the operations of deposition of the powder, formation of the gel and its drying. After that on the dry layer of the gel again uniformly apply the layer of the selected powder, humidify it with the electrolyte solution having the peptization properties in the given system, and conduct the drying of the formed sol, repeat, at least, once the operations of deposition of the powder, humidification of the layer with the solution having the peptization properties and the drying, then apply the clad layer by impregnation of the layer of the sol with the concentrated solution of the salts capable to formation at the thermal treatment of the oxide ceramics, the drying and the thermal treatment at the temperature of 350-600°С in the open air. The produced semi-finished product flush with the water and dry up at the temperature of not above 250°С. The invention allows to adjust the porosity of the composition materials with the selective layer and ensures the preset chemistry of the surface, the high efficiency and simplicity of the production process.

EFFECT: the invention ensures adjustment of the porosity of the composition materials with the selective layer, the preset chemistry of the surface, the high efficiency and simplicity of the production process.

3 cl, 3 tbl

FIELD: chemical industry; other industries; methods of production of the composite gradient-porous material.

SUBSTANCE: the invention is pertaining to the field of inorganic chemistry and the technology of production of the porous materials. On the surface of the substrate apply the uniform layer of the dry powder the metal oxide selected from the group of oxides of titanium, zirconium, aluminum or silicon, execute formation of the gel out of the selected oxide by humidification of the surface of the layer by the electrolyte solution having the coagulating properties in the given system, and conduct drying, then, at least, once repeat the operations of application of the powder, formation of the gel and its drying. After that on the dried layer of the gel again uniformly apply the layer the selected powder, humidify it with the electrolyte solution having the peptizating properties in the given system, and conduct the drying, repeat, at least, once, the operations of application of the powder, humidification of the layer by the solution with peptizating properties and drying, then conduct the annealing. The invention ensures production of the high-quality gradient-porous structures characterized by the high efficiency at simplification of the process of their production.

EFFECT: the invention ensures production of the high-quality gradient-porous structures characterized by the high efficiency at simplification of the process of their production.

4 cl, 2 tbl

FIELD: diaphragm technology; production of the composite oxygen- conducting diaphragms.

SUBSTANCE: the invention is pertaining to the diaphragm technology and may be used for separation of the gases. The composite oxygen-conducting diaphragm contains the solid ceramic layer with the ionic and-or electronic conductivity and at least one layer of the gas-permeable structure made out of the alloy containing the elements of the VIII and VI groups of Mendeleev's Periodic table of elements plus aluminum. The diaphragm consists of two layers of the gas-permeable structure and the solid ceramic layer arranged between them. The presented invention ensures the decrease of the difference of the linear expansion coefficients of the protective gas-permeable layer and the ceramic layer and prevention of the diffusion of the applied alloy into the ceramic layer.

EFFECT: the invention ensures the decreased difference of the linear expansion coefficients of the protective gas-permeable layer and the ceramic layer and prevention of the diffusion of the applied alloy into the ceramic layer.

6 cl, 3 dwg, 11 ex

FIELD: technology for producing semi-penetrable membranes for molecular filtration of gas flows and for division of reaction spaces in chemical reactors.

SUBSTANCE: method for producing gas-penetrable membrane includes two-sided electro-chemical etching of monocrystalline plate made of composition AIIIBV of n conductivity type or of semiconductor AIV with width of forbidden zone E≥1,0 electron volts and alloying level 1017-1020 1/cm3. Modes of aforementioned etching are set, providing for generation of simultaneously porous layers, while etching process is performed until moment of spontaneous stopping of electro-chemical process and generation of solid separating layer of stationary thickness on given part of plate area, determined using sharp bend on the curve of temporal dependence of anode current.

EFFECT: gas membrane, produced in accordance to method, has increased penetrability for molecules of light gases and increased selectivity characteristics at room temperature.

2 cl, 3 dwg, 3 ex

FIELD: chemical industry; methods of production of the olefins.

SUBSTANCE: the invention presents the method, in which from the source powders, fibers or fabrics consisting of carbides of elements of III-V groups of D.I.Mendeleev's periodic table, or aluminum oxides or silion oxides, or the materials representing glass or carbon fibers form the inorganic billet of the necessary form, in the macropores of the billet introduce the billet reinforcingpyrocarbon or impregnate it with phenol-formaldehyde resins with the subsequent carbonization. After that on the surface of the sintered or reinforced billet apply the gas-impermeable carbide layer of the adjustable depth (10-100 microns) by the gaseous phase depositions at the temperature of 800-1100°C, and then conduct halogenation of the carbide layer at the temperature of 400-1100°C. The method ensures production of the diaphragm suitable for separation of the gaseous mixtures.

EFFECT: the invention ensures production of the diaphragm suitable for separation of the gaseous mixtures.

2 cl, 1 tbl, 2 ex

FIELD: physics.

SUBSTANCE: asymmetrical track-etched membrane includes two systems of calibrated pores of different depth. The pores have isotropic tilt in the film depth due to irradiation of the film by heavy charged particles under different angles. The pores of both systems have multiple intersections. Penetration depth for branched cross-cut pore structure does not exceed pore length for the system with the largest pore diameter. Process of asymmetrical track-etched membrane production involves irradiation of polymer film, UV processing of film and further etching. Irradiation is conducted simultaneously by two groups of heavy nucleus fission fragments with different mass and track length in the irradiated polymer. Polymer film depth is not less than average track length for fission fragments with larger mass, and not more than average track length for fission fragments with smaller mass in the given polymer.

EFFECT: increase in efficiency of membrane without change to its selectivity and mechanical strength.

7 cl, 3 dwg, 5 ex

FIELD: polymers.

SUBSTANCE: invention relates to technology for making polymeric porous membranes used in electrolytic decomposition of water. Method involves preparing a molding solution based on polysulfone, TiO2 as a hydrophilic filling agent, pore-forming agent and a solvent, molding a membrane on backing, coagulation and the following annealing. Mixture of three similar oligomers and polymers of vinylpyrrolidone or three-four similar oligomers and polymers of ethylene glycol is used as a pore-forming agent. Invention provides creature of chemically stable and mechanically strength membranes used in electrolytic decomposition of water and showing the high specific conductivity, good separating properties with respect to gases O2 and H2, and sufficiently simple and inexpensive method for their making.

EFFECT: improved making membrane.

4 tbl, 8 ex

FIELD: separation solids from gas or liquid.

SUBSTANCE: method comprises affecting the film made of fluoropolymer by heavy ions, pickling the film, and laminating the porous substrate with the film produced.

EFFECT: simplified method.

21 cl, 9 dwg, 6 ex

FIELD: production of membranes; separation of liquids in microbiological, biochemical and pharmaceutical industries.

SUBSTANCE: proposed method includes preparation of molding solution by dissolving cellulose acetate in mixture of organic solvent, precipitant, water and plasticizer, application of molding solution on moving surface and drying. Molding solution thus prepared is subjected to thermostatting continued for 14-16 h at temperature of 23-26°C. Application of molding solution and molding are performed in confined working space at relative humidity of 15-50% and additional introduction of precipitant and organic solvent mixture into confined molding and evaporating space taken at ratio of (0.3-0.5) : (0.5-1.0) parts by mass in the amount of 1000-6000 mg per m3 of confined working space. During molding, rate of air flow is maintained at level between 0.8 and 0.9 m/s. Ratio of maximum size of pores to their minimum size does not exceed 1.3.

EFFECT: reduced ratio of maximum size of pores to their minimum size.

2 cl, 5 ex

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