Method for manufacturing of gas permeable membrane

FIELD: technological processes, filters.

SUBSTANCE: invention is related to the field of selective membranes manufacturing for molecular filtration of gas mixtures and may find application in portable fuel elements. Method for manufacturing of gas permeable membrane includes fragmentary application of metal coatings that are chemically inertial in solutions of hydrofluoric acid with oxidiser on both surfaces of single-crystal silicon plate. Plate is annealed under conditions that provide for creation of ohm contact between applied metal and silicon, and then pore formation process is carried out in silicon by treatment of plate in solution that contains hydrofluoric acid, oxidiser, substance that helps to restore oxidiser on metal surface, and surfactant. Plate treatment is carried out from both sides until pore formation fronts that distribute deep down into plate from surface sections not coated by metal meet each other, with development of separating nanosize layer of single-crystal silicon.

EFFECT: preparation of gas permeable membranes with high efficient permeability and strength with improved yield of membranes, and also simplification of their manufacturing process.

12 cl, 5 dwg, 3 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.

A method of obtaining a composite gas separation module (US patent No. 7175694, IPC B01D 53/22, published 13.02.2007 g)includes applying by chemical vapor deposition on a porous substrate made of stainless steel or alloys containing chromium and Nickel, an intermediate porous layer of palladium or palladium and metal 1B group and subsequent deposition on it of a continuous layer of palladium (~20 µm), perform the function vasoselective membrane. Composite gas separation module, obtained as described above has a high selectivity and permeability for hydrogen at temperatures over 350÷500°C.

The disadvantages of this method are its multi-stage, complexity and long duration of operations, and the rapid degradation obtained as described above composite gas separation module when used in conditions of significant temperature fluctuations, obukov the fair including the differences in coefficients of thermal expansion of the layer and the material of the porous substrate. 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 to 180°C.

The closest to the essential features of the claimed method is a method of obtaining a gas-permeable membrane (Patent RU №2283691, IPC B01D 67/00, published September 20, 2006). Prototype method includes bilateral electrochemical etching of single-crystal wafers of compound AIIIBVn-type conductivity or A semiconductorIVwith bandgap E≥1.0 eV and the doping level of 1017-1020cm-3while 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 disadvantages of the prototype method may include the need to use relatively complex electrochemical equipment, including electrochemical cell with a cathode, resistant to hydrofluoric acid solutions, the external circuit with the source of DC power and measuring devices. The l is additional difficult to create a reliable electrical connection of the processed semiconductor wafer with an external circuit, able to withstand long contact with chemically aggressive liquid or its vapors. In addition, the indirect nature of determining the end time of the process of forming the separation layer of the membrane is not possible to achieve a high reproducibility of obtaining membranes with the required parameters of the selectivity of gas separation. This is due to the fact that after the formation of the separation layer begins to develop a parasitic process of formation of secondary fronts of steam formation, moving under the mask in the tangential directions. Appearance while increasing over time, the local stresses caused by the flow resistance is devoted reaction products leads ultimately to local destruction of the pore walls, including the formed membrane layers.

One of the drawbacks of the membranes obtained by the method of the prototype, is the low mechanical strength, which is determined by the strength of a porous material with a total thickness comprising 100-200 μm. The disadvantages should also be considered a violation of the uniformity in thickness of the filtering layer, resulting in the manufacture of the membranes of the plane-parallel plates. This is due to the manifestation of edge effects during electrochemical etching, contributing to the increased etching rate at the periphery of the interaction region with what electrolitos, and, as a consequence, the concavity of the fronts of steam formation, and their incomplete connection at the completion of the process. As a result the magnitude of the effective permeability of the membrane for filtering gases, referred to the unit of its area, is significantly smaller maximum values achieved only locally in the areas of direct connection of the fronts of steam formation.

A method of obtaining layers of porous silicon on the surface of the crystalline silicon (see US patent No. 6790785, IPC H01L 21/02, published on September 14, 2004), does not require external electric power to be processed in solution material. The known method comprises applying to the original surface of the silicon thin discontinuous layer of nanoparticles of noble metals Au, Pt, Pd and subsequent etching of the obtained plate in a solution of hydrofluoric acid (HF)containing the oxidizing agent. As an oxidizer selected hydrogen peroxide (H2O2), and the recommended composition of the solution - HF, H2About2With5H5HE in a volume ratio of 1:1:1. In the etching of the porous layers occur on parts of the surface covered with particles of metal, and in the vicinity of these sites on the free surface of the silicon. Thus the rate of formation of porous layers and their structural characteristicssemmie vary depending on the type planted metal, the doping level of the source of silicon and the time of etching. In comparison with layers of mesoporous silicon, a standard electrochemical method, layers obtained by this method are more loose spongy structure and a rough surface that becomes apparent at the small, submicron thicknesses of such layers formed within 30 seconds of etching. A further increase in the exposure time in solution leads to the formation of rough, inhomogeneous porous layers.

The reason for the formation of porous silicon, with this method of obtaining, is the existence in contact with the electrolyte electrochemical pair of metal-silicon and localization of the components of this pair is possible in this system the cathodic and anodic reactions, namely the recovery of hydrogen peroxide with participation of electrons supplied from the metal and the oxidation of silicon, proceeding with the transfer of electrons to the metal particles. This creates the conditions for the reaction of the anions of fluorine with silicon and education in it nanopores.

The main disadvantage of this method is the nonstationarity of the process of steam formation. As known to occur in these conditions, mesoporous silica has high resistivity, constituting 104-106Ω·refer To the formation of a continuous porous layer is lost elec the historical contact of a semiconductor crystal with metal particles, and the continuation of the electrochemical process is possible only due to the migration of some fraction of such particles into the porous layer, followed by the front of steam formation. In the monotonic increase of the internal resistance of the circuit the potential jump at the front of steam formation decreases until a critical value that leads to the gradual attenuation of the propagation process then. However, a high concentration of a strong oxidant (H2About2in the HF solution contributes to the development of chemical etching of the already formed porous silicon, which causes erosion of the layer. This process is accelerated as the deceleration of steam formation, when the oxidant becomes consumed by the oxidation released into the solution of the primary reaction products containing silicon in the lower valence States. Therefore this method is not suitable for obtaining fairly thick (several tens of microns or more) homogeneous layers of porous silicon, which is a necessary condition for the production of silicon membranes selectively permeable to light gases in accordance with the proposed method.

An object of the invention is to develop a method for creating silicon selective gas-permeable membrane with increased strength to the reconstruction, with the possibility of a more uniform distribution on the area of the membrane through her stream filtering gases and higher effective permeability. The proposed method makes possible to simplify the manufacturing process of the membranes, including by eliminating technological operations related to the creation of an external electric circuit and maintain the outside options of carrying out the electrochemical process. In addition, the inventive method makes it possible to increase the yield of membranes without discontinuities separating layer, due to more accurate determination of the completion of its formation during the processing of wafers in the etching solution. The technical result of the proposed method is also expanding Arsenal of technical means of obtaining silicon selective gas-permeable membrane.

The task is solved by the fact that similar to prototype a method of manufacturing a gas-permeable membrane includes a two-sided etching of the monocrystalline silicon wafer to the moment of meeting propagating deep into the plate fronts of steam formation, obtaining the separation of nanoscale layer of monocrystalline silicon, which is vasoselective. Unlike the prototype, on both surfaces of monocrystalline silicon wafers pre is sustained fashion fragmentary applied metallic coating, chemically inert in the solution of hydrofluoric acid with an oxidant. Then annealing the wafer in an environment which fosters the formation of ohmic contact between the deposited metal and silicon. Next is the process of steam formation in areas of a silicon wafer not covered by metal, by processing the wafer in a solution containing hydrofluoric acid, an oxidizer, a substance promoting the restoration of the oxidizing agent on the metal surface, and surface-active agent that reduces interfacial tension.

Since the establishment of the separation gas-permeable nano silicon layer may be determined by the intensity passing through the plate light in the visible part of the spectrum.

The above solution may contain as oxidant hydrogen peroxide, as substances that help to restore the oxidant on the surface of the metal, hydrochloric acid as a surfactant methyl alcohol, ethyl alcohol, isopropyl alcohol, diethyl ether, tetrahydrofuran, acetic acid. As the oxidizing agent can also be used potassium permanganate, sodium persulfate, potassium chlorate and other compounds, which are stable in solutions of HF and having a value of standard oxidation potential >1B. However, these substances Produkty their recovery may contaminate the porous layers.

The quality of the coating can be applied to the metal part of the platinum group such as platinum or palladium.

The above-mentioned coating can be made of gold sublayer solicitousness metal selected from the group of chromium, titanium, tungsten, molybdenum, niobium, vanadium, tantalum, Nickel.

In the particular case of the method of coating is applied so that the mutual projection of the obtained fragments of the coating from one surface to another at least partially overlap each other.

The metal coating can be applied in the form of regularly spaced stripes.

Strip coating on one surface of a silicon wafer is preferably oriented at an angle to the strips of the coating on the other surface.

Optimal is the ratio of the width of the metal strips of the coating to the plate thickness of 1.5-2.0, and the distance between the strips of the coating is in the range of 0.5-1.0 mm when the thickness of the plates 120-200 µm for the crystallographic orientation of the surface plate (100) and 0.6-1.4 mm for orientation (111).

Strips of the coating can be interconnected at the periphery of the plate material, chemically inert to hydrofluoric acid solutions with oxidizing agent.

Mentioned separation of nanoscale layer of monocrystalline silicon has a thickness equal to 5-20 nm depending on the specific with the resistance of the source wafer of monocrystalline silicon.

The process of steam formation is accompanied by the formation of layers of uniformly porous silicon with a porosity of 60-80% and a pore size of 10-20 nm.

The combination of these features leads to the task of developing a simple reproducible method for creating silicon selective gas-permeable membrane with high structural strength, higher effective permeability for filtering gases and the possibility of a more uniform distribution of the gas flow area of the membrane.

The choice of coating material from a metal of the platinum sub-groups (for example, of platinum or palladium or gold sublayer solicitousness metal selected from the group of chromium, titanium, tungsten, molybdenum, niobium, vanadium, tantalum, Nickel, determined necessary in this case chemical resistance. The formation of the transitional silicide phase at the interface of silicon with a metal coating is critical to providing the necessary adhesion of the metal to the surface of the plate and appearance between him and the silicon disability (ohmic) contact, without impeding the transport of electrons from the front of steam formation in the area of the cathodic reaction on the metal surface. Chemical interaction between the silicon and the applied metal with the formation of adhesio the aqueous silicide layer is triggered short (1-5 minutes) annealing by heating to a temperature define the chemical nature of the metal. For example, annealing of the plate with a coating of platinum (Pt) optimal temperature is about 500°C, and for coating of gold with a sublayer of chromium (Au+Cr) - 350-400°C.

In the present method the creation of ohmic contact between the silicon and the metal coating, while performing the role of the electrode and chemically resistant coating ensures almost constant in time jump in potential between the electrolyte solution and travails crystal silicon. As a result, the process of steam formation develops at a constant speed until the formation of a continuous separating layer of silicon stationary thickness at the junction of the colliding fronts of steam formation. In contrast to the method-analogue of [US patent No. 6790785, IPC H01L 21/02, published on September 14, 2004], the implementation of this method effective area associated with the crystal silicon metal electrode (area marked fragments of coverage) remains unchanged, respectively, remain unchanged and conditions of occurrence of paired reactions recovery oxidant metal and steam formation in silicon. This provides the possibility of obtaining a homogeneous porous layers in silicon single crystals with a thickness of 100 microns, which allows us to use the proposed method DL is the fabrication of membranes, working in real conditions differential gas pressures at the inlet and outlet of the membrane.

If any "no-current" method of obtaining porous silicon using the oxidation potential of the environment to initiate the electrochemical process of steam formation, always have side processes chemical etching formed of a porous material. Least of these processes are shown when using a peroxide oxidizing agents (hydrogen peroxide (H2O2and persulfates S2O8-2). However, achieving technologically acceptable velocity of steam formation for the manufacture of gas-permeable membranes with a total thickness exceeding 100 μm, requires the solution of sufficiently high concentrations of peroxides. The development side of the chemical processes affecting mainly the near-surface region of the porous layer, resulting in a significant increase in the degree of porosity and pore size in comparison with the underlying areas. This becomes a cause of occurrence of cracks on the surface of the porous layer after removing them from the solution and evaporation of the liquid and causes a decrease in mechanical strength of the resulting membranes. Therefore there is a need for a marginal decrease in the concentration of oxidant in solution.

When used to is the amount of oxidizer H 2About2limit value of the potential of the metal electrode in the solution (E) is defined as

where E0=1.77 - default value of electrode potential polyreactive

R is the universal gas constant (8.314 j/mol·deg);

F - Faraday constant (96485 C/g·EQ);

[H2O2] active hydrogen peroxide concentration in the solution (mol/l);

[H+] active concentration of hydrogen cations in the solution (mol/l);

[H2O] - active concentration of water molecules in the solution (mol/l).

Since determining the pH of the etching solution of hydrofluoric acid is a weak acid (the ratio of dissociation in aqueous solutions - 6.8·10-4), as can be seen from expression (1), the electrode potential can be substantially increased by increasing the concentration of hydrogen cations in solution when added to a strong acid. The most effective in this regard is hydrochloric acid Hcl, which is also related to its ability to catalyze the decomposition of hydrogen peroxide resulting in the solution of the intermediate product is chlorine:

This catalytic process in the first place should be developed on the electrodes made of noble metals (A u, Pt, Pd), high is th adsorption activity as compared to chlorine anions (Cl -), and oxygen:

(Note: subscripts sol and ad denote respectively the identity of the particle solution and the adsorption layer.)

Described the possibility of increasing the potential of the electrode in a solution of N2About2and the speed of its recovery during the electrochemical process is designed to provide the necessary conditions for the occurrence of active steam formation in silicon at low concentration of oxidizing agent in the etching solution and to avoid, therefore, a noticeable erosion of porous layers, caused by secondary processes chemical etching.

For uniform porous layers and the planarity of the interface and the bulk silicon in the solution include surface-active substances (surfactants), which improves the wettability of the surface of silicon and metal.

The metal coating can be produced by any known method of thermal evaporation in vacuum, sputter deposition, electroplating deposition). The best is the application of metallic coatings on both surfaces of a silicon wafer in the form of regularly spaced strips interconnected at the periphery of the plate material that is chemically inert in the solution of hydrofluoric acid with an oxidant. This strips located on protivopul the different sides of the plate, preferably oriented at an angle relative to each other. In this case, after the process of steam formation in the open areas of a silicon wafer creates a regular system of homogeneous cells, within which there is a connection fronts of steam formation and formed the system of the desired separation of nanoscale layers that can perform getselection function of the membrane, and under the metal coating remains monocrystalline silicon, perform the function of reinforcing the frame of the membrane.

When sizing fragments of metal coatings must simultaneously required to be taken to increase the usable space and, accordingly, the effective permeability of the membrane, and provide the necessary mechanical strength. The first requirement is achieved by minimization of the transverse sizes of the fragments of metal coatings and optimization of the sizes of the exposed areas on the surface of the silicon wafer. But as the fronts of steam formation is distributed not only along the normal to travemate surface, but also in the tangential directions, under the fragments of the metal coating, the minimum transverse dimensions of the closed metal areas should be selected depending on the thickness of the original silicon wafer and its crystallographic orientation. Experimental is installed, when the orientation of the (100) surface of the plate width of the fragments of the coating shall be not less than 0.7 from its thickness and not less than 0.9 with orientation (111). Otherwise, at lower ratios may be closing porous layers under the surface of the metal coating, which breaks the electrical contact of the metal with silicon, and the process of steam formation is terminated. The optimal ratio of the width of the metal fragment to the thickness of the plate is approximately 1.5-2.0. At high ratios decreases the effective area of the membrane is equal to the total square of the separation of nanoscale layers, which reduces its effective permeability. To improve the uniformity in thickness of the separation of nanoscale layer to eliminate edge effects, affecting the normal speed of propagation of fronts of steam formation. For this purpose it is necessary to reduce the distance between the fragments of the metallic coating. Experimentally found optimal value of the distance between the fragments of the coating varies in the range 0.5-1.0 mm when the thickness of the plate with a crystallographic orientation of (100) surface in the range of 120-200 μm, and in the case of a plate with the crystallographic orientation of the surface (111) - in the range of 0.6 to 1.4 mm

Strips of the coatings can be connected between the in a on the periphery of the plate material, chemically inert in the solution of hydrofluoric acid with an oxidant. For example, such material may be covered with a platinum group metal or gold with silicidation sublayer.

The process of convergence fronts of steam formation can be controlled by the intensity passing through the silicon wafer of light (visually or with the aid of a sensor), putting a light source such as led or incandescent lamp) on one side of the plate and watching from the opposite side for the appearance of transparent areas, changing their configuration and intensity of light passing through them. This possibility is due to the fact that monocrystalline silicon, unlike obtained in this case mesoporous silicon is opaque to radiation of the visible range is already at thicknesses greater than a few microns. The moment of spontaneous termination of the process of steam formation in each local region of convergence fronts is determined by the stabilization in time of the intensity of light passing through the plate. Instead of visual inspection, you can use the readings of a sensor that is sensitive in the desired wavelength range (less than 0.67 microns). With the help of the photodetector is convenient to record the total process is completed over the entire area of the plate.

The minimum thickness of separating nanorazmernogo layer of monocrystalline silicon, obtained by the claimed method, is determined by the resistivity (doping level) of the original plate of monocrystalline silicon, and silicon wafers with a doping level of 1019-10201/cm3is 5-20 nm.

The integral values of porosity and pore size in the porous layers of silicon produced in accordance with the proposed method, depend on the doping level of the source crystal and the magnitude of the jump of the potential on the boundary: the semiconductor - electrolyte interface, defined, in this case, the concentration of hydrogen peroxide in the solution and the hydrogen ion exponent (pH). For Si p-type conductivity with a concentration of charge carriers 1018-1019cm-3in solutions containing from 0.05 to 0.2 parts by volume of H2O2(30%) and from 0.1 to 0.2 parts by volume Hcl (36%)was experimentally determined porosity of the formed layer was changed from 60 to 80%. According to scanning electron microscopy most of the time in all cases was the size of 10 to 20 nm. Therefore, porous silicon can not create significant diffusion resistance to the flow of molecules of light gases, the effective size of which is in the gas phase do not exceed 0.3 nm.

Thus, in the inventive method of obtaining silicon membranes, permeable to molecules of the lungs is of Azov (hydrogen, helium) is carried out using a smaller amount of technological equipment, does not require monitoring and adjustment of parameters of the electrochemical process that uses direct and more reliable method of fixing the date of termination of the process of steam formation. In addition, the inventive method allows for the mechanical reinforcement of the gas-permeable membrane, ensuring conservation of monolithic silicon, comprising vasoselective nanoscale separation layers between porous silicon; to improve the uniformity in thickness of the separation layer by leveling edge effects causing concavity converging fronts of steam formation by reducing the ratio between their lateral size and thickness of a silicon wafer, thus increasing the effective permeability of the membrane for filtering gases. All this together leads to increased yield membranes, improving the reproducibility of the fabrication technology of membranes and increase their quality.

The proposed method makes it possible, in particular, to create the anode of the hydrogen fuel cell with a uniform square supply hydrogen and distributed power collection.

The claimed technical solution is illustrated graphics.

Figure 1 shows the principles of the territorial scheme of the installation for carrying out the process of steam formation in the silicon wafer by the present method.

Figure 2 shows schematically the round monocrystalline silicon wafer with double-sided application of strips of metal coating so that the mutual projection strips of the coating from one surface to the other partly overlap each other and are oriented at an angle to each other.

Figure 3 schematically shows a rectangular single crystal silicon wafer with double-sided application of strips of metal coating so that the mutual projection strips of the coating from one surface to another are oriented at right angles to each other. The strips cover connected along the periphery of the plate material, chemically inert to hydrofluoric acid solutions with oxidizing agent.

Figure 4 schematically shows a gas-permeable membrane obtained by the present method from a silicon wafer, is shown in figure 3, in cross section along lines A-a, b-b and C-C.

Figure 5 shows a photograph of a gas-permeable membrane obtained by the present method in transmitted light.

The installation for carrying out the process of steam formation in the silicon wafer 1 by the present method (see figure 1) consists of the vessel 2 made from a material transparent to radiation with wavelengths of less than 0.67 microns. The container 2 contains a solution of 3, in which is immersed the original single crystal silicon layer is 1 with fragments deposited on both surfaces of the metal coatings 4 and 5. In the particular case of the method for the silicon wafer 1 in the tank 2 have between the radiation source 6 power supply 7, a lens 8 and the photodetector 9 by the registration device 10 using a PTFE holder 11.

The inventive method of manufacturing gas-permeable membrane is as follows: On both the surface of the monocrystalline silicon wafer 1, for example, by the method of thermal vacuum evaporation or magnetron sputtering is applied granular coating of chemically resistant in hydrofluoric acid with an oxidant metal (e.g. platinum or palladium) in the form of, for example, parallel strips 4 and strips 5. Preferably the strips 5 on one surface of the plate 1 are oriented at an angle to the projections of the strips 4 on the other surface of the plate 1 (see figure 2, 3). In this case, the mutual projection of the metal strips 4 and 5 from one surface to the other partly overlap each other. When used as a coating of gold previously, also fragments, put sublayer solicitousness metal. As a sub you can use 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 dual is x metal systems: a reference book in 2 books. - book 1. - Levinsky Y. - M.: metallurgy, 1990. - 400 C.). On the periphery of the plate for connection of the strips between them can cause a material chemically inert to the solutions of hydrofluoric acid with an oxidant, such as a platinum group metal or gold with silicidation sublayer.

After deposition of the metal coating in the form of strips 4 and 5 carry out the annealing of the plate 1 is preferably in vacuum or atmosphere is chemically inert with respect to silicon and the deposited metal gas (such as hydrogen, nitrogen or argon), ensuring the formation of ohmic contact between the metal coating and the silicon. About the formation of a barrier-free electrical contact may indicate the linearity of the current-voltage characteristics of the circuit between two unrelated fragments of the metallic coating. It was established experimentally that, for example, a plate with a coating of gold with a chromium sublayer enough to anneal in vacuum at a temperature of 350-400°C for 1-5 minutes. Then, the silicon wafer 1 is immersed in a container 2 with a solution of 3 using the locking edge of the holder 11 (see Fig 1).

Mandatory components of the solution 3, which provides the fundamental possibility of the formation of porous silicon in this system are the fluoride exposed therein the electrolytic dissocia the AI, and the oxidant. As a source of fluoride ions is optimal use of hydrofluoric acid is completely removed from the obtained porous layer after removing them from the solution. For uniform porous layers and the planarity of the interface and the bulk silicon in the solution include surface-active agents (surfactants)that improves the wettability of the surface of the silicon and metal solution and facilitate the removal of air bubbles generated hydrogen. To minimize the necessary concentration of the oxidant in the solution preferably also the presence of substances, shifting the equilibrium of the reactions occurring in the forward direction and/or performs the function of a catalyst. As the oxidizing agent can be used a substance taken from the group of hydrogen peroxide, permanganate, persulfate, chlorate, bromate or periodic alkali metal. As substances that help to restore the oxidant on the surface deposited on silicon metal, depending on the type of oxidizing agent may be used a substance taken from the group of hydrochloric acid (oxidant - H2O2), sulfuric acid (oxidant - MnO4-), the cations of silver (oxidant - S2O8-2). As surfactants may be used a substance taken the C group: methyl alcohol, ethyl alcohol, isopropyl alcohol, diethyl ether, tetrahydrofuran, acetic acid or acetone (if the oxidizer is not H2About2). In particular, the solution of providing a stable pore formation in contact with the metal silicon, may consist of a mixture of aqueous solutions of hydrogen fluoride (fluoride), hydrogen peroxide (oxidizing agent), hydrogen chloride (substance, providing a balance shift and catalysis) and isopropyl alcohol (surfactant component) in volumetric proportions: 7:2:3:6.

The process of bilateral processing of the plate 1 in a solution of 3 lead to the moment of meeting the fronts of steam formation extending deep into the plate 1 from uncoated metal strips 4 and 5 plots the surface, obtaining nanoscale separation layer 12 (figure 4) monocrystalline silicon between the layers 13 and 14 of porous silicon. Trajectory germination branching of the pores varies, usually near normal to the original surface and weakly depends on its crystallographic orientation. However, there is a distribution of pores and under the strips 4 and 5. For example, the lateral advancement of the porous layer 13 under the strips 4, is at the surface approximately 0.6-0.7 of depth of the porous layer 13 under an open surface. Hence, when the total thickness of the silicon place the ins 1 200 microns minimum width of the strips 4 shall be not less than 150 microns.

The time of the meeting of the fronts of steam formation with obtaining nanoscale separation layer 12 can be controlled by the intensity passing through the silicon wafer 1 light visually or with the help of the photodetector 9, placing the radiation source 6 (e.g., led or incandescent lamp) with power supply 7 with one side of the plate 1 and looking from the opposite side for the appearance of transparent areas on the site of the formation of nanoscale separation layer 12 in the plate 1, by changing their configuration and intensity of light passing through them. The moment of spontaneous termination of the process of steam formation in each local region of convergence fronts is determined by the stabilization in time of the intensity of light passing through the plate 1. Instead of visual inspection, you can use the evidence recording device 10 from the photodetector 9, which are sensitive in the desired wavelength range (less than 0.67 microns). With the help of the photodetector 9 is convenient to record the total process is completed over the entire area of the plate 1.

As a result of implementation of the proposed method are gas-permeable membrane with a system of regularly spaced separation of nanoscale layers 12 of monocrystalline silicon, which implies a more even distribution over the area of the membrane prohodjashei what about through her stream of filtered gases (figure 5).

Example 1. The source material was round (diameter 25 mm) silicon single-crystal plate of p-type conductivity with a resistivity of 0.005 Ohm·cm and a thickness of 145 μm. The silicon wafer was pre-degreased in acetone. Then put the sublayer solicitousness metal chromium of a thickness of 40 nm by thermal spraying in vacuum through a mask with Windows in the form of strips, and so struck gold with a thickness of 150 nm, and then repeating the spraying operation on the second side of the plate. When this strip was oriented relative to the projections of the bars printed on the opposite side, an angle of 30°. The plate was annealed in vacuum at a temperature of 350°C for 3 minutes. The plate coated with the metal strips were placed in a Teflon holder with window with a diameter of 18 mm and immersed in a solution obtained by mixing ethyl alcohol, hydrofluoric acid (40% HF), hydrochloric acid (36% HCl) and hydrogen peroxide (30% H2About2) in volumetric ratio of 6:6:3:2. The treatment was carried out at room temperature in a plastic cuvette with transparent walls. The process of steam formation led to the moment of meeting the fronts of steam formation and receiving a continuous separating layer of fixed thickness. The time of formation of a solid separation layer recorded visually on stabilisationtransition passing through the plate light (see 5). Once the plates were washed in ethanol and dried in air. After fabrication of the resulting membrane was tested for mechanical strength using a classic cross three-point bending. Experiments have shown that the critical stress fracture membranes manufactured by the present method, accounted for 58.4±5 MPa, which is more than 10 times the critical failure stress of a fully porous silicon wafer of the same size and thickness. The obtained membrane (when the total area of the plate equal to 4 cm2) is characterized by the following parameters: permeability to hydrogen at 20°C - 4,6·10-11·mol-1PA-1and at 100°C and 2.1·10-10·mol-1PA-1; permeability for helium at 20°C - 1.6 x 10-11·mol-1PA-1and at 100°C is 2.2·10-10·mol-1PA-1.

Example 2. Round (diameter 25 mm) silicon single-crystal wafer of p-type conductivity with a resistivity of 0.005 Ohm·cm and a thickness of 145 μm was manufactured gas-permeable membrane as in example 1. The differences lay in the fact that, as the coating was applied platinum, and the solution consisted of isopropyl alcohol, HF, H2About2and Hcl taken to volume ratios: 7:6:2:3. The obtained membrane (when the total area of the plate equal to 4 cm 2) is characterized by the following parameters: permeability to hydrogen at 20°C - 4,8·10-11·mol-1PA-1and at 100°C - 2,2-10-10·mol-1PA-1; permeability for helium at 20°C - 1,7-10-11·mol-1PA-1and at 100°C to 2.3·10-10·mol-1PA-1.

Example 3. Round (diameter 25 mm) silicon single-crystal wafer of p-type conductivity with a resistivity of 0.005 Ohm·cm and a thickness of 160 μm was manufactured gas-permeable membrane as in example 2, but in the quality of the coating applied palladium. The obtained membrane (when the total area of the plate equal to 4 cm2) is characterized by the following parameters: permeability to hydrogen at 20°C and 4.3-10-11·mol-1PA-1and at 100°C - 2.0-10-10·mol-1PA-1; permeability for helium at 20°C - 1.4 to 10-11·mol-1PA-1and at 100°C to 1.9·10-10·mol c-1PA-1.

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

As can be seen from the above data, the gas-permeable membrane made by the claimed method, have a greater resistance to ikonicheskim damage during Assembly and operation of the filters, especially when used in fuel cells (and therefore longer service life of the fuel element). In the manufacture of gas-permeable membrane of the claimed method requires fewer process equipment, used direct and more reliable method of fixing the date of termination of the process of steam formation. All this together leads to more reproducible manufacturing techniques membranes and increase their quality (in comparison with the gas-permeable membrane prototype membrane strength increased by more than an order of magnitude, and the permeability of hydrogen and helium has increased at least five times).

1. A method of manufacturing a gas-permeable membranes, including the fragmentary drawing on both surfaces of single-crystal silicon wafers of metal coatings, chemically inert in solutions of fluoride-hydrogen of the acid with an oxidant; annealing the wafer in an environment which fosters the formation of ohmic contact between the deposited metal and silicon, and the subsequent conduct of the process of steam formation in silicon by processing the wafer in a solution containing fluoride-hydrogen acid, an oxidizer, a substance promoting the restoration of the oxidizing agent on the metal surface, and surface-active substance, with the processing plate weuts both sides until the meeting of the fronts of steam formation, extending into the plate from the uncovered metal surface areas, obtaining the separation of nanoscale layer of monocrystalline silicon.

2. The method according to claim 1, characterized in that the said solution contains as the oxidant hydrogen peroxide, as substances that help to restore the oxidant on the surface of the metal, hydrochloric acid as a surfactant is a substance selected from the group of isopropyl alcohol, ethyl alcohol, methyl alcohol, diethyl ether, tetrahydrofuran, acetic acid.

3. The method according to claim 1, characterized in that the coating is applied, the metal included in the platinum group.

4. The method according to claim 1, characterized in that the said coating is made of a gold sublayer solicitousness metal selected from the group of chromium, titanium, tungsten, molybdenum, niobium, vanadium, tantalum, Nickel.

5. The method according to claim 1, characterized in that the coating is applied so that the mutual projection of the obtained fragments of the coating from one surface to another at least partially overlap each other.

6. The method according to claim 1, characterized in that the metallic coating is applied in the form of regularly spaced stripes.

7. The method according to claim 6, characterized in that the strips of the coating on one surface of the crest is the silicon plate oriented at an angle to the strips of the coating on the other surface.

8. The method according to claim 6, characterized in that the ratio of the width of the metal strips of the coating to the plate thickness is 1.5-2.0, and the distance between the metal strips is selected in the range of 0.5-1.0 mm when the thickness of the plates 120-200 µm for the crystallographic orientation of the surface plate (100) and 0.6-1.4 mm for orientation (111).

9. The method according to claim 6, characterized in that the strips cover connected along the periphery of the plate material, chemically inert in solutions of fluoride-hydrogen of the acid with an oxidant.

10. The method according to claim 1, characterized in that the formation of the separation gas-permeable nano silicon layer is fixed by the intensity passing through the plate light in the visible part of the spectrum.

11. The method according to claim 1, characterized in that the mentioned separation of nanoscale layer of monocrystalline silicon has a thickness equal to 5-20 nm.

12. The method according to claim 1, characterized in that the process of steam formation is accompanied by the formation of layers of uniformly porous silicon with a porosity of 60-80% and a pore size of 10-20 nm.



 

Same patents:

Amplifier-convertor // 2364981

FIELD: physics.

SUBSTANCE: invention concerns the vacuum emission technics and can be used at construction of products and devices of vacuum electronics, microwave frequency and microwave electronics, systems of visualisation of the information (screens of flat displays), lighting systems. An amplifier-converter design in structure: the autoemission cathode on the basis of carbon nanostructure materials, for example, carbon nanotubes; grids on the basis of multicoherent (in that specific case the mesh shape) monocrystal, or a polycrystalline diamond film; a collector of electrons, executed or in the form of multilayered film structure from a transparent for light layer of indium oxide - tin oxide, a luminescing layer (CdS, ZnS, P) and a submicronic layer of aluminium, transparent for a beam of electrones, or in the form of a continuous conducting electrode - depending on functional use of the device.

EFFECT: degradation stability - by means of use of autoemitters from CNT (low values of a threshold field and high mechanical durability); high spatial permission - by means of micron scale of meshes of a grid (multicoherent layer); dilation of a temperature range and radiation damage stability increase - by means of a choice as base substances of carbon nanotubes and diamond films.

6 cl, 14 dwg

FIELD: physics, computer facilities.

SUBSTANCE: offered invention concerns computer facilities and can be used in optical information processing devices. The offered optical subtracting nano-device contains an input optical Y-splitter, a radiant of the constant optical signal, two optical nano-fiber N-output splitters, two target optical nano-fiber a Y-splitter, two input optical nano-fiber couplers, two optical N-input nano-fiber couplers, optically interfaced among themselves in appropriate way, and two telescopic nanotubes - interior and exterior one.

EFFECT: solution of a problem of subtraction both coherent, and incoherent optical signals with speed, potentially possible for optical processor plans, and also a problem ofnanosized device implement.

1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to field of creating luminescent nanostructural composition ceramic materials on the basis of silicon dioxide and zinc orthosilicate (willemite) and can be applied in light-emitting and blinker devices development, for instance, plasma display panels, light matrix indicators, traffic lights, etc., which irradiate definite colour tone of visible spectrum. Luminescent nanostructural composition ceramic material, which contains silicon dioxide SiO2 and doped with manganese willemite Zn2SiO4, additionally contains zinc oxide ZnO, silicon dioxide representing crystobalite, willemite is doped with manganese by formula Zn2-xMnxSiO4, where variable x takes values in range from 0.05 to 0.15, material components are taken in following ratio: crystobalite - 45÷55 wt %, zinc oxide 5÷7 wt %, willemite 38÷50 wt %, cristobalite and zinc oxide grains size being in range from 55 to 70 nm, and sizes of willemite grains being in range from 10 to 22 nm.

EFFECT: created material has radiation of increased green light intensity in band 500÷570 nm, and allows increasing efficiency of glow centre excitation and increase quantum yield.

9 ex, 1 tbl, 1 dwg

FIELD: nanotechnology.

SUBSTANCE: invention relates to nanotechnology and nanomaterials and can be used at receiving of inorganic and organic-inorganic fine-grained and nano-structured metallised materials, metal-polymers and nanocomposite. Suspension of organic-inorganic nanostructures, containing nanoparticles of noble metals, implemented in the form of poly-complex in two-phase reacting system, consisting of two volume contacting immiscible liquids. Poly-complex includes organic molecules, containing amides in amount 2 or more, and nanoparticles of noble metals. Suspension is received by means of forming of two-phase reacting system, consisting of two contacting volumetric immiscible liquids, addition in it of restorative and synthesis of nanoparticles. Additionally metallised molecules of precursors are dissolved in hydrophobic phase, reducer is added into aqueous phase, and in the capacity of ligands there are used organic molecules, into content of which there are included amides in amount 2 or more. Invention provides receiving of new nano-structured organic-inorganic polymeric complexes on the basis of polyamines, containing nanoparticles of noble metals (Pd, Au) of size up to 10 nm, which allows high specific surface area and are characterised by narrow dispersion of dimensions.

EFFECT: it is provided high density of particles packing in organic-inorganic nano-structures and high performance of transformation of initial material into nanoparticles of noble metals.

23 cl, 12 dwg, 1 ex

FIELD: electrical engineering.

SUBSTANCE: invention relates to semiconductor electronics and can be used for making heavy duty and high-precision transistors. The transistor contains a first set, which includes N1>1000000 regions with the same conductivity, a second set which includes N2 >1000000 regions with the same conductivity, as well as a third set, which includes N3>1000000 regions with opposite conductivity. The regions are made with formation of a first set of separate same-type point p-n junctions between regions from the first and third sets and a second set of separate same-type point p-n junctions between regions from the second and third sets. Electrodes, adjacent regions included in at least one of the said sets, for which the condition Ni>1000000, where i∈{1, 2, 3}, is satisfied, are connected in parallel by one conductor, i.e. are connected into a single current node.

EFFECT: obtaining high-precision heavy duty transistors with stable electrical parametres.

21 cl, 9 dwg

FIELD: physics.

SUBSTANCE: invention is related to the field of nanomaterials application. It is suggested to use carbon of bulbous structure as sensitive element of detector in terahertz range of waves that absorbs electromagnet radiation (EMR) in the range of frequencies of 30 - 230 THz.

EFFECT: improved performance characteristics.

3 dwg

FIELD: chemistry.

SUBSTANCE: invention refers to the high-strength epoxide composition used for impregnation at production of high-strength glass-, carbon,- organic-, and boron plastics working in the wide temperature range and used in different industrial sectors (machinery construction, shipbuilding, aircraft and space industries, for production of the parts of complicated configuration e.g. thin- and thick-walled casings). The invention refers also to the method for preparation of the said composition including the following components (weight parts): 10-100 - diglycidyl resorcinol ether, 10-100 - product of epichlorohydrin condensation with triphenol, 6-12 - oligoether cyclocarbonates with mass ratio of cyclocarbonate groups in the range from 18 to 29, 28-50 - curing agent (primary aromatic amine), 0.5-2.5 - curing agent (tertiary amine), 0.25-1.25 - mixture of carbon and silicate nanomaterials. The mass ratio of diglycidyl resorcinol ether to product of epichlorohydrin condensation with triphenol is in the range from 1 : 9 to 9 : 1. Metaphenylen diamine or 4,4'-diaminodiphenylmethane or their eutectic mixtures in ratio from 40 : 60 to 60 : 40 are used as primary aromatic amine. Mono-, di and trimethylsubstituted pyridine or monovinylsubstituted pyridine are used as tertiary aromatic amine. The carbon nanomaterial is fullerene C2n, wherein n is no less than 30, the silicate nanomaterial is organobentonite, the fullerene : organobentonite ratio is in the range from 1 : 3 to 3 : 1. The method of composition preparation consists in stirring of nanomaterials mixture with oligoether cyclocarbonates by ultrasonic action at frequency 22-44 kHz during 30-45 min. Then the obtained suspension is mixed with beforehand prepared mixture of diglycidyl resorcinol ether and product of epichlorohydrin condensation with triphenol. After that the curing agent in the form of aromatic primary and tertiary amine mixture is added. The ready composition is cured in step mode with maximal curing temperature 155°C.

EFFECT: invention allows obtaining of the composition with high physical, mechanical and dissipative properties.

2 cl, 2 tbl, 6 ex

FIELD: construction.

SUBSTANCE: invention is related to the field of construction, namely to the field of construction works with application of water cement systems, and may be used in construction and repair works with application of concrete or mortar based on water-cement mixture. Method for control of setting and hardening processes in water-cement systems includes mixing of cement and water with previous treatment of water with acoustic oscillations with frequency from 17.5 to 22.5 kHz until level of energy introduced in water is from 3.0 to 40 kW-hr per 1 m3 of water. Invention is developed in dependent clauses.

EFFECT: expansion of facilities for effect at water-cement mixtures in process of their setting and hardening.

8 cl, 9 ex

Masonry mortar // 2363679

FIELD: construction.

SUBSTANCE: invention is related to masonry mortars and may be used for making structures out of bricks, concrete stones and light rock stones. Masonry mortar contains cement, filler, additive in the form of nano-catalysts and water. Filler used is fly ash created in gas treatment systems during sand drying, as nano-catalysts - carbon tubes or fullerenes at the following ratio of components: cement - 400 kg/cub.m; fly ash - 1250 kg/cub.m; nano-catalysts - 0.02 kg/cub.m; water - 340 kg/cub.m.

EFFECT: increased strength and frost resistance of masonry mortar.

1 tbl, 1 ex

FIELD: chemistry.

SUBSTANCE: invention relates to versions of transparent composition, applied, for instance, as under crystal filler, to solid-body device, and to method of transparent composition production. According to first version transparent composition contains, at least, one hardened aromatic epoxy resin, at least, one solvent, filler, and at least, one component selected from group including cycloaliphatic epoxy monomer, aliphatic epoxy monomer, hydroxyaromatic compounds and their combinations and mixtures. Filler represents colloidal silicon dioxide, functionalised with organosiloxane, and has particle size from 20 nm to 100 nm. If necessary, composition contains, at least, one component, selected from group including epoxy resins, acrylate resins, polyimide resins, fluoropolymers, benzocyclobutene resins, bismaleimide triazine resins, fluorinated polyallyl ethers, polyamide resins, polyimidoamide resins, phenolic cresol resins, aromatic polyester resins, resins of polyphenylene ester and polydimethylsiloxane resins. According to second version composition of under crystal filler contains cresol-novolac epoxy resin, at least, one component selected from group including cycloaliphatic epoxy resin, aliphatic epoxy resin, hydroxyaromatic compounds and their mixtures and combinations, at least, one solvent, dispersion of functionalised colloidal silicon dioxide, which has size of solid particles from 50 nm to 100 nm, and, at least, one catalyst. Solid-body device contains crystal, padding and transparent hardened composition of filler, located between crystal and padding. Filler composition contains, at least, one aromatic epoxy resin, dispersion of functionalised colloidal silicon dioxide, at least, one solvent, and, at least, one component selected from group including cycloaliphatic epoxy monomer, aliphatic epoxy monomer, hydroxyaromatic compounds and their combinations and mixtures. Functionalised colloidal silicon dioxide has size of solid particles from 50 nanometers to 100 nanometers. Method of manufacturing transparent under crystal filler composition includes the following stages. First, colloidal silicon dioxide is functionalised. Stable concentrated dispersion of functionalized colloidal silicon dioxide, with solid particle size from 50 nm to 100 nm, containing from 15 wt % to 75 wt % of silicon dioxide, is formed. Aromatic epoxy resin solution is mixed with, at least, one component, selected from group including cycloaliphatic epoxy monomer, aliphatic epoxy monomer, hydroxyl aromatic compounds and their mixtures and combinations, in solvent, with dispersion of colloidal silicon dioxide. Further solvent is removed and filler composition is hardened.

EFFECT: reduction of composition heat expansion coefficient and increase of temperature of its vitrifying.

9 cl, 6 tbl, 9 ex

FIELD: treatment facilities.

SUBSTANCE: invention relates to the method of filtering element production and to a filtering element, namely to a membrane filter. The filtering element production method involves the following procedures: applying membrane layer (1) to carrier body (2), etching of membrane chamber (3) on that side of carrier body (2) which is opposite to membrane layer (1) thus residual layer (5) of carrier body (2) remains, making pinholes (6) in membrane layer (1) to obtain a holed membrane, removing residual layer (5) by etching to release membrane layer (1). The feature of novelty consists in the fact that membrane layer (1) at stage S1 or later is subject to the additional treatment for the mechanical strength improvement in order to make it have a crystalline structure with the mechanical strength greater than that of the basic material of membrane layer (1) and/or a compacted structure as well as to create mainly internal mechanical prestress in it.

EFFECT: filtering element with high throughput capacity remains mechanically stable and withstands pressure loads including pressure fluctuations during its long service life.

31 cl, 5 dwg

FIELD: construction.

SUBSTANCE: invention is related to the field of membrane multilayer materials that may be used in construction. Multilayer material is suggested, comprising external screening layer from metal foil and fibrous packing material having volume density of 120-150 kg/m3 arranged of silica-alumina or glass fiber and coated on both sides with protective coating from microperforated nonwoven polypropylene or from glass tissue at surface density of coating of 50-350 g/m2.

EFFECT: material has reduced deformability and reduced heat emission.

6 cl, 1 tbl, 1 dwg

FIELD: nanotechnologies.

SUBSTANCE: invention is related to the field of membrane technology and nanotechnology. Selective nanofilter contains substrate with pores in the form of through holes on the whole surface, and pores are directed along substrate thickness, and active layer, at that substrate thickness is more than active layer thickness. Substrate is made with pore size of 50-100 nm, and active layer represents thin 100-150 nm-thick pore-free film of metal with high selective gas permeability, which is fixed to substrate with pore covering in the latter. Method of manufacture includes preparation of substrate, application of foil layer with applied metal film with selective gas permeability, their welding and foil removal.

EFFECT: invention provides for guaranteed throughput capacity, high strength and reliability.

4 cl, 5 dwg

FIELD: chemistry.

SUBSTANCE: present invention pertains to membrane technology. Proposal is given of metakaolinite Al2Si2O7 with high open porosity of over 55%, with bimodal distribution of pores on size and over 14% shrinkage potential, coated with refractory oxides, and meant for making multilayered ceramic membranes with selective permeability to oxygen. The invention can be used in catalytic membrane reactors, solid fuel oxide cells and oxygen separators. The substrate is obtained from suspension on a base of selected white-burning kaolins and clays with microcrystalline cellulose additives. The method involves burning the prepared and formed suspension, subsequent leaching in diluted acids and saturation with precursors of refractory oxides, particularly Lu2O3.

EFFECT: obtaining an asymmetric substrate, with little mismatch in shrinkage during sintering and with better chemical compatibility with ceramics.

12 cl, 4 dwg, 3 tbl, 13 ex

FIELD: chemistry.

SUBSTANCE: present invention can be used in the processes of separating gas mixtures, containing carbon dioxide gas and non-oxygen systems, such as hydrogen, inferior hydrocarbons, nitrogen, methane, ethylene, acetylene etc. The composite material for separating gases has a layer of porous substrate, with porosity not less than 30% and a selective layer made from a foil of foamed graphite with a nitrate history, put on the substrate.

EFFECT: high selective ability of the membrane with high flow output of hydrocarbons and hydrogen.

7 cl, 2 dwg, 3 tbl, 1 ex

FIELD: chemistry.

SUBSTANCE: proposed gas-permeable membrane from inorganic material consists of a porous substrate, made from graphite-like boron nitride, obtained during self-propagating high-temperature synthesis, and a selective layer based on mixed phosphorous and titanium oxides with general formula P0.03Ti0.97O2 or based on mixed oxides and nitrides with general formula Al Si N3O3C3P.

EFFECT: membrane has nano-structure properties with anisotropic effect, with non-symmetric gas transfer properties.

2 dwg

FIELD: motors and pumps.

SUBSTANCE: hydrocarbon material and dispersed catalyst are supplied to reaction chamber through the nozzle 3. Reaction chamber is formed by the central pipe 1 and the second to reactor axis pipe 2, which is made of metal nanopowders in the form of membrane permeable for hydrogen. Nozzles 6 and 7 are fixed to the external pipe 5 to supply blow-down gas and discharge hydrogen. Hydrocarbon material is supplied through the nozzle 4. Tubular-type membrane spit-flow reactor is equipped with swirl vanes for reaction mass. They are installed in reaction chamber. The reactor is also provided with pressure sensors, reagent and inlet and outlet product flow meters and thermocouple 8.

EFFECT: improved design of tubular-type reactor to perform highly endothermic gas-phase processes, increase initial raw material conversion and selectivity by olefins.

1 dwg

FIELD: technological processes.

SUBSTANCE: onto solid acetate substrate extruded on supporting copper mesh, metal layer is sputtered, above which layer of material is sputtered with lower coefficient of sputtering, acetate substrate is removed, and ion etching of prepared double-layer film is carried out until top layer is removed, and nano-openings are created in metal layer. As a result, metal membrane is produced with average radius of openings of 28.98 nm and density of openings of -23.6-106 1/mm3.

EFFECT: production of nanosize metal membranes with openings from 5 to 100 nm.

7 cl, 3 dwg

FIELD: technological processes; chemistry.

SUBSTANCE: method includes preparation of charge for creation of microcellular wafer, molding and sintering of wafer, application of membrane layer and further annealing. As wafer, microporous cordierite ceramics is used with pore size of 10 micrometer. Membrane layer is formed with deposition of polymer membrane suspension of nanocrystal powder of aluminium oxide onto wafer in ash of oxynitrate or aluminium oxychloride with further annealing at the temperature of 1200-1300°C for removal of polymer and layer sintering.

EFFECT: fire-resistant composite membrane with working temperatures that exceed 1000°C.

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

FIELD: chemistry.

SUBSTANCE: method of aluminium porous membranes production involves aluminium foil polishing, anodic oxidation, pore bottom opening at temperature 40-50°C in mixed concentrated fluorohydrogen, nitric and acetic acids in ratio as follows, volume percents fluorohydrogen acid : nitric acid : acetic acid as (2.5-3.5):(1.5-2.5):(4.5-5.5) and pore canal cleanup.

EFFECT: uniform pore opening without destructing work structure bases.

2 cl, 4 dwg

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