RU2351389C1 - Selective nanofilter and method for its manufacture - Google Patents

Abstract

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

Description

The invention relates to the field of nanotechnology and can be used to create chemical nanofilters, which are membranes mounted on a frame, providing mechanical strength of the membrane as a nanoporous functional element. In particular, the invention contemplates the construction of a selective nanofilter based on a metal film and a nanoporous membrane having a high selective gas permeability of metals (e.g., palladium or nickel for hydrogen).

A device is known that represents a mechanically strong system of a porous membrane - a porous substrate (US No. 7108813, B29C 65/00, B01D 39/00, B44C 1/22, publ. 09/19/2006).

The disadvantage of this two-layer membrane is that while ensuring the strength of the system as a whole, it has a throughput equal to the throughput of the pores in the substrate.

Known devices that are two-layer porous systems with different porosities (US No. 46666668, A61M 1/14, publ. 05/19/1987, or US No. 5114803, Н01М 8/10, publ. 05/19/1992, or US No. 5308712, Н01М 8 / 10, published on 05/03/1994).

However, obtaining such a system is a complex and time-consuming process that does not provide a high percentage of the quality yield of finished products with stable reliability properties and high throughput function.

A device is known that represents a system that includes a thin metal film deposited, in particular, by ion-atom sputtering of a metal on a porous substrate (US No. 2006/068253, H01M 8/10, 2/14, publ. 30.03.2006).

The disadvantage of this solution is that the ratio of the film thickness to the pore size of the membrane is such that the sprayed metal film-membrane significantly reduces the transmittance of the membrane. In addition, the use of the method of ion-atom deposition of metal does not allow one to obtain porosity equal to the natural gas permeability of metal films as applied to hydrogen atoms or other gases. In addition, such membranes are distinguished by sufficiently large dimensions and poor operational reliability.

This decision was made as a prototype for the claimed device.

A method for manufacturing a nanofilter is known from the same source. Therefore, this decision was also made as a prototype for the claimed method.

The present invention is aimed at solving the technical problem of creating a simple and reliable substrate-membrane system that provides guaranteed throughput of the gas component from the gaseous medium and maximum pressure differential strength.

The technical result obtained in this case is to improve operational characteristics, the efficiency of the throughput function for gases such as hydrogen, and the reliability and durability of the work.

The specified technical result for the device is achieved in that in a selective nanofilter containing a substrate made over the entire surface with pores in the form of through holes directed along the thickness of the substrate, and the active layer, while the thickness of the substrate is greater than the thickness of the active layer, the substrate is made with pore size 50-100 nm, and the active layer is a thin 100-150 nm thick non-porous metal film with high selective gas permeability, attached to the substrate with overlapping pores of the latter.

The specified technical result for the method is achieved in that the method of manufacturing a selective nanofilter is characterized by the following list of operations:

- a metal film with a high selective gas permeability is applied to a foil of an auxiliary metal by ion-atom deposition by a predetermined thickness to obtain a solid metal film with no structural porosity,

- on the surface of one side of the substrate with pores by the method of ion-atom deposition, an adhesive layer of a functional metal is applied,

- a foil with a film of metal with high selective gas permeability is placed on the substrate and the side with the film of metal with high selective gas permeability is pressed to the layer of functional metal on the substrate,

- then, first, a metal film with high selective gas permeability is welded by diffusion welding to the substrate,

- and then the foil of the auxiliary material is removed by its chemical dissolution.

These features are significant and are interconnected with the formation of a stable set of essential features sufficient to obtain the desired technical result.

The present invention is illustrated by a specific example of execution, which, however, is not the only possible, but clearly demonstrates the possibility of achieving the desired technical result.

Figure 1 shows a sectional view of a porous substrate;

figure 2 is the same as in figure 1, with the applied adhesive layer of functional metal;

figure 3 - foil of auxiliary metal with a film of metal with high selective gas permeability;

figure 4 - fixing the metal film on the substrate;

5 is a demonstration of the process of removing the foil by the electrolytic method.

According to the present invention, a novel design of a selective nanofilter used to separate, for example, hydrogen from a gas mixture is contemplated. The selective nanofilter is made two-layer with layers of significantly different porosity, the first of which is functional (gas components are separated on it), and the second provides mechanical strength and is the framework for the functional layer (substrate).

The selective nanofilter contains a substrate 1 (Fig. 1), made over the entire surface with pores 2 in the form of through holes directed along the thickness of the substrate. An active layer is fixed on the surface of one side of the substrate, while the thickness of the substrate is greater than the thickness of the active layer. The substrate is made with a pore size of 50-100 nm, and the active layer is a thin 100-150 nm thick non-porous metal film 3 with high selective gas permeability, attached to the substrate with overlapping pores of the latter. In this case, in relation to the process of separation of hydrogen atoms, the film of the active layer is made of palladium or nickel to pass hydrogen atoms. Naturally, for another gas, the choice of metal is determined by the degree of its gas permeability in the state of a thin film.

Since the substrate can be made, for example, of ceramic material, there are no conditions for the formation of bonds between the substrate and the metal film. The claimed solution uses the intermediate layer method, which, on the one hand, has very high adhesion, for example, with ceramics, and on the other hand, with the metal of the active layer. Such a diffusion sprayed layer is a bond between the metal layer and the ceramic. Instead of ceramics, other materials can be used, including metals. In this regard, the connection of the plate (membrane) with the substrate is durable and can be controlled by the result of execution.

The small film thickness allows to obtain high permeability at low temperatures. Typically, the thickness of the metal is determined from the strength conditions (for example, when a pressure drop of 1 atm is introduced into a vacuum), and therefore temperatures of 100-400 ° C are required for effective operation. It is impossible to use a free film of small thickness, therefore it is proposed to use a substrate as a base, and the small size of its pores will provide sufficient film strength and its indestructibility upon external loading during the separation process.

This selective nanofilter is made as follows.

On the foil 4 of the auxiliary metal (figure 3) by the method of ion-atom deposition, a film 3 of the desired metal with a given thickness is applied. For this, a metal with high selective gas permeability is selected for a given type of gas. Such a deposition method makes it possible to obtain a solid metal film, i.e. not having structural porosity. The technology for producing such films is described in the following works:

- Waldner V.O., Zabolotny V.T. Electrochemical studies of the defectiveness of coatings obtained by ion-atom deposition. // Physics and chemistry Materials, 2004, No. 1, pp. 35-37.

- Waldner V.O., Zabolotny V.T., Ivanov V.I., Starostin E.E. Diffusion welding with preliminary ion-atom deposition // Promising materials, 1997, No. 1, pp. 86-88.

On the surface of one side of the substrate 1 (figure 2) with a given porosity (pore size) by the method of ion-atom deposition, an adhesive layer 5 of a functional metal with a thickness of 10-50 nm is applied (so as not to change the pore size of the membrane). The question of using the ion-atom deposition method to obtain high precision nanorelief can be found on the website of the Training Center online on the Internet at: http: //www.eks.fel. mirea.ni/PhCMmdex/PhysCMScience/PhysCMEdSc/MishinaSit e / Foto-structs.html (05.04.2006), section "Nanotechnology for Ultra-High Speed Telecommunications. Photo-structures ”and the section“ Materials and Methods of Nanotechnology ”.

Then, the foil 4 with the film 3 is placed on the substrate 1 (Fig. 4), its side with a film of metal with high selective gas permeability is pressed to the functional metal layer 5 on the substrate, and it is welded by diffusion welding (i.e., holding in a pressed state at a temperature of 300 -500 ° C). Then the foil of the auxiliary material is removed by its chemical dissolution (it is chemically dissolved, for example, using the electrolytic method (figure 5). We obtain a substrate with a welded film of a functional metal.

The present invention is industrially applicable, can be manufactured using fairly well-established technologies. In this case, it is possible to manufacture filters of large sizes, since its strength is determined by the mechanical properties of the substrate.

Claims (4)

1. Selective nanofilter containing a substrate made over the entire surface with pores in the form of through holes directed along the thickness of the substrate, and an active layer, the thickness of the substrate being greater than the thickness of the active layer, characterized in that the substrate is made with a pore size of 50-100 nm and the active layer is a thin 100-150 nm thick non-porous metal film with high selective gas permeability, attached to the substrate with overlapping pores of the latter. 2. The selective nanofilter according to claim 1, characterized in that the film of the active layer is made of palladium or nickel to pass hydrogen atoms. 3. A method of manufacturing a selective nanofilter, characterized in that a metal film with a high selective gas permeability is applied to a foil of an auxiliary metal by ion-atom deposition to obtain a predetermined thickness to obtain a film of continuous metal not having structural porosity, on the surface of one side of the substrate with pores by the method An ion-atom deposition is applied to an adhesive layer of a functional metal, and then a foil with a metal film with high selective gas permeability is placed on the sub and press the side with the metal film with high selective gas permeability to the functional metal layer on the substrate, after which the metal film with high selective gas permeability is first welded by diffusion welding to the substrate, and then the auxiliary material foil is removed by chemical dissolution. 4. The method according to claim 3, characterized in that the welding of a metal film with high selective gas permeability to the substrate is carried out by holding in a pressed state at a temperature of 300-500 ° C.

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