CN100444939C - Nano sieve and its manufacturing method - Google Patents

Abstract

The present invention provides a nanometer screen mesh which comprises a film, a chassis for holding the film fixedly, and a side wall formed around the chassis, wherein the film comprises an aluminum oxide film with nanometer filtration hole structures arranged orderly in a certain direction; the diameters of nanometer filtration holes are from 5 to 400 nm. In addition, the present invention also provides a manufacture method of the nanometer screen mesh. The film provided by the nanometer screen mesh of the present invention has nanometer filtration hole structures arranged orderly in a direction, can enhance the effective utilization area of the films, and enhances the screen efficiency of the nanometer screen mesh. The nanometer screen mesh can be widely applied to the filtration and screening of a variety of powder bodies in nanometer levels.

Description

Nano sieve and its manufacturing method

【Technical field】

The invention relates to a screening device, in particular to a nanoscale screen and a manufacturing method thereof.

【Background technique】

At present, the production and application of nanotechnology are becoming more and more extensive, and in the application of many nanopowders, the consistency of powder particle size is often required. Commonly used methods for manufacturing nano-powders include chemical reduction method, vapor deposition method, sol-gel method, etc. Due to the influence of reaction conditions and the difficulty of controlling the reaction process, these methods cannot obtain nano-powders with a single particle size. Therefore, it is necessary to resort to In other methods, for example, by screening the nano-powder product prepared by the above-mentioned method, as long as the mesh diameter of the sieve is consistent, the nano-powder with uniform particle size can be screened.

Please refer to Figure 1, which is a schematic diagram of a traditional screen structure. The screen 1 includes a chassis 2 and a side wall 3 extending upward from the periphery of the chassis 2 . The bottom pan 2 includes a grid-shaped sieve pan 4 in the center and a peripheral pan 5 joined to the periphery of the sieve pan 4 . The traditional sieve 1 adopts a grid-shaped sieve plate 4, which can only screen macroscopic powder particles, but for nanoscale powders, the sieve 1 is no longer suitable, and some sieves with nanoscale porous structure materials must be used.

Chinese Patent No. 02110938.9 published on February 28, 2002 discloses a method for synthesizing barium-permanganite-type molecular sieves using manganese nodules and cobalt-rich crusts as raw materials. Use fresh manganese nodules or cobalt-rich crusts to react with oxidants to increase the oxidation state of manganese in the raw material; then implant magnesium ions into the manganese mineral lattice to make it play the role of template agent; after high-temperature hydrothermal reaction, each of the raw materials All kinds of iron-manganese oxides and hydroxides are transformed into barium calcium manganese-type molecular sieves. The molecular sieve obtained by the method has a 3×3 tunnel hole structure with a sieve hole diameter of about 0.69 nanometers. The nanosieve membrane has a small pore size and can be widely used in chemical catalysis, environmental engineering, high-performance batteries and other fields. However, its pore size is too small and too single to meet the requirements of nanoscale screens with different pore sizes.

Chinese patent application No. 01109223.8 published on February 28, 2001 discloses a nanosieve membrane, which includes a ceramic material support and a γ-MnO ₂ nanosieve membrane sintered on the support. The ceramic support body has micron-scale filter holes, the average pore size of the sieve membrane is 2-3nm, the primary particle size of γ- _MnO2 is 20-30nm, the aggregate particle size is 100-500nm, and the thickness of the film layer is 10-15 microns. The reactor uses a ceramic support to divide the γ-MnO ₂ nano-sieve membrane into two spaces. One side of the coated γ-MnO ₂ nano-sieve membrane is a catalytic reaction zone, and the other side is an open negative pressure zone. The nano-sieve membrane has a small pore size, which is beneficial to supporting catalyst particles and improving catalytic performance. However, its pores are formed by molecular intervals, so the pore area is relatively small relative to the area of the entire nanosieve membrane, that is, the opening rate is small, and its effective area cannot be fully utilized, resulting in a decrease in the screening rate of the nanosieve membrane, and thus the filtration efficiency. low.

In view of this, it is necessary to provide a nano sieve with high effective use area and high screening efficiency and its manufacturing method.

【Content of invention】

In order to overcome the disadvantages of low effective use area and low screening efficiency of nano-sieves in the prior art, the object of the present invention is to provide a nano-sieve with high effective use area and high screening efficiency.

Another object of the present invention is to provide a method for manufacturing the aforementioned nano-sieve.

In order to achieve the above-mentioned first purpose, the present invention provides a nano-sieve, which includes a film and a chassis for holding the film, the periphery of the chassis is formed with side walls; Alumina film with porous structure.

Moreover, the nanofilter pores are parallel to each other and substantially perpendicular to the surface of the film.

The nanometer filter holes are arranged in a hexagonal distribution.

The pore size range of the nanometer filter is 5 nm to 400 nm.

The opening ratio of the nanometer filter is above 10 ¹¹ /cm ² .

The thickness of the film ranges from 10 nanometers to 100 nanometers.

In order to achieve the above-mentioned second purpose, the present invention provides a method for manufacturing the above-mentioned nano-sieve, which includes the following steps:

providing an aluminum substrate;

Form an aluminum oxide film with a directional and regularly arranged nano-pore structure on the surface of the aluminum substrate;

Remove the aluminum substrate to obtain a self-supporting aluminum oxide film;

The membrane is held in the center of a chassis with a peripheral sidewall to form a nanosieve.

Wherein, the film forming method adopts anodic oxidation method.

The electrolyte of the anodic oxidation method adopts sulfuric acid, oxalic acid, phosphoric acid, chromic acid or mixed acids thereof.

The aluminum substrate is removed by etching with a mixed solution whose components and mass fractions correspond to: phosphoric acid: acetic acid: nitric acid: water = 72%: 15%: 8%: 5%.

Compared with the nano-sieve in the prior art, the nano-sieve provided by the present invention adopts an aluminum oxide film with a nano-pore structure, and the film can control its pore spacing by adjusting the voltage to obtain dense distribution and a certain direction. The nano-filter pore structure is regularly arranged, which can increase the effective use area of the membrane, speed up the screening rate of the nano-screen, and thus improve its screening efficiency.

【Description of drawings】

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of a traditional screen structure.

Fig. 2 is a schematic diagram of the nano-sieve structure of the present invention.

Fig. 3 is an enlarged schematic view of the surface structure of the film in the nanosieve of the present invention.

Fig. 4 is a schematic diagram of the manufacturing process of the nanosieve of the present invention.

【Detailed ways】

Referring to FIG. 2 , the nanosieve 10 provided by the present invention includes a film 11 , a base 12 for holding the film, and a sidewall 13 formed around the base 12 . Wherein, the chassis 12 is a base with a hollow center, so that the film 11 can be held at the center of the chassis 12 . The side wall 13 has a certain height and can hold a certain amount of powder to be screened (not shown). The membrane 11 is a porous aluminum oxide membrane, and nanometer filter holes 14 regularly arranged in a certain direction are formed in its thickness direction.

Please refer to FIG. 3 , which is an enlarged schematic diagram of the surface structure of the film 11 in the nanosieve 10 . Thin film 11 is made up of many unit cells 15 with hexahedron shape (as shown by dotted line in the figure), and each unit cell 15 center contains a cylindrical hole shape nano filter hole 14, and each unit cell 15 surrounds by hexagon There are six identical unit cells arranged therein, that is, the connecting line between the centers of the filter holes contained in each unit cell is a hexagon (as shown by the solid line in the figure). Wherein, the nanofilter hole 14 is a cylindrical through hole penetrating through the film 11 and perpendicular to its surface. The nanofilter holes 14 are parallel to each other, have the same size, and are arranged in a hexagonal distribution. The structure of the above-mentioned nano-pores 14 can be obtained by anodic oxidation, and by controlling the preparation conditions of anodic oxidation, such as adjusting the oxidation voltage, time and other preparation conditions, nano-pores 14 of various sizes can be obtained, usually in the range of 5 nanometers to 5 nanometers. Within the range of 400 nanometers, the depth is about 10 nanometers to 100 nanometers, which is equivalent to the thickness of the membrane 11 , and the opening ratio of the nanofilter holes 14 is at least 10 ¹¹ /cm ² .

The nano-sieve 10 provided by the present invention can pre-select the nano-filter holes 14 of the same size as the powder particles to be screened, so that the nanoparticles with uniform particle size can be screened out. When screening, it can be used together with other vibrating devices such as ultrasonic oscillators, and if necessary, the powder can be screened by flushing and filtering. Since the nano-filter holes 14 are densely distributed and regularly arranged in a certain direction, the effective area of the membrane 11 is increased, and the screening rate of the nano-sieve 10 is accelerated, and finally the screening efficiency of the nano-sieve 10 is improved.

Please refer to FIG. 4, which is a schematic diagram of the manufacturing process of the nano-sieve 10, which includes the following steps:

(1) Provide an aluminum substrate 16: select a relatively high-purity flat aluminum substrate 16 (aluminum alloy can also be used), and pretreat it, such as heat treatment, surface degreasing treatment and electrochemical polishing treatment, so that The surface of the pre-formed film becomes a flat and smooth smooth surface 17, which is convenient for anodic oxidation treatment.

(2) On the surface of the aluminum substrate 16, an aluminum oxide film 11 with a nano-filter hole 14 structure arranged regularly in direction is formed: the aluminum substrate 16 is treated in an acid electrolyte such as sulfuric acid, oxalic acid, phosphoric acid, chromic acid or its mixed acids. Anodizing is performed to smooth the surface 17 to form a porous aluminum oxide film 11 . In order to obtain uniform and evenly distributed nanofiltration pores 14, the above-mentioned anodizing step can be repeated after the film 11 is removed, and a second anodization can be performed to finally obtain a film 11 with regularly arranged nanofiltration pores 14 structure, and the nanofiltration The holes 14 are parallel to each other and extend from one surface of the film to the other. Lu Mei et al pointed out in "Journal of Lanzhou University" (Natural Science Edition), 2002, 38 (4), 47-54, "Preparation and Characterization of Porous Aluminum Oxide Membrane", that the pore spacing and The pore size increases with the increase of the applied oxidation voltage. Therefore, the relationship between the voltage and the pore spacing can be used to control the pore spacing by adjusting the voltage to adjust the distribution of the nanofiltration pores 14, thereby obtaining a thin film 11 with densely distributed nanofiltration pores 14, so that the thin film 11 has a higher Effective use of area. At the same time, by controlling the anodizing conditions, such as electrolyte type, oxidation voltage, temperature, time and current density, etc., nano-filter pores 14 with different pore sizes can be obtained, usually between 5 nm and 400 nm. For example, when sulfuric acid is used as the electrolyte, the pore diameter of the obtained nanofilter 14 is relatively small, usually about 20 nanometers; and when oxalic acid is used as the electrolyte, the pore diameter of the obtained nanofilter 14 is relatively large, usually above 40 nanometers.

(3) Remove the aluminum substrate 16 to obtain a self-supporting aluminum oxide film 11: the method for removing the aluminum substrate 16 can be an etching method, and a mixed acid is used as an etching solution. The mass fraction corresponds to: phosphoric acid: acetic acid: nitric acid: water = 72%: 15%: 8%: 5%. After the aluminum substrate 16 is removed by etching, a self-supporting aluminum oxide film 11 remains, and the thickness of the film 11 ranges from 10 nanometers to 100 nanometers. If it is desired to obtain nanofiltration pores 14 with a sufficiently large pore size, the self-supporting film 11 can also be subjected to pore expansion treatment.

(4) Aluminum oxide film 11 is held in the center of chassis 12 of a peripheral side wall 13 to form a nano-sieve 10: get a chassis 12 of peripheral side wall 13, the center of this chassis 12 is empty, and film 11 can be fixed In the center of the chassis 12, a nano-sieve 10 with nano-sieve holes is formed.

In addition, before the film 11 is used, it can be further subjected to surface treatment or heat treatment to improve its hardness, brittleness resistance and other related properties.

Compared with the existing nano-sieve, the nano-sieve 10 provided by the present invention adopts an aluminum oxide film 11 with a structure of nano-filter holes 14, and the film 11 can control its pore spacing by adjusting the voltage to obtain dense distribution and press The structure of the nano-filter holes 14 arranged regularly in a certain direction can increase the effective use area of the membrane 11 and speed up the screening rate of the nano-screen 10, thereby obtaining higher screening efficiency.

Claims (3)

1. A manufacturing method of nano-sieve, which may further comprise the steps: providing an aluminum substrate; Form an aluminum oxide film with a directional and regularly arranged nano-pore structure on the surface of the aluminum substrate; The components and their mass fractions correspond to: phosphoric acid: acetic acid: nitric acid: water = 72%: 15%: 8%: 5% of the mixed solution to etch and remove the aluminum substrate to obtain a self-supporting aluminum oxide film; The membrane is held in the center of a chassis with a peripheral sidewall to form a nanosieve. 2. The manufacturing method of the nano-sieve according to claim 1, characterized in that: the film forming method adopts an anodic oxidation method. 3. The manufacturing method of nano-screen according to claim 2, characterized in that: the electrolyte of the anodic oxidation method adopts sulfuric acid, oxalic acid, phosphoric acid, chromic acid or mixed acids thereof.

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