JPH02250905A - Porous body and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a porous body that is applied to, for example, nickel electrodes, separators, etc. of nickel-cadmium storage batteries, and a method for manufacturing the same.

Conventional technology Conventionally, sintered plates have been used for the nickel electrodes of nickel-cadmium storage batteries, and these sintered plates deposit active materials into the micropores of a microporous substrate made by sintering nickel powder. It is used for both positive and negative electrode plates. The current collector base of the sintered board is made of a 20 to 30 mesh nickel mesh or nickel plated with a thickness of about 0.0mm.
A perforated steel plate with 1 dew is used. Nickel carbonyl powder is usually used as the metal powder for sintering, and has an apparent density of 0.6 to 0*89 cm and an average particle size of 3 to 6 μm.
It is irregularly shaped powder of m. Furthermore, as a manufacturing method for the electrode plate, a paste of nickel powder made with water and a binder is coated on both sides of the current collector substrate to a certain thickness, and after drying, it is heated to about 10oO℃ in a reducing atmosphere. to create a microporous substrate. Furthermore, the method for filling the positive electrode active material involves immersing the microporous substrate in a solution containing nickel nitrate as a main component, drying it, and then immersing it in an aqueous sodium hydroxide solution to hydrate the nickel nitrate in the micropores of the substrate. It is converted into nickel, then washed with water and dried. This operation is repeated 6 to 6 times to fill the required amount of active material. In addition, there is a method of electrolyzing a nickel nitrate-impregnated substrate in an aqueous sodium hydroxide solution, or a method of thermally decomposing the substrate after impregnation. The filling method for the negative electrode active material is the same as that for the positive electrode active material, except that cadmium nitrate is used instead of nickel nitrate.

Next, in conventional nickel-cadmium storage batteries, a separator is inserted to prevent the positive and negative electrode plates from coming into contact with each other, and this uses a synthetic resin bottle, rod, or perforated plate. In the case of a sintered electrode plate, cloth or nonwoven fabric made of synthetic resin such as nylon or polypropylene, or a material overlaid with a microporous membrane such as Shichironon, etc., and a porous plate made of synthetic resin are used.

Problems to be Solved by the Invention In the positive electrode plate and negative electrode plate of these conventional nickel-cadmium storage batteries, the strength and specific surface area of the microporous substrate filled with the positive electrode active material and negative electrode active material, respectively, are still insufficient, and the porous material The challenge is to increase the strength and specific surface area of This increases the lifespan of the porous material.

The challenge is to increase electrodeposition efficiency. Furthermore, it is desirable that the separators of conventional nickel-cadmium storage batteries have high permeability to gases generated during charging and high diffusivity of electrolyte during charging and discharging. The problem was similar to that of porous materials.

The present invention solves the above-mentioned conventional problems.

Means to solve problems As a means to avoid this, the present invention provides a metal 1 alloy.

Zinc oxide whiskers blended into a holding material such as synthetic resin, glass, or ceramics are heat-treated and acid-treated.

Pores or continuous pores are formed in the holding material by sublimation or elution by either alkali treatment.

Note that the length of the zinc oxide whisker from the base to the tip is 3 μm or more. Further, the zinc oxide whisker has a core and needle-like crystal parts extending from the core in different axial directions. Furthermore, the number of axes of the needle-like crystal part of the zinc oxide whisker is four.

Next, the manufacturing method of the present invention includes a first step of blending zinc oxide whiskers into a holding material such as metal 2 alloy 1 synthetic resin, glass, ceramic, etc., and after the first step, heat-treating the zinc oxide whiskers. It is characterized by having a second step of subliming or dissolving by either acid treatment or alkali treatment to form pores or continuous pores.

Note that the length of the zinc oxide whisker from the base to the tip is 3 μm or more. Further, the zinc oxide whisker has a core and needle-like crystal parts extending from the core in different axial directions. Furthermore, the number of axes of the needle-like crystal part of the zinc oxide whisker is four.

Function The zinc oxide whisker used in the present invention has a unique tetrapod-like three-dimensional structure, so it has a metal 1 alloy 2
When incorporated into a holding material such as synthetic resin, glass, or ceramic, the needle-like crystal parts of zinc oxide whiskers bring about extremely efficient association with the needle-like crystal parts of other zinc oxide whiskers. Therefore, even if it is mixed with fine particles or short fibers of any holding material such as metal 9 alloy 9 synthetic resin, glass, ceramic, etc., it is possible to form a stable continuous crosslink with a small amount of blending. This has a high probability of creating continuous crosslinks compared to simple linear fibers or flake fillers, which have been considered advantageous for increasing the specific surface area of pores in conventional porous bodies. Tetrabod-shaped zinc oxide whiskers themselves have the property of subliming at a melting point of 180 C) and dissolving in acid (H2SO4)/fluorkali (NH40H), so they can be sublimed or eluted by heat treatment, acid treatment, or alkali treatment. I can do it. Therefore, metal 1 alloy 9 fine particles of any holding material such as synthetic resin, glass, ceramics, etc.

In addition to the pores between short fibers, continuous cross-linked pores formed by sublimation or elution of zinc oxide whiskers are added, and the specific surface area of the pores of the entire porous body is significantly increased by a small amount of zinc oxide whiskers. It is. Moreover, since the communicating cross-linked pores are formed with a small amount of zinc oxide whiskers, the strength of the porous body itself is sufficiently maintained by the contact bonding between the fine particles and short fibers of the holding material.

In addition, the present invention includes a first step of blending zinc oxide whiskers into a retaining material and molding, and after the first step, the zinc oxide whiskers are sublimated or eluted by any one of heat treatment, acid treatment, and alkali treatment. Continuous processing is possible by including the second step of forming pores. In particular, when firing in the first step, if it is heated above the melting point of zinc oxide whiskers of 1,800°C, the process will proceed directly to the second step, and the second step may even be included in the first step. be. In the second step, zinc oxide whiskers are eluted by acid treatment and alkali treatment, which is an extension of the first step, and the residual temperature promotes the elution. In this way, if the melting point of the holding material is lower than the melting point of zinc oxide whiskers, 18°C, acid treatment is required.

Alkaline treatment is effective.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 2 of the drawings.

Reference numeral 1 denotes a zinc oxide whisker (tetrabod-like zinc oxide whisker) having a core and needle-shaped crystal parts extending from the core in multiple axial directions, and this tetrabod-like zinc oxide whisker 1 is a metal having an oxide coating on its surface. It can be produced by heat treating zinc powder in an atmosphere containing oxygen. The obtained tetrabod-like zinc oxide whiskers 1 have an apparent bulk specific gravity of 0.02 to 0.1, and can be produced in an extremely large scale with a high yield of 70 wt% or more.

FIG. 1 is an electron micrograph of the tetrabod-like zinc oxide whisker 1 showing an example of the product, and shows the shape of the tetrabod-like zinc oxide whisker.

Dimensional features are clearly recognized. Further, the acicular crystal portions of the tetrabod-like zinc oxide whiskers are 3-axis, 2-axis, and 1-axis.
In some cases, crystals with four axes are mixed in, but this is due to a broken part of a crystal that originally had four axes. An X-ray diffraction diagram of this tetrabod-like zinc oxide whisker showed all ZnO peaks, and electron diffraction results also showed single crystallinity with few dislocations and lattice defects. Furthermore, the content of impurities was low, and as a result of atomic absorption spectrometry, ZnO was found to be 99.98%.

Note that simple needle-shaped zinc oxide whiskers can also be produced, for example, metallic zinc powder can be fired simultaneously with charcoal or the like to be produced on the wall of a crucible or the like.

FIG. 2 is an explanatory diagram of a fired body in which a powdered tetrabod-like zinc oxide whisker 1 is blended with a nickel powder 2.

Then, the tetrabod-like zinc oxide whiskers 1 easily aggregate to form a three-dimensional mesh structure with appropriate voids.
In addition, the acicular crystal parts extend between the nickel powders 2 and are randomly oriented to form a communicating bridge between the adjoining zinc oxide whiskers 1. Therefore, the first
After the process, when immersed in sulfuric acid (H2S04), the zinc oxide whiskers 1 are eluted, the continuous crosslinks also become pores, and the specific surface area of the pores increases significantly. That is, the specific surface area of the pores 3 and 4 of the porous body is significantly increased by the pores 3 between the nickel powders 2 and the continuous bridge-type pores 4 formed by the elution of the zinc oxide whiskers 1. Therefore, in order to use this porous material as the positive electrode of the nickel electrode of a nickel-cadmium storage battery, it is immersed in a solution containing nickel nitrate as a main component, dried, and then hydrated. The nickel nitrate in the pores is changed to nickel hydroxide, and then the process of washing with water and drying is repeated 6 to 6 times.
It is filled with the required amount of active material.

The nickel positive electrode of the nickel-cadmium storage battery formed in this manner has a large specific surface area of multiple pores, significantly increases electrodeposition efficiency, and enables high-performance charging and discharging.

Effect of the invention As described above, according to the present invention, metal 1 alloy.

Zinc oxide whiskers are blended into a holding material such as synthetic resin, glass, or ceramics, and then molded into them. Heat treatment, acid treatment,
In addition to the pores formed between fine particles, short fibers, etc. of the retaining material, zinc oxide whiskers are dissolved or eluted by either alkali treatment and have many pores formed in the retaining material. The specific surface area due to the continuous crosslinked pores formed by elution increases significantly, and high performance is realized as a porous body. For this purpose, bearings and other oil-containing mechanical parts, filters, throttle valves, contacts, electrodes, lamp wicks.

When applied to components such as backings and vibration isolators, it has excellent effects of reducing size and weight, and further improving workability, weather resistance, and durability.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph showing a zinc oxide whisker crystal structure used in an example of the present invention, and FIG. 2 is an explanatory diagram of a sintered body manufactured in the first step of the manufacturing method of the present invention. 1...Tetrabod-shaped zinc oxide whiskers, 2
...Nickel powder, 3 ... Pore, 4.
・・・・・・Communication hole.

Claims (10)

[Claims] (1) Zinc oxide whiskers blended into any holding material such as metal, alloy, synthetic resin, glass, ceramic, etc. are heat treated,
A porous body in which pores or continuous pores are formed in the holding material by sublimation or elution by either acid treatment or alkali treatment. (2) The porous body according to claim 1, wherein the zinc oxide whisker has a length from the base to the tip of 3 μm or more. (3) The porous body according to claim 1 or 2, wherein the zinc oxide whisker has a core portion and needle-like crystal portions extending in different axial directions from the core portion. (4) The porous body according to claim 3, wherein the number of axes of the needle-like crystal part of the zinc oxide whisker is 4. (5) The porous body according to claim 1, wherein the holding material is a metal for an electrode of a nickel-cadmium storage battery or a synthetic resin for a separator. (6) a first step of blending zinc oxide whiskers into any holding material such as metal, alloy, synthetic resin, glass, ceramic, etc.; and a heat treatment of the zinc oxide whiskers after the first step;
A method for producing a porous body, comprising a second step of sublimating or dissolving by either acid treatment or alkali treatment to form pores or continuous pores. (7) The method for producing a porous body according to claim 6, wherein the zinc oxide whisker has a length from the base to the tip of 3 μm or more. (8) Claim 6 or 7, wherein the zinc oxide whisker comprises a core and acicular crystal parts extending in different axial directions from the core.
A method for manufacturing the porous body described above. (9) The method for producing a porous body according to claim 8, wherein the number of axes of the needle-like crystal part of the zinc oxide whisker is 4. (10) The method for producing a porous body according to claim 6, wherein the holding material is a metal for an electrode of a nickel-cadmium storage battery or a synthetic resin for a separator.