JPH0372003A - Pressurized electric conductive metal powder and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture pressurized electric conductive powder having high electric conductivity coated with carbonaceous film or whisker by mixing organic compound containing carbon nitride or nitrogen and transition metal (alloy) powder and heating under inert gas atmosphere. CONSTITUTION:The organic compound containing the carbon nitride or the nitrogen shown with the usual formula: [(C3N3)2NxHy] (2<=x<=4, 0<=y<=8) and the powder of transition metal or alloy thereof are mixed. This mixed powder is heated at 400-1000 deg.C under inert gas atmosphere to obtain the pressurized electric conductive metal powder coated with the film or the whisker containing carbon or nitrogen on surfaces of the transition metal (alloy) particles. By incorporating this metal powder into soft resin or rubber, the pressurized electric conductive material having large range of electric conductivity is manufactured.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a transition metal powder coated with a carbonaceous or nitrogen-containing carbonaceous material, a method for producing the same, and a pressurized conductive material. A transition metal powder coated with a carbonaceous or nitrogen-containing carbonaceous material useful as a conductive material or a pressure-sensitive conductive material such as a pressure-sensitive switch or a conductive paste, and a method for producing the same, and further uses of the above-mentioned powder The present invention relates to a pressurized conductive material.

[Prior art and problems to be solved] Various pressurized conductive materials have been known in the past, in which conductive carbon black or metal particles are mixed with resin, rubber, etc.
Depending on the content of the conductive material, the resistance value can be varied over a considerable range.

Among these, those using carbon black are cheap and lightweight, but have the problem that the conductivity is not very high, while those using metal materials such as Ni can provide high conductivity. However, it is rather expensive and its surface is easily oxidized, which causes the problem that its conductivity decreases over time. Further, even when using conductive powder in which the surface of carbon particles is coated with a metal such as Ni by electroless plating, the surface is easily oxidized and a similar problem occurs.

[Means for Solving the Problem] In order to solve the above problems, the present inventor investigated materials that have oxidation resistance and conductivity, and found that organic materials containing nitrogen such as melamine and metal powder The present invention was achieved by discovering that a powder having excellent conductivity can be produced by reacting with metal powder or by thermally decomposing it on a metal powder using a hydrocarbon such as acetylene.

That is, the present invention provides a structure in which the surface of the transition metal or its alloy particles is a carbonaceous film or film containing carbon or nitrogen.
Pressurized conductive metal powder covered with scar and general formula [(C3N,)YNXHγ] (where 2≦x≦4
．． The above method is characterized in that the carbon nitride or nitrogen-containing organic compound represented by 0≦y≦8) and the transition metal or its alloy powder are mixed and then heated to a temperature of 400 to 1000°C in an inert atmosphere. A method for producing a pressurized conductive metal powder, and a system in which transition metal or alloy powder is present, which is characterized in that a gas containing a hydrocarbon or a nitrogen-containing organic compound is thermally decomposed at 300 to 1000°C. The present invention provides a method for producing the above-mentioned pressurized conductive metal powder, and further provides a pressurized conductive material characterized in that the pressurized conductive metal powder is incorporated into a soft resin or rubber.

First, a carbon nitride or nitrogen-containing organic compound represented by the general formula [(C,N,),NXIIy] (where 2≦x≦4.0≦y≦8) and a transition metal or its alloy powder were mixed. After that, in an inert atmosphere, 400 to 1000
A method for producing metal powder coated with carbonaceous material heated to a temperature of 0.degree. C. will be described in detail.

First, talking about raw materials, any transition metal in a broad sense such as Ni, Fe, Cu, Co, etc. can be used, and various alloys such as SUS can be used as alloys. Ni is preferable in terms of electrical characteristics when used for.

Moreover, the particle size is 1 to 20 μm, preferably 1 to 10 μm, considering the electrical characteristics of the produced coated powder.

Regarding the material to be coated, the general formula [(C3N,,2N
Carbon nitride, represented by 2≦x≦4. It was discovered that carbon nitride can be synthesized by using a compound containing a triazine ring of carbon and nitrogen as a reaction raw material, and as a method for producing carbon nitride,
We have already filed an application [“Carbon nitride and its manufacturing method” (Japanese Patent Application No. 173186/1986)], and subsequently,
An application was also filed for the above-mentioned compound of carbon nitride and alkali metal (Japanese Patent Application No. 1-27240).
The above structure is shown. Examples of nitrogen-containing organic compounds include melamine, urea, and dicyanamide.

After mixing the carbon nitride or nitrogen-containing organic compound and the transition metal or its alloy powder, heating is performed, and the ratio of the compound to be mixed is 1 to 20 g of carbon nitride or nitrogen-containing organic compound to 1 g of metal. Preferably, if it is less than 1g, the coating is insufficient, and if it is more than 20g, the coating is too large and the conductivity will not be high enough when used as a conductive material.The temperature of the nitrogen-containing organic compound is raised to a predetermined temperature. When heating, it is preferable to raise the temperature at a rate of 100°C/sin or more. If the heating rate is lower than 100°C/sin, evaporation and decomposition of organic substances will be difficult to occur on the powder, making it difficult to obtain a coated powder. I can't.

As a means of performing such rapid heating, 400 to 1000℃
Another possible method is to introduce the raw material mixture into a heated container.

On the other hand, there are no such restrictions for carbon nitride.
A temperature increase rate of about 10° C./1 Iin is sufficient.

The temperature in the reaction vessel is 400-1000°C, preferably 5°C.
00 to 800°C, and if the temperature is lower than 400°C,
If the decomposition does not progress sufficiently and the coating is not successful, and the temperature is higher than 100°C, carbonaceous precipitates may not precipitate on the metal powder, but only carbon powder may precipitate, or the metal powders may sinter together. The atmosphere in this case must be an inert atmosphere such as nitrogen, argon, helium, etc. so that the precipitated substance is not oxidized.

Next, in a system where powder of a transition metal or its alloy is present, a gas containing a hydrocarbon or a nitrogen-containing organic compound is
To explain the method for producing metal powder coated with a carbonaceous material that is thermally decomposed at 300 to 1000°C, the raw materials transition metal or its alloy powder and nitrogen-containing organic compound are:
Exactly the same raw materials can be used as in the production method described above. The hydrocarbon used may be any hydrocarbon as long as it can be carried into a heating vessel for thermal decomposition using a carrier gas such as nitrogen, but acetylene, ethylene, propylene, benzene, propane, etc. are preferable. The amount of carrier gas at this time is preferably up to 10 times the molar ratio of the raw material, more preferably 1 to 1.
It is 5 times more.

The decomposition temperature is in the range of 300 to 1000°C, preferably 500 to 800°C. At temperatures lower than 300°C, the decomposition of organic substances does not proceed sufficiently, while at temperatures higher than 1000°C, carbon itself decomposes and precipitates. However, it does not precipitate on the metal powder, and the powders sinter together to form a lump.

As described above, transition metal powder coated with carbonaceous material is produced by the two types of production methods described above, but carbon nitride [
(CJN?>2NxHy] (However, 2≦x≦4・
0≦y≦8) or a nitrogen-containing organic compound as a raw material, the substance precipitated on the metal has the general formula C,N Mp++
y (however, 0.7≦U≦20.0.0.001
≦β≦0.5. O≦γ≦1.0. A compound in which a part of the metal has entered a graphite structure represented by (M represents a transition metal) is deposited as a film or whisker. The above composition was confirmed by analysis using X-ray diffraction, ESCA spectrum, etc.

On the other hand, when hydrocarbons are used, of course, no nitrogen is present, and in some cases, nitrogen partially substituted with metal is produced.

Whether a whisker or a film is generated on the powder can be adjusted by controlling the precipitation rate during precipitation.After mixing the nitrogen-containing compound and the metal,
Precipitation can be adjusted by changing the heating rate, maintained temperature, etc. When performing precipitation by thermally decomposing a gas containing hydrocarbons or nitrogen-containing organic compounds, the dilution concentration, gas supply rate, and decomposition temperature can be adjusted. It can be adjusted by controlling etc.

The powder obtained by the above method, especially the powder coated with a whisker-like carbonaceous material, becomes conductive when mixed with various rubbers such as soft resin or silicone rubber because the powder itself is made of a conductive material. Moreover, the surface is whisker-like and the contact area is larger than that of ordinary point-contact particles, so the pressure causes extremely high conductivity at the point with the highest conductivity. It becomes a pressed conductive material that exhibits high conductivity and can therefore have a wide range of conductivity.

Examples of the soft resins used include polyisobutylene, polyethylene, vinyl chloride, thermoplastic elastomers such as phenolic resins, and soft fluororesins, while examples of rubber include silicone rubber, polybutadiene, butadiene styrene rubber, polychloroprene, polyisoprene, Fluororubber or the like may be used, and it may be added by kneading it into these resins or rubbers or by dissolving it in a solvent or the like.

In addition, in order to further improve the pressurized conductivity, a conductive powder such as conductive carbon black may be added as an auxiliary in some cases.

The pressurized conductive material obtained in this way can be used for various crime prevention,
Sensors for alarm devices, touch boards for swimming pools, surface switches for health equipment, counters, variable volume elements that can change the volume by pressure, especially 4E sensors for volume control keyboards, high-end robot hands, prosthetic hands, etc.
It can be used for useful purposes such as graphic input sensors.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 2.06 g of Ni powder with particle size ranging from 1 to IO μm
and 7.11 g of carbon nitride were mixed, heated to 650° C. in a nitrogen atmosphere in a quartz reaction tube, and reacted for 2 hours.

3.59 g of product was obtained as a black powder.

The SEX photograph of the product is shown in Figure 1, and as can be seen from the figure, the obtained powder is covered with whisker-like substances, with 55-4% of the Ni in the center being covered. The whisker content was 45 wt%.

In addition, analysis of the whiskers on the surface of this powder by elemental analysis, X-ray diffraction analysis, ESCA, IR, etc. revealed that its composition was CI N Ni, which had a layered structure similar to graphite, with some carbon, nitrogen, It was found that it was substituted with Ni.

Example 2 2.0 g of Ni powder and 7.2 g of melamine as in Example 1
were mixed and transferred in a short time into a quartz reaction tube heated to 650° C. in a nitrogen atmosphere to rapidly heat the mixture.

When taken out after reacting for 1 hour, the product was 2.4
It weighed 5g and was black in color.

The shape and composition of this powder are the same as that obtained in Example 1,
It was similar to Habo.

Example 3 5.02 g of Ni powder similar to Example 1 was prepared with an inner diameter of 40 m5,
Place it in the center of a quartz reaction tube with a length of 1,000 mm and a part of the heater that has a length of 5,000 mm, and after heating to 700°C, acetylene and argon are flowed at 40 cc/sin each, and N
pyrolyzed on the i surface. The product after 1 hour reaction is 5
．． It was 80g.

The shape and composition of this powder are the same as that obtained in Example 1,
It was similar to Habo.

Example 4 The reaction tube used in Example 3 was made vertical, and 10.8 g of Ni powder was dropped into the tube heated to 800° C., and at the same time acetylene and Ar were flowed at 40 cc/win″C″.

The product after 1 hour of reaction was 11.6 g.

The shape and composition of this powder are the same as that obtained in Example 1,
It was similar to Habo.

Example 5 3.0 g of the powder obtained in Example 1 was mixed with 66 g of a thermosetting resin (phenol resin Niresol type), 54 g of a solvent (Calpitot/Lea Upper Tate), and 12 g of carbon black to create a paste.

Apply this to a polyethylene terephthalate plate and
It was heated at ℃ for 2 hours to slightly harden it into a rubber state.

Next, the substrate with the rubber-like resin sheet adhered to it is placed on a substrate having two electrodes coated with ^U at regular intervals so that the rubber-like resin sheet is in contact with the electrodes, and pressure is applied from above. The resistance value was measured.

In this case, the pressure I Kg/cm2 is 690Ω/mouth,
340Ω/mouth at 2Kg/cl12, 3Kg/cm2
Then, it is 9oΩ/mouth, and if the pressure is not fully heated, it is 15
It was found that it exhibited excellent pressurized conductivity of 00Ω/mouth.

[Effects of the Invention] The powder of the present invention, which has a whisker-like surface and a transition metal interior, has the highest electrical conductivity under pressure when mixed into soft resin, rubber, etc. compared to other materials. This makes it a material with extremely high conductivity, and therefore an extremely excellent pressurized conductive material that can have a wide range of conductivity.

[Brief explanation of drawings]

FIG. 1 is an SEX photograph showing the particle structure of the produced powder. No. 1 Shishi 1 10μ ridge

Claims (4)

[Claims] (1) A pressurized conductive metal powder in which the surface of transition metal or its alloy particles is coated with a carbonaceous film or whiskers containing carbon or nitrogen. (2) General formula [(C_3N_3)_2N_x11y]
(However, 2≦x≦4, 0≦y≦8) After mixing carbon nitride or nitrogen-containing organic compound and transition metal or its alloy powder, in an inert atmosphere,
Claim characterized in that heating to a temperature of 1000°C (
1) The method for producing the pressurized conductive metal powder described above. (3) The pressurization according to claim (1), characterized in that a gas containing a hydrocarbon or a nitrogen-containing organic compound is thermally decomposed at 300 to 1000°C in a system in which a powder of a transition metal or its alloy is present. Method for producing conductive metal powder. (4) A pressurized conductive material characterized by incorporating the pressurized conductive metal powder according to claim (1) into a soft resin or rubber.