JPH03115578A - Method for coating powder particle - Google Patents

Abstract

PURPOSE:To efficiently coat powder particles with the compd. of the metal of a metal halide and nitrogen element by supplying metal halide vapor and gaseous nitrogen into a heat resistant tube generated by plasma and further supplying the powder particles thereto. CONSTITUTION:Gaseous Ar is supplied from a shielding gas introducing part 7 and a carrier gas introducing hole 5 into a quartz tube 3 and is filled thereon. The plasma is generated by the operation of a high-frequency generator 2 and a high-frequency output is increased. Cooling water is circulated to the quartz tube 3 and a nozzle structure 4. While H2 is supplied from the introducing part 7, the high frequency output is increased and, thereafter, a TiCl4 soln. kept at a prescribed temp. is supplied from the introducing part 7 into the quartz tube 3 by the gaseous Ar. The gaseous N2 is supplied therein as well. SiC powder is supplied from the introducing hole 5 into the quartz tube 3 and is brought into reaction, by which the surface of the SiC powder is coated with TiN. This powder is deposited on a powder capturing tray 9 in a powder capturing chamber 8. The coating of the surface of the SiC powder with the TiN is efficiently executed at the high speed in this way.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for coating powder particles.

[Conventional technology]

S i 3 N a * S i Cr A j!
Ceramics represented by sO3 are used industrially as sintered bodies, but when forming these sintered bodies, simply molding and heating the pure ceramic powder described above does not allow sintering. It is a well-known fact that a body is not formed.

Therefore, in order to sinter such materials, sintering aids are added, such as Y2O in 5isNn.

・Al t Os is added, 84C is added in sic, and AI, O! MgO is added to suppress crystal grain coarsening during sintering, and CO is most commonly used as a binder when sintering WC.

As described above, sintering of powder particles requires the addition of auxiliary agents, making the process and management complicated, and adding auxiliary agents may impair the original properties of the sintered material. many.

Therefore, the surface of the sintered material powder particles is coated with a substance that promotes sintering or a substance that improves the properties of the sintered body.

Regarding powder particle surface coating technology, fluid JiC
Some attempts have been made to use the VD method, but the coating speed is slow, the efficiency is low, and the coating conditions are severe, making it still impractical.

Furthermore, although there is a plating method, it has the same drawbacks as the fluidized bed CVD method.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
It is an object of the present invention to provide a method for coating powder particles with high coating speed, a wide range of coating materials, and excellent efficiency and applicability.

(Means for Solving the Problems) To this end, the present invention includes a first step of generating plasma by passing a high-frequency current through a coil surrounding a heat-resistant tube filled with a gas for plasma generation, and a step of generating plasma in the heat-resistant tube. a second step of supplying halide vapor and at least one gas selected from hydrocarbon gas, nitrogen gas, or ammonia gas; supplying powder particles into the heat-resistant tube; It is characterized by comprising a third step of coating a compound with at least one of the elements.

[Effect]

The first step is to generate plasma by passing a high-frequency current through a coil that surrounds a heat-resistant tube filled with gas for plasma generation.
Through this process, a high temperature and active plasma atmosphere can be created inside the heat-resistant tube.

Further, the second step of supplying metal halide vapor and at least one gas selected from hydrocarbon gas, nitrogen gas, and ammonia gas into the heat-resistant tube allows the coating material to be supplied in a gaseous state into the heat-resistant tube. can.

Furthermore, a third step of supplying powder particles into the heat-resistant tube and coating the powder particles with a compound of the metal of the metal halide and at least one element selected from carbon and nitrogen produces a metal carbide.

Metal nitrides or metal carbonitrides can be rapidly coated onto powder particles.

〔Example〕

An embodiment of the present invention will be explained with reference to the drawings. In the vertical cross-sectional view of FIG.
It is electrically connected to the high frequency generator 2. 3 is a quartz tube inserted into the coil 1, which can be water-cooled by a double wall structure (not shown). Reference numeral 4 denotes a nozzle structure attached to the upper end of the quartz tube 3, which is water-cooled by a cooling channel (not shown).

Reference numeral 5 denotes a carrier gas introduction hole that extends vertically through the center of the nozzle structure 4. 6 is a gap formed between the upper inner surface of the quartz tube 3 and the nozzle structure 4, 7 is a shield gas introduction part connected to the upper end of the gap 6, and 8 is the quartz tube 3
9 is a powder collection tray installed on the bottom of the powder collection chamber 8, and lO is an exhaust port connected to the upper end of the powder collection chamber 8. be.

In such an AT, first, as a first step, argon A is introduced into the shield gas introduction section 7 from a gas container (not shown).
was supplied at a flow rate of 4Qj!/sin, and argon was also supplied at a flow rate of 317w1n to the carrier gas introduction hole 5 via a powder supply device (not shown), and as a result, the quartz tube 3 was filled with argon gas. Afterwards, the high frequency generator 2 is activated to generate plasma, and the high frequency output is increased to 2.
While increasing the power to 0KW, the quartz tube 3. Cooling water is circulated through the nozzle structure 4.

Next, in the second step, hydrogen H3 is supplied from the shielding gas inlet 7 at a flow rate of 51/sin while the high frequency output is increased to 50 KW, and after the plasma is stabilized, the temperature is increased to 80°C from a titanium chloride generator (not shown). Heat-retaining titanium chloride TiCj! .

The solution is supplied into the quartz tube 3 from the shield gas introduction part 7 with a carrier gas of argon at a flow rate of 3 J/+win, and nitrogen gas N2 is supplied into the quartz tube 3 from the shield gas introduction part 7 at a flow rate of t21/sin. do.

Furthermore, as a third step, silicon carbide s with a particle size of 5 μm or less is
i c, When the powder is supplied into the quartz tube 3 from the carrier gas introduction hole 5 at a supply rate of 3 g/sin by an unillustrated non-supply device, there, 2 TiclJ + l'J
, + 2 Ht → 2TiN + 4HC1 reaction is performed to coat the surface of the silicon carbide particles with titanium nitride TiN, and then the silicon carbide particles are deposited on the powder collection pan 9 in the powder collection chamber 8. .

Therefore, if a predetermined amount of silicon carbide powder can be collected,
Stop the supply of titanium chloride solution, nitrogen gas, and hydrogen gas,
Plasma output is reduced to stop plasma generation, and then the supply of argon is stopped.

In addition, on the surface of the collected silicon carbide particles, 0, 1 to 0
．． A 3 μm thick titanium nitride was observed.

It is also possible to use silicon nitride SiN4 instead of silicon carbide as the powder to be supplied. Furthermore, silicon tetrachloride is used instead of titanium chloride, methane CH is used instead of nitrogen,
By supplying titanium chloride T i C1g and ammonia N Hs, coating of titanium nitride is possible, and titanium chloride, nitrogen and methane CH
If a is supplied, coating of titanium carbonitride TlCN is also possible.

According to such a method, the surfaces of the powder particles can be efficiently coated with metal carbide, metal nitride, or metal carbonitride, so that the following effects can be achieved.

(1) Since the coating speed of the powder particles is fast, the powder sintering efficiency is high, and therefore the sintering cost is reduced.

(2) Since there are fewer restrictions on coating materials, the range of application is wide, and therefore the practicality is increased.

(3) Since no sintering aid is required for sintering the powder particles, the sintering process is simplified and labor can be saved.

(4) Since no sintering aid is required for sintering the powder particles, the growth of crystal grains in the sintered body can be suppressed, thereby improving the mechanical properties and corrosion resistance of the sintered body.

〔Effect of the invention〕

In short, according to the present invention, the first step is to generate plasma by passing a high frequency current through a coil surrounding a heat-resistant tube filled with gas for plasma generation, and to supply metal halide vapor and hydrocarbon gas in the heat-resistant tube. , a second supplying at least one gas selected from nitrogen gas and ammonia gas.
and a third step of supplying powder particles into the heat-resistant tube and coating it with a compound of the metal of the metal halide and at least one element of carbon or nitrogen, thereby increasing the coating speed. The present invention is of particular benefit to the industrial sector because it provides a method for coating powder particles with high efficiency and applicability, with a wide range of coating materials.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Coil, 2... High frequency generator, 3... Quartz tube, 4... Nozzle structure, 5... Carrier gas introduction hole, 6... Gap, 7... Shield gas introduction Part, 8
...Powder collection chamber, ...Powder collection tray, ■0...Exhaust port,

Claims (1)

[Claims] A first step of generating plasma by passing a high-frequency current through a coil surrounding a heat-resistant tube filled with a gas for plasma generation, and a step of generating plasma in the heat-resistant tube with metal halide vapor and hydrocarbon gas, nitrogen gas, or ammonia gas. a second step of supplying at least one of the gases, and a second step of supplying powder particles into the heat-resistant tube and coating them with a compound of the metal of the metal halide and at least one element of carbon or nitrogen. A method for coating powder particles, characterized by comprising three steps.