CN1445163A - Technique for preparing ceramic powder of titanium carbide by using plasma chemical gas phase synthesis method - Google Patents

Abstract

A process for preparing TiC ceramic powder by plasma chemical gas-phase synthesis method includes such steps as quickly heating the gas to high temp by plasma of DC arc, thermally evaporating liquefied gas, reaction between TiCl4 and liquefied gas to generate TiC, crystallizing, growing, fast cooling, gas-solid separation by cloth-bag collector. Its advantages are high purity, fine granularity (nano class or submicron class), low cost and no environmental pollution.

Description

Process for preparing titanium carbide ceramic powder by plasma chemical vapor synthesis method

Technical Field

The invention relates to a process for preparing nano-scale and submicron-scale titanium carbide ceramic powder by using a plasma chemical vapor phase method.

Technical Field

The titanium carbide superfine ceramic powder is one of the most widely used carbide ceramic materials, has a series of advantages of high melting point, high strength, good thermal conductivity, large hardness, good high-temperature oxidation resistance and the like, is an important raw material for producing hard alloys, and can be used for manufacturing wear-resistant materials, cutting tool materials, mechanical parts and the like. The titanium carbide powder is prepared by reacting titanium dioxide or titanium powder with carbon black in a vacuum electric furnace at high temperature (1800-2000 ℃). The titanium carbide powder prepared by the method has high production cost and low purity.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a process for preparing titanium carbide ultrafine powder from titanium tetrachloride and liquefied gas by using a plasma chemical vapor synthesis method, which has low production cost, is suitable for industrial production and has high product purity.

The technical scheme of the invention is that firstly, a plasma working gas N is introduced into a plasma generator₂-H₂-Ar, in N₂9-13m³/h；H₂27-32m³The flow rate of/h was continuously injected, and 30 liters/min of Ar was injected, the plasma power supply was started, and a plasma arc was generated in the plasma generator (Ar gas was turned off after arcing was normal). The gas passing through the electric arc is heated to the high temperature of 4800-5200 ℃ and then enters a reactor, and then TiCl heated and evaporated by an evaporator is respectively added₄And feeding the liquefied gas conveyed by the flowmeter into the reactor to quickly decompose and keep the liquefied gas and TiCl₄The ratio of (1: 2) - (8) (the weight ratio of the injected liquid in unit time) is continuously injected, and the reaction temperature in the plasma reactor is kept at 1300-1700 ℃. Rapidly decomposing in a plasma reactor, generating solid TiC micro powder by utilizing free settling and quenching conditions,

and crystallizing and growing the generated TiC, cooling, and then realizing gas-solid separation by a cloth bag powder collector to obtain titanium carbide powder.

The invention has the following positive effects: the invention uses direct current arc plasma as heat source, the gas flowing through the arc is rapidly heated to high temperature and enters the reactor, and meanwhile, the gas is heated and steamed by the evaporatorLiquefied gas or TiCl₄And also enters a reactor to carry out rapid decomposition and synthesis reaction of titanium carbide.

The produced TiC is crystallized and grown in a very short time (millisecond order). Then the nano titanium carbide powder is rapidly cooled down after being sent to a cold environment by the airflow, and then the nano titanium carbide powder is obtained by gas-solid separation realized by a cloth bag powder collecting device. The titanium carbide prepared by the process has high purity, uniform particle size distribution and superfine particle size, can be adjusted into a plurality of specifications, has low production cost and high yield, is suitable for large-scale production, does not discharge three wastes, and meets the requirement of environmental protection.

Drawings

The attached drawing is a schematic diagram of the production device of the invention.

Detailed Description

As shown in the figure, the whole production device in the process mainly comprises a power supply and a microcomputer data acquisition system; a gas-liquid feedstock supply system; a water cooling circulation system; a powder synthesis and collection system; a post-processing system; exhaust gas treatment systems, and the like.

(1) Power supply and microcomputer data acquisition system: and the power supply is provided for the plasma generator, data acquisition is carried out, and the power of the plasma generator and the temperature of the reactor are controlled.

(2) Gas-liquid raw material supply system: the amount and ratio of the liquefied gas and titanium tetrachloride feedstock entering the reactor are quantitatively controlled to control the chemical composition of the reactants.

(3) A water cooling circulation system: cooling water is provided for the plasma generator and the material conveying pipeline, and the safe operation of the equipment is ensured.

(4) Powder synthesis and powder collection system: the system comprises a plasma reactor, a settler, a conveying pipeline and a powder collector, ensures that raw material gas can fully react in the reactor, and effectively collects reaction products.

(5) A post-processing system: and carrying out post-treatment on the collected powder material, effectively removing chloride ions in the powder, and metering and packaging.

(6) An exhaust gas treatment system: the system comprises a leaching tower and a treatment tank. The method is mainly used for treating gas generated in the reaction and protecting the environment.

The process comprises introducing working gas Ar into plasma, starting plasma power supply, generating plasma arc in a plasma generator, heating the gas to about 5000 deg.C to form plasma, introducing into a reactor, and heating the evaporated TiCl with an evaporator₄And liquefied gas are also fed into the reactor, under the action of plasma the decomposition and TiC synthesis reaction can be quickly made, the produced TiC can be crystallized and grown in a very short time (millisecond grade),fine particles with different particle sizes are formed at a controllable cooling speed, the particles are rapidly cooled down after being conveyed to a cold environment by airflow, and then the gas-solid separation is realized by a cloth bag powder collector to obtain TiC ultrafine powder.

The waste gas passing through the cloth bag is leached by water in the leaching tower to remove HCl and then is exhausted. And collecting the HCl-containing wastewater for sale.

TiC powder obtained from powder collector contains chlorine (Cl)^-) The amount is high, the titanium carbide powder is processed in a vacuum-nitrogen conversion heat treatment furnace for 3 to 6 hours, and then the titanium carbide powder is measured and packaged to obtain a finished product.

The process of the present invention is discussed in detail below with reference to examples.

Example 1: firstly, introducing plasma working gas N into a plasma generator₂-H₂-Ar, in N₂9m³/h；H₂27m³The flow rate of/h was continuously injected, and 30 liters/min of Ar was injected, the plasma power supply was started, and a plasma arc was generated in the plasma generator (Ar gas was turned off after arcing was normal). The gas passing through the electric arc is heated to 4800 ℃ and enters a reactor, and then TiCl heated and evaporated by an evaporator is respectively put into a reactor₄And feeding the liquefied gas conveyed by the flowmeter into the reactor to quickly decompose and keep the liquefied gas and TiCl₄The ratio of (1: 2) (weight ratio of injected liquid in unit time) was continuously injected, and the reaction temperature in the plasma reactor was maintained at 1300 ℃. Rapid decomposition and utilization in plasma reactorFree settling and quenching conditions to generate solid TiC micro powder,

the generated TiC is crystallized and grown up in a very short time (millisecond grade), and is cooled and then subjected to gas-solid separation by a cloth bag powder collector to obtain titanium carbide powder.

The embodiment achieves the high yield of 4.5kg of superfine titanium carbide powder produced per hour and the input-output ratio of less than or equal to 4: 1.

Performance indexes of the powder are as follows:

(1) crystal form of titanium carbide powder: face centered cubic crystals;

(2) average particle size of titanium carbide powder: d50 ═ 0.08 μm;

(3) specific surface area: 17m²(ii)/g; (4) purity: 98 percent.

Detecting items	TiC(％)	Free carbon (%)	∑0(％)	Cl-
					The result of the detection	98.3	0.45	0.8	0.22

Example 2: firstly, introducing plasma working gas N into a plasma generator₂-H₂-Ar, in N₂13m³/h；H₂32m³The flow rate of/h was continuously injected, and 30 liters/min of Ar was injected, the plasma power supply was started, and a plasma arc was generated in the plasma generator (Ar gas was turned off after arcing was normal). The gas passing through the arc is heated to 5200 deg.C and enters into the reactorThen respectively heating and evaporating TiCl by the evaporator₄And feeding the liquefied gas conveyed by the flowmeter into the reactor to quickly decompose and keep the liquefied gas and TiCl₄The ratio of (1: 5) (weight ratio of injected liquid in unit time) is continuously injected, and the reaction temperature in the plasma reactor is kept at 1450 ℃. Rapidly decomposing in a plasma reactor, generating solid TiC micro powder by utilizing free settling and quenching conditions,

the generated TiC is crystallized and grown up in a very short time (millisecond grade), and is cooled and then subjected to gas-solid separation by a cloth bag powder collector to obtain titanium carbide powder.

The embodiment achieves the high yield of 4.5kg of superfine titanium carbide powder produced per hour and the input-output ratio of less than or equal to 4: 1.

Performance indexes of the powder are as follows:

(1) crystal form of titanium carbide powder: face centered cubic crystals;

(2) average particle size of titanium carbide powder: d50 ═ 0.25 μm;

(3) specific surface area: 15m²/g；

(4) Purity: 98 percent.

Detecting items	TiC(％)	Free carbon (%)	∑0(％)	Cl-
					The result of the detection	98.0	0.38	0.9	0.21

Example 3: firstly, introducing plasma working gas N into a plasma generator₂-H₂-Ar, in N₂11m³/h；H₂30m³The flow rate of/h was continuously injected, and 30 liters/min of Ar was injected, the plasma power supply was started, and a plasma arc was generated in the plasma generator (Ar gas was turned off after arcing was normal). Heating the gas subjected to the electric arc to 5000 ℃ and then feeding the gas into a reactor, respectively feeding TiCl4 heated and evaporated by an evaporator and liquefied gas conveyed by a flowmeter into the reactor to rapidly decompose, and keeping the liquefied gas and the TiCl₄In a ratio of 1: 8 (weight ratio of injected liquid in unit time)) The injection was continued and the reaction temperature in the plasma reactor was maintained at 1700 ℃. Rapidly decomposing in a plasma reactor, generating solid TiC micro powder by utilizing free settling and quenching conditions,

the generated TiC is crystallized and grown up in a very short time (millisecond grade), and is cooled and then subjected to gas-solid separation by a cloth bag powder collector to obtain titanium carbide powder.

The embodiment achieves the high yield of 4.5kg of superfine titanium carbide powder produced per hour and the input-output ratio of less than or equal to 4: 1. Performance indexes of the powder are as follows: (1) crystal form of titanium carbide powder: face centered cubic crystals;

(2) average particle size of titanium carbide powder: d50 ═ 0.38 μm;

(3) specific surface area: 13m²/g；

(4) Purity: 98.4 percent.

Detecting items	TiC(％)	Free carbon (%)	∑0(％)	Cl-
					The result of the detection	98.4	0.35	1.0	0.24

Claims (1)

1. A process for preparing titanium carbide ceramic powder by plasma chemical vapor synthesis method is characterized in that firstly, plasma working gas N is introduced into a plasma generator₂-H₂-Ar, in N₂9-13m³/h；H₂27-32m³The flow rate of/h was continuously injected, and 30 liters/min of Ar was injected, the plasma power supply was started, and a plasma arc was generated in the plasma generator (Ar gas was turned off after arcing was normal). The gas passing through the electric arc is heated to the high temperature of 4800-5200 ℃ and then enters a reactor, and then TiCl heated and evaporated by an evaporator is respectively added₄And feeding the liquefied gas conveyed by the flowmeter into the reactor to quickly decompose and keep the liquefied gas and TiCl₄The ratio of (1: 2) - (8) (the weight ratio of the injected liquid in unit time) is continuously injected, and the reaction temperature in the plasma reactor is kept at 1300-1700 ℃. Rapidly decomposing in a plasma reactor, generating solid TiC micro powder by utilizing free settling and quenching conditions,

and crystallizing and growing the generated TiC, cooling, and then realizing gas-solid separation by a cloth bag powder collector to obtain titanium carbide powder.

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