CN109437917B

CN109437917B - Method for producing titanium nitride and titanium carbonitride by two-stage reduction nitridation

Info

Publication number: CN109437917B
Application number: CN201811556519.2A
Authority: CN
Inventors: 张国华; 吴柯汉
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2018-12-19
Filing date: 2018-12-19
Publication date: 2020-06-12
Anticipated expiration: 2038-12-19
Also published as: CN109437917A

Abstract

A method for producing titanium nitride and titanium carbonitride by two-stage reduction nitridation. The method comprises the following steps: (1) preparing materials: titanium dioxide and carbon black are used as raw materials and are mixed and stirred uniformly; (2) heating the mixed powder obtained in the step one in a high-temperature furnace, and preserving heat for 1-4 hours at 1300-1600 ℃ under an argon atmosphere at normal pressure to obtain a first-stage reduction product; (3) detecting the carbon content and the oxygen content of the first-stage reduction product obtained in the step two, regulating the carbon content according to the relation between the required product and the raw materials of carbon, oxygen and nitrogen, and carrying out ball milling and mixing; and (4) putting the mixed powder obtained in the third step into a high-temperature furnace, preserving heat for 2-8 hours at 1600-1800 ℃ in a nitrogen environment at normal pressure, and cooling to obtain the titanium nitride or the titanium carbonitride.

Description

Method for producing titanium nitride and titanium carbonitride by two-stage reduction nitridation

Technical Field

The invention belongs to the field of metal ceramics, and particularly relates to a preparation method of titanium nitride and titanium carbonitride.

Background

In recent years, titanium carbonitride and titanium nitride have high melting point, high hardness, low friction wear, corrosion resistance and other characteristics, and therefore have great application value in the preparation of cermets, cutting tools, electrode lining materials, coating materials and the like. Titanium carbonitride and titanium nitride have become a potential material to replace WC-Co cemented carbides, particularly in the cutting tool sector, due to their high hardness, high red hardness, high wear resistance and relatively low density. In metal cutting processing, the titanium carbonitride and titanium nitride-based metal ceramic cutting tool can resist the formation of cutting nodules, peeling and craters, and the size precision and the processing surface quality of high-speed grinding rough processing and semi-processing workpieces are superior to those of workpieces processed by WC-Co hard alloy cutting tools. In addition, titanium nitride has optical properties similar to gold, and is commonly used in the field of gold-like materials. Therefore, the development of titanium carbonitride and titanium nitride powder with high purity, fine granularity, uniform particle size dispersion and single phase has great value.

The method for preparing titanium nitride at home and abroad mainly focuses on a direct nitridation method and a one-step carbothermal reduction nitridation method. Wherein the direct nitration is carried out using Ti or TiH₂The method has the advantages of high product purity, uniform product granularity and high raw material cost. One-step carbothermal nitridation method using TiO₂Reacting with carbonaceous reducing agent in nitrogen atmosphere to obtain titanium carbide, and the method has the advantages that the raw material is preparedThe disadvantage is the high content of free carbon present in the product. In addition, a magnesiothermic reduction nitridation method is used, but the granularity of the product prepared by the method is extremely non-uniform, and the production process involves acid leaching and causes environmental pollution.

The method for preparing titanium carbonitride mainly focuses on a direct alloying method and a carbothermal reduction nitridation method. Wherein the direct alloying method directly uses TiC powder and TiN powder or Ti powder, and the TiC powder and TiN powder or Ti powder are directly obtained by solid solution at the temperature of more than 1700 ℃ after ball milling and mixing. The method has the problems of high use temperature, long time consumption, high energy consumption, high equipment requirement, large product particles and often reduced product purity due to the introduction of a sintering aid. Compared with a direct alloying method, the carbothermal reduction nitridation method has the advantages of low raw material cost, short process flow and relatively low temperature. However, because the existing carbothermic reduction nitridation method mainly uses one-step reaction synthesis, the reaction process is uncontrollable, the carbon mixing amount is inaccurate, the product purity is low, the granularity is uneven, the C/N ratio of the product is uncontrollable, and various titanium carbonitride and other problems exist in the product, the method is not used for industrial production. Some researchers have improved this process, and the method disclosed in the patent with publication number CN102718214A is: the method for controlling the C/N ratio in the titanium carbonitride is realized by adopting a nitrogen partial pressure control mode. However, CO/CO in the reaction product gas is still present in the process₂Uncontrollable, thereby causing the problem that the carbon distribution amount is difficult to control, and excessive carbon causes a large amount of free carbon in the product, so that the purity of the product is reduced. Also disclosed in patent publication No. CN103193231A is a method comprising: removing free carbon in the product by flotation. However, the method has the problem that the C/N ratio in the titanium carbonitride is uncontrollable, and simultaneously, because the one-stage reduction is adopted, the oxygen content in the product is high, the phase of the obtained product is difficult to be single, and the titanium carbonitride with various C/N ratios is easy to exist simultaneously. The process as disclosed in CN102976759A is again: the titanium carbonitride is prepared by a method of vacuum carbothermal reduction and nitrogen nitridation. The product prepared by the method has low oxygen content, but high-temperature vacuum equipment is needed, so that the method has high requirement on the equipment and is not easy for industrial production. The process as disclosed in CN108424147A is again: firstly low-temperature vacuum reduction and then high-temperature nitridationThe method of (3) is used for preparing the titanium carbonitride, and the C/N ratio in the product is controlled by controlling the nitriding time. The method can prepare the titanium carbonitride with low oxygen content, but has the following three problems: 1. vacuum equipment is needed, so that the industrial production is not easy to realize; 2. a rapid cooling device is needed, and the industrial implementation is difficult; 3. the C/N ratio of titanium carbonitride is controlled by controlling the nitriding time at 1300-1500 ℃, and the principle is that titanium carbide can react with nitrogen at the temperature, although titanium carbonitride can be produced, a byproduct, namely simple substance carbon, is generated

As shown, and this reaction is reversed at temperatures of 1600 ℃ and above, limiting the nitridation temperature, the solution process will be slow.

Therefore, the development of an industrially feasible production path of titanium carbonitride and titanium nitride with controllable C/N ratio, high purity and narrow particle size distribution has important significance. We propose a two-stage reductive nitridation process to produce titanium carbonitride and titanium nitride. The invention takes titanium dioxide and carbon black as raw materials, and TiC is prepared by first adopting carbothermic reduction under the atmosphere of normal pressure argon_xO_yAfter the precursor is quantitatively carbon-matched, the precursor is subjected to two-stage reduction nitridation under the atmosphere of normal-pressure nitrogen, so that high-purity titanium carbonitride or titanium nitride can be obtained. The method has the advantages that the carbothermic reduction reaction which is difficult to control the carbon distribution amount is separated out as the first stage reaction; the second stage of nitridation reaction is carried out at a temperature lower than 1500 ℃ and hardly reacts, and is only carried out in a high temperature region, and the gas product in the temperature region only generates CO, so that carbon can be easily and accurately matched, for example

As shown. Thus, the product TiC formed_xO_yAfter the values of x and y are determined by measuring the carbon oxygen content, the required product can be obtained by a precise carbon matching mode. In addition, the invention can prepare the titanium carbonitride or titanium nitride product with low free carbon and single phase at the temperature of 1600 ℃ at least. The method has obvious advantages in the aspects of cost, flow, purity and the like.

Disclosure of Invention

The invention discloses a method for producing titanium nitride and titanium carbonitride by two-stage reduction nitridation, which comprises the following steps:

step one, batching: titanium dioxide and carbon black are used as raw materials, and are mixed and stirred uniformly according to a certain mass ratio;

step two, first-stage reduction: heating the mixed powder obtained in the step one in a high-temperature furnace, and preserving heat for 1-4 hours at 1300-1600 ℃ under an argon atmosphere at normal pressure to obtain a first-stage reduction product;

step three, quantitatively preparing carbon: detecting the carbon content and the oxygen content of the first-stage reduction product obtained in the step two, regulating the carbon content according to the relation between the required product and the raw materials of carbon, oxygen and nitrogen, and carrying out ball milling and mixing;

step four, two-stage reduction nitridation: and (3) heating the mixed powder obtained in the step three in a high-temperature furnace, preserving heat for 2-8 hours at 1600-1800 ℃ under a normal-pressure nitrogen environment, and cooling to obtain the titanium nitride or titanium carbonitride with low oxygen content, low free carbon content and fine and uniform particle size.

The molar ratio of the titanium dioxide to the carbon black in the first step is 1: 1-3; the first-stage reduction product in the second step is TiC_xO_yIs a solid solution formed by titanium carbide and titanium monoxide; the titanium nitride or titanium carbonitride product prepared in the fourth step is pure and single phase, wherein the oxygen content is lower than 0.5 wt%, the grain diameter is less than 1 micron, and the grain dispersibility is good.

The invention has the beneficial technical effects that:

(1) titanium dioxide and carbon black are used as raw materials, titanium nitride and titanium carbonitride with high purity, fine and uniform granularity and good dispersibility can be prepared, the process flow is simple, and the industrial production is easy to realize;

(2) compared with a one-step direct reduction nitridation method, the method adopting two-stage reduction nitridation avoids the defect that the carbon content is difficult to control in the production process, the carbon-nitrogen ratio in the product is controllable, and the produced titanium nitride and titanium carbonitride have single phase, low oxygen content and extremely low free carbon content.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.

Example 1

The invention aims to analyze pure TiO₂Carbon black (99.85 wt.%) as raw material, based on TiO₂Mixing materials according to the molar ratio of C to C of 1:1.6, and then uniformly mixing the mixed materials by using a mortar; putting the mixed raw materials into a high temperature furnace, heating to 1400 ℃ at the heating rate of 5 ℃/min under the argon flow, preserving the heat for 4 hours, and then cooling to room temperature to obtain TiC_xO_yA precursor, the carbon content of which is measured to be 6.12 wt% and the oxygen content of which is measured to be 17.35 wt%; taking the preparation of TiN as an example, according to the reaction formula

Supplementing carbon by 6.90 wt%, ball milling at 200rpm for 3 hours, and uniformly mixing; and putting the mixed raw materials into a high-temperature furnace, heating to 1800 ℃ at the heating rate of 5 ℃/min under the nitrogen flow, preserving the heat for 2 hours, and then cooling to room temperature to obtain a titanium nitride product with the carbon content of about 0.23 wt%, the oxygen content of about 0.48 wt%, the nitrogen content of about 21.93 wt% and the particle size of less than 1 mu m. The analysis of X-ray diffraction (XRD) shows that the phase of the product is TiN, and no other phase exists; an electron microscope (SEM) shows that the finally obtained TiN particles have uniform particle size and good dispersibility.

Example 2

Example 2 is essentially the same as example 1, except that:

according to TiO aspect₂C in a molar ratio of 1:2Proportioning, heating to 1500 ℃ at the heating rate of 5 ℃/min under argon flow, preserving heat for 1 hour, and then cooling to room temperature to obtain TiC_xO_yA precursor, the carbon content of which is 10.48 wt% and the oxygen content of which is 11.90 wt% are measured; to prepare TiC_0.5N_0.5For example, according to the reaction formula

Supplementing 8.16 wt% of carbon, ball milling at 400rpm for 6 hours, and uniformly mixing; the mixed raw materials are put into a high temperature furnace, heated to 1700 ℃ at the heating rate of 5 ℃/min under the nitrogen flow, and then cooled to room temperature for 4 hours, thus obtaining TiC with the carbon content of about 9.66 wt%, the oxygen content of about 0.42 wt%, the nitrogen content of about 11.27 wt% and the grain diameter of less than 1 mu m_0.5N_0.5And (5) producing the product. XRD analysis shows that the product phase is TiC_0.5N_0.5No other phases; SEM shows that the final product has homogeneous particle size and high dispersivity.

Example 3

Example 3 is essentially the same as example 1, except that:

according to TiO aspect₂Proportioning materials with the molar ratio of C of 1:1.8, heating to 1600 ℃ at the heating rate of 5 ℃/min under argon flow, preserving heat for 4 hours, and then cooling to room temperature to obtain TiC_xO_yA precursor, the carbon content of which is 8.48 wt% and the oxygen content of which is 14.40 wt% are measured; to prepare TiC_0.3N_0.7For example, according to the reaction formula

Supplementing 8.11 wt% of carbon, ball milling at 300rpm for 4 hours, and uniformly mixing; the mixed raw materials are put into a high temperature furnace, heated to 1600 ℃ at the heating rate of 5 ℃/min under the nitrogen flow, and kept warm for 8 hours, and then cooled to room temperature to obtain TiC with the carbon content of about 5.75 wt%, the oxygen content of about 0.48 wt%, the nitrogen content of about 15.64 wt% and the grain diameter of less than 1 mu m_0.3N_0.7And (5) producing the product. XRD analysis shows that the product phase is TiC_0.3N_0.7No other phases; SEM shows that the final product has homogeneous particle size and high dispersivity.

Example 4

Example 4 is essentially the same as example 1, except that:

according to TiO aspect₂Proportioning materials with the molar ratio of C of 1:1.8, heating to 1600 ℃ at the heating rate of 5 ℃/min under argon flow, preserving heat for 4 hours, and then cooling to room temperature to obtain TiC_xO_yA precursor, the carbon content of which is 8.48 wt% and the oxygen content of which is 14.40 wt% are measured; to prepare TiC_0.7N_0.3For example, according to the reaction formula

Supplementing carbon by 15.83 wt%, ball-milling at 300rpm for 4 hours, and uniformly mixing; the mixed raw materials are put into a high temperature furnace, heated to 1600 ℃ at the heating rate of 5 ℃/min under the nitrogen flow, and kept warm for 8 hours, and then cooled to room temperature to obtain TiC with the carbon content of about 13.64 wt%, the oxygen content of about 0.37 wt%, the nitrogen content of about 6.82 wt% and the grain diameter of less than 1 mu m_0.7N_0.3And (5) producing the product. XRD analysis shows that the product phase is TiC_0.7N_0.3No other phases; SEM shows that the final product has homogeneous particle size and high dispersivity.

Claims

1. A method for producing titanium nitride and titanium carbonitride by two-stage reduction nitridation is characterized by comprising the following steps:

step one, batching: titanium dioxide and carbon black are used as raw materials, and are mixed and stirred uniformly according to a certain molar ratio;

step four, two-stage reduction nitridation: heating the mixed powder obtained in the step three in a high-temperature furnace, preserving heat for 2-8 hours at 1600-1800 ℃ under a normal-pressure nitrogen environment, and cooling to obtain titanium nitride or titanium carbonitride with low oxygen content, low free carbon content, fine and uniform granularity and controllable C/N ratio;

the molar ratio of the titanium dioxide to the carbon black in the first step is 1: 1-3;

the first-stage reduction product in the second step is TiC_xO_yIs a solid solution formed by titanium carbide and titanium monoxide.

2. The method of claim 1, wherein: the titanium nitride or titanium carbonitride product prepared in the fourth step is pure and single phase, wherein the oxygen content is lower than 0.5 wt%, the grain diameter is less than 1 micron, and the grain dispersibility is good.