CN100408511C

CN100408511C - Method for preparing silicon nitride/titanium nitride nano composite material

Info

Publication number: CN100408511C
Application number: CNB2006100300497A
Authority: CN
Inventors: 王连军; 朱鸿民; 江莞; 杨梅; 陈立东
Original assignee: Shanghai Institute of Ceramics of CAS; University of Science and Technology Beijing USTB
Current assignee: Shanghai Institute of Ceramics of CAS; University of Science and Technology Beijing USTB
Priority date: 2006-08-11
Filing date: 2006-08-11
Publication date: 2008-08-06
Anticipated expiration: 2026-08-11
Also published as: CN1923753A

Abstract

The invention discloses a preparing method of conductive silicon nitride/titanium nitride nanometer composite material, which comprises the following steps: adopting Si3N4 powder as core base in the liquid ammonia solution; making titanium halide and alkaline metal as reacting material; allocating Si3N4 and TiN with bulk rate at 90: 10-75: 25; synthesizing nanometer TiN on the Si3N4 particle surface; forming Si3N4 composite powder covered by TiN; heating the composite powder under 700-900 deg.c; sintering through SPS method rapidly; setting the sintering temperature at 1500-1650 deg.c and pressure at 50-70Mpa; insulating for 2-6min.

Description

A kind of preparation method of silicon nitride/titanium nitride nano composite material

Technical field

The present invention relates to the preparation of conductive silicon nitride ceramic composite, relate to or rather a kind of conductive silicon nitride (Si for preparing ₃N ₄The method of)/titanium nitride (TiN) nano composite material.Belong to the nitride silicon based composite material field.

Background technology

In high-performance ceramics, silicon nitride (Si ₃N ₄) pottery has high strength, high rigidity, good heat endurance, is one of structural material that has most development potentiality and application market.This agglomerating silicon nitride ceramics can be used to develop wear-resisting, corrosion-resistant, high temperature resistant goods such as sintex, sealing member, high-temperature bearing, nozzle, has vast market prospect.But hinder that it further develops be that reliability is low, problem such as poor toughness, preparation and tooling cost height.In order further to improve its mechanical property and to cut down finished cost, the material scholar adopts the enhancings such as fiber, whisker, particle to prepare composite.But owing to expensive, the complicated process of preparation of whisker, fiber and other material, reason such as restive, particle strengthens and has been subjected to favor, particularly adopts TiN to cause material scholars' very big interest as wild phase.This is that more valuable is that calculation of thermodynamics has shown TiN and Si because TiN has low-density, high-melting-point, high rigidity, good electric conductivity ₃N ₄Chemical compatibility.Therefore the material supply section scholars of countries in the world expect to prepare and utilize TiN enhanced good mechanical properties, the Si that resistivity is low ₃N ₄Based composite ceramic material so just can adopt discharge cutting machine (EDM) (can only process resistivity less than 5 * 10 ^-3The material of Ω cm) it is processed, can cut down finished cost significantly, process complicated shape, enlarge its range of application, in addition because the low-resistivity of material can also prepare high temperature Heating element and ignition device etc.

In order to realize this goal, the method for original adoption is with Si ₃N ₄Mix with the direct ball milling of TiN powder, sintering prepares block materials in nitrogen atmosphere then.For but guaranteeing the specific conductivity that block materials is certain, the content of the second phase titanium nitride is all very high, Cai the resistivity that is greater than 30% guaranteed matrix material at least is less than 5 * 10 ^-3Ω cm, result have damaged the high-temperature oxidation resistance of silicon nitride composite material.So the material scholars are making great efforts expectation and preparing good mechanical properties always, (resistivity is less than 5 * 10 for conduction ^-3Ω cm) and low TiN content enhanced Si ₃N ₄Matrix material.Nearest Japanese scientist (ShuichiKawano, Junichi Takahashi and Shiro Shimada, J.Mater.Chem., 12,2002, P361) reported that the employing chemical method prepares nano-TiO ₂Parcel Si ₃N ₄Composite granule, high-temperature ammonolysis then, wherein the content of titanium nitride has also surpassed 25vol%.Because the preparation of titanium nitride is difficulty relatively, usually adopt high temperature process, so these methods exist very big shortcoming, as TiN skewness, nano-powder reunite easily, particle diameter distributes wide, the problems such as the reaction encapsulation process is restive, have impurity, and manufacturing cycle is long.Because liquid phase reduction can (≤25 ℃) directly prepare nano TiN under cryogenic conditions, therefore utilize liquid ammonia solution can make one step of nano TiN original position be created on Si ₃N ₄Surface, thereby synthetic TiN parcel Si ₃N ₄Powder can be avoided the problems referred to above.

Summary of the invention

The object of the present invention is to provide a kind of conduction Si ₃N ₄The method of/TiN nano composite material is characterized in that a step original position synthesis of nano TiN parcel Si ₃N ₄Si ₃N ₄/ TiN composite nano-powder adopts spark plasma sintering technology (SPS) then, and preparation has the Si of premium properties conduction ₃N ₄/ TiN nano composite material.

Key problem in technology of the present invention is that the step original position of TiN coats, namely by selecting the halide (TiCl of titanium ₄, TiBr ₄Deng) and alkali metal (Na, K etc.) and Si ₃N ₄Powder is raw material, the synthetic composite granule of design raw material composition and ratio, Optimizing Process Parameters, control Monte Carlo method, has meticulous microstructure to obtain, a good conductive and mechanical properties sintered material.At first design the raw material composition and ratio, synthesis of nano TiN parcel Si in liquid ammonia solution ₃N ₄Composite nano-powder, then through Overheating Treatment, carry out at last the SPS sintering, main by control SPS sintering process parameter, comprise sintering temperature, pressure, heating rate, temperature retention time etc.Following each step is specifically arranged:

1, the selection of material powder and Si ₃N ₄The preparation of/TiN composite nano-powder

Take the halide of titanium, alkali metal as raw material, with Si ₃N ₄Powder is the nucleation matrix, and TiN is the halide with titanium, such as TiCl ₄Or TiBr ₄The liquid-phase reduction method generate, press Si ₃N ₄With synthetic TiN volume ratio be the design of preparing burden in 90: 10～75: 25, wherein, the halide of titanium (halogen) and alkali-metal mol ratio are 1: 4～1: 5, its building-up process is earlier with Si ₃N ₄Be placed in advance in the liquefied ammonia, the mode of stirring, vibration or ultrasonic dispersion makes it even dispersion, adds then the halide (TiCl of titanium ₄, TiBr ₄Deng) and alkali metal (Na, K etc.) react, reaction time 0.5-1.5 hour, filter then.Adopt vacuum, inert atmosphere or reducing atmosphere to heat-treat after filtration is finished, thermal treatment temp is between 700～900 ℃, and heat treatment time was at 2～6 hours.Adopt above-mentioned preparation technology, the powder transmission electron microscope analysis result who obtains shows nano TiN parcel Si ₃N ₄On particle surface, as shown in Figure 1.The Si that uses ₃N ₄Diameter of particle is 0.1-5 μ.

2, discharge plasma quick in situ reaction sintering (SPS)

This process is carried out under vacuum condition or nitrogen, can select graphite jig.In sintering process, need strict control process parameters, comprise sintering temperature, pressure, temperature rise rate, soaking time etc.Wherein, sintering temperature and heating rate are regulated by the size of pulse current and voltage.The temperature range of sintering is 1500～1650 ℃; The heating rate scope is 80～200 ℃/min; According to Si ₃N ₄Compare etc. with the TiN different volumes and to determine concrete sintering time, be generally 10～30min; Pressure limit is 50～70Mpa, and temperature retention time is 2-6min.For SPS is played a greater role, apply 5～10Mpa pressure before the sintering earlier, making has a contact between the powder, be warmed up to the sintering that required sintering temperature adds to 50-70MPa again.

Adopt above-mentioned preparation technology, the relative density of the sintered material that is obtained has reached 98.1%, and grain-size has the good mechanical performance simultaneously less than 500nm, and fracture toughness property has reached 4.7MPa.m ^1/2, and when the TiN volume content reaches 20%, prepared matrix material have a good electrical conductivity, resistivity is 3.6 * 10 ^-3Ω cm.

The invention provides a kind of have good mechanical property, the Si of conduction ₃N ₄/ TiN nano composite material and preparation method thereof.At first adopt halide, alkali metal and the Si of titanium ₃N ₄Powder is raw material, reacts preparation TiN parcel Si in liquid ammonia solution ₃N ₄Composite nano-powder, then through Overheating Treatment, last quick densifying sintering is with the control microstructure, on the basis that guarantees material excellent mechanical performances and electric conductivity, utilization rate, the machinability of material, the reliability of product are greatly improved, manufacturing cycle is short, energy consumption is low, environmental friendliness, and production cost significantly reduces, thereby has good industrialization prospect.

Description of drawings

Fig. 1 is the Si of embodiment 1 ₃N ₄Contrast transmission electron microscope photo before and after the particle parcel, wherein a is for before wrapping up; B. behind the parcel;

Fig. 2 is fracture scanning electron microscope (SEM) photo of the sintered compact of embodiment 2;

Embodiment

Embodiment 1

With Si ₃N ₄: TiN=90: 10 is example.At first with Si ₃N ₄Add even dispersion and in liquid ammonia solution, stir simultaneously, add then TiCl ₄React TiCl with K ₄With the mol ratio of K be 1: 4, the reaction time is 60 minutes, adopts subsequently vacuum drying oven to heat-treat, heat treatment temperature is 900 ℃, heat treatment time was at 4 hours.At last heat treated composite granule is packed into behind the graphite jig, put into SPS equipment and carry out sintering.Fig. 1 is this example Si ₃N ₄(a is for before wrapping up for contrast transmission electron microscope photo before and after the particle parcel; B. behind the parcel), nano TiN successfully is wrapped in Si as can be seen from Figure 1 ₃N ₄Particle surface.

The SPS preparation process is carried out under vacuum condition.Temperature rise rate is 80 ℃/min; Sintering temperature is 1600 ℃; Soaking time is 8min; Adopt two step pressing mode, institute's applied pressure is 10MPa before the sintering, and holding stage institute applied pressure is 70MPa.

Embodiment 2

With Si ₃N ₄: TiN=80: 20 is example.At first with Si ₃N ₄Join in the liquid ammonia solution and stir simultaneously, add then TiBr ₄React TiBr with Na ₄With the mol ratio of Na be to be 40 minutes in 1: 4.8 reaction time, adopt subsequently vacuum drying oven to heat-treat, heat treatment temperature is 700 ℃, heat treatment time was at 6 hours.At last heat treated composite granule is packed into behind the graphite jig, put into SPS equipment and carry out sintering.

The SPS preparation process is carried out under condition of nitrogen gas.Temperature rise rate is 80 ℃/min; Sintering temperature is 1550 ℃; Soaking time is 5min; Adopt two step pressing mode, institute's applied pressure is 10MPa before the sintering, and holding stage institute applied pressure is 60MPa.Fig. 2 is fracture scanning electron microscope (SEM) photo of this example sintered compact, and as can be seen from Figure 2 uniform particles is careful, and fracture mode is for prolonging brilliant fracture.This examples preparation Si ₃N ₄The resistivity of/TiN nano composite material is 3.6 * 10 ^-3Ω cm can adopt discharge cutting machine (EDM) that it is processed.

Claims

1. a TiN wraps up Si ₃N ₄The preparation method of nano composite material comprises batching, synthetic and sintering process, it is characterized in that concrete steps are:

(A) TiN parcel Si ₃N ₄The preparation of composite nano-powder is with Si ₃N ₄The halide solution of powder, titanium and alkali metal are raw material, and TiN generates with the reaction of liquid-phase reduction method,

(a) press Si ₃N ₄With the design of preparing burden in 90: 10～75: 25 of the volume ratio of TiN,

(b) with Si ₃N ₄The powder even dispersion in liquefied ammonia, as the nucleation matrix,

(c) halide solution and the basic metal that adds titanium again reacts, and reaction times 0.5-1.5 hour, wherein the halogenide of titanium and alkali-metal mol ratio were 1: 4～1: 5;

(d) filter and heat-treat, heat treatment temperature 700-900 ℃, be prepared into TiN parcel Si ₃N ₄Composite nano-powder;

(B) TiN with step (A) preparation wraps up Si ₃N ₄Composite nano-powder adopts plasma discharging SPS sintering method sintering, and sintering temperature 1500-1650 ℃, pressure are 50-70MPa, are incubated 2-6 minute.

2. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material is characterized in that described Si ₃N ₄The particle diameter of powder is 0.1-5 μ m.

3. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material, the halide that it is characterized in that described titanium is TiCl ₄Or TiBr ₄Described alkali metal is K or Na.

4. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material, atmosphere is vacuum, inert gas or reducing atmosphere when it is characterized in that in the step (A) (d) described heat treatment.

5. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material, the heat treatment time that it is characterized in that (d) in the step (A) is 2-6 hour.

6. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material, the heating rate when it is characterized in that the SPS sintering described in the step (B) is 80～200 ℃/min.

7. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material is characterized in that the described sintering time of step (B) is 10-30min.

8. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of nano composite material when it is characterized in that the described SPS sintering of step (B), applies earlier the pressure of 5-10MPa before arriving sintering temperature.

9. by the described TiN parcel of claim 1 Si ₃N ₄The preparation method of N nano composite material is characterized in that the crystallite dimension of the composite for preparing is less than 500nm.