CN100453508C

CN100453508C - Method for Synthesizing Silicon Nitride/Silicon Carbide Composite Powder by Chemically Inspired Combustion

Info

Publication number: CN100453508C
Application number: CNB2006100122517A
Authority: CN
Inventors: 杨筠; 杨坤; 林志明; 李江涛
Original assignee: Technical Institute of Physics and Chemistry of CAS
Current assignee: Technical Institute of Physics and Chemistry of CAS
Priority date: 2006-06-14
Filing date: 2006-06-14
Publication date: 2009-01-21
Anticipated expiration: 2026-06-14
Also published as: CN101088962A

Abstract

The invention belongs to the field of inorganic non-metallic materials, and particularly relates to a method for synthesizing Si by chemical excitation combustion₃N₄Method for preparing/SiC composite powderThe method is carried out. Silicon powder: 40-70 parts of carbon black: 20-50 parts of a chemical activator: 0.5-20 parts of the raw materials are mixed to obtain a mixture; grinding and activating the mixture at a rate of 0.3-1.0 g/cm³Filling the bulk density into a high-pressure reaction kettle, vacuumizing, filling nitrogen or argon to control the pressure to be 1-3 MPa, and inducing the mixture to perform self-propagating combustion synthesis reaction; preparation of Si separately₃N₄The powder is SiC composite powder or powder with SiC as main phase. The method has the advantages of simple and convenient process, short production period, low power consumption and low cost.

Description

The method of chemical pumping burning synthesizing silicon nitride/silicon carbide composite powder body

Technical field

The invention belongs to field of inorganic nonmetallic material, particularly a kind of chemical pumping burning synthesizing silicon nitride/silicon carbide (Si ₃N ₄/ SiC) the method for composite granule.

Background technology

Silicon nitride, silicon carbide ceramics are nearly 40 or the five ten years advanced high-temperature structural materials that grow up, and are typical case's representatives of non-oxide structure stupalith.They have good normal temperature and high-temperature behavior.Yet along with popularizing that stupalith is used, monophase materials exposes some shortcomings that can't overcome itself gradually, and is lower as fracture toughness property; The strength degradation that the sintering process grain growth causes etc. more and more cause people's attention so introduce the research of the nitride silicon based composite material of second phase in the silicon nitride ceramics matrix, and silicon carbide is a kind of that use at present is maximum, effect is best.Contain silicon nitride and silicon carbide biphase Si ₃N ₄/ SiC matrix material comprehensively has the advantage of silicon carbide high rigidity, silicon nitride high tenacity, has improved ceramic normal temperature and high-temperature behavior greatly, has improved ceramic stability, becomes the most rising stupalith.

Si ₃N ₄The preparation of/SiC matrix material mainly is divided into following several method: (1) is with Si ₃N ₄Mix back agglomerating method with two kinds of powder machineries of SiC; (2) reaction sintering; (3) carry out the agglomerating method with composite granule.The application just provides a kind of preparation Si ₃N ₄The method of/SiC composite granule is used for sintering high-performance Si ₃N ₄/ SiC matrix material.

At present, reported in literature prepares Si ₃N ₄The method of/SiC composite granule has gas-phase reaction method, carbothermal reduction-nitridation method, high-energy ball milling reaction method etc.The new former white first-class people of Japan prepares Si with gas-phase reaction ₃N ₄/ SiC composite granule, this composite granule mechanically mixes silicon nitride and silicon carbide powder further than simply, and the stupalith microstructure analysis for preparing with this composite granule shows this material Si ₃N ₄Crystal grain inside has the nano grade Sic particle, has constituted good nano SiC (the p)/Si of mechanical property ₃N ₄Matrix material.But its shortcoming is a desired raw material gas price costliness, the synthesis technique complexity, and equipment has high input, and preparation cost is very high.

The carbothermal reduction-nitridation method is the preparation Si that the research of Shanghai silicate institute is adopted ₃N ₄The method of/SiC composite granule.It is starting raw material that this method adopts home-made carbon black and aerogel silicon oxide, after the ball milling mixed number hour, puts into plumbago crucible, in High Temperature Furnaces Heating Apparatus, carries out carbothermic reduction reaction under the high pure nitrogen atmosphere, generates nanometer Si in 1500～1700 ℃ temperature range ₃N ₄/ SiC composite granule.The shortcoming of this method is, carbothermic reduction reaction energy consumption height, and the production cycle is long, and suitability for industrialized production is restricted.

People such as U.S. Shaw have studied with the synthetic Si of high-energy ball milling reaction method ₃N ₄/ SiC composite granule, this method are at NH with silica flour and graphite powder mix ₃Or N ₂Carry out high-energy ball milling in the atmosphere and handle,, both synthesized SiC/Si in the process of lapping through grinding for a long time ₃N ₄Composite granule.Yet this method only limits to the experimental study stage, also suitable distance will be arranged apart from suitability for industrialized production.

The combustion synthesis process that development in recent years is got up has advantages such as energy-conservation, efficient, low cost, the synthetic Si of burning ₃N ₄Powder has a large amount of research bases, and synthesizes SiC for burning, because the weak exothermal nature of reacting is difficult to directly prepare in the synthetic mode of burning, therefore adopts modes such as applying electric field, interpolation activator to promote to burn more and synthesizes the carrying out of SiC reaction.

Summary of the invention

The purpose of this invention is to provide a kind of chemical pumping burning synthesizing silicon nitride/silicon carbide (Si ₃N ₄/ SiC) the method for composite granule is in the technological process of synthesizing silicon nitride/silicon carbide composite powder body, by add chemical pumping agent NH in initial powder ₄Cl and tetrafluoroethylene, the synthetic Si of burning in nitrogen atmosphere ₃N ₄/ SiC composite granule.

A further object of the present invention is simultaneously from the preparation technology of composite granule, and some processing parameter of appropriate change can prepare the powder that principal phase is SiC.

Chemical pumping burning synthesizing silicon nitride/silicon carbide (Si of the present invention ₃N ₄/ SiC) composite granule or principal phase are the method for SiC powder, this method may further comprise the steps:

(1) batching:

In weight part, with silica flour: 40～70 parts, carbon black: 20～50 parts, the chemical pumping agent: 0.5～20 part is mixed, and obtains a mixture;

Wherein said chemical pumping agent is NH ₄Cl and tetrafluoroethylene, NH ₄The weight ratio of Cl and tetrafluoroethylene is 1: 1～1: 10;

(2) activation treatment:

The mixture that step (1) is obtained grinds activation treatment;

(3) combustion reactions:

Mixture after step (2) ground is with 0.3～1.0g/cm ³Loose density pack in the autoclave, after vacuumizing, charge into nitrogen, make pressure-controlling at 1～3MPa, bring out mixture then and carry out the self-propagating combustion building-up reactions;

(4) reaction is finished:

After the rising of the elder generation of the pressure in the reactor slowly dropped to initial pressure again, combustion synthesis reaction was finished, the releasing reactor internal pressure, and resultant powdered product is Si ₃N ₄/ SiC composite granule.

The present invention has expanded the combustiblecomponents scope of raw material by changing content and the nitrogen equipressure that grinds activatory time, chemical pumping agent, has realized the synthetic Si of burning ₃N ₄/ SiC composite granule.Si/C/N ₂Add chemical pumping agent NH in the reaction system ₄Cl, its effect is the activating velocity that quickens the mechanical milling process material powder, makes reactant can realize particulate refinement and activation in the short period of time.Having added chemical pumping agent tetrafluoroethylene in the system, has been the effect of inducing combustion building-up reactions.

In the present invention, the particle size range of employed Si powder is 0.1～110 μ m; The particle size range of carbon black is 10～30nm; Employed chemical pumping agent is NH ₄Cl and teflon mixture, wherein NH in the mixture ₄The weight ratio of Cl and tetrafluoroethylene is 1: 1～1: 10.

In the blending process of step of the present invention (1), preferred earlier silica flour and carbon black being mixed in proportion adds chemical pumping agent NH then ₄Cl carries out pre-activated and handles, and adds chemical pumping agent tetrafluoroethylene subsequently and carry out combination treatment (prevention chemical pumping agent tetrafluoroethylene is reunited) in process of lapping, also above chemical pumping agent can be added simultaneously and carry out mixing and ball milling.

Grind activation treatment for the mixture that step (1) is obtained, can adopt mechanical activation to handle, comprise that high-energy planetary formula ball milling, the horizontal rotor of high energy grind, high energy shakes grinding or stirring ball-milling etc., 1～10 hour ball milling time, preferred 1～5 hour.Then, the mix powder pine after grinding is loaded in the resistant to elevated temperatures container (for example porous graphite crucible), loose density is 0.3～1.0g/cm ³, put into reactor more together.The reactor that is used for the present invention is the high pressure vessel of the band watercooling jacket made with stainless steel.

In the present invention, adopt tungsten helix to make heating element, feed the electric current of 10～30A, bring out powder systems generation combustion synthesis reaction in the local heating mode.After the pressure fast rise in the reactor, illustrate that combustion synthesis reaction causes, the combustion synthesis reaction time is 10～30 minutes, the process that the pressure in the reactor slowly descends was both finished the process that is cooled to room temperature for reaction.Release reaction still internal pressure can obtain loose powdered product then, after the fine grinding, obtains Si ₃N ₄/ SiC composite granule.

From above preparation technology, to remove and change the nitrogen atmosphere in the reactor into pure argon atmosphere, the Si in the material powder, C blending ratio are suitably adjusted, and other reactive material and processing parameter are all with preparation Si ₃N ₄/ SiC composite granule can be prepared the powder that principal phase is SiC, no Si ₃N ₄Generate mutually.

The present invention compared with the prior art, its advantage is:

(1). the starting material powder is convenient can be got, and the raw material silica flour need not special processings such as pickling.

(2). the activation treatment time is only 1～10 hour ball milling time, preferred 1～5 hour; And combustion synthesis reaction is rapid, and whole combustion reaction time is 10～30 minutes, has shortened the whole production cycle.

(3). rely on the exothermic effect of raw material self to finish the self-propagating high-temperature reaction, after reaction is brought out, need not external energy, and the required electric energy of the chemical reaction that ignites can be ignored.Therefore, save energy reduces cost.

(4). owing to the introducing of chemical pumping agent and by grinding the equal activation treatment means of amorphous of introducing, realized being the direct ignition and the combustion synthesis reaction of weak thermopositive reaction agent system of principal phase with Si-C, and controlled reaction process effectively, make the synthetic required nitrogen pressure of burning reduce (reaction pressure 1～3MPa).And then reduced requirement to equipment, improved the production safety coefficient.

(5). the present invention can also prepare Si respectively by the adjustment to processing parameter and proportioning raw materials ₃N ₄/ SiC composite granule or principal phase are the powder of SiC, have realized the widespread use of this technology in low heat release combustion system.

Description of drawings

Fig. 1. the XRD spectra of the β-SiC powder of preparation in the embodiment of the invention 3.

Fig. 2. the β-SiC powder SEM photo of preparation in the embodiment of the invention 3.

Embodiment

Embodiment 1

Si powder, the carbon black of median size 30nm, the NH of median size 0.5 μ m ₄Cl and tetrafluoroethylene, by weight than 60: 30: 5: 5 take a sample, and they are put into the ball grinder ball milling 9 hours of vibromill, make its thorough mixing and activation; Material behind the admixture activation is placed the porous graphite crucible, make loose density be about 0.3～1.0g/cm ³, place a helically wound tungsten filament on the material upper strata, the tungsten filament diameter is 0.5mm, puts into the combustion synthesis reaction still more together; After vacuumizing, charge into high pure nitrogen, reach 2MPa up to nitrogen pressure from the reactor bottom; Helical tungsten filament is passed to the pulsed current of 10～30A, make its heating, bring out the material powder self-propagating combustion, combustion reactions continues to be cooled to room temperature after 10 minutes, reaction end gas is emitted again, and the fine grinding product promptly obtains combustion reaction products.Reaction product is carried out material phase analysis with Japan's D/MAX-IIB type X-ray diffraction analyser of science, and its result is Si ₃N ₄/ SiC composite granule.

Embodiment 2

Si powder, the carbon black of median size 20nm, the NH of median size 5 μ m ₄Cl and tetrafluoroethylene, by weight than 70: 25: 2: 3 take a sample, will claim earlier Si powder, carbon black and NH ₄Cl puts into the ball grinder ball milling 5 hours of planetary ball mill, makes its thorough mixing, tetrafluoroethylene is added again, and continues milled processed 1 hour; Mixed material is placed in the porous graphite crucible, make loose density be about 0.3～1.0g/cm ³, place a helical tungsten filament on the material upper strata, put into the combustion synthesis reaction still more together; After vacuumizing, charge into nitrogen to 1MPa from the reactor bottom; Helical tungsten filament is passed to the pulsed current of 12A, make its heating, bring out the material powder self-propagating combustion, combustion reactions continues to be cooled to room temperature after 30 minutes, emptying gas, and the fine grinding product promptly obtains reaction product.Reaction product is carried out material phase analysis with Japan's D/MAX-IIB type X-ray diffraction analyser of science, and with HITACHI S-4300 scanning electron microscopic observation products of combustion pattern, test result proves that combustion synthesized product is Si ₃N ₄/ SiC composite granule.

Embodiment 3

Si powder, the carbon black of median size 10nm, the NH of median size 44 μ m ₄Cl and tetrafluoroethylene, by weight than 52: 31: 2: 15 take a sample, and put into the ball grinder of oscillatory type ball mill, and ball milling 4.5 hours makes its thorough mixing and activation; Material behind the admixture activation is placed the porous graphite crucible, make loose density be about 0.3～1.0g/cm ³, place a helically wound tungsten filament on the material upper strata, the tungsten filament diameter is 0.5mm, puts into the combustion synthesis reaction still more together; After vacuumizing, charge into argon gas to 3MPa from the reactor bottom; Helical tungsten filament is passed to the pulsed current of 12A, make its heating, bring out the material powder self-propagating combustion, combustion reactions continues to be cooled to room temperature after 15 minutes, emptying gas, the fine grinding product, get final product reaction product.Reaction product is carried out XRD analysis with Japan's D/MAX-IIB type X-ray diffraction analyser of science, and with HITACHI S-4300 scanning electron microscopic observation products of combustion pattern, the test result demonstration, combustion synthesized product is pure β-SiC powder, no Si ₃N ₄Exist mutually.The XRD spectra of this powder and SEM photo are seen Fig. 1 and Fig. 2.

Claims

1. A method for chemically excited combustion synthesis of silicon nitride/silicon carbide composite powder, characterized in that the method may further comprise the steps:

(1) Ingredients:

In parts by weight, silicon powder: 40-70 parts, carbon black: 20-50 parts, chemical stimulant: 0.5-20 parts are mixed to obtain a mixture;

The chemical stimulant mentioned therein is NH ₄ Cl and polytetrafluoroethylene, and the weight ratio of NH ₄ Cl to polytetrafluoroethylene is 1:1 to 1:10;

(2) Activation treatment:

The mixture obtained in step (1) is subjected to grinding and activation treatment;

(3) Combustion reaction:

Put the ground mixture in step (2) into an autoclave with a bulk density of 0.3-1.0 g/cm ³ . After vacuuming, fill it with nitrogen to control the pressure at 1-3 MPa, and then induce the mixture to self-propagate. Combustion synthesis reaction;

(4) The reaction is complete:

When the pressure in the reactor first rises and then slowly drops to the initial pressure, the combustion synthesis reaction is completed, the pressure in the reactor is released, and the obtained powdery product is Si ₃ N ₄ /SiC composite powder.

2. A method for chemically stimulated combustion synthesis of SiC powder, characterized in that the method may further comprise the steps:

(1) Ingredients:

(2) Activation treatment:

(3) Combustion reaction:

Put the ground mixture in step (2) into an autoclave with a bulk density of 0.3 to 1.0 g/cm ³ . After vacuuming, fill it with argon to control the pressure at 1 to 3 MPa, and then induce the mixture to undergo autoclaving. Propagation combustion synthesis reaction;

(4) The reaction is complete:

When the pressure in the reactor first rises and then slowly drops to the initial pressure, the combustion synthesis reaction is completed, the pressure in the reactor is released, and the obtained powdery product is a powder whose main phase is SiC.

3. The method according to claim 1 or 2, characterized in that: the batching process of the step (1) is to mix silicon powder and carbon black in proportion, then add chemical stimulant NH ₄ Cl to activate Pretreatment followed by mixing treatment with chemical stimulant PTFE.

4. The method according to claim 1 or 2, characterized in that: the particle size range of the silicon powder is 0.1-110 μm; the particle size range of the carbon black is 10-30 nm.

5. The method according to claim 3, characterized in that: the particle size range of the silicon powder is 0.1-110 μm; the particle size range of the carbon black is 10-30 nm.

6. The method according to claim 1 or 2, characterized in that: the grinding activation treatment time is 1-10 hours.

7. The method according to claim 6, characterized in that: said grinding activation treatment adopts mechanical activation treatment, and the grinding activation treatment machine includes high-energy planetary ball mill, high-energy horizontal rotor mill, high-energy vibrating mill or stirring ball mill.

8. according to the described method of claim 1 or 2, it is characterized in that: the mixture after described step (2) grinding is packed in reactor, is that the mixture powder after grinding is first loosely packed in the high temperature resistant porous graphite crucible, and then put them together into the reaction kettle.

9. The method according to claim 1 or 2, characterized in that: the combustion synthesis reaction of the induced mixture is to use a tungsten helical wire as a heating element, and feed a current of 10-30A to induce the mixture to proceed by local heating. Self-propagating combustion synthesis reactions.

10. The method according to claim 9, characterized in that, the reaction time of the combustion synthesis is 10-30 minutes.