CN107128925A - A kind of method that non-hydrolytic sol-gel combination carbothermic method prepares SiC powder - Google Patents

Abstract

The present invention relates to a kind of method that non-hydrolytic sol-gel combination carbothermic method prepares SiC powder, belong to materials science field.The powder preparation method includes：First, with FeCl₃、Si(OC₂H₅)₄And SiCl₄Reaction solution is prepared for raw material, triggers non-hydrolytic sol-gel reaction to synthesize SiO by gelation processing₂Gel, in CH₂Cl₂SiO is obtained after middle ultrasound, washing, drying₂Xerogel.Then, by itself and carbon black（Graphite or activated carbon）Mixing obtains mixed powder, adds ball milling, drying after appropriate absolute ethyl alcohol, adds the compound that homogenizing is obtained after the PVA aqueous solution ageing mixtures that concentration is 2wt%.Finally, the compound of homogenizing is molded by forcing press, using bury carbon method in tube-type atmosphere furnace under an argon atmosphere through reduction and carbonization reaction prepare SiC powder.SiC powder synthesis temperature prepared by the present invention is relatively low, and powder dispersity is good, purity is high and particle diameter is smaller, can field provides a kind of new function material for military project is civilian etc..

Description

The method that a kind of non-hydrolytic sol-gel combination carbothermic method prepares SiC powder

Technical field

The invention belongs to materials science field, and in particular to prepared by a kind of non-hydrolytic sol-gel combination carbothermic method The method of SiC powder.

Background technology

Carborundum（SiC）Due to its excellent mechanical strength, chemical stability, corrosion resistance and higher heat transfer etc. Performance causes the very big concern of people, is widely used in grinding materials and grinding tool, refractory material, metallurgy, high-temperature structural ceramics etc. all Many industrial circles.Meanwhile, carborundum is as a kind of wide band gap semiconducter, and not only resistivity is adjustable, absorption band is wide, also with resistance to The features such as high temperature, high intensity, low-density, while its inoxidizability is better than carbons absorbing material, it is considered to be realize lightweight, thin Layer, broadband high temperature resistant inhale the preferred material of ripple.

At present, the preparation method of SiC material mainly includes vapour deposition process（CVD）, traditional carbothermic method etc., wherein, CVD equipment is expensive, and technological requirement is high, is unfavorable for large-scale production；And traditional carbothermic method power consumption is high, and prepare SiC sintering activities are poor.Presoma is first generally thus prepared using sol-gal process, then by carbothermic method relatively low At a temperature of prepare the more uniform SiC powder of granularity.

For example, Song Yong is just waited using industry silicasol and water soluble phenol resin as raw material, prepared using sol-gal process The precursor of organic-inorganic hybrid, the higher β-SiC micro mists of purity are made through carbothermic reduction reaction, but micro mist be by particle with What whisker was constituted mixes body, and there is agglomeration.（By organic-inorganic hybrid precursor for SiC nano powders [J] Materials Science and Engineering journal, 2004,22 (3):341-343）Force on the sunny side etc. use sol-gel process, using Fe as catalyst, Different-grain diameter, irregular β-SiC particulate are prepared through carbon thermal reduction.With the increase of Fe consumptions, the particle diameter of β-SiC powder and Mean grain size increase, and accumulate defect concentration and specific surface area then reduces.（Fe catalyst amounts are to β-SiC in sol-gel Accumulate influence [J] novel charcoal materials of defect and pattern, 2005,20 (4):324-328）

When preparing SiC material using sol-gel process, the factor such as hydrolysis time, pH value of solution, heat treatment temperature is to SiC material system Standby to influence larger, its SiC material prepared also has compared with the target material of well-crystallized, high purity, shape and size tunable Certain gap.In view of the shortcoming that above-mentioned hydrolyzed collosol-gelatin method is shown when preparing SiC powder, Robert The non-hydrolyzed collosol-gelatin technology that J.P.Corriu is proposed, it directly can pass through presoma without the hydrolysis of metal alkoxide Between take off the polycondensation reaction such as alkyl halide or de- ether polycondensation and form gel, the method technique is simple, and prepared oxide powder Particle is tiny, specific surface area is big, activity is high, and with reactivity height, the presoma that particle diameter is small, specific surface area is high, can promote Enter carbothermic reduction reaction progress.

For example, L. Bourget etc. are with silicon tetrachloride（SiCl₄）For raw material, surface area is prepared most using non-hydrolytic sol-gel method High reachable 869m²/ g silicon-dioxide powdery, at the same also have more mesopore pore passage structure, this be conducive to using diffusion reaction as The progress of main carbothermic reduction reaction.（Non-hydrolytic sol-gel routes to silica [J]. Journal of Non-Crystalline Solids, 1998, 242:81-91）If therefore, simple with both easily controllable, technique, again Can obtain has more high activity SiO₂The non-hydrolytic sol-gel process and CRN method of nanometer presoma are combined, right Reduction SiC powder synthesis temperature, shortening reaction time are significant.

The content of the invention

It is an object of the invention to overcome the shortcomings of that there is provided a kind of non-hydrolytic is molten in above-mentioned existing SiC powder technology of preparing The method that glue-gel combination carbothermic method prepares SiC powder.

In order to realize foregoing invention purpose, the invention provides following technical scheme：（1）By anhydrous ferric chloride, positive silicic acid Ethyl ester and silicon tetrachloride press certain molar ratio reaction solution, then by reaction solution heated gelization processing, trigger non-hydrolytic Sol gel reaction synthesizes SiO₂Gel, by SiO₂Gel obtains SiO in dichloromethane after ultrasound, washing, drying₂It is dry solidifying Glue；（2）By SiO₂Xerogel and carbon black（Graphite or activated carbon）Mixing obtains mixed powder by a certain percentage, in mixed powder plus Enter to add the PVA aqueous solution that concentration is 2wt% after drying through 60 DEG C after appropriate absolute ethyl alcohol, ball milling and be well mixed, and in room The compound of homogenizing is obtained after warm ageing mixture；（3）The compound of homogenizing is molded using forcing press, using burying carbon method in tubular type atmosphere SiC powder is prepared in stove through reduction and carbonization reaction under an argon atmosphere.

The composition of the reaction solution is：The mass percent of anhydrous ferric chloride is 0.05% ~ 0.5%, the matter of tetraethyl orthosilicate It is 45 ~ 65% to measure percentage, and the mass percent of silicon tetrachloride is 34.5% ~ 54.95%.

The temperature control of reaction solution heated gelization processing is：Heating-up temperature is 90 ~ 130 DEG C, and gelation time is 5 ~20h。

The composition of the mixed powder is：SiO₂Xerogel and carbon black（Graphite or activated carbon）Mass ratio be 0.5 ~ 2.

It is described homogenizing compound composition be：Additional concentration is that the mass percent of the 2wt%PVA aqueous solution is 1 ~ 10%, is stranded The material time is 12 ~ 24h.

It is described homogenizing compound molding technique parameter be：Briquetting pressure is 1 ~ 20MP, 10 ~ 60s of dwell time.

The carbo-thermal process of the SiC powder is：Reduction and carbonization temperature is 1200 ~ 1600 DEG C, and programming rate is 1 ~ 10 DEG C/min, 0.5 ~ 5h of soaking time, argon flow amount is 1.5 L/min.

The SiC powder that the present invention is prepared by non-hydrolytic sol-gel combination carbothermic method is characterized as：Crystallinity is good Good, purity is high, particle diameter distribution is uniform.Compared with the prior art, the present invention can simplify the preparation technology of SiC powder, reduction synthesis temperature Degree, reduces and prepares cost, improves the absorbing property of powder.SiC powder prepared by the present invention can be used as high temperature resistant absorbing material.

Beneficial effect

The present invention is compared with hydrolyzed collosol-gelatin technology, the SiO prepared using non-hydrolytic method₂Presoma has higher ratio table The activity of area and Geng Gao, can not only solve hydrolytic sol gel method and prepare SiO₂The deficiency that presoma is present, and combine Carbon thermal reduction technology can then reduce SiC powder synthesis temperature, shorten the reaction time, reduce production cost.The present invention can be China The fields such as high-temperature structural ceramics, Aero-Space, military project provide a kind of new function material, have broad application prospects and technology Progressive meaning.

Case is embodied

Embodiment 1

Reaction solution is prepared by raw material of 0.0195g anhydrous ferric chlorides, 13.5ml tetraethyl orthosilicate and 6.9ml silicon tetrachlorides, it is close After envelope, stirring are completely dissolved to anhydrous ferric chloride, reaction solution is transferred quickly to hold in bullet, 12h is reacted at 110 DEG C and obtains SiO₂ Gel.By SiO₂Gel prepares SiO with after dichloromethane ultrasound, washing and in drying 3h at 110 DEG C₂Xerogel.With SiO₂It is dry Gel is silicon source, and carbon black is carbon source, by SiO₂：The mass ratio of carbon black is 3:2 mix both, are added in mixed powder appropriate Absolute ethyl alcohol, and be put into ball mill, 60 DEG C of dryings after grinding 2h, are that 5% addition concentration is 2wt% by its mass percent The PVA aqueous solution be well mixed, in the compound that homogenizing is obtained after room temperature ageing mixture 12h, used forcing press with 6MP pressure Shaping, uses and buries carbon method to reduce in 1500 DEG C in tube-type atmosphere furnace under 3 DEG C/min heating rates, 1.5 L/min argon gas flow velocitys SiC powder is can be prepared by after carbonization 2.5h, its particle diameter is about 80nm, preferably, purity is high for dispersiveness.

Embodiment 2

Reaction solution is prepared by raw material of 0.0195g anhydrous ferric chlorides, 13.5ml tetraethyl orthosilicate and 6.9ml silicon tetrachlorides, it is close After envelope, stirring are completely dissolved to anhydrous ferric chloride, reaction solution is transferred quickly to hold in bullet, 15h is reacted at 100 DEG C and obtains SiO₂ Gel.By SiO₂Gel prepares SiO with after dichloromethane ultrasound, washing and in drying 3h at 110 DEG C₂Xerogel.With SiO₂It is dry Gel is silicon source, and graphite is carbon source, by SiO₂：The mass ratio of graphite is 1:1 mixes both, is added in mixed powder appropriate Absolute ethyl alcohol, and be put into ball mill, 60 DEG C of dryings after grinding 2h, are that 3% addition concentration is 2wt% by its mass percent The PVA aqueous solution be well mixed, in the compound that homogenizing is obtained after room temperature ageing mixture 15h, used forcing press with 5MP pressure Shaping, uses and buries carbon method to reduce in 1450 DEG C in tube-type atmosphere furnace under 2 DEG C/min heating rates, 1.5 L/min argon gas flow velocitys SiC powder is can be prepared by after carbonization 3h, its particle diameter is about 100nm, preferably, purity is high for dispersiveness.

Embodiment 3

Reaction solution is prepared by raw material of 0.0195g anhydrous ferric chlorides, 13.5ml tetraethyl orthosilicate and 6.9ml silicon tetrachlorides, it is close After envelope, stirring are completely dissolved to anhydrous ferric chloride, reaction solution is transferred quickly to hold in bullet, 10h is reacted at 120 DEG C and obtains SiO₂ Gel.By SiO₂Gel prepares SiO with after dichloromethane ultrasound, washing and in drying 3h at 110 DEG C₂Xerogel.With SiO₂It is dry Gel is silicon source, and activated carbon is carbon source, by SiO₂：The mass ratio of activated carbon is 2:1 mixes both, is added in mixed powder Appropriate absolute ethyl alcohol, and be put into ball mill, 80 DEG C of dryings after grinding 2h, are that 7% addition concentration is by its mass percent The 2wt% PVA aqueous solution is well mixed, and in the compound that homogenizing is obtained after room temperature ageing mixture 10h, is used forcing press with 8MP's Pressure forming, use bury carbon method with 3 DEG C/min heating rates, 1.5 L/min argon gas flow velocitys in 1550 DEG C in tube-type atmosphere furnace SiC powder is can be prepared by after reduction and carbonization 2h, its particle diameter is about 90nm, preferably, purity is high for dispersiveness.

Claims (7)

1. the method that a kind of non-hydrolytic sol-gel combination carbothermic method prepares SiC powder, it is characterised in that preparation SiC The method of powder comprises the following steps：（1）Anhydrous ferric chloride, tetraethyl orthosilicate and silicon tetrachloride are pressed into certain molar ratio Reaction solution, then by reaction solution heated gelization processing, trigger non-hydrolytic sol-gel reaction to synthesize SiO₂Gel, by SiO₂ Gel obtains SiO in dichloromethane after ultrasound, washing, drying₂Xerogel；（2）By SiO₂Xerogel and carbon black（Graphite or work Property charcoal）Mixing obtains mixed powder by a certain percentage, is added in mixed powder after appropriate absolute ethyl alcohol, ball milling through 60 DEG C of dryings The PVA aqueous solution that concentration is 2wt% is added afterwards to be well mixed, and in the compound that homogenizing is obtained after room temperature ageing mixture；（3）Will be equal The compound of change using forcing press be molded, using bury carbon method in tube-type atmosphere furnace under an argon atmosphere through reduction and carbonization react make It is standby go out SiC powder.

2. the method that a kind of non-hydrolytic sol-gel combination carbothermic method as claimed in claim 1 prepares SiC powder, its The composition for being characterised by reaction solution is：The mass percent of anhydrous ferric chloride is 0.05% ~ 0.5%, the quality hundred of tetraethyl orthosilicate Divide than being 45 ~ 65%, the mass percent of silicon tetrachloride is 34.5% ~ 54.95%.

3. the method that a kind of non-hydrolytic sol-gel combination carbothermic method as claimed in claim 1 prepares SiC powder, its It is characterised by that the temperature control that reaction solution heated gelization is handled is：Heating-up temperature be 90 ~ 130 DEG C, gelation time be 5 ~ 20h。

4. the method that a kind of non-hydrolytic sol-gel combination carbothermic method as claimed in claim 1 prepares SiC powder, its The composition for being characterised by mixed powder is：SiO₂Xerogel and carbon black（Graphite or activated carbon）Mass ratio be 0.5 ~ 2.

5. the method that a kind of non-hydrolytic sol-gel combination carbothermic method as claimed in claim 1 prepares SiC powder, its It is characterised by that the composition for being homogenized compound is：Additional concentration is that the mass percent of the 2wt%PVA aqueous solution is 1 ~ 10%, during ageing mixture Between be 12 ~ 24h.

6. the method that a kind of non-hydrolytic sol-gel combination carbothermic method as claimed in claim 1 prepares SiC powder, its It is characterised by that the molding technique parameter for being homogenized compound is：Briquetting pressure is 1 ~ 20MP, 10 ~ 60s of dwell time.

7. the method that a kind of non-hydrolytic sol-gel combination carbothermic method as claimed in claim 1 prepares SiC powder, its The carbo-thermal process for being characterised by SiC powder is：Reduction and carbonization temperature be 1200 ~ 1600 DEG C, programming rate be 1 ~ 10 DEG C/ Min, 0.5 ~ 5h of soaking time, argon flow amount are 1.5 L/min.