CN103387231B - Synthesis method of beta-SiC micro-powder and whiskers - Google Patents
Synthesis method of beta-SiC micro-powder and whiskers Download PDFInfo
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- CN103387231B CN103387231B CN201310303598.7A CN201310303598A CN103387231B CN 103387231 B CN103387231 B CN 103387231B CN 201310303598 A CN201310303598 A CN 201310303598A CN 103387231 B CN103387231 B CN 103387231B
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Abstract
The invention relates to the technical field of solid phase synthesis of silicon carbide micro-powder and especially relates to a synthesis method of beta-SiC micro-powder and whiskers. The synthesis method of the beta-SiC micro-powder and whiskers utilizes crushed and uniformly mixed carbon and silicon raw materials as reaction raw materials and is characterized by comprising the following steps of filling the reaction raw materials into a vacuum resistance furnace, closing the vacuum resistance furnace, carrying out vacuum-pumping on the vacuum resistance furnace so that the pressure in the vacuum resistance furnace is below 100Pa, supplying power to the vacuum resistance furnace to heat it to a temperature of 1400-1500K, carrying out heat preservation, stopping the power supply when the pressure in the vacuum resistance furnace is below 10Pa for more than 60min, and carrying out natural cooling to obtain the product. The synthesis method realizes accurate control of beta-SiC micro-powder and whisker synthesis conditions, has a simple process and a low production cost, and can realize industrial synthesis of the beta-SiC micro-powder and whiskers. The beta-SiC micro-powder and whiskers obtained by the synthesis method has high integrity, high purity and good quality.
Description
(1) technical field
The present invention relates to solid phase synthesis silicon carbide micro-powder technical field, particularly a kind of β
-the synthetic method of SiC micro mist and whisker.
(2) background technology
β
-siC micro mist and whisker have the very wide market requirement at production fields such as opticinstrument, electron device, the precision work of super-precision grinding grinding machine metal products, high grade refractory, structural ceramic materials.Current β-SiC micro mist and whisker synthesis method have solid phase method, liquid phase method and vapor phase process three kinds.Solid phase method has Acheson method, ESK method, vertical oven process and high temperature converter process, multicore oven process, carbon silicon direct reaction method and self-propagating method etc.; Liquid phase method has grown up since being the eighties in 20th century, comprise a variety of, wherein mainly contain the precipitator method (direct precipitation method, sluggish precipitation, coprecipitation method, sol-gel method etc.), solvent evaporated method, thermal decomposition method, colloid chemistry methods, hydrothermal decomposition method, electrolytic process and liquid interface reaction method.Vapor phase process synthesis micro mist is the new technology of development in recent years, because gas-phase reaction speed is fast, reactant is short in the high-temperature zone residence time, generates micro mist and mostly is indefiniteness, mainly comprise following several method: gas-phase reaction method (CVD) and evaporation-coacervation (PVD).
Solid phase method is the main method of traditional industrial production SiC powder, and output is more than 90% of SiC ultimate production, and its principle is carbothermic reduction reaction, has raw material cheap, is easy to the advantage realizing suitability for industrialized production.Acheson method is wherein topmost SiC production method, but the method state of the art is low, the mode of production falls behind, seriously polluted, thermo-efficiency is low, energy consumption is high, produce dangerous (easily spraying stove), quality product is low, added value of product is lower, CO gas do not reclaim, this and current national energy-saving reduce discharging policy and greatly run counter to.In recent years, the SiC mode of production of this high energy consumption, high pollution, low output is all tried hard to change by each state, maximizes as produced stove, changes the power supply mode of electrode, CO collection and confinement of gases recycling, achieve certain energy-saving effect, but fundamentally do not change its backward situation.
But, above method is not all considered to synthesize SiC micro mist and whisker under vacuum, and can not the accurately synthesis temperature of control SiC micro mist and whisker, atmosphere and pressure, synthesis temperature is high, cause β-SiC to synthesize and substantially rely on technical experience, this just causes certain randomness to production, is difficult to the micron-sized β of disposable synthesis of high purity-SiC micro mist and whisker.
(3) summary of the invention
The present invention in order to make up the deficiencies in the prior art, provide a kind of technique simple, control accurately, the synthetic method of production cost is low, product purity is high β-SiC micro mist and whisker.
The present invention is achieved through the following technical solutions:
A synthetic method for β-SiC micro mist and whisker, with the carbon raw material mixed after pulverizing and siliceous raw material for reaction material, comprises the steps:
(1) fixed carbon in carbon raw material and the SiO in siliceous raw material
2mass ratio be 1:1.6 ~ 1.7, reaction material loaded in vacuum resistance furnace, then reaction material being densified to tap density is 0.8 ~ 1.1g/cm
3;
(2) one block of porous corundum steel plate is added a cover, containing vacuum resistance furnace body of heater in reaction material surface after compaction, and being evacuated to furnace pressure to vacuum resistance furnace is below 100Pa, then to vacuum resistance furnace electrified regulation to 1400K ~ 1500K, starts insulation;
(3) when vacuum resistance furnace internal pressure maintained below 10Pa more than 60 minutes, stop powering to vacuum resistance furnace, naturally cooling, obtains β-SiC micro mist or β-SiC whisker that purity is more than 98.5%.
More excellent scheme of the present invention is:
In step (1), described carbon raw material is the mixture of one or more and graphite in refinery coke, hard coal, bituminous coal and carbon black, and wherein graphite accounts for 50 ~ 80% of mixture total mass; Described siliceous raw material is quartzite.
In step (2), the power supply system of described vacuum resistance furnace is, when reaction material core temperature is less than 800K, controlling vacuum oven surface load is 6 ~ 8w/cm
2, and make vacuum tightness maintain below 100Pa all the time; When reaction material core temperature is at 800 ~ 1200K, controlling vacuum resistance furnace surface load is 9 ~ 11w/cm
2, and make vacuum tightness maintain below 200Pa all the time; When reaction material core temperature is higher than more than 1200K, control vacuum resistance furnace 7 ~ 10w/cm
2, and make vacuum tightness maintain below 100Pa all the time.
Granularity after described carbon raw material pulverizing is less than 45 μm, and the granularity after siliceous raw material pulverizing is less than 75 μm.
Primitive reaction equation of the present invention is: 3C (s)+SiO
2(s) → SiC (s)+2CO (g).
The standard Gibbs free energy of this reaction can be expressed as:
，
Again because:
，
，
，
，
When
,
。
According to following table, order
, under can solving this condition, the equilibrium temperature of this reaction is 1507K, as long as namely under this reaction normal pressure when temperature could occur higher than 1507K, in order to the power of intensified response, the temperature of general normal pressure synthesis β-SiC micro mist will at more than 1800K.
In like manner, can calculate when system stagnation pressure
be respectively 10kPa, when 1kPa, 100Pa, 50Pa, 10Pa, 1Pa, corresponding balanced reaction temp is as shown in the table.
As can be seen from the above table, the raising of system vacuum can significantly reduce chemical reaction equilibrium temperature, as the condition of this reaction is controlled at below 100Pa, temperature of reaction at least can be reduced more than 298K, this has significant effect to energy-saving and cost-reducing in SiC Industrial processes, and the reduction of temperature of reaction also makes refractory materials in stove select grade to decrease, and greatly can reduce production cost.
The present invention compared with prior art has following advantage:
(1) vacuum (below 100Pa) carbon-thermal reduction method synthesizing β-SiC micro mist and whisker is adopted, compare normal pressure carbon-thermal reduction legal system for β-SiC micro mist and whisker, temperature of reaction reduces more than 298k, make reaction conditions gentleer, greatly reduce the requirement of refractory materials, there is significant effect of energy, significantly can reduce production cost.
(2) the micron-sized SiC powder of the method energy single sintering and whisker, and can according to the size of vacuum oven, a stove can go out SiC micro mist and crystal whisker products more than 1 ton.
(3) vacuum synthesis environment is adopted, greatly strengthen the effect of stove inner transmission matter and heat transfer, can Fast back-projection algorithm β-SiC micro mist and whisker at short notice, synthesized β-SiC micro mist and whisker purity are greater than 98.5%, β-SiC micro mist productive rate is up to more than 80%, β-SiC whisker productive rate more than 30%.
(4) vacuum synthesis environment is adopted, under high-temperature low-pressure, impurity volatilization is strengthened, the requirement of raw material is reduced greatly, the raw material that fixed carbon content is low, impurity is higher can be used, the raw material not meeting existing SiC manufacturing requirements is made as reaction raw materials, can greatly to have widened raw-material Application Range.
(5) adopt and automatically control and automatic monitored control system, be easy to realize precise controlling to in-furnace temperature and pressure, overcoming existing SiC production technology relies on experience to the blindness of the process of arranging production and randomness, decreases human factor to producing the disadvantageous effect caused.
(6) according to the requirement of synthesis variant production, formulate different power supply systems, and adjust power supply system with the change of vacuum tightness in stove, accurately can judge power failure opportunity.
The present invention accurately can control SiC micro mist and whisker synthesis condition, and technical process is simple, and production cost is low, can industrialization synthesizing β-SiC micro mist and whisker, and β-SiC micro mist and the whisker complete crystal form of synthesis, purity is high, quality good.
(4) embodiment
Embodiment 1:
(1) by levigate for the graphite of fixed carbon content 95% to 45 μm with thin micro mist, by levigate for the hard coal of fixed carbon content 90% to 45 μm with thin micro mist, by SiO
2content be 99% quartzite levigate to 75 μm with thin micro mist, by fixed carbon: SiO
2=1:1.6, graphite: three kinds of raw materials are carried out the obtained reaction material of fully mixing by the ratio of hard coal=4:1.
(2) by mix reaction material load in vacuum resistance furnace reaction chamber, reaction material is densified to tap density and is about 0.9g/cm
3.
(3) at the porous corundum cover plate that reaction material upper surface lid one reaction chamber length and width match.
(4) cover bell, closed furnace body, thermopair is installed and puts in place.
(5) open cooling system, automatic control system, drive vacuum pump and make vacuum oven pressure to below 100Pa.
(6) power: 1) at below in-furnace temperature 800K, adopt invariable power to power, control surface load is at 7w/cm
2; 2) at 800K-1200K, adopt invariable power to power, control surface load is at 9w/cm
2; 3) at 1200K-1500K, adopt Variable power to power, control within the scope of vacuum tightness 80Pa-20Pa, control surface load is at 8w/cm
2-10 w/cm
2in scope; 4) 1500K starts insulation, soaking time 2 hours, and the gas that smelting process produces is lighted by vacuum pump smoke outlet.
(7) when vacuum tightness in stove obviously rises and maintain below 10Pa 10 minutes, stop power supply.
(8) body of heater naturally cooling 10 hours, opens bell, takes out β-SiC micro powder product.
(9) β-SiC micro mist purity of above step acquisition is at 98.5%, β-SiC micro mist productive rate 85%, obtains high-purity β-SiC micro mist, then need by conventional de-carbon and HF acid cleaning process to a nearly step.
(10) β-SiC micro mist mean particle size less than 15 μm of above step acquisition, to obtain high-purity β-SiC micro mist of the narrower different grain size rank of size-grade distribution, then needs by conventional hierarchical technique.
Embodiment 2:
(1) by levigate for the graphite of fixed carbon content 95% to 45 μm with thin micro mist, by levigate for the hard coal of fixed carbon content 90% to 45 μm with thin micro mist, by SiO
2content be 99% quartzite levigate to 75 μm with thin micro mist, by fixed carbon: SiO
2=1:1.7, graphite: three kinds of raw materials are carried out the obtained reaction material of fully mixing by the ratio of hard coal=1:1.
(2) by mix reaction material load in vacuum resistance furnace reaction chamber, reaction material is densified to tap density and is about 0.9g/cm
3.
(3) at the porous corundum cover plate that reaction material upper surface lid one reaction chamber length and width match.
(4) cover bell, closed furnace body, thermopair is installed and puts in place.
(5) open cooling system, automatic control system, drive vacuum pump and make vacuum oven pressure to below 100Pa.
(6) power: 1) at below in-furnace temperature 800K, adopt invariable power to power, control surface load is at 7w/cm
2; 2) at 800K-1200K, adopt invariable power to power, control surface load is at 8w/cm
2; 3) at 1200K-1300K, adopt Variable power to power, control within the scope of vacuum tightness 50Pa-20Pa, control surface load is at 7w/cm
2-8 w/cm
2in scope; 4) 1300K starts insulation, soaking time 10 hours, and the gas that building-up process produces is lighted by vacuum pump smoke outlet.
(7) when vacuum tightness in stove obviously rises and maintain below 10Pa 10 minutes, stop power supply.
(8) body of heater naturally cooling 10 hours, opens bell, takes out β-SiC crystal whisker products.
(9) β-SiC micro mist purity that above step is obtained is more than 98.5%, and β-SiC productive rate 92%, wherein β-SiC whisker accounts for 40% of product, obtains high-purity β-SiC whisker, then need by conventional de-carbon and HF acid cleaning process to a nearly step.
(10) β-SiC whisker mean particle size less than 20 μm of above step acquisition, to obtain high-purity β-SiC whisker of the narrower different grain size rank of size-grade distribution, then needs by conventional hierarchical technique.
Embodiment 3:
(1) by levigate for the graphite of fixed carbon content 95% to 45 μm with thin micro mist, by levigate for the refinery coke of fixed carbon content 92% to 45 μm with thin micro mist, by SiO
2content be 99% quartzite levigate to 75 μm with thin micro mist, by fixed carbon: SiO
2=1:1.65, graphite: three kinds of raw materials are carried out the obtained reaction material of fully mixing by the ratio of refinery coke=2:1.
(2) by mix reaction material load in vacuum resistance furnace reaction chamber, reaction material is densified to tap density and is about 0.9g/cm
3.
(3) at the porous corundum cover plate that reaction material upper surface lid one reaction chamber length and width match.
(4) cover bell, closed furnace body, thermopair is installed and puts in place.
(5) open cooling system, automatic control system, drive vacuum pump and make vacuum oven pressure to below 100Pa.
(6) power: 1) at below in-furnace temperature 800K, adopt invariable power to power, control surface load is at 7w/cm
2; 2) at 800K-1200K, adopt invariable power to power, control surface load is at 9w/cm
2; 3) at 1200K-1400K, adopt Variable power to power, control within the scope of vacuum tightness 70Pa-20Pa, control surface load is at 8w/cm
2-9 w/cm
2in scope; 4) 1400K starts insulation, soaking time 6 hours, and the gas that building-up process produces is lighted by vacuum pump smoke outlet.
(7) when vacuum tightness in stove obviously rises and maintain below 10Pa 10 minutes, stop power supply.
(8) body of heater naturally cooling 10 hours, opens bell, takes out β-SiC micro mist and crystal whisker products.
(9) β-SiC micro mist that above step is obtained and whisker purity are more than 98.5%, and β-SiC productive rate 90%, obtains high-purity β-SiC whisker to a nearly step, then need by conventional de-carbon and HF acid cleaning process.
(10) β-SiC micro mist that obtains of above step and whisker mean particle size less than 20 μm, to obtain high-purity β-SiC whisker of the narrower different grain size rank of size-grade distribution, then need by conventional hierarchical technique.
Claims (2)
1. a synthetic method for β-SiC micro mist and whisker, with the carbon raw material mixed after pulverizing and siliceous raw material for reaction material, is characterized by, comprise the steps: the fixed carbon in (1) carbon raw material and the SiO in siliceous raw material
2mass ratio be 1:1.6 ~ 1.7, reaction material loaded in vacuum resistance furnace, then reaction material being densified to tap density is 0.8 ~ 1.1g/cm
3; Described carbon raw material is the mixture of one or more and graphite in refinery coke, hard coal, bituminous coal and carbon black, and wherein graphite accounts for 50 ~ 80% of mixture total mass; Described siliceous raw material is quartzite; (2) one block of porous corundum steel plate is added a cover, containing vacuum resistance furnace body of heater in reaction material surface after compaction, and being evacuated to furnace pressure to vacuum resistance furnace is below 100Pa, then to vacuum resistance furnace electrified regulation to 1400K ~ 1500K, starts insulation; (3) when vacuum resistance furnace internal pressure maintained below 10Pa more than 60 minutes, stop powering to vacuum resistance furnace, naturally cooling, obtains β-SiC micro mist or β-SiC whisker that purity is more than 98.5%.
2. the synthetic method of β-SiC micro mist according to claim 1 and whisker, is characterized in that: the granularity after described carbon raw material pulverizing is less than 45 μm, and the granularity after siliceous raw material pulverizing is less than 75 μm.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5021230A (en) * | 1987-04-22 | 1991-06-04 | Krstic Vladimir D | Method of making silicon carbide |
| CN1449994A (en) * | 2003-05-09 | 2003-10-22 | 西安科技学院 | Industrial preparation method for silica carbide crystal whisker and micropowder |
| CN1636870A (en) * | 2004-12-30 | 2005-07-13 | 清华大学 | Nanometer SiC powder preparing process |
| CN102596802A (en) * | 2009-08-26 | 2012-07-18 | Lg伊诺特有限公司 | System and method for manufacturing silicon carbide pulverulent body |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5021230A (en) * | 1987-04-22 | 1991-06-04 | Krstic Vladimir D | Method of making silicon carbide |
| CN1449994A (en) * | 2003-05-09 | 2003-10-22 | 西安科技学院 | Industrial preparation method for silica carbide crystal whisker and micropowder |
| CN1636870A (en) * | 2004-12-30 | 2005-07-13 | 清华大学 | Nanometer SiC powder preparing process |
| CN102596802A (en) * | 2009-08-26 | 2012-07-18 | Lg伊诺特有限公司 | System and method for manufacturing silicon carbide pulverulent body |
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