CN103387231A - 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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- CN103387231A CN103387231A CN2013103035987A CN201310303598A CN103387231A CN 103387231 A CN103387231 A CN 103387231A CN 2013103035987 A CN2013103035987 A CN 2013103035987A CN 201310303598 A CN201310303598 A CN 201310303598A CN 103387231 A CN103387231 A CN 103387231A
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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.At present β-SiC micro mist and whisker synthesis method have three kinds of solid phase method, liquid phase method and vapor phase processs.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 certainly spreads method etc.; Liquid phase method is to have grown up since the eighties in 20th century, comprise a variety ofly, 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 method, hydrothermal decomposition method, electrolytic process and liquid interface reaction method.The synthetic micro mist of vapor phase process 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 comprises 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 surpasses 90% of SiC ultimate production, and its principle is carbothermic reduction reaction, has a raw material cheap, is easy to realize the advantage of suitability for industrialized production.The Acheson method is topmost SiC production method wherein, 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 does 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, as producing stove, maximizes, and changes power supply mode, the CO collection and confinement of gases recycling of electrode, obtain certain energy-saving effect, but fundamentally do not changed its backward situation.
But, above method is not all considered synthetic SiC micro mist and whisker under vacuum condition, and can not accurately control synthesis temperature, atmosphere and the pressure of SiC micro mist and whisker, synthesis temperature is high, cause the synthetic basic technical experience that relies on of β-SiC, this has just caused 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, provides the synthetic method that a kind of technique is simple, control the β accurate, that production cost is low, product purity is high-SiC micro mist and whisker.
The present invention is achieved through the following technical solutions:
The synthetic method of a kind of β-SiC micro mist and whisker,, take the carbon raw material that mixes after pulverizing and siliceous raw material as reaction material, comprise 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 is packed in vacuum resistance furnace, then reaction material being densified to tap density is 0.8 ~ 1.1g/cm
3
(2) a porous corundum steel plate is added a cover on the reaction material surface after compacting, sealing vacuum resistance furnace body, and it is below 100Pa that vacuum resistance furnace is evacuated to furnace pressure, then to the vacuum resistance furnace energising, is heated to 1400K ~ 1500K, starts insulation;
(3) maintain below 10Pa while surpassing 60 minutes when vacuum resistance furnace internal pressure, stop the vacuum resistance furnace power supply, naturally cooling, obtain purity and be the β-SiC micro mist or β-SiC whisker more than 98.5%.
More excellent scheme of the present invention is:
In step (1), described carbon raw material is one or more and the mixture of 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, during less than 800K, controlling the vacuum oven surface load is 6 ~ 8w/cm when the reaction material core temperature
2, and make vacuum tightness maintain all the time below 100Pa; During at 800 ~ 1200K, controlling the vacuum resistance furnace surface load is 9 ~ 11w/cm when the reaction material core temperature
2, and make vacuum tightness maintain all the time below 200Pa; When the reaction material core temperature is above higher than 1200K, control vacuum resistance furnace 7 ~ 10w/cm
2, and vacuum tightness is maintained below 100Pa all the time.
Granularity after described carbon raw material is pulverized is below 45 μ m, and the granularity after siliceous raw material is pulverized is below 75 μ m.
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
,
Shown in following table, order
, can solve under this condition, the equilibrium temperature of this reaction is 1507K, namely should the reaction normal pressure under as long as could occur higher than 1507K when temperature, for the power of intensified response, generally the temperature of normal pressure synthesis β-SiC micro mist will be more than 1800K.
In like manner, can calculate when the system stagnation pressure
Be respectively 10kPa, 1kPa, 100Pa, 50Pa, 10Pa, during 1Pa, corresponding balanced reaction temp is as shown in the table.
As can be seen from the above table, the raising of system vacuum degree can significantly reduce the chemical reaction equilibrium temperature, be controlled at below 100Pa as the condition that will react, more than temperature of reaction can being reduced 298K at least, this is to saving energy and reduce the cost and have significant effect in the SiC Industrial processes, and the reduction of temperature of reaction also makes refractory materials in stove select grade to decrease, and can greatly reduce production costs.
The present invention compared with prior art has following advantage:
(1) adopt vacuum (100Pa is following) carbon thermal response method synthesizing β-SiC micro mist and whisker, compare the standby β of normal pressure carbon thermal response legal system-SiC micro mist and whisker, more than temperature of reaction reduces 298k, make reaction conditions gentleer, greatly reduce the requirement of refractory materials, have significant effect of energy, can significantly reduce production costs.
(2) the micron-sized SiC powder of the method energy single sintering and whisker, and can be according to the size of vacuum oven, a stove can go out SiC micro mist and crystal whisker products more than 1 ton.
(3) adopt the vacuum synthesis environment, greatly strengthened the effect of stove inner transmission matter and heat transfer, can be at short notice synthesizing β-SiC micro mist and whisker fast, the β of synthesized-SiC micro mist and whisker purity are greater than 98.5%, β-SiC micro mist productive rate is up to more than 80%, and β-SiC whisker productive rate is more than 30%.
(4) adopt the vacuum synthesis environment, the impurity volatilization is strengthened under high-temperature low-pressure, requirement to raw material reduces greatly, can use the raw material that fixed carbon content is low, impurity is higher, make the raw material that does not meet existing SiC manufacturing requirements can be used as reaction raw materials, greatly widened raw-material Application Range.
(5) adopt and automatically control and automatic monitored control system, temperature and pressure in stove is easy to realize meticulous control, overcome existing SiC production technology dependence experience arrange production blindness and the randomness of process, reduced the disadvantageous effect that human factor causes production.
(6), according to the requirement of synthetic variant production, formulate different power supply systems, and with the variation of vacuum tightness in stove, adjust power supply system, can accurately judge power failure opportunity.
The present invention can accurately control SiC micro mist and whisker synthesis condition, and technical process is simple, and production cost is low, but industrialization synthesizing β-SiC micro mist and whisker, synthetic β-SiC micro mist and the whisker crystalline form is complete, purity is high, quality is good.
(4) embodiment
Embodiment 1:
(1) with the graphite of fixed carbon content 95% levigate to 45 μ m with thin micro mist, the hard coal of fixed carbon content 90% is levigate to 45 μ m with thin micro mist, with SiO
2Content be 99% quartzite levigate to 75 μ m with thin micro mist, press fixed carbon: SiO
2=1:1.6, the ratio of graphite: hard coal=4:1 carries out three kinds of raw materials fully to mix and make reaction material.
(2) will mix reaction material pack in the vacuum resistance furnace reaction chamber, reaction material is densified to tap density is about 0.9g/cm
3.
(3) the porous corundum cover plate that is complementary in reaction material upper surface lid one reaction chamber length and width.
(4) cover bell, closed furnace body, install thermopair and put in place.
(5) open cooling system, automatic control system, drive vacuum pump and make vacuum oven pressure to 100Pa.
(6) power supply: 1) below temperature 800K, adopt permanent power power supply in stove, control surface is loaded at 7w/cm
22) at 800K-1200K, adopt permanent power power supply, control surface is loaded at 9w/cm
23) at 1200K-1500K, adopt and become the power power supply, to control in vacuum tightness 80Pa-20Pa scope, control surface is loaded 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 the vacuum pump smoke outlet.
(7) obviously rise and maintain below 10Pa 10 minutes when vacuum tightness in stove, stopping power supply.
(8) the body of heater naturally cooling is 10 hours, opens bell, takes out β-SiC micro powder product.
(9) β of above step acquisition-SiC micro mist purity, at 98.5%, β-SiC micro mist productive rate 85%,, if want a nearly step obtain high-purity β-SiC micro mist, need be passed through conventional de-carbon and HF acid cleaning process.
(10) β that obtains of above step-below SiC micro mist mean particle size 15 μ m,, if will obtain other high-purity β-SiC micro mist of the narrower different grain size level of size-grade distribution, need pass through conventional grading technology.
Embodiment 2:
(1) with the graphite of fixed carbon content 95% levigate to 45 μ m with thin micro mist, the hard coal of fixed carbon content 90% is levigate to 45 μ m with thin micro mist, with SiO
2Content be 99% quartzite levigate to 75 μ m with thin micro mist, press fixed carbon: SiO
2=1:1.7, the ratio of graphite: hard coal=1:1 carries out three kinds of raw materials fully to mix and make reaction material.
(2) will mix reaction material pack in the vacuum resistance furnace reaction chamber, reaction material is densified to tap density is about 0.9g/cm
3.
(3) the porous corundum cover plate that is complementary in reaction material upper surface lid one reaction chamber length and width.
(4) cover bell, closed furnace body, install thermopair and put in place.
(5) open cooling system, automatic control system, drive vacuum pump and make vacuum oven pressure to 100Pa.
(6) power supply: 1) below temperature 800K, adopt permanent power power supply in stove, control surface is loaded at 7w/cm
22) at 800K-1200K, adopt permanent power power supply, control surface is loaded at 8w/cm
23) at 1200K-1300K, adopt and become the power power supply, to control in vacuum tightness 50Pa-20Pa scope, control surface is loaded 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 the vacuum pump smoke outlet.
(7) obviously rise and maintain below 10Pa 10 minutes when vacuum tightness in stove, stopping power supply.
(8) the body of heater naturally cooling is 10 hours, opens bell, takes out β-SiC crystal whisker products.
(9) β that makes of above step-SiC micro mist purity is more than 98.5%, β-SiC productive rate 92%, and wherein β-SiC whisker accounts for 40% of product,, if want a nearly step obtain high-purity β-SiC whisker, need pass through conventional de-carbon and HF acid cleaning process.
(10) β that obtains of above step-below SiC whisker mean particle size 20 μ m,, if will obtain other high-purity β-SiC whisker of the narrower different grain size level of size-grade distribution, need pass through conventional grading technology.
Embodiment 3:
(1) with the graphite of fixed carbon content 95% levigate to 45 μ m with thin micro mist, the refinery coke of fixed carbon content 92% is levigate to 45 μ m with thin micro mist, with SiO
2Content be 99% quartzite levigate to 75 μ m with thin micro mist, press fixed carbon: SiO
2=1:1.65, the ratio of graphite: refinery coke=2:1 carries out three kinds of raw materials fully to mix and make reaction material.
(2) will mix reaction material pack in the vacuum resistance furnace reaction chamber, reaction material is densified to tap density is about 0.9g/cm
3.
(3) the porous corundum cover plate that is complementary in reaction material upper surface lid one reaction chamber length and width.
(4) cover bell, closed furnace body, install thermopair and put in place.
(5) open cooling system, automatic control system, drive vacuum pump and make vacuum oven pressure to 100Pa.
(6) power supply: 1) below temperature 800K, adopt permanent power power supply in stove, control surface is loaded at 7w/cm
22) at 800K-1200K, adopt permanent power power supply, control surface is loaded at 9w/cm
23) at 1200K-1400K, adopt and become the power power supply, to control in vacuum tightness 70Pa-20Pa scope, control surface is loaded 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 the vacuum pump smoke outlet.
(7) obviously rise and maintain below 10Pa 10 minutes when vacuum tightness in stove, stopping power supply.
(8) the body of heater naturally cooling is 10 hours, opens bell, takes out β-SiC micro mist and crystal whisker products.
(9) β that makes of above step-SiC micro mist and whisker purity are more than 98.5%, and β-SiC productive rate 90%,, if want a nearly step obtain high-purity β-SiC whisker, need pass through conventional de-carbon and HF acid cleaning process.
(10) β that obtains of above step-SiC micro mist and below whisker mean particle size 20 μ m,, if will obtain other high-purity β-SiC whisker of the narrower different grain size level of size-grade distribution, need pass through conventional grading technology.
Claims (4)
1. the synthetic method of β-SiC micro mist and whisker,, take the carbon raw material that mixes after pulverizing and siliceous raw material as reaction material, is characterized by, and comprises the steps: fixed carbon in (1) carbon raw material and the SiO in siliceous raw material
2Mass ratio be 1:1.6 ~ 1.7, reaction material is packed in vacuum resistance furnace, then reaction material being densified to tap density is 0.8 ~ 1.1g/cm
3(2) a porous corundum steel plate is added a cover on the reaction material surface after compacting, sealing vacuum resistance furnace body, and it is below 100Pa that vacuum resistance furnace is evacuated to furnace pressure, then to the vacuum resistance furnace energising, is heated to 1400K ~ 1500K, starts insulation; (3) maintain below 10Pa while surpassing 60 minutes when vacuum resistance furnace internal pressure, stop the vacuum resistance furnace power supply, naturally cooling, obtain purity and be the β-SiC micro mist or β-SiC whisker more than 98.5%.
2. the synthetic method of β according to claim 1-SiC micro mist and whisker, it is characterized in that: in step (1), described carbon raw material is one or more and the mixture of 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.
3. the synthetic method of β according to claim 1-SiC micro mist and whisker is characterized in that: in step (2), the power supply system of described vacuum resistance furnace is, during less than 800K, controlling the vacuum oven surface load is 6 ~ 8w/cm when the reaction material core temperature
2, and make vacuum tightness maintain all the time below 100Pa; During at 800 ~ 1200K, controlling the vacuum resistance furnace surface load is 9 ~ 11w/cm when the reaction material core temperature
2, and make vacuum tightness maintain all the time below 200Pa; When the reaction material core temperature is above higher than 1200K, control vacuum resistance furnace 7 ~ 10w/cm
2, and vacuum tightness is maintained below 100Pa all the time.
4. the synthetic method of β according to claim 1-SiC micro mist and whisker is characterized in that: the granularity after described carbon raw material is pulverized is below 45 μ m, and the granularity after siliceous raw material is pulverized is below 75 μ m.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106087061B (en) * | 2016-07-28 | 2018-05-22 | 李志文 | The method that powder quartz ore processes cubic silicon carbide whisker |
| CN114249594A (en) * | 2020-09-21 | 2022-03-29 | 山东硅纳新材料科技有限公司 | Preparation process of superfine silicon carbide powder |
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 |
-
2013
- 2013-07-19 CN CN201310303598.7A patent/CN103387231B/en not_active Expired - Fee Related
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 |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106087061B (en) * | 2016-07-28 | 2018-05-22 | 李志文 | The method that powder quartz ore processes cubic silicon carbide whisker |
| CN114249594A (en) * | 2020-09-21 | 2022-03-29 | 山东硅纳新材料科技有限公司 | Preparation process of superfine silicon carbide powder |
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