CN118084498B - Forming method of silicon carbide ceramic wafer boat - Google Patents
Forming method of silicon carbide ceramic wafer boat Download PDFInfo
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 121
- 239000000919 ceramic Substances 0.000 title claims abstract description 119
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 90
- 238000000034 method Methods 0.000 title claims abstract description 57
- 238000005245 sintering Methods 0.000 claims abstract description 95
- 239000006229 carbon black Substances 0.000 claims abstract description 39
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000000843 powder Substances 0.000 claims abstract description 30
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 28
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 28
- 239000010703 silicon Substances 0.000 claims abstract description 28
- 238000005470 impregnation Methods 0.000 claims abstract description 27
- 238000002360 preparation method Methods 0.000 claims abstract description 24
- 238000000465 moulding Methods 0.000 claims abstract description 16
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 15
- 239000010439 graphite Substances 0.000 claims abstract description 15
- 239000002002 slurry Substances 0.000 claims abstract description 14
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 238000005507 spraying Methods 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 10
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000008367 deionised water Substances 0.000 claims abstract description 8
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 8
- 229920001568 phenolic resin Polymers 0.000 claims abstract description 8
- 239000005011 phenolic resin Substances 0.000 claims abstract description 8
- 238000000498 ball milling Methods 0.000 claims abstract description 7
- 239000000203 mixture Substances 0.000 claims abstract 2
- 238000006243 chemical reaction Methods 0.000 claims description 49
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 45
- 229910021392 nanocarbon Inorganic materials 0.000 claims description 33
- 238000003756 stirring Methods 0.000 claims description 27
- 239000002245 particle Substances 0.000 claims description 24
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 21
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 claims description 18
- 239000011856 silicon-based particle Substances 0.000 claims description 18
- 238000009694 cold isostatic pressing Methods 0.000 claims description 16
- 230000032683 aging Effects 0.000 claims description 15
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 14
- IKHGUXGNUITLKF-UHFFFAOYSA-N Acetaldehyde Chemical compound CC=O IKHGUXGNUITLKF-UHFFFAOYSA-N 0.000 claims description 12
- 239000003792 electrolyte Substances 0.000 claims description 12
- 239000007864 aqueous solution Substances 0.000 claims description 10
- 238000010000 carbonizing Methods 0.000 claims description 10
- 229910052786 argon Inorganic materials 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- 238000001914 filtration Methods 0.000 claims description 5
- 238000003825 pressing Methods 0.000 claims description 3
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 claims 1
- 238000002955 isolation Methods 0.000 claims 1
- 239000000126 substance Substances 0.000 abstract description 9
- 238000005336 cracking Methods 0.000 abstract description 7
- 229910052799 carbon Inorganic materials 0.000 description 15
- 238000002791 soaking Methods 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 14
- 238000005452 bending Methods 0.000 description 11
- 238000005469 granulation Methods 0.000 description 8
- 230000003179 granulation Effects 0.000 description 8
- 238000005475 siliconizing Methods 0.000 description 8
- 239000004966 Carbon aerogel Substances 0.000 description 6
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 230000009471 action Effects 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000004580 weight loss Effects 0.000 description 4
- 241000872198 Serjania polyphylla Species 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000001272 pressureless sintering Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000007569 slipcasting Methods 0.000 description 2
- 230000008093 supporting effect Effects 0.000 description 2
- FRWYFWZENXDZMU-UHFFFAOYSA-N 2-iodoquinoline Chemical compound C1=CC=CC2=NC(I)=CC=C21 FRWYFWZENXDZMU-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- LTPBRCUWZOMYOC-UHFFFAOYSA-N beryllium oxide Inorganic materials O=[Be] LTPBRCUWZOMYOC-UHFFFAOYSA-N 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000006259 organic additive Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000011224 oxide ceramic Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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Abstract
The invention discloses a forming method of a silicon carbide ceramic wafer boat, which belongs to the technical field of silicon carbide ceramics, and comprises the following steps: preparing ceramic powder, molding, primary sintering, vacuum impregnation and secondary sintering; the preparation method comprises the steps of mixing large-grain-size silicon carbide powder, medium-grain-size silicon carbide powder, small-grain-size silicon carbide powder, coated carbon black, graphite, phenolic resin and deionized water according to parts by weight, and adding the mixture into a ball mill for ball milling to obtain slurry; spraying and granulating the slurry to obtain ceramic powder; the forming method can improve the chemical stability and high temperature tolerance of the silicon carbide ceramic wafer boat by reducing the free silicon content in the silicon carbide ceramic wafer boat, can avoid cracking in forming and reduce the size shrinkage rate after sintering, and can also ensure that the density and the hardness of the ceramic wafer boat are not reduced.
Description
Technical Field
The invention relates to the technical field of silicon carbide ceramics, in particular to a forming method of a silicon carbide ceramic wafer boat.
Background
The silicon carbide ceramic not only has excellent normal temperature mechanical properties, such as high bending strength, and excellent oxidation resistance, corrosion resistance and abrasion resistance. The silicon carbide ceramic has the greatest characteristics of high-temperature strength, the strength of the common ceramic material is obviously reduced at 1200-1400 ℃, the bending strength of the silicon carbide ceramic is still kept at a higher level at 1400 ℃, and the working temperature of the silicon carbide ceramic can reach 1600-1700 ℃. In addition, silicon carbide ceramics have high heat conductivity, and are inferior to beryllium oxide ceramics in ceramics, so that silicon carbide ceramics are widely used for sealing rings, bulletproof plates, nozzles, high-temperature corrosion-resistant parts, electronic equipment parts in high-temperature and high-frequency ranges, and the like.
The silicon carbide ceramic wafer boat has the following advantages: the high-temperature tolerance is good, and the silicon carbide ceramic wafer boat can be used in a high-temperature environment because of the high melting point of the silicon carbide ceramic; the silicon carbide ceramic wafer boat has low pollution, high temperature tolerance and good chemical stability; the hardness is high.
In the preparation of silicon carbide ceramic wafer boats, the main problem is the molding problem of the silicon carbide ceramic wafer boat. In view of the fact that silicon carbide ceramics cannot be manufactured like quartz, quartz can be manufactured into unit parts and then welded to be integrated, and because silicon carbide ceramics have high hardness and are difficult to process, in manufacturing silicon carbide ceramic wafer boats, it is necessary to directly mold and sinter raw materials of silicon carbide ceramics into an integrated single wafer boat. In addition, since the silicon carbide ceramic boat is also required to have high compactibility, only pressureless sintering and reactive sintering can be used in the preparation of the silicon carbide ceramic boat in order to achieve high compactibility. The difficulty of directly molding and sintering silicon carbide powder to prepare an integrated single-piece wafer boat is particularly great by a pressureless sintering method, so that a reaction sintering method is mainly used in the preparation of silicon carbide ceramic wafer boats at present.
The existing method for preparing the silicon carbide ceramic wafer boat by the reaction sintering method is that silicon carbide (generally 1-10 mu m) with certain grain size is directly adopted, mixed with carbon and then molded to form a blank body, then siliconizing is carried out at high temperature, part of silicon reacts with the carbon to generate silicon carbide, and then the silicon carbide is combined with the silicon carbide originally existing in the blank body, so that the compactness is improved.
The existing forming method for preparing the silicon carbide ceramic wafer boat by the reaction sintering method comprises slip casting, dry pressing, cold isostatic pressing and the like. Slip casting refers to a method of selecting proper dispergator to enable ceramic powder to be uniformly suspended in solution, preparing slurry, pouring the slurry into a model with water absorption, absorbing water, and forming a green body according to the model, wherein the method is suitable for batch forming of ceramic products with complex shapes, but the prepared ceramic products are coarse in shape and low in density; the dry press molding is to add a certain amount of organic additive into ceramic powder, and mold the ceramic powder in a mold under the action of external pressure, the method is easy to realize automation, but the ceramic powder is easy to crack due to uneven pressure in molding; the cold isostatic pressing is a forming process of placing a rubber mold filled with powder into a closed container, applying equal pressure in all directions through an oil pump, and preparing a compact green body under the action of high pressure, and is the most commonly used forming method of a silicon carbide ceramic wafer boat at present.
The existing method for preparing silicon carbide ceramic wafer boat by reaction sintering method has two methods, the first method is to raise the sintering temperature to the melting temperature of silicon to generate liquid phase of silicon, and the liquid phase silicon can directly infiltrate into a blank body to react with carbon to generate silicon carbide by capillary action; the second is to raise the sintering temperature to a temperature greater than the melting temperature of silicon, thereby generating silicon vapor that can infiltrate the green body. The first method has the problems that the content of the residual free silicon after sintering is too high and can reach 10-15%, so that the performance of the product is affected; the second method can reduce the content of residual free silicon to below 10%, the blank is turned in advance before sintering according to the shape and size requirements of the silicon carbide ceramic wafer boat, and then sintering is carried out, and the dimensional shrinkage after sintering can be controlled within 3%. Therefore, the second siliconizing method is the most commonly used siliconizing method of the silicon carbide ceramic wafer boat.
However, when the silicon carbide ceramic boat prepared by the second method is combined with the cold isostatic pressing method, although the content of free silicon in the prepared silicon carbide ceramic boat is reduced to less than 10%, the free silicon still exists, and the chemical stability of the silicon carbide ceramic boat is affected because the free silicon cannot be corroded by strong acid media such as alkali resistance, hydrofluoric acid and the like, the existence of the free silicon also affects the high temperature tolerance of the silicon carbide ceramic boat, the working temperature of the silicon carbide ceramic boat is reduced to less than 1350 ℃, in addition, the density of a blank prepared by cold isostatic pressing is high, the porosity is small, the siliconizing channel is reduced, residual carbon is increased, and the high temperature tolerance of the silicon carbide ceramic boat is reduced.
In order to solve the problems, the most commonly used method at present is to combine different carbons to prepare a blank, and utilize the different carbons to have different reactivity with silicon to carry out staged siliconizing so as to reduce the content of free silicon, and further reduce the dimensional shrinkage rate at the same time, thereby reducing the workload of high-precision processing after sintering and reducing the probability of cracks during high-precision processing. However, the method can cause the increase of sintering difficulty, internal defects are easy to occur during sintering, the density and hardness of the prepared silicon carbide ceramic wafer boat are reduced, and the dimensional shrinkage rate after sintering is increased.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention provides a forming method of the silicon carbide ceramic wafer boat, which can improve the chemical stability and high-temperature tolerance of the silicon carbide ceramic wafer boat by reducing the content of free silicon in the silicon carbide ceramic wafer boat, can avoid cracking in forming and reduce the dimensional shrinkage rate after sintering, and can ensure that the density and hardness of the ceramic wafer boat are not reduced.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a forming method of a silicon carbide ceramic wafer boat comprises the following steps: preparing ceramic powder, molding, primary sintering, vacuum impregnation and secondary sintering;
The preparation method comprises the steps of mixing large-grain-size silicon carbide powder, medium-grain-size silicon carbide powder, small-grain-size silicon carbide powder, coated carbon black, graphite, phenolic resin and deionized water, adding into a ball mill, and performing ball milling at a rotating speed of 300-400rpm, a ball-material ratio of 3-5:1 and a time of 10-15 hours to obtain slurry; spraying granulation is carried out on the slurry, the air inlet temperature is 250-270 ℃, the air outlet temperature is 65-85 ℃ and the rotating speed is 25000-30000rpm during the spraying granulation, thus obtaining ceramic powder;
In the preparation of the ceramic powder, the weight ratio of the large-grain-size silicon carbide powder to the medium-grain-size silicon carbide powder to the small-grain-size silicon carbide powder to the coated carbon black to the graphite to the phenolic resin to the deionized water is 25-30:35-40:100-110:9-10:5-6:6-8:120-150;
The grain diameter of the large grain diameter silicon carbide powder is 60-70 mu m;
the grain diameter of the medium grain diameter silicon carbide powder is 25-30 mu m;
The grain diameter of the small-grain-diameter silicon carbide powder is 1-3 mu m;
The particle size of the graphite is 3-5 mu m;
the preparation method of the coated carbon black comprises the steps of mixing acetaldehyde and first part of absolute ethyl alcohol, stirring at a stirring speed of 30-60rpm for 10-20min at room temperature, adding resorcinol, stirring for 10-20min after the adding is completed, adding triethylamine and second part of absolute ethyl alcohol, adding carbon black, stirring for 1-1.5h, filtering, aging filter residues in a baking oven at 75-85 ℃ for 3-4d, aging at room temperature for 8-10h, aging in a baking oven at 75-85 ℃ for 2-3d, carbonizing at 700-800 ℃ for 5-6h to obtain the coated carbon black;
In the preparation of the coated carbon black, the weight-volume ratio of acetaldehyde to the first part of absolute ethyl alcohol to resorcinol to triethylamine to the second part of absolute ethyl alcohol to the carbon black is 80-120mL to 700-800mL to 90-100g to 1.5-2.5g to 5000-6000mL to 1000-1200g;
the adding speed of the resorcinol is 5-6g/min;
The particle size of the carbon black is 1-2 mu m;
The molding is carried out, ceramic powder is added into a mold for prepressing, the prepressing pressure is 40-50MPa, the pressure maintaining time is 20-30s, then cold isostatic pressing molding is carried out, the cold isostatic pressing pressure is 180-225MPa, the pressure maintaining time is 8-10min, then pressure relief is carried out in a gradient pressure reducing mode, specifically, the pressure is reduced by 30-45MPa each time, and then the pressure is maintained for 20-30s, and then the pressure is reduced continuously, so that a blank body is obtained;
Placing the green body into a vacuum reaction sintering furnace, placing silicon particles with the size of 1-2mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.5-0.6 times of the weight of the green body, and then performing vacuum sintering for 3-4 hours at 1450-1500 ℃ to obtain a green body after primary sintering;
the method comprises the steps of vacuum impregnation, namely, impregnating a once sintered blank body in nano carbon sol with the weight being 15-20 times that of the blank body at room temperature, performing vacuum impregnation, ensuring that the blank body can be completely impregnated in the nano carbon sol during vacuum impregnation, wherein the vacuum degree of the vacuum impregnation is 0.08-0.09MPa, the time is 2-3h, drying the blank body in an oven at 110-130 ℃ for 7-8h, and carbonizing the blank body in an argon environment at 500-600 ℃ for 2-3h to obtain a vacuum impregnated blank body;
The preparation method of the nano carbon sol comprises the steps of dividing 12 high-purity graphite electrodes with the thickness of 5cm into 6 groups of positive and negative electrodes, placing the electrodes into a reaction tank filled with electrolyte, using citric acid aqueous solution with the concentration of 3-3.5wt%, connecting the electrodes in parallel, insulating and isolating the electrodes by using an insulating medium, then introducing high-frequency alternating current to the electrodes for reaction, controlling the frequency of the high-frequency alternating current to be 40-50kHz, the voltage to be 10-12V, the current density to be 2-3A/cm 2, controlling the temperature of the reaction tank to be 45-55 ℃ in the reaction, stirring once every 5-6 hours, controlling the stirring rotation speed to be 100-200rpm for 20-30min, and pouring out the electrolyte in the reaction tank after the anode electrode is replaced for 6-7d when the anode thickness is smaller than 1cm, thereby obtaining the nano carbon sol;
and (3) secondary sintering, namely placing the blank subjected to vacuum impregnation into a vacuum reaction sintering furnace, placing silicon particles with the size of 1-2mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.8-0.9 times of the weight of the blank, then performing vacuum sintering at 1450-1500 ℃ for 3-3.5h,1550-1600 ℃ for 3-3.5h, performing vacuum sintering at 1650-1700 ℃ for 2.5-3h, and naturally cooling to room temperature for fine processing to obtain the silicon carbide ceramic crystal boat.
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the forming method of the silicon carbide ceramic wafer boat, the used carbon source is improved, carbon black coated by carbon aerogel is used, after cold isostatic pressing, the carbon aerogel forms a uniform dispersion supporting system in a blank, in primary sintering, nano-scale air holes in the carbon aerogel can form a siliconizing channel, siliconizing is facilitated, and due to the supporting effect of the carbon aerogel, the linear shrinkage rate in primary sintering can be reduced, and by controlling the temperature and time in primary sintering, amorphous carbon and carbon black in the blank are preferentially reacted into silicon carbide to form a blank after primary sintering which is not fully densified; in the vacuum impregnation step, the nano carbon sol is used for vacuum impregnation, citric acid aqueous solution is used as electrolyte in the preparation of the nano carbon sol, citric acid plays a role in conducting electrons in the preparation of the nano carbon sol, a binder plays a role in vacuum impregnation, nano carbon in the nano carbon sol can improve the filling and adsorption effects of pores in a once sintered blank, in addition, citric acid also plays a role in improving a carbon source, in the vacuum impregnation, citric acid can also play a role in filling the once sintered blank, and then citric acid is carbonized in an argon environment to form porous carbon, so that a blank with high density, which is filled with nano carbon and carbonized citric acid together, is obtained, gaps formed between the nano carbon and pores in the once sintered blank still exist in the blank, the porous carbonized citric acid serves as a silicon channel, and in the secondary sintering, through heating and sintering, the full reaction of the carbon source and silicon is ensured, and the content of free silicon is reduced, so that sintering densification is realized;
(2) The forming method of the silicon carbide ceramic wafer boat can improve the chemical stability of the silicon carbide ceramic wafer boat, the silicon carbide ceramic wafer boat is completely soaked in 10wt% sodium hydroxide aqueous solution, and the weight loss rate is 0 after soaking for 1h at room temperature; the silicon carbide ceramic wafer boat is completely soaked in hydrofluoric acid aqueous solution with the concentration of 10 weight percent, and after being soaked for 1 hour at room temperature, the weight loss rate is 0;
(3) The forming method of the silicon carbide ceramic wafer boat can improve the high temperature tolerance of the silicon carbide ceramic wafer boat, and the bending strength of the silicon carbide ceramic wafer boat is 392-397MPa at 25 ℃ and 438-446MPa at 1400 ℃;
(4) The forming method of the silicon carbide ceramic wafer boat can avoid cracking in forming, and the silicon carbide ceramic wafer boat does not crack in cold isostatic pressing;
(5) The forming method of the silicon carbide ceramic wafer boat can reduce the dimensional shrinkage rate after sintering, and the sum of the linear shrinkage rates of the silicon carbide ceramic wafer boat after primary sintering and secondary sintering is 2.31-2.45%;
(6) The forming method of the silicon carbide ceramic wafer boat can ensure that the density and the hardness of the ceramic wafer boat are not reduced, and the density of the silicon carbide ceramic wafer boat is 3.16-3.18g/cm 3 and the Vickers hardness is 31-32GPa.
Detailed Description
Specific embodiments of the present invention will now be described in order to provide a clearer understanding of the technical features, objects and effects of the present invention.
Example 1
A forming method of a silicon carbide ceramic wafer boat specifically comprises the following steps:
1. Preparing ceramic powder: according to parts by weight, mixing 25 parts of silicon carbide powder with the particle size of 60 mu m, 35 parts of silicon carbide powder with the particle size of 25 mu m, 100 parts of silicon carbide powder with the particle size of 1 mu m, 9 parts of coated carbon black, 5 parts of graphite with the particle size of 3 mu m, 6 parts of phenolic resin and 120 parts of deionized water, adding into a ball mill, and performing ball milling at the rotating speed of 300rpm for 10 hours to obtain slurry, wherein the ball-material ratio is 3:1; spraying granulation is carried out on the slurry, wherein the air inlet temperature is 250 ℃, the air outlet temperature is 65 ℃ and the rotating speed is 25000rpm during the spraying granulation, so as to obtain ceramic powder;
The preparation method of the coated carbon black comprises the following steps: mixing 80mL of acetaldehyde and 700mL of absolute ethyl alcohol, stirring at a stirring speed of 30rpm for 10min at room temperature, slowly adding 90g of resorcinol, controlling the adding speed to be 5g/min, stirring for 10min after adding, adding 1.5g of triethylamine and 5000mL of absolute ethyl alcohol, adding 1000g of carbon black with a particle size of 1 mu m, stirring for 1h, filtering, aging the filter residue in a 75 ℃ oven for 3d, aging at room temperature for 8h, aging in a 75 ℃ oven for 2d, carbonizing at 700 ℃ for 5h, and obtaining coated carbon black;
2. And (3) forming: adding ceramic powder into a die, prepressing, wherein the prepressing pressure is 40MPa, the pressure maintaining time is 20s, then performing cold isostatic pressing, the cold isostatic pressing pressure is 180MPa, the pressure maintaining time is 8min, then performing pressure relief in a gradient pressure reducing mode, specifically, reducing the pressure by 30MPa each time, and then continuously reducing the pressure after maintaining the pressure for 20s to obtain a blank;
3. Primary sintering: placing the green body into a vacuum reaction sintering furnace, placing silicon particles with the size of 1mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.5 times of the weight of the green body, and then performing vacuum sintering for 3 hours at 1450 ℃ to obtain a once sintered green body;
4. Vacuum impregnation: at room temperature, soaking the once sintered blank in nano carbon sol with the weight of 15 times of the blank for vacuum soaking, ensuring that the blank can be completely soaked in the nano carbon sol during vacuum soaking, wherein the vacuum degree of vacuum soaking is 0.08MPa, the time is 2 hours, drying the blank in an oven at 110 ℃ for 7 hours, putting the blank into an argon environment, and carbonizing for 2 hours at 500 ℃ to obtain a blank after vacuum soaking;
The preparation method of the nano carbon sol comprises the following steps: dividing 12 high-purity graphite electrodes with the thickness of 5cm into 6 groups of positive and negative electrodes, placing the electrodes into a reaction tank filled with electrolyte, using citric acid aqueous solution with the concentration of 3wt%, connecting the electrodes in parallel, insulating and isolating the electrodes by using an insulating medium, then introducing high-frequency alternating current into the electrodes for reaction, wherein the frequency of the high-frequency alternating current is 40kHz, the voltage is 10V, the current density is 2A/cm 2 electrode surface area, the temperature of the reaction tank is controlled to be 45 ℃, stirring is carried out once every 5 hours, the rotation speed of each stirring is 100rpm, the time is 20min, when the anode thickness is less than 1cm, replacing the anode electrode, and pouring out the electrolyte in the reaction tank after 7d to obtain the nano carbon sol;
The carbon content of the nano carbon sol is 0.73wt%;
5. Secondary sintering: placing the vacuum-impregnated blank into a vacuum reaction sintering furnace, placing silicon particles with the size of 1mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.8 times of the weight of the blank, then vacuum sintering at 1450 ℃ for 3h,1550 ℃ for 3h, 1650 ℃ for 2.5h, naturally cooling to room temperature, and carrying out fine processing to obtain the silicon carbide ceramic wafer boat.
Example 2
A forming method of a silicon carbide ceramic wafer boat specifically comprises the following steps:
1. Preparing ceramic powder: according to parts by weight, 28 parts of silicon carbide powder with the particle size of 65 mu m, 38 parts of silicon carbide powder with the particle size of 27 mu m, 105 parts of silicon carbide powder with the particle size of 2 mu m, 9.5 parts of coated carbon black, 5.5 parts of graphite with the particle size of 4 mu m, 7 parts of phenolic resin and 130 parts of deionized water are mixed and then added into a ball mill for ball milling, the rotational speed during ball milling is 350rpm, the ball-to-material ratio is 4:1, and the time is 12 hours, so that slurry is obtained; spraying granulation is carried out on the slurry, wherein the air inlet temperature is 260 ℃, the air outlet temperature is 75 ℃ and the rotating speed is 28000rpm during the spraying granulation, so as to obtain ceramic powder;
The preparation method of the coated carbon black comprises the following steps: mixing 100mL of acetaldehyde and 750mL of absolute ethyl alcohol, stirring at 50rpm at room temperature for 15min, slowly adding 95g of resorcinol, controlling the adding speed to be 5.5g/min, stirring for 15min after adding, adding 2g of triethylamine and 5500mL of absolute ethyl alcohol, adding 1100g of carbon black with the particle size of 1.5 mu m, stirring for 1.2h, filtering, putting filter residues into an oven with the temperature of 80 ℃ for ageing for 3.5d, ageing at room temperature for 9h, putting into an oven with the temperature of 80 ℃ for ageing for 2.5d, putting into an argon environment, and carbonizing at the temperature of 750 ℃ for 5.5h to obtain coated carbon black;
2. and (3) forming: adding ceramic powder into a die, prepressing, wherein the prepressing pressure is 45MPa, the pressure maintaining time is 25s, then performing cold isostatic pressing, the cold isostatic pressing pressure is 200MPa, the pressure maintaining time is 9min, then performing pressure relief in a gradient pressure reducing mode, specifically, reducing the pressure by 40MPa each time, and then continuously reducing the pressure after the pressure is maintained for 25s to obtain a blank;
3. Primary sintering: placing the green body into a vacuum reaction sintering furnace, placing silicon particles with the size of 1.5mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.55 times of the weight of the green body, and then performing vacuum sintering at 1480 ℃ for 3.5 hours to obtain a once-sintered green body;
4. vacuum impregnation: at room temperature, soaking the once sintered blank in nano carbon sol with the weight of 18 times of the blank for vacuum soaking, ensuring that the blank can be completely soaked in the nano carbon sol during vacuum soaking, wherein the vacuum degree of vacuum soaking is 0.085MPa, the time is 2.5h, drying the blank in an oven at 120 ℃ for 7.5h, and carbonizing the blank in an argon environment at 550 ℃ for 2.5h to obtain a vacuum-soaked blank;
The preparation method of the nano carbon sol comprises the following steps: dividing 12 high-purity graphite electrodes with the thickness of 5cm into 6 groups of positive and negative electrodes, placing the electrodes into a reaction tank filled with electrolyte, using citric acid aqueous solution with the concentration of 3.2wt%, connecting the electrodes in parallel, insulating and isolating the electrodes by using an insulating medium, then introducing high-frequency alternating current into the electrodes for reaction, wherein the frequency of the high-frequency alternating current is 45kHz, the voltage is 11V, the current density is 2.5A/cm 2 of electrode surface area, controlling the temperature of the reaction tank to be 50 ℃ in the reaction, stirring once every 5.5h, the rotating speed of each stirring is 110rpm for 25min, changing the anode electrode when the anode thickness is less than 1cm, and pouring out the electrolyte in the reaction tank after 6.5d to obtain the nano carbon sol;
The carbon content of the nano carbon sol is 0.75wt%;
5. Secondary sintering: placing the vacuum impregnated blank into a vacuum reaction sintering furnace, placing silicon particles with the size of 1.5mm below the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.85 times of the weight of the blank, then vacuum sintering at 1480 ℃ for 3.2h, vacuum sintering at 1580 ℃ for 3.2h, vacuum sintering at 1680 ℃ for 2.7h, naturally cooling to room temperature, and carrying out fine processing to obtain the silicon carbide ceramic wafer boat.
Example 3
A forming method of a silicon carbide ceramic wafer boat specifically comprises the following steps:
1. Preparing ceramic powder: according to parts by weight, mixing 30 parts of silicon carbide powder with the particle size of 70 mu m, 40 parts of silicon carbide powder with the particle size of 30 mu m, 110 parts of silicon carbide powder with the particle size of 3 mu m, 10 parts of coated carbon black, 6 parts of graphite with the particle size of 5 mu m, 8 parts of phenolic resin and 150 parts of deionized water, adding into a ball mill, and performing ball milling at the rotating speed of 400rpm for a ball-material ratio of 5:1 for 15 hours to obtain slurry; spraying granulation is carried out on the slurry, wherein the air inlet temperature is 270 ℃, the air outlet temperature is 85 ℃ and the rotating speed is 30000rpm during the spraying granulation, so as to obtain ceramic powder;
the preparation method of the coated carbon black comprises the following steps: mixing 120mL of acetaldehyde and 800mL of absolute ethyl alcohol, stirring at a stirring speed of 60rpm at room temperature for 20min, slowly adding 100g of resorcinol, controlling the adding speed to be 6g/min, stirring for 20min after adding, adding 2.5g of triethylamine and 6000mL of absolute ethyl alcohol, adding 1200g of carbon black with a particle size of 2 mu m, stirring for 1.5h, filtering, aging filter residues in an oven at 85 ℃ for 4d, aging at room temperature for 10h, aging in an oven at 85 ℃ for 3d, carbonizing at 800 ℃ for 6h, and obtaining coated carbon black;
2. And (3) forming: adding ceramic powder into a die, prepressing, wherein the prepressing pressure is 50MPa, the pressure maintaining time is 30s, then performing cold isostatic pressing, the cold isostatic pressing pressure is 225MPa, the pressure maintaining time is 10min, then performing pressure relief in a gradient pressure reducing mode, specifically, reducing the pressure by 45MPa each time, and then continuously reducing the pressure after maintaining the pressure for 30s to obtain a blank;
3. Primary sintering: placing the green body into a vacuum reaction sintering furnace, placing silicon particles with the size of 2mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.6 times of the weight of the green body, and then performing vacuum sintering for 4 hours at 1500 ℃ to obtain a once-sintered green body;
4. Vacuum impregnation: at room temperature, soaking the once sintered blank in nano carbon sol with the weight of 20 times of the blank for vacuum soaking, ensuring that the blank can be completely soaked in the nano carbon sol during vacuum soaking, wherein the vacuum degree of vacuum soaking is 0.09MPa, the time is 3 hours, drying the blank in a baking oven at 130 ℃ for 8 hours, putting the blank into an argon environment, and carbonizing at 600 ℃ for 3 hours to obtain a blank after vacuum soaking;
The preparation method of the nano carbon sol comprises the following steps: dividing 12 high-purity graphite electrodes with the thickness of 5cm into 6 groups of positive and negative electrodes, placing the electrodes into a reaction tank filled with electrolyte, using citric acid aqueous solution with the concentration of 3.5wt%, connecting the electrodes in parallel, insulating and isolating the electrodes by using an insulating medium, then introducing high-frequency alternating current into the electrodes for reaction, wherein the frequency of the high-frequency alternating current is 50kHz, the voltage is 12V, the current density is 3A/cm 2 of electrode surface area, controlling the temperature of the reaction tank to be 55 ℃ during the reaction, stirring once every 6 hours, the rotating speed of each stirring is 200rpm for 30 minutes, and pouring out the electrolyte in the reaction tank after 6d when the thickness of the anode is less than 1cm, thereby obtaining the nano carbon sol;
The carbon content of the nano carbon sol is 0.68wt%;
5. Secondary sintering: placing the blank after vacuum impregnation into a vacuum reaction sintering furnace, placing silicon particles with the size of 2mm under the vacuum reaction sintering furnace, wherein the total weight of the silicon particles is 0.9 times of the weight of the blank, then vacuum sintering at 1500 ℃ for 3.5h, vacuum sintering at 1600 ℃ for 3.5h, vacuum sintering at 1700 ℃ for 3h, and naturally cooling to room temperature for fine processing to obtain the silicon carbide ceramic wafer boat.
Comparative example 1
In order to analyze the effect of the coated carbon black in the step of preparing the ceramic powder, this comparative example was changed on the basis of the molding method of the silicon carbide ceramic boat described in example 2 in that: in the step of preparing the ceramic powder in step 1, carbon black having a particle diameter of 1.5 μm was used in an equivalent amount instead of the addition of the coated carbon black.
Comparative example 2
In order to analyze the effect of the vacuum impregnation step, this comparative example was changed on the basis of the molding method of the silicon carbide ceramic boat described in example 2 in that: the step 4 vacuum impregnation step is omitted.
Comparative example 3
In order to analyze the effect of the combined action of the coated carbon powder and the vacuum impregnation step in the step of preparing the ceramic powder, this comparative example was changed on the basis of the molding method of the silicon carbide ceramic boat described in example 2 in that: in the step 1 of preparing the ceramic powder, carbon black having a particle diameter of 1.5 μm was used in the same amount instead of the addition of the coated carbon black, and the step4 of vacuum impregnation was omitted.
Test example 1
The silicon carbide ceramic boats prepared in examples 1 to 3 and comparative examples 1 to 3 were tested for flexural strength at 25 ℃, flexural strength at 1400 ℃, sum of linear shrinkage after primary sintering and secondary sintering, density, vickers hardness, and observed for occurrence of cracking in molding, and the test and observation results were as follows:
test example 2
The silicon carbide ceramic boats prepared in examples 1 to 3 and comparative examples 1 to 3 were washed, dried and weighed, and then completely immersed in 10wt% sodium hydroxide aqueous solution, and after immersing at room temperature for 1 hour, were taken out, washed, dried and weighed, and the weight loss rate was calculated as follows:
Test example 3
The silicon carbide ceramic boats prepared in examples 1 to 3 and comparative examples 1 to 3 were washed, dried and weighed, and then completely immersed in 10wt% hydrofluoric acid aqueous solution, and after immersing at room temperature for 1 hour, were taken out, washed, dried and weighed, and the weight loss rate was calculated, with the following calculation results:
as can be seen from the results of examples 1 to 3, the silicon carbide ceramic boats prepared in examples 1 to 3 were all better in bending strength at 25℃and 1400℃and the sum of linear shrinkage after primary sintering and secondary sintering, density, vickers hardness and chemical stability than those prepared in comparative examples 1 to 3, and the silicon carbide ceramic boats prepared in examples 1 to 3 were less prone to cracking during molding.
Comparative example 1 is inferior to examples 1-3 in all test results, and shows that adding coated carbon black in the preparation of ceramic powder, specifically carbon aerogel coated carbon black, can utilize the high specific surface area and high strength of carbon aerogel, improve the binding force between carbon black and other raw materials, reduce the linear shrinkage after sintering, improve the adsorption of silicon and the reactivity with silicon, reduce the content of residual silicon and residual carbon, thereby improving the bending strength of silicon carbide ceramic boat at 25 ℃, the bending strength at 1400 ℃, the density, the vickers hardness and the chemical stability, reducing the sum of the linear shrinkage after primary sintering and secondary sintering, and avoiding cracking in molding;
Comparative example 2 has all the test results which are inferior to examples 1-3 except that cracking occurs during molding, which shows that the nano carbon sol containing citric acid is used for vacuum impregnation of the primary sintered blank, then the citric acid is carbonized, the pores in the primary sintered blank are filled by the bonding effect of the citric acid and the small particle size and high adsorption performance of the nano carbon in the nano carbon sol, and then secondary sintering is performed, so that the bending strength of the silicon carbide ceramic boat at 25 ℃, the bending strength at 1400 ℃, the density, the Vickers hardness and the chemical stability can be improved, and the sum of the linear shrinkage rate after the primary sintering and the secondary sintering can be reduced;
All test results of comparative example 3 are inferior to those of examples 1-3, and comparative example 3 is a method commonly used in the prior art, and although the method uses different particle sizes and different types of carbon sources for compounding and sintering in stages, free silicon still exists in a certain content, so that the bending strength of the silicon carbide ceramic boat at 25 ℃, the bending strength at 1400 ℃ and the chemical stability are affected, and the sum of the linear shrinkage rates after primary sintering and secondary sintering is reduced; for density and vickers hardness, as siliconizing channels decrease, part of silicon cannot penetrate into pores, the porosity increases, residual carbon also occurs, the density and vickers hardness decrease, and the bending strength at 1400 ℃ also decreases further.
The percentages used in the present invention are mass percentages unless otherwise indicated.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The forming method of the silicon carbide ceramic wafer boat is characterized by comprising the following steps of: preparing ceramic powder, molding, primary sintering, vacuum impregnation and secondary sintering;
The preparation method comprises the steps of mixing large-grain-size silicon carbide powder, medium-grain-size silicon carbide powder, small-grain-size silicon carbide powder, coated carbon black, graphite, phenolic resin and deionized water according to parts by weight, and adding the mixture into a ball mill for ball milling to obtain slurry; spraying and granulating the slurry to obtain ceramic powder;
The preparation method of the coated carbon black comprises the steps of mixing acetaldehyde and first part of absolute ethyl alcohol, stirring for 10-20min at room temperature, adding resorcinol, stirring for 10-20min after the adding, adding triethylamine and second part of absolute ethyl alcohol, adding carbon black, stirring for 1-1.5h, filtering, aging filter residues at 75-85 ℃ for 3-4d, aging at room temperature for 8-10h, aging at 75-85 ℃ for 2-3d, carbonizing at 700-800 ℃ for 5-6h, and obtaining the coated carbon black;
placing the green body into a vacuum reaction sintering furnace, placing silicon particles below the vacuum reaction sintering furnace, and then performing vacuum sintering for 3-4 hours at 1450-1500 ℃ to obtain a green body after primary sintering;
The method comprises the steps of vacuum impregnation, namely, impregnating a once sintered blank body in nano carbon sol with the weight of 15-20 times of that of the blank body at room temperature for vacuum impregnation, ensuring that the blank body can be completely impregnated in the nano carbon sol during vacuum impregnation, drying the blank body in an oven with the temperature of 110-130 ℃, putting the oven into an argon environment, and carbonizing for 2-3 hours at the temperature of 500-600 ℃ to obtain a blank body subjected to vacuum impregnation;
And (3) secondary sintering, namely placing the blank subjected to vacuum impregnation into a vacuum reaction sintering furnace, placing silicon particles under the vacuum reaction sintering furnace, then performing vacuum sintering at 1450-1500 ℃ for 3-3.5h, performing vacuum sintering at 1550-1600 ℃ for 3-3.5h, performing vacuum sintering at 1650-1700 ℃ for 2.5-3h, naturally cooling to room temperature, and performing fine processing to obtain the silicon carbide ceramic wafer boat.
2. The method for forming a silicon carbide ceramic wafer boat according to claim 1, wherein the weight ratio of large-grain silicon carbide powder, medium-grain silicon carbide powder, small-grain silicon carbide powder, coated carbon black, graphite, phenolic resin and deionized water in the preparation of the ceramic powder is 25-30:35-40:100-110:9-10:5-6:6-8:120-150.
3. The method for forming a silicon carbide ceramic wafer boat according to claim 1, wherein in the preparation of the ceramic powder, the large-particle-size silicon carbide powder has a particle size of 60 to 70 μm;
the grain diameter of the medium grain diameter silicon carbide powder is 25-30 mu m;
The grain diameter of the small-grain-diameter silicon carbide powder is 1-3 mu m;
The particle size of the graphite is 3-5 mu m.
4. The method for forming a silicon carbide ceramic boat according to claim 1, wherein in the preparation of the coated carbon black, the weight-volume ratio of acetaldehyde, the first part of absolute ethyl alcohol, resorcinol, triethylamine, the second part of absolute ethyl alcohol, and carbon black is 80-120ml:700-800ml:90-100g:1.5-2.5g:5000-6000ml:1000-1200g;
the adding speed of the resorcinol is 5-6g/min;
the particle size of the carbon black is 1-2 mu m.
5. The method for forming a silicon carbide ceramic boat according to claim 1, wherein the forming is performed by adding ceramic powder into a mold, pre-pressing, cold isostatic pressing, and pressure relief by means of gradient depressurization to obtain a blank.
6. The method of forming a silicon carbide ceramic boat according to claim 5, wherein the pre-pressing pressure is 40-50MPa and the dwell time is 20-30s;
The pressure of the cold isostatic pressing is 180-225MPa, and the pressure maintaining time is 8-10min;
And the gradient depressurization is carried out, the pressure is reduced by 30-45MPa each time, and then the depressurization is continued after the pressure is maintained for 20-30 s.
7. The method of claim 1, wherein the size of the silicon grains in the primary sintering is 1-2mm, and the total weight of the silicon grains is 0.5-0.6 times the weight of the green body.
8. The method of claim 1, wherein the vacuum degree of vacuum impregnation is 0.08-0.09MPa and the time is 2-3h.
9. The method for forming a silicon carbide ceramic wafer boat according to claim 1, wherein the preparation method of the nano carbon sol is characterized in that 12 high-purity graphite electrodes with the thickness of 5cm are divided into 6 groups of positive and negative electrodes, the 6 groups of positive and negative electrodes are placed into a reaction tank filled with electrolyte, the electrolyte is aqueous solution of citric acid with the concentration of 3-3.5wt%, each group of electrodes are connected in parallel, insulating medium is used for insulating isolation between each electrode, then high-frequency alternating current pulse current is introduced into the electrodes for reaction, the frequency of the high-frequency alternating current pulse current is 40-50kHz, the voltage is 10-12V, the current density is 2-3A/cm 2 electrode surface area, the temperature of the reaction tank is controlled to be 45-55 ℃ in the reaction, the stirring speed is 100-200rpm for 20-30min each time, when the anode thickness is less than 1cm, and the electrolyte in the reaction tank is poured out after the anode electrode is replaced for 6-7d, so as to obtain the nano carbon sol.
10. The method of claim 1, wherein the size of the silicon grains is 1-2mm and the total weight of the silicon grains is 0.8-0.9 times the weight of the green body.
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