JP2018104241A - Process for producing silicon carbide - Google Patents
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 52
- 238000000034 method Methods 0.000 title claims abstract description 14
- 239000002994 raw material Substances 0.000 claims abstract description 92
- 238000010438 heat treatment Methods 0.000 claims abstract description 40
- 239000010936 titanium Substances 0.000 claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 10
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 10
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 10
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 14
- 239000011651 chromium Substances 0.000 claims description 13
- 229910052782 aluminium Inorganic materials 0.000 claims description 12
- 239000011572 manganese Substances 0.000 claims description 10
- 229910052804 chromium Inorganic materials 0.000 claims description 9
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 239000010703 silicon Substances 0.000 claims description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 3
- 238000003763 carbonization Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 abstract description 48
- 239000000463 material Substances 0.000 abstract description 8
- 239000003575 carbonaceous material Substances 0.000 abstract description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 abstract 2
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 239000002210 silicon-based material Substances 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 29
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 17
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 14
- 239000002245 particle Substances 0.000 description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 10
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 10
- 239000002253 acid Substances 0.000 description 10
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 9
- 238000002156 mixing Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000011780 sodium chloride Substances 0.000 description 5
- 229910004298 SiO 2 Inorganic materials 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000000428 dust Substances 0.000 description 4
- 239000001103 potassium chloride Substances 0.000 description 4
- 235000011164 potassium chloride Nutrition 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 230000009257 reactivity Effects 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 239000011449 brick Substances 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- 238000001953 recrystallisation Methods 0.000 description 3
- 239000011863 silicon-based powder Substances 0.000 description 3
- 238000000859 sublimation Methods 0.000 description 3
- 230000008022 sublimation Effects 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 229910003481 amorphous carbon Inorganic materials 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 238000006073 displacement reaction Methods 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- JEGUKCSWCFPDGT-UHFFFAOYSA-N h2o hydrate Chemical compound O.O JEGUKCSWCFPDGT-UHFFFAOYSA-N 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000011164 primary particle Substances 0.000 description 2
- 239000011163 secondary particle Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 229910052788 barium Inorganic materials 0.000 description 1
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
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- 230000005684 electric field Effects 0.000 description 1
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- -1 for example Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000002006 petroleum coke Substances 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229910021487 silica fume Inorganic materials 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000008399 tap water Substances 0.000 description 1
- 235000020679 tap water Nutrition 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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Abstract
Description
本発明は、炭化珪素の製造方法に関する。 The present invention relates to a method for producing silicon carbide.
炭化珪素単結晶は、その高硬度性、高熱伝導性、高温耐熱性から、成形砥石、セラミックス部品等の材料として使用されている。また、炭化珪素は、シリコンと比較すると、バンドギャップは約３倍、絶縁破壊電界強度は約１０倍という物性を有するので、シリコンに代わるパワー半導体用基盤の材料として注目されている。 Silicon carbide single crystals are used as materials for molding wheels, ceramic parts and the like because of their high hardness, high thermal conductivity, and high temperature heat resistance. In addition, silicon carbide is attracting attention as a power semiconductor substrate material that replaces silicon because it has properties of about 3 times the band gap and about 10 times the dielectric breakdown electric field strength compared to silicon.
パワー半導体用基盤の材料として使用される炭化珪素単結晶は、ドーパントとなるアルミニウム、チタンなどの金属元素の含有量が低いことが望まれる。炭化珪素単結晶の製造方法として、原料である炭化珪素粉末を２０００℃以上の高温条件下において昇華させ、炭化珪素を単結晶成長させる昇華再結晶法がよく知られており、工業的に広く使用されている。そのため、これら金属元素の含有量が低い炭化珪素粉末を昇華再結晶法における原料として用いることが好ましい。 The silicon carbide single crystal used as a power semiconductor substrate material is desired to have a low content of metal elements such as aluminum and titanium as dopants. As a method for producing a silicon carbide single crystal, a sublimation recrystallization method in which silicon carbide powder as a raw material is sublimated under a high temperature condition of 2000 ° C. or higher to grow a single crystal of silicon carbide is well known and widely used industrially. Has been. Therefore, it is preferable to use silicon carbide powder having a low content of these metal elements as a raw material in the sublimation recrystallization method.
従来から、一般的に、昇華再結晶法における原料としての炭化珪素粉末は、珪酸質原料及び炭素質原料からなる混合原料を、アチソン炉を用いて焼成して得た炭化珪素の塊状物を粉砕することにより製造している。そして、このようにして製造した炭化珪素粉末を、濃硫酸と濃硝酸とを混合した混酸を用いて洗浄することによって、アルミニウム、チタンなどの金属元素の含有量を低減させている。しかし、混酸の人体に対する危険性は極めて高いので、特殊な装置を用いる必要があった。 Conventionally, silicon carbide powder as a raw material in the sublimation recrystallization method is generally pulverized in a mass of silicon carbide obtained by firing a mixed raw material composed of a siliceous raw material and a carbonaceous raw material using an Atchison furnace. It is manufactured by doing. The silicon carbide powder produced in this way is washed with a mixed acid obtained by mixing concentrated sulfuric acid and concentrated nitric acid, thereby reducing the content of metal elements such as aluminum and titanium. However, since the danger of the mixed acid to the human body is extremely high, it is necessary to use a special device.
そこで、アチソン炉を用いた炭化珪素の製造過程において、不純物を低減させる方法が提案されている。例えば、特許文献１には、珪酸質原料及び炭素質原料からなる混合原料の混合モル比（Ｃ／ＳｉＯ２）を２．５〜４、且つ混合原料の不純物の含有率を１２０ｐｐｍ以下にすることにより、炭化珪素の不純物の含有率を５００ｐｐｍにすることが開示されている。 Therefore, a method for reducing impurities in the manufacturing process of silicon carbide using an Atchison furnace has been proposed. For example, in Patent Document 1, the mixing molar ratio (C / SiO 2 ) of a mixed raw material composed of a siliceous raw material and a carbonaceous raw material is 2.5 to 4, and the impurity content of the mixed raw material is 120 ppm or less. Discloses that the content of impurities of silicon carbide is 500 ppm.
また、特許文献２には、珪酸質原料、炭素質原料及びシリコン質原料からなる混合原料の混合モル比（Ｃ／Ｓｉ）を１．５以上３．０未満、且つシリコン原料中のシリコンの含有率を好ましくは９９．９質量％以上とすることにより、炭化珪素の不純物の含有率を低減することが開示されている。 Patent Document 2 discloses that the mixed molar ratio (C / Si) of a mixed raw material composed of a siliceous raw material, a carbonaceous raw material, and a silicon raw material is 1.5 or more and less than 3.0, and silicon is contained in the silicon raw material. It is disclosed that the content of impurities of silicon carbide is reduced by setting the rate to preferably 99.9% by mass or more.
しかしながら、上記特許文献１，２に開示された技術では、アルミニウム、鉄などの金属不純物は低減できるが、チタンを十分に低減させることができない。 However, with the techniques disclosed in Patent Documents 1 and 2, metal impurities such as aluminum and iron can be reduced, but titanium cannot be sufficiently reduced.
本発明は、不純物であるチタンの含有量の抑制を図ることが可能な炭化珪素の製造方法を提供することを目的とする。 An object of this invention is to provide the manufacturing method of the silicon carbide which can aim at suppression of content of the titanium which is an impurity.
本発明は、珪素を含む珪酸質原料及び炭素を含む炭素質原料からなり、かさ密度が０．４ｇ／ｃｍ３以上１．４ｇ／ｃｍ３以下である混合原料と発熱体とをアチソン炉の炉本体内に充填する工程と、前記発熱体を加熱する工程とを含み、炭化珪素の塊状物を製造する方法であって、前記発熱体を加熱する工程において、前記炉本体の空間に存するガスを前記アチソン炉外に排気することにより前記空間の圧力を前記アチソン炉外の雰囲気の圧力と比べて０Ｐａ以上１００Ｐａ以下に低くすることを特徴とする。 The present invention comprises a mixed raw material comprising a siliceous raw material containing silicon and a carbonaceous raw material containing carbon and having a bulk density of 0.4 g / cm 3 or more and 1.4 g / cm 3 or less and a heating element in an Acheson furnace. A method of producing a lump of silicon carbide, comprising a step of filling the main body and a step of heating the heating element, wherein in the step of heating the heating element, the gas existing in the space of the furnace body The pressure in the space is reduced to 0 Pa or more and 100 Pa or less as compared with the pressure in the atmosphere outside the Atchison furnace by exhausting outside the Atchison furnace.
発熱体を加熱する工程において、炉本体の空間に存するガスには不純物が含まれている。加熱が終了し冷却されると、生成される炭化珪素の表面にガスに含まれる不純物が析出する、あるいは炭化珪素粒子の内部に存在する空隙に不純物が析出する。 In the process of heating the heating element, the gas present in the space of the furnace body contains impurities. When heating is completed and cooled, impurities contained in the gas are deposited on the surface of the generated silicon carbide, or impurities are deposited in voids present inside the silicon carbide particles.
本発明によれば、発熱体を加熱する工程において、炉本体の空間に存するガスをアチソン炉外に排気するので、不純物もアチソン炉外に排気され、生成される炭化珪素の表面や粒子の内部に析出する不純物を抑制することが可能となる。 According to the present invention, in the step of heating the heating element, the gas existing in the space of the furnace body is exhausted outside the Atchison furnace, so that impurities are also exhausted outside the Atchison furnace, and the surface of silicon carbide and the inside of the particles are generated. It is possible to suppress impurities precipitated on the substrate.
なお、発熱体を加熱する工程の全期間に亘って、炉本体の空間に存するガスをアチソン炉外に排気しなくてもよく、その一部期間、好ましくは加熱終了前の所定の期間、例えば数十分から数時間だけ、ガスを排気してもよい。 Note that the gas existing in the space of the furnace body does not have to be exhausted outside the Atchison furnace over the entire period of the step of heating the heating element, and a partial period thereof, preferably a predetermined period before the end of heating, for example, The gas may be exhausted for several tens of minutes to several hours.
本発明において、前記炉本体の空間に存するガスを排気することにより、前記空間の圧力を前記アチソン炉外の雰囲気の圧力と比べて０Ｐａ以上１００Ｐａ以下低くする。 In the present invention, by exhausting the gas existing in the space of the furnace body, the pressure in the space is reduced by 0 Pa or more and 100 Pa or less as compared with the pressure of the atmosphere outside the Atchison furnace.
これは、炉本体の空間の圧力がアチソン炉外の雰囲気の圧力と比べて高いと、不純物を含んだガスが排気されないため、生成される炭化珪素の純度が低下するからである。一方、炉本体の空間の圧力がアチソン炉外の雰囲気の圧力と比べて１００Ｐａを超えて低いと、アチソン炉の内部に大量の外気が吸引され、炉本体内の温度が低下し、不純物ガスの析出が早まり不純物量が増加する、又は炭化珪素を生成するための一酸化珪素ガスがアチソン炉の外部に排気され過ぎ、炭化珪素の生成量が低下するからである。 This is because if the pressure in the space of the furnace body is higher than the pressure in the atmosphere outside the Atchison furnace, the gas containing impurities is not exhausted, and the purity of the generated silicon carbide is lowered. On the other hand, when the pressure in the space of the furnace body is lower than 100 Pa compared to the pressure in the atmosphere outside the Atchison furnace, a large amount of outside air is sucked into the inside of the Atchison furnace, the temperature inside the furnace body is lowered, and the impurity gas This is because the precipitation increases and the amount of impurities increases, or the silicon monoxide gas for generating silicon carbide is exhausted excessively outside the Atchison furnace, and the generated amount of silicon carbide decreases.
また、本発明において、前記混合原料のかさ密度は０．４ｇ／ｃｍ３以上１．４ｇ／ｃｍ３以下である。 In the present invention, the bulk density of the mixed raw material is 0.4 g / cm 3 or more and 1.4 g / cm 3 or less.
これは、混合原料のかさ密度が０．４ｇ／ｃｍ３未満であると混合原料中の空間が大きすぎて熱が伝わりにくくなり、炭化珪素の生成に寄与する一酸化珪素ガスの発生が減少し、炭化珪素の生成量が減少する。一方、混合原料のかさ密度が１．４ｇ／ｃｍ３を超えると、ガスの抜け道が形成されずに混合原料中の不純物がガスに含まれる割合が減少し、生成される炭化珪素に不純物が残存するからである。 This is because if the bulk density of the mixed raw material is less than 0.4 g / cm 3 , the space in the mixed raw material is too large to transmit heat, and the generation of silicon monoxide gas contributing to the generation of silicon carbide is reduced. The amount of silicon carbide produced decreases. On the other hand, when the bulk density of the mixed raw material exceeds 1.4 g / cm 3 , the ratio of impurities contained in the mixed raw material is reduced without forming a gas escape passage, and impurities remain in the generated silicon carbide. Because it does.
また、本発明において、前記混合原料に、前記混合原料に含まれるアルミニウム、鉄、チタン、クロム及びマンガンの総量に対してモル比で２以上５０以下の塩化物を添加することが好ましい。 Moreover, in this invention, it is preferable to add the chloride of 2-50 in molar ratio with respect to the total amount of aluminum, iron, titanium, chromium, and manganese contained in the said mixed raw material to the said mixed raw material.
これは、前記モル比が２未満であると、不純物を除去する効果が十分に発揮されない。一方、前記モル比が５０を超えると、生成される炭化珪素に塩素が残存し、好ましくないからである。 If the molar ratio is less than 2, the effect of removing impurities is not sufficiently exhibited. On the other hand, if the molar ratio exceeds 50, chlorine remains in the produced silicon carbide, which is not preferable.
以下、本発明の実施形態に係る炭化珪素の製造方法について説明する。本製造方法は、珪素を含む珪酸質原料及び炭素を含む炭素質原料からなる混合原料を、図１及び図２に示すアチソン炉１０を用いて焼成させることにより、炭素珪素を得るものである。 Hereinafter, the manufacturing method of the silicon carbide which concerns on embodiment of this invention is demonstrated. In this manufacturing method, carbon silicon is obtained by firing a mixed raw material composed of a siliceous raw material containing silicon and a carbonaceous raw material containing carbon using the Atchison furnace 10 shown in FIGS.
珪酸質原料は、例えば、天然珪砂、天然硅石粉、人造珪石粉、シリカフューム、非晶質シリカ、シリコン粉である。これらは１種を単独で又は２種以上を組み合わせて使用することができる。反応性の観点から、珪酸質原料として非晶質シリカを用いることが好ましい。 The siliceous raw material is, for example, natural silica sand, natural meteorite powder, artificial silica stone powder, silica fume, amorphous silica, or silicon powder. These can be used individually by 1 type or in combination of 2 or more types. From the viewpoint of reactivity, it is preferable to use amorphous silica as the siliceous raw material.
珪酸質原料の酸化珪素純度は、水分を除いて、９９．９％以上であることが好ましい。 The silicon oxide purity of the siliceous raw material is preferably 99.9% or more excluding moisture.
珪酸質原料の粒度は、平均粒子径が好ましくは６００μｍ以下、より好ましくは１００μｍ以下、特に好ましくは５０μｍ以下の粒度分布となるものであることが好ましい。平均粒子径が６００μｍを超えると反応性が著しく悪くなって不純物を含有する一酸化珪素（ＳｉＯ）ガスの発生量が減少し、炭化珪素の純度を高めることができなくなるからである。 As for the particle size of the siliceous raw material, the average particle size is preferably 600 μm or less, more preferably 100 μm or less, and particularly preferably 50 μm or less. This is because when the average particle diameter exceeds 600 μm, the reactivity becomes extremely poor, the amount of silicon monoxide (SiO) gas containing impurities decreases, and the purity of silicon carbide cannot be increased.
炭素質原料は、例えば、石油コークス、石炭ピッチ、カーボンブラック、各種有機樹脂である。これらは１種を単独で又は２種以上を組み合わせて使用してもよい。 Examples of the carbonaceous raw material include petroleum coke, coal pitch, carbon black, and various organic resins. These may be used alone or in combination of two or more.
炭素質原料の灰分は、０．５％以下であることが、炭化珪素の純度を高める点から好ましい。 The ash content of the carbonaceous raw material is preferably 0.5% or less from the viewpoint of increasing the purity of silicon carbide.
炭素質原料の粒度は、一次粒子の平均粒径が好ましくは１５０ｎｍ以下、より好ましくは７５ｎｍ以下の粒度分布となるようなものであることが好ましい。一次粒径の平均粒径が１５０ｎｍを超えると、反応性が悪くなるからである。 The particle size of the carbonaceous raw material is preferably such that the average particle size of the primary particles has a particle size distribution of preferably 150 nm or less, more preferably 75 nm or less. This is because if the average primary particle size exceeds 150 nm, the reactivity becomes worse.
そして、炭素質原料の二次粒子の平均粒径は、好ましくは１２５０μｍ以下、より好ましくは５００μｍ以下であることが好ましい。二次粒子の平均粒径が１２５０μｍを超えると珪酸質原料との均質混合が悪くなり、反応性に悪影響を及ぼすからである。 And the average particle diameter of the secondary particle of a carbonaceous raw material becomes like this. Preferably it is 1250 micrometers or less, More preferably, it is preferable that it is 500 micrometers or less. This is because when the average particle size of the secondary particles exceeds 1250 μm, the homogeneous mixing with the siliceous raw material is deteriorated and the reactivity is adversely affected.
珪酸質原料と炭素質原料を混合して混合原料Ａとする。二酸化珪素に対する炭素の混合モル比（Ｃ／ＳｉＯ２）は２．５以上４．０以下であることが好ましい。この混合モル比は、炭化珪素の組成に影響を与える。混合モル比が２．５未満、又は４．０を超えると、生成される炭化珪素に未反応の珪酸質原料又は炭素質原料が多く残存するので、好ましくない。ここで、混合モル比の範囲は、より好ましくは２．８以上３．６以下、特に好ましくは３．０以上３．３以下である。 A mixed raw material A is prepared by mixing a siliceous raw material and a carbonaceous raw material. The mixed molar ratio of carbon to silicon dioxide (C / SiO 2 ) is preferably 2.5 or more and 4.0 or less. This mixing molar ratio affects the composition of silicon carbide. When the mixing molar ratio is less than 2.5 or exceeds 4.0, a large amount of unreacted siliceous material or carbonaceous material remains in the produced silicon carbide, which is not preferable. Here, the range of the mixing molar ratio is more preferably 2.8 to 3.6, and particularly preferably 3.0 to 3.3.
混合原料Ａに塩化物を添加してもよい。塩化物の添加量は、混合原料Ａの不純物（アルミニウム（Ａｌ）、鉄（Ｆｅ）、チタン（Ｔｉ）、クロム（Ｃｒ）及びマンガン（Ｍｎ））の総量に対して、モル比で２以上５０以下であることが好ましい。２未満であると、不純物を除去する効果が十分発揮されない。一方、５０を超えると、生成される炭化珪素中に塩素が残存し、好ましくない。 Chloride may be added to the mixed raw material A. The amount of chloride added is 2 or more and 50 by molar ratio with respect to the total amount of impurities (aluminum (Al), iron (Fe), titanium (Ti), chromium (Cr) and manganese (Mn)) of the mixed raw material A. The following is preferable. If it is less than 2, the effect of removing impurities is not sufficiently exhibited. On the other hand, if it exceeds 50, chlorine remains in the produced silicon carbide, which is not preferable.
塩化物は、例えば、第２族元素、すなわち、ベリリウム（Ｂｅ）、マグネシウム（Ｍｇ）、カルシウム（Ｃａ）、ストロンチウム（Ｓｒ）、バリウム（Ｂａ）の何れかの塩化物、塩化ナトリウム又は塩化カリウム、あるいはこれらの混合物である。塩化物は、純粋な塩化物であっても、無水物又は水和物であってもよい。塩化物は、不純物が少ない高純度であることが好ましく、例えば純度９５％以上であることが好ましい。 The chloride is, for example, a group 2 element, that is, a beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) chloride, sodium chloride or potassium chloride, Or a mixture of these. The chloride may be pure chloride, anhydride or hydrate. The chloride is preferably highly pure with few impurities, for example, preferably 95% or more in purity.
混合原料Ａのかさ密度は、０．４ｇ／ｃｍ３以上１．４ｇ／ｃｍ３以下であることが好ましい。混合原料Ａのかさ密度が０．４ｇ／ｃｍ３未満であると、混合原料Ａ中の空間が大きくなり過ぎ、熱が伝わりにくくなり、炭化珪素の生成に寄与する一酸化珪素ガスの発生が減少し、炭化珪素の生成量が減少する。一方、混合原料Ａのかさ密度が１．４ｇ／ｃｍ３を超えると、ガスの抜け道が形成されず、混合原料Ａ中の不純物が一酸化珪素ガスと共に排気される割合が減少し、生成される炭化珪素に不純物が残存するからである。 The bulk density of the mixed raw material A is preferably 0.4 g / cm 3 or more and 1.4 g / cm 3 or less. When the bulk density of the mixed raw material A is less than 0.4 g / cm 3 , the space in the mixed raw material A becomes too large, heat is hardly transmitted, and the generation of silicon monoxide gas contributing to the generation of silicon carbide is reduced. As a result, the amount of silicon carbide produced decreases. On the other hand, when the bulk density of the mixed raw material A exceeds 1.4 g / cm 3 , no gas escape passage is formed, and the ratio of the impurities in the mixed raw material A exhausted together with the silicon monoxide gas is reduced and generated. This is because impurities remain in silicon carbide.
上述した混合原料Ａは、図１及び図２を示したアチソン炉（電気抵抗炉）１０を用いて焼成される。以下、アチソン炉１０について説明する。 The mixed raw material A mentioned above is baked using the Atchison furnace (electric resistance furnace) 10 shown in FIGS. Hereinafter, the Atchison furnace 10 will be described.
アチソン炉１０は、全体として上方が開放された箱状の炉本体１１と、図１の炉本体１１の左右方向（図２の前後方向）の端部にそれぞれ配置された電極１２と、炉本体１１の上部を覆うフード（覆体）１３と、炉本体１１内のガスをアチソン炉１０の外部に排気するための排気機構１４とを備えている。 The Acheson furnace 10 includes a box-shaped furnace body 11 whose upper part is opened as a whole, electrodes 12 disposed at end portions in the left-right direction (front-rear direction in FIG. 2) of the furnace body 11 in FIG. 11 is provided with a hood (covering body) 13 that covers the upper portion of 11 and an exhaust mechanism 14 for exhausting the gas in the furnace body 11 to the outside of the Atchison furnace 10.
炉本体１１は、底壁１１ａ、底壁１１ａの前後端部にそれぞれ形成された前後壁１１ｂ、並びに底壁１１ａの左右方向端部に形成され前後壁１１ｂの間に形成された側壁１１ｃからなる。炉本体１１は、ここでは、縦断面が矩形状であり全体とし上面が開放された直方体形状であるが、縦断面が台形状、又は全体として舟形形状などであってもよい。 The furnace body 11 includes a bottom wall 11a, front and rear walls 11b formed at the front and rear end portions of the bottom wall 11a, and a side wall 11c formed between the front and rear walls 11b at the left and right end portions of the bottom wall 11a. . Here, the furnace body 11 has a rectangular parallelepiped shape with a rectangular vertical cross section and an open upper surface as a whole, but the vertical cross section may have a trapezoidal shape or a boat shape as a whole.
炉本体１１は、ここでは、耐火温度が１４００℃程度の直方体形状の耐火煉瓦１５を積み重ねることによって構成されている。なお、炉本体１１は、底壁１１ａを一枚又は複数枚の板状体から構成するなど、その構成は限定されない。 Here, the furnace main body 11 is configured by stacking refractory bricks 15 having a rectangular parallelepiped shape with a fireproof temperature of about 1400 ° C. The structure of the furnace body 11 is not limited, for example, the bottom wall 11a is composed of one or a plurality of plate-like bodies.
電極１２は、炉本体１１の側壁１１ｃにそれぞれ固定され、その一端が炉本体１１の内側に露出している。電極１２の材質は、電気を通すことができれば特に限定されず、例えば、黒鉛粉、カーボンロッドである。 The electrodes 12 are respectively fixed to the side walls 11 c of the furnace body 11, and one end thereof is exposed to the inside of the furnace body 11. The material of the electrode 12 is not particularly limited as long as it can conduct electricity, and is, for example, graphite powder or carbon rod.
フード１３は、例えば金属製であり、炉本体１１の上部空間を全体に亘って覆っている。フード１３には、開閉可能な扉１３ａが設けられており、扉１３ａを閉鎖することにより炉本体１１の上部空間を密閉することができ、扉１３ａを開放することにより炉本体１１の上部空間をアチソン炉１０の外部雰囲気と連通することができるように構成されている。扉１３ａを開放すれば、炉本体１１の上部空間とアチソン炉１０の外部雰囲気とは連通され同じ圧力となる。 The hood 13 is made of metal, for example, and covers the entire upper space of the furnace body 11. The hood 13 is provided with a door 13a that can be opened and closed. The upper space of the furnace body 11 can be sealed by closing the door 13a, and the upper space of the furnace body 11 can be opened by opening the door 13a. It is configured to be able to communicate with the external atmosphere of the Atchison furnace 10. If the door 13a is opened, the upper space of the furnace body 11 and the external atmosphere of the Atchison furnace 10 are communicated with each other and have the same pressure.
排気機構１４は、炉本体１１の上部空間に存するガスをアチソン炉１０の外部の雰囲気に排気可能に構成されている。例えば、排気機構１４は、フード１３に形成された開口１３ｂと一端が接続された排気通路１６と、排気通路１６内のガスを吸引するブロア、ファンなどの吸引装置１７と、排気通路１６の開閉度を調整可能なダンパ１８と、排気通路１６の他端に接続され、通過するガス内の粉塵を捕集する粉塵捕集装置１９とを備えている。 The exhaust mechanism 14 is configured to be able to exhaust the gas existing in the upper space of the furnace body 11 to the atmosphere outside the Atchison furnace 10. For example, the exhaust mechanism 14 includes an opening 13 b formed in the hood 13 and one end connected to an exhaust passage 16, a suction device 17 such as a blower and a fan for sucking gas in the exhaust passage 16, and opening and closing of the exhaust passage 16. A damper 18 capable of adjusting the degree and a dust collecting device 19 connected to the other end of the exhaust passage 16 and collecting dust in the passing gas are provided.
このように構成された排気機構１４によれば、吸引装置１７による排気通路１６内のガスを吸引して排気通路１６内の圧力を負圧とすることにより、排気通路１６を介して炉本体１１の上部空間の圧力が低下し、この上部空間に存するガスが粉塵捕集装置１９で粉塵が捕集されたうえで、アチソン炉１０の外部雰囲気に排出される。そして、炉本体１１の上部空間の圧力はダンパ１８による排気通路１６の開度に応じて定まる。 According to the exhaust mechanism 14 configured in this way, the gas in the exhaust passage 16 is sucked by the suction device 17 and the pressure in the exhaust passage 16 is set to a negative pressure, so that the furnace main body 11 is passed through the exhaust passage 16. The pressure in the upper space is reduced, and the gas existing in the upper space is collected by the dust collecting device 19 and then discharged to the atmosphere outside the Atchison furnace 10. The pressure in the upper space of the furnace body 11 is determined according to the opening of the exhaust passage 16 by the damper 18.
なお、排気機構１４の構成は上述した構成に限定されない、例えば、吸引装置１７の代わりに、又は吸引装置１７と共に、図示しない送風装置を排気通路１６に接続してもよい。また、ダンパ１８を備えず、吸引装置１７の吸引力を制御することによって、炉本体１１の上部空間の圧力を調整してもよい。 The configuration of the exhaust mechanism 14 is not limited to the above-described configuration. For example, a blower (not shown) may be connected to the exhaust passage 16 instead of the suction device 17 or together with the suction device 17. Further, the pressure in the upper space of the furnace body 11 may be adjusted by controlling the suction force of the suction device 17 without providing the damper 18.
次に、アチソン炉１０を用いた炭化珪素の製造方法について説明する。 Next, a method for manufacturing silicon carbide using the Atchison furnace 10 will be described.
まず、炉本体１１の上下方向半分程度、すなわち電極１２が位置する高さ程度にまで、混合原料Ａを充填する。 First, the mixed raw material A is filled up to about half of the vertical direction of the furnace body 11, that is, to the height where the electrode 12 is located.
そして、電極１２間を接続するように、黒鉛などの炭素質粉末を密実に充填し、発熱体Ｂを形成する。発熱体Ｂの形態は、粉状でも棒状でもよい。また、発熱体Ｂが棒状の場合、その形状も特に限定されず、例えば円柱状でも角柱状でもよい。 Then, carbonaceous powder such as graphite is densely filled so as to connect the electrodes 12 to form the heating element B. The form of the heating element B may be powder or rod. Moreover, when the heat generating body B is rod-shaped, the shape is not particularly limited, and may be, for example, cylindrical or prismatic.
発熱体Ｂの不純物の含有率は、混合原料Ａに含まれる不純物の含有率よりも小さいことが好ましい。具体的には、発熱体Ｂの不純物の含有率は好ましくは１２０ｐｐｍ以下、より好ましくは７０ｐｐｍ以下、さらに好ましくは５０ｐｐｍ以下、特に好ましくは２５ｐｐｍ以下である。発熱体Ｂの不純物の含有率を、混合原料Ａに含まれる不純物の含有率よりも小さくすることによって、より高純度の炭化珪素を生成することができる。 The impurity content of the heating element B is preferably smaller than the impurity content contained in the mixed raw material A. Specifically, the content of impurities in the heating element B is preferably 120 ppm or less, more preferably 70 ppm or less, still more preferably 50 ppm or less, and particularly preferably 25 ppm or less. By making the content rate of the impurities of the heating element B smaller than the content rate of the impurities contained in the mixed raw material A, it is possible to produce higher purity silicon carbide.
さらに、この発熱体Ｂ及び露出した混合原料Ａの上の炉本体１１内に混合原料Ａを充填する。 Further, the mixed raw material A is filled into the furnace body 11 on the heating element B and the exposed mixed raw material A.
その後、電極１２間を通電して発熱体Ｂを通電発熱させ、発熱体Ｂが１６００℃〜３０００℃、より好ましくは１６００℃〜２５００℃となるように加熱する。これにより、発熱体Ｂの周囲で順次直接還元反応が起こり、炭化珪素の塊状物が生成され、発熱体Ｂを中心として略同心円状に成長する。 Thereafter, the electrode 12 is energized to cause the heating element B to generate heat and the heating element B is heated to 1600 ° C. to 3000 ° C., more preferably 1600 ° C. to 2500 ° C. As a result, a direct reduction reaction occurs sequentially around the heating element B, and a lump of silicon carbide is generated and grows substantially concentrically around the heating element B.
加熱時、扉１３ａを開放して、炉本体１１の上部空間とアチソン炉１０の外部雰囲気とを連通していてもよい。また、扉１３ａを閉鎖して、炉本体１１の上部空間を密閉した状態とし、この上部空間の圧力がアチソン炉１０の外部の雰囲気と比較して０Ｐａ以下１００Ｐａ以上低くなるように、ダンパ１８を制御する。 During heating, the door 13a may be opened to allow communication between the upper space of the furnace body 11 and the external atmosphere of the Atchison furnace 10. Further, the door 13a is closed to close the upper space of the furnace body 11, and the damper 18 is set so that the pressure in the upper space is lower than 0 Pa or lower and 100 Pa or higher compared to the atmosphere outside the Atchison furnace 10. Control.
なお、扉１３ａを閉鎖していても、排気機構１４により炉本体１１の上部空間に存するガスを排気すると、耐火煉瓦１５間の隙間を介してアチソン炉１０の炉外から当該空間に外部雰囲気のガス（空気）が流入する。これにより、吸引装置１７で炉本体１１の上部空間のガスを吸引することにより、炉本体１１内全体のガスが吸引されることになる。 Even if the door 13 a is closed, if the gas existing in the upper space of the furnace body 11 is exhausted by the exhaust mechanism 14, an external atmosphere is introduced into the space from the outside of the Acheson furnace 10 through the gap between the refractory bricks 15. Gas (air) flows in. As a result, the gas in the upper space of the furnace body 11 is sucked by the suction device 17, whereby the gas in the entire furnace body 11 is sucked.
炉本体１１内の空間の圧力のほうが外部雰囲気の圧力より高いと、不純物を含んだガスが排気されないため、生成される炭化珪素の純度が低下する。一方、炉本体１１内の空間の圧力が外部雰囲気の圧力に比べて１００Ｐａを超えて低いと、炉本体１１内に大量の外気が吸引され、炉本体１１内の温度が低下し、不純物ガスの析出が早まり不純物量が増加する、又は炭化珪素を生成するための一酸化珪素ガスが炉本体１０の外部に排気され過ぎ、炭化珪素の生成量が低下する。 If the pressure in the space in the furnace body 11 is higher than the pressure in the external atmosphere, the gas containing impurities is not exhausted, so that the purity of the generated silicon carbide is lowered. On the other hand, when the pressure of the space in the furnace body 11 is lower than 100 Pa compared to the pressure in the external atmosphere, a large amount of outside air is sucked into the furnace body 11, the temperature in the furnace body 11 is lowered, and the impurity gas Precipitation increases and the amount of impurities increases, or silicon monoxide gas for generating silicon carbide is exhausted too much to the outside of the furnace body 10, and the amount of silicon carbide generated decreases.
以上にように生成された炭化珪素の塊状物を回収して、用途に応じた方法で粉砕する。粉砕方法は、一般的な粉砕機を用いて粉砕すればよい。粉砕機は、例えば、ジェットミル、ボールミル、磨砕機、ジョークラッシャー、ロールミル、ピンミルである。粉砕コスト及び生産性の観点からはボールミルを用いることが好ましい。 The lump of silicon carbide produced as described above is collected and pulverized by a method according to the application. The pulverization method may be performed using a general pulverizer. Examples of the pulverizer include a jet mill, a ball mill, an attritor, a jaw crusher, a roll mill, and a pin mill. From the viewpoint of grinding cost and productivity, it is preferable to use a ball mill.
粉砕されて得られた炭化珪素粉末は、粉砕の際に混入した不純物を除去するため、酸洗浄することが好ましい。使用する酸は、フッ酸、塩酸、硫酸、硝酸などを使用することができる。コスト、取り扱いしやすさの観点から塩酸を使用することが望ましい。 The silicon carbide powder obtained by pulverization is preferably acid-washed in order to remove impurities mixed during pulverization. As the acid to be used, hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid and the like can be used. It is desirable to use hydrochloric acid from the viewpoint of cost and ease of handling.
炭化珪素粉末は、酸洗浄後、酸を除去するため、水で洗浄し、乾燥する。水として、例えば、水道水、イオン交換水、蒸留水を用いることができる。ただし、高純度の炭化珪素粉末が必要である場合は、イオン交換水又は蒸留水で洗浄することが望ましい。 The silicon carbide powder is washed with water and dried to remove the acid after acid washing. As water, for example, tap water, ion exchange water, or distilled water can be used. However, when high-purity silicon carbide powder is required, it is desirable to wash with ion-exchanged water or distilled water.
以下、本発明の実施例及び比較例を説明する。ただし、本発明はこれら実施例に限定されない。 Examples of the present invention and comparative examples will be described below. However, the present invention is not limited to these examples.
各実施例及び比較例において、不純物の含有率は「ＪＩＳ Ｒ １６１６（２００７） ファインセラミックス用炭化けい素微粉末の化学分析方法」に規定された加圧酸分析法によるＩＣＰ分析により測定した。より具体的には、Ａｌ，Ｆｅ，Ｃｒ，Ｍｎの各不純物についてはＩＣＰ−ＡＥＳ分析によって、ＴｉについてはＩＣＰ−ＭＳ分析によって測定した。 In each of the examples and comparative examples, the impurity content was measured by ICP analysis using the pressurized acid analysis method defined in “JIS R 1616 (2007) Chemical analysis method of fine silicon carbide powder for fine ceramics”. More specifically, each impurity of Al, Fe, Cr, and Mn was measured by ICP-AES analysis, and Ti was measured by ICP-MS analysis.
（実施例１）
珪酸質原料として、太平洋セメント株式会社試製の非晶質シリカを用意した。この非晶質シリカは、不純物として、Ａｌを０．５ｐｐｍ、Ｆｅを１．０ｐｐｍ、Ｔｉを１．０ｐｐｍ、Ｃｒを１．０ｐｐｍ、Ｍｎを１．０ｐｐｍ、それぞれ含有していた。
Example 1
An amorphous silica produced by Taiheiyo Cement Co., Ltd. was prepared as a siliceous material. This amorphous silica contained 0.5 ppm of Al, 1.0 ppm of Fe, 1.0 ppm of Ti, 1.0 ppm of Cr, and 1.0 ppm of Mn as impurities.
炭素質原料として、東海カーボン株式会社のアモルファスカーボン粉末（商品名：シースト６００）を用意した。このカーボン粉末は、不純物として、灰分を０．３％、Ａｌを４３ｐｐｍ、Ｆｅを３４ｐｐｍ、Ｔｉを２．３ｐｐｍ、Ｃｒを２．０ｐｐｍ、Ｍｎを１．１ｐｐｍ、それぞれ含有していた。 As a carbonaceous raw material, Tokai Carbon Co., Ltd. amorphous carbon powder (trade name: Seast 600) was prepared. This carbon powder contained 0.3% of ash, 43 ppm of Al, 34 ppm of Fe, 2.3 ppm of Ti, 2.0 ppm of Cr, and 1.1 ppm of Mn as impurities.
そして、上記非晶質シリカと上記アモルファスカーボン粉末カーボンとをＣ／ＳｉＯ２のモル比が３となるように混合して混合原料Ａとした。混合原料Ａには塩化物を添加しなかった。 The amorphous silica and the amorphous carbon powder carbon were mixed so that the molar ratio of C / SiO 2 was 3 to obtain a mixed raw material A. No chloride was added to mixed raw material A.
この混合原料Ａのうち１００ｇを容積５００ｍｌのメスシリンダーに入れ、振動機を用いて２分間振動を与え、測定者がメスシリンダーのメモリを読み取ることにより、混合原料Ａの体積を測定した。そして、測定した体積を重量１００ｇで除してかさ密度を求めた。 100 g of the mixed raw material A was placed in a graduated cylinder having a volume of 500 ml, vibrated for 2 minutes using a vibrator, and the measurer read the memory of the graduated cylinder to measure the volume of the mixed raw material A. Then, the bulk density was determined by dividing the measured volume by the weight of 100 g.
混合原料Ａと発熱体Ｂ用黒鉛粉とを炉本体１１に充填した。発熱体Ｂ用黒鉛粉として、太平洋セメント株式会社試製のものを用いた。発熱体Ｂ用黒鉛粉は、不純物として、Ａｌを３．５ｐｐｍ、Ｆｅを５．１ｐｐｍ、Ｔｉを２．５ｐｐｍ、Ｃｒを１．０ｐｐｍ、Ｍｎを１．０ｐｐｍ、それぞれ含有していた。 The furnace body 11 was filled with the mixed raw material A and the graphite powder for the heating element B. As the graphite powder for the heating element B, a product manufactured by Taiheiyo Cement Co., Ltd. was used. The graphite powder for heating element B contained, as impurities, 3.5 ppm of Al, 5.1 ppm of Fe, 2.5 ppm of Ti, 1.0 ppm of Cr, and 1.0 ppm of Mn.
そして、扉１３ａを開放にした状態で、排気機構１４による排気を行いながら、２５００℃で２４時間焼成して、炭化珪素の塊状物を得た。 And it baked at 2500 degreeC for 24 hours, exhausting by the exhaust mechanism 14 in the state which opened the door 13a, and obtained the lump of silicon carbide.
そして、得られた炭化珪素の塊状物をトップグラインダーを用いて粒径が２ｍｍ以下となるように粉砕し、この粉砕物を３５重量％の塩酸に２４時間浸漬した。浸漬後、酸を除去するため、イオン交換水で洗浄を行い、大型乾燥機を用いて１５０℃で乾燥して炭化珪素粉末を得た。得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．１５ｐｐｍと小さかった。 The obtained silicon carbide lump was pulverized using a top grinder so that the particle size was 2 mm or less, and the pulverized product was immersed in 35 wt% hydrochloric acid for 24 hours. After the immersion, in order to remove the acid, it was washed with ion exchange water and dried at 150 ° C. using a large dryer to obtain a silicon carbide powder. When the content rate of impurities in the obtained silicon carbide powder was measured, the content rate of Ti was as small as 0.15 ppm.
（実施例２）
実施例１と同じ混合原料Ａ及び発熱体Ｂ用黒鉛粉を、実施例１と同じように炉本体１１に充填し、扉１３ａを閉鎖した状態で、排気機構１４による排気を行いながら、２５００℃で２４時間焼成した。
(Example 2)
While mixing the same raw material A and heating element B graphite powder as in Example 1 into the furnace main body 11 in the same manner as in Example 1 and closing the door 13a, exhausting by the exhaust mechanism 14 is performed at 2500 ° C. For 24 hours.
電極１２への通電終了２時間前に、炉本体１１の上部空間の圧力がアチソン炉１０の外部雰囲気の圧力に比べて１０Ｐａ低くなるように、排気機構１４による排気量を調節した。通電終了後、炉本体１１が冷却するまで、炉本体１１の上部空間の圧力がアチソン炉１０の外部雰囲気の圧力に比べて１０Ｐａ低くなる状態を維持するように排気を続行し、炭化珪素の塊状物を得た。 Two hours before the end of energization of the electrode 12, the exhaust amount by the exhaust mechanism 14 was adjusted so that the pressure in the upper space of the furnace body 11 was 10 Pa lower than the pressure in the external atmosphere of the Atchison furnace 10. After the energization is completed, until the furnace body 11 cools, the exhaust is continued so that the pressure in the upper space of the furnace body 11 is 10 Pa lower than the pressure in the external atmosphere of the Atchison furnace 10, and a lump of silicon carbide is formed. I got a thing.
そして、得られた炭化珪素の塊状物を、実施例１と同様に、粉砕、酸浸漬、洗浄及び乾燥を行い、炭化珪素粉末を得た。得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．２１ｐｐｍと小さかった。 And the obtained silicon carbide lump was crushed, acid dipped, washed and dried in the same manner as in Example 1 to obtain silicon carbide powder. When the content rate of impurities in the obtained silicon carbide powder was measured, the content rate of Ti was as small as 0.21 ppm.
（実施例３）
炉本体１１の上部空間の圧力がアチソン炉１０の外部雰囲気の圧力に比べて１０Ｐａではなく９０Ｐａ低くなるように排気機構１４の排気量を調整したことを除き、実施例２と同様にして、炭化珪素粉末を得た。
(Example 3)
Carbonization was performed in the same manner as in Example 2 except that the displacement of the exhaust mechanism 14 was adjusted so that the pressure in the upper space of the furnace body 11 was 90 Pa lower than the pressure in the external atmosphere of the Atchison furnace 10 instead of 10 Pa. Silicon powder was obtained.
得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．２８ｐｐｍと小さかった。なお、全ての実施例及び比較例において、作業者が混合原料Ａ及び発熱体Ｂ用黒鉛粉を炉本体１１に手作業で充填している。 When the content rate of impurities in the obtained silicon carbide powder was measured, the content rate of Ti was as small as 0.28 ppm. In all examples and comparative examples, the operator manually fills the furnace body 11 with the mixed raw material A and the graphite powder for the heating element B.
（実施例４）
実施例１と同じ混合原料Ａに、この混合原料Ａ中の不純物（Ａｌ，Ｆｅ，Ｔｉ，Ｃｒ及びＭｎ）のモル数の３倍となるモル数の塩化ナトリウム（ＮａＣｌ）を添加したものを原料とした。塩化ナトリウムとしては、関東化学株式会社製の特級のもの（分子量５８．４４）を用いた。混合原料Ａに塩化ナトリウムを添加したもののかさ密度を実施例１と同様にして測定した。
Example 4
A raw material obtained by adding sodium chloride (NaCl) in the number of moles which is three times the number of moles of impurities (Al, Fe, Ti, Cr and Mn) in the mixed raw material A to the same mixed raw material A as in Example 1. It was. As the sodium chloride, a special grade (molecular weight 58.44) manufactured by Kanto Chemical Co., Ltd. was used. The bulk density of the mixed raw material A to which sodium chloride was added was measured in the same manner as in Example 1.
塩化物を混合原料Ａに添加したことを除いては実施例１と同様にして、炭化珪素粉末を得た。得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．１０ｐｐｍと小さく、実施例１におけるＴｉの含有率と比較しても小さかった。 A silicon carbide powder was obtained in the same manner as in Example 1 except that the chloride was added to the mixed raw material A. When the content rate of impurities in the obtained silicon carbide powder was measured, the content rate of Ti was as small as 0.10 ppm, which was smaller than the Ti content in Example 1.
（実施例５）
実施例１と同じ混合原料Ａに、この混合原料Ａ中の不純物（Ａｌ，Ｆｅ，Ｔｉ，Ｃｒ及びＭｎ）のモル数の３倍となるモル数の塩化カリウム（ＫＣｌ）を添加したものを原料とした。塩化カリウムとしては、関東化学株式会社製の特級のもの（分子量７４．５５）を用いた。混合原料Ａに塩化カリウムを添加したもののかさ密度を実施例１と同様にして測定した。
(Example 5)
A raw material obtained by adding potassium chloride (KCl) in the number of moles which is three times the number of moles of impurities (Al, Fe, Ti, Cr and Mn) in the mixed raw material A to the same mixed raw material A as in Example 1. It was. As the potassium chloride, a special grade (molecular weight 74.55) manufactured by Kanto Chemical Co., Inc. was used. The bulk density of the mixed raw material A to which potassium chloride was added was measured in the same manner as in Example 1.
塩化物を混合原料Ａに添加したことを除いては実施例１と同様にして、炭化珪素粉末を得た。得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．１１ｐｐｍと小さく、実施例２におけるＴｉの含有率と比較しても小さかった。 A silicon carbide powder was obtained in the same manner as in Example 1 except that the chloride was added to the mixed raw material A. When the content rate of the impurities in the obtained silicon carbide powder was measured, the Ti content rate was as small as 0.11 ppm, which was small even when compared with the Ti content rate in Example 2.
（比較例１）
実施例１と同じ混合原料Ａ及び発熱体Ｂ用黒鉛粉を、実施例１と同じように炉本体１１料に充填し、２５００℃で２４時間焼成し、炭化珪素の塊状物を得た。なお、焼成中は、実施例１と異なり、排気機構１４による排気を行わなわなかった。
(Comparative Example 1)
The same mixed raw material A and graphite powder for heating element B as in Example 1 were filled in the furnace body 11 material in the same manner as in Example 1, and baked at 2500 ° C. for 24 hours to obtain a lump of silicon carbide. During firing, unlike the first embodiment, the exhaust mechanism 14 was not exhausted.
そして、得られた炭化珪素の塊状物を、実施例１と同様に、粉砕、酸浸漬、洗浄及び乾燥を行い、炭化珪素粉末を得た。得られた炭化珪素における不純物の含有率を測定したところ、Ｔｉの含有率は０．４５ｐｐｍと実施例１と比較して大きかった。また、Ａｌ、Ｆｅ、Ｃｒの含有率も実施例１と比較して大きかった。 And the obtained silicon carbide lump was crushed, acid dipped, washed and dried in the same manner as in Example 1 to obtain silicon carbide powder. When the content rate of impurities in the obtained silicon carbide was measured, the content rate of Ti was 0.45 ppm, which was larger than that in Example 1. Further, the contents of Al, Fe, and Cr were larger than those in Example 1.
（比較例２）
炉本体１１の上部空間の圧力がアチソン炉１０の外部雰囲気の圧力に比べて１０Ｐａではなく１１０Ｐａとなるように排気機構１４の排気量を調整したことを除き、実施例２と同様にして、炭化珪素粉末を得た。
(Comparative Example 2)
Carbonization was performed in the same manner as in Example 2 except that the displacement of the exhaust mechanism 14 was adjusted so that the pressure in the upper space of the furnace body 11 was 110 Pa instead of 10 Pa as compared to the pressure in the external atmosphere of the Atchison furnace 10. Silicon powder was obtained.
得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．４０ｐｐｍと実施例２と比較して大きかった。また、Ａｌ、Ｆｅ、Ｃｒの含有率も実施例２と比較して大きかった。 When the content rate of impurities in the obtained silicon carbide powder was measured, the content rate of Ti was 0.40 ppm, which was larger than that in Example 2. Moreover, the content rate of Al, Fe, and Cr was also large compared with Example 2.
（比較例３）
珪酸質原料として、実施例１と同じ非晶質シリカを用意し、この非晶質シリカを造粒機を用いて直径４ｍｍ程度に造粒した。そして、この造粒した珪酸質原料と実施例１と同じ炭素質原料とをＣ／ＳｉＯ２のモル比が３となるように混合して混合原料Ａとした。この混合原料Ａのかさ密度を実施例１と同様にして求めた。かさ密度は０．３５ｇ／ｃｍ３であった。混合原料Ａには塩化物を添加しなかった。
(Comparative Example 3)
The same amorphous silica as Example 1 was prepared as a siliceous raw material, and this amorphous silica was granulated to a diameter of about 4 mm using a granulator. And this granulated siliceous raw material and the same carbonaceous raw material as Example 1 were mixed so that the molar ratio of C / SiO 2 might be 3, and it was set as the mixed raw material A. The bulk density of this mixed raw material A was determined in the same manner as in Example 1. The bulk density was 0.35 g / cm 3 . No chloride was added to mixed raw material A.
実施例１と同じように炉本体１１に上記混合原料Ａ及び実施例１と同じ発熱体Ｂ用黒鉛粉を充填して、実施例１と同様にして焼成して塊状物を得た。しかし、得られた塊状物は、ＸＲＤを用いて分析した結果、シリカとカーボンの塊状物であり、炭化珪素ではなかった。 As in Example 1, the furnace body 11 was filled with the mixed raw material A and the same graphite powder for the heating element B as in Example 1, and baked in the same manner as in Example 1 to obtain a lump. However, as a result of analysis using XRD, the obtained lump was a lump of silica and carbon, and was not silicon carbide.
（比較例４）
実施例１と同じ混合原料Ａ及び発熱体Ｂ用黒鉛粉を、実施例１と同じように炉本体１１に充填した。充填の際、振動バイブレーターを用いて原料に振動を与え、さらに上からプレートを用いて加圧をした。
(Comparative Example 4)
The furnace raw material 11 was filled with the same mixed raw material A and heating element B graphite powder as in Example 1. At the time of filling, the raw material was vibrated using a vibration vibrator, and further pressurized from above using a plate.
なお、この混合原料Ａのうち１００ｇを容積５００ｍｌのメスシリンダーに入れ、振動機を用いて２分間振動を与え、さらに上からプレートを用いて同様の圧力が加圧した。そして、この状態で、測定者がメスシリンダーのメモリを読み取ることにより、混合原料Ａの体積を測定し、測定した体積を重量１００ｇで除してかさ密度を求めたところ１．５４ｇ／ｃｍ３であった。混合原料Ａには塩化物を添加しなかった。 In addition, 100 g of this mixed raw material A was put into a graduated cylinder having a volume of 500 ml, and a vibration was applied for 2 minutes using a vibrator, and the same pressure was applied from above using a plate. In this state, the measurer reads the memory of the graduated cylinder to measure the volume of the mixed raw material A, and the bulk density is calculated by dividing the measured volume by the weight of 100 g, which is 1.54 g / cm 3 . there were. No chloride was added to mixed raw material A.
その後、実施例１と同様に、扉１３ａを開放にした状態で、排気機構１４による排気を行いながら、２５００℃で２４時間焼成して、炭化珪素の塊状物を得た。 Thereafter, in the same manner as in Example 1, with the door 13a opened, the exhaust mechanism 14 was evacuated and baked at 2500 ° C. for 24 hours to obtain a lump of silicon carbide.
そして、得られた炭化珪素の塊状物を、実施例１と同様に、粉砕、酸浸漬、洗浄及び乾燥を行い、炭化珪素粉末を得た。 And the obtained silicon carbide lump was crushed, acid dipped, washed and dried in the same manner as in Example 1 to obtain silicon carbide powder.
得られた炭化珪素粉末における不純物の含有率を測定したところ、Ｔｉの含有率は０．５２ｐｐｍと実施例１と比較して大きかった。また、Ａｌ、Ｆｅ、Ｃｒの含有率も実施例１と比較して大きかった。 When the content rate of impurities in the obtained silicon carbide powder was measured, the content rate of Ti was 0.52 ppm, which was larger than that in Example 1. Further, the contents of Al, Fe, and Cr were larger than those in Example 1.
表１に結果をまとめた。 Table 1 summarizes the results.
１０…アチソン炉、 １１…炉本体、 １１ａ…底壁、 １１ｂ…前後壁、 １１ｃ…側壁、 １２…電極、 １３…フード、 １３ａ…扉、 １３ｂ…開口、 １４…排気機構、 １５…耐火煉瓦、 １６…排気通路、 １７…吸引装置、 １８…ダンパ、 １９…粉塵捕集装置、 Ａ…混合原料、 Ｂ…発熱体。
DESCRIPTION OF SYMBOLS 10 ... Atchison furnace, 11 ... Furnace main body, 11a ... Bottom wall, 11b ... Front and rear wall, 11c ... Side wall, 12 ... Electrode, 13 ... Hood, 13a ... Door, 13b ... Opening, 14 ... Exhaust mechanism, 15 ... Fire brick 16 ... exhaust passage, 17 ... suction device, 18 ... damper, 19 ... dust collecting device, A ... mixed raw material, B ... heating element.
Claims (2)
前記発熱体を加熱する工程とを含み、炭化珪素の塊状物を製造する方法であって、
前記発熱体を加熱する工程において、前記炉本体の空間に存するガスを前記アチソン炉外に排気することにより前記空間の圧力を前記アチソン炉外の雰囲気の圧力と比べて０Ｐａ以上１００Ｐａ以下に低くすることを特徴とする炭化珪素の製造方法。 Filled in the furnace body of the Atchison furnace with a mixed raw material and a heating element consisting of a siliceous raw material containing silicon and a carbonaceous raw material containing carbon and having a bulk density of 0.4 g / cm 3 or more and 1.4 g / cm 3 or less. And a process of
Heating the heating element, and producing a lump of silicon carbide,
In the step of heating the heating element, the pressure in the space is lowered to 0 Pa or more and 100 Pa or less compared to the pressure of the atmosphere outside the Atchison furnace by exhausting the gas existing in the space of the furnace body outside the Atchison furnace. A method for producing silicon carbide, comprising:
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| JP2021147283A (en) * | 2020-03-19 | 2021-09-27 | 太平洋セメント株式会社 | Composite particle and manufacturing method thereof |
| JP7483192B2 (en) | 2020-03-19 | 2024-05-15 | 太平洋セメント株式会社 | Composite particles and method for producing same |
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