推荐回答(5个)
碳化硅是由硅与碳元素以共价键结合的非金属碳化物,硬度仅次于金刚石和碳化硼。化学式为SiC。无色晶体,外表氧化或含杂质时呈蓝黑色。具有金刚石结构的碳化硅变体俗称金刚砂。金刚砂的硬度挨近金刚石,热安稳性好,2127℃时由β-碳化硅转变成α-碳化硅,α-碳化硅在2400℃依然安稳。对氢氟酸水溶液和浓硫酸安稳,对浓氢氟酸与硝酸的混合酸或磷酸则不安稳。在空气氛中被熔融的碱分化。它分为人工合成碳化硅和天然碳化硅。天然碳化硅称为碳硅石,首要赋存于金伯利岩及火山角闪岩中,但其量甚少,无挖掘价值
工业用碳化硅为人工碳化硅,SiC含量为95%~99.5%,常含少量的游离碳,以及Fe2O3、Si和SiO2等杂质。碳化硅按结晶类型可分为六方晶系(α-SiC)和立方晶系(β-SiC),六方晶系又因其结晶排列的周期性不同有六方晶胞的晶型(2H、4H、6H……等)和菱形晶胞的晶型(15R、21R、27R……等),碳化硅的同质多晶结构有100多种。工业碳化硅为α-SiC和β-SiC的混合物,色彩有黑色和绿色两种。纯洁的碳化硅为无色通明,含杂质时呈黑色、绿色、蓝色及黄色。六方和立方晶系,晶体为板状,复三方柱状。具有玻璃光泽,密度为3.17~3.47g/cm3,莫氏硬度9.2,显微硬度30380~33320MPa;熔点:在大气中2050℃开端分化,在复原气氛下2600℃开端分化;弹性模量为466、480MPa;抗拉强度为171.5MPa;耐压强度为1029MPa;线膨胀系数为(25~1000℃)5.0×10-6/℃;热导率(20℃)为59W/(m·K)。化学性质安稳,在HCl、H2SO4和HF中煮沸也不受浸蚀,但在浓H3PO4中于230℃开端分化。
金刚砂又名碳化硅(SiC)是用石英砂、石油焦(或煤焦)、木屑(生产绿色碳化硅时需要加食盐)等原料通过电阻炉高温冶炼而成。
碳化硅由于化学性能稳定、导热系数高、热膨胀系数小、耐磨性能好,除作磨料用外,还有很多其他用途,例如:以特殊工艺把碳化硅粉末涂布于水轮机叶轮或汽缸体的内壁,可提高其耐磨性而延长使用寿命1~2倍;用以制成的高级耐火材料,耐热震、体积小、重量轻而强度高,节能效果好。低品级碳化硅(含SiC约85%)是极好的脱氧剂,用它可加快炼钢速度,并便于控制化学成分,提高钢的质量。此外,碳化硅还大量用于制作电热元件硅碳棒。
碳化硅的用处:
碳化硅制品具有耐高温、耐磨、耐热震、耐化学腐蚀、耐辐射和杰出的导电性、导热性等特别功用,因而在国民经济各部门中具有广泛的用处。
1、在电气工业中,碳化硅可用做避雷器阀体、硅碳电热元件、远红外线发生器等。
2、在航天工业中,用碳化硅制造的燃气滤片、燃烧室喷嘴已用于火箭技能中。
3、在炭素工业中,碳化硅首要用来出产炼铁高炉用砖在石墨电极出产中,碳化硅还用做耐氧化涂层电极的涂层耐火烧结料的配猜中,以添加涂层对温度急剧改变的承受才能。
4、在特种炭素资料——生物炭的制造中,常以丙烷和三氯甲基硅烷为气体质料,经高温热解反响,在石墨基体上堆积生成含硅热解炭涂层,以添加制品的硬度、强度和耐磨性。
碳化硅的用途:
1、在半导体范畴的使用
碳化硅一维纳米资料因为本身的微观描摹和晶体结构使其具有更多独特的优异功用和愈加广泛的使用远景,被普遍认为有望成为第三代宽带隙半导体资料的重要组成单元。
2、在光伏范畴的使用
光伏逆变器对光伏发电效果非常重要,不只具有直沟通改换功用,还具有最大限度地发挥太阳电池功用的功用和体系故障维护功用。
3、在航空范畴的使用
碳化硅制造成碳化硅纤维,碳化硅纤维首要用作耐高温资料和增强资料,耐高温资料包含热屏蔽资料、耐高温输送带、过滤高温气体或熔融金属的滤布等。
碳化硅制品可用反应烧结法制造。将粒度配比合适的a-Sic粉与胶体石墨在瓷球磨筒中均匀混合20h,加入结合剂羧甲基纤维素或聚乙烯醇的酒精溶液,在钢模中成型,压力为50~70MPa。
碳化硅熔点高、比重低、莫氏硬度9.2,强度较高,热震稳定性较好,不溶于水和酸,但能溶解在熔融碱中。碳化硅在800~1140℃之间的抗氧化能力差,因为此时生成的氧化膜(SiO2)较疏松,起不到充分保护作用。当温度升高,达到1550℃时,其抗氧化性能变好。
碳化硅可用于制造磨料、磨具:用于制造硅碳棒、硅碳管等电阻发热元件:用于制造喷气飞机、燃气轮机、火箭发动机尾喷管等,用于制造熔融金属输送管道、过滤器、坩埚等
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