【作者】 代智杰；

【导师】 王晓刚；

【作者基本信息】 西安科技大学 ， 材料学， 2008， 硕士

【摘要】 β-SiC具有高强度、高硬度、抗高温氧化性、高化学稳定性、高导热性和低热膨胀系数等多方面的卓越性能,引起各国科学家的广泛研究。通过理论研究和实验探索,西安科技大学王晓刚教授等人发明了一种制备β-SiC微粉和晶须的新技术,并且可用该技术规模化制备β-SiC微粉。然而,该方法制备出的β-SiC微粉初产物粒度范围宽,各个粒级堆垛在一起,并且含有SiO2、石墨、无定形碳以及铁、镁、钙等杂质,不能满足市场对于β-SiC微粉的要求。因此,期望通过合理的分级与纯化工艺方法得到能够应用于工业中的大批量粒度分布范围窄的优质β-SiC微粉产品。首先,本文对影响分级与纯化效果的微粉团聚现象、微粉“复颗粒”、粗颗粒杂质等因素进行了研究。确定了分散β-SiC微粉的最佳分散剂为V1,分散剂的最佳用量为固含量的0.5%;对微粉初产物进行球磨以打开微粉复颗粒;并通过筛分对β-SiC微粉初产物进行初步除杂。其次,结合国内外分级机的优点,以垂直上升流理论、液固两相流水平溢流理论、离心沉降理论、湿法筛分及平衡轨道等理论为依据,设计了一种新型浓缩过滤分级机。采用该分级机能够有效分离出14μm以上不同级别的β-SiC微粉颗粒,且分级精度和效率较高。对三足离心机进行分级实验,结果表明该分级机可以有效分离出0~1μm、0~2μm、0~3μm等级别的微粉颗粒。因此,结合浓缩过滤分级机和三足离心机的特点,将两种分级机联合起来对β-SiC微粉进行分级,最终确定了分级工艺路线。再次,通过静态煅烧法、功能性提纯炉除碳法、浮选法三种除碳方法的比较,将静态煅烧法和浮选法相结合除石墨及无定形碳,以获得小批量、高纯度的β-SiC微粉;将功能性提纯炉除碳法和浮选法相结合除石墨及无定形碳,以获得大批量、纯度为99%的β-SiC微粉。通过酸洗和水洗相结合工艺除去微粉中的SiO2、游离Si、Fe2O3、CaO、Al2O3等杂质,选择氢氟酸、试剂A、试剂B进行酸洗处理,利用自来水和蒸馏水进行水洗处理。通过烘干和二次球磨工艺得到最终微粉产品。最后通过粒度测试、XRD分析、SEM分析、能谱分析及化学分析对β-SiC微粉分级产品进行检测,结果表明本研究的纯化工艺是对β-SiC微粉提纯的一种有效工艺过程,β-SiC的含量最高可达99.90%。并且利用本研究的分级与纯化工艺,本课题组已经能够批量生产纯度高于99%的粒度为0~1μm、0~2.5μm、0~5μm等β-SiC微粉产品,部分产品已投入国内外市场。更多还原

【Abstract】 Due to the various excellent performances of high strength、high rigidity\resist high temperature oxidation、high chemical stability、high temperature conductivity and low expansion coefficient,β-SiC had been abroad researched by scientists of apiece nation. With the theory and experimentation research, one new patented techonlogy of preparingβ-SiC micropowder and whisker was invented by professor wang xiao gang in Xi An university of science and technology. Using the new technology,β-SiC micropowder could be manufactureed on an industrialized scale. However, theβ-SiC micropowder raw producation can not be satisfied market require because of wise granularity range and all grains stowing together, and coataining SiO2、graphite、amorphism carbon and iron、magnesium、calcium etc.So we hope to get a lot of high qualityβ-SiC micropowder with sharp granularity range which can be used in industry by using Classification and Purification Techniques in reason .First, for the sake of actualizing Classification and Purification Techniques well forβ-SiC micropowder , the effect factors of micropowder reunite、compound particles and impurities was studied.We made sure that V1 was the best dispersant by studying many dispersant ofβ-SiC micropowder; and undone the compound particles through abrading experiment; get rid of some impurities passing screen.Second, A new filtration enrichment classifier was designed by combining uprightness ascend、liquid-solid phase level floding、centrifugal sedimentation and wet sieving theory. It was shown that the design of filtration enrichment classifier was right , and that can grade bigger than 14μm ofβ-SiC micropowder. Though three legs centrifugal machine, The grading experiment was shown that the grader can separate thin grain. So we could gradeβ-SiC micropowder by combining filtration enrichment classifier and three legs centrifugal machine, and the class craftwork was made. Through purification experiment, we made sure an efficient technique of getting rid of impurities. The measure of removing carbon was made by comparing static state calcine divisor、functionality purification furnace and floatation. The impurities of silicon dioxide、dissociate silicon、ferric oxide、calcium and alumina ect were removed by combining acid and water cleanout. We chose hydrofluoric acid、reagent A and B、tap and distilled water as regent.Through drying and second abrade technics,we got the final micropowder. The conduct was tested by grain size and XRD、SEM、energy chart and chymical analysis, it was shown that the purification technique was an effective process toβ-SiC micropowder.The content ofβ-SiC is to 99.9%. Using the Classification and Purification Techniques, someβ-SiC micropowder product with high content more than 99.9% has been ploughed into market that with sharp granularity range of 0~1μm、0~2.5μm、0~5μm and so on.更多还原