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1、摘要碳化硅工程陶瓷具有优异的高温力学和化学性能而广泛应用于现代工业的各个领域。固相烧结碳化硅陶瓷具有很高的机械强度，且生产工艺简单，一般采用B 4C+C做烧结助剂，经常存在原料粒径过大，分布不均，小颗粒团聚，影响烧结体的最终性能。本文在前人研究的基础之上，采用不同粒径和混合相粉体作为原料，B4C为烧结助剂，水溶性酚醛树脂作为粘结剂，将原料在去离子水中分散，经过湿法球磨制成成分均一的浆料，并进行喷雾造粒及干压成型，最后进行无压烧结并测试烧结体性能。在该过程中，本文优化了碳化硅混合粉体固相烧结配方；考察了影响最终烧结体致密度的各个因素及其作用机理，确定了各环节最优工艺参数，并对烧结中出现的异常现象
2、做出解释。研究表明，本次试验所制备的浆料呈现剪切稀化特性，浆料属于非牛顿假塑性流体；浆料粘度主要受到固相含量和PH值的影响，本次采用粘结剂对浆料粘度影响并不明显。最终得出，分散剂PEG+TMAH添加量为1%+0.2wt%，浆料粘度为5055%，PH值为99.5时，在12r/min 剪切速率下，浆料粘度为400500mpas，最适合喷雾造粒。其最佳参数为：热风进口温度280290，出口温度90100 ，雾化器转速1800020000r/min ，蠕动泵进料转速 6570r/min。造粒粉料流动性与原粉相比有了很大提高，松装密度从0.530.55g/cm 3上升到0.905g/cm3，休止角从48
3、51下降到23；造粒粉料粒径分布在 200120目（即75m120m）之间的颗粒均占了全部粉料的 80%以上，粉料分布范围较窄。在对粉料进行干法成型时，在70MPa压力下，不同粘结剂含量造粒粉料均可以完全破碎，在110120MPa下素坯密度达到最大 2.016g/cm3，过大压力导致坯体分层。粘结剂含量越大，所得素坯密度越高。但粘结剂过多在烧结时产生过多的残余碳及挥发相，对烧结制品不利，其添加量应视烧结实验确定。本实验基于前人研究基础之上，采用1mB 4C代替3mB 4C后，达到同程度的致密化烧结时，烧结温度从2065下降到2000，保温时间缩短为30min，且B4C最佳添加量为 11.5wt
4、%。将不同粒径-SiC 添加到 1m的-SiC 作为原料，进行烧结试验，结果当-SiC 粒径为1m 时，最终的烧结体密度最高达到3.15g/cm3，维氏硬度为23.98GPa，断裂韧性为4.44MPam 1/2。最终得出，在-SiC中添加合理粒径的-SiC有利于烧结体晶粒的细化和硬度提高，但对其韧性的改善效果并不明显。在烧结温度上升到为1400 时通入Ar 气，气氛压力0.04MPa，可防止烧结时烧结体表面石墨层的形成。关键词：-SiC 水基浆料 喷雾造粒 模压成型 固相烧结研究类型：应用研究型 Silicon carbide engineering ceramics has excellen
5、t high temperature mechanical and chemical properties ,so its widely used in every field of modern industry.Solid phase sintering silicon carbide ceramics has high mechanical strength, and simple production technology, generally USES the B4C + C to do sintering additives, usually raw material partic
6、le size is too big, uneven distribution, the small particles together, these will be influence the final performance of sintered body In this paper on the basis of previous studies, using different particle size alpha and beta mixed phase powder as raw materials, B4C for sintering additives, water s
7、oluble phenolic resin as binder, the materials will be scattered in deionized water, after wet grinding ball into a homogeneous paste, and spray granulation and dry forming, finally doing the without pressure sintering and sintering body performance test In this process, we optimize the silicon carb
8、ide mixed powder solid phase sintering formula; Examines the influence of sintered body eventually send density of each factors and mechanism, identify various links the optimum process parameters, and explain the abnormal phenomenon in sintering . According research that the size preparative presen
9、t the characteristics of present thin shear in the experiment , size belong to the Newton false plastic fluid; Paste viscosity is mainly affected by the solid content and the PH value, the size of the adhesive viscosity influence is not obvious. So we can finally concluded that the dispersant PEG +
10、TMAH add content is 1% + 0.2 wt %, paste viscosity for 50 to 55%, PH value for 9 9.5, in 12 r/min shear rate, paste viscosity for 400 500 mpa s, these are the most suitable for spray granulation.The best parameters is: hot air inlet temperature 280 290 , the temperature of 90 100 export, mist maker
11、speed 18000 20000 r/min, wriggle pump feeding speed 65 70 r/min. Granulation powder and powder liquidity has the very big enhancement, apparent density loose from 0.53 0.55 g/cm3 rose to 0.905 g/cm3, rest mode from 48 51 Angle down to 23 ; Granulation powder size distribution in 200 120 mesh (or 75
12、m 120 m) between particles are accounted for more than 80% of all powder, powder distribution area is limited. When powder materials is in dry molding and 70 MPa pressure, the different binder content powder granulationcan be broken completely, in 110 120 MPa the next meal billet density achieve max
13、imum 2.016 g/cm3, too much stress caused porcelain body stratification. Binding agent content, the bigger the income the higher density meal billet.But binder in sintering produced too much residual carbon and volatile, its adverse to sintering products, the adding dosages should be determined by th
14、e sintering experiment.This experiment based on the former research foundation, using 1 mB4C instead of 3 mB4C, when achieving the degree of sintering densification , the sintering temperature down from 2065 descend to 2000 , holding time shorten for 30 min, and B4C best additives for 1 1.5 wt %. We
15、 can use different particle size beta SiC to add to 1 m alpha SiC as raw material, and have the sintering experiment, the results is when beta SiC particle size for 1 m, the highest density of sintered body finally reached 3.15 g/cm3, vickers hardness of 23.98 GPa, the fracture toughness of 4.44 MPa
16、 m1/2. The finally conclusion is that we add the reasonable size beta SiC in alpha SiC to the benefit of the grain refinement and hardness improving, but it is not obvious about the toughness of improving effect. When the sintering temperature rise to 1400 , into the Ar gas, and the atmosphere pressure for 0.04 MPa, it can prevent the formation of graphite layers in the sintering
