空气气氛中烧成Si_3N_4-SiC复合材料的性能、相组成和显微结构  

Properties,phase composition and microstructure of Si_3N_4-SiC composites fired in air atmosphere

作　　者：吴宏鹏[1] 任颖丽[1] 王林俊[1] 孙加林[1] 洪彦若[1] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083

出　　处：《耐火材料》2005年第4期249-252,共4页Refractories

基　　金：国家自然科学基金资助项目(50172007);国家自然科学基金重点基金资助项目(50332010)。

摘　　要：以氮化硅细粉(粒度<0.088mm,w(βSi3N4)>95%)、碳化硅(w(SiC)>98%,粒度分别为2.8～0.9mm、0.9～0.15mm、<0.115mm和<0.063mm四级)、硅粉(粒度<0.045mm,w(Si)>98%)和硅灰(w(SiO2)=98.3%)为原料,以木质素磺酸钙水溶液作成型结合剂,采用150MPa的压力成型为65mm×114mm×230mm的Si3N4-SiC、Si3N4-SiC-Si和Si3N4-SiC-SiO2三种试样。在空气气氛中,以50℃·h-1的升温速度升至800℃保温4h,再升至1450℃保温2h,自然冷却至室温后,测定烧成后试样的常温耐压强度、常温抗折强度、1400℃下的高温抗折强度、显气孔率、体积密度和残氮率,并采用XRD、SEM和EPMA等手段分析烧后试样的相组成和显微结构。结果表明:3种试样在空气气氛中烧成后的高温(1400℃)和常温抗折强度都比较高,显气孔率都比较低,而耐压强度则以Si3N4-SiC试样的最高;烧成后试样中心区域的残氮率以Si3N4-SiC-Si试样的最高,Si3N4-SiC-SiO2试样的次之,Si3N4-SiC试样的最小;在空气气氛中烧成后,Si3N4-SiC试样中的Si3N4分解较多,SiC-Si3N4-Si试样的表面和内部都明显含有单质Si,SiC-Si3N4-SiO2试样表面区域的SiNO晶体发育很好,而内部区域的晶体发育较小。Using Si3 N4 powder （ 〈0. 088 mm, w（ β-Si3 N4 ） 〉 95 % ）, SiC （ w（ SiC ） 〉 98 %, four granularities used. 2.8 - 0.9 mm,0.9-0.15 mm, 〈0.115 mm and 〈0.063 mm）,Si powder（ 〈0.045 mm,w（Si） 〉98% ） and silica fume（ w（ SiO2 ） =98.3% ） as starting materials, calcium lignosulphonate solution （35%） as binder, the specimens with dimensions of 65 mm ×114 mm ×230mm of SiaN4 -SiC,SiaN4 -SiC -Si and SiaN4 -SiC - SiO2 system are prepared under 150 MPa pressure. The specimens are heated in ambient atmosphere at 50℃@ h^-1 till 800 ℃,soaking for 4 h then heated to 1450 ℃ and soaking for another 2 h, cooling to room temperature. The properties of cold crushing strength, MOR, hot MOR at 1400℃, apparent porosity, bulk density and remained nitrogen rate of the fired specimens are determined, and their phase compositions and microstructures are analyzed by means of XRD, SEM, EPMA. The results show that the fired specimens of the three system all show high cold and hot MOR, low apparent porosity,and SiaN4 -SiC specimen has the highest cold crushing strength ;the core area of Si3N4 -SiC -Si specimen has the highest remained nitrogen rate,followed by SiaN4 - SiC -SiO2 specimen and lowest SiaN4 -SiC specimen. After fired in air atmosphere, more Si3 N4decomposed for Si3 N4 -SiC specimen;the surface and core area have Si element left in the matrix for SiC -Si3N4 -Si specimen and Si2N2O crystal grows better in surface area than in core area for SiC - Si3 N, - SiO2 specimen.

关 键 词：氮化硅 碳化硅 复合材料 空气气氛 烧结性能 相组成 显微结构 Si3N4-SiC复合材料 烧成 高温抗折强度 

分 类 号：TQ174.758[化学工程—陶瓷工业] S782.39[化学工程—硅酸盐工业]