SiC陶瓷的低温烧结及其结构与性能
发布时间：2018-10-30 14:18
【摘要】：SiC陶瓷具有硬度大、强度高、热膨胀系数低、耐磨损、抗腐蚀等优异性能,作为机械密封件及耐磨、耐腐蚀件的应用前景广阔。本文开发一种无保护气氛下的SiC陶瓷低温常压烧结新技术,采用原料颗粒级配、烧结助剂类型及含量、粘结剂选择与含量、压制压力、烧结工艺(烧结温度、保温时间)等的优化设计,低温烧结制备力学性能优良的SiC陶瓷材料,并对其结构与性能的关系开展研究。相比于CaO-Al2O3-Y2O3和BaO-Al2O3-CaO而言,BaO-Al2O3-Y2O3体系助烧效果更佳。在无保护气氛下烧结,该烧结助剂与SiC粉体表面氧化形成Si02反应形成粘度适中且与SiC颗粒表面润湿性良好的助烧熔体,借助于液相粘性压紧效应和液相快速传质,促进SiC陶瓷内的物质传输,加速致密化。该助烧熔体在SiC陶瓷烧结后的冷却过程中大多以钡长石晶体(BAS)的形式析出,同时,还析出Y2Si2O7、CaAl2Si2O8等氧化物第二相,有效避免了形成脆性玻璃相对SiC陶瓷结构与性能的不利影响。烧结SiC陶瓷中SiC颗粒与第二相结合紧密,SiC相断口较为平整,呈现主体解理断裂特征,第二相断口粗糙,增大了断裂裂纹扩展的路径,有利于提高SiC陶瓷材料的韧性。采用3.5μm和0.5μm两种粒径的SiC粉体,按3：1的重量比级配,添加5 wt%的石蜡粘结剂,在400 MPa的压制压力下压制的陶瓷素坯致密度最大(2.00g/cm3)。添加含量为30 wt%的BaO-Al2O3-Y2O3烧结助剂,采用独特的埋粉工艺,于1550℃保温30 min烧结制备的SiC陶瓷的性能最佳,其密度、抗弯强度和断裂韧性分别达到3.14g/cm3、520 MPa和6.7 MPa·m1/2。
[Abstract]:SiC ceramics have excellent properties such as high hardness, high strength, low coefficient of thermal expansion, wear resistance, corrosion resistance and so on. In this paper, a new low temperature and atmospheric pressure sintering technology for SiC ceramics in unprotected atmosphere is developed. The raw material particle gradation, sintering assistant type and content, binder selection and content, pressing pressure, sintering process (sintering temperature, etc. The optimum design of holding time etc., the preparation of SiC ceramics with excellent mechanical properties by low temperature sintering, and the study on the relationship between structure and properties were carried out. Compared with CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO, the effect of BaO-Al2O3-Y2O3 system is better than that of CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO. When sintered in unprotected atmosphere, the sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. The sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. Promote material transport in SiC ceramics and accelerate densification. During the cooling process of SiC ceramics, most of these melts are precipitated in the form of barium feldspar crystal (BAS), and the second phase of oxides such as Y _ 2Si _ 2O _ 7 and CaAl _ 2Si _ 2O _ 8 are also precipitated. The unfavorable effect of brittle glass formation on the structure and properties of SiC ceramics was effectively avoided. The SiC particles in the sintered SiC ceramics are closely combined with the second phase, and the SiC phase fracture surface is relatively flat, showing the main cleavage fracture characteristics. The second phase fracture surface is rough, which increases the path of fracture crack propagation, and is conducive to improving the toughness of SiC ceramics. Two kinds of SiC powders, 3.5 渭 m and 0.5 渭 m, were prepared by 3:1 gradation, and 5 wt% paraffin binder was added. The maximum density (2.00g/cm3) of the ceramic blank was obtained under the pressure of 400 MPa. The properties and density of the SiC ceramics sintered at 1550 鈩，
本文编号：2300242
[Abstract]:SiC ceramics have excellent properties such as high hardness, high strength, low coefficient of thermal expansion, wear resistance, corrosion resistance and so on. In this paper, a new low temperature and atmospheric pressure sintering technology for SiC ceramics in unprotected atmosphere is developed. The raw material particle gradation, sintering assistant type and content, binder selection and content, pressing pressure, sintering process (sintering temperature, etc. The optimum design of holding time etc., the preparation of SiC ceramics with excellent mechanical properties by low temperature sintering, and the study on the relationship between structure and properties were carried out. Compared with CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO, the effect of BaO-Al2O3-Y2O3 system is better than that of CaO-Al2O3-Y2O3 and BaO-Al2O3-CaO. When sintered in unprotected atmosphere, the sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. The sintering agent reacted with SiC powder to form a kind of sintering melt with moderate viscosity and good wettability with SiC particle surface. Promote material transport in SiC ceramics and accelerate densification. During the cooling process of SiC ceramics, most of these melts are precipitated in the form of barium feldspar crystal (BAS), and the second phase of oxides such as Y _ 2Si _ 2O _ 7 and CaAl _ 2Si _ 2O _ 8 are also precipitated. The unfavorable effect of brittle glass formation on the structure and properties of SiC ceramics was effectively avoided. The SiC particles in the sintered SiC ceramics are closely combined with the second phase, and the SiC phase fracture surface is relatively flat, showing the main cleavage fracture characteristics. The second phase fracture surface is rough, which increases the path of fracture crack propagation, and is conducive to improving the toughness of SiC ceramics. Two kinds of SiC powders, 3.5 渭 m and 0.5 渭 m, were prepared by 3:1 gradation, and 5 wt% paraffin binder was added. The maximum density (2.00g/cm3) of the ceramic blank was obtained under the pressure of 400 MPa. The properties and density of the SiC ceramics sintered at 1550 鈩，
本文编号：2300242
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