Mechanical behaviour of ceramics
Mechanical behaviour of ceramics
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DOI：
10.1007/978-3-540-73448-2_7
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
J. Rösler;M. Bäker;H. Harders
中科院分区：
文献类型：
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作者：
J. Rösler;M. Bäker;H. Harders
工程陶瓷几乎完全由粉末制成，因为它们由于其高熔化温度而不能在液态下铸造。1例如通过在干燥状态下冷压，将粉末形成为近净形绿色体。或者，陶瓷可以通过将它们与增塑剂或液体溶剂混合来成形。这种类型的工艺的一个例子是粉浆浇注，其中陶瓷粉末与流体（通常是水或酒精）混合并倒入多孔陶瓷模具中。模具的毛细作用使陶瓷粉末除湿。干燥后，陶瓷具有足够的刚性，可以从模具中取出。在注塑成型中，陶瓷粉末与聚合物粘合剂混合，并与注塑成型聚合物类似地加工。接着，在高温下压实绿色体，在此之前仅通过机械或粘合剂松散结合的陶瓷粉末颗粒化学结合。标准工艺是烧结、热压和热等静压（HIP）[126]。当烧结是在没有外部载荷的情况下进行时，其他过程需要承受单轴或静水应力。图7.1示意了烧结过程。在压实过程中，材料扩散到颗粒之间的接触区域，由减少表面获得的能量驱动。接触面积变圆并变得更大。该过程的一个结果是部件收缩多达30%至40%。2
Engineering ceramics are almost exclusively made from powders because they cannot be cast in the liquid state due to their high melting temperature. 1 The powder is formed to a near-net shape green body, for instance by cold compaction in the dry state. Alternatively, ceramics can be shaped by mixing them with a plasticiser or a liquid solvent. One example for this type of process is slip casting where ceramic powder is mixed with a fluid (usually water or alcohol) and poured into a porous ceramic mould. The capillarity of the mould dehumidifies the ceramic powder. After drying, the ceramic is sufficiently rigid to be taken out of the mould. In injection moulding, the ceramic powder is mixed with a polymer binder and processed similarly to an injection moulded polymer. However, the larger abrasion of the ceramic powder has to be taken into account.Next, the green body is compacted at high temperature, whereupon the ceramic powder particles, previously only loosely bound mechanically or by binders, bind chemically. Standard processes for this are sintering, hot pressing, and hot isostatic pressing (hip)[126]. While sintering is done without external load, the other processes superimpose uniaxial or hydrostatic stresses. Figure 7.1 sketches a sintering process. During compaction, material diffuses to the contact area between the particles, driven by the energy gained in reducing the surface. The contact areas round off and become larger. One consequence of this process is that the component shrinks by as much as 30% to 40%. 2