Textured h‐BN Ceramics Prepared by Slip Casting
Textured h‐BN Ceramics Prepared by Slip Casting
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DOI：
10.1111/j.1551-2916.2010.04273.x
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发表时间：
2011-05
影响因子：
3.9
通讯作者：
D. Ni;Guo‐Jun Zhang;Y. Kan;Y. Sakka
中科院分区：
文献类型：
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作者：
D. Ni;Guo‐Jun Zhang;Y. Kan;Y. Sakka
本文报道了以不规则形状和片状的六方氮化硼（h-BN）为起始材料，采用滑移铸造和放电等离子烧结法制备的h-BN陶瓷的织构行为。在本研究中，通过添加2.5 wt%聚醚亚胺分散剂，制备了具有30 vol%固体负载的分散良好的h-BN乙醇基悬浮液。结果表明，两种h-BN在滑移铸造过程中均表现出较强的取向性，其特点是BN晶体的c面取向与铸造方向垂直。分析和实验结果表明，滑移铸造过程中乙醇的流动和h-BN的表面特性是织构形成的主要原因。因此，取向度对绿体厚度非常敏感，当绿体厚度超过一定值时，取向度减小，最终消失。在1800℃/50 MPa烧结后，不规则形状和片状h-BN的密度分别达到理论密度的92.0%和88.9%。制备的氮化硼陶瓷的导热系数对晶粒取向有很强的依赖性，沿氮化硼层的导热系数明显高于沿氮化硼层的导热系数。
This paper reports the texturing behavior of hexagonal boron nitride (h-BN) ceramics prepared by slip casting, followed by spark plasma sintering, using either irregularly shaped or plate-like h-BN as the starting materials. In this study, well-dispersed h-BN ethanol-based suspensions with 30 vol% solid loading were prepared by adding 2.5 wt% polyetherimide dispersant. It was found that both kinds of h-BN exhibited a substantially strong orientation during slip casting, which was featured by the alignment of the c-planes of the BN crystals perpendicular to the casting direction. Analysis and experimental results revealed that the texture development resulted from ethanol flow during slip casting and intrinsical surface properties of h-BN. Consequently, the orientation degree was very sensitive to the thickness of green bodies, which decreased when the thickness exceeded a certain value, and finally disappeared. Densities of ∼92.0% and 88.9% of the theoretical for the irregularly shaped and plate-like h-BN, respectively, were achieved after sintering at 1800°C/50 MPa. The thermal conductivity of the as-prepared BN ceramics showed a strong dependence on the grain orientation, being substantially higher along the BN layers than across them.