SILICON OXYCARBIDE GLASSES .2. STRUCTURE AND PROPERTIES
SILICON OXYCARBIDE GLASSES .2. STRUCTURE AND PROPERTIES
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DOI：
10.1557/jmr.1991.2723
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发表时间：
1991-12-01
影响因子：
2.7
通讯作者：
DOREMUS, RH
中科院分区：
文献类型：
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作者：
RENLUND, GM;PROCHAZKA, S;DOREMUS, RH
碳氧化硅玻璃由有机硅树脂热解形成，仅含有硅、氧和碳。 该玻璃在 X 射线衍射至 1400 摄氏度时仍保持非晶态，加热至该温度后在透射电子显微照片 (TEM) 中没有显示出任何特征。 在较高温度（1500-1650 摄氏度）下加热后，X 射线衍射中会出现碳化硅线，TEM 和电子衍射中会发现碳化硅和石墨的细晶区域。 XPS表明玻璃中的硅-氧键与无定形和结晶硅酸盐中的硅-氧键相似；有些硅同时与氧和碳键合。 碳与硅或碳键合；玻璃中没有碳-氧键。 红外光谱与这些结论一致，显示出硅-氧和硅-碳振动，但没有来自碳-氧键。 Si-29-NMR 显示了硅周围有四种不同键合基团的证据。 由这些结果推导出来的碳氧化硅结构是硅氧四面体的随机网络，其中一些硅与一个或两个碳取代了氧键合；这些碳又以四面体方式与其他硅原子键合。 仅存在非常小的碳-碳键区域，这些区域未键合在网络中。 这种“游离”碳将玻璃染成黑色。 当玻璃被加热到 1400 摄氏度以上时，这种网络复合材料会在微小区域内重新排列成石墨和碳化硅晶体。 碳氧化硅玻璃的密度、热膨胀系数、硬度、弹性模量、折射率和粘度都比石英玻璃中的这些性能稍高，这可能是因为碳氧化物网络中的碳化硅键导致了更紧密、更紧密堆积的结构。 碳氧化物玻璃在高达 1600 摄氏度及更高的温度下高度稳定，因为氧气和水在其中缓慢扩散。
Silicon oxycarbide glass is formed by the pyrolysis of silicone resins and contains only silicon, oxygen, and carbon. The glass remains amorphous in x-ray diffraction to 1400-degrees-C and shows no features in transmission electron micrographs (TEM) after heating to this temperature. After heating at higher temperature (1500-1650-degrees-C) silicon carbide lines develop in x-ray diffraction, and fine crystalline regions of silicon carbide and graphite are found in TEM and electron diffraction. XPS shows that silicon-oxygen bonds in the glass are similar to those in amorphous and crystalline silicates; some silicons are bonded to both oxygen and carbon. Carbon is bonded to either silicon or carbon; there are no carbon-oxygen bonds in the glass. Infrared spectra are consistent with these conclusions and show silicon-oxygen and silicon-carbon vibrations, but none from carbon-oxygen bonds. Si-29-NMR shows evidence for four different bonding groups around silicon. The silicon oxycarbide structure deduced from these results is a random network of silicon-oxygen tetrahedra, with some silicons bonded to one or two carbons substituted for oxygen; these carbons are in turn tetrahedrally bonded to other silicon atoms. There are very small regions of carbon-carbon bonds only, which are not bonded in the network. This "free" carbon colors the glass black. When the glass is heated above 1400-degrees-C this network composite rearranges in tiny regions to graphite and silicon carbide crystals. The density, coefficient of thermal expansion, hardness, elastic modulus, index of refraction, and viscosity of the silicon oxycarbide glasses are all somewhat higher than these properties in vitreous silica, probably because the silicon-carbide bonds in the network of the oxycarbide lead to a tighter, more closely packed structure. The oxycarbide glass is highly stable to temperatures up to 1600-degrees-C and higher, because oxygen and water diffuse slowly in it.