Energetics of Si<sub><i>x</i></sub>O<sub><i>y</i></sub>C<sub><i>z</i></sub>Polymer-Derived Ceramics Prepared Under Varying Conditions
作者:Riham Michelle Morcos、Alexandra Navrotsky、Tamas Varga、Yigal Blum、Dongjoon Ahn、Fabrizia Poli、Klaus Müller、Rishi Raj
DOI:10.1111/j.1551-2916.2008.02543.x
日期:2008.9
Incorporation of carbon at the molecular level can create unusual amorphous and nanostructures of Si–C–O polymer‐derived ceramics by controlled pyrolysis of crosslinked polysiloxanes. These ceramics can resist crystallization to ultrahigh temperatures. In this work, we support earlier studies that the resistance to crystallization of these nanodomain networks is due to thermodynamic as well as kinetic factors. Calorimetric measurements of heats of dissolution in a molten oxide solvent show that these ceramics posses a negative enthalpy relative to their crystalline constituents (silicon carbide, cristobalite, and graphite). Si–C–O ceramics pyrolyzed at 1000° and 1450°C appear somewhat more energetically stable than those prepared at 1200°C.
在分子层面纳入碳可以通过对交联聚硅氧烷进行控制热解,生成异常的无定形和纳米结构的Si–C–O聚合物衍生陶瓷。这些陶瓷能够抵抗结晶至超高温。在此项研究中,我们支持早期研究的观点,即这些纳米域网络的抗结晶性是由于热力学和动力学因素。在熔融氧化物溶剂中测定溶解热的量热测量结果表明,这些陶瓷相对于其晶态组分(碳化硅、白榴石和石墨)具有负焓值。在1000°C和1450°C下热解的Si–C–O陶瓷似乎比在1200°C下制备的陶瓷在能量上更为稳定。