Substituent Effects on the Reactivity of the Silicon−Carbon Double Bond. Resonance, Inductive, and Steric Effects of Substituents at Silicon on the Reactivity of Simple 1-Methylsilenes
作者:William J. Leigh、Rabah Boukherroub、Corinna Kerst
DOI:10.1021/ja981435d
日期:1998.9.1
-diazomethanes leads to the formation of reactive silenes which can be detected directly in solution, allowing detailed studies of the kinetics and mechanisms of their reactions with nucleophiles. Over 30 transient silenes have now been studied by these methods, providing the opportunity to systematically assess the effects of substituents at silicon and carbon on the reactivity of the Si=C bond.
Oxidation of methylsilenes with molecular oxygen. A matrix isolation study
作者:Martin Trommer、Wolfram Sander、Andreas Patyk
DOI:10.1021/ja00078a016
日期:1993.12
investigated in O 2 -doped argon matrices. All silenes 1 are easily photooxidized in matrices containing more than 1% O 2 , but trimethylsilene (1c) is the only silene that exhibits thermal reactivity toward oxygen at temperatures as low as 20-40 K. The photochemical reactivity increases from 1a to 1c with increasing number of methyl groups at the double bond and decreasing ionization potential. Key intermediates
已在 O 2 掺杂的氩基质中研究了 1-甲基硅烯(2-硅丙烯)(1a)、1,1-二甲基硅烯(1b)和 1,1,2-三甲基硅烯(1c)的光化学和热氧化。所有 silene 1 在含有超过 1% O 2 的基质中很容易被光氧化,但三甲基硅烷 (1c) 是唯一一种在低至 20-40 K 的温度下对氧气表现出热反应性的 silene。光化学反应性从 1a 增加到 1c双键上的甲基数量增加,电离电位降低。1 的光化学和热氧化的关键中间体是硅二氧杂环丁烷 9
Polarized infrared spectroscopy of matrix-isolated dimethylsilylene and 1-methylsilene
作者:Charles A. Arrington、Kenneth A. Klingensmith、Robert West、Josef Michl
DOI:10.1021/ja00315a010
日期:1984.2
Attribution des spectres IR du dimethylsilylene et du methyl-1 silene basee sur une comparaison avec des spectres calcules a l'aide de la methode MNDO, et avec des spectres de molecules semblables
Attribution des specters IR du dimethylsilylene et dumethyl-1 silene basee sur une 比较 avec des specters calcules a l'aide de la methode MNDO, et avec des specters de分子 semblables
Inorganic polymer-derived tubular SiC arrays from sacrificial alumina templates
作者:Hao Wang、Xiao-Dong Li、Taek-Soo Kim、Dong-Pyo Kim
DOI:10.1063/1.1915510
日期:2005.4.25
An inorganicpolymer-derivedSiCarray with a well-aligned tubular structure, tailored diameter, and wall thickness were prepared by using sacrificialalumina membrane as a template. After being pyrolyzed at 1250 °C, the template was etched away by treating with HF solution. The SiC tubes displayed a series of properties, such as high adsorption, high-temperature resistance, and electrically semiconductor
通过使用牺牲氧化铝膜作为模板,制备了具有良好排列的管状结构、定制的直径和壁厚的无机聚合物衍生的 SiC 阵列。在 1250°C 下热解后,通过用 HF 溶液处理蚀刻掉模板。碳化硅管显示出一系列性能,如高吸附性、耐高温性和电半导体。通过本方法制备的 SiC 阵列由于其固有特性而在光学领域和作为催化剂载体具有潜在应用。
Synthesis, Structures, and Properties of Bulk Si(O)C Ceramics from Polycarbosilane
Bulk Si(O)C ceramics are fabricated from polycarbosilane (PCS) by bulk pyrolysis along the route of cross linking, warm‐pressing, and pyrolysis. The PCS was thermally oxidized for cross linking at various temperatures as a critical step toward the bulk transformation of PCS into bulk Si(O)C ceramics. The degree of cross linking of PSC affects the densities and bonding qualities of the warm‐pressed powder compacts and, hence, the resultant ceramics. Under optimized processing conditions, crack‐free bulk Si(O)C ceramics are obtained with a bulk density attaining 2.2 g/cm3. Despite the existence of a considerable amount of oxygen in the ceramics (16.08 wt%), resulting from the thermal oxidation processing, the ceramics show the characteristics of structures and properties of SiC‐based ceramics. 29Si‐solid state nuclear magnetic resonance spectra (NMR) reveal that the as‐pyrolyzed X‐ray amorphous Si(O)C phase consists mainly of SiC4 coordination units in the ceramic network, with the remainder being silicon‐coordinated carbon and oxygen. Microhardness tests show that the as‐pyrolyzed amorphous Si(O)C ceramics have a high hardness, attaining 24.91 GPa at a load of 2 N, and 19.82 GPa at a load of 10 N. Upon annealing at 1300°C in argon, the amorphous ceramics crystallized into nanophase β‐SiC ceramics, and the ceramics kept the bulk nature of the amorphous ceramics with an increased density. The 29Si‐solid state NMR spectrum indicates that the nanophase β‐SiC ceramics consist of SiC4 units together with some mixed coordination units, namely SiO2C2 and SiOC3. The hardness of the crystallized nanophase Si(O)C ceramics attains 23.20 GPa at a load of 10 N. The present study demonstrates the possibility of fabricating bulk Si(O)C ceramics via the polymer‐processing route, resulting in ceramics with promising structural and mechanical properties.