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71.
72.
The adsorption and thermal decomposition of ketene on Si(l 11)-7 × 7 were investigated using various surface analysis techniques. When the surface was exposed to ketene at 120 K, two CO stretching modes at 220 and 273 meV appeared in HREELS, corresponding to two adsorbed ketene states. After the sample was annealed at ?250 K, the 273 and the 80 meV peaks vanished, indicating the disappearance of one of the adsorption states by partial desorption of the adsorbate. In a corresponding TPD measurement, a desorption peak for ketene species was noted at 220 K. Annealing the sample at 450 K caused the decomposition of the adsorbate, producing CHx and O adspecies. Further annealing of the surface at higher temperatures resulted in the breaking of the CH bond, the desorption of H and O species and the formation of Si carbide. The desorption of H at 800 K was confirmed by the appearance of the D2 (m/e = 4) TPD peak at that temperature when CD2CO was used instead of CH2CO. 相似文献
73.
A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies. 相似文献
74.
《Surface and interface analysis : SIA》2003,35(3):251-255
From large‐scale production, two monocrystalline silicon solar cells of different quality, i.e. ISC = 3.0 A (good cell) and ISC = 1.6 A (bad cell), have been studied by XPS combined with 4 keV Ar+ depth profiling. Depth profiling was carried out through the anti‐reflection coating (TiO2), the passivation layer (SiO2) and up into the phosphorus‐doped silicon bulk. At the solar cell surface the elemental composition is similar for both cells, although the bad one presents slightly more carbon, phosphorus and lead but less silver than the good one. During profiling, carbon and silver could be followed by XPS. It was found that the carbon content is distinguishably higher in the bad cell than in the good one. Furthermore, it was found that silver atoms have not diffused in the same way in both cells. Only the good cell presents silver atoms up into the silicon bulk. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
75.
以脉冲微型反应技术研究了脱铝八面沸石对异丙苯的催化裂化行为,并与反应条件下表面酸性进行了关联。样品裂化活性随骨架Si/Al比增加呈山峰形变化,Si/Al=5.38时最大;反应条件下酸中心数随脱铝深度增加却单调降低。动力学数据表明,样品裂化反应速度常数与强质子酸中心数随骨架Si/Al比增加具有平行的山峰形变化规律,Si/Al比为8.87附近的样品最高。 相似文献
76.
采用磁控溅射方法分别在ITO玻璃和硅片上成功制备了具有良好C轴取向的ZnO薄膜.并研究了溅射气压,基底温度,以及氧偏压对ZnO薄膜物性的影响,从而确定了制备ZnO薄膜的最佳溅射条件. 相似文献
77.
Nils Siegbahn Mats-Olle Maånsson Klaus Mosbach 《Applied biochemistry and biotechnology》1987,12(2):91-105
A soluble, bifunctional enzyme complex has been prepared by crosslinking lactate dehydrogenase and alcohol dehydrogenase with
glutaraldehyde. The crosslinking was performed on a solid phase while the active sites of alcohol dehydrogenase and lactate
dehydrogenase were held adjacent to one another with the aid of a bis-NAD analog. Subsequently, the enzyme complex was released
from the solid phase. The soluble enzyme complex was then purified by using NAD-Sepharose as an affinity adsorbent. Based
on gel filtration experiments, the complex was estimated to consist of one of each dehydrogenase.
By using a third enzyme, lipoamide dehydrogenase, which competes with lactate dehydrogenase for NADH produced by alcohol dehydrogenase,
the effect of site-to-site orientation was studied. It was found that about 83% of the NADH produced by alcohol dehydrogenase
was oxidized by site-to-site oriented lactate dehydrogenase compared to a figure of only about 61% obtained in an identical
system of separate enzymes. This indicates that given two alternative routes, the preference for the one to lactate dehydrogenase
over the one to lipoamide dehydrogenase is enhanced when lactate dehydrogenase and alcohol dehydrogenase are site-to-site
oriented. 相似文献
78.
N. N. Zemlyanskii I. V. Borisova A. K. Shestakova Yu. A. Ustynyuk E. A. Chernyshev 《Russian Chemical Bulletin》1998,47(3):469-474
The first stable dibenzosilafulvene, 9-{[8-(dimethylaminomethyl)-1-naphthyl]phenylsil-1-ylium}fluoren-9-ide (7a), was obtained in one step from 9-fluorenyllithium and chloro[8-(dimethylaminomethyl)-1-naphthyl]phenylsilane as a stable
solvate with THF. The structure of the zwitterionic compound7a was established by1H,13C, and29Si NMR in solution and in the solid state. The reactions of compound7a with crotonaldehyde, ethanol, and triethylethylidenephosphorane are described. The data on the synthesis of alkoxy- and alkylthiochloro-9-fluorenylsilanes
and their phosphonium salts are given.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 486–491, March, 1998. 相似文献
79.
80.
A. Yamazaki Y. Inoue M. Koike T. Sakamoto R. Otsuka 《Journal of Thermal Analysis and Calorimetry》1993,40(1):85-97
Thomsonite with ideal chemical composition and with an ordered framework structure was synthesised hydrothermally from zeolite Na?A, which was ground to X-ray amorphous, with 0.05 mol dm?3 CaCl2 solution at 200°C. The dehydration behaviour of the prepared thomsonite was examined by TG-DTA. It was revealed that thomsonite lost most of zeolitic water below 450°C in three steps at about 180°, 340° and 390°C. The peak profiles of, the two higher-temperature endotherms were sharp and similar, and the weight loss at each step was approximately equal. 相似文献