A29Si NMR study of natural and synthetic melanophlogites,the silica analogues of the clathrate hydrates of type I

²⁹Si MAS NMR spectra of natural melanophlogite as well as of synthetic melanophlogite indicate that the room temperature lattice structure has lower symmetry than expected from its proposed crystal structure. On heating the samples to temperatures above room temperature, the structure undergoes a reversible phase transition with a transition temperature characteristic of the locality. For the synthetic melanophlogite, the transition is over the range 298 K to 338 K. From low temperature NMR spectra it is concluded that the low temperature forms of synthetic melanophlogite and of melanophlogite from Sicily differ in their crystal lattice symmetries due to their characteristic guest species.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena.On leave Mineralogisches Institut, CAU KIEL, FRG     

Characterization of the SiOT Angle and Cation Effects on 29Si Chemical Shifts Of Zeolites

The quantitative relationships between ²⁹Si chemical shifts and (a) the SiOT (T = Al or Si) angles and (b) the nature of the cations of the alkali forms of zeolites can be account for by the changes of charge density and p electron population of the Si atoms as calculated by the extended Hückel method on cluster models.     

激光刻蚀硅表面的形貌及其对浸润性的影响

利用脉冲激光在Si表面刻蚀具有不同宽度和深度的微槽形貌, 通过测量接触角的大小研究其浸润特性, 并分析了形貌与浸润性的关系. 结果表明, 在Si表面刻蚀微槽深度一定的条件下, 刻蚀微槽宽度越宽, 接触角越小; 在Si表面刻蚀微槽宽度一定的条件下, 刻蚀微槽越深, 接触角越大, 最高可达165°. 而且Si表面上刻蚀后产生的细微尖峰结构对其浸润特性有显著的影响. 因此, 利用激光刻蚀表面方法可以在一定程度上调控固体表面的润湿性能.     

锂离子电池用多孔硅/石墨/碳复合负极材料的研究

在两步高能球磨和酸蚀条件下制得了多孔硅/石墨复合材料，并对其进行碳包覆制成多孔硅/石墨/碳复合材料。通过TEM，SEM等测试手段研究了多孔硅材料的结构。作为锂离子电池负极材料，电化学测试结果表明多孔硅/石墨/碳复合材料相比纳米硅/石墨/碳复合材料有更好的循环稳定性。同时，改变复合体配比、热解碳前驱物、粘结剂种类和用量也会对材料的电化学性能产生较大的影响。其中使用质量分数为10％的LA132粘结剂的电极200次循环以后充电容量保持在649.9 mAh·g^-1，几乎没有衰减。良好的电化学性能主要归因于主活性体-多孔硅颗粒中的纳米孔隙很好地抑制了嵌锂过程中自身的体积膨胀，而且亚微米石墨颗粒和碳的复合也减轻了电极材料的体积效应并改善了其导电性。     

脱铝八面沸石的研究(Ⅳ)——异丙苯催化裂化

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。     

Molekulares S=GeCl2 Matrix-IR-Untersuchungen und ab initio SCF-Rechnungen

The Molecule S?GeCl₂. Matrix IR Investigation and Ab initio SCF Calculation Molecular S?GeCl₂ is found in a matrix reaction between the high-temperature molecule Ge?S and Cl₂. A structure analog to that of phosgene can be derived from the isotopical shifts (⁷⁰Ge/⁷²Ge/⁷³Ge/⁷⁴Ge/⁷⁶Ge and ³⁵Cl/³⁷Cl) within the IR spectra. The normal coordinate analysis results for the Ge?S force constant a value of 4.21 mdyn/Å. The spectroscopic results are confirmed by ab initio SCF calculations.     

SiC缓冲层对Si表面生长的ZnO薄膜结构和光电性能的改善

用脉冲激光沉积(PLD)技术制备了ZnO/SiC/Si和 ZnO/Si薄膜并制成了紫外探测器。利用X射线衍射(XRD),光致发光(PL)谱,I-V曲线和光电响应谱对薄膜的结构和光电性能进行了研究。实验结果表明:SiC缓冲层改善了ZnO薄膜的结晶质量和光电性能,其原因可能是SiC作为柔性衬底能够减少ZnO与Si 之间大的晶格失配和热失配导致的界面缺陷和界面态。     

SEM–EDX and SAM–AES Investigations on Rochow Contact Masses

Appropriate Rochow contact masses have been investigated by the spatial resolution techniques SEM–EDX and SAM–AES. The results gave evidence of the existence and the catalytic action of (X-ray)-amorphous copper–silicon (Cu–Si) surface species, i.e. extremely highly dispersed particles or two-dimensional species. The well-known Rochow promoter zinc seems to act as a moderator rather than as a real accelerator. It ensures a stable rate for the reaction by neutralizing the detrimental action of silicon impurities. The silicon impurities make the whole of the silicon surface reactive and in this way cause a general blockade of the silicon surface by inactive copper species. Zinc localizes the reaction. The silicon surface remains partly free, and active Cu–Si surface species can be formed by lateral diffusion of copper onto the silicon surface that is still free. © 1997 by John Wiley & Sons, Ltd.     

29Si NMR谱对[SiW11(CH3SiOSiCH3)O39]4-结构的验证

Keggin结构杂多酸的有机衍生物[SiW_(11)(RSiOSiR)O_(39)]~(4-)(R=C_2H_5、C_6H_5、NC(CH_2)_3、C_3H_7)已有报道,根据其红外光谱中出现1040cm~(-1)(Si-O-Si的振动峰),Knoth提出了图1的结构。从中可以看出RSiOSiR基占据了Keggin结构杂多酸[SiW_(11)O_(39)]~(8-)的空缺齿顶位置。当然处于齿顶位置的硅原子和中心位置的硅原子的化学环境显然是不同的,所以可用~(29)Si NMR来鉴定这两种硅原子,并推测其结构。     

Synthesis and Hydrogen-Bond Patterns of Aryl-Group Substituted Silanediols and -triols from Alkoxy- and Chlorosilanes

Organosilanols typically show a high condensation tendency and only exist as stable isolable molecules under very specific steric and electronic conditions at the silicon atom. In the present work, various novel representatives of this class of compounds were synthesized by hydrolysis of alkoxy- or chlorosilanes. Phenyl, 1-naphthyl, and 9-phenanthrenyl substituents at the silicon atom were applied to systematically study the influence of the aromatic substituents on the structure and reactivity of the compounds. Chemical shifts in ²⁹Si NMR spectroscopy in solution, correlated well with the expected electronic situation induced by the substitution pattern on the Si atom. ¹H NMR studies allowed the detection of strong intermolecular hydrogen bonds. Single-crystal X-ray structures of the alkoxides and the chlorosilanes are dominated by π-π interactions of the aromatic systems, which are substituted by strong hydrogen bonding interactions representing various structural motifs in the respective silanol structures.