水浴条件下YAG倍频、三倍频激光切割Si片比较

对Nd∶YAG固体激光器倍频、三倍频激光输出在空气和水浴环境下刻蚀Si片进行了研究,分析了刻蚀速率和样品表面形貌,得出了在355 nm刻蚀波长下,水浴环境中,刻蚀速率最快,刻槽宽度最小,小于10 μm的实验结论,为工业应用提供参考.     

扩镓Si基溅射Ga2O3氮化反应生长GaN薄膜

采用射频磁控溅射在扩镓硅基上溅射Ga2O3氮化反应生长GaN薄膜。用X射线衍射(XRD)、扫描电镜(SEM)、选区电子衍射(SAED)、光电能谱(XPS)和荧光光谱(PL)对样品进行结构、形貌、组分和发光特性的分析。XRD、SAED和XPS分析证明,采用此方法得到六方纤锌矿结构的GaN多晶膜。SEM显示薄膜由均匀、结合紧密的纳米微晶粒组成,其直径约为50～100nm。PL发光谱显示位于344nm处,相对于365nm明显蓝移的带边峰,此发光峰应归功于自由载流子的复合。     

Spectro M8型直读光谱仪分析生铁中硅、锰和磷

用 HB 30 0 0型磨样机制取样品 ,Spectro M8型直读光谱仪分析生铁中硅、锰和磷 ,方法可行 ,数据准确 ,取得了理想效果。     

焙烧对HL沸石结构的影响

运用MAS NMR研究了焙烧对HL沸石结构的影响. 结果表明,高温焙烧将引起HL沸石骨架的脱铝,当焙烧温度高于650 ℃后,沸石骨架脱铝明显;²⁷Al MAS NMR谱表明,从沸石上脱下来的铝,部分形成了NMR不可测的无定形态,且随焙烧温度的升高,NMR不可测铝增多.     

Thermal Preparation and Application of a Novel Silicon Fertilizer Using Talc and Calcium Carbonate as Starting Materials

The deficiency of available silicon (Si) incurred by year-round agricultural and horticultural practices highlights the significance of Si fertilization for soil replenishment. This study focuses on a novel and economical route for the synthesis of Si fertilizer via the calcination method using talc and calcium carbonate (CaCO₃) as starting materials. The molar ratio of talc to CaCO₃ of 1:2.0, calcination temperature of 1150 °C and calcination time of 120 min were identified as the optimal conditions to maximize the available Si content of the prepared Si fertilizer. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) characterizations elucidate the principles of the calcination temperature-dependent microstructure evolution of Si fertilizers, and the akermanite Ca₂Mg(Si₂O₇) and merwinite Ca₃Mg(SiO₄)₂ were identified as the primary silicates products. The results of release and solubility experiments suggest the content of available metallic element and slow-release property of the Si fertilizer obtained at the optimum preparation condition (Si-OPC). The surface morphology and properties of Si-OPC were illuminated by the results of scanning electron microscope (SEM), surface area and nitrogen adsorption analysis. The acceleration action of CaCO₃ in the decomposition process of talc was demonstrated by the thermogravimetry-differential scanning calorimetry (TG-DSC) test. The pot experiment corroborates that 5 g kg⁻¹ soil Si-OPC application sufficed to facilitate the pakchoi growth by providing nutrient elements. This evidence indicates the prepared Si fertilizer as a promising candidate for Si-deficient soil replenishment.     

The ternary system cerium–palladium–silicon

Phase relations in the ternary system Ce–Pd–Si have been established for the isothermal section at 800 °C based on X-ray powder diffraction and EMPA techniques on about 130 alloys, which were prepared by arc-melting under argon or powder reaction sintering. Eighteen ternary compounds have been observed to participate in the phase equilibria at 800 °C. Atom order was determined by direct methods from X-ray single-crystal counter data for the crystal structures of τ₈—Ce₃Pd₄Si₄ (U₃Ni₄Si₄-type, Immm; a=0.41618(1), b=0.42640(1), c=2.45744(7) nm), τ₁₆—Ce₂Pd₁₄Si (own structure type, P4/nmm; a=0.88832(2), c=0.69600(2) nm) and also for τ₁₈—CePd_1−xSi_x (x=0.07; FeB-type, Pnma; a=0.74422(5), b=0.45548(3), c=0.58569(4) nm). Rietveld refinements established the atom arrangement in the structures of τ₅—Ce₃PdSi₃ (Ba₃Al₂Ge₂-type, Immm; a=0.41207(1), b=0.43026(1), c=1.84069(4) nm) and τ₁₃—Ce_3−xPd_20+xSi₆ (0≤x≤1, Co₂₀Al₃B₆-type, Fm3¯m; a=1.21527(2) nm). The ternary compound Ce₂Pd₃Si₃ (structure-type Ce₂Rh_1.35Ge_4.65, Pmmn; a=0.42040(1), b=0.42247(1), c=1.72444(3) nm) was detected as a high-temperature compound, however, does not participate in the equilibria at 800 °C. Phase equilibria in Ce–Pd–Si are characterized by the absence of cerium solubility in palladium silicides. Mutual solubility among cerium silicides and cerium–palladium compounds are significant whereby random substitution of the almost equally sized atom species palladium and silicon is reflected in extended homogeneous regions at constant Ce-content such as for τ₂—Ce(Pd_xSi_1−x)₂ (AlB₂-derivative type), τ₆—Ce(Pd_xSi_1−x)₂ (ThSi₂-type) and τ₇—CePd_2−xSi_2+x. The crystal structures of compounds τ₄—Ce_~8Pd_~46Si_~46, τ₁₂—Ce_~29Pd_~49Si_~22, τ₁₅—Ce_~22Pd_~67Si_~11, τ₁₇—Ce_~5Pd_~77Si_~18 and τ₁₈—CePd_1−xSi_x (x~0.1) are still unknown.     

Bonding and correlation analysis of various Si2CO isomers on the potential energy surface

At various levels of theory, singlet and triplet potential energy surfaces (PESs) of Si₂CO, which has been studied using matrix isolation infrared spectroscopy, are investigated in detail. A total of 30 isomers and 38 interconversion transition states are obtained at the B3LYP/6‐311G(d) level. At the higher CCSD(T)/6‐311+G(2d)//QCISD/6‐311G(2d)+ZPVE level, the global minimum ¹1 (0.0 kcal/mol) corresponds to a three‐membered ring singlet O‐cCSiSi (¹A′). On the singlet PES, the species ¹2 (0.2 kcal/mol) is a bent SiCSiO structure with a ¹A′ electronic state, followed by a three‐membered ring isomer Si‐cCSiO (¹A′) ¹3 (23.1 kcal/mol) and a linear SiCOSi ¹4 (¹Σ⁺) (38.6 kcal/mol). The isomers ¹1, ¹2, ¹3 , and ¹4 possess not only high thermodynamic stabilities, but also high kinetic stabilities. On the triplet PES, two isomers ³1 (³B₂) (18.8 kcal/mol) and ³7 (³A″) (23.3 kcal/mol) also have high thermodynamic and kinetic stabilities. The bonding natures of the relevant species are analyzed. The similarities and differences between C₃O, C₃S, SiC₂O, and SiC₂S are discussed. The present results are also expected to be useful for understanding the initial growing step of the CO‐doped Si vaporization processes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

A Brody theorem for orbifolds

We study the Kobayashi pseudodistance for orbifolds, proving an orbifold version of Brody’s theorem and classifying which one-dimensional orbifolds are hyperbolic.     

Strong density results in trace spaces of maps between manifolds

We deal with strong density results of smooth maps between two manifolds and in the fractional spaces given by the traces of Sobolev maps in W ^1,p .     

Weighted-Hardy functions with Hadamard gaps on the unit ball

We prove that an analytic function f on the unit ball B with Hadamard gaps, that is, (the homogeneous polynomial expansion of f) satisfying n_k+1/n_k?λ>1 for all k∈N, belongs to the space if and only if . Moreover, we show that the following asymptotic relation holds . Also we prove that lim_r→1(1-r²)^α‖Rf_r‖_p=0 if and only if . These results confirm two conjectures from the following recent paper [S. Stevi?, On Bloch-type functions with Hadamard gaps, Abstr. Appl. Anal. 2007 (2007) 8 pages (Article ID 39176)].