Phonon anomalies in La2CuO4 + δ

The phonon dispersion of oxygen doped La₂CuO_{4 +} has been investigated by inelastic neutron scattering on a large single crystal with 0.02 (T_c = 31 K). Most of the phonons were found to be very similar to those of La_1.9Sr_0.1CuO₄. However, in measurements of a phonon branch which exhibits a pronounced anomaly in (La, Sr)₂CuO₄ a two-peak structure was observed: one series of peaks corresponds to the phonon frequencies of undoped La₂CuO₄, the other one to that of La_2–xSr_xCuO₄ with x 0.1. This finding is presumably associated with a phase separation into domains with low and high , respectively.     

H2O—N2,H2O—H2O混合气体中H2O分子谱线的压力展宽系数

本文用改进的Ｂｕｃｋｉｎｇｈａｍ势模型，用ＩＯＳ方法计算了Ｈ２Ｏ－Ｎ２－Ｈ２Ｏ－Ｈ２Ｏ混合气体中Ｈ２Ｏ分子谱线在常温下的压力展半宽度，我们的计算结果与现有的实验值符合得较好。说明我们所采用的方法和势模型是比较成功的。     

Reconfirmation of the existence of δ2 in dental amalgams

The 90°C endotherm peak in the thermogram of a conventional dental amalgam is due to two overlapping peritectic transitions involving SnHg-2 and HgAgSn-1, respectively. The aim of the present study is to separate these two events and thus confirm that the 2 phase is indeed a part of an amalgam microstructure. The materials used in this study were: sample 1, 1+1 wt% Sn; sample 2, 1+2 wt% Sn; sample 3, 1+3 wt% Sn; and sample 4, a commercial conventional amalgam with 48 wt% Hg. In powder form, they were exposed to 1 wt% NaCl solution at 37 °C for up to 45 days. At 15 day intervals, samples were withdrawn from the solution, washed, dried and then characterized by the differential scanning calorimetry (DSC) technique. Corrosion of Sn from ternary 1 matrix and intergranular 2 in respective materials during their exposure to the NaCl solution led to the following: (a) a progressive increase in 11 transition temperature in samples 1 and 2; (b) a gradual decrease in 2 peak and its disappearance in sample 2; and (c) in samples 3 and 4, initial splitting of the 90°C peak into two distinct endotherms associated with 2 and 1, respectively. Continued corrosion of the last two materials produced further changes in 2 and 1 in a manner similar to that seen in samples 1 and 2. On the basis of these observations, we have concluded that the 90°C endotherm is a valid indicator of the existence of the 2 phase in dental amalgams.     

高温下H2O—N2,H2O—H2O混合气体中H2O分子谱线的半宽度

本文用ＩＯＳ方法和我们改进的Ｂｕｃｋｉｎｇｈａｍ势计算了Ｈ２Ｏ－Ｎ２，Ｈ２Ｏ－Ｈ２Ｏ混合气体中Ｈ２Ｏ分子谱线在高温下（６００Ｋ，９００Ｋ，１２００Ｋ，１５００Ｋ）的压力加宽半宽度。分析了谱线半宽度随温度变化的规律，同时也讨论了半宽度与加宽和补加宽分子大小的关系。     

Resonance Effect on the Tunneling Reaction: H+H2→H2+H in Solid Hydrogen

The tunneling abstraction reaction: H+H₂H₂+H in -irradiated solid hydrogen has been studied using electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) spectroscopy and gas-chromatography. The rate constant for the tunneling reaction in solid hydrogen was found to decrease with the increase in the concentration of ortho-H₂ molecules in solid hydrogen. We concluded that the decrease in the rate constant is due to the energy level mismatching between reactant species of H+H₂ trapped and product species of H₂+H trapped in the reverse induced by inhomogeneous intermolecular interactions between ortho-H² molecules in solid hydrogen. This result indicates that resonance effects play an important role in tunneling reactions in solids.     

壳聚糖H2O2法降解研究

着重讨论了壳聚糖的主要降解方法及使用氧化降解法制备低聚壳聚糖的情况.采用正交设计,探讨降解条件对产物脱乙酰度、特性粘度等的影响.     

Synthesis and capacitive property of δ-MnO2 with large surface area

δ-MnO₂ with layered structure is synthesized in a mixed system of KMnO₄ and C₃H₆O (epoxypropane) by a facile low-temperature hydrothermal method at 90 °C for 24 h. The obtained product is characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and N₂ adsorption–desorption, and its electrochemical property was investigated by cyclic voltammetry method. Experiment results show that the as-synthesized product has a layered structure and a high specific surface area of 188 m² g⁻¹, and C₃H₆O existing in the reaction system plays a crucial role for the formation of δ-MnO₂ particles. Electrochemical characterization indicates that the prepared material exhibits an ideal capacitive behavior with the initial capacitance value of 296 F g⁻¹ in 1 mol L⁻¹ Na₂SO₄ aqueous solution at a scan rate of 5 mV s⁻¹ and good cycling behavior.     

高纯PH3和B2H6中微量H2、O2、N2的分析

前言 半导体工艺过程及大规模集成电路生产中所使用的高纯PH3和B2H6，由于其中含有O2、N2等杂质成份，直接影响了电子产品的质量，所以，必须严格地加以检测和控制。目前，一些发达国家对特气产品中杂质的监控十分重视，且都相应地研制出专门仪器进行检测。如法国TBT公司所研制的TBT色谱仪，对磷烷、硅烷、砷烷及乙硼烷中永久性气体杂质和总烃杂质都能进行检测。     

Fermi Surface and Superconducting Gap of Triple-Layered Bi2Sr2Ca2Cu3O10 + δ

We present a comprehensive study performed with high-resolution angle-resolved photoemission spectroscopy on triple-layered Bi₂Sr₂Ca₂Cu₃O_{10 +} single crystals. By measurements above T _C the Fermi surface topology defined by the Fermi level crossings of the CuO₂-derived band was determined. A hole-like Fermi surface as for single and double-CuO₂ layered Bi-based cuprates is found, giving new input to the current debate of the general Fermi surface topology of the high-T _C superconductors. Furthermore, we present measurements of the superconducting gap of Bi-2223 and show that there are clear indications for a strong anisotropy of the superconducting gap. The universal properties of this phase in comparison to the other Bi-based cuprates will be discussed.     

Carbon δ-doping GaAs superlattices

Carbon -doping GaAs superlattices incorporating 50 layers have been grown either by chemical beam epitaxy (CBE) using CBr₄ as the source of the carbon or by metallorganic vapour phase epitaxy (MOVPE) using CCl₄. Infrared (IR) localized vibrational mode (LVM) spectroscopy showed that carbon atoms were incorporated on the As sublattice and that hydrogen was incorporated as H-C_As pairs during growth by MOVPE. The hydrogen was removed by an anneal at 600 C for 15 min in N₂, leading to an increase in the carrier concentration. High resolution X-ray diffractometry (HRXD) was used to measure the strain in the layers. Simulation of the 400 diffraction profiles using dynamical theory was used to determine the thickness (~ 1 nm) and peak concentrations (in excess of 2 × 10²⁰ cm^–3) of the -doped layers. Device applications and -layers in AIAs are briefly considered.     

X-ray powder diffraction and IR study of NaMg(H2O)2[BP2O8]·H2O and NH4Mg(H2O)2[BP2O8]·H2O

NaMg(H₂O)₂[BP₂O₈]·H₂O was prepared by hydrothermal synthesis and was characterized by X-ray powder difraction and IR method. The title compound was synthesized from MgCl₂·6H₂O, NaBO₃·4H₂O, and (NH₄)₂HPO₄ with variable molar ratios using hydrothermal method by heating at 165 °C for 3 days. The X-ray powder diffraction data was indexed in hexagonal system, the unit cell parameters were found to be as a = 9.428, c = 15.82 Å, Z = 4 and the space group is P6₁22. It is isostructural with M^lM^ll(H₂O)[BP₂O₈] type compounds where M^l = Na, K; M^ll = Mg, Mn, Fe, Co, Ni and Zn. In addition NH₄Mg(H₂O)₂[BP₂O₈]·H₂O was also synthesized the first time in this research. Its unit cell parameters and hkl values were in good agreement with the sodium magnesium compound. The unit cell parameters are a = 9.529, c = 15.736 Å. The indexed X-ray powder diffraction data of both compounds which were not reported in the literature is presented in this work. The IR data of NaMg(H₂O)₂[BP₂O₈]·H₂O is also reported.     

Layered δ-MnO2 as positive electrode for lithium intercalation

Layer structured δ-MnO₂ was synthesized by a microwave-assisted hydrothermal method. The morphology of the product consists of flower-like spheres that range from about 200 nm to 3 μm in diameter and are composed of sheets about 5-10 nm in thickness. When tested in the voltage range of 2 to 4.5 V vs. Li⁺/Li in coin cells, the separator is blocked, handicapping Li⁺ conductivity and leading to cell failure. When tested in the voltage range of 2 to 4 V in ethylene carbonate/dimethyl carbonate (EC/DMC), the δ-MnO₂ delivers an initial reversible capacity of 143.7 mAh g⁻¹ and can maintain 120 mAh g⁻¹ at the 60th cycle. The δ-MnO₂ electrode shows good cycling stability at different current densities and delivers a discharge capacity of about 90 mAh g⁻¹ at 1 C, indicating that it is a promising cathode material for lithium ion batteries.     

结构振劝的H2／H∞混合最优控制

讨论了柔性结构振动的混合Ｈ２／Ｈ∞最优控制问题,结构振动控制器的鲁棒稳定性转化为Ｈ∞最优控制问题,以及振动控制的最优二次性能转化为Ｈ２最优控制问题,并提出了利用遗传算法求解了Ｈ２／Ｈ∞的方法,通过结构振动主动控制的计算机仿真,表明用遗传优化算法解Ｈ２／Ｈ∞最优控制是有效的。仿真结果还表明,Ｈ２和Ｈ∞性能指标是相互矛盾的。本方法能有效地处理Ｈ２和Ｈ∞性能指标的折衷问题,以得到闭环系统的鲁棒稳定性和良     

N2H4·H2O水热体系ZnO微晶的结晶特性

研究了低浓度（0.01～0.20mol/L）N2H4.H2O条件下ZnO微晶的低温水热结晶特性。N2H4.H2O弱碱性和N2H5＋吸附配位性影响ZnO微晶的形核和各晶面的生长速率。随着N2H4.H2O浓度的提高,ZnO微晶分别呈板条状、六角片状和六角棒束状。碱性分散剂和超声的分散作用影响主要在成核阶段;受分散剂弱碱性的影响,0.20mol/L N2H4.H2O显现出强的还原性,N2气泡模板生长机制使所制ZnO微晶呈六角管状晶须束。     

High-Pressure Reactions in the CeCo3–H2 and GdNi3–H2Systems

Reactions in the CeCo₃–H₂and GdNi₃–H₂systems were studied at hydrogen pressures of up to 0.2 GPa. Using hydrogen absorption–desorption isotherms, the compositions of the high-pressure hydrides were determined to be CeCo₃H_6.8(–70°C) and GdNi₃H_5.1(–50°C). According to x-ray diffraction studies, high-pressure hydrogen absorption to above the stoichiometry CeCo₃H₄is accompanied by insignificant volume changes. In the GdNi₃–H₂system, the hydride phase amorphizes at high hydrogen contents.     

Novel self-assembled decavanadate clusters forming 1D molecular chains and 2D molecular arrays: [HMTA-H···H2O][HMTA-CH2OH][H3V10O28{Na(H2O)4}]·4H2O and [Na2(H2O)10] [H3V10O28 {Na(H2O)2}]·3H2O

Two novel materials, [HMTA-H··H₂O] [HMTA-CH₂OH] [H₃V₁₀O₂₈[Na(H₂O)₄}]·4H₂O, 1 and [Na₂(H₂O)₁₀][H₃V₁₀O₂₈[Na(H₂O)₂}]·3H₂O, 2 containing decavanadate clusters interconnected through hydrated sodium cations forming 1D molecular chains and 2D molecular arrays have been self-assembled from acidified, aqueous vanadate solution in the presence of organic bases, hexamethylenetetramine and 1,3,5-triazine respectively.