Complexes with substituted 2,5-dihydroxy-p-benzochinones AEC6X2O4·4H2O AE=Ca2+ X=Cl,Br

In the isostructural compounds AEC₆X₂O₄·4H₂O (AE=Ca²⁺, Sr²⁺; X=Cl, Br) chains consisting of [C₆X₂O₄]²⁻ are interlinked to layers by common water molecules. AE²⁺ has CN 8. In its coordination sphere there are 4 water molecules and 4 oxygen atoms of different [C₆X₂O₄]²⁻, which chelate AE²⁺. On dehydration the structure is destroyed. AE and X obviously influence disorder phenomena of water.     

添加剂对储能材料CaCl2·6H2O+Ca(NO3)2·4H2O 相变温度和过冷温度的影响及其熔盐结构

本文研究了储能材料CaCl_2·6H_2O-Ca(NO_3)_2·4H_2O的储能性能,并对影响其储能性能的结晶过冷问题和盐水分离问题进行了详细研究。发现单组分成核剂SrCl_2·6H_2O、BaCO_3、BaCl_2对该体系的过冷问题改性效果较好,能使熔盐的过冷度降低到2.3℃左右;增稠剂羧甲基四乙酸钠(CMC)对盐水分离问题有一定的改善,但会增大熔盐的过冷度。混合成核剂SrCl_2·6H_2O(2%)+BaCl_2(1%)+CMC (0.5%)对熔盐过冷问题改性较好,可使过冷度降低到1.8℃左右。储能材料改性前后相变焓变化不大,均在140J/g左右。在此基础上研究了熔盐CaCl_2·6H_2O和Ca(NO_3)_2·4H_2O的微观存在形式,从微观结构方面对熔盐存在的过冷和盐水分离问题进行了初步讨论。     

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。     

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。     

Substitution Effect of Pr for Ca in Bi2Sr2CaCu2O8+δ System

The Bi₂Sr₂CaCu₂O₈₊ system samples doped with Pr on Ca sites were synthesized. Resistivity temperature dependence, X-ray powder diffraction, and photoemission experiments have been performed. Both X-ray diffraction and photoemission measurements show that Pr ion enters the lattice with a valence higher than 3⁺, which supports the hole-filling mechanism of the suppression of superconductivity.     

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.     

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.     

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.     

Subsolidus Phase Relations in the Systems M2 +O–M2+O–V2O5(M+ = Li, Na, K, Rb, Cs; M2+ = Mg, Ca)

Subsolidus phase relations in the M₂O(M₂CO₃)–MgO–V₂O₅ and M₂O(M₂CO₃)–CaO–V₂O₅ (M = Li, Na, K, Rb, Cs) systems are studied. Twenty mixed vanadates are obtained, of which Rb₂CaV₂O₇, Cs₂CaV₂O₇, LiMg₄(VO₄)₃, RbCaVO₄, and CsCaVO₄ are identified for the first time. Structural data are summarized for all of the mixed vanadates: the space group and lattice parameters are indicated for 14 compounds (for 6 compounds, such data are obtained for the first time), and I and d data are presented for 8 compounds. Partial series of Ca₃(VO₄)₂-based solid solutions with the general formula Ca_{3 – x} M_2x (VO₄)₂ (M = Na, K, Rb, Cs) are identified in the range 0 < x 0.14. Six phase diagrams (M⁺ = Li, Rb, Cs; M²⁺ = Mg, Ca) are investigated and are compared with the phase diagrams of the other ternary systems in question. The key features of the ternary phase diagrams and, hence, the reactivity of the constituent oxides are shown to vary systematically in going from Li₂O to Cs₂O and from MgO to SrO, which is interpreted in terms of the variation in the ionic radius of the alkali and alkaline-earth metals.     

63Cu NMR in the normal state of HgBa2Ca2Cu3O8+δ

We present a⁶³Cu NMR study of HgBa₂Ca₂Cu₃O₈₊ underdoped single crystals with T_c 115 K. While the uniform spin susceptibility decreases below T_o 370 K, relaxation rate measurements demonstrate the opening of a spingap at Q = (, ) below T* 230 K, the highest temperature reported so far. The characteristic energy of spin fluctuations is shown to be higher than in underdoped YBa₂Cu₃O_7–, and the analysis of the quadrupole and hyperfine couplings suggests that the in-plane Cu-O hybridization is also stronger. The T-dependence of T₁ is the same in the three CuO₂ planes which seems hardly compatible with the pure interlayer spin-pairing picture.     

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.     

XRD and PES Studies of the Bi2Sr2Ca1−xPrxCu2O8+δ System

The Bi₂Sr₂CaCu₂O_8+δ system samples doped with Pr on Ca sites were synthesized. Resistivity measurements, x-ray powder diffraction, and photoemission experiments were performed. The experiment results show that Pr ions entered the lattice and chemical environment plays a major role in the shift of core-level spectra and valence-band spectra.     

FAAS法测定大气降水中的k+、Na+、Ca2+和Mg2+

本文应用FAAS法直接测定大气降水中阳离子K+、Na+、Ca2+、Mg2+。通过对火焰状态的选择,以减少和抑制电离的干扰。方法简便、快速、准确。加标回收率在94.0%-105.2%之间,RSD<5.07%。     

Electrical Conductivity of H2V12 – y W y O31 + δ · nH2O and H x V x W1 – x O3 · nH2O

The electrical conductivity of H₂V_{12 – y} W _y O_{31 +} · nH₂O (0 y 3) and H _x V _x W_{1 – x} O₃ · nH₂O (x = 0, 0.08, 0.17, 0.25, 0.33) prepared by the sol–gel method was measured between 293 and 473 K at a relative humidity of 12%. Partial substitution of tungsten for vanadium or V⁵⁺ and H⁺ for tungsten was found to reduce the conductivity of the phases studied. The only exception is the x = 0.33 phase. Below 373 K, the activation energy of conduction is 0.22–0.29 eV in the amorphous phases (0 y 3; x= 0.25, 0.33) and 0.06–0.11 eV in the crystalline phases (x = 0, 0.08, 0.17). The possible mechanisms of electrical transport are discussed.     

Upper Critical Field of Four-CuO2-Layer TlBa2Ca3Cu4O11+δ Single Crystals

Magnetic measurements have been performed on single crystals of TlBa ₂ Ca ₃ Cu ₄ O ₁₁₊ in the magnetic fields up to 5.5 T. No change in the onset temperature of superconducting transition (T _c ) was observed in the magnetic fields between 0.4 and 5.5 T, while the superconducting transitions were broadened significantly in the same field. The linear temperature-dependence of the magnetization was found in a large temperature range below T _c . The slope of the magnetization versus temperature decreased significantly with increasing magnetic field. The experimental findings indicated that the upper critical field (H _C2 ) in this compound was very large and traditional methods of deriving H _C2 value were not applicable. Using the measured magnetization in the reversible region, the H _C2 properties of TlBa ₂ Ca ₃ Cu ₄ O ₁₁₊ single crystals have been studied based on a new model developed by Hao et al.     

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.     

Excess Conductivity Analysis of Bi1.8Pb0.4Sr2Ca2Cu3O10+δ Added with Nano-ZnO and Nano-Fe2O3

Superconductor samples of type Bi_1.8Pb_0.4Sr₂Ca₂Cu₃O_10+δ added with nano ZnO and Fe₂O₃ were synthesized by the conventional solid-state reaction technique. The samples were characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and electrical resistivity measurements. Excess conductivity analysis of the investigated samples was carried out as a function of temperature using Aslamazov and Larkin (AL) model. The analysis showed four different fluctuation regions namely critical (cr), three-dimensional (3D), two-dimensional (2D) and short-wave (sw). The zero temperature coherence length along c-axis, effective layer thickness of the two-dimensional system and inter-layer coupling strength were estimated as a function of nano-oxides concentration. In addition, the thermodynamics, lower and upper critical magnetic fields as well as critical current density were calculated from the Ginzburg number N _G . It was found that the low concentration of nano-ZnO addition up to x=0.2 wt.% improved the physical properties of (Bi,Pb)-2223 phase. In contrary, these properties were deteriorated for x>0.2. These results indicated that the addition of a low amount of nano-ZnO during the final processing of (Bi,Pb)-2223 samples can be effectively improved the flux pinning ability, while the addition of a high amount of nano-ZnO decreased the volume fraction and increased the resistance of grain boundaries. Moreover, the addition of nano-Fe₂O₃ had a negative effect on the superconducting parameters of the (Bi,Pb)-2223 phase. This behavior was attributed to the decrease in the volume fraction of (Bi,Pb)-2223 phase with the increasing of nano-Fe₂O₃.     

Li2Ca2Si2O7生物陶瓷的矿化活性研究

如何有效治疗牙周炎并实现受损牙周骨组织再生,一直是牙周疾病治疗中具有挑战性的问题,而矿化是牙周正常发育和功能中关键因素之一.本研究旨在探讨硅酸钙锂(Li2Ca2Si2O7)生物陶瓷对人牙周膜成纤维细胞增殖、矿化的影响及用于牙周骨组织再生的可能性.采用溶胶-凝胶法制备合成了Li2Ca2Si2O7陶瓷粉体.通过体外模拟体液...