Ab initio structure determination of new compound Ba3(BO3)(PO4)

The crystal structure of new compound Ba₃BPO₇ was determined by ab initio method from high-resolution conventional X-ray powder diffraction data. The Rietveld refinement converged to R_p=5.92%, R_wp=8.87%, R_exp=5.00% with the following details: Hexagonal, space group P6₃mc, a=5.4898 (1) Å, c=14.7551(1) Å, Z=2. The basic unit of the structure is the [BaO₁₀]-[BO₃]-[PO₄] polar polyhedra-chain composed of Ba1-B-P-O cluster. These chains, running along c-axis, stack in a HCP mode to build the whole structure with triangular prism channels. The channels are parallel to c-axis too, in which Ba2 and Ba3 are located.     

抗癌药物的电化学研究(Ⅱ)道诺霉素在DNA修饰石墨粉末微电极上的电化学行为及分析应用

研究了道诺霉素 ( DNM)在石墨粉末微电极和 DNA修饰石墨粉末微电极上的电化学行为 ,并分析了产生差别的原因。在此基础上 ,提出了测定微量 DNM的方法 ,DNM浓度在 1 .0× 1 0 - 7～ 1 .0× 1 0 - 5mol/L之间其微分脉冲伏安 ( DPV)峰电流与浓度有良好的线性关系 ,检出限为 5 .0× 1 0 - 8mol/L。采用标准加入法测定了模拟样品中的 DNM,回收率在 94%～ 1 0 8%之间 ,结果令人满意     

触头用银合金粉末的氧化性能和氧化后的组织结构

通过热重实验和扫描电子显微等方法，研究了４种触头用银合金粉末的氧化性能及氧化后的组织结构。发现Ａｇ－Ｓｎ－ＲＥ合金粉末氧化以后，在粉末表层形成一层纯银层，其组织结构理想；它的氧化性能最好，适于制备触头材料。Ａｇ－Ｓｎ－ＲＥ合金粉末的优良氧化性能与其氧化后理想的组织结构有关。稀土元素可以降低合金粉末的氧化温度，其它影响作用有待于进一步研究。     

溶胶-凝胶法合成纳米铬酸锶镧的工艺研究

以硝酸镧、硝酸铬、硝酸锶为原料，乙二醇为分散剂，柠檬酸为胶溶剂，用溶胶-凝胶法合成纳米级的铬酸锶镧粉体。利用TG，DSC，XRD分析研究了粉料的晶化过程。利用HREM分析了煅烧温度、含锶量对粉料粒径的影响。研究表明，获得纳米晶的最佳烧结温度在800℃。随着锶掺杂量的增加，粉料的粒径逐渐变小。     

纳米晶复合Nd2Fe14B/α-Fe合金制备与磁性能的研究

采用熔体快淬及晶化处理工艺制备Nd11Fe71Co8V1.5Cr1B7.5纳米晶合金。经21m·s-1快淬及640℃ 4min晶化处理后,制成的粘结磁体的磁性能最佳,为:Br=0.64T,JHc=903.5kA·m-1,(BH)max=71kJ·m-3。添加Cr元素可提高内禀矫顽力,从而提高最大磁能积。     

钙钛矿型LaNiO3、LaMnO3的形成条件

用混合硝酸盐分解法和柠檬酸络合法分别制取了单一钙铁矿型多晶粉末LaNiO_3和LaMnO_3. XRD分析表明LaNiO_3的形成经历了混合氧化物转化为LaNiO_3的同相反应; 而LaMnO_3晶相直接由无定形相转化而来。根据DTA、TG、IR分析两者的形成, NO_3~-离子都起了重要作用. 同时讨论了络合剂柠檬酸的作用.     

In situ neutron powder diffraction investigation of the hydration of tricalcium aluminate in the presence of gypsum

The hydration of a 1:3 molar ratio of tricalcium aluminate, Ca₃Al₂O₆, to gypsum, CaSO₄·2D₂O, was investigated at temperatures of 25, 50, and 80 °C using time-of-flight powder neutron diffraction combined with multiphase Rietveld structural refinement. It was shown that ettringite, Ca₆[Al(OD)₆]₂(SO₄)₃·∼26D₂O, was the first and only hydration product of the system, in contrast to a prior investigation which suggested the occurrence of a precursor phase prior to the formation of ettringite. Kinetics data showed that the hydration reaction is very sensitive to temperature: hydration at 25 °C was characterized by a single kinetic regime while hydration at higher temperatures consisted of two distinct kinetic regimes. The presence of two kinetic regimes was attributed to a change in either the dimensionality of the growth process or a change in the rate controlling mechanism in the hydration reaction.     

The ordered phase of methylammonium lead chloride CH3ND3PbCl3

The perovskite-structured compound methylammonium lead chloride orders into a low-temperature phase of space group Pnma, in which at 80 K each of the orthorhombic axes , and is doubled with respect to the room temperature disordered cubic phase (). The structure was solved by ab initio methods using the programs EXPO and FOX. This unusual cell basis for space group Pnma is not that of a standard tilt system. This phase, in which the methylammonium ions, are ordered shows distorted octahedra. The octahedra possess a bond angle variance of 60.663°² and a quadratic elongation of 1.018, and are more distorted than those in the ordered phase of methylammonium lead bromide. There is also an alternating long and short Pb-Cl bond along a, due to an off-center displacement of Pb within the octahedron. This suggests that the most rigid unit is actually the methylammonium cation, rather than the PbCl₆ octahedra, in agreement with existing spectroscopic data.     

Insights on the origin of the structural phase transition in BaV10O15 from electronic structure calculations and the effect of Ti-doping on its structure and electrical transport properties

Band structure calculations at the level of LMTO-ASA provide insight into the electronic structure of BaV₁₀O₁₅ and the origin of the structural phase transition. A crystal orbital Hamiltonian population/integrated crystal orbital Hamiltonian population analysis provides evidence that the crystallographic phase transition is driven by V-V bond formation. As well, the energy bands near the Fermi level are very narrow, <1 eV, consistent with the fact that the observed insulating behavior can be due to electron localization via either Mott-Hubbard correlation and/or Anderson disorder. The partial solid solution, BaV_10−xTi_xO₁₅, was examined to study the effect of Ti-doping at the V sites on the structure and electronic transport properties. In spite of the non-existence of “BaTi₁₀O₁₅”, the limiting x=8, as indicated by a monotonic increase in the cell volume and systematic changes in properties. This limit may be due to the difficulty of stabilizing Ti²⁺ in this structure. For x=0.5 both the first order structural phase transition and the magnetic transition at 40 K are quenched. The samples obey the Curie-Weiss law to x=3 with nearly spin only effective moments along with θ values which range from −1090 K (x=0.5) to −1629 K (x=3). For x>3 a very large, ∼2×10⁻³ emu/mol, temperature independent (TIP) contribution dominates. Conductivity measurements on sintered, polycrystalline samples show semiconducting behavior for all compositions. Activation energies for Mott hopping derived from high temperature data range from ∼0.1 eV for x=0-1 and fall to a plateau of 0.06 eV for x=3-7. Low temperature data for x=3, 5 and 7 show evidence for Mott variable range hoping (VRH) with a T^1/4 law and in one case between 5 and 17 K, a Efros-Shklovskii correlated hopping, T^1/2 law, was seen, in sharp contrast to BaV₁₀O₁₅ where only the E-S law was observed up to 75 K. Seebeck coefficients are small (<35 μV/K), positive, roughly TIP and increase with increasing x up to x=5. This may point to a Heikes hopping of holes but a simple single carrier model is impossible. The compositions for x>3 are remarkable in that local moment behavior is lost, yet a metallic state is not reached. The failure of this system to be driven metallic even at such high doping levels is not fully understood but it seems clear that disorder induced carrier localization plays a major role.     

TiCl4-Cr还原偶联活泼卤化物及芳醛、芳酮的研究

低价钛化合物在有机合成和有机反应中有着广泛的应用。我们曾研究了低价钛对α,α,α-三卤甲基苯的脱卤偶联、对2,2-二芳