Nd:LuVO4晶体缺陷的研究

采用提拉法生长的Nd:LuVO4晶体是一种适合二极管泵浦的新型激光晶体,运用化学腐蚀结合光学显微术和同步辐射白光X射线形貌术对Nd:LuVO4晶体缺陷进行观察,结果表明:晶体的主要缺陷为位错和小角晶界.利用高分辨X射线衍射仪进一步验证了这一结果.并初步讨论了缺陷形成的原因.     

Crystal structure, vibrational spectra, and thermal decomposition and nitrogen adsorption behaviour of a new tetramanganese(II) dipyrophosphate decahydrate, Mn4(P2O7)2·10H2O

A new manganese(II) pyrophosphate, Mn₄(P₂O₇)₂·10H₂O, has been synthesized and characterized by single-crystal X-ray diffraction [orthorhombic space group Pnma, with unit cell parameters of a=9.3288(3) ?, b=25.9532(9) ?, c=8.4783(3) ?; Z=4]. All the pyrophosphate anions show non-linear P–O–P bonds with an average angle of 128.60°. The framework of this new pyrophosphate is made up of packed layers of MnO₆ octahedra connected by double-tetrahedra P₂O₇ groups and a layer of Mn(H₂O)₆ units. The [P₂O₇]⁴⁻ anions adopt a bent, near-staggered conformation. The absence of coincidences for the majority of the IR and Raman bands is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted in part on the basis of factor group effects. The structural changes occurring during heating have been investigated by TG-ATD. When Mn₄(P₂O₇)₂ ^.10H₂O is gradually heated, it decomposes into an intermediate hydrated salt at 96°C and then to anhydrous Mn₂P₂O₇ at 325°C. This thermal behaviour is different from that of Zn₄(P₂O₇)₂·10H₂O. The crystal structure of the new managenese(II) pyrophosphate is compared with the known structures of Zn₄(P₂O₇)₂·10H₂O, Mn₂P₂O₇·2H₂O and anhydrous Mn₂P₂O₇. The adsorption and desorption isotherms of Mn₄(P₂O₇)₂·10H₂O, Zn₄(P₂O₇)₂·10H₂O and MnKHP₂O₇·2H₂O have been investigated by BET measurements and the results show that the capacity for N₂ sorption of the Mn(II) salt is two times lower than is that of the Zn(II) isotype and two or three times higher than is that of MnKHP₂O₇·2H₂O.     

钨酸钡晶体本征点缺陷的模拟计算

本文利用晶格动力学软件GULP模拟计算了钨酸钡晶体的本征点缺陷,首先利用驰豫拟合的方法得到离子之间的相互作用势,利用这些相互作用势计算得到的结果与实验结果吻合得很好,在此基础上计算晶体本征缺陷的生成能,通过对本征点缺陷生成能的分析得到以下结论:钨酸钡晶体内V2+O的数量要大于V2-Ba的数量;钨酸钡晶体内缺陷态主要以V2-Ba-V2+O空位对和F色心形式存在.     

溶胶-凝胶法制备Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷

采用凝胶预碳化处理工艺制备了颗粒粒径较小,无硬团聚的Ca0.4Sr0.6Bi4Ti4O15纳米粉体,以Ca0.4Sr0.6Bi4Ti4O15非晶团簇粉体为陶瓷素坯的原料,同组分高浓度的Ca0.4Sr0.6Bi4Ti4O15溶胶为粘结剂,制备了Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷,研究了Ca0.4Sr0.6Bi4Ti4O15粉体的相结构和微观形貌以及陶瓷的显微结构和铁电性能.实验结果表明:700 ℃焙烧粉体呈现为非晶团簇,800 ℃焙烧粉体形成了纯层状钙钛矿结构,粒径在100～150 nm之间,无硬团聚;950 ℃烧结的Ca0.4Sr0.6Bi4Ti4O15细晶陶瓷结构致密,晶粒尺寸在0.2～0.5 μm之间,其铁电性能优良,剩余极化Pr=12.5 μC/cm2,矫顽场强Ec=50 kV/cm.     

Ecofriendly synthesis and biological evaluation of 4-(4-nitro-phenyl)-2-phenyl-1,4-dihydro-benzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxylic acid ethyl ester derivatives as an antitubercular agents

An ecofriendly route has been investigated for the synthesis of 4-(4-nitro-phenyl)-2-phenyl-1,4-dihydro-benzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxylic acid ethyl ester derivatives by one-pot, three-component condensation of ethyl benzoylacetate, aromatic aldehydes, and 2-amino benzimidazole using 260?mol% of citric acid as reaction mediator. Citric acid is an inexpensive, nontoxic, and green medium with smoothly activates the rate of reaction. The synthesized compounds were assessed for in vitro antimycobacterial activity against Mycobacterium tuberculosis H₃₇RV strain using the microplate alamar blue assay (MABA). The results indicate that among all the synthesized compound series, P-4 and P-9 compounds illustrate effective activity with a minimum inhibitory concentration of 25?µg/ml.     

Regioselective,Asymmetric Formal Hydroamination of Unactivated Internal Alkenes

We report the regioselective and enantioselective formal hydroamination of unsymmetrical internal alkenes catalyzed by a copper catalyst ligated by DTBM‐SEGPHOS. The regioselectivity of the reaction is controlled by the electronic effects of ether, ester, and sulfonamide groups in the homoallylic position. The observed selectivity underscores the influence of inductive effects of remote substituents on the selectivity of catalytic processes occurring at hydrocarbyl groups, and the method provides direct access to various 1,3‐aminoalcohol derivatives with high enantioselectivity.