Synthesis and structure of {NH2(C2H5)2}2[(UO2)2(C2O4)(CH3COO)4] · 2H2O

Single crystals of the compound {NH₂(C₂H₅)₂}₂[(UO₂)₂C₂O₄(CH₃COO)₄] · 2H₂O (I) are synthesized, and their structure is investigated using X-ray diffraction. Compound I crystallizes in the monoclinic system with the unit cell parameters a = 9.210(2) ?, b = 14.321(3) ?, c = 12.659(3) ?, β = 105.465(13)°, V = 1609.2(6) ?³, space group P2₁/c, Z = 2, and R = 0.0198. The structural units of crystals I are binuclear groups of the composition [(UO₂)₂C₂O₄(CH₃COO)₄]²⁻ with an island structure, which belong to the crystal-chemical group A ₂ K ⁰² B ₄⁰¹ (A = UO₂²⁺, K ⁰² = C₂O₄²⁻, B ⁰¹ = CH₃COO⁻) of the uranyl complexes, diethylammonium cations, and water molecules. The uranium-containing groups are joined into a three-dimensional framework through electrostatic interactions with diethylammonium cations and a system of hydrogen bonds, which are formed with the participation of the atoms involved in the composition of the water molecules, oxalate ions, acetate ions, and diethylammonium cations. Original Russian Text ? L.B. Serezhkina, A.V. Vologzhanina, N.A. Neklyudova, V.N. Serezhkin, 2009, published in Kristallografiya, 2009, Vol. 54, No. 1, pp. 65–67.     

非线性光学晶体CsB3O5研究进展

非线性光学晶体CsB3O5(CBO)具有大的非线性光学系数、优秀的紫外波段透过能力和高的抗光损伤阈值,在紫外高功率密度全固态激光系统的频率转换方面展现出良好的应用前景。本文综述了CBO晶体的研究概况,报道了高质量CBO晶体生长、折射率温度系数、热学性能及278 nm紫外激光输出的最新研究结果。     

Glass formation and structure of glasses in B2O3―Bi2O3―MoO3 system

The purpose of this paper is to study the glass formation tendency in the ternary system B₂O₃―Bi₂O₃―MoO₃ and to define the main structural units building the amorphous network. A wide glass formation area was determined which is situated near the Bi₂O₃―B₂O₃ side. A liquid phase separation region was observed near the MoO₃―B₂O₃ side for compositions containing below 25 mol% Bi₂O₃ and their microheterogeneous structure was observed by SEM. The phase formation was characterized by X-ray diffraction (XRD). By DTA was established the glass transition temperature (T_g) in the range of 380-420 °C and crystallization temperature (T_x) vary between 420 and 540 °C. The main building units forming the amorphous network are BO₃ (1270 and 1200 cm^− 1), BO₄ (930-880, 1050-1040 cm^− 1), MoO₄ (840-760 cm^− 1) and BiO₆ (470 cm^− 1). It was proved that Bi₂O₃ favors the BO₃ → BO₄ transformations while MoO₃ preserves BO₃ units in the amorphous network.     

自润滑Al2O3/TiC/CaF2复合陶瓷材料摩擦特性

为了探索自润滑陶瓷材料的开发及应用,采用冷压烧结工艺制备Al2O3/TiC/CaF2自润滑复合陶瓷材料。在摩擦磨损实验机上对其进行摩擦磨损实验,并对其摩擦磨损行为及自润滑效应进行分析。结果表明:在实验过程中,Al2O3/TiC/CaF2复合陶瓷材料物理机械性能优于同条件下制备的Al2O3/TiC复合陶瓷材料,且具有较低的摩擦因数和磨损率,其减摩抗磨效果明显,具有一定的自润滑效应,其减摩抗磨机理为摩擦驱动下CaF2存在于摩擦副表面,形成减摩抗磨层,在表面形成一层平整、光滑的自润滑层,增加摩擦表面实际接触面积,起到自润滑效应。     

Nd2O3对Al2O3基复合陶瓷耐磨性能及微观结构的影响

在Ca O-Mg O-Si O2作为复合烧结助剂降低氧化铝陶瓷温度的前提下,研究不同添加量的稀土氧化物Nd2O3对陶瓷烧结温度、磨损率、显微结构的影响。通过设计Nd2O3在六铝酸钙中固溶和Nd2O3在Al2O3单晶表面扩散的实验,探索Nd2O3对氧化铝陶瓷耐磨性能影响的机理。结果表明:加入过量的Nd2O3会破坏晶界结合强度,导致陶瓷的耐磨性能变差;而少量Nd2O3的加入能有效提高晶界间结合强度和陶瓷的致密度,改善耐磨性能,耐磨性提高幅度约42.7%。     

0.2wt% Bi2O3、CuO、B2O3对5Ca0.6La0.267TiO3-5Ca(Mg1/3Nb2/3)O3微波介质陶瓷的性能影响

采用传统的固相反应法,研究了三种烧结助剂Bi2O3、CuO、B2O3对5Ca0.6La0.267TiO3-5Ca(Mg1/3Nb2/3)O3微波介质陶瓷的烧结性能和介电性能的影响。实验结果表明,掺入0.2wt%的Bi2O3、CuO、B2O3产生了液相,有效地降低了体系的烧结温度。Bi2O3和CuO的加入没有改变烧结体的微观形貌,它们介电常数和品质因数随烧结温度的变化趋势和体积密度趋于一致,均在体积密度最大时最高。当温度大于1300℃时,加入0.2wt%B2O3试样有柱状晶体生成,并随着烧结温度的升高而增多,柱状晶体的存在可能促使Q×f值较大的提高,当烧结温度过高时(1350℃),由于柱状晶体过多使得烧结体不均匀导致Q×f值下降。Bi2O3、CuO、B2O3的加入没有改变烧结体的晶相组成,因此所有烧结体均有近零的温度系数。结果表明,加入0.2wt%B2O3的5Ca0.6La0.267TiO3-5Ca(Mg1/3Nb2/3)O3在1325℃烧结温度具有最佳的介电性能:εr=54.87,Q×f=55 726 GHz,τf=-0.6 ppm/℃。     

Crystal and molecular structure of Sr2( Edta ) · 5H2O, Sr2(H2 Edta )(HCO3)2 · 4H2O, and Sr2(H2 Edta )Cl2 · 5H2O strontium ethylenediaminetetraacetates

Three Sr²⁺ compounds with the Edta ⁴⁻ and H₂ Edta ²⁻ ligands—Sr₂(Edta) · 5H₂O (I), Sr₂(H₂ Edta)(HCO₃)₂ · 4H₂O (II), and Sr₂(H₂ Edta)Cl₂ · 5H₂O (III)—are synthesized, and their crystal structures are studied. In I, the Sr(1) atom is coordinated by the hexadentate Edta ⁴⁻ ligand following the 2N + 4O pattern and by two O atoms of the neighboring ligands, which affords the formation of zigzag chains. The Sr(2) atom forms bonds with O atoms of five water molecules and attaches itself to a chain via bonds with three O atoms of the Edta ⁴⁻ ligands. The Sr(1)-O and Sr(2)-O bond lengths fall in the ranges 2.520(2)–2.656(3) and 2.527(3)–2.683(2) ?, respectively. The Sr(1)-N bonds are 2.702(3) and 2.743(3) ? long. In II and III, the H₂ Edta ²⁻ anions have a centrosymmetric structure with the trans configuration of the planar ethylenediamine fragment. The N atoms are blocked by acid protons. In II, the environment of the Sr atom is formed by six O atoms of three H₂ Edta ligands, two O atoms of water molecules, and an O atom of the bicarbonate ion, which is disordered over two positions. In III, the environment of the Sr atom includes six O atoms of four H₂ Edta ²⁻ ligands and three O atoms of water molecules. The coordination number of the Sr atoms is equal to 8 + 1. In II and III, the main bonds fall in the ranges 2.534(3)–2.732(2) and 2.482(2)–2.746(3) ?, whereas the ninth bond is elongated to 2.937(3) and 3.055(3) ?, respectively. In II, all the structural elements are linked into wavy layers. The O-H…O interactions contribute to the stabilization of the layer and link neighboring layers. In III, hydrated Sr²⁺ cations and H₂ Edta ^– anions form a three-dimensional [Sr₂(H₂ Edta)(H₂O)₃] _n ²ⁿ⁺ framework. The Cl⁻ anions are fixed in channels of the framework by hydrogen bonds with four water molecules. In II and III, the N-H groups form four-center N-H…O₃ hydrogen bonds, which include one intermolecular and two intramolecular components. PACS numbers: 61.66.Hq Original Russian Text ? I.N. Polyakova, A.L. Poznyak, V.S. Sergienko, 2009, published in Kristallografiya, 2009, Vol. 54, No. 2, pp. 262–267.     

Structure, thermal, and infrared analyses of [NH3(CH2)3NH3]2[Ni(HP2O7)2(H2O)2] ? 4H2O

[NH₃(CH₂)₃NH₃]₂[Ni(HP₂O₇)₂(H₂O)₂] 4H₂O (NiDAP) is a new diphosphate of transition metallic and organic cations obtained from a mixture of H₄P₂O₇, 2NiCO₃ Ni(OH)₂ 4H₂O and NH₂(CH₂)₃NH₂ in a 1:1/6:1 molar ratio. This mixed organo-mineral compound crystallizes in the triclinic system, P¯, with the unit cell dimensions: a = 7.3678(3)~Å, b = 7.8018(5)Å, c = 11.1958(7)Å, = 76.914(4), = 81.052(4), = 85.46(1), V = 618.57(6)ų and Z = 1. The crystal structure of NiDAP consists of a complex anion, [Ni(HP₂O₇)₂(H₂O)₂]^4– and a diammoniumpropane cation. The complex anion is built up from two neutral water molecules (OW1) and two diphosphosphoric anions coordinated to Ni(II) in a bidentate chelating manner. (OW1) molecules link anionic complexes, [Ni(HP₂O₇)₂(H₂O)₂]^4– to create a thick bidimensional layers parallel to the (a, b) plane. These layers are interconnected in three dimensions through hydrogen bonds established between organic cations, the remaining water molecules OW2, OW3, and some external oxygen atoms of the anionic complex arrays. NiDAP was also characterized by IR spectroscopy, TG-DTA, and DSC analyses.     

Y2O3/ZrO2复合泡沫陶瓷烧结的初步研究

本文采用有机泡沫浸渍法制备了Y2O3/ZrO2双层复合、Y2O3/Y2O3-ZrO2/ZrO2三层复合及Y2O3和ZrO2单相泡沫陶瓷,分析了两种复合泡沫陶瓷层间的结合及各层显微结构随烧结温度的变化,并与单相氧化物陶瓷进行了对比。结果表明:双层复合陶瓷层间有较大缝隙,这是因为两种氧化物陶瓷烧结不同步造成的。三层复合陶瓷中Y2O3-ZrO2混合中间层的存在减弱了Y2O3、ZrO2烧结不同步引起的层间应力,层间结合明显改善,并大大减少了泡沫陶瓷表面宏观裂纹。两种复合陶瓷的ZrO2内层的烧结程度都低于单相ZrO2,这主要是因为先于ZrO2烧结的Y2O3外层阻碍了内部气体的排出从而阻碍ZrO2的烧结所致。     

Synthesis and X-ray structural investigation of K8[(UO2)2(C2O4)2(SeO4)4] · 2H2O

Single crystals of the compound K₈[(UO₂)₂(C₂O₄)₂(SeO₄)4] · 2H₂O (I) are synthesized, and their structure is investigated using X-ray diffraction. Compound I crystallizes in the monoclinic system with the unit cell parameters a = 14.9290(4) ?, b = 7.2800(2) ?, c = 15.3165(4) ?, β = 109.188(1)°, V = 1572.17(7) ?³, space group P2₁/n, Z = 2, and R = 0.0297. The uranium-containing structural units of crystals I are dimers of the composition [(UO ₂)₂(C₂O₄)₂(SeO₄)₄]⁸⁻, which belong to the crystal-chemical group AB ⁰¹ B ² M ¹ (A = UO₂²⁺, B ⁰¹ = C₂O₄²⁻, B ² = SeO₄²⁻, M ¹ = SeO₄²⁻) of the uranyl complexes. The [(UO₂)₂(C₂O₄)₂(SeO₄)₄]⁸⁻ dimers are joined into a three-dimensional framework through electrostatic interactions with the outer-sphere potassium cations. Original Russian Text ? L.B. Serezhkina, E.V. Peresypkina, A.V. Virovets, A.G. Verevkin, D.V. Pushkin, 2009, published in Kristallografiya, 2009, Vol. 54, No. 1, pp. 68–71.     

Surface kinetics of nitrogen dissolution and its correlation to the slag structure in the CaO―SiO2, CaO―Al2O3, and CaO―SiO2―Al2O3 slag system

The kinetics of nitrogen dissolution into molten slag at 1873 K was investigated by an isotope exchange technique. Rate constants were correlated with the molten slag structure obtained from FT-IR spectra. The rate constant in the CaO―SiO₂ binary system showed a maximum value at a specific slag composition followed by a decrease in the rate due to excess O²⁻ blocking the surface sites for nitrogen adsorption. The rate constant in the CaO―Al₂O₃ binary system was comparatively constant within the experimental range of 45 mass% to 60 mass%. The rate constant in the CaO―SiO₂―Al₂O₃ ternary slag system was measured within the boundary of the liquidus line and showed a close correlation with the slag structure. Furthermore, the rate constant in the CaO―SiO₂―Al₂O₃ ternary system was found to be significantly higher compared to the binary system due to the correlated effect of lower binding energies of the Al―O bonds and the increased number of reaction sites available when smaller Si―O tetrahedral were simultaneously present with Al―O bonds.     

共沉淀法制备Gd2Zr2O7纳米粒子

采用反向滴定共沉淀法制备了Gd2Zr2O7纳米粒子,用XRD、SEM、TEM、TG-DTA等测试手段分析了煅烧温度和时间、体系温度、pH值、初始浓度、表面活性剂含量(SDBS)对前驱体的物相、形貌及晶粒大小的影响。结果表明:五种因素分别对Gd2Zr2O7相变化无影响,以氨水做沉淀剂经反向滴定,当体系温度为0℃、母盐溶液初始浓度为0.01mol/L、pH值为11、SDBS含量2wt%时,在1100℃煅烧3 h制备出近球形的Gd2Zr2O7纳米粒子,粒径约40 nm。     

光敏化La2O3/TiO2催化剂的制备及其光催化性能研究

采用溶胶-凝胶法和水热法制备了La2O3/Ti O2复合物,将此种La2O3/Ti O2复合物利用叶绿素提取液浸泡后,制得了光敏化La2O3/Ti O2复合物,并采用透射电子显微镜、X-射线衍射仪、比表面积测定仪和紫外-可见分光光度计等对样品进行了表征。结果表明:La2O3/Ti O2催化剂的颗粒粒径在3~10 nm之间,BET比表面积为173.53 m2/g,光敏化La2O3/Ti O2复合物具有较好的可见光响应性能。在可见光下研究了几种光催化剂对水中六价铬离子的光催化还原效果,光催化结果表明:以光敏化La2O3/Ti O2复合物为催化剂,在可见光下光催化还原含Cr6+废水180 min后,Cr6+脱除率达到78.7%。     

Sandwich-Type Manganese-Substituted Polyoxometalate, [(α-B-ZnW9O34)2W2Mn2(H2O)2]8?

Abstract  

The novel dimeric manganese-substituted polyoxotungstate Na₁₀[(α-B-ZnW₉O₃₄)₂W₂Mn₂(H₂O)₂](OH)₂·34H₂O (1) has been designed and synthesized from the hydrothermal reaction of Na₂WO₄·2H₂O, MnCl₂·4H₂O, and ZnCl₂ in a Teflon-lined stainless steel autoclave at 140°. X-ray diffraction analysis results reveal that compound (1) crystallizes in the monoclinic system, space group P2(1)/n, with a = 13.0901(3) ?, b = 17.8242(4) ?, c = 21.2401(5) ?, β = 93.6380(10)°, Z = 1, V = 4945.8(2) ?³, F(000) = 5244, Dc = 3.974 g/cm⁻³, μ(Mo-Kα) = 2.4037 cm⁻¹, λ(Mo-Kα) = 0.71073 ?. The structure was refined to R = 0.0631 and wR = 0.1532. The polyoxoanion of [(α-B-ZnW₉O₃₄)₂W₂Mn₂(H₂O)₂]⁸⁻ consist of two Keggin lacunary α-B-ZnW₉O₃₄ ¹²⁻ moieties linked via a rhomblike W₂Mn₂O₁₆ group leading to a sandwich-type structure.     

Synthesis and structure of K2[(UO2)4(O)2(OH)2(C2O4)(CH3COO)2(H2O)2]·2H2O

Single crystals of the compound K₂[(UO₂)₄(O)₂(OH)₂(C₂O₄)(CH₃COO)₂(H₂O)₂]·2H₂O (I) are synthesized, and their structure is investigated using X-ray diffraction. Crystals of compound I belong to the triclinic system with the unit cell parameters a = 7.6777(6) ?, b = 7.9149(7) ?, c = 10.8729(9) ?, α = 72.379(2)°, β = 86.430(3)°, γ = 87.635(2)°, V = 628.33(9) ?³, space group P , Z = 1, and R ₁ = 0.0323. The main structural units of the crystals are [(UO₂)₄(O)₂(OH)₂(C₂O₄)(CH₃COO)₂(H₂O)₂]²⁻ chains, which belong to the crystal-chemical group A ₄ M ₂³ M ₂² K ⁰² B ₂⁰¹ M ₂¹ (A = UO₂²⁺, M ³ = O²⁻, M ² = OH⁻, K ⁰² = C₂O₄²⁻, B ⁰¹ = CH₃COO⁻, M ¹ = H₂O) of the uranyl complexes. The chains are formed by linking the centrosymmetric tetramers of the composition (UO₂)₄(O)₂(OH)₂(CH₃COO)₂(H₂O)₂ via tetradentate bridging oxalate ions. The uranium-containing groups are joined into a three-dimensional framework through the electrostatic interaction with potassium cations and a system of hydrogen bonds, which are formed with the participation of atoms involved in the composition of the water molecules, hydroxide ions, and uranyl ions. Original Russian Text ? L.B. Serezhkina, A.V. Vologzhanina, N.A. Neklyudova, V.N. Serezhkin, 2009, published in Kristallografiya, 2009, Vol. 54, No. 3, pp. 483–487.     

Controlling metal–insulator transition in the hetero-epitaxial VO2/TiO2 bilayer grown on Al2O3

Hetero-epitaxial VO₂/TiO₂ bilayers were synthesized on Al₂O₃ substrates by using pulsed laser deposition, and their physical properties with the changes of oxygen pressure and the substrate orientation were investigated. A metal–insulator transition of the VO₂ was observed only in a narrow oxygen pressure range of 5–20 mTorr. As the oxygen pressure increased, X-ray diffraction peak for the (2 0 0)VO₂ shifted to a lower 2θ position, while the metal–insulator transition temperature (T_MI) decreased by ∼7 K. On the other hand, T_MI was largely varied with substrate orientation. The (2 0 0)VO₂/TiO₂ on the c-plane sapphire showed the highest T_MI of about 350 K, while the (0 0 2)VO₂/TiO₂ on the m-plane sapphire displayed the lowest T_MI of about 310 K. The (1 0 1)VO₂/TiO₂ on the r-plane and the a-plane exhibited T_MI∼340 and 330 K, respectively. The observed variations of T_MI with the oxygen pressure and substrate orientation were presumably due to the change in oxygen content of the VO₂ layer and/or in lattice strain.     

Synthesis and Structural Studies of [Na(C7H6O4)(H2O)3](C7H5O4)?·?2H2O

Abstract  The mononuclear complex [Na(C₇H₆O₄)(H₂O)₃](C₇H₅O₄) · 2H₂O has been synthesized and characterized by IR, single crystal X-ray and thermal analysis. The compound crystallizes in the monoclinic space group P2₁ with a = 3.623(2) ?, b = 15.872(6) ?, c = 15.650(5) ?, β = 93.13(4)°, V = 896.6(7) ?³ and Z = 2. The central sodium ion is six coordinated with distorted octahedral geometry by two oxygen atoms from two bridging 3,5-dihydroxybenzoate ligands and four ones from different water molecules. The notable feature of the title complex is the formation of a three-dimensional network, through the combination of coordination bonds, hydrogen bonds and π···π interactions. There are one-dimensional channels in the structure, filled in by water molecules. The compound dehydrates in the temperature range of 70–125 °C and then is stable up to 230 °C. Index Abstract  The mononuclear complex [Na(C₇H₆O₄)(H₂O)₃](C₇H₅O₄) · 2H₂O has been synthesized and characterized by IR, single crystal X-ray and thermal analysis.      

Gd2Ti2O7/ZrO2（3Y）陶瓷制备及力学性能研究

用共沉淀法合成Gd2Ti2O7纳米粉体,经真空烧结制备不同ZrO2(3Y)含量的Gd2Ti2O7/ZrO2(3Y)陶瓷。用XRD、SEM和力学性能试验等测试手段研究样品的物相、形貌和力学性能。结果表明:Gd2Ti2O7/ZrO2(3Y)陶瓷的力学性能随ZrO2(3Y)含量增加显著提高,ZrO2(3Y)含量为90vol%时,样品的维氏硬度、抗弯强度和断裂韧性最大值分别达到20.95GPa、199.21MPa和8.17MPa·m1/2。其原因是ZrO2(3Y)固溶导致晶粒尺寸减小,过饱和析出ZrO2(3Y)的颗粒弥散增韧,以及ZrO2(3Y)应力诱导相变增韧作用。     

Sb2O3掺杂对Pr6O11压敏电阻微结构和电学性能的影响

采用传统陶瓷工艺制备了Sb2O3掺杂的Pr6O11压敏电阻,并利用现代分析测试技术对其微结构和电学性能进行了研究。样品的相结构比较简单,除了Pr6O11主相外,未发现明显的第二相。样品的相对密度及晶粒尺寸随着Sb2O3掺杂量的提高而降低。非线性系数、压敏电压和晶界电阻都呈现出先降低后增加的趋势,非线性系数最高可达134。分析表明,Sb掺杂不与Pr6O11发生固相反应,其高温分解所产生的蒸汽压会降低Pr6O11压敏电阻的相对密度、晶粒尺寸及势垒高度,电学性能的变化要归结于相对密度、晶粒尺寸及势垒高度的共同作用。     

Synthesis and Crystal Structure of a New Mixed Alkali Oxalate A1?x(NH4)x(H2C2O4)(HC2O4)(H2O)2 with A?=?K, Rb

Abstract  

In the present study we report the synthesis, crystal structure, spectroscopic and thermal analysis of mixed alkali A_1−x (NH₄) _x (H₂C₂O₄)(HC₂O₄)(H₂O)₂ with A = K, Rb. Single crystal refinements showed that the two compounds Rb_0.86(NH₄)_0.14(H₂C₂O₄)(HC₂O₄)(H₂O)₂ and K_0.53(NH₄)_0.47(H₂C₂O₄)(HC₂O₄)(H₂O)₂ adopt P − 1 space group. The nine fold coordination cationic sites are randomly occupied by Rb⁺/NH₄ ⁺ and K⁺/NH₄ ⁺ respectively for rubidium and potassium compounds. The structure consists of a three-dimensional network formed by the succession along (c) axis of corrugated sheets formed by alkali polyhedra layers in the packing of four-membered rings [A₄(HC₂O₄)₂(H₂C₂O₄)₂] linked and bridged by oxalate groups that behave as bi and tetradentate ligand under three different coordination modes. The stability of the crystal lattice is ensured by interesting hydrogen bonding contacts: N–H···O and O–H···O. The thermal behavior under air reveals two anomalies at 368 and 402 K attributed respectively to a structural phase transition probably due to the reorientation of ammonium tetrahedral and to the release of crystalline water. IR spectroscopy further confirms that this material loses crystallization water gradually in the temperature range 400–460 K.