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.     

Short range antiferromagnetic ordering in vitreous Fe2O3P2O5

An outline is given of the theory of neutron magnetic scattering from amorphous materials, and data are presented for vitreous 0.79 Fe₂O₃ · P₂O₅. The magnetic correlation function shows that at low temperatures the glass exhibits short-range antiferromagnetic ordering with Fe³⁺?Fe³⁺ interionic distances similar to those found in crystalline FePO₄. The neutron data are not consistent with a previous suggestion that the material is microcrystalline.     

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%。     

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。     

Infrared transmission of (R2O OR R’O)–(TiO2, Nb2O5 OR Ta2O5)-Al2O3 glasses

The new families of aluminate glasses obtained by the present authors from their melts in the systems K₂O–Ta₂O₅–Al₂O₃, Na₂O–K₂O–Ta₂O₅–Al₂O₃, K₂O –Cs₂O– Ta₂O₅–Al₂O₃, K₂O–Nb₂O₅–Al₂O₃, Na₂Oz.sbnd;K₂O–TiO₂–Al₂O₃, BaO–TiO₂–Al₂O₃, BaO–ZrO₂–TiO₂–Al₂O₃ and Na₂O–K₂O–BaO–ZrO₂–Ta₂O₅–TiO₂ –Al₂O₃ showed high transmissions of visible and infrared (IR) radiation ranging from 0.4 to about 6 μm, as well as high refractive indices up to 2.0. Their physical and chemical properties such as glass-forming ability, softening temperature, hardness and hygroscopicity were comparable to conventional silicate glasses. These properties are useful for IR applications. The cause of the high IR transmission of the aluminate glasses was interpreted in terms of the masses of the constituent cations and the single bond strengths of the cations with oxygen ions.     

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。     

Tb3+-Eu3+共掺杂2ZnO·2.2B2O3·3H2O的制备和发光性能

采用水热法合成了Tb3+和Eu3+共掺的2ZnO.2.2B2O3.3H2O红色荧光粉。通过固定Eu3+的掺杂浓度为3%(物质的量比:Eu∶Zn=3%),改变Tb3+的掺杂浓度(2%～15%),研究Tb3+掺杂浓度对红色荧光粉晶相结构和光学性能的影响。用X射线衍射和荧光光谱仪对样品的结构和发光性能进行表征,结果表明:随着Tb3+掺杂浓度的升高,样品由晶态向无定形的玻璃态转变;Eu3+的发光强度也逐渐增强;Tb3+与Eu3+之间存在能量传递的过程,且当采用不同的激发波长(220 nm和393 nm)激发时,其能量传递的过程也不一样。     

Small polaron conduction in V2O5P2O5 glasses

Dc conductivity measurements have been made between 90 and 520 K on three bulk samples of V₂O₅P₂O₅ glass. Heat treatment is found to result in a reduction of the activation energy at a given temperature and this is most noticeable at low temperatures. The behaviour at low temperatures can be described using Mott's variable range hopping arguments, and at high temperatures by non-adiabatic small polaron hopping between nearest neighbours. At intermediate temperatures a simple model is used in which excitations by optical and acoustic phonons are considered to make independent contributions to the jump frequency. Mott's theory is extended to the polaron case for $\text{T>}\text{1}\text{4}\text{?}$ and is shown to be in good agreement with results. Values for $\text{r}{}_{\mathrm{<mtext>p</mtext>}}\text{(～2.8}\text{A}\text{?}\text{)}$ the polaron radius and $\text{α(～3.5}\text{A}\text{?}{}^{\mathrm{?1}}\text{)}$ the electron decay constant are shown to be consistent with the model for small polarons. A method is suggested for obtaining α and N(E_F) from the ac conductivity and the slope of 1nσ versus $\text{1}\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$ at low temperatures. Values of N(E) are obtained which correlate with those obtained by the previous analysis. This implies that the disorder energy separating adjacent sites Δ₀ is large (～0.4 eV) in these materials.     

Invar effect in n-Nb2O5, αht-Nb2O5, and L-Nb2O5

An X-ray diffraction analysis of two commercial sets of niobium pentaoxide (Nb₂O₅) of Nbo-Pt grade has been performed. Each set reveals the coexistence of three modifications: n-Nb₂O₅, α_ht-Nb₂O₅, and L-Nb₂O₅. Anomalous behavior in the structural characteristics, with the occurrence of plateaus upon heating (the invar effect), is established for each phase. It is suggested that the coincidence of the temperature ranges with constant unit-cell parameters in Nb₂O₅ and complex Nb-containing oxides indicates the unified nature of the invar effect, which is related to the defect state of objects under study. Original Russian Text ? L.A. Reznichenko, V.V. Akhnazarova, L.A. Shilkina, O.N. Razumovskaya, S.I. Dudkina, 2009, published in Kristallografiya, 2009, Vol. 54, No. 3, pp. 517–526.     

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/℃。     

KLi(HC3N3O3)·2H2O晶体的电光效应和生长研究

本文采用电光系数的粉末测试方法,探索发现了新型电光晶体KLi(HC₃N₃O₃)·2H₂O。根据粉末样品的红外反射光谱和拉曼光谱,计算获得晶格振动对电光系数的贡献值,再加上粉末倍频效应推算的有效非线性光学系数,最终计算出KLi(HC₃N₃O₃)·2H₂O的电光系数为2.37 pm/V,与商用电光晶体β-BBO相当。采用水溶液法进行晶体生长,测试不同原料生长晶体时的过热和过冷曲线,优化生长工艺,获得35 mm×25 mm×10 mm透明晶体。采用X射线定向技术辅以压电系数测量,确定了晶体形貌与各向异性生长速率的对应关系。     

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.     

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%。     

MgO-Al2O3-ZrO2复合粉的制备与表征

以Mg Cl2·6H2O,Al Cl3·6H2O和Zr OCl2·8H2O为原料,NH3·H2O为沉淀剂,采用溶胶-凝胶法制备了三种Mg O/Al2O3/Zr O2质量比分别为10.0/41.4/48.6、15.0/39.1/45.9、20.0/36.8/43的Mg O-Al2O3-Zr O2复合粉。借助X-ray荧光分析仪、同步热分析仪、X-ray衍射仪、激光粒度分析仪、扫描电子显微镜对Mg O-Al2O3-Zr O2复合粉进行了表征。研究结果表明:Mg O-Al2O3-Zr O2复合粉前驱体的分解在600℃之前完成,之后随着温度升高,复合粉体析晶程度逐渐提高,在800℃的热处理温度下四方相少量析出,Mg O和Al2O3仍处于非晶相,此状态下的复合粉应具有较高的反应活性;制得的Mg O-Al2O3-Zr O2复合粉体化学成分均匀性好,粒径较细,且与氧化锆原料尺寸相匹配,可作为氧化锆质定径水口改性的添加剂。     

原位生成Fe-Al/Al2O3复合陶瓷涂层

采用化学镀法制备Fe包覆Al核(Al)-壳(Fe)结构复合粉体,以Fe-Al复合粉体为喷涂材料,利用等离子喷涂法在Q235钢基体上制备涂层,在喷涂过程中Fe、Al反应生成Fe-Al金属间化合物和Al2O3,通过控制Fe-Al和Al2O3粉体的混合比例实现涂层的梯度化。利用SEM、XRD研究涂层微观结构与组成,并测试分析了涂层的抗热震性与结合强度。结果表明,涂层主要由Al2O3、Al、Fe3Al和Fe O等组成,喷涂过程中Fe-Al发生反应原位生成了Fe3Al金属间化合物,以Fe-Al为底层的Fe Al/Al2O3梯度涂层的结合强度和抗热震性均明显高于Al2O3涂层,涂层成分的梯度分布和Fe3Al的原位形成改善了涂层的结合状态,提高了结合强度和抗热震性。     

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.     

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.     

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。     

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.     

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。