ZrW2O8的合成及高温转变过程

ZrW2O8是具有负热膨胀各向同性的化合物材料.本文使用ZrOCl2*8H2O,H2WO4,浓氨水为原料采用化学沉淀法制备ZrW2O8粉末.通过高温XRD,常温XRD、TG-DSC等分析手段对产物结构进行表征,结果表明采用化学沉淀法在1150～1200℃短时间内(1h)可以生成单一ZrW2O8粉末.采用SEM技术分析了该粉末的形貌和尺寸.并对前驱体的高温转变过程进行了初步探讨.     

Phase composition and microwave dielectric properties of (Zn,Ni)TiNb2O8 solid solution

The Zn_1?xNi_xTiNb₂O₈ (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized by the conventional solid-state reaction method. The crystal structure and microwave dielectric properties were investigated by XRD, SEM and dielectric measurements. The XRD patterns of Zn_1?xNi_xTiNb₂O₈ ceramics showed that (Zn, Ni)TiNb₂O₈ phase and (Ni, Zn)_0.5Ti_0.5NbO₄ phase were obtained. With the increase of sintering temperature and Ni content, the amount of the second phase [(Ni, Zn)_0.5Ti_0.5NbO₄] enhanced, resulting in the increase of dielectric constant and the decrease of Q × f value. Moreover, the temperature coefficient of resonant frequency (τ_f) shifted to a positive value with increasing Ni content. In conclusion, the excellent microwave dielectric properties were obtained for Zn_0.7Ni_0.3TiNb₂O₈ ceramics sintered at 1,125 °C for 4 h: ε_r = 41.36, Q × f = 31,760 GHz, τ_f = ?9.2 ppm/°C. Furthermore, to realize the zero value for τ_f, a proper adjustment of Ni doping and sintering temperature can be feasible in this system.     

X-ray characterization and electrical properties of SrCeO3 — SrZrO3 solid solution

The crystallographic structure of the SrCeO₂-SrZrO₂ solid solution was determined and the crystallographic constants were calculated from X-ray diffractometry data. The specific electrical conductivities were also determined in the temperature range 800° to 1200°C at different oxygen partial pressures. The thermal gap was calculated and related to the lattice parameters.     

Synthesis and characterization of β type solid solution in the binary system of Bi2O3-Eu2O3

We have investigated Bi₂O₃-Eu₂O₃ binary system by doping with Eu₂O₃ in the composition range from 1 to 10 mole% via solid state reactions and succeeded to stabilize β-Bi₂O₃ phase which is metastable when pure. Stability of β-Bi₂O₃ polymorph was influenced by heat treatment temperature. Tetragonal type solid solution was obtained in 3–6 mole% addition range when annealed at 750°C and the range was 2–7 mole% when annealed at 800°C. We have also carried out investigations on lattice parameters, microstructural properties and elemental compositions of this β type solid solution for each doping ratio. Lattice parameters increased with amount of Eu₂O₃ addition. Our experimental observations strongly suggested that oxygen deficiency type non-stoichiometry is present in doped β type solid solutions.     

高压制备AgSbTe_2的微结构及高温电学性能研究

采用高压合成技术,制备出了热电材料AgSbTe2,并且研究了AgSbTe2样品微结构和高温电学输运性质。X射线衍射测试结果表明,高压合成的AgSbTe2样品中含有微量的Sb2Te3,电子能谱测试结果表明Ag、Sb、Te 3种元素分布很均匀。电学性能测试表明,在高压的作用下,AgSbTe2样品的载流子浓度增大;随着测试温度的升高,电导率降低,Seebeck系数增大。4 GPa高压合成的AgSbTe2样品在573 K温度下具有最高的功率因子(约18.1μW/(cm·K2))。     

固相合成法制备ZrW2O8陶瓷及其电学行为研究

按Zr和W的原子比为1:2.1,通过固相反应技术,在1200℃加热24h,然后在冰水中快速冷却,得到立方晶相的ZrW2O8产物,XRD分析表明产物的纯度很高,基本上没有杂项,对样品的电学性能进行了测试,用物性测量系统PPMS测量了在T=39800A/m下样品的磁化率(M)随温度的变化,经过分析表明,样品在15和250K左右出现的磁化率明显变化和WO3的相转变温度吻合.     

Magnetic and structural characterization of the solid solution CdFe2O4NiFe2O4

By means of Mössbauer spectroscopy magnetization measurements and powder diagrams, the structural and magnetic properties of the isomorphous series Cd_1?xNi_xFe₂O₄ has been studied. The cationic distribution depends on the relative concentration of Cd and Ni. The exchange integrals between the two sites in the spinel have been obtained.     

Synthesis, characterization, and electrical properties of regioregular alkyl-substituted PEDOTt

The regioregular hexyl-substituted poly(3,4-ethylenedioxy-2-thiophenylthiophene) (PEDOTt), structurally alternating copolymer of EDOT and thiophene, was synthesized via the Grignard Metathesis (GRIM) using catalytic amounts of Ni(dppp)Cl2. The products were characterized by 1H NMR spectroscopy, UV-vis spectroscopy and XRD. The alkyl-substituted conjugated polymer showed an enhancement of solubility in common organic solvents. Based on XRD data, the regioregular hexyl-substituted poly(3,4-ethylenedioxy-2-thiophenylthiophene) (PEDOTt) shows better crystallinity than the regiorandom hexyl-substituted PEDOTt owing to self-ordering. In addition, regioregular hexyl-PEDOTt has a conductivity of 0.788 S/cm by iodine doping.     

Synthesis,characterization, electrical and sensing properties of ZnO nanoparticles

The present study investigates the electrical and sensing properties of mechanically compacted pellets of nanosized zinc oxide powders synthesized by chemical method at room temperature in alcohol base using Triethanolamine (TEA) as capping agent. Synthesized ZnO particles has been characterized for its optical, structural, morphological properties using UV–VIS spectrophotometer, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The ZnO particles have hexagonal wurtzite structure and the particles are of 20–30 nm in size. The electrical properties of the prepared material have been investigated with Impedance Spectroscopy at different temperatures and frequencies and other laboratory setup. Resistivity, I–V curves, AC impedance of ZnO nanoparticles pellets with temperature was investigated and response was compared with commercial ZnO. Piezoelectric and oxygen sensing property of ZnO were also examined. Dynamic hysteresis of sintered ZnO pellet using axis ACCT TF analyzer 2000HS did not show polarization retention by sample. Oxygen sensing of ZnO pellet has been investigated for different concentrations of oxygen for the temperature range of 200–350 °C. The decrease of the current flow through the ZnO pellet with increasing oxygen concentration indicates the application of ZnO in oxygen sensing. The prepared ZnO particles were also used for preparing nanofluids of different concentrations and were characterized by measuring thermal conductivity using hot wire method which shows sigmoidal behavior over a temperature range of 10–50 °C.     

S2O2-8/Al-Zn-O固体酸的制备及表征

用溶胶-凝胶法制备了S2O82-/Al-Zn-O固体酸,考察了制备条件对其催化乙酸-正丁醇合成乙酸正丁酯催化性能的影响,并借助XRD、IR、TG/DSC、SEM等多种测试技术对其结构进行了表征。实验结果表明,制备条件对S2O28-/Al-Zn-O固体酸的催化性能有一定的影响,在最佳制备条件下,其酯化率可达98.06%。     

Ca3CO2O6的柠檬酸盐溶胶-凝胶合成、表征及电学性能

具有一维Co-O链的Ca3CO2O6是一类新型高温热电材料。通过柠檬酸盐溶胶-凝胶法合成粉体，采用常压烧结方式制备陶瓷体。结果表明，在700℃煅烧干凝胶就可以生成片状的Ca3CO4O9晶体，随着煅烧温度的升高，在850℃保温2h的条件下，Ca3CO4O9基本转化为短棒状的Ca3CO2O6晶体。Ca3CO2O6为P型半导体，电阻率随着温度的升高而降低，Sccbcck系数随着温度的升高而增加，功率因子也呈现单调增加。     

Influence of Gd2O3 on phase,microstructure, and electrical properties of ZnO varistor ceramics

Journal of Materials Science: Materials in Electronics - Gd2O3-doped ZnO varistor ceramics were successfully prepared through the solid reaction sintering route. The influence of Gd2O3 additive on...     

Synthesis and characterization of arsenate/phosphate hydroxyapatite solid solution

A series of arsenate substituted hydroxyapatite was directly prepared through aqueous precipitation method. Characterization studies from elemental analysis, XRD, FT-IR spectra and SEM have confirmed the forming of the arsenate/phosphate hydroxyapatite solid solutions. The XRD analysis indicated that the unit cell a and c parameters did not vary smoothly with the degree of substitution as expected by the Vegard's Law. The solids with As/(P + As) = 0.46–1.0 were typically needle-like crystals; those with As/(P + As) = 0–0.46 large tabular. In FT-IR spectra, the area of the phosphate peak was gradually suppressed and that of the arsenate peak increased as the proportion of the arsenate increased.     

纳米氧化铋基材料高温相变的研究

以分析纯Bi(NO3)3·5H2O和Y(NO3)·6H2O为原料制备纳米β-Bi2O3和Bi2O3-Y2O3(75%(摩尔分数)Bi2O3 25%(摩尔分数)Y2O3)粉体,平均粒度分别为40和30nm.经TG-DTA、高温XRD以及高温拉曼的研究结果表明,亚稳态的纳米β-Bi2O3粉体在升温过程中于420℃先向低温稳定的α-Bi2O3转变,在720℃时向δ-Bi2O3相转变,降温过程则是由δ→β→α.由于纳米Bi2O3具有很高的活性,使得相变温度比微米Bi2O3有所降低.纳米Bi2O3-Y2O3复合粉体升温过程中,Y2O3的固溶反应在较低温度(400℃)开始,500℃时β-Bi2O3完全转变为δ相,同时Y2O3完全固溶到δ-Bi2O3晶体中.Y2O3的掺杂使得Bi2O3的β→δ相转变温度大幅降低.     

Synthesis,characterization and electrical properties of a lead sodium vanadate apatite

The lacunary lead sodium vanadate apatite Pb₈Na₂(VO₄)₆ was synthesized by the solid-state reaction method. The compound was characterized by X-ray powder diffraction, infrared (IR) absorption spectroscopy and Raman scattering spectroscopy.By comparing the effect of vanadate and phosphate ions on electrical properties, it was concluded that Pb₈Na₂(VO₄)₆ apatite is better conductor than Pb₈Na₂(PO₄)₆ apatite.     

Synthesis, characterization and electrical properties of carbon coated LiCoPO4 nanoparticles

Lithium cobalt phosphate (LiCoPO4) nanoparticles were synthesized using modified polyol process. Shape and size of LiCoPO4 nanoparticles were controlled by using poly (vinylpyrrolidone) (PVP) stabilizer. Coating of carbon over the LiCoPO4 nanoparticles was done using the resin coating process to enhance its conductivity. XRD and FTIR results respectively confirm the crystalline phase and structure of pure and carbon coated LiCoPO4 nanoparticles. SEM-EDX results confirm size and shape and also the presence of carbon over LiCoPO4 nanoparticles. Electrical conductivity of pure and carbon coated LiCoPO4 nanoparticles were evaluated by analyzing the measured impedance data using the win fit software. More than three orders of conductivity enhancement was observed in carbon coated LiCoPO4 nanoparticles when compared to pure ones. Further, transport properties like temperature dependence conductivity, AC conductivity, dielectric constant and electric modulus studies were made to find out the bulk and relaxation properties of LiCoPO4 nanoparticles.     

Synthesis, characterization and electrical properties of poly(dibromoaniline-co-aniline)s

The chemical copolymerization of aniline and 2,5-dibromoaniline or 2,6-dibromoaniline by oxidation with K₂Cr₂O₇ in H₂SO₄/acetonitrile media has been carried out. Copolymer composition can be effectively controlled varying the monomer feed ratio. When substituted aniline fraction is increased in the copolymer, the electrical conductivity () decreases; this effect is more important when 2,6-dibromoaniline is used. Thus, the conductivity can be controlled in a broad range, from 1.2 to 10^–6–10^–11 S·cm^–1 depending on the substituted aniline and the feed ratio. The relations between copolymer compositions and comonomer feed molar ratios shows that the aniline is slightly more reactive than dibromoanilines during the copolymerization process. All the copolymers were shown to be more processable than polyaniline.     

纳米Ce0.8Zr0.2O2固溶体的溶剂热制备与催化性能研究

以硝酸铈和硝酸锆为原料用溶剂热的方法在甲酸中120℃加热24h制得了纳米Ce0.8Zr0.2O2固溶体材料,利用X射线衍射（XRD）、Raman光谱、扫描电镜（SEM）和投射电镜（TEM）对其进行了表征。在乙酸和正丁醇制备乙酸丁酯的反应中考察了其催化活性。XRD和Raman光谱显示出所制备的样品形成了具有氧化铈立方结构的均一固溶体。TEM结果表明所合成的Ce0.8Zr0.2O2的粒径〈100nm。在酯化反应中,Ce0.8Zr0.2O2固溶体具有较高的催化活性,且容易和反应液分离。反复实用10次后,其催化活性基本上保持不变。     

Subsolidus,high temperature phase relations in the systems Al2O3-Cr2O3-ZrO2, MgO-Cr2O3-ZrO2 and MgO-Al2O3-ZrO2

In the temperature range 1600 to 1900° C, the system A₂O₃-Cr₂O₃-ZrO₂ is characterized by the coexistence of ZrO₂ (unstablilized) and an (Al, Cr)₂O₃ solid solution series. In the systems MgO-Cr₂O₃-ZrO₂ and MgO-Al₂O₃-ZrO₂ a nearly stoichiometric spinel coexists with both stabilized and unstabilized ZrO₂. At temperatures above 1600°C a new ternary Mg-Al-Zr oxide becomes stable in the MgO-rich part of the MgO-Al₂O₃-ZrO₂ system.