Advanced Materials Research Vol. 1058

Abstract: In this paper, we have presented a comprehensive study about the preparation, structure and electrical conductivity of Ag-doped La_1-x-ySr_xCu_yMnO_3-δ (0.05≤x≤0.4, y=0.1) ceramics. We first doped Ag into La_1-x-ySr_xCu_yMnO_3-δ compounds using a sol-gel method and then the gels were sintered at 1000°C by Muffle furnace. The structure variation was systematically characterized by the X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that that silver merged well into the lattice of La_1-x-ySr_xCu_yMnO_3-δ and z at.% Ag-doped La_1-x-ySr_xCu_yMnO_3-δ compounds precipitated only in one phase. As indicated by the conventional four-probe method and UV-Vis diffuse reflectance spectroscopic (DRS), the addition of Ag was dramatically effective in enhancing the electrical conductivity, whereas a slight effect of the addition of Ag on UV-Vis diffuse reflection was observed. Furthermore, the electrical conductivity increased with the enhanced sintering temperature within the temperature of 1000 °C, which proved that the dominant mechanism of the conductivity of Ag-doped ceramics was hole hopping transfer.

Abstract: Doping effect on the lattice parameters, vibration modes, dielectric and piezoelectric properties of LiSbO₃, LiTaO₃ and LiNbO₃ substituted lead-free K_0.5Na_0.5NbO₃ (KNN) ceramics are investigated. All compositions are crystallized in morphotropic phase boundary region. Enhanced piezoelectric and electromechanical response d₃₃ ~176–197 pC/N, k_p ~45%–48%, and k_t ~34%–47% obtained in the doped ceramics are due to the presence of the polymorphic phase transition between orthorhombic and tetragonal phase at room temperature.

Abstract: SnO₂ ceramics were synthesized by SPS. Phase compositions and microstructures are examined by XRD, SEM and EDS, respectively. Sb₂O₃ used in our research were beneficial to lower the sintering temperature and promote the densification of SnO₂ ceramics. The SEM results show a homogeneous microstructure is approached consistent with the density measurement at 850-1000 °C. The XRD show all antimony ions came into the lattice of SnO₂ to substitute for tin ions when the content of Sb₂O₃ are 0.1-2.5 mol%. The grain boundary are no SnO and Sb₂O₃, only SnO₂. The mechanism of SPS sintering process is the local high temperature to produce the abnormal growth of the grain, and evaporation-condensation; and solid solution of Sb³⁺ go into the SnO₂ lattice produce oxygen vacancy to promote densification

Abstract: The humidity controlling materials using diatomite as the major raw material were prepared by dry pressing molding process. Effects of various diatomite contents and sintering temperatures on the final products were investigated. The samples were also characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and then tested adsorption-desorption performances by temperature and humidity chamber. The results indicate that the equilibrium moisture adsorption reaches to 338 g/m² when diatomite content is fixed at ~70% and sintering temperature is holding at 1050°C, respectively.

Abstract: Si₃N₄-SiC-C refractory composites were prepared under the condition of 1100 °C × 1 h with Si₃N₄ and SiC as the raw material and the sucrose and phenolic resin as the binder. The effects of the amount of the sucrose in the binder on the properties of Si₃N₄-SiC-C refractory composites were studied. The results indicated that increasing the ratio of sucrose in the binder can improve the properties of the materials.

Abstract: Anorthite good sintering properties and strength, there promotion prospects in oil and gas fields in the ceramic proppant fracturing. In this experiment, fly ash, coal and limestone as raw materials by high-temperature reaction sintering ceramics, Explore mineral composition, the sintering temperature of the final preparation phase of the resulting composition and physical properties of the impact, better product performance obtained at 1250 °C.

Abstract: Iridium trichloride hydrate and acetyl acetone were used as raw materials, Tris – acetylacetonate - iridium (III) was synthesis by the method of solutions - precipitating method. Composition and structure of obtained organic complex were investigated by means of Elemental Analysis, IR, ¹HNMR and UV-vis. Effect of sodium bicarbonate solution concertation on the synthesis yield also been studied. The results demonstrated that two oxygen atoms in acetyl acetone form chelated hexatomic ring with iridium ions. The highest yield was 19.9% when the concentration of sodium bicarbonate was 0.56mol/l.

Abstract: Yttrium aluminum garnet (YAG) with a chemical composition of Y₃Al₅O₁₂ is an important advanced structural and functional material.The preparation conditions were a pH of 9, a titration rate of 10ml/minute and a reaction time of 60 minutes. The analysis shows that the YAG precursor does not have an obvious characteristic crystalline diffraction peak, the characteristic diffraction peak of YAG was found after the calcination of the YAG precursor at 1100¡æ for 1 hour, the characteristic diffraction peak of YAG is strong, which indicates that the YAG crystalline phase is integrated and pure. The pore microstructure of porous YAG ceramics marked differed with an increase in the sintering temperature, the compressure strength of porous YAG ceramics is increased with an increase in the sintering temperature, the compressure strength shows the opposite rule with the prosity, which indicaties the mechanical properties of materials are effacted with the densification effect of materials.

Abstract: To obtain high-performance alumina powder for high-tech application, a comparative study was carried out for the spheroidization of two types of alumina powder using radio-frequency argon-oxygen thermal plasma. The morphology, crystallography, and particle size distribution of spheroidized alumina powder were analyzed. The effect of feed rate on the spheroidization efficiency was investigated. The results show that when the powder flow rate was 35 g/min, the spheroidization efficiency reached up to 100%, and the alumina powder had perfect sphericity, while the spheroidization efficiency decreased with increasing powder flow rate. The X-ray diffraction analysis reveals that the spheroidized alumina powder had mixed crystal structures with a stable α phase and a part of metastable phase. The particle size distribution analysis shows that the particle size of the spheroidized alumina powder did not change obviously. These results will help us to better understand the process engineering of the spheroidization of ceramic powder using radio-frequency argon-oxygen thermal plasma, and provide simultaneously technical assistance for industrialization.

Abstract: s: In this study, nitrogen-doped ZnO thin films with different nitrogen content were produced by a wet chemical process. The optical properties and the structure of these ZnO films were investigated by LT-PL spectrum, Raman spectrum, SEM and XRD. XRD result showed that the cubic ZnO phase appeared in the 10% nitrogen-doped ZnO films, which might be attributed to the stress in these ZnO film. Moreover, results of SEM measurement proved that the nitrogen atoms were introduced into the lattice of nanoZnO crystal. In addition, LT-PL spectra also confirmed that this new appeared phase was a cubic ZnO phase, due to the lack of the new PL mission peak. Key words: ZnO, wet chemical method, luminescence, XRD