Hydrothermal Synthesis and Low-Temperature Sintering of Zinc Gallate Spinel Fine Particles

Nanosized powders of single-phase zinc gallate (ZnGa₂O₄) spinel were hydrothermally synthesized from solutions in the presence of NaOH over the pH range of 1.9 to 7.0 and from solutions above pH 7.0, i.e., the very basic medium (pH of 13.85), by removing the residual ZnO phase by washing with aqueous H₂SO₄ from the precipitate mixtures of zinc gallate spinel particles and ZnO. A very wide compositional range (Zn/2Ga = 0.705–1.157) of zinc gallate spinel solid solutions could be hydrothermally synthesized in the form of nanosized particles from acid and very basic mediums (pH of 2.4–13.85) in the presence of NaOH. These hydrothermally synthesized spinel powders showed good sinterability and almost full densification at 1100°C for 1 h. Dense sintered bodies consisting of single-phase zinc gallate spinel were fabricated at 1100°C using zinc gallate spinel powders having almost stoichiometric composition formed from the solution at pH 9.95 in the presence of aqueous ammonia.     

Hydride Vapor Phase Epitaxy of GaN Thick Films by the Consecutive Deposition Process Using GaCl3

GaN buffer and main layers were grown by the conventional hydride vapor phase epitaxy technique using GaCl₃ consecutively. The deposited buffer layers were investigated by atomic force microscopy and X-ray analysis. To examine the behavior of the buffer layers at main layer growth temperature, heat treatment was conducted at 900°C. Based on the results of the buffer layer study, GaN thick films were grown at 1050°C. Optimum deposition conditions of buffer layer from the buffer and main layer studies generally coincided. On the φ scanning pattern, the GaN films grown on (0001) Al₂O₃ were single-crystalline. Band-edge emission dominated photoluminescence was observed at room temperature.     

氮化镓低维纳米结构的制备与表征

主要是以氧化镓为原料,通过气相沉积法,制备出GaN纳米线和纳米带.通过X-射线衍射（XRD）,扫面电镜（SEM）和高分辨透射电镜（HRTEM）等测试手段对其形貌进行了表征和分析.研究了实验过程中工艺条件的改变对所制备GaN纳米结构形貌特征的影响.对两种GaN纳米材料的拉曼散射光谱进行了分析.     

Effect of heat-treatment on the surface properties of gallium phosphide nanosolids by Raman spectroscopy

Raman spectra of gallium phosphide （GAP） nanosolids （unheated and heat-treated at 598 and 723 K, respectively） were investigated. It was observed that both the longitudinal optical mode （LO） and the transverse optical mode （TO） displayed an asymmetry on the low-wavenumber side. The scattering bands were fitted to a sum of four Lorentzians which were assigned to the LO mode, surface phonon mode, TO mode, and a combination of Ga-O-P symmetric bending and sum band formed from the X-point TA ＋ LA phonons, respectively. Analysis of the characteristic of surface phonon mode revealed that the surface phonon peak of the GaP nanosolids could be confirmed. In the infrared spectrum of the GaP nanoparticles, we observed the bands on account of symmetric stretching and bending of PO2, as well as stretching of Ga-O The Raman scattering intensity arising from the Ga-O-P linkages increased as increasing the heat-treatment temperature.     

The Problem of Estimating the Uncertainty of the Fixed Point Temperature Due to the Presence of Impurities

The main problems in estimating the uncertainty due to the presence of impurities in the material: the absence in the documents of a unique definition of the quantity being measured – the fixed point temperature, the lack of agreed methods of realizing the fixed points and the insufficient justification of the equations used for the estimate, are analyzed. The results of a measurement of the melting point of gallium are presented, which differ in the conditions in which they were realized – with one and two liquid-solid interfaces and different solidification conditions, are presented. The reasons for the considerable difference between the values of the temperatures obtained in these experiments are discussed.     

Change in the decomposition mode of 1-propanamine due to the presence of cations in MFI zeolite

The adsorption and thermal analysis of 1-propanamine has been compared over MFI zeolites which contain H, Ga, and In cations. In the case of H⁺-containing materials, NH₃ and propene are simultaneously desorbed above 600 K. This behavior, is well known and characteristic of the Hofmann elimination reaction. However, a distinctly different mode of reaction is observed in the case of Ga and In containing materials. NH₃ is released below 600 K, propene and other products are released above 600 K, and a stable residue remains above 800 K. It is suggested that such behavior results from Lewis acid interactions of Ga or In cations with propanamine.On leave from the Bulgarian Academy of Sciences, Institute of Organic Chemistry.     

Propane conversion over zeolite catalysts: Comments on the role of Ga

The activation of propane using zeolite H-Y and Ga³⁺ exchanged zeolite Y indicates that in the presence of Ga³⁺ the mechanism of propane activation is changed from a cracking pathway to a dehydrogenation pathway. The presence of both Ga³⁺ and H⁺ are required to achieve this effect.     

Fe—Ga—O系平衡测定

在钼丝炉内氩气保护下，利用固体电解质定氧探头测定了含镓１．８７％～６．２１％范围内Ｆｅ－Ｇａ－Ｏ三元系平衡时的氧活度，通过处理得到镓在铁液中的标准溶解自由能等热力学参数与温度的关系。     

ADSORPTION OF GALLIUM WITH N_503LEVEXTREL RESIN

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Hydrogen sorption sites in the gallium containing hybrid catalysts used for the aromatization of light alkanes

Gallium species which were incorporated initially in the oxide form, were all in the (+3) oxidation state in the hybrid catalyst and exhibited two types of hydrogen chemisorption sites, s_hw and s_hs. The stronger sorption sites shs which predominated at higher gallium dispersion, corresponded probably to the most effective surface configuration for gallium in the aromatization ofn-butane.