Thermodynamics and kinetics analysis of in-situ synthesizing AlN

AIN powders were prepared by in-situ synthesis technique. It is a reaction of binary molten Al-Mg alloys with highly pure nitrogen. It was confirmed through thermodynamics calculation that Mg element in Al-Mg alloys can decrease oxygen content in the reacting system. Thus, nitridation reaction can be performed to form AIN. Moreover, an analysis of kinetics shows that the nitridation reaction of Al-Mg alloys can be accelerated and transferred rapidly with the increment of Mg content.

Mechanical alloying of Fe-Mn and Fe-Mn-Si

The ball milling of Fe-24Mn and Fe-24Mn-6Si mixed powders has been performed by the high energy ball milling technique. By employing X-ray diffraction and Mossbauer measurements, the composition evolution during the milling process has been investigated. The results indicate the formation of paramagnetic Fe-Mn or Fe-Mn-Si alloys with a metastable fee phase as final products, which imply that the Fe and Mn proceed a co-diffusion mechanism through the surface of fragmented powders. The thermal stability and composition evolution of the as-milled alloys were discussed comparing with the bulk alloy. (C) 1999 Published by Elsevier Science S.A. All rights reserved.

中国畜牧业现状与可持续发展措施的研究

畜牧业是否成长为农村经济的支柱产业,是衡量一个国家农业发达程度的主要标志。现阶段.我国畜牧业的增长方式、发展路径、动力、市场和地位都发生了重大变化,给畜牧业的可持续发展提出了许多新问题和新挑战。近年来.我国畜牧业的发展取得了举世嘱目的成就,促进了国民经济的快速发展,丰富了城乡人民物质和文化生活的需要。随着经济的发展和人们生活水平的逐步提高.对畜牧产品的需求将有较大增长,大力加强和发展畜牧业将是我国农业的最终方向。依据现有统计资料,结合我国畜牧业的实际情况,根据"十一五"规划和建设社会主义新农村的要求,文章分析了畜牧业发展的地位,探讨了畜牧业存在的问题.并提出了相应的对策和建议。

Photostimulated luminescence of BaFBr:Eu2+ phosphors

After x-irradiation for 10 s, luminescence from BaFBr:Eu2+ phosphors by photostimulation of longer wavelength than F absorption bands was observed and assigned to the surface states or intrinsic defects of the powders. It is found that the luminescence by photostimulation into F bands can be reduced via electron migration from F centers into the surface states or intrinsic defects, thus reducing the x-ray storage or image stability. Surface passivation can lower these defects and improve the phosphors or imaging plate quality. (C) 1996 American Institute of Physics.

Nontoxic electrodes of solid amalgams

This is a review of electrodes based on nontoxic solid amalgams (MeSAE) (prepared by amalgamation of soft metal powders) in connection with some other kinds of voltammetric electrodes is given. Information is summarized on various types of MeSAEs (esp. AgSAE, CuSAE, AuSAE), pretreatment of their surfaces, their hydrogen overvoltage in aqueous solutions, conditions for their testing, electroanalytical parameters and use, in compared with the hanging mercury drop electrode (HMDE). Although the solid amalgam electrodes do not reach the quality of the HMDE, in many cases they represent its possible alternative. The broad range of voltammetric applications of the MeSAEs, especially of the AgSAEs, their good mechanical stability, simple handling, and new aspects of their use in electrochemical techniques are documented by numerous examples.

Crystallographic and electrochemical characteristics of melt-spun Ti–Zr–Ni–Y alloys

Ti45Zr30Ni25Yx (x = 1, 3, 5 and 7) alloys were prepared by melt-spinning at wheel velocity of 20 m s(-1). The effect of additive Y on phase structure and electrochemical performance of melt-spun alloys was investigated. Ti45Zr30Ni25Yx melt-spun alloys were composed of I-phase and amorphous phase. T

Crystallographic and electrochemical characteristics of melt-spun Ti-Zr-Ni-La alloys

Ti-based icosahedral quasicrystalline phase (I-phase) exhibited excellent hydrogen storage property for special structure. Unfortunately, the application as the negative electrode material of the nickel-metal hydride batteries was limited due to the poor electrochemical kinetics. Meanwhile, rare-earth element was beneficial to the electrochemical properties of Ti, Zr-based alloy.

Synthesis and characterization of (Zn,Cd)TiO3 by a modified sol-gel method

Ilmenite-type (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) was synthesized by a modified sol-gel route including the Pechini process via two-step heat treatments. The thermal stability of (Zn1-xCdx)TiO3 depended on the amount of cadmium content. The as-synthesized (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) showed higher thermal stability than that of ZnTiO3. The variation of the dielectric constant of all synthesized (Zn1-xCdx)TiO3 samples for all measurement frequencies showed a similar tendency.

Studies on the magnetism of cobalt ferrite nanocrystals synthesized by hydrothermal method

Fe-Co/CoFe2O4 nanocomposite and CoFe2O4 nanopowders were prepared by the hydrothermal method. The structure of magnetic powders were characterized by X-ray diffraction diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermal gravity analysis (TGA) and differential thermal analysis (DTA) analysis, X-ray photoelectron spectrometry (XPS), and Fourier transform infrared spectra (FTIR) techniques, while magnetic properties were determined by using a vibrating sample magnetometer (VSM) at room temperature.

Characterization of High Melt Strength Polypropylene Synthesized via Silane Grafting Initiated by In Situ Heat Induction Reaction

High melt strength polypropylene (HMSPP) was synthesized by in situ heat induction reaction, in which pure polypropylene (PP) powders without any additives were used as a basic resin and vinyl trimethoxysilane (VTMS) as a grafting and crosslinking agent. The grafting reaction of VTMS with PP was confirmed by FTIR. The structure and properties of HMSPP were characterized by means of various measurements. The content of grafted silane played a key role on the melt strength and melt flow rate (MFR) of HMSPP. With increasing the content of grafted silane, the melt strength of HMSPP increased, and the MFR reduced. In addition, due to the existence of cross-linking structure, the thermal stability and tensile strength of HMSPP were improved compared with PP.

Bulk ultrafine binderless (W0.4Al0.6)C prepared by high pressure sintering

Pure (W0.4Al0.6)C powder of about 1 mu m in diameter was sintered by the high pressure sintering (HPS) process without the addition of any binder phase. The microstructure, Vickers micro hardness and density versus the sintering time and temperature are well described. The most suitable sintering condition under pressure of 4.5 GPa is 1873 K for 8 min. Under this sintering condition, the hardness can reach 2295 kg mm(-2) and the relative density can reach 98.6%.

A novel and efficient route to Se nano/microstructures with controllable phase and shape

In this paper, we demonstrate a novel and efficient route by which the shape-controlled synthesis of t-Se nano/microstructures including nanowires, nanorods, nanobelts, microtubes, and flowers, as well as uniform spheres of a-Se, can be readily realized based on solution-mediated heat treatment with commercially available Se powders. X-ray diffraction (XRD), energy-dispersive X-ray spectra (EDS), Raman spectra, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were used to characterize the samples.

Size-controlled synthesis and characterization of quantum-size SnO2 nanocrystallites by a solvothermal route

By using ethylenediamine as both an alkali and ligand, quantum size SnO2, nanocrystallites were synthesized with a solvothermal route. The transmission electron micrographs (TEM) were employed to characterize the morphologies of the products. The crystal sizes of the as-synthesized SnO2 were ranged form 2.5 to 3.6 nm. The crystal structure and optical properties of the products were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, optical absorption spectra, photoluminescence and Raman spectra.