A comparative study of the gas sensing behavior of nanostructured nickel ferrite synthesized by hydrothermal and reverse micelle techniques

A comparative study of gas sensing behavior of nanocrystalline nickel ferrite synthesized by micro-emulsion and hydrothermal method to liquefied petroleum gas (LPG) is presented. Nanocrystalline nickel ferrite synthesized by hydrothermal method indicated higher electrical conductivity and gas sensitivity at low operating temperature compared to nanocrystalline nickel ferrite synthesized by reverse micelle technique. This difference in the gas sensing behavior can be attributed to the presence of more oxygen vacancies (i.e. non-stoichiometry) in the hydrothermally synthesized nickel ferrite. Incorporation of palladium had a catalytic effect and the operating temperature was significantly reduced in both the samples. The higher operating temperature of the reverse micelle nickel ferrite material makes the sensor response speed faster (∼10 s) compared to the hydrothermally synthesized material (∼1 min).     

Synthesis of LiFePO4 with fine particle by co-precipitation method

LiFePO₄ is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO₄ because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe²⁺ in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO₄ is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO₄ fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property.     

Electrical conductivity and gas sensitivity of Zn-Sb-O thick films

The thick film of Zn-Sb-O was prepared by coating the paste of nanoparticles mixture (Sb₂O₃:ZnO=1:3) on the alumina substrate, followed by sintering at 500-900 °C for 2 h in air. The electrical resistance and gas-sensing properties to benzene, alcohol and acetone of Zn-Sb-O films were found to be dependent on the change of phase structure caused by sintering temperature.     

Preparation of Plate Fe_(60)Co_8Zr_(10)Mo_5W_2B_(15) Bulk Amorphous Alloy and Its Fracture Toughness

1Introduction Duwez[1]synthesizedthefoilAu Siamorphousalloyforthefirsttimewithrapidsolidification,whichinitiatedthepreparationofamorphousalloysintheprocessofalloysolidification,andthereaftertheresearchonamorphousal loysdevelopedrapidly.Since1980s,withthec…     

Grain growth kinetics in Dy-doped Bi0.5Na0.5TiO3 ceramics

Dysprosium-doped bismuth sodium titanate ceramics were prepared using the conventional mixed-oxide method. The amount of dysprosium used was varied from 0 to 2 at.%. The mixed powders were calcined at 800 °C and checked for phase purity using X-ray diffraction technique. The calcined powders were then cold-pressed into pellets and sintered at 1050 °C for the time ranging from 2 to 48 h. The ceramics were checked for phases and microstructures using an X-ray diffractometer and a scanning electron microscope, respectively. The analysis showed that undoped BNT ceramics sintered at longer time exhibited a significant grain growth with non-uniform grain size distribution and shape. The Dy-doped BNT however showed a much more limited grain growth behavior, resulting in smaller grain size and more equiaxed grain shape. It was also found that all Dy-doped BNT ceramics sintered at 48 h possessed lower porosity than those sintered for shorter time.     

Effects of compressive and tensile stress on the growth mode of epitaxial oxide films

Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO₃/SrTiO₃ (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO₃ with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO₃ films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress.     

微型生化分析仪样品室温度控制系统研究

结合微型生化分析仪样品室的要求,设计了一种基于单片机的微型生化分析仪样品室温度控制系统.它以AT89S51为核心,采用单总线高精度数字温度传感器DS18B20对样品室温度采样,同时利用汇编语言编写温度设定与控制程序,采用半导体制冷的方式,实现了温度在25℃、30℃、32℃和37℃四个温度值的稳定,控制精度达±0.5℃.     

Preparation of one-dimensional polymer films by modification of a hydroxymethylbenzene self-assembled monolayer on iron with alkyltriethoxysilanes for preventing iron corrosion

A self-assembled monolayer (SAM) of p-hydroxymethylbenzene HOCH₂C₆H₄ - (HOMB) moiety adsorbed on iron by the formation of a covalent bond between carbon and iron atoms was prepared by electrochemical derivatization of an iron electrode with p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH₂C₆H₄N₂BF₄. The electrode covered with the HOMB SAM was modified with alkyltriethoxysilanes C_nH_2n+1Si(OC₂H₅)₃ (C_nTES, n = 8 or 18) to prepare a film of one-dimensional polymer. The protective ability of the polymer film was determined by polarization measurement of the covered electrode in an aerated 0.5 M NaCl solution. The ability was enhanced by modification of the HOMB SAM with C_nTES markedly. The iron surface coated with the one-dimensional polymer film of the HOMB SAM modified with C₈TES was characterized by contact angle measurement and FTIR reflection and X-ray photoelectron spectroscopies. The persistence in the protective ability of the polymer film against iron corrosion in 0.5 M NaCl may be associated with the strong adsorption via the covalent bond, revealed by electron-probe microanalysis.     

Irving B. Harris: A Legacy of Vision and Generosity.

Presents a brief tribute to Irving B. Harris upon his passing. Harris played a central role in launching the Harris School of Public Policy Studies and the Center for Human Potential and Public Policy at the University of Chicago. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

VSC8150在波分复用系统开销提取中的应用

波分复用系统将不同波长的光复用在一起进行传输,以满足对传输容量和传输距离的各种需求。介绍了一种开销监视与提取的设计方法,使用VSC8150提取承载在波分复用系统相应波长上SDH信号的开销。分析了VSC8150的工作原理,管脚和外部接口,以及与FPGA、单片机共同完成B1重新计算,开销提取,B1,J0提取。此外,还提出将帧丢失,帧失步等错误状态传送给单片机和网管的方法。本设计增强了波分复用系统网管管理参数,功能和灵活性,这会在系统维护时带来较大的方便。该设计已经成熟应用在实际的波分复用系统中。