Catalytic Oxidative Decomposition of Hydrazine in Vapor Phase over Nanosized Au/γ‐Al2O3

The catalytic activity of nanosized Au/γ‐Al₂O₃, synthesized by a deposition‐precipitation process, on oxidative decomposition of hydrazine in air is discussed. The catalyst exhibited an excellent activity at low temperatures. The activity was strongly dependent upon the gold cluster size. The impacts of certain pertinent operating parameters including the particle size of the catalyst, temperature, hydrazine concentration, and feed flow rate on the extent of the reaction were investigated. The results were reproducible with a mean absolute deviation of 3 %. Deactivation of the catalyst during the reaction was found to be unlikely. Finally, a kinetic model based on the Eley‐Rideal formulation was proposed for the reaction and a correlation was made between the data predicted from the model and those determined experimentally.     

NH3 adsorption and dissociation on a nanosized iron cluster

We employed spin-polarized density functional theory to study the bonding and dissociation of NH₃ and its fragment on a nanosized icosahedral Fe₅₅ cluster. The site-preference investigations, suggest that for NH₃, only the interaction perpendicular to the cluster is favorable (−0.37 eV < B.E.(NH₃) < +0.05 eV). Stable geometries of N and H on the high symmetry adsorption site of Fe₅₅ have been calculated as well. Both of these atoms have similar behavior: only the hollow or top sites are stable. Possible dissociation paths of the NH₃ to atomic nitrogen and hydrogen were identified. The calculated lowest reaction barrier for the overall process is 1.48 eV. The rate limiting step is the first hydrogen removal from the NH₃. Our results suggest that the catalytic activity of iron surfaces towards ammonia-like molecules is enhanched when the metal is in the nanostructured phase.     

Spray-drying technology for the synthesis of nanosized LiMn2O4 cathode material

Spinel LiMn₂O₄ cathode material has been synthesized by a spray-drying method for lithium ion batteries. During the entire process, the as-prepared powders were characterized using TGA/DTA, XRD, FTIR, SEM and TEM. The results showed that this method not only reduces the sintering time to 5 h at 750 °C, but also decreases the average particle size of LiMn₂O₄ powders to the order of nanometers. The electrochemical performance of nanosized LiMn₂O₄ was investigated by the galvanostatic charge-discharge tests. The data indicate that the nanosized LiMn₂O₄ has a specific capacity of about 130 mA h g^− 1 (1/5 C), and at higher rate (1 C), still has good cycling stability.     

纳米级二氧化锆的制备技术和表征手段

纳米二氧化锆是一种新型的高科技材料，有着广泛而重要的用途。本文根据国内外研制制备的最新进展及其发展趋势，综述了纳米级二氧化锆的制备技术及表征方法。     

电石渣制备纳米碳酸钙的初步研究

分别采用XRD和DTA/TG等手段,分析了电石渣的矿物组成和热行为。对电石渣代替石灰石制备纳米碳酸钙的技术进行了实验研究。结果表明,电石渣的主要成份是氢氧化钙。对电石渣采用水洗、过筛、干燥、煅烧等方式预处理后,可以代替石灰石用于制备纳米碳酸钙。经XD和TEM分析,所制得的纳米碳酸钙为球状方解石型,平均粒径为60nm。     

Influence of Zn^2＋ or Cu^2＋ on Reduction and Recalcination Behavior of Fe2TiO5

Fe2O3, TiO2, CuO and ZnO powders were mixed according to the formula of （1-x）TiO2 xCuO-Fe2O3 or （1-x）TiO2 xZnO-Fe2O3 （x=0, 0.2 0.4, 0.6, 0.8, 1）, and well ball-milled with H2O for 3 h to ensure homogeneity of the powdered solids, then fired at 1200℃ for 4 h. The fired samples were reduced at 500℃ with hydrogen gas. The reduced samples were subjected to recalcination at 500℃ in CO2 atmosphere. Both of fired, reduced and calcined samples were characterized by X-ray diffraction, vibrating sample magnetometry, reflected light microscopy and scanning electron microscopy. Different phases were formed after firing of Cu^＋2 or Zn^2＋ substituted Fe2TiO5. Magnetization （Bs） of the formed phases after firing are very low corresponding to diluted magnetic semiconductors （DMS） and increases with increasing the substituted cations （Cu^＋2 or Zn^2＋）. The reduction of the fired samples enhanced the Bs values whereas the reducibility increases with increasing the Cu^＋2 or Zn^2＋ content. Samples show different tendency toward CO2 decomposition which is very important for environmental minimization for CO2.     

硝酸氧化法氧化锡陶瓷材料的制备,掺杂与气敏性能

采用正交试验法研究了硝酸氧化法ＳｎＯ２陶瓷材料的工艺条件对ＳｎＯ２收率和环境的影响。用Ｘ射线衍射法测得了不同热处理温度下陶瓷材料的晶体结构,并计算了平均晶粒尺寸。研究了晶粒尺寸和贵金属掺杂对ＳｎＯ２气敏性能的影响,得到了ＳｎＯ２气敏陶瓷的优化工艺条件。     

Electrochemical investigation on silicon/titanium carbide nanocomposite film anode for Li-ion batteries

A Si/TiC nanocomposite film was synthesized by a surface sol-gel method in combination with a following heat-treatment process. The electrochemical properties of the film anode for lithium ion batteries were investigated by galvanostatic charge-discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectrum (EIS). Because of the homogeneous distribution of Si active particles in TiC matrix, the Si/TiC composite showed reversible lithium storage capacities of about 1000 and 1300 mAh g^− 1 at 160 and 80 mA g^− 1 even after 80 cycles, respectively. Using two-parallel diffusion path model, the reactive mechanisms of Li with Si/TiC composite film were interpreted. The chemical diffusion coefficients of the Si/TiC nanocomposite film at different electrode potentials were also discussed.     

Preparation of rare-earth carbonate nanosized particles monolayer by using potentiostatic technique

Gadolinium carbonate and samarium carbonate nanosized particles monolayers were prepared on copper grids coated with carbon film by using potentiostatic technique. The particles were obtained by homogeneous precipitation in aqueous solution by reaction with the thermal decomposition products of urea. The electrocatalytic activity of nanosized particle film was investigated.     

Low temperature synthesis of nanosized Mn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> ferrites and their characterizations

Nanosized Mn_1−x Zn _x Fe₂O₄ (x = 0, 0·1, 0·3, 0·5, 0·6, 0·7, 0·9) mixed ferrite samples of particle size < 12 nm were prepared using the co-precipitation technique by doping the Zn²⁺ ion impurities. Autoclave was employed to maintain constant temperature of 80°C and a constant pressure. The X-ray analysis and the IR spectrum analysis were carried out to confirm the spinel phase formation as well as to ascertain the cation distribution in the ferrite samples. This clearly points to the fact that the Zn²⁺ ion’s presence is not restricted to A-site alone for some of the Mn-Zn ferrite series. The real part of a.c. susceptibility measurements clearly indicated the superparamagnetic behaviour of the ferrite samples. There is a systematic decrease in the particle size, Curie temperature and magnetization with the increase in the Zn²⁺ ion doping, measured using magneto thermal gravimetric analysis (MTGA) and vibrating sample magnetometer (VSM), respectively. The lattice constant is found to be constantly decreasing till x = 0·6 and beyond this an unusual slight increase in the lattice constant is found.