硅钨酸/TiO_2复合光催化材料光解水催化性能研究

采用浸渍法制备了复合杂多酸H4SiW12O40/TiO2光催化材料,并用XRD、FT-IR和UV-Vis-DRS研究了其结构形态,同时考察了H4SiW12O40/TiO2光催化剂对光解水制氧的应用研究。结果表明,H4SiW12O40/TiO2仍然保留Keggin结构,TiO2均匀固载在H4SiW12O40中,H4SiW12O40与TiO2之间仅仅是简单的物理吸附。在紫外光辐射下光催化分解水制氧的实验中,H4SiW12O40/TiO2的光催化析氧速率高达231.37μmol/(L.h),为纯H4SiW12O40的1.37倍。     

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.     

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。     

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。     

Influence of CsCl addition on the nanostructured voids and optical properties of 80GeS2-20Ga2S3 glasses

The influence of CsCl content on the void evolution in (80GeS₂-20Ga₂S₃)_100-x(CsCl)_x, x = 0; 5; 10; 15, chalcogenide glasses and changes of the optical response of these glasses due to CsCl addition are investigated. It is shown that structural agglomeration of voids occurs at addition and increasing of CsCl amount in base glasses. Supersaturation of GeS₂-Ga₂S₃-CsCl glasses by CsCl results in the contraction of void volumes in (80GeS₂-20Ga₂S₃)₈₅(CsCl)₁₅. By applying positron-positronium decomposition algorithm it was established that CsCl not only transforms voids in glass, but also forms new positron-trapping sites in Ge-Ga-S glassy matrix. Therefore, CsCl addition results in the shift of fundamental transmission edge in the visible region. It is shown that doping by larger concentrations of CsCl may lead to “supersaturation” of base glasses and that adding 10 mol% of CsCl is apparently an optimal doping level in view of further modification of glasses with rare-earth ions.     

Low-temperature solid oxide fuel cells with La1−xSrxMnO3 as the cathodes

La_1−xSr_xMnO₃ (LSM) has been widely developed as the cathode material for high-temperature solid oxide fuel cells (SOFCs) due to its chemical and mechanical compatibilities with the electrolyte materials. However, its application to low-temperature SOFCs is limited since its electrochemical activity decreases substantially when the temperature is reduced. In this work, low-temperature SOFCs based on LSM cathodes are developed by coating nanoscale samaria-doped ceria (SDC) onto the porous electrodes to significantly increase the electrode activity of both cathodes and anodes. A peak power density of 0.46 W cm⁻² and area specific interfacial polarization resistance of 0.36 Ω cm² are achieved at 600 °C for single cells consisting of Ni-SDC anodes, LSM cathodes, and SDC electrolytes. The cell performances are comparable with those obtained with cobalt-based cathodes such as Sm_0.5Sr_0.5CoO₃, and therefore encouraging in the development of low-temperature SOFCs with high reliability and durability.     

纳米粉体存在下的乳液聚合

综述了近年来关于纳米粉体存在下的乳液聚合的研究情况,讨论了纳米粉体存在下乳液聚合 的聚合机理、聚合场所和稳定性,并阐述了它的发展方向。     

XPS, TEM and SAD investigations of nanosized CoxByHz particles obtained by two different borohydride methods

The nanosized Co, B, H, particles synthesized by the ‘tea’ and ‘antigravity’ methods using a borohydride reduction process have been subjected to structure and composition studies by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and selected area diffraction (SAD). The amounts of the elements Co, B, O₂, H₂ and C as mean volume values, and surface values for the as-prepared particles, as well as after Ar⁺ etching to a depth of about 15 nm and 30 nm from the initial particle surface, are determined. About 1.5 atoms of cobalt per atom of boron correspond to samples obtained by the ‘antigravity’ method. The binding energy (BE) of 1s electrons of boron atoms has only one value. These particles are angular and are in the typical nanocrystalline state. In the case of samples prepared by the ‘tea’ method, two atoms of cobalt per atom of boron are found. The presence of two kinds of BE (B¹ and B¹¹) of 1s electrons of boron atoms in the particles obtained by the ‘tea’ method is observed and almost equal amounts of these two states are established in the spectrum. The particles' shape and structure are typical of the amorphous state. The fact that there is one peak when the ‘antigravity’ method is applied, in contrast to the two peaks with the ‘tea’ method indicates the presence of a metal amorphous state in the latter case.     

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.