Properties and Photoelectrocatalytic Behaviour of Sol-Gel Derived TiO2 Thin Films

Titanium dioxide (TiO₂) thin films have been prepared on indium doped tin oxide (ITO) glass by sol-gel dip-coating method. Properties of the films were determined as a function of heat-treatment by X-ray diffraction, scanning electron microscopy and photoelectrochemical tests. The films heat-treated at higher temperatures show better crystallinity and photoresponse. The microscopic structure on the film after heat-treatment is attributed to the incorporation of organic polymer into the precursor solution. The performance of the electrodes treated at different temperature on photoelectrocatalytic degradation of methyl orange was investigated. The effect of applied potential and the ability of the electrode to be repeatedly used in photoelectrocatalytic degradation were also evaluated.     

Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction

The pyrolyzed carbon supported ferrum polypyrrole(Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid(TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction(ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry(CV) and rotating disk electrode(RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of-1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction(XRD), scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C–Sn–C, an additional beneficial factor for the ORR.     

Magnetic domain structures of precipitation-hardened SmCo 2：17-type sintered magnets： Heat treatment effect

The typical magnetic domains of Sm（CObalFe0.25Cuo.07Zr0.02）7.4 magnets quenched through various heattreatment steps have been revealed by using magnetic force microscopy （MFM）. For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered magnet to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain （so-called interaction domain） is a characteristic magnetic domain pattern of the SmCo 2：IT-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk SraCo 2：17-type sintered magnets.     

二氧化钛微晶结构相变与光致发光

以钛酸四丁脂为前驱体制备了二氧化钛(TiO₂)胶体,将其粉末在不同温度下作热处理,采用差热分析、X射线衍射、荧光光谱等手段对样品进行测试。结果表明,随着热处理温度升高,TiO₂由板钛矿相经锐钛矿相向金红石相转变,在808℃左右出现一级相变。原始粉末样品以及在600℃以下热处理的样品,在400nm处可观察到TiO₂纳米晶的带边发光,在470nm处可观察到表面态发光;当热处理温度达到850℃时,主晶相转变为金红石相,400nm处的带边发光峰消失,位于470nm处发光峰成为最强峰,但强度减弱,并且样品发光的波长范围明显变窄。其原因是,随着热处理温度升高,晶粒不断长大,量子限域效应减弱乃至消失,晶粒的表面状况发生变化,导致样品的荧光发射行为发生变化。     

二氧化锡纳米粉末的热处理与微结构

采用溶胶－凝胶法制得了二氧化锡干凝胶粉体，并在不同温度下热处理得到不同粒径的二氧化锡纳米级超微粉，采用热重法和差热分析，Ｘ－射线粉天衍射，透射电镜等方法观察了不同温度热处理后纳米粉体的途径，形貌，聚集状态等的变化。     

晶粒边界对Nd2Fe14B/α-Fe纳米复合材料性能的影响

用快淬急冷技术制备了Nd₁₀Fe_84-xB₆In_x(x=0和1)系列薄带磁体.利用添加和挥发微量In元素的方法从宏观表现上研究了晶粒边界对晶粒之间交换耦合和磁硬化等性能的影响.发现晶粒边界性质以不同方式影响着磁体矫顽力和剩磁比.某些晶界特性,像缺陷、应力等主要影响磁硬化机制;而另外一些性能,如晶界类型、边界处的自旋取向及结晶学相关性等则控制着交换耦合的强度. 关键词： 晶界 纳米复合材料 热处理 微量添加     

MORPHOLOGICAL AND MICROSTRUCTURAL CHANGES DURING THE HEATING OF SPHERICAL CALCIUM ORTHOPHOSPHATE AGGLOMERATES PREPARED BY SPRAY PYROLYSIS

1. Introduction Calcium phosphates, e.g., hydroxyapatite (Ca10(PO4)6(OH)2HAp) and calcium orthophosphate (Ca3(PO4)2), are wellknown to be suitable bone and tooth implant materials(Jarcho et al., 1979; Hench, 1998). For example, the po-rous form of HAp has been used as a bone substitute forbiological fixation, whereas the dense form has applica-tions including space filler for bioactive fixation (Hench,1998; Metger et al., 1999). In the case of Ca3(PO4)2, twophases exist, namely α and…     

燃煤电站锅炉颗粒Hg形态及其释放动力学参数

采集了一台320 MW机组锅炉在三个过量空气系数下的飞灰样品,将采集的飞灰筛分为四个粒径,测定了各飞灰样品的含炭量;对各飞灰样品进行两种加热方式的热处理,利用LUMEX全自动测汞仪测定了处理前后各飞灰样品的汞含量。根据飞灰中汞随温度的释放规律确定了飞灰中汞的形态,对加热过程颗粒Hg释放动力学参数进行了计算。测试与分析结果表明,粒径小的灰颗粒中汞浓度较高;过量空气系数增加后,飞灰含碳量降低,但飞灰中汞随过量空气系数的变化随粒径的不同有所不同;飞灰中含汞化合物的主要形态为HgCl₂和HgS,过量空气系数增加,飞灰中HgCl₂比例减少,HgS比例增加,HgO与HgSO₄的比例基本不变。停留时间是影响颗粒Hg生成的关键因素。过量空气系数越大,灰颗粒Hg释放的活化能就越大,大颗粒飞灰Hg释放活化能相对较大。     

后热处理对304不锈钢激光熔覆Ni60/h-BN自润滑耐磨复合涂层组织和摩擦学性能的影响

采用激光熔覆技术在304不锈钢表面制备了Ni60/h-BN自润滑耐磨复合涂层,对涂层在600℃(去应力退火)进行1 h和2 h热处理,分析了热处理前后复合涂层的显微组织、硬度和摩擦学性能的变化.结果表明:三种涂层中,热处理1 h后涂层的显微硬度最大(最高值HV0.5765.0),在10 N干摩擦条件下,其摩擦系数为0.39,磨损率为3.37×10~(–6)mm/(Nm),该涂层表现出最好的耐磨减摩性能,磨损机理主要表现为轻微的磨粒磨损;未热处理的涂层摩擦系数为0.53,磨损率为6.39×10~(–6) mm/(Nm),磨损机理主要表现为脆性断裂、黏着磨损和磨粒磨损;热处理2 h后的涂层摩擦系数为0.39,磨损率为5.29×10~(–6)mm/(Nm),磨损机理主要表现为磨粒磨损和轻微黏着磨损.在本文试验条件下,后热处理1 h可有效提高激光熔覆自润滑耐磨涂层的硬度并改善其耐磨减摩性能.     

Effects of heat-treatment on electrochemical behavior

The polyacenic semiconductive (PAS) material is a typical amorphous carbon prepared by pyrolysis of phenolformaldehyde resin, and is actually utilized as anode of high-capacity rechargeable batteries. In this work, change in the discharging amount of Li⁺ before and after heat-treatment of the PAS electrodes at the various doping level was examined in detail. As a result, the doped Li can be classified into two types: (i) heat-resistant Li-dopant (or Li-dopant with high diffusion coefficient) and (ii)heat-fragile Li-dopant (or Li-dopant with low diffusion coefficient). The latter Li-dopants are generated above the doping level of 30% ([Li]/[C]→0.3) and is considered to be the origin of high-capacity of PAS anode compared with that of graphite anode. This aspect is also supported by the ESR, ⁷Li-NMR, and XPS observation results. This revised version was published online in August 2006 with corrections to the Cover Date.