纳米CeO2单晶的制备与热处理对粒径的影响

以Ce(NO3)3·6H2O为铈源、NH3·H2O为沉淀剂,用化学沉淀法通过对陈化时间的控制,制备了单分散的单晶纳米CeO2粒子,并用XRD、TEM、ED、BET、TG-DTA等测试手段对产物的物相结构、形貌和纳米尺度进行了表征.XRD分析表明,制得的纳米CeO2粒子为萤石结构且晶型比较完整. 通过控制热处理的温度和陈化时间可以控制粒子的大小.TEM和ED分析表明产物颗粒基本为球形,分散性较好且为单晶. 通过TG-DTA结果可以断定所制备的前驱体结构式为CeO2·1/2H2O.     

蠕墨铸铁生产中蠕化率的控制

讨论炉料、化学成分、蠕化剂质量、处理后包内保留时间和温度对蠕墨铸铁蠕化率的影响。介绍如何控制、检测蠕化率，并对如何防止蠕化衰退提出建议。实践表明，蠕化率可以稳定在55％-85％的范围内。     

Thermal spray vitrification process for the removal of lead-based paint from steel structures: An applications note

Lead-based paints and primers have long been used to protect steel structures from corrosion, but are now recognized as environmental hazards. During lead-based paint removal via abrasive blasting, federal, state and local environmental requirements mandate the use of containment structures to prevent contamination of air, soil, or water. The thermal spray vitrification (TSV) process was developed and optimized in laboratory experiments to remove hazardous lead-based paint. TSV consists of thermal spraying a molten glass onto the painted surface. As the glass strikes the substrate, it reacts with the paint, and organic components are pyrolyzed, while lead ions are trapped on the glass surface. Quenching stresses in the glass cause it to crack and spall off the substrate. The resulting glass fragments are collected, and further remelted to completely immobilize lead (Pb) ions in the glassy iron (Fe) silicate matrix. The glass waste is thus rendered non-hazardous, as determined by the Toxicity Characteristic Leaching Procedure (TCLP). The TSV process was field tested on a fire hydrant, using minimal personal protective equipment and without using a containment structure. The lead-containing paint was removed, without producing hazardous waste, leaving de-painted surfaces suitable for repainting.     

Effects of carbon content and solidification rate on thermal conductivity of grey cast iron

The thermal conductivity or diffusivity of pearlitic grey irons with various carbon contents is investigated by the laser flash method. The materials are cast in controlled thermal environments and produced in three dissimilar cooling rates. The cooling rate together with the carbon content largely influence the thermal conductivity of grey iron. Linear relationships exist between the thermal conductivity and the carbon content, the carbon equivalent and the fraction of former primary solidified austenite transformed into pearlite. The work shows that optimal thermal transport properties are obtained at medium cooling rates. Equations describing the thermal conductivity of pearlite,solidified as pre-eutectic austenite, and the eutectic of grey iron are derived. The thermal conductivity of pearlitic grey iron is modeled at both room temperature and elevated temperature with good accuracy.     

Effect of heat treatment on thermal stability of Ti40 alloy

Five new heat treatment processes were designed, which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500, 550℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments, and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes, the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature, some defects and uneven grain boundaries are remained, which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃for 4 h is recommended the best heat treatment process for Ti40 alloy.     

Effect of particle size on thermo-physical properties of SiC_p/Cu composites fabricated by squeeze casting

For the electronic packaging applications, copper matrix composites reinforced with different sized SiC particles (10 μm, 20 μm and 63 μm) were fabricated by squeeze casting technology. And the effect of particle size on their thermo-physical properties was discussed. The composites are free of porosity and the SiC particles are distributed uniformly in the composites. It is found that the mean linear thermal expansion coefficients(20 - 100 ℃ ) of SiCp/Cu composites are in the range of (8.4 - 9.2) × 10-6/℃, and smaller expansion coefficient can be obtained for the composites with finer SiC particles because of the larger restriction in expansion through interfaces. Their thermal conductivities are reduced with the decrease of SiC sizes. This is attributed to the fact that the negative effect of interfacial thermal resistance becomes increasingly dominant as the particles becomes smaller.     

TiAl ALLOYS PREPARED BY THERMAL EXTRUSION OF ELEMENTAL POWDER MIXTURES

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车轮的热烈和磨损机理与抗热裂耐磨车轮的研制

本文研究了车轮踏面的热裂和磨损机理,结果表明,车轮热裂主要与其含碳量和硬度有关;在使用合成闸瓦时,车轮踏面的磨损率与新形成的“白层”(马氏体)的断裂韧性有关。研制的抗热裂耐磨车轮(55SiMn)取得了明显的运用效果。     

Formation of texture of Ni48Mn31Ga21 polycrystalline alloy by thermal simulation pack rolling technology

1 Introduction Heusler type Ni2MnGa magnetic shape memoryalloy, which is a new kind of functional material withferromagnetism and thermoelastic martensitictransformation, attracts the interests of many people allover the world in recent years. The alloy …     

喷涂距离对热障涂层拉伸强度的影响

用等离子喷涂方法，在不同的喷涂距离（d）下制备出ZrO2陶瓷涂层，通过涂层的拉伸实验、X射线衍射和扫描电镜分析，研究了喷涂距离对涂层拉伸强度（σ）的影响规律。结果表明：d=70、80mm时，σ较高，最高可达9．14MPa；d〈70mm时，粘接层的氧化明显加剧，热生长氧化物的量明显增加，降低了ZrO2涂层与粘接层之间的结合强度，导致σ下降；d〉80mm时，随着喷涂粒子的速度降低，撞击到喷涂表面后不能完全铺展，导致σ下降。