Initial stages of the high-temperature corrosion of commercial Fe-Cr-Ni alloys in a carburizing atmosphere of low oxygen partial pressure

The early stages of corrosion of AISI 314, HK 40, and Alloy 800H have been studied in a strongly carburizing (a_C=0.8), weakly oxidizing atmosphere at 1098 K. Samples with electropolished and cold-worked surfaces were exposed for up to 400 min. at temperature, in a conventional corrosion rig or in a reaction vessel which was installed within an X-ray photoelectron spectrometer. The latter facility allowed the effects of the specimen heating rate and the rat of gas flow to be investigated. Examination of the corrosion products was accomplished with the aid of XPS, SEM, TEM, and conventional metallography. Initially, surface layers comprised of -Cr₂O₃, (Mn, Cr)₃O₄, and SiO₂ formed, with layer structure, microstructure, and composition being functions of alloy composition and surface condition. Only on the cold-worked surfaces did a well-developed duplex oxide, consisting of an outer, Cr-rich oxide layer and an inner, SiO₂ layer, form. In good agreement with the predicted value of 1.9 wt.%, between 1.4 and 2 wt.% Si in the alloy was required to form a complete SiO₂ layer. After an incubation period, -Cr₂O₃ became unstable and transformed to M₇C₃; the carbides then grew by diffusion of metal from the alloy substrate. The presence of manganese, as (Mn, Cr)₃O₄, in the surface oxide influenced the mode of carbide growth, whereas the rate of carbide growth was severely suppressed by a continuous SiO₂ layer which acted as a diffusion barrier both to metal and to carbon. It is argued that the SiO₂ layer is most effective in reducing carburization when it is free from or contains very few structural defects.     

Surface modification of spherical LiNi1/3Co 1/3 Mn1/3O2 with Al2O3 using heterogeneous nucleation process

To improve the cycle stability at high voltage and high charge/discharge rate, spherical LiNi1/3Co1/3Mn1/3O2 was coated with Al2O3 by using heterogeneous nucleation process, and the physical and electrochemical properties were studied. The SEM images show that there is a uniform coating on the modified spherical LiNi1/3Co1/3Mn1/3O2. The electrochemical tests indicate that the properties of LiNi1/3Co1/3Mn1/3O2 coated with 0.5% aluminum oxide are the best. The initial capacities are 150 and 173 mA.h/g at the rate of I C in the voltage range of 2.7-4.3 V and 2.7-4.6 V, respectively, and the discharge capacities maintain about 99% and 85% after 30 cycles, respectively. While those of the bare LiNi1/3Co1/3Mn1/3O2 are only 90% and 75%, respectively. The CV tests of LiNi1/3Co1/3Mn1/3O2 show that Al203-coating can restrain the oxide-reduction peak currents fading during the charge/discharge course.     

铸造／热压Pr—Fe—B磁体的矫顽力及其与晶粒尺寸关系

研究了铸造/热压 r_(19)Fe_(74.5)B_5Cu_(1.5)永磁体的磁硬化特点.发现磁体反磁化过程受反向畴的形核控制.矫顽力与晶粒尺寸的对数存在线性关系: _iH_c(MA/m)=1.7312—0.4816Ind(μm)根据反向畴形核的随机性和矫顽力的统计特性讨论了该式的物理意义。     

液态金属快速结晶的热力学驱动力

采用超高真空无容器悬浮熔炼技术使液态Ｆｅ和Ｎｉ的过冷度分别达２００和２３５Ｋ，借助量热法测定出其比热各为４８．６和４０．５Ｊ·ｍｏｌ~（－１）·Ｋ~（－１）．据此精确计算出深过冷Ｆｅ和Ｎｉ快速结晶的热力学驱动力△Ｇ_（ＬＳ），并与Ｔｕｒｎｂｕｌｌ模型和Ｄｕｂｅｙ－Ｒａｍａｃｈａｎｄｒａｒａｏ模型的近似计算结果相比较，发现这两种近似模型在过冷度超过１００Ｋ时均产生大于１％的偏差．进一步分析发现，△Ｇ_（ＬＳ）的计算偏差对深过冷液态金属中晶体形核率的影响极大，因此快速凝固研究中应尽可能精确计算△Ｇ_（ＬＳ）．     

基于VC++的金属凝固过程微观组织演变的可视化研究

以Al-4%Cu合金为例，利用热焓法处理结晶潜热，再根据相变热传导的等效热容法有限元理论，求解了该合金凝固过程的温度场分布；结合连续形核模型和枝晶尖端生长的动力学模型，进行了温度场与晶粒组织形成过程的耦合模拟；通过调用VC＋＋的图形设备接口函数库和设备环境功能，实现了晶粒形成过程的计算机可视化。     

脉冲电流对Sn—Pb合金凝固组织的影响

研究了脉电流流对Ｓｎ－１０％Ｐｂ合金凝固组织的实验，实验表明，粗大的富Ｓｎ树枝状初晶细化成近球状结构，提出了一个脉冲电流对凝固组织影响的唯象机制，用经典的均匀形核理论和电动力学理论导出了脉冲压力与脉冲电流之间和成核率与脉冲压力之间的关系，脉冲电流产生的大小不同的脉冲压力对晶核的形成和长大产生不同程度的影响是导致不同观测结果的基本原因。     

基于防冰专项管理平台及手持终端的输电线路覆冰观测与应用

针对贵州电网输电线路覆冰现状及目前线路观冰存在数据上报不及时、数据收集整理难等主要问题,引入了基于防冰专项管理平台及手持终端的输电线路覆冰观测思路,通过建立防冰专项管理平台、建立移动专线网络通道、固化覆冰数据收集及计算模板,以移动式手持终端为载体,实现现场观冰基础数据直接调用、现场覆冰数据填写、覆冰照片拍摄、现场自动计算覆冰厚度及覆冰比值、现场观冰数据实时上传及后台覆冰数据统计分析等管理,大大提高了输电线路现场观冰工作效率。     

亚微米碳化硅粉末的制备

采用硅酸乙脂和酚醛树脂为原料,合成了具有高混合度的Ｃ／ＳｉＯ２混合物。高温碳热反应后,得到亚微米级的球状粉末,并且粉末粒度分布范围小。本文对碳热反应中一氧化硅的损失作了定量分析。结果表明,较高Ｃ／ＳｉＯ２比导致较低一氧化硅损失和较高的碳化硅产量。在１５００℃反应后,Ｃ／ＳｉＯ２＝３时,一氧化硅的损失达约２０％。而当Ｃ／ＳｉＯ２＝５时,损失＜５％。较高的Ｃ／ＳｉＯ２比对碳化硅的形成速度有明显的促进作     

考虑灰色关联权重的PSO-LSSVM输电线路覆冰厚度预测模型

为了提高输电线路覆冰厚度预测精度,利用灰色关联分析确定覆冰影响因素对输电线路覆冰增长量的影响权重,采用PSO算法对LSSVM的参数优化,建立了考虑灰色关联权重的PSO-LSSVM输电线路覆冰厚度预测模型。采用实际运行线路的覆冰增长数据进行仿真分析,并与其他覆冰预测模型对比,考虑灰色关联权重的PSO-LSSVM输电线路等值覆冰厚度预测模型的均方根误差、平均相对误差和全局最大误差分别为0.575、3.124%和4.015%,均小于其他三种预测模型,验证了模型的正确性和实用性。     

Targeted Nanoparticle Thermometry: A Method to Measure Local Temperature at the Nanoscale Point Where Water Vapor Nucleation Occurs

An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water. The average nucleation temperature for water without gas is 560 K but this temperature is lowered by 100 K when gas is introduced into the water. The authors are able to measure the temperature inside the bubble during bubble formation and find that the temperature inside the bubble spikes to over 1000 K because the heat source (optically‐heated nanorods) is no longer connected to liquid water and heat dissipation is greatly reduced.