Role of the Initial Formation of the Iron Nano-Particles in the Multi-Walled Carbon Nanotubes Growth Process

Careful preparation of the iron nano-particle catalyst for carbon nanotubes (CNTs) fabrication has crucial importance for initial growth of multi-wall carbon-nanotubes (MWCNTs). Thin iron layer was thermally deposited in a high vacuum onto the surface of the SiO2/Si wafer at about 300 K. The sample was heated up to 700℃ in a hydrogen atmosphere, and then the sample was heated once again at750℃ in ethylene atmosphere. After hydrogen treatment continuous Fe layer was changed into many well separated Fe nano-peaks. AFM, SEM and HR-TEM studies of deposited MWCNTs allow us to propose a growth mechanism for long, straight MWCNTs.     

纳米氧化铁粉体分散技术研究进展

阐述了纳米氧化铁粉体的团聚及分散原理 分散技术,指出了目前在制备纳米氧化铁粉体和分散技术中存在的问题,提出了建议和发展方向。     

电力变压器三维漏磁场及铁芯拉板涡流损耗的计算

应用双标量磁位的表面阻抗法计算了一台电力变压器的三维漏磁场,将计算的漏磁通密度和铁芯拉板的最高温升与测量值进行了比较,结果能满足工程设计要求。分析了铁芯拉板的宽度、开槽数及变压器负载电流对拉板涡流损耗的最高温升高的影响。     

钢铁制造工业中信息流的应用研究

新经济时代信息流已经应刖到各行各业,冶金工业也不例外,当代冶金企业的经营越来越全球化、无形化、网络化。冶金过程的信息流贯穿于工业结构优化,生产组织决策与管理及连续／准连续生产中信息的获取、处理、利用、反馈和存储等多个方面。文中还探讨了企业分层结构中各信息流的实现及信息流的发展方向。     

Removal of iron from milk of lime to produce pure precipitated calcium carbonate

ABSTRACT

Milk of lime (MOL) suspension is widely utilized in many industries; however, in some of the applications, such as the production of precipitated calcium carbonate (PCC), the suspension must be of high purity and quality. In other words, the amounts of iron and magnesium should be so little so that the final PCC product would be of high quality. The effects of initial temperature, quicklime particle size, amount of initial solid present, agitation rate, and time on the recovery of hydrated lime and iron/magnesium reduction efficiency were investigated through a central composite design (CCD) of experiments. The iron reduction efficiency and the weight recovery of hydrated lime were obtained as 91% and 98.5%, respectively. The reduction of magnesium was not significant in this stage. Moreover, approximately the whole existing SiO₂ was eliminated.     

黄钠铁矾渣及其浸取液中铁的测定

黄钠铁矾渣中铜的含量较高,用重铬酸钾容量法来测定其中的铁时,干扰铁的测定,需预分离才能准确测量。但在用铁还原法浸取黄钠铁矾渣后的浸出液中,由于部分铜被除去,铜的含量降低,不干扰铁的测定,无须预分离,直接测定。试验结果表明,当铜的含量占铁量的4%时,干扰铁的测定。     

MgFe2O4纳米复合氧化物的制备和气敏性能

用反滴定化学共沉淀法制备了纳米尺寸尖晶石型的复合金属氧化物MgFe2O4粉体.用X射线粉末衍射分析、透射电镜等手段研究了其结构特性.MgFe2O4粉体颗粒均匀,700℃煅烧1 h粉体平均粒径约为20 nm.研究表明煅烧温度对材料的结构及性能有较大的影响.以MgFe2O4纳米粉体为原料制备了旁热式气敏元件,测试了元件的敏感特性和响应恢复特性.结果显示,MgFe2O4是一种良好的n型半导体气敏材料,700℃煅烧1 h所得纳米粉体制作的元件在300℃工作温度时对CH3COCH3有较高灵敏度和良好的选择性,对体积分数为1 000×10-6的CH3COCH3的灵敏度可达36.87.并对气敏机理给予了解释.     

Development of slope mass rating system using K-means and fuzzy c-means clustering algorithms

Classification systems such as Slope Mass Rating(SMR) are currently being used to undertake slope stability analysis. In SMR classification system, data is allocated to certain classes based on linguistic and experience-based criteria. In order to eliminate linguistic criteria resulted from experience-based judgments and account for uncertainties in determining class boundaries developed by SMR system,the system classification results were corrected using two clustering algorithms, namely K-means and fuzzy c-means(FCM), for the ratings obtained via continuous and discrete functions. By applying clustering algorithms in SMR classification system, no in-advance experience-based judgment was made on the number of extracted classes in this system, and it was only after all steps of the clustering algorithms were accomplished that new classification scheme was proposed for SMR system under different failure modes based on the ratings obtained via continuous and discrete functions. The results of this study showed that, engineers can achieve more reliable and objective evaluations over slope stability by using SMR system based on the ratings calculated via continuous and discrete functions.     

铸件中缩孔缺陷成因分析

通过对铸铁材料的概述，详细分析了铸件中常见缺陷——缩孔的特征、危害以及形成原因，从而探讨抑制此类缺陷的对策。