Effect of bismuth replacement at barium site in Y-Ba-Cu-O system

X-ray diffraction, electron paramagnetic resonance, microwave absorption and resistivity measurements were carried out on YBa_2−x Bi _x Cu₃O₇ (0≤x≤0·5) superconductors in order to study the effect of bismuth on the structural and superconducting properties. A decrease in sintering temperature increased the amount of impurity phase. Transition from an orthorhombic (superconducting) phase to tetragonal structure produced no significant change in EPR zero-field signal at liquid nitrogen temperature (LNT). The non-resonance signal height decreased on higher concentration of bismuth. Sintered YBa_2−x Bi _x Cu₃O₇ superconductor had a strong EPR zero-field signal at LNT. We have evaluated particle size from XRD and EPR studies. The average particle size was about 0·4μm.     

电炉钢外来夹杂控制的研究

介绍了夹杂物的来源,包括内生夹杂和外来夹杂,着重于二次氧化产物、卷渣、内衬侵蚀.同时介绍了鄂钢电炉厂在冶炼和连铸过程中控制夹杂物的操作实践.     

含杂质流体的流量测量

结合工程实例.介绍了几种实用的含杂质流体的流量测量方案,供自动化仪表设计及维堆护人员参考。     

催化裂化干气回收乙烯用于制备环氧乙烷的研究

叙述了在YS型银催化剂作用下，利用催化裂化干气回收的乙烯制备环氧乙烷的实验研究。结果表明：在银催化剂上催化氧化生成环氧乙烷的过程中，使用回收的乙烯，催化剂的初选择性可达80％；在保持环氧乙烷时空产率不变，经过2000h催化剂稳定性试验后，选择性下降了3—4个百分点，反应温度上升约10℃，与用聚合级乙烯为原料进行比较，催化剂初选择性低2—3个百分点、稳定性略差。该结果为用回收乙烯生产环氧乙烷提供了试验依据。     

ERD facility for analysis of hydrogen and deuterium in solids

Hydrogen is the lightest element in nature, and so, its detection and quantitative analysis is difficult by the conventional methods utilized for other elements. In the recent years the technique of elastic recoil detection analysis (ERD) using 1–2 MeV He⁺ beam has been developed to quantitatively and simultaneously analyze hydrogen and its isotopes in solids. Such a facility has been set up using the 2 MeV Van-de-Graaff accelerator at IIT Kanpur. It facilitates H and D analysis in a material up to a depth of ∼ 1μm with a detection sensitivity of 0·1 at.% and depth resolution of about 300 ?. The application potential of this setup is illustrated by presenting the results of measurements performed on Al:H:D systems prepared by plasma source ion implantation and highT _c YBCO pellets exposed to humid atmosphere.     

Hydrogen incorporation in Ni–P films prepared by electroless deposition

Electroless NiP films, with 12 to 16 wt % P, were deposited from a moderately acid solution. Thermogravimetric analysis indicates the presence of occluded hydrogen in the layers, which desorbs upon heating. The amount of incorporated hydrogen decreases when the pH of the solution or the nickel sulfate concentration is increased; by contrast it increases with hypophosphite concentration. Cyclic voltammetry, using an electrochemical quartz crystal microbalance, confirms the existence of parasitic reactions, namely the reduction of protons of the solvent during the cathodic process and oxidation of hydrogen during the dissolution of the layers. This behaviour is in qualitative agreement with the proposed reaction scheme.     

杂质元素对金属镝压缩强度的影响

研究了金属镝中所含Ｓｉ、Ｃａ、Ｆｅ和Ｏ４种杂质元素对其压缩力学性能的影响。结果表明，Ｓｉ元素和Ｏ元素含量的增加会降低镝的压缩强度，与此同时，其塑性也有明显地降低。金属镝中所含Ｃａ元素和Ｆｅ元素对其压缩强度的基本没有影响。     

非掺杂InP的低温光致发光研究

研究了2K低温下非有意掺杂InP单晶的光致发光谱,对近带边的辐射跃迁进行了仔细分析,报道了InP单晶在大功率光激发时束缚于中性施主的激子跃迁发光相对减弱、而束缚于中性受主的激子跃迁发光相对增强的现象,并探讨了其机制,确认了材料中存在Mg、Zn等残余受主杂质,并计算得到Mg受主的离化能为41.5meV.     

硅铁生产中杂质元素的控制

分析了硅铁生产中Al、Ca、C、Ti等主要杂质元素的来源，并相应采取精料入炉、炉外精炼、重熔和控制浇铸温度等方法进行控制，在降低硅铁杂质含量上取得较好效果。     

Effect of Hydrogen Heat Treatment on the Chemical Composition of Aluminum Nitride Powder

The effect of hydrogen heat treatment on impurity contents in aluminum nitride powder of different fineness is studied. Thermodynamic calculations are provided pointing to the possibility of forming gaseous hydrogen compounds with impurity elements. It is established that as a result of treatment the contents of impurity elements, i.e. oxygen, carbon, sulfur, are reduced by a factor of 3-13. The optimum hydrogen heat treatment regime is determined: a temperature of 1323 K and an exposure time of 30 min.