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.     

颗粒表面改性法制备PTC粉体的研究

本文介绍了一种通过液相颗粒表面改性技术添加二次掺杂物来制备ＰＴＣ粉体的新方法。即将烧结助熔剂Ａｌ２Ｏ３，ＳｉＯ２以及受主杂质ＭｎＯ采用溶液形式，包裹在ＢａＴｉＯ３基粉体颗粒表面进行改性，由此可以得到二次掺杂物Ａｌ２Ｏ３、ＳｉＯ２和ＭｎＯ分布均匀的ＰＴＣ粉体。     

50kg／m钢轨轨底缺陷的检验和分析

钢轨轨底缺陷有三种：底伤、结疤和底裂缺陷。取２０根有底缺陷５０ｋｇ／ｍＵ７１Ｍｎ钢轨做试样，通过低倍、断口、金相检验和扫描电能谱分析，详细描述了轨底缺陷的宏观和微观特征，研究出钢轨轨底缺陷出现的规律臁其产生的原因。通过对比试验，发现淄博１号保护渣有利于改善钢锭表面质量，提高钢轨一级品率。     

New Ferro Powder for Selective Laser Sintering of Dense Parts

The paper describes a new powder composition specially developed for selective laser sintering (SLS). The aim is to obtain a ferro powder that can be sintered without need for a (sacrificial) polymer binder and that results in quasi dense parts that do not need any post-processing like furnace sintering, infiltration or HIP. The powder is a mixture of different types of particles (Fe, Cu, Ni and Fe₃P). The composition and mixture ratio are justified by using phase diagrams. The powder has been tested using an own developed Nd: YAG SLS machine. The influence of process parameters (laser power, scan velocity, scan spacing and scan strategy) and the microstructural characteristics have been investigated. Attention is devoted to the binding mechanism (liquid phase sintering, through melting) and to the quality of resulting parts (density, balling effect,…).     

佛尔哈德法测定氯化除汞上清液中的氯量

控制pH4-6，用锌粉还原氯化除汞上清液中的汞（Ⅱ）离子，取置换后液加入过量的硝酸银标准溶液，以硫酸铁铵溶液作指示剂，用硫氰酸钾标准滴定溶液滴定来测定氯量。该方法的检出限：0．25mg／100mL，回收率：98％-101％。     

Optimal Conditions for Preparing Ultra-Fine CeO2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor (SCISR) from Ce(NO3)3·6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide (CeO2) powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce(NO3)3 and NH4HCO3 solutions were 0.25 and 0.3 mol·L-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g·L-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r·min-1, 80 ℃, 20 min, 5～6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8～2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point group was O5H-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor (STR).     

Advances in titanium metal injection molding

The approaches to production of titanium powder injection molded parts are reviewed. Historically, oxygen levels have been too high for structural use (particularly with the Ti-6Al-4V alloy). However, recent advances in starting powders, binders and sintering facilities now allow oxygen levels in the Ti-6Al-4V alloy to be controlled to about 0.2 wt.% oxygen. This should result in significant expansion of the titanium PIM market place into aerospace, automobiles, surgical instruments, dentistry, communication devices (such as computers and cell phones), knives and guns. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 5–6 (455), pp. 118–125, 2007.     

Preparation of ultra fine nickel-copper bimetallic powder for BME-MLCC

The preparation of ultra fine nickel-copper bimetallic powder with two-stage chemical reduction method was investigated. Reductive sugar and hydrazine hydrate were employed as reducing agent in different reductive stage, respectively. Reaction of CuSO₄·5H₂O with reductive sugar at 70 °C gives cuprous oxide and copper particles, then as-prepared mixture and nickelous hydroxide were reduced by hydrazine hydrate, and nickel-copper powder having excellent dispersibility was prepared. Influences of nickel added on composition and dispersibility of powder were studied. TG/DTG/DTA of nickel-copper powder, which is stable in room temperature, were discussed with thermal analyzer. Relation of nickel content to oxidation temperature was investigated. Ni-Cu bimetallic powder particles have a fully coated structure when nickel content is up to 30%. As-prepared nickel-copper powder was applied in base metal electrode-multilayer ceramic capacitor (BME-MLCC). The end termination has high adhesion force, fairly good densification, low resistivity, excellent solderibility behavior and resistance behavior to soldering.     

激光熔覆用钴基合金粉末的研究

对激光熔覆用WFLC－11钴基合金粉末的激光熔覆工艺和熔覆层性能进行了研究，获得了WFLC－11钴基合金粉末激光熔覆层厚度与最小比能量关系曲线和熔覆层的组织、高温硬度等性能数据，为选择和使用WFLC－11钴基合金粉末提供了依据。     

激光焊接超细基胎体金刚石薄壁钻

采用激光焊接超细预合金粉胎体，开发了新的薄壁钻产品，通过对与现有的产品工艺、性能测试以及实际使用分析对比，结果表明：激光焊接与普通钎焊相比结合强度提高2－3倍，克服了胎体脱落问题，胎体耐磨性提高了50％－120％，其中轴向磨损速率提高1．2倍；钻削速度提高30．4％，工矿适应性增加，使用寿命提高25％－108％。