Preparation of Compound Ultrafine CeO2 by Wet-Solid-Phase Mechanochemical Modification

To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was proposed.The effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was investigated.The phase evolutions of preparation process were characterized by XRD.SEM micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized particles.The method is readily available in raw material, low in cost, simple in process, and has great potential for industrialization.The compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process.     

低松装密度水雾化铜粉工艺的研究

本文研究了氧化 还原法生产铜粉的新工艺 ,该工艺是通过氧化还原将水雾化铜粉加以表面改性 ,形成海绵状的粉末 ,显著降低水雾化铜粉的松装密度 ,这种铜粉既具有电解铜粉低的松装密度 ,又具有水雾化铜粉高的流动性。讨论了氧化时间、氧化温度对铜粉松装密度的影响。本工艺是一种新型环保、节能、可替代电解法生产铜粉的先进工艺     

Powder Deposition in Three Parallel-Oriented Dies of Different Shapes

Uniformity of bulk density distribution during the die filling process is required to minimize quality problems, such as distortion and cracking, for powder compacts. Understanding the die filling process is necessary in ensuring a uniform powder deposition. The second-generation pressure deposition tester (PDT-II) was used to investigate the deposition process and final pressure distribution of powder filling in toroidal, cylindrical, and E-shaped dies. All tests were conducted using a spray-dried free-flowing granular powder. The results indicated that for toroidal dies: (1) the area around 0° orientation (the leeward end) had the highest pressure values (1186.7 to 2498.0 Pa), with the average pressure values of the remaining area 353.7-648.0 Pa; (2) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; (3) the highest feed shoe speed (500 mm/s) led to the most nonuniform pressure distribution among the three speeds; (4) higher feed shoe speed did not always result in higher final pressure values; and (5) the right die tended to have higher final pressure values (215.0 to 2498.0 Pa) than the center die (95.4 to 2052.5 Pa). For E-shaped dies: (1) the final pressure values of the middle leg (308.9 to 760.7 Pa) were higher than those of the left and the right legs (148.9 to 530.3 Pa); (2) the area along the backside had the highest final pressure value (1054.6 to 1303.8 Pa); (3) the pressure distribution was symmetrical about the centerline parallel to the feed shoe movement direction; and (4) neither the center die nor the right die always had higher pressure values than the other one at all locations. Comparison between cylindrical and toroidal dies indicated that: (1) neither of the two die shapes (cylinder and toroid) led to consistently higher or lower final pressure values at all locations and (2) for all three feed shoe speeds, the toroidal die had higher average final pressure values in the 0° orientation.     

Hydrogen Absorption and Release Behavior in Hydrogen Decrepitation Process of Nd-Fe-B Alloys

The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0.0015% at 1073K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523-723K for 1h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet.     

激光法合成SiC超细粉末物理化学过程的研究——Ⅰ.实验规律及粉末特性

用50W连续波CO_2激光器为热源,诱发SiH_4和C_2H_4反应,合成SiC超细粉末。实验确定了反应腔体内压力p、气源中的C/Si原子比、喷嘴内径2r以及激光功率密度与粉末特性之间的关系,并对合成的产物进行物理、化学表征。     

高强度烧结钢

为开拓粉末冶金材料新的应用领域，近年来对高强度烧结钢进行了大量的研究与开发。本文简要介绍Ｈｏｇａｎａｓ公司开发的一些高强粉末冶金材料及对一些高强度烧结材料尺寸变化的控制。     

影响凹印铜金粉印金光泽度的主要因素

在研究国内外铜金粉的微观形貌、厚度、水面遮盖率、定向排列、光泽度和粒度分布的基础上，分析了影响凹印铜金粉印金光泽度的主要因素。结果表明，国产铜金粉颗粒级差大、细小颗粒所占比例过多、金属片太厚、水面遮盖率小、定向排列不好等是影响国产铜金粉印金光泽度的主要因素。     

粉末冶金铁基烧结炉的现状与展望

评述了国内外粉末冶金铁基烧结炉的发展动向和具体改进装备。即功能带设计、脱蜡装置,烧结带气氛控制,淬火带的设想,加热元件配置及新型可塑性耐火材料。     

我国钨冶炼技术的新进展

综述了近年来我国钨冶炼在开发处理多种资源的工艺技术，钨钼分离技术，从低品位钨矿物原料和含钨废料中生产高纯APT，钨冶炼技术装备和自动化水平，膜分离技术在开发无污染钨冶炼工艺的应用，超细钨粉等方面的最新进展和成果。在此基础上，展望了我国今后钨冶炼发展的方向。     

高合金铁基烧结材料在轧钢导位中的应用研究

本文研究了高合金铁基烧结材料在轧钢导位中的应用。实验表明,通过粉末冶金液相烧结技术,可以获得具有优良综合性能的制品,材料密度ρ≥7.5 g/cm3,硬度≥55 HRC,抗弯强度≥1 000 MPa,冲击韧度αk≥3.9 J/cm2,满足了轧钢导位辊的工作要求。材料利用率可达95%以上、降低了制备成本。使用寿命是普通轧辊寿命的3~6倍,适用于线材和小型型材的轧钢生产。