Fabrication of Porous Copper with Directional Pores by Continuous Casting Technique Through Thermal Decomposition of Hydride

Lotus-type porous copper with aligned long cylindrical pores was fabricated by continuous casting technique through thermal decomposition method (TDM) in an argon atmosphere of 0.1 MPa. A pellet of titanium hydride was supplied into molten copper with adjusting the time interval to maintain the constant concentration of hydrogen to be dissolved in the melt, when the transfer velocity of the unidirectional solidification is changed. Long lotus-type porous copper slabs were fabricated with constant solidification velocity. The effect of the transfer velocity on the porosity and pore size was investigated. The average pore diameter was independent of the transfer velocity, but the porosity is slightly dependent on the velocity. It is apparent that the continuous casting technique can be applicable for production of lotus metals through TDM.     

Fabrication of Porous Aluminum with Directional Pores through Continuous Casting Technique

Lotus-type porous aluminum with slender directional pores is fabricated via a continuous casting technique in pressurized hydrogen or a mixed gas containing hydrogen and argon. The influence of solidification conditions such as hydrogen partial pressure, solidification velocity, temperature gradient, and melt temperature on the porosity and pore size is investigated. The porosity and pore size increase upon increasing the hydrogen partial pressure or the melt temperature, whereas the porosity and pore size decrease upon increasing the solidification velocity or the temperature gradient. Furthermore, the mechanism of pore formation in lotus aluminum is examined based on the results of an improved model of hydrogen mass balance in the solidification front, which was originally proposed by Yamamura et al. The results from the present model agree with the experimental results. We conclude that the diffusion of hydrogen rejected in the solidified aluminum near the solid/liquid interface is the most important factor for pore formation because the difference in hydrogen solubility between solid and liquid aluminum is very small.     

Preparation of Monodispersed Iron Nanoparticles by Thermal Decomposition

Monodispersed iron nanoparticles were prepared by thermal decomposition of iron carbonyl at low temperatures of 160–180 °C in kerosene. The iron nanoparticles were spherical and their average size was decreased from 11.2 nm to 8.6 nm with increasing decomposition temperatures in the range of 160 °C to 180 °C. The as-prepared iron nanoparticles were amorphous, but the surface of the particles was easily oxidized to be spinel structured.     

Fabrication of Two-Layered Aluminum Foam Having Layers with Closed-Cell and Open-Cell Pores

Two-layered aluminum foam having layers with both closed-cell and open-cell pores was fabricated using the precursor foaming process and the sintering dissolution process. It was found that a two-layered Al foam with different pore structures but similar compression properties in each layer can be obtained. This foam is expected to have a region with superior thermal insulation and a region with superior heat release properties.     

Fabrication of Porous Aluminum with Controllable Open-Pore Fraction

Aluminum with an open-pore structure was fabricated through nitridation of an AA6061-2 pct Mg-1 pct Sn powder mixture, where interconnected permeable AlN shells developed on each AA6061 particle and imparted strength to the assembly. The resulting intershell spaces form an open-pore structure. When such an open-pore structure is heated above the liquidus of the core, an open-closed pore transformation occurs, where the molten core in each shell spontaneously migrates to fill the open pores outside, leaving a closed pore inside each shell. Based on this finding, porous AA6061 with different open-pore fractions was fabricated by heating open-pore structures of AA6061 into the semisolid region, where the liquid fraction changes with temperature. The mechanism for the open-closed pore transformation is identified through detailed microstructural and thermodynamic analyses. Criteria for the open-closed pore transformation are specified. Additionally, net shape fabrication of porous aluminum with controlled pore features is realized using the novel concept.     

Titanium Carbonitride Composite with Iron ― Chromium Binder

Wetting of titanium carbonitride with iron ― chromium alloys has been studied in the concentration range 2-30 mass% Cr. Chromium is shown to be a surface-active additive that decreases wetting angles in the TiCN ― (Fe ― Cr) system. The results of the investigations made it possible to choose the optimum composition of titanium-carbonitride material. A technology has been developed for the fabrication of new composite and some properties of this composite have been determined.     

Titanium Carbonitride Composite with Iron ― Chromium Binder

Wetting of titanium carbonitride with iron ― chromium alloys has been studied in the concentration range 2-30 mass% Cr. Chromium is shown to be a surface-active additive that decreases wetting angles in the TiCN ― (Fe ― Cr) system. The results of the investigations made it possible to choose the optimum composition of titanium-carbonitride material. A technology has been developed for the fabrication of new composite and some properties of this composite have been determined.

     

电感耦合等离子体原子发射光谱法同时测定铬铁矿中铬和铁

利用电感耦合等离子体发射光谱法,建立了一种快速测定铬铁矿中铬和铁量的一种方法。样品利用高铝坩埚和过氧化钠进行熔融后,用热水浸取后再用硝酸酸化,在选定铬(267.716{97})和铁(238.204{107})作为测定波长的条件下,进行电感耦合等离子体发射光谱法测定。干扰试验表明,一般铬铁矿中存在的其他杂质元素均不干扰测定。按照实验方法应用于2个铬铁矿样品中进行铬和铁的测定,相对标准偏差(RSD,n=10)小于0.350%,回收率为101%~103%。并与标准样品的认定值比较,结果吻合。     

Gamma-Nitriding of Porous Iron PM Components

Abstract

The heat-treatment and properties of some ferrous sintered alloys are investigated. The approach has been to introduce nitrogen to enhance the heat-treatment response during the heat-treatment cycle. The process is known as γ-nitriding to distinguish it from the ferritic nitriding process which is a surface-hardening treatment. Addition of H₂S to the γ-nitriding atmosphere may be used to improve machinability. It is suggested that the economics of the process may be favourable enough for the process to be commercially viable.     

APT热分解动力学的研究

研究采用热重分析法,获得等速升温条件下APT失重变化与温度变化及反应时间的关系TG曲线。据APT的失重率,绘出DTG曲线,并以TG和DTG曲线为基础,采用非等温动力学的基本方程,对试验数据进行线性回归,建立了APT热分解动力学的数学模型。失重曲线表明APT的热分解是四个阶段进行,第一阶段为126.2℃左右时脱水,第二阶段为209.4℃左右时分解成无定型铵钨青铜(AATB),第三阶段为310.5℃左右时结晶成铵钨青铜(ATB),第四阶段为482.3℃左右时分解成蓝钨。试验结果表明:在不同的升温速率条件下,APT热分解的指前因子是随着热解温度的升高而逐渐减小。活化能在第二阶段达到最大值。反应级数在第一、二阶段在0.6⁰.76,第三阶段在0.90.76,第三阶段在0.9¹.37,第四阶段为1.0左右。生产中宜采取三段控温,其他阶段控速的方式,提高生产效率,减少能耗。     

Effect of Hot Deformation on Formation and Growth of Thermal Fatigue Crack in Chromium Wear Resistant Cast Iron

Chromium wear resistant cast iron is widelyusedin engineering, mining and power industry forits high strength,hardness and wear resistance .Inproduction process , some wear-resistant parts ser-ving in alternative stress due to rapid heating andcooling rate ofteninduces thermal fatigue andresultsinfailure .The badthermal fatigue property of chro-mium wear resistant cast iron is due to eutectic car-bides which distribute as continuous net in matrix.Recent researches showthat hot deformation can …     

Fabrication of High-Porosity Lotus-Type Porous Aluminum in Vacuum

Lotus-type porous aluminums with porosities from 10 to 26 pct were fabricated with the Bridgman-type directional solidification method (Gasar). A vacuum atmosphere is critical to obtain high-porosity lotus-type porous aluminum by the Gasar process. The lotus-type porous aluminum was directionally solidified under a pure hydrogen pressure of 0.2 to 16 kPa. The influence of hydrogen pressure on the porosity and pore size in vacuum was investigated. The porosity and pore size increase with decreasing hydrogen pressure, but there exists a maximum porosity at some critical hydrogen pressure. Since a low hydrogen pressure is adopted, the effect of capillary pressure and hydrostatic pressure on the porosity becomes important. With the decreasing of hydrogen pressure, the influence of hydrostatic pressure and capillary pressure on porosity becomes stronger and stronger. The influence of melt height, which is proportional hydrostatic pressure, on porosity and pore size was investigated. The calculated porosities considering capillary pressure and hydrostatic pressure are in good agreement with experimental results.

     

多孔钛的粉末冶金法制备及其力学性能

采用粉末冶金法成功制备出力学性能与骨匹配的开孔型多孔钛,其孔隙率分布在8.6%～35.4%之间,平均孔径随孔隙率增加而增加;抗压强度随孔隙率的增加而降低,分布在252～848 MPa之间;通过应力-应变曲线计算得到其弹性模量在7.2～9.9 GPa之间,接近人骨弹性模量。此多孔钛有望成为理想的人工骨修复材料。     

废弃聚氯乙烯热解脱氯的研究

高炉喷吹废塑料是20世纪90年代初由德国提出的处理废塑料的最佳方法，在国外高炉喷吹废塑料的实践中，含氯废塑料的处理一直是个难题，作对含氯废塑料的热解法脱氯进行了实验室基础研究。结果表明：在隔绝空气或用氮气保护的条件下，以一恒定的温度加热，氯脱除率超过90%，处理后的含氯废塑料可以直接喷入高炉。     

苯甲酸铒的热分解反应机理研究

由水热法合成了苯甲酸铒配合物,用元素分析、ＩＲ表征了该配合物。它为层状结构。用ＴＧ、ＤＴＡ、ＩＲ研究了它的热分解机理。在氮气气氛下,热分解分两步进行：第一步分解生成二碳酸一氧盐和有机化合物;第二步二碳酸一氧盐进一步分解生成氧化物和二氧化碳。第一步中生成的有机化合物主要成分为二苯甲酮、９,１０－蒽醌和１,３－二苯基异苯并呋喃等。