喷雾干燥法制备钼合金微粉的研究

钼合金的制备过程广泛采用原料粉末混匀、坯料压制、烧结成型的粉末冶金方法,因此原料粉末混合的均匀程度、纯度、粉末粒径和形貌对钼合金制品的性能有重要影响。本文采用溶液喷雾干燥法制备前驱体粉末,再将前驱体粉末在氢气气氛下进行高温还原制备钼钨合金粉和钼钌镍复合粉,研究了喷雾干燥工艺参数（溶液浓度、进料速度、干燥温度等）和还原热处理工艺参数（还原气氛、温度、时间等）对钼合金微粉粒径、成分和形貌的影响,此外还分析了钼钨合金化和钼钌镍复合粉钎焊性能。结果表明,采用溶液喷雾干燥结合还原热处理工艺,可获得粒径0.5~3μm的球形钼钨固溶体合金粉和0.5~2μm的球形钼钌镍复合粉,且钼钌镍复合粉在钼板上钎焊时具有优异的润湿性。     

中温固体氧化物燃料电池铁系阳极催化剂的性能研究

采用水系流延法制备多孔氧化钇稳定氧化锆(Yttria-Stabilized Zirconia,YSZ)流延片与有机流延法制备YSZ电解质薄膜,经叠压共烧后获得多孔YSZ/致密YSZ薄膜复合基体。通过化学浸渍法分别在复合基体多孔YSZ层内浸渍了Fe(NO_3)_3、Co(NO_3)_2和Ni(NO_3)_2溶液来制备浸渍阳极SOFC单电池(以LSM+YSZ为阴极)。初步研究了铁系阳极催化剂的性能,测试了不同阳极SOFC单电池在不同温度下的电性能并采用SEM观察了不同浸渍阳极的形貌。进一步对Co-YSZ和Ni-YSZ阳极单电池的抗积碳性能进行了测试与比较。结果表明:在氢气气氛中钴的催化活性最高,镍次之,铁最差;在乙醇气氛中钴的催化活性仍要好于镍,而且Co-YSZ阳极单电池的抗积碳性要明显优于Ni-YSZ阳极单电池。铁系催化剂中Co的催化性能和抗积炭性能最佳。     

有机泡沫浸渍法制备泡沫镍的研究

为制备纯度较高、对环境友好的泡沫镍,利用氢气还原Ni Cl2的原理,将氯化镍涂覆在40 ppi聚氨酯泡沫孔筋表面,除去聚氨酯泡沫后,在加热炉中还原并烧结制备出泡沫镍。研究了还原后泡沫金属的组成以及烧结温度对泡沫金属收缩率、电导率以及抗拉强度的影响。结果表明:烧结温度为1100℃时,利用40 ppi聚氨酯泡沫制备出的泡沫镍孔隙率为94.4%、电导率为1×106S/m、抗拉强度为2.67 MPa。     

MH-Ni电池用新型镍纤维阳极材料的制备及性能

报道了可以代替泡沫镍作ＮＨ－Ｎｉ电池阳极骨和镍纤维毡的制备工艺,研究了镍纤维丝径,镍毡的单重对孔径尺寸,孔隙率,比表面积的影响,经过在氢气和氩气２种气氛中进行烧结,保证了镍毡的抗拉强度和延伸变形率,可以制备出性能优良的镍纤维毡。     

烧结工艺对NiFeX合金性能和组织的影响

采用氢气/氩气气氛烧结和氩气气氛保护热压3种烧结工艺制备了3种不同成分的Ni基合金. 密度测试、金相、 XDR以及SEM和EDX分析显示 在氢气/氩气气氛下烧结时, NiFeCuAlSn和NiFeCuAlZn样品出现体积膨胀、密度下降和孔隙率增加现象; 通过气氛保护热压制备的样品致密度高且孔隙率低; Ni-Fe样品形成Fe*Ni固溶体, 而NiFeCuAlX(X=Zn/Sn)样品基体主要由细小的Ni3Al和较粗大的Ni及Fe*Ni组成, 其他元素均固溶于其中.     

粉末注射成形铜的烧结工艺研究

采用粉末注射成形技术制备铜制件,研究粉末注射成形中烧结工艺参数对烧结效果的影响,以获得理想的注射成形工艺及烧结工艺参数.通过采用真空烧结和氢气气氛烧结、改变烧结升温速率和烧结温度,对比了烧结件的烧结质量和烧结收缩等情况.结果表明,铜粉末注射成形坯的烧结必须在氢气气氛保护下进行;烧结升温速率不宜过快或过慢,本研究采用5℃/min的升温速率效果较好;烧结温度低于且接近铜的熔点温度,烧结温度高,烧结件收缩率大但致密度也大.     

流延浸渍法制备Cu-CeO2-YSZ固体氧化物燃料电池阳极

通过流延浸渍法制备Cu-CeO2-YSZ阳极,采用淀粉做造孔剂,确定了多孔YSZ基体的制备工艺,主要包括造孔剂用量及流延浆料配比.并通过复合流延制备多孔YSZ支撑的多孔-YSZ/致密-YSZ复合基体,以Pt浆为阴极,通过电池放电考察了氢气条件下多孔YSZ孔隙率、Ce和Cu的浸渍条件等对Cu-CeO2-YSZ阳极性能影响.结果表明,原料中淀粉含量为65%(质量分数),1500℃烧结6 h得到多孔YSZ孔隙率可达到70%左右.采用真空顺次浸渍法制备20%Cu-10?O2-YSZ(质量分数)阳极,其电池800℃时的最大功率密度为113 mW/cm2.     

添加镍的石墨-无铅锡青铜复合涂层

在无铅锡青铜CuSn10和石墨的混合粉中加入硝酸镍和聚乙烯醇(PVA)的水溶液,经过还原气氛下的一次烧结,然后镍颗粒被粘附到CuSn10粉和石墨粉表面,经过冷轧和二次烧结得到石墨-CuSn10复合涂层。结果表明:镍的添加能改善石墨与CuSn10基体之间的界面结合,显著提高复合涂层的硬度和耐磨减摩性。添加镍的石墨-CuSn10复合涂层的耐磨减摩性能优于CuSn10Pb10涂层,是一种理想的无铅铜基滑动轴承材料。     

石墨烯-镍纳米复合材料的制备及性能

采用激光烧结的方法制备了石墨烯增强镍基纳米复合材料,XRD和Raman测试结果表明,激光烧结后石墨烯存在于所制备的复合材料中,且石墨烯的结构和性能没有改变。显微硬度测试结果显示,石墨烯的添加使得石墨烯-镍纳米复合材料的硬度比激光烧结纯镍的硬度提高了约3倍。用电化学极化法研究了激光烧结的石墨烯-镍纳米复合材料和纯镍在3.5%Na Cl溶液中的腐蚀行为,石墨烯-镍纳米复合材料的腐蚀电位比激光烧结纯镍的腐蚀电位有所降低,且腐蚀电流也略有增大,说明其耐腐蚀性能较激光烧结纯镍有所下降。     

硬质合金的烧结气氛及其控制

叙述了硬质合金生产中烧结气氛的作用．气氛对碳化物湿润性的影响，硬质合金烧结气氛的种类。对氢气、真空烧结的待点及其控制进行了分析，提出的氢气烧结转向真空烧结是硬质合金工业发展的必然趋势。     

氧化物—空气半燃料电池用贮氢合金电极的烧结制备及其电化学特性

研究了应用在空气－氢化物半燃料电池上的制备配套金属氢化物厚型电极烧结技术，将贮氢合金与细镍粉和一定的添加剂形成浆料涂覆在泡沫镍基体，测试不同烧结参数对贮氢合金电极的电化学性能的影响，烧结电极合金的电化学活化特性和高倍率放电能力与传统的粘结式电极有较大的提高，为设计适合电动车用高能量密度空气－氢化物燃料电池，分别选用冲孔镍箔带，冲孔铜箔带和铜编织网作为集流体进行比较实验。结果表明，选定冲孔铜箔带是适宜于设计空气－氢化物燃料电池用厚型氢化物电极。     

Rapid discharge sintering of nickel-diamond metal matrix composites

In this study rapid discharge sintering (RDS) and furnace sintering of nickel-diamond metal matrix composites (MMCs) is compared. Nickel-diamond powder composites (80-20% by weight respectively) were uniaxially pressed into 20 mm discs at compaction pressures of 100, 200 and 300 MPa. Discharge sintering was carried out using a microwave plasma formed with hydrogen and hydrogen/nitrogen as the discharge gases and tube furnace sintering carried out in a argon or a hydrogen/nitrogen (3:1) atmosphere. Discs pressed to 300 MPa were treated at both 850 and 1000 °C. The properties of the sintered nickel-diamond composites were characterized using density, approximate flexural strength, hardness, wear resistance, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The RDS samples sintered at 1000 °C achieved the maximum approximate disc flexural strength of 473 MPa within a 20 min treatment time compared with 6 h for furnace sintered samples. Samples sintered using the RDS technique exhibited increased hardness values and a finer nickel matrix over furnace sintered samples. Using the RDS technique it has been possible to process nickel-diamond MMCs without oxidation or graphitisation at temperatures above 900 °C. Minimal diamond destruction was observed during abrasive wear testing of the RDS samples compared with damage and pull-out observed for furnace sintering.     

Electrochemical characterization of vacuum sintered copper alloyed austenitic stainless steel

The aim of this work is the study of the electrochemical behaviour and corrosion resistance of copper alloyed vacuum sintered stainless steel. The presence of copper can improve the passivability of sintered stainless steel and, as a consequence, the corrosion resistance; moreover, vacuum sintering allows materials with good chemical and mechanical properties to be produced, avoiding the interaction between the metal and the sintering atmosphere. Microstructural characterization was carried out: copper evaporation during sintering and a different solubility of copper in AISI 304L and AISI 316L were indicated. This last result was related to the surface oxides stability of the steels in the sintering condition. The electrochemical characterization in an acid environment showed different behaviour as a function of the copper amount and of its presence as solid solution. These results were compared with similar measurements of wrought materials or samples sintered in a nitrogen-containing atmosphere.     

Impact and dynamic deformation behavior of mechanically alloyed tungsten heavy alloy

93W-5.6Ni-l.4Fe tungsten heavy alloy was fabricated by mechanical alloying process using elemental powders of tungsten, nickel and iron, followed by sintering at temperatures of 1445~1485°C under hydrogen atmosphere. The tungsten heavy alloy sintered using mechanically alloyed powders showed finer tungsten particles about 5~18 μm with high density above 99% at shorter sintering time than that fabricated by conventional liquid-phase sintering process. Charpy impact energy of mechanically alloyed tungsten heavy alloy increased with increasing the matrix volume fraction and with decreasing the W/W contiguity. The high strain rate dynamic deformation behavior of tungsten heavy alloys using torsional Kolsky bar test exhibited different fracture modes dependent on microstructure. While the brittle intergranular fracture mode was dominant when the tungsten particles were contiguously interconnected in tungsten heavy alloys solid-state sintered below 1460°C, the ductile shear fracture mode was dominant when the tungsten particles were surrounded by ductile matrix phase in tungsten heavy alloys liquid-phase sintered above 1460°C.     

Porous and dense Ni hollow fibre membranes

Nickel hollow fibre membranes were prepared by extruding a polymer solution containing suspended nickel (Ni) powder to green hollow fibres, which were then sintered at elevated temperature under an argon atmosphere. The hollow fibres were characterized by a scanning electron microscope (SEM), X-ray diffractometer (XRD), mercury porosimeter, gas permeation test and conductance measurements. Porous Ni hollow fibres with micron-sized pore structures can be obtained directly by sintering the green fibre at relatively lower temperatures. Heated at a higher temperature (i.e., 950 °C), the Ni hollow fibres became gas-tight membranes which are of great interest for hydrogen separation.     

Microstructural control of and mechanical properties of mechanically alloyed tungsten heavy alloys

93W-5.6Ni-l.4Fe tungsten heavy alloys with controlled microstructures were fabricated by mechanically alloying of elemental powders of tungsten, nickel and iron by two different process routes. One was the full mechanical alloying of blended powders with a composition of 93W-5.6Ni-l.4Fe, and the other was the partial mechanical alloying of blended powders with a composition of 30W-56Ni-14Fe followed by blending with tungsten powders to form a final composition of 93W-5.6Ni-l.4Fe. The raw powders were consolidated by die compaction followed by solid state sintering at 1300°C for 1 hour in a hydrogen atmosphere. The solid state sintered tungsten heavy alloys were subsequently liquid phase sintered at 1445∼1485°C for 4-90 min. The two-step sintered tungsten heavy alloy using mechanically alloyed 93W-5.6Ni-l.4Fe powders showed tungsten particles of about 6-15 μm much finer than those of 40 um in a conventional liquid phase sintered tungsten heavy alloy. An inhomogeneous distribution of the solid solution matrix phase was obtained in the two-step sintered tungsten heavy alloy using partially mechanically alloyed powders. The two-step sintered tungsten heavy alloy using mechanically alloyed 93W-5.6Ni-l.4Fe powders showed larger elongation of 16% than that of 1% in the solid state sintered tungsten heavy alloy due to the increase in matrix volume fraction and decrease in W/W contiguity. Dynamic torsional tests of the two-step sintered tungsten heavy alloys showed reduced shear strain at maximum shear stress than did the sintered tungsten heavy alloys using the conventional liquid phase sintering.     

Effect of Pre-annealing on Sintering of Stainless Steel Fiber Felt

Stainless steel fiber felt is a class of unique porous metal materials. This study investigates the effect of pre-annealing on the sintering of stainless steel fiber felt through quantitative characterization of sintered joints based on synchrotron radiation experiments. The sintered joint size was found to follow a marked normal distribution in fiber felt samples sintered with and without pre-annealing. However, pre-annealing prior to sintering led to a significant reduction in the total number of sintered joints as well as a reduction in the percentage of large sintered joints. Consequently, fiber felt samples sintered with pre-annealing achieved less than half the tensile strength of those sintered without pre-annealing. Delamination through fracture of sintered joints was pronounced in fiber felt samples sintered with pre-annealing, while failure occurred mainly through fracture of individual fibers in those sintered without pre-annealing. It was concluded that sintering without pre-annealing is necessary for the fabrication of high-strength fiber felt products and the reasons are briefly discussed.     

Preparation of oriented linear copper fiber sintered felt and its performance

Long metal fibers were manufactured in horizontal lathe with a multi-tooth tool. Based on the coarse antler surface structure of copper fibers, a new sintering technology was put forward to manufacture a kind of oriented linear copper fiber sintered felt. The sintering mechanism of oriented linear copper fiber sintered felt was studied. Compared with sintered copper-wire felt, the characteristics of sintered copper-fiber felts were analyzed in details. Owing to the coarse antler surface structure of copper fibers, oriented linear copper-fiber felt was sintered under the condition ofmicro/nano scale range, and copper fibers easily bonded together in the sintering process. Microchannels with micro-scale coarse antler surface structure were constructed. These characters give oriented linear copper fiber felt some new merits： high filtration accuracy, high flow capability, low resistance loss, good capability to resistance pressure, stable and uniform pore, high specific surface area. The properties of oriented linear copper fiber sintered felt were analyzed.     

Enhanced Densification and Hardness of Titanium Bodies Sintered by Advanced Hydrogen Sintering Process

A new sintering technique for enhancing a densification and hardness of sintered titanium body by supplying hydrogen was developed (Hydrogen Sintering Process, HSP). The HSP was developed by only injecting hydrogen into an argon atmosphere during the core time. As a result, sound titanium sintered bodies with high density and hardness were obtained by the HSP. In addition, a pore size and number of the HSP specimens were smaller than those of the argon atmosphere specimen. It was found that the injecting hydrogen into the argon atmosphere by HSP can prevent the formation of oxide layers, resulting in enhanced densification and hardness.