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951.
952.
以元素混合粉为原料,研究了耐热不锈钢的注射成形工艺.重点讨论了烧结温度、时间及气氛对耐热不锈钢致密度、力学性能及微观组织的影响,获得的最佳工艺为烧结温度1375℃,时间60 min,真空气氛.在此条件下制备了致密度98.12%、抗拉强度510 MPa、铁素体组织的PIM耐热不锈钢. 相似文献
953.
Nanostructured C-Cu thin films were deposited by reactive sputtering method and co-sputtering method. The relationships between microstructures, properties, and depo-sition parameters were studied and the results obtained from TEM, AFM, and XPS.indicate that the thin films are nanostructural, and have good in-depth uniformity. Theselected area electron diffraction (SAED) found that the nanosize Cu particles havethe fcc structure and the others are amorphous carbon or nanocrystallized graphiticcarbon. The peak positions of the Cu and C in XPS indicate them to be at the ele-mental state. In the IR transmission spectrum, diamond two-phonon absorption andgraphite Raman peaks were observed, which suggests microcrystal diamond particlesand graphite components exist in the C-Cu film. The higher electrical resistivity wasobtained. 相似文献
954.
<正> 含钨铸铁中碳化物的形貌、结构及分布,对铸铁性能有显著的影响。碳化物结构和性质各不相同,不易用一般金相方法观察全部形貌,更不易把形态和碳化物相一一对应起来。我们从电化学原理出发,研究了样品中碳化物在碱性介质中的电化学行为,找出一种示差侵蚀显示组织的方法。实验证明,这种方法还可能应用于钢铁或其它合金鉴定组织结构。 相似文献
955.
采用提拉法生长出了掺钕钨酸铋钠(分子式Nd:NaBi(WO4)2,简称Nd:NBW)和掺钕钨酸钇钠(分子式Nd:NaY(WO4)2,简称Nd:NYW)晶体。通过TG-DTA分析得到Nd:NBW的熔点为936.2℃,Nd:NYW的熔点为1209.07℃。由吸收光谱可以看出,Nd:NBW在802nm有较强的吸收峰,Nd:NYW在804nm,752nm,586nm附近有较强、较宽的吸收峰,二者均适合于LD泵浦;并计算了晶体中Nd^+3+的吸收截面积。通过比较Nd:NBW和Nd:NYW的红外光谱和拉曼光谱结果,认为二者结构基本相同,为四方晶系、白钨矿结构、141/a空间群。 相似文献
956.
Electric and mechanical performances of Bi0.5Sb1.5Te3 prepared by spark plasma sintering 总被引:1,自引:0,他引:1
Thermoelectric (TE) materials are a kind of functional materials which can be used to convert directly heat energy to electricity or reversely.The thermoelectric effects hold great potential for application in power generation and refrigeration.Bi2Te3 and its alloys are well known as best TE materials currently available near room temperature.This paper studies respectively the effects of spark plasma sintering (SPS) on electric performance of Bi0.5Sb1.5Te3 thermoelectric materials that are prepared through vacuum melting and ball milling.Through X-ray Diffraction and cold field emission scanning electric microscope s4800, the phase constituent and microstructure of the TE materials samples were analyzed.Electric conductivity and power factor can be improved with the rise of Spark Plasma Sintering temperature (from 300 to 500 ℃) and pressure(from 30 to 60 MPa), and the density and mechanical strength of Bi0.5Sb1.5Te3 thermoelectric material increase, too. 相似文献
957.
Understanding the Influence of Copper Nanoparticles on Thermal Characteristics and Microstructural Development of a Tin-Silver Solder 总被引:1,自引:0,他引:1
D.C. Lin T.S. Srivatsan G-X. Wang R. Kovacevic 《Journal of Materials Engineering and Performance》2007,16(5):647-654
This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag,
and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process
revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag
solder, which is 6.5 °C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature
recordings revealed the same temperature level of 221 °C for both melting (from solid to liquid) and final solidification
(after recalescence) of the Sn-3.5%Ag solder. Addition of copper nanoparticles was observed to have no appreciable influence
on melting temperature of the composite solder. However, it does influence solidification of the composite solder. The addition
of 0.5 wt.% copper nanoparticles lowered the solidification temperature to 219.5 °C, while addition of 1.0 wt.% copper nanoparticles
lowered the solidification temperature to 217.5 °C, which is close to the melting point of the ternary eutectic Sn-Ag-Cu solder
alloy, Sn-3.7Ag-0.9Cu. This indicates the copper nanoparticles are completely dissolved in the eutectic Sn-3.5%Ag solder and
precipitate as the Cu6Sn5, which reinforces the eutectic solder. Optical microscopy observations revealed the addition of 1.0 wt.% of copper nanoparticles
to the Sn-3.5%Ag solder results in the formation and presence of the intermetallic compound Cu6Sn5. These particles are polygonal in morphology and dispersed randomly through the solder matrix. Addition of microsized copper
particles cannot completely dissolve in the eutectic solder and projects a sunflower morphology with the solid copper particle
surrounded by the Cu6Sn5 intermetallic compound coupled with residual porosity present in the solder sample. Microhardness measurements revealed the
addition of copper nanopowder to the eutectic Sn-3.5%Ag solder resulted in higher hardness. 相似文献
958.
为了研究压铸模与铝合金金属间化合物的形成与分解过程,进行了热浸铝试验.试验结果表明金属间化合物的形成与分解是一个连续不断的循环过程,两者之间的相互关系导致了钢基的失重以及体积的减少. 相似文献
959.
960.