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991.
992.
X. Deng G. Piotrowski J. J. Williams N. Chawla 《Journal of Electronic Materials》2003,32(12):1403-1413
Intermetallic-layer formation and growth in Pb-free solder joints, during solder reflow or subsequent aging, has a significant
effect on the thermal and mechanical behavior of solder joints. In this study, the influence of initial intermetallic morphology
on growth rate, and kinetics were examined in a Sn-3.5Ag solder reflowed on Cu. The initial morphology of the intermetallic
was tailered by cooling in water, air, or furnace conditions. Solder aging was conducted at 100°C, 140°C, and 175°C and aged
for 0–1,000 h. Cooling rate, aging temperature, and aging time played an important role on microstructure evolution and growth
kinetics of Cu6Sn5 (η) and Cu3Sn (ɛ) intermetallic layers. Prior to aging, faster cooling rates resulted in a relatively planar Cu6Sn5 layer, while a nodular Cu6Sn5 morphology was present for slower cooling. Intermetallic-growth rate measurements after aging at various times, indicated
a mixed growth mechanism of grain-boundary and bulk diffusion. These mechanisms are discussed in terms of the initial intermetallic
thickness and morphology controlled by cooling rate, diffusion kinetics, and the competition between Cu6Sn5 and Cu3Sn growth. 相似文献
993.
994.
In this experimental work, a dense tubular Pd–Ag membrane reactor is used for carrying out the acetic acid steam reforming reaction for producing a CO-free hydrogen stream. The influence of the different flow configurations, as well as the sweep factor and the reaction pressure is analysed. A Ni-based commercial catalyst was packed in the lumen side of the membrane reactor and the experimental tests were performed at a reaction temperature of 400 °C and at a H2O/acetic acid feed molar ratio of 10/1. Results in terms of CO-free hydrogen recovery, hydrogen yield and products selectivities are proposed. Moreover, a comparison between the performances of the membrane reactor and a traditional reactor working at the same operative conditions is illustrated and discussed. 相似文献
995.
996.
Tsung-Ming Chao Shinn-Jen Chang Cha-Wen Chang Chia-Chen Li 《Journal of surfactants and detergents》2020,23(4):841-851
Silver (Ag) nanoparticle has extremely high surface energy and it is difficult to find an efficient dispersant to prevent its agglomeration in suspensions. A new brush copolymer, succinic anhydride modified epoxy-amine poly[(propylene oxide)-co-(ethylene oxide)]-grafted polymer (EPOA), which can efficiently disperse concentrated aqueous suspensions of Ag nanoparticles is revealed. The dispersion efficiency of EPOA for the dispersion of a 60 nm-Ag nanoparticles in aqueous suspension is studied by measuring its sedimentation and rheological behavior, and the results are compared with those of a commercially available dispersant, ammonium poly(acrylic acid) (PAA-NH4). Interactions between the dispersants and the Ag nanoparticles are characterized by zeta potential and adsorption analyses. Theoretical calculations are conducted to clarify the adsorption and the dominant dispersion stabilization mechanisms of the dispersants. Compared with PAA-NH4, EPOA obtains a higher stable suspension of Ag nanoparticles with less significant sedimentation over 1 month. The dispersion homogeneity of the suspension remains excellent even at an extremely high solid loading of 30–40 wt%. According to adsorption analysis, it is suggested that both EPOA and PAA-NH4 adsorb via single-point attachment through the carboxyl group on the Ag surface. Based on theoretical calculations, the Ag nanoparticles are better stabilized by EPOA via an electrosteric dispersion mechanism. 相似文献
997.
Jianyong Zhai Huanqi Cao Ming Zhao Chen Wang Yuxian Li Hao Tong Ziyi Li Shougen Yin Daming Zhuang 《Ceramics International》2021,47(2):2288-2293
Sputtering with copper indium gallium selenide (CIGS) ceramic targets could produce smooth CIGS thin films that are preferred for preparing two-terminal tandem devices. However, grain sizes prepared in this way are small and device efficiency was low. To increase the grain size, in this report, an Ag layer was pre-sputtered beneath CIGS. The Ag doping layer increased the grain size and improved the crystalline alignment. Consequently, the Ag-doped films exhibited improved charge mobility. From X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy characterizations, we obtained an optimized Ag thickness of 15 nm. Short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF) were all improved after doping with 15-nm Ag. Increasing the annealing temperature from 550 °C to 575 °C, the grains was enlarged further, with the power conversion efficiency (PCE) increasing to 14.33% and VOC to 545 mV. Upon the smooth CIGS film, a thin conformal perovskite layer was fabricated without polishing. This work demonstrates a simple way to fabricate smooth and highly-crystalline CIGS films that can be used for tandem solar cells. 相似文献
998.
The content of defects and manipulation of oxygen vacancies in ceria (CeO2) nanomaterials through doping have been widely used as effective strategies to rationally control its reactivity for diverse applications. In this work, a facile and simple fabrication method of CeO2 nanorod crystals is demonstrated where; defects content and oxygen vacancies were tailored by doping with transition metal (Iron, Fe) ions. The effect of Fe-doping level (Ce0.95Fe0.05O2 and %, Ce0.9Fe0.1O2) on the structural, morphological, and optical properties of ceria nanorods was explored in detail. Undoped and Fe-doped CeO2 nanorods were further explored for their use in photocatalytic activity and humidity sensing applications. The results revealed superior photocatalytic activity of Ce0.9Fe0.1O2 by showing about 90% degradation of organic dye within 80 min of reaction time. Further, the same sample demonstrated excellent humidity sensing capabilities with faster response (~19 s) and recovery rate (~ 49 s) at 100% humidity conditions than other investigated samples. This work presents a systematic study on the fluencies of Fe doping in CeO2 nanorod crystals to better understand the role of oxygen vacancies for tailoring their structural and optical properties for proficient environmental and sensing applications. 相似文献
999.
T. H. Chuang H. M. Wu M. D. Cheng S. Y. Chang S. F. Yen 《Journal of Electronic Materials》2004,33(1):22-27
Intermetallic compounds formed during the soldering reactions between Sn-3.5Ag and Cu at temperatures ranging from 250°C to
375°C are investigated. The results indicate that scallop-shaped η-Cu6(Sn0.933 Ag0.007)5 intermetallics grow from the Sn-3.5Ag/Cu interface toward the solder matrix accompanied by Cu dissolution. Following prolonged
or higher temperature reactions, ɛ-Cu3 (Sn0.996 Ag0.004) intermetallic layers appear behind the Cu6(Sn0.933 Ag0.007)5 scallops. The growth of these interfacial intermetallics is governed by a kinetic relation: ΔX=tn, where the n values for η and ɛ intermetallics are 0.75 and 0.96, respectively. The mechanisms for such nonparabolic growth
of interfacial intermetallics during the liquid/solid reactions between Sn-3.5Ag solders and Cu substrates are probed. 相似文献
1000.
Ag/SnO2电接触材料的制备及烧结条件对密度的影响 总被引:1,自引:0,他引:1
以AgNO3和Sn(Ⅳ)盐为原料,采用水热还原法合成了银氧化锡(Ag/SnO2)复合粉体.复合粉体经压片、烧结制得片状Ag/SnO2电接触材料.通过XRD和SEM等手段对制得的Ag/SnO2复合粉体进行表征,系统考察了烧结时间、烧结温度、SnO2含量等因素对Ag/SnO2电接触材料密度的影响.结果表明,所得Ag/SnO2粉体为高度分散的球形颗粒; Ag/SnO2粉体经压片后,于750℃烧结3h所得电接触材料的密度最大;且材料的相对密度随其中SnO2含量的增加而略有降低,当SnO2含量在8%~16%(质量分数)之间时,所得Ag/SnO2电接触材料的相对密度均达到了97%以上. 相似文献