张法明
,
常江
,
伯克尔 伊博哈德
新型炭材料
doi:10.1016/S1872-5805(09)60030-5
采用水溶性的聚乙烯醇修饰多壁碳纳米管表面,研究了聚乙烯醇修饰的碳纳米管在水浴摇床Tris-HCl缓冲溶液中的溶解过程.通过红外光谱,差示扫描量热仪,透射电镜及X光衍射的方法对聚乙烯醇修饰的碳纳米管在溶解过程中的显微结构变化进行了研究.结果表明:浸泡21d后,聚乙烯醇修饰的碳纳米管部分溶解于缓冲溶液,形成无定形碳碎片;但大部分碳纳米管没有溶解,仍然保持管状结构.揭示出聚乙烯醇修饰的碳纳米管的溶解过程为:碳-碳键在浸泡过程中发生断裂,碳纳米管的部分溶解产生了无定形碳碎片与残留纳米管层片,残留纳米管层片进一步溶解最终成为无定形碳.提出与讨论了聚乙烯醇修饰的碳纳米管在Tris-HCl缓冲溶液中可能的溶解机理是:修饰后的碳纳米管表面具有很多缺陷和断裂的碳键,在缓冲溶液中聚乙烯醇的溶解导致嫁接位置的碳管壁的碳原子的释放,最终导致其管状结构的破坏.
关键词:
碳纳米管
,
表面修饰
,
溶解
,
结构稳定性
,
生物医学应用
Fuquan LI
,
Chunqing WANG
,
Yanhong TIAN
材料科学技术（英文）
The interfacial phenomena of the Sn-Pb solder droplet on Au/Ni/Cu pad are investigated. A continuous AuSn2 and needle-like AuSn4 are formed at the interface after the liquid state reaction (soldering). The interfacial reaction between the solder and Au layer continues during solid state aging with AuSn4 breaking off from the interface and felling into the solder. The kinetics of Au layer dissolution and diffusion into the solder during soldering and aging is analyzed to elucidate intermetallic formation mechanism at the solder/Au pad interface. The concentration of Au near the solder/pad interface is identified to increase and reach the solubility limit during the period of liquid state reaction. During solid state reaction, the thickening of Au-Sn compound is mainly controlled by element diffusion.
关键词:
Sn-Pb solder droplet
,
老化
,
溶解
,
钎料熔滴
Qiangang XU
,
Haifeng ZHANG
,
Bingzhe DING
,
Zhuangqi HU
材料科学技术（英文）
The wetting behavior of molten Bi on polycrystalline Cu substrate and single crystal Cu substrate was studied by the sessile drop method in the temperature range from 673 to 873K. At low temperature the wetting behaviors of molten Bi on both types of Cu substrate were similar. However, at high temperature, the equilibrium contact angle of polycrystalline Cu substrate was lower than that of single crystal Cu substrate, because the preferred dissolution of grain boundaries leads to a smaller liquid/solid interfacial energy for polycrystalline Cu substrate. The formation mechanism of arrow-shaped Cu grains at the Bi/single crystal Cu interface is also discussed.
关键词:
Wettability
,
null
,
null
,
null
Wantang FU
,
Yi XIONG
,
Jun ZHAO
,
Yong LI
,
T.Furuhara
,
T.Maki
材料科学技术（英文）
The microstructural evolution of pearlite during severe cold rolling in Fe-0.8C binary alloy and Fe-1Mn-0.8C ternary alloys was investigated by using SEM, TEM and XRD etc. The results show that the deformed pearlite consists of irregularly bent lamella, coarse lamella with shear-band and fine lamella. As the rolling reduction increases, the proportion of fine lamella increases. The strong plastic deformation, amorphization and dissolution of cementite take place during the severe cold rolling. The maximum carbon content in ferrite reaches 0.15 mass% after 90% cold rolling.
关键词:
Pearlite
,
null
,
null
,
null
,
null
,
null
S.K.Sadrnezhaad
,
E.Ahmadi
,
M.Mozammel
材料科学技术（英文）
Kinetics of dissolution of silver present in precious metal scraps in HNO3 was studied in temperature range of 26~85℃. Dissolution rate of silver was much faster than that of copper at all temperatures. Effects of particle size, stirring speed, acid concentration and temperature on the rate of dissolving of silver were evaluated. Dissolution rate decreases with particle size and increases with temperature. Dissolving was accelerated with acid concentrations less than 10 mol/L. Concentrations greater than 10 mol/L resulted in slowing down of the dissolution rate. Shrinking core model with internal diffusion equation t/τ=1-3(1-x)2/3+2(1-x) could be used to explain the mechanism of the reaction. Silver extraction resulted in activation energies of 33.95 kJ/mol for Ag-Au0:04-Cu0:10 and 68.87 kJ/mol for Ag-Cu0:23 particles. Inter-diffusion of silver and nitrate ions through the porous region of the insoluble alloying layer was the main resistance to the dissolving process. Results were tangible for applications in recycling of the material from electronic silver-bearing scraps, dental alloys, jewelry, silverware and anodic slime precious metal recovery.
关键词:
Silver
,
null
,
null
,
null
,
null
,
null
