Ag含量对WC-12Co/Ag涂层高温摩擦性能的影响

采用超音速火焰喷涂技术制备了三种不同Ag含量(10%,15%和20%)的WC-12Co/Ag涂层,将其高温摩擦性能与WC-12Co涂层进行对比。通过微观检测手段分析了Ag在涂层中的分布形态;检测了500℃,不同载荷(50N,100N,150N和200N)条件下,WC-12Co/Ag涂层摩擦因数随摩擦行程增加而变化的情况;并观察了涂层高温摩擦试验后磨痕微观形貌以及Ag元素的分布状态。试验结果表明:Ag元素在涂层中均匀分布,涂层中的Ag主要以单质的形式存在;在500℃条件下,当Ag含量大于15%时,Ag元素在磨损界面处形成一定厚度的连续润滑膜,起到良好的自润滑作用。     

Electrotransport and diffusion of Co,Fe, and Ag in γ-Cerium

Electrotransport mobilities and diffusion coefficients were obtained for radiotracer impurities of Fe, Co, and Ag in Ce. The iron and cobalt moved toward the anode with mobilities of ～10^?3 cm²/v-s in the range of 550° to 650°C. The silver moved to the cathode with mobilities of ～10^?5 cm²/v-s in the range of 600° to 700°C. The, diffusion coefficients obtained fit an Arrhenius equationD=D _o e ^?ΔH/RT with the following parameters: Fe:D _o=3.3×10^?4, ΔH=4.6 kcal/mole Co:D _o=10^?2, ΔH=11 kcal/mole Ag:D _o=1.4, ΔH=28 kcal/mole The results are compared with other rare-earth diffusion data, and the possibility of a substitutional-interstitial diffusion mechanism, is considered.     

金属添加方式对NiFe基/NiFe2O4金属陶瓷微观组织的影响

采用粉末冶金法制备了2种金属陶瓷,通过X射线衍射和扫描电镜(SEM)分析发现金属相添加方式(尤其是Al的添加方式)对陶瓷的结构和组成有较大的影响,当Al以单质形式加入时,它会改变原有尖晶石的成分,形成新的尖晶石,同时,还会导致各金属元素的局部分布不均匀现象;合金化后Al的扩散得到了较好的控制,并没有改变原有陶瓷成分.2种金属陶瓷中的陶瓷相在高温烧结中都存在不稳定性,出现了离解现象.金属含量不同,金属陶瓷中陶瓷相和金属相的烧结机理也不同.     

NiFe2O4/NiFeCuAlSn金属陶瓷的导电性能

对用粉末冶金法制备的几种NiFe2O4／NiFeCuAlSn金属陶瓷电阻率进行了测试与分析，结果表明：随着合金含量的增加，样品的导电性由半导体陶瓷导电性向金属导电性转变；在600-800℃温度范围内，由于样品中金属相的氧化加剧，导致导电性能下降，当金属含量为80％时，在1000℃下金属陶瓷中金属相氧化严重，并存在NiFe2O4陶瓷相被还原的现象，电阻率大幅上升；金属陶瓷导电性能的提高取决于金属相在陶瓷中的分布形貌，网状分布的金属相能有效地提高金属陶瓷的导电性能。     

The dissolution behavior of metals from Ag/Cu and Ag/Au alloys in acidic and cyanide solutions

The dissolution behavior of silver, copper, and gold from silver/copper and silver/gold alloys in acid and cyanide solutions has been investigated using a rotating disc. Oxygen or ferric ion was used as an oxidant. The effect of composition of alloys, rotation speed, concentration of lixiviants, and temperature on the overall dissolution kinetics of these metals has been studied. The dissolution rate of silver was reduced due to galvanic effect, when it was leached from a silver/copper alloy disc in acidic media at relatively low oxidation potentials. On the other hand, when the oxidation potential was high, the galvanic effect of the dissolution rate became less pronounced. In the case of the silver/gold system in cyanide solutions, the effect of alloy composition on the dissolution rate of gold and silver was not as much as in the case of silver/ copper alloy systems. This may be attributed to the fact that both gold and silver are noble, and therefore, the electromotive forces of these two metals are not significantly different. Formerly with the South Dakota School of Mines and Technology Formerly Visiting Professor, South Dakota School of Mines and Technology     

三维ZnO/CdS/NiFe层状双金属氢氧化物光电催化氧化甲烷

将甲烷以低能耗的方式直接转化为甲醇等高附加值的化学品一直是可持续化工产业的重要目标和重大挑战。本文制备了三维（3D）ZnO/CdS/NiFe层状双金属氢氧化物（LDH）核/壳/分层纳米线阵列（NWAs）结构材料并将其用于室温、模拟阳光照射下甲烷的光电催化氧化。结果表明3D ZnO/CdS/NiFe-LDH具有优异的光电化学性能及催化活性,甲烷气氛下的光电流密度达到了6.57 mA·cm?2（0.9 V vs RHE）,其催化甲烷生成甲醇及甲酸产量分别是纯ZnO的5.0和6.3倍,两种主要产物的总法拉第效率达到54.87%。CdS 纳米颗粒（NPs）的沉积显著提升了复合物对可见光的吸收,促进了光生载流子的分离。而具有三维多孔结构的NiFe-LDH纳米片的引入改善了甲烷氧化表面反应动力学,起到了优异的助催化作用;并且有效抑制了O₂?-的产生,防止O₂?-进一步将甲醇及甲酸氧化为CO₂,提高了甲醇及甲酸的选择性。最后,提出了三维ZnO/CdS/NiFe-LDH复合材料光电催化甲烷转化为甲醇及甲酸的机理,为甲烷低能耗转化为高价值化学品提供了新思路。      

Ag/AgCl/Cl- coated silver-stripe reference electrode

Severe airway obstruction caused by tonsillar enlargement can result in disturbances in body growth. In this study, 1136 children between 7 and 12 years of age, were evaluated and the size of their tonsils was investigated with regard to height and weight. This study was performed in the course of school screening, and correlation between estimated tonsil size and height and weight of the children was sought. Statistically, no such correlation was found (P > 0.05).     

Ag/SnZn复合熔断丝的研制

研究了Ag／SnZn复合熔断丝的设计原则，考察了含Ag45％，Sn与Zn比例为93：7的复合熔断丝的电压降大小、时间一电流特性并与所要求的性能指标进行了对比．结果表明，所研制的Ag／SnZn复合熔断丝的性能指标符合要求．     

Directional solidification and characterization of near eutectic Sm2Co17/Co alloys

The effects of directional solidification processing on the microstructural, compositional, and magnetic properties of near eutectic Co-Sm alloys (∼9 at. pct Sm) have been studied. Because these sytems have high melting temperatures (T _m > 1000 °C) and are quite reactive to oxidizing environments, special containment techniques during solidification were developed. Initial investigations have been performed at modest thermal gradients in the liquid,G _L ≤ 60 °C/cm (1 °C/cm = 10⁻² K/m), and over a range of furnace (solidification) velocities, 0.8 ≤V ≤ 45.4 cm/h (1 cm/h = 2.8 × 10⁻⁶m/s). Since the range ofG _L/V values, a measure of the degree of interfacial morphological stability, was rather low, aligned dendritic morphologies, macrosegregation, and transition to rod eutectic growth were encountered. The primary dendrite spacing for near eutectic Sm₂Co₁₇/Co scaled withV ^−1/2 and varied from ∼50 μm for V ≥20 cm/h to hundreds of microns forV < 10 cm/h while the rod eutectic diameter and interred spacing were an order of magnitude smaller. For both dendritic and cooperative growth, the associated permanent magnet properties were rather poor,e.g., remanence less than 4 kG (1 gauss = 10⁻⁴ Tesla) and coercive force less than 1 kOe (1 Oe = 79.577 A/m) for the smallest dendrite and rod diameter dimensions encountered, although the magnetic hardness for the rod eutectic was larger than for the dendritic microstructure. Magnetization as a function of sample orientation indicated that the easy axis of magnetization was primarily along the direction of solidification for both ferromagnetic phases.