Alloy Temperature Dependence of Offset Voltage and Ohmic Contact Resistance in Thin Base InGaP/GaAs HBTs

研究了薄基区HBT合金温度对残余电压Voffset和欧姆接触电阻Rcontact的影响,给出了薄基区HBT的最佳合金温度区域.用肖特基钳位理论解释了合金温度过高导致Voffset偏大的现象.从晶体管基本物理机制推导出Voffset与集电极、发射极面积比Ac/Ae的关系,并用此解释了U形发射极HBT具有较小Ac/Ae的原因,进一步证明了U型发射极结构的优越性.     

Formation of PdNiZn thin film at oil‐water interface: XPS study and application as Suzuki‐Miyaura catalyst

Nanosheet of PdNiZn and nanosphere of PdNiZn/reduced‐graphene oxide (RGO) with sub‐3 nm spheres have been successfully synthesized through a facile oil‐water interfacial strategy. The morphology and composition of the films were determined by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive analysis of X‐ray (EDAX) and elemental mapping. In the present study, we have developed a method to minimize the usage of precious Pd element. Due to the special structure and intermetallic synergies, the PdNiZn and PdNiZn/RGO nanoalloys exhibited enhanced catalytic activity and durability relative to Pd nanoparticles in Suzuki‐Miyaura C‐C cross‐coupling reaction. Compared to classical cross‐coupling reactions, this method has the advantages of a green solvent, short reaction times, low catalyst loading, high yields and reusability of the catalysts.     

Epitaxy of Si:C on Si(001) via methyldichlorosilane

Methyldichlorosilane (CH₃SiHCl₂) is compared to methylsilane (CH₃SiH₃) for vapor phase epitaxy of cubic silicon - carbon (NO :) (Si:C) alloys on Si (001). Parameters of interest are growth rate, percent carbon and crystallinity. Carbon incorporation efficiency and experimental window for epitaxial growth are similar for both precursors. The two precursors differ in Si contribution to the film growth rate.     

Influence of aspect ratio and anisotropy distribution in ordered CoNi nanowire arrays

The size effects on magnetic properties of nanowires arrays were studied varying the nanowires diameter and maintaining the same periodicity among them, for two different nominal compositions of Co and Ni in the alloy form. The competition among magnetocrystalline and shape anisotropies changes drastically from smallest to biggest diameters altering the easy axis direction. In the case of 75% of Co in alloy, experimental values of the effective anisotropy constant (K_eff) vary from positive to negative depending on the diameter, which means a reversal of the easy axis direction. For 50% of Co the shape anisotropy dominates over the magnetocrystalline for all studied diameters.     

Dislocation driven chromium precipitation in Fe-9Cr binary alloy: a positron lifetime study

The influence of initial heat treatment on anomalous Cr precipitation within high temperature solubility region of the Fe–9Cr alloy has been investigated using positron lifetime studies. Air-quenched samples with pre-existing dislocations exhibited a distinct annealing stage in positron lifetime between 800 and 1100?K corresponding to Cr-precipitation. During this stage, Transmission Electron Microscopy showed fine precipitates of average size 4 nm, dispersed throughout the sample and from Energy-dispersive X-ray spectroscopy (EDS) analysis they are found to be Cr-enriched. The presence of dislocations is found to be responsible for Cr precipitation.     

Role of compositional changes on thermal,magnetic,and mechanical properties of Fe-P-C-based amorphous alloys

This work aimed to tune the comprehensive properties of Fe-P-C-based amorphous system through investigating the role of microalloying process on the crystallization behavior,glass forming ability(GFA),soft magnetic features,and mechanical properties.Considering minor addition of elements into the system,it was found that the simultaneous microalloying of Ni and Co leads to the highest GFA,which was due to the optimization of compositional heterogeneity and creation of near-eutectic composition.Moreover,the FeCoNiCuPC amorphous alloy exhibited the best anelastic/viscoplastic behavior under the nanoindentation test,which was owing to the intensified structural fluctuations in the system.However,the improved plasticity by the extra Cu addition comes at the expense of magnetic properties,so that the saturation magnetization of this alloying system is significantly decreased compared to the FeCoPC amorphous alloy with the highest soft magnetic properties.In total,the results indicated that a combination of added elemental constitutes,i.e.,Fe69Co5Ni5Cu1P13C7 composition,provides an optimized state for the comprehensive properties in the alloying system.     

A study on the phase transformation behaviour of Cu-20wt.Sn alloy produced using powder metallurgy method: Experimental and molecular dynamics modelling

In this study, Cu-20wt.Sn alloy was produced by powder metallurgy (PM) method by using high purity element powders. The phases in the microstructure of the produced alloy were determined by XRD study. The phase transformation behaviour of the alloy was investigated by DSC and modelling method. Moreover, the Cu-20wt.Sn alloy system was modelled with molecular dynamics (MD) simulation based on modified Embedded Atom Method (MEAM). The radial distribution function (RDF) was calculated to determine the structural properties of system during the phase transformations. The experimental results showed that the transformation ($\alpha +\delta$) → ($\alpha +\gamma$) occur at temperature above 500°C. The simulation results showed that the phase transformation $\alpha +\delta \to \alpha +\gamma$ occurs at 550°C temperature. Our simulation results are in reasonable agreement with the experimental data.     

Effect of transition elements on dispersoid formation and elevated-temperature mechanical properties in 6082 aluminum alloy

ABSTRACT

The effect of transition elements, specifically Mn, Cr, V, and Mo, on dispersoid formation and mechanical properties in 6082 aluminum alloy was studied. The elevated-temperature mechanical properties were evaluated based on the compressive yield strength and creep resistance. The results indicated that the addition of Mn to the 6082 alloy resulted in the formation of a large number of the thermally stable α-Al(MnFe)Si dispersoids, thereby significantly improving the elevated-temperature mechanical properties of the alloy. Subsequent additions of Cr, V, and Mo increased the amount of Mn-bearing intermetallic phases, which decreased the supersaturation levels of Mn and Si in the α-Al, and consequently decreased the volume fraction of the dispersoids. The alloys containing Cr, V, and Mo exhibited similar yield strengths at 300°C and higher yield strengths at room temperature compared to the alloy containing only Mn. The size effect of the smaller dispersoids containing Cr, V, and Mo together with the solid-solution hardening of these elements could balance out the strength decrease resulting from the decreased volume fraction of the dispersoids. The additions of Cr, V, and Mo significantly increased the creep resistance of the Mn-containing 6082 alloy. Vanadium induced the highest creep resistance followed by Cr and Mo. Solute atoms of these elements with low diffusivity in the aluminum matrix contributed significantly to increasing the creep resistance at 300°C.     

FeNi Alloy Nanoparticles Encapsulated in Carbon Shells Supported on N-Doped Graphene-Like Carbon as Efficient and Stable Bifunctional Oxygen Electrocatalysts

The development of cost-effective and durable oxygen electrocatalysts remains highly critical but challenging for energy conversion and storage devices. Herein, a novel FeNi alloy nanoparticle core encapsulated in carbon shells supported on a N-enriched graphene-like carbon matrix (denoted as FeNi@C/NG) was constructed by facile pyrolyzing the mixture of metal salts, glucose, and dicyandiamide. The in situ pyrolysis of dicyandiamide in the presence of glucose plays a significant effect on the fabrication of the porous FeNi@C/NG with a high content of doped N and large specific surface area. The optimized FeNi@C/NG catalyst displays not only a superior catalytic performance for the oxygen reduction reaction (ORR, with an onset potential of 1.0 V and half-wave potential of 0.84 V) and oxygen evolution reaction (OER, the potential at 10 mA cm⁻² is 1.66 V) simultaneously in alkaline, but also outstanding long-term cycling durability. The excellent bifunctional ORR/OER electrocatalytic performance is ascribed to the synergism of the carbon shell and FeNi alloy core together with the high-content of nitrogen doped on the large specific surface area graphene-like carbon.