Effect of C/Ti ratio on the laser ignited self-propagating high-temperature synthesis reaction of Al-Ti-C system for fabricating TiC/Al composites

TiC/Al composite was successfully synthesized utilizing laser ignited self-propagating high-temperature synthesis (SHS) of Al-C-Ti system with the different C/Ti molar ratio. When the molar ratio of C to Ti is below 1:1 in the starting materials, in addition to fine TiC particulates, a large amount of Al₃Ti phase was found in the composites; however, when the molar ratio of C to Ti is 1:1 in the starting materials, the Al₃Ti phase was almost completely eliminated and the distribution of TiC particulates generally appeared to be more homogeneous throughout the products synthesized.     

Characterization of Ni nanowires after annealing

The effect of Ni nanowires, fabricated by electrodeposition in self-ordered AAO templates, was studied. NiO and Ni₂O₃ nanofibers were fabricated by simple heat-treatment in air and in an atmosphere of pure O₂. Ni nanowires after vacuum annealing exhibit pronounced preferential orientation of Ni (111) at 600 °C. Grain growth resulted in size effects and induced the transformation of NiO to Ni₂O₃ during annealing in air. Ni was oxidized to Ni₂O₃ (∼ 500 °C) in an atmosphere of pure O₂. The stable Ni-oxides Ni₂O₃ are formed during annealing at a higher temperature (∼ 900 °C) in air and in an atmosphere of pure O₂.     

Effect of cerium on the growth and crystalline quality of KDP crystals

The effect of the addition of cerium in potassium dihydrogen phosphate, grown from aqueous solution by the temperature lowering method using bi-direction seed rotation technique has been studied. The optimal addition of trivalent cerium ions considerably prevents other bivalent transition metal ions (Co, Ni, Mn) from entering into the crystal lattice and results in reduced defects and dislocations. A simple microcontroller based bi-directional accelerated seed rotation control setup is designed and employed to avoid stagnant regions or re-circulating flows in the solution. High-resolution XRD analysis of the (002) plane reveals that the Ce³⁺ added KDP exhibited better crystalline perfection and contains less dislocation.     

超支化聚合物的性能、合成及其功能化应用研究

超支化聚合物，具有多端基的“缺陷核壳”空间结构，化学反应性活泼，易于改性，与相应的线型聚合物相比，拥有特殊的性能，在多领域展现出广阔的应用前景。随着合成技术的进步，它们的应用研究，尤其是功能化的应用研究，成为多年来的研究热点。主要介绍超支化聚合物的结构、性能、合成及其功能化应用研究概况。     

The effect of zirconium addition on the microstructure and properties of chopped carbon fiber/carbon composites

Carbon/carbon composites containing zirconium were prepared using chopped carbon fiber, mesophase pitch and Zr powder by the traditional process including molding, carbonization, densification and graphitization. The influence of Zr on the microstructure and properties of the composites were investigated. Results show that Zr can improve the interface bonding, promote more perfect and larger crystallites and enhance the conductive/mechanical properties of the composites. The high in-plane thermal conductivity of 464 W/(m K) and excellent bending strength of 83.6 MPa was obtained for a Zr content of 13.9 wt% at heat treatment temperature(HTT) of 2500 °C. However the conductive/mechanical properties of the composites decrease dramatically for an higher HTT of 3000 °C. SEM micrograph of the fracture surface for the composites shows that lower disorder crystallite arrangement of fiber and carbon matrix come into being in the composites during HTT of 3000 °C, which should be responsible for the low properties. Correlation between the content of Zr and the microstructure and properties are discussed.     

Conduction band states of transition metal (TM) high-k gate dielectrics as determined from X-ray absorption spectra

This paper uses X-ray absorption spectroscopy to study the electronic structure of the high-k gate dielectrics including TM and RE oxides. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d^* states, which define the optical band gap, E_g, and the conduction band offset energy with respect to crystalline Si, E_B. E_g and E_B scale with the atomic properties of the TM and RE atoms providing important insights for identification high-k dielectrics that meet performance targets for advanced CMOS devices.     

A Golden Section approach to optimization of automotive friction materials

A Golden Section approach combined with relational grade analysis is proposed as an experimental design tool helpful in the development of new automotive friction materials. Golden Section was used to design the volume fraction of the components systematically. The changes in friction performance (friction coefficient and wear) measured using Friction Assessment and Screening Test (FAST) can be correlated with component variations by use of relational grade analysis. This approach was utilized to optimize a non-metallic friction material containing seven ingredients including two fibers (aramid and slag fiber), four fillers (Al₂O₃, BaSO₄, graphite and nitrile rubber) and one binder (benzoxazine). The volume fraction of seven components was varied simultaneously in order to optimize the parameters of friction coefficient and wear with a minimum number of tests. Three phases were performed to find the optimal proportion of the components. The optimized friction performance was obtained after doing 19 formulation experiments.     

Crystallization behaviour of Ni-Co-base metallic glasses by isochronal and isothermal annealing

The crystallization behaviour of three amorphous alloys, Co₅₀Ni₂₅Si₁₅B₁₀, Ni₅₀Co₂₅Si₁₅B₁₀ and Ni₅₀Co₂₅P₁₅B₁₀, was studied by means of differential thermal analysis in conjunction with scanning transmission electron microscopy. Isochronal annealing showed a strong dependence of crystallization on scan rate over the range of 1.99 to 20.70 K min^–1. At high Co/Ni ratios, a sequential two-stage crystallization process involving primary MS-I phase followed by MS-II phase precipitation was observed. At low Co/Ni ratios MS-I and MS-II crystallization were concurrent and inseparable. Replacement of the metalloid Si with P as the glass-former dramatically reduced the activation energy for crystallization as well as the crystallization temperature. A mechanistic understanding of these findings was pursued in light of TEM/STEM microanalysis     

Effect of Heavy Rare Earth Dopants on Hydrogen Incorporation in SmCo 2:17 Type Magnet

Previous studies showed that the temperature coefficient of obviously decreases with increasing the content of heavy rare earth element in SmCo magnet. But the investigation on the hydrogen incorporation in SmCo magnet is limited. In this paper, we would like to report the effect of heavy rare earth dopant on hydrogen incorporation in SmCo 2:17 type magnet. The relationship between temperature and pressure in hydrogenatied magnet is studied using XRD, DTA, and magnetic measurement. Based on the experimental results, the initial hydrogenation temperature decreases with increasing the content of heavy rare earth, however, the initial saturation pressure enhances. During the hydrogenation, the temperature region shrinks with increasing heavy rare earth doping.