RAO Jianxi Naval Academy of Engineering
,
Wuhan
,
China MA Ruzhang University of Science and Technology Beijing
,
Beijing
,
China HE Yusheng Tsinghua University
,
Beijing
,
China MA Ruzhang Professor
,
Department of Metal Physics
,
University of Science and Technology Beijing 100083
,
Beijing
,
China
金属学报(英文版)
Measurements by using the ultrasonic technique together for electric resistance verified that the first sound velocity valley on cooling is mainly due to the soft-mode of driving the com- mensurate phase transition,and the second one due to the soft-mode of driving the martensitic transformation.The starting point,R_s,and finishing point,R_f,of the commensurate phase transition of the alloy have been determined.
关键词:
incommensurate phase transition
,
null
,
null
QIAO Lijie LIU Rui XIAO Jimei University of Science and Technology Beijing
,
Beijing
,
China
金属学报(英文版)
The effects of stress components on nucleation sites and propagation directions of stress cor- rosion cracks in brass were investigated with specimens under mode Ⅱ and mode Ⅲ loadings. The results indicated that under mode Ⅱ loading,stress corrosion cracks nucleated on the site with maximum normal stress component and propagated along the plane perpendieular to the maximum normal stress,under mode Ⅲ loading,the stress corrosion crack was not evident on the 45°plane due to the general corrosion in aqueous solution with high NH_4OH concentra- tion,while stress corroded in aqueous solution with low NH_4OH concentration, numerous cracks with spacings of 10—150μm were found on the 45°plane with maximum normal stress and no stress corrosion cracks was observed on the plane with maximum shear stress.
关键词:
stress corrosion cracking
,
null
,
null
,
null
Applied Physics Letters
The dielectric resonance and multiple magnetic resonances which correspond to multiple microwave absorptions in the 2-18 GHz range have been studied in the composite Fe/TiO(2). The Fe grain size is found to have great impact on the dielectric resonance in this metal-semiconductor composite. The polarization mechanism is attributed to interfacial polarization. The multiple magnetic resonances can be ascribed to the natural resonance and exchange resonances, which can be explained by Aharoni's exchange resonance theory. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3496393]
关键词:
ferromagnetic particles;carbon nanotubes;absorption;permeability
Douxing LI and Hengqiang YE (Laboratory of Atomic imaging of Solids
,
Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang
,
110015
,
China)
材料科学技术（英文）
The present paper summarizes the current status of high resolution electron microscopy (HREM)and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction,subnanometer level analysis, image simulation and image processing.
关键词:
材料科学技术（英文）
Molecular structures of adsorbed waters at metal surfaces are essential to understanding the widespread processes ranging from ice nucleation, to water involved catalytic surface reactions, to many phenomena of biological and astrochemical importance. Instead of providing a comprehensive literature survey, we focus in this review on detailed structural information, such as water orientations and occupation sites, of intact waters at low temperatures and ultrahigh vacuum conditions investigated by various surface techniques. Despite progresses made in direct imaging the surface waters at high resolutions, as exemplified in a close-packed (e.g. Pd(111)) and an open metal surfaces (e.g. Cu(110)) supported waters, structural mysteries remain at diverse metal surfaces. We highlight experimental challenges and discuss structural mysteries in elucidating surface water structures at molecular levels.
关键词:
Water monolayer;Surface structure;Transition metal surfaces;scanning-tunneling-microscopy;density-functional theory;vibrational-spectra;ice;pt(111);adsorption;dissociation;ru(0001);excitation;molecules
Jibiao Li Shenglong Zhu Fuhui Wang
材料科学技术（英文）
Molecular structures of adsorbed waters at metal surfaces are essential to understanding the widespread processes ranging from ice nucleation, to water involved catalytic surface reactions, to many phenomena of biological and astrochemical importance. Instead of providing a comprehensive literature survey, we focus in this review on detailed structural information, such as water orientations and occupation sites, of intact waters at low temperatures and ultrahigh vacuum conditions investigated by various surface techniques. Despite progresses made in direct imaging the surface waters at high resolutions, as exemplified in a close-packed (e.g. Pd(111)) and an open metal surfaces (e.g. Cu(110)) supported waters, structural mysteries remain at diverse metal surfaces. We highlight experimental challenges and discuss structural mysteries in elucidating surface
water structures at molecular levels.
关键词:
Water monolayer
,
surface structure
,
transition metal surfaces
J.Q.ZHANGD.J.YOUNG
中国腐蚀与防护学报
Metaldusting attacks iron, low and high alloy steels and nickel-or cobalt-base alloys by disintegrating bulk metals and alloys into metal particles in a coke deposit. It occurs in strongly carburising gas atmospheres (carbon activity aC>1) at elevated temperatures (400 ℃~1000 ℃). This phenomenon has been studied for decades, but the detailed mechanism is still not well understood. Current methods of protection against metal dusting are either directed to the process conditions-temperature and gas composition-or to the development of a dense adherent oxide layer on the surface of the alloy by selective oxidation. However, metal dusting still occurs by carbon dissolving in the base metal via defects in the oxide scale. The research work at UNSW is aimed at determining the detailed mechanism of metal dusting of both ferritic and austenitic alloys, in particular the microprocesses of graphite deposition, nanoparticle formation and underlying metal destruction. This work was carried out using surface observation, cross-section analysis by focused ion beam and electron microscopic examination of coke deposits at different stages of the reaction. It was found that surface orientation affected carbon deposition and metal dusting at the initial stage of the reaction. Metal dusting occurred only when graphite grew into the metal interior where the volume expansion is responsible for metal disintegration and dusting. It was also found that the metal dusting process could be significantly changed by alterations in alloy chemistry. Germanium was found to affect the iron dusting process by destabilising Fe3C but increasing the rate of carbon deposition and dusting, which questions the role of cementite in ferritic alloy dusting. Whilst adding copper to iron did not change the carburisation kinetics, cementite formation and coke morphology, copper alloying reduced nickel and nickel-base alloy dusting rates significantly. Application of these fundamental results to the dusting behaviour of engineering alloys is discussed.
关键词:
metal dusting
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null
,
null
,
null
,
null
,
null
Journal of Applied Physics
To date, high compressive ductility and energy absorption have been achieved in amorphous metal foams based on high-toughness Pd- and Zr-based metallic glasses and are known to result from two extrinsic toughening mechanisms: bending of struts and shear band arrest by pores. We study here a syntactic amorphous metallic foam produced by infiltration of a bed of hollow crystalline iron spheres with a low-toughness Mg-based metallic glass (Mg60Cu21Ag7Gd12). After quenching to vitrify the matrix, this foam exhibits much higher compressive failure strain and energy absorption than the monolithic metallic glass, an improvement which is assigned to an intrinsic mechanism, i.e., composite toughening by the network of hollow ductile iron spheres.(C) 2007 American Institute of Physics.
关键词:
glass matrix composites;mechanical-properties;enhanced plasticity;syntactic foams;alloys;fabrication;damage
Applied Physics Letters
The magnetotransport behaviors of a series of rare earth manganites with the same A-site cational mean radius and different A-site ionic radii variance (A-site disorder) are investigated. It is found that the system's ground state transforms from ferromagnetic metal to cluster-glass insulator with increasing A-site disorder. In the cluster-glass state, the magnetization shows the steplike behavior, indicating the existence of short-range magnetically ordered clusters. The significant effect of the A-site disorder on the electronic phase separation is revealed by detecting the cluster-glass ground state at low temperature. (c) 2006 American Institute of Physics.
关键词:
manganese oxide perovskites;phase-separation;cation disorder;double-exchange;magnetoresistance;resistivity
