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ABSTRACT: The effects of Co addition on the properties of Ni8−xMn4Ga4Cox ferromagnetic shape memory alloys are systematically investigated by first-principles calculations. The formation energy results indicate that the added Co preferentially occupies the Ni sites in Ni2MnGa alloy. The total energy difference between the paramagnetic and the ferromagnetic austenite plays an important role on the Curie transformation. The electronic density of states gives rise to the difference in the magnetic properties.
Applied Physics Letters 04/2011; 98(16):164103-164103-3. · 3.84 Impact Factor
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Journal of Applied Crystallography 01/2011; 44:1164-1168. · 5.15 Impact Factor
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ABSTRACT: The fundamental theory of crystal twinning has been long established, leading to a significant advance in understanding the nature of this physical phenomenon. However, there remains a substantial gap between the elaborate theory and the practical determination of twinning elements. This paper proposes a direct and simple method - valid for any crystal structure and based on the minimum shear criterion - to calculate various twinning elements from the experimentally determined twinning plane for Type I twins or the twinning direction for Type II twins. Without additional efforts, it is generally applicable to identify and predict possible twinning modes occurring in a variety of crystalline solids. Therefore, the present method is a promising tool to characterize twinning elements, especially for those materials with complex crystal structure.
Journal of Applied Crystallography 12/2010; 43(Pt 6):1426-1430. · 5.15 Impact Factor
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Advanced Engineering Materials 11/2010; 12(10):1024 - 1028. · 1.18 Impact Factor
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Advanced Engineering Materials 11/2010; 12(10):1082 - 1085. · 1.18 Impact Factor
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ABSTRACT: In the last decade, a large amount of microarray gene expression data has been accumulated in public repositories. Integrating and analyzing high-throughput gene expression data have become key activities for exploring gene functions, gene networks and biological pathways. Effectively utilizing these invaluable microarray data remains challenging due to a lack of powerful tools to integrate large-scale gene-expression information across diverse experiments and to search and visualize a large number of gene-expression data points.
Gene Expression Browser is a microarray data integration, management and processing system with web-based search and visualization functions. An innovative method has been developed to define a treatment over a control for every microarray experiment to standardize and make microarray data from different experiments homogeneous. In the browser, data are pre-processed offline and the resulting data points are visualized online with a 2-layer dynamic web display. Users can view all treatments over control that affect the expression of a selected gene via Gene View, and view all genes that change in a selected treatment over control via treatment over control View. Users can also check the changes of expression profiles of a set of either the treatments over control or genes via Slide View. In addition, the relationships between genes and treatments over control are computed according to gene expression ratio and are shown as co-responsive genes and co-regulation treatments over control.
Gene Expression Browser is composed of a set of software tools, including a data extraction tool, a microarray data-management system, a data-annotation tool, a microarray data-processing pipeline, and a data search & visualization tool. The browser is deployed as a free public web service (http://www.ExpressionBrowser.com) that integrates 301 ATH1 gene microarray experiments from public data repositories (viz. the Gene Expression Omnibus repository at the National Center for Biotechnology Information and Nottingham Arabidopsis Stock Center). The set of Gene Expression Browser software tools can be easily applied to the large-scale expression data generated by other platforms and in other species.
BMC Bioinformatics 01/2010; 11:433. · 2.75 Impact Factor
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ABSTRACT: Three simple capping molecules (urea, 3-aminopropanol, and polyethylene glycol) with different functional groups (-NH(2) for urea, -NH(2) and -OH for 3-aminopropanol, and -O- for polyethylene glycol) have been designed to prepare magnetite (Fe(3)O(4)) particles with various shapes. The crystal structure, morphologies, and magnetic properties of the products have been characterized by X-ray diffraction, electron microscopy, and vibrating sample magnetometer. The results indicate that the capping functional groups play a major role in determining the size, shape, and thus magnetic properties of the magnetite nanocrystals. The morphology evolution of the magnetite under the hydrothermal condition is discussed in detail, particularly for the interaction between the various capping groups and surface structure and chemistry of the nanocrystals.
Journal of the American Ceramic Society 01/2009; 92(3):631-635. · 2.27 Impact Factor
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ABSTRACT: A general calculation method is proposed to characterize the crystalline planes and directions of a faceted nanoparticle using transmission electron microscopy (TEM) imaging and diffraction modes. With the determination of the edge vectors and then the plane normal vectors in the screen coordinate system of TEM, their Miller indices in the crystal coordinate system can be calculated through coordinate transformation. The method is helpful for related studies of the determination of the surface structure of nanoparticles.
Journal of Applied Crystallography 01/2009; 42:519-524. · 5.15 Impact Factor
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ABSTRACT: Heterogeneous photocatalysis used in the field of environmental remediation have attracted global interest both with respect to applied and fundamental points of views. Catalytic properties of nanostructured materials could benefit from the manipulation of particle shape and thereafter the exposed specific surface. In this paper, iron hydroxide nanorods photocatalyst was synthesized hydrothermally via two reactions using ferric and ferrous ions as iron source separately. The microstructure and morphology of the synthesized iron oxyhydroxide were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). Photocatalytic ability to decompose methyl orange under UV-visible illumination was revealed in presence of hydrogen peroxide.
01/2009: pages 137-139;
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11/2008: pages 421 - 433; , ISBN: 9780470444191
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11/2008: pages 389 - 396; , ISBN: 9780470444191
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ABSTRACT: Effects of a magnetic field on low-angle misorientation distribution and CSL boundary occurrence in ferrite in 42CrMo steel during the austenite to ferrite and pearlite transformation were investigated. The results show that a magnetic field can considerably lower the frequency of low-angle misorientations in ferrite lamellae and raise the occurrence of Σ coincidence boundaries, especially Σ 3 in ferrite. But no obvious effect on crystallographic orientation distribution, or texture, was detected.
Journal of Materials Science 01/2005; 40(4):903-908. · 2.02 Impact Factor
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ABSTRACT: The influence of an axial high magnetic field (up to 12 T) on the stability and morphology of the liquid–solid interface of a binary alloy has been investigated experimentally during the directional solidification of the Al–0.85 wt.% Cu and Zn–2.0 wt.% Cu alloys. Experimental results indicate that the high magnetic field caused the breakdown of a planar interface into cellular undulations and the formation of an irregular shape. Specifically, for the Zn–2.0 wt.% Cu peritectic alloy, a wavy band-like structure appears under a high magnetic field. Moreover, the high magnetic field promoted the enrichment of the solute Cu element in the diffusion boundary layer. A theory about the magnetization and solute build-up in the diffusion boundary layer under a high magnetic field for a binary alloy has been proposed. This magnetization and solute build-up could be partly responsible for the breakdown of the planar interface and the formation of the band-like structure in a peritectic alloy. Moreover, the stresses in the solid near the interface under a high magnetic field were analyzed, measured and simulated numerically. It is suggested that they are responsible to the interface irregularity, and are also capable of inducing the interface instability.
Acta Materialia. 57(5):1689-1701.
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ABSTRACT: The effects of a strong magnetic field on Al–Al2Cu and Pb–Sn lamellar eutectics during directional solidification have been investigated experimentally. The results show that the application of a strong magnetic field caused “tilting and oscillatory” morphological instabilities and deformation of the eutectic lamellae. Moreover, it was found that the Al–Al2Cu eutectic grain became aligned under a strong magnetic field and that with an increase in the magnetic field intensity this alignment was gradually enhanced. Further, the stresses caused by the magnetization force and the thermoelectric magnetic force during directional solidification under a strong magnetic field were analyzed and it was found that they are likely responsible for the “tilting and oscillatory” morphological instabilities and deformation. This is experimental evidence that the stresses imposed on a solid are capable of inducing the morphological instabilities of lamellar eutectics. The magnetic crystalline anisotropy of the Al2Cu phases and the growth relationship between the primary Al2Cu phase and the eutectic phases was investigated and it was found that the Al2Cu phase had a remarkable magnetic crystalline anisotropy which determined the growth of the Al–Al2Cu eutectic grain. Thus, alignment of the Al–Al2Cu eutectic grain under a strong magnetic field may be attributed to the magnetic crystalline anisotropy of the Al2Cu phase. Based on the growth behaviour of Al–Al2Cu and Pb–Sn lamellar eutectics under a strong magnetic field, an alignment model of lamellar eutectics during directional solidification under a strong magnetic field is proposed.
Acta Materialia. 58(4):1403-1417.
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ABSTRACT: The effect of a high magnetic field on the morphology and preferred orientation relationship of the Al–Al3Ni fiber eutectic has been investigated during directional solidification. Results indicate that an application of a high magnetic field has decreased the eutectic spacing and caused the appearance of the band-like structure. Moreover, it has been found that a high magnetic field has changed the preferred orientation relationship of the Al–Al3Ni eutectic. Indeed, the application of a 12 T high magnetic field has caused the preferred orientation relationship of the Al{3 3 1}//Al3Ni{0 0 1}; Al [1 1 0]//Al3Ni[0 1 0] in the case of no magnetic field to transfer into the Al{0 0 1}//Al3Ni{1 0 2}; Al[1 0 2]// Al3Ni[0 1 0]. Further, in order to investigate the nucleation and growing mechanism of the Al–Al3Ni eutectic, the growth and morphology relationships between the Al–Al3Ni eutectic and the primary Al and Al3Ni phases have been investigated during volume and directional solidification, respectively. It has been found that the growth and orientation of the primary Al3Ni phase and the heating flow extraction direction have determined the growth of the Al–Al3Ni eutectic. This implies that the Al–Al3Ni eutectic growth may be capable of being controlled by adjusting the alignment of the Al3Ni eutectic phase and the heating flow extraction direction. The above experimental results have been discussed from the effect of a high magnetic field on the diffusion process and the epitaxial growth of the eutectic.
Acta Materialia.
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ABSTRACT: The effects of magnetic field on nucleation barrier of the phase transformation from austenite to ferrite at different cooling rates in 42CrMo steel have been investigated. The microstructures of ferrite and pearlite aligned along the magnetic field direction (parallel to the hot-rolling direction) are obtained at a cooling rate of 10 °C/min, resulting from the kinetic effects of the applied magnetic field during cooling and the microstructural influences of an inhomogeneous deformation occurring during the previous hot rolling. In this case, the formation of ferrite grains at higher temperatures is attributed mainly to the preferential nucleation at austenite boundaries. However, a fairly uniform microstructure of randomly distributed ferrite and pearlite is formed at a high cooling rate of 46 °C/min in the magnetic field of 14 T, as a result of both intergranular and intragranular nucleation at relatively low temperatures. Probing into this issue is helpful to gain a better understanding of kinetic influences of magnetic field on the phase transformation from austenite to ferrite.
Journal of Magnetism and Magnetic Materials.
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ABSTRACT: Fabrication of porous polymer films is important for its potential applications in industry and everyday life. In this study, a thermoresponsive polymer poly(N-isopropylacrylamide-co-butylmethacrylate) (PNIBMA) was introduced to fabricate porous films on the glass surface. PNIBMA can alter its structure with temperature and has a lower critical solution temperature (LCST) of about 20 °C. The porous film of PNIBMA was prepared by drying a drop of PNIBMA solution (in CHCl3) on a glass surface under a moist air flow. Atomic force microscope (AFM) images showed that the porous polymer film contained many layers of vacant spheres with diameters of about 1 μm. This unique surface characteristic endowed the porous film with higher hydrophobicity than a flat PNIBMA film made by direct coating. This study expanded the materials for porous films fabrication in the field of thermoreponsive polymers and should be of great potential in scientific researches and industry applications.
Colloids and Surfaces A: Physicochemical and Engineering Aspects.
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ABSTRACT: An as-quenched structural steel is tempered at 600 and 650 °C for 1 h without and with a 14-T magnetic field. The magnetic field can effectively prevent the directional growth of cementite along martensite plate boundaries and twin boundaries by increasing both the cementite/ferrite interfacial energy and the magnetostrictive strain energy. Finally, particle-like cementite is obtained. Moreover, the magnetic field can obviously retard the formation and growth of `distortion-free' regions in the matrix, though without having any noticeable effect on the orientation distribution of the `distortion-free' part. Investigating this subject contributes to the understanding of the way a magnetic field influences phase transformation in solid metallic materials.
Acta Materialia.
