检索结果-内蒙古大学图书馆

Temperature, magnetic field, and pressure dependence of the crystal and magnetic structures of the magnetocaloric compound Mn1.1Fe0.9(P0.8Ge0.2)

引用

Physical Review B 2009年第17期80卷 174415-174415页

作者： D. M. Liu Q. Z. Huang M. Yue J. W. Lynn L. J. Liu Y. Chen Z. H. Wu J. X. Zhang Key Laboratory of Advanced Functional Materials Ministry of Education Beijing University of Technology 100 Pingleyuan Chaoyang District Beijing 100022 China NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 USA Department of Materials Science and Engineering University of Maryland College Park Maryland 20742 USA Neutron Scattering Laboratory China Institute of Atomic Energy P.O. Box 275(30) Beijing 102413 China

Neutron powder-diffraction studies of the crystal and magnetic structures of the magnetocaloric compound Mn1.1Fe0.9(P0.8Ge0.2) have been carried out as a function of temperature, applied magnetic field, and pressure. The data reveal that there is only one transition observed over the entire range of variables explored, which is a combined magnetic and structural transformation between the paramagnetic (PM) and ferromagnetic phases (Tc≈255 K for this composition). The structural part of the transition is associated with an expansion of the hexagonal unit cell in the direction of the a and b axes and a contraction of the c axis as the FM phase is formed, which originates from an increase in the intralayer metal-metal bond distance. The application of pressure is found to have an adverse effect on the formation of the FM phase since pressure opposes the expansion of the lattice and hence decreases Tc. The application of a magnetic field, on the other hand, has the expected effect of enhancing the FM phase and increasing Tc. We find that the substantial range of temperature/field/pressure coexistence of the PM and FM phases observed is due to compositional variations in the sample. In situ high-temperature diffraction measurements were carried out to explore this issue, and reveal a coexisting liquid phase at high temperatures that is the origin of this variation. We show that this range of coexisting phases can be substantially reduced by appropriate heat treatment to improve the sample homogeneity.

关键词： bond lengths crystal structure ferromagnetic materials ferromagnetic-paramagnetic transitions heat treatment iron compounds magnetic structure magnetocaloric effects manganese compounds neutron diffraction paramagnetic materials phosphorus compounds solid-state phase transformations

来源：评论

学校读者我要写书评

暂无评论

Broadband absorption enhancement in anisotropic metamaterials by mirror reflections

引用

Physical Review B 2009年第12期80卷 125103-125103页

作者： Jiong Yang Xinhua Hu Xin Li Zheng Liu Zixian Liang Xunya Jiang Jian Zi Department of Physics and Surface Physics Laboratory Fudan University Shanghai 200433 People’s Republic of China Department of Material Science Fudan University Shanghai 200433 People’s Republic of China Laboratory of Advanced Materials Fudan University Shanghai 200433 People’s Republic of China Polar Research Institute of China Shanghai 200136 People’s Republic of China State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Science Shanghai 200050 People’s Republic of China

Nonresonant anisotropic metamaterials (AMMs), such as nanotube arrays, can be applied to achieve broadband absorption of electromagnetic (EM) waves. However, the AMMs should be very thick (∼1000 wavelengths) to attain high absorption. Here, we propose that using a slanted or corrugated metallic mirror, a thin AMM (∼3 wavelengths) is sufficient to obtain high absorption in a wide wavelength range (absorption >87% for wavelengths of 0.5–3 μm) and over a wide angular range. Unlike common absorptions, EM waves in an ambient medium (air) is first coupled with a propagating wave in the AMM and is then converted into a lossy wave by mirror reflections.

关键词： enhancement mirror reflections AMMs Reflection Atlantic Meridional Mode broadband wavelengths absorption diffusion waves Anisotropy electromagnetic waves Mirrors left-handed materials Refractive surgery enhancement

来源：评论

学校读者我要写书评

暂无评论

Optical Spectroscopy of Superconducting Ba0.55K0.45Fe2As2: Evidence for Strong Coupling to Low-Energy Bosons

引用

Physical Review Letters 2009年第18期102卷 187003-187003页

作者： J. Yang D. Hüvonen U. Nagel T. Rõõm N. Ni P. C. Canfield S. L. Bud’ko J. P. Carbotte T. Timusk Department of Physics and Astronomy McMaster University Hamilton Ontario L8S 4M1 Canada Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and Engineering Tianjin University Tianjin 300072 People’s Republic of China National Institute of Chemical Physics and Biophysics Akadeemia tee 23 12618 Tallinn Estonia Ames Laboratory and Department of Physics and Astronomy Iowa State University Ames Iowa 50011 USA The Canadian Institute of Advanced Research Toronto Ontario M5G 1Z8 Canada

Normal state optical spectroscopy on single crystals of the new iron arsenide superconductor Ba0.55K0.45Fe2As2 shows that the infrared spectrum consists of two major components: a strong metallic Drude band and a well-separated midinfrared absorption centered at 0.7 eV. It is difficult to separate the two components unambiguously but several fits using Lorentzian peaks suggest a model with a Drude peak having a plasma frequency of 1.6 to 2.1 eV and a midinfrared peak with a plasma frequency of 2.5 eV. Detailed analysis of the frequency dependent scattering rate shows that the charge carriers interact with a broad bosonic spectrum extending beyond 100 meV with a very large coupling constant λ=3.4 at low temperature. As the temperature increases this coupling weakens to λ=0.78 at ambient temperature. This suggests a bosonic spectrum that is similar to what is seen in the lower Tc cuprates.

关键词： Single crystals

来源：评论

学校读者我要写书评

暂无评论

Bubble growth in the preparation of mesophase-pitch-based carbon foams

引用

Carbon 2009年第8期47卷 2145-2145页

作者： Mei-Xian Wang Cheng-Yang Wang Ming-Ming Chen Tong-Qi Li Zi-Jun Hu Key Laboratory for Green Chemical Technology of State Education Ministry School of Chemical Engineering and Technology Tianjin University Tianjin 300072 China National Key Laboratory of Advanced Functional Composite Materials Aerospace Research Institute of Materials and Processing Technology Beijing 100076 China

来源：评论

学校读者我要写书评

暂无评论

The preparation and properties of SiO2/Si3N 4 microwave transparent composites

The preparation and properties of SiO2/Si3N 4 microwave tran...

引用

59th International Astronautical Congress 2008, IAC 2008

作者： Fan, Jinpeng Li, Zhongping Zhang, Dahai Feng, Zhihai Wang, Jinming Chen, Li National Key Laboratory of Advanced Functional Composite Materials Aerospace Research Institute of Materials and Processing Technology Beijing 100076 China

ISBN: (纸本)9781615671601

Quartz fiber reinforced silicon nitride composites were prepared with quartz fabric and polysilazane precursor by precursor infiltration and pyrolysis (PIP) method. The preparation method and dielectric, ablative and mechanical performance of the composites were focused on. It has been found that the composites have stable dielectric constants at room temperature and still have high values at high temperatures. In addition, to overcome the brittle rupture caused by strong bonding between interfaces, a boron nitride was designed and the mechanical properties were improved. The composites obtained by this method are one of excellent high temperature microwave transparent materials.

关键词： Silicon nitride

来源：评论

学校读者我要写书评

暂无评论

Preparation and reduction behavior of Mo-Cu powders by Sol-Gel

引用

Journal of Physics: Conference Series 2009年第1期188卷

作者： Ming Zhao Jinshu Wang Wei Liu Meiling Zhou Corresponding author: Jingshu Wang Key Laboratory of Advanced Functional Materials Ministry of Education College of Material Science and Engineering Beijing University of Technology Beijing 100124 China

Mo-Cu composite powders were prepared by the Sol-Gel method using citric acid as chelating reagent. The composition, morphology and particle size of the powders were studied by the XRD and TEM. TEM observation result shows the particle size of Mo-Cu powders is about 150nm after reduction and the Mo grains are covered homogeneously by Cu on the surface. The reduction behavior and mechanism were analyzed systematically. Temperature programmed reduction (TPR) results indicate that the appropriate two-step reduction temperatures are 500°C and 700°C, respectively. The results from FT-IR show that the bond of Mo=O is weakened due to the bond of Cu-O-Mo, which leads to the increase of the reduction capability of the Mo-Cu composite oxide powders.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Origin and tuning of the magnetocaloric effect in the magnetic refrigerant Mn1.1Fe0.9(P0.8Ge0.2)

引用

Physical Review B 2009年第1期79卷 014435-014435页

作者： Danmin Liu Ming Yue Jiuxing Zhang T. M. McQueen Jeffrey W. Lynn Xiaolu Wang Ying Chen Jiying Li R. J. Cava Xubo Liu Zaven Altounian Q. Huang Key Laboratory of Advanced Functional Materials Ministry of Education Beijing University of Technology 100 Pingleyuan Chaoyang District Beijing 100022 China NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Materials Science and Engineering University of Maryland College Park Maryland 20742 USA Department of Physics and Center for the Physics of Materials McGill University 3600 University Street Montreal Quebec Canada H3A 2T8

Neutron-diffraction and magnetization measurements have been carried out on a series of samples of the magnetorefrigerant Mn1+yFe1−yP1−xGex. The data reveal that the ferromagnetic and paramagnetic phases correspond to two very distinct crystal structures, with the magnetic-entropy change as a function of magnetic field or temperature being directly controlled by the phase fraction of this first-order transition. By tuning the physical properties of this system we have achieved a magnetic-entropy change [magnetocaloric effect (MCE)] for the composition Mn1.1Fe0.9P0.80Ge0.20 that has a similar shape for both increasing and decreasing field, with the maximum MCE exceeding 74 J/kg K—substantially higher than the previous record. The diffraction results also reveal that there is a substantial variation in the Ge content in the samples which causes a distribution of transition temperatures that reduces the MCE. It therefore should be possible to improve the MCE to exceed 100 J/kg K under optimal conditions.

关键词： crystal structure entropy ferromagnetic materials germanium alloys iron alloys magnetisation magnetocaloric effects manganese alloys neutron diffraction paramagnetic materials phosphorus alloys refrigerants solid-state phase transformations

来源：评论

学校读者我要写书评

暂无评论

Synthesis of Leucite from Potash Feldspar

引用

Journal of Wuhan University of technology(Materials science) 2008年第4期23卷 452-455页

作者： ZHANG Yi QU Chi WU Jianqing LU Ming RAO Pinggen LIU Xiaoxi Key Laboratory of Specially Functional Materials and Advanced Manufacturing Technology Ministry of Education South China University of Technology Guangzhou 510640 China College of Materials Science and Engineering South China University of Technology Guangzhou 510640 China

Leucite particles were synthesized from feldspar mixed with 0% to 52% potassium nitrate fired from 800 ℃ to 1 200 ℃ by solid state method. The X-ray Diffraction （XRD） patterns show that in the temperature range from 800 ℃ to 1 200 ℃, the leucite can be removed as the single crystalline phase. Kalsilite may be crystallized with leucite at 800 ℃, but can be eliminated after prolonged heating. The scanning electron Microscopy （SEM） images clearly display the that crystals of micrometer scale leucite, and the leucite crystals distribute evenly in the matrix. The Thermal expansion coefficient （TEC） of the samples fabricated is as high as 20.52×10^-6 ℃^-1 measured from 20 ℃ to 500 ℃. The mechanism of transformation from feldspar to leucite was proposed.

关键词： leucite synthesis potash feldspar

来源：评论

学校读者我要写书评

暂无评论

Effect of moisture on chemical stability and hydrogen permeability of Ni-BaCe0.9y0.1O3-δ cermet

Effect of moisture on chemical stability and hydrogen permea...

引用

作者： Fang, Shumin Yang, Jing Chen, Chushen Liu, Wei Laboratory of Advanced Functional Materials and Devices Department of Materials Science and Engineering University of Science and Technology of China Hefei 230026 China

Ni-BaCe0.9Y0.1O3-δ mixed protonic-electronic conductor can be used to separate hydrogen from syngas. Considering that water exists in syngas, it is necessary to evaluate the effect of moisture on chemical stability and hydrogen permeability of the cermet. In this paper, hydrogen permeation rates of Ni- BaCe0.9Y 0.1O3-δ (40:60 in volume ratio) in different water partial pressures were measured at intermediate temperatures (600-750δC). It is found that hydrogen permeation rate of the cermet is highest at an appropriate water partial pressure. Samples after experiment were analyzed by XRD, ICP and pH value measurement, in which Ba(OH)2 and doped CeO2 were found. The reaction of water with samples resulting in insulating Ba(OH)2 and doped CeO2 is contributed to the decrease of hydrogen permeation in excessive water partial pressure.

关键词： Cermets

来源：评论

学校读者我要写书评

暂无评论

High temperature properties of hydrogenated Ti50Zr25Co25 rapidly quenched alloy

引用

Journal of Physics: Conference Series 2009年第1期144卷

作者： S Jayalakshmi E Fleury D J Sordelet Center for Advanced Functional Metals Korea Institute of Science and Technology (KIST) Seoul 136-791 Korea Materials and Engineering Physics Program AMES Laboratory AMES Iowa 50011-3310 USA

The high temperature properties of hydrogenated Ti50Zr25Co25 ribbons were investigated up to 380°C. As indicated by tensile tests at room temperature, hydrogen-induced strengthening occurred until ~21 at.% hydrogen. At this range of hydrogen concentration (Hconc) varying from 0 to ~21 at.%, tensile tests conducted at high temperatures (300 to 400°C; strain rate: 10-4s-1) showed that in addition to enhancement in strength, elongation larger than 20% was obtained. The temperature range at which such property improvements occurred depends on the hydrogen concentration. The change in the mechanical properties in this range of Hconc and temperature is attributed to the corresponding changes in the thermal behaviour of the alloy, along with the inherent structural modifications induced by hydrogen addition.

关键词：

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：