非晶态TM—Zr合金的磁性

本文详细地介绍了这类非晶态合金在磁性质、临界行为、自旋波激发、混磁性及吸氢对磁结构影响等方面的研究进展．     

非晶态磁性理论综述

研究非晶态磁性理论是近几年才真正开始的.随着对非晶态磁性材料的研究日益深入,应用前景越来越明显,提出了从理论上阐明非晶态材料中磁相互作用和磁性现象特点的要求.更广泛地从整个固体物理的发展上看,从过去对晶体的研究,到对非晶态材料的各种物理性质,如半导性、超导性、磁性等的研究,是固体物理发展的重要方面.过去的固体理论中,晶体的点阵结构可以说是一个很重要的基础.然而现在的实验和理论都表明,对于许多物理性质,这种结构都不是决定性的条件,例如非晶态材料中同样可以形成能带结构,出现超导性、铁磁性或反铁磁性.因此,研究非晶态…     

非晶态磁性合金的研究与应用

本文简要地介绍了国内外非晶态合金近年来的生产情况，介绍了非晶态合金在电力变压器方面应用的现状及其意义，列举了非晶态台金在电子变压器方面应用的实例，介绍了一些与非晶态磁性合金的应用密切相关的技术进展和研究工作，评述了非晶态磁性合金的发展前景．     

非晶物质中的临界现象

非晶态材料有着复杂的原子结构(短程有序、长程无序)和特殊的物理性质,其临界现象和相变问题一直受到学术界关注.非晶合金,又称为金属玻璃,是一种新型的非晶态材料,具有很高的强度和优异的弹性.从微观的角度来看,非晶合金可以看作是一个多粒子系统.临界现象的研究对认识和理解多粒子系统之间的相互作用有深刻的意义.本文主要讨论非晶合金中的临界现象,包括非晶合金从制备过程、微观结构到宏观的力学性能以及磁性方面存在的临界现象,并分析这些临界现象之间的内在联系,进而深入理解非晶合金的微观结构对其宏观性质的影响.这为认识非晶合金的形成本质,提高服役可靠性,探索具有实际应用价值的非晶合金提供理论依据.     

氢分子在Na2Al6团簇上的吸附和解离性能

氢的物理和化学吸附是氢存储的基本形式,而H₂分子的解离能垒是决定可逆储氢动力学性能的重要因素.纳米团簇是研究材料储氢性能的重要物质层次,研究氢与Na-Al团簇的相互作用性质能够了解纳米尺度的Na-Al氢化物的储氢性能.本文利用密度泛函理论,计算研究了H₂分子在较小的合金团簇Na₂Al₆上的吸附与解离性能.结果表明H₂分子在Na₂Al₆团簇上是弱的物理吸附,但很容易发生解离.氢分子的解离能垒很低,解离可以在环境温度下发生,纳米结构的Na₂Al₆团簇具有良好的化学储氢性能.     

非晶材料与物理近期研究进展

由于结合了金属和玻璃的特性,非晶合金表现出许多新奇和优异的力学和物理性质,在很多领域具有广泛的应用前景.非晶合金具有连续可调的成分、简单无序的原子结构、丰富多变的材料性质,为研究非晶态物理中的许多共性科学问题提供了理想的模型材料.块体非晶合金的发展更是将玻璃和液体及其相关科学问题的研究推进到凝聚态物理和材料科学的研究前沿.中国科学院物理研究所极端条件物理重点实验室亚稳材料合成、结构及性能研究组(EX4组)近二十年来一直致力于非晶材料和物理的研究,在新型非晶合金的制备、物性以及相关机理的研究上取得了许多重要成果.本文介绍团队最近在非晶材料和物理机理方面取得的研究成果,包括非晶合金的动力学行为和调控、非晶合金的表面动力学、功能应用以及材料探索新方法等.     

非晶态物理与软磁材料的产业化

由于非晶态材料具有独特的结构和优异的性能,其发现和发展对相关传统材料及其应用领域产生了巨大的冲击和深远的影响.从1960年首次发现非晶合金至今已有40余年,基础研究和应用开发均取得长足进展,特别是作为软磁材料的非晶合金带材已经实现了产业化,并获得了广泛应用.文章综述了非晶态物理方面的一些基本问题,以及非晶软磁合金的发展历程和产业化现状.     

氢对几种非晶态合金磁性的影响

本文研究了电解充氢对3种不同成分的非晶态合金磁性的影响。实验结果表明,充氢后试样变得很脆,软磁特性显著变劣,但饱和磁化强度σ₃和平均超精细场H_f显著提高。将试样在室温下放置,随着氢气的外逸,磁性、韧性以及H_f可得到逐步恢复。 关键词：     

H2在二维共价有机骨架上吸附的蒙特卡罗模拟研究

使用巨正则蒙特卡罗方法预测H2分子在六种具有不同结构和组分的二维共价有机骨架材料(2D COFs)中的物理吸附行为.研究结果表明:(1)在所研究的温度和压力范围内,ILCOF-1表现出最优异的氢存储性能,是目前2D COFs中储氢量最高的材料之一;其它5种COFs的储氢量低于其它2D COFs中储氢量较高的COF-5,-8,-10和TP-COF,而与COF-1,-6和Pc-PBBA COF相差不多.(2)与3D COFs相比,本文所研究的所有COFs的储氢量均低于目前储氢量最高的COF-105和COF-108;除ILCOF-1外,其它5种COFs材料均低于COF-102和COF-103.根据模拟计算的结果,分析了表面积、孔直径和等量吸附热等因素对COFs储氢性能的影响.对COFs储氢能力的强化提出了一些建设性意见.     

第四届全国非晶态材料和物理学术讨论会在西安召开

由中国科学院数理学部和中国物理学会联合主办的第四届全国非晶态材料和物理学术讨论会于1985年5月9日至13日在西安市举行.来自全国70多个单位的220余名代表参加了会议.会上就非晶态半导体物理、工艺和物性,非晶态金属的结构,结构弛豫和稳定性,工艺和应用,基础物性及其它等方面内容,分五个学术组交流了约二百篇论文.并就非晶硅、微晶硅研究的现状和展望,国内、外非晶态金属薄带和薄膜的研究和应用,某些非晶态合金的原子和电子结构,金属玻璃的内耗以及非晶态快离子导体等方面组织了16篇专题报告,对普遍感兴趣的问题还组织了专题讨论会.美国从…     

铁基软磁非晶/纳米晶合金研究进展及应用前景

非晶合金通常是将熔融的金属快速冷却、通过抑制结晶而获得的原子呈长程无序排列的金属材料.由于具有这种特殊结构,铁基软磁非晶合金具有各向同性特征、很小的结构关联尺寸和磁各向异性常数,因而具有很小的矫顽力H_c,但可和晶态材料一样具有高的饱和磁感强度B_s.优异的软磁性能促进了铁基软磁非晶合金的应用研究.目前,铁基软磁非晶/纳米晶合金带材已实现大规模工业化生产和应用,成为重要的高性能软磁材料.本文回顾了软磁非晶合金的发现和发展历程,结合成分、结构、工艺对铁基非晶/纳米晶合金软磁性能的影响,介绍了相关基础研究成果和工艺技术进步对铁基软磁非晶/纳米晶合金研发和工业化应用的重要贡献.并根据结构、性能特征将铁基软磁非晶合金研发与应用分为三个阶段,指出了目前铁基软磁非晶合金研发与应用中面临的挑战和发展方向.     

储氢材料与金属氢化物-镍电池

储氢合金是金属氢化物-镍电池的关键材料，文中简要评述了稀土镍系合金、Laves相系合金、镁基合金、钒基固溶体和纳米管材料作为储氢电极材料的研究进展与目前存在问题，并简要介绍了动力金属氢化物-镍电池的开发动态。     

铀基非晶合金的发展现状

铀基非晶合金是非晶家族中的特殊成员,受限于铀元素的高活性与放射性特点,目前这类非晶材料的研究极不充分.本文结合非晶合金的最新发展动态简要介绍了铀基非晶发展历史,较系统地总结了本团队的最新铀基非晶研究工作:首先较详细地介绍了新型铀基非晶的制备技术、成分体系、形成规律与晶化行为,澄清了其形成机制与热稳定性;结合高分辨电镜分析展示了其微观结构特点;采用纳米压痕技术揭示了这类非晶的微纳力学性能;利用电化学测试方法评估了其耐腐蚀性能.这些结果丰富了非晶材料的内涵,有助于深化对非晶物理基础科学问题的理解,并推动新型铀合金材料的发展,为这种材料的潜在工程应用奠定了基础.     

NANOSTRUCTURED Zr-BASED ALLOYS-PHASE FORMATION AND MECHANICAL PROPERTIES

Newly developed nanostructured Zr/Ti-Al-TM multiphase alloys can provide a large bandwidth of interesting properties, such as mechanical properties. Bulk materials with nanocrystalline/ amorphous and (nano)quasicrystalline/ amorphous microstructure with different volume fractions of nanophases and with different grain sizes can be obtained by slowly cooling the melt as well as by solid state reactions. Multiphase structures are realized either by partial de-vitrification of bulk glass-forming alloys or by defined addition of inert compounds upon alloying. Special preparation techniques e.g. copper mould casting and subsequent controlled annealing and mechanical alloying combined with hot consolidation of powders are described. The phase formation and transformation processes and the thermal stability of such materials in dependence on alloy composition and processing parameters are discussed in detail. Currently, the exploration of properties with respect to potential applications of these nanostructured alloys is still at the beginning. First investigations on the contributions of different phases/ volume fractions to the overall mechanical behaviour will be shown. At room temperature, the deformation behaviour of amorphous/crystalline bulk samples is governed by contributions of all existing phases yielding a high strength of the material.     

Applied research on amorphous magnetic materials

Amorphous magnetic materials are increasingly becoming an industrial reality, with a variety of applications to electronics and electrical engineering. Many research lines are in progress for what concerns the production techniques, the understanding of the structure and properties of amorphous ribbons, the optimization and extension of their applications. The fast quenching methods used to obtain amorphous materials will first be reviewed, also describing an experimental apparatus set up by the authors for laboratory investigations of rapid solidification processes. Becauses of the non equilibrium structure of amorphous metallic alloys, various relaxation effects are expected to occur, which may partially limit the use of these materials. Studies of these relaxation phenomena, performed by different methods, including Mossbauer spectroscopy will also be reviewed, showing their importance in better understanding the amorphous structure. Finally much attention will be devoted to actual applications of amorphous magnetic materials. Emphasis will be placed on the prospective applications of amorphous ribbons characterized by very low power losses to magnetic cores of distribution transformers, pointing to the possible advantages, but also to the technical problems involved with the substitution of crystalline laminations with the new amorphous materials.     

A mechanism for the formation of annealed compact oxide layers at the interface between anodic titania nanotube arrays and Ti foil

We propose a mechanism for the growth of crystalline anodic titanium-oxide (ATO) nanochannel arrays based on thermodynamic considerations and structural imperfections. Both amorphous and crystalline ATO films were obtained from the anodization of a titanium foil. Amorphous ATO nanotubes have a single-layer form, which makes them inefficient for use in photo-catalytic and solar-cell applications. Annealed ATO nanotubes are considered non-stoichiometric if the effect of oxygen partial pressure on the composition is significant. The driving force behind growing crystalline ATO nanotubes is the drawing of oxygen from the atmosphere to the oxygen site, which consequently decreases the concentration of oxygen vacancies in the anatase phase. The small ionization energies of titanium ions produce the stoichiometric defects. A diagram showing Gibbs energy and Kroger–Vink notation to indicate the strong influence of the non-stoichiometric ATO structure is deduced.     

What we have learned from studies on chemical properties of amorphous alloys?

Amorphous alloys have many attractive characteristics including extremely high corrosion resistance if the sufficient amounts of corrosion-resistant elements are added. The superiority of amorphous alloys is based on the homogeneous single phase nature without any chemical and physical heterogeneities. Although there are processing limitations to avoid the formation of heterogeneous crystalline structure in addition to no welding technology without crystallization, the application of corrosion-resistant amorphous alloys is expected particularly to the very aggressive environments, where any conventional crystalline metallic materials cannot be used. Some amorphous bulk alloys showed zero corrosion mass loss due to spontaneous passivation even in 12 M HCl. Production of amorphous bulk alloys became possible for selected compositions. The homogeneous single phase nature is also effective to form useful catalysts with unique composition and structure. An example of catalysts is for carbon dioxide methanation useful for supply of renewable energy in the form of methane.     

Structural and thermodynamic properties of metallic hydrides used for energy storage☆

Nowadays, energetic needs are mainly covered by fossil energies leading to pollutant emissions mostly responsible for global warming. Among the different possible solutions for the greenhouse effect reduction, hydrogen has been proposed for energy transportation. Indeed, H₂ can be seen as a clean and efficient energy carrier. However, beside the difficulties related to hydrogen production, efficient high capacity storage is still to be developed. Hydrogen can be stored as a compressed gas, in liquefied tanks or absorbed in solids. Many metals and alloys are able to store large amounts of hydrogen. This latter solution is of interest in terms of safety, global yield and long time storage. However, to be suitable for applications, such compounds must present high capacity, good reversibility, fast reactivity and sustainability. In this paper, we will review on the structural and thermodynamic properties of metallic hydrides. Their solid–gas hydrogenation behaviour and the related absorption–desorption isotherm curves are examined as a useful criterion for the selection of suitable materials for applications. The storage performances obtained with these alloys are reported and some solutions to common problems such as corrosion, passivation, decrepitation, poor kinetic and short cycle life are discussed.     

Comparative study on the hydrogen storage capacity of crystalline and amorphous nanomaterials of MoO<Subscript>3</Subscript>: effect of a catalytic Pd capping

Hydrogen storage capacities were investigated for two forms of MoO₃ nanomaterial, amorphous of low crystallinity, and other highly crystalline, using the quartz crystal microbalance technique. Effect of a catalytic Pd capping on the nanomaterials was evaluated. MoO₃ materials were grown using the gas condensation method, and both the amorphous and crystalline samples were composed of orthorhombic phases with Mo⁶⁺ oxidation state. For 4-min measurements, uncapped amorphous MoO₃ achieved a higher storage capacity than its crystalline counterpart, while Pd-capped samples exhibited lower values due to slower kinetics. Then, Pd-capped samples were measured using longer H2 exposure times of 30 min, finding that Pd-capped crystalline MoO₃ sample exhibited higher hydrogen storage capacity than its amorphous counterpart. Pd capping was found to affect the hydrogenation of the underlying oxide layer, mainly due to differences in long-range order and layered structure between crystalline and amorphous MoO₃ samples.