Fei LIU
,
Congting SUN
材料科学技术（英文）
Micro/nanostructured crystals with controlled architectures are desirable for many applications in optics, electronics, biology, medicine, and energy conversions. Low-temperature, aqueous chemical routes have been widely investigated for the synthesis of particles, and arrays of oriented nanorods and nanotubes. In this paper, based on the ideal crystal shapes predicted by the chemical bonding theory, we have developed some potential chemical strategies to tune the microstructure of functional materials, ZnS and Nb2O5 nanotube arrays, MgO wiskers and nestlike spheres, and cubic phase Cu2O microcrystals were synthesized here to elucidate these strategies. We describe their controlled crystallization processes and illustrate the detailed key factors controlling their growth by examining various reaction parameters. Current results demonstrate that our designed chemical strategies for tuning microstructure of functional materials are applicable to several technologically important materials, and therefore may be used as a versatile and effective route to the controllable synthesis of other inorganic functional materials.
关键词:
Functional materials
,
materials
,
Chemical
,
strategy
Yinong Liu
材料科学技术（英文）
Thermoelastic martensitic transformations represent a unique collection of martensitic transformations that provide the working mechanisms for a range of functional materials. Such transformations present a unique thermodynamic system, whose basic principles apply to a wider spectrum of solid-state transformations, including processes such as magnetoelastic, electroelastic and optoelastic transformations. Owing to their unique ability to produce a mechanical work output, these transformation systems have great potential to serve as functional materials in a range of innovative designs as actuators and sensors. Understanding the thermodynamic laws governing these phenomena is of both fundamental significance for the understanding and characterization of the behaviour of these systems and practical importance as designing tools for the development of functional devices. This paper attempts to present a concise overview of the thermodynamic theories developed in the past few decades largely on typical examples of thermoelastic and magnetoelastic martensitic transformations in shape memory alloys.
关键词:
Martensitic transformations
,
null
Surface & Coatings Technology
To understand the physical mechanism of electromagnetic response and potential energy conversion mode in nanostructured materials, especially in metal/dielectric nanocomposite multilayers, a theoretical framework has been suggested. It involves the prerequisite of response, transmission effect, mode of response, plasma model, efficiency of response mode, and size effect of constitutive characteristics. Experimental results have proved that the size effect exists for electrical conductivity, optical constants, permittivity, permeability and carrier density in ultrathin Al, Ti and Fe films as the thickness of the film decreases to a nanometer size range. Principles for designing nanostructures are discussed. (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
metal/dielectric multilayer;nanostructure;electromagnetic response
Acta Physica Sinica
A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the dehydrogenation properties and its influence mechanics on several high-density hydrogen storage materials (MgH(2), LiBH(4), LiNH(2) and NaAlH(4)) and their alloys. The results show that MgH(2), LiBH(4), LiNH(2) and NaAlH(4) high-density hydrogen storage materials are relatively stable and have high dehydrogenation temperature. Alloying can reduce their stability, but the stability of a system is not a key factor to the dehydrogenation properties of high-density hydrogen storage materials. The width of band gap of hydrogen storage materials can characterize the bond strength basically, the wider the energy gap is, the harder the bond breaks, and the higher the dehydrogenation temperature is. The bonding peak of the valence band top of LiNH(2) is attributed mainly to the Li-N bonding, the N-H bond constitutes the low peak, which makes the dehydrogenation temperature of LiNH(2), high, though LiNH(2) has a narrow band gap in respect to LiBH(4) and NaAlH(4), which makes the ammonia release in the dehydrogenation process. Alloying makes the band gap narrow, and the Fermi level goes into the conduction band, which improves the dehydrogenation properties. It was found from the charge population analysis that B-H bond in LiBH(4) is the strongest, H-N bond in LiNH(2) is the weakest, so LiNH(2) is relatively easy to release hydrogen. After alloying, the bond strength of X-H is weakened in every hydrogen storage material, and the N-H bond strength in LiMgNH(2) is the lowest. Therefore, it is perspective to develop LiNH(2) as hydrogen storage from the lowering of dehydrogenation temperature.
关键词:
hydrogen storage material;first-principles calculation;dehydrogenation;ability
Shijie Zhang
材料科学技术（英文）
Considering the unique properties of small spacecraft, such as light weight, low power-consumption and high heat flux density, a new kind of lightweight boron carbide (B4C) radiation-protection coating material was proposed. New techniques for preparing LSMO thermal control coating and B4C radiation-protection coating were developed. The sample piece of multi-functional structure was manufactured by using the proposed materials, and a series of performance tests, such as thermal control and radiation-protection behaviors were evaluated. Test results show that: the emissivity of the multi-functional structure varies from 0.42 to 0.86 at 240 K to 353 K and the phase transition temperature is about 260 K. The electron radiation-protection ability of the multi-functional structure is 3.3 times better than that of Al material. The performance index of this multi-functional structure can meet the requirements for space application in on-board electronic equipment.
关键词:
Coating material
Transactions of Nonferrous Metals Society of China
A simplified model was proposed targeting at the isotropic high porosity metal materials with well-distributed structure. From the model the mathematical relationship between elongation and porosity was deduced for those materials, and the relationship formula was derived generally for actual high porosity metals at last, whose validity is supported by the representative experiment on a nickel foam prepared by electrodeposition.
关键词:
high porosity metal material;elongation;porosity
Science in China Series E-Technological Sciences
A geometrical model has been established based on the structure feature of high porosity metal materials, the mathematical relationship between electrical resistivity and porosity for high porosity materials with even structure has then been deduced conveniently, and the formula for calculating the electrical resistivity of high porosity materials through porosity, which is easy to know, has been acquired further. Besides, the theoretical formula was verified to coincide with the test results well by the application taking nickel foam as an example.
关键词:
high porosity material;electrical resistivity;calculation formula;deduction;foams
