L.L. Hench
,
I. Xynos
,
A. Edgar
,
L. Buttery
,
J. Polak
,
钟吉品
,
刘宣勇
,
常江
无机材料学报
doi:10.3321/j.issn:1000-324X.2002.05.001
三十年前发现,生物玻璃能与骨形成骨键结合.这种特殊的材料已经有超过15年的临床应用,并有数以千计的成功病例.研究表明,骨的键合及骨再生和修复(骨形成作用)涉及玻璃表面的离子快速交换反应、生物活性表面反应层的成核和生长、由可溶硅和钙组成的临界浓度的离子溶解产物的释放.生物活性玻璃的分子生物学机理研究表明,它的生物活性响应看起来是由基因控制的.具有骨促进作用的A类生物活性玻璃通过直接对那些调节诱发细胞周期开始和进程的基因的直接控制,从而加强了其骨形成和促进作用.不能够形成新骨的细胞从细胞总体中被消除,这一特征是当成骨细胞在生物惰性材料或者B类生物活性材料培养时所没有的.骨前细胞细胞周期的基因调控生物学结果是成骨细胞的快速繁殖和分裂,这也导致了骨的迅速再生.对生物活性玻璃基因基础的理解,可以为设计新一代活化基因的玻璃材料、以及新一代活化基因的组织工程用生物降解支架材料提供重要的依据.如果我们能用玻璃激活基因,可以肯定,有一天我们就能用玻璃来控制基因.
关键词:
生物玻璃
,
基因活化
,
溶解硅
,
组织工程
Journal of Vacuum Science & Technology a-Vacuum Surfaces and Films
Chromium nitride (CrN) films were deposited on Si wafers by arc ion plating (AIP) at various negative bias voltages and several groups of N-2/Ar gas flux ratios and chamber gas pressures. The authors systematically investigated the influence of negative bias voltage on the synthesis, composition, microstructure, and properties of the AIP CrN films. In this part (Part I), the investigations were mainly focused on the macroparticle distributions and film-growth characteristics. The results showed that macroparticle densities on the film surfaces decreased greatly by applying negative bias voltage, which can be affected by partial pressure of N-2 and Ar gases. From the statistical analysis of the experimental results, they proposed a new hybrid mechanism of ion bombardment and electrical repulsion. Also, the growth of the AIP CrN films was greatly altered by applying negative bias voltage. By increasing the bias voltage, the film surfaces became much smoother and the films evolved from apparent columnar microstructures to an equiaxed microstructure. The impinging high-energy Cr ions accelerated by negative bias voltages were deemed the inherent reason for the evolution of growth characteristics. (c) 2008 American Vacuum Society.
关键词:
chromium nitride films;hybrid coating system;structure zone model;si-n coatings;mechanical-properties;tin films;thin-films;pulse bias;vacuum;evaporation
Acta Materialia
Cyclic deformation behavior of Cu-30% Zn single crystals oriented for single slip was studied at constant plastic shear strain amplitudes (gamma(pl)) in the range of 3.8 x 10(-5)-6.4 x 10(-3) in order to understand systematically the fundamental fatigue behavior of low stacking fault energy materials. Results indicate that the cyclic hardening behavior strongly depends on the strain amplitude applied. For low strain amplitudes (gamma(pl) <3 x 10(-4)), cyclic saturation occurred after an initial cyclic hardening stage, but for high strain amplitudes (gamma(pl) greater than or equal to 6.0 x 10(-4)) saturation could not be reached until fatigue failure. The initial cyclic hardening rate (theta(0.2)) was found to decrease with increase in the applied strain amplitude. Slip bands were found to behave very similarly to Luders band appearance at the beginning as well as in the middle stage of cyclic deformation. Particularly, the similarity of the cyclic hardening behavior at low and high strain amplitudes to the work hardening response in stages I and II of tensile deformation of the same alloy has been pointed out. Cyclic stress was further decomposed into two terms, the effective stress and the internal stress, and both were found to increase continuously with cyclic deformation. It has been demonstrated that the activities of secondary slips played an important role in the continuous cyclic hardening at high gamma(pl). A comparison of the present result with previous relevant work on both wavy and planar slip materials has been attempted. The transition of wavy slip mode to planar slip mode of Cu-Al and Cu-Zn alloys has been discussed in terms of the electron-atom ratio and the critical Value of the ratio for such a transition is found to be 1.18-1.19 for both alloys. (C) 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.
关键词:
stress-strain response;dislocation-structures;alpha-brass;fatigue;alloys;cu-16;temperature;amplitude
新型炭材料
Electrochemical capacitors (ECs) store energy in eletric double-layers formed along the interface of electrode material and electrolyte, this produces an extremely large capacitance compared with the traditional capacitors. The fundamental principles of electrochemical capacitors are briefly introduced, and the key materials used like electrode materials, electrolytes, separator and current collector materials are summarized. Electrochemical capacitors with pseudocapacitance, such as metal oxides, polymers and hybrid capacitors, are also discussed. The characteristics, possible application fields, the development state, the future R&D prospects for electrochemical capacitors are highlighted.
关键词:
electrochemical capacitors;supercapacitors;storage of electric energy;principles
王猛
,
林鑫
,
苏云鹏
,
沈淑娟
,
黄卫东
金属学报
对亚包晶、过包晶以及接近包晶点分成的Zn-Cu二元合金进行了定向凝固实验, 研究其在45 K/mm的温度梯度以及2—6400 μm/s凝固速度下的组织选择及深化规律, 发现Zn-2%Cu的低速度凝固组织为η相单相生长, 高速下为η相胞晶+胞晶间ε相的组织; Zn-2.7%Cu, Zn-3%Cu以及Zn-4%Cu的低速凝固组织为η相基体+ε相定向枝晶, 高速凝固组织为η相胞晶+ε相等轴晶, 基于最高界面生长温度判据, 在充分形核假设下对凝固过程中的相选择规律进行了分析, 并与实验结果较好的吻合.
关键词:
Zn-Cu包晶合金
,
null
,
null
Physica Status Solidi B-Basic Research
Within the framework of the linear spin wave approximation, the quantum fluctuations of spins at zero temperature in four-sublattice ferrimagnetic systems are studied by employing retard Green's functions. The effects of exchange constants on the quantum fluctuations of spins are discussed for three different spin-configurations. The magnetic properties of these spin configurations are related to their magnetically structural symmetry. When the parameters of the exchange couplings are adjusted, the crossover of the spin configurations results in the strong quantum fluctuations, owing to the behaviors of the non-three-dimensional magnetically system. When two of the four exchange-constants in the present four-sublattice bulk systems are set to be zero, the system behaves as a non-three-dimensionally magnetic system, although the structure of the system is still three-dimensional. All the exchange couplings involve in the quantum competition of the systems, but the effects of antiferromagnetic and ferromagnetic exchange couplings are different evidently. The antiferromagnetic exchange couplings play an important role in a balance of the quantum competition.
关键词:
heisenberg-antiferromagnet;3-layer superlattices;magnetic-structures;phase-transition;internal energy;ferromagnet;lattice;magnetoresistance;3-sublattice;dependence
陈志永
,
才鸿年
,
常亚喆
,
张新明
,
刘楚明
金属学报
采用取向分布函数和取向线分析方法研究了初始自由分布和具有近似立方织构的多晶铝轧制织构的演变规律.结果表明: 随着轧制变形的进行, 对于初始自由分布的样品, 晶粒取向主要向α, β取向线附近聚集, 其形变织构主要由C, S及B织构组成, 且3种织构成分密度值相差不大; 对于初始具有近似立方织构的样品, 晶粒取向主要向β取向线上聚集, 其形变织构主要由C, S织构组成, B织构成分相对较弱. 2种情况下S织构成分体积分量均比C, B织构高.
关键词:
多晶铝
,
rolling deformation
,
initial texture
,
random distribution
