STUDY ON THE RESPONSE TO LOW-VELOCITY IMPACT OF A COMPOSITE PLATE IMPROVED BY SHAPE MEMORY ALLOY

Improvement from the pseudo-elastic effect of shape memory alloy (SMA) on the low-velocity impact (LVI) resistance of a composite plate is investigated by the finite element method (FEM).The stiffness matrix of the dynamic finite element equation is established step by step and the martensite fraction is obtained at each time step.The direct Newmark integration method is employed in solving the dynamic finite element equation,while the impact contact force is determined using the modified Hertz's law.It is found that SMA can effectively improve the performance of a composite structure subjected to low-velocity impact.Numerical results show that the deflection of a SMA-hybrid composite plate has been reduced approximately by thirty percent when the volume fraction of the embedded SMA reaches 0.3.     

Self-assembled monolayers on magnesium alloy surfaces from carboxylate ions

Self-assembled monolayers (SAMs) of carboxylate salts (C_n−1H_2n−1COONa, n = 12, 16, 18) were successfully formed on Mg alloy substrate in ethanol solution and characterized by the contact angle measurement, ATR-FTIR, ellipsometry and XPS. The SAMs were regularly and densely anchored to the Mg alloy substrate via monodentate bonding with the tilting angles of about 40°, 33° and 27° for C12, C16 and C18 monolayers, respectively. Electrochemical impedance spectroscopy (EIS) proved the corrosion protection of SAMs for Mg alloy substrate with protective efficiency (PE) of even up to 98.5%.     

射频溅射功率对FeZrBCu软磁合金薄膜巨磁阻抗效应的影响

用射频溅射法制备了FeZrBCu软磁合金薄膜.研究了不同溅射功率对FeZrBCu薄膜软磁特性和巨磁阻抗效应的影响.用电子探针显微镜测量发现，当溅射功率为240W时，薄膜样品中Fe的原子含量为8732%，Cu的原子含量为29%.这种样品的矫顽力最小，为68A/m，饱和磁化强度约为111×105⁵A/m，软磁性能最佳，巨磁阻抗效应最大，溅态膜在 13MHz最大巨磁阻抗比纵向为17%，横向为11%.重点分析了阻抗的电阻、电感分量及横向有 效磁导率随频率的变化，得到在低频下主要是磁电感 关键词： 铁基合金 薄膜 巨磁阻抗效应     

Biomimetic apatite formation and biocompatibility on chemically treated Ti‐6Al‐7Nb alloy

Alkali treatment of the Ti‐6Al‐7Nb alloys with subsequent heat treatment has been adopted as an important surface treatment procedure for apatite formation in dental implants. This study examined the effects of alkali treatment on the precipitation of apatite on a Ti‐6Al‐7Nb alloy. All samples were immersed in a Hanks' Balanced Salts Solution [simulated body fluid (SBF)] at pH 7.4 and 36.5 °C for 15 days. The surface structural changes of samples due to the alkali treatment and immersing in SBF were analyzed by XRD, SEM and XPS. The cell toxicity was evaluated based on the optical density of the surviving cells. The samples were implanted into the abdominal connective tissue of mice for 4 weeks. A sodium titanate hydrogel layer was formed after immersion in an NaOH solution. A dense and uniform bone‐like apatite layer precipitated on the alkali and heat‐treated Ti‐6Al‐7Nb alloy in the SBF. There was a significant difference in cell toxicity between the treated and untreated Ti‐6Al‐7Nb (P < 0.05). The thickness of the fibrous capsule formed around the implant body was decreased significantly by the alkali and heat treatment (P < 0.05). The alkali treatment samples showed a better biocompatibility than the commercial metal samples. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of magnesium addition on the wetting of alumina by aluminium

In this report the wetting behaviour between polycrystalline alumina substrates and molten aluminium doped with magnesium as a wetting agent has been studied using the sessile drop technique. The time required for equilibrium attainment is investigated. To explore the formation of possible phases at the interface, electron microscopic studies along with EDX analysis have been employed. It is found that magnesium reduces the time and temperature required for equilibrium in the Al/Al₂O₃ system. The Al-7 wt% Mg and Al-10 wt% Mg alloys can wet alumina at temperatures as low as 900 °C. It is also found that molten aluminium doped with magnesium can wet polycrystalline alumina at temperatures below 1000 °C. A thin reaction layer was observed at the Al-Mg/Al₂O₃ interface in the present study.     

非晶Ni-Cu-P合金化学沉积过程的多重分形谱研究

用原子力显微镜测定了SiTiNPd基体,经不同沉积时间得到的非晶Ni13.1wt%Cu9.3wt%P薄膜的表面形貌,得到了AFM图像的多重分形谱.结果表明:随着沉积时间的增加,多重分形谱的宽度增加,Δf(Δf=f(αmin)-f(αmax))增大.说明沉积表面高度分布随着沉积时间的增加,不均匀性显著增加,镀层在水平和垂直方向生长并逐渐形成连续致密的镀层.这与对AFM图的观察是一致的 关键词： 多重分形谱 Ni-Cu-P合金 化学沉积 AFM图像     

The Rh influence on the surface distribution of the ternary alloy Pt-Pd-Rh

Using the modified analytical embedded atom method (MAEAM) and combining with Monte Carlo computer simulations, the surface segregations of Pd-Rh and Pt-Pd-Rh have been simulated. The simulation results indicate that Pd enriched at both Pd-Rh and Pt-Pd-Rh (1 1 1) surface, but in the ternary ones, the surface Pd concentrations are influenced by bulk Rh compositions. Differences and similarities of the surface segregations between Pt-Pd, Pd-Rh and Pt-Pd-Rh have been discussed. Because of the lack of the experimental data, we finally compared present simulation results with available experiment data and theory calculation results of Au-Cu-Ni and Cu-Ag-Au. It is shown that the present results of simulations are in qualitative agreement with the experimentally observed trends, and it will be helpful for a better understanding of the segregation behaviors in Pt-Pd-Rh.     

rf reactive co-sputtered Au-Ag alloy nanoparticles in SiO2 thin films

We have studied formation of Au-Ag alloy nanoparticles in sputtered SiO₂ thin films. Silica thin films containing Au-Ag nanoparticles were deposited on quartz substrates using rf reactive magnetron co-sputtering technique. The films heat-treated in reducing Ar + H₂ atmosphere at different temperatures. They were analyzed by using UV-vis spectrophotometry, atomic force microscopy and X-ray photoelectron spectroscopy (XPS) methods for their optical, surface morphological as well as structural and chemical properties. The optical absorption of the Au-Ag alloy nanoparticles illustrated one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. XPS results showed that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Using lateral force microscopy analysis, we have found that the alloy particles were uniformly distributed on the surface with grain size of about 20 nm.     

压力对Zr46.75Ti8.25Cu7.5Ni10Be27.5大块非晶合金玻璃转变和晶化动力学的影响

利用X射线衍射和差示扫描量热分析研究了高温高压下Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5大块非晶合金的玻璃转变和晶化行为，结果发现压力降低了该大块非晶合金中的自由体积、热焓和晶化激活能. 关键词： 大块非晶合金 高压 差示扫描量热分析 玻璃转变     

石墨颗粒／CuAIMn形状记忆合金复合材料中的位错内耗峰

利用渗流技术制备出了以石墨颗粒为阻尼增强相、以Cu-11．9A1-2．5Mn（wt％）形状记忆合金为基体的复合材料，对该合金的内耗行为进行了研究．在淬火态样品的内耗-温度曲线上观察到两个内耗峰，分别位于240℃和370℃附近．对其中低温峰的变化规律和机理进行了研究．实验发现，低温峰仅在复合材料中出现，峰位与频率无关，峰高随频率升高而上升；随升温速率增加，峰高增加，峰位移向高温；随石墨颗粒体积分数增加，峰高增加；经多次热循环后该内耗峰消失．由以上特征和微观观察，可以证明该峰起因于外加交变应力与位错的相互作用．