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31.
Metallic materials are the most used materials as orthopedic or dental implants due to
their excellent mechanical properties. However they are not able to create a natural bonding with
the mineralized bone and occasionally suffer localized corrosion. This work describes the
electrochemical behavior of a hybrid sol–gel thin film with the addition of green inhibitor. These
films enhance the ability of the implant to make a union with the existing bone and improve its
resistance to aggressive environment. An ethanol solution of the polymerized vinyltrimethoxysilane
(PVTMS) was mixed with an aqueous solution of henna extract (Lawsonia inermis) and refluxed to
give homogeneous sols. Nanostructure hybrid PVTMS/henna thin films were deposited on the
stainless steel 316L by spin-coating. The morphology, composition and adhesion of hybrid sol–gel
coatings have been examined by SEM, EDX and pull-off test, respectively. Addition of high
additive concentrations (0.1%) did not disorganize the sol–gel network. Direct pull-off test
recorded a mean coating-substrate bonding strength larger than 20.6 MPa for the hybrid sol–gel
coating. The effect of henna extract, with various added concentrations from 0.012% to 0.1%, on
the anticorrosion properties of sol–gel films have been characterized by electrochemical impedance
spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution
and has been compared to the bare metal. Henna extract additions (0.05%) have significantly
increased the corrosion protection of the sol–gel thin film to higher than 90%. The in vitro
bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface
of the doped sol–gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol–gel thin films are practical
hybrid films in biomedical applications. 相似文献
32.
Effect of SrCO<Subscript>3</Subscript> addition on the dynamic compressive strength of ZTA 下载免费PDF全文
Ceramic parts usually experience dynamic load in armor applications. Therefore, studying the dynamic behaviors of ceramics is important. Limited data are available on the dynamic behaviors of ceramics; thus, it is helpful to predict the dynamic strength of ceramics on the basis of their mechanical properties. In this paper, the addition of SrCO3 into zirconia-toughened alumina (ZTA) was demonstrated to improve the fracture toughness of ZTA due to the formation of the SrAl12O19 (SA6) phase. The porosity of ZTA was found to be increased by the addition of SrCO3. These newly formed pores served as the nucleation sites of cracks under dynamic load; these cracks eventually coalesced to form damaged zones in the samples. Although the K IC values of the samples were improved, the dynamic strength was not enhanced because of the increase in porosity; in fact, the dynamic strength of ZTA ceramics decreased with the addition of SrCO3. 相似文献
33.
夹层板系统以其优越的力学性能在工程领域得到广泛应用。对夹层板系统在不同加载速率下的压缩力学性能进行了试验研究。首先对钢-聚氨酯-钢夹层板系统进行了准静态压缩试验,得到夹层板系统的准静态等效应力-应变曲线;并对同一组试样,基于分离式霍普金森压杆试验装置,进行了动态冲击压缩试验。近似等效SHPB试验原理,分析夹层板系统的动态力学性能。比较分析结构的破坏形式和原因,为新型结构的优化设计和应用提供参考。 相似文献
34.
Nano-Structured Carbide-Derived Carbon Films and Their Tribology 总被引:3,自引:0,他引:3
Michael McNallan Daniel Ersoy Ranyi Zhu Allen Lee Christopher White Sascha Welz Yury Gogotsi Ali Erdemir Andriy Kovalchenko 《清华大学学报》2005,10(6):699-703
Carbide-derived carbon (CDC) is a form of carbon produced by reacting metal carbides, such as SiC or TiC, with halogens at temperatures high enough to produce fast kinetics, but too low to permit the rearrangement of the carbon atoms into an equilibrium graphitic structure. The structure of CDC is derivative of the original carbide structure and contains nanoscale porosity and both sp2 and sp3 bonded carbon in a variety of nanoscale structures. CDC can be produced as a thin film on hard carbides to improve their tribological performance. CDC coatings are distinguished by their low friction coefficients and high wear resistance in many important industrial environments and by their resistance to spallation and delamination. The tribology of CDC coatings on SiC surfaces is described in detail. 相似文献
35.
Mechanical activation(MA) of malachite was carried out by dry planetary grinding(DPG) and wet Isa grinding(WIG) methods. When the rotational speed was increased to 400 r/min in DPG, the specific surface area of malachite reached the maximum and the particle size reached the minimum of 0.7–100 μm. Agglomeration occurred between mineral particles when the rotational speed was increased to 580 r/min in DPG.However, no agglomeration was observed among particles with sizes 0.4–3 μm in WIG. X-ray diffraction analysis showed that, at a 580 r/min rotational speed in DPG, the amorphization degree of malachite was 53.12%, whereas that in WIG was 71.40%, indicating that MA led to amorphization and distortion of crystal structures. In addition, in the Fourier transform infrared(FT-IR) spectra of activated malachite, the bands associated with –OH, CO_32-and metal lattice vibrations of Cu–O and Cu–OH were weakened, and a new H–O–H bending mode and peaks of gaseous CO_2 appeared, indicating that MA decreased the band energy, enhanced dihydroxylation, and increased the chemical reactivity of the malachite.Furthermore, the leaching behavior of copper ore was greatly improved by MA. 相似文献
36.
以人工智能中智能规划方法为基础,对军用软件测试用例自动生成技术进行了研究。现有的许多规划器都不能避免组合爆炸问题的发生,而这一问题又是导致规划失败的一个重要问题,针对这一现象,以IPP规划器为例,提出目标分解法对规划器所需事实文件进行划分,并对IPP规划器应用多事实文件处理算法进行扩展,扩展后的MF-IPP规划器能够处理多个事实文档,有效避免了组合爆炸问题的发生。将该方法应用到军用主控软件GUI(Graphical User Interface)测试用例自动生成中,主要思想是首先利用规划器生成初始测试用例,其次提出解扩展的方法来完善测试用例的生成。针对测试用例生成问题进行了比对分析,结果显示,MF-IPP可以很好地防止组合爆炸问题的发生。所生成的测试用例生成时间短、覆盖率高,不仅能够很好地辅助软件测试人员进行测试用例的编写,还能应用于自动化软件测试。 相似文献
37.
Parker CV Aynajian P da Silva Neto EH Pushp A Ono S Wen J Xu Z Gu G Yazdani A 《Nature》2010,468(7324):677-680
Doped Mott insulators have a strong propensity to form patterns of holes and spins often referred to as stripes. In copper oxides, doping also gives rise to the pseudogap state, which can be transformed into a high-temperature superconducting state with sufficient doping or by reducing the temperature. A long-standing issue has been the interplay between the pseudogap, which is generic to all hole-doped copper oxide superconductors, and stripes, whose static form occurs in only one family of copper oxides over a narrow range of the phase diagram. Here we report observations of the spatial reorganization of electronic states with the onset of the pseudogap state in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(8+x), using spectroscopic mapping with a scanning tunnelling microscope. We find that the onset of the pseudogap phase coincides with the appearance of electronic patterns that have the predicted characteristics of fluctuating stripes. As expected, the stripe patterns are strongest when the hole concentration in the CuO(2) planes is close to 1/8 (per copper atom). Although they demonstrate that the fluctuating stripes emerge with the onset of the pseudogap state and occur over a large part of the phase diagram, our experiments indicate that the stripes are a consequence of pseudogap behaviour rather than its cause. 相似文献
38.
Mehdi Haj Hojjatollah Mansouri Reza Vafaei Golam Reza Ebrahimi Ali Kanani 《矿物冶金与材料学报》2013,20(6):529-534
The hot compression behavior of AISI 321 austenitic stainless steel was studied at the temperatures of 950–1100℃ and the strain rates of 0.01–1 s?1 using a Baehr DIL-805 deformation dilatometer. The hot deformation equations and the relationship between hot deformation parameters were obtained. It is found that strain rate and deformation temperature significantly influence the flow stress behavior of the steel. The work hardening rate and the peak value of flow stress increase with the decrease of deformation temperature and the increase of strain rate. In addition, the activation energy of deformation (Q) is calculated as 433.343 kJ/mol. The microstructural evolution during deformation indicates that, at the temperature of 950℃ and the strain rate of 0.01 s?1, small circle-like precipitates form along grain boundaries; but at the temperatures above 950℃, the dissolution of such precipitates occurs. Energy-dispersive X-ray analyses indicate that the precipitates are complex carbides of Cr, Fe, Mn, Ni, and Ti. 相似文献
39.
Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining 下载免费PDF全文
The hot deformation characteristics of 1.4462 duplex stainless steel (DSS) were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800–1100℃ and strain rates of 0.001–1 s?1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-Hollomon parameter (Z) increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6.×1015 (lnZ=35.5), a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction (EBSD) confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate. 相似文献
40.
Biodegradable starch/poly (vinyl alcohol) film reinforced with titanium dioxide nanoparticles 总被引:1,自引:0,他引:1 下载免费PDF全文
Zahra Hejri Ali Akbar Seifkordi Ali Ahmadpour Seyed Mojtaba Zebarjad Abdolmajid Maskooki 《矿物冶金与材料学报》2013,20(10):1001-1011
Biodegradable starch/poly (vinyl alcohol)/nano-titanium dioxide (ST/PVA/nano-TiO2) nanocomposite films were prepared via a solution casting method. Their biodegradability, mechanical properties, and thermal properties were also studied in this paper. A general full factorial experimental approach was used to determine effective parameters on the mechanical properties of the prepared films. ST/PVA/TiO2 nanocomposites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results of mechanical analysis show that ST/PVA films with higher contents of PVA have much better mechanical properties. In thermal analysis, it is found that the addition of TiO2 nanoparticles improves the thermal stability of the films. SEM micrographs, taken from the fracture surface of samples, illustrate that the addition of PVA makes the film softer and more flexible. The results of soil burial biodegradation indicate that the biodegradability of ST/PVA/TiO2 films strongly depends on the starch proportion in the film matrix. The degradation rate is increased by the addition of starch in the films. 相似文献