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The effects of pH and temperature of a stannate bath on the quality of stannate chemical conversion coatings formed on AZ91 D magnesium alloy by using the potentiostatic polarization technique at E = −1.1 V were investigated in order to improve uniformity and corrosion protection performance of the coating films. It was found that the uniformity and corrosion resistance of coating films deposited by potentiostatic polarization were closely associated with pH and temperature of the coating bath. The pH and temperature to obtain the best coating film were investigated as a function of corrosion protection performance evaluated by curves of potentiodynamic anodic polarization conducted in borate buffer solution. Scanning electron microscope observation and electrochemical corrosion tests of the stannate-coated samples confirmed significant improvement in uniformity and corrosion resistivity of coating films deposited by the potentiostatic technique by modifying the pH and temperature of the coating bath. It was also found that uniformity and corrosion resistivity of the coating films deposited by the potentiostatic technique were considerably improved compared to those of coatings deposited by the simple immersion method at the best conditions of pH and temperature of the coating bath. 相似文献
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M.C.F. Alves S. Boursicot V. Bouquet S. Députier I.T. Weber I.M.G. Santos 《Thin solid films》2010,519(2):614-618
SrSnO3 thin films were prepared by pulsed laser deposition on amorphous silica and single crystal substrates of R-sapphire, (100)LaAlO3 and (100)SrTiO3. High quality epitaxial (100) oriented films were obtained on LaAlO3 and SrTiO3 while a texture was revealed for films on sapphire deposited at the same deposition temperature of 700 °C. Amorphous films were obtained on silica but a post annealing at 800 °C induced crystallization with a random orientation. The screening of deposition temperature showed epitaxial features on SrTiO3 from 650 °C while no crystallization was observed at 600 °C. The influence of substrate and deposition temperature was confirmed by Scanning Electron Microscopy and Atomic Force Microscopy observations. 相似文献
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To examine variations in the transparent conducting properties after annealing at high temperatures, 300-nm thick Sb-doped Sn1 − xHfxO2 (x = 0.00-0.10) films were deposited onto silica glass substrates by the RF sputtering method and annealed in air up to 1000 °C at 200 °C increments. After annealing, all the Sb-doped SnO2 films were transparent and electrically conductive, but large cracks, which decreased the electrical conductivity, were generated in several films due to crystallization or the thermal expansion difference between the film and substrate. Only the film deposited at room temperature in an Ar and O2 mixed atmosphere did not crack after annealing, and its electrical conductivity exceeded 100 S cm− 1 even after annealing at 1000 °C in air. Hf-doping blue shifted the fundamental absorption edges in the UV region in the Sb-doped Sn1 − xHfxO2 films. Additionally, the optical transmission at 310 nm, T310, increased as the Hf concentration increased, whereas the electrical conductivity was inversely proportional to the Hf concentration. On the other hand, thinner films (150-nm thick) with x = 0.00 showed both a high electrical conductivity over 100 S cm− 1 and a high transparency T310 = 65% after high temperature annealing. 相似文献
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Corrosion phenomenon of magnesium alloys is one of the limits for using magnesium alloys in automotive and aerospace industries. The aim of this study is the development of Sn-containing protective oxide coating by a simple plasma electrolytic oxidation in KOH/KF/Na3PO4 electrolyte on AZ91D magnesium alloy in galvanostatic mode. The film morphology and composition were analysed by SEM coupled with EDS, XRD and Raman spectroscopy. In the oxide, tin is mainly incorporated as crystallised MgSn(OH)6 compound in the layer. The main properties of Sn-containing oxide coating on AZ91D are both keeping the corrosion rate at open-circuit conditions at an acceptable value, and providing a sufficient passivation plateau to reduce the pitting sensibility. The lather characteristic, revealed by pitting tests, addresses the major drawback of magnesium alloys which often undergo important galvanic coupling in service. Consequently, the addition of low stannate concentration in the electrolyte to form Sn-rich anodic oxide on magnesium alloys represents an interesting way to synthesize protective coatings by PEO in a short time of anodization. 相似文献
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对AZ31镁合金表面采取锡酸盐化学转化处理,采用对比试验测定了转化膜在质量分数3.5%NaCl溶液中的腐蚀率,利用扫描电镜(SEM)及能谱(EDS)观察分析了转化膜的形貌和元素含量.结果表明:经锡酸盐转化后的AZ31镁合金的腐蚀率为2.65mm/a,未经转化的AZ31镁合金的腐蚀率为30.36mm/a,耐蚀性有明显提高;锡酸盐转化液pH值在3.5~12范围时对AZ31镁合金均形成了转化膜保护层. 相似文献
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Abdelhedi Aydi Annie SimonRégnault Von Der Mühll Najmeddine AbdelmoulaHamadi Khemakhem 《Journal of Alloys and Compounds》2011,509(29):7773-7777
The present work reports the elaboration and physical investigation of new compounds of the following composition Ba1−xNax(Ti1−ySny)1−xNbxO3 (BTSnNxy). The studied ternary system presents some continuous solid solutions between the next 3 phases: the NaNbO3 antiferroelectric phase that becomes easily ferroelectric at low rate substitutions, the BaTiO3 ferroelectric phase and the paraelectric stannate phase BaSnO3. Two different dielectric behaviors can be observed once some substitutions are made either in A or B sites of an ABO3 perovskite. These substitutions modify the dielectric properties of the material. The introduction of Sn4+ and Ti4+ cations in the B site favors, respectively, a decrease of the transition temperature and an increase in the value of the real dielectric permittivity. The transition temperature should be modulated by varying the rate of cationic substitution. Some relaxor materials can be obtained at a temperature around room temperature. 相似文献
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The effects of solution composition and temperature on the microstructure and corrosion resistance of stannate conversion coatings on AZ61 magnesium alloys were investigated. The conversion coating consisted of a porous layer as under layer intimately contacted with the magnesium plate and a hemispherical particle layer as major overlay formed right on top of the porous layer. During the coalescence of the hemispherical particles to form a complete coating on the magnesium alloy, some sites of discontinuity inevitably left and determined the corrosion resistance of the coating evaluated using a salt spray test. Increasing bath stannate ion concentration and lowering bath pH increased the population density of the hemispherical particles whose size was accordingly reduced. The corrosion resistance of the conversion coating was improved with finer particles, which were preferably formed at less alkaline solution with higher stannate ion contents. Furthermore, the conditions favoring the formation of finer particles also reduced the immersion time necessary for producing the conversion coating with optimal corrosion resistance. 相似文献
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Thin films of CaSnO3:Tb-Mg perovskite phosphor were prepared on silica glass substrates or SrTiO3 (100) single crystal substrates by RF sputtering method. Intense green photoluminescence originating from Tb ions was observed from the films under uv (λex = 254 nm) excitation. Furthermore, electroluminescence devices using the CaSnO3:Tb-Mg phosphor were fabricated and their luminescence properties were examined. The device fabricated on the SrTiO3 substrate showed electroluminescence above an applied ac voltage of 500 V and green electroluminescence was clearly observed from the CaSnO3:Tb-Mg phosphor layer. Essence of the electroluminescence in the present devices was discussed along with an estimation of the electric field strength in the phosphor layer. 相似文献