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1.
《Acta Materialia》2002,50(4):691-701
The high temperature cyclic oxidation resistance of Ti–50Al can be improved by anodic coating in phosphoric acid aqueous solution (4 wt% H3PO4) at 18°C. Sparking occurs sporadically on the surface as the voltage is over 300 V and the instantaneous current density after 45 min of anodization increases with increasing voltage. The anodic films are amorphous and contain substantial amount of phosphorus. Cyclic oxidation test indicates that the anodization can remarkably reduce the oxidation in air at 800°C and the improvement increases with increasing anodizing voltage up to 400 V, at which the parabolic oxidation rate constant can be reduced to about 1/600 of that for as-homogenized Ti–50Al. Raman spectra show that the anodic film can slow down the formation of rutile and α-Al2O3 during oxidation. The doping effect of phosphorus ions in titanium oxide accounts for the improvement of high temperature oxidation of Ti–50Al. 相似文献
2.
Y. H. Kim D. Y. Jeong P. M. Shirage S. Y. Kim U. C. Chung W. S. Chung 《Metals and Materials International》2007,13(3):217-221
The surface roughness of a substrate is typically influenced by grain boundaries, grooves and voids. In an effort to improve
the surface roughness, a textured {113} <121> Ag substrate was electropolished using a new method that causes the formation
of an oxidation layer at the constant current density before electropolishing at a constant voltage of 1.75 V vs. SCE. The
constant current density and potential were determined using the anodic polarization method. The pH effect for the optimized
electropolishing condition was also investigated by adding phosphoric acid. The edges of the grain boundaries, grooves and
voids became smoother when a constant current density was supplied with the pre-oxidation. A RMS (root mean square) value
of 5.90-nm regarding the surface roughness of the Ag substrate was obtained without a final surface treatment before electropolishing,
while a RMS surface roughness value of 34.12-nm was obtained for an Ag substrate that was given a final surface treatment
for mechanical polishing. 相似文献
3.
W. D. Münz 《工业材料与腐蚀》1972,23(2):101-105
Investigations on the morphology of aluminium hydroxides and anodic aluminium oxide films using scanning electron microscope Hydroxide films of spongy structure are originated on aluminium surfaces if aluminium is trated with hot water for short periods. By increasing the reaction time the hydroxide layers start to become more compact until films are growing coherent showing a porous surface. If the reaction time exceeds 4 hours at a reaction temperature of 98°C crystalline scales appear on the top of the films. During the anodic oxydation of hydroxide coated aluminium in citric acid solutions, thin hydroxide films transform into barrier layer type oxides. If the anodization occurs in aggressive electrolytes the existing hydroxide dissolves and oxide layers with porous structure are obtained. Oxide layers produced by anodizing in hot citric acid solutions in the absence of a hydroxide film show a current density dependent morphology. At higher current densities barrier layer type oxides are growing. Using low current densities oxide layers with a character are predominating. 相似文献
4.
《稀有金属材料与工程》2005,22(2):30-33
通过对TiO2多孔膜阳极氧化制备工艺的研究,提出了其成膜机理。实验以硫酸为电解液,以纯钛(TAl)为阳极,铜片为阴极,采用了恒压和恒流2种阳极氧化方式,在纯钛的表面获得TiO2多孔膜。用FESEM观察其孔径分布在100nm~200nm之间,并且随着阳极氧化电压和电流密度的增加,多孔膜的孔径有增大的趋势。最后,讨论了在硫酸电解液中TiO2多孔膜的形成机制。 相似文献
5.
WANG Wei TAO Jie ZHANG Weiwei TAO Haijun WANG Ling 《稀有金属(英文版)》2005,24(4):330-335
Anatase titanium dioxide is an active photocatalyst, but it is difficult to immobilize on the substrate. A crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation in this work. Constant voltage and constant current anodic oxidation were adopted with sulphuric acid used as the electrolyte, pure titanium as the anode and copper as the cathode. The morphology and structure of the porous film on the substrate were analyzed with the aid of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD). The effects of the parameters of anodic oxidation (such as voltage, the concentration of sulphuric acid, anodization time and current density) on the aperture and the crystalline phase of the TiO2 porous film were systematically investigated. The results indicate that the increase of current density facilitates the augment of the aperture and the generation of anatase and mille. In addition, the forming mechanism of anatase and mille TiO2 porous films was discussed. 相似文献
6.
The effects of electrolyte pH and temperature on the structure and properties of anodic oxide films formed on niobium in phosphoric acid solution with the addition of NH4OH for pH adjustment have been investigated. The film thickness formed at the same voltage slightly increased with increasing pH and significantly increased with increasing electrolyte temperature. The capacitance of the film was independent of electrolyte pH in an acid region, while it notably increased with increasing pH in an alkaline region. The relative permittivity of the film changed 43.7-80.5 when the electrolyte pH was increased from 1.6 to 10. The incorporation depth and content of phosphorus in the film were markedly suppressed at pH 10, and nitrogen was found to penetrate into a depth of 70%. Furthermore, the apparent transport number of Nb5+ ion decreased from 0.26 to 0.02 by a pH increase from 1.6 to 10. The notable changes in structure and dielectric properties of the anodic niobia film formed in the alkaline region would primarily be caused by the different incorporation behavior of electrolyte species such as phosphorous and nitrogen. 相似文献
7.
非恒温电解液中AA5083Al-Mg合金阳极氧化膜的制备及其耐蚀性 总被引:1,自引:0,他引:1
采用硼酸-硫酸-草酸电解液在铝合金表面制备有序多孔层,研究阳极氧化过程中电流随时间的变化,分析界面反应并计算膜层的生长效率。采用扫描电子显微镜、交流阻抗和动电位极化曲线研究膜层的微结构及其在不同温度环境下的耐蚀性。结果表明:在氧化层界面双离子层浓度的增大有利于提高膜层的生长效率。所制备的阳极氧化膜厚度为8-9μm,孔径为10-14 nm,膜层的微观形貌受金属基体组织结构的影响较大。在沸水封闭后膜层为分层结构,表面呈细片状。氧化膜层封闭后能够明显降低试样的自腐蚀电流密度,且耐蚀性随着环境温度的升高而具有更好的稳定性。 相似文献
8.
A.F. Yetim 《Surface & coatings technology》2010,205(6):1757-1763
The wear performances of titanium oxide films, produced by anodic oxidation, in vacuum conditions were investigated. Anodic oxidation treatments were carried out at − 3 and 40 °C temperatures using H2SO4(1.5 M)-H3PO4(0.3 M) solution and voltage of 200 V. Wear tests were performed at ambient air, pressures of 10− 3 mbar and 10− 6 mbar. Anodizing process produced a porous oxide layer on the surface. Although the pore size decreased with increasing process temperature, surface roughness decreased. Hardness results showed that anodic oxidation at lower temperatures produced oxide film with higher hardness. Wear rate of CP-Ti significantly decreased with anodic oxidation treatment in all wear conditions since oxide film acted like a solid lubricant. The best wear resistance was obtained from the hard-anodized samples both in ambient air and vacuum conditions. 相似文献
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12.
铝导线混合酸阳极氧化绝缘膜工艺 总被引:1,自引:0,他引:1
试验研究了铝扁导线混合酸阳极氧化工艺方法,得到了绝缘性能优良的氧化铝膜。膜层击穿电压达到250V。同传统的硫酸阳极氧化工艺相比,该膜层脆性低、韧性好、槽温范围宽;同草酸阳极氧化工艺相比,该工艺所需时间短、耗能少、生产效率高。可以满足除铁器电磁线圈绕组导线的生产和使用要求。 相似文献
13.
A. W. Hothersall 《金属精饰学会汇刊》2013,91(1):29-40
The results are presented of a quantitative study of the phosphoric acid anodizing of high purity aluminium. The effects of electrolyte concentration, temperature, anodizing time, current density and air agitation on the coating weight, metal loss, coating ratio and density of the anodic coating were investigated.The use of phosphoric acid anodic coatings as a base for electrodeposition is discussed with particular reference to plating in a copper pyrophosphate solution and the growth of copper deposits in the anodic film. Tests on chromium/nickel/copper electrodeposits on 38 aluminium alloy are briefly described. 相似文献
14.
E. P. Grishina A. V. Zhirov P. N. Belkin A. I. Dikusar 《Surface Engineering and Applied Electrochemistry》2008,44(5):390-395
The possibility to increase the corrosion stability of steel 45 by its anodic electrothermochemical oxidation in aqueous solutions of ammonium acetate (10–15%) is shown. Tests of oxidized samples in a sulfuric acid solution (0.5 M) allowed finding a shift of their potential to the positive range (up to 0.3 V) with respect to the platinized electrode, which was accompanied by a decrease in the conductivity of the oxide layer. The minimum corrosion rate [0.7 g/(m2 day)] in the 5% NaCl solution was obtained for the specimen oxidized at a voltage of 200 V. 相似文献
15.
《Synthetic Metals》1997,88(3):249-254
The electrochemical oxidation of aniline in 0.8 M HCl solution is carried out using repeated potential cycling between 0 and 1.1 V (versus SCE). Its anodic peak current at 1.0 V for the first scan is markedly retarded in the presence of resorcinol or phloroglucinol, and decreases with increasing their concentrations. However, this peak current is slightly affected by hydroquinone, because it is oxidized electrochemically before oxidation of aniline. The experiment of the rotating ring-disk electrode shows that both the disk current at 1.0 V and the ring current for electrolysis of aniline are simultaneously decreased in the presence of resorcinol. This means that a soluble intermediate cation generated at the disk electrode is captured by resorcinol. There are four anodic peaks and three reduction peaks on the cyclic voltammograms during oxidation of aniline by repeated potential cycling. From the temperature dependence of the separate anodic peak currents, the activation energy of each reaction is calculated. For the first scan, the oxidation of aniline at 1.0 V involves two different activation energies at temperatures from 1 to 35 °C. Both activation energies are smaller than 21 kJ mol−1. The values fall into the range of activation energies for a general propagation reaction and termination reaction of free radical polymerization. These experimental facts indicate that the initial stage of aniline oxidation is the most likely to involve the formation of a radical cation. 相似文献
16.
钛上阳极氧化生成TiO2光催化薄膜的结构与性能 总被引:3,自引:0,他引:3
研究了电化学阳极氧化在钛上制备的纳米晶多孔TiO2光催化薄膜的结构与光催化特性。将工业纯钛片或钛箔暴露于电介质溶液并加一定电压,钛表面将氧化生长多孔TiO2薄膜。适当控制氧化电压、溶液温度,得到非晶氧化膜,再进行晶化处理,得到锐钛矿相纳米晶TiO2薄膜。其晶粒尺寸约在10nm~30nm。用SEM,TEM,XRD表征TiO2薄膜的形貌与相结构。用光谱仪测定了薄膜对入射光的吸收特性,表明电化学氧化制备的纳米晶二氧化钛薄膜对近紫外入射光产生强烈的吸收,显示纳米结构的量子效应。测定了薄膜对酸性红溶液的光催化降解效率,结果表明反应30min后薄膜对酸性红的光催化降解率可达95%以上。 相似文献
17.
Il Song Park Tae Gyu Woo Min Ho Lee Seung Geun Ahn Myung Sik Park Tae Sung Bae Kyeong Won Seol 《Metals and Materials International》2006,12(6):505-511
Anodic oxidation is the process of creating a titanium oxide layer with various defects more dense and stable. In this study,
a dense, stable and porous oxide layer was formed using anodic spark oxidation on pure titanium surface and hydroxyapatite
crystals were formed on its surface via a hydrothermal treatment. A mixture of 0.02M−GP (Glycerolphosphate disodium salt)
and 0.2M-CA (Calcium acetate) was used as an electrolyte. By increasing the anodizing voltage to 220, 260, 300, and 360 V,
the effects of the anodizing voltage were examined by evaluating the film properties after anodization and a hydrothermal
treatment. Breakdown occurred around 230 V. As the voltage increased after breakdown, the pore size increased. After the hydrothermal
treatment, the amount of HA crystal precipitation was also increased as the voltage increased. The mean surface roughness
(Ra) of the anodizing surface was also increased as the voltage increased. The Ra value was larger in the hydrothermally treated
group compared with the group treated with anodization as a result of the HA crystals present on the surface after the hydrothermal
treatment. Corrosion resistance of the surface modified by anodization was significantly increased in a saline solution compared
to that for the non-treated group; this increased further after the hydrothermal treatment. These increases were most likely
due to a thick stable oxide layer formed through anodization. Thus, it is believed that titanium with its surface modified
through anodic spark oxidation would be a suitable biomaterial due to its corrosion resistance and biocompatibility. 相似文献
18.
The effect of a high applied voltage up to 30 V between two copper conductors is investigated in a 0.05 mol L−1 sodium chloride solution. It appears that the potential is mainly applied to the anode/electrolyte interface and that, after a fast decay, the overall current density reaches a constant value, which is independent of the applied potential. This “passive” behaviour is attributed to the formation of a copper(I) chloride layer at the surface of the anode that limits the dissolution rate of copper in the electrolyte. It is shown that electromigration of chloride ions trough the CuCl layer controls the overall anodic reaction. 相似文献
19.
WANG Wei TAO Jie WANG Tao WANG Ling 《稀有金属(英文版)》2007,26(2):136-141
Anatase titanium dioxide is an active photocatalyst, however, it is difficult to be immobilized on the substrate. The crystalline TiO2 porous film was prepared directly on the surface of pure titanium by anodic oxidation. The film was then used for photocatalysis via the methyl orange degradation method. The effects of anodization voltage, pH value, TiO2 film area and degradation time on the photocatalyst were investigated respectively by UV-visible spectrum. It was indicated that the TiO2 film prepared by anodic oxidation at 140 V had the best photocatalysis capability and the degradation of methyl orange was accelerated with acid addition. 相似文献
20.
The study investigates the behaviour of tungsten species during anodizing of a metastable solid-solution Al-3.5 at.%W alloy at a current density of 5 mA cm− 2 in 0.4 M phosphoric acid at 293 K in order to elucidate the development of pores in anodic alumina. Quantitative measurements of film compositions, by ion beam analysis, have been employed to determine the loss of film species, with film morphologies examined by transmission electron microscopy. The findings indicate anodizing efficiencies, from the period of embryo cell formation to major pore growth, in the range 58-74%. The reduced efficiency is due to loss of aluminium species to the electrolyte. Notably, tungsten species are retained within the anodic films. The anodizing behaviour is consistent with cell and pore development due to flow of material in the barrier layer, under the influences of field-assisted plasticity and film growth stresses. The flow, in combination with the slow migration of tungsten species in the anodic alumina, leads to alumina cells with an outer tungsten-free region and an inner tungsten-containing region. 相似文献