Photocatalytic Activity of TiO_(2) Coatings Fabricated on Al_(2)O_(3) by Mechanical Coating Technique

The titanium coatings were prepared on Al_(2)O_(3) balls by mechanical coating technique (MCT),and then the coatings were oxidized to titanium oxides(TiO_(2)) films at 300-600 ℃.The effects of different milling time and oxidation temperature on thickness of films were studied.The composition and microstructure of the films were analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS).The results show that the thickest coatings with an average thickness of 20 μm were obtained at the milling time of 15 h.In addition,with the increase of the oxidation temperature,the oxidation of the film is increased.When the milling time is 15 h,the oxidation temperature is 500 ℃,and the addition of photocatalyst is 1 g/mL.The films have the best photocatalytic performance when the degradation rate of methyl orange solution reaches the maximum value of 74.9 %,and the films have a good reusability.

Fabrication of Sn Coatings on Alumina Balls by Mechanical Coating Technique and Relevant Process Analysis

Sn coatings were fabricated by mechanical coating technique for the first time. The coatings were characterized by XRD and SEM, among others. The SEM showed that the coatings had an irregular and uneven morphology. The influence of the rotation speed of planetary ball mill on the evolution and formation of the coatings was also investigated. The results indicated that continuous Sn coatings can be formed under a moderate rotation speed. In other words, the coatings cannot be formed when rotation speed was too high or too low. The evolution of the coatings was examined and discussed. The results showed that it followed the universal evolution law of metal coatings which included four stages. However, the exfoliation of the coatings was not seen even the milling time reached 30 h.

Anti-oxidation characteristics of Cr-coating on surface of Ti-45Al-8.5Nb alloy by plasma surface metallurgy technique

TiAl-based alloys have received extensive attention recently due to their excellent properties. However, the weak oxidation resistance at temperatures higher than 800℃ can limit their further high-temperature structural applications.To improve the oxidation resistance of a high-Nb-content γ-TiAl alloy(Ti-45 Al-8.5 Nb, in units of at.%), a chromium(Cr)coating is prepared by using the plasma surface alloying technique, separately, at 800℃ and 1000℃. The x-ray diffraction(XRD) patterns reveal that an oxide surface layer consisting of Cr2O3, Al2O3, and TiO2 is produced on the Cr-coated Nb containing γ-TiAl substrates during the initial oxidation. However, the Cr2O3 is dominated in the oxide surface layer after being isothermally oxidized for 300 h. The oxidation kinetic curves are composed of a parabolic law stage(≤ 90 h) and a biquadratic law stage(≥ 90 h), fit by weight–gain curves. Due to diffusion in the fabrication process and oxidation process,the Cr-coated specimens have an adhesion force after being isothermally oxidized, specifically 69 N for a specimen after oxidation for 300 h. These results demonstrate that the Cr coating enhances the oxidation resistance and adhesion of a Ti-45 Al-8.5 Nb alloy, which may provide a new feasible scheme for designing oxidation protection layers.

Corrosion behavior of micro-arc oxidation coating on AZ91D magnesium alloy in NaCl solutions with different concentrations

Ceramic oxide coatings were prepared on AZ91D magnesium alloys in alkaline silicate solution using micro-arc oxidation（MAO） technique.The corrosion behavior of MAO coating on AZ91D magnesium alloys in NaCl solutions with different concentrations（0.1%,0.5%,1.0%,3.5% and 5.0% in mass fraction） was evaluated by electrochemical measurements and immersion tests.The results showed that the corrosion rate of the MAO coated AZ91D increased with increasing chloride ion concentration.The main form of corrosion failure was localized corrosion for the MAO coated AZ91D immersed in higher concentration NaCl solutions（1.0%,3.5% and 5.0%）,while it was general corrosion in dilute NaCl solutions（0.1% and 0.5%）.Two different stages of the failure process of the MAO coated AZ91D could be identified：1） occurrence of the metastable pits and 2） growth of the pits.Different equivalent circuits were also proposed based on the results of electrochemical impedance spectroscopy（EIS） for the MAO coated AZ91D immersed in different concentrations of NaCl solutions for 120 h.

Corrosion Inhibition Mechanism of Rare Earth Metal on LC4 Al Alloy with Spilt Cell Technique

A new method of studying the corrosion inhibition mechanism of rare earth metal（REM） on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3, the influence of corrosive performance of CeCl3 on LC4 super-power aluminum ＂alloy in the 0.1 mol· L^-1 NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl3 solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry （EDS）. By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al.

Structural Surface Crack Monitoring Method Based on Electrical Potential Technique and Modern Surface Technology

Crack monitoring plays a great role in modern structural health monitoring, however, most of the conventional crack inspections have disadvantages in terms of the accuracy, expense, reliability, durability and level of instrumentation required. Thus, development of a simple and reliable crack inspection technique that allows continuous monitoring has been desired. In this paper, electrical potential technique and modern surface technology are employed together to develop a new structural surface crack monitoring method. A special crack monitoring coating sensor based on electrical potential technique was deposited on the hot spot of the structure by modern surface technology. The sensor consists of three layers： the isolated layer, the sensing layer and the protective layer. The isolated layer is prepared by anodic oxidation technology, the sensing layer is made of ion plated copper, and the protective layer is made of silicone. The thickness of each layer is at micrometer magnitude. The electrical conductivity of the sensor is very stable, and the fatigue performance of the specimen with or without coating sensor is nearly unchanged. The crack monitoring experiment result shows that there are two sudden rises of the coating sensor electrical potential values, corresponding to different stages of the crack initiation and propagation. Since the width of the surface coating sensor is only 0.5 mm, this crack monitoring sensor can detect the propagation of cracks less than 0.5 mm long. The method proposed takes the simplicity of electrical potential technique and can monitor surface crack of nearly all kinds of structures precisely. The results of this paper may form the basis of a new crack monitoring system.

Coating Protection for Production Facilities of Offshore Oil Fields

This paper describes coating protection of production facilities of offshore oil fields based on the practice of development of Bohai Offshore Oil Field, with focus laid on the selection of coating systems, surface preparation, coating application, as well as coating inspection for four types of major production facilities.

High Area NiMo-RuO_2 Composite Coating as Hydrogen Electrode

The preparation method of NiMo-RuO2 composite coating, micrographic surface feature and roughness factor of the coating, influence of content of RuO, on electrocatalytic activity, steady-state polarization curves and electrochemical parameters, and stability of the electrode in 30% KOH contaning 10×10-6Fe3+ were repored. Experement results showed the NiMo-RuO2 electrode has more excellent elec-trocatalytic activity and stability than NiMo electrode.

Compound Ceramic Coatings Grown by Micro-plasma Oxidation on Ti-6Al-4V Alloy

Compound ceramics coatings on the Ti-6Al-4V alloy were prepared by the direct current micro-plasma oxidation （MPO） in NaAlO2 solution. The composition and morphology of the coatings were studied with the X-ray diffraction （XRD） and the scanning electron microscopy （SEM）, respectively. Inductively coupled plasma atomic emission spectrometer technique was used to analyze the solution features of Ti-6Al-4V alloy in the process of preparation. The results reveal that Al2TiO5 forms in the coatings at the initial stages of MPO reaction, and its content changes rapidly with the reaction continuing： after 20 min, the ceramics coatings are composed of α-Al2O3, 7-Al2O3 and Al2TiO5, but after 40 min, its main composition is of α-Al2O3. The content of Ti in the solution will increase when the MPO time extends, and as will Al in the anode area until, after 30 min, it reaches the maximum and keeps constant from then on. Both substrata of Ti and Al in the electrolyte join the MPO reaction at the initial stage, where the formation of Al2TiO5 happens; but as the MPO reaction prolongs, more and more Al in the electrolyte will take part in the reaction, leading to the appearance of a large amount ofAl2O3.

Deflection Reduction of GaN Wafer Bowing by Coating or Cutting Grooves in the Substrates

GaN films on sapphire substrates are obtained using the metal-organic chemical vapor deposition growth technique.We present two methods to reduce the GaN wafer bowing caused by the mismatch of the thermal expansion coefficients(TECs)between the film and the substrate.The first method is to use coating materials on the back side of the substrate whose TECs are smaller than that of the GaN films.The second is to cut grooves on the back side of the sapphire substrate and filling the grooves with appropriate materials(e.g.,tungsten,silicon nitride).For each method,we minimize wafer bowing and even reduce it to zero.Moreover,the two methods can reduce stress concentration and suppress the propagation of cracks in the GaN/sapphire structure.

Study progression in application of process analytical technologies on film coating

Film coating is an important unit operation to produce solid dosage forms,thereby,the monitoring of this process is helpful to find problems in time and improve the quality of coated products.Traditional methods adopted to monitor this process include measurement of coating weight gain,performance of disintegration and dissolution test,etc.However,not only do these methods cause destruction to the samples,but also consume time and energy.There have recently emerged the applications of process analytical technologies(PAT)on film coating,especially some novel spectroscopic and imaging technologies,which have the potential to real-time track the progress in film coating and optimize production efficiency.This article gives an overview on the application of such technologies for film coating,with the goal to provide a reference for the further researches.

A UTD SOLUTION FOR THE RADIATED FIELD FROM MONOPOLE ON A CONDUCTING CYLINDER SURFACE WITH A DIELECTRIC COATING

A can0nical problem is investigated for high frequency electromagnetic radiation from amonopo1e on a conducting cylinder with c0ating-At first, the exact solution of this problem is given interms of Dyadic Green's function method. Then, using Watson transformation and high frequency asymptotic approximate technique to the exact soluton, a UTD soultion is obtained. The radiation field excitedby a monopole is expressed in terms of the compound Fock' S functions (CFF), which reduce to the geomertrical optics result in the deep lit region and the creeping waves in the shadow region.

Effect of Spin Coating Speed on Some Optical Properties of ZnO Thin Films

This paper reports the synthesis and characterization of ZnO thin films prepared by sol-gel spin coating technique. The sol-gel was prepared from zinc acetate dehydrate as a precursor, 2-me- thoxyethanol as a solvent and di-ethanolamine as a stabilizer, and then deposited on glass substrate using spin coater at the coating speed of 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm and 6000 rpm. After pre-heated at 150℃, the samples were post-heated at 250oC and also annealed at 400℃. X-ray diffraction (XRD) of the films showed polycrystalline hexagonal structure, with (002) orientation as most intense peak having a grain size of 28.1 nm. The absorbance of the film decreases with increasing wavelength and the transmittance was generally high between visible regions from 280 nm - 1200 nm. The ZnO films deposited at a spinning speed of 2000 rpm had highest transmittance of 88% in the visible region from 280 nm - 1200 nm. The energy band gap was found to be in the range of 3.23 - 3.40 eV. The thicknesses of the films decreased with increase in coating speed. Based on these results, ZnO thin films obtained could have useful application in transparent conducting oxide electrode in solar cells.

Development of a Low Temperature Sol-Gel-Derived Titania-Silica Implant Coating

Objective of this study was to develope low temperature sol-gel coatings for shape memory metal (NiTi) and evaluate their biocompatibility on NiTi suture material. A series of low temperature TiO2 and TiO2-SiO2 sol-gel coatings were prepared on glass substrates. The silica content of TiO2-SiO2 coatings ranged from 0 to 30 mol%. The coatings were also prepared with polyethyleneglycol (PEG). The contact angle and photocatalytic activity measurements were used to evaluate the surface properties of the coatings. Stability of the coatings was tested in simulated body fluid (SBF). The TiO2-SiO2 90/10 film made with PEG was more hydrophilic, showed photocatalytic activity and was crack-free after the SBF test, thus it was chosen to animal experiment as a new experimental coating. Uncoated NiTi suture and the suture coated with high temperature TiO2 were used as reference materials. NiTi sutures were inserted subcutaneously on the back of rat for four weeks. In routine histological examinations all materials showed good biocompatibility with mild inflammatory cell reaction. No significant differences in the soft tissue response among the materials were observed. Both the high and new low temperature processed sol-gel coatings remained attached on the sutures confirming the suitability of the coating technique on thin NiTi sutures.

Fabrication of ZrO_2/Mo-Si/Ni Functionally Graded Material by Dip-Coating

A slurry dip-coating technique was developed for fabrication of Zr02/Mo-Si/Ni functionally graded material (FGM)on the stainless steel substrate. The rheological behavior of ZrO2-Ni-ethanol slurry was characterized by viscositytest. The amount of polyvinyl butyral (PVB) additives, which served as the dispersant and binder in ZrO2-Ni-ethanolslurry, was optimized. The results showed that the characters of mixed slurries with added 9 vol. pct (relativelyto total powders) MoSi2 powders prepared by mechanical alloying changed little. The stainless steel substrate wascoated several times by dipping in the slurries, and followed by drying in air every dipping. After debinding in Arin graphite die, the coated FGM plate was finally hot pressed at 1300℃ for 1 h under the pressure of 5 MPa in Arin the same die. Microstructural observations of the sintered FGM specimens revealed that the graded layers wereformed on the stainless steel substrate, in which no cracks were observed.

植物油基聚氨酯包膜肥料研究进展

缓释肥包膜材料采用的聚氨酯主要由石油基原料制备,由于石油基聚氨酯成本高、环境风险较大,近年来逐渐被生物基聚氨酯所取代。在众多的生物基材料中,植物油因价格低廉、来源广泛、无毒性、可生物降解等特点,成为缓控释肥料膜材的研究热点。本文分别综述了植物油基多元醇的制备方法,植物油基聚氨酯包膜的分类,植物油基聚氨酯包膜肥料的改性及应用。环氧开环、酯交换反应、氨解法、加氢甲酰化以及臭氧氧化还原是植物油改性制备植物油基多元醇的常用技术手段。丙烯酸酯、环氧树脂、有机硅、氟改性、纳米材料等是植物油基聚氨酯包膜材料改性的常用原料,试验证明植物油基聚氨酯包膜肥料具有减少氨挥发、氮淋溶,提高氮素利用效率的作用。如何提高植物油基聚氨酯交联密度、降低生产成本、深入揭示缓释机理以及扩大在大田试验的应用场景将是今后研究的重点。

添加CeO_(2)对激光熔覆Ni基/WC复合涂层的影响

为了提高Q235钢材在海水中的耐腐蚀性能,扩大其应用场合,使其能够服役于富含Cl离子的海洋环境,采用激光熔覆技术,在Q235钢表面制备出添加不同质量分数CeO_(2)改性的Ni基/WC复合熔覆层,并利用扫描电镜、能谱仪和电化学工作站等仪器对熔覆层的组织与性能进行了测试。结果表明,适量CeO_(2)的加入可以促进晶粒细化与组织的均匀分布,提高熔覆层在NaCl溶液(质量分数为3.5%)中的耐腐蚀性能;当添加的CeO_(2)质量分数达到1%时,熔覆层具有最高的平均硬度与最好的耐海水腐蚀性能;过高的CeO_(2)含量则会加剧电偶腐蚀效应,降低其耐腐蚀性能。该研究为后续在Q235钢材表面制备耐腐蚀的激光熔覆合金涂层、改善合金材料表面性能提供了理论参考依据。

镁合金表面化学转化涂层研究进展

作为最具潜力的轻量化材料,镁及镁合金具有密度低、比强度高、生物相容性好、电磁屏蔽强等优点,在生物医学、电子器件乃至建筑工程领域都受到了广泛关注。然而,镁在某些使用场景中容易发生腐蚀,因此找到最合适的使用场景以及在使用场景下提供足够的保护是镁及镁合金的重要研究课题。通过表面处理技术在基体上制备保护涂层是提高镁及镁合金耐蚀性的有效方法。现有的表面处理技术有很多种,如气相沉积技术、阳极氧化、电镀和化学镀、激光束改性技术、离子注入、化学转化技术等。其中化学转化技术具有成本低、制备简单、处理效率高等优点且不需要复杂昂贵的设备,对样品几何形状也没有限制。本文基于近年来国内外化学转化涂层的发展,综述了镁合金在生物医用、电子器件以及建筑工程领域化学转化涂层的研究现状,并对不同领域化学转化涂层的发展进行了展望。

La_(2)O_(3)掺杂铁基记忆合金涂层组织与性能研究

为了探究La_(2)O_(3)对激光熔覆形状记忆合金涂层组织和性能的影响,采用宽带激光熔覆技术在42CrMo中碳钢表面制备了掺杂La_(2)O_(3)的Fe17Mn5Si10Cr5Ni形状记忆合金复合涂层,通过表征得到了La_(2)O_(3)对复合涂层的显微组织、维氏硬度、耐磨性、耐蚀性和表面残余应力的影响结果。结果表明,La_(2)O_(3)显著降低了晶粒尺寸,掺杂质量分数w=0.009时,晶粒尺寸达到最小值3.03μm,而复合涂层具有最大硬度454.7 HV 0.2,磨损量最低;并得到最低的自腐蚀电流为4.287×10^(-7)A/cm^(2),最高的自腐蚀电位为-0.843 V,涂层保护率达到94.83%,La_(2)O_(3)明显提高了涂层的耐腐蚀性能;此时涂层的残余应力由拉应力转变为压应力,并在Fe-Mn-Si/La_(2)O_(3)产生的最大残余压应力值为-378 MPa。此项研究为低应力高性能激光熔覆涂层的开发和推广提供了实践参考。