金属基耐高温陶瓷涂层抗热冲击性能的研究

为提高金属基陶瓷涂层的抗热冲击性能，以无机胶粘剂磷酸二氢铝、耐磨陶瓷骨料氧化铝、碳化硅和氧化镁混合后涂覆于金属表面制得陶瓷涂层。通过交替加热及冷却试验测试该陶瓷涂层的抗热冲击性能，并与其他人的研究数据进行比较。所得涂层抗热冲击次数超过10次，超过了其他人的实验数据，这是由于涂层与基体在界面处相互扩散形成过渡层。另外，宏观上的机械联锁有利于提高涂层与基体在界面处的结合，从而提高了其抗热冲击性能。     

金属基抗菌涂层发展现状

对金属材料表面有机抗菌涂层、无机抗菌涂层(包括金属离子型抗菌涂层和光催化剂型抗菌涂层)以及复合抗菌涂层等进行了论述.综述了国内外抗菌涂层的研究现状,指出其发展趋势.     

预处理对钼基片镀钌层结合力的影响

常用的钼基片镀钌前预处理工艺包括碱洗除油、阳极浸蚀、酸洗、活化、预镀冲击镍.讨论了预处理工艺中碱洗工艺方案、阳极浸蚀的电流密度和时间,以及预镀冲击镍的电流波形对钌镀层结合力的影响.在65℃的50 g/L氢氧化钠溶液中以阳极电流密度16 A/dm<'2>处理2 min,在体积分数为200 mL/L的硫酸溶液中以阳极电流密...     

Room temperature deposition of functional ceramic films on low-cost metal substrate

In various practical applications, such as high power actuators, high sensitivity sensors, and energy harvesting devices, polycrystalline piezoelectric films of 1–100?µm thickness and sizes ranging from several µm² to several cm² are required. With conventional film deposition processes, such as sol-gel, sputtering, chemical vapor deposition, or pulsed laser deposition, it is difficult to fabricate films with higher thickness due to their low deposition rate and high interfacial stress. The aerosol deposition method (AD), a relatively new deposition technique, can be used to fabricate highly dense thick films at room temperature by the consolidation of submicrometer-sized ceramic particles on various ceramic, metal, glass, and polymer substrates. Ferroelectric BaTiO₃ ceramic films of different thicknesses ranging from 1 to 30?µm were fabricated on a low-cost metallic substrate at room temperature using the AD method. Surface morphology and adhesion of the film were analyzed. Analysis of internal residual stresses revealed an equibiaxial compressive stress state in the as-processed film. Electrical characterization of films annealed at 500?°C shows an enhanced polarization value of ~?14?µC/cm² over that of the as-processed film. This improved property is related to the decreasing internal residual stress. In addition, the BT films prepared in this work were found to withstand electric fields greater than 100?kV/mm, which is possibly related to the inherent relatively defect-free structure of AD films.     

Interfacial adhesion between polymer separation layer and ceramic support for composite membrane

An in situ characterization method for mechanical and adhesive properties of organic/ceramic composite membranes is built on the basis of nanoindentation technique in this work. The polydimethylsiloxane (PDMS) was used as the separation layer with the support of porous ZrO₂/Al₂O₃ ceramic tubes. The effects of roughness of the ceramic support and the viscosity of PDMS solution on the mechanical properties of the PDMS separation layer and the interfacial adhesion at the interface were investigated in detail. It was found that when the roughness of the ceramic support increased and the viscosity of PDMS solution decreased, the interfacial adhesion strength of PDMS/ceramic composite membrane increased, but these two variables had little effect on the mechanical properties of the PDMS separation layer. Our results indicate that the mechanical interlocking dominates the adhesion between the PDMS separation layer and the porous ceramic support. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Carbon nanotubes improve the adhesion strength of a ceramic splat to the steel substrate

A scratch technique was used to measure the adhesion strength of plasma sprayed carbon nanotube (CNT) reinforced aluminum oxide (Al₂O₃) splat on the steel substrate. The effect of adding carbon nanotube on the adhesion strength of a single splat was studied by varying the CNT content as 0, 4 and 8 wt.% in the Al₂O₃ matrix. Higher lateral force was required by the nanoindenter tip to detach CNT reinforced Al₂O₃ splats as compared to Al₂O₃ splat. The adhesion strength increased significantly from 0.52 ± 0.05 MPa for Al₂O₃ splat to 4.21 ± 0.49 MPa for Al₂O₃-4 wt.% CNT splat and 7.36 ± 3.96 MPa for Al₂O₃-8 wt.% CNT splat. A high variation in the adhesion strength of Al₂O₃-8 wt.% CNT splat was due to varying degree of CNT dispersion in the matrix. A significant increase in the adhesion strength of Al₂O₃-CNT splat was attributed to its better mechanical interlocking with the substrate as a result of enhanced melting and spreading caused by the higher thermal conductivity of nanotubes. CNTs also form anchors between the splat and the substrate resulting in higher adhesion strength.     

Work of adhesion in ceramic oxide/liquid metal systems

On the basis of experimental data given in the literature, a model for the determination of the work of adhesion was successfully applied in non-reactive oxide Al₂O₃ ZrO₂ UO₂/liquid metal systems. According to this model, the non-transition metals interact with oxides via dispersion forces, whilst the transition metals additionally establish chemical-type equilibrium bonds with the oxide surface. The assumptions of the model for both system categories are discussed and they are in good agreement with other theoretical and experimental findings.     

电解液组成对医用钛合金微弧氧化生物陶瓷层的影响

采用微弧氧化技术在钛合金表面制备了羟基磷灰石(HA)陶瓷膜。研究了电解液中乙酸钙、乙二胺四乙酸二钠(EDTA-2Na)质量浓度对膜层Ca、P含量和二者原子比的影响。随电解液中乙酸钙质量浓度增大,膜层表面孔隙率基本不变,膜层Ca含量增大,P含量减少,钙磷原子比增大。随电解液中EDTA-2Na质量浓度增大,膜层表面孔隙率先增后减,膜层中Ca含量明显增大,P含量略微增大,钙磷原子比明显增大。电解液的最佳组成为:K2HPO4·3H2O 6.8 g/L,Ca(CH3COO)2 26.5 g/L,EDTA-2Na 20 g/L。此时陶瓷膜层表面孔隙率高达11.10%,钙磷原子比为1.65,十分接近HA的钙磷原子比(1.67)。     

Correlating the adhesion of an acrylic coating to the physico-mechanical behavior of a polypropylene substrate

In this study, the adhesion strength of an acrylic coating onto a polypropylene (PP) based substrate was studied. The adhesion strength of the PP containing various wt% of oxidized wax was found to be dependent on the surface free energy of the substrate. To this end, the geometric mean and the acid-base approaches were used to estimate the surface free energy, both of which shown to exist a direct relation between surface hydrophilicity and the content of the oxidized wax. The viscoelastic behavior of the adherend also contributed to the coating adhesion. The viscoelastic response of the blends was investigated using dynamic mechanical thermal analysis (DMTA) and universal testing machine (UTM) for the bulk properties of the substrate and a depth sensing indentation technique for its near-surface, respectively. Bulk and near-surface moduli were decreased as a result of incorporation of wax additive into PP matrix. These were attributed to the homogeneous distribution of low molecular weight wax chains in the polymeric matrix and hence their impact on substrate integrity. The DMTA analysis showed a single phase matrix for all blends. Using a linear trend line, the adhesion test results revealed a good correlation to surface free energy calculations compared with the substrate modulus. The weaker effect of substrate modulus on surface adhesion was ascribed to the substrate plasticity and/or development of internal stresses in the coating layer. However, the glass transition temperature of the coating suggested that the internal stresses in coating layer were responsible to relax prior to conducting adhesion measurement.     

The effect of silane layer drying temperature on epoxy coating adhesion on silane-pretreated aluminum substrate

In this study, 3-glycidoxypropiltrimethoxysilane was used as an adhesion promoter to enhance the adhesion strength of epoxy coating on an aluminum (Al) substrate. Silane layer drying temperature was investigated as a factor that has an influence on the adhesion of polymeric coating on metal substrate and also on its performance in wet and corrosive environments. FTIR tests were carried out to study Al/silane interactions. Drying the silane layer at high temperatures formed a condensed siloxane layer that improved the bonding strength as well as the performance of the protective coating in corrosive environments. The highest dry and wet pull-off strengths were obtained at drying temperatures of 100 and 125°C, respectively.     

Oxidation behaviour and microstructure of a dense MoSi2 ceramic coating on Ta substrate prepared using a novel two-step process

Tantalum (Ta) alloys are important ultra-high-temperature structural materials owing to their excellent high-temperature mechanical properties and processability. However, they exhibit poor high-temperature oxidation resistance. In this study, a dense MoSi₂ ceramic coating was prepared on a Ta substrate using an innovative multi-arc ion plating process and halide activated pack cementation in order to improve its ultra-high-temperature oxidation resistance. This ceramic coating exhibited a low roughness space arithmetic (287.1 ± 26.3 nm) and a dense structure. The relationship between the thickness of the coating and the duration of pack-cementation at 1250 ℃ was parabolic. The coating had a service life of more than 12 h at 1750 ℃, and showed excellent high-temperature oxidation resistance because of the uniform and dense structure of the coating and the rapid formation of a dense SiO₂ layer with low O₂ permeability during high-temperature oxidation.     

Porous hydroxyapatite coating on strong ceramic substrate fabricated by low density slip coating-deposition and coating-substrate co-sintering

This study aims at developing a process technique, which can deposit porous scaffold-like hydroxyapatite (HA) coatings on strong ceramic substrates. As a first trial, micro-porous HA coatings on strong zirconia-based substrates are fabricated by the following technique—consisting of low-density HA-slip coating-deposition on the micro-porous substrates pre-sintered at 900 °C, and coating-substrate co-sintering at 1300 °C. The final co-sintering process ensures a strong bonding between the HA coating and the zirconia-based substrate after minimizing the mismatch in thermal expansion coefficients by adding alumina in HA coating and HA in zirconia-based substrate. The presence of porosity in the HA coating also reduces the mismatch. HA decomposition during the co-sintering process is discussed.     

Effect of microstructure on the adhesion strength of TiBx coating on Ti6Al4V substrate

TiB_x coatings were deposited on Ti6Al4V and Si (100) wafer substrates by D.C. magnetron sputtering with various target-to-substrate distances (T.S. distances) from 50 mm to 200 mm. The influence of T.S. distance on the microstructure, hardness and adhesion strength of TiB_x coatings and Ti6Al4V substrate system was investigated. Results showed that the microstructure of TiB_x coatings transformed from dense to fibre columnar grain with the increase in T.S. distance, whilst the hardness decreased from 20.9 GPa to 9.4 GPa. The Rockwell-C indentation adhesion strength grade was also improved from HF6 to HF1. An adhesion evaluation factor G, which is related to the mechanical properties and the microstructure of TiB_x coating, is proposed based on the test results. The adhesion strength increased with G, which corresponded well with the results of indentation test. The high-speed rubbing test with a sliding speed of 300 m/s was performed to check the Al-adhesion resistance of the TiB_x coating against Al–hBN seal coating.     

Towards improving wet‐adhesion in a metal oxide‐polymer coating system

An investigation using a variable radius roll adhesion test (VaRRAT) revealed an irreversible increase in the wet‐adhesion in a metal–oxide–polymer system, under specific experimental conditions. This observation is further confirmed by the T_g measurements and the ATR‐FTIR studies. The increase in wet‐adhesion is attributed to late H₂O‐catalyzed curing of the previously partially cured polymers (epoxy ring opening), as well as the formation of nanocomposite layer within the epoxy primer matrix, because of precipitation of the nanocrystals including zinc ammine complexes formed as a result of dissolution of the zinc/aluminum alloy as well as the metal oxide pigments by the amine crosslinker. High activation energy of ～100 kJ mol^?1 indicated a chemical process to be responsible for the adhesion gain. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3318–3327, 2006     

In situ measurement of water at the organic coating/substrate interface

In situ and quantitative information on the water layer at the organic coating/substrate interface is crucial for understanding and preventing the failure of organic coating systems. A technique, based on a two-layer model derived rigorously from internal reflection theory, has been developed for measuring in situ the thickness and amount of the water layer at the organic coating/substrate interface. The technique gives new insight into the processes by which water degrades the coating/substrate bonds. In this technique, a transparent or an opaque organic coating of sufficient thickness is applied to an internal reflection element (IRE) with or without a thin metallic film, which is used as the substrate. A water chamber is attached to the organic-coated specimen. After adding water to the chamber, Fourier transform infrared-multiple internal reflection (FTIR-MIR) spectra are taken automatically at specified time intervals without disturbing the specimens or the instrument. Water uptake in the coating and FTIR-MIR spectra of water on the coating-free substrate are also used for the analysis. Examples of clear and pigmented coatings on untreated and treated substrate surfaces are given to demonstrate the technique. Results of water accumulation at the coating/iron interface with and without applied electrical potentials are given. In addition to measuring water at the coating/substrate interface, the technique provides a means for studying the transport of water through a coating adhered to a substrate. Information on water at the interface and its transport properties through coatings applied to a substrate is valuable for interpreting corrosion, blistering and delamination of organic coating systems, and for developing models for use in predicting the serivce lives of protective coatings.     

A novel ultra-high-temperature oxidation protective MoSi2-TaSi2 ceramic coating for tantalum substrate

To protect refractory metal against oxidation at ultra-high temperatures, a MoSi₂-TaSi₂ ceramic coating was prepared on a pure tantalum (Ta) substrate using a novel three-step process, which included dip-coating with a molybdenum slurry, vacuum sintering, and halide-activated pack cementation (HAPC). The original coating had a MoSi₂-TaSi₂ double-layer structure from the surface to the substrate. After oxidation at 1700°C for 8 h in air, the coating exhibited a complex multi-layer structure composed of SiO₂-Mo₅Si₃-MoSi₂-(Mo,Ta)₅Si₃-TaSi₂-Ta₅Si₃ from the outer layer to the inner layer, due to the high-temperature phase transition and diffusion of Si and O. The coating effectively protected the Ta substrate at 1700°C for 12 h without failure, thereby demonstrating great improvement to its service life in an ultra-high-temperature aerobic environment. The protective effect was attributed to the integrity of the ceramic coating and the formation of a dense, uniform SiO₂ film that effectively lowered the inward oxygen diffusion rate.     

Plasma etching and plasma polymerization coating of carbon fibers. Part 1. Interfacial adhesion study

Unsized AS-4 carbon fibers were etched by RF plasma and then coated via plasma polymerization in order to enhance their adhesion to vinyl ester resin. Gases utilized for plasma etching were Ar, N₂ and O₂, while monomers used in plasma polymerization coating were acetylene, butadiene and acrylonitrile. Plasma etchings were carried out as a function of plasma power (30–70 W), treatment time (1–10 min) and gas pressure (20–40 mtorr). Plasma polymerizations were performed by varying the treatment time (15–60 s), plasma power (10–30 W) and gas pressure (20-40 mtorr). The conditions for plasma etching and plasma polymerization were optimized by measuring interfacial adhesion with vinyl ester resin via micro-droplet tests. Plasma etched and plasma polymer coated carbon fibers were characterized by SEM, XPS, FT-IR and α-Step, dynamic contact angle analyzer (DCA) and tensile strength measurements. In Part 1, interfacial adhesion of plasma etched and plasma polymer coated carbon fibers to vinyl ester resin is reported, while characterization results including tensile strength of carbon fibers are reported in Part 2. Among the treatment conditions, a combination of Ar plasma etching and acetylene plasma polymer coating provided greatly improved interfacial shear strength (IFSS) of 69 MPa, compared to 43 MPa obtained from as-received carbon fiber. Based on the SEM analysis of failure surfaces and load-displacement curves, the failure was found to occur at the interface between plasma polymer coating and vinyl ester resin.