铝及铝合金涂装前处理的研究现状及展望

涂装前的处理关系到最终产品的质量。重点介绍了铝及铝合金表面无铬磷酸盐化学转化处理、稀土转化处理和有机硅烷化处理的特点及应用情况，并对今后的发展方向进行了展望。     

高性能无溶剂低表面处理涂料

带油涂装是低表面处理涂料中的一个难题,从环保方面考虑,开发无溶剂的低表面处理涂料非常重要.研制了一种可以在带油带锈表面和一定潮湿环境下涂装的新型高性能无溶剂低表面处理涂料,探讨了固化剂体系、颜基比、附着力促进剂、环境温度等对涂料力学性能和耐蚀性的影响.结果表明:涂膜柔韧性1 mm,耐冲击性≥45cm,各种附着力均大于8...     

Dissipation Measurements in Steel Sheets Under Cyclic Loading by Use of Infrared Microthermography

Abstract:  Heterogeneous dissipation in steel sheets due to cyclic loading is difficult to measure, especially in the transverse direction because of the high conductivity and low thickness of the sheets. The goal of this article is thus to develop an experimental protocol allowing for the dissipation field determination from infrared thermography. The protocol is based on a specific differential measurement and an asynchronous acquisition. It reduces measurement artefacts due to coating, rigid body motion, convection, and optical deleterious effects. It is eventually applied to different specimens.     

The adsorption of an epoxy acrylate resin on aluminium alloy conversion coatings

A thermodynamic study of the adsorption of an epoxy acrylate resin used for UV-cured coatings on two different anticorrosion pretreatments on aluminium alloys relevant to aerospace industry has been undertaken. Aluminium alloy Al2219 specimens, treated with an inorganic chromate based conversion coating (Alodine 1200S) and an organic titanium based conversion coating (Nabutan STI/310), were immersed in solutions of different concentrations of the resin and adsorption isotherms were determined by assessing the uptake of the adsorbate, as a function of solution concentration, by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show different behaviour for the two substrates, which can be attributed to the organic component of the titanium based coating. In the case of the inorganic conversion coating a clear plateau is achieved at relatively low concentrations and at a lower level of adsorption than for the hybrid coating. The data for both the coatings conform well to the Langmuir model, the organic coating, as well as showing a higher level of adsorption of the resin, also presents oscillatory behaviour at low concentration, which is shown to be complementary to the behaviour of the reactive diluent included with the epoxy acrylate to aid processing. A discussion of this competitive adsorption of the epoxy resin and the diluent on the different substrates is presented, based on considerations of the chemistry of the systems under investigation.     

Microencapsulation of Fish Oil by Spray Granulation and Fluid Bed Film Coating

Abstract: The stability of microencapsulated fish oil prepared with 2 production processes, spray granulation (SG) and SG followed by film coating (SG-FC) using a fluid bed equipment, was investigated. In the 1st process, 3 types of fish oil used were based on the ratios of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (10/50, 33/22, and 18/12). Each type was emulsified with soluble soybean polysaccharide (SSPS) and maltodextrin to produce 25% oil powders. In the 2nd process, 15% film coating of hydroxypropyl betacyclodextrin (HPBCD) was applied to the granules from the 1st process. The powder stability against oxidation was examined by measurement of peroxide values (PV) and headspace propanal after storage at room temperature and at 3 to 4 °C for 6 wk. Uncoated powder containing the lowest concentration of PUFA (18/12) was found to be stable during storage at room temperature with maximum PV of 3.98 ± 0.001 meq/kg oil. The PV increased sharply for uncoated powder with higher concentration of omega-3 (in 33/22 and 10/50 fish oils) after 3 wk storage. The PVs were in agreement with the concentration of propanal, and these 2 parameters remained constant for most of the uncoated powders stored at low temperature. Unexpectedly, the outcomes showed that the coated powders had lower stability than uncoated powders as indicated by higher initial PVs; more hydroperoxides were detected as well as increasing propanal concentration. The investigation suggests that the film-coating by HPBCD ineffectively protected fish oil as the coating process might have induced further oxidation; however, SG is a good method for producing fish oil powder and to protect it from oxidation because of the “onion skin” structure of granules produced in this process.     

Active protection coatings with layered double hydroxide nanocontainers of corrosion inhibitor

Novel LDH-based nanocontainers of corrosion inhibitor are developed in the present work. The reservoirs are composed by nanostructured layered double Mg/Al and Zn/Al hydroxides with divanadate anions located in the interlayer regions. The nanocrystalline LDHs (layered double hydroxides) are able to release vanadate ions in a controllable way.XRD, EDS and SEM methods were used in this work to study morphological and structural properties of the synthesized LDH powders. Corrosion protection effect of the LDH powders directly added to corrosive electrolyte or to commercial coatings used for aeronautical application has been studied by electrochemical impedance spectroscopy and standard accelerated corrosion tests. Aluminium alloy 2024 was used here as substrate.The results demonstrate that both of the LDH pigments being added to corrosive media confer corrosion inhibition effect, especially Zn/Al based nanocontainers obtained by the anion-exchange approach. The coatings doped with Zn/Al LDH-nanocontainers provide well-defined self-healing effect and confer corrosion protection properties superior than currently used environmentally unfriendly chromate-based systems.     

浅析涂料生产工艺中的静电危害及防护措施

文章分析了静电产生的原因与危害,并针对涂料生产的工艺特点,总结了主要产生静电的工艺过程以及预防静电的措施和实例。     

Structural design of current-mode biquad filters

This work describes how to generate and design a novel current-mode biquad filter model using tunable multiple-output operational transconductance amplifiers and grounded capacitors (MO-OTA-Cs) for synthesizing both transmission poles and zeros. Transfer functions of low-pass, band-pass, high-pass, notch and all-pass are realized based on the filter model. The theory focuses mainly on establishing a relationship between the cascaded MO-OTA-Cs and the multiple-loop feedback matrix, which makes the structural generation and design formulas. All the filter architectures contain only grounded capacitors, which can absorb parasitic capacitances and require smaller chip areas than floating ones. The simulation results are also presented to confirm the theoretical analysis.     

Influence of undercoating on rolling contact fatigue performance of Fe-based coating

The aim of this paper was to address the influence of undercoating on the rolling contact fatigue (RCF) performance of coatings. The Fe-based alloy and Ni/Al alloy were deposited on substrates as surface coating and undercoating by plasma spraying. The failure modes were investigated for two kinds of coatings. RCF performances were compared using Weibull distribution plot. The results showed undercoating played an important role on increasing RCF life of coating for the higher bond strength, and decreasing the scatter of RCF life data. The deposited undercoating could influence the failure mode of coating and prevent the occurrence of catastrophic delamination.     

Special features of preparation and application of ultra‐thin tungsten electrodes

The process of the formation of welding aerosol (WA) and the factors affecting its quantitative composition are investigated. The experimental results show that the amount of the main components of the WA in manual coated electrode arc welding increases without exceeding the maximum permissible concentration.