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891.
Elisabete Almeida Dulcínea Santos Jorge Uruchurtu 《Progress in Organic Coatings》1999,37(3-4):131-140
Among recently developed waterborne coatings, epoxy and acrylic based coatings have a special place. To study this kind of anticorrosive coatings, use is normally made of natural exposure and laboratory tests. The literature has recently reported that the salt spray test is not suitable for selecting/studying anticorrosive waterborne coatings. In this paper, the authors present the main results obtained in an experimental study involving laboratory tests and natural exposure in two atmospheric test sites of different corrosivity categories. The natural exposure and accelerated tests are complemented by other measurements in the laboratory, involving water uptake, adhesion and electrochemical measurements, to understand the anticorrosive performance of the paint systems under study. As accelerated tests, salt spray and prohesion were used. Indirect measurements of adhesion were made using cross-cut and pull-off tests. Electrochemical impedance spectroscopy (EIS) and noise (EN) were used for electrochemical characterization. The study concludes that the best anticorrosive behaviour was shown by epoxy-polyamide paint systems, including zinc-rich primers. The correlation between the results of salt spray and natural exposure in marine test sites was significantly better than that obtained using the prohesion test. The electrochemical results showed that it is very important to pay special attention when interpreting this kind of results. 相似文献
892.
Development and the Implementation of High-Temperature Reliable Heaters in Plasma Spray Technology 总被引:1,自引:1,他引:0
Maria Prudenziati 《Journal of Thermal Spray Technology》2008,17(2):234-243
Many problems have been encountered during development of reliable high-temperature heaters by means of atmospheric plasma
spray and procedures commonly adopted in thermal spray technology, especially due to poor steel substrate corrosion resistance,
notably affected by grit-blasting operations, but also deriving from contamination of insulating layers, dielectric arcs,
and failures due to hot spots in the heating elements. While seeking the origin of these problems, a close scrutiny of every
single step of the preparation process and analyses of the coatings were carried out using laser confocal scanning microscopy,
optical and electronic microscopy, fluorescence analysis, X-ray diffraction, and ancillary techniques. The electrical properties
of both alumina layers and metal strips prepared with Ni, NiCr, NiAl commercial powders for the heating elements were studied
and cross-related to the failures in the heaters. The article reports the main results of these investigations, delineates
the innovations introduced to overcome or circumvent the problems, and underlines the distinct characteristics of new heaters,
whose reliability has been proven up to now with temperatures of up to 600 °C in air. 相似文献
893.
894.
Hygroscopic Coatings Control Surface White Discoloration of Peeled (Minimally Processed) Carrots During Storage 总被引:1,自引:0,他引:1
LUIS CISNEROS-ZEVALLOS MIKAL E. SALTVEIT JOHN M. KROCHTA 《Journal of food science》1997,62(2):363-366
White discoloration on peeled carrots is partially due to surface dehydration which can be controlled with hygroscopic coatings: e.g., polyhydric alcohols and salt solutions. This study was performed at 2.5, 7.5, 10, and 15°C, using a model system controlling relative humidity at 33, 75 or 98% or a commercial system with low-density polyethylene (LDPE) plastic film bags. The moisture sorption properties of propylene glycol, sorbitol, glycerol and calcium chloride enabled them to keep the carrot surface moist and maintain a transparent surface layer through which the underlying orange color was visible. This effect was only observed at high relative humidities (e.g., 98% RH). Similar effects were observed on treated peeled carrots stored in LDPE bags. The moisturized appearance provided by the hygroscopic coatings during storage was effective at several different temperatures. 相似文献
895.
Fumikazu Imai Kimio Kunimori Takaaki Manabe Toshiya Kumagai Hisakazu Nozoye 《Thin solid films》1997,310(1-2):184-193
We synthesized titanium oxide thin films on MgO(100) single-crystal substrates by two reactive deposition methods and compared the structures of the thin films formed by these methods. In one method (pulsed-molecular-beam deposition method), molecular oxygen is supplied to the substrates by using a pulsed-molecular-oxygen beam source and deposition of one unit layer of titanium and subsequent supply of molecular oxygen are repeatedly performed. In the other method (radical beam deposition method), atomic oxygen is irradiated to the substrates by using an atomic oxygen beam generated by the radical beam source and irradiation of the atomic oxygen and deposition of titanium are simultaneously performed. In the case of the pulsed-molecular-beam deposition method, the crystal structure was changed by increasing the number of oxygen pulses supplied from the beam source. We found that the crystal structure of titanium oxide depended on the composition ratio of O:Ti in the film. The maximum ratio of O:Ti attainable by this method was 1.85, and at this ratio, (100)-oriented pseudorutile was formed. In the case of the radical beam deposition method, (100)-oriented anatase was formed below the titanium deposition rate of 0.10 nm/s and pseudorutile (TiO2−δ) was formed above 0.15 nm/s. The pseudorutile structure synthesized on this experiment was very stable in air. We concluded that the crystal structure of the pseudorutile is a new crystal structure of titanium oxide. 相似文献
896.
The aircraft hookpoint used for an arrested landing is exposed to various forms of heavy wear and impact. Nowhere is this
more true than training field landings, where the hookpoint is subjected to drag along a concrete runway for possibly thousands
of feet while flying at high speeds and heavy downloads. After extensive screening, a series of materials were subjected to
special impact tests and concrete wear tests. Ten coatings, applied by thermal spray, were selected for future arrestment
testing on the basis of these results. 相似文献
897.
Precipitation and coating techniques that proved successful for lead scandium niobate were tried with lead scandium tantalate. The Ta2 O5 did not prove to be a useful substrate for the precipitating carbonates, but the resulting fine-particle-size powder lowered the sintering temperature to 1375° with only 0.4 wt% PbO loss. Annealed samples showed shifts in the dielectric response and sharpening of infrared and X-ray diffraction patterns, but little development of super lattice. 相似文献
898.
Luchen Hwan Steven Suib Francis Galasso 《Journal of the American Ceramic Society》1989,72(7):1259-1261
A study of a silicon carbide-coated boron fiber showed that it retained its room-temperature strength after being heated to 1000°C for 24 h in air. This fiber was consolidated successfully in a titanium matrix at 930°C without degradation, although previous results with another silicon carbide-coated boron fiber indicated that there might be a reaction problem at this temperature. 相似文献
899.
The growth of the powder coating business is affected by the toxicological effects of the raw materials used in the coating formulation and the saturation of the present market for powder coatings, being limited to general metal applications only. This has a strong influence on the long-term research programmes at both raw materials suppliers and powder paint producers. In the last decade of the 20th century, we witness appearance of several new types of toxicologically-safe powder coating systems on the commercial scale. At the same time, there is strong evidence of efforts to penetrate new market fields where powder coatings are not typically used. This includes the markets for automotive clear top coatings, can and coil coatings, coatings for industrial wood, plastics and paper. The new developments in the chemistry of powder coatings are followed by changes and improvements in the production technology for powder coatings as well as developments of new application techniques. This paper summarises the research work on chemistry, production and application technology of powder coatings and tries to extrapolate the tendencies in the years to come in order to predict the achievements and the impacts on the paint industry. 相似文献
900.
Thin films of titanium nitride (TiN) were deposited on glass substrates by KrF excimer laser ablation of titanium over a very broad nitrogen pressure range with different target–substrate distances at room temperature. The as-deposited TiN thin films were analyzed by X-ray diffraction and transmission electron microscopy. It was found that the as-deposited thin films are normally a mixture of TiN and metallic titanium, and the TiN-to-Ti ratio of the as-deposited thin film depends on both the nitrogen pressure and the target–substrate distance. High-purity TiN thin films can be obtained only in a very narrow deposition parameter range. A compound parameter (the product of the nitrogen pressure and the target–substrate distance) is proposed to optimize the deposition of high-purity TiN thin films, and the possible mechanism is also discussed. It was also revealed that the as-deposited TiN thin films are polycrystalline with an average grain size of about 20 nm. 相似文献