In the quest for an electroplated selective black coating stable to 500 °C in air, black cobalts have been prepared by three techniques to yield (a) plated cobalt sulphides, (b) plated cobalt oxide-hydroxide, and (c) cobalt oxide prepared by thermal oxidation of electropolated cobalt metal. The optical properties of the various coatings are analyzed before and after exposure to air for extended periods of time at temperatures in the 300 °–500 °C range. The sulfide black cobalt is not acceptable as a high-temperature selective absorber due to severe thermal degradation. The plated oxide is a good selective absorber to about 400 °C, and the thermally oxidized black to a slightly higher temperature, but degrades at 500 °C. Structure studies via scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and x-ray photoemission spectroscopy (XPS) are reported which yield a full account of the coating chemistry before and after heating. The studies reveal that the high solar absorptance of the acceptable black cobalt coatings is due to a continuation of a porous outer layer grading into nondense oxides of cobalt; either CoO or Co3O4, depending on the film. Absorption is intrinsic but not due to metal particles as in black chrome. A limited amount of optical degradation occurs upon heating the oxide black cobalt in air due to oxidation of hydroxide. However, the major degradation problem is shown to be substrate oxidation in contrast to black chrome where film oxidation is the principal problem.
It has recently been shown that the stress of many refractory thin films deposited by dc-magnetron sputtering can be influenced by the sputtering pressure. Usually the transition from compressive to tensile stress is too sharp for pressure to be a reliable variable for stress control. This is particularly true in applications such as x-ray optics and lithography where extremely low stress is required owing to minimal substrate rigidity. In this paper, we show that there exists a broad region of the parameter space of current, pressure, and rf-substrate bias where tungsten and molybdenum may be deposited with low stress. A detailed study of the effects of these parameters upon stress, plasma etch rate, and resistivity is reported.
An in depth characterization of the electrodeposited solar absorber black chrome resulting in refinement of the microstructural model of the coating is presented in light of current studies in valence band Auger electron spectroscopy, x-ray photoelectron spectroscopy, thermal desorption spectroscopy, secondary ion mass spectroscopy, and the chromium electrodeposition mechanism. Through the presented model, the structural and chemical parameters of the coating are linked to its optical response with the degradation of the optical response at elevated temperatures related to changes in these parameters. The degradation process is divided into two distinct phases. First, upon heating to low temperatures (≲300 °C) the chromium hydroxide localized on the surface and within the microstructure of the film decomposes producing H2O and chromium oxide leaving an expected microvoid-metallic particle structure. Heating to temperatures in excess of 300 °C leads to the second degradation phase. The fine chromium crystallites comprising the film undergo oxidation and the metallic chromium component, responsible for the intrinsic optical absorption, is diminished. The optical model of the solar absorbing film has been refined within the effective medium approach to account for the flat response in the visible part of the spectrum.
Abstract. We determined the cytotoxic effect of iron nanoparticles of 70 nm, with a single per oral administration in an experiment on white outbred mice. Morphological changes were evaluated in the internal organs. Thus, changes depend on the concentration of nanoparticles at long-term per oral exposure: identified violations of the structure of the liver, kidneys and spleen as venous plethora and degeneration of cells at 250 and 500 mkg / kg dose of nanoparticles are reversible, changes in the organs were pronounced with a dosage of 1000 mkg / kg.
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