Some problems which arise in the characterization of surfaces and coatings by internal reflection spectroscopy are described. The ir spectra of bare CaF(2) trapezoids and of ThF(4)- and ZnSe-coated trapezoids exhibit absorption bands in the same spectral region as those of H(2)O and hydrocarbon impurities. In accord with previous investigations, it is observed that the absorptance due to water is much greater in the ThF(4) films than in the ZnSe films or on the CaF(2) surfaces. These results suggest that the water is distributed throughout the ThF(4) films, whereas for ZnSe it resides primarily on the surface. In addition, a number of interesting observations on the desorption and adsorption of water and hydrocarbons to these materials are made. The experimentally observed absorptances are analyzed on the basis of the reflectance for a threelayer system. The analysis enables reasonably quantitative values for the absorption coefficient to be determined for these thin-film coatings.
CSN BF no. 2 has only three hot blast stoves. Owing to the operational risks as well as output losses associated with the BF operation with just two hot blast stoves, the revamping time of this equipment becomes a crucial issue, requiring special attention in each phase of the project from planning to execution so as to shorten the time as much as possible. According to this context, the present paper describes in detail the main technologies used in the last revamping of hot blast stoves carried out in February 2007. These technologies included an accelerated cooling down curve, air conditioning system (good working condition) and convection heating system, which in association with an innovative construction methodology, involving movable and multilevel platforms, has allowed the project to be completed from blow to blow in a record time of just 67 days and 10 h, resulting in a reduction of costs around R$3?4m.
The optical performance of dichroic beam splitters developed for deuterium fluoride (DF) laser applications as shared-aperture components is presented. These components simultaneously provide high reflectance/transmittance in the 3.8-microm DF laser output band and high transmittance/reflectance in the long-wave-length 8-14--m band. Optical evaluation of the reflecting dichroic yields absorption and transmission losses of <0.2 and 0.1%, respectively, at DF laser wavelengths and average transmittance 80% in the 8-14-microm band. The 3.8-microm transmitting dichroic yields absorptance losses of <0.4% in the DF laser band and average reflectance of >50% in the 8-14-microm region.
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