Modelling of gas permeation through ceramic coatings produced by thermal spraying

An analytical model has been developed for simulation of gas permeation through thermal spray coatings, and for prediction of the permeability. The model is based on a geometrical representation of the coating microstructure. This involves thin splats, with limited inter-splat bridging, and microcracks within the splats. Important variables include the thickness (smallest dimension) of the inter-splat pores and intra-splat microcracks. Uniform values of these parameters are used in the model. Predicted permeabilities are compared with experimental data obtained using plasma-sprayed zirconia coatings, both in the as-sprayed state and after heat treatments sufficient to generate significant microstructural changes via sintering effects. In general, good agreement is obtained and it is concluded that the model constitutes a useful tool for exploration of gas permeation characteristics in coatings or layers produced by thermal sprayin

The Effect of a High Thermal Gradient on Sintering and Stiffening in the Top Coat of a Thermal Barrier Coating (TBC) System

Superalloy substrates coated with plasma sprayed CoNiCrAlY bond coats and yttria-stabilized zirconia top coats have been subjected to a high heat flux in a controlled atmosphere chamber. The sintering exhibited by the top coat under these conditions has been studied and compared with the behavior observed during isothermal heating, both when attached to the substrate and when detached. Sintering has been characterized by (a) microstructural examinations, (b) dilatometry, in both in-plane and through-thickness directions, and (c) stiffness measurements, using both cantilever bending and nanoindentation. A numerical heat flow model has been used to explore the stress state under isothermal and thermal gradient conditions. Sintering proceeds faster at higher temperature, but is retarded by the presence of tensile stresses (from differential thermal expansion between coating and substrate) within the top coat. Sintering occurs preferentially near the free surface of the top coat under gradient conditions, not only because of the higher temperature, but also because the in-plane stress is more compressive in that region

Effects of Na2Cr2O7 Inhibitor on the Corrosion Potential Response of Steel Reinforced Concrete in Saline Medium

Electrochemical monitoring method of the open circuit potential was used to investigate the effect of the concentrations of Na2Cr2O7 on the corrosion potential response of steel reinforced concrete in sodium chloride medium. In the study, five different concentrations of Na2Cr2O7 admixtures were employed in a system of replicated samples of steel-reinforced concrete specimens partially immersed in 3.5% NaCl to simulate marine and saline environments. Forty days measured responses from these were subjected to the statistical analyses of the Normal and the Weibull distribution functions and tested using the Kolmogorov-Smirnov goodness of fit criteria. Results obtained from the analyses identified 4 g Na2Cr2O7 with optimal averaged potential response inhibition performance by the Normal model which showed better agreements in its models of Na2Cr2O7 potential test data than that obtained from the Weibull model of the same data. These bear pertinent implications on the need for suitability studies of appropriate statistical distribution for studying performance of corrosion inhibitors even as suggestions were proffered for addressing results conflicts among replicates of steel reinforced concrete samples employed

Impurity band in clean superconducting weak links

Weak impurity scattering produces a narrow band with a finite density of states near the phase difference $\phi =\pi$ in the mid-gap energy spectrum of a macroscopic superconducting weak link. The equivalent distribution of transmission coefficients of various cunducting quantum channels is found.Comment: 4 pages, 4 figures, changed conten

Assessment of Cr, Cd and Pb levels in tobacco leaves and selected cigarette samples from Ilorin Metropolis Kwara State, Nigeria

The levels of Cr, Cd and Pb in tobacco leaves and some cigarette samples from Ilorin metropolis, Kwara State, Nigeria were collected and analyzed after wet digestion with a freshly prepared 65% HNO3 and 35% HCl using atomic absorption spectrophotometry Model No PM 8251 single pen recorder. The results obtained reveal the presence of Cr and Cd in all samples including tobacco leaves. However, Pb was not found in all the samples within the limit of determination. The concentration ranges of Cr and Cd in the samples are 60-100 μg/g and 4-20 μg/g respectively, which was found to be lower than the WHO standard.Keywords: Cigarettes, Tobacco, Heavy metals, Digestio

Доцiльнiсть використання димедролу пiд час кетамiнового наркозу при малих хiрургiчних втручаннях

The article deals with the problems of providing anaesthesia in small surgery to ketamin in combination with dimedrol and droperidol. This combination allowed the realization of anaesthesia at 38 patients during surgery intervention to anal region and oppening abscesses of the diverse localization. This combination is safe and doesn't reqire complicated anaesthetic devices. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/1314

Gender peculiarities of English neologisms verbalizing the life of teenagers and youth of the XXI century

The present article deals with the analysis of gender peculiarities of English neologisms verbalizing the life of teenagers and youth of the XXI century. In view of the development of society and appearance of new realities in the life of man for the last decades there has appeared a growing number of new words for the reflection of the modern life. Here we talk about the so-called “neological boom” (Заботкина В.И., 1989; Булдакова В.П., 2012 and others). The analysis of literature on the theory of neology has allowed to ascertain that the language undergoing constant changes is a dynamic system and its enrichment by neologisms is a striking demonstration of that. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3660