Application of laser cladding technology to improve the interface of thermal barrier coatings

The present study is focused on improvement of the adhesion properties of the interface between plasma-sprayed coatings and substrates by laser cladding technology (LCT), Within the laser-clad layer there is a gradient distribution in chemical composition and mechanical properties that has been confirmed by SEM observation and microhardness measurement. The residual stress due to mismatches in thermal and mechanical properties between coatings and substrates can be markedly reduced and smoothed out. To examine the changes of microstructure and crack propagation in the coating and interface during loading, the three-point bending test has been carried out in SEM with a loading device. Analysis of the distribution of shear stress near the interface under loading has been made using the FEM code ANSYS, The experimental results show clearly that the interface adhesion can be improved with LCT pretreatment, and the capability of the interface to withstand the shear stress as well as to resist microcracking has been enhanced.

Schottky barrier heights of tantalum oxide, barium strontium titanate, lead titanate, and strontium bismuth tantalate

The Schottky barrier heights of various metals on the high permitivity oxides tantalum pentoxide, barium strontium titanate, lead zirconate titanate, and strontium bismuth tantalate have been calculated as a function of the metal work function. It is found that these oxides have a dimensionless Schottky barrier pinning factor S of 0.28-0.4 and not close to 1 because S is controlled by Ti-O-type bonds not Sr-O-type bonds, as assumed in earlier work. The band offsets on silicon are asymmetric with a much smaller offset at the conduction band, so that Ta2O5 and barium strontium titanate are relatively poor barriers to electrons on Si. © 1999 American Institute of Physics.

Schottky barrier heights of tantalum oxide, barium strontium titanate, lead zirconate titanate and strontium bismuth tantalate

Schottky barrier heights of various metals on tantalum pentoxide, barium strontium titanate, lead zirconate-titanate and strontium bismuth tantalate have been calculated as a function of metal work function. These oxides have a dimensionless Schottky barrier pinning factor, S, of 0.28 - 0.4 and not close to 1, because S is controlled by the Ti-O type bonds not Sr-O type bonds, as assumed previously. Band offsets on silicon are asymmetric with much smaller offset at the conduction band, so that Ta2O5 and barium strontium titanate (BST) are relatively poor barriers to electrons on Si.

Elastodynamic erosion of thermal barrier coatings

The finite element method is used to analyze the elastodynamic response of a columnar thermal barrier coating due to normal impact and oblique impact by an erosive particle. An assessment is made of the erosion by crack growth from preexisting flaws at the edge of each column: it is demonstrated that particle impacts can be sufficiently severe to give rise to columnar cracking. First, the transient stress state induced by the normal impact of a circular cylinder or a sphere is calculated in order to assess whether a 2D calculation adequately captures the more realistic 3D behavior. It is found that the transient stress states for the plane strain and axisymmetric models are similar. The sensitivity of response to particle diameter and to impact velocity is determined for both the cylinder and the sphere. Second, the transient stress state is explored for 2D oblique impact by a circular cylindrical particle and by an angular cylindrical particle. The sensitivity of transient tensile stress within the columns to particle shape (circular and angular), impact angle, impact location, orientation of the angular particle, and to the level of friction is explored in turn. The paper concludes with an evaluation of the effect of inclining the thermal barrier coating columns upon their erosion resistance. © 2011 The American Ceramic Society.

Lengua y derecho a la educación en la Comunidad Autónoma del País Vasco : reflexiones jurídicas sobre el tránsito hacia un nuevo modelo

The article analyzes the legal regime of Euskara in the education system of the Autonomous Community of the Basque Country (capv). In the capv, the legislation recognizes the right to choose the language of study during the educational cycle. The students are separated into different classrooms based on their language preference. This system of separation (of language models) has made it possible to make great strides, although its implementation also suggests aspects which, from the perspective of a pluralistic Basque society on its way towards greater social, political and language integration, call for further reflection The general model for language planning in the capv was fashioned in the eighties as a model characterized by the guarantee of spaces of language freedom, and the educational system was charged with making the learning of the region’s autochthonous language more widespread. At this point, we already have a fair degree of evidence on which to base an analysis of the system of language models and we are in a position to conclude that perhaps the educational system was given too heavy a burden. Official studies on language performance of Basque schoolchildren show (in a way that is now fully verified) that not all the students who finish their mandatory period of schooling achieve the level of knowledge of Euskara required by the regulations. When faced with this reality, it becomes necessary for us to articulate some alternative to the current configuration of the system of language models, one that will make it possible in the future to have a Basque society that is linguistically more integrated, thereby avoiding having the knowledge or lack of knowledge of one of the official languages become a language barrier between two communities. Many sides have urged a reconsideration of the system of language models. The Basque Parliament itself has requested the Department of Education to design a new system. This article analyzes the legal foundations on which the current system is built and explores the potential avenues for legal cooperation that would make it possible to move towards a new system aimed at guaranteeing higher rates of bilingualism. The system would be sufficiently flexible so as to be able to respond to and accommodate the different sociolinguistic realities of the region.

Proposal for improving fishing opportunities off Pt. Loma by construction of an artificial reef

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