Ceramic barriers avoid catalyst diffusion to produce better multiwall carbon nanotubes (CNT) on carbon fiber fabrics (CF). We developed a simple method to produce efficiently a silica layer from TEOS pyrolysis at similar conditions of CNT growth from camphor and ferrocene mixtures. This protective layer prevents iron diffusion and allows the vertical alignment of CNTs.

Titanium dioxide (TiO2) thin films are widely used in transparent optoelectronic devices due to their excellent properties, as well as in photocatalysis, cosmetics, and many other biomedical applications. In this work, TiO2 thin films were deposited onto AISI 304 and AISI 316L stainless steel substrates by atomic layer deposition, followed by comparative evaluation of the mixture of anatase and rutile phase by X-ray diffraction, Raman maps, morphology by SEM-FEG-AFM, and adhesion of the films on the two substrates, aiming to evaluate the scratch resistance. Raman spectroscopy mapping and X-ray diffraction with Rietveld refinement showed that the films were composed of anatase and rutile phases, in different percentages. Scratch testing using a diamond tip on the TiO2 film was employed to evaluate the film adherence and to determine the friction coefficient, with the results showing satisfactory adherence of the films on both substrates.

Thin films are one the best choice to improve materials properties. Instead of entire replacement of the material in a component, which may be expensive, a coating process is a good option to achieve required properties precisely where they are required. Generally, coating depends on deposition methods which consist of chemical or physical interactions to form a film on substrate surface. Residual internal stresses are generated during cooling stage after deposition process, due to always present difference in thermal expansion coefficient of film and substrate materials. These stresses produce either failure or performance reduction on component utilization. Raman spectroscopy was used to evaluate these residual stresses. In this work Raman spectrum behavior was analyzed under different residual stress conditions of DLC films deposited on a 4050 steel/ molybdenum alloy steel substrates. The comparative method used at three different bias tensions of -550, -650 and -750 V showed that residual stress increases with increasing bias voltage. The normal compressive load to produce delamination in scratching test decreased from 16 N to 9 N with bias voltage increase from -550 V to -750 V, as expected due to higher interface stresses.Keywords: Residual stress; Bias voltage; DLC film. ReSumoFilmes finos são ótimas escolhas para a melhoria das propriedades de materiais. Ao invés da substituição de um material em um componente onde pode gerar um alto custo, o processo de revestimento é uma boa opção para adquirir as propriedades necessárias. Geralmente, o revestimento depende de métodos de deposição que consiste em interações químicas ou físicas para formar um filme sobre o substrato. A tensão residual ocorre geralmente durante o processo de resfriamento após a deposição devido a diferença de coeficientes de expansão entre os materiais entre o filme e o substrato. Além de causar falhas no material, a tensão residual pode reduzir consideravelmente as propriedades do componente em que ocorre a deposição. Nesse trabalho a espectropia Raman foi utilizada para avaliar as propriedades de um filme, especificamente a tensão residual entre o filme e uma liga 4050 de aço/molibdênio. Foi avaliado a tensão residual considerando três diferentes tensões de deposição, tais que -550v, -650v e -750v. A análise mostrou que a tensão residual aumenta quando há aumento da tensão aplicada para deposição. A carga normal de compressão para delaminação foi reduzida de 16 N para 9N quando há aumento da tensão aplicada, resultado esperado devido ao aumento das tensões residuais entre o filme e o substrato. Palavras-chave: