Li diffusion and electrochromism in amorphous and crystalline vanadium oxide thin film electrodes

Amorphous vanadium oxide films were synthesized onto ITO-coated glass substrates by the hot filament metal oxide deposition technique. The as-deposited samples were heat-treated in an argon atmosphere. X-ray diffraction analysis revealed that the films treated at 200 and 300 ºC were still amorphous, while those treated at 400 and 500 ºC were crystalline, with a V2O5 structure. All electrodes were electrochemically reversible for Li+ intercalation, exhibiting the electrochromic effect, observed from optical transmittance measurements at 632.8 nm. The Li-diffusion coefficient, DC, was measured by the galvanostatic intermittent titration technique (GITT) as function of the inserted charge. For the crystalline films it was observed that the optical absorbance and the DC increase with increasing Li insertion in the single-phase regions of crystalline Li xV2O5 and decrease in the two-phase regions. For the latter, an effective DC was considered. The presence of other vanadium oxides mixed to the V2O5 matrix was inferred for the crystalline films from the chronopotentiometric and DC measurements

Desenvolvimento e avaliação de uma fonte DC de alta tensão para utilização em sistema de deposição de filmes finos por pulverização catódica

RESUMO O trabalho em questão está relacionado ao projeto e construção de uma fonte de alta tensão em corrente contínua utilizando materiais e dispositivos adquiridos no comércio local visando sua aplicação no processo de pulverização catódica. Essa técnica permite a deposição de filmes finos de metais, óxidos e nitretos sobre substratos sólidos. Como teste de funcionamento e aplicação da fonte DC, com a mesma instalada em canhão de pulverização em alto vácuo, filmes finos de diferentes espessuras de cobre, aço inoxidável 304 e tungstênio foram depositados e estudados. Análise de espessura, morfologia, e resistência elétrica e resistividade foram conduzidas. Filmes com resistividade elétrica dependente das espessuras foram obtidos. A fonte DC se mostrou confiável em operação e permite a deposição de uma infinidade de materiais nas mais diferentes espessuras sobre vários tipos de substratos

Li diffusion and electrochromism in amorphous and crystalline vanadium oxide thin film electrodes

Amorphous vanadium oxide films were synthesized onto ITO-coated glass substrates by the hot filament metal oxide deposition technique. The as-deposited samples were heat-treated in an argon atmosphere. X-ray diffraction analysis revealed that the films treated at 200 and 300 ºC were still amorphous, while those treated at 400 and 500 ºC were crystalline, with a V2O5 structure. All electrodes were electrochemically reversible for Li+ intercalation, exhibiting the electrochromic effect, observed from optical transmittance measurements at 632.8 nm. The Li-diffusion coefficient, DC, was measured by the galvanostatic intermittent titration technique (GITT) as function of the inserted charge. For the crystalline films it was observed that the optical absorbance and the DC increase with increasing Li insertion in the single-phase regions of crystalline Li xV2O5 and decrease in the two-phase regions. For the latter, an effective DC was considered. The presence of other vanadium oxides mixed to the V2O5 matrix was inferred for the crystalline films from the chronopotentiometric and DC measurements.Filmes amorfos de óxido de vanádio foram depositados sobre substratos de vidro recobertos com ITO, pela técnica de deposição de filmes de óxidos metálicos por filamento aquecido. Os espectros de difração de raios-X mostraram que os filmes como-depositados tratados termicamente em atmosfera de argônio em 200 e 300 ºC continuaram amorfos e os tratados a 400 e 500 ºC tornaram-se policristalinos, com a estrutura do V2O5. Os eletrodos foram eletroquimicamente reversíveis sob intercalação de Li+, exibindo o efeito eletrocrômico, observado por medidas da transmitância ótica em 632,8 nm. O coeficiente de difusão do Li, DC, foi medido pela técnica de titulação galvanostática intermitente (GITT) em função da carga inserida. Para os filmes cristalinos, a absorbância ótica e o DC aumentam com a quantidade de Li inserido, nas regiões de fase única de Li xV2O5 cristalino e decrescem nas regiões de duas fases. Para essas, um DC efetivo foi considerado. Nos filmes cristalinos foi inferida a presença de outros óxidos de vanádio misturados à matriz de V2O5, através das medidas de cronopotenciometria e de DC.788794Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Influence of DLC Film Deposition on the Corrosion and Micro-abrasive Wear Tests of the 2524-T3 Al Alloy

The 2524-T3 aluminium (Al) alloy produced by ALCOA may be used as skin material by the aircraft industry. Some studies are available in the literature about fatigue and fatigue - corrosion behaviour of 2524-T3 Al alloy. However, the corrosion mechanisms are not yet fully understood since the material has a very complex microstructure due to impurities and the addition of alloying elements which lead to an increase in the localized corrosion process. It is known that the corrosion process in Al alloys, most of the time, is due to the galvanic coupling of the intermetallic particles (IMs) and the Al matrix. Thus, the use of protective coatings appears as a possible alternative against the advancement of the corrosion process of the 2524-T3 alloy. In this way, a set of DLC films was obtained by using physical vapor deposition (PVD) method and characterized by various techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Atomic force microscopy (AFM) and Raman spectroscopy. The deposited films on the surface of the 2524-T3 Al alloy were characterized electrochemically by using potentiodynamic polarization curves (PPc), electrochemical impedance spectroscopy (EIS) and mechanically by using micro-abrasive wear tests (MAWTs). The results show an advantage in using the PVD method to produce thin films on the 2525-T3 Al alloy surfaces, as the wear resistance of the Al alloy coated by DLC film is higher than for the bare material and the corrosion resistance of the material is not compromised.  DOI: http://dx.doi.org/10.17807/orbital.v11i2.1321</p