Titanium Dioxide Films for Photocatalytic Degradation of Methyl Orange Dye

The aim of this work was to characterize and evaluate the influence of the thickness on the photocatalytic efficiency of titanium dioxide thin films on the degradation of methyl orange dye under UV light irradiation. The films of 280 and 468 nm thick were deposited on borosilicate substrates at 400°C by the MOCVD technique using titanium isoproxide IV as precursor. XRD analyses showed the formation of anatase-TiO2 phase. Cross-sectional FE-SEM images show that the films presented a dense columnar structure and grown perpendicularly to the substrate surface. The photocatalytic activity of the catalysts was studied using UV-vis spectrophotometry The TiO2 film with 468 nm of thickness presented higher photocatalytic activity exhibiting 69% of dye degradation. The increase of grain size and thickness of the films promoted an improvement of photocatalytic efficiency

Electrochemical Characterization of an Optical Fiber Laser- Treated Biomaterial

The implant manufacturing process includes texturization to enhance its adhesion and marking the final products for their identification, long-term quality control and traceability. Marking is carried out after cleaning and prior to sterilization. These marks eventually can concentrate stress leading to premature failure. The marked areas are defective regions that affect the passive film formed on the metallic biomaterials used for implants favoring the onset of various corrosion types, such as pitting, crevice or fatigue. This study aims to evaluate the effect of a Yb optical fiber laser marking processes used for metallic implants on the localized corrosion resistance of the austenitic stainless steel ISO 5832-1. This is one of the most used materials for manufacturing implants. The electrochemical behavior of the marked areas obtained by this method was evaluated in a phosphate-buffered saline (PBS) solution with pH of 7.4 and the results were compared with unmarked samples. All tested surfaces were prepared according to the recommendations for the use in surgery. For localized corrosion resistance evaluation, electrochemical tests such as monitoring the open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and cyclic potentiodynamic polarization measurements were performed. The results showed that the laser marks affect the protector characteristics of the biomaterial’s passive film. Lower pitting resistance was associated to the laser marked areas

Effect of pre-oxidation on high temperature sulfidation behavior of FeCr and FeCrAl alloys

High temperature corrosion of structural alloys in sulfur bearing environments is many orders of magnitude higher than in oxidizing environments. Efforts to increase sulfidation resistance of these alloys include addition of alloying elements. Aluminum additions to iron-chromium alloys bring about increase in sulfidation resistance. This paper reports the effect of pre-oxidation on the sulfidation behavior of Fe-20Cr and Fe-20Cr-5Al alloys in H2-2% H2S environment at 800 °C. The surfaces of sulfidized specimens were also examined. Pre-oxidation of the two alloys results in an incubation period during subsequent sulfidation. After this incubation period, the Fe-20Cr alloy showed sulfidation behavior similar to that when the alloy was not pre-oxidized. The incubation period during sulfidation of the Fe-20Cr-5Al alloy was significantly longer, over 45 h, compared to 2 h for the Al free alloy. Based on the microscopic and gravimetric data a mechanism for sulfidation of these alloys with pre-oxidation has been proposed

High temperature oxidation resistance of rare earth chromite coated Fe-20Cr and Fe-20Cr-4Al alloys

Doped lanthanum chromite has been used in solid oxide fuel cell (SOFC) interconnects. The high costs involved in obtaining dense lanthanum chromite have increased efforts to find suitable metallic materials for interconnects. In this context, the oxidation behavior of lanthanum chromite coated Fe-20Cr and Fe-20Cr-4Al alloys at SOFC operation temperature was studied. Isothermal oxidation tests were carried out at 1000 °C for 20, 50 and 200 hours. Cyclic oxidation tests were also carried out and each oxidation cycle consisted of 7 hours at 1000/°C followed by cooling to room temperature. The oxidation measurements and the results of SEM/EDS as well as XRD analyses indicated that lanthanum chromite coated Fe-20Cr and Fe-20Cr-4Al alloys were significantly more resistant to oxidation compared with the uncoated alloys

Evaluation of Carbon thin Films Using Raman Spectroscopy

<div><p>Carbon thin films deposited by the magnetron sputtering technique were evaluated by Raman spectroscopy to study the influence on their crystallinity caused by different parameters like the carbon deposition time, the different buffer-layers and substrates employed and also two distinct heat treatments. The present results showed that the choice of these parameters plays an important role in the production of these films. The results also indicate the possibility of using the technique for the production of carbon thin films to be employed in future in applications with controlled content of structural defects, predominance of ordered sp2 bondings and tendency of graphitization.</p></div

Oxidation behavior of FeCr and FeCrY alloys coated with an aluminium based paint

A variety of metallic components rely on properties that are specific to the alloy and its surface. Coatings have been extensively used to protect metallic surfaces from the aggressive effects of the environment to which it is exposed. In this investigation, the high temperature oxidation behavior of a FeCr and a FeCrY alloy coated with an aluminium based paint has been studied. The objective was to form the more resistant alumina surface layer on an aluminium free alloy. Aluminium based paint coated and uncoated specimens of the two alloys were oxidized for up to 200 hours at 1000 °C in air. The oxidized specimens were examined in a scanning electron microscope coupled to an energy dispersive system and the surfaces were analyzed by X ray diffraction analysis. The aluminium based paint coating increased the oxidation resistance of the alloys, mainly over extended periods. The FeCrY alloy coated with the Al based paint exhibited the highest oxidation resistance