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Abstract : Metal Oxide Porous Coatings for Implantant Materials
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Abstract: The paper presents the results of survey, dedicated to synthesis of metal oxide coatings on porous materials applied for implant surgery (stainless steel 12X18H9T, titanium alloy and high-purity niobium VT5). This article examines kinetic features of electrochemical formation of anodic oxide coatings on steel, niobium and titanium. It is shown that for steel anodic treatment method does not provide a reliable surface passivation (no current decay, the surface indicates the transition to the passive state). Analysis of polarization dependences obtained on niobium and titanium in electrolytes with an activator (F-), indicates surface passivation (current slump), and at potentials above 2 on the surface of a transition curves in transpassive state (as evidenced by the current increase). Consequently, it can be concluded that presence of F- results surface activation of titanium and niobium electrode (F- oxide reacts to form water-soluble complexes) that promotes nucleation and formation of pores of the porous structure of the oxide coating. SEM results verify the presence of self-organized porous oxide film synthesized on titanium and niobium in solutions containing F-. Keywords: Oxidation, anodic film, coating, implantant. |
Abstract : Alumina Surface Treated TiO2 – From Process to Application
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Abstract: Titanium dioxide (TiO2) has found widespread use. Typically it is used in another matrix to impart certain properties. For example, it is widely used as a white pigment for paints and polymers. The aim of this research work was to achieve improvements in the sense of processability as well as the dispersion performance of alumina surface treated pigmentary TiO2in polymer matrix. Wet chemical method was used to modify the surface of the TiO2 pigment. Surface treatment included precipitation of hydrous oxides of aluminium on the surface of TiO2 particles. During controlled surface treatment, agglomeration has been avoided, which has been proved to improve applicative properties of TiO2 particles. In addition to that, organic additives were applied to enhance performance attributes of the pigmentary TiO2. The effectiveness of surface treatment was determined using scanning-transmission (STEM) and transmission (TEM) electron microscopy. Quantitative evaluation of quality and dispersion of the pigments has been performed using Filter pressure test. Lower pressure generated during filter pressure test when particles were well dispersed in a polymer matrix. Surface treatment also affected pigment processibility; i.e. filterability and settling, which is of high importance for process planning. Keywords: Titanium dioxide, Surface treatment, Coatings, Alumina, Dispersibility. |
Abstract : Processing, Adhesion and Corrosion-inhibiting Properties of Poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene], (MEH-PPV) on Aerospace Aluminum Alloys
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Abstract: Researchers at the Naval Air Warfare Center Weapons Division (NAWCWD) and Wright-Patterson Air Force Base (WPAFB) investigated poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene], (MEH-PPV) for its potential corrosion-inhibition properties on aerospace aluminum alloy AA2024-T3. Solution processing of the polymer, as well as adhesion testing and accelerated weathering tests were performed on MEH-PPV full military aerospace coatings. Wet and dry tape adhesion testing, as well as pencil hardness, impact flexibility and pneumatic adhesion tensile test instrument (PATTI) testing were used to demonstrate the adhesion performance of MEH-PPV on aluminum substrates. The results showed that MEH-PPV had acceptable adhesion characteristics when compared to hexavalent chromium (Cr(VI)) based coatings in all of these tests. Accelerated weathering analysis was performed on MEH-PPV coatings to determine their corrosion protection and weathering resistance capabilities. These tests included neutral salt spray (NSS) exposure and xenon-arc lamp testing. The results showed that while MEH-PPV does not exhibit significant color change after 500 hours of xenon arc lamp exposure, the polymer has poor corrosion protection performance under aggressive salt environments. Keywords: Poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene](MEH-PPV), hexavalent chromium (Cr(VI)), chromate conversion coating (CCC), adhesion testing, pencil hardness, impact flexibility, accelerated weathering testing. |
Abstract : Electronic Bond Structure of Carbon Nitride Thin Film Deposited by HiPIMS and dc Magnetron Plasma
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Abstract: We report the difference in electronic bond structure and surface chemical property of amorphous carbon nitride (a-CNx) film as a function of N/C which has been deposited by high power impulse magnetron sputtering (HiPIMS) and DC magnetron (dc-MS) plasma. The spectroscopic analyses suggest that the presence of oxide layer is the major cause for the surface charging in the core level peak. The core electron peaks (C1s, N1s and O1s) in x-ray photoelectron spectroscopy (XPS) show higher surface charging in HiPIMS compare to the film deposited by dc-MS plasma. The core peaks are moved gradually toward its virgin position as the etching duration is increased from 1 min to 80 mins. The films deposited by HiPIMS retain a higher N/C ratio following ion etching as compared to those deposited by DC magnetron sputtering suggesting denser films with a higher degree of cross-linking. Keywords: Carbon nitride, HiPIMS, dc-MS, a-CNx disintegration by Ar-sputter clean, Surface charging, X-ray photoelectron spectroscopy. |
