Photoluminescence and concentration quenching of Pr3+ doped BaTa2O6 phosphor

The pure and Pr3+ doped TTB-BaTa2O6 phosphors were obtained by the solid state reaction method at 1 425 °C for 20hours. X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses confirmed a single phase of BaTa2O6up to 10 mol % Pr2O36. SEM analysis also shows that BaTa2O6 grain size decreased with the increasing Pr2O36 concentration.The chemical composition of Pr3+ doped BaTa2O6 structures was confirmed by Energy Dispersive Spectroscopy(EDS) analysis. BaTa2O6:Pr3+ phosphors exhibited on a strong red emission at 620,9 nm, a green emission at 548,3 nm and a red emission at 655,2 nm. Emission intensity increased with Pr3+ doping concentration up to 1,5 mol %, then decreased due to concentration quenching

Effect of heat treatment on the wear and corrosion behaviors of a gray cast iron coated with a COLMONOY 88 alloy deposited by high velocity oxygen fuel (HVOF) thermal spray

The present work has been conducted in order to determine the influence of heat treatment on the wear and corrosion behaviours of a gray cast iron substrate coated with a Ni base coating deposited by HVOF thermal spray. The wear resistance of the coatings was obtained using a reciprocating wear tester by rubbing a 10 mm diameter steel ball on the coatings at normal atmospheric conditions. Corrosion tests were performed using potentiodynamic polarization measurements in a 3,5 % NaCl solution. It was observed that the corrosion and wear resistance of the coatings increased along with the reduction of porosity and roughness by the heat treatment

Effect of Mill Type on Morphology of AA6013 Aluminium Powder

ABSTRACTIn conventional recycling method, metal chips are cast after pressing and melting in electric arc furnace. Material loss occurs during the recycling from liquid metal due to the several reasons. Direct recycling method which produces the aluminium powder from aluminium chips using mechanical mill can be an alternative to conventional recycling method. Thus material and energy losses, and labour cost will be reduced by direct recycling method without melting.In this study, the particle morphology of powder direct recycled from AA6013 aluminium alloy chips with cryogenic, disc and ball type grinders is investigated. Mechanical milling resulted flaky and irregular shaped AA6013 particles. It was ascertained that the chips did not break sufficiently in despite of the long duration milling mechanisms by ball mill. Cryogenic mill provides the energy required for milling mechanisms to act. Disc mill has the highest impact energy was determined. Consequently, efficiency of ball mill is lower than the efficiency of cryogenic and disc type mills. Shape factors of powders produced with ball and cryogenic mills were found greater than that of the powder produced by disc mill. Disc mill has the most efficient and effective impact energy which produces the smaller particles per minute, was determined.Keywords: Direct recycling method, powder production, scrap chips, aluminium alloy.

The Study of Electroless Ni-P/Ni-B Duplex Coating on HVOF-Sprayed Martensitic Stainless Steel Coating

High velocity oxygen fuel sprayed stainless steel coatings have been widely used in various industries to repair damaged components. However, its broad application is limited due to its comparatively low hardness and inferior tribological properties. In this work, electroless Ni-P/Ni-B duplex coating with a thickness of ≈ 40 μm was deposited on surfaces of HVOF-sprayed 420 martensitic stainless steel substrate, and its structural, corrosion and tribological properties were characterized. Experimental results showed that upper Ni-B coating deposited on the surface of first Ni-P layer by duplex treatment exhibited superior hardness, wear and corrosion resistances as compared to the HVOF-sprayed 420 martensitic stainless steel coating with a thickness of about 150 μm

Electroless Ni–B Coating of Pure Titanium Surface for Enhanced Tribocorrosion Performance in Artificial Saliva and Antibacterial Activity

In the present study, the surface of commercial pure (Grade 2) titanium was coated with electroless Ni–B. The surface morphology, microstructure and phase identification were analysed by X-Ray Diffraction (XRD) and Field Emission Gun Scanning Electron Microscope (FEG-SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS). The tribocorrosion performance in a laboratory simulated artificial saliva was investigated using a reciprocating ball-on-plate tribometer coupled to an electrochemical cell. The antibacterial property of the electroless Ni–B film coated on pure titanium was basically investigated. From this study, it may be concluded that this electroless Ni–B coating process cannot only improve the hardness and tribocorrosion performance of the pure titanium, but can also provide antimicrobial activity

Effect of B4CB_4C Content on the Mechanical and Tribological Performances of Polypropylene

Boron carbide ($B_4C$) reinforced polypropylene (PP) was prepared by twin-screw extrusion and injection molding. In the present study, the effect of $B_4C$ content on the mechanical properties and wear behavior of the PP composites was studied. The tribological properties of the PP composites were investigated by a reciprocating wear tester under dry friction conditions. The results of the mechanical and wear test showed that the hardness and yield strength increased with increasing $B_4C$ content, while the incorporation of $B_4C$ into PP largely increased wear and friction under dry sliding. The composites have higher wear rates in comparison with unfilled PP and the greater the difference, the greater are the sliding velocities

Corrosion and tribocorrosion behavior of cast and machine milled Co-Cr alloys for biomedical applications

In this study, the electrochemical behavior and tribocorrosion performance of cobalt-chromium (Co-Cr) alloys produced by different fabrication methods (casting and CAD/CAM milling technique) have been investigated in the laboratory-simulated artificial saliva. The results have shown that the maximum tribocorrosion resistance was obtained for milled Co-Cr alloy because of higher corrosion resistance and hardness of milled Co-Cr alloy compared too those of cast Co-Cr alloy. Moreover, the lowest friction coefficient was achieved for milled Co-Cr alloy

Recycling of Pure Magnesium Chips by Cold Press and Hot Extrusion Processes

This study aims to recycle pure magnesium chips by a two-stage mechanical processing method. In the present study, the feasibility of recycling pure magnesium chips with the help of commercially pure magnesium powder was investigated. For this study, the magnesium chips mixed with different amount of magnesium powders in the range of 25-75 wt%, after mixing by hand and cold press, are subjected to hot extrusion to provide homogeneous microstructure. Furthermore, the effect of magnesium powder and their amounts on the mechanical properties and corrosion behaviour of the recycled magnesium alloys were studied. The results of the mechanical and corrosion test showed that the hardness and compressive yield strength decreased with increasing chip content, while increase in the chip weight fraction in the initial mixture resulted in a significant increase of corrosion resistance