Effects of Diamond Nanoparticles on the Microstructure, Hardness and Corrosion Resistance of Chromium Coatings
Vladimir Petkov,
Radoslav Valov
Issue:
Volume 8, Issue 6, November 2020
Pages:
125-130
Received:
20 October 2020
Accepted:
4 November 2020
Published:
27 November 2020
Abstract: Electrodeposited coatings of chromium and diamond nanoparticles on steel were obtained. The chromium is plated directly on the steel matrix without any intermediate layers. The influence of the electrodeposition current density, the electrodeposition time and the concentration of diamond nanoparticles in the chromium-plating electrolyte on the microstructure, the phase composition, the microhardness and the corrosion resistance of the chromium coatings were investigated. The phase and chemical compositions of the composite coating (chromium and diamond nanoparticles) were examined using X-ray Diffraction (XRD) and Scanning Electron Microscopy - Energy-Dispersive X-ray Spectroscopy (SEM-EDS) techniques. The microstructure and microhardness were examined with a metallographic microscope and a microhardness tester. The corrosion resistance was investigated in 3.5 wt % NaCl solution using the gravimetric method. The bond between the chromium coating and the steel matrix has diffusion character. A sublayer of separate irregular shape formations appears at concentration of diamond nanoparticles 25 g/l and more. The formation of these structures depends only on the concentration of diamond nanoparticles and is not influenced by the other electrodeposition parameters. With the increase of the concentration of diamond nanoparticles in the electrolyte the rate of chromium coating deposition increases and respectively the thickness of the coating increases also. This increase is more than twice the thickness of chromium coating without nanodiamonds. The microhardness of the composite coatings rises also compared to unmodified chromium coating. With the increase of the concentration of the diamond nanoparticles 2 times greater microhardness is achieved and up to 5 times greater corrosion resistance compared to monochromium coating. The values of the other electroplating parameters are constant.
Abstract: Electrodeposited coatings of chromium and diamond nanoparticles on steel were obtained. The chromium is plated directly on the steel matrix without any intermediate layers. The influence of the electrodeposition current density, the electrodeposition time and the concentration of diamond nanoparticles in the chromium-plating electrolyte on the micr...
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Modified Sulfonated Glucose-Catalyzed Esterification of Palm Fatty Acid Distillate: Kinetics and Fuel Properties
Haruna Mavakumba Kefas,
Robiah Yunus,
Umer Rashid,
Yun Hin Taufiq-Yap
Issue:
Volume 8, Issue 6, November 2020
Pages:
131-138
Received:
11 November 2020
Accepted:
24 November 2020
Published:
16 December 2020
Abstract: The employment of sugar acid catalysts for biodiesel synthesis from non-edible palm fatty acid distillate (PFAD) has received huge research interest in recent times by reason of their stability and high catalytic performance. Notwithstanding, the need to extend research on the kinetic characteristics of these heterogeneous catalysts is important in order to understand their reaction mechanisms. The present investigation deals with the kinetics for the esterification of PFAD by means of modified sulfonated carbonized glucose catalyst to biodiesel in a three necked conventional reflux batch reactor. The efficient catalyst was synthesized by sulfonation of incomplete carbonized glucose. The pseudo-homogeneous first and second order (equimolar) mechanism was utilized to interpret the data at optimum operating conditions of 10:1 molar fraction of methanol to PFAD, 4 h time of reaction and 4 wt.% quantity of catalyst at varying reaction temperature of 50-65°C. Furthermore, some important properties of the PFAD biodiesel produced were assessed utilizing ASTM methods. The experimental data best fitted the bimolecular model (equimolar) second order model. The activation energy was calculated to be 55.08 kJmol-1 which indicates that the catalyst was very active in the esterification of the PFAD to biodiesel. Most of the measured fuel properties of the PFAD biodiesel were comparable with the ASTM standards.
Abstract: The employment of sugar acid catalysts for biodiesel synthesis from non-edible palm fatty acid distillate (PFAD) has received huge research interest in recent times by reason of their stability and high catalytic performance. Notwithstanding, the need to extend research on the kinetic characteristics of these heterogeneous catalysts is important in...
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