Browsing by Author "Daoush, Walid M."

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Experimental investigations on the synthesis of W-Cu nanocomposite through spark plasma sintering
(ELSEVIER, 2015) Elsayed, Ayman; Li, Wei; El Kady, Omayma A.; Daoush, Walid M.; Olevsky, Eugene A.; German, Randall M.
Elemental powders of nanosized tungsten and chemically deposited nanosized copper were used for preparing tungsten/copper composites, which are used as electric contact components. A composite of 70 wt.%W/30 wt%Cu (52 vol%W/48 vol% Cu) composition was prepared by three powder metallurgy techniques. Elemental mixing, mechanical milling and electroless Cu coating on tungsten particles were used for the synthesis. The obtained powder blends underwent consolidation by rapid hot pressing using the spark plasma sintering (SPS) route at 950 degrees C under vacuum and by conventional vacuum pressureless sintering for comparison. The elemental powders and the sintered composites were investigated by optical microscopy and SEM. Electrical conductivity, hardness, transverse rupture strength, and wear properties were measured. Results show that the synthesis of the composite by the investigated route yields good performance. Samples prepared by SPS have shown better mechanical properties than those prepared by compaction and sintering due to their fine microstructure. (C) 2015 Elsevier B. V. All rights reserved.
Fabrication of PtNi bimetallic nanoparticles supported on multi-walled carbon nanotubes
(TAYLOR & FRANCIS LTD, 2015) Daoush, Walid M.; Imae, Toyoko
Platinum/nickel bimetallic nanoparticles supported on multi-walled carbon nanotubes (xPtNi/CNTs) were synthesised. The fabrication process includes the chemical modification on the graphene surface of CNTs by acid treatment and the subsequent deposition of Pt or PtNi bimetallic nanoparticles with different compositions of Pt (x = 100, 90, 80 and 70wt%). The deposition was carried out using ethylene glycol as a reducing agent in the polyol method or using poly(amidoamine) dendrimer as a platform and sodium borohydride as a reducing agent to load the metal nanoparticles on the CNT surface. The structures of the produced PtNi/CNT nanoparticles were investigated by ultraviolet absorption spectra, X-ray diffraction (XRD) and the composite ratio consisting of 70wt% of metal content and 30wt% of CNTs was confirmed by the thermogravimetric analysis. The morphology and the phase identification of the produced PtNi/CNT nanoparticles were investigated by high-resolution scanning electron microscope, transmission electron microscope and XRD measurements. It was observed that the deposited Pt and PtNi bimetallic nanoparticles on the surface of CNTs had average particle sizes of 2-16nm, when they were prepared from the polyol method. On the other hand, the PtNi/CNT nanoparticles prepared by using a dendrimer as an intermediate had a smaller particle size and more uniform size distribution of the quantum dot size ranged from 2 to 4nm.
Microstructure and properties of BN/Ni-Cu composites fabricated by powder technology
(TAYLOR & FRANCIS LTD, 2018) El-Tantawy, Ahmed; Daoush, Walid M.; El-Nikhaily, Ahmed E; https://cutt.ly/seHTA1W
Microsize Powders of Ni and Cu were prepared by water atomization technique to fabricate metal matrix composites containing various percentages of nanosized boron nitride particles (1, 2, 3, 4, 5wt. % of BN in a matrix containing (20wt. %Ni and 80wt. %Cu). The prepared mixtures were cold compacted under 400MPa, and sintered for 2h at 1000 degrees C in a controlled atmosphere of 3:2 N-2/H-2 gas mixtures. The microstructure and the chemical composition of the prepared powders as well as the consolidated composites were investigated by X-ray diffraction as well as field emission scanning electron microscope (FESEM) equipped with an energy dispersive spectrometer (EDS). The produced Cu and Ni powders have spheroid shape of size less than 100 microns, but the investigated BN has an equiaxed particle shape and particle size of approximate to 500nm. It has been also observed that BN and Ni particles were homogeneously distributed in the Cu matrix of the present BN/Ni-Cu composites. The density, electrical resistivity, saturation magnetization and hardness of the composites were measured. It was observed that, by increasing BN content, the relative density was decreased, while the saturation magnetization, electrical resistivity and hardness were increased.
Microstructure, physical properties and hardness of alumina short fibres/nickel matrix composites fabricated by powder technology
(SAGE PUBLICATIONS LTD, 2014) Daoush, Walid M.; Elkady, Omayma A.
Nickel matrix composites reinforced with different weight percent of alumina short fibres have been fabricated by powder technology route. The alumina short fibres were encapsulated by nickel layers using the electroless deposition technique. The produced alumina/nickel composite powders underwent cold compaction and sintering at 850?. The alumina/nickel powders as well as the consolidated composites were investigated by optical microscope, scanning electron microscope, XRD and VSM. It was observed that the surface of the alumina short fibres was completely coated with nickel layer and the microstructures of the consolidated compacts show homogeneous distribution of the alumina short fibres in the nickel matrix. The density, electrical conductivity, coercivity, retentivity, saturation magnetization and hardness of the produced alumina short fibres/nickel composites were measured. The relative sintered density and the saturation magnetization were decreased, but the retentivity, the coercivity and the hardness were increased by increasing the alumina short fibres weight percent in the nickel matrix.
Structural health monitoring capabilities in ceramic-carbon nanocomposites
(ELSEVIER, 2014) Inam, Fawad; Bhat, Badekai R.; Vo, Thuc; Daoush, Walid M.
A novel method for analysing structural health of alumina nanocomposites filled with graphene nanoplatelets (GNP), carbon nanotubes (CNTs) and carbon black nano-particles (CB) is presented. All nanocomposites were prepared using novel colloidal processing and then by Spark Plasma Sintering. Good homogeneous dispersion was observed for all carbon filled materials. Nanocomposite bars were indented to produce sub-surface damage. Change in electrical conductivities were analysed after indentation to understand structural damage. For correlating change in electrical conductivity and indentation damage and understanding damage tolerance, mechanical properties were compared. Because of the systematically induced indentation damage, a sharp decrease of 86% was observed in the electrical conductivity of CNT nanocomposite as compared to 69% and 27% in the electrical conductivities of GNP nanocomposites and CB nanocomposites respectively. CNTs impart superior damage sensing capability in alumina nanocomposites, in comparison to GNP and CB, due to their fibrous nature, high aspect ratio and high electrical conductivity. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.