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Daoush, W.M.,Lim, B.K.,Nam, D.H.,Hong, S.H. Taylor Francis 2014 Journal of experimental nanoscience Vol.9 No.6
Carbon nanotube/silver (CNT/Ag) nanocomposites include CNT volume fraction up to 10vol.% were prepared by chemical reduction in solution followed by spark plasma sintering. Multiwalled CNTs underwent surface modifications by acid treatments, the Fourier transform infrared spectroscopy data indicated several functional groups loaded on the CNT surface by acid functionalisation. The acid-treated CNTs were sensitised and activated. Silver was deposited on the surface of the activated CNTs by chemical reduction of alkaline silver nitrate solution at room temperature. The microstructures of the prepared CNT/Ag nanocomposite powders were investigated by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy and X-ray powder diffraction analysis. The results indicated that the produced CNT/Ag nanocomposite powders have coated type morphology. The produced CNT/Ag nanocomposite powders were sintered by spark plasma sintering. It was observed from the microstructure investigations of the sintered materials by HRSEM that the CNTs were distributed in the silver matrix with good homogeneity. The hardness and the tensile properties of the produced CNT/Ag nanocomposites were measured. By increasing the volume fraction of CNTs in the silver matrix, the hardness values increased but the elongation values of the prepared CNT/Ag nanocomposites decreased. In addition, the tensile strength was increased by increasing the CNTs volume fraction up to 7.5vol.%, but the sample composed of 10vol.% CNT/Ag was fractured before yielding.
Daoush, W.M.,Park, H.S.,Lee, K.H.,Moustafa, S.F.,Hong, S.H. MPR Pub. Services 2009 INTERNATIONAL JOURNAL OF REFRACTORY METALS AND HAR Vol.27 No.4
Fabrication by powder technology routes, as well as microstructure characterization and measurement of hardness and magnetic properties of two types of (Ta,Nb)C sintered carbides having different composition of Ni and Co binders were carried out in the present study. Each carbide binder composition mixer was cold pressed in a uniaxial direction die at 400MPa followed by vacuum sintering at 1450<SUP>o</SUP>C. Nearly full dense (Ta,Nb)C sintered carbides with a relative density between 99.5% and 99.8% were obtained. The highest macrohardness values were observed for composition of (Ta,Nb)C-5wt%Co and (Ta,Nb)C-5wt%Ni of 1400 H<SUB>V</SUB> and 1300 H<SUB>V</SUB> respectively. The magnetic B-H hysteresis loops were measured at 0.8T by the VSM method. In the case of (Ta,Nb)C-Co, higher magnetic saturation values of 47emu/g were obtained for (Ta,Nb)C-30wt%Co and 13.5emu/g for (Ta,Nb)C-5wt%Co. However, the magnetic saturation values for the prepared carbide having a composition of (Ta,Nb)C-Ni displayed smaller magnetic saturation than the corresponding (Ta,Nb)C-Co carbides. On the other hand, the coercivities of the (Ta,Nb)C-Co has higher value than those of (Ta,Nb)C-Ni. As the metal binder phase was increased, the coercivity decreased. The influence of the distribution of Ta, Nb, Co and Ni in the carbide phase and the metal binder phase were investigated by EDAX compositional analysis and its relation with the hardness and the magnetic properties were studied.