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Iqbal, M.Z.,Kelekci, O.,Iqbal, M.W.,Eom, J. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.59 No.-
The defect formation mechanism in chemical vapor deposition grown single layer graphene devices has been investigated by increasing electron beam (e-beam) irradiation doses gradually up to 750e<SUP>-</SUP>/nm<SUP>2</SUP>. The evolution of D peaks in Raman spectra provides an evidence of strong lattice disorder due to e-beam irradiation. Particularly, the trajectory of D and G peak intensities ratio (I<SUB>D</SUB>/I<SUB>G</SUB>) suggests that the transformation of graphene from crystalline to the nanocrystalline and then towards amorphous form with increasing irradiation dose. The defect parameters were calculated by phenomenological model of amorphization trajectory for graphitic materials. The mobility decreasing gradually from ~1200 to ~80cm<SUP>2</SUP>/V s with gradual increase of irradiation dose, which implies the formation of localized states in e-beam irradiated graphene. The Dirac point is shifted towards negative gate voltage which indicates the n-doping in graphene with increasing e-beam irradiation dose.
Surface Texturing for Low Friction Mechanical Components
Iqbal, K. Y. Mohd,Segu, D. Z.,Pyung, H.,Kim, J. H.,Kim, S. S. Korean Tribology Society 2015 한국윤활학회지(윤활학회지) Vol.4 No.1
Laser surface texturing (LST), a surface engineering modification, has been considered as one of the new processes used to improve tribological characteristics of materials by creating artificially patterned microstructure on the contact surface of mechanical components. In LST technology, the laser is optimized to obtain or manufacture the dimples with maximum precision. The micro-dimples reduce the coefficients of friction and also improve the wear resistance of materials. This study investigates the effect of dimple density is investigated. For this purpose, a ball-on-disc type tester is used with AISI 52100 bearing steel as the test material. Discs are textured with a 5% and 10% dimple density. Experimental work is performed with normal loads of 5 N, 10 N, and 15 N under a fixed speed of 150 rpm at room temperature. The effect of the textured surface is compared to that of the untextured one. Experimental results show that the textured surface yields lower friction coefficients compared to those of untextured surfaces. Specifically, the 10% dimple density textured surface shows better friction reduction behavior than the 5% dimple density textured sample, and has an 18% improvement in friction reduction compared with the untextured samples. Microscopic observation using a scanning electron microscope (SEM) shows that the major friction mechanisms of the AISI 52100 bearing steel are adhesion, plastic deformation, and ploughing.