Muhammad Asif

Development of magnesium-graphene nanoplatelets composite

In recent years, graphene has attracted a great research interest in all fields of sciences due to its unique properties. Its excellent mechanical properties lead it to be used in nanocomposites for strength enhancement. In current work, a new magnesium-graphene nanoplatelets composite is fabricated for the first time using semi-powder metallurgy method. The effect of graphene nanoplatelets addition on the mechanical behaviour of pure magnesium under both tension and hardness is investigated. The results demonstrate that graphene nanoplatelets are distributed homogeneously in the magnesium matrix, therefore act as an effective reinforcing filler to prevent the deformation. Compared to monolithic magnesium, the magnesium/0.3 wt% graphene nanoplatelets composite exhibited improved elastic modulus, yield strength, ultimate tensile strength and Vickers hardness. The improvement in elastic modulus, yield strength (0.2%), ultimate tensile strength and Vickers hardness for magnesium/0.3 wt% graphene nanoplatelets composite relative to pure magnesium are up to +10.6%, +5%, +8% and +19.3%, respectively. In addition to tensile and hardness tests for the analysis of mechanical properties of as synthesized composite, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction are used to investigate the surface morphology, elemental percentage composition and phase analysis, respectively.

Improved performance of a MnO2@PANI nanocomposite synthesized on 3D graphene as a binder free electrode for supercapacitors

In the current study, we have synthesized a binder free nickel foam graphene MnO2@PANI (MnO2@PANI/graphene) nanocomposite by simple hydrothermal method followed by in situ polymerization. The graphene grown on nickel foam is used as a 3D scaffold conducting substrate for binder free nanocomposite electrode synthesis. Morphological characterization of the nanocomposite reveals growth of the MnO2 intercalated PANI nanorods-like network. The electrochemical study demonstrates very interesting electrode activation phenomenon, i.e. increase in specific capacitance upto 1500 charge–discharge cycles. The activated MnO2@PANI/graphene nanocomposite exhibits a maximum specific capacitance of 1369 F g−1 at 3 A g−1 current density and excellent rate capability of more than 70% by varying current density from 3 A g−1 to 15 A g−1. The activated electrode displays good cyclic stability by retaining SC over 83% after 5000 cycles.

Synthesis of a highly efficient 3D graphene–CNT–MnO2–PANI nanocomposite as a binder free electrode material for supercapacitors

Graphene based nanocomposites have been investigated intensively, as electrode materials for energy storage applications. In the current work, a graphene-CNT-MnO2-PANI (GCM@PANI) nanocomposite has been synthesized on 3D graphene grown on nickel foam, as a highly efficient binder free electrode material for supercapacitors. Interestingly, the specific capacitance of the synthesized electrode increases up to the first 1500 charge-discharge cycles, and is thus referred to as an electrode activation process. The activated GCM@PANI nanocomposite electrode exhibits an extraordinary galvanostatic specific capacitance of 3037 F g-1 at a current density of 8 A g-1. The synthesized nanocomposite exhibits an excellent cyclic stability with a capacitance retention of 83% over 12 000 charge-discharge cycles, and a high rate capability by retaining a specific capacitance of 84.6% at a current density of 20 A g-1. The structural and electrochemical analysis of the synthesized nanocomposite suggests that the astonishing electrochemical performance might be attributed to the growth of a novel PANI nanoparticle layer and the synergistic effect of CNT/MnO2 nanostructures.

Highly efficient synthesis of carbon nanocoils on alumina spheres

Carbon nanocoils (CNCs) and carbon nanotubes (CNTs) can be selectively synthesized on the surfaces of alumina spheres using an Fe2(SO4)3/SnCl2 catalyst with different molar ratios of Fe to Sn by a thermal chemical vapor deposition method. On increasing the catalyst concentration, the average coil diameter, fiber diameter and pitch of the CNCs are increased. Furthermore, different productivities of CNCs can be obtained on the alumina spheres with diameters of 2 mm, 1 mm and 500 μm. It is discovered that on decreasing the diameter of alumina spheres, the thickness of the carbon layer is also decreased, resulting in a negative effect on the yield of the CNCs. A high yield of CNCs grown on 500 μm alumina spheres can be achieved by increasing the catalyst concentration to improve the thickness of the carbon layer.