Mujibur Khan
Assistant Professor, Department of Mechanical Engineering Georgia Southern University
- Statesboro GA
Mujibur Khan is an expert in Hybrid Polymer-Nanoparticle Fibers, Electrospinning and Solution Spinning, and Polymeric Fibers.
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Atomistic simulation of nanoindentation response of Fe-10%Cr bi-crystal alloys with Σ5 and Σ3 tilt boundaries
International Journal of Computational Materials Science and EngineeringM. Khan et al.
2015
In this research, nanoindentation responses of Fe-10%Cr bi-crystal structures containing Σ5{310}⟨001⟩ and Σ3{111}⟨110⟩ tilt grain boundaries (GBs) have been investigated using atomistic simulation technique. Deformation analyses identify the nucleation of 1/2⟨111⟩, ⟨001⟩ and 1/6⟨111⟩ types of dislocations within the material. The {110} slip planes are found to be more active than the {123} and {100} slip planes. Load-displacement response and corresponding changes in contact area have been recorded and used to measure material hardness and reduced modulus. The lengths of the nucleated dislocations are measured and used to estimate dislocation density within the plastic zone beneath the indenter. Dislocation motion has been found to be much easier in model with Σ3 boundary and the early interaction of the dislocation with the boundary affects the shape of the load-displacement curve, contact area on the indented surface, and the volume of the plastic zone. The hardness of the material has been found to be affected primarily by the interaction of the dislocation with the boundary, rather than by the dislocation density within the plastic zone. Both the boundaries exhibit maximum resistance to slip transmission even at the maximum indentation depth.
Investigation of synthesis and processing of Cellulose, Cellulose Acetate and Poly(ethylene oxide) nanofibers incorporating anti-cancer/tumor drug cis-Diammineplatinum (II) dichloride using...
Journal of Polymer EngineeringM. Khan et al.
2015
A model anti-cancer/tumor drug cis-diammineplatinum (II) dichloride (cisplatin) was loaded into micro- and nanofibers of cellulose, cellulose acetate (CA) and poly(ethylene oxide) (PEO), using various electrospinning techniques. Single-nozzle electrospinning was used to fabricate neat fibers of each category. Drug loading in cellulose fibers was performed using single-nozzle electrospinning. Encapsulation of cisplatin in CA and PEO-based fibers was performed using coaxial electrospinning. Morphological analysis of the fibers was performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The various categories of fibers exhibited diverse morphological features depending on the material compositions and applied process parameters. The drug-loaded cellulose nanofibers showed attached particles on the surface. These particles were composed of both the polymer and the drug. The CA-cisplatin fibers exhibited drug encapsulation within various diverse morphological conformations: hierarchical structures such as straw-sheaf-shaped particles, dendritic branched nanofibers and swollen fibers with large beads. However, in the case of PEO fibers, drug encapsulation was observed inside repeating dumbbell-shaped structures. Morphological development of the fibers and corresponding mode of drug encapsulation were correlated with process parameters such as applied voltage, concentrations and relative feed rates of the solutions and conductivities of the solvents.
Encapsulation of Cancer Drug 5-Fluorouracil into Polyethylene Oxide Nanofibers through Coaxial Electrospinning
Nano CommunicationsM. Khan
2015
Hybrid nanocomposite fibers from a blend of Ultrahigh molecular weight polyethylene (UHM-WPE)+Nylon-6+single-walled carbon nanotubes (SWCNT) were produced using a solution spinning process, both with and without a compatibilizer, Polyethylene-graft-Maleic Anhydride (PEG-g-MAH). The loading of Nylon-6, PE-g-MAH and SWCNTs was 20, 3, and 2 wt% of UHMWPE. A comparative morphological study of the fibers was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis. SEM images of hybrid fiber cross-sections have shown polymer-coated SWCNTs aligned along the direction of extrusion inside the polymer. The blends with compatibilizer have shown rough and indistinct interfacial separation of the constituent phases, as seen in both cross-sectional and longitudinal views of fibers in SEM micrographs. Whereas, the samples without compatibilizer showed distinct minor polymer phase as droplets. DSC results indicate reduction of crystallinity, crystallization rate and lamellar size in the compatibilized blends. Comparative FTIR analysis of the fiber blends showed the presence of new absorbance peaks (at 1753.62 and 1210–990 cm–1) suggesting formation of imide linkages between the UHMWPE backbone and Nylon-6 chains in the blends with compatibilizer via reactive functional groups present in the PE-g-MAH. The appearance of these peaks were more prominent when nanotubes were present in the blend.
Morphological Characteristics of Solution Spun Nanocomposite Fibers Synthesized from Ultra High Molecular Weight Polyethylene, Nylon-6 and Carbon Nanotubes, Compatibilized...
Polymer ScienceM. Khan
2015
Hybrid nanocomposite fibers from a blend of Ultrahigh molecular weight polyethylene (UHM-WPE)+Nylon-6+single-walled carbon nanotubes (SWCNT) were produced using a solution spinning process, both with and without a compatibilizer, Polyethylene-graft-Maleic Anhydride (PEG-g-MAH). The loading of Nylon-6, PE-g-MAH and SWCNTs was 20, 3, and 2 wt% of UHMWPE. A comparative morphological study of the fibers was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis. SEM images of hybrid fiber cross-sections have shown polymer-coated SWCNTs aligned along the direction of extrusion inside the polymer. The blends with compatibilizer have shown rough and indistinct interfacial separation of the constituent phases, as seen in both cross-sectional and longitudinal views of fibers in SEM micrographs. Whereas, the samples without compatibilizer showed distinct minor polymer phase as droplets. DSC results indicate reduction of crystallinity, crystallization rate and lamellar size in the compatibilized blends. Comparative FTIR analysis of the fiber blends showed the presence of new absorbance peaks (at 1753.62 and 1210–990 cm–1) suggesting formation of imide linkages between the UHMWPE backbone and Nylon-6 chains in the blends with compatibilizer via reactive functional groups present in the PE-g-MAH. The appearance of these peaks were more prominent when nanotubes were present in the blend.
Experimental study of thermopower of SWCNTs and SiC nanoparticles with B–P (born–phosphorus) sol–gel dopants
Energy MaterialsM. Khan et al.
2015
Seebeck coefficients of randomly distributed single-walled carbon nanotubes (SWCNTs) combined with Silicon Carbide (SiC) nanoparticles were experimentally determined. The Seebeck coefficients of pristine SiC/SWCNT samples were compared with those of SiC/SWCNT samples doped with P-type (Boron) and N-type (Phosphorous) sol–gel dopants. Pristine SiC/SWCNT samples were prepared by depositing SiC nanoparticles and SWCNTs on a non-conductive glass substrate. Doped SiC/SWCNT samples were prepared by coating each half of the samples alternately with B and P sol–gel dopants. Thermoelectric circuits were prepared by creating hot and cold junctions on the P and N-doped ends of the SiC/SWCNT samples with conductive Silver epoxy and Alumel (Ni–Al) wire. Voltage, current and resistance were measured across the samples against temperature difference. The SWCNTs used were approximately 60% semiconducting and 40% metallic. The Seebeck coefficient for pristine SWCNTs was 0.10 ± 0.006 mV per degree Celsius. When diffused with B–P, the Seebeck coefficient increased to 0.308 mV per degree Celsius. Pristine SiC nanoparticles showed no presence of thermoelectric (TE) effect, but substantial TE effects were observed upon inclusion of SWCNTs. Although the samples with various SWCNT compositions showed similar Seebeck coefficients, the current, resistance and power factor (PF) changed accordingly. Resistance of the pristine SWCNTs slightly decreased with increase in temperature. Structure–property relations were determined using scanning electron microscopy (SEM) and Raman spectroscopy. It was revealed that fibre-like SWCNTs created randomly distributed networks with nano-contact junctions inside the SiC matrix. Diffusion of dopants into CNTs in the doped samples increased the charged carrier concentration enhancing the thermopower of SWCNTs. Analysis of the Raman spectra showed an upshift in the tangential vibrational G-band modes of SWCNTs when doped with an electron-acceptor dopant (Boron), and a downshift in the case of an electron-donor dopant (Phosphorus). Incorporation of the dopant materials in the SWCNT structure was also evidenced by the presence of disorder induced D-band peaks in the doped SWCNTs.
