Sushant Sharma

Structural transformation in thin films of binary alloys

Structural transformation in thin films of binary alloys of 1st and 6th group elements, prepared by vacuum evaporation, has been studied by the author in detail by electron diffraction. The alloys chosen for the investigation were Ag2Te, Ag2Se, Ag2S, Cu2Te and Cu2Se. The study of thin films of these alloys revealed that there occurs a transformation in structure and on heating, the temperatures of transformation are higher compared to the alloys in the bulk state. It has also been observed that the temperatures of structural transformation during heating and cooling are different. No quantitative explanation of the result has been given and it is expected that detailed discussion of the results will be published later.

Synergistic effect on static and dynamic mechanical properties of carbon fiber-multiwalled carbon nanotube hybrid polycarbonate composites

Carbon fiber (CF) and multiwalled carbon nanotube (MWCNT)-reinforced hybrid micro–nanocomposites are prepared through melt mixing followed by injection moulding. The synergistic effect on both the static and dynamic mechanical properties with MWCNT/aMWCNT and CF reinforcement in a polycarbonate matrix is investigated by utilizing dynamic mechanical analysis, and flexural and tensile measurements. The enhancement in the flexural modulus and strength of the composite specimens as compared to pure PC for maximum loading of CF is 128.40% and 39.90%, respectively, which further improved to 142.94% and 42.60%, respectively, for CF-functionalized MWCNTs. Similarly, the storage modulus of the composite specimens reinforced with a maximum loading of CF and CF-functionalized MWCNTs show an increment of 176.57% and 203.33%, respectively over pure PC at 40 °C. Various types of parameter such as the coefficient C factor, degree of entanglement and adhesion factor have been calculated to analyze the interaction between fillers and the polymer matrix. Composite specimens containing 2 wt% of functionalized MWCNTs show a lower C value than the as-synthesized MWCNTs, which is indicative of a higher effectiveness of functionalized MWCNT-containing composite specimens. These results are well supported by optical microscopy and Raman spectroscopy by confirming the distribution of reinforcements and the interaction to PC, respectively.

Significant improvement in static and dynamic mechanical properties of graphene oxide-carbon nanotube acrylonitrile butadiene styrene hybrid composites

Herein, hybridization of graphene nanosheets and carbon nanotubes (CNTs) has been made to solve the problem of restacking of graphene nanosheets and agglomeration of CNTs. The multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (RGO) and graphene oxide–carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites have been prepared using micro-twin-screw extruder. The effect of these reinforcements on static and dynamic mechanical properties of composites is studied. The ultimate tensile strength and elastic modulus for 7 wt.% GCNT–ABS composites show enhancement of 26.1 and 71.3% over pure ABS matrix, respectively. Various parameters such as coefficient “C” factor (the ratio of storage modulus of the composite to polymer in glassy and rubbery regions), degree of entanglement, crosslink density and adhesion factor have been calculated to analyze the interaction between fillers and polymer matrix. The 3-D hybrid structure of GCNTs overcomes the associated problem of CNTs agglomeration and graphene restacking. GCNT hybrid composites show higher dispersion as well as effectiveness for increased filler amount as compared to RGO and MWCNTs based composites. GCNTs prove its superiority over MWCNTs and RGO by showing a synergistic effect in the glass transition temperature and storage modulus. Raman spectroscopy and scanning electron microscopy are used to confirm the interaction and distribution of the filler and matrix, respectively.

Improved thermomechanical and electrical properties of reduced graphene oxide reinforced polyaniline – dodecylbenzenesulfonic acid/divinylbenzene nanocomposites

HYPOTHESIS Various efforts are going on to improve the electrical properties of carbon fiber reinforced polymer (CFRP) composites. Conducting polymer is one the promising material to achieve the desired electrical properties of CFRP composites without compromising the mechanical properties as a lighting sticking material. EXPERIMENTS In present study, in addition to conducting polymer polyaniline (PANI), another conducting phase reduced graphene oxide (RGO) was incorporated in PANI based system. The RGO was synthesized and incorporated in different weight (0-0.5 wt%) fraction in dodecylbenzenesulfonic acid (DBSA) doped PANI-divinylbenzene (DVB) polymer to get PANI-DBSA/DVB nanocomposite. The mechanical and interfacial interaction was analyzed by universal testing machine (UTM) and transmitted electron microscopy (TEM). FINDINGS The addition of optimum 0.3 wt% RGO improved flexural strength and modulus of PANI-DSBA/RGO-DVB composite by 153% and 32% respectively over neat PANI-DBSA/DVB nanocomposite. The maximum electrical conductivity 0.301 S/cm, glass transition temperature (Tg) and thermal stability of nanocomposite realized at 0.3 wt% of RGO. Raman spectroscopy and HRTEM confirmed the improvement of interfacial bonding by H-bonding and π-π interaction. For the 1st time we are reporting RGO utilisation for the improvement of thermomechanical and electrical interfacial properties of PANI-DBSA/DVB nanocomposite for the structural applications.

PREPARATION AND CHARACTERIZATION OF SUPERCONDUCTING BISRCACU2-OXIDE

The preparation of a high-temperature superconducting phase of the Bi-Sr-Ca-Cu-O system is described. The surface morphology of calcined and sintered material has been studied. The sintered material, thus prepared, has been characterized by electron microscopic techniques. The structure at various local regions has been investigated by electron diffraction and lattice imaging. The composition has been determined by electron probe micro-analysis. The study revealed intergrowth in the system, giving various values of thec parameter in local regions.