M. Yaqub Khan

An Investigation on Novel Poly(thiourea-amide)-based Nanocomposites Reinforced with Silica Nanotubes

A straightforward condensation technique was used to prepare new poly(thiourea-amide) (PTA), in this attempt. Halloysite silica nanotubes (SiNTs) were prepared and utilized as fillers to produce novel organic-inorganic hybrid materials. Fine compatibility in PTA/SiNTs was confirmed by FESEM; where halloysite filler render unique uniformly and spherically pact morphology. SiNTs loading in polyamide produced mechanically and heat stable nanocomposites. Consequently, tensile strength of hybrids increased with SiNTs content 52.17–55.24 MPa. A 10% gravimetric loss (516–559°C) and glass transition temperature of PTA/SiNTs (161–168°C) also were shown to be noteworthy. Using silica nanotubes, nanohybrids with fine potential for several applications can be obtained.

Fuel cell membranes prepared from multi-walled carbon nanotubes and silica nanotubes-filled sulfonated polyamide/sulfonated polystyrene porous blend films

A sulfonated polyamide (PA-S) was first synthesized through polycondensation of sulfonated 4,4′-oxydianiline and terephthaloyl chloride. The sulfonation of polystyrene (PS-S) was conducted using a mild sulfonating reagent (98% H2SO4). Two categories of mechanically robust and thermally stable nanocomposites, based on multi-walled carbon nanotube (MWCNT) and silica nanotube (SiNT), i.e. PS-S/PA-S/MWCNT and PS-S/PA-S/SiNT, were prepared by solution blending. Scanning electron micrographs showed good dispersion of filler and adhesion of matrix on the surface of nanotube. Accordingly, a symmetric membrane structure with dense porous top layer, porous sublayer, and fully developed micropores at the bottom were observed. The porous membrane structure was accountable for the excellent water retention capability, and so, higher proton conductivity of new hybrids. Increasing the amount of nanotube from 0.5 to 2 wt.% increased the ultimate tensile stress of functional PS-S/PA-S/MWCNT nanocomposites 51.8–62.2 MPa compared with non-functional filler (33.4 MPa) and PS-S/PA-S/SiNT. A rapport between nanotube loading and thermal stability of the materials was also observed as the glass transition in PS-S/PA-S/MWCNT nanocomposites increased from 202 to 206℃. MWCNT-based blend membranes had higher ion exchange capacity (IEC), around 2.99–3.42 mmol/g. Novel membranes with high IEC value achieved high proton conductivity of 1.28–2.23 S/cm in a wide range of humidity values at 80℃ which was higher than that of perfluorinated Nafion®117 membrane (1.1 × 10−1 S/cm) at 80℃ (94% relative humidity; RH) which was used as benchmark. Moreover, a H2/O2 fuel cell using the PS-S/PA-S/MWCNT (IEC 3.42 mmol/g) also showed better performance than that of Nafion®117 at 40℃ and 30% RH.

Solitary and periodic wave solutions of Calogero–Bogoyavlenskii–Schiff equation via exp-function methods

Abstract In this paper, some proficient techniques, called the exp-function method, modified exp-function method and improved modified exp-function method are implemented to compute generalized solitary and periodic wave solutions of the nonlinear Calogero–Bogoyavlenskii–Schiff equation. It has been attempted to show the compatibility and reliability of these mathematical techniques. The first partial differential equation is converted into an ordinary differential equation by a suitable transformation, then a trial solution is assumed. Results indicate complete consistency and effectiveness of the suggested schemes.

Existence regimes for shocks in inhomogeneous magneto-plasmas having entropy

The finding of connection of plasma density and temperature with entropy gives an incitement to study different plasma models with respect to entropy. Nonlinear dissipative one- and two-dimensional structures (shocks) are investigated in nonuniform magnetized plasma with respect to entropy. The dissipation comes in the medium through ion-neutral collisions. The linear dispersion relation is derived. The Korteweg–deVries-Burgers and Kadomtsev-Petviashvili-Burgers equations are derived for nonlinear drift waves in 1-D and 2-D by employing the drift approximation. It is found that vd/u ( vd is the diamagnetic drift velocity and u is the velocity of nonlinear structure) plays a significant role in the shock formation. It is also found that entropy has a significant effect on the strength of shocks. It is noticed that  vd/u  determines the rarefactive and compressive nature of the shocks. It is observed that upper and lower bounds exist for the shock velocity. It is also observed that the existing regimes for ...