Processing and characterization of conductive carbon nanotube nanocomposite nanofibers and microfibers

Nanotechnology and nanocomposites -- Fiber technology -- Nanofibers -- Electrospinning -- Nanocomposite nanofibers -- Melt spinning -- Originality of the work -- Materials, processing and characterization -- Processing and mixing procedure -- Morphology, structure and properties of conductive PS/CNT nanocomposite electrospun mat -- Fundamental study of crystallization, orientation and final properties of electrospun PET/carbon nanotube nanofibers -- Structure and properties of melt-spun PET/MWCNT nanocomposite fibers -- Empirical modeling of electrospun CNT-based nanocomposite nanofibers

Exploring the possibility of chemisorption of ethylene on graphene with and without defects

The effect of structural defects on graphene interaction with other molecules is of high interest. In this study, the interaction of ethylene molecules with pristine graphene (PG) and defective graphenes including single (SVG) and double (DVG) vacancies, were investigated using dispersion-corrected periodic density functional theory (DFT). We used various pairs of pseudopotentials and dispersion-corrected methods to calculate the exchange-correlation energies and long-range energies, respectively. We conducted the calculations in the ethylene-graphene equilibrium distance where vdW interaction as a long-range interaction was dominant. Both adsorption and deformation energies were calculated to examine the possibility of ethylene chemisorption. It was found that there is a critical distance from the graphene surface, where the nature of adsorption of adsorbate molecule changes from physisorption to the possible chemisorption depending on the energetical costly distortion induced in adsorbate molecule. In the case of ethylene adsorption on the graphene structures studied here, the mentioned critical distances follow the order SVG < DVG < PG. However, in the range of vdW domination and in comparison with PG, ethylene interacts more with SVG due to the presence of a dangling bond and interacts less with DVG due to the presence of a hole. Furthermore, the interactions of ethylene with reconstructed trivacancy were studied. Moreover, all possible orientations for ethylene adsorption on graphene structures were considered and energetically compared. All calculations were done on fully optimized reconstructed geometries of vacancies with structural characteristics, i.e., reconstruction length and formation energies comparable to those reported in the literature

Physical and Mechanical Properties of Electrospun PLA Nanofibers in the Presence of Silicone Rubber Nanoparticles

Hypothesis: Nowadays, polymer nanofibers have been extensively used in different industries especially for medical applications. Electrospinning is a simple, versatile and cost-effective technique to prepare nanofibers. For biomedical applications such as tissue engineering poly(lactic acid) (PLA), a biocompatible and biodegradable polymer, has gained great interest. To improve the physical and mechanical properties of electrospun PLA, nanofibers and nanoparticles can be included.Methods: PLA nanofibers were prepared through electrospinning. Silver nitrate was added to increase the conductivity of electrospinning solution, resulting in finer nanofibers. To improve morphology and mechanical properties of the electrospun fibers, silicone rubber nanoparticles (NSR) were added into the electrospinning solution. Scanning and transmission electron microscopies (SEM and TEM) were employed to investigate the morphology of electrospun nanofibers and dispersion of nanoparticles, respectively. To investigate thermal and mechanical properties of the obtained nanofibers, differential scanning calorimetry (DSC) and tensile test were used.Findings: To obtain poly(lactic acid) electrospun nanofibers with fine and defect-free morphology, PLA was dissolved in a mixture of dichloromethane and dimethylformamide (DCM/DMF) solvents with a volumetric ratio of 3/2 Electrospinning solution with 7% poly(lactic acid) containing 0.5% (by wt) silver nitrate led to defect-free nanofibers with a diameter of less than 200 nm. Inclusion of silicone rubber nanoparticles of 1% resulted in finer nanofibers with a diameter of about 123 nm. This was attributed to enhanced elasticity of the solution with addition of elastomeric nanoparticles. Adding silicone rubber nanoparticles increased the cold crystallization temperature and decreased the crystallinity of polylactic acid. Toughness of nanofibers considerably increased in the presence of silicone rubber nanoparticles without sacrificing modulus and strength, indicating high capability of NSR as an impact modifie