Enhanced thermal properties of graphene oxide-incorporated polymeric microspheres.

Polystyrene (PS) microspheres coated with graphene oxide (GO) were prepared and the variation of their thermal properties according to the GO loading was examined. The GO content in the PS-GO nanocomposites was controlled by the GO dispersions at various concentrations. The GO was coated onto the surface of the PS microspheres through the strong ionic interaction between polyvinylpyrrolidone and the GO sheet. The thermal properties of the GO incorporated PS microspheres were affected by the GO, which disturbed the chain activity and exhibited effective heat shielding. It also delayed the permeation of oxygen and hindered the escape of volatile degradation products from the PS-GO nanocomposites. In addition, the thermal degradation temperature of the nanocomposites was increased above 15 degrees C and their T(g) was also increased above 4.0 degrees C. PS-GO exhibited higher thermal conductivity (0.173 W/mK) than that of pure PS (0.117 W/mK).

Morphology and pore characteristics of bacterial cellulose/multiwalled carbon nanotube composite cryogels.

Bacterial cellulose/multiwalled carbon nanotube (MWCNT) composite cryogels were prepared via sol-gel chemistry using epichlorohydrin as a crosslinker. Their morphology and pore characteristics were examined under various conditions. The bacterial cellulose/MWCNT composite cryogels had a macroporous structure that contained mesopores and micropores due to the MWCNTs that were homogeneously incorporated in the macroporous network structure.

Adsorption behavior of carbon nanotubes on polystyrene surfaces.

Polystyrene (PS) was prepared using two different polymerization methods (dispersion polymerization and seed polymerization) to investigate the steric stabilizer effect during the adsorption process of carbon nanotubes (CNTs) on the surface of PS microspheres. Experiments with different microsphere diameters and difference types of CNTs were conducted to analyze the curvature effect of the spheres on the adsorption mechanism. The results showed that PS microspheres prepared through dispersion polymerization exhibited preferable adsorption behavior compared to PS spheres prepared through seed polymerization, suggesting that poly(N-vinylpyrrolidone) led to improved adsorption interactions between the CNTs and the PS microspheres in the CNTs dispersion. Additionally, the PS diameter and CNT curvature were examined with respect to the adsorption behavior between the PS microspheres and the CNTs. Multiwalled carbon nanotubes (MWCNTs) were found to be well adsorbed on the surface of PS microspheres measuring 2 microm. However, the MWCNTs were adsorbed much less on the surface of submicron-sized PS microspheres, compared with thinwalled carbon nanotubes (TWCNTs). On the other hand, TWCNTs were found to be suitable for adsorption on submicron-sized PS microspheres. These results also indicate that the curvature of the CNTs and the polymer microspheres are important to the CNT adsorption process.

Nanoporous silica membranes fabricated using multiwalled carbon nanotubes.

Nanoporous silica membranes were fabricated using 3-aminopropyltriethoxysilane (APS) and acyl chloride-functionalized multiwalled carbon nanotubes (MWCNTs). The amine groups of silane reacted with the functional groups (e.g., acid chloride) that were attached to the sidewall of the MWCNTs. The APS that was grafted to the sidewall of the MWCNTs was polymerized in order to coat the MWCNTs wall through heating. The thickness of the silica layer on the surface of the MWCNTs was controlled by adjusting the growth time of the SiO2 layer. Approximately 20 nm-sized pores were formed through the removal of the MWCNTs using a simple thermal process, but some traces of the MWCNTs still remained. The porous properties of the nanoporous silica membrane were analyzed from the nitrogen adsorption-desorption isotherms that were obtained using a surface area and porosimetry analyzer. The structure and composition of the silane-modified MWCNTs were characterized using scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy.

Ag-doped multiwalled carbon nanotube/polymer composite electrodes.

Two types of carbon nanotube (CNT) based films were fabricated by adsorbing two different types of multiwalled carbon nanotubes (MWCNTs) on bacterial cellulose membrane templates. A bacterial cellulose membrane consists of ribbon-shaped nanofibrils that are arranged to form a porous 3D network. These characteristics lead to the uniform deposition of MWCNTs on the membrane structure and the final CNT based films with high surface areas. Two types of MWCNTs were used: (1) MWCNTs that had been purified by an acid treatment and (2) Ag-doped MWCNTs, which consisted of MWCNTs with Ag nanoparticles attached to their surfaces. The morphologies of the Ag-doped MWCNTs and CNT based films were examined using transmission electron microscopy. In addition, the electrical conductivity and electrochemical properties of the CNT based films were measured using a four-point probe and a cyclic voltammeter, respectively. The cyclic voltammetry data showed that the Ag particles attached to the MWCNT surfaces influenced the electrochemical properties of the CNT based films.