Hyungu Im

The thermal conductivity of embedded nano-aluminum nitride-doped multi-walled carbon nanotubes in epoxy composites containing micro-aluminum nitride particles.

Amino-functionalized nano-aluminum nitride (nano-AlN) particles were doped onto the surfaces of chlorinated multi-walled carbon nanotubes (MWCNTs) to act as fillers in thermally conducting composites. These synthesized materials were embedded in epoxy resin. Then, the untreated micro-aluminum nitride (micro-AlN) particles were added to this resin, whereby the composites filled with nano-AlN-doped MWCNTs (0, 0.5, 1, 1.5, 2 wt%) and micro-AlN (25.2, 44.1, 57.4 vol%) were fabricated. As a result, the thermal diffusivity and conductivity of all composites continuously improved with increasing nano-AlN-doped MWCNT content and micro-AlN filler loading. The thermal conductivity reached its maximum, which was 31.27 times that of the epoxy alone, when 2 wt% nano-AlN-doped MWCNTs and 57.4 vol% micro-AlN were added to the epoxy resin. This result is due to the high aspect ratio of the MWCNTs and the surface polarity of the doped nano-AlN and micro-AlN particles, resulting in the improved thermal properties of the epoxy composite.

Effect of homogeneous Al(OH)3 covered MWCNT addition on the thermal conductivity of Al2O3/epoxy-terminated poly(dimethylsiloxane) composites

Aluminum hydroxide covered multiwalled carbon nanotubes (A-MWCNTs) were synthesized as a conducting additive to alumina-epoxy-terminated poly(dimethylsiloxane). The measured diffusivity and calculated conductivity exhibited dissimilar behavior between several Al2O3 concentrations as a function of A-MWCNT loading, which correlated with the interface density and interconnectivity of the structures. The fabricated heterostructured A-MWCNT did not have a significant effect on the thermal conductivity of the composite because of phonon scattering at the interface. A small amount of A-MWCNT was feasible for establishment of a heat conductive percolating network with the greatest enhancement of thermal conductivity and diffusivity at an A-MWCNT loading of 1.0 and 2.0 wt%. Continuously increasing thermal transport properties were observed with the 49.1 vol.% Al2O3 loading which derived from a lower interface density nanowire and polymer matrix with enhanced interconnectivity.

Characteristics of thermoplastic polyurethane composites containing surface treated multiwalled carbon nanotubes for the underwater applications

AbstractThermoplastic polyurethane elastomer (TPU) is used as an encapsulant in undersea sonar devices. In order to fabricate desirable composites for underwater applications, TPU prepared from poly(tetramethylene glycol) (PTMG), and methyl diphenyl diisocyanate (MDI) was blended with a multiwalled carbon nanotube (MWCNT). TPU grafted MWCNT (TPU-g-MWCNT) were prepared to fabricate a composite that has better mechanical strength and interfacial adhesion between the TPU matrix and the MWCNTs. The tensile strength of the composite increased with increasing MWCNT content. At a fixed MWCNT content in the composite, the TPU/TPU-g-MWCNT composite exhibited superior tensile strength compared to the TPU composite with pristine MWCNT. The swelling ratio of TPU composite with pristine MWCNT was higher than that of TPU. However, the swelling ratio of the TPU/TPU-g-MWCNT composite was lower than the latter when the composite contains more than 0.5 wt% of TPU-g-MWCNT. In addition, the TPU/TPU-g-MWCNT composite exhibited enhanced mechanical strength and a reduced swelling ratio as compared to TPU after being impregnated with seawater or paraffin oil.

Low swelling poly(ester) urethane composite containing modified hollow glass microspheres for seawater-resistant encapsulant

AbstractA novel poly(ester) urethane system filled with poly(ester) urethane grafted with hollow glass microspheres was fabricated via a melt mixing method for use as an underwater encapsulant. The poly(ester) urethane/ poly(ester) urethane grafted with hollow glass microsphere (HGM) composites (PU/PU-g-HGM composites) were prepared using various PU-g-HGM contents. Studies of these composites showed that the swelling ratio of PU/PUg-HGM composites in seawater and paraffin oil decreased with increasing HGM content of grafted poly(ester) urethane, while the tensile strength of PU/PU-g-HGM composites could be incrementally increased by rising PU-g-HGM content. This finding is due to the enhanced interfacial adhesion between poly(ester) urethane and poly(ester) urethane-grafted HGM due to good compatibility between these components. The tensile strength of the PU/PU-g-HGM composites in seawater (or paraffin oil) also exhibited higher levels than those of poly(ester) urethane and PU/ pristine HGMs composites in seawater (or paraffin oil) as the immersion time increased. Therefore, the PU/PU-g-HGM composites were expected to have potential applications as underwater encapsulants.