Daeheum Kim

Enhancement of electrical and thermomechanical properties of silver nanowire composites by the introduction of nonconductive nanoparticles: experiment and simulation.

Electrically conductive polymer nanocomposites have been applied extensively in many fields to develop the next generation of devices. Large amounts of conductive nanofillers in polymer matrices are, however, often required for a sufficiently high electrical conductivity, which in turn deteriorates the desired thermomechanical properties. We illustrate a novel but facile strategy to improve the electrical conductivity and the thermomechanical property of silver nanowire/polymer nanocomposites. We find that one may increase the electrical conductivity of silver nanowire/polymer nanocomposites by up to about 8 orders of magnitude by introducing silica nanoparticles with nanocomposites. The electrical percolation threshold volume fraction of silver nanowires decreases from 0.12 to 0.02. Thermomechanical properties also improve as silica nanoparticles are introduced. We carry out extensive Monte Carlo simulations to elucidate the effects of silica nanoparticles at a molecular level and find that van der Waals attractive interaction between silica nanoparticles and silver nanowires dominates over the depletion-induced interaction between silver nanowires, thus improving the dispersion of silver nanowires. Without silica nanoparticles, silver nanowires tend to aggregate, which is why additional silver nanowires are required for a desired electrical conductivity. On the other hand, with silica nanoparticles mixed, the electrical percolating network is likely to form at a smaller volume fraction of silver nanowires.

Enzymatic production of glycerol carbonate from by-product after biodiesel manufacturing process.

Glycerol carbonate is one of the higher value-added products derived from glycerol. In this study, glycerol carbonate (GC) was synthesized by transesterification of glycerol and dimethyl carbonate (DMC) using Novozym 435 (Candida antarctica Lipase B) at various conditions. For the enzymatic production of GC, the optimum conditions were the amount of enzyme (75 g/L), DMC/glycerol molar ratio (2.00), reaction temperature (60°C) and organic solvent (acetonitrile). Experimental investigation of the effect of water content revealed that the conversion of GC was maximized with no added water. The addition of surfactant such as Tween 80 increased the GC conversion, which finally reached 96.25% under the optimum condition and with surfactant addition.

Effects of silica particles on the electrical percolation threshold and thermomechanical properties of epoxy/silver nanocomposites

We experimentally and theoretically demonstrated that the addition of silica particles could improve both the electrical conductivity and the thermomechanical properties of epoxy/silver nanocomposites. As silica particles were added, the electrical percolation threshold concentration of silver nanoparticles decreased and the electrical resistivity of the composite decreased by about 8 orders of magnitude. The coefficient of thermal expansion also decreased with increasing volume fraction of silica particles. Molecular simulations showed that the additional silica particles made the effective intermolecular interactions between silver nanoparticles attractive, thereby enhancing the formation of an electrical percolation network.

Effects of size and interparticle interaction of silica nanoparticles on dispersion and electrical conductivity of silver/epoxy nanocomposites

The agglomeration of nanoparticles (NPs) occurs due to attractive interaction between NPs and worsens the physical properties of materials such as electrical conductivity. When the attractive interaction is sufficiently strong, the agglomerates of NPs may be arrested dynamically in non-equilibrium state with a large relaxation time. We show that when conductive silver NPs form agglomerates in epoxy matrices, one can tune the effective interaction between silver NPs in epoxy matrices by introducing auxiliary non-conductive silica NPs and may prevent the agglomeration easily. More interestingly, as the size of the auxiliary silica NPs decreases, the silver NPs disperse better, thus increasing the electrical conductivity by orders of magnitude. We also perform Monte Carlo simulations and show that the auxiliary silica NPs influence the morphology of silver NPs not entropically but energetically.

Effect of Modification of SeO 2 /Acrylamide Ratios on Diffraction Efficiencies in PVA/AA Photopolymer Films

The highest diffraction efficiency(DE) value after illumination and post-curing of photopolymer films were obtained at the

Facile preparation of epoxy nanocomposites with highly dispersed graphite nanosheets and their dielectric properties

SeO_2

Study of Diffraction Efficiency Values for Photopolymer Films Added TiO 2 Nanoparticles

/Acrylamide(AA) Ratios of AA 3.0 g,

Diffraction Efficiency Improvement of PVA/AA/SeO 2 Photopolymer with Various Film Thickness and Eosin Y Contents

SeO_2

Characterization and preparation of bioinspired resorbable conduits for vascular reconstruction

1.0g and the DEs were stable values of over 90%. By the addition of

A new configuration of LCD-polarized stereoscopic projection system without light loss

SeO_2