Pyoung-Chan Lee

Thermal transformation of solvent-processable organosilicon compounds into inorganic silicone-based thin films

In this study, a solution-processable precursor, decaphenycyclopentasilane (DPCPS) was synthesized and successfully converted into an inorganic thin film through the heat treatment process. When the DPCPS coating was heat-treated at various temperatures up to 900 °C, the organic DPCPS was converted into an inorganic compound composed of Si, C and O atoms in the form of SiCxOy. The relative compositions of Si, C, and O changed with the heat-treatment temperatures changing the carbon content, for example, from 88.9% for the pristine DPCPS to 3.0% for the specimen heat-treated over 700 °C, consequently becoming SiC0.05O1.7. The dielectric constant of the heat-treated DPCPS could be tailored with the heat treatment temperatures from high- to low-dielectric materials, i.e., 10.8 at 300 °C and 2.3 at 900 °C, providing tunable dielectric properties for various optoelectronic applications. The resulting inorganic thin films had excellent coating characteristics with low RMS roughness (<1.0 nm).

Negative-type photolithography of functionalized gold nanoparticles

ConclusionsThiol-stabilized gold nanoparticles ranging in size from 2 to 13 nm were synthesized using a two-phase reduction method. The thiol-stabilized gold nanoparticles formed micropatterns on a glass substrate through UV irradiation and chemical oxidation. Overall, the micro-pattern obtained through this simple procedure has great potential in the electronics industry.

Flame retardancy and thermal stability of polyurethane foam composites containing carbon additives

Polyurethane (PU) is an important class of polymers that have wide application in a number of different industrial sectors. The goal of this work was the synthesis of flame-retarded PU foam with expandable graphite (EG) or commercial graphene. The flame retardancy and thermal stability of the foams has been studied through cone calorimeter analysis, the limited oxygen index and thermal conductivity. The presence of expandable graphite brings an improvement in fire behavior. In particular, the limited oxygen index increases in a linear way and the highest limited oxygen index values are obtained for EG-PU foams. The results from the cone calorimeter are in agreement with those of oxygen index; EG filled foams show a considerable decrease of maximum-heat release rate (M-HRR) with respect to unfilled foams. The results of thermal conductivity show that an increase in expandable graphite amount in PU foams lead to an increased conductivity.