arXiv subjects

Wonjun Park

Publications and source records attributed to Wonjun Park.

3 recordsLinked to original sources

arXiv2017

High-performance Thermal Interface Material Based on Few-layer Graphene Composite

We developed high-performance thermal interface materials (TIMs) based on few-layer graphene (FLG) composite, where FLG was prepared by the interlayer catalytic exfoliation (ICE) method. We experimentally demonstrated feasibility of FLG composites as TIMs by investigating their thermal and mechanical properties, and reliability. We measured the thermal interface resistance ($R_{int}$) between FLG composite TIMs (FLGTs) and copper and to be 3.2$\pm$1.7 and 4.3$\pm$1.4 $mm^2$K/W for 5 vol.% and 10 vol.% FLGTs at 330 K, respectively, comparable to or even lower than that of many commercial TIMs. In addition, the thermal conductivity ($κ_{TIM}$) of FLGTs is increased by an enhancement factor ($β$) of ~17 as the FLG concentration increases from 0 to 10 vol.%. We also characterized Vickers hardness and glass transition temperature ($T_g$) of our FLGTs. We find that our FLGTs are thermally and mechanically reliable within practical operating temperature and pressure ranges.

cond-mat.mtrl-sci↗

arXiv2017

Electrical and thermal conductivities of reduced graphene oxide/polystyrene composites

The author reports an experimental study of electrical and thermal transport in reduced graphene oxide (RGO)/polystyrene (PS) composites. The electrical conductivity ($σ$) of RGO/PS composites with different RGO concentrations at room temperature shows a percolation behavior with the percolation threshold of ~ 0.25 vol.%. Their temperature-dependent electrical conductivity follows Efros-Shklovskii (ES) variable range hopping (VRH) conduction in the temperature range of 30 to 300 K. The thermal conductivity ($κ$) of composites is enhanced by ~ 90 % as the concentration is increased from 0 to 10 vol.%. The thermal conductivity of composites approximately linearly increases with increasing temperature from 150 to 300 K. Composites with a higher concentration show a stronger temperature dependence in the thermal conductivity.

cond-mat.mtrl-sci↗

arXiv2017

Compressive mechanical response of graphene foams and their thermal resistance with copper interfaces

We report compressive mechanical response of graphene foams (GFs) and the thermal resistance ($R_{TIM}$) between copper (Cu) and GFs, where GFs were prepared by the chemical vapor deposition (CVD) method. We observe that Young's modulus ($E_{GF}$) and compressive strength ($σ_{GF}$) of GFs have a power law dependence on increasing density ($ρ_{GF}$) of GFs. The maximum efficiency of absorbed energy ($η_{max}$) for all GFs during the compression is larger than ~0.39. We also find that a GF with a higher $ρ_{GF}$ shows a larger $η_{max}$. In addition, we observe that the measured $R_{TIM}$ of Cu/GFs at room temperature with a contact pressure of 0.25 MP applied increases from ~50 to ~90 $mm^2K/W$ when $ρ_{GF}$ increases from 4.7 to 31.9 $mg/cm^3$.

cond-mat.mtrl-sci↗