Youngjae Yu

Controlling the anisotropy of two-dimensional materials with orientation-dependent heat transfer characteristics is a possible solution to resolve severe thermal issues in future electronic devices. We demonstrate a dramatic enhancement in the in-plane thermal conductivity of stretchable poly(vinyl alcohol) (PVA) nanohybrid films containing small amounts (below 10 wt %) of hexagonal boron nitride ( h-BN) nanoplatelets. The h-BN nanoplatelets were homogeneously dispersed in the PVA polymer soluti

Abstract Composites of polyamide 6 ( PA 6), powdered synthetic graphite and pitch‐based carbon fiber were melt processed to explore the effect of the filler contents on the anisotropic properties of the resulting composites. Optical microscopy and mechanical properties were used to determine the dispersion of graphite and carbon fiber in the PA 6 matrix. The relationship between the structure and properties showed the anisotropic filler orientation along the three principal directions. Thermal e

In recent years, many researchers believe that global energy consumption can be significantly reduced by passive daytime radiative cooling (PDRC) without any electricity input. Over a decade, PDRC has been developed to enhance solar reflectivity and emissivity in the long-wavelength infrared (LWIR) region; however, sustainable materials for radiative cooling have not been sufficiently investigated. In the present study, the preparation of an eco-friendly polymer structure for effective radiative

The effects of addition of an organoclay on the morphology and the mechanical properties of blends of an amorphous polyamide (a-PA) and an elastomer (with and without grafted maleic anhydride) prepared via melt processing are reported. Transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS) were employed to obtain a detailed quantitative analyses of the morphology of the elastomer particles for these nanocomposites containing 80 wt % a-PA and 20 wt % elastomer. Stress−strai

In this study, we investigated the thermal conductivities and mechanical properties of polyetherimide (PEI) composites using polyimide (PI)-coated h-BN (PI-BN) particles. We found that PI-coated h-BN effectively increased adhesion with the PEI matrix, imparting enhanced mechanical and thermal stability and thermal conductivity with increasing BN content. The thermal conductivity of the PEI composite containing 60 wt% PI-BN was 3.3 W m(-1) K(-1), while the thermal conductivity of the PEI/BN compo

Abstract While most selective emitter materials are inadequate or inappropriate for building applications, here we present a techno-economically viable optical coating by integrating glass bubbles within a polymer film. A controlled glass bubble volume concentration from 0 to 70% leads to a selective solar reflectivity increase from 0.06 to 0.92 while the mid-infrared emissivity remains above 0.85. Outdoor measurements show the polymer coating on a concrete surface can provide a temperature redu

Abstract Summary: Polymer blend nanocomposites containing linear low density polyethylene (LLDPE), nylon 6 and organoclays were prepared by melt mixing, and their morphologies and structures were examined with a field emission scanning electron microscope (FE‐SEM) and an X‐ray diffractometer (XRD). The size of phase‐separated domains decreased considerably with increasing content of organoclay. The d ‐spacing of organoclay in the nanocomposites was increased from about 18.6 to over 28 Å. This ef

Abstract Current research has focused on effective solutions to mitigate global warming and the accelerating greenhouse gas emissions. Compared to most cooling methods requiring energy and resources, passive daytime radiative cooling (PDRC) technology offers excellent energy savings as it requires no energy consumption. However, existing PDRC materials encounter unprecedented problems such as complex structures, low flexibility, and performance degradation after stretching. Thus, this study repo