Publications by authors named "Kyung-Jun Hwang"

Radiative cooling in textiles is one of the important factors enabling cooling of the human body for thermal comfort. In particular, under an intense sunlight environment such as that experienced with outdoor exercise and sports activities, high near-infrared (NIR) reflectance to block sunlight energy influx along with high IR transmittance in textiles for substantial thermal emission from the human body would be highly desirable. This investigation demonstrates that a nanoscale geometric control of textile structure alone, instead of complicated introduction of specialty polymer materials and composites, can enable such desirable NIR and IR optical properties in textiles.

View Article and Find Full Text PDF

In this study, we prepared chitosan beads cross-linked with epichlorohydrin (CB-ECH) to improve the removal of nitrate in groundwater. It was confirmed that CB-ECH exhibited higher thermal stability and well-developed nano-pores compared to the pure chitosan beads (CB) by the thermogravimetric analyzer, nitrogen gas adsorption and desorption isotherm, and field emission scanning microscopy analysis. The CB-ECH showed a higher nitrate adsorption amount than the pure CB.

View Article and Find Full Text PDF

In this study, we have prepared a composite adsorbent with highly dispersed Mn and Ag nanocatalyst on the surface of activated carbon (AC) by applying the Radio-Frequency (RF) thermal plasma technique for the efficient removal of VOCs. The ACs before and after metal impregnation with RF plasma treatment were characterized by SEM, TEM, EDS, and nitrogen adsorption analysis. Adsorption behaviors of toluene, acetaldehyde, and formaldehyde on ACs before and after modification were also investigated in fixed-bed systems.

View Article and Find Full Text PDF

In this study, walnut-shaped V₂O₃ particles with high photocatalytic activity in the visible light were synthesized by hydrothermal process. The V₂O₃ samples synthesized with the various temperature conditions of the hydrothermal process were characterized using XRD, SEM, TEM, UV-Visible spectrometer and N₂gas adsorption/desorption analysis. For investigating the photocatalytic performance of synthesized V₂O₃ particles in the visible light condition, photodegradation experiments of methylene blue (MB) solution under artificial sunlight irradiation was conducted.

View Article and Find Full Text PDF

Mesoporous gamma alumina (MGA) was synthesized using aluminum trash containers by a low temperature hydrothermal method for effectively removing phosphate from wastewater. The effects of precursor concentrations in gel precipitation process over the pore size and surface area of MGA were investigated in detail. The phosphate removal by prepared MGAs were rigorously investigated through adsorption isotherms and kinetics of phosphate.

View Article and Find Full Text PDF

In this work, we prepared basalt based nanostructured zeolite 13X by alkali fusion and hydrothermal synthesis process. The sample prepared was characterized using XRD, SEM, and low-temperature nitrogen analysis. The adsorption equilibrium and kinetic characteristics of ammonia nitrogen (NH₄-N) and phosphate phosphorus (PO₄-P) were investigated.

View Article and Find Full Text PDF

A zeolitic 4A type material was successfully prepared from natural basalt rock by applying an alkali fusion process and hydrothermal synthesis. In particular, the optimum synthetic conditions were examined at different crystallization times. Several methods such as XRD, SEM, EDX, and N and CO adsorption analysis were used to characterize the synthesized 4A type zeolite.

View Article and Find Full Text PDF

Correction for 'Dye adsorption mechanisms in TiO2 films, and their effects on the photodynamic and photovoltaic properties in dye-sensitized solar cells' by Kyung-Jun Hwang et al., Phys. Chem.

View Article and Find Full Text PDF

In this work, ZnS microspheres consisting of nanoblocks were synthesized by a simple, template-free approach employing a hydrothermal reaction at different temperatures, using Zn(CH3COO)2 and Na2S2O3 · 5H2O as starting materials in the aqueous solution. The synthesized samples were characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET). The photocatalysts were evaluated using photodecomposition of methylene blue under UV-C light.

View Article and Find Full Text PDF

The preparation of a poly(vinyl alcohol)/poly(acrylic acid)/glyoxal film (PVA = poly(vinyl alcohol); PAA = poly(acrylic acid)) with high tensile strength and hydrophobic properties by using the crosslinking reaction for OH group removal is reported herein. PAA was selected as a crosslinking agent because the functional carboxyl group in each monomer unit facilitates reaction with PVA. The OH groups on unreacted PVA were removed by the addition of glyoxal to the PVA/PAA solution.

View Article and Find Full Text PDF

The adsorption mechanism for the N719 dye on a TiO2 electrode was examined by the kinetic and diffusion models (pseudo-first order, pseudo-second order, and intra-particle diffusion models). Among these methods, the observed adsorption kinetics are well-described using the pseudo-second order model. Moreover, the film diffusion process was the main controlling step of adsorption, which was analysed using a diffusion-based model.

View Article and Find Full Text PDF

TiO2 nanofibers were prepared from a mixture of titanium-tetra-isopropoxide and poly vinyl pyrrolidone by applying the electrospinning method. The samples were characterized by XRD, FE-SEM, TEM and BET analyses. The diameter of electrospun TiO2 nanofibers is in the range of 70 approximately 160 nm.

View Article and Find Full Text PDF

For dye-sensitized solar cell (DSSC), highly ordered nanoporous TiO2 materials with crystalline frameworks were successfully synthesized from different silica templates including SBA-15, KIT-6 and MSU-H. A photoelectrode in DSSC was fabricated by adsorbing cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium dye (N719) onto the prepared TiO2 nanoparticles. The samples were characterized by XRD, TEM, FE-SEM, AFM and Brunauer-Emmett-Teller (BET), and FT-IR analysis.

View Article and Find Full Text PDF

Quasi-solid-state dye-sensitized solar cell was fabricated by sandwiched polymer electrolyte containing liquid electrolytes between the dye-sensitized TiO2 electrode and a Pt electrode. The influence of hydrochloric acid treatment of TiO2 photoelectrode on the photoelectronic performance was investigated. Quasi-solid-state dye-sensitized solar cell showed better photoelectronic performance when the TiO2 electrode was treated with hydrochloric acid than that without treatment.

View Article and Find Full Text PDF

Titanium particles of single-phase anatase nanocrystallites were prepared by the hydrolysis of titanium tetraisopropoxide. A dye-sensitized solar cell (DSSC) was fabricated by adsorbing cis-bis(isothiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylato)-ruthenium(II)bis-tetrabutylammonium dye (N719) onto TiO2 film. The samples were characterized by XRD, TEM, FE-SEM, AFM, and Brunauer-Emmett-Teller (BET) analysis.

View Article and Find Full Text PDF