김지운 교수

Dielectric capacitors can store and release electric energy at ultrafast rates and are extensively studied for applications in electronics and electric power systems. Among various candidates, thin films based on relaxor ferroelectrics, a special kind of ferroelectric with nanometer-sized domains, have attracted special attention because of their high energy densities and efficiencies. We show that high-energy ion bombardment improves the energy storage performance of relaxor ferroelectric thin

Abstract Understanding and ultimately controlling the large electromechanical effects in relaxor ferroelectrics requires intimate knowledge of how the local‐polar order evolves under applied stimuli. Here, the biaxial‐strain‐induced evolution of and correlations between polar structures and properties in epitaxial films of the prototypical relaxor ferroelectric 0.68PbMg 1/3 Nb 2/3 O 3 –0.32PbTiO 3 are investigated. X‐ray diffuse‐scattering studies reveal an evolution from a butterfly‐ to disc‐sh

In this study, polyaniline (PANI)/graphene nanosheet (GNS) composites were synthesized through chemical oxidation polymerization by changing the weight ratio of aniline monomers. To examine the morphological structure of the composites, scanning electron microscopy and transmission electron microscopy (TEM) were conducted. TEM results revealed that fibril-like PANI with a diameter of 50 nm was homogeneously coated on the surface of the GNS. The electrochemical properties of the composites were s

Abstract Liquid metals (LMs) and alloys are attracting increasing attention owing to their combined advantages of high conductivity and fluidity, and have shown promising results in various emerging applications. Patterning technologies using LMs are being actively researched; among them, direct ink writing is considered a potentially viable approach for efficient LM additive manufacturing. However, true LM additive manufacturing with arbitrary printing geometries remains challenging because of

In this study, the back passivation layers (BPLs) were developed to protect hydrogenated amorphous silicon (a-Si:H) thin films of transparent solar cells from humidity and contaminants. Metal oxide compound films with Al (Al₂O₃) and Ti (Al_<i>x</i>Ti_<i>y</i>O_<i>z</i> (ATO)) were fabricated by plasma-enhanced atomic layer deposition for the BPLs on transparent solar cells. The BPLs of Al₂O₃ films applied to the transparen

A new system using <TEX>$TiO_2$</TEX> (nano-sized, band-gap 3.14 eV)-impregnated spherical ZnS (micro-sized, band-gap 2.73 eV) nano/micro-composites (Ti 0.001, 0.005, 0.01, and 0.05 mol %/ZnS) was developed to enhance the production of hydrogen from methanol/water splitting. The ZnS particles in a spherical morphology with a diameter of about 2-4 mm which can absorb around 455 nm were prepared by hydrothermal method. This material was used as a photocatalyst with loading by nano-sized <TEX>$TiO_

The electrochemical performance of Li–S cells used in large-scale battery systems was investigated with various conditions. Li/S cells were fabricated with different loading thicknesses and electrolyte ratios and used in coin cells and single-sided and double-sided pouch cells. The optimal conditions for the Li/S cell were as follows: a loading thickness of 28 µm and an electrolyte ratio of 20 ul/mg_S. The coin and single-sided and doubled-pouch cells had discharge capacities of 1009, 973, and 9

Abstract Liquid metals and alloys are attracting renewed attention owing to their potential for application in various advanced technologies. Eutectic gallium‐indium (EGaIn) has been focused on in particular because of its integrated advantages of high conductivity, low melting point, and low toxicity. In this study, the colloidal behavior of nano‐dispersed EGaIn in nonpolar oils is investigated. Although the nonpolar oil continuous phase is commonly considered to be free of electric charges, el

KTaO 3 heterostructures have recently attracted attention as model systems to study the interplay of quantum paraelectricity, spin-orbit coupling, and superconductivity. However, the high and low vapor pressures of potassium and tantalum present processing challenges to creating heterostructure interfaces clean enough to reveal the intrinsic quantum properties. Here, we report superconducting heterostructures based on high-quality epitaxial (111) KTaO 3 thin films using an adsorption-controlled

We investigated the (de)activation of Raney nickel-iron anodes in various oxygen evolution reaction (OER) environments using accelerated deactivation testing (ADT) under the conditions of on/off voltage control (ADT1), constant current density (ADT2), and cyclic voltammetry (ADT3). ADT1 caused activation under OER conditions by promoting the leaching of residual zinc and thus increasing the electrode surface area and oxygen vacancy content, whereas deactivation was observed under the conditions