A molding-type power inductor is an inductor that uses a hybrid material that is prepared by mixing a ferrite metal powder coated with an insulating layer and an epoxy resin, which is injected into a coil-embedded mold and heated and cured. The fabrication of molding-type inductors requires various techniques such as for coil formation and insertion, improving the magnetic properties of soft magnetic metal powder, coating an insulating film on the magnetic powder surface, and increasing the packing density by well dispersing the powder in the epoxy resin. Among these aspects, researches on additives that can disperse the metal soft magnetic powder having the greatest performance in the epoxy resin with high charge have not been reported yet. In this study, we investigated the effect of silanes, KBM-303 and KBM-403, and a commercial dispersant on the dispersion of metal soft magnetic powders in epoxy resin. The sedimentation height and viscosity were measured, and it was confirmed that the silane KBM-303 was suitable for dispersion. For this silane, the packing density was as high as about 72.49%. Moreover, when 1.2 wt% of dispersant BYK-103 was added, the packing density was about 80.5%.

The computational fourier-transform moire (CFTM) method has been briefly explained and this method was used to perform strain analysis of a misfit dislocation in a strained Si/Si_0.55Ge_0.45 layer. An essential advantage of the CFTM method is that it does not require unwrapping, such that errors due to improper unwrapping can be excluded. The analysis results revealed that the Si layer was grown with tensile stress on Si_0.55Ge_0.45 and lattice constant of the Si layer along the growth direction was 1.9% smaller than that of Si_0.55Ge_0.45. On the other hand, strain of the misfit dislocation in the strained Si/Si_0.55Ge_0.45 layer was maximum at the dislocation core due to an extra half-plane and the e_xx and e_yy values were positive and negative, respectively, along the direction of a burgers vector.

Mullite (3Al₂O₃·2SiO₂) has emerged as a promising candidate for high-temperature structural materials due to its erosion resistance, chemical and thermal stabilities, relatively low thermal expansion coefficient, excellent thermal shock and creep resistances, and low dielectric constant. However, since the pure mullite sintering temperature is as high as 1,600~1,700℃, there is an increasing need for a sintering additive capable of improving the strength characteristics while lowering the sintering temperature. Herein we have tried to obtain the optimal sintering additive composition by adding MgO, Cr₂O₃, and Y₂O₃ to mullite, followed by sintering at 1,325~1,550℃ for 2 h. With additives of 2 wt% of MgO, 2 wt% of Cr₂O₃, 4 wt% of Y₂O₃, A density of 3.23 g/cm³ was obtained for the sintered body at 1,350℃ upon using 2 wt% MgO, 2 wt% Cr₂O₃, and 4 wt% Y₂O₃ as additives. The three-point flexural strength of that was 275 MPa and the coefficient of thermal expansion (CTE) was 4.15 ppm/℃.

Energy harvesting characteristics of trapezoidal piezoelectric cantilever generator, which has a lead zirconate titanate (PZT) laminate film, were compared by longitudinal (3-3) and transverse (3-1) modes. The PZT laminate film, fabricated by a conventional tape casting process, was cofired with Ag electrode at 850℃ for 2 h. A multi-layered Ag electrode by a planar pattern and an interdigitated pattern was applied to the PZT laminate to implement the 3-3 and 3-1 modes, respectively. The energy harvesting performance of the 3-3 mode trapezoidal piezoelectric cantilever generator was better than that of the 3-1 mode. An extremely high output power density of 26.7 mW/cm³ for the 3-3 mode was obtained at a resonant frequency of 145 Hz under a load resistance of 50 ㏀ and acceleration of 1.3 G, which is ~3-times higher than that for the 3-1 mode. Therefore, the 3-3 mode is considered significantly efficient for application to high-performance piezoelectric cantilever generator.

In this study, we investigated the effect of electrode pattern design on the thermal shock resistance and temperature uniformity of a ceramic heater. A cordierite substrate with a low thermal expansion coefficient was fabricated by tape casting, and a tungsten electrode was printed and used as a heating element. The temperature distribution of the ceramic heater was calculated by a finite-element method (FEM) by considering various electrode patterns, and the tensile stress distribution due to the thermal stress was calculated. In the electrode pattern with a single-line width, the central part of the ceramic heater was heated to the maximum temperature, and the position of the ceramic heater having a double-line width was changed to the maximum temperature, depending on the position of the minimum line width pattern. The highest tensile stress was found along the edges of the ceramic heater. The temperature gradient at the edge determined the tensile stress intensity. The smallest tensile stress was observed for electrode pattern D, which was expected to be advantageous in resisting thermal shock failures in ceramic heaters.

There is growing interest in power inductors in which metal soft magnetic powder and epoxy resin are combined. In this field, the process technology for increasing the packing density of magnetic particles in an injection molding process is very important. However, little research has been reported in this regard. In order to improve the packing density, we investigated and compared the sedimentation heights of pastes for three types of soft magnetic alloy powders as a function of the mixing ratios and the type of resin used. Experimental results showed that the packing density was the highest (71.74%) when the mixing ratio was 80：16：4 (Sendust：Fe-Si：CIP) according to the particle size using an SE-4125 resin. In addition, the packing density was found to be inversely related to the layer separation distance. As a result, it was confirmed that the dispersion of solid particles in the paste was important for curing; however, the duration of the curing process can greatly affect the packing density of the final composite.

Electrical behaviors of plasma-sprayed Al₂O₃-TiO₂ coatings have been investigated in terms of their TiO₂ content. On increasing the TiO₂ content from 6 to 30 wt%, the DC electrical conductivity increased by several orders of magnitude. From impedance spectroscopy analysis, the total conductivity of the grains and grain boundaries and their respective activation energies were determined without the electrode effects that could impede ionic transfer. An electron transference number was also estimated, ranging between 6.5% and 7.3% for 13 wt% TiO₂ and between 0.4% and 0.7% for 30 wt% TiO₂ in the coating. Because of the high electronic contribution to the total conductivity, the Al₂O₃-TiO₂ coating could be a new candidate material to obtain superior electrical conductivity as well as corrosion and wear resistances.

Ga-doped ZnO (GZO) films were deposited by an RF magnetron sputtering method on glass substrates using ZnO as a target containing 5 wt% Ga₂O₃ powder (for Ga doping). The structural, electrical, and optical properties of the GZO thin films were investigated as a function of the substrate temperatures. The deposition rate decreased with increasing substrate temperatures from room temperature to 350℃. The films showed typical orientation with the c-axis vertical to the glass substrates and the grain size increased up to a substrate temperature of 300℃ but decreased beyond 350℃. The resistivity of GZO thin films deposited at the substrate temperature of 300℃ was 7×10^-4 Ωcm, and it showed a dependence on the carrier concentration and mobility. The optical transmittances of the films with thickness of 3,000 Å were above 80% in the visible region, regardless of the substrate temperatures.

Randomly patterned and wet chemical etching processes were used to treat anti-glare of display cover glasses. The surface and optical properties of grain size and surface morphology controlled by randomly patterned etching and wet chemical solution etching were investigated. The surface morphology and roughness of the etched samples were examined using a spectrophotometer and a portable surface roughness (Ra) measuring instrument, respectively. The gloss caused by reflection from the glass surface was measured at 60° using a gloss meter. The surface of the sample etched by the doctor-blade process was more uniform than that obtained from a screen pattern etching process at gel state etching process of the first step. The surface roughness obtained from the randomly patterned etching process depended greatly on the mesh size, which in turn affected the grain size and pattern formation. The surface morphology and gloss obtained by the etching process in the second step depended primarily on the mesh size of the gel state etching process of the first step. In our experimental range, the gloss increased on decreasing the grain size at a lower mesh size for the first step process and for longer reaction times for the second step process.

An all-transparent ultraviolet (UV) photodetector was fabricated by structuring p-NiO/n-SnO₂/ITO on a glass substrate. SnO₂ is an important semiconductor material because of its large bandgap, high electron mobility, high transmittance (as high as 80% in the visible range), and high stability under UV light. For these reasons, SnO₂ is suitable for a range of applications that involve UV light. In order to form a highly transparent p-n junction for UV detection, SnO₂ was deposited onto a device containing NiO as a high-transparent metal conductive oxide for UV detection. We demonstrated that all-transparent UV photodetectors based on SnO₂ could provide a definitive photocurrent density of 4 nA cm^-2 at 0 V under UV light (365 nm) and a low saturation current density of 2.02 nA × cm^-2. The device under UV light displayed fast photoresponse with times of 31.69 ms (rise-time) and 35.12 ms (fall-time) and a remarkable photoresponse ratio of 69.37. We analyzed the optical and electrical properties of the NiO/SnO₂ device. We demonstrated that the excellent properties of SnO₂ are valuable in transparent photoelectric device applications, which can suggest various routes for improving the performance of such devices.

Fe₃O₄ was prepared on the TiO₂-coated natural mica substrate. The natural mica has an average particle size of 22 ㎛. The substrate was coated on TiO₂ thin films using hydrothermal synthesis at pH 1.5-2.5 at 75℃. The Fe precursor solution was prepared by mixing FeSO₄ (for Fe²⁺ ion) and FeCl₃ (for Fe³⁺ ions) with different molar ratios such as 1/2, 1/1, 2/1, 3/0, and Fe₃O₄ only. X-ray diffraction analysis shows that the crystal structure depends on the FeCl₃-to-FeSO₄ molar ratio. Fe₃O₄ crystal phase could be obtained at higher FeSO₄ contents.

As a ZnO varistor is subjected to electrical and environmental stresses, it degrades gradually, which may result in power interruption by short circuit. This study investigates changes in the electrical characteristics of ZnO varistors due to deterioration owing to energy absorption, and determines the optimal parameters for on-line diagnosis of the varistor. Two types of varistors were used for an accelerated aging experiment involving the application of the 8/20 μs standard lightning impulse current. The electrical characteristics in terms of the reference voltage, total leakage current, resistive leakage current, and third-harmonic component of the total leakage current were measured, and their change rates were analyzed. The results revealed that the total leakage current increased slightly with an increase in the varistor absorbed energy, while the resistive leakage current and the third-harmonic component increased apparently. Therefore, the third-harmonic component of the total leakage current was proposed as the optimal parameter for on-line monitoring of ZnO varistor conditions.

Mg/Al layered double hydroxide with two-dimensional (2D) nanostructures was synthesized by a hydrothermal technique. The morphology and aspect ratio of Mg₄Al₂(OH)₁₄3H₂O were controlled by the concentration and kinds of the hydrolysis agent, and temperature. The aspect ratio of Mg₄Al₂(OH)₁₄3H₂O layered double hydroxides with the 2D hexagonal crystal structure was tailored from about 12.6 to about 45.7. The intercalated CO₃^2- anions of the synthesized 2D Mg₄Al₂(OH)₁₄3H₂O layered double hydroxides were exchanged to NO₃^- anions. The bulk 2D Mg₄Al₂(OH)₁₄3H₂O layered double hydroxides with the increased space between two layers due to the anion exchange were exfoliated in a formamide solution. The aspect ratio of the exfoliated 2D Mg₄Al₂(OH)₁₄3H₂O layered double hydroxides increased to 570.3.