• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.427-432
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• 2024

The polymer crystallization process, promoting the formation of ferroelectric β-phase, is essential for developing polyvinylidene fluoride (PVDF)-based high-performance piezoelectric energy harvesters. However, traditional high-temperature annealing is unsuitable for the manufacture of flexible piezoelectric devices due to the thermal damage to plastic components that occurs during the long processing times. In this study, we investigated the feasibility of introducing a flash lamp annealing that can rapidly induce the β-phase in the PVDF layer while avoiding device damage through selective heating. The flash light-irradiated PVDF films achieved a maximum β-phase content of 76.52% under an applied voltage of 300 V and an on-time of 1.5 ms, a higher fraction than that obtained through thermal annealing. The PVDF-based piezoelectric energy harvester with the optimized irradiation condition generates a stable output voltage of 0.23 V and a current of 102 nA under repeated bendings. These results demonstrate that flash lamp annealing can be an effective process for realizing the mass production of PVDF-based flexible electronics.

• Korean Journal of Optics and Photonics
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• v.35 no.3
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• pp.115-120
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• 2024

Magneto-optical (MO) materials have attracted much attention, since they can be utilized for various optical applications, such as magnetic field sensors, optical current sensors, optical isolators, and optical circulators. In this study, alumino-borosilicate (ABS) glasses with high concentrations of Dy³⁺ ions were fabricated by a conventional melt-quenching technique, and the dependence of their thermal, optical, and magneto-optical properties on Dy³⁺ ion concentration was investigated. The MO property of the glasses was investigated by measurement of Faraday rotation at 1550 nm. The Faraday rotation angle increased linearly with the increase of Dy³⁺ ion concentration in the glasses. A very high Verdet constant of -6.86 rad/(T·m) was obtained for glass with a Dy³⁺ ion concentration of 30 mol%. In addition, the ABS-Dy glasses showed good thermal stability of greater than 128 ℃ against crystallization, and high optical transmission of 70% in the visible to near-infrared windows of 480-720, 1390-1560, and 1800-2400 nm. Due to the high Verdet constant and good thermal stability, the ABS-Dy glasses in this study could be candidate optical materials for MO device applications at 1550 nm.

• Korean Chemical Engineering Research
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• v.45 no.2
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• pp.160-165
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• 2007

The synthesis and the characterization of Low Silica X (LSX) zeolite for nitrogen adsorption have been studied. The performance of LSX zeolite for nitrogen adsorption was compared to that of the commercial zeolite. The $Na_2O/(Na_2O+K_2O)$ ratio in the gel and the crystallization time were fixed as the synthetic factor. The LSX zeolite was formed at the $Na_2O/(Na_2O+K_2O)$ ratio of 0.75. The formation of LSX zeolite was confirmed by XRD and SEM. The Si/Al ratio was investigated by using XRF and FT-IR. The synthesized LSX zeolite showed a lower Si/Al ratio than the NaY and NaX zeolites although they have a same faujasite structure. The Si/Al ratio of the LSX zeolite converged close to 1. 1A (Li, Na, K) and 2A (Mg, Ca, Ba) group elements were ion-exchanged to the LSX zeolite. As the charge density of cation rises, the amount of nitrogen adsorbed increased. $Li^+$ ion-exchanged LSX zeolite showed the highest nitrogen adsorption weight. When the Li/Al ratio was over 0.65, nitrogen adsorption increased remarkably. $Li^+$ ions located on the supercage (site III, III') in the LSX zeolite played a role as nitrogen adsorption sites. When the $Ca^{2+}$ ions were added to the LiLSX zeolite by ion-exchange method, the performance for nitrogen adsorption increased more. The performance for the nitrogen adsorption was the highest at the Ca/Al ratio of 0.26. Nitrogen adsorption capacity of LiCaLSX (Ca/Al=0.26) zeolite was superior to the commercial NaX zeolite.

• The Journal of the Petrological Society of Korea
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• v.19 no.2
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• pp.141-156
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• 2010

Dokdo Island, Korea, is located in the East Sea belonging to back arc basin. In this study we examined petrology and geochemistry of massive tuffaceous breccia (MTB) from Dongdo (Eastern islet) and Seodo(Western islet), the two largest islands of Dokdo. Field studies and chemical analysis distinguish the MTB in Dongdo and Seodo. The Dongdo MTB (DMTB) is exposed up to 50 m on the ocean cliff and it has dominant basalt and trachybasalt with moderate amount of trachyte and scoria. On the other hand, Seodo MTB (SMTB), which is preserved between trachyte dike and trachyandesite, is composed of roughly equal amounts of basalt, trachybasalt and trachyte. The location of the islets were related to the source vent having in contact with underlying trachyte lava and differential pyroclastic deposits made them different characteristics. According to trace element analysis of trachytic volcanic clasts, the Ba concentration ranges from 66 to 103 ppm and Sr varies from 44 to 56 ppm in DMTB. However, Br and Sr in SMTB correspondingly showed relatively wide ranges: Br 785-1259 ppm and Sr 466-1230 ppm. These differential trends between DMTB and SMTB, along with the difference in P and Ti, indicate that the crystallization of alkali feldspar, feldspathoid, biotite, apatite and titanium took place differently. Nevertheless, DMTB and SMTB are similar in REE patterns and they are correspondingly characterized by high LREE, low HREE and similar $(La/Yb)_N$ values with 23.9-40.2 in DMTB and 27.4-32.9 in SMTB. These patterns suggest that Dongdo and Seodo might be originated from coeval magma suites. Dokdo island shows high concentrations of Ba, K and Rb. These signatures mark a result attributed to the mantle upwelling because the magma derived from the asthenosphere was metasomatized with subduction-related fluids.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.154-155
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• 2012

The promise of nano-crystalites (nc) as a technological material, for applications including display backplane, and solar cells, may ultimately depend on tailoring their behavior through doping and crystallinity. Impurities can strongly modify electronic and optical properties of bulk and nc semiconductors. Highly doped dopant also effect structural properties (both grain size, crystal fraction) of nc-Si thin film. As discussed in several literatures, P atoms or radicals have the tendency to reside on the surface of nc. The P-radical segregation on the nano-grain surfaces that called self-purification may reduce the possibility of new nucleation because of the five-coordination of P. In addition, the P doping levels of ${\sim}2{\times}10^{21}\;at/cm^3$ is the solubility limitation of P in Si; the solubility of nc thin film should be smaller. Therefore, the non-activated P tends to segregate on the grain boundaries and the surface of nc. These mechanisms could prevent new nucleation on the existing grain surface. Therefore, most researches shown that highly doped nc-thin film by using conventional PECVD deposition system tended to have low crystallinity, where the formation energy of nucleation should be higher than the nc surface in the intrinsic materials. If the deposition technology that can make highly doped and simultaneously highly crystallized nc at low temperature, it can lead processes of next generation flexible devices. Recently, we are developing a novel CVD technology with a neutral particle beam (NPB) source, named as neutral beam assisted CVD (NBaCVD), which controls the energy of incident neutral particles in the range of 1~300eV in order to enhance the atomic activation and crystalline of thin films at low temperatures. During the formation of the nc-/pm-Si thin films by the NBaCVD with various process conditions, NPB energy directly controlled by the reflector bias and effectively increased crystal fraction (~80%) by uniformly distributed nc grains with 3~10 nm size. In the case of phosphorous doped Si thin films, the doping efficiency also increased as increasing the reflector bias (i.e. increasing NPB energy). At 330V of reflector bias, activation energy of the doped nc-Si thin film reduced as low as 0.001 eV. This means dopants are fully occupied as substitutional site, even though the Si thin film has nano-sized grain structure. And activated dopant concentration is recorded as high as up to 1020 #/$cm^3$ at very low process temperature (＜ $80^{\circ}C$) process without any post annealing. Theoretical solubility for the higher dopant concentration in Si thin film for order of 1020 #/$cm^3$ can be done only high temperature process or post annealing over $650^{\circ}C$. In general, as decreasing the grain size, the dopant binding energy increases as ratio of 1 of diameter of grain and the dopant hardly be activated. The highly doped nc-Si thin film by low-temperature NBaCVD process had smaller average grain size under 10 nm (measured by GIWAXS, GISAXS and TEM analysis), but achieved very higher activation of phosphorous dopant; NB energy sufficiently transports its energy to doping and crystallization even though without supplying additional thermal energy. TEM image shows that incubation layer does not formed between nc-Si film and SiO2 under later and highly crystallized nc-Si film is constructed with uniformly distributed nano-grains in polymorphous tissues. The nucleation should be start at the first layer on the SiO2 later, but it hardly growth to be cone-shaped micro-size grains. The nc-grain evenly embedded pm-Si thin film can be formatted by competition of the nucleation and the crystal growing, which depend on the NPB energies. In the evaluation of the light soaking degradation of photoconductivity, while conventional intrinsic and n-type doped a-Si thin films appeared typical degradation of photoconductivity, all of the nc-Si thin films processed by the NBaCVD show only a few % of degradation of it. From FTIR and RAMAN spectra, the energetic hydrogen NB atoms passivate nano-grain boundaries during the NBaCVD process because of the high diffusivity and chemical potential of hydrogen atoms.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.197-206
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• 1999

The stochiometric mixture of evaporating materials for the $AgInSe_2$single crystal thin films were prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the $AgInSe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $C_0$ were 6.092 $\AA$ and 11.688 $\AA$, respectively. To obtain the single crystal thin films of AgInSe$_2$, the mixed crystal was deposited on thoroughly etched semi-insulator GaAs(100) substrate by HWE system. The source and substrate temperature were fixed to $610^{\circ}C$ and $450^{\circ}C$ respectively, and the thickness of the single thin films was obtained to 3.8 $\mu\textrm{m}$. The crystallization of single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray dirrfaction (DCXD). The Hall effect was measured by the method of van der Pauw and carrier density and mobility dependence on temperature were studied. The carrier density and mobility of $AgInSe_2$single crystal thin films deduced from Hall data are $9.58{\times}10^{22} electron/m^3,\; 3.42{\times}10^{-2}m^2/V{\cdot}s$ at 293 K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $AgInSe_2$single crystal thin film, the spin orbit coupling $\Delta$So and the crystal field splitting $\Delta$Cr were obtained to 0.29 eV and 0.12 eV at 20 K respectively. From PL peaks measured at 20 K, 881.1 nm (1.4071 eV) and 882.4 nm (1.4051 eV) mean $E_x^U$ the upper polariton and $E_x^L$ the lower polariton of the free exciton $(E_x)$, also 884.1 nm (1.402 eV) express $I_2 peak of donor-bound exciton emission and 885.9 nm (1.3995 Ev) emerges $I_1$ peak of acceptor-bound exciton emission. In addition, the peak observed at 887.5 nm (1.3970 eV) was analyzed to be PL peak due to DAP.

• Economic and Environmental Geology
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• v.22 no.4
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• pp.327-339
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• 1989

Cassiterite, tantalite, columbite and tantalian rutile are found as accessory minerals in Soonkyoung tin-bearing pegmatites. These minerals occur as finely disseminated specks of up to micro-size in diameter and coarse grain size varying from 0.5-50mm in albite, muscovite and quartz assemblage. Cassiterite geneally shows a moderate to intense pleochroism, having a color brownish yellow to deep reddish brown. The substitution of $Ta^{+5}$, $Nb^{+5}$, $Ti^{+4}$ and Fe* for $Sn^{+4}$ in cassiterite ranges 0.01-0.10 mol%. The zoned cassiterite give a higher Ta/Nb ratios in margin than the ratios in core. This is due to the preferential $Ta^{+5}$ affinity to lower temperature during the crystallization of cassiterite. Tantalite-columbite and tantalian rutile occur in cassitertie with exsolution texture and/or infiltrate into the micro-fissures of cassiterite with micro quartz vein. The compositions of tantalite-columbite show the wide ranges of $Ta_2O_5$ : 14-46 wt.%, $Nb_2O_5$ : 60-28 wt. % and FeO*: 10.15 wt.%. The variation of chemical composition in tantalit-columbite exhibits the decreasing trends of $Mn^{+2}/M^{+2}+Fe^*$ with $Ta^{+5}/Ta^{+5}+Nb^{+5}$ increasing. These trends of vatiations indicate that the Ta/Nb fractionation are enhanced by higher Ta-complex activity in late stage of pegmatite consolidation and lower activity of F in agreements with the F-and Li-micas not to be developed in Soonkyoung tin-bearing pegmatite.

• Journal of Sericultural and Entomological Science
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• v.25 no.1
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• pp.1-20
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• 1983

It has been known that the insect molting hormone and its analogues exist also in plant kingdom and their concentration has been found to be about 0.1~2.0% of dry matter, which is equivalent to $10^3{\sim}10^5$ times of those in insects. This study was carried out; 1) to isolate the phytoecdysones from Korean Achyranthes radix and characterize their physico-chemical properties. 2) to investigate the biological activity of this phytoecdysone on Bombyx mori larvae. The resuls were summarized as follows; 1. The extraction method of phytoecdysones was optimized by three consecutive reflux for 1hr using 200g of dried and milled radix per 1l methanol. 2. The purification from the crude extract was made by a series of steps such as precipitation of gum-type polymer with n-Butyl acetate, adsorption on technical grade silica and chromatography with neutral alumina. The conditions of each step were optimized and the resulting crude crystal was about 500mg per kg dry radix. 3. The crude crystal from the cultivated Achyranthes(Achyranthes japonia) contained ecdysterone (20-hydroxyecdysone) and inokosterone in the proportion of one to one. In order to separate these, a series of processes such as acetylation, separation by alumina column chromatography deacetylation by alcoholysis, deionization and crystallization were introduced and optimized 125mg of ecdysterone and 18mg of inokosterone per kg dry radix were thus obtained. 4. The wild Achyranthes (Achyranthes obtusifolia) radix was found to contain the ecdysterone only. A 285mg of ecdysterone was crystallized per kg dry radix. 5. Isolated ecdysterone, inodosterone and acetylated compounds were characterized by IR., UV., NMR spectroscopy, mp, TLC and densitometry. 6. Ligation experiment was undertaken to confirm the biological activity of the purified ecdysterone; the ecdysterone could induce larval-pupal metamorphosis in the ligated abdomen of 4th instar larvae injecting 0.5~1.0${\mu}g$. 7. By ecdysterone feeding experiment using artificial diet, it was elucidated that the critical time of feeding would be the first half of each instar resulting in increased weight of silk layer. 8. The ecdysterone was fed to 5th instar silkworm at the level of 1, 2, 3, 5ppm of dry feed of artificial diet containing 5% mulberry leaves for 72hrs. At 2ppm of the concentration. body weight and silk layer weight were arrived at maximum. But at higher concentrations body weight and silk layer weight decreased than the control group. At 2ppm of the concentration, body weight was increased by 12.5%. 9. Feeding 2ppm of ecdysterone at the later half of 5th instar, the duration of larvae was shortened.

• The Journal of the Petrological Society of Korea
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• v.9 no.2
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• pp.84-98
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• 2000

Daejeon-sa basalt in the Mt. Juwang area composed of 12 basalt flows alternate with 9 peperites and each basalt and peperite has the variety of thickness. Peperites yielded in Daejeon-sa basalt are mixed of basalt with reddish shale, of which textural type is globular peperite. Basalts yielded in Daejeon-sa basalt are massive basalt without vesicule, although sometimes vesicules are founded in upper within a flow unit. The basalt has mainly pseudomorph of olivine as phenocryst, and also plagioclase and clinopyroxene phenocryst. Matrix is mainly subophitic texture. The plotting result on the TAS diagram shows these basalts belong to the sub-alkaline, and it can be subdivided into calc-alkaline series on the basis of the diagram of Si02 vs. K20 and of alkali index vs. A1203 diagram. According to plots of wt.% oxides vs. wt.% MgO, abundances of A1203 and CaO increase with decreasing MgO while F ~ dOecre~ase . With decreasing MgO compatible elements decrease while incompatible elements increase. In spider diagram of MORB-normalized trace element patterns, HFS elements are nearly similiar with MORB, but LIL elements are enriched. Especially, contents of Ce, F: and Sm are enriched but Nb is depleted. In the chondrite-normalized REE patterns light REEs are enriched than heavy REEs. Tectomagmatic discrimination diagrams shows basalts in the study area are formed in the tectonomagmatic environment of subduction zone under continental margin. This result accord with characters of chemical composition mentioned above. Cr vs. Y diagram and CeM, vs. Ce diagram show that the primary magma of the basalts may formed by the about 15% partial melting of garnet-peridotite in the mantle wedge. After then, Daejeon-sa basalts may formed from evolved magma undergone mainly olivine fractional crystallization and contarnination of crustal materials before eruption.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.200-213
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• 2002

The Andong granitoid batholith represents five temporally distinct episodes (phases) of igneous activity. The batholith represents a plutonic complex of five pulsatively emplaced distinct intrusive multiphases. The petrochemical data show that the plutons fall into calc-alkaline series except for the Yean pluton, and plot within the diaenostic range for I-type origin and continental arc orogenic tectonic setting. Each pluton reveals systematic compositional variations of major and trace elements with $SiO_2$ or MgO, but different variation trends for some elements and considerably different REE patterns. Thus discontinuous, inconsistent variations in the elements indicate that the five plutons can not be explained by simple fractional crystallization from the same primary magma, but were intruded and solidified from the independent magmas of chemically heterogeneous origin. In the Andong, Dosan and Pungsan plutons, high values of molar CaO/(MgO+$FeO^{t}$ ) combined with low $Al_2$$O_3$/(MgO+$FeO^{t}$ ) and $K_2$O$Na_2$O ratios suggest a magma originated by dehydration melting of a metabasaltic to metatonalitic protolith. Whereas the Imha pluton show similar values of CaO/(MgO+$FeO^{t}$ ), but significantly higher ratios of $Al_2$$O_3$/(MgO+$FeO^{t}$ ) and $K_2$O$Na_2$O implying to a metagreywacke protolith.