• Korean Journal of Metals and Materials
• /
• v.50 no.3
• /
• pp.243-247
• /
• 2012

A ruthenium (Ru) catalytic layer and a conventional Pt layer were assessed as counter electrodes (CE) for dye sensitized solar cells (DSSCs). Ru films with different thicknesses of 34, 46, and 90 nm were deposited by atomic layer deposition (ALD). Pt layers with the same thicknesses were prepared by sputtering. $0.45cm^2$ DSSCs were prepared and their properties were characterized by FE-SEM, cyclic voltammetry (CV), impedance spectroscopy (EIS), and current-voltage (I-V). FE-SEM revealed that the crystallized Ru films and Pt films had been deposited quite conformally. CV showed that the catalytic activity of Pt was much greater than that of Ru. In addition, although the catalytic activity of Pt did not depend on the thickness, that of Ru showed an increase with increasing thickness. Impedance analysis revealed high charge transfer resistance at the Ru interface and a decrease with increasing Ru thickness, whereas Pt showed low resistance with no thickness dependence. Despite the relatively small catalytic activity of Ru, the I-V result revealed the average energy conversion efficiency of Ru and Pt to be 2.98% and 6.57%, respectively. These results suggest that Ru can be used as counter electrodes in DSSCs due to its extremely low temperature process compatibility.

• Animal Bioscience
• /
• v.34 no.6
• /
• pp.985-992
• /
• 2021

Objective: Artificial insemination plays an important role in genetic improvement in the goat farming system. The aim of this study was to investigate the effect of cervical application of hyaluronan (HA) on the fertility in goats after cervical artificial insemination using frozen-thawed (F-T) semen. Methods: After oestrous synchronisation with progesterone sponges and pregnant mare serum gonadotropin injection, both nulli- and multi-parous goats, were randomly allocated to 2 groups, and were inseminated with 0.25 mL of F-T semen (150×106 spermatozoa) twice at 52 h and 56 h after sponge removal. Prior to the insemination, goats in Group 1 only were given topical cervical HA application at 48 h after sponge removal. Site of insemination was recorded as os-cervix or intra-cervix or intra-uterus. Pregnancy was tested ultrasonographically 42 days after insemination. The data on pregnancy rates and percentage of animals according to the site of semen deposition were compared by Chi-square analysis. Results: The overall pregnancy rate was significantly (p<0.004) higher in goats with prior application to the cervix with HA (63.3%) than without (36.0%). Same pattern was observed in the pregnancy rates of nulli- and multi-parous goats in both the groups. Percentage of nulliparous goats according to the site of insemination in the HA group did not differ between first and the second insemination. However, in multiparous goats the percentage of animals inseminated intra-cervically was significantly increased (p≤0.05) between the first and the second inseminations. Conclusion: The results suggest that significantly higher fertility rate in the "HA goats" compared to the "without HA" group was because of deeper insemination facilitated by topical cervical application of HA. The deeper insemination into the cervical canal increase the rate of fertilisation when the cervical artificial insemination is performed.

• Journal of Electrochemical Science and Technology
• /
• v.12 no.1
• /
• pp.58-66
• /
• 2021

Spiral-wound woven wire meshes packed bed rotating cylinder electrode was used for the simultaneous removal of cadmium (Cd) and copper (Cu) from a binary solution. The effects of weight percent of each metal on the removal and current efficiencies were studied at an operating current of 345A, while the effect of current on the removal efficiency of both metals was investigated at three levels of current (240, 345.and 400 mA). The experiments were carried out at constant rotation speed 800 rpm, pH = 3, and a total concentration of metals (500 ppm). The results showed that the removal efficiency of copper increased from 89% to 99.4% as its weight percent increased from 20% to100%. In a similar fashion, the removal efficiency of cadmium increased from 81% to 97% as its weight percent increased from 20% to100%. The results confirmed that the removal efficiency of any metals declined in the presence of the other. Increasing of current resulted in increasing the removal efficiency of both metals at different weight percents. The results confirmed that current efficiencies for removing of copper and cadmium simultaneously decline with increasing of electrolysis time and weight percent of cadmium or with decreasing the weight percent of copper. Current efficiency was higher at the initial stage of electrolysis for all weight percents of metals. The results showed that the decay of copper concentration was exponential at all weight percents of copper, confirming that the electrodeposition of copper is under mass transfer control in the presence of cadmium. While the decay of cadmium concentration was linear at lower weight percent of cadmium then changed to an exponential behavior at high weight percent of cadmium in the presence of copper.

• Journal of the Semiconductor & Display Technology
• /
• v.21 no.2
• /
• pp.85-89
• /
• 2022

We reported on annealing effect on Ga₂O₃/Al₂O₃/SiC devices grown by radio frequency sputtering method. Post-deposition annealing at 900 ℃ was performed, which results in crystallization in the Ga₂O₃ films. The major peaks (-401) and (403) of Ga₂O₃ which was thermally treated at 900 ℃ appears in the x-ray diffraction (XRD) results. Auger electron spectroscopy (AES) shows that Ga and Al atoms seems to be diffused into the opposite direction Al₂O₃ and Ga₂O₃ after annealing. Transfer and output characteristics of back-gate transistor were analyzed where SiC substrate is used as gate material. On-state current and on/off ratio increased almost 10⁹ and 10⁶ times higher in the 900 ℃ annealed sample.

• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.1
• /
• pp.71-75
• /
• 2022

Graphene oxide was stirred with a ZnCl₂:NaCl electrolyte and electrochemically coated by cyclic voltammetry to simplify the electron transpfer layer film forming process for organic solar cells and to fabricate an organic solar cell having it. The device structure is FTO/ZnO:graphene/P3HT:PCBM/PEDOT:PSS/Ag. Morphology and chemical properties of ETL were confirmed by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. As a result of XPS measurement, ZnO metal oxide and carbon bonding were simultaneously confirmed, and ZnO and graphene peaks were confirmed by Raman spectroscopy. The electrical characteristics of the manufactured solar cell were specified with a solar simulator, and the ETL device coated twice at a rate of 0.05 V/s showed the highest photoelectric conversion efficiency of 1.94%.

• Journal of Surface Science and Engineering
• /
• v.55 no.2
• /
• pp.96-101
• /
• 2022

The effects of the growth temperature on the structural, optical, and morphological properties of BaWO₄:Sm³⁺ phosphor thin films were investigated. The BaWO₄:Sm³⁺ thin films were grown on quartz substrates at several growth temperatures by radio-frequency magnetron sputtering. All the thin films crystallized in a tetragonal structure with a main BaWO₄ (112) diffraction peak. The 830 nm-thick BaWO₄:Sm³⁺ thin films grown at 300 ℃ exhibited numerous polygon-shaped particles. The excitation spectra of BaWO₄:Sm³⁺ thin films consisted of a broad excitation band in the 200-270 nm with a maximum at 236 nm due to the O^2--Sm³⁺ charge transfer and two small bands peaked at 402 and 463 nm, respectively. Under 236 nm excitation, the BaWO₄:Sm³⁺ thin films showed an intense red emission peak at 641 nm due to the ⁴G_5/2→⁶H_9/2 transition of Sm³⁺, indicating that the Sm³⁺ ions occupied sites of non-inversion symmetry in the BaWO₄ host lattice. The highest emission intensity was observed for the thin film grown at 300 ℃, with a 51.8% transmittance and 5.09 eV bandgap. The average optical transmittance in the wavelength range of 500-1100 nm was increased from 53.2% at 200 ℃ to 60.8% after growing at 400 ℃. These results suggest that 300 ℃ is the optimum temperature for growing redemitting BaWO₄:Sm³⁺ thin films.

• Korean Chemical Engineering Research
• /
• v.61 no.1
• /
• pp.52-57
• /
• 2023

This study is a basic research for the development of high performance flexible electrode material. To enhance its electrochemical property, CuO nanoparticles (CuO NPs) were introduced and dispersed on surface of CNT fiber through electrochemical deposition method. The CNT fiber/CuO NPs electrode was fabricated and applied to electrochemical non-enzymatic glucose sensor. Surface morphology and elemental composition of the CNT fiber/CuO NPs electrode was characterized by scanning electron microscope (SEM) with energy dispersive X-ray spectrometry (EDS). And its electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. The CNT fiber/CuO NPs electrode exhibited the good sensing performance for glucose detection such as high sensitivity, wide linear range, low detection limit and good selectivity due to synergetic effect of CNT fiber and CuO NPs. Based on the unique property of CNT fiber, CuO NPs were provide large surface area, enhanced electrocatalytic activity, efficient electron transport property. Therefore, it is expected to develop high performance flexible electrode materials using various nanomaterials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.6
• /
• pp.668-674
• /
• 2024

Recently, as environmental issues caused by gas stoves have led to the widespread adoption of induction appliances, specialized cookware for induction is essential. However, due to the inability of ceramic containers to be directly used on induction cooktops, a conductive coating is required on the bottom of the cookware, presenting limitations such as complex deposition processes and extended coating times in existing methods including thermal spraying, dip coating, and transcription method. We confirmed the potential of heat-resistant cookware for induction use by coating the bottom of the ceramic container with Ag through a simple manufacturing process of screen-printing and measuring its thermal conductivity and reliability. The Ag-coated ceramic cookware produced by screen-printing demonstrated similar thermal conductivity and reliability to those made using the traditional method of transfer printing. In addition, the adhesive strength before and after thermal shock testing was even superior in the screen-printing method, which suggests a higher expected lifespan. As a result, it is expected that induction-compatible heat-resistant ceramic containers with excellent performance and lifespan will be manufactured through the screen-printing process, which is more cost-effective and efficient compared to other methods.

• Journal of Radiation Protection and Research
• /
• v.20 no.4
• /
• pp.255-263
• /
• 1995

Root uptakes of $^{54}Mn,\;^{60}Co,\;^{85}Sr\;and\;^{137}Cs$ by rice were studied through a greenhouse experiment in which the upper 20 cm of the culture box was filled with an acidic loamy-sandy soil and a mixed solution of the radionuclides was applied to the surface water on the soil 2 days before, and 5 different times after, transplanting. Percent uptakes of the radionuclides to rice tops varied $3.4{\sim}13.7%,\;0.03{\sim}0.1%,\;0.6{\sim}1.5%,\;0.02{\sim}0.15%$, respectively, with application time. Among radionuclides, soil-to-plant transfer factors decreased, on the whole, in the order of $^{54}Mn>^{85}Sr>^{60}Co{\geq}^{137}Cs$, and among plant parts, in the order of straw > chaff > hulled seed. Transfer factors $(m^2/kg-dry)$ in hulled seed were, depending on application time, $1.2{\times}10^3{\sim}5.0{{\times}10^3\;for\;^{54}Mn,\;1.6{\times}10^5{\sim}2.6{\times}10^4\;for\;^{60}Co,\;1.1{\times}10^4{\sim}7.6{\times}10^4\;for\;^{85}Sr\;and\;5.2{\times}10^5{\sim}7.0{\times}10^4\;for\;^{137}Cs$. The highest factors of all the radionuclides in straw came from the application at 67 days after transplanting while those of $^{54}Mn,\;^{60}Co\;and\;^{85}Sr$ in hulled seed appeared at later applications. The data from this studv can be referred to in assessing the radiological impact of an accidental contamination during the rice growth.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.15 no.1
• /
• pp.71-78
• /
• 2009

Korea Marine Environment Management Corporation (KOEM) has waste oil facilities in 13 ports to collect and treat waste oil, bilge, etc. from ships based upon the Marine Environment Management Act of Korea and MARPOL 73/78 convention. Those facilities were designed and have been operated simply to discharge water under the level 15 ppm of oil contents. However, bad smells occurred from rotten organic matters in waste water and direct discharge of harmful substances to receiving water caused civil appeals. Therefore, KOEM tried to develop new process for treatment of oily waste water from ships, which could mitigate harmful substances, save cost, calm down civil appeals and contribute to marine environment preservation. This process consists of 3 steps to remove oil contents via gravity variation at first, $O_3$ input to contact water and organism deposition by inputting condensate deposits. Then finally upper water will be discharged, and the deposited substances in the bottom will be compressed through spinning machine to transfer to the designated contractors for treatment of wastes. This is very effective and innovative in that it could reduce 3 or 4 steps compared with existing process and mitigate not only waste oil concentration but also hard resolving materials such as colloid, ABS, phosphorus, nitrogen and bad smells. This method is expected to minimize bad smells and harmful gases, to save more than 10% of maintenance cost, and to arrange the good base for garbage treatment business dealing with waste water and bad smell.