• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1523-1528
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• 2014

Silicon quantum dots (Si QDs) were synthesized by etching silicon nanopowder with aqueous hydrofluoric acid (HF) and nitric acid ($HNO_3$). Then, the hydride-terminated Si QDs (H-Si QDs) were functionalized by 1- octadecene (ODE). By only controlling the etching time, the maximum luminescence peak of octadecylterminated Si QDs (ODE-Si QDs) was tuned from 404 nm to 507 nm. The average optical gap was increased from 2.60 eV (ODE-Si QDs-5 min) for 5 min of etching to 3.20 eV (ODE-Si QDs-15 min) for 15 min of etching, and to 3.40 eV (ODE-Si QDs-30 min) for 30 min of etching. The electron affinities (EA), ionization potentials (IP), and quasi-particle gap (${\varepsilon}^{qp}_{gap}$) of the Si QDs were determined by cyclic voltammetry (CV). The quasi-particle gaps obtained from the CV were in good agreement with the average optical gap values from UV-vis absorption. In the case of the ODE-Si QDs-30 min sample, the difference between the quasi-particle gap and the average optical gap gives the electron-hole Coulombic interaction energy. The additional electronic levels of the ODE-Si QDs-30 min and ODE-Si QDs-15 min samples determined by the CV results are interpreted to have originated from the Si=O bond terminating Si QD.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.5-5
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• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.

• Nutrition Research and Practice
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• v.10 no.3
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• pp.265-273
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• 2016

BACKGROUND/OBJECTIVES: The inhibitory effect of Hijikia fusiforme (HF) extracts on degenerative osteoarthritis was examined in primary cultured rat cartilage cells and a monosodium iodoacetate (MIA)-induced osteoarthritis rat model. MATERIALS/METHODS: In vitro, cell survival and the expression of matrix metalloproteinases (MMPs), collagen type I, collagen type II, aggrecan, and tissue inhibitor of metalloproteinases (TIMPs) was measured after $H_2O_2$ ($800{\mu}M$, 2 hr) treatment in primary chondrocytes. In vivo animal study, osteoarthritis was induced by intra-articular injection of MIA into knee joints of rats, and then RH500, HFE250 and HFE500 were administered orally once a day for 28 days. To determine the anti-inflammatory effects of HFE, nitric oxide (NO), prostaglandin $E_2$ ($PGE_2$) expression were measured. In addition, real-time PCR was performed to measure the genetic expression of MMPs, collagen type I, collagen type II, aggrecan, and TIMPs. RESULTS: In the in vitro assay, cell survival after $H_2O_2$ treatment was increased by HFE extract (20% EtOH). In addition, anabolic factors (genetic expression of collagen type I, II, and aggrecan) were increased by HFE extract (20% EtOH). However, the genetic expression of MMP-3 and 7, known as catabolic factors were significantly inhibited by treatment with HFE extract (20% EtOH). In the in vivo assay, anabolic factors (genetic expression of collagen type I, II, aggrecan, and TIMPs) were increased by oral administration of HFE extract. However, the genetic expression of MMP-3 and 7, known as catabolic factors, and production of NO and $PGE_2$ were significantly inhibited by treatment with oral administration of HFE extract. CONCLUSION: HFE extract inhibited articular cartilage degeneration through preventing extracellular matrix degradation and chondrocyte injury.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.220-224
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• 2000

Ultra-fine $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$ferrite powders have been prepared by the sol-gel method. The crystallographic and magnetic properties of the sample have been investigated by means of x-ray diffraction, Mossbauer spetroscopy and vibrating sample magnetometry. The formation of nano crystallized particles is confirmed. The x-ray diffractions of all samples with various compositions clearly indicate the presence of spinel structure. The Mossbauer spectra could be fitted as the superposition of two sextets due to F $e^{3+}$ A-site and B-site. The IS and QS values nearly constant with substituted Co-Ti contents, whereas $H_{hf}$ of B-site decreases with increasing Co-Ti substitution in $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$. The magnetic behaviour of powders shows that the saturation magnetization and the coercivity decrease with increasing x in $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$.$.X>.

• Journal of Powder Materials
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• v.10 no.5
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• pp.344-347
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• 2003

Pure tantalum powder has been produced by combining Na as a reducing agent, $K_2$TaF$_{7}$ as feed material, KCl and KF as a diluent in a stainless steel (SUS) bomb, using the method of metallothermic reduction. And we examined various types of after-treatment that affect the high purification of powder. A significant amount of impurities contained in recovered powder was removed in various conditions of acid washing. In particular, 20% (HCl + HNO$_3$) was effective in removing heavy metal impurities such as Fe, Cr and Ni, 8% H$_2$SO$_4$ + 8% $Al_2$(SO$_4$)$_3$ in removing fluorides such as K and F from non-reactive feed material, and 2% $H_2O$$_2$ + 1 % HF in removing oxides that formed during reaction. Significant amounts of oxygen and part of light metal impurities could be removed through deoxidation and heat treatment process. On the other hand, because it is difficult to remove completely heavy metal impurities such as Fe, Cr, and Ni through acid washing or heat treatment process if their contents are too high, it is considered desirable to inhibit these impurities from being mixed during the reduction process as much as possible.

• Resources Recycling
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• v.20 no.6
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• pp.56-62
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• 2011

Zirconium is used in nuclear reactors as a structural material due to its excellent corrosion resistance and to low neutron crosssection. Variation in the distribution and solubility of Zr(IV) with solution pH was obtained. Distribution of Zr(IV) containing species in HCl and $HNO_3$ solution was analyzed by considering the complex formation of Zr(IV) species with the anion of the inorganic acid. Bromley interaction parameter between $ZrO^{2+}$ and nitrate ion was estimated by using the reported data on the solvent extraction of Zr(IV) by Cyanex272 from $HNO_3$ solution. This Bromley parameter can be utilized in calculating extraction isotherm of Zr(IV) and in predicting the separation factor between Zr(IV) and Hf(IV).

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.339-347
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• 2010

Enhancement of bond strength between new and old composite usually requires increasing the surface roughness to promote mechanical interlocking. This study evaluated the effect of different surface treatments on repair bond strength of resin composite after aging condition. Air abrasion with Al2O3, chairside silicacoating, and silanization provided higher resin-resin bond strength values compared to control group and HF group. Air abrasion is necessary to repair a resin restoration and additional application of silane seems to have good effects on bond strength.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.3
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• pp.155-161
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• 1992

A simple, fast yet sensitive method is described for the determination of fifty elements in coal by inductively coupled plasma mass spectrometry. The method involves complete dissolution of coal with mixed acid $(HNO_3, HF, HClO_4)$ in hish pressure Teflon bomb and subsequent inductively coupled plasma mass spectrometric(ICP-MS) measurement. The accuracy of the method, being evaluated by the analysis of NIST SRMs (1632a, 1632b) is better than 20% RSD for most elements. The limits of detection defined by two times $\sigma$ (standard deviation of operational blank) are in order of sub-ppm to ppm, which are low enough to quantitate most elements. However, the determiantions for few elements such as V, As, Se are severely interfered by molecular ions such that their accurate determiantions are not possible. Analytical results for twentyon coals from eight countries including six ones world major coal producing, Korea, Japan, China, I.C.S., U.S.A., Canada, Australia, and South Africa are presented. While the results for major elements agree well with the existing ones, those for a few trace elements disagree considerably. The existing values are considerably higher. It is not possible to judge which are more accurate. However, the exisisting values are more likely to be errorous inasmuch as they are obtained without using high purity reagents and clean laboratory techniques.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.162-165
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• 2003

The corrosion characteristics of diffusion barrier in Copper CMP has been investigated. Key experimental variables that has been investigated are the corrosion rate by different agents containing slurry of Cu CMP. Whenever Cu and Ta films were corroded adding each oxidizer, the corrosion rate of Ta was much lower than that of Cu. That is, the difference in the corrosion rates of Ta by oxidizer was not larger as compared with Cu. As corroded by complexing agents, the corrosion rate of Ta was close to O. The corrosion rate of Ta increased as added $HNO_3$ and $CH_3COOH$ compared with the reference slurry; on the other hand, it decreased with addition of HF. In addition, resulting corrosion rate went up with lower pH of agent. The corrosion rates by agents were however significant small; hence, it doesn't affect on the removal rate of Cu CMP practically. Consequently, this can be explained by assuming that the mechanical effect dominates than the chemical effect on the polishing rate of Ta(TaN).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.5
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• pp.67-73
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• 2010

Paper packaging materials are essential in protection and transportation of commercial or industrial products. Raw materials for packaging paper production are mainly obtained from various grades of waste paper. For this reason, the recycled fibers from waste paper would probably have possibility of containing heavy metals. This study was focused on the development of optimum pre-treatment method for the quantitative analysis of mercury. The optimum pre-treatment for open digestion system were obtained at the treatment conditions of acid combination with $HNO_3/HCl/H_2O_2$ or $HNO_3/H_2SO_4$ at $80^{\circ}C$. The optimum pre-treatment conditions in closed digestion system were determinated by the acid combination with $HNO_3/HCl/H_2O_2/HF$ in microwave at 320 W for 20 min. The recovery rate in open digestion system was 85~94% and in closed digestion system was indicated as about 100%. Therefore, the closed system is superior than the open system in pre-treatment method for the quantitative analysis of mercury, and the detected mercury contents in the sample of KOCC, AOCC and kraft sack paper were measured below 1 ppm.