• Korean Journal of Soil Science and Fertilizer
• /
• v.6 no.4
• /
• pp.221-226
• /
• 1973

In order to investigate the silica effect of insufficient wollastonite to the official standard (above than 15% of suluble silica (N/2 HCl) on rice plant as silica fertilizer, 9 kinds of wollastonites and slag were adopted to examine the amount of silica absorbed by rice straw during growing period, and soluble silica of wollastonites extracted by 7 buffer solutions were compared with silica content in rice straw. Crystalls of ingredient in wollastonite ores were identified by X-ray diffractometer. The results were that silica content of rice plant at growing stages were increased as same ratio of soluble silica. content in wollastonite. Wollastonite containing more than 10% of souble silica (N/2 HCl) could be applied as fertilizer because absorbed amount of silica by rice plant from them are higher than from slag which contained 30% of soluble silica. Wollastonite powder mixed with impure ores in which soluble silica could not be extracted had the same effect on silica absorption of straw as wollastonite powder which contained conformable amount of soluble silica. The soluble silica of wollastonite extracted by buffer solutions (2% citric acid, N. NaOAc, N. $NH_4OAc$, Petermann solution, 0.1M. EDTA, and Hot water) had high significant relation to silica content in rice straw, but soluble silica extracted N/2 hydrochloric acid solutilon, also, had deep relation to them in rice straw. The adequate solution to extract silica from wollastonites is N/2 hydrochloric acid solution because its extracted silia amount is much higher than other solution (about one hundred times) and can be determined by gravimetric analysis. X-ray diffraction pattern would identify qualitatively purity of wollastonite, and large amount of soluble silica was extracted from wollastonite which was appeared to be weathered.

• Korean Journal of Food Science and Technology
• /
• v.39 no.5
• /
• pp.534-540
• /
• 2007

In this study, waxy rice starch was chemically modified using phosphorous oxychloride ($POCl_3$, 0.002-0.008%). Then the physicochemical properties of resulting cross-linked waxy rice starches were investigated in order to reduce the steeping time of Yukwa (a Korean oil-puffed rice snack) processing. The swelling powers of the cross-linked waxy rice starch samples were higher than the native waxy rice starch at temperatures above $60^{\circ}C$, and their increases were proportional to the $POCl_3$, concentration. The solubility of the cross-linked waxy rice starch was lower (1.6-3.4%) than the native waxy rice starch (2.7-6.1%). However, the moisture sorption isotherm of the cross-linked waxy rice starch was not significantly different from the native waxy rice starch. The rapid visco analyze. (RVA) pasting temperatures $(65.4-67^{\circ}C)$ of the cross-linked waxy rice starch were lower than those of the native starch $(67^{\circ}C)$. The RVA peak viscosities (287-337 RVU) of the cross-linked waxy rice starch were higher than that of native starch (179 rapid visco units (RVU)), and increased with increasing $POCl_3$ concentration. For the differential scornning calorimeter thermal characteristics, although Tc shifted toward higher temperatures with cross-linking, the To, Tp, and amylopectiin melting enthalpy of the cross-linked waxy rice starch showed no differences compared to the native waxy rice starch. The X-ray diffraction patterns of both the native and cross-linked waxy rice starches showed typical A-type crystal patterns, suggesting that cross-linking mainly occurs in the amorphous regions of starch granules. Therefore, the cross-linking reaction did not change the crystalline region, but altered the amorphous region of the waxy rice starch molecules, resulting in changes of solubility and RVA pasting properties in the cross-linked waxy rice starch. In summary, since cross-linked waxy rice starch has a high puffing efficiency and no browning reaction, it may be applicable for Yukwa processing without a long steeping process.

• Journal of the Korean Magnetics Society
• /
• v.18 no.2
• /
• pp.67-70
• /
• 2008

$Tb_2Bi_1Ga_xFe_{5-x}O_{12}$(x=0, 1) fabricated by sol-gel and vacuum sealed annealing process. $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$(x=0, 1) have been studied by x-ray diffraction(XRD), vibrating sample magnetometer, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structures were found to be a cubic garnet structure with space group Ia3d. The determined lattice constants $a_0$ of x = 0, and 1 are $12.497\AA$, and $12.465\AA$, respectively. The distribution of gallium and iron in $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$ is studied by Rietveld refinement. Based on Rietveld refinement results, the terbium and bismuth ions occupy the 24c site, iron ions occupy the 24d, l6a site, and nonmagmetic gallium ions occupy the 16a site. In order to verify the magnetic site occupancy of iron and gallium, we have taken $M\ddot{o}ssbauer$ spectra for $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$(x=0, 1) at room temperature. From the results of $M\ddot{o}ssbauer$ spectra analysis, the absorption area ratios of Fe ions for $Tb_2Bi_1Fe_5O_{12}$ on 24d and 16a sites are 60.8 % and 39.2 %, respectively, and the absorption area ratios of Fe ions for $Tb_2Bi_1Fe_5O_{12}$ on 24d and 16a sites are 74.7 % and 25.3 %, respectively. It is noticeable that all of the nonmagnetic Ga atoms occupy the 16a site by vacuum annealing process.

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

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.24 no.6
• /
• pp.229-236
• /
• 2014

A stoichiometric mixture of evaporating materials for $MnAl_2S_4$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $MnAl_2S_4$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were $630^{\circ}C$ and $410^{\circ}C$, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The temperature dependence of the energy band gap of the $MnAl_2S_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.7920eV-5.2729{\times}10^{-4}eV/K)T^2/(T+786 K)$. In order to explore the applicability as a photoconductive cell, we measured the sensitivity (${\gamma}$), the ratio of photocurrent to dark current (pc/dc), maximum allowable power dissipation (MAPD) and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in S vapour compare with in Mn, Al, air and vacuum vapour. Then we obtained the sensitivity of 0.93, the value of pc/dc of $1.10{\times}10^7$, the MAPD of 316 mW, and the rise and decay time of 14.8 ms and 12.1 ms, respectively.

• Economic and Environmental Geology
• /
• v.47 no.2
• /
• pp.87-96
• /
• 2014

The objectives of this study were to characterize the physicochemical properties and mineralogy of Hwangto (yellow residual soils) from the southwestern part of Korea and to understand the soil-forming processes of the residual soils from their parent rocks. Both the yellowish residual soils as well as the unweathered and weathered parent rocks were obtained from Jangdong-ri, Donggang-myun, Naju, Jeollanam-do, Korea. The soil samples were examined to analyze the said soil's physicochemical properties such as color, pH, and particle size distribution. A scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis were performed in order to understand the mineralogy, chemical composition, and morphology of the soils. Two thin sections of a parent rock were analyzed to study its mineral composition. A particle size analysis of the soils indicates that the residual soil consists of mainly silt and clay (approximately 95%) and that soil textures are silty clay or silt clay loam. The soil colors of the residual soil are dark brown (7.5YR 3/4) through yellowish red (5YR 4/6). The pH of the residual soil ranges from 4.3 to 5.1. The major minerals of the parent rocks were quartz, biotite, chlorite, and plagioclase. The mineralogy of the sand fraction of the residual soil was quartz, biotite, muscovite and sanidine. The mineralogy of the silt fraction of the residual soil was quartz, biotite, muscovite, Na-feldspar, K-feldspar, and sanidine. The clay mineralogy of the soil was goethite, kaolinite, ilite, hydroxy-interlayed vermiculite(HIV), vermiculite, mica, K-feldspar and quartz. The mineral composition of the residual soil and the parent rock indicates that feldspar and mica in the parent rock weathered into illite, vermiculite and hydroxy-interlayed vermiculite(HIV), and finally changed into kaolinite and halloysite in the yellowish residual soils.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.29 no.6
• /
• pp.317-328
• /
• 2019

In this work, we investigated clay and raw materials from China (black clay, red clay, white clay) and Korea (Cheonan clay, Obu clay) used for the manufacture of porcelain products. According to chemical analysis results, feldspar components containing CaO, K₂O, Na₂O and quartz are found in clay materials besides primary clay such as kaollinte, for the clay materials from Korea, which is found more in clay materials from Korea than from China. For the Fe₂O₃ content, governing whiteness of porcelain products, more iron oxide (> 5 %) is found in Korean clays (Cheonan clay, obu clay, red clay) compared to those form China (black, white clay). Through X-ray diffraction analysis, kaolinite and Halloysite are found to be main phases for all the raw materials and second phases such as quartz and pyrophyllite are found. Using these clay materials, raw materials for porcelain products were produced, and the physicochemical properties were investigated for sintered samples. Absorption rate is in order of Baekja-A < Baekja-B < Yeonbuncheong < Jinbuncheong < Cheongja, and the sample, sintered at 1250℃ in reductive atmosphere, exhibits the lowest absorption rate. Comparing the color of the sintered samples, the samples sintered in oxidative atmosphere (L^* value: 86~95 %) show higher whiteness value than those sintered in reductive atmosphere (L^* value: 81~93 %). For the Cheongja and Buncheong, the samples sintered in reductive atmosphre shows higher whiteness, L^* values, and low a^*/b^* value, which is due to reduction of iron oxide (Fe₂O₃).

• Korean Journal of Food Science and Technology
• /
• v.50 no.2
• /
• pp.191-197
• /
• 2018

This study investigated the influence of starch extraction (ST-EX) solutions on the extraction yield and characteristics of Chinese yam (CY) starches from domestic Dioscorea batatas. Ascorbic acid (VitC), $Na_2S_2O_3$, $NaHCO_3$, and $Na_2CO_3$ were used as ST-EX solutions (0.4%, w/v). The extracted CY starches were examined for ST-EX yield, chemical composition, size distribution, X-ray diffraction, solubility, swelling power, gelatinization, and pasting viscosity. The highest ST-EX yield was obtained from $NaHCO_3$, followed by VitC. Lower protein content, relative crystallinity, and gelatinization enthalpy were found in CY starches from alkaline ST-EX solutions ($NaHCO_3$ and $Na_2CO_3$). Size distribution and gelatinization temperature did not generally differ for CY starches from the different ST-EX solutions. Pasting viscosities increased in the order from $Na_2CO_3$ > $Na_2S_2O_3$ > $NaHCO_3$ > VitC ST-EX solutions. Thus, VitC may be most appropriate to extract CY starch from Dioscorea rhizomes, considering its ST-EX yield, total starch content, and variation in pasting viscosity.

• Journal of Soil and Groundwater Environment
• /
• v.11 no.6
• /
• pp.35-42
• /
• 2006

Experimental study was conducted to identify the active agent for reductive dechlorination of TCE in cement/Fe(II) systems. Several potential materials-hematite (${\alpha}-Fe_2O_3$), lepidocrocite (${\gamma}$-FeOOH), akaganeite (${\beta}$-FeOOH), ettringite ($Ca_6Al_2(SO_4)_3(OH)_{12}$)-that are cement components or parts of cement hydrates were tested if they could act as reducing agents by conducting TCE degradation experiments. From the initial degradation experiments, hematite was selected as a potential active agent. The pseudo-first-order degradation rate constant ($k\;=\;0.637\;day^{-1}$) for the system containing 200 mM Fe(II), hematite and CaO was close to that ($k\;=\;0.645\;day^{-1}$) obtained from the system containing cement and 200 mM Fe(II). CaO, which was originally added to simulate pH of the cement/Fe(II) system, was found to play an important role in degradation reactions. The reactivity of the hematite/CaO/Fe(II) system initially increased with increase of CaO dosage. However, the tendency declined in the higher CaO dosage region, implying a saturation type of behavior. The SEM analysis revealed that the hexagonal plane-shaped crystals were formed during the reaction with increasing degradation efficiency, which was brought about by increasing the CaO dosage. It was suspected that the crystals could be portlandite or green rust ($SO_4$) or Friedel's salt. The XRD analysis of the same sample identified the peaks of hematite, magnetite/maghemite, green rust ($SO_4$). Either instrumental analysis predicted the presence of the green rust ($SO_4$). Therefore, the green rust ($SO_4$) would potentially be a reactive agent for reductive dechlorination in cement/Fe(II) systems.

• Journal of the Mineralogical Society of Korea
• /
• v.22 no.3
• /
• pp.241-248
• /
• 2009

Kaolinite was synthesized from amorphous $SiO_2$ and $Al(OH)_3{\cdot}xH_{2}O$ as starting materials by hydrothermal reaction conducted at $250^{\circ}C$ and $30\;kg/cm^2$. The acidity of the solution was adjusted at pH 2. The synthesized kaolinite was characterized by XRD, IR, NMR, FE-SEM, TEM and EDS to clarify the formational process according to the reaction time from 2 to 36 hours. X-ray diffraction patterns showed after 2 h of reaction time, the starting material amorphous $Al(OH)_3{\cdot}xH_{2}O$ transformed to boehmite (AlOOH) and after the reaction time 5 h, the peaks of boehmite were observed to be absent thereby indicating the crystal structure is partially destructed. Kaolinite formation was identified in the product obtained after 10 h of reaction and the peak intensity of kaolinite increased further with reaction time. The results of TGA and DTA revealed that the principal feature of kaolinite trace are well resolved. TGA results showed 13 wt% amount of weight loss and DTA analysis showed that exothermic peak of boehmite observed at $258^{\circ}C$ was decreased gradually and after 10 h of reaction time, it was disappeared. After 5 h of the reaction time, the exothermicpeak of transformation to spinel phase was observed and the peak intensiy increased with reaction time. The results of FT-IR suggested a highly ordered kaolinite was obtained after 36 hours of reaction. It was identified by the characteristic hydroxide group bands positioned at 3,696, 3670, 3653 and $3620\;cm^{-1}$. The development of the hydroxyl stretching between 3696 and $3620\;cm^{-1}$, depends on the degree of order and crystalline perfection. TEM results showed that after 15 h reaction time, curved platy kaolinite was observed as growing of (001) plane and after 36 h, the morphology of synthetic kaolinite exhibited platy crystal with partial polygonal outlines.