• Economic and Environmental Geology
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• v.27 no.3
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• pp.237-246
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• 1994

Tin mineralizations in South Korea have been found only in the Ulchin and Sangdong areas. They appear to be in close spatial association with the Wangpiri granitoid in the UlChin area, and the Nonggeori and Naedeogri granites in the Sangdong area. However, previous works have revealed that there are considerable differences in geological setting, mineralogical and geochemical compositions among these granitoids concerned. The roles of discriminant and multiple regression analysis have been examed to establish geochemical differences among the tin-granitoids and to identify elements relating to tin mineralizations. The data set used in this study consists of 60 observations with 29 elements which are cited from pre-existing publications. A stepwise discriminant analysis determined the group of variables that differentiate between samples from four training sets; Buncheon, Wangpiri, Nonggeori and Naedeogri granitoids. These granitoids were most effectively discriminated on the basis of major elements FeO, CaO and $P_2O_5$ and also by the trace elements Rb and Zr. Results of the multiple regression analysis shows that the level of Sn in granitoids depends positively on ones of MnO, Rb and FeO and negatively $P_2O_5$. Graphical representation of discriminant scores on sampling locations greatly aid recognition of differences in the geochemical characteristics in terms of spatial distribution of granitoids examed. The application of the discriminant analysis provides a potential means of identifying and comparing geochemical characteristics.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.1
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• pp.21-24
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• 2002

The electrode materials for welding machine in automobile industry such as Cu-Cr, Cu-Zr and Cu-$Al_2O_3$ require the high electrical conductivity and the proper hardness. Therefore the effects of solution heat treatment and aging treatment on the electrical conductivity and hardness of Cu-0.8wt%Cr and Cu-1.2wt%Cr alloys have been investigated. Cu-0.8wt%Cr alloy showed the higher electrical conductivity and hardness than Cu-1.2wt%Cr alloy and both alloys showed the better electrical conductivity at $930^{\circ}C$ among 930, 980 and $1030^{\circ}C$ solution heat treatment temperatures. The electrical conductivity and hardness in both alloys were not affected by aging treatment but remarkably affected by solution heat treatment temperature. The final drawing process reduced electrical conductivity and increased hardness more in Cu-1.2wt%Cr alloy.

• Transactions on Electrical and Electronic Materials
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• v.6 no.2
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• pp.35-38
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• 2005

Pb(Zr$_{0.8}$Ti$_{0.2}$)O$_{3}$ powders, prepared by the sol-gel method, were mixed with an organic vehicle and the PZT thick films were fabricated by the screen-printing techniques on Pt/Ah03 substrates. The structural properties were examined as a function of sintering temperature. The particle size distribution of the PZT powder derived from the sol-gel process is uniform with the mean particle size of about 2.6 m. As a result of the DTA, the formation of the polycrystalline perovskite phase was observed at around $890^{circ}$CC. In the X-ray diffraction analysis, all PZT thick films showed a perovskite polycrystalline structure without a pyrochlore phase. The perovskite crystallization temperature of PZT thick films was about $890^{circ}$C. The average thickness of the PZT thick films was approximately 80-90 m.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.575-581
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• 1995

Zr0.94Y0.06O1.97 powder was synthesized by the ultrasonic spray pyrolysis with various concentrations of starting solution and the influence of powder characteristics on sintering behavior was investigated. Powders prepared at 75$0^{\circ}C$ were characterized as narrowly distributed submicron spherical particles, which were crystalline, nonagglomerated, and compositionally homogeneous. The changes in concentration from 0.01 to 01. mol/ι increased mean particle size from 0.24 to 0.38${\mu}{\textrm}{m}$ and decreased the specific surface area from 14.2 to 2.9$m^2$/g. The relative density of the specimen from the powders, prepared with the solution concentration of 0.01 mol/ι, was 98% after sintering for 2 hr at 1,45$0^{\circ}C$ and the monoclinic phase was observed after sintering at 1,55$0^{\circ}C$. As the concentration of starting solution was increased, the formation temperature of monoclinic phase was lowered.

• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.707-712
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• 1990

The basic zirconium sulfate was prepared from ZrOCl2.8H2O and H2SO4 in the 9$0^{\circ}C$ aqueous solution. The pH and amount of unreacted zirconium in the solution that reacton had completed was 0.2 and 10%. As the pH was increased to 1.4 by NH4OH theresulting precipitates were the mixtures of the basic zirconium sulfate and the zirconium hydroxide although the precipitates were recovered completely. The thermal decomposition behavior of this sample has been examined by thermal analysis(TG-DTA), X-ray diffraction study, infrared spectroscopy and sulfur analysis. As a result, it was found that the precipitates have perfectly been decomposed at 85$0^{\circ}C$ accompanying to the release of a molecule of water below 25$0^{\circ}C$ and 85% sulfate at about $600^{\circ}C$. The thermally decomlposed products were initially amorphous phase, which were become metastable tetragonal phase with increment of temperature and finally transformed to the stable monoclinic phase at 100$0^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.229-233
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• 2000

In this study, the temperature coefficient of resonant frequency($TCF_r$), dielectric and piezoelectric properties of $Pb_{1-x}Sr_x[(Sb_{1/2}Nb_{1/2})_{0.035}(Mn_{1/3}Nb_{2/3})_{0.065}(Zr_{0.49},Ti_{0.51})_{0.90}]O_3$ ceramics were investigated with the Sr substitution to Pb site. The dielectric constant was increased according to the increase of Sr substitution and electromechanical coupling factor($k_t$) also showed the highest values of 0.485 when the Sr substitution was 5 mol%. Moreover, the mechanical quality factor($Q_{mt}$) showed the highest value of 233 when the Sr substitution was 2 mol%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.325-326
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• 2006

In this study, in order to develop piezoelectric device for multilayer piezoelectric ultrasonic motor, low temperature sintering $Pb(Mn_{1/3}Nb_{2/3})_{0.02}(Ni_{1/3}Nb_{2/3})_{0.12}(Zr_{0.48}Ti_{0.52})_{0.86}O_3$ system ceramics were fabricated according to the variations of forming pressure of casting sheet. At the 300[$kgf/cm^2$] forming pressure, the maximum density of 7.8[$g/cm^3$] was obtained. At the 350[$kgf/cm^2$] forming pressure, the maximum values of effective electromechanical coupling factor $k_{cff}\;=\;0.24$ and mechanical quality factor Qm=628 were obtained.

• Clean Technology
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• v.19 no.3
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• pp.264-271
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• 2013

In this study, we optimized the removal condition of contaminants attached on the scrap surface to recycle the scrap generated from the Zr alloy tube manufacturing process back to the nuclear grade. The main contaminant is remnant of watersoluble cooling lubricant that is used in the pilgering manufacture during the tube production, and it is assumed to be compressed and carbonized on the surface of tube. Zirlo alloy tube of ${\phi}9.50mm$, which has high occurrence frequency of scrap, was selected as the object to be cleaned, and cleaning abilities of reagents were evaluated by measuring the characteristics of contaminants remained and by analyzing the surface of the tube after cleaning process. For evaluation of each cleaning agent, we selected two types of sodium hydroxide series and three types of potassium hydroxide series. Furthermore, to confirm dependence on tempe-rature and ultrasonic intensities, cleaning at the room temperature, $40^{\circ}C$, and $60^{\circ}C$ was conducted, and results showed that higher the cleaning temperature and higher the ultrasonic intensity, better the cleaning effect. As a result of the bare-eye inspection, while the use of sodium hydroxide provided satisfactory condition on the tube surface, the use of potassium hydroxide series provided satisfactory condition on the tube surface only when the ultrasonic intensity was over 120 W. In the cleaning effect analysis using the gravimetric method, cleaning efficiency of sodium hydroxide series was as high as 97.6% ($60^{\circ}C$, 120 W), but since the tube surface condition was poor after the use of potassium hydroxide, the gravimetric method was not appropriate. In the analytical result of surface contaminants on the tube surface, C, O, Ca, and Zr were detected, and mainly C and O dominated the proportion of contaminants. It was also found that the degree of cleaning on the tube affected the componential ratio of C and O; if the degree of cleaning is high, or if cleaning is well-conducted, the proportion of C is decreased, and the proportion of O is increased. Based on these results, optimal cleaning for application in the industry can be expected by categorizing cleaning process into three steps of Alkali cleaning, Rinsing, and Drying and by adjusting cleaning parameters in each step.

• Ocean and Polar Research
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• v.26 no.2
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• pp.231-243
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• 2004

Sequential extraction was carried out on twenty two subsamples of three ferromanganese crusts from three seamounts (Lemkein, Lomilik, and Litakpooki) near the Marshall Islands in the western Pacific. The extraction was designed to fractionate Fe-Mn crust forming elements into low defined groups: (1) exchangeable and carbornate, (2) Mn-oxide, (3) Fe-oxyhyd.oxide, and (4) residual fraction. X-ray diffraction result shows that target material were well removed by each extraction step except for CFA in phosphatized crusts generation. According to chemical analysis of each leachate, most of elements in the Fe-Mn crusts are bound with two major phases. Mn, Ba, Co, Ni, Zn, (Fe, Sr, Cu, and V) are strongly bounded with Mn-oxide $({\delta}-MnO_2)$ phase, whereas Fe, Ti, Zr, Mo, Pb, Al, Cu,(V, P, and Zn) show chemical affinity with Fe-oxyhydroxide phase. This result indicates that significant amount of Al, Ti, and Zr can not be explained by detrital origin. Ca, Mg, K, and Sr mainly occur as exchangeable elements and/or carbonate phase. Outermost layer 1 and inner layer 2 which are both young crusts generations are similar in chemical speciations of elements. However, some of Fe-oxyhydroxide bounded elements (Pb, Y, Mo, Ba, Al, and V) in phosphatized innermost layer 3 are released during phosphatization and incorporated into phosphate (Pb, Y, Mo, and Ba) or Mn-oxide phase (Al and V). Our sequential extraction results reveal that chemical speciations of elements in the hydrogenetic crusts are more or less different from interelemental relationship calculated by statistical method based on bulk chemistry.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.605-612
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• 1990

In Pb1-xLax(Zry, Tiz)1-x/4O3 system, it selects the composition 7/65/35 (x=7, y=65, z=35) that was reported to have eminent Pyroelectric properties, and that is sintered with PbZrO3＋0.3wt.% PbO2 atmosphere powder. From the sintered ceramic and Poly Vinyl Alcohol, the thin wafers are fabricated with 0-3connectivity, and they are researched in Pyroelectric properties and the others according to volume ratio between ceramic and polymer. It was possible to fabricate the film containing ceramic up to 80vol% in PVA polymer. The increment of PLZT ceramic volume fraction improve the pyroelectric coefficient of the composite. On Pyroelectric coefficient and the figure of merit, a little inflection caused by glass point(Tg) of PVA appeared. The degree of inflection is proportioned to the amount of PVA.