• Journal of the Korean Ceramic Society
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• v.14 no.4
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• pp.230-235
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• 1977

In this paper the conditions of surface crystallization of glass were studied. The basic glass which is apt to crystallize, with $SiO_2$ 72.50, $Al_2O_3$ 5, 00, $Na_2O$ 8.00 $K_2O$ 3.50, CaO 5.00, MgO 3.00, $B_2O_3$ 3.00 Wt% is chosen. The strain point and softening point of this glass is 4$25^{\circ}C$ and 778$^{\circ}C$ each, and between the two temperatures we could get grystal on its surface by immersion in salt baths during some controlled hours. The kind of crystal on the surface of glass was confirmed by X-ray diffraction analysis and the change of the thickness of crystalline layers depending on temperature and time, was surveyed by using optical microscope. The results are as follows; 1. The chloride group is more suitable than sulfate group for the treating salt. 2. In the condition with 50 LiCl.50NaCl at 62$0^{\circ}C$ for 2 hrs and with 50 LiCL.20-30 NaCl.30-20 $CaCl_2$ at 72$0^{\circ}C$ for 15-20 min. we could get the best crystalline layers. 3. The crystal was silica-O and petalite with a little tridymite and nepheline. 4. The thickness of crystalline layers increased with increasement of temperature and time.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.406-412
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• 1994

The ion-exchange properties of $Ca^{2+}$ and $Mg^{2+}$ ions have been studied in ${\delta}-Na_2Si_2O_5$ synthesized from water glass. Results show that optimum temperature for synthesis of ${\delta}-Na_2Si_2O_5$ was $725^{\circ}C$. Ion-exchange isotherms for $Ca^{2+}$ and $Mg^{2+}$ exchange for $Na^+$ in the synthetic ${\delta}-Na_2Si_2O_5$ show that the ion-exchange capacity of magnesium is better than that of calcium, and the ion-exchange of magnesium is less sensitive for temperature than that of calcium. When initial pH of solution is increased between 2 and 6, the ion-exchange capacities of magnesium and calcium decrease a little. However, they are almost constant above pH 6 because of alkali buffer effect of ${\delta}-Na_2Si_2O_5$. In the thermodynamic studies, it was found that Gibbs free energies of reaction of calcium ion-exchange are larger than those of magnesium ion-exchange with inverse order of selectivity. The standard enthalpy and entropy of reaction of calcium ion-exchange are larger than those of magnesium ion-exchange.

• Cement
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• s.51
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• pp.20-30
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• 1973

1) electron-microprobe를 응용하여 $CaO-SiO_2-Al_2O_3$ 계에서 생성한 $C_2S$, $C_3S$ 에 존재하는 sulfate의 solid, solution을 정량적으로 구할 수 있었으며 이 결과로 $C_2S$ 에 $Al_2O_3$, $SO_3$ 등이 solid soln 등으로 침적되고 이들이 $C_3S$의 생성을 억제한다는 mechanism이 확인되었다. 2) phase equilibrium(상평형)에 의하면 $Na_2SO_4$, $K_2SO_4$는 mineralizer로서 작용하며 $C_3S$ 의 생성을 돕는다. 그러나 $K_2SO_4$ 와 $Al_2SO_3$ 가 결합상태로 존재할 경우는 1,400 $^{\circ}C$에서 광범위한 liquid를 생성하며 quenching하면 glass질과 $\beta-C_2S$ 만이 얻어지고 $C_3S$ 는 생성되지 않는다. 또 이를 1,250 $^{\circ}C$ 까지 서냉하면 $C_2S$ 와 Ca, K, Al, S, 등을 함유한 새로운 물질이 생성된다. 3) $CaO-SiO_2-Al_2O_3-Fe_2O_3$ 계에서 $C_3S$ 의 생성에 미치는 $Na_2SO_4$, $K_2SO_4$ 의 영향을 실험실적으로 검토한 결과 complex interaction이 확인되었으며 $Na_2SO_4$ 는 어떤 경우에는 mineralizing effect를 상실한다는 재미 있는 사실이 발견되었다.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.35-41
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• 1999

In this study we investigated the effects of process variables on the bond strength, and its dependency upon the interfacial chemistry when the joined $ZrO_2$ toughened $Na\beta$"-alumina to $\alpha$-alumina using B$_2$$O_3$-$SiO_2$-Al$_2$$O_3$-CaO glass sealant. We observed that bond strength is mainly determined by the strength of the glass, which, in turn, depends on the glass composition established after joining reaction. Joining at $950^{\circ}C$ for 15min yielded the highest average bond strength of 66MPa. Different types of interfacial reaction seem to occur at each interface. After joining at $950^{\circ}C$ for 15min we found that Ca and Si diffuse much deeper(~15$\mu\textrm{m}$) into the $\beta$"-alumina composite than into the $\alpha$-alumina(<1$\mu\textrm{m}$) as a result of ion exchange reaction and more effective grain boundary diffusion. Thermal expansion coefficient of the glass was found to have changed more closely to those of the $\beta$"-alumina composite and $\alpha$-alumina, which put the glass under a slight compressive stress.ressive stress.

• Economic and Environmental Geology
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• v.36 no.3
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• pp.225-232
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• 2003

Three piston cores. obtained from the northwestern Ulleung Basin of the East Sea, are analyzed to study the tephrostratigraphy of the late Quaternary core sediments and to reveal the comparative characteristics of the tephra layers. The cores consist mainly of the muddy sediments that are partly interbedded with lapilli tephra and ash layers. The muds are further divided into hemipelagic and turbiditic mud facies. The hemipelagic facies is dominated by bioturbated mud and crudely laminated mud, whereas the turbiditic facies includes mainly thinly laminated mud and homogeneous mud, and often alternates with non-turbiditic muds. According to microscopic observation and EDX analysis, three tephra layers of the Ulleung-Oki (U-Oki; ca. 9.3 ka), Aira-Tanzawa (AT: ca. 22~24.7 ka) and Ulleung-Yamato (U-Ym; ca. 25~33 ka) are identified in the study cores. Among these, the U-Oki and U-Ym layers, originating from the Ulleung Island, consist mainly of massive-type glass shards with alkali feldspar. Both of the tephra layers contain a lower content of SiO$_2$ (57~66.5 wt.%) and a higher content of Na$_2$O+K$_2$O (11~16 wt.%) than the AT layer (SiO$_2$=75~78.5 wt.%, Na$_2$O+K$_2$O=6.5~9 wt.%) that consists of typical plane-type and/or bubble-wall glass grains. Compared with that of the U-Ym layer, a sedimentary facies of the U-Oki layer is very thick and contains three stratigraphic units, probably due to relatively large and different supplies of pyroclastic sediments. Thus, the eruption of Ulleung Volcano (ca. 7,300 B.C.) is thought to have had a more powerful effect on depositional environment than the U-Ym eruption.

• Korean Journal of Heritage: History & Science
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• v.41 no.1
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• pp.5-19
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• 2008

Thirty six samples of Western asia glass vessel shards which were excavated from South Mound of Hwangnamdaechong were each measured for thickness, pore size and specific gravity and analyzed for ten major compositions and thirteen trace elements. The glass samples with colorless, greenish blue and dark purple blue were well classified by principal component analysis(PCA). All glass shards of Hwangnamdaechong belonged to Soda glass system ($Na_2O-CaO-SiO_2$) which have the range of 14~17% $Na_2O$ and 5~6% CaO. The corelation coefficients of (MgO, $K_2O$) and (MnO, CuO) showed above 0.90. The concentrations of thirteen trace elements apparently differentiated from colorless, greenish blue and dark blue glasses. We found that thirteen trace elements were very important indices for studying raw material of glass and the origin of glass making. Colorless glass : The specific gravity is $1.50{\pm}0.04$. Circle or oval circle pores are observed with regular direction in internal zone and the longest one is about 0.35 mm. The raw material of sodium must be the plant ash because sodium glasses contain HCLA(High CaO, Low $Al_2O_3$) and HMK(high MgO, high $K_2O$) and suggested to Sasanian glass. The total amount of coloring agent of colorless glass is below 1 % which is too small to attribute to the color. Greenish blue glass : The specific gravity is $1.58{\pm}0.04$. The fine pores which are 0.1~0.2mm are dispersed in internal zone. Sodium glasses are distributed to HCLA and HMK. Therefore the greenish blue glass also have used plant ash for raw material of sodium with the same as colorless glass. It was also suggested to the glass of Sasanian. The total amount of coloring agent of greenish blue glass is about 4% under the influence of working MnO, $Fe_2O_3$ and CuO. Dark purple blue glass : The specific gravity is $1.48{\pm}0.19$. There are rarely pores in internal zone. They are distributed to HCLA and LMK(Low MgO, Low $K_2O$) and suggested to Roman glass. The raw material of sodium is estimated to natron. The total amount of coloring agents of greenish blue is about 3% by $Fe_2O_3$ and CuO. These studies for western asia glass shards from South Mound of Hwangnamdaechong could be used in the future as the standard data which could be compared with those of other several graves in Korea and dispersed in foreign areas.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.187-192
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• 2000

We prepared $SiO_2-Na_2O-R_mO_n$ thin films based on economics of water glass and investigated optical, mechanical properties of product thin films. Coating sol stabilized with 1 N HCl and 1 N $NH_4OH$, was fabricated by using water glass and calcium nitrate, and aluminum nitrate as starting materials. As-coated films on stainless steel, Si wafer and soda-lime-silica glass by spinning were finally annealed at 500, 750 and $900^{\circ}C$. Micro hardness and nitrogen content in film surface of annealed films were measured by Knoop hardness tester and EDX, respectively. Field Emission Scanning Electron Microscope (FE-SEM) and UV-VIS spectroscopy were adopted to analyze surface morphology and thickness and reflectance of our films.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.200-207
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• 2011

Abstract: The effect of lead free glass frit compositions on the properties of thick film conductor and resistor pastes were investigated. Two types lead free frits, HBF-A(without $Bi_2O_3$) and HBF-B(with $Bi_2O_3$) were made from $SiO_2$, $B_2O_3$, $Al_2O_3$, CaO, MgO, $Na_2O$, $K_2O$, ZnO, MnO, $ZrO_2$, $Bi_2O_3$. And Ag based conductor pastes and $RuO_2$ based resistor paste were prepared by mixed with these frits and functional phase(Ag and $RuO_2$), and organic vehicle. The properties of thick film conductor and resistor sintered at $850^{\circ}C$ were studied after printing on $Al_2O_3$ substrate. The morphology of the sintered films surface were SEM and EDS were carried out to analysis the chemical composition on resistor surface and state of Ru atom in frit matrix.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.436-442
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• 1997

The bimodal distribution of CuCl nano-crystals precipitated in alumino-borosilicate glass matrix (30SiO2-45B2O3-7.5Al2O3-7.5Na2O-7.5CaO-2.5GeO2(mole %)) was investigated by TEM and the temperature dependent optical spectroscopy. Two types of CuCl particles with different size were observed by TEM and it was confirmed by the splitting of Z3 absorption peak at low temperature and the occurrence of deflection point in the optical spectra with temperature.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.335-335
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• 2010

$SiO_2$, $B_2O_3$, $Al_2O_3$, CaO, MgO, $Na_2O$, $ZrO_2$, $Bi_2O_3$를 이용하여 성질이 다른 두 종류의 무연계 프릿트를 제조하여 특성을 표준화 하였고, 이들 무연계 프릿트를 이용하여 Ag계 도체 및 $RuO_2$계 저항페이스트롤 제조하여 특성에 미치는 프릿트 조성의 영향을 연구하였다. $B_2O_3$를 첨가하여 퍼짐특성이 큰 프릿트의 경우 더 우수한 페이스트 특성을 나타내었다.