• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.2
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• pp.20-32
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• 1992

$Na_2O-CaO-MgO-Al_2O_3-SiO_2$ glass was taken as a basic glass and then $Li_2O$ O.5wt%, $K_2O$ 2.0wt% were substituted to $Na_2O$content, MgO 12.0wt %, ZnO 6.0wt % to CaO content. And also nucleation agent $ZrO_2 and $CaF_2$ were added to 1-2wt% respectively. The crystal according to the compositions appeared wollastonite, diopside and diopside.tremolite. The glasses substituted NazO by LizO was decreased thermal expansion coeffcient but substituted by ZnO was opposite direction and both of them increased bending strength. In the ratio of ZrOz to CaF, each 1: 1 and 1: 2 have shown considerable crystal growth at $1000^{circ}C~1050^{\circ}C$ and high bending strength, but the glass in the ratio 1: 2 have shown lowest thermal expansion coefficient. The activation energy was at the glass in the ratio of ZrO, to CaFz 1:2 evaluated 55.24kvsl/mol by Ozawa type and 53.05kal/mol by kissinger type.

• Journal of the Korean Society of Clothing and Textiles
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• v.6 no.1
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• pp.9-15
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• 1982

The influence of builders on calcium deposition on the fabric was studied by laundering the cotton fabric with sodium carbonate, sodium metasilicate, sodium tripolyphosphate and built detergents in hard water. The laundry variables were: 1) Washing cycles: 5, 10, 20, 30 and 40 cycles. 2) Water hardness: 100 ppm, 150 ppm, 200 ppm and 300 ppm. 3) Builders: $Na_2\;CO_3,\;Na_2\;SiO_3$ and STPP. 4) Detergents: Na-DBS, $Na-DBS+Na_2CO_3,\;Na-DBS+Na_2\;SiO_3,\;Na-DBS+STPP,\;Na-DBS+Na_2\;CO_3+STPP$, and $Na-DBS+Na_2\;SiO_3+STPP$. The fabric was washed for 15 minutes at 23+$1^{\circ}C$ in a washing machine(Gold Star WP 3007) under the similar condition with those of home laundering, and rinsed 3 times in the same water hardness for 5 minutes. The calcium deposits on the fabric was determined by EDTA-BACK titration methods. The results of this study were as follows: 1) The amount of calcium deposits on the fabric was increased with increasing wash cycles. This deposit was due to the build up of insoluble calcium carbonate. 2) As the water hardness increased, the amount of calcium deposits on the fabric was increased. 3) Alkaline builders, such as, $Na_2CO_3$ and $Na_2SiO_3$, promoted calcium deposition on the fabric, however STPP prevented calcium deposition on the fabric. 4) Fabric laundered with $Na-DBS+Na_2CO_3$ showed the highest calcium deposits on the fabric, and decreased with the order of $Na_2CO_3$, $Na-DBS+Na_2SiO_3$, and Na-DBS. And fabrics washed with phosphate-built detergents showed a small amount of calcium deposition.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.270-273
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• 2012

x mol% (x = 0 ~ 20) Na2CO3 excess Bi2.5Na3.5Nb5O18 (BNN) particles were synthesized using molten salt as a flux. The secondary phases were observed at stoichiometric ratio of BNN precursors and their intensity decreased with increasing Na contents. The results of SEM images showed that all particles existed in a platelet shape and the particle increased in size with higher increasing Na contents. Plate-like NaNbO3 particles were developed using BNN precursor obtained by a topochemical microcrystal conversion. XRD analysis of NaNbO3 particles showed that a single perovskite phase and the intensity of (h00) peaks increased with increasing Na contents in BNN precursor. SEM images showed that the size of plate-like NaNbO3 was significantly changed by controlling Na contents in BNN precursors.

• Corrosion Science and Technology
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• v.11 no.2
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• pp.65-69
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• 2012

One dimensional(1D) $Na_2Ti_6O_{13}$ nanorods with 70 nm in diameter was synthesized by a molten salt method. Using the synthesized nanorods, about 750 nm thick $Na_2Ti_6O_{13}$ film was coated on Fluorine-doped tin oxide(FTO) glasss substrate by the Layer-by-layer self-assembly(LBL-SA) method in which a repetitive self-assembling of ions containing an opposite electric charge in an aqueous solution was utilized. Using the Kubelka-Munk function, the band gap energy of the 1D-$Na_2Ti_6O_{13}$ nanorods was nalyzed to be 3.5 eV. On the other hand, the band gap energy of the $Na_2Ti_6O_{13}$ film coated on FTO was found to be a reduced value of 2.9 eV, resulting from the nano-scale and high porosity of the film processed by LBL-SA method, which was favorable for the photo absorption capability. A significant improvement of photocurrent and onset voltage was observed with the $Na_2Ti_6O_{13}$ film incorporated into the conventional $Fe_2O_3$ photoelectrode: the photocurrent increased from 0.25 to 0.82 mA/$cm^2$, the onset voltage decreased from 0.95 to 0.78 V.

• Journal of the Korean Ceramic Society
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• v.18 no.1
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• pp.27-34
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• 1981

The phase separation of low-alkali borosilicate glass with the composition of $6.25Na_2O$.$18.75B_2O_3$.$75.00SiO_2$(mole%) substituting $Li_2O$ for $Na_2O$ was studied. The phase separation in the temperature range of transformation was examined with various heating temperatures and soaking times. Durability to water, thermal expansion and specific density of the specimen were investigated and the microstructure of the separated phase was also observed by transmission electron micrograph techniques. The maximum alkali extraction result with the best phase separation effect was obtained when $Na_2O$ of the base glass was replaced with $1.88Li_2O$ (mole %) and electron micrograph of carbon film replica of $1.88Li_2O$$4.37Na_2O$.$18.75B_2O_3$.$75.00SiO_2$ (mole %) glass showed that the glass consisted of homogeneous two phases. The minimum specific density was shown with the specimen treated at 57$0^{\circ}C$ and it was also shown that the longer the treating time the lower the specific density. The apparent activation energies of approximately 45 kcal/mole by the alkali extraction and 43kcal/mole by the thermal expansion method were derived from the Arrhenius plots, respectively.

• Journal of the Korean Ceramic Society
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• v.24 no.1
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• pp.9-16
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• 1987

Physical and electrical properties of ${\beta}$-Al2O3 were investigated as function of Na2O content from 6.67 wt.% to 13.19 wt.%. The majority phase is ${\beta}$-Al2O3 and the small amount of ${\beta}$"-Al2O3 exists in the specimens sintered at 1600$^{\circ}$for 30 mins. In the case of specimens with 8.54 wt.% Na2O sintered at 1600$^{\circ}C$, the relative amount of ${\beta}$-Al2O3 phase increases and that of ${\beta}$"-Al2O3 phase decreases with increasing sintering time, and then ${\beta}$"-Al2O3 phase does not exist if sintering time is over 8 hrs. As the Na2O content is increased, the 3-Point MOR and the resistivity are decreased. However, density and 3-Point MOR with increasing sintering time are decreased due to increasing the enclosed pore trapped inside of the exaggerated grains. As the sintering time is increased, the average grain size and the duplexity of microstructure are increased, and the resistivity is slightly decreased.

• Journal of Sensor Science and Technology
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• v.32 no.4
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• pp.238-245
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• 2023

0.75(Bi_1/2Na_1/2)TiO₃-0.25SrTiO₃ (BNT-25ST) ceramics with high densities were successfully prepared at a sintering temperature of 1,000℃ by adding a mixture of 1 mol% CuO and 0.5 mol% Na₂CO₃ or 0.5 mol% CuO and 0.25 mol% Na₂CO₃. Double polarization-electric field (P-E) hysteresis curves and sprout-shaped bipolar strain-electric field (S-E) hysteresis curves with small negative strains were observed in the pristine and CuO-added BNT-25ST ceramics whereas the Na₂CO₃-added sample showed similar P-E and S-E curves to a typical ferroelectric. The pristine BNT-25ST ceramics showed an extremely large strain and a large-signal piezoelectric strain constant (d₃₃^*): 0.287 % at 80 kV/cm and 850 pm/V at 20 kV/cm. Similar values, 0.248 % at 80 kV/cm and 655 pm/V at 20 kV/cm, were obtained in the CuO-added sample. However, the pristine and CuO-added samples showed large hysteresis in unipolar S-E curves at an electric field of less than 20 kV/cm. The Na₂CO₃-added sample showed smaller values of the strain and d₃₃^* but displayed a linear change and small hysteresis in the unipolar S-E curve. The co-added sample with CuO and Na₂CO₃ displayed intermediate P-E and S-E hysteresis curves.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.77-77
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• 2009

$Pb(Zr,Ti_O_3$계 세라믹스는 우수한 압전 특성으로 인하여 압전변압기 및 액츄에이터, 센서 등 많은 분야에 응용이 되어져 왔다. 그러나, 최근 들어 $1000^{\circ}C$에서 급속도로 많은 휘발을 하는 PbO는 환경 및 인체에 나쁜 영향을 미칠 뿐 아니라 사용 후의 처리도 어려워 선진국에서는 사용을 제한하거나 줄이고 있는 추세에 있다. 따라서, PbO를 포함하지 않은 무연 (Lead-free)계 압전 세라믹스에 대한 연구가 많은 관심을 끌고 있으며 앞으로는E 장래성 있는 하나의 이슈 분야가 될 것이다. 이러한 Pb-based System 세라믹스를 대체 할 재료로서 $(Bi_{1/2}Na_{1/2})TiO_3$나 Tungsten-Bronze type, $(K_{1/2}Na_{1/2})NbO_3$ 등이 주로 연구가 되고 있다. 특히, alkali niobate를 기초로 한 $(K_{1/2}Na_{1/2})NbO_3(NKN)$은 무연 압전 물질로서 많은 주목을 받고 있다. 그러나, NKN의 주요 성분인 K 의 높은 조해성 때문에 일반적인 고상방법으로는 고 밀도의 세라믹을 얻기 힘들뿐더러 낮은 상전이 온도 때문에 많은 응용에는 제약이 되고 있다. 이러한 세라믹의 단점을 보완하고자 Hot forging, RTGG, SPS 등 과 같이 특수한 소결방법을 사용하여 고밀도의 세라믹을 제작하지만 이 방법들은 제품 대량 생산에 있어 경제적으로나 복잡한 제조과정을 고려할 때 매우 비효율적이라고 판단된다. 그러므로 $BaTiO_3$, $LiTaO_3$, Mg, Ca등을 첨가 시켜 소결을 향상시키고 고밀도를 얻기 위해 많은 연구가 진행 중이다. 따라서 본 연구에서는 Pb-based계의 세라믹스를 대체할 우수한 특성의 세라믹스를 제작하고자 기존의 $(K_{1/2}Na_{1/2})NbO_3(NKN)$세라믹스에서 낮은 용융온도 때문에 소결하기 어려운 $KNbO_3$를 제거한 $NaNbO_3$에 $LiNbO_3$와 $BaTiO_3$를 추가한 $NaLiNbO_3-BaTiO_3$세라믹스에 $K_4CuNb_8O_{23}$(KCN)을 첨가함으로서 이에 따른 압전 및 유전 특성을 조사하였다.

• Korean Journal of Crystallography
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• v.13 no.1
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• pp.25-30
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• 2002

The M/sub 1-x/Na/sub 2x/Al₂(BO₃)₂O (M = Ca and Sr) solid solution systems have been shown interstitial solid solutions and continuous substitutional solid solutions. The symmetry around the Eu site of yEu/sup 3+/ : M/sub 1-x/Na/sub 2x/Al/sub 2-y/Mg/sub /(BO₃)₂O (M = Ca and Sr) changes the intensities and the chromaticities of transitions. The Eu/sup 3+/ion can be very bright and efficient and have the desired emission wave-length depending on the site symmetry of the Eu/sup 3+/ion site. As the amount of Na in the Eu/sup 3+/ion doped Ca/sub 1-x/Na/sub 2x/Al₂(BO₃)₂O system increases, the Eu site symmetry is going to be a noncentrosymmetric site. With increasing x, the decreased intensity in the /sup 5/D/sub 0/→/sup 7/F₁(590 nm) transition relates to the low symmetry of the Eus/up 3+/-doped Ca/sub 1-x/Na/sub 2x/Al₂(BO₃)₂O system, because of the Ca-centered octahedron in the CaAl₂(BO₃)₂O compound. The SrAl₂(BO₃)₂O compound also provides an improved chromaticity due to the lower site symmetry of Eu/sup 3+/ion.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.1-3
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• 2006

Well-shaped NaA zeolite cubic crystals of a large size of $5-7{\mu}m$ were synthesized by a hydrothermal method in a mother solution having a $3.55Na_2O:Al_2O_3:1.6SiO_2:593\~2000H_2O$ composition. Thermal treatment of NaA zeolite crystals resulted in the formation of a crystalline phase of $NaAlSiO_4-Camegeite$ between 800 and $900^{\circ}C$. Even at $1000^{\circ}C,\;NaAlSiO_4$ phase was found as a major product. Environmental Scanning Electron Microscopy (ESEM), High Resolution Transmission Electron Microscopy (HRTEM), X-Ray powder Diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, and DTA/TGA and BET analyses were used to characterize the initial materials and the obtained products after various heat treatments.