• Journal of the Korean Vacuum Society
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• v.7 no.4
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• pp.403-409
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• 1998

In this study, the effects of multi-dipole type of magnets on the characteristics of the inductively coupled plasmas and $SiO_2$ etch properties were investigated. As the magnets, 4 pairs of permanent magnets were used and, to etch $SiO_2, C_2F_6, CHF_3, C_4F_8, H_2$, and their combinations were used. The characteristics of the magnetized inductively coupled plasmas were investigated using a Langmuir probe and an optical emission spectrometer, and $SiO_2$ etch rates and the etch selectivity over photoresist were measured using a stylus profilometer. The use of multi-dipole magnets increased the uniformity of the ion density over the substrate location even though no significant increase of ion density was observed with the magnets. The use of the magnets also increased the electron temperature and radical densities while reducing the plasma potential. When $SiO_2$ was etched using the fluorocarbon gases, the significant increase of $SiO_2$ etch rates and also the increase of etch uniformity over the substrate were obtained using the magnets. In case of gas combinations with hydrogen, $C_4F_8/H_2$ showed the highest etch rates and etch selectivities over photoresist among the gas combinations with hydrogen used in the experiment. By optimizing process parameters at 1000 Watts of inductive power with the magnets, the highest $SiO_2$ etch rate of 8000 $\AA$/min could be obtained for 50% $C_4F_8/50% H_2$.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.364-371
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• 2013

The sintering behavior of monolithic SiC is examined using the binary sintering additive of $Al_2O_3$-rare earth oxide ($RE_2O_3$, where RE = Sc, Nd, Dy, Ho, or Yb). Through hot pressing at 20 MPa and $1750^{\circ}C$ for 1 h in an Ar atmosphere for 52 nm fine ${\beta}$-SiC powder added with 5 wt% sintering additive, a SiC density of > 97% is achieved, which indicates the effectiveness of $Al_2O_3-RE_2O_3$ system as a sintering of additive for SiC. Based on this result, 7 wt% of $Al_2O_3-Sc_2O_3$ is tested as an additive system for the fabrication of a continuous SiC fiber-reinforced SiC-matrix composite ($SiC_f$/SiC). Electrophoretic deposition combined with the application of ultrasonic pulses is used to efficiently infiltrate the matrix phase into the voids of $Tyranno^{TM}$-SA3 fabric. After hot pressing, a composite density of > 97% is obtained, along with a maximum flexural strength of 443 MPa.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.190-195
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• 2009

Na-tetrasilicic fluorine mica powders were synthesized by skull melting method. The staring materials having chemical composition of $Mg_3(OH)_2Si_4O_{10}:Na_2SiF_6:SiO_2=8.3:24.8:66.9$ mol% were charged into a cold crucible of 13 cm in diameter and 14cm in height and heated by R.F. generator at working frequency of 2.84 MHz. The materials were maintained for 1hr as a molten state and cooled down in the container. In this study, the specific electric resistance of mica was estimated and the columnar and plate shaped mica were synthesized.

• Journal of the Korean Chemical Society
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• v.43 no.1
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• pp.52-57
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• 1999

The anionic complexes, [ln($C_6F_5)_4$]-, which are thermal and moisture sensitive, have been prepared by the reaction of In($C_6F_5)_3{\cdot}D(D=CH_3CN$, O($C_2H_5)_2$) with the system ($CH_3)_3SiC_6F_5$/CsF, $C_6F_5$MgBr or Cd($C_6F_5)_2$. The stable anionic indium(III) complexes are obtained through cation exchange with PNPCI ([PNP]= bis(triphenylphosphino)ammonium). The pure substance is obtained by column chromatography. These new anionic complexes are unambiguously identifed by NMR-spectroscopy, IR spectroscopy, molecular weight, DTA/TG and elemental analysis.

• Journal of the Korean Vacuum Society
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• v.6 no.1
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• pp.91-96
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• 1997

The electrical characteristics and the plasma parameters of planar inductively coupled plasmas (ICP) have been measured. The resistance of the total load including the coil and the plasma varied from 1 to 4 W and the inductance from 1.5 m to 2 mH when the power was changed from 100 to 1000 W and the pressure from 1 to 10 mTorr. The density of electron measured by Langmuir probe was over $10^{11}/\textrm{cm}^3$ and the temperature varied between 3 and 5 eV as the process conditions were changed. Bias modulation was adopted as a new method to improve the selectivity of $SiO_2$on Si in $C_4F_8$ (octafluorocyclobutane) plasma. The selectivity was improved as the duty ratio decreased, but the etch rate of $SiO_2$decreased below 400$\AA$/min. $H_2$addition to $C_4F_8$ plasma showed that the etch selectivity could be higher than 50 and the etch rate of $SiO_2$over 2000$\AA$/min when 60% $H_2$was added.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.178-183
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• 2002

Zinc fluosilicate ($ZnSiF_6$, 15% aqueous solution) was prepared using zinc oxide (ZnO) and fluosilicic acid ($H_2SiF_6$) by soluiton synthetic method. The fluidity and hydration properties of cement which was added $ZnSiF_6$ (aq.) as an additive for cement were studied. At water to cement ratio (W/C) equals to 0.45, the initial fluidity and slump loss of cement paste which the addition of $ZnSiF_6$ (aq.) was increased from 1.0% to 4.0% based on cement weight were investigated. Initial fluidity of cement paste was measured by mini-slump test and slump loss was examined by measuring the fluidity variation of cement paste with time elapsed from 0 min to 120 min at intervals 30 min. Also, the effect of $ZnSiF_6$ addition on the setting and hydration of cement paste when $ZnSiF_6$ increased in the addition range 1.0% to 3.0% were investigated. The fluidity of cement paste which was added 2.1% $ZnSiF_6$ (aq.) presented the highest value among all addition ranges. The setting time of cement paste was retarded gradually and the heat evolution of hydrated cement was reduced with the increasing of $ZnSiF_6$ addition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.1
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• pp.15-18
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• 2009

To enhance near UV-visible absorption region and to applied phosphor convert-white LEOs (PC-WLEDs), a red phosphor composed of ${Y_2}{SiO_5}:\;EU^{3+}$, $Bi^{3+}$ compounds was prepared by the conventional solid-state reaction. The photoluminescence (PL) shown that samples were excited by near UV light 395 nm for measurement of PL spectra. Emission spectra of samples have shown red emissions at 612 nm ($^5D_0{\to}^7F_2$). The enhanced near $UV{\sim}$ visible excitation spectrum with a broad band centered at 258 nm and 282 nm originated in the transitions toward the charge transfer state (CTS) due to the $Eu^{3+}-Bi^{3+}-O^{2-}$ interaction. The other excitation band at $350\;nm{\sim}480\;nm$, corresponding to the transitions $^7F_0{\to}^5L_9$ (364 nm), $^7F_0{\to}^5G_3$ (381 nm), $^7F_0{\to}^5L_6$ (395 nm), $^7F_0{\to}^5D_3$, (415 nm) and $^7F_0{\to}^5D_2$ (466 nm), occurred due to enhanced the f-f transition increasing $Bi^{3+}$ and $Eu^{3+}$ ions. The PL intensity increased with increased as concentration of $Bi^{3+}$ and the emission intensity becomes with a maximum at 0.125 mol.

• Journal of the Mineralogical Society of Korea
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• v.30 no.2
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• pp.45-57
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• 2017

Two single crystals of fully dehydrated $Cd^{2+}$-exchanged zeolites Y were prepared by the exchange of ${\mid}Na_{75}{\mid}[Si_{117}Al_{75}O_{384}]-FAU$ ($Na_{75}-Y$, Si/Al = 1.56) with aqueous $0.05M\;Cd(NO_3)_2$ (pH = 3.65) at 294 K, followed by vacuum dehydration at 723 K (crystal 1) and a second crystal, similarly prepared, was exposed to zeolitically dried benzene for 72 hours at 294 K and evacuated (crystal 2). Their structures were determined crystallographically using synchrotron X-rays and were refined to the final error indices using $F_o$>$4{\sigma}(F_o)$ of $R_1/wR_2=0.040/0.121$ and 0.052/0.168, respectively. In crystal $1({\mid}Cd_{36}H_3{\mid}[Si_{117}Al_{75}O_{384}]-FAU)$, $Cd^{2+}$ ions primarily occupy sites I and II, with additional $Cd^{2+}$ ions at sites I', II', and a second site II. In crystal $2({\mid}Cd_{35}(C_6H_6)_{24}H_5{\mid}[Si_{117}Al_{75}O_{384}]-FAU)$, $Cd^{2+}$ ions occupy five crystallographic sites. The 24 benzene molecules are found at two distinct positions within the supercages. The 17 benzene molecules are found on the 3-fold axes in the supercages where each interacts facially with one of site IIa $Cd^{2+}$ ions. The remaining 7 benzene molecules lie on the planes of the 12-rings where each is stabilized by multiple weak electrostatic and van der Waals interactions with framework oxygens.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.749-755
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• 2004

Fluosilicic acid ($H_2SiF_6$) is recovered as aqueous solution which absorbs $SiF_4$ produced from the manufacturing of industrial-graded $H_3PO_4$ or HF. Generally, fluosilicate salts prepared by the reaction between $H_2SiF_6$ and metal salts. Addition of fluosilicate salts to cement endows odd properties through unique chemical reaction with the fresh and hardened cement. In this study, two-component fluosilicate salt based chemical admixtures (MZ) of $4\%,\;6\%$, and $8\%$ concentration were prepared by the reaction of $H_2SiF_6$ ($25\pm2\%$) and metal salts. The effect of concentration of MZ at a constant adding ratio on the hydration and watertightness of cement were investigated respectively. In a cement containing MZ, metal fluorides such as $CaF_2$ and soluble silica by hydrolysis were newly formed during hydration. The total porosity of the hardened cement was lower in the presence of U because of packing role of metal fluoride and pozzolanic reaction of soluble $SiO_2$. Consequently, the watertightness of the hardened paste containing MZ was more improved than non-added (plain) due to an odd hydration between cement and MZ.

• The Korean Journal of Ceramics
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• v.1 no.3
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• pp.131-136
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• 1995

It has been reported that the biocement obtained by mixing $CaO-SiO_2-P_2O_5$ glass powders with ammonium phosphate solution has biocompatibility as will as high strength. The hardening mechanism and hydroxyapatite forming mechanism were discussed when $53.6%CaO_1,\; 38.1%SiO_2,\; 7.7P_2O_6,\; 0.6%CaF_2$(mole %) glass powder was reacted with ammonium phosphate solution and reacted in tris-buffer solution, respectively. High strength hardened biocement was obtained for the specimen with $CaNH_4PO_4\;H_2O$ crystal when the glass powder was mixed with ammonium phosphate solution, and hydroxyapatite crystal was rapidly formed only in the sample with $CaNH_4PO_4\;H_2O$ crystal when it was reacted in tris-buffer solution.