• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.485-491
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• 1993

Porous glass in the ZrO2.SiO2 system containning up to 30mol% zirconia were prepared by the sol-gel method from metal alkoxides and their pore characteristics with reaction parameters were investigated. The gels were made by hydrolyzing and condensation of the mixed metla alkoxides and were converted into the porous glass by heating up to $700^{\circ}C$. As a results, the mean pore radius became larger with increasing contents of HCl, H2O and hydrolysis temperature, and an alcohol with a large molecular weight for making the porous glass. In the case of 20ZrO2.80SiO2 porous glass with heated at $700^{\circ}C$, HCl and H2O content was 0.3mol and 4mol, the specific surface area was 284$m^2$/g, average mean pore radius was about 19.4$\AA$, porosity was 22.55% and pore characteristics depended on heating temperature.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.572-580
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• 2003

Synthesizing behavior and microstructural evolution of $CaZrO_3$and $m-ZrO_2$in a thermal reaction process of $ZrSiO_4$-$xCaCO_3$mixtures, where x is 7 and 19, were investigated to determine the addition amount of CaO in CaO:$ZrO_2$:$SiO_2$ternary composition. CaZrO$_3$-Ca$_2$SiO$_4$precursor prepared by the mixture of $ZrSiO_4$and CaCO$_3$in aqueous suspending media was controlled to the acidic (pH=4.0) condition with HCI solution to enhance the thermal reaction. The addition amount of dispersant into the $ZrSiO_4$-$xCaCO_3$slip increased with increasing mole ratio of $CaCO_3$, which was associated with the viscosity of slip. Decarbonation reaction was activated with an increase of the addition amount of $CaCO_3$, showing different final temperatures in $ZrSiO_4$-$7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures as about 980 and 116$0^{\circ}C$, respectively, for finishing decarbonation reaction. The grain morphology was changed to spherical shape for all samples with an increase of sintering temperature. The grain size and phase composition of the synthesized composites depended on the mixture ratio of Zrsi04 and CacO3 powders, indicating that the main crystals were m-ZrO2 ($\leq$3 $\mu\textrm{m}$) and $CaZrO_3$ ($\leq$ 7 $\mu\textrm{m}$) in $ZrSiO_4$$>-7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures, respectively.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.668-676
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• 1990

Glass in the ZrO2-SiO2 system containing up to 30mol% ZrO2 were prepared by heating the gel made from the mixed solutions of Zr(OC3H7)4 and partial hydrolysed Si(OC2H5)4. As a result, the monolith gel was made from the HCl and water content as 2.7$\times$10-3 and 8 molar ratio to alkoxide and drying temoperature as 4$0^{\circ}C$. Heating rate of dry gel maintained under 0.5$^{\circ}C$/min and heating at a temperature as 90$0^{\circ}C$ was found to be for making the transparent glass.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.709-715
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• 1996

The influence of an electric field on the combustion synthesis of ${Ti}_{5}{Si}_{3}$-x ${ZrO}_{2)$(0 $\leq$ x $\leq$0.6)was investigated. Composite of X $\geq$0.45 can only be synthesized in the presence of an electric field. Although in the absence of an electri field the system with x = 0.45 and x=0.6 can sustain a nonsteady combustion wave, the reaction is not complete. That is, an unstable wave propagates to the middle of the sample and them becomes extinguished. Wave velocity o the ${Ti}_{5}{Si}_{3}-{ZrO}_{2}$ Composites slightly increases with the imposition of external field across the sample.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.35-40
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• 1992

Porous glass in the ZrO2-SiO2 system containing up to 30 mol% zirconia were prepared from the mixed solutions of Zr(O.nC3H7)4 and partially prehydrolyzed TEOS by the sol-gel method. Pore characteristics, physical properties and alkali resistance were investigated. The gels converted into the porous glass by heating at $700^{\circ}C$, it was found that the glass like skeleton was already made up in lower temperature regions. The specific surface area of the porous glass was 227 $m^2$/g, average mean pore size was about 19$\AA$ and porosity was 19.2%, pore characteristics and physical properties depended on heating temperature. Alkali resistance of the porous glass increased as the zirconia content increased, because of the appearance of Zr-enriched layer at glass surface.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.385-393
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• 1995

Akali-resistant porous glass was prepared by phase separation in Na2O-B2O3-SiO2 system containing ZrO2 and MgO. ZrO2 was added for alkali-resistance and MgO for anti-cracking during leaching. Optimal content of ZrO2 for alkali-resistance was 7wt% and devitrification by heat treatment resulted from further addition. Pore size and pore volume were decreased and specific surface area was increased with ZrO2 addition due to depression in phase separation. Addition of 3mol% MgO to mother glass containing 7wt% ZrO2 was effective for anti-crack during leaching. In this case, with phase separation at 55$0^{\circ}C$ and 5$25^{\circ}C$ for 20 hrs. crack-free porous glasses could be prepared. The relation between pore size r and heat treatment time t at 55$0^{\circ}C$ was D=25.58＋18.16t. According to measurement of gas permeability, the mechanism of gas permeation was Knudsen flow. N2 and He permeability of porous glass which was prepared by heat treatment at 55$0^{\circ}C$ for 20 hrs. were 0.843$\times$10-7mol/$m^2$.s.Pa and 2.161$\times$10-7mol/$m^2$.s.Pa respectively.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1260-1266
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• 1996

The effects of SiO2 MnO2 and sintering atmospheres (O2, N2) on the piezoelectric properties and densification behaviors of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 were investigated. The addition of SiO2 to the system enhanced the rate of densification but supressed the rate of grain growth. On the other hand the addition of MnO2 to the system did not nearly affect the rate of densification but increased slightly the rate of grain growth The densification of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 containing of SiO2 or MnO2 was promoted with increasing the partial pressure of O2. The relative dielectric constant ($\varepsilon$r) and piezoelectric constant (d33) of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 containing of SiO2 or MnO2 sintered under O2 atmosphere were higher than under N2 atmosphere. Whereas the mechanical quality factor (Qm) of specimens sintered under O2 atmosphere were lower than under N2 atmosphere. Thus the sintering atmosphere of O2 and N2 in Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 containing of SiO2 or MnO2 acted as donor and acceptor respectively. As the amount of SiO2 increased the relative dielectric constant ($\varepsilon$r) and piezoelectric constant (d33) of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 but the mechanical quality factor (Qm) did not nearly change, In the case of the addition of MnO2 to the system the relative dielectric constant ($\varepsilon$r) and piezoelectric constant (d33) of Pb0.98Cd0.02Zr0.36Ti0.39Ni0.083Nb0.167O3 sintered under O2 atmosphere decreased rapidly with increasing the amount of MnO2 but they were unchanged with increasing the amount of MnO2 under N2 sintering atmosphere. Therefore the differences of the relative dielect-ric constant ($\varepsilon$r) and piezoelectric constant (d33) due to sintering atmosphere were diminished as the amount of MnO2 increased.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.5-6
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• 1993

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.229-234
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• 2018

The glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system was synthesized by using $ZrO_2$, $ZrSiO_4$, $ZrOCl_2$ and $Zr(SO_4)_2$, which is a raw material of Zr serving as a nucleation agent. It was confirmed that Avrami parameter of these four glasses is over 3 for bulk crystallization. The glass synthesized by $ZrOCl_2$, and $Zr(SO_4)_2$ showed high melting quality during the melting process. It is also observed that the Zr component is uniformly distributed in the glass. Various characterizations was evaluated, including composition analysis and bending strength.

• International Journal of Ocean System Engineering
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• v.2 no.4
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• pp.244-249
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• 2012

In this study, a monolithic MoSi2 matrix reinforced with 20 vol% SiC particles, a SiC/MoSi2 composite matrix reinforced with 20 vol% ZrO2 particles, and a ZrO2/MoSi2 composite were fabricated using hot press sintering at $1350^{\circ}C$ for 1 h under a pressure of 30 MPa. The Vickers hardness and sliding wear resistance of the monolithic MoSi2, ZrO2/MoSi2, and SiC/MoSi2 composite were investigated at room temperature. A wear behavior test was carried out using a disk-type wear tester with a silicon nitride ball. The ZrO2/MoSi2 composite showed an average Vickers hardness value and excellent wear resistance compared with the monolithic MoSi2 and SiC/MoSi2 composite at room temperature.