• 한국세라믹학회지
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• 제25권4호
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• pp.373-379
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• 1988

$\alpha$-Al2O3-15m/o ZrO2 powder was prepared by a sol-gel method from boehmite and zirconium acetate. The transformation temperature of boehmite to $\alpha$-Al2O3 in the system Al2O3-ZrO2 was increased due to the coupled crystallization. On the other hand, the transformation temperature from boehmite to $\alpha$-Al2O3-15m/o ZrO2 could be prepared at 110$0^{\circ}C$ for 100min. The specific surface area of the product of $\alpha$-Al2O3-15m/o ZrO2 was 13.2$m^2$/g.

• 한국세라믹학회지
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• 제39권7호
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• pp.704-709
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• 2002

ZrO$_2$가 분산된 $Al_2$O$_3$/ZrO$_2$ 복합체의 기계적 성질을 향상시키기 위하여 분산되는 ZrO2의 입자크기를 공침법에 의해 초미립으로 균질하게 분산시키기 위한 방안을 고찰하여 보았다. 일반적으로 $Al_2$O$_3$와 ZrO$_2$ 분말의 기계적혼합에 의해 제조되는 경우 분산되는 ZrO$_2$ 출발입자의 크기도 크고 소결시에도 비교적 빠르게 성장하므로 본 연구에서는 상용의 이소결성 $\alpha$-Al$_2$0$_3$ 분말(Sumitomo:AES-11(0.5$mu extrm{m}$)) 및 저온 소결용 초미립 알루미나(Taimei Chemical(0.22$\mu\textrm{m}$))에 ZrOC1$_2$. 8$H_2O$ 와 Y(NO$_3$)$_3$를 pH 9.5의 조건에서 공침하여 $\alpha$-Al$_2$0$_3$입자 표면에 초미립의 미세한 Zr(OH)$_4$ 침전 입자가 부착되도록 하였다. 이를 150$0^{\circ}C$-1$600^{\circ}C$의 온도에서 소결하여 작은 크기의 ZrO$_2$ 입자가 균질하게 분산된 $Al_2$O$_3$/ZrO$_2$ 복합체를 제조하였으며 이의 기계적성질을 관찰하였다.

• 한국세라믹학회지
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• 제22권1호
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• pp.11-18
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• 1985

The effect of stress induced phase transformation on $Al_2 O_3$ matrix dispersed with $ZrO_2-Y_2O_3$ has been studied. In order to determinate the mechanical properties three $Al_2O_3-ZrO_2$ composite series containing 1, 3 and 5 mole% $Y_2O_3$ were prepared. The starting materials were $Al_2O_3$ and $ZrO_2-Y_2O_3$ which was prepared from the aqueous solution of high purity $YCl_3$.$6H_2O$ and $ZrOCl_2$.$8H_2O$. Powder mixtures of $Al_2O_3-ZrO_2$ containing $Y_2O_3$ have been prepared by ball-milling with methanol and the samples were formed by isostatic press and sintered at 150$0^{\circ}C$ for 2hrs. After sintering. the specimens were polished for mechanical determination. The relative density of sintered specimens were also measured. It was found that the addition of 1, 3mole% to {{{{ { ZrO}_{2 } }} allowed full retention of the tetragonal phase in $Al_2O_3-ZrO_2$ but partially stabilized zirconia (PSZ) was produced by additions of 5 mole% $Y_2O_3$.The critical stress-intensity factor KIc of $A_2O_3-ZrO_2$ (containing 1 mole% $Y_2O_3$) composite materials increased with increasing $ZrO_2$ content, The maximum value of KIC=7Mn/$m^3$/2 at 20 mole% $ZrO_2$ exhibited about twice that of the $Al_2 O_3$ The modulus of rupture exhibited a trend similiar to KIC The maximum value of MOR was 580MN/m2. As the amount of Y2O3 increase it was observed that the maximum of KIC and MOR decreased : Additions of 3 mole% $Al_2O_3$ $Y_2O_3$ allowed the maximum of KIC 6MN/$m^3$/2 MOR 540MN/$m^2$ at 15 mole% $ZrO_2$ additions of 5 mole% $Y_2O_3$ allowed the maximum of KIC 5MN/$m^3$/2 MOR 410MN/$m^2$ at 10 mole% $ZrO_2$.

• 한국세라믹학회지
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• 제37권1호
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• pp.50-56
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• 2000

Precursor gels with the composition of xZrO2·(100-x)SiO2 systems (x=10, 20 and 30 mol%) were prepared by the sol-gel method. Kinetic parameters, such as activation energy, Avrami's exponent, n, and dimensionality crystal growth value, m, have been simultaneously calculated from the DTA data using Kissinger and Matusita equations. The crystallite size dependence of tetragonal to monoclinic transformation of ZrO2 was investigated using XRD, in relation to the fracture toughness. The crystallization of tetragonal ZrO2 occurred through 3-dimensional diffusiion controlled growth(n=m=2) and the activation energy for crystallization was calculated using Kissinger and Matusita equations, as about 310∼325±10kJ/mol. The growth of t-ZrO2, in proportion to the cube of radius, increased with increasing heating temperature and hteat-treatment time. It was suggested that the diffusion of Zr4+ ions by Ostwald ripening was rate-limiting process for thegrowth of t-ZrO2 crystallite size. The fracture toughness of xZrO2·(100-x)SiO2 systems glass ceramics increased with increasing crystallite size of t-ZrO2. The fracture toughness of 30ZrO2·70SiO2 system glass ceramics heated at 1,100℃ for 5h was 4.84 MPam1/2 at a critical crystaliite size of 40 nm.

• 한국재료학회지
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• 제13권9호
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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.

• 한국세라믹학회지
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• 제44권6호
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• pp.291-296
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• 2007

Porous $Al_2O_3-(m-ZrO_2)$ composites were fabricated by pressureless sintering, using different volume percentages (40% - 60%) of poly methyl methacrylate (PMMA) powders as a pore-forming agent. The pore-forming agent was successfully removed, and the pore size and shape were well-controlled during the burn-out and sintering processes. The average pore size in the porous $Al_2O_3-(m-ZrO_2)$ bodies was about $200\;{\mu}m$ in diameter. The values of relative density, bending strength, hardness, and elastic modulus decreased as the PMMA content increased; i.e., in the porous body (sintered at $1500^{\circ}C$) using 55 vol % PMMA, their values were about 50.8%, 29.8 MPa, 266.4 Hv, and 6.4 GPa, respectively. To make the $Al_2O_3-(m-ZrO_2)$/polymer hybrid composites, a bioactive polymer, such as PMMA, was infiltrated into the porous $Al_2O_3-(m-ZrO_2)$ composites. After infiltration, most of the pores in the porous $Al_2O_3-(m-ZrO_2)$ composites, which were made using 60 vol % PMMA additions, were infiltrated with PMMA, and their values of relative density, bending strength, hardness, and elastic modulus remarkably increased.

• 한국재료학회지
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• 제15권9호
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• pp.608-612
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• 2005

Microstructure and mechanical properties of fibrous $A1_2O_3-(m-ZrO_2)/t-ZrO_2$ composite were investigated depending on the dimensional array. By the change of stacking arrangement of fibrous filaments, 2 and 3-dimensional fibrous composites were successfully obtained without bulk defects such as shrinkage cavity and cracks. The maximum mechanical properties were achieved In the 3-dimensional array composite, due to the fine fibrous and dense microstructure control, in which the values of vickers hardness, fracture toughness and bending strength were about 1507 Hv, $7.2MPa{\cdot}m^{1/2}$ and 650 MPa, respectively.

• 한국세라믹학회지
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• 제37권12호
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• pp.1178-1186
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• 2000

타일의 내마모성과 내산성을 향상시키기 위해 결정화유리가 최근에 새로운 유약 재료로서 소개되고 있다. 신 유약의 연구에 사용된 조성은 $Ca_2$ZrSi$_4$O$_{12}$ 상에 근접하는 CaO-ZrO$_2$-SiO$_2$계의 유리조성의 분말로, 마이크로파 가열 (2.45 GHz)에 의해서 900-120$0^{\circ}C$의 0-20분간 소성되어 평가되었다. 그 결과, 100$0^{\circ}C$ 이상에서 소성한 시편은 내부 결정화를 나타내었으며, 결정상은 미세(5$mu extrm{m}$)한 크기를 갖는 $Ca_2$ZrSi$_4$O$_{12}$가 주 결정상이며, $Ca_2$ZrSi$_4$O$_{12}$, CaSiO$_3$, SiO$_2$의 세 상이 나타났다. 소결체의 미세구조는 사용한 유리분말의 입도의 영향을 받았다. 미세분말 (<38$\mu\textrm{m}$)을 이용한 소결체의 조직이 조세분말 (45-150$\mu\textrm{m}$)의 경우보다 수축율면에서 높았으며 낮은 기공도를 갖는 미세구조를 가졌다. 마이크로파에 의한 유리분말의 소성은 1000-120$0^{\circ}C$ 구간에서 10분 이내 결정화가 완료되는 급속 가열 공정이었으며 CaO-ZrO$_2$-SiO$_2$계 결정화 유리 제조에 균일한 체적가열을 할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.335-338
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• 1999

The effect of monoclinic $ZrO_2$(pure) and tetragonal $ZrO_2$ containing 5.35wt% $Y_2$$O_3$(Y-TZP) addition on the mechanical properties and thermal shock resistance of $Al_2$$O_3$ ceramic were investigated. The addition of $ZrO_2$(m) and Y-TZP increased sintering density of $Al_2$$O_3$. The vickers hardness increased with increasing the volume fraction of Y-TZP going through a maximum at 20wt%. The hardness of the specimens was found to be depend on the sintering density. With increasing the volume fraction of $ZrO_2$(m) and Y-TZP, the fracture toughness of the composite is increased. This result may be taken as evidence that toughening of ${Al_2}{O_3}$ can also be achieved by the transformation toughening and microcrack toughening of $ZrO_2$. The property of the& shock for ${Al_2}{O_3}$-$ZrO_2$ composites was improved by increasing the volume fraction of monoclinic $ZrO_2$(pure).Grain size increased with increasing the volume fraction of $ZrO_2$.

• 전자공학회논문지 IE
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• 제49권2호
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• pp.1-8
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• 2012

단사정 구조의 순수 $ZrO_2$ 또는 5.35wt%의 $Y_2O_3$를 첨가한 정방정 구조의 $Y_2O_3(Y-TZP)$를 $Al_2O_3$에 첨가하여 그 기계적 특성 및 열충격 저항성을 연구하였다. $ZrO_2(m)$와 Y-TZP의 첨가량이 커짐에 따라 $Al_2O_3$의 소결 밀도가 증가하였다. 또한 Y-TZP의 첨가량이 증가함에 따라 비커스 경도도 증가하였고 첨가량 20wt%에서 최고값을 나타내었다. 시편의 경도는 소결 밀도에 의존함을 알 수 있었다. $ZrO_2(m)$나 Y-TZP 첨가량의 증가는 파괴인성을 향상시키는 결과를 얻을 수 있었다. 이러한 결과로 $Al_2O_3$의 경도는 $ZrO_2$의 transformation toughening 뿐 아니라 미세균열 강화에서도 얻어짐을 알 수 있었다. 단사정 구조의 순수 $ZrO_2$의 첨가는 $Al_2O_3-ZrO_2$의 열 충격 저항성을 향상시켰다. 결정입도는 $ZrO_2$의 첨가량이 증가함에 따라 커진다.