• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.708-712
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• 2009

ITO films were achieved by sintering at $500{\sim}550{^{\circ}C}$. This was possible by inducing a seeding effect on an ITO sol by producing crystalline ITO nanoparticles in situ during heat treatment. Two kinds of ITO sols (named ITO-A and ITO-B) were prepared at 2.0 wt% from indium acetate and tin(IV) chloride in different mixed solvents. The ITO-A sol showed a high degree of crystallinity of ITO without any detectable Sn$O_2$ on XRD at $350{^{\circ}C}$/1 h, but the ITO-B sol showed a small amount of Sn$O_2$ even after annealing at $600{^{\circ}C}$/1 h. The 10 wt% ITO-A//ITO-B showed the sheet resistance of 3600$\Omega$/□, while the ITO-B sol alone showed 5200 $\Omega$/□ by sintering at $550{^{\circ}C}$ for 30 min. Processing parameters were studied by TG/DSC, XRD, SEM, sheet resistance, and visible transmittance.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.343-348
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• 2009

$NiO{\cdot}(Co_{0.25}Mn_{0.75})_2O_3$(Mn-Ni-Co) and $Ba_{0.5}Sr_{0.5}TiO_3$(BST) thick films were screen printed on Pt patterned alumina substrate to investigate the effects of sintering temperature on humidity and temperature sensing properties of ceramic sensors. A raise in sintering temperature increased resistance and B constant of the Mn-Ni-Co temperature sensor. This may have derived from the synergic effects of the reduction in charge carriers caused by the substitution of Co for Mn as well as the formation of microcracks from the difference in thermal expansion coefficients. Dependence of resistance on humidity of the Mn-Ni-Co temperature sensor, however, was not found. BST films sintered at temperatures in the range of $1100^{\circ}C$ to $1150^{\circ}C$ showed excellent humidity sensing properties. The BST humidity sensor was faster in its response than the Mn-Ni-Co temperature sensor. The humidity sensor, however, proved to be unstable under various temperatures, suggesting a need for a temperature stabilizing device. In contrast, the Mn-Ni-Co temperature sensor was stable under humid conditions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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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 $ZrO_2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.319-320
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• 2006

In order to improve the ESD(Electrical Static Discharge) resistance of multilayer chip varistors, we have investigated ZnO-$Pr_6O_{11}$ based chip varistor by applying tape casting technology, whose fundamental component were ZnO : $Pr_6O_{11}$ :$Co_3O_4$: $Y_2O_3$: $Al_2O_3$=93.67: 2.53:2.53:1.25 : 0.015 (wt %). The effect of sintering condition on the multilayer chip varistors and electric properties was studied. The electrical properties and ESD resistance of multilayer chip varistor could be influenced the sintering temperature and condition.

• Journal of Powder Materials
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• v.16 no.6
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• pp.442-448
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• 2009

$ZrB_2$-based composites are candidate materials for ultra-high temperature materials (UHTMs). $ZrB_2$ has become an indispensable ingredient in UHTMs, due to its high melting temperature, relatively low density, and excellent resistance to thermal shock or oxidation. $ZrB_2$ powders are usually synthesized by solid state reactions such as carbothermal, borothermal, or combined carbothermal reaction. SiC is added to this system in order to enhance the oxidation resistance of $ZrB_2$. In this study, $ZrB_2$?based composites were successfully synthesized and densified through two different processing paths. $ZrB_2$ or $ZrB_2$ 25 vol.%SiC was fully synthesized from oxide starting materials with reducing agents after heat treatment at 1400$^{\circ}C$. Besides, $ZrB_2$?20 vol.%SiC was fully densified with $B_4C$ as a sintering additive after hot pressing at 1900$^{\circ}C$. The synthesis mechanism and the effect of sintering additives on densification of $ZrB_2$ ?SiC composites were also discussed.

• Journal of Powder Materials
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• v.18 no.2
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• pp.188-195
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• 2011

The aim of this study was to investigate microstructures and mechanical properties of nano-sized Ti-35 wt.%Nb-7 wt.%Zr-10 wt.%CPP composite fabricated by high energy mechanical milling (HEMM) and pulse current activated sintering (PCAS). Grain growth of the mechanically milled powder was prevented by performing PCAS. The principal advantages of calcium phosphate materials include: similarity in composition to the bone mineral, bioactivity, osteoconductivity and ability to form a uniquely strong interface with bone. The hardness and wear resistance property of nano-sized Ti-35 wt.%Nb-7 wt.%Zr-10 wt.%CPP composites increased with increasing milling time because of decreased grain-size of sintered composites.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.314-314
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• 2010

The SiC-$ZrB_2$ composites were fabricated by combining 40vol.% of Zirconium Diboride(hereafter, $ZrB_2$) powders with Silicon Carbide(hereafter, SiC) matrix. TheSiC+40vol.%$ZrB_2$ composites were manufactured through Spark Plasma Sintering(hereafter, SPS) under argon atmosphere, uniaxial pressure of 50MPa, heating rate of $100^{\circ}C$/min, sintering temperature of $1,500^{\circ}C$ and holding time of 5min. But one on/off pulse sequence(one pulse time: 2.78ms) is 10:9(hereafter, SZ10), and the other is 48:8(hereafter, SZ48). The physical and mechanical properties of the SZ12 and SZ48 were examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via X-Ray Diffraction(hereafter, XRD) analysis. The apparent porosity of the SZ10 and SZ48 composites were 9.7455 and 12.2766%, respectively. The SZ10 composite, 593.87MPa, had higher flexural strength than the SZ48 composite, 324.78MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had Positive Temperature Coefficient Resistance(hereafter, PTCR).

• Korean Journal of Materials Research
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• v.23 no.7
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• pp.353-358
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• 2013

To improve coating ability and the life of the coating, Ti based composite materials with hydroxyapatite(HA) should be developed. The raw materials of Ti-26wt%, Nb-1wt%, and Si with 10wt% HA were mixed for 24 h by a mixing machine and milled for 1 h to 6 h by planetary mechanical ball milling. Ti-26%Nb-1%Si-(10%HA) composites, composed of nontoxic elements, were fabricated successfully by spark plasma sintering(SPS) at $1000^{\circ}C$ under 70MPa. The relative density of the sintered Ti-Nb-Si-HA composites using the 24 h mixed powder, and the 6 h milled powder, was 91% and 97 %, respectively. The effects of HA contents and milling time on microstructure and mechanical properties were investigated by SEM and hardness tester, respectively. The Vickers hardness of the composites increased with increasing milling time and higher HA content. The Young's modulus of the sintered Ti-26%Nb-1%Si-10%HA composite using the 6 h-milled powder was 55.6 GPa, as obtained by compression test. Corrosion resistance of the Ti-26wt%Nb-1wt%Si composite was increased by milling and by the addition of 10wt%HA. Wear resistance was improved with increasing milling time. Biocompatibility of the Ti-Nb-Si alloys was improved by the addition of HA.

• Membrane Journal
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• v.15 no.4
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• pp.349-354
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• 2005

YSZ (yttria-stabilized zirconia) determined with an electrolyte that analyzed thermal stability along sintering condition and an electric characteristic. As sintering temperature increases by SEM, grain grows and it showed that pore decreases relatively. and confirmed effect by grain size. It evaluated that particle internal resistance and electric performance by resistance in an electrolyte and electricity conductivity measurement through ac impedance measurement in temperature of $800\~1000^{\circ}C$ in 2-probe method In order to recognize an electric characteristic. In dry process and wet process, density was each 6.13, 6.25 $g/cm^3$ and the relative density was each 98, 99$\%$ when sintering condition is $1400^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.171-182
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• 1995

Five eucryptite and ten spodumene compositional powders were syntehsized from three sillimanite group, two kaolin group, and five pyrophyllite group silicate minerals. Those powders were isotatically pressed and fired at 1200~135$0^{\circ}C$ for 2 hrs, and then the sintered bodies were characterized. Silicate minerals with molar ratio of Al2O3 to SiO2 correspond to those of eucryptite and spodumene are kaolin and pyrophyllite group silicate minerals, respectively. Sintering characteristics of eucryptite from kaolin group and spodumene from pyrophyllite group mineral were superior to those from other silicate minerals. Eucryptite sintered bodies with 95~97% relative densities and densified microstructures can be obtained using Hadong pink kaolin as starting materials by sintering over broad temperature zone(1250~135$0^{\circ}C$). The eucryptite sintered bodies which were fired at 130$0^{\circ}C$ for 2hrs, from Hadong pink kaolin had within 3.0wt% microstructural compositional variations compaired with stoichiometric compound, and had good negative thermal expansiion property with -3.55$\times$10-6/$^{\circ}C$ thermal expansion coefficient. Spodumene sintered bodies which were prepared from pyrophyllite group silicate minerals, had dense microstructures and high densities by densification through liquid phase sintering with enlarged temperature range. The specimens which were fired at 130$0^{\circ}C$ for 2 hrs from Gusipyrophillite, had dense microstructure with crystallines mainly, and low thermal expansion property with 0.62$\times$10-6/$^{\circ}C$ thermal expansion coefficient. The porous texture and residual glass phase in LAS system ceramics which were prepared from silicate minerals, tend to increase the thermal expansion properties of sintered bodies to positive direction.