• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.29-36
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• 1985

This study was carried out to research on the optimum condition of $MgAl_2O_4$ spinel synthesis and the chara-ceteristics of its sintered bodies. In this study the used materials-MgO $Al_2O_3$-were prepared from the extragrade chemicals $Mg(OH)_2 Al(OH)_3$ respectively. The tendency to spinel synthesis and sintering condition were discussed about additives of SEM and the characteristics of sintered bodies were measured by TMA etc, The results were as follows ; 1. The addion of $TiO_2$ promoted more effectively the sinterbility than that of $MnO_2$. 2. Residual $\alpha$-$Al_2O_3$ and MgO in theorectical composition samples were disappeared at 1$600^{\circ}C$ 3. When added MnO2 residual $\alpha$-$Al_2O_3$ and MgO were disappeared at 150$0^{\circ}C$ and 1$600^{\circ}C$ respectively. 4, . When added $TiO_2$ residual $\alpha$-$Al_2O_3$ and MgO were disappeared at 150$0^{\circ}C$ and 134$0^{\circ}C$ respectively.

• Transactions of Materials Processing
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• v.29 no.1
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• pp.44-48
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• 2020

Aluminum nitride (AlN), as a substrate material in electronic packaging, has attracted considerable attention over the last few decades because of its excellent properties, which include high thermal conductivity, a coefficient of thermal expansion that matches well with that of silicon, and a moderately low dielectric constant. AlN films with c-axis orientation and thermal conductivity characteristics were deposited by using Pulsed Laser Deposition (PLD). The epitaxial AlN films were grown on sapphire (c-Al₂O₃) single crystals by PLD with AlN target and Y₂O₃ doped AlN target. A comparison of different targets associated with AlN films deposited by PLD was presented with particular emphasis on thermal conductivity properties. The quality of AlN films was found to strongly depend on the growth temperature that was exerted during deposition. AlN thin films deposited using Y₂O₃-AlN targets doped with sintering additives showed relatively higher thermal conductivity than while using pure AlN targets. AlN thin films deposited at 600℃ were confirmed to have highly c-axis orientation and thermal conductivity of 39.413 W/mK.

• Journal of Powder Materials
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• v.20 no.4
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• pp.291-296
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• 2013

SKD11 (ASTM D2) tool steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is characterized by a relatively high attainable hardness and numerous, large, chromium rich alloy carbide in the microstructure. SKD11 tool steel provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms. The CNTs was good additives to improve the mechanical properties of metal. In this study, 1, 3 vol% CNTs was dispersed in SKD11 matrix by mechanical alloying. The SKD11+ CNT hybrid nanocomposites were investigated by FE-SEM, particle size distribution, hardness and wear resistance. The CNT was well dispersed in the SKD11 matrix and the mechanical properties of the composite were improved by CNTs addition. It shows good feasibility as cold work die tool.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1057-1060
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• 2001

By comparison of the experimental results in two systems of ZnO varistors, its appear that Sb$_2$O$_3$is the indispensable element for twinning in ZnO varistors, and the Zn$_{7}$Sb$_2$O$_{12}$ spinel acts as the nucleus to form twins. A1$_2$O$_3$is not the origin of twinning in ZnO varistor, but it was found that A1$_2$O$_3$could strengthen the twinning and form a deformation twinning by ZnA$_{12}$O$_4$-dragging and pinning effect. The inhibition ratios of grain growth and nonuniformity of two systems ZnO varistors increase with the increase of A1$_2$O$_3$content. The twins affect the inhibition of grain growth, the mechanism could be explained follow as : twins increase the mobility viscosity of ZnO grain and grain boundary, and drag ZnO grain and liquid grain boundary during the sintering, then the grain growth is inhibited, and the microstructure becomes more uniform.orm.m.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.412-422
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• 1990

Porous SiC ceramics were proposed to be promising materials for high-temperature thermoelectric energy conversion. Throughthe thermoelectric property measurements and microstructure observations on the porous alpha SiC and the mixture of $\alpha$-and $\beta$-SiC, it was experimentally clarified that elimination of stacking faults and twin boundaries by grain growth is effective to increase the seebeck coefficient and increasing content of $\alpha$-SiC gives rise to lower electrical conductivity. Furthermore, the effects of additives on the thermoelectric properties of 6H-SiC ceramics were also studied. The electrical conductivity and the seebeck coefficient were measured at 35$0^{\circ}C$ to 105$0^{\circ}C$ in argon atmospehre. The thermoelectric conversion efficiency of $\alpha$-SiC ceramics was lower than that of $\beta$-SiC ceramics. The phase homogeneity would be needed to improve the seebeck coefficient and electrical conductivity decreased with increasing the content of $\alpha$-phase. In the case of B addition, XRD analysis showed that the phase transformation did not occur during sintering. On the other hand, AlN addiiton enhanced the reverse phase transformation from 6H-SiC to 4H-SiC, and this phenomenon had a great effect upon the electrical conductivity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.308-311
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• 2003

The mesoporous TiO2 film for the dye-sensitized solar cell was prepared by the spin coating using nano particle $TiO_2$ slurry. In order to obtain the good dispersion of nano size $TiO_2$ particles in slurry, the pH of solvent, the sort and quantity of solvent additive and the quantity of surfactant were adjusted. The experimental range of pH was $2\;{\sim}\;4$. The basic solvent for slurry was dilute $HNO_3$ and the solvent additives were ethylene glycol, propylene glycol and butylene glycol. The degree of particle dispersion was indirectly estimated by the viscosity of slurry and the microstructure after sintering. As results, the lower the pH of solvent was the lower the viscosity of the slurry became. The addition of ethylene glycol and propylene glycol to dilute $HNO_3$ brought about the lowering of viscosity and the enhancement of stability in slurry. The addition of surfactant lowered the viscosity of slurry. It was possible to obtain the homogeneous and uniformly dispersed mesoporous TiO2 film using the dilute HNO3 solvent of pH 2 with the addition of ethylene glycol, propylene glycol and neutral surfactant.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.463-466
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• 2001

In recent year, Ferroelectric $BLT(Bi_{4-x}La_{x}Ti_{3}O_{12})$ is a promising candidate materials. This study was practiced to make good conditions of BL T targets. In this study, calcination and sintering temperature were kept at $750^{\circ}C$, $1100^{\circ}C$ for 2 hour respectively. the density obtained 7.612, 7.98, $7.877g/cm^{3}$ as $La_{2}O_{3}$ contents were 0.0mol%, 0.25mol%, 0.5mol%. Especially, the lanthanum content of 0.5 mol% measured C-axis (117) preferred orientation more than the others targets in the XRD. In $\varepsilon_{r}-f$ relationship using by HP 4194 A impedance analyzer, the 0.5 mol% observed above 200 relative dielectric constant. but the dissipation factor was higher than others targets at 100Hz~13MHz range. SEM photograph with the content of $La_{2}O_{3}$ was observed like rod and plate types.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.942-946
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• 2004

The crystalline and dielectric properties on Al$_2$O$_3$ filled glass frit (CaO-Al$_2$O$_3$-SiO$_2$-MgO-B$_2$O$_3$) with admixtures of TiO$_2$ have been investigated. The dielectric constant value of 7.5 ∼ 7.8, qualify factor value of 700 were obtained for glass frit : Al$_2$O$_3$(50 : 50 wt%) ceramics. Addition of TiO$_2$ less than 5 wt% slightly increased the dielectric constant from 7.8 to 8.8 due to higher dielectric constant of TiO$_2$. With increasing the amount of TiO$_2$ up to 5 wt%, the temperature coefficient of dielectric properties was improved. When the TiO$_2$ 5 wt% were added, dielectric properties were dielectric constant 8.8, quality factor 840 and the temperature coefficient of dielectric 45 ppm/$^{\circ}C$ at a sintering temperature 920$^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.3-7
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• 1994

In this study, to improve sintering condition, anisotropic Property(k$\_$t//k$\_$p/) of electromechanical coupling coefficients, and hydrostatic piezoelerlric constants d$\_$h/ and g$\_$h/, MnO$_2$impurity was added to the (Pb$\_$0.76/Ca$\_$0.24)[(Co$\_$$\frac{1}{2}$W$\_$$\frac{1}{2}$/)$\_$0.04/Ti$\_$0.96/]O$_3$ System ceramics for hydrophone. And the structural, electrical properties of them were investigated. As a results. tetragonality was decreased with MnO$_2$ additives and density was the highest value of 7.06(g/㎤) at H2-3 specimen. Electromechanical coupling coefficients of H2-3 specimen were k$\_$t/=49 and k$\_$p/ 0, which exibited the hightest hydrostatic piezoelectric constants of d$\_$h/=64.52[10$\^$-1/C/N] and g$\_$h/=35.92[10$\^$-3/ Vm/N].

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.239-242
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• 1990

The effect of $CaCo_3$, $SrCo_3$, $SiO_2$ and $H_3BO_3$ in the range of 0.1-1.0 wt% on strontium ferrites consisting of the magnetoplumbite phase $SrO-5.7Fe_2O_3$ were investigated. The hysteresis loop, density, demagnetization curve and the intrinsic coercive force were measured on anisotropic ferrite. The particle diameter and 0.5(wt%) of second additive $CaCo_3$ is particularly important for the properties of anisotropic ferrite. When the particle diameter is decreased from 1.98(${\mu}m$) to 1.07(${\mu}m$), the remance is increased from 2900 to 4010(G) and the coercive force from 2150 to 2850(Oe) at a sintering temperature 1230 ($^{\circ}C$). Remance Br(G), coercleve force(Oe) and maximum energy product of sample A-16 are87(%), 56(%), 67(%) of S-W model theoretical value.