• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.953-955
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• 1999

The (1-x)$MgTiO_3-SrTiO_3$ (x=0. 0.1, 0.2, 0.3) ceramics were prepared by the conventional mixed oxide method. The structural properties were investigated with sintering temperature and composition ratio by XRD, SEM and BT-TGA. Increasing the sintering temperature from $1300^{\circ}C$ to $1600^{\circ}C$, second phase was decreased and grain size was increased. The average gram size of the 0.8$MgTiO_3-SrTiO_3$ ceramics sintered at $1600^{\circ}C$ were $3.61{\mu}m$.

• Ceramist
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• v.9 no.6
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• pp.42-48
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• 2006

The structural ceramic, such as $A1_2O_3,\;ZrO_2\;and\;Si_3N_4$ have applied as several parts of precision machines, automotives and instruments for semiconductor. The mechanical properties depended on purity, morphology and microstructure of the ceramic and its fabrication process. High purity and fine starting powder for the structural ceramic was prepared mainly by wet process and powder processing such as milling, mixing, drying and granulating strongly influenced on the fabrication process. Powder processing included powder synthesis technology is essential for ceramic manufacture. Also, the advanced mechanical treat[neat in powder processing to create nano composite powder was developed to improve several properties of ceramic materials. Innovation of powder processing will lead to improve mechanical and functional properties of the ceramics.

• Journal of the KSME
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• v.34 no.5
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• pp.326-333
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• 1994

신소재의 보편적인 정의는 "재료의 원료를 새로 개발하거나, 종래의 원료에 개선된 제조기술 또는 응용기술을 적용시켜 종래에 없던 우수한 특성, 기능을 갖게 하는 소재"라고 한다. 즉, 고 부가 가치의 금속, 세라믹스, 폴리머, 복합재료를 총칭하여 신소재 또는 첨단소재(advanced materials) 라고 하며, 산업기기의 중요한 기능소재로서 기계공업의 발전에 필수적이다. 1970년대부터 1980 년대 초반에 걸쳐 본격적으로 시작된 세라믹스에 관한 연구는 제조 및 사용분야 전반에 걸쳐 기술혁신을 가져왔다. 그후 천연 광석분말만이 아니라 새로운 화학적 방법으로 제조된 분말을 사용하여 창출된 재료라는 뜻으로 "뉴(new)세라믹스"라고 불려지거나, 개선된 제조기술을 통하여 재료의 섬세한 미세조직을 얻음으로 우수한 특성을 갖는 재료라는 뜻으로 "파인(fine)세라믹스" 등의 이름이 붙여지게 되었다. 이제 센서용 소재는 물론이고, 가위, 손목시계 케이스, 바이오 세라믹스 등에 이르기까지 10년 전보다 훨씬 다양하게 세라믹스를 사용한 물체를 발견할 수 있다. 이들 세라믹스 중 기계적, 또는 열 응력을 받는 구조물에 적용되는 것을 구조 세라믹 스(structural ceramics)라고 한다. 이 글에서는 차세대 자동차 및 항공기에까지 적용이 시도되고 있는 이들 구조세라믹스를 대상으로 하여 일반적으로 제조법, 응용분야, 연구동향 및 전망을 정리하고자 한다.조법, 응용분야, 연구동향 및 전망을 정리하고자 한다.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.175-176
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• 2008

In this study, the sintering properties and structural properties of the $Mg_5Ta_4O_{15}$cation-deficient perovskite ceramics with $Li_2CO_3$ additions are investigated. The cation-deficient perovskite ceramics are prepared through the solid-state route. According to the XRD pattern, $Mg_4Ta_2O_9$, $MgTa_2O_6$ and $Mg_5Ta_4O_{15}$ phase existed in sintered pure $Mg_5Ta_4O_{15}$ ceramics. With $Li_2CO_3$, additions, the peak intensities of $Mg_4Ta_2O_9$ and $MgTa_2O_6$ phase were reduced. Also, diffraction intensity of the $Mg_5Ta_4O_{15}$ phase was increased with increments of $Li_2CO_3$ additions. The bulk densities were increased with increasing of $Li_2CO_3$ amount and approach the theoretical density of the $Mg_5Ta_4O_{15}$ ceramics, more and more. Microstructure of the $Mg_5Ta_4O_{15}$ ceramics were densified more and more by additions of $Li_2CO_3$. The bulk density of $Mg_5Ta_4O_{15}$+5wt% $Li_2CO_3$ ceramics sintered at $1500^{\circ}C$ for 10 hours was $5.88g/cm^3$.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.455-461
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• 2015

Porous ceramics with tailored pore size and shape are promising materials for the realization of a number of functional and structural properties. A novel method has been reported for the investigation of the role of SiC in the formation of $SiO_2$ foams by colloidal wet processing. Within a suitable pH range of 9.9 ~ 10.5 $SiO_2$, particles were partially hydrophobized using hexylamine as an amphiphile. Different mole ratios of the SiC solution were added to the surface modified $SiO_2$ suspension. The contact angle was found to be around $73^{\circ}$, with an adsorption free energy $6.8{\times}10^{-12}J$. The Laplace pressure of about 1.25 ~ 1.6 mPa was found to correspond to a wet foam stability of about 80 ~ 85%. The mechanical and thermal properties were analyzed for the sintered ceramics, with the highest compressive load observed at the mole ratio of 1:1.75. Hertzian indentations are used to evaluate the damage behavior under constrained loading conditions of $SiO_2$-SiC porous ceramics.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.7
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• pp.347-351
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• 2004

The $ZnNb_2O_{6}$ ceramics with CuO(1, 3, 5wt%) were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $950^{\circ}C$∼$1075^{\circ}C$ for 3hr in air The structural properties and the microwave dielectric properties of $ZnNb_2O_{6}$ ceramics were investigated with sintering temperature and the addition of CuO. Increasing the addition of CuO, the peak of second phase($Cu_3Nb_2O_{8}$) was increased. The grain size of the $ZnNb_2O_{6}$ ceramics with CuO was increased with CuO addition at same temperature. The dielectric constant of $ZnNb_2O_{6}$ ceramics with CuO was increased with sintering temperature and CuO addition. While the quality factor of the $ZnNb_2O_{6}$ ceramics with lwt% CuO depended on sinterability, the quality factor of $ZnNb_2O_{6}$ with 3wt% and 5wt% CuO depended on second Phase due to the CuO addition. The optimum dielectric Properties of $\varepsilon$$_{r}$ = 21.73 Q${\times}$f = 19,276 were obtained from the condition of 3wt% CuO addition and sintering temperature of $1025^{\circ}C$(3hr).

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.417-428
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• 2016

In this review, an attempt is made to calculate one-dimensional (1-D) electron density profiles from experimentally determined (00l) XRD intensities and possible structural models as well in an effort to understand the collective intracrystalline structures of intercalant molecules of two-dimensional (2-D) nanohybrids with heterostructures. 2-D ceramics, including layered metal oxides and clays, have received much attention due to their potential applicability as catalysts, electrodes, stabilizing agents, and drug delivery systems. 2-D nanohybrids based on such layered ceramics with various heterostructures have been realized through intercalation reactions. In general, the physico-chemical properties of such 2-D nanohybrids are strongly correlated with their heterostructures, but it is not easy to solve the crystal structures due to their low crystallinity and high anisotropic nature. However, the powder X-ray diffraction (XRD) analysis method is thought to be the most powerful means of understanding the interlayer structures of intercalant molecules. If a proper number of well-developed (00l) XRD peaks are available for such 2-D nanohybrids, the 1-D electron density along the crystallographic c-axis can be calculated via a Fourier transform analysis to obtain structural information about the orientations and arrangements of guest species in the interlayer space.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.568-573
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• 2011

AZO (Al doped ZnO) thin films were deposited on the quartz substrates with thickness variation from 25 to 300 nm by using PLD (pulsed laser deposition). XRD (x-ray diffractometer), SPM (scanning probe microscopy), Hall effect measurement and uv-visible spectrophotometer were employed to investigate the structural, morphological, electrical and optical properties of the thin films. XRD results demonstrated that films were preferrentially oriented along the c-axis and crystallinity of film was improved with increase of film thickness. As for the surface morphologies, the mean diameter and root mean square of grains were increased as the film thickness was increased. When the film thickness was 200 nm, the lowest resistivity of $4.25{\times}10^{-4}\;{\Omega}cm$ obtained with carrier concentration of $6.84{\times}10^{20}\;cm^{-3}$ and mobility of $21.4\;cm^2/V{\cdot}S$. All samples showed more than 80% of transmittance in the visible range. Upon these results, it is found that the samples thickness can affect their structural, morphological, optical and electrical properties. This study suggests that the resistivity can be improved by controlling film thickness.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.685-689
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• 2011

The goal of this investigation was to produce a zirconia-family black ceramics that has enhanced functionality and reliability. Color zirconia ceramics have been produced by adding pigments. Pigments cause structural defects within zirconia and result in a drop in physical properties. Using environmentally friendly rice husk, we produced a black zirconia that is free of structural defects. In optimal firing conditions for black zirconia the calcining temperatures of the molding product are changed from $400^{\circ}C$ to $1200^{\circ}C$, and the firing temperatures are changed from $1400^{\circ}C$ to $1600^{\circ}C$. Color of testing the specimens was analyzed using Ultraviolet (UV) spectroscopy. Scanning Electron Microscope (SEM), EDAX (EDX), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out in order to examine impregnation properties and crystal phases. Universial Test Machine (UTM) was used to measure the flexual strength as well as the compressive strength. From experimental results, it was found that in optimal firing conditions the sample was calcined from $1000^{\circ}C$ to $1500^{\circ}C$. Commission internationalde I'Edairage (CIE) values of manufactured black zirconia color were $L^*$ = 29.73, $a^*$ = 0.23, $b^*$ = -2.68. The bending strength was 918 MPa and the compressive strength was 2676 MPa. These strength values are similar to typical strength values of zirconia, which confirms that carbon impregnation did not influence physical properties.

• Korean Journal of Crystallography
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• v.17 no.1
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• pp.14-18
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• 2006

MOCVD 공정방법에 의해 수직정렬된 ZnO 나노선을 합성하고 공정조건 제어에 의해 합성되는 나노선의 물리적, 광학적 특성이 어떻게 변화하는지를 고찰하고자 하였다. 온도 및 산소분압제어 등의 공전변수 제어를 통하여 ZnO 나노 구조체는 나노선, 나노로드 뿐만 아니라 나노바늘 (nano-needle) 등 다양한 구조로 변화되었으며 그 직경 및 길이도 제어가 가능하였다. 전체적으로 양호한 특성의 wurzite 구조를 나타내었으며 기판에 수직인 방향으로 [0001] 방향으로 성장하였다. 광학특성에서는 나노선 직경이 작아질수록 주방출 피크의 천이현상이 관찰되었다.