• 공업화학
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• 제8권2호
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• pp.179-190
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• 1997

준역청탄, 유연탄, 무연탄 및 국내 무연탄을 포함하는 54종의 석탄회분을 대상으로 화학조성 및 광물분석 그리고 용융온도를 측정하여 화학조성이 용융온도에 미치는 영향을 고찰하였다. 석탄회의 구성 산화물중 CaO와 MgO, 그리고 $Fe_2O_3$가 용융온도를 낮추는 산화물임을 알 수 있었다. $Fe_2O_3$에 의한 용융온도 감소 효과는 환원성분위기에서 증가되었다. 산-염기도에서 염기성분의 함량이 증가할수록 용융온도는 감소하였다. 그러나 산-염기도와 용융온도와의 상관관계는 $Fe_2O_3$/CaO비가 증가함에 따라 낮아졌다. 산화성분위기보다는 환원성분위기에서 용융온도가 낮았으며 이때 분위기 변화에 따른 용융온도차는 $Fe_2O_3$의 함량보다는 $SiO_2/Al_2O_3$비와 밀접한 상관성을 보여주었다. 석탄회의 용융온도(연화)를 예측하기 위한 다중회귀분석결과 산화성분위기에서는 Base/Acid, $Fe_2O_3$/CaO, $SiO_2/Al_2O_3$, $(SiO_2/Al_2O_3){\cdot}(Base/Acid)$ 그리고 환원성분위기에서는 Base/Acid, $Fe_2O_3$/CaO, $SiO_2$, $TiO_2$등을 독립변수로 사용함으로써 비교적 상관성이 높은 관계식을 얻을 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1545-1547
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• 2000

The mechanical and electrical properties of the hot-pressed and annealed $\beta$-Sic-$TiB_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_3$. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_{5}Y_{3}O_{12}$). The relative density and the mechanical properties of composites were increased with increasing $Al_{2}O_{3}+Y_{2}O_3$ contents because YAG of reaction between $Al_{2}O_3$ and $Y_{2}O_3$ was increased. The Flexural strength showed the highest value of 432.5MPa for composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. Owing to crack deflection, crack bridging, phase transition and YAG of fracture toughness mechanism. the fracture toughness showed 7.1MPa${\cdot}m^{1/2}$. For composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature The electrical resistivity and the resistance temperature coefficient respectively showed the lowest of 6.0${\sim}10^{-4}{\Omega}{\cdot}$ cm and 3.1${\times}10^{-3}/^{\circ}C$ for composite added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of 25$^{\circ}C$ to 700$^{\circ}C$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권10호
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• pp.467-474
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• 2006

The effect of pressureless-sintered temperature on the densification behavior, mechanical and electrical properties of the $SiC-TiB_2$ electroconductive ceramic composites was investigated. The $SiC-TiB_2$ electroconductive ceramic composites were pressureless-sintered for 2 hours at temperatures in the range of $1,750{\sim}1,900[^{\circ}C]$, with an addition of 12[wt%] $Al_2O_3+Y_2O_3(6:4\;mixture\;of\;Al_2O_3\;and\;Y_2O_3)$ as a sintering aid. The relative density, flexural strength, vicker's hardness and fracture toughness showed the highest value of 84.92[%], 140[MPa], 4.07[GPa] and $3.13[MPa{\cdot}m^{1/2}]$ for $SiC-TiB_2$ composites of $1,900[^{\circ}C]$ sintering temperature at room temperature respectively. The electrical resistivity was measured by the Pauw method in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. The electrical resistivity showed the value of $5.51{\times}10^{-4},\;2.11{\times}10^{-3},\;7.91{\times}10^{-4}\;and\;6.91{\times}10^{-4}[\Omega{\cdot}cm]$ for ST1750, ST1800, ST1850 and ST1900 respectively at room temperature. The electrical resistivity of the composites was all PTCR(Positive Temperature Coefficient Resistivity). The resistance temperature coefficient showed the value of $3.116{\times}10^{-3},\;2.717{\times}10^{-3},\;2.939{\times}10^{-3},\;3.342{\times}10^{-3}/[^{\circ}C]$ for ST1750, ST1800, ST1850 and ST1900 respectively in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. It is assumed that because polycrystallines, such as recrystallized $SiC-TiB_2$ electroconductive ceramic composites, contain of porosity and In Situ $YAG(Al_5Y_3O_{12})$ crystal grain boundaries, their electrical conduction mechanism are complicated. In addition, because the condition of such grain boundaries due to $Al_2O_3+Y_2O_3$ additives widely varies with sintering temperature, electrical resistivity of the $SiC-TiB_2$ electroconductive ceramic composites with sintering temperature also varies with sintering condition. It is convinced that ${\beta}-SiC$ based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1148-1151
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• 2002

Dielectric ceramics with nominal composition of $(Ba_{0.93}Sr_{0.07}O)-0.5Sm_2O_3-4.5TiO_2$ was prepared using the conventional mixed oxide process-derived powder. Effect of $SiO_2$, $MnO_2$ and $Al_2O_3$ impurity addition on the microwave properties was examined in some detail. Measured relative permittivity $(\varepsilon_r)$ values were in the range of 53 to 59 and showed little dependence on impurity addition. In contrast, quality factor $(Q{\cdot}f)$ and temperature coefficient of resonant frequency $(\tau_f)$ values were greatly influenced by the type and the amount of impurities. It was found that 0.1~0.2wt% addition of $Al_2O_3$ was most effective for improving the properties, where ${\varepsilon}_r$, $Q{\cdot}f$ and $\tau_f$ values were 57.7, 10000, and +7ppm/$^{\circ}C$, respectively.

• 보존과학회지
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• 제8권1호
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• pp.10-15
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• 1999

강릉 보광리 도요지에서 출토된 분청 도편의 성분과 미세구조의 특징을 EDS부착의 주사전자현미경과 X선 회절분석기, 열팽창측정기를 이용하여 조사하였다. 도편의 태토 성분은 $SiO_2(73-78\%),\;Al_2O_3(13-16\%)$, $RO{\cdot}R_2O(4-5\%,\;R=Ca,\;Mg,\;Na,\;K),\;R_xO_y(3-6\%,\;R=Fe,Ti)$로 구성되어 있으며, $SiO_2$의 양은 많은 편이나 $Al_2O_3$의 양은 적은 편이었다. 유약은 CaO 함량이 $21-30\%$로 높은 것으로 보아 석회계열의 유약으로 생각된다. 또한 도편의 소성온도는 $1150^{\circ}C$부근의 온도로 추정된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.124-125
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• 2007

The composites were fabricated $\beta$-SiC and $TiB_2$ powders with the liquid forming additives of 8, 12, 16[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid by pressureless annealing at $1,650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the pressureless annealed SiC-$TiB_2$ electroconductive ceramic composites. The relative density, the flexural strength, the Young's modulus and the Vicker's hardness showed the highest value of 82.29[%], 189.5[MPa], 54.60 [GPa] and 2.84[GPa] for SiC-$TiB_2$ composites added with 16[wt%] $Al_2O_3+Y_2O_3$ additives at room temperature. The relative density of SiC-$TiB_2$ composites was lowered due to gaseous products of the result of reaction between SiC and $Al_2O_3+Y_2O_3$. The electrical resistivity showed the lowest value of 0.012[${\Omega}{\cdot}cm$] for 16[wt%] at 25[$^{\circ}C$]. The electrical resistivity was all negative temperature coefficient resistance (NTCR) in the temperature ranges from 25[$^{\circ}C$] to 700[$^{\circ}C$].

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.865-868
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• 2002

$SnO_2$ powders were prepare by precipitating $Sn(OH)_4$ from an aqueous solution of $SnCl_4{\cdot}5H_2O$, pH 9.5. The effects of stability and sensitivity of $SnO_2$ thick film sensors added with various amounts, $SiO_2$, $Al_2O_3$, $ZrO_2$, $TiO_2$ have been investigated. It is shown that the 3wt% $Al_2O_3$ or $SiO_2$ can improve the stability of $SnO_2$ gas sensor at an operating temperature of $350^{\circ}C$.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.75-75
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• 2018

Commercially pure titanium (CP-Ti) and Ti-6Al-4V alloys have been widely used in implant materials such as dental and orthopedic implants due to their corrosion resistance, biocompatibility, and good mechanical properties. However, surface modification of titanium and titanium alloys is necessary to improve osseointegration between implant surface and bone. Especially, when titanium oxide nanotubes are formed on the surface of titanium alloy, cell adhesion is greatly improved. In addition, plasma electrolytic oxide (PEO) coatings have a good safety for osseointegration and can easily and quickly form coatings of uniform thickness with various pore sizes. Recently, the effects of bone element such as magnesium, zinc, strontium, silicon, and manganese for bone regeneration are researching in dental implant field. The purpose of this study was researched on the surface morphology of PEO-treated Ti-6Al-4V alloy after anodic titanium oxide treatmentusing various instruments. Ti-6Al-4V ELI disks were used as specimens for nanotube formation and PEO-treatment. The solution for the nanotube formation experiment was 1 M $H_3PO_4$ + 0.8 wt. % NaF electrolyte was used. The applied potential was 30V for 1 hours. The PEO treatment was performed after removing the nanotubes by ultrasonics for 10 minutes. The PEO treatment after removal of the nanotubes was carried out in the $Ca(CH_3)_2{\cdot}H_2O+(CH_3COO)_2Mg{\cdot}4H_2O+Mn(CH_3COO)_2{\cdot}4H_2O+Zn(CH_3CO_2)_2Zn{\cdot}2H_2O+Sr(CH_2COO)_2{\cdot}0.5H_2O+C_3H_7CaO_6P$ and $Na_2SiO_3{\cdot}9H_2O$ electrolytes. And the PEO-treatment time and potential were 3 minutes at 280V. The morphology changes of the coatings on Ti-6Al-4V alloy surface were observed using FE-SEM, EDS, XRD, AFM, and scratch tester. The morphology of PEO-treated surface in 5 ion coating solution after nanotube removal showed formation or nano-sized mesh and micro-sized pores.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1559-1561
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• 2002

적외선 확산반사형 결정화유리를 응용한 레이저 여기용 공진기를 제작하여 미세구조 분석 및 레이저 여기 효율특성을 조사하였다. 출발물질로는 Cordierite를 주결정상으로 하는 MAS(MgO, $Al_2O_3$, $SiO_2$) 3성분계 조성에 결정화 유도용 조핵제로 $TiO_2$를 첨가하였으며, 형성된 유리 용융물을 흑연제 몰드에 부어 공진기를 제조하였다. 용융물 중 일부를 2단계 열처리를 행하여 상분석을 실시한 결과 Cordierite($2MgO{\cdot}2Al_2O_3{\cdot}5SiO_2$)와 Rutile($TiO_2$)이 주결정상으로 관찰되었으며, 열처리 온도를 변화시켜 생성된 입자의 크기에 따른 확산반사율간의 관계를 조사한 결과, $1100{\sim}1200nm$에서 열처리된 시편의 경우 $500{\sim}2200nm$의 영역에서 95% 이상의 확산반사율을 나타내었다. 대표적인 고체레이저인 Nd:YAG의 경우, $700{\sim}900nm$ 파장이 주흡수대이며, 이를 결정화유리로 제조된 공진기의 레이저 효율특성실험에 이용하였다. 수냉 및 단일 펄스의 조건에서 $1.7{\sim}1.9%$의 효율을 나타내었다.

• 자원환경지질
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• 제43권3호
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• pp.269-278
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• 2010

우리는 단청안료의 착색제에 대한 특성을 살펴보았고, 이번 연구가 우리 전통 단청의 색을 재현하는데 기여하길 바란다. 광주 전남지역 목조 고건축물에서 자연적으로 박리가 일어난 부분의 단청안료 시료를 채취하고, 이를 XRD와 EDS-SEM분석을 이용하여 착색제를 분석하였다. 백색안료에서는 고대부터 착색제로 사용되어온 석고$(CaSO_4{\cdot}2H_{2}O)$,석영$(SiO_2)$, 백연석$(PbCO_3)$ 및 호분$(CaCO_3)$과 현대에서 많이 사용되는 산화지당$(TiO_2)$이 모든 시료에서 확인되었다. 적색안료에서는 고대부터 착색제로 사용된 석간주$(Fe_{2}O_{3})$와 연단$(Pb_{3}O_{4})$ 및 현대안료 착색제인 C. I. pigment orange $13(C_{32}H_{24}C_{12}N_{8}O_{2})$이 확인 되었지만, 진사(cinnabar, HgS)는 관찰되지 않았다. 황색안료에서는 납을 주성분으로 하는 황연인 홍연석$(PbCrO_4)$과 고대부터 사용된 밀타승(PbO)이 확인되었다. 청색안료에서는 착색제인 소달라이트 $(Na_{4}BeAlSi_{4}O_{12}Cl)$와 노제안$(Na_{8}Al_{6}Si_{6}O_{24}SO_{4})$이 확인되었으며, 현대안료 착색제인 C. I. pigment blue $29(Na_{7}Al_{6}Si_{6}O_{24}S_{3})$ 도 확인되었다. 녹색안료에서는 착색제로 카루머타이트(calumetite, $Cu(OHCI)_{2}{\cdot}2H_{2}O$), 에스콜라이트$(Cr_{2}O_{3})$, 디크롬트리옥사이드(dichromium trioxide, $Cr_{2}O_{3}$), 에머랄드그린$(C_{2}H_{3}As_{3}Cu_{2}O_{8})$ 및 현대안료 착색제인 C. I. pigment green$(C_{32}H_{16}-XCl_{x}Cu_{8})$이 확인되었다. 흑색안료에서는 먹(송연)이 확인 되었다.