무알칼리 다성분 La₂O₃-Al₂O₃-SiO₂ 유리의 조성과 몇 가지 물성의 관계

강은태,양태영,황종희,Kang, Eun-Tae,Yang, Tae-Young,Hwang, Jong-Hee 한국세라믹학회 2011 한국세라믹학회지 Vol.48 No.2

Non-Alkali multicomponent $La_2O_3-Al_2O_3-SiO_2$ glasses has been designed and analyzed on the basis of a mixture design experiment with constraints. Fitted models for thermal expansion coefficient, glass transition temperature, Young's modulus, Shear modulus and density are as follows: ${\alpha}(/^{\circ}C)=8.41{\times}10^{-8}x_1+5.72{\times}10^{-7}x_2+2.13{\times}10^{-7}x_3+1.09{\times}10^{-7}x_4+1.10{\times}10^{-7}x_5+1.15{\times}10^{-7}x_6+2.72{\times}10^{-8}x_7+2.41{\times}10^{-7}x_8-1.08{\times}10^{-8}x_1x_2+4.28{\times}10^{-8}x_3x_7-2.02{\times}10^{-8}x_3x_8-1.60{\times}10^{-8}x_4x_5-2.71{\times}10^{-9}x_4x_8-2.19{\times}10^{-8}x_5x_6-3.89{\times}10^{-8}x_5x_7$ $T_g(^{\circ}C)=7.36x_1+15.35x_2+20.14x_3+8.97x_4+13.85x_5+4.22x_6+28.21x_7-1.44x_8-0.84x_2x_3-0.45x_2x_5-1.64x_2x_7+0.93x_3x_8-1.04x_5x_8-0.48x_6x_8$ $E(GPa)=2.04x_1+14.26x_2-1.22x_3-0.80x_4-2.26x_5-1.67x_6-1.27x_7+3.63x_8-0.24x_1x_2-0.07x_2x_8+0.14x_3x_6-0.68x_3x_8+0.29x_4x_5+1.28x_5x_8$ $G(GPa)=0.35x_1+1.78x_2+1.35x_3+1.87x_4+9.72x_5+29.16x_6-0.99x_7+3.60x_8-0.48x_1x_6-0.50x_2x_5+0.08x_3x_7-0.66x_3x_8+0.94x_5x_8$ ${\rho}(g/cm^3)=0.09x_1+0.51x_2-4.94{\times}10^{-3}x_3-0.03x_4+0.45x_5-0.07x_6-0.10x_7+0.07x_8-9.60{\times}10^{-3}x_1x_2-8.20{\times}10^{-3}x_1x_5+2.17{\times}10^{-3}x_3x_7-0.03x_3x_8+0.05x_5x_8$ The optimal glass composition similar to the thermal expansion coefficient of Si based on these fitted models is $65.53SiO_2{\cdot}25.00Al_2O_3{\cdot}5.00La_2O_3{\cdot}2.07ZrO_2{\cdot}0.70MgO{\cdot}1.70SrO$.

(40-x)BaO⋅xFe₂O₃⋅60P₂O₅ 유리의 Fe³⁺이온에 관한 전자스핀공명 연구

강은태,Kang, Eun-Tae 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.3

(40-x)BaO${\cdot}xFe_2O_3{\cdot}60P_2O_5$ glasses with $5{\leq}x{\leq}35mol%$ were investigated by ESR spectroscopy. Two resonances observed near g=2.0 and g=4.3. The line at g=4.3 disappeared with the increase of the $Fe_2O_3$ content. The resonance at $g{\approx}2.0$ displayed characteristic signal consisting of superposed extremely broad and narrow components. The broader one indicates the presence of the association of two or more $Fe^{3+}$ ions, antiferromagnetically and the narrow one is related to the microclusters involving iron ions. Temperature dependence of the ESR integrated intensity revealed short-range antiferromagnetic character for $x{\geq}15mol%$.

혼합물계획법에 의한 Li₂O-ZrO₂-SiO₂ 유리의 이온전도도와 조성의 관계

강은태,김명중,김재동,Kang, Eun-Tae,Kim, Myoung-Joong,Kim, Jae-Dong 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.4

The ionic conductivity of $Li_2O-ZrO_2-SiO_2$ glasses has been designed and analyzed on the basis of a mixture design experiment with constraints. Fitted models for the activation energy and the ionic conductivity are as follows: $Q(kJ/moi)=54.8565x_1+144.825x_2+133.846x_3-170.908x_1x_3-334.338x_2x_3$ $log{\sigma}(300K)=-5.00245x_1-1.17876x_2-15.5173x_3+17.4522x_1x_3$. The electrical properties are very sensitive to the ratio of $Li_2O/SiO_2$. The effect of $ZrO_2$ is less than that of this ratio but $ZrO_2$ component attributes to the reduction of the activation energy. The optimal composition for best ionic conduction based on these fitted models is $55Li_2O{\cdot}10ZrO_2{\cdot}35SiO_2$. Its activation energy and ionic conductivity at 300 K are 46.98 kJ/mol and $1.08{\times}10^{-5}{\Omega}^{-1}{\cdot}cm^{-1}$, respectively.

Rietveld Refinement에 의한 NASICON의 결정구조

강은태,정훈,최진삼,최진범,Kang, Eun-Tae,Cheong, Hoon,Choi, Jin-Sam,Choi, Jin-Beom 한국재료학회 1996 한국재료학회지 Vol.6 No.5

고상반응법과 sol-gel법으로 제조된 NASICON의 상온과 25$0^{\circ}C$에서의 X선 회절 데이터를 리트벨트 분석을 행하였다. monoclinic에서 rhombohedral로 상전이가 일어나도 원자들의 변위는 매우 작았다. 이들 상간의 ZrO6 팔면체와 Si(P)O4 사면체고 구성된 골격은 다소 다르게 나타남으로 인하여 Na 이온의 자리도 변하였다. 이들 방법으로 제조된 NASICON은 Zr이 부족한 비화학양론 화학식, Na 1+x+4yZr2-xSixP3-xO12으로 표현될 수 있었다. 제조법에 따라 Na 이온들의 자리 점유율이 변화하였다. 상온에서는 Na(1)과 Na(3)자리의 자리 점유율의 합이 거의 1에 가까웠으나, 25$0^{\circ}C$에서는 Na(1)과 mid Na 자리를 단위 화학식 당 한 개를 약간 상회하는 Na 이온이 점유하였다. 상온과 25$0^{\circ}C$에서의 Na 이온의 이동 경로가 다름을 알 수 있었다. 또한 25$0^{\circ}C$에서는 Na(1)자리와 Na(2)자리 사이에 mid Na가 존재하며, 이 자리가 Na 이온의 이동에 중요한 역할을 함을 알 수 있었다.

수열처리에 의한 폐병유리의 다공질 재료화

임동규,강은태,Lim, Dong-Kyu,Kang, Eun-Tae 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.3

Porous materials were manufactured by hydrothermal treatment of waste bottle glass without foam agent. Factorial design was applied to analyze data by statistical methods and deal with the important factors for a process. The largest effect for porosity was for temperature of hydrothermal treatment. Amount of water and temperature-water interaction appeared to have little effect. The particle size of raw material was also identified as a major factor by one-way ANOVA and the porosity decreased as the size increased. The sintering temperature was not statistically significant for the porosity but was significant for the pore size. The porous material had compressive strength and thermal conductivity comparing with those of ALC (autoclaved lightweight concrete), although it has higher porosity than for ALC.

동시 증착 스퍼터링 공정에 의해 증착된 Pd-barium zirconate membrane의 구조분석

변명섭,강은태,조우석,김진호,황광택,Byeon, Myeong-Seop,Kang, Eun-Tae,Cho, Woo-Seok,Kim, Jin-Ho,Hwang, Kwang-Taek 한국결정성장학회 2012 韓國結晶成長學會誌 Vol.22 No.1

Barium zirconate는 화학적 안정성이 우수하고 고온에서의 프로톤 전도성이 뛰어나지만, 프로톤 전도도에 비해 전자전도도가 현저히 떨어진다. 따라서 본 연구에서는 높은 수소 분리 특성을 위해 다공성 지지체 상에 Pd-Barium zirconate를 얇고 치밀한 박막으로 제조하고자 하였고, dual sputtering법을 이용하여 성공적으로 증착하였다. X-선 회절 분석을 통해 증착된 $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ 박막은 300 이상에서부터 $BaZrO_3$(Pm-3m) 결정상으로 결정화됨을 확인할 수 있었으며 표면과 단면에 대한 구조적 형상은 SEM과 TEM을 통해 관찰하였다. 관찰 결과 증착된 분리막은 치밀하였고 부채꼴의 주상으로 결정이 성장함을 확인할 수 있었다. Barium zirconate exhibits good thermo-chemical stability and proton conduction at high temperatures, but shows poor electron conductivity. Therefore, for high efficiency of hydrogen separation, a very thin and dense Pd-Barium zirconate membrane has to be coated on a porous substrate. A thin and dense Pd-Barium zirconate membrane was successfully synthesized on a porous substrate by means of dual sputtering method. The structural and chemical features of the $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ membranes sputtered at $300^{\circ}C$ and $400^{\circ}C$ were investigated by X-ray diffractometry, and it was found that a well-crystallized membrane, Pm-3m space group of $BaZrO_3$, was synthesized. The surface and cross-sectional morphologies of membrane were assessed by SEM (scanning electron microscopy) and TEM(transmission electron microscopy) of the surface and of cross sections. The cross sectional observation of Pd-$BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ membrane by dual sputtering shows that the coating is quite dense with columnar structure.

LAS (β-spodumene)와 Fe₂O₃ 첨가에 따른 Al₂TiO₅의 소결체 특성 연구

김상훈,강은태,김응수,황광택,조우석,Kim, Sang-Hun,Kang, Eun-Tae,Kim, Ung-Soo,Hwang, Kwang-Taek,Cho, Woo-Seok 한국결정성장학회 2012 韓國結晶成長學會誌 Vol.22 No.1

$Al_2TiO_5$에 LAS(${\beta}$-spodumene)와 $Fe_2O_3$를 첨가하여 고상법으로 세라믹 소결체를 제조하였다. $Al_2TiO_5$에 첨가된 LAS는 액상을 형성하고, $Fe_2O_3$는 입자 성장을 억제시켜 소결체를 치밀화하였다. 첨가제의 양을 변화시켜 소결특성, 기계적 특성 및 열충격 특성에 대하여 조사하였다. $Fe_2O_3$가 20 wt% 첨가된 LAS를 $Al_2TiO_5$에 20 wt% 첨가하였을 때, 꺽임 강도는 120 MPa 이상이었고, 열충격에 대한 저항성은 $1200^{\circ}C$ 이상으로 우수함을 확인하였다. $Al_2TiO_5$ ceramics were sintered by a solid-state reaction. LAS (${\beta}$-spodumene) and $Fe_2O_3$ were added to the $Al_2TiO_5$ composition for enhancement of sintering behavior such as mechanical strength and thermal shock resistance. The sintered body was much densified by addition of LAS and $Fe_2O_3$ because LAS formed the liquid-phase and $Fe_2O_3$ suppressed the grain growth. We have systematically investigated the sintering characteristics, microstructures, mechanical properties, and thermal shock resistance according to the change of the amount of additive. When the additive of LAS (20 wt%)-$Fe_2O_3$ was added to $Al_2TiO_5$, it confirmed that superior mechanical properties of the fracture strength of over 120 MPa and the thermal shock resistance of over $1,200^{\circ}C$ were achieved.

고상반응법을 이용한 LAS계의 CaCO₃와 ZrO₂ 첨가에 따른 소결체 특성 연구

김상훈,강은태,김응수,황광택,조우석,Kim, Sang-Hun,Kang, Eun-Tae,Kim, Ung-Soo,Hwang, Kwang-Taek,Cho, Woo-Seok 한국결정성장학회 2011 한국결정성장학회지 Vol.21 No.5

저열팽창 특성을 갖는 난소결 물질인 LAS($Li_2O-Al_2O_3-SiO_2$)계를 고상 소결로 제조하였다. LAS계의 ${\beta}$-spodumene($Li_2O-Al_2O_3-4SiO_2$) 조성에 소결 조제로 $CaCO_3$를 첨가하였고, 강도 증가를 위하여 $ZrO_2$를 첨가하였다. 첨가제의 양의 변화와 소결 온도의 변화에 따른 소결 특성, 미세 구조, 기계적 특성 및 열팽창 특성에 대하여 조사하였다. 0.1 mol%의 $CaCO_3$을 첨가하였을 때, 치밀화가 증진됨을 미세구조 관찰에 의해 확인하였으며, $ZrO_2$의 첨가로 강도가 증진됨을 확인하였다. Dilatometer로 측정한 열팽창 계수는 선택된 전 조성에서 값이 $1.2{\sim}1.7{\times}10^6/^{\circ}C$임을 확인하였다. LAS ($Li_2O-Al_2O_3-SiO_2$) ceramics were sintered by a solid-state reaction. $CaCO_3$ and $ZrO_2$ were added to the ${\beta}$-spodumene ($Li_2O-Al_2O_3-4SiO_2$) composition of the LAS system for enhancement of sintering behavior and mechanical strength, respectively. We have investigated the sintering characteristics, microstructures, mechanical properties and thermal expansion characteristics according to the change of the amount of additive and sintering temperature of the ${\beta}$-spodumene. At 0.1 mol% $CaCO_3$, the densification of ${\beta}$-spodumene was significantly improved. At 0.04 mol% $ZrO_2$, the strength of ${\beta}$-spodumene was also improved. For all the selected all compositions, the thermal expansion coefficient was measured by a dilatometer, which revealed 1.2 to $1.7{\times}10^6/^{\circ}C$.

침전법과 착체중합법을 이용한 Ga₂O₃ 분말의 합성 및 결정구조 분석

정종열,김상훈,강은태,한규성,김진호,황광택,조우석,Jung, Jong-Yeol,Kim, Sang-Hun,Kang, Eun-Tae,Han, Kyu-Sung,Kim, Jin-Ho,Hwang, Kwang-Teak,Cho, Woo-Seok 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.3

Gallium oxide ($Ga_2O_3$) powders were synthesized using a precipitation method and a polymerized complex method. TG-DSC, SEM, and XRD were performed to investigate the phase and morphology of the $Ga_2O_3$. In situ high-temperature XRD analysis revealed the crystal structure of $Ga_2O_3$ at different temperatures. The $Ga_2O_3$ obtained using the precipitation method and polymerized complex method were generally spherical-shaped particles and their average particle size was approximately 80 nm and $1{\mu}m$, respectively. The crystal structure of the $Ga_2O_3$ prepared by the precipitation method was changed from rhombohedral to monoclinic at $700^{\circ}C$, while monoclinic $Ga_2O_3$ was obtained directly from the precursor by the polymerized complex method.

착체중합법을 이용한 Ga₂O₃ 나노 분말의 합성

정종열,김상훈,강은태,한규성,김진호,황광택,조우석,Jung, Jong-Yeol,Kim, Sang-Hun,Kang, Eun-Tae,Han, Kyu-Sung,Kim, Jin-Ho,Hwang, Kwang-Teak,Cho, Woo-Seok 한국결정성장학회 2013 韓國結晶成長學會誌 Vol.23 No.6

본 연구에서는 InGaZnO 산화물 반도체를 제조하기 위한 출발물질 중 하나인 $Ga_2O_3$ 분말을 착체중합법을 이용하여 합성하였다. 함께 사용되는 다른 출발 물질인 $In_2O_3$와 ZnO 분말 입자가 수십 nm 크기로 제조되는 반면 $Ga_2O_3$ 분말입자는 아직까지 수 ${\mu}m$ 크기의 입자가 사용되기 때문에 입도의 균일성을 확보하기 위해 착체중합법의 공정을 최적화하여 $Ga_2O_3$ 나노 분말을 합성하고 그 물성을 분석하였다. $Ga_2O_3$ 나노 분말 합성의 출발물질로 ethylene glycol, citric acid, $Ga(NO_3)_3$를 사용하였으며 $500{\sim}800^{\circ}C$에서 $Ga_2O_3$ 나노 입자을 합성하였다. TG-DTA 분석을 통해 전구체에서 유기물이 소실되는 온도를 확인하였고, XRD 분석을 통해 $Ga(NO_3)_3$ 농도 및 열처리 온도에 따른 $Ga_2O_3$ 나노 입자의 결정성을 확인하였다. SEM 분석을 이용하여 $Ga_2O_3$ 나노 입자의 미세 구조 및 입도 분포를 확인하였다. In this study, we report the synthesis and characteristics of gallium oxide ($Ga_2O_3$) nanoparticles prepared by the polymerized complex method. $Ga_2O_3$ nanoparticles were synthesized using $Ga(NO_3)_3$, ethylene glycol, and citric acid as the starting materials at a low temperature of $500{\sim}800^{\circ}C$. The temperature of the weight reduction by the loss of organic precursor was revealed using TG-DTA analysis. The crystal structural change of $Ga_2O_3$ nanoparticles by the annealing process was investigated by XRD analysis. The morphologies and the size distributions of $Ga_2O_3$ nanoparticles were analyzed using SEM.