• 한국안전학회지
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• 제14권1호
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• pp.19-24
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• 1999

A two dimensional thermo elasto-plastic finite clement stress analysis was performed to study stress distributions in functionally gradient material. The upper $ZrO_2$ surface is heated at 1200K until a steady state is established and cooled at 300K. The influences on the thermal stress distributions due to the difference of compositional gradient exponent p were investigated. In this study, we obtained the thermal stresses are low for p=1.

• KSBB Journal
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• 제13권5호
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• pp.477-482
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• 1998

A biosensor with PZT piezoelectric ceramic crystal was developed for the detection of formaldehyde gas. Poled PZT piezoelectric ceramic disk was made from ZrO2, TiO2 and Nb2O5, together with the addition of PbO and polyvinyl alcohol, through various processes of mixing, calcination drying, crushing, forming, sintering, polishing, ion coating and poling. Oscillator circuit of sensor was made of operational amplifier(AD811AN). Formaldehyde dehydrogenase was immobilized onto a piezoelectic ceramic crystal, together with the cofactors, reduced glutathione and nicotinamide adenine dinucleotide. The effect of flow rate on the sensitivity was determined by varing the flow rate of carrier gas from 24.7mL/min to 111.7mL/min through detector cell. The results indicated that as the flow rate was increased, the recovery rate was increased. And a significant increase in the sensitivity was observed in enhanced flow rate of carrier gas. Frequency difference(ΔF) of immobilized PZT piezoelectic disk increased proportionally to the concentration gas and reproduced to repeated exposures of formaldehyde gas(28ppm, Δ68Hz).

• 한국결정성장학회지
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• 제23권3호
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• pp.124-128
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• 2013

본 연구에서는 안정화제로, 패각으로부터 정제한 CaO를 사용하여 Skull melting법으로 큐빅 지르코니아를 성장시켰다. 꼬막 패각을 HCl을 0.1~1 mol%로 1차 처리한 후 수화반응을 거쳐 최적의 처리시간과 농도를 검토하였다. HCl을 1 mol%의 농도로 처리했을 때 가장 순도가 높았으며 수화반응시 $45^{\circ}C$의 온도로 24시간 동안 반응시킬 때 완전한 $Ca(OH)_2$ 를 얻을 수 있었다. $Ca(OH)_2$를 $1200^{\circ}C$에서 5시간 처리하였을 때 CaO의 순도가 가장 높게 측정되었다. 패각으로부터 얻어진 CaO를 $ZrO_2$에 첨가하여 함량을 10~30 mol% 로 변화시켜 Skull melting법으로 단결정을 성장시켰다. Skull melting법에 사용된 고주파 발진기의 주파수는 약 3.4 MHz이며 단결정의 하강속도는 시간당 3 mm로 4 cm 길이로 성장시켰다. 실험결과 CaO의 함량이 15 mol% 일 때 결정성이 가장 우수했다.

• 한국세라믹학회지
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• 제24권3호
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• pp.243-250
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• 1987

9mol% 의 MgO로 $1650^{\circ}C$에서 4시간 고상반응과 동시에 소결시킨 부분안정화 지르코니아 소결체(9MZ-PSZ)를 소성후 냉각중 $1200^{\circ}C$~$1400^{\circ}C$의 온도범위에서 열처리하여 이의 열분해 반응, 열충격기등 및 기전력 특성에 대하여 조사하였다. 열충격시럼 전과 후의 강도, 열팽창률, X-선 회절분석에 의한 단사정사 함률과 상전이, 밀도 및 갈바닉 전위를 측정하였으며 SEm에 의한 미세구조를 관찰하였다. 입체부근의 미소화학분석은 $1350^{\circ}C$ 열처리 시편에 한하여 EDX 로 정량하였다. 9MZ-PSZ 시편의 열처리에 의하여 입방정상의 $ZrO^{2}$는 상기 온도범위에서는 준안정-정방정상의 $ZrO^{2}$와 MgO로 열분해되는데, 이때 생성된 준안정 정방정상은 열충격 시험후의 잔류강도를 응력유기상전이 효과에 의해 증가시킨다. 또한 MgO는 입계에 연속적으로 존재하는데 이런하 MgO의 연속상을 통한 열전도롤 인하여 PSZ의 열충격 저항이 크게 향상된다. 이때 PSZ의 열분해 속도와 단사정상 함량은 열처리 온도가 $1400^{\circ}C$에서 $1200^{\circ}C$로 감소됨에 따라 증가한다. 갈바닉전의 측정결과 이상의 열처리에 의하여도 양호한 기전력 특성을 갖는 지르코니아 고체전해질을 제조할 수 있다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.339-342
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• 1998

Ferroelectric L $a_2$ $Ti_2$ $O_{7}$(LTO) thin films were prepared by chemical solution deposition processes. Acetylacetone was used as chelating agent and nitric acid was added in the stock solution to control hydrolysis and condensation reaction rate. The LTO thin films were spin-coated on Pt/Ti/ $SiO_2$/(100)Si and Pt/Zr $O_2$/ $SiO_2$/(100)Si substrates. After multiple coating, dried thin films were heat-treated for decomposition of residual organics and crystallization. The role of acetylacetone in Ti iso-propoxide stabilization by possibly substituting $O^{i}$Pr ligand was studied by H-NMR. B site-rich impurity phase, i.e. L $a_4$ $Ti_{9}$ $O_{24}$, was found after annealing, where its appearance was dependent on process temperature indicating the possible reaction with substrate. Dielectric and other relevant electrical properties were measured and the results were compared between modified sol-gel and MOD processes.s.s.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.51-54
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• 2003

Tb-doped lead zirconate titanate($Pb_{1.1}(Zr_{0.6}Ti_{0.4})O_3$; PZT) thin films on $Pt(111)/Ti/SiO_2/Si(100)$ substrates prepared by a sol-gel method. Films have a Zr/Ti ratio of 60:40 and perovskite phase structure. The effect on the structural and electrical properties of films measured according to Tb content. Dielectric and ferroelectric properties of PZT thin films were altered significantly by Tb-doping. The PZT thin film with higher dielectric constant and improved leakage current characteristic was obtained by adding 0.3 mol% Tb. At 100 kHz, the dielectric constant and the dielectric loss of the 0.3 mol% Tb-doped PZT thin film were 1611 and 0.24, respectively The remanent polarization(2Pr) of the 0.3 mol% Tb-doped PZT thin film was $61.4\;{\mu}C/cm^2$ and the coercive field was 61.9 kV/cm. Tb-doped PZT thin films showed improved fatigue characteristics comparing to the undoped PZT thin film.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.869-877
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• 2020

A 24-month Advanced Power Reactor 1400 (APR1400) core with a very-low-boron (VLB) concentration has been investigated for an inherently safe and high-performance PWR in this work. To develop a high-performance APR1400 which is able to do the passive frequency control operation, VLB feature is essential. In this paper, the centrally-shielded burnable absorber (CSBA) is utilized for an efficient VLB operation in the 24-month cycle APR1400 core. This innovative design of the VLB APR1400 core includes the optimization of burnable absorber and loading pattern as well as axial cutback for a 24-month cycle operation. In addition to CSBA, an Er-doped guide thimble is also introduced for partial management of the excess reactivity and local peaking factor. To improve the neutron economy of the core, two alternative radial reflectors are adopted in this study, which are SS-304 and ZrO₂. The core reactivity and power distributions for a 2-batch equilibrium cycle are analyzed and compared for each reflector design. Numerical results show that a VLB core can be successfully designed with 24-month cycle and the cycle length is improved significantly with the alternative reflectors. The neutronic analyses are performed using the Monte Carlo Serpent code and 3-D diffusion code COREDAX-2 with the ENDF/B-VII.1.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.179-182
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• 2001

The chloride volatilization method for the recovery of zirconium and removal of uranium from zirconium containing metallic wastes formed in spent fuel reprocessing was studied using the simulated alloy waste, i.e. the mixture of Zr foil and UO$_2$/U$_3$O$_{8}$ powder. When the simulated waste was heated to react with chlorine gas at 350- l00$0^{\circ}C$, the zirconium metal changed to volatile ZrCl$_4$showing high volatility ratio (Vzr) of 99%. The amount of volatilized uranium increases at higher temperatures causing lowering of decontamination factor (DF) of uranium. This is thought to be caused by the chlorination of UO$_2$ with ZrCl$_4$vapor. The highest DF value of 12.5 was obtained when the reaction temperature was 35$0^{\circ}C$. Addition of 10 vol.% oxygen gas into chlorine gas was effective for suppressing the volatilization of uranium, while the volatilization ratio of zirconium was decreased to 68% with the addition of 20 vol.% oxygen. In the case of the mixture of Zr foil and U$_3$O$_{8}$, the V value of uranium showed minimum (44%) at 40$0^{\circ}C$ with chlorine gas giving the highest DF value 24.3. When the 10 vol.% oxygen was added to chlorine gas, the V value of zirconium decreased to 82% at $600^{\circ}C$, but almost all the uranium volatilized (Vu=99%), which may be caused by the formation of volatile uranium chlorides under oxidative atmosphere.ere.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1991년도 추계학술대회 논문집
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• pp.68-72
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• 1991

In this study, to improve temperature stability 0.05 Pb(Sn$\_$$\frac{1}{2}$/Sb$\_$$\frac{1}{2}$/O$_3$ - 0.35PbTiO$_3$ - 0.60PbZrO$_3$ + 0.4[wt%]MnO$_2$ piezoelctric oeramics of low dielectric constant and large mechanical quality factor were manufactured with the addition of Cr$_2$O$_3$by Hot Press method. And the SAW delay line was fabricated and the propagation characteristics of SAW was investigated, and the SAW filter was fabricated on C4 added by 0.2[wt%] Cr$_2$O$_3$and its frequency characteristics was investigated. The specimen, whose propagation characteristics of surface acoustic wave were the best, was C4 added by 0.2[wt%] Cr$_2$O$_3$, and its electromechanical coupling factor(ks$^2$) was 3.11[%] and its temperature coefficient of the center frequency (C$\_$fo/) was -21.27[ppm/$^{\circ}C$]. The 31[MHz] SAW IF filter of C4 scarcely had diffraction phenomena and its group delay time was 1.4673 ${\pm}$40[ns] in the pass band, and the insertion loss was -24.419[dB] on no impedance matching.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.324-324
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• 2010

핵융합의 고체형 증식(Helium Cooled Solid Breeder : HCSB) 블랑켓(Blanket Module)은 삼중수소 증식을 위해서 Li4SiO4, Li2TiO3, Li2O 및 Li2ZrO3 등의 페블이 고려되고 있다. 이러한 페블을 제조하기 위해서는 먼저 각각의 분말 제조가 선행되어야 한다. 한국의 Test Blanket Module(TBM)은 Li4SiO4 페블을 개발을 개발하여 사용할 예정이고 옵션으로 Li2TiO3 페블을 개발하는 것으로 되어 있다. Li4SiO4 페블을 개발하기 위해서 먼저 분말합성이 필수적이다. Li4SiO4 분말을 합성에 하기 위해서는 Lithium 금속염과 실리카 졸을 용매 및 폴리머 캐리어로서의 두 가지 기능을 하는 에틸렌글리콜에 첨가한 후 가열하여 완전히 용해시킨 후 혼합 용액을 건조시켜 겔형의 전구체를 제조한다. 이를 하소한 후 결정화시켜 Silicate 분말을 얻는데 이때의 건조, 하소 및 결정화 온도의 조건에 따른 분말의 크기 및 특성이 각각 다르다. 즉, 바인더 물질의 비율과 합성온도에 따라 특성이 약간씩 다른 분말을 얻을 수 있었다. 이렇게 얻어진 Silicate 분말은 지르코니아 볼을 이용하여 약 24 시간 동안 볼 밀링 과정을 통해 입도가 작은 미세한 Silicate 분말로 만들었다. 합성된 분말은 여러 가지 시험 및 분석을 통해서 검증되었으며, 불순물 등은 관찰되지 않았다.