• 제목/요약/키워드: Calcined powder

검색결과 254건 처리시간 0.027초

NiO가 도핑된 BaZr0.85Y0.15O3-δ의 소결거동 및 전도도에 관한 연구 (A Study on Sintering Behavior and Conductivity for NiO-doped BaZr0.85Y0.15O3-δ)

  • 박영수;김진호;김혜경;황광택
    • 한국수소및신에너지학회논문집
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    • 제23권6호
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    • pp.670-677
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    • 2012
  • Perovskite-type oxides such as doped barium zirconate ($BaZrO_3$) show high proton conductivity and chemical stability when they are exposed to hydrogen and water vapour containing atmospheres, thus it can be applicable to the hydrogen separation and the fuel cell electrolyte membranes. However the high temperature ($1700-1800^{\circ}C$) and long sintering times (24h) are generally required to prepare the fully densified $BaZrO_3$ pellets. These sintering conditions lead to the limitation of the grain size growth and the degradation of conductivity due to the acceleration of BaO evaporation at $1200^{\circ}C$. Here we demonstrate NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ with lower calcination and sintering temperature, less experimental procedure and lower process cost than the conventional mixing method. The stoichiometry of $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ was optimized by the control of excess amount of Ba (5mol%) to minimized BaO evaporation. We found that the crystal size of NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ was increased with increase of calcination temperature from XRD analysis. NiO-doped $BaZr_{0.85}Y_{0.15}O_{3-{\delta}}$ powder was calcined at $1000^{\circ}C$ for 12h when its showed the highest conductivity of $3.3{\times}10^{-2}s/cm$.

부분 안정화 지르코니아의 파괴거동 (Fracture Behaviour of PSZ Composite)

  • 김환;임은극;고정하;황규홍
    • 한국세라믹학회지
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    • 제21권3호
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    • pp.239-244
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    • 1984
  • The effect of tetragonal $ZrO_2$ phase on the mechanical behavior in 7 mole% calcia partially stabilized zirconia has been studied. The $ZrO_2$ powder containg 7 mole% CaO prepared by Hot Petroleum Drying Method calcined at 80$0^{\circ}C$ for 1 hour was nearly 100% tetragonal but as the calcining temperature increased certain amount of monoclinic phase appeared. The sintered specimen at 1$700^{\circ}C$ for 5 hours was aged at 130$0^{\circ}C$ for 0, 24, 48, 72 hours. X-ray diffraction data showed that in the aged specimen monoclinic tetragonal and cubic phase coexisted. The Kc value of aged specimen for 48 hr was about 4.5MN/m3/2 much greater than unaged sample. But aged for 72 hr the KiC value was decreased. The increasing of toughness in PSZ is based on the Stress-Induced Phase Transformation that is metastable tetra-gonal $ZrO_2$ changes t stable monoclinic phase within the stress field of crack and the mechanical fracture energy absorption is occured But in this case due to certain amount of tetragonal phase transformed to monoclinic phase during cooling the microcrack effect by transformation also considered. Trerefore both Stress-Induced Phase Transformation and inclusion induced microcracking effect contrbute to the increase of fracture toughness of 7 mole% CaO-$ZrO_2$ containing monoclinic and tetragnola phase simulataneously.

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Preparation of LiCoO$_2$from Used Lithium Ion Battery by Hydrometallurgical Processes

  • Lee, Churl-Kyoung;Rhee, Kang-In;Yang, Dong-Hyo;Yu, Hyo-Shin
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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    • pp.240-244
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    • 2001
  • Recycling process involving mechanical, thermal, hydrometallurgical, and sol-gel step has been applied to recover cobalt and lithium from spent lithium ion batteries and to synthesize LiCoO$_2$from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt could be concentrated with 2-step thermal and mechanical treatment. Leaching behaviors of the lithium and cobalt in nitric acid media was investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO$_3$solution turned out to be an effective reducing agent by enhancing the leaching efficiency. O f many possible processes to produce LiCoO$_2$, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO$_2$with nitric acid, the molar ratio of Li/Co in the leach liquor was adjusted at 1.1 by adding a fresh LiNO$_3$solution. Then, 1 M citric acid solution at a 100% stoichiometry was also added to prepare a gelatinous precursor. When the precursor was calcined at 95$0^{\circ}C$ for 24 hr, purely crystalline LiCoO$_2$was successfully obtained. The particle size and specific surface area of the resulting crystalline powders were 20 пm and 30 $\textrm{cm}^2$/g, respectively The LiCoO$_2$powder was proved to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance.

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Oxalate법으로 합성한 LSCF의 pH 변화에 따른 공기극 특성 (Properties of Synthesis LSCF Cathode with pH Control using Oxalate Method)

  • 이미재;최병현;김세기;지미정
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2007년도 추계학술대회 논문집
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    • pp.17-18
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    • 2007
  • Solid oxide fuel cells are clean, pollution-free technology for the electrochemical generation of electricity at high efficiency. Specially, the polarization resistance between electrolyte and electrode of SOFC unit cell is of importance, because it is desirable to develop SOFC operating at intermediate temperature below $800^{\circ}C$. The LSCF cathode prepared using modified oxalate method was investigated with different electrolyte. A precursor was prepared with oxalic acid, ethanol and $NH_4OH$ solution. The LSCF precursor was prepared at $80^{\circ}C$, and pH control was 2, 6, 8, 9 and 10. The precursor powder was calcined at $800^{\circ}C$, $1000^{\circ}C$ and $1200^{\circ}C$ for 4hrs. The crystal of LSCF powders show single phase at pH 2, 6, 8 and 9, and the average particle size was about $3{\mu}m$. The LSCF cathode with heat treatment at $1200^{\circ}C$ showed a plot of electric conductivity versus temperature. Unit cell prepared from the LSCF cathode, buffer layer between cathode and electrolyte and the LSGM, YSZ, ScSZ and CeSZ electrolyte. Also interface reaction between LSCF, buffer layer and electrolyte were measured by EPMA and the polarization resistance for unit cell with cycle measure using a Solatron 1260 analyzer.

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$\beta$-$Al_2O_3$의 제조 및 전기전도도 (Preparation and Electrical Conductivity of $\beta$-$Al_2O_3$)

  • 송효일;김응수;윤기현
    • 한국세라믹학회지
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    • 제23권3호
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    • pp.1-8
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    • 1986
  • The preparation and electrical conductivity of $\beta$-$Al_2O_3$ are investigated as a function of $Na_2O$ content from the-oretical composition of $\beta$-$Al_2O_3$ to that of $\beta$"-$Al_2O_3$. $\beta$-$Al_2O_3$ $\beta$"$Al_2O_3$$\alpha$-Al2O3 and ${\gamma}$-NaAlO2 phases appear in the calcined powder at 125$0^{\circ}C$ for 2 hours. The majoity phase is $\beta$-$Al_2O_3$ in sintered specimens at 155$0^{\circ}C$ and 1$650^{\circ}C$ for 30 mins respectively and ${\gamma}$-4NaAlO_2$ phase also exists when Na2O content is over 10.39w/o ${\gamma}$-4NaAlO_2$ phase does not affect the grain growth of $\beta$-$Al_2O_3$ in sintering at 155$0^{\circ}C$ but acts as a reactive liquid for the abnormal grain growth of $\beta$-$Al_2O_3$in sintering at 1$650^{\circ}C$ The electrical conduction of $\beta$-$Al_2O_3$is predominated by 4Na^+$ ion. Contribution of ionic con-ductivity to total conductivity is gradually decreased with increasing temperature at given oxygen pressure and to -tal conductivity is increased by positive hole due to interstitial oxygen with increasing oxygen pressure.

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Cathode Materials LaNi1−xCuxO3 for Low Temperature Solid Oxide Fuel Cells

  • Sun, Juncai;Wang, Chengli;Li, Song;Ji, Shijun
    • 한국세라믹학회지
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    • 제45권12호
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    • pp.755-759
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    • 2008
  • New cathode materials $LaNi_{1-x}{Cu_x}{O_3}$ (typically $LaNi_{0.8}Cu_{0.2}O_3$) were synthesized using a co-precipitation method. The structure and morphology of the powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composite material [$Ce_{0.8}Sm_{0.2}O_{2-\ddot{a}}$(SDC) and carbonate (${Na_2}{CO_3},{Li_2}{CO_3}$)], NiO and $LaNi_{1-x}{Cu_x}{O_3}$ were used as the electrolyte, anode and cathode, respectively. The electrochemical performance of La-Ni-Cu-O perovskite oxide at low temperatures ($400{\sim}550^{\circ}C$) was studied. The results showed that $LaNi_{0.8}Cu_{0.2}O_3$ precursor powder prepared through a co-precipitation method and calcined at $860^{\circ}C$ for 2 h formed uniform grains with diameters in the range of $400{\sim}500\;nm$. The maximum power density and the short circuit current density of the single cell unit at $550^{\circ}C$ were found to be $390\;mW/cm^2$ and $968\;mA/cm^2$, respectively.

착체중합법을 이용한 (Ni,Mg)Al2O4 Cyan 나노 무기안료 합성 (Synthesis of (Ni,Mg)Al2O4 Ceramic Nano Pigment by a Polymerized Complex Method)

  • 손보람;윤대호;한규성;조우석;황광택;김진호
    • 한국세라믹학회지
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    • 제50권3호
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    • pp.195-200
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    • 2013
  • Here, we report preparation of cyan ceramic nano-pigment for inkjet printing and the Ni substitutional effects on the cyan color. $MgAl_2O_4$ was selected as the crystalline host network for the synthesis of nickel-based cyan ceramic nano-pigments. Various compositions of $Ni_xMg_{1-x}Al_2O_4$ ($0{\leq}x{\leq}1$) powders were prepared using the polymerized complex method. The powder was then preheated at $400^{\circ}C$ for 5 h and finally calcined at $1000^{\circ}C$ for 5 h. XRD patterns of $Ni_xMg_{1-x}Al_2O_4$ showed a single phase of the spinel structure in all the compositions. The particle sizes ranged from 20 to 50 nm in TEM observations. The characteristics of the color tones of $Ni_xMg_{1-x}Al_2O_4$ were analyzed by UV-Visible spectroscopy and CIE $L^*a^*b^*$ measurement. CIE $L^*a^*b^*$ measurement results indicate that the pigment color changes from light cyan to deep cyan due to the decrease of the $a^*$ and $b^*$ values with an increase of an Ni substitutional amount. In addition, the thermal stability and the binding nature of $Ni_xMg_{1-x}Al_2O_4$ are also discussed using TG-DSC and FT-IR results respectively.

Sol-Precipitation법으로 제조된 WO3 나노분말을 이용한 후막 센서의 NO2 감지 특성 (NO2 Sensing Characteristics of WO3 Thick Film Sensors Using Nanosized WO3 Powders Prepared by Sol-Precipitation Process)

  • 류현욱;박경희;김인천;홍광준;박진성
    • 한국재료학회지
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    • 제12권12호
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    • pp.930-934
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    • 2002
  • Nanosized $WO_3$ powders were synthesized by the sol-precipitation process using $WCl_{6}$ as the starting material, ethanol as a solvent and $NH_4$OH solution as a precipitant, followed by a washing-drying treatment and calcination. The effects on the powder crystallinity and microstructure of calcination temperature were investigated with XRD and FE-SEM. The $WO_3$ powders calcined at $500^{\circ}C$ and $700^{\circ}C$ showed good crystallinity and their mean particle size was 30nm and 70nm, respectively. These powders were used for the preparation of pastes which were printed as thick films on alumina substrates with comb-type Pt electrodes. The particle size strongly influenced the $NO_2$ gas sensing property of the thick films. A significant reduction in the $NO_2$ sensitivity was observed for the film prepared from larger particle size, having thus a larger grain size. For the film having a smaller grain size, on the other hand, the higher $NO_2$ sensitivity was observed and the sensitivity increased with $NO_2$ concentration.

Enhanced Magnetic Properties of BiFe1-$_xNi_xO_3$

  • Yoo, Y.J.;Hwang, J.S.;Park, J.S.;Kang, J.H.;Lee, B.W.;Lee, S.J.;Kim, K.W.;Lee, Y.P.
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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    • pp.183-183
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    • 2011
  • Multiferroic materials have been widely studied in recent years, because of their abundant physics and potential applications in the sensors, data storage, and spintronics. $BiFeO_3$ is one of the well-known single-phase multiferroic materials with $ABO_3$ structure and G-type antiferromagnetic behavior below the Neel temperature $T_N$ ~ 643 K, but the ferroelectric behavior below the Curie temperature $T_c$~1,103 K. In this study, the $BiFe_{1-x}Ni_xO_3$ (x=0 and 0.05) bulk ceramics were prepared by solid-state reaction and rapid sintering with high-purity $Bi_2O_32$, $Fe_3O_4$ and NiO powders. The powders of stoichiometric proportions were mixed, as in the previous investigations, and calcined at 450$^{\circ}C$ for $BiFe_{1-x}Ni_xO_3$ for 24 h. The obtained powders were grinded, and pressed into 5-mm-thick disks of 1/2-inch diameter. The disks were directly put into the oven, which has been heated up to 800$^{\circ}C$ and sintered in air for 20 min. The sintered disks were taken out from the oven and cooled to room temperature within several min. The phase of samples was checked at room temperature by powder x-ray diffraction using a Rigaku Miniflex diffractometer with Cu K${\alpha}$ radiation. The Raman measurements were carried out by employing a hand-made Raman spectrometer with 514.5-nm-excitation $Ar^+$ laser source under air ambient condition on a focused area of 1-${\mu}m$ diameter. The field-dependent magnetization measurements were performed with a superconducting quantum-interference-device magnetometer.

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기능성 용매인 [Bmim][$CF_3SO_3$]를 이용한 수소화반응용 탄소 담지 팔라듐 촉매 제조 (Preparation of Palladium on Carbon for Hydrogenation Catalyst Using [Bmim][$CF_3SO_3$] as an Effective Solvent)

  • 태현만;전승혜;유계상
    • 공업화학
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    • 제24권1호
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    • pp.82-86
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    • 2013
  • 기능성 용매인 1-buthyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][$CF_3SO_3$])를 이용하여 팔라듐 입자를 제조하였다. 제조된 입자의 형상은 기능성용매의 농도에 영향을 받았다. 또한 hexafluoropropylene 수소화 반응용 촉매를 제조하기 위하여 탄소 담지 팔라듐 입자를 제조하였다. 촉매 제조 시 기능성용매의 농도와 소성온도를 변화해 가면서 최적의 촉매제조 조건을 구하고자 하였다. 수소화 촉매의 반응활성의 상기의 두 가지 제조조건에 따라서 크게 달라지는 것이 관찰되었다. 동일한 반응조건에서 기능성용매와 팔라듐 전구체의 몰 비가 동일하고 소성온도가 $500^{\circ}C$에서 제조된 촉매가 가장 우수한 반응성을 보였다.