• 한국세라믹학회지
• /
• 제24권1호
• /
• pp.17-22
• /
• 1987

This study is to detect the synthetic condition for the formation of Sr-Ferrite(SrFe12O19) by hydrothermally reaction. Mixed suspension of SrCl26H2O and FeCl3 6H2O were fixed on pH and were subjected to autoclavings at various temperature(150∼300$^{\circ}C$), reaction time(2hrs.∼48hrs.). The Sr-Ferrite powders were synthesized at 150$^{\circ}C$ for 36hrs, 200$^{\circ}C$ for 4hrs and 250$^{\circ}C$ for 2hrs. Synthesized powders were increased particle sizes at longer reaction time and higher reaction temperature. It has hexagonal ferrite M-type structure and has high purity of SrO.5.6 Fe2O3 composition.

• 한국주조공학회지
• /
• 제29권1호
• /
• pp.27-32
• /
• 2009

The microstructure of Al-7Si-0.4Mg-1Fe alloy mainly consists of aluminum dendrites, Al-Si eutectics, and $Al_5FeSi$ needles. When Mn was added to the alloy, the substantial amount of $Al_5FeSi$ phase was changed into Al(Mn,Fe)Si, however the needle-like morphology was almost unchanged. Combined additions of Cr or Sr with Mn to the base alloy resulted in rod-like Al(Mn, Fe,Si)Si phase. The tensile properties of as-cast alloys were enhanced by the Mn addition, especially when it was added with Sr. The tensile properties after T6 heat treatment was a little improved with 0.7%Mn addition, but Cr or Sr additions with Mn didn't show any positive effect on the properties of heat-treated alloys.

• Korean Chemical Engineering Research
• /
• 제57권4호
• /
• pp.584-588
• /
• 2019

디젤엔진 시스템은 미세먼지 배출의 엄격해진 저감/제어 기준을 충족하기 위해서 산화촉매는 매우 중요한 기술 중에 하나이다. 본 연구에서는 효율적인 soot산화의 촉매로 Ag 나노입자가 loading된 $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$ 섬유상 web 촉매를 제시하였다. 제조된 촉매는 FE-SEM, EDS mapping, XRD, XPS 분석을 통해 특성을 평가하였다. Soot 산화성능측정결과 Ag의 효율적인 촉매특성과 증가된 soot입자와 표면의 접촉면적으로 인하여 50% 산화온도 평가($T_{50}=490^{\circ}C$)에서 자연적인 산화보다 $151^{\circ}C$ 가속화된 것을 확인하였다. 따라서 Ag가 loading된 촉매와 3차원적인 web 구조는 soot 산화에 효율적인 촉매후보군으로 확인하였다.

• Bulletin of the Korean Chemical Society
• /
• 제35권6호
• /
• pp.1613-1618
• /
• 2014

Perovskite-type oxides are promising oxygen carriers in producing oxygen-enriched $CO_2$ gas stream for oxyfuel combustion. In this study, a new series of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ (x = 0.2, 0.4, 0.6, 0.8) was prepared and used to produce $O_2/CO_2$ mixture gas. The phase, crystal structure, and morphological properties of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ were investigated through X-ray diffraction, specific surface area measurements, and environmental scanning electron microscopy. The oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ was studied in a fixed-bed reactor system. Results showed that the different x values of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ have no obvious effects on crystalline structure. However, the oxygen desorption performance of $SrCo_{1-x}Fe_xO_{3-{\delta}}$ is improved by Co doping. Moreover, $SrCo_{0.8}Fe_{0.2}O_{3-{\delta}}$ synthesized via a new EDTA method has a larger BET surface area ($40.396m^2/g$), smaller particle size (48.3 nm), and better oxygen production performance compared with that synthesized through a liquid citrate method.

• 한국자기학회지
• /
• 제11권6호
• /
• pp.256-261
• /
• 2001

Sr계 페라이트의 자기적 특성향상을 위하여 화학량론적 조성 SrFe$_{12}$O$_{19}$[SrM]에서 원소치환을 실시한 SrFe$_{11.7}$Zn$_{0.3}$O$_{19}$[Zn$_{0.3}$-SrM] 및 Sr$_{0.7}$La$_{0.3}$Fe$_{11.7}$Zn$_{0.3}$O$_{19}$[(La-Zn)$_{0.3}$-SrM] 화학조성으로 혼합한 후 공기 중 하소를 실시하여 하소분의 특성을 조사하였고, 소결조제로서 SiO$_2$, CaCO$_3$ 및 SrCO$_3$를 첨가하여 평균입도 0.80$\mu\textrm{m}$까지 습식 미분쇄를 행한 후, slurry 농도를 조절하여 외부자장 8 kOe을 인가하면서 disk 형태로 성형한 후 공기 중에서 소결하여 Sr 페라이트를 제조하여 소결 결정상태 및 자기적 특성을 조사하였다. Sr 페라이트 하소분의 자기특성은 화학량론적인 조성 SrFe$_{12}$)$_{19}$[SrM]에서 포화자화 (Ms/g)값이 61.06 emu/g에서 단독 Zn을 치환한 SrFe$_{11.7}$Zn$_{0.3}$O$_{19}$[Zn$_{0.3}$-SrM] 조성에서는 포화자화(Ms/g)값이 66.90 emu/g로 향상되었고, (La-Zn)$_{0.3}$-SrM 조성으로 원소치환을 실시한 하소분말을 사용하여 제조한 페라이트의 자기특성은 잔류자속밀도(B,) 4.21 kG, 최대에너지적(BH$_{max}$) 4.19 MGOe치 자기특성 값을 나타내었다.내었다.TEX> max/) 4.19 MGOe치 자기특성 값을 나타내었다.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 춘계학술발표대회
• /
• pp.45.1-45.1
• /
• 2011

Cobalt-free $La_xSr_{4-x}Fe_6O_{13}$ ($0{\leq}x{\leq}2$) oxide have been synthesized and investigated as a potential cathode material for solid oxide fuel cells (SOFCs). $Sr_4Fe_6O_{13}$ consists of alternating perovskite layers ($Sr_4Fe_2O_8$) containing iron cations in octahedral oxygen coordination and $Fe_4O_5$ layers where iron cations have 5-fold coordination of two types-square pyramids and trigonal bipyramids. Our preliminary electrochemical testes of pristine $Sr_4Fe_6O_{13}$ show a rather high area specific resistance ($0.47{\Omega}cm^2$ at $700^{\circ}C$) for ~20 ${\mu}m$ thick layers with CGO electrolyte. The electrochemical performances are improved by La addition up to x=1 ($La_1Sr_3Fe_6O_{13}$, $0.06{\Omega}cm^2$ at $700^{\circ}C$). In addition, thermal expansion coefficient (TEC) values of $La_1Sr_3Fe_6O_{13}$ specimen demonstrated $15.1{\times}10^{-6}\;^{\circ}C^{-1}$ in the range of 25-900$^{\circ}C$, which provides good thermal expansion compatibility with the CGO electrolyte. An electrolyte supported (300-${\mu}m$-thick) single-cell configuration of $La_1Sr_3Fe_6O_{13}$/CGO/Ni-CGO delivered a maximum power density of 584 $mWcm^{-2}$ at $700^{\circ}C$. In addition, an anode supported single cell by YSZ electrolyte (10-${\mu}m$-thick) with a porous CGO interlayer between the cathode and the electrolyte to avoid undesired interfacial reactions exhibited 1,517 $mWcm^{-2}$ at $800^{\circ}C$. The unique composition of $La_1Sr_3Fe_6O_{13}$ with low thermal expansion coefficient and higher electrochemical properties could be a good cathode candidate for intermediate temperature SOFCs with CGO and YSZ electrolyte.

• 한국전기전자재료학회논문지
• /
• 제11권10호
• /
• pp.931-939
• /
• 1998

Preparation of the hexagonal Sr-ferrite powsers with high performance by co-spraying precusor of the FeCl$_2$+SrCO$_3$ at a low temperature was proved as a cost =-effective method. The co-spray roasting was carried out in the temperature range of 300~$700^{\circ}C$ after SrCO$_3$ powders were mixed into 12FeCi$_2$.4$H_2O$ liquor. By this low temperature roasting method fine particles of multi-phased FeO$_2$+SrCO$_3$ were formulated. Powders calcined at 105$0^{\circ}C$ for 1 hour show the best magnetic property of M\ulcorner=69.96 emu/g, M\ulcorner=36.98 emu/g, and \ulcornerH\ulcorner=4.31 Oe. This calcining temperature is lower than that of the conventional dry method by 10$0^{\circ}C$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
• /
• pp.49-52
• /
• 1998

Preparation of hexagonal strontium-ferrite by modified spray co-roasting(MSC:H) which is expected to shorkn the length of the process and to elevate the magnetic properties of hard ferrite was studied. We prapared $Fe_2O_3/SrCO_3$ mixture powders by MSCR after stirring ionized $FeCI_2$ in distilled water with solid state $SrCO_3$. And then calcined the mixture powders up to $1150^{\circ}C$ for Sr-ferrite powders It is possible to prepare hexaferrite powders with high saturation magnetization (Ms > 69 emu/g) , coercivity (Hc > 4000 Oe) The nlagnetic values of saturation magnetization iire higher than those achieved by the conventional technique.

• Bulletin of the Korean Chemical Society
• /
• 제25권1호
• /
• pp.97-100
• /
• 2004

Tetragonal $K_2NiF_4$-type $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$ solid-solution have been synthesized by citrate based sol-gel method. The valence state of iron was determined by Mossbauer spectroscopy and subsequent iodometric titration clearly showed that the copper ions in this solid-solution are in the mixed valence state Cu(II/III). When x ${\geq}$ 0.3, Fe(III) is competing with the mixture of Cu(II) and Cu(III) and $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$ exhibits a metallic character. No evidence for Cu(II)-O-Fe(IV) ${\leftrightarrow}$ Cu(III)-O-Fe(III) valence degeneracy was observed. In contrast, a small amount of Fe(IV) is observed with increasing x (x = 0.4 and 0.5), revealing a semiconducting behavior. These results suggest that the electronic interaction of Cu(III)-O-Fe(III) contributes greatly to the metallic character, while the electronic interaction of Cu(II)-O-Fe(IV) deteriorates the metallic character of $La_{2-2x}Sr_{2x}Cu_{1-x}Fe_xO_{4-y}$.

• 멤브레인
• /
• 제21권2호
• /
• pp.155-162
• /
• 2011

$Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ (BSCF) 조성을 갖는 치밀한 관형 분리막은 압출 성형 방법으로 제조하였다. $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ 관형 분리막의 구조적 특성은 x-선 회절분석기 (XRD)와 전자 주사 현미경 (SEM)을 이용하여 분석하였으며, 상대밀도는 94.10%를 보였다. 산소투과량 분석은 700~$950^{\circ}C$ 범위에서 공급 측과 투과 측의 운전조건에 따라 측정되었다. 공급 측과 투과 측에서 대기 중 공기와 진공펌프를 사용할 경우, $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ 관형 분리막의 산소투과량은 $900^{\circ}C$에서 1.37 mL/$min{\cdot}cm^2$로 높게 나타났다.