• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 2003년도 추계 학술발표회 논문집
• /
• pp.51-55
• /
• 2003

고상법에 의해 제조된 NiFe$_2$O$_4$의 열적거동은 열화학 사이클에 의해 H$_2$제조를 위해서 연구되었다. NiFe$_2$O$_4$의 환원반응은 800 $^{\circ}C$부터 시작하였고 무게감소는 1000 $^{\circ}C$까지 0.2-0.3 wt% 감소하였다. 이 반응에서 NiFe$_2$O$_4$의 B위치의 Fe$^3$이온과 결합된 산소의 방출에 의해 NiFe$_2$O$_4$는 환원되어진다. 환원산화 반응을 위해 NiFe$_2$O$_4$의 구조는 스피넬 구조를 갖는다. 여기서 $H_2O$ 분해반응은 환원된 NiFe$_2$O$_4$의 산화반응에 의해 H$_2$가 제조된다. 그러므로 NiFe$_2$O$_4$는 환원반응시 비교적 낮은 온도에서 산소를 방출하고, 환원산화 반응 중 결정구조의 변화 없이 매우 안정하게 H$_2$를 생산할 수 있기 때문에 열화학 사이클반응에서 우수한 재료로 평가된다.

• 한국수소및신에너지학회논문집
• /
• 제14권4호
• /
• pp.298-304
• /
• 2003

The thermal behavior of $NiFe_2O_4$ prepared by a solid-state reaction was investigated for $H_2$ generation by the thermochemical cycle. The reduction of $NiFe_2O_4$ started from $800^{\circ}C$, and the weight loss was 0.2-0.3 wt% up to $1000^{\circ}C$. In the $H_2O$ decomposition reaction, $H_2$ was generated by oxidation of reduced $NiFe_2O_4$. The crystal structure of $NiFe_2O_4$ maintained during the redox reaction of 5 cycles. From this observation, the lattice oxygen in $NiFe_2O_4$ is released without the structural change during the thermal reduction and oxygen deficient $NiFe_2O_4$ can be restored to the spinel structure of $NiFe_2O_4$.

• Journal of Magnetics
• /
• 제21권1호
• /
• pp.40-45
• /
• 2016

Nickel substituted nano-sized ferrite powders, $Co_{1-x}Ni_xFe_2O_4$, $Mn_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ($0.0{\leq}x{\leq}0.2$), were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently compared. The lattice constants decreased as quantity of nickel substitution increased, while the particle size decreased in $Co_{1-x}Ni_xFe_2O_4$ ferrite but increased for the $Mn_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ferrites. For the $Co_{1-x}Ni_xFe_2O_4$ and $Mn_{1-x}Ni_xFe_2O_4$ ($0.0{\leq}x{\leq}0.2$) ferrite powders, the $M{\ddot{o}}ssbauer$ spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of $Mn_{0.8}Zn_{0.1}Ni_{0.1}Fe_2O_4$ consisted of two Zeeman sextets and one single quadrupole doublet due to the ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explain the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. The saturation magnetization decreased in the $Co_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ferrites but increased in the $Mn_{1-x}Ni_xFe_2O_4$ ferrite with nickel substitution. The coercivity decreased in the $Co_{1-x}Ni_xFe_2O_4$ and $Mn_{1-2x}Zn_xNi_xFe_2O_4$ ferrites but increased in the $Mn_{1-x}Ni_xFe_2O_4$ ferrite with nickel substitution. These variations could thus be explained by using the site distribution equations, particle sizes and spin magnetic moments of the substituted ions.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2004년도 학술논문집
• /
• pp.285-291
• /
• 2004

LiCl-$Li_2O-O_2$ 용융염계에서 용융염 취급장치의 구조재료를 위한 평가의 일환으로 Inconel 718, X-750, Haynes 75, 263 합금의 부식거동을 분위기온도; $650^{\circ}C$, 부식시간: 24~168h, $Li_2O$농도; 3wt%, 혼합가스농도; Ar-10%$O_2$에서 조사하였다. LiCl-$Li_2O-O_2$ 용융염계에서 부식속도는 Haynes 263 ＜ Haynes 75 ＜ Inconel X-750 ＜ Inconel 718 순서로 나타났으며, Haynes 263 합금이 가장 우수한 내부식성을 나타내었다. Haynes 75의 부식생성물은 $Cr_2O_4$, $NiFe_2O_4$, $LiNiO_2$, $Li_2NiFe_2O_4$, Inconel 718의 부식생성물은 $Cr_2O_4$ 및 $NiFe_2O_4$ 이며 Haynes 263은 $Li(Ni,Co)O_2$, $NiCr_2O_4$ 및 $LiTiO_2$, Inconel X-750은 $Cr_2O_3$, $NiFe_2O_4$,$FeNi_3$, (Al,Nb,Ti)$O_2$의 부식생성물을 나타내었다. Haynes 263은 국부부식의 거동을 보이는 반면, Haynes 75, Inconel 718 및 Inconel X-750은 전면 부식 거동을 나타내었다.

• 한국방사성폐기물학회:학술대회논문집
• /
• 한국방사성폐기물학회 2003년도 가을 학술논문집
• /
• pp.373-378
• /
• 2003

$LiCl-Li_2O_2$용융염계에서 용융염 취급장치의 구조재료를 위한 평가의 일환으로 오스테나이트 합금인 Fe-base 및 Ni-base 합금의 부식거동을 분위기온도; 650~$725^{\circ}C$, 부식시간: 24~168h, $Li_2O$농도; 3wt%, 혼합가스농도: Ar-10%$O_2$에서 조사하였다. $LiCl-Li_2O_2$ 용융염계에서 Ni-base 합금이 Fe-base 합금보다 높은 내부식성을 나타내었으며, 또한 Fe-base 합금에서 Fe의 함량이 낮고 Ni의 함량이 높은 경우 부식저항성이 증가하였다. 아울러 Fe-base 합금의 부식생성물은 $Cr_2O_3$, $FeCr_2O_4$ Ni-base 합금에서는 $Cr_2O_3$, $NiFe_2O_4$로 나타났다.

• 한국수소및신에너지학회논문집
• /
• 제19권6호
• /
• pp.505-513
• /
• 2008

The two-step thermochemical cycle was examined on the $CeO_2$, YSZ, and $ZrO_2$-supported $NiFe_2O_4$ to investigate the effects of support material addition. The supported $NiFe_2O_4$ was prepared by the aerial oxidation method. Thermal reduction was conducted at 1573K and 1523K while water-splitting was carried out at 1073K. Supporting $NiFe_2O_4$ on $CeO_2$, YSZ and $ZrO_2$ alleviated the high-temperature sintering of iron-oxide. As a result, the supported $NiFe_2O_4$ exhibited greater reactivity and repeatability in the water-splitting cycle as compared to the unsupported $NiFe_2O_4$. Especially, $ZrO_2$-supported $NiFe_2O_4$ showed better sintering inhibition effect than other supporting materials, but hydrogen production amount was decreased as cycle repeated. In case of $CeO_2$-supported $NiFe_2O_4$, improvement of hydrogen production was found when the thermal reduction was conducted at 1573K. It was deduced that redox reaction of $CeO_2$ activated above 1573K.

• 한국세라믹학회지
• /
• 제34권10호
• /
• pp.1074-1082
• /
• 1997

Microstructure and permeability as a function of sintering temperature and composition were studied on the Ni$\delta$Cu0.4-$\delta$Zn0.6Fe2O4 ($\delta$=0, 0.1, 0.2, 0.3, 0.4) which was prepared by Cu2+ substitution for Ni2+ in Ni.0.4Zn0.6Fe2O4, then followed by 8 wt% CuO and 1wt% Bi2O3 as sintering aids. It was found that NiCuZn ferrite in which Cu2+ is substituted for Ni2+ is more effective in reduction of sintering temperature than Ni.0.4Zn0.6Fe2O4, containing CuO as a sintering aid. The specimen $\delta$=0.2 sintered at 90$0^{\circ}C$ for 2hr exhibited the highest initial permeability value ($\mu$o=280 at 1Mhz), but the real permeability decreased at the frequency under 10 MHz. EPMA analysis showed that Ni$\delta$Cu0.4-$\delta$Zn0.6Fe2O4 ($\delta$=0.4), sintered at 95$0^{\circ}C$ for 2hrs consisted of three phase regions of Ni.0.3Cu0.1Zn0.6Fe2O4 region, Cu and Bi liquid existed at the 3-point boundary, although the stabilization energy of Ni2+ is higher than that of Cu2+ in B site.

• 대한금속재료학회지
• /
• 제49권1호
• /
• pp.52-57
• /
• 2011

Nickel ferrite ($NiFe_2O_4$) powder was prepared through the ceramic route by calcination of a stoichiometric mixture of nickel oxide (NiO) and iron oxide ($Fe_2O_3$). The pressed pellets of $NiFe_2O_4$ were isothermally reduced in pure hydrogen at 800, 900, 1000 and $1100^{\circ}C$. Based on thermogravimetric analysis, the reduction behavior and the kinetic reaction mechanisms of the synthesized ferrite were studied. The initial ferrite powder and various reduction products were characterized by XRD, SEM, reflected light microscope and VSM to reveal the effect of hydrogen reduction on the composition, microstructure, magnetic properties and reaction kinetics of the produced Fe-Ni alloy. Complete reduction of the $NiFe_2O_4$ was achieved with synthesis of homogeneous nanocrystalline Fe-Ni alloys. Arrhenius equation with the approved mathematical formulations for a gas-solid reaction was applied for calculating the activation energy ($E_a$) values and detecting the controlling reaction mechanism.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
• /
• pp.506-508
• /
• 2000

Oxide of the form $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ present properties that make them useful as multilayer chip NTC thermistor for mobile phone NTC thermistor electric properties of $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ system has been measured as a function of temperature and composition. In $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ composition, it can be seen that resistivity and B-constant were increased as the ratio of $Mn_{3}O_{4}/F_{2}O_{3}$ and $Mn_{3}O_{4}$/NiO was increased. In particular, resistance change ratio (${\Delta}R$), the important factor for reliability varied within ${\pm}1%$, indicating the compositions of these products could be available for mobile phone.

• 한국가스학회지
• /
• 제2권2호
• /
• pp.40-47
• /
• 1998

이산화탄소를 분해할 목적으로 황산철과 수산화나트륨을 이용하여 $Fe_3O_4$를 합성하였다. 합성조건은 황산철과 수산화나트륨의 혼합당량비를 0.50${\~}$l.50까지로 반응온도는 $40^{\circ}C$, 반응시간은 20시간으로 하였다. 또한 혼합당량비를 1.00으로 고정하고, 여기에 $NiCl_2,\;RhCl_3$를 mole$\%$로 첨가하여 합성하였다. 이 합성된 $Fe_3O_4$의 구조변화에 미치는 Ni과 Rh의 영향을 XRD, SEM으로 비교 검토하였다.