• 한국재료학회지
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• 제13권8호
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• pp.531-536
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• 2003

The electromagnetic properties and microstructures of the ferrites based on ($Ni_{0.2}$ $Cu_{0.2}$ $Zn_{0.6}$)$_{1.085}$($Fe_2$$O_3$)$_{0.915}$ were investigated by changing the amount of additive SnO$_2$and CaO and the sintering temperatures. Addition of $SnO_2$caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ($Ni_{0.2} $Cu_{0.2}$ $Zn_{ 0.6}$)$_{1.085}$ ($Fe_2$$O_3$)$_{0.915}$ composition was sintered at $1150^{\circ}C$ rather than $1300^{\circ}C$. Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% $SnO_2$and 0.4 wt% CaO were added at the same time.

• Korean Chemical Engineering Research
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• 제48권2호
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• pp.157-163
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• 2010

CRT 용 shadow mask의 생산속도 향상을 위해 첨가제를 투입한 염화제이철 수용액을 개발하였고 이를 shadow mask의 식각속도 향상에 적용하였다. $Fe(ClO_4)_3$ 첨가제를 종래의 식각용액인 염화제이철 수용액에 투입한 결과, shadow mask의 식각속도가 크게 향상되었으며, 이때 첨가제의 농도가 증가할수록 식각속도가 증가함을 알 수 있었다. 또한 첨가제가 투입된 식각용액으로 순수 니켈과 철-니켈 합금(Invar 강)의 식각속도를 비교한 결과, 대부분의 공정조건에서 둘 사이의 식각속도 차이가 작음을 알 수 있었고, 이는 첨가제의 투입에 따라 니켈과 철의 식각속도가 모두 향상된 결과로 해석되었다. 첨가제의 주입에 따라 식각속도가 증가하는 이유는, 첨가제 내의 음이온인 $ClO^{4-}$가 염화제이철 수용액 내의 $Cl^-$에 비해 전자를 이동하는 가교로서의 역할이 우수하여 전자를 더 빠르게 이동시킬 수 있기 때문인 것으로 추정된다.

• 대한금속재료학회지
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• 제50권5호
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• pp.375-381
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• 2012

Magnesium prepared by mechanical grinding under $H_2$ (reactive mechanical grinding) with transition elements or oxides showed relatively high hydriding and dehydriding rates when the content of additives was about 20 wt%. Ni was chosen as a transition element to be added. $Fe_2O_3$ was selected as an oxide to be added. Ti was also selected since it was considered to increase the hydriding and dehydriding rates by forming Ti hydride. A sample $Mg-14Ni-3Fe_2O_3-3Ti$ was prepared by reactive mechanical grinding, and its hydrogen storage properties were examined. This sample absorbs 4.02 wt% H for 5 min, and 4.15 wt% H for 10 min, and 4.42 wt% H for 60 min at n = 2. It desorbs 2.46 wt% H for 10 min, 3.98 wt% H for 30 min, and 4.20 wt% H for 60 min at n = 2. The effects of the Ni, $3Fe_2O_3$, and Ti addition, and hydriding-dehydriding cycling were discussed.

• 한국물환경학회지
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• 제25권6호
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• pp.979-983
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• 2009

The mean pH of wastewater discharged from the plating process is 2, so a less amount of alkali is required to raise pH 2 to 5. In addition, if sodium sulfite is used to raise pH 5 to 9 in the secondary treatment, caustic soda or slaked lime is not necessary or only a small amount is necessary because sodium sulfite is alkali. Thus, it is considered desirable to use only $FeSO_4{\cdot}7H_2O$ in the primary treatment. At that time, the free cyanide removal rate was highest as around 99.3%, and among heavy metals, Ni showed the highest removal rate as around 92%, but zinc and chrome showed a low removal rate. In addition, the optimal amount of $FeSO_4{\cdot}7H_2O$ was 0.3g/L, at which the cyanide removal rate was highest. Besides, the free cyanide removal rate was highest when pH value was 5. Of cyanide removed in the primary treatment, the largest part was removed through the precipitation of ferric ferrocyanide: $[Fe_4(Fe(CN)_6]_3$, and the rest was precipitated and removed through the production of $Cu_2[Fe(CN)_6]$, $Ni_2[Fe(CN)_6]$, CuCN, etc. Furthermore, it appeared more effective in removing residual cyanide in wastewater to mix $Na_2SO_3$ and $Na_2S_2O_5$ at an optimal ratio and put the mixture than to put them separately, and the optimal weight ratio of $Na_2SO_3$ to $Na_2S_2O_5$ was 1:2, at which the oxidative decomposition of residual cyanide was the most active. However, further research is required on the simultaneous removal of heavy metals such as chrome and zinc.

• 한국대기환경학회지
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• 제22권4호
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• pp.431-439
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• 2006

Catalytic oxidation of benzene, toluene and xylene (BTX) using regenerated metal oxide catalysts (ZnO-CuO, NiO, $Fe_2O_3$, ZnO, CrO) were investigated in a fixed bed flow reactor to evaluate their feasibility for the purpose of removing volatile organic compounds (VOCs). Four kinds of pre-treatment methods such as gas (air and hydrogen), acid aqueous solution, alkali aqueous solution and cleaning agent were used to find out the optimal regeneration conditions. The physico-chemical properties of the used and regenerated catalysts were characterized by BET and TPR (Temperature Programmed Reduction). The used catalysts showed high conversion ratio and the catalytic ability of toluene oxidation was in the order of ZnO-CuO>$Fe_2O_3$>NiO>ZnO>CrO. We found that the acid aqueous pre-treatment (0.1 N HNO$_3$) was the best way to enhance the catalytic activity of $Fe_2O_3$. In addition, air and hydrogen gas treatment were optimal for NiO and ZnO-CuO catalysts, respectively. Furthermore, the decomposition of BTX depends on the type of a catalyst and a gas molecule.

• 한국자기학회지
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• 제15권5호
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• pp.282-286
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• 2005

공침법으로 제조한 Ni-Cu-Zn ferrite를 사용하여 전파흡수체로 사용할 저온소결용 ferrite를 연구하였다. Ni 첨가량에 따른 조성비 및 가소온도와 소결온도 변화를 시켜 전파흡수특성 및 물리적 특성을 고찰하였다. XRD pattern을 통하여 spinel구조를 가짐을 확인하였고, 공침법으로 제조된 Ni-Cu-Zn ferrite 미분말이 나노입자 크기를 보였다 소결온도가 $1100^{\circ}C$이고 Ni 함량이 많을 수록 투자율이 낮고 손실계수도 높게 측정되어 흡수 능력도 좋아짐을 알 수 있고, MHz 영역에서 사용할 수 있다고 사료된다. 그리고 소결온도 $1100^{\circ}C$이고 $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_{2}O_3)_{0.98}$ 조성일 때가 가장 손실이 크므로 전파흡수체로 사용할 조성임을 확인 할 수 있었다.

• 한국분말재료학회지
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• 제15권1호
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• pp.23-30
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• 2008

Ni-20Cr-20Fe-5Nb alloy with or without $Y_2O_3$ was manufactured by mechanical alloying process and consolidated by spark plasma sintering (SPS). The grain size of the alloy with $Y_2O_3$ was smaller than that of alloy without $Y_2O_3$ which results from the effect of $Y_2O_3$ suppressing grain growth. The tensile strength at room temperature was increased by the addition of $Y_2O_3$ but decreased abruptly at temperature above $600^{\circ}C$. It seems to result from the change of deformation mechanism due to fine grain size, that is, grain boundary sliding is predominant at above $600^{\circ}C$ while internal dislocation movement is predominant at below $600^{\circ}C$. After conventional heat treatment process of solution treatment and aging, a small amount of ${\delta}(Ni_3Nb)$ phase was formed in Ni-20Cr-20Fe-5Nb alloy while a large amount of ${\gamma}"(Ni_3Nb)$ was formed in Inconel 718 in the previous report. This is due to exhaustion of Nb content by the formation of NbC during consolidation.

• 한국주조공학회지
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• 제17권3호
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• pp.258-266
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• 1997

The purpose of this study is to improve hardness and wear resistance of high strength yellow brass by adding Fe, Cr, Mn, Si and Ni. Results showed that NiO, $FeCr_2O_4$ and intermetallic compound $Mn_5Si_3$ were produced when Ni, Fe-Cr and Mn-Si were added to the yellow brass. The hardness and wear tests showed the best results with the presence of the product precipitates and intermetallic compound. The calculation of relative wear resistance by volume fraction of each phases showed that the relative wear resistance of $Mn_5Si_3$ had the highest value, that of ${\beta}$ phase had the lowest. Observation of the worn surface showed that the main wear mechanism were found to be the abrasive wear, and also showed that the wear is caused by mechanical failure at the early stage.

• 한국세라믹학회지
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• 제51권3호
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• pp.224-230
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• 2014

Nano-sized gadolinium-doped ceria (GDC)/nickel particle-dispersed $La_ySr_{1-y}Ti_{1-x}Fe_xO_3$ (LSFTO)-based composite solid oxide fuel cell anodes were fabricated by an infiltration method and the effects of the GDC/Ni nanoparticles on the anode polarization resistance and cell performance were investigated in terms of the infiltration time and nickel content. The anodic polarization resistance of the LSFTO anode was significantly enhanced by GDC and/or Ni infiltration and it decreased with increasing infiltration time and Ni content, respectively. It is believed that the observed phenomena are associated with enhancement of the ionic conductivity and catalytic activity in the nanocomposite anodes by the addition of GDC and Ni. Power densities of cells with the LSFTO and LSFTO-GDC/Ni nanocomposite anodes were 150 and $300mW/cm^2$ at $800^{\circ}C$, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1990년도 추계학술대회 논문집
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• pp.71-77
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• 1990

This paper is studied on the sintering characteristics of Ni-Zn ferrites. The specimen ferrites was composed of 20 mol% NiO, 30mol% ZnO, 50 mol% Fe$_2$O$_3$, and 0.0025 mol%, 0.005 mol%, 0.01 mol% Nb$_2$O$\_$5/, Bi$_2$O$_3$, V$_2$O$\_$5/, wee used as minor additives. Sintering was carried out at 1100$^{\circ}C$. As results from the experiments, the high value of initial permeability of 6X10$^2$∼9X10$^2$ can be achieved at 500KHz∼1000KHz. The value of loss factor 1X10￣$^2$∼2X10$^2$ can be achieved at 500KHz∼1000KHz. The lowest 1/(${\mu}$XQ) value was obtained in the specimen with the addition of 0.005mol% fracyion for V$_2$O$\_$5/.