• Journal of Magnetics
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• 제10권3호
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• pp.84-88
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• 2005

Nanoparticles $Ni_{0.7}Zn_{0.3}Fe_2O_4$ is fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with XRD, SEM, $M\ddot{o}ssbauer$ spectroscopy, and VSM. $Ni_{0.7}Zn_{0.3}Fe_2O_4$ powders annealed at $300^{\circ}C$ have a spinel structure and behaved superparamagnetically. The estimated size of $Ni_{0.7}Zn_{0.3}Fe_2O_4$ nanoparticle is about 11 nm. $Ni_{0.7}Zn_{0.3}Fe_2O_4$ annealed at 400 and $500^{\circ}C$ has a typical spinel structure and is ferrimagnetic in nature. The isomer shifts indicate that the iron ions were ferric at the tetrahedral (A) and the octahedral (B). Blocking temperature $(T_B)\;of\;Ni_{0.7}Zn_{0.3}Fe_2O_4$ nanoparticle is about 260 K. The magnetic anisotropy constant of $Ni_{0.7}Zn_{0.3}Fe_2O_4$ annealed $300^{\circ}C$ were calculated to be $1.7X10^6\;ergs/cm^3$. Also, temperature of the sample increased up to $43^{\circ}C$ within 7 minutes under AC magnetic field of 7 MHz.

• Journal of Welding and Joining
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• 제19권5호
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• pp.512-519
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• 2001

Sink roll has been used in molten Zn-0.2%Al alloy bath of continuous galvanizing line in sinking and stabilizing process of the steel strip in molten metal bath. In this process, although the scraper scraps off the sink roll surface, the dross compounds is builded up on the sink roll surface and the life time of the sink roll is shorten by the dross compounds. The present study was investigated the application of the spray coating layer on sink roll body for improving durability In molten Zn-0.2%Al alloy. Through the durability tests in molten Zn-0.2%Al alloy with various ceramic and cermet coating layer, the optimum bond and top coating material was obtained. As the results, the system of STS430F base metal, WC-l7Co bond and $ZrO_2-SiO_2$ top coating was clarified to be the best quality of durability in molten Zn-0.2%Al alloy.

• Bulletin of the Korean Chemical Society
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• 제33권7호
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• pp.2133-2139
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• 2012

A new system using $TiO_2$ (nano-sized, band-gap 3.14 eV)-impregnated spherical ZnS (micro-sized, band-gap 2.73 eV) nano/micro-composites (Ti 0.001, 0.005, 0.01, and 0.05 mol %/ZnS) was developed to enhance the production of hydrogen from methanol/water splitting. The ZnS particles in a spherical morphology with a diameter of about 2-4 mm which can absorb around 455 nm were prepared by hydrothermal method. This material was used as a photocatalyst with loading by nano-sized $TiO_2$ (20-30 nm) for hydrogen production. The evolution of $H_2$ from methanol/water (1:1) photo splitting over the $TiO_2$/ZnS composite in the liquid system was enhanced, compared with that over pure $TiO_2$ and ZnS. In particular, 1.2 mmol of $H_2$ gas was produced after 12 h when 0.005 mol % $TiO_2$/ZnS nano/micro-composite was used. On the basis of cyclic voltammeter (CV) and UV-visible spectrums results, the high photoactivity was attributed to the larger band gap and the lower LUMO in the $TiO_2$/ZnS composite, due to the decreased recombination between the excited electrons and holes.

• 한국세라믹학회지
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• 제38권3호
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• pp.287-292
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• 2001

본 실험은 목적은 CRT(Cathode Ray Tube)용 청색 형광체인 ZnS:Ag 분말 표면에 액상법으로 SnO$_2$를 균일하게 코팅하는 공정조건을 연구하는 것이다. 용매로서 물을 사용하고, Sn의 공급물질로서 SnCl$_4$.4$H_2O$, 침전 촉매로서 CO(NH$_2$)$_2$를 각각 사용하여, 균일 침전 방법으로 ZnS:Ag 분말표면에 SnO$_2$를 코팅할 수 있었다. 초기에 첨가되는 SnCl$_4$.4$H_2O$의 량이 Sn/Zn의 몰비기준으로 0.017인 경우에 ZnS:Ag 분말표면에 Sn(OH)$_4$가 균일하게 코팅되지만, 그 이상 첨가되면 과량의 Sn(OH)$_4$가 입자들 사이에 응집되었다. 코팅된 Sn(OH)$_4$는 비정질 구조로 규명되었으며, 이를 SnO$_2$결정상으로 전이시키기 위하여 300~$700^{\circ}C$ 범위 내에서 열처리를 행하였다. 비정질 Sn(OH)$_4$는 20$0^{\circ}C$이하에서 탈수되었고 45$0^{\circ}C$부터 SnO$_2$로 결정화되기 시작하였다. 순수한 ZnS의 경우, 50$0^{\circ}C$이하에서는 상변화가 없으나, $600^{\circ}C$에서 일부 산화되었으며 $700^{\circ}C$에서는 완전히 ZnO로 산화되므로, ZnS의 산화방지 및 SnO$_2$의 결정화를 동시에 만족하는 최고 열처리온도는 50$0^{\circ}C$로 규명되었다. 그러나 ZnS에 SnO$_2$가 코팅된 시편의 경우에는 $600^{\circ}C$가 되어도 ZnS 상이 거의 산화되지 않았고, $700^{\circ}C$에서도 ZnS와 ZnO 상이 공존한 것으로 보아 SnO$_2$코팅이 ZnS의 산화를 억제하는 것으로 나타났다.

• 한국환경보건학회지
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• 제16권2호
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• pp.83-87
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• 1990

This study was carried out to investigate the pollution of heavy metals in soil of seven stations from the upper spot (Yeungchun Dam) of Kumho River to the downstream(Gangchang Bridge). The results obtained were as follows: 1. The content of heavy metals in soil of Kumho River basin was highest at Gangchang Bridge [expresed in $\mu$g/g : Mn(246.0), Cd(1.90), Fe(551.2), Cu(108.2), Zn(86.4), Cr(80.2), respectively]. Whereas, the content of heavy metals expect for Mn, Cu was lowest at Yeungchun Dam [Cd(0.40), Fe(548.0), Zn(30.7), Cr(6.2), respectively] Also, the content of Cr, Zn was increased when the sampling areas are changed from upstream to downstream except for Hayang Bridge, and Hayang Bridge was the diverging point of the heavy metals content. 2. There were relatively correlated between Mn : FE, Cu, Zn, Cr, Fe : Cu, Zn, Cr(0.40 < $\left$\mid${r}\right$\mid$$ < 0.70), and were high correlated between Cd : Mn, Fe, Cu, Zn, Cu : Zn, Zn : Cr(0.70 < $\left$\mid${r}\right$\mid$$ < 0.90). Particularly, there was higest correlated between Cd : Cr, Cu : Cr(0.90< $\left$\mid${r}\right$\mid$$ < 1.0)

• 한국표면공학회지
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• 제32권4호
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• pp.547-554
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• 1999

The interfacial reaction, spangle and coating thickness of galvanized steel in Ni added Zn-0.18Al bath have been investigated. The size of spangle and thickness of reaction layer were observed under an optical microscope, SEM and EDS. Analysing the experimental results concerning spangle size of galvanized steel it was found that Ni addition in Zn-0.18Al bath tended to be minimized spangle size. For Zn-0.18Al bath, addition of 0.1Ni suppressed the formation of Fe-Zn intermetallic compounds but increased with Ni content above 0.1%. The coating thickness of galvanized steel was reduced with Ni addition in Zn-0.18Al bath, especially in Zn-0.18Al-0.05Ni bath. Addition of Al in Ni containing bath resulted in forming the Al-Ni intermetallic compounds such as $Al_3$Ni$_2$ and $Al_2$Ni which consist most of top precipitates.

• Journal of Magnetics
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• 제15권4호
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• pp.165-168
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• 2010

$Li_{0.1}Zn_{0.9}O$ and $MgFe_2O_4$ powders were synthesized using chemical methods and mixed in different proportions to prepare a mixture of $Li_{0.1}Zn_{0.9}O$ and $MgFe_2O_4$ that was thermally treated between 900 to $1100^{\circ}C$ for 1 hour. Structural characterization was done using X-ray powder diffraction measurements. Grain sizes and morphologies of $Li_{0.1}Zn_{0.9}O$, $MgFe_2O_4$, and $Li_{0.1}Zn_{0.9}O+MgFe_2O_4$ samples were observed using a scanning electron microscope. Variation of magnetic properties of the $Li_{0.1}Zn_{0.9}O+MgFe_2O_4$ samples due to the addition of $Li_{0.1}Zn_{0.9}O$ was studied in relation to the structural changes occurring due to the thermal treatment. In particular, changes in the cationic distribution between the tetrahedral and octahedral positions were studied with respect to the increase of the annealing temperature. Magnetization was found to be dependent on the cations distributed in the tetrahedral and octahedral sites of the $MgFe_2O_4$.

• 한국세라믹학회지
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• 제26권4호
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• pp.505-513
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• 1989

The sintering behavior and grain growth of ZnO in 99.0mol% ZnO-1.0mol% Bi2O3 which are the basic compositions of ZnO varistor were studied. The microstructrual observation confirmed that the final sintered density was mainly determined at the initial stage of sintering, i.e. grain rearrangement and grain growth which were induced by the penetration of eutectic melts formed at eutectic temperature(74$0^{\circ}C$). But when the liquid penetration was terminated, the grain growth did not promote further densification. Activation energy of the grain growth of ZnO in the system of 99.0mol% ZnO-1.0mol% Bi2O3 was 44.8$\pm$1.8Kcal/mol.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.70-73
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• 1989

(1-x-y)Pb($Zn_{1/3}Nb_{2/3})O_3-Ba(Zn_{1/3}Nb_{2/3})O_3-PbTiO_3(0.12{\leq}x{\leq}0.21, 0.24{\leq}y{\leq}0.33$) ternary compound ceramics were fabricated by the mixed oxide method. The sintering temperature and time were 1050 [$^{\circ}C$], 2[hr]. Morphotropic phase boundary region was chosen for the composition. 0.55 PZN-0.21 BZN-0.24 PT specimen had the highest value of relative dielectric constants, 5353. The curie temperature of specimens were increased linearly with PT content. Near the morphotropic phase boundary, electro-mechanical coupoling factor and mechanical quality factor of the specimens had the highest values.

• 한국환경농학회지
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• 제9권2호
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• pp.121-131
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• 1990

도시생활하수의 처리에서 생산된 물질인 sludge를 토양개량제로 토양에 처리하여 재배한 식물체중 Cd 및 Zn의 흡수 축적되는 정도를 비교분석하기 위하여, sludge를 0. 22.5, 45.0, 90.0t $ha^{-1}$ 수준으로 토양에 처리하고 쪽파, 무우, 감자, 배추 등 4종의 작물을 pot 재배하여 각 식물체 부위별 Cd 및 Zn 농도를 분석하고 토양중에서 의 이들 중금속 농도의 증가 요인과 식물체중의 Cd 및 Zn함량 증가와의 관계를 통계분석한 결과는 다음과 같다. 1. 공시작물체 중의 Cd 및 Zn 함량은 sludge 처리량이 증가할수록 증가하였다. 2. 공시작물 뿌리중의 Cd 및 Zn함량도 sludge 처리량이 증가할수록 증가하였으며 쪽파>감자>배추>무우순으로 증가하였다. 3. 작물별 잎중의 Cd 함량은 쪽파>무우>감자>배추 순으로 증가하였고 Zn 농도는 배추>감자>무우>양파 순으로 증가하였다. 4. 식물체 부위별 Cd농도가 가장 낮았던 부위는 감자의 괴경, 무우뿌리, 배추잎으로 그 범위가 0.03-0.12ppm 이었다. 5. Sludge 90.0t $ha^{-1}$ 수준으로 토양에 처리하여 재배한 식물체 중의 Cd함량은 부위에 따라 원토양에서 재배한 식물체중 함량의 1.2-10배까지 흡수축적 되었고, Zn함량은 0.4-2.3배 증가하였다 6. Sludge처리에 의한 Cd 및 Zn농도 증가에 대한 식물체 부위 중의 흡수 축적율은 쪽파의 뿌리에서 Cd의 경우를 제외하고는 거의 일정하였다.