• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
• /
• pp.130-131
• /
• 2013

Nanostructured oxides are widely used in heterogeneous catalysis where their catalytic properties are closely associated with the size and morphology at nanometer level. The effect of particle size has been well decumented in the past two decades, but the shape of the nanoparticles has rarely been concerned. Here we illustrate that the redox and acidic-basic properties of oxides are largely dependent on their shapes by taking $Co_3O_4$, $Fe_2O_3$, $CeO_2$ and $La_2O_3$ nanorods as typical examples. The catalytic activities of these rod-shaped oxides are mainly governed by the nature of the exposed crystal planes. For instance, the predominant presence of {110} planes which are rich in active $Co^{3+}$ on $Co_3O_4$ nanorods led to a much higher activity for CO oxidation than the nanoparticles that mainly exposed the {111} planes. The simultaneous exposure of iron and oxygen ions on the surface of $Fe_2O_3$ nanorods have significantly enhanced the adsorption and activation of NO and thereby promoted the efficiency of DeNOx process. Moreover, the exposed surface planes of these rod-shaped oxides mediated the reaction performance of the integrated metal-oxide catalysts. Au/$CeO_2$ catalysts exhibited outstanding stability under water-gas shift conditions owing to the strong bonding of gold particle on the $CeO_2$ nanorods where the formed gold-ceria interface was resistant towards sintering. Cu nanoparticles dispersed on $La_2O_3$ nanorods efficiently catalyzed transfer dehydrogenation of primary aliphatic alcohols based on the uniue role of the exposed {110} planes on the support. Morphology control at nanometer level allows preferential exposure of the catalytically active sites, providing a new stragegy for the design of highly efficient nanostructured catalysts.

• 통합자연과학논문집
• /
• 제1권3호
• /
• pp.247-249
• /
• 2008

자성 결정체인 $Fe_3O_4$ 나노 입자를 합성하기위하여 강한 극성 용매인 2-pyrrolidone을 연전도 반응매개체로 하여 용액 내에 $FeCl_3{\cdot}6H_2O$을 용해시켜 2-pyrrolidone의 비등점까지 나노 결정체 고온 열분해 방법을 이용하여 제조되었다. 고온 열분해 후, $Fe_3O_4$ 나노 입자는 methanol/diethyl ether (1:3)에 의해서 침전되어졌다. 합성된 $Fe_3O_4$ 나노 입자는 고결정도, 고자기성을 가지고 있으며, 수용성의 자성 나노 결정체이다. 합성된 $Fe_3O_4$ 나노 입자의 크기와 결정도는 transmission electron microscope (TEM, Tecnai F20)를 이용하여 특성 분석하였으며, area electron diffraction (SAED) pattern과 HRTEM을 이용하여 나노입자의 격자 패턴 (lattice fringes)을 확인하였다.

• 청정기술
• /
• 제21권1호
• /
• pp.39-44
• /
• 2015

본 연구에서는 다섯 종의 씨앗(춘채, 아욱, 양배추, 배추, 당근)을 이용하여 금속산화물 나노입자(CuO, NiO, Fe₂O₃, Co₃O₄, TiO₂, ZnO)들이 씨앗발아와 발아지수에 미치는 영향을 조사하였다. CuO, ZnO, NiO 나노입자는 씨앗 활성에 뚜렷한 독성 영향을 나타내었으며, 나노입자종류에 따라 상이한 민감도를 나타내었다. 각 나노입자에 대한 독성순서(EC₅₀ 범위)는 다음과 같다: CuO 6~27 mg/L > ZnO 16~86 mg/L > NiO 48~112 mg/L. 나머지 조사 대상 나노입자인 Co₃O₄, TiO₂, Fe₂O₃은 최대 1,000 mg/L 높은 농도 노출에도 뚜렷한 영향을 나타내지 않았다. 씨앗별 상이한 민감도를 나타내었으며, 가장 민감한 종인 아욱의 씨앗발아 EC₅₀은 CuO 5.5 mg/L ZnO 16.4 mg/L, NiO 53.4 mg/L로 조사되었다. 씨앗별 나노입자에 대한 독성 영향은 CuO > ZnO > NiO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂ 나타났으나, 당근씨앗은 NiO [EC₅₀ 80.4(71.41~90.54) mg/L]와 ZnO [EC₅₀ 85.8(69.31~106.29) mg/L]가 유사한 독성을 나타내었다.

• Advances in nano research
• /
• 제3권2호
• /
• pp.111-121
• /
• 2015

$CoFe_2O_4$ nanotubes and porous nanorods were prepared via a simple one-pot template-free hydrothermal method and were used as an adsorbent for the removal of dye contaminants from water. The properties of the synthesized nanotubes and porous nanorods were characterized by electron diffraction, transmission electron microscopy and x-ray powder diffraction. The Adsorption characteristics of the $CoFe_2O_4$ were examined using polar red dye and the factors affecting adsorption, such as, initial dye concentration, pH and contact time were evaluated. The overall trend followed an increase of the sorption capacity reaching a maximum of 95% dye removal at low pHs of 2-4. An enhancement in the removal efficiency was also noticed upon increasing the contact time between dye molecules and $CoFe_2O_4$ nanoparticles. The final results indicated that the $CoFe_2O_4$ nanotubes and porous nanorods can be considered as an efficient low cost and recyclable adsorbent for dye removal with efficiency 94% for Cobalt ferrite nanotubes and for Cobalt ferrite porous nanorods equals 95%.

• 센서학회지
• /
• 제25권3호
• /
• pp.223-228
• /
• 2016

In this work, we prepared porous WO3 nanofibers (NFs) functionalized by bio-inspired catalytic $Cr_2O_3$ and $Co_3O_4$ nanoparticles as highly sensitive and selective $H_2S$ gas sensing layers. Highly porous 3-dimensional (3D) NFs networks decorated by well-dispersed catalyst NPs exhibited superior $H_2S$ gas response ($R_{air}/R_{gas}$ = 46 at 5 ppm) in high humidity environment (95 %RH). In particular, the sensors showed outstanding $H_2S$ selectivity against other interfering analytes (such as acetone, toluene, CO, $H_2$, ethanol). Exhaled breath sensors using $Cr_2O_3$ and $Co_3O_4$ catalysts-loaded $WO_3$ NFs are highly promising for the accurate detection of halitosis.

• 한국세라믹학회지
• /
• 제48권5호
• /
• pp.454-457
• /
• 2011

We report the preparation of nanocrystalline cobalt ferrite, $CoFe_2O_4$, particles using recycled $Co_3O_4$ and their surface coating with silica using micro emulsion method. Firstly, the $Co_3O_4$ powders were separated from waste cemented carbide with acid-base chemical treatment. The cobalt ferrite nanoparticles with the size 10 nm are prepared by thermal decomposition method using recycled $Co_3O_4$. $SiO_2$ was coated onto the $CoFe_2O_4$ particles by the micro-emulsion method. The $SiO_2$-coated $CoFe_2O_4$ particles were studied their physical properties and characterized by X-ray diffraction (XRD), high resolution-transmission electron microscopy (TEM) analysis and CIE Lab value.

• Korean Journal of Chemical Engineering
• /
• 제35권11호
• /
• pp.2207-2219
• /
• 2018

Activated carbon (AC) was synthesized from Phoenix dactylifera stones and then modified by $CoFe_2O_4$ magnetic nanocomposite for use as a Cr(VI) adsorbent. Both $AC/CoFe_2O_4$ composite and AC were fully characterized by FTIR, SEM, XRD, TEM, TGA, and VSM techniques. Based on the surface analyses, the addition of $CoFe_2O_4$ nanoparticles had a significant effect on the thermal stability and crystalline structure of AC. Factors affecting chromium removal efficiency like pH, dosage, contact time, temperature, and initial Cr(VI) concentration were investigated. The best pH was found 2 and 3 for Cr adsorption by AC and $AC/CoFe_2O_4$ composite, respectively. The presence of ion sulfate had a greater effect on the chromium sorption efficiency than nitrate and chlorine ions. The results illustrated that both adsorbents can be used up to seven times to adsorb chromium. The adsorption process was examined by three isothermal models, and Freundlich was chosen as the best one. The experimental data were well fitted by pseudo-second-order kinetic model. The half-life ($t_{1/2}$) of hexavalent chromium using AC and $AC/CoFe_2O_4$ magnetic composite was obtained as 5.18 min and 1.52 min, respectively. Cr(VI) adsorption by AC and $AC/CoFe_2O_4$ magnetic composite was spontaneous and exothermic. In general, our study showed that the composition of $CoFe_2O_4$ magnetic nanoparticles with AC can increase the adsorption capacity of AC from 36 mg/L to 70 mg/L.

• Korean Chemical Engineering Research
• /
• 제54권5호
• /
• pp.636-647
• /
• 2016

Magnetite nanoparticles ($Fe_3O_4$ NPs) were synthesized by co-precipitating method under optimized condition. The $Fe_3O_4$ NPs coated with sodium dodecyl sulfate-thenoyltrifluoroacetone ($Fe_3O_4$ NPs-SDS-TTFA) were then exerted as the magnetic solid phase extraction (MSPE) adsorbent for the extraction process prior to introducing to a flame atomic adsorption spectrometry (FAAS). The synthesized $Fe_3O_4$ NPs-SDS-TTFA were applied for the extraction of Pb(II) ions from different water samples. The characterization studies of nanoparticles were performed via scanning electron microscopy-energy dispersive micro-analysis (SEM-EDAX), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) techniques. The substantial parameters affecting the extraction efficiency were surveyed and optimized. A dynamic linear range (DLR) of $10-400{\mu}g\;L^{-1}$ was obtained and the limit of detection (LOD, n=7) and relative standard deviation (RSD%, n= 6, $C=20{\mu}g\;L^{-1}$) were found to be $2.3{\mu}g\;L^{-1}$ and 1.9%, respectively. According to the results, the proposed method successfully applied for the extraction of Pb(II) ions from different environmental water samples and satisfactory results achieved.

• 센서학회지
• /
• 제17권4호
• /
• pp.281-288
• /
• 2008

Polyacrylonitrile(PAN)/metal oxide(MO) nanocomposite mats with a thickness of 0.12 mm were electrospun by adding 0 to 10 wt% of MO nanoparticles ($Fe_2O_3$, ZnO, $SnO_2$, $Sb_2O_3-SnO_2$) into PAN. Pt electrode was patterned on $Al_2O_3$ substrate by DC sputtering and then the PAN(/MO) mats on the Pt patterned $Al_2O_3$ were electrically wired to investigate the $CO_2$ gas sensing properties. As the MO content rose, the fiber diameter decreased due to the presence of lumps caused by the presence of MOs in the fiber. The PAN/2% ZnO mat revealed a faster response time of 93 s and a relatively short recovery of 54 s with a ${\Delta}R$ of 0.031 M${\Omega}$ at a $CO_2$ concentration of 200 ppm. The difference in sensitivity was not observed significantly for the PAN/MO fiber mats in the $CO_2$ concentration range of 100 to 500 ppm. It can be concluded that an appropriate amount of MO nanoparticles in the PAN backbone leads to improvement of the $CO_2$ gas sensing properties.

• 청정기술
• /
• 제28권2호
• /
• pp.110-116
• /
• 2022

본 연구에서는 NdFeB 영구자석 스크랩으로부터 회수한 철(Fe) 부산물을 이용하여 산화철(FeO_x) 나노입자를 합성하였고, 열처리 온도가 FeO_x 나노입자의 물성에 미치는 영향을 관찰하였다. 이를 위해 D.I. water에 약 10 wt%로 희석한 철 부산물 용액에 2.0 M 암모니아(NH₄OH) 용액을 투여하여 산화철 전구체를 석출하였고, 이를 300 ℃, 400 ℃, 500 ℃ 및 600 ℃로 각각 열처리하여 FeO_x 나노 입자를 합성, 열처리 온도에 따른 FeO_x 나노 입자의 물성을 관찰하였다. X-ray diffraction (XRD) 분석 결과 열처리 온도가 증가할수록 <104> 회절 피크가 성장하여 500 ℃ 이상에서 α-Fe₂O₃ 결정구조와 일치하는 회절 피크가 검출되었다. BET (Brunauer-Emmett-Teller) 비표면적 분석 결과 400 ℃ 이상에서 열처리 온도가 증가할수록 비표면적이 감소하는 경향을 나타내었다. HRTEM (high resolution transmission electron microscope) 관찰 결과 rod 형 나노입자가 관찰되었고, 열처리 온도 증가에 따라 나노입자의 크기가 증가하는 경향을 나타내었다.