The control of particle size distribution for fabricated alumina nanoparticles using a thermophoretic separator

Kim, Byungkwon,Song, Jungho,Kim, Jeong-Yeol,Hwang, Jungho,Park, Dongho VSP 2019 Advanced powder technology Vol.30 No.10

<P><B>Abstract</B></P> <P>Control of the particle size distribution of fabricated alumina nanoparticles from general alumina powder with a large geometric standard deviation (GSD) was studied. A thermophoretic separator was used to control the GSD of the nanoparticles, and unevaporated and primary particles were separated to yield a small GSD. The fabricated nanoparticles were characterized by field emission scanning electron microscopy (FESEM) and a scanning mobility particle sizer (SMPS). We confirmed that the GSD of the nanoparticles was controlled by the thermophoretic separator. A temperature difference between 79 K and 151 K was applied to the thermophoretic separator for control of the nanoparticle GSD. The GSD of the fabricated alumina nanoparticles was improved from 1.74 to 1.44.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Alumina nanoparticles were fabricated using a plasma torch and thermophoretic separator. </LI> <LI> The method allowed separation of primary nanoparticles and control of their size distribution. </LI> <LI> Controlled particle size will enhance applications employing alumina nanoparticles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Roles of alumina, a base catalyst, a fine particle effect on the metastable phase Stabilization of the tetragonal zirconia at temperatures of 600-800 ℃

Rifki Septawendar,Suhanda,Soesilowati,Bambang Sunendar Purwasasmita 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.4

Nanoparticles of the tetragonal alumina-stabilized zirconia were synthesized from zirconium salt of ZrOCl2 • 8H2O and approximately 23 wt % alumina stabilizer with ammonia as a base catalyst and sucrose as a gelling agent at a room temperature. In the preparation process of nanoparticles of alumina-stabilized zirconia, the calcination was conducted at temperatures of 500-800 ℃. The calcined powder was analyzed and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) studies. The tetragonal phase of ZrO2 started to crystallize at a low temperature of 500 ℃. Further phase transformation of the alumina-stabilized zirconia maintained the tetragonal ZrO2 at 600 ℃. Besides, the addition of sucrose by weight ratio of 1 : 6 to the total weight precursors produced nanoparticles of alumina-stabilized zirconia less than 20 nm in size at that temperature. The tetragonal phase of ZrO2 was stable and no transition alumina was identified at 800 ℃. It is suggested that alumina is in solid solution in the tetragonal zirconia polymorph at that temperature. The typical SEM images show high agglomeration of ultrafine microstructures of alumina-stabilized zirconia nanoparticles at that temperature. The results indicate that the method represents an effective methodology for the preparation of alumina-stabilized zirconia nanoparticles at a lower temperature than 800 ℃.

Preparation and application of polystyrene-grafted alumina core-shell nanoparticles for dielectric surface passivation in solution-processed polymer thin film transistors

Kim, Kimyung,Park, Min Soo,Na, Yaena,Choi, Jongwan,Jenekhe, Samson A.,Kim, Felix Sunjoo Elsevier 2019 ORGANIC ELECTRONICS Vol.65 No.-

<P><B>Abstract</B></P> <P>Polystyrene-grafted alumina nanoparticles were synthesized by silane coupling between dimethylchlorosilane-terminated polystyrene (PS) and gamma-type alumina nanoparticles and characterized. The surface grafting density of the polystyrene chains on the nanoparticles was estimated to be 0.13 molecules per square nanometer. The Al<SUB>2</SUB>O<SUB>3</SUB>-PS nanoparticles are solution processable in organic solvents, including ethyl acetate, butyl acetate, and toluene, which enabled preparation of blends with polystyrene or poly (methyl methacrylate). The dielectric constant of the Al<SUB>2</SUB>O<SUB>3</SUB>-PS nanoparticle/polymer blend films is composition tunable from 2.59 to 7.79. The alumina-PS nanoparticles and their blends with polymers were found to form efficient surface passivation films on the oxide dielectric layer in organic field-effect transistors (OFETs).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polystyrene-grafted alumina core-shell nanoparticles were synthesized through simple silane coupling and the processability in various organic solvents was improved. </LI> <LI> Structure, electrical properties, composite film formation of alumina-PS nanoparticles were characterized. </LI> <LI> Alumina-PS nanoparticles were applied as a surface modification agent in organic field-effect transistors. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Influence of Interface Structure on Dielectric Properties of Epoxy/Alumina Nanocomposites

Jinhong Yu,Genglin Wang,Ruimei Huo,Chao Wu,Xinfeng Wu,Pingkai Jiang 한국고분자학회 2012 Macromolecular Research Vol.20 No.8

Alumina (Al2O3) nanoparticles with three different interface structures have been selected as reinforcement fillers for epoxy nanocomposite, that is surface untreated Al2O3 nanoparticles, γ-aminopropyl-triethoxysilane modified Al2O3 nanoparticles (Al2O3-APS), and hyperbranched aromatic polyamide grafted Al2O3 nanoparticles (Al2O3-HBP). The interface structures of the Al2O3 nanoparticles were characterized by X-ray diffraction and atomic force micrographs. Our studies reported the influence of the interface structure of Al2O3 nanoparticles on the morphology and dielectric properties of epoxy nanocomposites. It was found that the incorporation of the Al2O3-APS and Al2O3-HBP nanoparticles not only improved the dispersion of the nanoparticles in the epoxy matrix, but also enhanced the glass transition temperatures (Tgs) and largely influenced the dielectric properties of the epoxy nanocomposites as compared with the nanocomposites filled with the surface untreated Al2O3 nanoparticles. The improvement of Tgs, volume resistivity, dielectric strength, and the reduction of dielectric loss could be attributed to the good dispersion and special interface structure of the Al2O3 nanoparticles in the epoxy matrix.

Alumina nanoparticles immobilization onto the NaX zeolite and the removal of Cr (III) and Co (II) ions from aqueous solutions

Meghedi Deravanesiyan,Masoud Beheshti,Akbar Malekpour 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

The immobilization of alumina nanoparticles onto the NaX zeolite granules, using the sol–gel and aphysical method, for the removal of Cr (III) and Co (II) was investigated. Alumina nanoparticlesimmobilized zeolite (ANIZ) was characterized by SEM/EDX, XRD and AAS. The results suggested theformation of nanoscale alumina ( 30–50 nm) on the zeolite (loading 8–10 wt%) and the stability of thezeolite structure after the immobilization of alumina nanoparticles. ANIZ showed a good capacity for theremoval ofmetal ions. Kinetic and equilibrium data were best fitted with the pseudo second ordermodeland the Langmuir model respectively.

Effect of alumina nanoparticles in the fluid on heat transfer in double-pipe heat exchanger system

김성현,전병희,Hyun Uk Kang 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.5

This study was performed to investigate the convective heat transfer coefficient of nanofluids made of several alumina nanoparticles and transformer oil which flow through a double pipe heat exchanger system in the laminar flow regime. The nanofluids exhibited a considerable increase of heat transfer coefficients. Although the thermal conductivity of alumina is not high, it is much higher than that of the base fluids. The nanofluids tested displayed good thermal properties. One of the possible reasons for the enhancement on heat transfer of nanofluids can be explained by the high concentration of nanoparticles in the thermal boundary layer at the wall side through the migration of nanoparticles. To understand the enhancement of heat transfer of nanofluid, an experimental correlation was proposed for an alumina-transformer oil nanofluid system.

Fabrication of alumina/polysulfone nanocomposite membranes with biofouling mitigation approach in membrane bioreactors

Maryam Homayoonfal,Mohammad Reza Mehrnia,Samane Rahmani,Yasaman Mohades Mojtahedi 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.22 No.-

In this study, polysulfone/alumina nanocomposite membranes were synthesized with the principal aimof reducing biofouling in membrane bioreactors. The filtration experiments indicate that aluminananoparticles can increase water flux by enhancing membrane hydrophilicity while maintaining theseparation efficiency through decreasing porosity. Altogether, as confirmed by AFM images, thedevelopment of roughness results in biofilm formation reduction on the membrane surface layer. Onthe whole, presence of alumina nanoparticles up to the polymer concentration of 0.03 wt.% will result inan augment in separation yield up to 7%, four times higher water flux, and 83% reduction in membranefouling.

Enhanced Water Flux by Fabrication of Polysulfone/Alumina Nanocomposite Membrane for Copper(II) Removal

Muhammad Ayaz,Amir Muhammad,Mohammad Younas,Asim Laeeq Khan,Mashallah Rezakazemi 한국고분자학회 2019 Macromolecular Research Vol.27 No.6

In the current study, polysulfone (PSF) membranes incorporated with nano alumina (Al2O3) were synthesized by a phase inversion method to improve the efficiency of the PSF membrane for wastewater treatment. Dimethylformamide was used as solvent while polyvinylpyrrolidone was used as a pore former. Different concentrations of nanoparticles of Al2O3 were used in the casting solution to get an optimum condition for the highest water flux. Cross section morphology of the membranes was investigated through scanning electron microscope. Membranes were characterized by pure water flux, permeability, hydrophilicity, porosity, and retention of Cu(II). All the mixed matrix nanocomposite membranes showed higher water flux than the nascent PSF membrane due to their increased porosity and hydrophilicity with the addition of nano alumina. Cu(II) rejection was also enriched by composite membranes due to a high number of adsorption sites on membranes surface as a result of better hydrophilicity and dispersion of nano alumina. The membrane with 0.1 wt% nano Al2O3showed the best performance in terms of water flux (32.60 L·m-2·h-1) and significant Cu(II) removal (61.95%) compared to other membranes after continuous treatment of 150 min. The reusability test of the PAl0.1 membrane confirmed the durability of the composite membranes after several cycles using ethylenediaminetetraacetic acid as a regenerator.

표면처리 된 알루미나 나노입자를 포함하는 철도차량 회전 기기용 나노유체 윤활유의 분산안정성과 마모특성 연구

서현진,김보경,마상견,현준수,김윤호 한국철도학회 2019 한국철도학회논문집 Vol.22 No.7

Rotational components used in railway vehicles have been required to use high-performance lubricants forspecial driving environments, such as high load and long-term use. In particular, bearings installed in axle deceleratorsor gearboxes are difficult to replace and expensive, so a high performance lubricant is required to extend the bearingservice life. Recently, there have been reports that when nanoparticles are introduced into lubricating oil, lubricationcharacteristics and cooling characteristics can be improved. Lubricants containing nanoparticles for various rotatingmachines are being developed. Here, we developed a nanofluid-based lubricant including alumina nanoparticles for railwayrolling equipment. The surface of the alumina nanoparticles, having an average diameter of 45 nm, was treated witha self-assembled monolayer of 3-aminopropyl triethoxy silane to improve the dispersibility with the base-oil to preparea nanofluid lubricant. Surface treatment of alumina nanoparticles was confirmed by thermal analysis and transmissionelectron microscopy equipped with elemental analysis. In various compositions, nanofluid lubricants were prepared bymixing alumina nanoparticles with or without surface treatment with lubricating oil for gearbox. According to the surfacetreatment and content of alumina nanoparticles, the long-term dispersion stability of nanofluid lubricant was quantitativelyanalyzed by Turbiscan. The wear characteristics of the nanofluid lubricant were evaluated using a 4-ball test.

Carbonate 침전법을 이용한 α-알루미나의 나노파티클 코팅

임종민,김상우,Lim, Jong-Min,Kim, Sang-Woo 한국분말야금학회 2007 한국분말재료학회지 (KPMI) Vol.14 No.2

Nanocrystalline transient aluminas (${\gamma}$-alumina) were coated on core particles (${\gamma}$-alumina) by a carbonate precipitation and thermal-assisted combustion, which is environmentally friend. The ammonium aluminum carbonate hydroxide (AACH) as a precursor for coating of transient aluminas was produced from precipitation reaction of ammonium aluminum sulfate and ammonium hydrogen carbonate. The crystalline size and morphology of the synthetic, AACH, were greatly dependent on pH and temperature. AACH with a size of 5 nm was coated on the core alumina particle at pH 9. whereas rod shape and large agglomerates were coated at pH 8 and 11, respectively. The AACH was tightly bonded coated on the core particle due to formation of surface complexes by the adsorption of carbonates, hydroxyl and ammonia groups on the surface of the core alumina powder. The synthetic precursor successfully converted to amorphous- and ${\gamma}$-alumina phase at low temperature through decomposition of surface complexes and thermal-assisted phase transformation.