Alumina Nanoparticles (alumina + nanoparticle)

Distribution by Scientific Domains


Selected Abstracts


The effects of alumina and silica nanoparticles on the cure kinetics of bisphenol E cyanate ester

POLYMER ENGINEERING & SCIENCE, Issue 6 2010
Xia Sheng
Nanoparticles can be used as fillers to reinforce polymers, forming nanocomposites with better thermomechanical properties than composites with macrosized fillers. Furthermore, the addition of nanoparticles may influence the curing behavior of the polymer matrix during processing. In this study, the effect of various loadings of alumina or silica nanoparticles on the cure kinetics of bisphenol E cyanate ester (BECy) is investigated by differential scanning calorimetry (DSC). Alumina nanoparticles are shown to have a catalytic effect on the cure of BECy. The greater catalytic effect of alumina nanoparticles, compared with silica, is attributed to the increased number of hydroxyl groups on the surface and the Lewis acidity of ,-phase alumina. Kinetic parameters were obtained from dynamic DSC experiments. For an autocatalytic model of the cure process, the kinetic parameters obtained from the model suggest that the addition of alumina nanoparticles changed the cure reaction mechanism of BECy. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


Antibacterial and Abrasion-Resistant Alumina Micropatterns,

ADVANCED ENGINEERING MATERIALS, Issue 7 2009
Laura Treccani
In this work, a novel processing route to fabricate alumina surfaces that feature remarkable antibacterial and abrasion-resistant properties is reported. By combining micropatterning with antibacterial enzymes and alumina nanoparticles, we fabricated surfaces that present a feasible and highly interesting alternative to improve, e.g., systems employed for water transport containing abrasive agents, aggressive media and microorganisms. [source]


Critical heat flux enhancement in pool boiling using alumina nanofluids

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2010
Ramakrishna Hegde
Abstract The pool boiling characteristics of dilute dispersions of alumina nanoparticles in water were studied. Consistent with other nanofluid studies, it was found that a significant enhancement in critical heat flux (CHF) can be achieved at modest nanoparticle concentrations (<0.1% by volume). During experimentation and subsequent inspection, formation of a porous layer of nanoparticles on the heater surface occurred during nucleate boiling. This layer significantly changes surface texture of the heater wire surface which could be the reason for improvement in the CHF value. 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20301 [source]


Kinetic Studies of Mullite Synthesis from Alumina Nanoparticles and a Preceramic Polymer

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2008
Flavio Griggio
The crystallization kinetics of mullite formation in a diphasic precursor consisting of a silicone resin filled with commercial ,-alumina nanoparticles (15 nm mean particle size, specific surface area of 100 m2/g), heated in air from 1250 to 1350C, was studied by X-ray diffraction. Transitional ,-alumina and amorphous silica from the pyrolysis of the preceramic polymer exhibited a remarkable reactivity, as demonstrated by a very low incubation time (from 500 s at 1250C to 20 s at 1350C), a high mullite yield (about 80 vol%, after 100 s at 1350C), and a low activation energy for nucleation (67760 kJ/mol). The activation energy values found were lower than those reported previously for other diphasic systems, including sol,gel precursors. Besides the high specific surface of nanosized ,-alumina particles, the low energy barrier could be attributed to the highly reactive silica deriving from the oxidation of Si,CH3 bonds in the silicone and to the homogeneous dispersion of the nanosized filler inside the preceramic polymer. Furthermore, the possibility of applying plastic shaping processing methods to the mixture of a preceramic polymer and nanosized filler makes this approach particularly valuable, in comparison, for instance, with sol,gel based alternatives. [source]


Mechanical properties of Al2O3/polymethylmethacrylate nanocomposites

POLYMER COMPOSITES, Issue 6 2002
Benjamin J. Ash
Alumina/polymethylmethacrylate (PMMA) nanocomposites were produced by incorporating alumina nanoparticles, synthesized using the forced gas condensation method, into methylmethacrylate. The particles were dispersed using sonication and the composites were polymerized using free radical polymerization. At an optimum weight percent, the resulting nanocomposites showed, on average, a 600% increase in the strain-to-failure and the appearance of a well-defined yield point when tested in uniaxial tension. Concurrently, the glass transition temperature (Tg) of the nanocomposites dropped by as much as 25C, while the ultimate strength and the Young's modulus decreased by 20% and 15%, respectively. For comparison, composites containing micron size alumina particles were synthesized and displayed neither phenomenon. Solid-state deuterium NMR results showed enhanced chain mobility at room temperature in the nanocomposites and corroborate the observed Tg depression indicating considerable main chain motion at temperatures well below those observed in the neat polymer. A hypothesis is presented to relate the thermal and mechanical behavior observed in the composites to the higher chain mobility and Tg depression seen in recent ultrathin polymer film research. [source]


The effects of alumina and silica nanoparticles on the cure kinetics of bisphenol E cyanate ester

POLYMER ENGINEERING & SCIENCE, Issue 6 2010
Xia Sheng
Nanoparticles can be used as fillers to reinforce polymers, forming nanocomposites with better thermomechanical properties than composites with macrosized fillers. Furthermore, the addition of nanoparticles may influence the curing behavior of the polymer matrix during processing. In this study, the effect of various loadings of alumina or silica nanoparticles on the cure kinetics of bisphenol E cyanate ester (BECy) is investigated by differential scanning calorimetry (DSC). Alumina nanoparticles are shown to have a catalytic effect on the cure of BECy. The greater catalytic effect of alumina nanoparticles, compared with silica, is attributed to the increased number of hydroxyl groups on the surface and the Lewis acidity of ,-phase alumina. Kinetic parameters were obtained from dynamic DSC experiments. For an autocatalytic model of the cure process, the kinetic parameters obtained from the model suggest that the addition of alumina nanoparticles changed the cure reaction mechanism of BECy. POLYM. ENG. SCI., 2010. 2009 Society of Plastics Engineers [source]


Production of Highly Loaded Nanocomposites by Dispersing Nanoparticles in Epoxy Resin

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2010
H. Nolte
Abstract The objective of this study was the investigation of techniques for dispersing alumina nanoparticles with different surface modifications in epoxy resin. In order to prepare the matrix suspension, high contents of fillers (up to 50,wt,%) were dispersed by conducting shear mixing techniques in a high performance laboratory kneader. The intention was to attain solutions that were stable against re-agglomeration, while the mass fraction and the product fineness were maintained as high as possible. Therefore, both the formulations and the dispersion parameters were varied systematically. An epoxy resin was used as a carrier fluid and a corresponding amine hardener system was chosen. Tests were performed using alumina particles and surface modified alumina particles at different particle concentrations. Furthermore, the effect of diluting the colloidal suspensions and the resulting long term stability were also examined. The matrix suspension was examined with respect to viscosity, stability and particle size distribution. [source]