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Sample Dimensions (sample + dimension)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Role of various elliptical shapes for efficient microwave processing of materials

AICHE JOURNAL, Issue 6 2007
Tanmay Basak
Abstract A detailed theoretical analysis has been carried out to assess the role of various elliptical shapes/cross sections on microwave heating of 2-D cylinders for beef and oil samples. Two types of elliptical cross sections are considered as type A (ellipse with major axis along the horizontal plane), and type B (ellipse with minor axis along the horizontal plane.) A preliminary analysis on microwave heating of samples has been shown via average power within a sample vs. sample radius of circular cross section for beef and oil samples. Several regimes (I,III) based on small and large radius for circular cross sections have been selected. The effect of elliptical shapes for type A and B configurations has been studied initially via average power vs. aspect ratio distributions for various regimes. The grayscale images of power absorption have been analyzed further for elliptical cross section with varying aspect ratios for regimes I,III where aspect ratio and types of configuration are shown to influence spatial power absorptions. The detailed temperature profiles have also been shown to illustrate the role of elliptical shapes on uniform heating and thermal runaway. Depending on the material dielectric properties and sample dimension, either type A or B or both configuration has been recommended. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]

Pressureless Rapid Sintering of UO2 Assisted by High-frequency Induction Heating Process

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2008
Jae Ho Yang
Heat generation of uranium dioxide (UO2) powder and its pressureless rapid sintering behaviors have been studied using a high-frequency induction heating apparatus. The porous graphite housing has been used to prevent heat loss and to preheat the uranium oxides, simultaneously. At an elevated temperature, UO2 powder generated extra heat by itself. The synergism of individual heat generation between the graphite and UO2 powder could effectively heat the UO2 to the sintering temperature of 1700°C. Using this process, densification behavior of cylindrical and disk-type UO2 green pellets according to the heating rate and grain structure of sintered UO2 pellets were investigated. Rapid sintering caused a large crack around the circumference of the sintered pellet. The formation of cracks could be avoided when the heating rate or sample dimension are properly reduced. A dense and crack-free UO2 pellet with a relative density of up to 96% was produced within 5 min of the process time. The induction heat sintering process can be a potential candidate for the rapid fabrication of ceramics and composites. [source]

Cross-Linked Poly(, -caprolactone/D,L -lactide) Copolymers with Elastic Properties

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2002
Antti O. Helminen
Abstract Cross-linked , -caprolactone (CL) and D,L -lactide (DLLA) copolymers with elastic properties were synthesized in three steps. First, the monomers were copolymerized in ring-opening polymerization to obtain telechelic star-shaped oligomers with almost completely random monomer distribution. The oligomers were methacrylated with methacrylic anhydride in the second step and cured in a third. Molar CL/DLLA compositions of 30/70, 50/50, 70/30, 90/10, and 100/0 were used to obtain elastic structures with a wide range of properties. The effect of the average length of the copolymer block on the properties of the networks was evaluated with three different co-initiator contents (0.5, 1.0, and 2.0/100) in the oligomer synthesis. The oligomers were characterized by 13C NMR spectroscopy, size-exclusion chromatography (SEC), and differential-scanning calorimetry (DSC). The formation of elastic networks was confirmed by the absence of a flow region in dynamic mechanical analysis (DMA), the increase in Tg in DSC, and the full recovery of the sample dimensions after tensile testing. In addition, gel contents were high and the samples swelled in CH2Cl2. The networks possessed break stresses from 0.7,9.7 MPa with elongations from 80,350%. Networks with 100 or 90% of , -caprolactone retained their form in vitro for 12 weeks, but an increase in lactide content made the networks more vulnerable to hydrolysis. Water absorption of the polymers during hydrolysis. [source]

Magnetoabsorption coefficient of donor impurities in CdS quantum dot

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2006
A. Didi Seddik
Abstract A theoretical study of the donor-related absorption coefficient in spherical CdS quantum dots (QD) in the presence of a uniform magnetic field is performed. The wave functions and the eigenvalues of the initial and final states are obtained in the effective-mass approximation by using a variational method and a perturbation method, respectively. The results obtained show that the absorption coefficient presents essentially two peaks; one associated with on-center donors and another related to transitions involving donors at the QD edge. The dependences of the absorption coefficient on sample dimensions, the magnetic field strength and the light polarization are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Micromechanics for fiber volume percent with a photocure vinyl ester composite

POLYMER COMPOSITES, Issue 3 2007
Richard C. Petersen
Micromechanics for fiber volume percent (Vf) from 0.0Vf to 54.0 Vf were conducted using (3 mm long × 9 ,m diameter) high-purity quartz fibers in a visible-light vinyl ester particulate-filled photocure resin. MTS fully articulated four-point bend fixtures were used with a 40 mm test span and 50 × 2 × 2 mm3 sample dimensions. Specimens were tested following the combined modified ASTM standards for advanced ceramics ASTM-C-1161,94 and polymers ASTM-D-6272,00 for modulus, flexural strength, and yield strength. Experimental data provided reliable statistical support for the dominant fiber contribution expressed through the rule-of-mixtures theory as a valid representation of micromechanical physics. The rule-of-mixtures micromechanics described by Vf could explain 92, 85, and 78% of the variability related to modulus, flexural strength, and yield strength respectively. Statistically significant improvements with fiber addition began at 10.3Vf for modulus, 5.4Vf for flexural strength, and 10.3Vf for yield strength, p < 0.05. In addition, correlation matrix analysis was performed for all mechanical test data. An increase in Vf correlated significantly with increases in modulus, flexural strength, and yield strength as measured by the four-point bending test, p < 10,10. All mechanical properties in turn correlated highly significantly with one another, p < 10,9. POLYM. COMPOS., 28:294,310, 2007. © 2007 Society of Plastics Engineers [source]