scholarly journals The modelling of the toughening of epoxy polymers via silica nanoparticles: The effects of volume fraction and particle size

Polymer ◽  
2013 ◽  
Vol 54 (26) ◽  
pp. 7022-7032 ◽  
Author(s):  
D.J. Bray ◽  
P. Dittanet ◽  
F.J. Guild ◽  
A.J. Kinloch ◽  
K. Masania ◽  
...  
Keyword(s):  
Particle Size ◽  
Silica Nanoparticles ◽  
Volume Fraction ◽  
Epoxy Polymers

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

scholarly journals A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 491
Author(s):  
Alina E. Kozhukhova ◽  
Stephanus P. du Preez ◽  
Aleksander A. Malakhov ◽  
Dmitri G. Bessarabov
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Combustion Temperature ◽  
Volume Fraction ◽  
Morphological Characteristics ◽  
Al Alloy ◽  
Impregnation Method ◽  
Case Scenario ◽  
Worst Case ◽  
Thermal Distribution

In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC.

Effects of Particles Size of Nanosilica on Properties of Polybenzoxazine Nanocomposites

2015 ◽  
Vol 659 ◽  
pp. 394-398 ◽  
Author(s):  
Nutthaphon Liawthanyarat ◽  
Sarawut Rimdusit
Keyword(s):  
Particle Size ◽  
Silica Nanoparticles ◽  
Primary Particle ◽  
Mechanical And Thermal Properties ◽  
Particle Sizes ◽  
Barrier Effect ◽  
Degradation Temperature ◽  
Maximum Value ◽  
Wetting Behaviors ◽  
Composite Samples

Polybenzoxazine nanocomposites filled with three different sizes of silica nanoparticles are investigated for their mechanical and thermal properties. In this research, silica nanoparticles with primary particle sizes of 7, 14 and 40 nm were incorporated in polybenzoxazine matrix at a fixed content of 3% by weight. From the experimental results, the storage modulus of the polybenzoxazine nanocomposite was found to systematically increase with decreasing the particle sizes of nanosilica suggesting better reinforcement of the smaller particles. Glass transition temperature was found to slightly increase with the addition of the silica nanoparticles. The uniformity of the composite samples were also evaluated by thermogravimetric analysis to show good dispersion of the silica nanoparticles in the composite samples as a result of high processability of the benzoxazine resin used i.e. low A-stage viscosity with good wetting behaviors. Degradation temperature at 5% weight loss (Td,5) of polybenzoxazine nanocomposites filled with different particle sizes of silica nanoparticles was found to increase from the value of 325 °C of the neat polybenzoxazine to the maximum value of about 340 °C with an addition of the nanosilica of the smallest particle size used. Finally, the smaller nanosilica particle size was also found to show more pronounced effect on Td,5enhancement of the composite samples as a result of greater barrier effect from larger surface area of the smaller particles.

A Parametric Numerical Study of Radiative Transfer in Thermotropic Materials

2013 ◽  
Author(s):  
Adam C. Gladen ◽  
Susan C. Mantell ◽  
Jane H. Davidson
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Parametric Study ◽  
Volume Fraction ◽  
Numerical Study ◽  
Anisotropic Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Size Parameter

A thermotropic material is modeled as an absorbing, thin slab containing anisotropic scattering, monodisperse, spherical particles. Monte Carlo ray tracing is used to solve the governing equation of radiative transfer. Predicted results are validated by comparison to the measured normal-hemispherical reflectance and transmittance of samples with various volume fraction and relative index of refraction. A parametric study elucidates the effects of particle size parameter, scattering albedo, and optical thickness on the normal-hemispherical transmittance, reflectance, and absorptance. The results are interpreted for a thermotropic material used for overheat protection of a polymer solar absorber. For the preferred particle size parameter of 2, the optical thickness should be less than 0.3 to ensure high transmittance in the clear state. To significantly reduce the transmittance and increase the reflectance in the translucent state, the optical thickness should be greater than 2.5 and the scattering albedo should be greater than 0.995. For optical thickness greater than 5, the reflectance is asymptotic and any further reduction in transmittance is through increased absorptance. A case study is used to illustrate how the parametric study can be used to guide the design of thermotropic materials. Low molecular weighted polyethylene in poly(methyl methacrylate) is identified as a potential thermotropic material. For this material and a particle radius of 200 nm, it is determined that the volume fraction and thickness should equal 10% and 1 mm, respectively.

Electroacoustic Study of n-Hexadecane/Water Emulsions

2001 ◽  
Vol 54 (8) ◽  
pp. 503 ◽  
Author(s):  
Linggen Kong ◽  
James K. Beattie ◽  
Robert J. Hunter
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Volume Fraction ◽  
Sodium Dodecyl ◽  
Surfactant Solution ◽  
Minimum Size ◽  
Water Mixture ◽  
Concentrated Suspensions ◽  
Minimum Concentration ◽  
Median Diameter

n-Hexadecane-in-water emulsions were investigated by electroacoustics using a prototype of an AcoustoSizer-II apparatus. The emulsions were formed by passing the stirred oil/water mixture through a homogenizer in the presence of sodium dodecyl sulfate (SDS) at natural pH (6–7). With increasing oil-volume fraction, the particle size increased linearly after 5 and also after 20 passages through the homogenizer, suggesting that surface energy was determining particle size. For systems in which the surfactant concentration was limited, the particle size after 20 passages approached the value dictated by the SDS concentration. With ample surfactant present, the median diameter was a linear function of the inverse of the total energy input as measured by the number of passes. There was, however, a limit to the amount of size reduction that could be achieved in the homogenizer, and the minimum size was smaller at smaller volume fractions. Dilution of the emulsion with a surfactant solution of the same composition as the water phase had a negligible effect on the particle size and changed the zeta potential only slightly. This confirms results from previous work and validates the equations used to determine the particle size and zeta potential in concentrated suspensions. The minimum concentration of SDS that could prevent the emulsion from coalescing for the system with 6% by volume oil was 3 mM. For this dilute emulsion, the particle size decreased regularly with an increase in SDS concentration, but the magnitude of the zeta potential went through a strong maximum at intermediate surfactant concentrations.

The Effect of Particle Size on the Electromechanical Properties of PZT/PVDF

2009 ◽  
Vol 66 ◽  
pp. 238-241
Author(s):  
Xiao Fang Liu ◽  
Hua Jun Sun ◽  
Ming Wei ◽  
C.X. Xiong
Keyword(s):  
Particle Size ◽  
Piezoelectric Ceramic ◽  
Electromechanical Coupling ◽  
Piezoelectric Properties ◽  
Volume Fraction ◽  
Relative Dielectric Constant ◽  
Connectivity Pattern ◽  
Conventional Solid State Reaction ◽  
Pressing Method ◽  
Dielectric And Piezoelectric Properties

The Nb modified PZT piezoelectric ceramic was synthesized by conventional solid-state reaction, where all of different particle sizes had the same physical properties. 0-3 modified PZT/PVDF composites were formed by hot-pressing method. The particle size effect of modified PZT on the relative dielectric and piezoelectric properties of the composites were investigated. The relative dielectric constant εr, piezoelectric constant d33 and electromechanical coupling factor kp were higher in the composite containing larger PZT particle size. The microstructures of the composites were studied by SEM, the composite with the finer PZT particle size was more homogeneous, but larger particle size was easy to be contacted. In a high volume fraction particle-loaded composite, some piezoelectric ceramic particle appeared to be in contact, as in a 1-3 connectivity pattern. The larger particle size of modified PZT itself could be seen as the grain of modified PZT contact in a 1-3 connectivity pattern and easy to be contacted each other compared to the finer particle size in the composites, thus reducing the resistance of the composites and the poling process became effective, which led to higher properties. The optimal particle size of PZT is about 100μm, the Nb modified PZT/PVDF (volume fraction 70/30) composite show higher dielectric and piezoelectric properties than the others, εr=156.6, d33=69pC/N and kp=0.358.

Effect of Particle Size of W-Brass Composite on Gamma-Ray Absorption Coefficient

2015 ◽  
Vol 754-755 ◽  
pp. 19-23
Author(s):  
Kahtan S. Mohammed ◽  
Ali Basheer Azeez ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Kamarudin Hussin ◽  
Azmi B. Rahmat
Keyword(s):  
Particle Size ◽  
Absorption Coefficient ◽  
Gamma Ray ◽  
Vickers Microhardness ◽  
Volume Fraction ◽  
Milled Powder ◽  
Microstructural Characterization ◽  
Effect Of Particle Size ◽  
Gamma Ray Attenuation ◽  
Attenuation Values

In this study, the dependence of gamma-ray absorption coefficient on amount and particle size of tungsten (W) in W-brass sintered compacts was investigated. To attain this goal, two sets of different W wt. % were prepared (W 65wt. %, W75wt. % and W85 wt. %). One set has compacts of as received powder and the other set has compacts of ball milled powder. The results showed that gamma-ray attenuation coefficient is inversely proportional to the particle size of the tested sintered compacts and directly proportional to the W content. Vickers microhardness, attenuation properties and microstructural characterization were carried out on the sintered samples. The attenuation test was conducted using gamma spectrometer with Genie 200 software. The samples of ball milled powder and of the highest volume fraction of W showed the highest hardness and attenuation values.

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