Addition Of Alumina Particles Research Articles

Thermo‐mechanical property enhancement of rigid polyurethane foam using silica and alumina as hybrid fillers over single filler

AbstractSilica and alumina particles were loaded in the rigid polyurethane foam composite as hybrid fillers. After the successful addition of silica and alumina as fillers, various properties of the foam composite were enhanced up to a particular weight percentage (7.5 wt% of silica and alumina each) with respect to alumina loaded foams. Hard urea domains are well distributed in the urethane matrix which indicates the absence of the peak representing H‐bonded urea in the Fourier‐transform infrared spectroscopy results. The addition of hybrid fillers into the rigid polyurethane foam matrix improved the compressive strength of the foam composite by 14% in comparison to alumina loaded foams due to the synergistic effect of the hybrid fillers. The foam composite at 7.5 wt% loading of hybrid fillers was successful in decreasing the thermal conductivity by 9% with respect to the thermal conductivity of the unloaded foam. There was a reduction in the gross calorific value up to 7% in the hybrid filler loaded foam composite when compared with that of the alumina loaded composite. Hence, hybrid fillers should be added to enhance the composite's properties by a greater extent.Highlights From the compressive test results, an increase in the compressive strength up to 14% was observed in the samples loaded with hybrid fillers with respect to the samples loaded with alumina due to the synergistic effects of the two fillers. For the foam composite loaded with alumina, the gross calorific value decreased up to 6% when compared to the unloaded foam. The gross calorific value decreased by a further 7% when hybrid fillers were added to the polyurethane foam composite with respect to the alumina loaded foam composite. The foam composite loaded with 7.5 weight % of hybrid fillers had lower values of thermal conductivity when compared with that of the unloaded polyurethane foam. We propose the addition of both alumina and silica as hybrid filler particles as they enhanced the various properties of the polyurethane foam composite to a greater extent than the addition of alumina particles as a single filler and have potential to replace unloaded polyurethane foams in different applications.

Abnormal texture evolution of accumulative roll bonded Al–Cu by adding alumina particles

Evolution of the texture of an Al–Cu composite after addition of alumina particles was investigated in details using X-Ray Diffraction (XRD) method. Composite samples were produced by the Accumulative Roll Bonding (ARB) and alumina particles were uniformly added to the composite using anodizing technique. The process was accompanied by cutting, stacking and rolling the lamellar materials up to seven times. In early stage of ARB, a shear texture close to the Rotated Cube formed for the Al side. This texture development was also confirmed by microstructural investigation on shear bands during deformation employing optical and scanning electron microscopy. In the last two cycles, a nearly random orientation of grains was developed. For the Cu side, however, the recrystallized Cube texture component was prominent for early ARB cycles due to the recrystallization phenomenon. Moreover, a mixture of rolling and recrystallized texture was detected for the Cu side at higher ARB cycles. Furthermore, evaluation of the grain boundaries showed an increase in the number of high angle grain boundaries for the final ARB cycles in both Al and Cu sides, confirming the occurrence of grain refinement during ARB. Localized particle deformation zone (PDZ) around alumina particles was also proposed to have a contribution to textural evolution of the composite.

Fracture toughness of alumina filler filled glass fabric reinforced epoxy composites

Micron sized alumina particles (≤10 µm) are incorporated between the plies of a conventional glass fabric reinforced epoxy (GE) composite to improve the fracture toughness ( K IC ). The influence of the alumina filler content (0, 7.5, and 10 wt%) on K IC are investigated. These composites are prepared by hand layup assisted by the vacuum bagging method. The prepared composites are evaluated for K IC at room temperature, elevated temperature (100 °C) and at cryogenic temperature (−15 °C). The K IC test was conducted utilizing single notched edge bend specimen under mode I according to ASTM D5045 standard. The test results indicated that K IC of GE is improved by addition of alumina particles. Furthermore, these composites maintained higher K IC at −15 °C and decreased significantly at elevated temperature. The maximum K IC is recorded at particle loading of 10 wt% GE hybrid composite.

Influence of Alumina Particles on Tribology of Autocatalytic Ni-P Coatings at High Temperature

The present work considers the effects of incorporation of hard Al2O3 particles on the structure, microhardness, and tribological behavior of electroless Ni-P coatings at room temperature and elevated temperature. Ni-P (9% P) coating shows a typical amorphous structure that changes to a mixture of nanocrystalline and amorphous structure due to the addition of alumina particles. The incorporation of Al2O3 particles is found to enhance the overall hardness and wear resistance of the Ni-P coating. Exposure to high temperature during tribological tests acts as brief heat treatment, initiating microstructural changes in the coating which further increases the hardness of the deposit. The scanning electron micrograph of the worn surface of the coating reveals both abrasive and adhesive wear phenomena governing the wear mechanism at elevated temperature. The development of the oxide layer is another important characteristic of the coatings examined under high temperatures (around 500°C).

Thermal Properties of Composite Polymer Electrolytes Poly(Ethylene Oxide)/Sodium Trifluoroacetate/Aluminum Oxide (PEO)10CF3COONa + x wt.% Al2O3.

Polymeric membranes of poly(ethylene oxide) (PEO) and sodium trifluoroacetate (PEO:CF3COONa) combined with different concentrations of aluminum oxide (Al2O3) particles were analyzed by impedance spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). DSC results show changes in the crystalline fraction of PEO when the concentration of Al2O3 is increased. TGA analysis showed thermal stability up to 430 K showing small changes with the addition of alumina particles. The decrease in crystalline fraction for membranes with low Al2O3 concentration is associated with the increase in conductivity of (PEO)10CF3COONa + x wt.% Al2O3 composites.

Effect of alumina on the performance and characterization of cross-linked PVA/PEG 600 blended membranes for CO2/N2 separation

In this work, poly(vinyl) alcohol (PVA)/poly(ethylene) glycol (PEG) 600 g/mol cross-linked membranes with different alumina (Al2O3) content were synthesized. The membranes were then characterized by FTIR, TGA, DSC, SEM, mechanical strength and permeation properties for carbon dioxide and nitrogen gases at different operating temperatures. The FTIR results confirmed the acetal linkages of cross-linking at 1083 cm−1 and the presence of stretching and bending peaks of Al-O bond at 598 and 444 cm−1, respectively. TGA results showed that the thermal stabilities of the membranes improved with the addition of alumina particles. DSC analysis proved that the glass transition temperature of the membranes increased with the addition of alumina content. SEM images confirmed the uniform distribution of alumina particles in the membranes. Sol gel testing was also carried out to determine the degree of swelling and gel content. It was also concluded that at 25 °C and 1.5 bar, 6 wt.% Al2O3 filled membrane demonstrated maximum ideal selectivity of CO2/N2 as 79.8 and the highest permeability of CO2 as 394 Barrers, which surpassed the Robeson upper bound limit 2008. It was also found that the increase in temperature resulted in enhancement of CO2 permeability of alumina filled membrane at the cost of reduction in CO2/N2 ideal selectivity and at 70 °C; optimum gas separation properties were achieved.

Study the Effect of Rotational Speed and Pouring Temperature on the Wear Resistance and Hardness of Alloy (A380) Reinforced with Different Volume Fraction of Alumina Particles

In this study a cylindrical liner was produced by horizontal centrifugal casting process. The liner was composed from aluminum alloy (A380) matrix reinforced with alumina particles (Al2O3) with grain size of (63−125)μ and volume percent of 10,15 and 20%. The die was rotated at different speeds and its temperature was remained constant at (350)ºC.In this present study it was concluded that any increase in temperature difference between pouring and die temperature will reduce the surface defects. This study reveals that increasing the rotational speed refines the grain size but cause the alumina particles to be concentrated at the outer surface. Finally it was found that the addition of alumina particles increases both hardness and wear resistance of the alloy.

Corrosion Resistance of Ni/Al2O3 Nanocomposite Coatings

Nickel matrix composite coatings with ceramic disperse phase have been widely investigated due to their enhanced properties, such as higher hardness and wear resistance in comparison to the pure nickel. The main aim of this research was to characterize the structure and corrosion properties of electrochemically produced Ni/Al 2 O 3 nanocomposite coatings. The coatings were produced in a Watts bath modified by nickel grain growth inhibitor, cationic surfactant and the addition of alumina particles (low concentration 5 g/L). The process has been carried out with mechanical and ultrasonic agitation. The Ni/Al 2 O 3 nanocomposite coatings were characterized by SEM, XRD and TEM techniques. In order to evaluate corrosion resistance of produced coatings, the corrosion studies have been carried out by the potentiodynamic method in a 0.5 M NaCl solution. The corrosion current, corrosion potential and corrosion rate were determined. Investigations of the morphology, topography and corrosion damages of the produced surface layers were performed by scanning microscope techniques. DOI: http://dx.doi.org/10.5755/j01.ms.22.1.7407

UV-cured Al2O3-laden cellulose reinforced polymer electrolyte membranes for Li-based batteries

A methacrylate based plasticised polymer electrolyte membrane is prepared via a rapid and facile UV curing process, the major concerns of mechanical integrity are overcome by simply using appropriately modified cellulose handsheet laden with nano-sized acidic alumina particles as a reinforcement. The use of the cellulose handsheets greatly enhances the flexibility and mechanical properties of the membrane while the addition of alumina particles helps to maintain satisfactory conductivity values. The reinforced composite electrolyte membrane is also tested in a real lithium cell, exhibiting excellent performance which account for its use in futuristic lithium batteries having low cost, environmentally friendly and easily scalable properties.

Corrosion Behavior of Aluminum Wire for Overhead Transmission Lines: Investigation and Analysis

SummaryThe corrosion behavior of aluminum wire used for overhead transmission lines was studied in four corrosion environments: (1) sodium chloride solution, (2) sodium chloride solution with addition of alumina particles, (3) aluminum chloride solution, (4) aluminum chloride solution with addition of alumina particles. The corrosion tests and polarization measurements revealed that environments 2 and 4 with alumina particles roughened and rapidly corroded the surface of the aluminum wire. It is considered that wet and dry environments of overhead transmission lines change aluminum hydroxide, present as a corrosion product, to alumina (aluminum oxide), which acts as an abrasive and weakens the surface of the aluminum wire. It is also shown that the corrosion of the aluminum wire occurs in an abrasive corrosion environment caused by alumina and corrosion fatigue due to vibration of the overhead wires. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 18–24, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22486

Influence of Liquid-Surface Vibration on Sonochemiluminescence Intensity

The influence of surface vibrations on the intensity of sonochemiluminescence (SCL) produced by pulsed ultrasound with a frequency of 151 kHz is investigated through optical measurement of the vibration amplitude. Pulsed ultrasound inhibits the generation of large degassing bubbles that scatter sound waves, thereby restricting the effective spatial region for sonochemical reactions. The vibration amplitude of the liquid surface becomes gradually significant with pulsed ultrasound as the power applied to the transducer increases. At this time, the SCL intensity increases and then decreases after displaying a peak because the resonance of standing wave cannot be maintained stably by the surface vibration. The SCL intensity during high-amplitude pulsing becomes almost zero if the distance between the highest position of the liquid surface and its position in the absence of ultrasound becomes close to larger than one-quarter of the ultrasound wavelength. This condition for the liquid surface vibration provides a limit for establishment of a resonant standing wave that is effective for sonochemical reaction. Adding particles provides nucleation sites for cavitation bubbles, thereby inhibiting the vibration of the surface of the upper liquid level. The SCL intensity is enhanced by the addition of alumina particles under pulsed excitation at relatively low applied powers.

Production of Al–20 wt.% Al 2O 3 composite powder using high energy milling

High energy ball milling was used to produce a nanostructured Al matrix composite reinforced by submicron α-alumina particles. Scanning electron microscopy analysis as well as tap and green density measurements were used to optimize the milling time needed for the completion of the mechanical milling process. Results show that addition of alumina particles as the reinforcement has a drastic effect on the size, morphology and pressability of the powder. Scanning electron microscopy shows that distribution of alumina particles in the Al matrix reaches a full homogeneity after steady state. This would increase the hardness of powder due to a nano-structured matrix and oxide dispersion strengthening.

Relationship between static bending and compressive behaviour of particle-reinforced cement composites

Innovative particle-reinforced materials made of alumina particles and cement-based matrix were designed, manufactured and tested to evaluate the potential use of ceramic aggregates in concretes. These particle-reinforced composites were tested in three-point bending and uniaxial compression conditions to determine the influence of the shape and size of the ceramic inclusions, and the addition of silica fume on the mechanical properties. A specific methodology combining post-mortem observations with a statistical analysis of tensile failure stresses (average strength and Weibull modulus) was conducted to deduce the origin of failure for each cement-based composite (porosity or ceramic particles/matrix decohesion). A remarkable correlation is observed between bending failure stress level and the average strength measured under uniaxial compression loading. As main conclusion, addition of alumina particles in a mortar appears to strengthen or to weaken the composite depending on whether silica fume is used in the cementitious matrix.

Compressive Creep Studies on Alumina Particulate Reinforced Alumino-Silicate Glass

The effect of alumina particulate reinforcement on the high temperature compressive creep behaviour of alumino-silicate glass was characterized in the stress and temperature range of 3 to 50 MPa and 1023 to 1123 K, respectively. The resulting strain rates varied from $10^{-6} to 10^{-2} s^{-1}$, and the composites exhibited Newtonian viscous flow. The creep activation energies ~720±50 kJ mol-1. XRD and density measurements on the sintered and tested samples indicated that there was no crystallization or cavitation in the glass or the composites. It was found that addition of alumina particles moderately increased the creep resistance of the glass and that these materials have the potential for superplasticity

Casting and HIPping of Al-based metal matrix composites (MMCs)

The commercially available Al (trade mark A-356 Al) alloy, with approximately 7 wt% Si, 0.4 wt%Mg and other small amount of elements, is the most common type of Al foundry alloy due to its excellent castability. The needle-like Si phase embedded in the Al matrix is the most typical structural feature of this alloy system and the morphology of the Si phase has been shown to be important in determining the mechanical properties of this alloy. Much work has been done to modify the Si phase morphology by heat treatment or addition of grain refiners such as Sodium and Strontium. The present work describes the microstructural changes by the addition of alumina particles into molten Al, focusing on the effect of the alumina particle on the location, amount and morphology of the Si or eutectic phase in the matrix. Since the alumina particles are not wettable by molten Al, small amount of reactive agent such as Li was added to the Al. Reasonable alumina particle distribution within the matrix Al was achieved by low temperature mixing and gravity casting technique under open atmosphere. The cast MMC bars were processed by Hot Isostatic Pressing (HIPping) in order to densify the MMCs. The cast and HIPped MMCs were examined and mechanically tested. Results show that the 0.2% Yield Strength was improved over the unreinforced Al alloy.

High strain rate tensile properties of an (Al 2O 3 particles)-(Al alloy 6061-T6) metal matrix composite

The metal matrix composite materials consist of 10, 15 and 20 vol.% alumina particles in an aluminium alloy 6061-T6 matrix. Specimens were taken from hot-extruded rods and the tensile tests were carried out at various strain rates. High strain rate tests were performed by the split-Hopkinson-bar method. The fracture surfaces were observed with a scanning electron microscope to understand the fracture mechanisms. From the results, it can be concluded that: (1) the alumina-reinforced composites are more sensitive to strain rate than the unreinforced material, (2) the strain rate sensitivity of the ultimate tensile strength of these composites increases with increasing temperature and (3) the addition of alumina particles will reduced the ductility of aluminium alloy 6061-T6, irrespective of the strain rate and temperature.

Improvement of the fluidisability of Ni/SiO 2 aerogels by reducing interparticle forces

Ni/SiO 2 aerogels belong to group C of the Geldart particle classification, which is usually very difficult to fluidise. This behaviour is due to interparticle forces too large to be overcome by the drag force exerted by the fluidising gas. Based on the theoretical expression of the van der Waals force, practical ways of decreasing the interparticle forces, and thereby improving the quality of aerogel fluidisation, are proposed: increase of initial bed porosity, presence of Ni under oxidized rather than metallic form, high humidity of the fluidising gas and addition of alumina particles.

The Influence of Alumina Dispersions on the Diffusion-Creep Behaviour of Polycrystalline Copper

AbstractThe creep behaviour of powder-compacted copper and copper containing 0.5, 1.0 and 1.5 vol.-%alumina has been investigated in the range where the stress-directed lattice diffusion of vacancies is expected to control. Addition of alumina particles is shown to change the initial flow characteristics from Newtonian, where the creep rate έ is proportional to the applied stress σ, to Bingham type, where έ is proportional to an effective stress σέ. This effective stress is defined by σέ = σ − σ0, where σ0 is a threshold value that increases linearly with volume fraction of alumina and below which no deformation occurs. The proportionality constant between έ and σE is shown to be identical to that between έ and σ and is given by the Nabarro-Herring equation as BΩD/d2 kT, where B is a numerical constant, Ω the atomic volume, D the lattice self-diffusion coefficient, D the grain size, and kT has its usual meaning. Above the threshold stress, creep rate decreases with strain and this curvature is more pronou...