Volume Fraction Of Alumina Research Articles

Mechanical and physical characterization of powder metallurgy based aluminium metal matrix hybrid composite

Powder metallurgy based metal matrix composites (MMCs) are widely used to develop components in various fields such as aerospace, automotive, electronics due to improved physical and mechanical properties. In the present work, the physical and mechanical properties of cylindrical sintered hybrid composite samples have been investigated. Four verities of hybrid composite samples were made from aluminum powder mixed with 2 and 7 vol% of silicon carbide and, 3 and 8 vol% of alumina. Five different sintering conditions (combinations of temperatures and sintering time) were employed. The density and hardness of each sintered specimen were measured. Cold compression tests were carried out for the estimation of compressive strength. An increase in the volume fraction of alumina in Al/SiC reduces the density, hardness and compressive strength. The flow stress of cold compressed composites has been characterized by the Voce equation. The proposed powder metallurgy (PM) based route for the fabrication of aluminium matrix composite shows significant improvement in physical and mechanical properties relative to those of commercial aluminium.

Hybrid nanofluid flow and heat transfer over a permeable biaxial stretching/shrinking sheet

Purpose The purpose of this paper is to examine the axisymmetric flow and heat transfer of a hybrid nanofluid over a permeable biaxial stretching/shrinking sheet. Design/methodology/approach In this study, 0.1 solid volume fraction of alumina (Al2O3) is fixed, then consequently, various solid volume fractions of copper (Cu) are added into the mixture with water as the base fluid to form Cu-Al2O3/water hybrid nanofluid. The hybrid nanofluid equations are converted to the similarity equations by using the similarity transformation. The bvp4c solver, which is available in the Matlab software is used for solving the similarity equations numerically. The numerical results for selected values of the parameters are presented in tabular and graphical forms, and are discussed in detail. Findings It is found that dual solutions exist up to a certain value of the stretching/shrinking and suction parameters. The critical value λc < 0 for the existence of the dual solutions decreases as nanoparticle volume fractions for copper increase. The temporal stability analysis is performed to analyze the stability of the dual solutions, and it is revealed that only one of them is stable and physically reliable. Originality/value The present problem is new, original with many important results for practical problems in the modern industry.

Strength Performance of Micro Alumina Reinforced Direct Recycled AA6061 Chips Based Matrix Composite

Ultimate tensile strength (UTS) becomes a primary concern in direct recycling of metal chips. This study investigates the influences of preheating temperature, preheating time and volume fraction of alumina on the tensile strength performance. The parameters of temperature, time and volume fraction of micro alumina were varied between 450 - 550 oC, 1 - 3 hours and 5 - 15% respectively. The full factorial design with center point analysis was employed to analyse the effect of process variables on the response. A total of 19 experimental runs were performed through the hot extrusion operation. The preheating temperature and volume fraction were identified as the key variables affecting the UTS. An optimum UTS was obtained for the profile extruded at 550 oC, 3 hours duration and 5% volume fraction of alumina.

The Study of Gum Arabic as Surfactant on the Stability of Water-based Alumina Nanoparticle Suspensions

The stability study of alumina nanoparticle suspensions has been investigated by using gum arabic as a surfactant. The effect of particle volume fraction of alumina nanoparticle and gum arabic concentration were observed. The stability of the suspension was characterized using zeta potential and particle size distribution analysis. Several volume fractions of alumina and gum arabic concentration were dispersed in water as a solvent for suspension stability. The result showed that the stability of water-based alumina nanoparticle suspensions was increase with the decreasing of particle volume fraction and increasing of gum arabic concentration. The particle size distribution was narrow with decreasing particle volume fraction and increasing gum arabic concentration. The hydrodynamic diameter of the particles was smaller with the increasing of gum arabic concentration. The smallest particle size recorded was 164.6 nm at 0.5% gum arabic concentration. Zeta potential values were increased with the increasing of gum arabic concentration. The highest zeta potential was recorded at -36.0 mV. It can be concluded that gum arabic can be used for stabilization of water-based alumina nanoparticle suspensions.

Microstructures and mechanical characterizations of high-performance nacre-inspired Al/Al2O3 composites

Herein, we adopted a simple way to fabricate nacre-inspired “brick-and-mortar”-structured composites with freeze-cast alumina and pure Al. The ceramic layer thickness (2.5–16.6 μm) and alumina volume fraction (8–48%, resulting from the volume shrinkage of the scaffolds after sintering) were controlled by varying the slurry concentration (5, 10, 15 and 20 vol%). The Al/8 vol% Al2O3 composite, with a relatively thick metal layer (24.8 ± 5.7 μm) and low density (2.78 g/cm3), exhibited a bending strength of 319 ± 13 MPa and fracture toughness of 138 ± 7 MPa m1/2. Compared to the Al/8 vol% Al2O3 composite, the Al/20–48 vol% Al2O3 composites had higher bending strengths (332–368 MPa) but lower fracture toughness values (87–41 MPa m1/2). The relationships between the cracking modes and structural features in the composites were discussed to account for the strengthening and toughening mechanisms. This work provides new ideas and solutions concerning the design and fabrication of nacre-mimetic metal-ceramic composites.

Effect of Alumina Addition on the Rheological Behavior of Shear Thickening Fluids

Shear thickening fluids (STF) have attracted much attention in many applications including body armor. In this study, suspensions of silica colloidal particles and polyethylene glycol fluid were prepared at varying volume fractions φ = 0.3 to 0.52 and their rheological behavior was investigated. It was found that the suspensions exhibited a Newtonian behavior for φ < 0.4, whilst a shear thinning followed by a thickening behavior could clearly be observed for φ > 0.4. Furthermore, the critical shear rates for the onset of shear thickening was found to decrease with increasing silica volume fraction but the corresponding critical shear stresses were independent of the volume fraction. To improve the ballistic protective performance, small amount of hard material particles, such as alumina, were added into the silica suspension of φ = 0.5. It was shown that the critical shear rates of the reinforced-STFs decreased with increasing volume fraction and decreasing alumina particle size. However, higher thickening ratio was observed for the alumina additive with agglomerated structure and this ratio increased with increasing alumina volume fraction.

An experimental and numerical study of novel nano-grained [formula omitted]-TiAl/Al2O3 cermets

In this paper, a microstructure-based finite element model for nano-grained (γ+α2)-TiAl/Al2O3 cermets is proposed based on a modified variational formulation of the Gurson model for an elastic-plastic porous material. In the modeling approach, the high volume fraction of alumina, variability in material characteristics, and microstructural features (e.g., inclusion size) are considered. Mechanical properties and microstructure inputs are derived from nanoindentation and microscopy analysis performed for this study, as well as using available information in the literature. Once developed, modeling results are validated against experimental quasi-static compressive stress-strain measurements using digital image correlation techniques. The validation is extended by comparing experimental observations and computational outputs of the ratio of the lateral to axial strain (as a measure of deformation), and reasonable agreement is found. Once the model is validated for an experimentally known condition, the effect of varying the mechanical properties (e.g., strain hardening parameters and elastic modulus) and microstructure variables (e.g., alumina volume fraction and porosity) on material responses are then explored. These results serve as a foundation for future microstructure optimization.

Comparative study of heat transfer and friction characteristics of water-based Alumina–copper and Alumina–CNT hybrid nanofluids in laminar flow through pipes

In this experimental work, a comparative study of convective heat transfer and drop in pressure characteristics of Alumina–Cu/water and Alumina–CNT/water hybrid nanofluids in fully developed laminar flow in a uniformly heated tube with circular cross section is presented. For this, Alumina–Cu hybrid nanoparticles (90:10 proportion was taken. Below this proportion for, e.g., 80:20, the nanofluid was not stable. Coagulation was happening) were prepared by using a hydrogen reduction technique. Characterization was done for the prepared powder through XRD and scanning electron microscope (SEM) to validate the chemical constitution, to establish the size of the particle and to investigate the morphology of surface. The synthesized Alumina–Cu hybrid nanopowder is dispersed in deionized water in an ultrasonic bath to form a well-dispersed 0.1% volume concentration of hybrid nanofluid. Carbon nanotube (CNT) functionalization was done by acid treatment method to convert the CNT surface from hydrophobic to hydrophilic. Scanning electron microscope was used for characterization of the aluminum oxide particles and functionalized multi-walled carbon nanotubes. To prepare 0.1% volume fraction of Alumina–CNT/water nanofluid, required quantities of Alumina powder and functionalized CNT were dispersed in deionized water in 90:10 proportion. Experiments were conducted in the laminar flow range with water, Alumina/water and hybrid nanofluids, and the results obtained have been compared. The convective heat transfer experimental results showed greater enhancement with Alumina–CNT/water hybrid fluid compared to Alumina–Cu/water hybrid fluid. The maximum enhancements of 30.65% and 20.48% in Nusselt number have been obtained for 0.3% volume fraction of Alumina–CNT/water hybrid nanofluid and Alumina–Cu/water hybrid nanofluid, respectively, at Reynolds number of 1350 as compared to the Nusselt number of water.

Thermomechanical properties of alumina-filled plasticized polylactic acid: Effect of alumina loading percentage

Polylactic acid (PLA) is one of the most widely studied renewable and biodegradable polyesters and is expected to replace petrochemical-based synthetic polymers. In this study, we investigated the effect of the alumina volume fraction on the thermal and mechanical properties of polyethylene glycol (PEG)-plasticized PLA. The alumina particles were treated with maleic acid to improve their interaction with the PLA matrix. The field-emission scanning electron microscopy results revealed that the addition of alumina eliminated voids, leading to improved interfacial interactions between the PLA and alumina particles. The thermal conductivity of the neat PLA increased from 0.278 to 0.66 wm−1 k−1 with the addition of 30% alumina, which accounts for 137% increase. The tensile strength and Young's modulus of the neat PLA dropped by 52% and 56%, respectively, on the addition of 15% PEG plasticizer. However, the elongation at break increased from 5.4% to 207%, which was associated with a drop on the glass transition temperature values. The dynamic mechanical analysis results showed a drop in the storage modulus and height of the tan δ peak, revealing the increased flexibility of the composite after the inclusion of the plasticizer. The addition of 30% alumina exhibited a 41.6% increase on the stiffness of the PEG-blended PLA.

Mechanical behavior of Al-matrix nanocomposites produced by stir casting technique

Aluminium matrix composites (AMCs) have emerged as a material for aircraft and automotive applications owing to its superior specific strength, stiffness, controlled co-efficient of thermal expansion, light weight and excellent wear resistance. The current research study emphases on the production of aluminium (AA6082) matrix composites reinforced in different volume fractions of alumina (50nm) particulates by using stir casting method. The volume fraction of reinforcement was varied from 0% to 3% in stages of 1%. The produced composites were examined by using scanning electron microscope (SEM). Hardness and tensile strength of the composite was studied. The mechanical properties of these composites were compared with matrix alloy. Microstructural results revealed the homogeneous distribution of nano alumina particles in the matrix. The test results revealed that the hardness and tensile strength of the composite increase with an increase in the volume fraction of alumina particle content, this may be due to good interfacial bonding between the reinforcement and the matrix.

Prediction of Weight Percentage Alumina and Pore Volume Fraction in Bio-Ceramics Using Gaussian Process Regression and Minimax Probability Machine Regression

In Bio-ceramics, the alumina weight percentage and pore volume fraction play a vital role for its biocompatibility in human body. There are many experimental methods which are employed for achieving the required quality in it. In this work, for preparation of Al2O3/SiC ceramic cake, the amount of Silicon Carbide (SiC) is taken as input parameter. The weight percentage Alumina and pore volume fraction are taken as output parameters. Two machine learning models such as Gaussian Process Regression (GPR) and Minimax Probability Machine Regression (MPMR) are applied for predicting the above two output parameters. The performance of the above two models are compared. The Gaussian Process Regression outperforms the Minimax Probability Machine Regression marginally and the result of the Gaussian is encouraging for predicting the above two outputs.

Effect of microstructure on mechanical properties and residual stresses in interpenetrating aluminum-alumina composites fabricated by squeeze casting

Aluminum-alumina composites with interpenetrating network structure are interesting structural materials due to their high resistance to elevated temperature and frictional wear, good heat conductivity, enhanced mechanical strength and fracture toughness. In this paper aluminum-alumina bulk composites and FGMs are manufactured by pressure infiltration of porous alumina preforms with molten aluminum alloy (EN AC-44200). Influence of the interpenetrating microstructure on the macroscopic bending strength, fracture toughness, hardness and heat conduction is examined. Special focus is on processing-induced thermal residual stresses in aluminum-alumina composites due to their potentially detrimental effects on material performance in structural elements under in-service conditions. The residual stresses are measured experimentally in the ceramic phase by neutron diffraction and simulated numerically using a micro-CT based Finite Element model, which takes into account the actual interpenetrating microstructure of the composite. The model predictions for two different volume fractions of alumina agree fairly well with the neutron diffraction measurements.

Numerical Analysis of Heat Transfer in Unsteady Nanofluids in a Small Pipe with Pulse Pressure

In the present paper, developing turbulence forced convection flows were numerically investigated by using water-Al2O3 nano-fluid through a circular compact pipe which has 4.5mm diameter. Each model has a steady state and uniform heat flux (UHF) at the wall. The whole numerical experiments were processed under the RPM 100 to 500 and the nano-fluid models were made by the Alumina volume fraction. Single-phase fluid models were defined through nano-fluid physical and thermal properties calculations, Two-phase models (mixture granular model) were processed in 100nm diameter. The results show that comparison of nusselt number and heat transfer rate are improved as the Al2O3 volume fraction increased. All of the numerical flow simulations are processed by the FLUENT. The results show an increase from volume fraction concentration and an increase in heat transfer coefficient with increasing RPM.

Analysis of laminar nanofluid forced convection heat transport through the CFD

In the present paper, developing laminar forced convection flows were numerically investigated by using water-Al2O3 nano-fluid through a circular compact pipe which has 4.5mm diameter. Each model has a steady state and uniform heat flux (UHF) at the wall. The whole numerical experiments were processed under the Re = 1050 and the nano-fluid models were made by the Alumina volume fraction. Single-phase fluid models were defined through nano-fluid physical and thermal properties calculations, Two-phase model (mixture granular model) were processed in 100nm diameter. The results show that Nusselt number and heat transfer rate are improved as the Al2O3 volume fraction increased. All of the numerical flow simulations are processed by the FLUENT. The results show the increment of thermal transfer from the volume fraction concentration.

CFD Analysis of nanofluid forced convection heat transport in laminar flow through a compact pipe

In the present paper, developing laminar forced convection flows were numerically investigated by using water-Al2O3 nano-fluid through a circular compact pipe which has 4.5mm diameter. Each model has a steady state and uniform heat flux (UHF) at the wall. The whole numerical experiments were processed under the Re = 1050 and the nano-fluid models were made by the Alumina volume fraction. A single-phase fluid models were defined through nano-fluid physical and thermal properties calculations, Two-phase model(mixture granular model) were processed in 100nm diameter. The results show that Nusselt number and heat transfer rate are improved as the Al2O3 volume fraction increased. All of the numerical flow simulations are processed by the FLUENT. The results show the increment of thermal transfer from the volume fraction concentration.

Numerical analysis of heat transfer in unsteady nanofluids in a small pipe with pulse pressure

In the present paper, developing turbulence forced convection flows were numerically investigated by using water-Al2O3 nano-fluid through a circular compact pipe which has 4.5mm diameter. Each model has a steady state and uniform heat flux(UHF) at the wall. The whole numerical experiments were processed under the RPM 100 to 500 and the nano-fluid models were made by the Alumina volume fraction. A single-phase fluid models were defined through nano-fluid physical and thermal properties calculations, Two-phase models(mixture granular model) were processed in 100nm diameter. The results show that comparison of nusselt number and heat transfer rate are improved as the Al2O3 volume fraction increased. All of the numerical flow simulations are processed by the FLUENT. The results show an increase from volume fraction concentration and an increase in heat transfer coefficient with increasing RPM.

Mechanical properties of hybrid composites prepared by ice-templating of alumina

Ceramic-polymer hybrid composites are often designed for its high strength and low density. Ice-templating (freeze casting) is a promising method for preparation of such composites. However, the most of the reported mechanical properties were gained from a small volume of material. In this work 70cm3 of the lamellar composite with lamella length, up to 70mm was prepared by ice-templating followed by polymer infiltration. The volume of ceramic (alumina) in starting suspensions was varied from 25 to 45vol.% and the same manufacturing process was applied. The fracture toughness and flexural strength were determined on prepared beams from plates by loading in bending. The fractographic analysis conducted on the fracture surfaces and obtained mechanical properties demonstrated that an optimal strength/density ratio lies between 51 and 55% of alumina volume fraction. The density ranking from 2.6 to 2.8cm−3 of these composites results in values of Weibull strength above 110MPa.

Fracture Analysis and Mechanical Properties of Magnesium Based Composites

Mechanical properties and microstructure and fracture analysis of a magnesium alloys based composite series with different volume fraction of alumina dispersoid nanoparticles were studied. The initial states of the composites were further treated by severe plastic deformation (SPD) using equal channel angular pressing (ECAP) in order to achieve microstructures with very fine grains of matrix. Microstructure parameters, in particular the matrix grain size, average size of the dispersed particles and their distribution, were observed using optical microscopy. The average grain sizes of MMCs decreased evidently with the increase of the weight percentage of Al2O3 particles additions and ECAP passes. The heat deformation process of such materials, besides the formation of incorporated Al2O3 particles, also leads to the creation of intermetallic compound Mg17Al12. Fracture surfaces after tensile tests at room and elevated temperature were studied by SEM. The fracture of studying materials were characterized as the ductile fracture due to the existence of a large number of dimples.In summary, it has been shown that mechanical properties are affected by lattice, physical parameters of phases within the composite systems. They are also affected by microstructure and substructure, which depend on the technology of compaction and densification.

Nacre-like hybrid films: Structure, properties, and the effect of relative humidity

Functional materials often are hybrids composed of biopolymers and mineral constituents. The arrangement and interactions of the constituents frequently lead to hierarchical structures with exceptional mechanical properties and multifunctionality. In this study, hybrid thin films with a nacre-like brick-and-mortar microstructure were fabricated in a straightforward and reproducible manner through manual shear casting using the biopolymer chitosan as the matrix material (mortar) and alumina platelets as the reinforcing particles (bricks). The ratio of inorganic to organic content was varied from 0% to 15% and the relative humidities from 36% to 75% to determine their effects on the mechanical properties. It was found that increasing the volume fraction of alumina from 0% to 15% results in a twofold increase in the modulus of the film, but decreases the tensile strength by up to 30%, when the volume fraction of alumina is higher than 5%. Additionally, this study quantifies and illustrates the critical role of the relative humidity on the mechanical properties of the hybrid film. Increasing the relative humidity from 36% to 75% decreases the modulus and strength by about 45% and triples the strain at failure. These results suggest that complex hybrid materials can be manufactured and tailor made for specific applications or environmental conditions.

COMPARATIVE STUDY BETWEEN DIFFERENT FILLERS USED AS REINFORCEMENTS OF RUBBER THERMAL INSULATORS

Solid rocket motors typically include an outer case or shell that houses solid propellant grains. Internal insulation in a solid rocket motor is a layer of heat-barrier material placed between the internal surface of the case and the propellant which. The aim of the present study is to develop and characterize an asbestos-free rubber for use as rocket motor insulator which needs to be taken into account for protecting in the planning of space missions, in their design, and in their operation. Such insulation is based on aramid fiber in the pulp form, alumina and/or silica aerosol as reinforcement for Ethylene Propylene Diene Monomer (EPDM). Different formulations based on these fillers were prepared. The fillers dispersed in the EPDM polymeric matrix to obtain a homogenous master batch for curing. The physical, mechanical (density, hardness, tensile strength and elongation) and thermal properties (effective thermal conductivity) of different compositions were obtained. The ablation resistance of samples with different compositions was measured. Thermo-gravimetric analyses versus reinforcement content were obtained. The effect of changing aramid fiber in the pulp form, alumina and/or silica aerosol volume fractions was studied. For application for solid rocket motor insulation, Reinforcement of EPDM with KP improves the performance of the material with respect to mechanical properties and thermal properties (thermal conductivity) while not improving well the performance with respect to ablation resistance. Using hybrid reinforcement content (KP + Al + Si) inside EPDM improves the performance of EPDM with respect to mechanical properties, thermal properties, ablation resistance and decomposition resistance. The best volume fraction which gives the best performance of the insulation material is 10 Phr KP + 5 Phr Al + 5 Phr Si. A new type of insulation material using the hybrid reinforcements was developed for the first time.