Al Nanocomposites Research Articles

Hot deformation behaviour of bimodal sized Al2 O3 /Al nanocomposites fabricated by spark plasma sintering.

The deformation behaviour of bimodal sized Al2 O3 /Al nanocomposites were investigated by hot compression tests conducted in the temperature range 350-500°C and strain rates of 0.001, 0.01 and 0.1 s-1 . The dynamic recrystallisation behaviour of the nanocomposites strongly depended on the forming parameters. The bimodal sized Al2 O3 particles played a crucial role in the recrystallised microstructure. The addition of bimodal sized Al2 O3 particles led to a significant increase of activation energy of plastic deformation, corroborating the enhanced resistance of the nanocomposite to hot deformation. This was also reflected by the increased compressive yield strength in the nanocomposite due to both dislocation strengthening caused by n-Al2 O3 and preventing the grain growth due to the presence of μ-Al2 O3 at grain boundaries. It was found that with the decrease of Z values, local strain induced by deformation was released and the grain size of aluminium matrix gradually increased, indicating that the main softening mechanism of the bimodal sized Al2 O3 /Al nanocomposites was dynamic recrystallisation (DRX). The lower the Z value was, the easier the DRX occurred. The highly beneficial role of the bimodal sized Al2 O3 reinforcement in improving the high-temperature performance of aluminium matrix nanocomposite was discussed.

Superior strength of tri-layered Al–Cu–Al nano-composites processed by high-pressure torsion

This investigation demonstrates that a solid-state reaction occurs by the application of high-pressure torsion (HPT) in the production of nanostructured multilayered hybrid Al–Cu systems. Three-layered stacks of Al/Cu/Al were subjected for up to 200 revolutions of HPT under an applied pressure of 6.0 GPa. Microstructural and mechanical properties analysis were carried out after HPT using X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectrometry (EDX), microhardness measurements and tensile tests. The SEM observations revealed the formation of a multi-nano-layered structure in the whole volume of the disks. Further investigations with the use of TEM demonstrated that each nano-layer consists of nano-grains having sizes of about 20 nm. Analysis by XRD and selected area electron diffraction (SAED) confirmed the formation of intermetallic CuAl2 and Cu9Al4 phases in the layered structures. The experiments also showed a significant improvement in microhardness (up to ∼450 Hv) and tensile properties (over 900 MPa of UTS after 200 turns) when compared to both Al-1050 and 99.95%Cu alloys in the initial state and after HPT processing. The results demonstrate that HPT offers an outstanding opportunity for producing novel nanostructured Al–Cu multilayered composites having unique mechanical properties.

Effect of SiC addition on the mechanical properties and wear behavior of Al-SiC nanocomposites produced by accumulative roll bonding

In this study, we manufactured Al and Al-SiC nanocomposites (SiC vol.% = 1, 2 and 4) using accumulative roll bonding (ARB) at room temperature. Mechanical and wear characteristic of the manufactured samples was studied. The uniform dispersion of SiC particles was achieved after five ARB cycles. The EDX mapping images reveal that the SiC reinforcement particles were homogeneously distributed into the Al matrix. After five ARB cycles, relatively small amount of nano-grains were observed in Al-SiC nanocomposite, indicating the effectiveness of the ARB process of achieving near nanostructure. It was observed that Vickers microhardness improve with increasing accumulative roll bonding cycles. Furthermore after 5 cycles, Vickers microhardness tests results showed that the highest hardness value of 66 HV is attributed to the sample containing 4 vol.% of SiC, much higher than the hardness value of the ARB-processed aluminum of 51 HV. Experimental results indicated that the wear resistance of this nanocomposite improved by increasing the number of ARB cycles due to SiC particles act as a solid lubricant.

Magnetite-metal organic framework core@shell for degradation of ampicillin antibiotic in aqueous solution

Fe3O4@SiO2@MIL-53-NH2 (Al) nanocomposite (FeSi@MN NC) in core@shell structure was prepared by the synthesis of NH2-MIL-53 (Al) on the Fe3O4@SiO2 nanoparticles (FeSi NPs) using hydrothermal method. For synthesis of NH2-MIL-53 (Al) on FeSi NPs, the salt linker was used instead of protonated linker. The NC was used as an active photocatalyst for photodegradation of ampicillin (AMP) in aqueous solution. Diffuse reflectance spectra (DRS) studies showed that the FeSi@MN NC absorbs visible light irradiation, and therefore, it can be photoactivated under visible light. The TEM image of FeSi@MN NC indicated the rose-leaves of the NH2-MIL-53(Al) have been well encapsulated on the surface of FeSi sample. The results showed that the FeSi@MN core@shell has the larger surface area, suitable superparamagnetism, and good photocatalytic activity for degradation of AMP. The FeSi@MN core–shell exhibited higher photocatalytic activity compared to Fe3O4@SiO2@MIL-53 (Al) (FeSi@M) core@shell.

Optimization of the microstructure and mechanical properties of heterogeneous Al-Al2O3 nanocomposites

High-energy ball milling and hot-press sintering were employed to synthesize heterogeneous aluminum (Al) matrix nanocomposites reinforced by 5 vol.% alumina (Al2O3) nanoparticles. The heterogeneous structure was formed by the nonuniform distribution of Al2O3 nanoparticles in Al matrix, and it composed of an isolated irregular soft phase (pure Al) and a continuous hard phase (Al reinforced by Al2O3 nanoparticles). It was found that the size of soft phase is optimized with increasing ball milling time, resulting in an increase in the yield strength and ultimate strength, as well as retained failure strain. It is worth noting that the ultimate strength of heterogeneous Al nanocomposite with milling time of 20 h (referred to as Heter-20) reached 610 MPa under compression testing. In particular, the introduced soft phase exhibited severe plastic deformation and interface microcracks under compression, which led to higher failure strain (∼30% for Heter-20) and toughness compared to traditional homogeneous Al matrix composites. Furthermore, coexistence of brittle and ductile fractures was observed in the heterogeneous Al nanocomposites under quasi-static compression.

Wear analysis of CNT-AL Nanocomposites using surface response method

Carbon nanotube (CNT) reinforced aluminium (Al) nano-composites were produced using powder metallurgy route with different weight percent of CNT in to the Al matrix. The wear behaviour of CNT-Al nano-composite was studied using a pin-on-disc tribometer against AISI4340 steel disc. Experiments were conducted using different sliding velocities of 0.5, 0.65 and 0.8 m/s and a normal load of 5, 7.5 and 10 N. Design Expert (DOE) version 6.0.8 was used to optimize the process variable for wear and friction test of the developed CNT-Al nano-composite using face centered central composite design based on response surface methodology and confirmed that 1.5 wt% was the optimum CNT-Al nano-composite formulations. The result showed that higher hardness value of the material showed a lesser wear rate and better wear resistance. The result showed that the wear rate of the developed nano-composite decreased with the increasing of CNT content but up to 1.5 wt% CNT into the nano-composite. The wear rate values varied from 2-0.6 x10-3 mm3/m (2, 0.2, 0.17. 0.3 and 0.6 mm3/m x10-3 for 0 wt%, 1 wt%, 1.5 wt%, 2 wt% and 2.5 wt% CNT respectively). These results also showed that the rate of wear decreases with the increase in normal load and sliding speed. DOE confirm the accuracy of the experimental result for the evaluation of the developed CNT-Al nano-composite. Keywords: Wear testing, Sliding wear, Wear modelling, Metal-matrix composite and CNTAl nano-composite

Aluminum composites reinforced by γ-graphynes: The effect of nanofillers porosity and shape on crystal growth and composite strengthening

Graphyne and graphdiyne nanofillers (nanoplatelets and nanotubes), are embedded in Aluminum matrices originating graphyne and graphdiyne/Al nanocomposites. Pristine Al and the nanocomposites are melted and then recrystallized at a fixed colling rate, 1 K/ps. Al nanocomposites with planar nanofillers show a 46–53% increase in nucleation temperature and 78–88% recrystallization yield while Al nanocomposites with tubular nanofillers present a 16–32% increase in nucleation temperature and a 65–75% recrystallization yield. Al nanocomposites with planar nanofillers present a 26–36% increase in the Young's modulus, while Al nanocomposites with tubular nanofillers show a 23–31% increase in the Young's modulus. The improved mechanical properties of graphyne and graphdiyne/Al nanocomposites depend on i) the elasticity and shape (planar vs tubular) of the nanofillers ii) the level of recrystallization of the Al matrix and iii) the interfacial adhesion in the interface between the nanofillers and the Al matrix. Graphyne pore size positively affects interfacial adhesion.

Tribological characterization of particulate-reinforced aluminum metal matrix nanocomposites: A review

Aluminum (Al)-based composites are on increasing usage in sectors like ground transportation, aerospace, sports, and infrastructure because of the improved properties such as high strength to weight ratio, corrosion, fatigue, and wear resistance. Several applications involving dynamic contact stresses require excellent wear and frictional performance for improved life. Nanocomposites are found to perform exceedingly better than microcomposites and alloys in several lab scale tribological investigations carried out so far in the last decade. In this article, an attempt is made to review those published reports about dry sliding tribological behavior of particulate-reinforced Al nanocomposites. Wear and friction being system properties are found to get influenced by intrinsic factors such as reinforcement, fabrication method, microstructure; extrinsic parameters like load, speed, contact conditions and the system generated in situ tribolayer all being interrelated.

Assessment of carbon nanotubes (CNT) and fly ashes (FA) reinforced Al nanocomposites properties synthesised by powder metallurgy

Abstract In this paper properties of Al metal matrix composites reinforced with carbon nanotubes (CNTs) and fly ashes (FAs) synthesized by powder metallurgy technique were investigated. Density, hardness and compression tests were carried out for the mechanical properties of the specimens. The experimental results showed that addition of FA increases hardness up to 8 wt. % and then decreases while hardness of the composite decreases with increase in CNT content. The results also showed that addition of FAs decreases density values while, addition of CNTs increases density of the composites. The compression strength properties of the composites improved over matrix material.With the aid of scanning electron microscope it was observed that CNTs and fly ashes were well dispersed and embedded in the matrix.XRD and EDS results showed no carbide formation or contamination during the processing of the composites

Enhanced strength and ductility of Al-SiC nanocomposites synthesized by accumulative roll bonding

This paper present experimental study on improving mechanical properties of Al and Al-xSiC nanocomposites (x=1, 2 and 4%) synthesized by Accumulative Roll Bonding (ARB) technique. SEM, EDX and XRD analysis was used to characterize the structural changes in the manufactured materials while tensile and microhardness tests were used to characterize their mechanical properties. Homogeneous distribution of SiC nanoparticles was achieved after five ARB cycles. A significant strength improvement was achieved for processed Al and Al-SiC nanocomposites after five ARB cycles due to grain refinement, grain misorientation and SiC strengthening. The grain refinement and grain misorientation contributed the strength improvement by 161% and 46%, respectively, while the addition of 1% SiC nanopartciles contributed by 78% which is increased to 101% for 4% SiC. The ductility is reduced after the zero ARB cycle however it increased with increasing the number of ARB cycles reaching 8.2 and 5.8% for Al and Al-4% SiC nanocomposites, respectively, after 5 ARB cycles. The fracture shape in the ARBed samples is a combination of necking and shearing with a tendency to shearing shape for Al-SiC nanocomposites.

Experimental and Digimat-FE based representative volume element analysis of exceptional graphene flakes/aluminium alloy nanocomposite characteristics

The present article is focused on the in-house synthesis of graphene nano-flakes (size range: 3–8 nm) reinforced Al-alloy (AA6005 series) nanocomposites using stir casting process. The microstructure of the obtained Al nanocomposites at different concentration of flake shaped graphene nanoparticles (GRNPs) show that the particles at 2 wt% and 4 wt% found to be distributed extensively on the surfaces of Al alloy matrix but observed negligible across the grain boundary whereas in the case of 6 wt% concentrated developed composite specimen, the GRNPs were observed to be well dispersed both on the surfaces and grain boundary of the matrix. With the addition of the particles, there found to be the formation of more voids in the nanocomposite specimens. The experimental characterization results reveal that with the increase in graphene content to 6 wt%, the tensile strength, compressive strength, impact energy, hardness and wear resistance of the nanocomposites were increased by 9% to 36%, 30% to 44%, 9.8 J, 36.03 HRB and 33% respectively as compared to unreinforced alloy. It was observed that the composites with increased concentration of reinforcement exhibits brittle behaviour and at 6 wt% GRNPs, the elongation is almost found to be 50% lower than the unreinforced one. Further, a 3D microstructure representative volume element (RVE) model of aluminium nanocomposite is generated using Digimat-FE software. Then, microstructural deformation behaviour of the nanocomposite is realized by RVE model. The simulation results reveal that the tensile property of the aluminium nanocomposites predicted using RVE model is in well agreement with the experimental values.

Amorphous Co–Cu–Al mixed metal oxide nanoparticles modified BiVO4 to improve photocatalytic desulfurization

Amorphous Co–Cu–Al nanocomposite modified BiVO4 (CoCuAl/BiVO4) has been synthesized. The results revealed that CoCuAl nanocomposite with the size of around 10 nm evenly loaded on BiVO4 surface, which could enhance visible light response capacity and charge separated rate of BiVO4. When they were used for visible light photocatalytic desulfurization, desulfurization efficiency of thiophene could be sharply improved over CoCuAl/BiVO4. Obviously, this work provide a simple and economic method for modifying photocatalyst property.

Assessment of wear properties of MWCNT and FA reinforced Al nanocomposites produced by powder metallurgy technique

Mono reinforced composites have limited capability in providing high specific strength and low wear rate. To vanquish the limitations, bi-reinforcements such as carbon nanotube (CNTs) and fly ash(FAs) were used in alumnium metal matrix. In this work wear and friction properties of composite fabricated by powder-metallurgy were investigated. It was found that CNT and FA reinforced aluminium composite (Al/CNT-FA) manifests improved tribological properties over unreinforced matrix material and mono reinforced composites. The worn surfaces reveal that the wear was governed by the combination of adhesive and abrasive wear mechanism.

Enhanced hydrogenation and hydrolysis properties of core-shell structured Mg-MOx (M = Al, Ti and Fe) nanocomposites prepared by arc plasma method

In this work, three amphoteric metal oxides (Al2O3, TiO2 and Fe2O3) are introduced into Mg ultrafine powders via arc plasma method in order to improve hydrogen absorption properties of Mg and hydrolysis performances of MgH2. The phase components, particle size distribution, microstructures and compositions of pure Mg and core-shell structured Mg-MOx nanocomposites at various states are carefully characterized. Among all composites, the addition of TiO2 followed by passivation shows the best promotion effects on hydrogen absorption and hydrolysis performances. The passivated Mg-TiO2 composite absorbs 5.5 wt% of H2 in less than 5 min at 623 K and the hydrogenated composite produces more than 1000 mL g−1 H2 in 660 s (maximum 1525 mL g−1 for 1 h) in 0.1 M MgCl2 water solution at 298 K. The activation energy of hydrolysis decreases from 53.42 kJ mol−1 H2 for hydrogenated pure Mg powder (passivated) to 45.14 kJ mol−1 H2 for the hydrogenated Mg-TiO2 powder (passivated). Corresponding analyses reveal that TiO2 formed on the surface of Mg particles, together with the defects in Mg lattice accounts for the improved hydrogen absorption properties, the enhanced hydrolysis rate and yield of the hydrogenated Mg-TiO2 powder.

Impact of Nano-Scale Distribution of Atoms on Electronic and Magnetic Properties of Phases in Fe-Al Nanocomposites: An Ab Initio Study.

Quantum-mechanical calculations are applied to examine magnetic and electronic properties of phases appearing in binary Fe-Al-based nanocomposites. The calculations are carried out using the Vienna Ab-initio Simulation Package which implements density functional theory and generalized gradient approximation. The focus is on a disordered solid solution with 18.75 at. % Al in body-centered-cubic ferromagnetic iron, so-called -phase, and an ordered intermetallic compound FeAl with the D0 structure. In order to reveal the impact of the actual atomic distribution in the disordered Fe-Al -phase three different special quasi-random structures with or without the 1st and/or 2nd nearest-neighbor Al-Al pairs are used. According to our calculations, energy decreases when eliminating the 1st and 2nd nearest neighbor Al-Al pairs. On the other hand, the local magnetic moments of the Fe atoms decrease with Al concentration in the 1st coordination sphere and increase if the concentration of Al atoms increases in the 2nd one. Furthermore, when simulating Fe-Al/FeAl nanocomposites (superlattices), changes of local magnetic moments of the Fe atoms up to 0.5 are predicted. These changes very sensitively depend on both the distribution of atoms and the crystallographic orientation of the interfaces.

Micromechanical analysis of elastic modulus of carbon nanotube-aluminum nanocomposites with random microstructures

The formation of Al4C3 interphase in carbon nanotube (CNT)-reinforced aluminum (Al) nanocomposites is a critical issue which must be well-known to more realistic estimations of mechanical behavior of such materials. In this work, the effect of Al4C3 interphase on the elastic modulus of Al nanocomposites reinforced with randomly distributed CNTs is investigated using a numerical micromechanical model based on the finite element method (FEM). Moreover, the influences of the CNT volume fraction and diameter on the elastic modulus of Al nanocomposites are explored. The results reveal that Al4C3 interphase significantly affects the elastic modulus of Al nanocomposites especially as the CNT diameter decreases. It can be observed that with increasing interphase thickness, the elastic modulus of the nanocomposite increases. The applicability of the presented model in predicting the elastic modulus of CNT-reinforced Al nanocomposites is investigated by comparing the results of the FEM with those of experiment available in the literature. Furthermore, the results of the FEM with and without Al4C3 interphase for aligned continuous and discontinuous CNT-reinforced Al nanocomposites are presented. It is found that the effect of the interphase on the elastic modulus of nanocomposites reinforced with continuous CNT is more important than that of nanocomposites reinforced with discontinuous CNT.

Oxidation effect on the shear strength of graphene on aluminum and titanium surfaces

We report the interfacial shear strength of graphene on pure and oxidized Ti and Al metal surfaces using density functional theory calculations. Our results show significant changes to the graphene-metal bonding properties in the presence of an oxide phase. In particular, the strongly chemisorbed interface between graphene and pure Ti is drastically weakened by the formation of a metal-oxide phase, while the weakly physisorbed interface between graphene and pure Al is significantly strengthened through the metal oxide formation. These oxidation effects can be modulated to some extent by the presence of vacancy or Stone-Wales defects which increases the binding interactions of weaker graphene-metal interfaces. These dramatic changes to the interfacial properties by surface oxidation explain the results of recent carbon nanotube pull-out experiments from Al and Ti metal-matrix nanocomposites.

Structure and Chemistry of Cu–Fe–Al Nanocomposite Catalysts for CO Oxidation

High-active Fe–Al and Cu–Fe–Al nanocomposite catalysts were synthesized by fusion of aluminium, iron, and copper salts and then tested in the oxidation of CO. It was found that the activity of Fe–Al catalysts depends on the Fe concentration and the maximum is achieved when the Fe2O3 content is approximately 82 wt%. The addition of Cu leads to a significant increase in activity. Using adsorption techniques, X-ray diffraction, X-ray absorption spectroscopy, and Fourier-transform infrared spectroscopy, morphology, structure, and chemistry of the catalysts were studied. It was shown that the Fe–Al catalysts consist of Fe2O3 and Al2O3 phases mainly. Alumina is in an amorphous state whereas iron oxide forms nanoparticles with the protohematite structure. The Al3+ cations partially dissolute in the Fe2O3 lattice. X-ray absorption spectroscopy indicated that the Cu–Fe–Al catalysts in addition contain CuO and CuFe2O4 oxides in an amorphous state.

Achieving Exceptional Tensile Properties and Improved Microstructural Stability in Nanocrystalline Ni Via Amorphous Interfacial Phase by Codepositing Al Nanoparticles

A thin amorphous interfacial phase within microstructure is one of the promising strategies for designing better nanostructured materials. Nickel and Ni–Al nanocomposites fabricated by pulsed electrodeposition are deformed in tension and selected samples are heated to elevated temperatures. Here, the authors report that a well‐dispersed Al nanoparticle, possessing a thin layer of amorphous oxide shell, reinforcement in nanocrystalline Ni matrix enhances tensile strength by ≈60% without losing ductility and also provides better microstructural stability due to existence of local microstructural gradient.

Adsorptive performance of MOF nanocomposite for methylene blue and malachite green dyes: Kinetics, isotherm and mechanism

In the present study, Fe3O4@AMCA-MIL-53(Al) nanocomposite was utilized for the adsorptive removal of highly toxic MB and MG dyes from aqueous environment. The batch adsorption tests were performed at different contact time, pH, Fe3O4@AMCA-MIL-53(Al) dose, initial concentration of dyes and temperature. The maximum adsorption capacity of MB and MG dyes onto of Fe3O4@AMCA-MIL-53(Al) using Langmuir equation was 1.02 and 0.90 m mol/g, respectively. The isotherm and kinetic studies revealed that adsorption data were well fitted to Langmuir isotherm and pseudo-first-order kinetics models. Various thermodynamic parameters were also calculated and interpreted. The positive and negative values of ΔH° and ΔG° indicated that the adsorption was endothermic and spontaneous, respectively. The adsorptive binding of MB and MG on Fe3O4@AMCA-MIL53(Al) nanocomposite was directed by carboxylate and amide groups through electrostatic interaction, π−π interaction and hydrogen bonding. The desorption of both dyes from Fe3O4@AMCA-MIL-53(Al) was also performed using mixed solution of 0.01 M HCl/ethanol. Thus, we conclude that the Fe3O4@AMCA-MIL-53(Al) was an outstanding material for the removal of dyes from aqueous environment.