Nano-sized Alumina Particles Research Articles

Novel Alumina Dispersion-Strengthened 316L Steel Produced by Attrition Milling and Spark Plasma Sintering

Alumina dispersion-strengthened 316L stainless steels were successfully produced using attrition milling and spark plasma sintering. Two different composites (316L/0.33 wt% and 316L/1 wt% Al2O3) were prepared by powder technology. The attrition milling produced a significant morphological transformation of the globular 316L starting powders and provided a homogeneous distribution of the nanosized alumina particles. The XRD results confirmed that the 316L steel was an austenitic γ-Fe3Ni2. The formation of a ferrite α-Fe phase was detected after milling; this was transformed to the austenitic γ-Fe3Ni2 after the sintering process. The addition of nanosized alumina particles increased the composites’ microhardness significantly to 2.25 GPa HV. With higher amounts of alumina, the nanosized particles tended to agglomerate during the milling process. The friction coefficient (FC) of the 316L/0.33 wt% Al2O3 and the 316L/1 wt% Al2O3 decreased because of the increase in the composite’s hardness; FC values of 0.96, 0.93 and 0.85, respectively, were measured respectively for the 316L reference, the 316L/0.33 wt% and the 316L/1 wt% Al2O3. The 316L/0.33 wt% Al2O3 composite had a higher flexural strength of 630.4 MPa compared with the 316L/1 wt% Al2O3 with 386.6 MPa; the lower value of the latter was related the agglomeration of the alumina powder during attrition milling.

Characterization of steel lined with multilayer micro/nano-polymeric composites

This work studied comparison of the mechanical and barrier resistance properties between different structures of three multilayers polymeric coating on each side of the steel coupons. Epoxy filled with 1 wt%, 2 wt%, and 3 wt% micron or nano-sized alumina (Al2O3) particles represented the coating layers to steel on both sides. Barrier resistance was performed by immersing the coated steel specimens in salt solution and in a citric acid medium. Adding alumina (Al2O3) particles in micron and nano size to epoxy coatings improved the barrier resistance, tensile, and hardness under dry and wet conditions as compared to pure epoxy coating. Further increases in Al2O3 micro/nanoparticles cause deterioration in tensile strength and barrier resistance. The steel lined with epoxy filled with 1 wt% Al2O3 nanoparticles has a maximum tensile strength of 299.5 MPa and 280.9 MPa under dry and wet conditions, respectively. However, the steel lined with epoxy filled with 1 wt% Al2O3 microparticles has a tensile strength of 296.5 MPa and 275.4 MPa under dry and wet conditions, respectively. Good properties were observed with stepwise graded micro/nanocomposite coatings. The steel lined with epoxy filled with 3 wt% Al2O3 nanoparticles has maximum hardness of 46 HV and 40 HV under dry and wet conditions, respectively.

Forecasting of water thermal conductivity enhancement by adding nano-sized alumina particles

Operating fluids play an important role in heat transfer equipment. Water is inexpensive popular operating fluid with extensive applications, but its thermophysical properties are not good enough, especially for high temperature processes. Therefore, modification of its inherent characteristics by adding nano-sized solid particles found high popularities. Thermal conductivity is one of the most important thermophysical properties of an operating fluid in relatively all energy-based processes. Variation of thermal conductivity of nanofluids with different operating conditions is required to be understood in such processes. Therefore, the focus of this study is concentrated on modeling of thermal conductivity of water-alumina nanofluids using four different smart paradigms. Multilayer perceptron, radial basis function, cascade feedforward, and generalized regression neural networks are employed for the considered task. The best structure of these paradigms is determined, and then, their accuracies are compared using different statistical indices. Accuracy analyses confirmed that the generalized regression neural network outperforms other considered smart methodologies. It predicted more than 280 experimental datasets with excellent absolute average relative deviation = 0.71%, mean square error = 0.0006, root mean square error = 0.023 and regression coefficient (R2) = 0.9675. In the final stage, the proposed paradigm is used for investigation of the effect of influential parameters on the thermal conductivity of water-alumina nanofluids. This type of accurate and straightforward paradigm can broaden our insight about thermal behavior of homogeneous suspension of nano-size alumina particles in water.

Comparative Analysis of the particle size on the porosity and the tensile properties of aluminium based metal matrix nano-composites

Milling a mixture of aluminium and manganese dioxide (MnO2) powders mixed in ratio of 1:7 by weight and the particle size has been varied by milling in a vibratory disc mill for 450, 600 and 750 min at 700 rpm to obtain Nano-sized alumina particles. Melting commercially pure aluminium followed by addition of different duration of milled powder mix while stirring the melt to synthesis nano-composites. The remaining aluminium powder will melt when the powder mixture will be added to molten Al-Mg alloy during composite processing. The remaining manganese oxide will also react with molten Al-Mg alloy during solidification processing of composite and generate alumina particles (in-situ). The reaction between manganese dioxide and molten alloy releases manganese for alloying with the molten Al-Mg alloy. To enhance wetting of resulting alumina particles by the melt, magnesium is added. It is observed that the porosity in the cast composite increases with increasing addition of particles milled for a given time and it is interesting to observe that for the same amount of addition, powders milled for higher milling time cause higher porosity. There is increasing strength and ductility compared with base alloy and composite prepared with 2wt% addition of different duration milled powder. The tensile properties for AM alloy shows yield strength of 75.9 MPa, tensile strength of 169.8 MPa and elongation of 11.12%. Tensile properties of different composites for addition of 2 wt% powder mix milled for 450, 600 and 750 min shows that 113.3 MPa, 91.8 MPa and 77.3 MPa of yield strength respectively, 250 MPa, 225.2 MPa and 216.8 MPa of tensile strength respectively and 25.65%, 25.68% and 23.91% of elongation respectively. For addition of 2 wt% powder mix milled for 450 min, there is improvement in yield strength by about 25%, tensile strength by about 35% and ductility by more than 120% in the nano-composite over those observed in the base alloy.

A study on processing and hot corrosion behaviour of HVOF sprayed Inconel718-nano Al2O3 coatings

In the present work, processing and hot corrosion behaviour of Inconel718-nano-Al2O3 based composite coatings with varying nano-Al2O3 contents (10, 20 and 30 wt. %) was studied. The nano-Al2O3 powders were synthesised by using manual granulation technique. The composite coatings were deposited on grey cast iron (GCI) substrate by using a high-velocity oxy-fuel process (HVOF). Hot corrosion behaviour of bare and coated specimens was determined at 900 °C in a high-temperature furnace for 50 h. The weight change data was used to establish the oxidation kinetics of bare and coated specimens. The coating with the highest proportion of nano-Al2O3 content exhibited the maximum hardness and corrosion resistance. The nano-sized alumina particles enhanced the hardness of the coatings by posing a higher constraint to the plastic deformation during the indentation. The presence of nano-Al2O3 and various protective oxides (Cr2O3, NiCr2O4, and TiO2) resulted in the improved corrosion resistance of coatings in comparison to the GCI substrate.

A novel approach for the production and characterisation of aluminium–alumina hybrid metal matrix composites

In this study, aluminium–alumina hybrid metal matrix composites were developed using stir–squeeze casting with ultrasonic stirring. Scrap aluminium alloy wheels (SAAWs) were used as the matrix material, with 1, 2, and 3 wt% of nanosized alumina ((Al2O3)n) particles as well as 4, 5.5, and 7 wt% of microsized alumina ((Al2O3)m) particles as reinforcement components. An experimental study was conducted using the Taguchi method with an L9 orthogonal array, and the multiobjective optimisation based on ratio analysis technique was used for optimisation. The effects of different ratios of nanosized and microsized alumina particles as well as ultrasonic parameters, namely amplitude and pulse time, on the microstructure and mechanical properties were evaluated and compared. Pin-on-disc wear tests were conducted in the dry condition under uniform load to determine the influence of nanosized and microsized alumina on the wear behaviour. The results revealed that SAAWs reinforced with 1 wt% of nanosized alumina particles and 5.5 wt% of microsized alumina particles and having an amplitude of 100% and pulse on-time of 180 s exhibited lower porosity and metal loss (wear) as well as higher hardness, tensile strength, and compressive strength than other composites.

Dual‐Scale Al2O3 Particles Coating for High‐Performance Separator and Lithium Metal Anode

Herein, the polyethylene (PE) separators are coated by micro/nanoalumina particles. The alumina particles with different sizes play different roles. The microalumina mainly enhances the thermal stability of the polyolefin separator and provides large channels for lithium‐ion diffusion. The nanoalumina particles are helpful in improving the lithium‐ion transference number by increasing the contact interface area of electrolyte/alumina. The lithium‐ion transference number of the separators with different coatings increases from 0.32 to 0.40, mainly due to the ratio of micro/nanoalumina particles. Meanwhile, ion conductivity increases from 0.30 to 0.40 mS cm−1. As a result, the cycling stability of the lithium metal anode is greatly improved by the synergetic effect of microsized alumina particles and nanosized alumina particles.

Corrosion characteristics of an automotive coolant formulation dispersed with nanomaterials

Abstract This paper summarizes the anti-corrosive and anti-erosive properties of water-ethylene glycol based commercial coolant dispersed with nanomaterials. Multiwalled carbon nanotubes (MWCNTs), silver nanoparticles (Ag) and nanosized alumina particles (Al2O3) are dispersed in 0.5% weight in automotive coolants and tested for anti-corrosive properties as per ASTM standards. Prior to dispersion, the nanomaterials are surface modified to get good stability in coolant solutions. The corrosion resistance is measured in terms of weight loss of materials that is commonly used in automotive systems. It is found that oxidized MWCNTs are suitable to automotive systems while silver and Al2O3 nanoparticles are found to be deleterious in nature.

Impacts of Heat-Conducting Solid Wall and Heat-Generating Element on Free Convection of Al2O3/H2O Nanofluid in a Cavity with Open Border

Development of modern electronic devices demands a creation of effective cooling systems in the form of active or passive nature. More optimal technique for an origination of such cooling arrangement is a mathematical simulation taking into account the major physical processes which define the considered phenomena. Thermogravitational convection in a partially open alumina-water nanoliquid region under the impacts of constant heat generation element and heat-conducting solid wall is analyzed numerically. A solid heat-conducting wall is a left vertical wall cooled from outside, while a local solid element is placed on the base and kept at constant volumetric heat generation. The right border is supposed to be partially open in order to cool the local heater. The considered domain of interest is an electronic cabinet, while the heat-generating element is an electronic chip. Partial differential equations of mathematical physics formulated in non-primitive variables are worked out by the second order finite difference method. Influences of the Rayleigh number, heat-transfer capacity ratio, location of the local heater and nanoparticles volume fraction on liquid circulation and thermal transmission are investigated. It was ascertained that an inclusion of nanosized alumina particles to the base liquid can lead to the average heater temperature decreasing, that depends on the heater location and internal volumetric heat generation. Therefore, an inclusion of nanoparticles inside the host liquid can essentially intensify the heat removal from the heater that is the major challenge in different engineering applications. Moreover, an effect of nanosized alumina particles is more essential in the case of low intensive convective flow and when the heater is placed near the cooling wall.

Combination of back stress strengthening and Orowan strengthening in bimodal structured Fe–9Cr–Al ODS steel with high Al addition

Oxide dispersion strengthened (ODS) steels of Fe–9Cr–xAl (x = 0.4, 2.5, 4.5 and 8.0 wt%) have been fabricated by mechanical alloying, hot isostatic pressing and subsequent forging. Both the ferrite matrix and yttria particles were coarsened by the addition of Al. However, a bimodal structure consisting of coarse grains closely surrounded by fine grains is formed, and develops with increasing Al addition. Moreover, at the same time, nano-sized alumina particles precipitate in the interior of the bimodal ferrite grains. The tensile strength increases gradually with Al addition due to back stress strengthening combined with Orowan strengthening. The formation mechanism of the bimodal structure and intragranular precipitation of the Al added ODS steels were also discussed.

Magnetic Levitation and Some Mechanism of YBa2Cu3O7-δ Superconductor Doped with Nano-sized Al2O3

Magnetic levitation still remains one of the most interesting properties of the high-temperature cuprate superconductors, when these materials are manipulated with nanoparticles. There is not only a technological point of view, but also a theoretical interest in understanding their mechanism more precisely. In this study, we report magnetic levitation, structural and mechanical analyses on YBa2Cu3O7-δ (noted Y-123) polycrystalline samples superconductor added with nano-sized Al2O3 particles. Magnetic levitation experiment was used to investigate the superconductivity state of the samples. X-ray diffraction (XRD) with the Rietveld refinement technique was carried out to characterize phase identification and lattice structures of samples. XRD results reveal that the lattice parameters change for Y-123 phases. The differential of resistivity dρ/dT has been calculated and the effect of addition of nano-sized Al2O3 particles in the critical superconducting temperature T c has been reported. The calculated densities versus d-spacing for YBCO ceramic samples added with nano-sized alumina particles have been obtained. Superconducting parameters are affected by the addition of nano-sized Al2O3 particles, and results are discussed with relevance to the structural and some mechanism of YBa2Cu3O7-δ bulk superconductor.

Influence of Combined Helical and Pass Rolling on Structure and Residual Porosity of an AA6082-0.2 wt % Al2O3 Composite Produced by Casting with Ultrasonic Processing

The influence of combined (helical and pass) rolling on the structure, residual porosity, and microhardness of an AA6082-0.2 wt % Al2O3 composite produced by casting with ultrasonic processing was evaluated in comparison with the matrix alloy. The nanosized alumina particles resulted in a more homogeneous and fine-grained structure of the composite after deformation with higher microhardness in comparison with the matrix alloy. However, the residual porosity of the AA6082-0.2 wt % Al2O3 composite was retained even after combined rolling on the level typical of alloys produced by the method, which may be a result of relatively low stresses and strains introduced during deformation.

X-Ray diffraction line profile analysis of the microstructure of micro- and nanosized alumina particles

X-ray diffraction line profile analysis is adapted to investigate the microstructure of alumina. The structure of electrocorundum and corundum powders produced from pseudoboehmite with submicronic and nanometer-sized particles is analyzed. The lognormal size distribution parameters and their dependence on the conditions of corundum synthesis are determined. The structure of dislocations in corundum with different synthesis prehistories is analyzed, and structural features of the studied material are revealed.

Distribution of Alumina in Aluminum Prediction Based on Thermodynamic and Diffusion Analysis

A significant recent revision of the solubility of oxygen in liquid aluminum has prompted a re-evaluation of the presence of alumina in the solidified metal. A simple analysis based on thermodynamics and diffusion results in an interesting configuration of nanosized alumina particles distributed in Al.

Amino-functionalization of colloidal alumina particles for enhancement of the infiltration behavior in a silica-based ceramic core

The surface characteristics of nano-sized alumina particles were modified to include amine functional groups to enhance the infiltration behavior in a silica-based ceramic core, inhibiting crystallization of the cristobalite phase in order to improve mechanical properties. In this study, polymer-based polyethylenimine (PEI) or silane-based (3-Aminopropyl)triethoxysilane (APTES) were used as precursors in amine group addition. The specimens were characterized by the C-H stretching vibration and N-H bending vibration or the symmetric stretching vibration of siloxane group (Si-O-Si) in the FT-IR spectra, depending on the nature of the molecular structure of the precursor molecule. The dispersion properties were also improved through electrostatic repulsion or steric hindrance. These modifications resulted in a PEI-grafted colloidal alumina particle that induced a more rapid infiltration process with greater efficiency than did the APTES-treated particle. The rapid infiltration of the ceramic core suppressed the formation of the cristobalite phase, improved the flexural strength from 3.2 to 10.2MPa, and reduced the linear shrinkage rate from 1.91–1.05%.

Effect of the particle size and the debinding process on the density of alumina ceramics fabricated by 3D printing based on stereolithography

In this study, Al2O3 ceramics were printed by stereolithography from particles with different particle size distributions, which are the micro-sized Al2O3, nano-sized Al2O3, and a mixture of both. The influence of the particle size and the debinding method on the density and morphology of the sintered bodies were investigated. The density of the samples containing both micro-sized and nano-sized alumina particles is highest among the three samples. Furthermore, the samples subjected to the vacuum debinding showed a higher density compared with the samples subjected to the traditional thermal debinding. The results suggest that the combination of a powder with a bimodal particle size distribution and the vacuum debinding process offers an effective way to print 3D ceramics with a good performance through stereolithography.

Ultrafast ultrasonic-assisted joining of bare α-alumina ceramics through reaction wetting by aluminum filler in air

Bare α-alumina ceramics were directly bonded together in air through ultrasonic-assisted joining by pure aluminum filler within seconds. It was found that rapid wetting through in-situ reaction of elemental aluminum and oxygen, undercutting of the melted aluminum on ceramic surfaces, and large scale growth of fresh nano-sized alumina particles probably combined successively during the joining, attributing to the acoustic cavitation, the streaming and the micro-jetting by ultrasound effects. Ceramic-composed joints were successfully obtained with fracture strength of 101.5MPa within 90s at as low as 973K.

Dielectric Properties of Epoxy/Micro-sized Alumina Composite and of Epoxy/Micro-sized/Nano-sized Alumina Composite

Epoxy/micro-sized alumina composite was prepared, and the effects of alumina content on the dielectric properties were investigated in order to develop an insulation material for gas-insulated switchgears (GIS). Nano-sized alumina (average particle size: 30 nm) was also incorporated into the epoxy/micro-sized alumina composite. Dielectric tests were carried out in ASTM D 150, and capacitance (Cp) and dielectric loss (tanδ) were measured. The dielectric constant increased with increasing alumina content in the epoxy/micro-alumina system and the epoxy/micro-alumina/nano-alumina system. As 1,3-diglycidyl glyceryl ether (DGE) content increased, the dielectric constant decreased and dielectric loss increased. This ocurred as a result of the weak electric field enhancement due to homogeneous dispersion of micro- and nano-sized alumina particles in an epoxy composite.

Mechanical Properties of Epoxy Nanocomposites Using Alumina as Reinforcement - A Review

Polymers and their composites find use in many engineering applications as alternative products to metal-based ones and, nowadays, have wide technical applications. One of the most used composite materials is the epoxy resins (EP), which is a thermoset polymer matrix. After cure, this material displays some excellent mechanical, thermal, electrical and chemical properties. For these reasons, it has been widely used for a wide range of automotive and aerospace applications, as well as for shipbuilding or electronic devices. However, EP has poor resistance to crack propagation and is brittle. So, in recent years, a considerable amount of research has been carried out to improve the performance of the toughness of EP. The most common studied technique consist to reinforce the EP matrix with rigid nanoparticle fillers, such as alumina, silica, mica, talc, organoclays, nanoclays, carbon nanotubes, TiO2, among others. Among these nanofillers type, nanosize alumina particles has not been widely studied. However, recent studies have reported that the use of functionalized nanosize alumina particles as nanofiller can significantly improve the properties of the nanocomposite, even with low contents. These results, combined with the low cost of the alumina, show that the reinforcement of EP with alumina nanoparticles is a viable solution. In this paper, an attempt is made to review and highlight some recent findings and also some trends to show future directions and opportunities for the development of polymer nanocomposites reinforced with alumina nanoparticles.

A comparative study on low cycle fatigue behaviour of nano and micro Al2O3 reinforced AA2014 particulate hybrid composites

Aluminium based metal matrix composites have drawn more attraction due to their improved properties in structural applications for the past two decades. The fatigue behaviour of composite materials needs to be studied for their structural applications. In this work, powder metallurgy based aluminium (AA2014) alloy reinforced with micro and nano-sized alumina particles were fabricated and consolidated with the hot extrusion process. The evaluation of mechanical properties in the extruded composite was carried out. This composite was subjected to low cycle fatigue test with a constant strain rate. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) images were used to evaluate the fatigue behaviour of aluminium-nano composite samples. Enhanced mechanical properties were exhibited by the nano alumina reinforced aluminium composites, when compared to the micron sized alumina reinforced composites. The failure cycle is observed to be higher for the nano alumina reinforced composites when compared with micron sized alumina composites due to a lower order of induced plastic strain.