Al2O3 Particle Size Research Articles

Optimization of parameters that affect wear of A356/Al2O3 nanocomposites using RSM, ANN, GA and PSO methods

PurposeThis study aims to present a novel methodology for the evaluation of tribological properties of new nanocomposites with the A356 alloy matrix reinforced with aluminium oxide (Al2O3) nanoparticles.Design/methodology/approachMetal matrix nanocomposites (MMnCs) with varying amounts and sizes of Al2O3 particles were produced using a compocasting process. The influence of four factors, with different levels, on the wear rate, was analysed with the help of the design of experiments (DoE). A regression model was developed by using the response surface methodology (RSM) to establish a relationship between the observed factors and the wear rate. An artificial neural network was also applied to predict the value of wear rate. Adequacy of models was compared with experimental values. The extreme values of wear rate were determined with a genetic algorithm and particle swarm optimization using the RSM model.FindingsThe combination of optimization methods determined the values of the factors which provide the highest wear resistance, namely, reinforcement content of 0.44 wt.% Al2O3, sliding speed of 1 m/s, normal load of 100 N and particle size of 100 nm. Used methods proved as effective tools for modelling and predicting of the behaviour of aluminium matrix nanocomposites.Originality/valueThe specific combinations of the optimization methods has not been applied up to now in the investigation of MMnCs. In addition, using of small content of ceramic nanoparticles as reinforcement has been poorly investigated. It can be stated that the presented approach for testing and prediction of the wear rate of nanocomposites is a very good base for their future research.

Highly anisotropic thermal conductivity and electrical insulation of nanofibrillated cellulose/Al2O3@rGO composite films: effect of the particle size

Nanofibrillated cellulose (NFC) film has received tremendous attention due to its excellent electrical insulation, which shows great application prospects in the field of electronic devices. However, the low efficient heat dissipation of NFC film largely limits its use in advanced applications. In this work, the reduced graphene oxide hybrid fillers loaded alumina (Al2O3) particles with different sizes were synthesized by different drying methods, and then they were mixed with NFC to prepare a series of NFC-based composite films. The effect of Al2O3 particle sizes on the thermal conductivity of NFC-based composite films was studied. The results showed that the surface areas of l-Al2O3 particles were smaller than that of s-Al2O3 particles, resulting in the smaller interface thermal resistance and superior thermal conductivity of the film containing l-Al2O3 particles. The NFC-based composite films showed great potential for applications in thermal management by adjusting the particle size of fillers.

Effect of parameters: Milling time and wt. % Al2O3 on mass density and hardness of Al2O3/Cu micro-composite

The new technologies require materials with multi-functional properties that cannot be met by conventional materials. Alumina (Al2O3) and pure copper (Cu) can be combined to form a multi-functional material with mechanical, tribological, and thermo-electrical properties. In this study, ceramic material Al2O3 with 0 wt.%, 1 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, and 5 wt. % were added into the pure Cu matrix using a powder metallurgy method at various milling times. Different weight ratios of Al2O3 and Cu powders were pressed using a hydraulic press machine and sintered in a muffle furnace. A scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to examine the surface morphograph and chemical elements of the micro-composite, respectively. The presence of Al2O3 in the sample is revealed by surface morphograph. The SEM images of the Al2O3/Cu micro-composite at various milling times show that the agglomeration tendency of the Al2O3 particles, as well as the Al2O3 particle size, decreases with increasing milling time. The presence of chemical elements such as Cu, Al, and O in the micro-composite is indicated by EDX analysis. The addition of Al2O3 particles into pure Cu reduces the mass density of the micro-composite samples and increases slightly as the milling time increases. The hardness analysis reveals that as the wt. % of Al2O3 particles and milling duration increases, the hardness value of pure Cu increases. The hardness of an Al2O3/Cu micro-composite is strongly dependent on the wt. % of Al2O3 particles, the Al2O3 particle size, the existence of porosity, the milling duration, and the distribution of the Al2O3 particles in the micro-composite samples.

The Effect of Sandblasting on Bond Strength of Soft Liners to Denture Base Resins: A Systematic Review and Meta-Analysis of In Vitro Studies.

Objectives This study aimed to evaluate the effect of sandblasting on the bond strength of denture base resin to soft liners. Materials and Methods This report follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Embase, Cochrane, Scopus, and OpenGrey databases were searched for in vitro studies that compared sandblasting with no treatment in terms of the tensile, shear, and peel bond strength of resilient lining materials (acrylic-based or silicone-based) to polymethyl methacrylate denture base resin. Based on the outcome, the analysis was carried out in three groups of tensile, shear, and peel bond strength. Subgroup analysis was done for the effect of size of particles on sandblasting, blasting pressure, and type of soft liner whenever possible. Heterogeneity was evaluated among the studies, and meta-analysis was performed with random effect models (p < .05). Results After screening, 16 articles met the inclusion criteria for meta-analyses. No treatment showed significantly higher tensile (p < 0.001) or peel (p=0.04) bond strength, although shear bond strength of sandblasted resin was significantly better (p=0.008). Results of subgroup analyses of particle size favored the control group in 50 µ Al2O3 particle size (p < 0.001). In analyses of blasting pressure, the control group had significantly better tensile bond strength than specimens with blasting pressure ≤1 bar (p < 0.001) while specimens with blasting pressure beyond 1 bar showed significantly more tensile strength than control group (p=0.03). In silicon-based liners, groups without any surface treatment had significantly higher tensile bond strength (p < 0.001). Conclusion According to the in vitro studies, sandblasting would not lead to significant increase in bond strength of soft liner to the denture base resin.

Influence of Al203 particle mixed dielectric fluid on machining performance of Ti6Al4V

In this research work, an attempt was made to machine Ti6Al4V titanium alloy utilizing AA6061/10 Gr composite tool. The composite tool was fabricated using stir casting technique and Al2O3 particles of size 5 μm were incorporated in the dielectric fluid to enhance the machining performance. Experiments were conducted by varying Al203 concentration, pulse on time, current, and pulse off time, and the responses Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) were recorded. Experiments runs were planned using Taguchi orthogonal array. The results revealed that adding powder increases MRR and TWR owing to the excessive heat generation and bridging effect respectively. The best surface finish was attained due to the increase in spark gap and complete flushing of machined debris. Coating of materials over the machined specimen was observed when the parametric value of Ton was higher than 60 μs under PMEDM conditions. Pits, craters and cracks were observed on the machined topography which was eliminated when 5 g l−1 of Al2O3 particles were added to dielectric fluid. MEIOT technique was utilized for optimization and it was observed that Ton 15 μs, Toff 4 μs and current 7 A and powder concentration of 10 g l−1 results in best machining performance.

Effects of particle size of raw materials on phase formation and optical properties of Ce3+-doped Y3Al5O12 phosphors

The effects of the particle size of the Al2O3 raw material on the phase formation and optical properties of Ce3+-doped Y3Al5O12 (YAG:Ce3+) phosphors prepared by a solid-state reaction were investigated, along with the crystallinities, photoluminescent properties, and Ce3+ contents of the phosphors. Reducing both the Al2O3 particle size and distribution influenced the efficient formation of the YAG phase, with the final YAG phase content increasing from 48.4% to 83.5%. The amount of Ce3+ also increased with the formation of the YAG phase, and the external quantum efficiency was improved by a factor of ∼1.4. Considering both the particle size and the size distribution is important when selecting raw materials, which provides an effective way of optimizing phosphor performance.

Impact of Al2O3 Particle Size on the Open Porosity of Ni/Al2O3 Composites Prepared by the Thermal Oxidation at Moderate Temperatures

The performance of attractive Ni-based composites can be affected by changing their microstructures, e.g., introducing pores. Here, we report a novel, relatively low-cost process to fabricate Ni/Al2O3 composites with open porosity modified by the size of Al2O3 particles. The mixture of powders was subjected to thermal oxidation twice in air after a maximal temperature of 800 °C was reached in a stepwise manner and maintained for 120 min. The oxidation kinetics were determined thermogravimetrically. The open porosity was evaluated by an Archimedes’ principle-based method. Localization and quantification of NiO, newly formed on the Ni particle surface and acting as a mechanical bonding agent, were explored by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffractometry. Larger ceramic particles prevented merging of NiO layers on adjacent Ni particles more efficiently; therefore, the open porosity increased from 21% to 24.2% when the Al2O3 particle diameter was increased from 5–20 µm to 32–45 µm. Because both Ni/Al2O3 composites exhibited similar flexural strength, the composite with larger Al2O3 particles and the higher open porosity could be a better candidate for infiltration by molten metal, or it can be directly used in a variety of filtration applications.

Surface Topography Analysis of Mg-Based Composites with Different Nanoparticle Contents Disintegrated Using Abrasive Water Jet.

This study investigated the effect of abrasive water jet kinematic parameters, such as jet traverse speed and water pressure, on the surface of magnesium-based metal matrix nanocomposites (Mg-MMNCs) reinforced with 50 nm (average particle size) Al2O3 particles at concentrations of 0.66 and 1.11 wt.%. The extent of grooving caused by abrasive particles and irregularities in the abrasive waterjet machined surface with respect to traverse speed (20, 40, 250 and 500 mm/min), abrasive flow rate (200 and 300 g/min) and water pressure (100 and 400 MPa) was investigated using surface topography measurements. The results helped to identify the mode of material disintegration during the process. The nanoindentation results show that material softening was decreased in nanocomposites with higher reinforcement content due to the presence of a sufficient amount of nanoparticles (1.11 wt.%), which protected the surface from damage. The values of selected surface roughness profile parameters—average roughness (Ra), maximum height of peak (Rp) and maximum depth of valleys (Rv)—reveal a comparatively smooth surface finish in composites reinforced with 1.11 wt.% at a traverse speed of 500 mm/min. Moreover, abrasive waterjet machining at high water pressure (400 MPa) produced better surface quality due to sufficient material removal and effective cleaning of debris from the machining zone as compared to a low water pressure (100 MPa), low traverse speed (5 mm/min) and low abrasive mass flow rate (200 g/min).

Phase Transformations and Subsurface Changes in Three Dental Zirconia Grades after Sandblasting with Various Al2O3 Particle Sizes.

Although sandblasting is mainly used to improve bonding between dental zirconia and resin cement, the details on the in-depth damages are limited. The aim of this study was to evaluate phase transformations and subsurface changes after sandblasting in three different dental zirconia (3, 4, and 5 mol% yttria-stabilized zirconia; 3Y-TZP, 4Y-PSZ, and 5Y-PSZ). Zirconia specimens (14.0 × 14.0 × 1.0 mm3) were sandblasted using different alumina particle sizes (25, 50, 90, 110, and 125 µm) under 0.2 MPa for 10 s/cm2. Phase transformations and residual stresses were investigated using X-ray diffraction and the Williamson-Hall method. Subsurface damages were evaluated with cross-sections by a focused ion beam. Stress field during sandblasting was simulated by the finite element method. The subsurface changes after sandblasting were the emergence of a rhombohedral phase, micro/macro cracks, and compressive/tensile stresses depending on the interactions between blasting particles and zirconia substrates. 3Y-TZP blasted with 110-µm particles induced the deepest transformed layer with the largest compressive stress. The cracks propagated parallel to the surface with larger particles, being located up to 4.5 µm under the surface in 4Y- or 5Y-PSZ subgroups. The recommended sandblasting particles were 110 µm for 3Y-TZP and 50 µm for 4Y-PSZ or 5Y-PSZ for compressive stress-induced phase transformations without significant subsurface damages.

One-Pot Synthesis of Alumina-Titanium Diboride Composite Powder at Low Temperature.

Alumina-titanium diboride (Al2O3-TiB2) composite powders were synthesised via aluminothermic reduction of TiO2 and B2O3, mediated by a molten chloride salt (NaCl, KCl, or MgCl2). The effects of salt type, initial batch composition, and firing temperature/time on the phase formation and overall reaction extent were examined. Based on the results and equilibrium thermodynamic calculations, the mechanisms underpinning the reaction/synthesis processes were clarified. Given their evaporation losses at test temperatures, appropriately excessive amounts of Al and B2O3 are needed to complete the synthesis reaction. Following this, phase-pure Al2O3-TiB2 composite powders composed of 0.3–0.6 μm Al2O3 and 30–60 nm TiB2 particles were successfully fabricated in NaCl after 5 h at 1050 °C. By increasing the firing temperature to 1150 °C, the time required to complete the synthesis reaction could be reduced to 4 h, although the sizes of Al2O3 and TiB2 particles in the resultant phase pure composite powder increased slightly to 1–2 μm and 100–200 nm, respectively.

The effect of light scattering in stereolithography ceramic manufacturing

This research simulated the light scattering caused by ceramic particles' presence during stereolithography ceramic manufacturing and revealed the phenomena in the process. The theoretical derivation and calculation of a classic single-particle scattering model were used to verify the reliability of the simulation model. The light scattering simulation confirmed the effects of particle distribution, input energy, and relative refractive index, which were all supported by experiments. The simulation also showed the different scattering edge and the surface roughness at the micron level with verified experiment. Besides, as the particle size of Al2O3 particles increased, the curing thickness increased, the degree of side scattering increased slightly, and the regularity of the curing edge decreased. It was found through simulation that adding an appropriate amount of carbon powder can solve SiO2 inability to print. This study provides valuable guidance to the control of the light-cured 3D printing process for ceramics.

Microstructural and mechanical properties of Al2O3 reinforced Al7010 matrix composites, fabricated by stir casting

The microstructural and mechanical properties of alumina reinforced Al7010 matrix composites, fabricated by stir casting, were investigated by varying size and volume fractions of alumina particles. The optical microscope, micro Vickers hardness tester, tensile tester, and impact testers were used to evaluate the microstructure and mechanical properties of produced alumina reinforced Al7010 matrix composites. Results show that the alumina reinforced Al7010 matrix composites, incorporating lower volume fractions of alumina particles, exhibited much better morphological and mechanical properties than composites with higher volume fractions. The composite with 14% alumina particles of size 15 µm exhibited uniform dispersion of alumina particles in the Al7010 matrix with superior interfacial bonding and negligible agglomeration of alumina particles and excellent morphological properties. On the other hand, the composite, having 21% alumina particles of size 1 µm demonstrated very poor morphological properties and intensive agglomeration of alumina particles. Similarly, the maximum values of Rm (349 MPa) and ƐT (3.41%) were also offered by composite, incorporating 14% Al2O3 particles of size 15 µm attributed to the uniform dispersion and negligible agglomeration of alumina particles throughout the matrix. The composite with 21% alumina particles of size 1 µm offered the minimum values of Rm (172 MPa) and ƐT (1.69%) due to the presence of intensive agglomeration of alumina particles. The superior impact toughness (11.4 J) and the overall optimum combination of morphological and mechanical properties were offered by the composite with 14% alumina particles of size 15 µm.

Study on the Al2O3p/Al composites prepared by Al-calcined kaolin system

In this study, in-situ Al2O3p/Al composite was prepared by the exothermic dispersion method from Al-calcined kaolin system. Thermodynamic analysis was carried out by calculating Gibbs free energy. The reaction kinetics of the system was studied by differential scanning calorimetry and Kissinger equation. The effects of heating temperature and holding time on the microstructure of the composites were analysed. The results showed that the reaction activation energy of the system continued to increase with the progress of the reaction. With the extension of the reaction time at 800°C, the particle size of Al2O3 increased slowly. When the holding time was 50 min, the density and hardness of the composite material were 2.7 g cm−3 and 64HV respectively.

Effect of Al2O3 particle size reduction on aluminium dust explosion

To investigate the effect of Al2O3 particle size on an aluminum explosion, the overpressure and flame velocity in a vertical duct were evaluated. The results show that the inhibitory effect of submicron Al2O3 is best, while the inhibitory effect increases with increasing inerting ratio. However, the inhibitory effect of micron Al2O3 does not increase significantly after the inerting ratio exceeds 40%. For high-concentration aluminum powder, 0.8 μm Al2O3 with an inerting ratio less than 20% promotes aluminum explosion. As the inerting ratio increases beyond 20%, however, the overpressure decreases. Furthermore, Al2O3 inhibits the formation of the intermediate product AlO and decreases the flame brightness. As the inerting ratio of 0.8 μm Al2O3 reaches 50%, the white patches in the flame image disappear. The results of scanning electron microscopy showed that the explosion products agglomerate and some dot-like protrusions appear on the surface of the unburned aluminum particles. The inhibition mechanism was qualitatively investigated. Physical heat absorption is proven to play a limited role. Thermal radiation and chemical inhibition play a key role. The chemical effect mainly influences the surface reaction energy source.

Effect of Al–Nb–B2O3–CuO system reaction products on microstructure and wear resistance of A356 alloy

The aim of present work is study the effcet of Al-Nb-B2O3-CuO system reaction products on microstructure and properties of A356 alloy. B2O3 powder, Al powder, CuO powder and Nb powder were used as raw materials to form Al–Nb–B2O3–CuO reaction system, and A356 alloy was refined by in situ reaction and near-liquidus casting. The size, phase, morphology and distribution of in situ reaction products were observed and analysed by optical microscope, x-ray diffractometer, scanning electron microscope and transmission electron microscope. The products of the Al–Nb–B2O3–CuO reaction system are mainly Al3Nb, NbB2 and Al2O3. The ratio of the prefabricated block is 8:1:1:2 . When the prefabricated block was added at 2.5 wt%, the particle size of NbB2, Al3Nb and Al2O3 is 0.5–1 μm. The microstructure of A356 alloy is fine and uniform. The average grain size is refined to less than 20 μm. Compared with untreated A356 alloy, the wear rate is reduced from 2.091% to 0.882%, and the average hardness of the alloy is increased from 41.3HRC to 58.2HRC.

Improved biodegradability of zinc and its alloys by sandblasting treatment

Zinc (Zn) and its alloys have been considered as potential materials for osteosynthesis implants. Nonetheless, the relatively slow degradation rates within bone environments impede their further application. Herein, sandblasting surface treatment with two Al2O3 particle sizes (125 μm and 250 μm) was employed to accelerate the degradation rates of Zn and two Zn alloys, a Zn4Ag and a Zn-2Ag-1.8Au-0.2V (wt%). The degradation processes of Zn and Zn alloys were significantly increased after sandblasting treatment mainly due to the increased surface roughness and embedded Al2O3 particles in the surfaces. However, an increase of sandblasting particle size from 125 μm to 250 μm did not affect the degradation rates. Moreover, the mean relative metabolic activities of Saos-2 osteoblasts below 70% were observed for alloys treated with 250 μm Al2O3 particles, indicating apparent cytotoxic effects. The results showed that the size of the sandblasting particles had no direct effect on the degradation rate but on the cytotoxicity. Therefore, sandblasting treatment with appropriate particles might be a promising surface modification to accelerate the biodegradability of Zn and its alloys.

Effect of α-Al2O3 Particle Size in a Slurry on the Physical Properties of Chemically Strengthened Thin Glass Prepared by the Spray Method.

Chemical strengthening is considered as the most suitable method for strengthening thin glass sheets used in mobile phones. The spray method of chemical strengthening requires a slurry to be sprayed on the glass sample to be strengthened. This slurry is prepared by mixing various compounds. In this study, the influence of α-Al2O3 particle size in the slurry on the physical properties of the chemically strengthened glass prepared by the spray method was investigated. The compressive stress (CS) was dramatically enhanced as the particle size of Al2O3 in the slurry decreased. The glass sample with 13 nm α-Al2O3 including the KNO3-Al2O3 slurry exhibited the highest CS of 905 MPa, and the depth-of-layer (DOL) of this sample was 37 μm. The same slurry composition also achieved the highest bending strength of 640 MPa under different heat treatment conditions. The optimization of the heat treatment conditions, such as temperature and time duration, resulted in the highest value of CS (916 MPa) obtained for the sample heated at 400 °C for 1.5 h, and the maximum DOL (65 μm) was obtained for the sample at 480 °C for 4 h.

Al2O3-10 wt% Fe composite prepared by high energy ball milling: Structure and magnetic properties

In the present work, Al2O3-10 wt% Fe composite powders were manufactured by mechanical alloy using different milling times. The morphology, structure and magnetic properties were carefully investigated and explained through the results of SEM, XRD (with Rietveld refinement), Mössbauer spectroscopy and magnetic measurements at low-temperatures. After 50 h of milling, the results reveal α-Fe particles uniformly distributed in Al2O3 and a decrease of the average particle size of Al2O3–Fe composite. Besides, XRD data show a decrease of crystallite sizes, accompanied by an increase of the lattice micro-strain. For samples milled for 30 h and 50 h, the Mössbauer spectra recorded at 300 K showed a superparamagnetic component related to very fine hematite crystallites with a maximum absorption relative area of 10%. The M − H curves recorded at 6 K showed a small reduction in saturation magnetization, and an improvement in remanence magnetization and coercivity field with milling time, while the M-T curve of the sample milled for 50 h shows a peak at 185 K, related to the Morin transition of the hematite phase.

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.

Effect of Al2O3 Particle Size on Mechanical Properties of Ultrasonic-Assisted Stir-Casted Al A356 Matrix Composites

In this study, aluminum A356 (AlSi7Mg0.3) alloy matrix composites reinforced with various fractions (0.5, 1.0 and 1.5 wt%) of Al2O3 particles having two different particle sizes (nano- and micro-size) were produced, and the effect on mechanical properties of aluminum metal matrix composite was examined. Ultrasonic-assisted mechanical stirring process (hybrid stirring) was used in order to improve the distribution of reinforcements in the matrix. T6 heat treatment process was applied afterward. Microstructures were characterized by metallographic analysis, grain size measurement and DAS measurements. Mechanical properties were evaluated with uniaxial tensile tests, charpy tests and hardness tests. The highest values of ultimate tensile strength (UTS) and elongation were obtained with 0.5 wt% of nano-Al2O3 addition among all compositions. Compared to the reference sample, UTS values are increased 8.7% and 3.9% with 0.5 wt. of nano-Al2O3 and 1.5 wt% of micro-Al2O3 addition, respectively. Moreover, the Charpy impact energy was increased with a maximum of 41% with 0.5% nano-Al2O3 addition. As a result, 0.5 wt% of nano-Al2O3 addition yields the optimum properties according to the quality index calculations.