Al2O3 Nanocomposites Research Articles

Structural Properties and Catalytic Activity of Binary Poly (vinyl alcohol)/Al2O3 Nanocomposite Film for Synthesis of Thiazoles

A solution casting technique was applied to prepare a binary poly (vinyl alcohol)/Al2O3 nanocomposite. The structural properties of nanocomposite were investigated using Fourier-transform infrared spectra, field emission scanning electron microscope, energy dispersive X-ray analyses, and X-ray diffraction. The hybrid PVA/Al2O3 film exhibited a conspicuous catalytic performance for synthesis of thiazole derivatives under mild reaction conditions. Moreover, the optimization of catalytic efficiency and reusability of this nanocomposite have been investigated.

Micromechanical modeling of damage in elasto-plastic nanocomposites using unit cell representative volume element and cohesive zone model

The article aims to investigate elasto-plastic nanocomposites damage behavior dependence on the interfacial bonding between metal and ceramic phase. To this end, a unit cell representative volume element and cohesive element model were developed numerically to simulate matrix and reinforcement phases and the bonding between them. Through experimental study, commercial pure Al and Al2O3 are used as raw materials to produce Al–5%Al2O3 nanocomposite by using high energy ball milling followed by cold compaction and sintering. The developed model with cohesive interface elements is validated and approximately it is identical with experimental results available in the literature and others done during this work for Al–5%Al2O3 nanocomposite. Numerical results show the validity of representative volume element with cohesive elements model to accurately simulate the stress-strain behavior of nanocomposites which highly reduce the computation cost of 3D models and binarization errors for simulating real microstructure. The results show that the interfacial bonding between ceramic and matrix phase has a large influence on the prediction of the stress-strain behavior which highlight that the assumption of considering fully bonded interface in the simulation of nanocomposites is inaccurate. The ultimate interface strength is the most critical parameter that affects the decohesion behavior between matrix and reinforcement nanoparticles which makes the bonding between these two phases a critical issue in production of nanocomposites. This highlights the immense demand of finding new methods to improve adhesion between reinforcement and matrix phases for production of nanocomposites with improved properties.

High cycle fatigue behavior of magnesium matrix nanocomposite at elevated temperatures

In this article, the high cycle fatigue (HCF) behavior of AZ31B/1.5 vol.% Al2O3 nanocomposite was investigated at elevated temperatures. To understand the influence of nano-sized reinforcing particles, the results were compared to those of monolithic AZ31B samples. The effect of reinforcing particles and temperature was studied on tensile, compressive, and HCF behaviors of the specimens. According to the results, the nanocomposite showed improved mechanical properties in comparison to the monolithic alloy at all temperatures. The results of HCF tests at 100 °C and 200 °C revealed that the enhanced ultimate tensile strength in the composite is the most important factor in modifying the HCF behavior, especially at the higher temperature. Unlike the tensile and the compressive tests, increasing the temperature from 100 °C to 200 °C reduces the impact of the reinforcing particles on the fatigue behavior of the composite, which could be attributed to the formation of magnesium oxide on the samples surfaces.

Tribological behavior of aluminum nanocomposites studied by application of response surface methodology

An aluminum Al-0.8Al2O3 and Al − 1.6Al2O3 nanocomposite was prepared by a novel ultrasonic assisted stir casting method. A three-level Box-Behnken design of experiment was developed using response surface methodology. Dry sliding wear tests were performed as per the experimental design using a pin-on disc setup at room temperature. Analysis of variance (ANOVA) was applied to investigate the influence of process parameters, viz., wt.% reinforcement, load and sliding distance, and their interactions on specific wear rate and coefficient of friction. Further, a mathematical model has been formulated by applying response surface method in order to estimate the tribology characteristics such as wear and COF of the nanocomposites. The specific wear rate and coefficient of friction are significantly influenced by % of Al2O3 and load. The wear test parameters were optimized for minimizing specific wear rate and COF using desirability function approach. A set of optimum parameters of combination for AMMNC was identified as Al2O3–1.1 wt.%; load, 34 N and sliding distance, 2931 m with specific wear rate, 1.06 g/N-m; and coefficient of friction, 0.305. The AFM image of Al6061–1.1Al2O3 nanocomposite at optimized condition confirms the improvement in the wear surface smoothness of the nanocomposite compared to Al6061.

Failure analysis using online acoustic emission and tribological behavior of Al6061-Al2O3 nano composite

In this paper Al-Al2O3 nanocomposites were prepared through liquid metallurgy route and their microstructure, mechanical and tribological properties are analyzed. The pin-on-disc equipment under dry sliding conditions was used to determine the wear characteristics of prepared nanocomposites. The worn surfaces of nanocomposite Al-Al2O3 nano-composite have been characterized by SEM. The hardness of the cast nanocomposite samples was measured by using Vickers micro hardness tester. In tensile test specimens, the acoustic emission (AE) technique was used to monitor the acoustic energy released during the deformation process and for the early crack detection of the composite material. The investigation shows that Al-1.2Al2O3 nano-composites have improved wear resistance, least co-efficient of friction, best surface smoothness than the Al6061 matrix alloy. The AFM image of Al-1.2Al2O3 nanocomposite confirms the improvement in the wear surface smoothness of the nanocomposite compared to Al6061 matrix alloy.

Photoactive ZnO–Al2O3 Transparent Coatings and Nanocomposites Prepared by a Simple Polymer-Salt Synthesis

The article presents the study of ZnO–Al2O3 thin coatings prepared by a polymer-salt method using the polyvinylpyrrolidone and zinc nitrate and tin (IV) chloride solutions. The materials were studied by spectroscopic methods and SEM analysis. It was found that prepared coatings have transparency in visible spectral range and demonstrate the ability to generate singlet oxygen under UV irradiation.

Fabrication of a 3,4‐Diaminotoluene Sensor Based on a TiO2 ‐Al2O3Nanocomposite Synthesized by a Fast and Facile Microwave Irradiation Method

AbstractA fast and facile synthesis of TiO2‐ Al2O3 nanocomposite based on Microwave (MW) irradiation is presented. The nanocomposite development were corroborated by X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy‐dispersive X‐ray (EDX),and Fourier transform infrared spectroscopy (FT‐IR)analysis. The XPS analyzed results affirmed that elements on the nanocomposite surface were Al and O. Electrochemical properties of the as prepared TiO2‐Al2O3 nanocomposites were studied thoroughly to determine the sensing activity of the nanocomposites towards 3,4‐Diaminotoluene (3,4‐DAT) which is a harmful or hazardous chemical using I−V method. Selective electrochemical sensor using TiO2‐Al2O3 nanocomposite onto glassy carbon electrode (GCE) was assembled and the details electrochemical investigation of 3,4‐Diaminotoluene (3,4‐DAT) was developed. It was calibrated using in range of 3,4‐DAT concentration and data were plotted as current versus concentration. Considering the highest linearity (r2=0.99)of calibrated range, the linear dynamic range (1.0 pM∼ 1.0 μM) was found. Employing the slope of calibration curve, the sensitivity (0.5024×103 μAμM−1cm−3) and detection limit (0.19 ± 0.01 pM) were estimated. Besides this, the selective 3,4‐DAT chemical sensor was shown long‐term stability and precious reproducibility with very short response time without any interference effect.

Spark plasma sintering of ZrO2–Al2O3 nanocomposites at low temperatures aided by amorphous powders

In present work, ZrO2-5 wt% Al2O3 and ZrO2-10 wt% Al2O3 nanocomposites are fabricated through spark plasma sintering. Al2O3–ZrO2 amorphous powders and polycrystal Al2O3 powders and are doped in the polycrystalline ZrO2 powders, respectively. When doped with amorphous powders, the sintering of ZrO2–Al2O3 nanocomposites is promoted, and ZrO2-5 wt% Al2O3 and ZrO2-10 wt% Al2O3 nanocomposites with relative densities of 99% are obtained after spark plasma sintering at 1200 °C; however, when sintering of polycrystalline ZrO2 and polycrystalline Al2O3 powders, the relative densities are merely 93%. The enhanced sinterability is due to the metastability and phase transformation of the amorphous powders, which act as sintering aids. The nanocomposites with near-theoretical density show refined microstructure with homogenous mixture of ZrO2 and Al2O3 grains, which further leads to excellent mechanical properties. This article provides new ideas for low-temperature sintering of nanocomposites via using doping amorphous powders.

Thermal Stability of the Structure and Microhardness of the Al–0.05 vol % Al2O3 Nanocomposite Fabricated by Accumulative Roll Bonding

The evolution of the microstructure and microhardness of the Al–0.05 vol % nAl2O3 nanocomposite (where nAl2O3 are aluminum nanoparticles) and aluminum without nanoparticles fabricated by accumulative roll bonding with annealing in a temperature range of 373–573 K is investigated. Ball-shaped Al2O3 nanoparticles with an average diameter of 50 nm are introduced between rolled plates of technically pure aluminum from the first to fourth rolling cycles, while the fifth to the tenth rolling cycles are performed without nanoparticles. The average grain size and aspect ratio of elements of the material grain–subgrain structure in the initial state and after annealing at 473 K are measured using transmission electron microscopy. It is shown that the nanocomposite microhardness is 5–13% higher than the corresponding value of HV for aluminum over the entire studied annealing temperature range. The main factor of the higher nanocomposite microhardness is precipitation hardening due to Al2O3 nanoparticles. The contribution of the substructural and grain-boundary hardening is identical in both materials. The thermal stability of the nanocomposite microhardness is only ~25 K higher than that of aluminum, which is caused by the nonuniform distribution of nanoparticles in the matrix and their low volume fraction. The high thermal stability of the fine-grain structure itself, formed by accumulative roll bonding, when compared with other methods of intense plastic deformation, also plays a role. It is established that most Al2O3 nanoparticles remain at the grain boundaries of nanocomposite after annealing at 473 K; therefore, the ability to fasten the boundary by Al2O3 nanoparticles under the conditions under study is retained at least to 473 K.

Augmentation of ferromagnetism in CuO–Al2O3 nanocomposite synthesized via solution combustion method

The finite size effect of CuO nanoparticles and their effect on the magnetic behavior of a CuO–Al2O3 nanocomposite synthesized via a solution combustion method are discussed here. It is observed that the introduction of CuO nanoparticles of ∼20 nm in size on the surfaces of Al2O3 nanosheets strongly influences the magnetic moment of the nanocomposite. The X-ray diffraction pattern reveals the presence of a CuO phase in the CuO–Al2O3 nanocomposite. Electron microscopy imaging shows the presence of CuO nanoparticles distributed over the surfaces of Al2O3 nanosheets. Magnetic measurements performed at 5 and 300 K revealed a strong enhancement in the saturation magnetization of the CuO–Al2O3 nanocomposite at both temperatures. This increase is due to the formation of CuO nanoparticles on the surfaces of the Al2O3 nanosheets. These CuO nanoparticles show a ferromagnetic nature due to the uncompensated surface Cu2+ spins of the copper ions. The presence of the Cu2+ state in the CuO nanoparticles in the CuO–Al2O3 nanocomposite was confirmed by X-ray photoelectron spectroscopy (XPS) measurements.

Experimental study on tribological properties of Cu–Al2O3 nanocomposite hybridized by graphene nanoplatelets

Mechanical and tribological properties of Cu–Al2O3 nanocomposite hybridized by silver (Ag) coated graphene nanoplatelets (GNPs) were studied. Four different GNPs content, 0.3, 0.6, 0.9 and 1.2 wt% were considered to highlight its influence on the properties of the produced hybrid nanocomposite. The synthesis of hybrid nanocomposites involves ball milling and hot pressing. Microstructural observations showed homogenous distribution of both Al2O3 and GNPs. The results showed significant hardness improvement with increasing GNPs content reaching 55.2% compared to the pure Cu due to the grain refinement, high strength of GNPs and the reinforcing of grain boundaries by the precipitation of GNPs. Moreover, the wear resistance is increased while the coefficient of friction is decreased by increasing GNPs content. Among the all manufactured samples, Cu-10 wt% Al2O3 +1.2 wt% GNPs shows the highest mechanical and the wear resistance. Additionally, it shows the lowest coefficient of friction highlighting its importance for tribological applications.

Thermal stability of Al—0,05 vo1.% Al2O3 nanocomposite fabricated by accumulative roll bonding

Thermal stability of Al—0,05 vo1.% Al2O3 nanocomposite fabricated by accumulative roll bonding

Effect of nanoparticle reinforcement on mechanical properties and erosion–corrosion behavior of cast aluminum

AbstractThe effect of mixing alumina (Al2O3) nanoparticles in pure aluminum has been investigated, with a characterization of the mechanical properties and erosion–corrosion (E–C) behavior. Specimens of pure aluminum and Al with nanoparticles added as reinforcement have been produced by casting. Uniform dispersion of nanoparticles in the molten aluminum matrix has been achieved by mechanical stirring. Mechanical properties such as yield strength, ultimate strength, modulus of elasticity, and hardness of the new composites have been measured. E–C tests have been conducted to investigate the effect of the nanoparticle additives on the weight loss and surface properties of the new composites. Scanning electron microscopy, electron backscatter diffraction, and energy dispersive spectrometry have been employed to analyze, characterize, and compare pure aluminum and the composites. Al–Al2O3 nanocomposites have been obtained successfully and with a reasonable distribution by adding 1 wt.-% of alumina nanoparticles (100 nm or 20 nm in size) to molten aluminum. The alumina nanoparticles have increased the yield strength and hardness of the new composites when compared to pure aluminum. Enhancement in E–C resistance is also observed under various conditions.

Mechanical and wear behavior of AA7075 aluminum matrix composites reinforced by Al2O3 nanoparticles

An attempt was made to synthesize aluminum alloy (AA) 7075 matrix reinforced with 0, 1, 3, 5 wt% Al2O3 particulates by using stir casting technique. Mechanical properties and wear behavior were examined. The hardness and tensile properties were obtained before and after addition of Al2O3 particulates to reveal the extent improvement. Wear behavior was examined by using a pin-on-disc device to validate the improvement of the wear resistance. The results showed that adding of Al2O3 reinforcement were significantly enhanced the mechanical properties. The ultimate tensile strength (UTS) and yield tensile strength (YTS) were observed 133 MPa, 35 MPa for the unfilled aluminum matrix, whereas 152 MPa and 47 MPA were achieved at 5 wt% Al2O3 nanocomposites which resulted in 14.3 and 34.3% improvement, respectively. The hardness was observed 57 BHN and 72 BHN at 0 wt% and 5 wt% Al2O3 respectively, resulting in an improvement of 26.3%.

Preparation, characterization, and photocatalytic activity of Bi2O3–Al2O3 nanocomposite

In this investigation, Bi2O3–Al2O3 nanocomposite was synthesized by a non aqueous sol–gel route, and the nanocomposite was distinguished using XRD, SEM, EDX, FTIR, Raman and UV–Vis spectroscopy. According to the XRD results, the average crystal sizes of powder was estimated 23 nm. The SEM results show spherical and semispherical nanoparticles with average diameter of 33 nm. The photocatalytic activity of Bi2O3–Al2O3 nanoparticle was evaluated by degradation of methylene blue (MB) and methyl orange (MO) solution under UV irradiation. The important factors in degradation such as photocatalyst dosage, and pH on degradation of MB and MO was investigated. According to the obtained results, Bi2O3–Al2O3 nanocomposite shows higher photocatalytic activities than Al2O3 due to nanoparticles size and the unique structural characteristics. The results of degradation tests illustrate that 90.0% of MB and 60.0% of MO degrades using Bi2O3–Al2O3 nanocomposite under UV light and optimum condition.

Characterization and Formation Mechanism of Ni3Si–Al2O3 Nanocomposite Prepared by Mechanochemical Reduction Method

In this present work, Ni3Si–Al2O3 nanocomposite powders were synthesized by mechanical milling using NiO, Si and Al as raw materials. The phase transformation, formation mechanism and microstructure evolution of the powders during mechanical milling were investigated by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), transition electron microscopy (TEM) and microhardness measurements. Results showed that the Ni3Si, Al2O3 and Ni31Si12 phases formed after 5 h of milling with a rapid mechanically induced self-propagating synthesis mode. The average grain size and internal strain of Ni3Si and Al2O3 after 30 h of milling were (16.8 nm, 1.27%) and (19.6 nm, 0.94%), respectively. The maximum microhardness value of 813 HV was obtained in the 30 h milled powder. The relationship between the hardness and grain size of the powders satisfies the Hall–Petch relationship. Ni3Si–Al2O3 nanocomposite powders are very stable during heating at 950 °C. By annealing of the milled powders leads to grain growth, internal strain and microhardness of Ni3Si powder decrease and transformation of disordered structure to an ordered state. A long-range ordering parameter (LRO) of 0.97 for the ordered Ni3Si can be achieved after annealing at 950 °C for 2 h.

Investigation into microstructural evolutions, mechanical properties and thermal analysis of Al(Zn)/Al2O3 nano-composite fabricated by mechanical milling and SPS method

In this research paper, synthesis and characterization of bulk nanostructured Al(Zn) solid solution and Al(Zn)/Al2O3 nanocomposite were investigated. For this purpose, fully dense Al(Zn) solid solution and Al(Zn)/Al2O3 nanocomposite were produced by spark plasma sintering method. Consolidated samples were characterized by nanoindentation and nanoscratch tests. Differential thermal analysis revealed that the reaction temperature between Al and zinc oxide in the as-blended and as-milled conditions and hence formation of Al(Zn)/Al2O3 is in the range of 600 to 700 °C. Uniform dispersion of alumina nanoparticles in the Al(Zn) matrix increased the hardness and modulus of elasticity of the Al(Zn)/Al2O3 nanocomposite, significantly. In addition, it was found that the plasticity index of Al(Zn)/Al2O3 nanocomposite was lower than that of nanostructured Al(Zn) solid solution while the wear resistance of nanocomposite sample was noticeably larger than that of solid solution sample.

A Self-propagating high-temperature synthesis process for the fabrication of Fe(Cr)–Al2O3 nanocomposite

Self-propagating high-temperature synthesis (SHS) was used to fabricate a Fe(Cr)-Al2O3 nanocomposite. The composite was fabricated by the reactions between the powders of Fe, Fe2O3, Cr2O3, and Al. The effect of blending ratio and mechanical activation of the initial powders and the precursor compressing pressure on the microstructure of the final product was studied by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The significance of the effect of each of the aforementioned parameters on the quality of the composite (assessed by measuring the compressive strength and wear resistance) was determined using a full-factorial design of experiments method. The results showed that the best molar powder ratio that produced the most homogeneous product through a sustainable SHS reaction was Fe:Fe2O3:Cr2O3:Al = 10:1:1:4. A lower Fe content caused the Fe(Cr) phase to melt and separate from the rest of the materials.

Dry Milling of Aluminum and Ceramic Nanoparticles for a Particulate-Injection Casting of Aluminum Matrix Nanocomposites

Nanocomposites of aluminum matrix reinforced with nanomaterials made using conventional casting techniques usually contain an incomplete dispersion of nanoparticles in the matrix. Recently, the use of aluminum powders for the entrance of nanoparticles into the melt by semi-solid particulate-injection casting has been examined to improve the dispersion of nanoparticles. In this study, A356–1 wt% SiC and A356–1 wt% Al2O3 nanocomposites were produced using this mentioned method and the results were compared with the nanocomposites reinforced with the same amount of SiC and Al2O3 nanoparticles but without the addition of aluminum powders. The experimental results indicated that even without having any pre-treatment on the as-received nanoceramics, they will be dispersed to some extent in the matrix owing to semi-solid shear stress introduced via the rotation of the stirrer. However, it was found that the ball milling process with aluminum powders was effective for increasing the number of isolated nanopowders dispersed in the matrix, although some large clusters of nanopowders were detected that counteracted the otherwise potentially useful effects of the increased dispersion of single nanoparticles.

Experimental investigation on mechanical properties of Al 7075/Al2O3/Mg NMMC’s by stir casting method

There is an increasing demand for light-weight, affordable and rapidly processed products as a result of their significant level of superiority these days. In the present research, the effect of mechanical stir casting on 7075 based lightweight aluminium alloy established together with nano-Al2O3 with average particle size (20–30) nanometre and wt.% of (1.0, 2.0,3.0, and 4.0) has been studied. Several scientists exposed that non-consistent distribution of nanoparticles possessing high porosity in the matrix. Electric stir casting could protect against the difficulties encountered with mechanical stir casting. By infusing Al2O3 particulates right into aluminium alloy the aluminium 7075/1% Wt. Al2O3 is giving area to nanocomposite. By including 1%, micro magnesium powder improved the wettability of the reinforcement. Optical microscope, SEM, studies carried out for the evaluation of composites. SEM micrographs reported that the nanoparticles were consistently distributed throughout the matrix and the active grain microstructure studies were preformed. The hardness, tensile strength, and impact results of Al7075/1% Wt. Al2O3 nanocomposites have been improved as compared with the Al7075 base alloy.