Nano-alumina Content Research Articles

Electrochemical behavior and electro-crystallization mechanism of Cu-Ni/Nano-Al2O3 coating with a deposition current density dependence

In this work, preparation of Cu-Ni/Nano-Al2O3 composite coating with (111)-preferred orientation on the surface of the H64 brass via electrodeposition technique. Variation of the deposition current density was found to play a key role in the control of the microstructure and strongly influence the corrosion resistance of the composite coating. Electrochemical impedance spectroscopy results indicated that the increase of nano-alumina content in composite coating is caused by the change of polarization mode. Under different current densities, the Ni (111) plane is only preferred orientation and the relative texture coefficient reaches the highest value of 54.36% at 5 A•dm−2. The crystallite size of these coatings is about 10–55 nm dependent on current density, and high current density could refine the size. The microstructure of the coating changed from cauliflower to spherical with increasing deposition current density. Moreover, the Cu-Ni/Nano-Al2O3 composite coating obtained at 5 A•dm−2 increased the polarization resistance and coating resistance of the H64 brass by about 50% and 83%, respectively. The corrosion potential (Ecorr) of Cu-Ni/Nano-Al2O3 composite coating is shifted towards the nobler direction from − 1.191 V to − 0.063 V(Ag/AgCl) with the current density increases. The corrosion mechanism of Cu-Ni/Nano-Al2O3 composite coating has gone through two stages corresponding to two-time and three-time constant of EEC models, respectively. The Cu-Ni/Nano-Al2O3 has large potential merits in field of corrosion.

Aptness of nano alumina (Al2O3) with high range water reducer-incorporated concrete

PurposeThe purpose of this paper is to study the effect of nano alumina (Al2O3) on the properties of fresh concrete, hardened concrete and microstructure of concrete incorporated with high range water reducer (HRWR). This initiative was taken to improve characteristic properties of concrete using nano alumina because nano alumina can be easily be manufactured from a scrap of industrial aluminum products, so its incorporation in concrete will not only reduce industrial aluminum waste but will also change the morphology of concrete at the microstructural level.Design/methodology/approachTo accomplish the objectives of the research, four different concrete mixes with the constant water–cement ratio (W/C) and superplasticizer (SP) content 0.4 and 0.6% by weight of cement, respectively, were prepared, whereas nano alumina content was altered by 0.3% and 0.4% by weight of cement. Fresh property of concrete was analyzed by using slump cone test, whereas hardened properties of concrete were analyzed through compression test and flexural strength test. The interaction of nano alumina with concrete composite was evaluated using an X-ray diffraction test.FindingsIt was observed that 0.6% superplasticizer by weight of cement increased workability by 22% but with the addition of 0.3%, nano alumina by weight of cement workability decreased by 31%. Compressive strength increased by 4.88% with the addition of 0.6% superplasticizer but with the addition of 0.3% nano alumina by weight of cement compressive strength increased by 18.60%. Also, flexural strength increased by 1.21% with the addition of 0.6% superplasticizer by weight of cement but with the addition of 0.3% nano alumina by weight of cement flexural strength increased by 8.76%. With the addition of superplasticizer, alite and belite phases remained un-hydrated but with the addition of nano alumina alite phase was hydrated while belite phase was un-hydrated. The size of belite crystals in mixes having nano alumina was less than that of mix having 0.6% superplasticizer. Also with the addition of nano alumina, a calcium aluminum silicate phase was formed which was responsible for the increment of strength in mixes having nano alumina.Originality/valueIncorporation nano alumina (Al2O3) in concrete will not only reduce industrial aluminum waste but will also reduce CO2 emission. Nano alumina (Al2O3) also changes morphology of concrete at micro structural level.

Effects of nano-alumina on mechanical properties and wear resistance of WC-8Co cemented carbide by spark plasma sintering

The effects of adding different nano-alumina on the structure, mechanical properties and wear resistance of WC-8Co cemented carbide during spark plasma sintering (SPS sintering) were investigated. The results show that the nano-alumina is dissolved in the Co phase, which results in a larger proportion of FCC-Co in the γ phase on the surface of the WC-Co cemented carbide. Under the scanning electron microscope, it is observed that the grains of cemented carbide are refined, and when the addition amount is 0.5 wt%, the effect of WC grain refinement is the most significan. The hardness, flexural strength and fracture toughness showed a trend of increasing first and then decreasingwith nano-alumina added. The peak value is reached when the nano-alumina content is 0.5 wt%, Which means that the alloy has the best combination of mechanical properties, that is, hardness reaches 1716 HV30, bending strength reaches 2728 MPa, and fracture toughness is 12.95 MPa·m1/2. Adding nano-alumina is beneficial to improve the wear resistance of cemented carbide. As a matter of course, when the content of nano-alumina is 0.5 wt%, the friction coefficient is the lowest, the wear rate is the smallest, and the wear resistance is the best.

The influence mechanism of nano-alumina content in semi-solid ceramic precursor fluid on the forming performance via a light-cured 3D printing method.

The use of three-dimensional (3D) printing technology to form ceramic materials can greatly reduce the technical difficulty and cost of preparing special-shaped ceramic parts. In this work, the formation of the 3D structure of ceramic products was achieved through light-curing 3D printing technology. The semi-solid ceramic precursor fluid prepared from nano alumina particles (Al2O3), photocurable polyurethane acrylate (PUA) and isobornyl methacrylate (IBOMA) resin was used to realize ceramic fluid with self-made light-curing 3D printing equipment. The solidification and forming of the ceramic material was achieved through secondary high temperature sintering. In order to reveal the influence mechanism of nano-alumina content in a ceramic slurry on the forming process and performance of light-curing 3D printing, the composition, micro morphology and mechanical properties of 3D printing ceramic samples under different preparation conditions were investigated. The research results show that the relationship of the ratio of alumina to the forming performance was not a monotonic function in the mathematical sense. When the mass ratio of the resin system and alumina was 1 : 2.50, the performance of the formed sample was the best. At this time, the Vickers strength of the sintered ceramic part was 79 GPa, the bending strength was 340 MPa, and the fracture toughness was 2.90 MPa m−2. This work laid a theoretical and practical foundation for the realization of high-quality, low-cost, and rapid ceramic manufacturing technology in the future.

Behaviour of micro- and nano-alumina-reinforced Mg–3Zn–0.7Zr–1Cu alloy composites processed at different sintering temperatures

This study aims to develop a magnesium-based hybrid composite via a powder metallurgy (PM) technique by simultaneously reinforcing the matrix (Mg–3Zn–0.7Zr–1Cu) alloy with micro-alumina (3.0 wt%) and nano-alumina (0.5 wt% and 1.0 wt%) particulates. The extensive processing involved two different sintering temperatures (400 and 450 °C) followed by hot extrusion and a heat treatment process. The study aimed to add to our understanding of the effects of sintering temperature and alumina content on the physical characteristics of Mg-based composites. It was revealed that increasing sintering temperature improves the density of composites by increasing their diffusion rates. In addition, significant improvements in the hardness, tensile properties and compressive properties of the composites were observed at higher sintering temperatures. It was also discovered that composites with higher alumina concentrations experienced agglomeration and were more porous than other composites. A micro-structural examination showed that composites with higher concentrations of nano-alumina had a finer grain structure than other composites and underwent a marginal reduction in grain size. However, the tensile and compressive properties of composites decreased when the nano-alumina content was increased to 1.0 wt%. The magnesium hybrid composite containing 3.0 wt% micro-alumina and 0.5 wt% nano-alumina sintered at 450 °C displayed the greatest tensile strength properties in all composites studied. A transformation from brittle to mixed-mode failure, with sufficient evidence of increased plastic deformation, was also noted in the hybrid composites. The present study suggests that adding up to 0.5 wt% nano-alumina and employing a higher sintering temperature enhances the overall characteristics of magnesium/alumina micro-composites.

Fabrication and Mechanical Behavior of Aluminum Matrix Composites Reinforced with Nano Alumina Particles

In the present work, nano alumina (Al2O3) reinforced aluminum (Al) matrix composites with various alumina content (0-2.5wt.%) were fabricated by powder metallurgy method. This method occurs of mixing, ultrasonic dispersion, filtering, drying, pressing, and sintering processes. The effects of nano alumina amount on the Vickers hardness, apparent density, compressive strength, and microstructure of nano alumina reinforced aluminum matrix composites were investigated. The maximum apparent density (2.66 g/cm3), Vickers hardness (43±1 HV), and compressive strength (130±3 MPa) were determined at Al-2wt.%Al2O3 composite. After 2wt.% nano alumina content, the agglomeration was detected by a scanning electron microscope (SEM). This agglomeration deteriorated the mechanical properties of nano alumina reinforced aluminum composites.

Effects of nano-alumina content on the formation of interconnected pores in porous purging plug materials

The physical properties and microstructure of porous purging plug materials added with different nano-alumina contents and firing temperatures were investigated by means of X-ray diffraction, scanning electron microscopy, air permeability, pore size distribution, mean pore size, apparent porosity, bulk density, and cold crushing strength (CCS) tests. The results showed that the addition of nano-alumina had a great effect on the physical properties and microstructure of the porous purging plug materials. With increasing nano-alumina content in the composition, the main phase was α-Al2O3 in all compositions and the mean pore size, apparent porosity and air permeability all increased due to the increased number of pores and pore size of the specimens which facilitated the formation of interconnected pores. When the sintering temperature was changed from 1550°C to 1650°C, some of the smaller pores vanished due to solid phase sintering, which reduced the apparent porosity, and some open pores connected to form interconnected pores, which promoted increased air permeability. In addition, the strength and porosity were found to follow the relationship σ = σ0 exp (-b P). When the apparent porosity increased, the CCS decreased, and vice versa.

Improving Impact Strength in FSW of Polymeric Nanocomposites Using Stepwise Tool Design

ABSTRACTIn recent years, many studies have been conducted on process parameters of polymers friction stir welding, while material parameters are still facing serious problems especially in polymeric nanocomposites. In the present study, the impact behavior of friction stir–welded polycarbonate (PC) nanocomposites under different material and process conditions has been investigated using Taguchi approach. A stepwise tool design procedure has been carried out to enhance the welding process. The samples containing various weight percentages of alumina nanoparticles have been welded under different welding process parameters. The analysis of variance results illustrated that nanoalumina content is the most effective parameter on impact strength followed by rotational and transverse speeds. Impact strength of welded samples was conspicuously improved up to 15% by adding 2 wt% of nanoalumina compared with pure PC samples. Also increasing rotational speed and decreasing transverse speed leads to increase of impact strength. In order to optimize the process, signal-to-noise ratio analysis was performed. The results indicated that the optimum levels of input parameters that give the maximum impact strength are as following: 2 wt% of nanoalumina, 2500 rpm of rotational speed, and 8 mm/min of transverse speed which causes 26.14% improvement in impact strength of samples.

Tensile and hardness properties of polycarbonate nanocomposites in the presence of styrene maleic anhydride as compatibilizer

AbstractIn this study, the tensile strength and M‐Rockwell hardness of polycarbonate (PC)‐nanoalumina composites are investigated under various processing parameters. For this purpose, PC using a twin‐screw extruder is melt compounded with nanoparticle of Al2O3 in the presence of styrene‐co‐maleic anhydride (SMA) as the compatibilizer. Influences of weight percentage of nanoalumina and injection processing parameters including injection pressure and holding pressure (all in four levels) are investigated on tensile and hardness properties of nanocomposite samples using Taguchi's L16 orthogonal array. The scanning electron microscopy (SEM) results reveal that an appropriate distribution of nanoparticles in polymeric matrix is achieved. According to the results, nanoalumina content is the most effective parameter on tensile strength and hardness with about 51% and 85% contribution, respectively. Results indicate that by addition 1.5 wt% of nanoalumina, the tensile strength and hardness of samples increase as much as 4.5% and 11%, respectively. Also, the results reveal that injection pressure and holding pressure are also effective parameters to change hardness and tensile strength.

Optimization of molar concentration of AlCl3 salt in the sol–gel synthesis of nanoparticles of gamma alumina and their application in the removal of fluoride of water

Nanoparticles of gamma alumina prepared by sol–gel method, using alcoholic aluminum chloride (AlCl3) precursor has been demonstrated as an effective adsorbent for fluoride removal of water. Increasing the molar concentration of AlCl3 from 0.1 to 0.25 M was found to increase the nanoalumina content in the same ratio with good yield. Different analytical techniques like thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and Brunauer, Emmett and Teller surface area analysis were employed for the characterization of the synthesized nanoparticles whereas batch adsorption studies were performed for the understanding of adsorption kinetics of fluoride in water of neutral pH. Adsorption kinetics has exhibited excellent fluoride removal capability of ~23 mg/g from the nanoparticles derived using up to 0.2 M AlCl3 precursor. Nanoparticles derived from 0.25 M AlCl3 have shown comparatively less fluoride removal (~18 mg/g). Langmuir equilibrium model was found more suitable for describing the fluoride adsorption mechanism. Presence of sulphate, carbonate, nitrate, and chloride anions in water influenced the fluoride removal efficiency noticeably.

Influence of nano-alumina on curing kinetics and corrosion resistance of alumina based ceramic coatings

With thermal chemical reaction, the nano-alumina ceramic coatings were prepared on A3 steel. Influence of nano-alumina on curing kinetics was investigated by differential scanning calorimetry (DSC) analysis and thermogravimetric analysis (TGA). It was found that all samples show the outstanding heat resistance. However the temperature and the enthalpy of curing decreased with the increase in a nano-alumina content. A model was established to explain the decrease. The physical combination and the decrease in activation energy are the major reason for the decrease. Also electrochemical tests were conducted to investigate the corrosion behavior of the nano-alumina coatings. Corrosion current densities (icorr) decreased with the increase in the nano-alumina content. This indicated that nano-alumina improved the corrosion resistance of the ceramic coatings. Because the uniformity of ceramic coatings is improved due to the fact that nano-alumina particles fill the pores and spaces of coatings, and nano-alumina particles provide the high physical combination between particles.

Physical and thermo-mechanical characterizations of resin-based dental composite reinforced with silane-modified nanoalumina filler particle

The aim of this study was to analyze the effect of adding different weight percentages of nanoalumina particles on mechanical properties of resin-based dental composite materials. The composite specimens were prepared by dispersion of different percentage weight fractions (0 wt%, 1 wt%, 2 wt% and 3 wt%) of silane-modified nanoalumina filler in a monomer system containing 50% bisphenol-A glycidyl methacrylate, 49% tri-ethylene glycol dimethacrylate, 0.2% Camphorquinone and 0.8% Ethyl 4-dimethylaminobenzoate. The filler particle before and after silane treatment was characterized using Fourier-transform infrared spectroscopy and transmission electron microscopy. The presence of C = O bond and Si–O–Si linkage between the monomer and filler was clearly indicated. Mechanical behavior of the light-cured samples was evaluated using compressive strength test, three-point flexural strength test, Vicker Micro hardness tests, dynamic mechanical analysis and simultaneous thermal analysis. The results indicated a more than 16% increase in the compressive strength in the samples containing nanoalumina filler particles. Vickers hardness of composite was increased by approximately 28% with respect to unfilled composite. The flexural modulus of composite mixed with alumina nanoparticles was increased from 1.7 to 5.1 GPa, while the values of composite were slightly decreased from 84.5 to 59.5 MPa. The dynamic mechanical analysis result revealed that the glass transition temperature was found to be increased by 30 ℃ compared to unfilled composite. It was also found that the 1 wt% nanoalumina content recorded the highest value of storage modulus. The weight loss profile and thermal stability from thermogravimetric analysis results revealed that the composite filled with 2 wt% nanoalumina content exhibited maximum thermal stability.

Wear Behavior and Micro-structural Study of Al/Al2O3Nano-composites Before and After Heat Treatment

In this study; an advanced ultrasonic assisted stir casting technique has been adopted to incorporate nano-sized Al2O3particle into aluminum alloy 6061 to form particulate nano composite material. Dry sliding wear testing of Aluminum matrix nano composites were performed before and after heat treatment using a pin-on-disc tribometer. The content of Al2O3 nano particles in the composite was varied from 0 to 3.0 weight% and the effect of parameters on wear rate were studied. The sliding wear test is conducted for different loads, speeds and weight % of nano Al2O3particles. The results have shown that wear rate of composite reduces with increasing the nano alumina content. For the same working conditions and processing parameter, wear rate increases with increase in load and with increase in speed. Also, a significant improvement in wear resistance was observed in the heat treated Al-Al2O3 nano-composite as compared un-heat treated composite samples.

Material Characterization and Microwave Substrate Applications of Alumina‐Filled Butyl Rubber Composites

Composites of butyl rubber with micron alumina (BRAL) and nanoalumina (BRnAL) have been prepared by sigma mixing. The stress‐strain curves of both BRAL and BRnAL composites show the mechanical flexibility of the composites. The dielectric and thermal properties of both composites were studied as a function of ceramic loading. For 0.1 volume fraction of micron alumina loading, the composites have attained a relative permittivity (εr) of 2.82 and loss tangent (tanδ) of 0.0023 at 5 GHz, and for the same volume fraction of nanoalumina content, the composite showed εr of 3.15 and tanδ of 0.014 at 5 GHz.

Phase transformation, microstructural and mechanical properties of hydroxyapatite/alumina nanocomposite scaffolds produced by freeze casting

Abstract Freeze casting is an effective fabrication technique that allows producing scaffolds with variable porosity, pore size, pore orientation and compressive strength. To our knowledge, the present study is the first investigation on the replacement effects of microparticles with nanoparticles in bone scaffolds prepared through the freeze casting method. In this study, the effect of nano-alumina content on phase transformation, microstructural and mechanical properties of hydroxyapatite/nano-alumina (HA/nAl 2 O 3 ) nanocomposite scaffolds, fabricated through the freeze casting method at different cooling rates, has been investigated. In the first stage, slurries with 15 vol% solid loading and different nano-alumina content were prepared. In the next stage, cooling rates of 1 and 4 K/min were applied to synthesize the porous scaffolds, followed by sintering at 1250 and 1350 °C. The characteristics of the initial powders, and phase composition, microstructure, pore size, pore distribution and mechanical strength of the scaffolds were assessed. The porosity of the synthesized scaffolds was in a range of 78–85%, and the compressive strength varied from 0.2 to 4 MPa as a function of nAl 2 O 3 concentration, cooling rate, and sintering temperature. Surprisingly, further addition of nAl 2 O 3 not only affected the microstructural features, but also provided mechanisms to improve the mechanical strength of the scaffolds.

Fabrication and Mechanical Properties of Nano-Al<sub>2</sub>O<sub>3</sub> Based Composite Ceramic Tool Material

The Al2O3(nm)/SiC（μm）/Al2O3（μm）ceramic tool materials were fabricated by the hot-pressing technique. Effect of the compositions on microstructure and mechanical properties is investigated. With nano-particles content decreasing, the flexural strength increased and fine grains can be obtained. When the nano-alumina content is 60wt%, the grain of this sample is fine, the Vickers hardness and flexural strength are 16.24 GPa and 678 MPa, respectively.

Properties of Al 2O 3 nano-particle reinforced copper matrix composite coatings prepared by pulse and direct current electroplating

Cu–Al 2O 3 nano-composite coatings have high potential for use in applications in which high mechanical properties together with high corrosion resistance are required. In the present study it is intended to produce copper nano-alumina composite coatings with various nano-alumina contents in order to investigate the effect of alumina reinforcement particles on corrosion resistance and mechanical properties such as hardness and wear resistance. The composite coatings were deposited using direct current (DC) and pulse current (PC) plating. The microstructures of the coatings produced from both methods were examined via scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The wear behaviors, micro hardness, coating thickness, corrosion rate and coating porosity were examined using appropriate methods. Compared to DC deposition, PC plating facilitated higher amounts of particle incorporation with more uniform distribution. The results indicated that the mechanical properties of the applied coatings with incorporated nano-alumina reinforcement were far more superior as compared to its own matrix as well as non-composite copper coatings. It was also found out that increasing the amount of nano-alumina content in the coating, led to enhanced general properties of the coatings.

Microstructure and phase evolution of alumina–spinel self-flowing refractory castables containing nano-alumina particles

The microstructure and phase composition of alumina–spinel self-flowing refractory castables added with nano-alumina particles at different temperatures are investigated. The physical and mechanical properties of these refractory castables are studied. The results show that the addition of nano-alumina has a great effect on the physical and mechanical properties of these refractory castables. With the increase of nano-alumina content in the castable composition, the mechanical strength is considerably increased at various temperatures. It is shown that nano-alumina particles can affect formed phases after firing. The platy crystals of CA6 are detected inside the grain boundaries of tabular alumina and spinel grains in samples fired at 1500°C. CA6 phase can be formed at lower temperatures (1300°C) with the addition of nano-alumina particles. As a result of using nanometer-sized alumina particles with high surface area, the solid phase sintering of the nano-sized particles and CA6 formation can occur at lower temperatures.

The Dielectric Response of Polar and Non-Polar Nanodielectrics

In order to understand the relationship between the dielectric properties and the structure of polymer nanocomposites, especially the role of the interface on dielectric response, two polymers with different polarity were used to form nanocomposites with nanoalumina powder, a typical polar inorganic compound. Consequently, two kinds of nanodielectrics with very different interfaces were produced. In the epoxy nanodielectric, broad band dielectric spectroscopic measurements show that no difference is found between the unfilled resin and the nanocomposite under dry conditions. However, their dielectric responses are very different when they contain about 0.4 % b.w. absorbed water, a concentration that occurs under ambient exposure conditions. The findings suggest that the sites for absorbed water in the epoxy nanocomposites are very different to those in the unfilled thermoset and relate to the large interfacial internal surface in these materials. In this case all the relaxation processes can be well described by the Havriliak-Negami function, which give useful information on the dynamics and activation energies associated with the relaxation processes. In polyethylene nanocomposites, dielectric measurements show that the incorporation of nanoalumina produces a dielectric loss peak in the low frequency. This relaxation peak moves to high frequency with increasing nanoalumina content and the peak becomes broader. In the presence of 0.06 % b.w. absorbed water this peak also shows the same type of unusual dielectric loss behavior as that observed in the undried epoxy nanodielectrics. This behavior is thought to arise from the interplay between interfacial water mobility and bonding rather than the host polymer.

Electrodeposition of Zn–Ni–Al 2O 3 nanocomposite coatings under ultrasound conditions

The Zn–Ni–Al 2O 3 nanocomposite coatings with high nano-alumina content and uniformly dispersed nano-alumina particles were fabricated using eletrodeposition technique with the aid of ultrasound. The properties of nanocomposite coatings were investigated by SEM, electrochemical technique, and Vickers hardness tester. The results demonstrate the anticorrosion properties and the hardness of Zn–Ni–Al 2O 3 composite coatings fabricated under the ultrasonic vibration were improved significantly as compared to the Zn–Ni alloy. The properties were not only related to the nano-alumina content in the composite coating, but also related to the dispersion and combination state of nano-alumina particles in the matrix.