Al2O3 Hybrid Research Articles

Performance of R134a vapour compression refrigeration system by using Gr and Al2o3 hybrid nano lubricants

Nowadays, in many developing countries like India they are facing the shortage of energy. The Refrigeration system has become the major consumer of energy for many industrial as well as household applications. So, it is the need to enhance the energy efficiency of the refrigeration systems. Performance of the refrigeration system can be improved either by increasing the rate of heat absorption in evaporator or by reducing the compressor power. Use of efficient lubricant oil can help to remove the heat generated in the compression process which leads to less power consumption. Development in Nanotechnology makes it possible to develop a new class of lubricant called nanolubricant, in which nanoparticles are added in base lubricant oil to enhance the thermal properties. The two step technique with ultrasonic agitation force is used tosynthesise stable nanolubricant. The present study investigates the performance of an R-134a refrigerant vapour compression refrigeration system using nanolubricant with different volume concentrations (0.05%, 0.075%, 0.1% and 0.2%) of Graphene/Aluminium nanoparticles to mineral oil (MO) experimentally. The result shows maximum enhancement in COP approximately as 85% for 0.075 % volume fraction Nano lubricant as compared to base fluid. Use of nanolubricant saves approximately 27% compressor power.

Mechanical and tribological properties of high entropy carbide-based micro-nano ceramic composites

(NbTaTiWZr)C-based micro-nano composites were fabricated by spark plasma sintering employing multi-layer graphene (MLG), Ni, and Al2O3 as reinforcements. It is demonstrated that excellent mechanical properties were achieved for MLG, Ni, and Al2O3 hybrid addition with a hardness of 21.73 GPa, a flexural strength of 572.4 MPa, and a fracture toughness of 7.65 MPa m1/2. Enhanced densification together with inhibited grain growth contributed to the simultaneously improved hardness and flexural strength. The major toughening mechanisms were determined as microcracks, crack deflection, crack bridging, crack stopping, MLG wall, MLG pull-out, MLG bending, and MLG wrapping grains. Furthermore, outstanding tribological performance occurred to the (High entropy ceramic) HEC-Ni-Al2O3-MLG with a friction coefficient of 0.23 and wear rate of 4.32 × 10−7mm3N−1m−1, as a function of graphene acting as a lubricating friction layer and the enhanced mechanical responses.

Atomic Layer Deposition of γ‐Al2O3 on Hexagonal Boron Nitride: A Hybrid Support for Metallocene Catalysts

AbstractHexagonal boron nitride (hBN), also known as white graphene, has recently gained larger attention due to its unique physical and chemical properties. Owing to its excellent thermal conductivity and stability, hBN has been reported as an effective filler in many polymers. This study explores the potential of hBN as a catalyst support and filler for olefin polymerization. We report the atomic layer deposition (ALD) of γ‐Al2O3 on hydroxyl‐functionalized hBN. The alumina precursor, methylaluminoxane, showed high selectivity, depositing Al species only on the B‐OH sites, while B−O‐O−B sites remained unreacted. The hBN/γ‐Al2O3 hybrid was characterized by Fourier transform infrared (FTIR) spectroscopy, X‐Ray diffraction and transmission electron microscopy (TEM). The deposition of the aluminum over the hBN sheets was confirmed. The hBN/γ‐Al2O3 was used as a support for metallocene catalysts. The supported catalyst complex was highly active and produced ethylene‐propylene polymers with molecular weights up to 10 times higher, as demonstrated by gel permeation chromatography (GPC)

Investigating run-in and steady-state wear mechanisms of Al-7075 alloy hybrid composite for brake rotor applications

An effective way for creating superior-grade metal matrix composites (MMCs) using Al composites is the stir-casting technique. Stir-casting stands out among the array of available methods, being a frequently adopted technique. This study focuses on producing Al7075/B4C + Al2O3 hybrid MMCs by incorporating different weight proportions of Al2O3 (3–12%) while maintaining a consistent weight proportion of B4C (6%). The microstructural analysis demonstrates that the B4C/Al2O3 particles are evenly dispersed throughout the Al matrix. A complete investigation was carried out to evaluate the Run in and steady state wear mechanism and hardness throughout distinct phases. Notably, when contrasted with the interface and matrix phases, the particle phase (Top phase) of the hybrid composites achieves the highest hardness. The wear rate and coefficient of friction of the composites were both decreased by the addition of B4C/Al2O3 particles. The composites reinforced with B4C/Al2O3 showed the greatest decreases in wear rate and coefficient of friction. A comparison of the wear characteristics of the created composite and the conventional brake drum material, namely cast iron, was also done with regard to industrial sustainability. It was discovered that the wear rate of B4C/Al2O3-reinforced composites was comparable to that of automotive industry-used cast iron brake drums. According to SEM data, abrasive wear at lower stresses and adhesive wear at higher loads mostly helped in material removal.

Enhancing mechanical and corrosion properties of GO and Al2O3 reinforced Cu composite coatings

Despite their significant functions and properties, the performance characteristics of Al2O3 ceramic particles and graphene oxide (GO) within hybrid copper composite coatings have been seldom investigated. This study successfully fabricated a Cu-GO- Al2O3 composite coating featuring fine particulate spherical network-like structures on St37 low carbon steel using an ultrasonic-electroless coating method. The effects of Al2O3-decorated graphene oxide hybrid reinforcement on the texture and nanomechanical properties of the copper matrix were examined. The tribological performance of the Cu-GO- Al2O3 composite coating under dry sliding conditions was evaluated, and the wear mechanism was investigated in detail. Results demonstrate that the Cu-GO- Al2O3 composite coating effectively reduces the wear rate and friction of the GO/ Al2O3 hybrid reinforced composite coating. Potentiodynamic polarization tests indicated that the Cu-GO- Al2O3 composite coating exhibits higher corrosion resistance compared to the copper matrix. The enhanced mechanical, tribological, and corrosion properties of the Cu-GO- Al2O3 composite coating are primarily attributed to: (i) the fine particulate spherical network-like structure; (ii) the synergistic effect of the GO and ceramic particle hybrid with a decorated structure; (iii) the formation of graphene oxide/ Al2O3 nanorolls in tribofilms and the excellent self-lubrication properties of graphene oxide. The Cu-GO- Al2O3 composite coating significantly improves the frictional and electrochemical properties of the copper matrix, offering new perspectives for next-generation electrical contacts and nanoelectromechanical systems.

MHD radiating flow in a hybrid solution of C2H6O2–H2O to disperse Ag–Al2O3 hybrid nanoparticles taking into account the effects of nanoparticle shapes

MHD radiating flow in a hybrid solution of C2H6O2–H2O to disperse Ag–Al2O3 hybrid nanoparticles taking into account the effects of nanoparticle shapes

Characterization, optimization, and performance evaluation of PCM with Al2O3 and ZnO hybrid nanoparticles for photovoltaic thermal energy storage

The electrical efficiency of the photovoltaic (PV) panel is affected significantly with increased cell temperature. Among various approaches, the use of Phase Change Materials (PCMs) with nanoparticles is currently one of the most effective for reducing and managing the temperature of PV panels. In this study, paraffin wax as PCM with different loading levels (0.5 %, 1 %, and 2 %) of hybrid nanoparticles Al2O3 and ZnO were successfully synthesized and their effects on the performance of the Photovoltaic-Thermal (PVT) system were investigated experimentally. Additionally, a prediction model was developed to analyze the interaction between the operating factors (independent variable) and response factors (dependent variable) of the PVT/PCM and PVT with Hybrid nano-PCM (PVT/HNPCM) systems based on response surface methodology (RSM). Experimental results showed that compared to only PCM, the thermal conductivity of HNPCM increased by 24.68 %, 28.57 %, and 41.56 % for the inclusion of 0.5 %, 1 %, and 2 % hybrid nanomaterial respectively. The electrical efficiency of the PVT/HNPCM, and PVT/PCM system enhanced by 31.46 % and 28.70 % respectively compared to the conventional PV system in this study. With a cooling-water mass flow rate of 0.0021 kg/s, the highest thermal efficiency of 47 % was achieved for the PVT/PCM system, whereas 51.28 % was achieved for the PVT/HNPCM system. The analysis of the variance test yielded a P value <0.0001 which is less than 0.05 for the model of overall efficiency for PVT/PCM and PVT/HNPCM system, indicating the suggested model's appropriateness and statistical significance. These optimal conditions are observed when the solar intensity ranges from 774 W/m2 to 809 W/m2 and the mass flow rate is 0.002 kg/s for both the PVT/PCM and PVT/HNPCM systems. However, these systems advance sustainable urban development and climate goals by combining PV panels' electrical generation with thermal energy harvesting, boosting overall energy efficiency in the built environment.

Experimental optimization of the performance of a plate heat exchanger with Graphene oxide/water and Al₂O₃/water nanofluids

The heating and cooling process is a major industrial challenge. The efforts to improve the design of heat transfer improvement mainly center around expanding the heat transfer area (through the geometry of the heat exchanger) and inducing turbulence to eliminate the boundary layer. A solution to increase the thermal efficiency of the heat exchanger and reduce costs is the use of materials such as nanofluids with ideal thermal and thermophysical properties. Here, to enhance the effectiveness of nanofluids and prevent sedimentation, atomic stabilization was the main focus by combining surfactants with nanofluids at specific weight concentrations and applying ultrasonic vibrations to increase stability. In this paper, the influence of using Graphene oxide (GO)/water and AL2O3/waternanofluids and the GO–AL2O3 /water hybrid nanofluid was investigated at 0.01 %, 0.02 %, 0.03 % wt concentrations. The effect on heat transfer and thermal efficiency of a plate heat exchanger relative to the base fluid (water) was examined. The nanofluids were stabilized in several stages to optimize the thermodynamic properties of the base fluid. The thermal efficiency of the nanofluids (η) reaches to its maximum at the highest weight concentration (0.03 %) with GO nanoparticles at 37 %, AL2O3 at 21 %, and the GO–AL2O3 hybrid at 26 %. GO nanoparticles had the most significant impact on the heat exchanger performance, with an optimized heat exchanger performance of 15.94 %, followed by the hybrid at 11.86 %, and AL2O3 at 7.4 %.

Enhancing wear and corrosion resistance of TiO2–Al2O3 hybrid coatings by the development of TiO2–Al2O3 bilayer film coatings

Sol-gel fabricated TiO2–Al2O3 bilayer coatings were deposited on 316L surfaces with several combinations of layers. Microstructural, corrosion, and wear features of the fabricated film coatings were examined compared to the TiO2–Al2O3 hybrid coating containing 65 % TiO2, which achieved the highest protection against corrosion and wear in the previous study. The electrochemical properties were determined through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests, whereas dry sliding tests were performed using an Al2O3 ball under 1 N. Regardless of the production parameters, rutile and α-Al2O3 phases were produced in all manufactured coatings with similar thicknesses. The coatings consisting of TiO2 at the top layers showed better anti-corrosive performance due to a dense, low-porosity, and continuous morphology of TiO2 nanoparticles, while the coatings containing Al2O3 at their top layers were determined to exhibit higher wear resistance. All bilayer film coatings increased the anti-corrosion and anti-wear performance of the hybrid coating.

A Comprehensive Study on the Optimization of Drilling Performance in Hybrid Nano-Composites and Neat CFRP Composites Using Statistical and Machine Learning Approaches

Carbon fiber-reinforced polymer (CFRP) composites have gradually replaced metals due to their exceptional strength-to-weight ratio compared to metallic materials. However, the drilling process often reveals various defects, such as surface roughness, influenced by different drilling parameters. This study explores the drilling quality of uni-directional CFRP composites, as well as hybrid Al2O3 alumina and hybrid SiC silicon carbide nano-composites, through experimental exploration using step, core, and twist drills. Response surface methodology (RSM) and statistical tools, including main effect plots, ANOVA, contour plots, and optimization techniques, were used to analyze the surface roughness of the hole. Optimization plots were drawn for optimal conditions, suggesting a spindle speed of 1500 rpm, feed of 0.01 mm/rev, and a 4 mm drill diameter for achieving minimum surface roughness. Furthermore, two machine learning models, artificial neural network (ANN) and random forest (RF), were used for predictive analysis. The findings revealed the robust predictive capabilities of both models, with RF demonstrating superior performance over ANN and RSM. Through visual comparisons and error analyses, more insights were gained into model accuracy and potential avenues for improvement.

Optimization of drilling parameters on delamination and burr formation in drilling of neat CFRP and hybrid CFRP nano-composites

Carbon fibre-reinforced polymer (CFRP) composites have exceptional mechanical advantages such as high specific strength and stiffness, lightweight, and high damping capacity, making them very attractive for aircraft, aerospace, automotive, marine, and sporting applications. However, various defects such as delamination, burr formation, and surface roughness are observed during the drilling of CFRP composites, which are influenced by various drilling process parameters. In this work, the drilling quality of uni-directional CFRP composites. and the hybrid Al2O3 and hybrid SiC nano-composites are investigated experimentally using different types of drills such as step drill, core drill, and twist drill, as there is a limited study done on the comparative analysis of the impact of the above drills on the delamination factor and burr area on the above CFRP and hybrid nano-composites. The design of the experiment table was developed using response surface methodology (RSM) for input process parameters of spindle speed, feed, drill diameter, and drill type. The output surface characteristics (delamination factor and burr area) of the hole were measured quantitatively using the stereo zoom optical microscope. The main effect plots, contour plots, and analysis of variance (ANOVA) were used to examine the effect of spindle speed, feed, drill diameter, and drill type on exit delamination and burr formation. The analysis of main effect plots, contour plots, and analysis of variance showcased the optimum process parameters, such as a high spindle speed of 5500 rpm, low feed of 0.01 mm/rev, and drill diameter of 4 mm. The step drill demonstrated the least damage mechanism among drill geometries, followed by the twist and core drills. The minimum drilling damage was observed for the Al2O3 hybrid nano-composite compared to the neat CFRP composites.

Significance of Inclined MHD on Hybrid Nanoliquid Flow in an Annulus Using Modified Buongiorno Model in the Presence of Two Different Heat Sources: Response Surface Methodology

In this modern fluid field technology, hybrid nanoliquid are of great interest to researchers because of their thermal properties which provide superior heat transfer improvements compared to nanoliquid. Thus, in this study, the heat and mass transport characteristics in a horizontal annular duct filled with the water-based Cu–Al2O3 hybrid nanoliquid is analyzed using the modified Buongiorno model (two-phase model). The two different heat sources namely, temperature-related heat source (THS) and exponential space-related heat source (ESHS) are analyzed in thermal analysis. An inclined magnetism and viscous dissipation aspects are also taken into account. The correlation for effective thermal conductivity and viscosity are modeled by utilizing the experimental work of Corcione. The coupled nonlinear equations were solved numerically using the finite difference method. Further, the heat transport rate is optimized using the response surface methodology (RSM). The significance of effective parameters on the flow structure, thermal pattern, concentration field, heat and mass transport rate are visualized through two-dimensional (2D) and three-dimensional (3D) surface plots. It is noticed that the chaotic motion of nanoparticles advances the thickness of the thermal and solutal boundaries. The velocity field has an inverse association with the applied magnetic field and its angle of inclination. The consequence of the Reynolds number is favorable for the velocity and temperature fields. The heat transport is more dominated by the Reynolds number compared to the chaotic motion of nanoparticles and thermophoretic aspect. Furthermore, the sensitivity of the Nusselt number to the Reynolds number, chaotic motion of nanoparticles and thermophoretic aspect are always negative.

Hybrid composite with WC/Y–TZP–Al2O3 ceramic matrix and dispersed Hadfield steel particles

Low-temperature and short-time sinter-forging has been used to obtain a dense WC/Y–TZP–Al2O3 hybrid ceramic–matrix composite with dispersed Hadfield steel with high fracture toughness. The hardness and К1С fracture toughness were 13.7 ± 0.3 GPa and 7.4 ± 0.4 MPa m1/2, respectively. The composite contained phases such as Y–TZP–Al2O3 eutectics and hypereutectic grains, WC agglomerates, γ-Fe particles as well as small amounts of Al2(WO4)3 and MnFe2O4. No t-ZrO2→m-ZrO2 transformational toughening occurred during mechanical loading so that enhanced fracture toughness resulted from forming a dense microstructures with ductile metallic interlayers between ceramic and tungsten carbide grains.

Aerosol metal-organic framework-derived Ni–Zn–Al hybrid catalyst for efficient methane Bi-reforming

Bi-reforming of methane (BRM) has emerged as a promising advancement in hydrogen production via direct carbon utilization. To promote BRM, metal-organic framework (MOF)-derived Ni–ZnO–Al2O3 hybrid catalyst was developed via aerosol-assisted approach. The results demonstrated that the incorporation of Al2O3 nanoparticle cluster and ZnO with Ni alloy enhanced the catalytic activity. Superior conversions of reactants and operation stability of the MOF-derived Ni–ZnO–Al2O3 hybrid catalyst was observed, and a high turnover frequency (TOFCH4) of 2.86 s−1 at a moderate operating temperature (650 °C) was achieved. Further, the H2/CO ratio of 1.4–6.5 was attained through the proper adjustment of feed ratios (H2O/CH4, CO2/CH4) and reaction temperature (600–700 °C). Overall, the newly fabricated MOF-derived Ni–ZnO–Al2O3 hybrid catalyst via aerosol-assisted method, demonstrated significant improvements in reducing the required operating temperature of BRM, which is beneficial for simultaneous reduction of the CO2 generated from the methane reforming plus energy consumption, and advancing the development of low-carbon H2 production.

Controlled doping rates of graphene oxide in aluminum for high electrical performance and oxygen reduction reaction

The brush coating method allows the advantage of being able to produce thin films simply and quickly. This study introduces a method for thin-film production by brushing a solution containing graphene doped in Al2O3 using the sol–gel method. Graphene oxide (GO) is suitable for semiconductors with bandgap values of about 1.7 eV at room temperature, and the characteristics of the thin films were analyzed according to the doping ratio. First, X-ray photoelectron spectroscopy measurements were obtained to analyze the chemical composition of the thin-film surface. Since graphene is a carbon isomer, the characteristic of oxygen vacancies was confirmed by the increasing C–C bond intensity with increasing GO doping concentration. In addition, Raman analysis was performed to analyze the concentration of molecular groups of compounds for defects in graphene. Thereafter, through atomic force microscopy measurements, as the graphene doping ratio increased, the average roughness increased from 1.785 to 33.67, the residual DC voltage also increased by about 48.42 %, and the polar anchoring energy also increased by about 16.33 %. In addition, response-time–transmittance measurements were performed to measure the electro-optical properties of the thin film, and excellent Vth and stable response speed were obtained. Additionally, the validity of the results was supported through bandgap analysis. Finally, the degree of alignment of liquid–crystal molecules on the film surface was confirmed by polarized optical microscopy and pretilt angle measurements, and the suitability of the thin film for display devices was shown via transmittance measurements. As a result, GO:Al2O3 hybrid thin film is an excellent candidate for use as an alignment film for solar energy, secondary batteries, and next-generation liquid crystal displays.

Thermal efficiency and hydraulic performance evaluation on Ag–Al2O3 and SiC–Al2O3 hybrid nanofluid for circular jet impingement

Thermal efficiency and hydraulic performance evaluation on Ag–Al2O3 and SiC–Al2O3 hybrid nanofluid for circular jet impingement

Thermally stratified Cu–Al2O3/water hybrid nanofluid flow with the impact of an inclined magnetic field, viscous dissipation and heat source/sink across a vertically stretching cylinder

AbstractA numerical study of the thermally stratified flow of H2O based Cu − Al2O3 hybrid nanofluid over a linearly stretching cylinder placed vertically in a porous media has been performed. The influences of viscous dissipation, thermal source/sink, and an inclined magnetic field were also considered. Using appropriate similarity transformations, the non‐linear mathematical equations of the flow model are translated into a dimensionless form. The in‐build finite difference Matlab code Bvp4c is used to attain the numerical solution of the transformed non‐linear ordinary differential equations (ODEs). Influences of nanoparticles when added to the water and also the flow parameters’ impacts on the flow rate and thermal transport rate are shown in graphs and tables. The results showed that the absolute value of the shear stress of the hybrid nanofluids was enhanced by up to 33% compared to the considered nanofluid. The study also revealed that the heat transport rate in the convective flow region was much higher in hybrid nanofluid as compared to nanofluid. For Cu − Al2O3/water hybrid nanofluid, the temperature went negative for high thermal stratification. The present study has important implications for the design and optimization of heat transfer devices that use thermally stratified hybrid nanofluids. The results also provide novel insights into the flow behavior of these fluids, that can be used to improve our understanding of their physical properties.

Selective Synthesis of a Gasoline Fraction from CO and H2 on a Co-SiO2/ZSM-5/Al2O3 Catalyst

This article reports on a simple method for producing high-octane gasoline from CO and H2 on a Co-Al2O3/SiO2/HZSM-5/Al2O3 hybrid catalyst. In the selected pressure range (0.5, 1.0, and 2.0 MPa), it was found that a decrease in pressure and an increase in temperature contribute to an increase in the content of branched hydrocarbons. The optimal technological parameters of the process were determined to ensure high selectivity and productivity for C5–C10 hydrocarbons: pressure—1.0 MPa, ratio H2/CO = 2, gas space velocity—1000 h−1, temperature—250 °C. The selectivity for the gasoline fraction is 65.2%, and the ratio of branched to linear hydrocarbons (iso/n index) is 2.3. Under the specified technological conditions, an experimental batch of gasoline fraction (1000 cm3) was produced at the pilot plant during 400 h of continuous operation. The main physicochemical and operational parameters of the experimental gasoline fraction of hydrocarbons have been determined. The octane number determined by the research method according to GOST R 52947-2019 is 78.5 units.

Natural Convection in Trapezoidal Cavity containing Hybrid Nanofluid

In this paper, a numerical study of natural convection in a trapezoidal cavity with left heated wall, right cold wall and filled with Cu – Al2 O3 and water hybrid nanofluid. The remaining walls of the cavity are kept at adiabatic. An enhancement in heat transfer is observed with the increase of three different parameters. Based upon the numerical predictions, the effect of Rayleigh number, inclination of the slopping wall, solid volume fraction of nanoparticles on flow and patterns as well tested. We found that acute slopping wall, high Rayleigh number and Cu – Al2 O3 nanoparticles with high concentration are effective to enhance the rate of heat transfer. We also developed a new correlation for the average Nusselt number as a function of the angle, effective thermal conductivity and viscosity as well as Rayleigh number.

Numerical modeling and multi-objective optimization of direct absorption solar collectors using mono and hybrid nanofluids

Over the years, the development of nanofluids has created new possibilities for research in the field of renewable energy. There has been rapid progress in the study of the optical characteristics of nanofluids for their potential use in Direct Absorption Solar Collectors (DASCs). Nanofluids may significantly improve photothermal conversion because of their enhanced optical properties. This study introduces a numerical model aimed at assessing the performance of DASC using mono and hybrid nanofluids. The model achieves this goal by solving the coupled radiation transfer equations in a participating medium together with the thermal energy equations. The realistic incident solar spectrum and effective optical properties of copper and alumina nanoparticles are also considered. The mathematical model is validated with experimental results from the literature. A parametric study is then carried out to study the sensitivity of the DASC performance on some design and operation parameters, such as the aspect ratio, heat transfer coefficient, and incident angle. The influence of copper and alumina nanoparticles on the DASC efficiency is also studied and compared. Due to their optical characteristics, it is established that the useful gain in copper-based nanofluid is much higher than in alumina-based nanofluid. Moreover, the use of Cu–Al2O3 hybrid nanofluid is studied at different combinations of volume fractions to understand the techno-economic impact on the DASC technology. The use of response surface methodology allows studying how modifications in the concentration of individual nanoparticles used in DASC can influence both its cost and performance. A multi-objective optimization is then performed at various loadings of the nanoparticles to maximize the DASC efficiency and minimize the total cost of the working fluid. Finally, Pareto front solutions are obtained as a guide for selecting the optimum combinations of nanoparticles that optimize the cost and performance of the DASC.