Addition Of Al2O3 Nanoparticles Research Articles

Influence of Al2O3 Nanoparticles on the Morphology and Growth Kinetics of Cu-Sn Intermetallic Compounds in Sn-Ag-Zn/Cu Solder Joints

Intermetallic compounds (IMCs) growth can simultaneously bring about low-resistance electrical pathways and drastically reduce joint lifetime. Recently, incorporated trace nanoparticles into the free-Pb solder were found to promote the performance of the solder joints. Sn3Ag0.9Zn (SAZ) nano-composite solders were developed by doping 0.5 wt.% Al2O3 nanoparticles into the SAZ solder. The IMCs formation and growth behavior at the interfacial reactions between the SAZ-0.5Al2O3 nano-composite solder and the Cu substrate during soldering at temperatures ranging from 250 to 325 °C for 30 min were investigated. The results showed that after the addition of Al2O3 nanoparticles into the SAZ solder, the elongated-type IMCs layer changed into a prism-type IMCs layer, and Ag3Sn nanoparticles were absorbed on the grain surface of the interfacial Cu6Sn5 phase, effectively suppressing the growth of the IMCs layers. The activation energies (Q) for the IMCs layers (Cu6Sn5 + Cu3Sn) were determined to be 36.4 and 39.1 kJ/mol for the SAZ/Cu and SAZ-Al2O3/Cu solders, respectively.

Thermal performance evaluation of the parabolic trough solar collector using nanofluids: A case study in the desert of Algeria

The use of Parabolic Trough Solar Collector (PTSC) is currently the best option for widespread application in industries operating at temperatures from 60 to 400 °C. Numerous studies have been conducted to enhance the thermal performance of the PTSC using synthetic oils as heat transfer fluids. In this study, the thermal performance of parabolic collectors was enhanced using Metallic Oxide Nanofluids (CuO, SiO2, Al2O3, TiO2) based on Therminol VP-1™ at 4 % volumetric concentration as heat-transmitting fluids. A thermal model was developed and validated through experimental and theoretical study, while the results showed good compatibility in the outlet temperature with an error rate of 0.184 % for experimental and 0.29 % for theoretical studies. Moreover, various theoretical models of the thermal properties of nanofluids were analyzed to determine the model that matches and simulates this study. The findings indicated that nanofluids enhanced the thermal efficiency of the PTSC system compared to pure Therminol VP-1™. Specifically, CuO/Therminol VP-1™ demonstrated the most significant improvement, increasing thermal efficiency by 1.03 %. Furthermore, the results also showed that the addition of CuO, TiO2, Al2O3, and SiO2 nanoparticles led to an increase in outlet temperature by 9.57 %, 6.04 %, 5.21 %, and 3.08 %, respectively.

On the effect of nanoparticles in different PCM configurations in the thermal performance of a packed bed energy storage system

When it comes to storing energy and releasing it when needed, packed bed storage systems are considered to be one of the most efficient systems available. This paper studies the thermal performance of the melting process in a packed bed system using spherical capsules through CFD modeling. The effective packed bed model was used to simulate the fluid flow in the packed bed and enthalpy porosity method was used to solve the phase change material (PCM) domain. The capsules were filled with three various types of phase change materials, while water was utilized as the heat transfer fluid (HTF). Due to the importance of configurations of materials in the packed beds, the effects of various layouts of them on the performance of the system were investigated. Moreover, Al2O3 nanoparticles as a cheap and easily available nanoparticles were added to the materials. Also, the change in inlet flow rate of the HTF was examined. According to the results, positioning the materials in decreasing order of melting temperature in the flow direction is able to decline the charging time of the system by about 1600 s and increase the charging efficiency by 6.8 %. The addition of Al2O3 nanoparticles was able to decrease the charging time by about 1900 s in the best case and increase the system's efficiency by about 7.5 %. Increasing the inlet flow rate of HTF from 2.5 × 10−5 to 5 × 10−5 (1.5–3 Lit/min) reduced the charging time about 1800 s.

Effect of surface modification on the thermophysical properties of ethylene glycol dispersed with Al2O3 nanoparticles for solar thermal applications

This study focuses on investigating the effects of surface modification on the stability and thermal conductivity of ethylene glycol dispersed with aluminium oxide (Al2O3) nanoparticles. Aluminium oxide (Al2O3) nanoparticles were dispersed in ethylene glycol after surface modification with the surfactant Cetrimonium bromide (CTAB) at concentrations of 1, 0.5, 0.25 and 0.125 mass percent. The thermal conductivity and dynamic viscosity at various concentrations were evaluated in the temperature range from 20°C to 170°C, in contrast to prior studies in which the properties were determined in the range from 20°C to 60°C. The stability of the suspension dispersed with CTAB proved to be excellent, and the nanofluids remained stable for one month due to its excellent electrostatic interaction with the surface of Al2O3 nanoparticles. The addition of Al2O3 nanoparticles to ethylene glycol led to a significant improvement in thermal conductivity, which is between 15% and 25%. The influence of the surfactant is clear from the results, and it shows that CTAB is the most suitable surfactant for metal oxide nanoparticles. The experimental data are compared with the data available in the literature in the temperature range from 30°C to 60°C and are found to be in good agreement.

Effects of refined grains and doped nanoparticles on fabricating Al2O3 ceramics using binder jetting

Adding sintering additives to fabricate alumina ceramics via the binder jetting (BJ) technique effectively enhances material properties. However, it is still limited by the disadvantages of low relative density and poor mechanical properties. This study proposed reducing matrix particle size and adding nanoscale particles using binder jetting to address the poor densification and strength of printed alumina (Al2O3) samples. Additionally, their effects on the mechanical properties and manufacturability of the material were explored. Numerical simulations were carried out before the experiments to predict the impact of particle stacking on the powder bed using the discrete element method (DEM). Then, filler particles with an average 40 μm size replaced the original 106 μm-sized Al2O3 particles. Subsequently, Al2O3 nanoparticle content in the samples was gradually increased, and the relevant properties of the sintered samples with different compositions were tested. Consequently, the size of the Al2O3 particles and the addition of Al2O3 nanoparticles significantly affects the physical and mechanical properties of the samples. The sample with 106 μm-sized particles has a compressive strength of 58 MPa, while reducing the particle size to 40 μm increases its compressive strength by 26 %. Moreover, the sample's compressive strength could reach up to 330 MPa, an increase of 513 %, and the hardness reaches 1215 HV (11.91 GPa) by expanding the Al2O3 nanoparticles content to 30 %. Additionally, using Al2O3 nanoparticles further reduces the sintering temperature, significantly improving the practicality of Al2O3 printing using binder jetting.

Microdroplet formation of water and alumina nanofluid in a T-junction microchannel

A scarcity of studies about nanofluids’ utilization in droplet formation inside microdevices currently hovers in the literature although potential applications of nanoparticles in a microfluidic environment are foreseen. For this purpose, experimentally assessing both nanofluid and microdroplet characteristics is fundamental. This work reports a series of experimental tests on the microdroplet formation of distilled water (DIW) and DIW-based aluminum oxide (Al2O3) nanofluid in a microfluidic T-junction. While water and nanofluid are used as the dispersed phase, mineral oil is used as the continuous phase. Microdroplet formation in the squeezing, transitional, and dripping regimes is characterized and scaling laws for the non-dimensional droplet volumes are presented. The effects of flow rate, capillary number, microchannel aspect ratio, and nanoparticle concentration are investigated. The addition of Al2O3 nanoparticles to the water is observed to have a major impact in the transitional regime (up to 40% increase), whereas in the dripping regime its influence is lower, with less than 10% difference. This was attributed to the nanofluid's enhanced interfacial tension and viscosity compared to the DIW, as well as possible adsorption at the surface.

Heat-Insulated Regenerated Fibers with UV Resistance: Silk Fibroin/Al2O3 Nanoparticles.

The various wastes generated by silkworm silk textiles that are no longer in use are increasing, which is causing considerable waste and contamination. This issue has attracted widespread attention in countries that use a lot of silk. Therefore, enhancing the mechanical properties of regenerated silk fibroin (RSF) and enriching the function of silk are important directions to expand the comprehensive utilization of silk products. In this paper, the preparation of RSF/Al2O3 nanoparticles (NPs) hybrid fiber with different Al2O3 NPs contents by wet spinning and its novel performance are reported. It was found that the RSF/Al2O3 NPs hybrid fiber was a multifunctional fiber material with thermal insulation and UV resistance. Natural light tests showed that the temperature rise rate of RSF/Al2O3 NPs hybrid fibers was slower than that of RSF fibers, and the average temperature rose from 29.1 °C to about 35.4 °C in 15 min, while RSF fibers could rise to about 40.1 °C. UV absorption tests showed that the hybrid fiber was resistant to UV radiation. Furthermore, the addition of Al2O3 NPs may improve the mechanical properties of the hybrid fibers. This was because the blending of Al2O3 NPs promoted the self-assembly of β-sheets in the RSF reaction mixture in a dose-dependent manner, which was manifested as the RSF/Al2O3 NPs hybrid fibers had more β-sheets, crystallinity, and a smaller crystal size. In addition, RSF/Al2O3 NPs hybrid fibers had good biocompatibility and durability in micro-alkaline sweat environments. The above performance makes the RSF/Al2O3 NPs hybrid fibers promising candidates for application in heat-insulating and UV-resistant fabrics as well as military clothing.

Design optimization on solidification performance of a rotating latent heat thermal energy storage system subject to fluctuating heat source

The combination of latent heat storage (LHS) technology with the Organic Rankine Cycle represents a widely recognized solar thermoelectric conversion means. However, this technology is hindered by the instability of solar energy and the poor thermal conductivity of thermal storage materials. This study addresses the challenges posed by solar energy fluctuations by implementing a sinusoidal heat source condition during the heat release process of LHS system. Furthermore, a comprehensive approach is taken to enhance heat transfer, incorporating both active methods such as rotational conditions, and passive methods using metal nanoparticles and high-performance fins. The Taguchi method is employed to optimize rotation speed, heat source amplitude, and half-period of the latent heat storage unit, and the resulting heat release performance is compared between different structures and the optimized structures. The findings from optimal design analysis reveal that rotation speed has the most significant influence on mean heat discharging rate and solidification time, followed by the heat source amplitude and half-cycle period. There is a notable interaction between heat source amplitude and half-cycle period. Compared to the initial structure, the optimal structure identified through the optimal design shortens the solidification time by 11.18%, increases the mean heat discharging rate by 13.04% and raises the average temperature response by 18.82%. Furthermore, the addition of Al2O3 nanoparticles further enhances heat discharging properties. Specifically, the presence of 2.5% and 5% Al2O3 nanoparticles shortens unit solidification time by 9.52% and 18.83% and increases the mean heat release rate by 7.69% and 17.26%. It is noted that the incorporation of rotating-fit nanoparticles partly compensates for the limitations of increased viscosity and particle settlement associated with metal nanoparticles, although it does not fully address the challenges related to reduced heat storage/release.

Effect of Al2O3 nanoparticles addition on the thermal characteristics of paraffin wax

Phase change materials are well employed in thermal energy storage systems due to their high thermal storage capacity; however, the problem with phase change materials lies in their low thermal conductivity. The experimental work presented here investigates the effect of adding Alumina (Al2O3) nanoparticles to paraffin wax (Bio-PCM). The resultant nanofluids contain nanoparticles with 1 % and 3 % volume fractions, with corresponding mass fractions of 4 % and 11 %, respectively. It was found that the thermal properties of the prepared nanofluids under investigation exhibit a nonlinear increase in the thermal conductivity with the volume fraction of nanoparticles. A reduction in the latent heat of paraffin wax-based nanofluids was also observed as the volume fraction of nanofluids increased. The results also show the dependence of thermal conductivity on the temperature, where more significant enhancement was observed as the temperature increased. The optimal volume fraction of nanoparticles suspended in the wax was determined to be at 1 % VF with a thermal conductivity value of 0.307 W/m.K at room temperature and latent heat of 207.43 J/g with a melting temperature of 33.63 °C. Furthermore, a stability test was performed to test the thermal conductivity of the mixture under continuous melting and solidification cycles.

Effect of Al2O3 nanoparticles additions on wear resistance of plasma electrolytic oxidation coatings on TC4 alloys

To enhance the tribological properties of TC4 alloy, the plasma electrolytic oxidation (PEO) method was utilized to prepare the coating incorporated various contents of Al2O3 nanoparticles (0, 3, 6, 9, 12 and 15 g/L) on TC4 alloy. The phase composition, chemical compositions, elemental distribution and microstructure of the coatings were investigated by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray computer tomography (XCT). The results revealed that the introduction of Al2O3 nanoparticles into the electrolyte promoted the formation of Al2TiO5 phase in the PEO coatings, and most of the nanoparticles were embedded into the coatings which reduced porosity of the coatings, but increased surface roughness. Also, the increase in the addition of Al2O3 nanoparticles enhanced the microhardness of the PEO coatings due to the formation of Al2TiO5. The tribological behavior of the PEO coatings was improved significantly owing to the high microhardness and porous structure of the coatings. The primary wear mechanism of the coating with 12 g/L Al2O3 nanoparticles was abrasive wear as this coating formed a lubrication zone during the wear process. Besides, the friction coefficient and wear loss mass of the PEO coating prepared with 12 g/L Al2O3 nanoparticles additive exhibited the excellent wear resistance compared to its counterparts.

Enhancement of Water Based Mud Cutting Carrying Capacity Using Aluminium Oxide (Al2o3) Nanoparticle

This research seeks to determine how much Al2O3 nanoparticles can alter the rheological properties and cutting carrying capacity of bentonite-water drilling fluids when different concentration is applied. The aim is to explore these phenomena. The purpose of the research is to produce and describe drilling fluid using nanoparticles and evaluate its cutting-capture capability. The study examined the physiochemical, rheological, and filtration properties, as well as the cutting carry index (CCI) of samples produced from drilling in various concentrations of Al2O3nanoparticles. The control mud was created using bentonite with a concentration of 2.8g (0% Al2O3) without any nanoparticles. Al2O3 was discovered to enhance the plastic viscosity, apparent viscousness, and yield point, but inhibit the gel strength of the drilling fluid. Nevertheless, The Power Law Model was used to describe the Rheological behavior of the prepared mud samples, with a flow behavior index (n) less than 1, which indicated that the formulated muddy samples were all pseudo plastic fluids, ideally suitable for drilling fluid. According to the study, the addition of MgO and Al2O3 nanoparticles can affect the cutting carrying index, resulting in a high-cutting carrying Index that enhances the hole cleaning potential of the drilling mud. The findings of this study indicate a high cutting carrying capacity index, indicating the feasibility of using nanoparticles in drilling operations.

Experimental investigation of usage of POE lubricants with Al2O3, graphene or CNT nanoparticles in a refrigeration compressor.

In this study, the use of nanolubricants containing Al2O3, graphene, and carbon nanotubes (CNTs) at different mass fractions in a refrigeration compressor was experimentally investigated. The required electrical power of the compressor was measured to determine the effect of the use of nanolubricants. Nanoparticles used in the preparation of nanolubricants were gradually added to the lubricant to determine the optimum nanoparticle mass fraction for each nanoparticle type. Thus, it was found that the compressor operated safely and efficiently with nanolubricants. Furthermore, the optimum mass fractions were determined to be 0.750% for Al2O3, 0.250% for graphene, and 0.250% for CNTs for operating conditions of this study. As a result, the required electrical power of the compressor decreased by 6.26, 6.82, and 5.55% with the addition of Al2O3, graphene, and CNT nanoparticles at optimum mass fractions of 0.750, 0.250, and 0.250% to the lubricant, respectively, compared to the compressor using pure oil. Moreover, density and dynamic viscosity of the nanolubricant samples used in the experiments were also measured, and their kinematic viscosity, which is an important parameter for lubricants, was calculated. It was determined that the kinematic viscosity continuously increased with increasing nanoparticle fraction. In conclusion, nanolubricants containing nanoparticles above the optimum mass fraction increase the required electrical power of the compressor. It is concluded that nanoparticle fractions should not be used above the optimum value in nanolubricant applications.

Correlation between microstructure, phase composition and oxidation behavior of CoNiCrAlY/nano-Al2O3 coatings using satellited feedstock deposited by LPPS process

In this study, satellited CoNiCrAlY/2, 4 wt% nano-Al2O3, and conventional CoNiCrAlY feedstocks were deposited through the low-pressure plasma spraying (LPPS) process on Inconel738 substrate. The oxidation test was done at 1050 °C for 10 min and 5, 50, 100, 150, and 200 h. The microstructure and phase composition of the powders and coatings were characterized by the FESEM and XRD, respectively. The results showed that the CoNiCrAlY and Al2O3 powders comprised γ-CoNiCr and β-(Co,Ni)Al, and α-Al2O3, respectively. In contrast, the as-sprayed coatings included supersaturated γ-CoNiCr and meta-stable γ-Al2O3 phases. With the increase in the percentage of nanoparticles (from 2 to 4 wt%), the amount of porosity (from 2 to 3.76 vol%), and the roughness of the coating (from 6.1 to 7.5 μm) increased. With oxidation time, dissolved β-(Co,Ni)Al was recovered and then gradually consumed to create a thermally grown oxide (TGO) layer. In the composite coatings, the transformation of γ-Al2O3 to stable α-Al2O3 occurred, creating defects across the TGO layer. Therefore, with the addition of Al2O3 nanoparticles, the oxidation rate was continuously increased. The oxidation rate constant (Kp × 10−13) of conventional and composite coatings (2, 4 %) was measured as 3.89, 4.35 and 5.08 cm2.s−1, respectively.

Influence of TiO2 and Al2O3 Nanoparticles Addition on Thermal, Wettability and IMC Growth of Sn-3.0Ag-0.5Cu Lead-Free Solder at Different Reflow Temperature

This study investigated the influence of adding 0.50 wt% and 1.0 wt% titanium dioxide (TiO2) and aluminium oxide (Al2O3) nanoparticles on the properties of Sn3.0Ag0.5Cu (SAC305) lead-free solder alloy. In terms of thermal properties, SAC305 lead-free solder with or without addition of TiO2 and Al2O3 nanoparticles, the melting temperature is very similar and comparable. The wetting performance of the SAC305 nanocomposite solder was determined by the contact angle. The best contact angle recorded is 31.65° at reflow temperature of 250°C for 0.50 wt% addition of TiO2 and Al2O3 nanoparticles. The thickness of the IMC layer was observed using an Optical Microscope and measured. Results show that the thickness of the IMC layer decreased when TiO2 and Al2O3 nanoparticles were reinforced into the SAC305 solder system, which shows significant decrease when 0.50wt% of TiO2 and Al2O3 nanoparticles were added. However, beyond 0.50 wt% the thickness of IMC layer increases along with increasing reflow temperature. The results reveal that the adsorption effect of TiO2 and Al2O3 nanoparticles will restrict the growth of the IMC layer under controlled concentration of the nanoparticles and reflow temperature. The optimal parameters to enhance the performance of SAC305 solder by reinforcing TiO2 and Al2O3 nanoparticles are reflowed at 250°C at 0.50 wt% concentration of TiO2 and Al2O3 nanoparticles.

The Investigation of Thermoacoustic Methods for Nanofluid Stability on Heat Exchanger

Due to various engineering applications, nanofluids have gained much attention in the last decade. A Nanofluid is a nanometer-sized particle such as metal, oxide, carbide, etc., dispersed into a base heat transfer fluid. The heat exchanger is a device to transfer heat between fluids. Heat exchanger plays a very important role in modern industry. The new innovative fluid called nanofluid is introduced to improve the overall heat transfer and heat transfer rate. Thermoacoustic is a system which uses sound waves and a non-flammable mixture of inert gases to generate an effect. This paper investigates the enhancement of the heat transfer coefficient of a nanofluid containing alumina (Al2O3) nanoparticle with a volume fraction of 0.4% and sonification at 100 Hz, 500 Hz and 1000 Hz. The addition of Al2O3 nanoparticles will affect the characteristics of the nanofluids, which affect the values of density, specific heat, thermal conductivity, and dynamic viscosity. And the addition of the thermoacoustic method with the sonification of acoustic waves can stabilise the effect of Brownian motion in the nanofluid flow. The maximum results are obtained using acoustic waves at 1000 Hz at high temperatures.

Effect of moisture absorption on the flexural strength of phenolic matrix composites reinforced with glass fibers and aluminum oxide nanoparticles

AbstractIn this research, the effect of adding aluminum oxide nanoparticles on the flexural strength of glass/phenolic composites that were exposed to water environment was experimentally investigated. To make glass/phenolic composites, IL‐800 phenolic resin, H002 hardener, T400 bidirectional glass fibers and Al2O3 nanoparticles were used. Four‐layer composite plates were made by hand layup method. Beam‐shaped samples were extracted from the plates with the help of laser cutting method. Rectangular composite beams made of glass/phenolic and Al2O3/glass/phenolic were subjected to three‐point flexural test. The moisture absorption test was continued until the amount of water absorption reached a constant level. Bending test was performed on the samples before and after immersion in water. Based on the results, the average flexural strength of the samples after water absorption shows a decrease of about 15%. This parameter is equal to 118.96 MPa for glass/phenolic composite samples immersed in water, and by adding 0.25 wt% of Al2O3 nanoparticles into the matrix material of glass/phenolic composite samples, the flexural strength reaches 142.54 MPa, which shows an increase of 19.82% compared to samples without nanoparticles. Furthermore, the amount of flexural modulus decreases after water absorption, and the addition of nanoparticles in the base material can compensate this reduction. Scanning electron microscopy images illustrate that the addition of Al2O3 nanoparticles into the phenolic resin can enhance the strength of matrix material and improve the adhesion of glass fibers to the resin.Highlights Addition of nano Al2O3 reduces water absorption of glass/phenolic composites. Nano Al2O3 improves composite flexural strength after water absorption. Addition of nano Al2O3 increases the adhesion between the layers of the specimens.

Performance comparison of PTCs with nanoparticles in water and nanoparticle in thermal oil

The use of nanoparticles to improve the thermal efficiency of PTCs has become a popular area of research. In this study, we present a comparative analysis of the effects of nanoparticles on the thermal performance of PTCs using water and thermal oil as heat transfer fluids. To obtain accurate temperature estimates, we developed a mathematical model that considers heat transfer in both axial and radial directions. The model includes a two-phase flow homogenous model for the liquid phase, as well as nanoparticle concentration, to achieve the best temperature estimation. We validated our model using experimental data and found that the maximum relative error was 2.3% for water and a lower error of 1.5% for thermal oil. Our analysis of thermal efficiency and exergetic efficiency showed that the addition of Al2O3 nanoparticles led to greater improvements in the thermal efficiency for water, even at the same range of nanoparticle concentration. Furthermore, our results demonstrated that exergetic efficiency was generally higher for water than for thermal oil. Overall, this study highlights the potential benefits of using nanoparticles to enhance the thermal efficiency of PTCs. Our findings could help guide the design and optimization of PTC systems in various applications.

Influence of hardness of nanoparticle additive in PTFE solid lubricant on tribological properties of GCr15 steel with bionic texture

The surface microstructure of biomimetic Procambarus clarkia claw was prepared on the surface of GCr15 steel, then PTFE solid lubricants dispersed with three different hardness nanoparticles (C, ZnO, Al2O3) were filled in. The results of the tribological experiment show the textured surface lubricated by PTFE with Al2O3 nanoparticles reflected the best performances. Because PTFE stored by the bionic texture could be supplied to the friction surface to form a solid lubrication film. Due to the addition of Al2O3 nanoparticles, the hardness and wear resistance of the film are improved, thus avoiding a large loss of PTFE. And the process of "rolling-embedding PTFE surface-exposing-rolling" occurs. As a final, the surface tribological properties of GCr15 steel can be significantly improved.

Characterization of BiFeO3–Al2O3 nano-composites: A study of structural, microstructural, electrical, and magnetic properties

Results: of the studies on the structural, magnetic, and electrical properties of BiFeO3–Al2O3 nanocomposites prepared using the sol-gel method have been reported. The X-ray diffraction results confirm bi-phase structure of the composites with the presence of some impurity phases of Bi25FeO40 and Bi24A12O39. Field emission scanning electron microscopy images revealed the crystalline nature composed of grain and grain boundaries of both the pure and composite samples. Energy-dispersive X-ray spectroscopy confirms the absence of unwanted components. Magnetic characterization reveals weak ferromagnetic behaviour of BiFeO3 and composites while diamagnetic behaviour of Al2O3. The maximum saturation magnetization in the pure BFO sample is ∼ 6 emu/gm, but this magnetization is lowered by up to 63% and is determined to be ∼ 3.8 emu/gm with the 30% addition of Al2O3 in the BFO matrix. Electrical measurements demonstrate that the addition of Al2O3 nanoparticles leads to a reduction in the dielectric constant, loss tangent, and ac conductivity. A.C. conductivity was found to follow Jonscher's universal power law and to be dominated by the correlated barrier hopping mechanism in the conduction process, according to frequency-dependent ac conductivity analysis. Additionally, impedance analysis reveals a field-induced excitation of charge carriers, resulting in a noteworthy reduction in sample impedance. Overall electrical properties have been discussed in the context of oxygen vacancies, secondary phases, defects, and disorder in details

Inhibition of asphaltene deposition by Al2O3 nanoparticles during CO2 injection

Carbon dioxide flooding is of interest due to its high oil-sweep efficiency for enhanced oil recovery and contribution to the reduction of greenhouse gas emissions. However, when CO2 is injected into deep geological strata, asphaltene may precipitate. In this work, the effect of Al2O3 nanoparticles on the deposition of asphaltene was examined by assessing the variations of bond number and interfacial tension at different pressures and a temperature of 60 °C. The asphaltene onset point and intensity were characterized using the bond number, which proved a better indicator of changes in oil droplet shape and interfacial tension with gravity. Synthesized mixtures of toluene and n-heptane that contained two different kinds of asphaltenes were used as M and D oil samples. A 0.06 mass% addition of Al2O3 nanoparticles, which worked best for reduction of interfacial tension, was also applied at various pressures. Addition of nanoparticles to the oils prevented asphaltene precipitation in both synthetic samples by altering the slope of the plot of interfacial tension with pressure by 49.7% for the M sample and 9.0% for the D sample. The Al2O3 nanoparticles were found to be more effective at inhibiting asphaltene precipitation for the M oil sample due to its lower H/C ratio and higher nitrogen content.