This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). The Editor-in-Chief has retracted this article because the authors did not have the ownership of the data reported in this article (Fig. 5 and Table 1). All authors agree to this retraction.

In this study, porous carbon has been prepared through potassium hydroxide (KOH) activation of coconut fiber (CF) and subsequent carbonization in the presence of an inert gas. The activated carbons (AC) were prepared via carbonization of the precursor at different temperatures. Subsequently, their electromagnetic wave absorption (EMWA) performance was investigated at X-band frequency. The phase crystallinity, porous features, and degreeof graphitization of the activated carbons were studied using XRD, nitrogen adsorption/desorption isotherm, and Raman spectroscopy, respectively. Using the BET method, the activated carbon prepared at 750. C displayed a high specific surface area of 602.9 m2g-1and an average pore size of 6 nm, which confirms the extant of mesopores. The EMWA was studied using COMSOL Multiphysics software based on the finite element method. Results show that the activated carbon prepared at 750.C attained an optimal reflection loss of45.6 dB at 10.96 GHz with a corresponding effective bandwidth of 3.5 GHz at a thickness of 3.0 mm. In conclusion, this study interestingly shows that porous carbon obtained from coconut fiber has great potential for attenuating electromagnetic waves.

Water-based processing of graphene-typically considered as physicochemically incompatible with water in the macroscale-emerges as the key challenge among the central postulates of green nanotechnology. These problematic concerns are derived from the complex nature of graphene in the family of sp2-carbon nanoallotropes. Indeed, nanomaterials hidden under the common "graphene" signboard are very rich in morphological and physicochemical variants. In this work, inspired by the adhesion chemistry of mussel biomaterials, we have synthesized novel, water-processable graphene-polylevodopa (PDOPA) hybrids. Graphene and PDOPA were covalently amalgamated via the "growth-from" polymerization of l-DOPA (l-3,4-dihydroxyphenylalanine) monomer in air, yielding homogeneously PDOPA-coated (23 wt %) (of thickness 10-20 nm) hydrophilic flakes. The hybrids formed >1 year stable and water-processable aqueous dispersions and further conveniently processable paints of viscosity 0.4 Pa·s at 20 s-1 and a low yield stress τ0 up to 0.12 Pa, hence exhibiting long shelf-life stability and lacking sagging after application. Demonstrating their applicability, we have found them as surfactant-like nanoparticles stabilizing the larger, pristine graphene agglomerates in water in the optimized graphene/graphene-PDOPA weight ratio of 9:1. These characteristics enabled the manufacture of conveniently paintable coatings of low surface resistivity of 1.9 kΩ sq-1 (0.21 Ω·m) which, in turn, emerge as potentially applicable in textronics, radar-absorbing materials, or electromagnetic interference shielding.

The continuing depletion of light oil supplies and the rapidly growing demand for energy are forcing oil and gas companies to explore unconventional oil extraction techniques. The structure and flow rate implies an impact on the trapping and mobilization of oil in the reservoir. This article studies the effect of pore geometry and dynamics on water-oil displacement as a two-phase flow system. The pore geometries of sandstone were extracted using the non-destructive 3D micro computational tomography (micro-CT) technique. Two-phase flow simulations were performed using COMSOL Multiphysics on the micro-CT images to show the effect of the capillary number and the flow pattern. Velocity and relative permeability of the non-wetting phase at different points of the porous structure was computed. The effect of viscosity of wetting fluid on the pore structure was also studied to evaluate the parameters affecting enhanced oil recovery (EOR).

Reservoir fluid is one of the major parameters that play a significant role in oil mobility, the fluid flow through the porous of the reservoir, the mechanism at which this fluid has been migrated are some of the major concerns in enhanced oil recovery industries. So, it of great significance to use an appropriate technique to calculate or to predict the oil recovery from the reservoir. The study aims to use an artificial neural network (ANN) model with electromagnetic parameters such as real and imaginary permittivity, real and imaginary permeability, and reflection loos at different concentrations of NaCl electrolyte. Deep neural network (DNN) approach with 280 nodes in each hidden layer and one output, it was revealed from the obtained result the correlation coefficient given by the DNN is R2 of 0.994 for estimated recovery factor and R2 of 0.894 for predicted recovery factor. This research result shows a good prediction of RF with the reservoir rock and fluid properties in terms of cost and production effectiveness.

To tackle the problem of electromagnetic (EM) pollution and the adverse effect of EM interference, tremendous research works have been aimed at the realization of the optimal EM wave absorbing materials. In this study, Fe3O4@C microspheres with a regular size of 5–7 μm were prepared via a simple hydrothermal process and subsequent high-temperature calcination. The carbon microspheres were produced from the pyrolysis of a carboxyl and carbohydrate group. The Fe3O4@C microspheres are made up of Fe3O4 nanoparticles entangled with even distribution on the carbon microsphere. The Fe3O4@C microspheres displayed a good BET surface area (181.89 m2/g). A Fe3O4@C-30 sample exhibited a minimum reflection loss value of −47 dB at 16.89 GHz, with 2.0 mm matching thickness. Large amounts of EM waves transmit through the material due to favorable impedance match at the Fe3O4@C microspheres air interface, this resulted in low reflections of the EM waves at the boundary.

Determining the crude oil concentration changes as an essential factor in reservoir engineering, via proposed modified optical fiber sensor, offers a novel approach in oil production optimization. A highly sensitive optical fiber probe is fabricated via partially removing the cladding and coating the sensing part with zinc oxide/silver (ZnO/Ag) heterostructre layer. The ZnO outer layer has three configurations including nanoparticle, horizontally and vertically oriented nanorods. The fabricated optical fiber sensors are subjected to detect the crude oil concentration variations through detection of both wavelengths shift and intensity changes. The effect of ZnO outer layer shape, and the type of light source is used, on sensitivity of the probe is examined. Comprehensive investigation on shape dependent structural and optical properties of ZnO outer layer demonstrates that vertically oriented ZnO has larger surface area, higher average dispersion relation, better crystallinity, larger surface roughness and better adhesion (interaction) with crude oil molecules and these characteristics are responsible for its superior performance compare to other ZnO configurations. For the probe coated with vertically aligned ZnO nanorods when the infrared (IR) light source is used, the intensity and wavelength sensitivity of 0.044 dB/Delta %crude oil and 0.112 nm/Delta %crude oil are obtained respectively. (C) 2020 Elsevier Ltd. All rights reserved.

This work provides an analysis of the effect of nanofluids on the wettability of sandstone for the application of enhanced oil recovery. The wettability of sandstone with brine and nanofluids of ZnO, BiFeO3, and SrFeO3 is studied experimentally using contact angle calculations. Also, the direct simulations for the displacement of oil with brine and nanofluids are carried out on a micro-CT scanned porous sandstone structure for the measurement of capillary pressure and relative permeability. Fluid properties such as viscosity and density of the nanofluids, brine, and oil to be used in simulations were obtained using viscometer and densimeter. The experimental results show that the contact angle of crude oil on the sandstone surface has a higher value for nanofluids as 125.89° for ZnO, 122.88° for BiFeO3, and 104.98 for SrFeO3 as compared to brine 28.66°, which means the wettability of the system changes from oil-wet to water-wet by the addition of nanofluids. The simulation results indicate that BiFeO3 nanofluid has a greater tendency to change the wettability of porous medium as compared to brine, ZnO, and SrFeO3 nanofluids, as it shows better values of relative permeability and capillary pressure.

Electromagnetic absorption properties of sandstone saturated with Strontium ferrite (SrFeO3) nanofluid are discussed in this paper. The synthesis of nanoparticles was carried out using the sol–gel combustion method and calcinated at a temperature of 300–400 °C in a furnace. X-ray diffraction pattern verified the crystalline structure of SrFeO3, and FESEM images confirmed the morphology of nanoparticles. The dielectric and magnetic studies were carried out using the vector network analyzer (VNA) to measure the dielectric losses in dry sandstone and the sandstone saturated with SrFeO3 nanofluids. Comparative analysis of the electric permittivity, complex permittivity, and the dielectric losses of sandstone with SrFeO3 provided an insight about the microwave absorbing properties. Simulations of these materials with electromagnetic field verified experimental results, as SrFeO3 has the greater capacity to absorb the electromagnetic waves and can be used as a potential material for enhanced oil recovery.

Graphene and its derivatives have been a promising material in all area of science and technology for many decades. In the recent years, its outlooks and applications in oil and gas upstream industry are of a major importance. As a result of its exceptional chemical, electrical, structural, and mechanical properties, it can act as a good agent for the recovery of trapped oil. The aim of this review was to provide insight on application of graphene nanoparticles in upstream industries. Furthermore, the advances of graphene synthesis techniques and its impacts on oil mobility ratio in enhancing oil recovery process were analyzed. Extensively, the mechanism of oil recovery enhancement using graphene nanoparticles were discussed. Graphene nanoparticles shows a positive impact on both rheological and stabilization characteristics of drilling fluids, wettability alteration, interfacial tension, and improving the emulsion stability. The challenges of graphene nanoparticles in enhance oil recovery are explained and its solution.

Accurate monitoring of concentration changes in saline solution is prerequisite to control and minimize the negative effect of salt in water resources. A highly sensitive refractive index (RI) sensor is fabricated via coating a novel zinc oxide/silver (ZnO/Ag) bi-layer having different ZnO nanostructure shapes as an outer layer on partially unclad silica fiber. When the ZnO layer contact to different saline concentrations, its band-gap is altered and modifies the RI of the ZnO layer. The coupling of the evanescent light with surface plasmon resonance (SPR) wave and absorption of evanescent light by the external medium are responsible for observing wavelength shift and intensity changes in the detected spectrum. For vertically oriented ZnO nanorods sample when IR light is used as a light source, by increasing the saline concentration from 0% to 20%, the wavelength is shifted from 1564.4 nm to 1573.3 nm and the intensity is dropped to 77% of its maximum value. The superior sensitivity obtained for vertically oriented ZnO sample is attributed to the larger surface area, higher average dispersion relation, better crystallinity, larger surface roughness and greater adhesion (interaction) with salt molecules compare to the other samples. The experimentally demonstrated highest intensity and wavelength sensitivity are 36 dB/RIU and 255 nm/RIU respectively.

Recently, electromagnetic (EM) interference as an adverse effect of the proliferation of technologies utilizing EM waves has become a serious problem. EM wave absorbers have been extensively utilized as an effective means of eliminating EMI. Activated carbon derived from agricultural waste has been identified as potential material to fabricate an ideal EM wave absorber. This study investigates activated carbon prepared from coconut fiber as an EM wave absorber at X-band frequency. Coconut fiber Activated carbon at 600 °C exhibited the highest surface area of 228.689 m2/g and 5.9 nm number of pores which is beneficial for microwave absorption. COMSOL Multiphysics software was used to simulate the EM scattering parameters of the coconut fiber activated carbon. A good microwave absorption performance was observed minimum reflection loss value of −41.78 dB at 10.8 GHz at a thickness of 4.0 mm. This result shows that activated carbon prepared from coconut fiber can function as an EM wave absorber at X-band frequency.

The need to recover high viscosity heavy oil from the residual phase of reservoirs has raised interest in the use of electromagnetics (EM) for enhanced oil recovery. However, the transformation of EM wave properties must be taken into consideration with respect to the dynamic interaction between fluid and solid phases. Consequently, this study discretises EM wave interaction with heterogeneous porous media (sandstones) under different fluid saturations (oil and water) to aid the monitoring of fluid mobility and activation of magnetic nanofluid in the reservoir. To achieve this aim, this study defined the various EM responses and signatures for brine and oil saturation and fluid saturation levels. A Nanofluid Electromagnetic Injection System (NES) was deployed for a fluid injection/core-flooding experiment. Inductance, resistance and capacitance (LRC) were recorded as the different fluids were injected into a 1.0-m long Berea core, starting from brine imbibition to oil saturation, brine flooding and eventually magnetite nanofluid flooding. The fluid mobility was monitored using a fibre Bragg grating sensor. The experimental measurements of the relative permittivity of the Berea sandstone core (with embedded detectors) saturated with brine, oil and magnetite nanofluid were given in the frequency band of 200 kHz. The behaviour of relative permittivity and attenuation of the EM wave was observed to be convolutedly dependent on the sandstone saturation history. The fibre Bragg Grating (FBG) sensor was able to detect the interaction of the Fe3O4 nanofluid with the magnetic field, which underpins the fluid mobility fundamentals that resulted in an anomalous response.

The advancement of nanotechnology has contributed immensely in solving major problems in engineering and medical applications. Versatility of nanofluids made of nanoparticles is attributed mainly to the size, shape, type and ionic composition of the particles. Specifically, the use of nanofluids for heat augmentation and mass transport is of wide application and it is accruing interest from researchers. Nonetheless, experimental approach may be cumbersome and expensive. To this end, Lattice Boltzmann method (LBM) has shown its capability in the study of complex flow systems that have complicated geometries (e.g. porous media) with acceptable accuracy while using a simple algorithm. In this review, we present a rich summary of the latest findings on the application of LBM fornanofluids related heat and mass transfer processes with emphasis on porous media and also highlight current challenges for future research.

Salinity magnitude changes are a critical factor for determining the chemistry of natural water bodies and biological processes. Label-free refractive index sensors are promising devices for detecting these changes. A polymer optical fiber (POF) sensor modified with cladding treatment and a bi-layer zinc oxide/silver (ZnO/Ag) nanostructure coating to determine sodium chloride concentration changes through refractive index variations in water is experimentally demonstrated. The use of three ZnO nanostructure shapes, nanoparticles and horizontally and vertically oriented nanorods, as an external layer and a broad spectrum light source from the visible (Vis) to the near infrared (NIR) region are investigated to achieve optimum sensitivity. The rms roughness, optical band-gap and zeta potential (ZP) value for the vertically oriented sample are 148 nm, 3.19 eV and 5.96 mV, respectively. In the NIR region the wavelength-intensity sensitivity values of probes coated with ZnO nanoparticles and horizontally and vertically oriented nanorods are 104 nm RIU-1-12 dB RIU-1, 63 nm RIU-1-10 dB RIU-1 and 146 nm RIU-1-22 dB RIU-1, respectively, and in the Vis area the values are 65 nm RIU-1-14 dB RIU-1, 58 nm RIU-1-11 dB RIU-1 and 89 nm RIU-1-23 dB RIU-1, respectively. The maximum amplitude sensitivity is obtained for the probe coated with vertically aligned ZnO nanorods in the NIR area due to the deeper penetration of evanescent waves, a higher surface-volume ratio, better crystallinity, more adhesive interactions with salt molecules, larger surface roughness and higher-order dispersion compared to the other coated ZnO nanostructures.

We have successfully fabricated and demonstrated a simple, cost-effective and easy to use of fiber Bragg grating (FBG) based on single mode, and multimode fiber which have been employed for temperature monitoring. The study purposely compared the performance of two types of FBGs; single mode FBG (SM-FBG) and multimode FBG (MM-FBG). The FBGs sensor is fabricated by phase mask technique which being exposed to ArF excimer laser with 20 mm uniform grating length and 99% reflectivity. The proposed FBG is studied for temperature monitoring starting at room temperature until 120 °C, and the configurations with SM-FBG and MM-FBG achieved a sensitivity of 10.9 pm/°C and 13.23 pm/°C, respectively whereas linear response correlation coefficient of 0.98229 and 0.99929. These show the MM-FBG has better sensitivity to be used in sensor applications.

The development of effective recovery techniques that can resolve the complexities of high interfacial tension (IFT), high viscosity and wettability in petroleum reservoirs will aid efforts to meet the world’s growing energy demands. Nanoparticles prove to be able to form adsorption layers on surfaces of sandstone and significantly change wettability and IFT. Despite the remarkable properties of graphene nanopaticles, not many studies have researched their potential application in EOR. In this study, sandstone coreplugs infused with crude oil, brine and carbon nanofluids (carbon nanocomposite and graphene) were characterized using field emission scanning electron microscopy (FESEM), Fourier Transform Infrared (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). IFT measurements were performed for oil/brine/CNPs and graphene nanofluid. The measured IFT values for brine/oil, carbon nanofluid/oil and graphene nanofluid/oil are 39–40 mN/m, 41–44 mN/m, and 9.8–11.4 mN/m, respectively. Spectroscopic analyses show that graphene has a stronger interaction (higher adsorption) on sandstone compared to the normal carbon nanoparticles, which is indicated by the lower Si–O Raman, lower FTIR transmittance for C–H peaks and the emergence of loss feature phenomenon in the XPS spectra of graphene infused with sandstone. The relatively lower FTIR transmittance intensities, well distributed carbon atoms and detected D' and D+D' Raman shifts also support the high interaction of graphene with oil and rock surface. The higher IFT reduction by graphene nanofluids is attributed to the combined high hydrophobicity and hydrophilic natures, which provides a dynamism for their detachment at the biphasic liquid/fluid interface.

Applications of nanotechnology have grown enormously in recent years in various fields, such as drug delivery, energy storage, information technology, electronic devices and petroleum industry. The petroleum industry is using nanotechnology in a variety of applications, but the use of nanofluids with base fluid in the presence of the electromagnetic field in the reservoir for enhanced oil recovery (EOR) is a novel technique. After primary and secondary recovery from the reservoir, there is still an estimated amount of 50% oil remains there in most reservoirs, which cannot be extracted by conventional methods. Some studies regarding the magnetic and dielectric nanofluids in the presence of electromagnetic radiation have been carried out to recover the residual oil from depleted oil reservoirs. Such studies have shown promising results and yielded a consistent improvement in comparison to the conventional polymers and brine used in the industrial practice. However, some challenges like low sweep efficiency, potential formation damage, rheological improvement and high costs affect the further application of nanofluids for EOR technologies. The current study is a review of the activation of nanofluids using electromagnetic radiation for enhanced oil recovery, and the evaluation of mechanisms adopted for the prospects of this technology.

There are a few studies on the use of ferro-nanofluids for enhanced oil recovery,despite their magnetic properties;hence,it is needed to study the adsorption of iron oxide (Fe2O3 and Fe3O4) nanoparticles (NPs) on rock surfaces.This is important as the colloidal transport of NPs through the reservoir is subject to particle adsorption on the rock surface.Molecular dynamics simulation was used to determine the interfacial energy (strength) and adsorption of Fe2O3 and Fe3O4 nanofluids infused in reservoir sandstones.Fourier transform infrared spectroscopy and X-ray photon spectroscopy (XPS) were used to monitor interaction of silicate species with Fe2O3 and Fe3O4.The spectral changes show the variation of dominating silicate anions in the solution.Also,the XPS peaks for Si,C and Fe at 190,285 and 700 eV,respectively,are less distinct in the spectra of sandstone aged in the Fe3O4 nanofluid,suggesting the intense adsorption of the Fe3O4 with the crude oil.The measured IFT for brine/oil,Fe2O3/oil and Fe3O4/oil are 40,36.17 and 31 mN/m,respectively.Fe3O4 infused with reservoir sandstone exhibits a higher silicate sorption capacity than Fe2O3,due to their larger number of active surface sites and saturation magnetization,which accounts for the effectiveness of Fe3O4 in reducing IFT.

Catalytic activity of nanomaterials under applied electromagnetic field is a green method which is based on change in spin orientation of nanocatalyst. However, interaction of magnetic and dielectric nanocatalysts with electromagnetic field is not well understood. Here, we propose a kinetic model utilizing electromagnetic field effect on activation energy. This field causes weakening of the bond of the reactant molecules and reduction in activation energy of nanocatalysts. The underlying mechanism is singlet to triplet conversion with the change in spin orientation of gases and nanocatalysts at ambient condition. The results show that saturation magnetization and net spin of Fe3O4 nanocatalysts are higher than ZnO nanocatalyst by 6,764 and 56 times, respectively. Hence, 36.60% reduction in activation energy and 9.70% increase in rate constant for Fe3O4 results in 566.87% increment in urea yield. These findings will pave the way for a new insight on electromagnetic application for industrial chemical reaction.