Reduced Graphene Oxide Content Research Articles

Experimental Investigation of the Enhancement of Heat Transfer Rate in Automobile Radiator Using Low Concentration Hybrid Nanofluids

Engine coolant, also called antifreeze, is essential to a vehicle's performance since it controls engine temperature, keeps the cooling system from freezing in cold weather and prevents corrosion. To increase engine cooling efficiency, this study looks into using low-concentration hybrid nanofluids to accelerate heat transfer rates in automobile radiators. To maximise heat dissipation within the radiator system, the project focuses on the synthesis, characterisation and practical applications of these nanofluids. Through an extensive literature review, various nanoparticles, including metallic and oxide-based particles, were evaluated for their compatibility and effectiveness in enhancing heat transfer. The chosen nanoparticles underwent thorough characterisation for size, shape and surface properties to determine their suitability for dispersion in a base coolant. Reduced Graphene is known for its good thermal conductivity, making it an ideal candidate for enhancing cooling rates in various applications hence keeping this in mind, this experiment compares and investigates the heat transfer rate in the radiator of an automobile with a hybrid combination of Reduced Graphene Oxide (RGO) + Copper Oxide (CuO) with ethylene glycol and distilled water, at volume fractions of 0.001%, 0.005% and 0.01%. The results show a notable increase in the efficiency of the radiator both in terms of pressure drop and effectiveness. A maximum of 9.2 and 1.5 times increase in temperature drop is recorded at 0.001%, a maximum of 12.3 and 2.08 times increase in temperature drop is noted at 0.005% and the highest of 17.9 and 3.03 times increase in temperature drop is tabulated at 0.01% volume fraction of copper oxide and 0.01% the volume fraction of RGO hybrid nanofluid. It can safely be concluded that compared to the sixty experiments conducted, the recommended nanofluid among them would be Ethylene Glycol and Distilled Water + 0.01% concentration of RGO and CuO hybrid as they have exhibited higher pressure drop, effectiveness and reduction in temperature.

Broadband electromagnetic wave absorption properties of RGO cement-based composite

In this study, a cement-based composite was prepared using reduced graphene oxide (RGO) as a raw material via an ethanol liquid-phase mixing pre-dispersion process. The microstructure of cement-based composites with varying RGO contents was discussed, and a systematic investigation was conducted into the electromagnetic wave absorption (EWA) performance of RGO-cement composites within the frequency range of 2–18 GHz. The results indicate that the RGO content significantly impacts its wave absorption performance. Notably, at an RGO content of 3.0 wt%, the wave absorption performance experiences substantial enhancement. For instance, the minimum reflection loss (RLmin) of −48.33 dB at 8.9 GHz with a coating thickness of 2.6 mm is achieved, while an effective absorption bandwidth (EAB) of 5.02 GHz is attained with a thickness of only 1.6 mm, covering nearly the entire Ku-band. The incorporation of high specific surface area RGO into cement materials results in abundant interface polarization losses and additional electromagnetic wave transmission paths, effectively boosting the EWA performance. Consequently, these materials exhibit significant potential for applications in the field of electromagnetic wave shielding.

Facile synthesis of MOF–808/RGO-based 3D macroscopic aerogel for enhanced photoreduction CO2

Three-dimensional (3D) macroscopic aerogels have emerged as a critical component in the realm of photocatalysis. Maximizing the integration of materials can result in enhanced efficiency and selectivity in photocatalytic processes. In this investigation, we fabricated MOF-808/reduced graphene oxide (RGO) 3D macroscopic aerogel composite materials employing the techniques of hydrothermal synthesis and freeze-drying. The results revealed that the macroscopic aerogel material exhibited the highest performance in CO2 reduction to CO, particularly when the concentration of RGO was maintained at 5 mg mL−1. In addition, we synthesized powder materials of MR-5 composite photocatalysts and conducted a comparative analysis in terms of photocatalytic CO2 reduction performance and electron transfer efficiency. The results showthat the macroscopic aerogel material boasts a high specific surface area, an abundant internal pore structure, and increased active sites. These attributes collectively enhance light energy utilization, and electron transfer rates, thereby, improving photothermal and photoelectric conversion efficiencies. Furthermore, we conducted in-situ FT-IR measurements and found that the M/R-5 aerogel exhibited the best CO2 adsorption capacity under a CO2 flow rate of 10 mL min−1. The density functional theory results demonstrate the correlation between the formation pathway of the product and the charge transfer pathway. This study provides useful ideas for realizing photocatalytic CO2 reduction of macroscopic aerogel materials in gas–solid reaction mode.

Interfacial Growth of Large Area Single-Crystalline Silver Sheets Through Ambient Microdroplets.

The creation of micrometer-sized sheets of silver at the air-water interface by direct deposition of electrospray-generated silver ions (Ag+) on an aqueous dispersion of reduced graphene oxide (RGO), in ambient conditions, is reported. In the process of electrospray deposition (ESD), an electrohydrodynamic flow is created in the aqueous dispersion, and the graphene sheets assemble, forming a thin film at the air-water interface. The deposited Ag+ coalesce to make single-crystalline Ag sheets on top of this assembled graphene layer. Fast neutralization of Ag+ forming atomic Ag, combined with their enhanced mobility on graphene surfaces, presumably facilitates the growth of larger Ag clusters. Moreover, restrictions imposed by the interface drive the crystal growth in 2D. By controlling the precursor salt concentration, RGO concentration, deposition time, and ion current, the dimensionality of the Ag sheets can be tuned. These Ag sheets are effective substrates for surface-enhanced Raman spectroscopy (SERS), as demonstrated by the successful detection of methylene blue at nanomolar concentrations.

Thermal diffusity in copper benzene-1,3,5-tricarboxylate–reduced graphite oxide mechanical composites

Metal organic frameworks (MOFs) and particularly copper benzene-1,3,5-tricarboxylate (HKUST-1) are excellent materials for gas storage (e.g., CH4, N2, H2 adsorption) and gas separation. In this work, reduced graphene oxide (RGO)–HKUST-1 mechanical mixtures were studied in order to reveal the effect of RGO content on the pressure tolerance of the texture and heat conductivity. HKUST-1 was obtained by two different synthesis routes. Air-dried MOF and RGO were thoroughly mixed prior to the compression. Powder XRD and Raman spectroscopy were used to characterize the response of the crystal structure, while low-temperature nitrogen adsorption was used the follow the adsorption properties of the pellets. Finally, the "flash" heat pulse method was used to assess the thermal properties. The gas adsorption isotherms revealed that the adsorption capacity decreases when RGO is added. Based on Raman and XRD results, we found that the synthesis route has an effect on multiple scales. We experimentally confirmed that evaluation of the thermal diffusivity requires a model more complex than the simple Fourier equation, due to the inherent heterogeneous structure of the material. A good approximation of the Fourier coefficient of thermal diffusivity was obtained using the parameters of the Guyer–Krumhansl equation. The heat pulse experiments also revealed possible size-dependent behavior.

PVDF/RGO membranes and the potential of adsorption technology: rhodamine dye removal

Due to the generation of difficult-to-separate waste by industrial and agricultural activities, the concern for preserving the environment and natural resources has gained significant attention in scientific discussions, as the increased concentration of these materials has impacted the entire food chain. In this perspective, the production of polymeric micro and nanofiber membranes for pollutant remediation has been extensively studied to mitigate these impacts. Using a solution blow spinning technique with a commercial airbrush, membranes with concentrations of 1%, 3%, and 5% by mass were created. Scanning electron microscopy (SEM/FEG) analysis revealed the presence of smooth fibers with an average diameter below 100 nm, along with some imperfections attributed to the higher concentration. Structural results confirmed the presence of Reduced Graphene Oxide (RGO) in the membranes. Adsorption tests showed that membranes with higher RGO content exhibited greater dye removal capacity within a 120-hour timeframe.

Synergistic effects of fabrication techniques and the interface structure on the tribological properties of reduced graphene oxide/CuCr composites

While the copper/graphite composite offers commendable anti-friction and wear resistance, it falls short in fulfilling the demands of specific applications such as special brushes, high-speed rail overhead conductors, and sliding contact materials. Due to its exceptional mechanical, electrical, frictional, and wear-resistant properties, reduced graphene oxide (RGO) is considered a promising reinforcement material for copper-based wear-resistant materials. In this study, we synthesized RGO/CuCr composites using flake powder metallurgy and spark plasma sintering (SPS) techniques. The formation and evolution of lubricative films on the RGO/CuCr composite's worn surface were scrutinized, alongside the effects of reinforcement concentration and frictional load on friction-wear characteristics. Notably, increasing the RGO content from 0 to 4.0 vol% led to a reduction in the average friction coefficient from 0.81 to a minimum of 0.314, concurrent with a 62.4% drop in the wear rate. The overall enhancement in properties can largely be credited to the optimized interfacial adhesion between RGO and the CuCr matrix facilitated by in-situ interfacial carbides and the inherent self-lubrication capability of RGO. A developed physical model showcased a direct relationship between the friction coefficient of RGO/CuCr composites and the experimental load, offering a quantitative interpretation of the load's influence on the composite's friction coefficient. Therefore, this research paves a theoretical and practical pathway to engineer high-performing RGO-reinforced copper matrix composites for wear-resistant applications.

Influence of reduced graphene oxide content on dielectric, optical energy band gap, and I–V characteristics of PVDF/PANI/RGO nanocomposites

Influence of reduced graphene oxide content on dielectric, optical energy band gap, and I–V characteristics of PVDF/PANI/RGO nanocomposites

The permeability, mechanical and snow melting performance of graphene composite conductive-pervious concrete

Snow on the roads poses a serious threat to the safety of vehicles, and the traffic system will be paralyzed under harsh conditions. In this study, composite conductive concrete with straight pervious channels were prepared by using carbon fiber, steel fiber and reduced graphene oxide (RGO) as conductive materials to remove snow from roads as soon as possible. The effects of RGO on the workability, mechanical properties and electrical conductivity of composite conductive concrete were studied, and the influence of pervious channels on snow melting efficiency and energy consumption of composite conductive concrete snow melting slabs were analyzed. Results showed that the permeability coefficient of composite conductive concrete with pervious channels reached 6.28 mm/s, meeting the requirements of pavement pervious concrete. For the RGO content of 0.09 % cement mass, the mechanical properties and conductivity of the composite conductive concrete were improved because of the filling effect of nano-RGO on the matrix, while it exerted adverse effects when RGO contents were over 0.09 %. The pervious channels weakened the mechanical and conductive properties of composite conductive concrete. However, compared with the composite conductive concrete without straight pervious channels, the snow melting time and energy consumption were reduced by more than 10 % and 15 %, respectively.

Preparation of Polyindole-MnO2/Reduced Graphene Oxide-based Ternary Composite System for Supercapacitive Application

ABSTRACT A polyindole-MnO2 (PIn-MnO2)/reduced graphene oxide (RGO)-based ternary composite system has been assembled by an in-situ polymerization. In this system, the concentration of RGO has been varied by the interval of 0.25 wt.% in fixed quantity of PIn-MnO2 system. The mean crystallite size of RGO was observed to be 6.64 nm calculated by using Debye–Scherrer formula. This study demonstrates the dispersion of RGO nanoparticles in PIn-MnO2 system to optimize the supercapacitive properties. As expected, the supercapacitive properties of PIn-MnO2-RGO composites were influenced by the addition of RGO nanoparticles and it is optimized for 0.5 wt.% of RGO concentration. The 0.5 wt.% RGO-loaded PIn-MnO2-RGO composite shows specific capacitance of the order 1750 Fg−1 at a scan rate of 50 mV s−1. The main accomplishment of present work is that the 0.5 wt.% RGO-loaded composite shows long-term stability, which is capacitance retention up to 6000 cycles. Similarly, galvanostatic charge/discharge curves of 0.5 wt.% RGO-loaded composite show long and nearly symmetric behavior, which is suitable for range of practical applications.

Preparation and Photocatalytic Degradation of ZnO Graphene Composites

A series of ZnO graphene composites with different reduced graphene oxide (RGO) contents (0%, 2%, 4%, 6% and 8% (mass fraction)) were prepared by solvothermal method. The composite samples were characterized by XRD, SEM and pl. The results show that all the composite samples doped with RGO do not change the structure of ZnO; Pure ZnO samples are spherical particles with grain size of about 40 nm. After adding RGO, the grain size of the samples is uneven, and the agglomeration of the composite samples increases gradually with the increase of RGO content; The emission peaks of all composites are near 373 nm. With the increase of RGO content, the intensity of the intrinsic emission peak of the composites decreases first and then increases. The introduction of RGO makes the absorption peak has a slight red shift, which improve the visible-light absorption ability of the composites. With the increase of RGO content, the photocatalytic performance of the composites increased first and then decreased. When the RGO content was 6% (mass fraction), the photocatalytic performance of the composites was the best, and the degradation rate and reaction rate constants reached 71.97% and 0.017 min-1 respectively.

Effective removal of hexavalent chromium by novel modified alginate-based biocomposites: Characterization, kinetics and equilibrium studies

This study aims to synthesise novel biocomposites by combining fungal hyphae (Aspergillus oryzae or Penicillium roqueforti) and reduced graphene oxide to evaluate their adsorption potential for hexavalent chromium (Cr(VI)) from synthetic solutions and real wastewater. Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analyses were used to characterize the effects of the carbon-based materials on microbial structure. In addition, independent variables including with a contact time (1–11 h), reduced graphene oxide concentration (0.1–1 g.L−1), and initial Cr(VI) concentration (10–50 mg L−1) were tested in batch-scale laboratory experiments by response surface methodology. Accordingly, maximum adsorption was achieved at 11 h contact time, 1.0 g L−1 rGO, and 50 mg L−1 Cr(VI) with a removal rate of 98.9%. The pseudo-first-order and Freundlich isotherm models were well fitted. The results show that these biocomposites can serve as novel adsorbent for the removal of Cr(VI) from wastewater.

Reduced graphene oxide (RGO) reinforced Mg biocomposites for use as orthopedic applications: Mechanical properties, cytocompatibility and antibacterial activity

Magnesium (Mg) has attracted wide interest in orthopedic applications as they exhibit great biodegradability and strong biocompatibility, while corrosion is the main concern for Mg that should be addressed prior to biomedical applications. In this work, ZM31 (Mg-3Zn-1Mn)/xRGO ( x = 0, 0.5, 1 and 1.5 wt%) biocomposites were synthesized by semi-powder metallurgy method. The results showed that the RGO acting as an effective reinforcing filler to prevent deformation and showed better compressive strength (282.3 ± 9 MPa) and revealed enhancement in failure Strain (7.8 ± 2.1%) at 1 wt% RGO concentration compared to Mg alloy (244.5 ± 9 MPa and 7.1 ± 1.5% respectively). Moreover, fracture analysis indicated a more ductile fracture of the nanocomposites after the incorporation of RGO. Crack bridging, crack deflection and crack branching are dominant mechanisms for reinforcement of Mg-based containing RGO. Mg composites containing 0.5 wt% RGO showed a low corrosion rate (2.75 mm/year), while more incorporation of RGO resulted in an increased corrosion rate (4.38 mm/year). In addition, the degradation rate of ZM31 alloy (2.57 mg.cm − 2 .d −1 ) obviously decreased with the addition of 0.5 wt% RGO (1.84 mg.cm − 2 .d −1 ) in the SBF. Besides, continuous apatite layers were created on the composites in the SBF solution. Also, the cell culture examinations showed good cell viability and adhesion on composites with 0.5 and 1 wt% RGO, which was demonstrated by the SEM and MTT assay The alkaline phosphatase (ALP) activity of the ZM3–0.5RGO composite was considerably higher than that of ZM31 matrix alloy in 24 h and 48 h, implying higher osteoblastic differentiation. The antibacterial behavior toward both bacteria ( E. coli and S. aureus ) exhibited that escalating RGO concentration in Mg-matrix composites leads to further inhibition of bacteria growth. These findings suggested that ZM31–0.5RGO biocomposite could be a more promising candidate for orthopedic implants.

Polypyrrole-reduced graphene oxide coated delignified wood for highly efficient solar interfacial steam generation

A solar interfacial steam generator is a device that localizes the solar energy at the water–air interface for water evaporation. The solar interfacial steam generator can be applied in various evaporation-based thermal systems to enhance system efficiency by reducing heat dissipation. In this study, a bio-inspired polypyrrole-reduced graphene oxide coated wood was fabricated and investigated for evaporation and solar-to-vapor conversion efficiency improvement with different polypyrrole-reduced graphene oxide ratios. Thanks to the synergistic effect of highly solar-absorbed polypyrrole and water-attracted reduced graphene oxide, and the efficient heat transfer two-dimensional pathway, the polypyrrole-reduced graphene oxide coated wood showed an outstanding water evaporation performance. The highest water evaporation rate obtained by the polypyrrole-reduced graphene oxide coated wood with the reduced graphene oxide content of 60 % was 1.49 kg·m−2·hr-1, showing a nearly 10 % and 19 % improvement compared to polypyrrole and reduced graphene oxide coated woods, respectively. The corresponding solar-to-vapor conversion efficiency (93.1 %) was also beyond most of the wood-based interfacial steam generators in the literature. The transient heat transfer and evaporation performances of the polypyrrole-reduced graphene oxide coated wood were also firstly investigated based on the developed transient models. It is expected that the remarkable results of this study can help to promote and facilitate the study and application of interfacial steam generators in various thermal systems.

The effect of reduced graphene oxide content on the microstructural and mechanical properties of copper metal matrix composites

This study focuses on the relationship between the microstructure and the resulting mechanical and thermal properties of copper (Cu)/reduced graphene oxide (rGO) composites produced by spark plasma sintering as a function of rGO content (varying from 0 to 0.4 wt%). At the lowest rGO loading (0.025 wt%) the strength of the composite was double that of unreinforced Cu, with higher rGO fractions showing progressively lower improvements. Unexpectedly, the composites displayed a tensile yield drop (discontinuous yielding) on straining in contrast to the unreinforced Cu, ascribed to the influence of rGO nanoparticles pinning dislocations, causing a shortage of mobile dislocations. At loadings below 0.1 wt% rGO, the Cu-rGO interface was free of cracks, impurities, and voids, and the composites contained nano-sized Cu grains and well-distributed rGO nanoparticles with negligible agglomeration. However, at loadings beyond 0.1 wt% rGO, pores and rGO agglomerates were observed. The results suggest that an effective dispersion of rGO is critical, and the primary strengthening mechanisms relate to microstructure refinement, load transfer strengthening, and dislocation pinning. This work points to the efficacy of very low loadings in significantly improving strength with only a minor decrement in thermal diffusivity (<10%), opening up a number of applications.

Reduced graphene oxide accelerates the dissipation of 14C-Triclosan in paddy soil via adsorption interactions

Reduced graphene oxide (RGO) is one of common carbon nanomaterials, which is widely used in various fields. Triclosan is an antimicrobial agent added in pharmaceuticals and personal care products. Extensive release of RGO and triclosan has posed potential risks to humans and the environment. The impact of RGO on the fate of triclosan in paddy soil is poorly known. 14C-Triclosan was employed in the present study to determine its distribution, degradation and mineralization in paddy soil mixed with RGO. Compared with the control, RGO (500 mg kg−1) significantly inhibited the mineralization of 14C-triclosan, and reduced its extractability by 6.5%. The bound residues of triclosan in RGO-contaminated soil (100 and 500 mg kg−1) were 2.9–13.3% greater than that of the control at 112 d. RGO also accelerated the dissipation of triclosan, and its degradation products in both treatments and controls were tentatively identified via 14C-labeling method and LC-Q-TOF-MS analysis. The concentrations of the major metabolites (methyl-triclosan and dechlorinated dimer) were inversely related with the concentrations of RGO. RGO at 50 mg kg−1 or lower had a negligible effect on the degradation of triclosan in paddy soil. Triclosan was strongly adsorbed onto RGO-contaminated soil, which may play a vital role in the fate of triclosan in RGO-contaminated paddy soil. Interestingly, RGO had little effect on triclosan-degrading bacteria via soil microbial community analysis. This study helps understand the effects of RGO on the transformation of triclosan in paddy soil, which is of significance to evaluate the environmental risk of triclosan in RGO-contaminated soil.

Voltammetric determination of acetaminophen in pharmaceutical preparations and human urine using glassy carbon paste electrode modified with reduced graphene oxide

A completely new direct voltammetric method has been developed for determination of acetaminophen (APAP), known as popular analgesic drug. The present electroanalytical method is based on anodic oxidation of APAP at the glassy carbon paste electrode modified with reduced graphene oxide (RGO). Key experimental conditions were studied, resulting in a set of optimal conditions: acetate buffer (pH 5.0) as working medium electrolyte, content of RGO, parameters of squarewave voltammetry including the potential step of 5 mV, potential amplitude of 50 mV, and frequency of 40 Hz. If peak area is used for evaluation, a linear range from 1.2 × 10–6 to 2.2 × 10–4 mol L−1 characterized by determination coefficient of 0.9971, limits of quantification and detection, 9.3 × 10–7 mol L−1 and 3.1 × 10–7 mol L−1, respectively, will be obtained. Under validation, the precision was described by relative standard deviation of 2.9% for the model sample analysis. Finally, the developed voltammetric method was compared with a reference high-performance liquid chromatography method in the analysis of commercially available pharmaceutical preparation and human urine collected from five healthy volunteers.Graphical abstract

Retention of graphene oxide and reduced graphene oxide in porous media: Diffusion-attachment, interception-attachment and straining

The aggregation, deposition and retention of graphene oxide (GO) and reduced graphene oxide (RGO) were investigated systematically to estimate their mobility in the environment. RGO aggregates faster than GO, resulting in weaker diffusive transfer and a lower deposition rate on oxide surfaces. In NaCl, the critical deposition concentration of RGO (CDCRGO) is smaller than CDCGO on the SiO2 surface, indicating that RGO achieves favorable deposition at lower ionic strength. In CaCl2, Ca2+ bridging causes close CDCGO and CDCRGO. The retention process was observed in the photolithographic SiO2 and Al2O3 micromodels. GO and RGO particles approach collectors mainly via interception before attachment. The interactive forces have a limited effect on the particle retention. The larger RGO aggregates cause greater extent interception and straining, resulting in lower mobility than GO in porous media. The mobility of GO and RGO show different trends in quartz crystal microbalance with dissipation (QCM-D) and in micromodels because the interception and straining mechanisms exist in pore space. Micromodel observation confirms the processes of interception and straining. The combination of QCM-D and micromodel experiments provides the connection of diffusion-attachment, interception-attachment and straining, which comprehensively explains the higher mobility of GO than RGO in porous media.

Relation between chemical composition, morphology, and microstructure of poly(ether ether ketone)/reduced graphene oxide nanocomposite coatings obtained by electrophoretic deposition

The effect of the chemical composition on the morphology and microstructure of poly(ether ether ketone) (PEEK)/reduced graphene oxide (RGO) nanocomposite coatings is analyzed. RGO induced three main morphological features in the nanocomposites: (i) a large-scale co-continuous morphology related to nanosheets whose basal planes were mainly aligned with the coating surface, (ii) a dendritic morphology of PEEK domains, and (iii) irregular domains related to the deposition of PEEK particles wrapped by the nanosheets. The development of these morphological features was influenced by the RGO content, allowing the modification of the surface roughness. RGO also induced changes in the melting and non-isothermal crystallization of the polymeric matrix and promoted transcrystallinity in PEEK that, in turn, was a key factor in the development of the final microstructure. In addition, polymer chain mobility was observed to be hindered at high nanofiller concentrations, increasing the glass transition temperature, and diminishing the recrystallization of the polymeric matrix.

Plasma processing of Fe-P/rGO powder for making robust wear resistance and anticorrosion coating over mild steel

Phosphating is a widely used metal pre-treatment process due to its ability to improvise pitting corrosion resistance, wear-resistance, and adherence properties. In the present investigation, we report the manufacturing of spray grade powder of Fe-P metal ingot by mechanical hammering, milling and sieving process. The Fe-P powder and its blending with reduced graphene oxide (rGO) (2 and 4 vol%) were successfully coated over mild steel by the thermal plasma spray method for the first time. Successful retention of rGO was observed even after thermal plasma spraying of Fe-P/rGO (2 vol% and 4 vol%), which was challenging and yet to be reported. The morphological investigation of the top-coat layer and cross-section was analysed using a field emission scanning electron microscope (FESEM). The presence of G, D and 2D bands at 1580 cm−1, 1350 cm−1, and 2700 cm−1, respectively in the Raman spectra were the straightforward demonstration of the retention of rGO. Hardness and air-jet erosion tests were performed to evaluate mechanical properties in view of exploring commercial applications of such coatings. We found that Fe-P-rGO composite coatings exhibited improved hardness, erosion, and corrosion resistance properties with increasing reduced graphene oxide content.