جستجوی مقالات مرتبط با کلیدواژه « Graphene » در نشریات گروه « مواد و متالورژی »

Solar cells are one of the most important equipment’s in the field of clean and novel energy that can be used without chemical pollution. Solar cells are very valuable equipment that by using them, in addition to reducing environmental pollution, can benefit from clean energy. Solar cells are generally used in various industries, including aerospace, clean energy and even transportation. In the meantime, increasing the efficiency of solar cells is of great importance, and the development of quantum science has made a significant contribution to this issue. The use of quantum dots containing different materials such as graphene, carbon, gallium, lead and similar materials can increase the efficiency of solar cells from 3 to more than 50% on average. Also, the power conversion efficiency in solar cells developed with quantum dot technology reports from 1 to more than 15% improvements compared to conventional solar cells. In this research, to summarize the latest achievements in this field, an overview of the importance of quantum dots about the development of solar cells has been done.

An extensive review of the literature showed that both graphene and Cloisite 30B nanosheets are widely employed to modify the crystalline structure and piezoelectic properties of polyvinylidene fluoride (PVDF). Due to the similarity in the geometry of these nanoparticles a comparative study is reported to find the stems of difference in their effects on crystalline structure of PVDF. Scanning electron microscopy (SEM) of these composites showed that large and wide graphene particles are dispersed in PVDF matrix whereas their thickness is well below 100 nanometers. Meanwhile, a careful inspection of SEM micrographs of Cloisite 30B loaded composites revealed existence of smaller particles with almost the same particles thicknesses. Both techniques of Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray diffraction (WXRD) witnessed changes in the crystalline structure of PVDF. The overall finding was that Cloisite 30B improves the polar beta phase of PVDF crystals, whereas a revers effect was found in the presence of graphene nanosheets. These observations were accounted for by differences in surface geometry and surface free energy (surface tension and interfacial tension). Based on the data available for surface properties of these two nanosheets it was found that surface properties of Cloisite 30B is very close to those of PVDF, whereas the surface properties of graphene are far from those of PVDF. Also a lower interfacial tension was found to be active in PVDF-Cloisite 30B system compared to that operative in PVDF-graphene system. An intimate interface along with proper surface texture led to higher content of PVDF’s beta crystals in case of Cloisite 30B nanocomposite

An extensive review of the literature showed that both graphene and Cloisite 30B nanosheets are widely
employed to modify the crystalline structure and piezoelectic properties of polyvinylidene fluoride (PVDF).
Due to the similarity in the geometry of these nanoparticles a comparative study is reported to find the stems
of difference in their effects on crystalline structure of PVDF. Scanning electron microscopy (SEM) of these
composites showed that large and wide graphene particles are dispersed in PVDF matrix whereas their
thickness is well below 100 nanometers. Meanwhile, a careful inspection of SEM micrographs of Cloisite 30B
loaded composites revealed existence of smaller particles with almost the same particles thicknesses. Both
techniques of Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray diffraction (WXRD)
witnessed changes in the crystalline structure of PVDF. The overall finding was that Cloisite 30B improves
the polar beta phase of PVDF crystals, whereas a revers effect was found in the presence of graphene
nanosheets. These observations were accounted for by differences in surface geometry and surface free energy
(surface tension and interfacial tension). Based on the data available for surface properties of these two
nanosheets it was found that surface properties of Cloisite 30B is very close to those of PVDF, whereas the
surface properties of graphene are far from those of PVDF. Also a lower interfacial tension was found to be
active in PVDF-Cloisite 30B system compared to that operative in PVDF-graphene system. An intimate
interface along with proper surface texture led to higher content of PVDF’s beta crystals in case of Cloisite
30B nanocomposite.

In this study, an epoxy-based nanocomposite reinforced with copper oxide-graphene oxide hybrid was investigated. Initially, the hybrid powder of CuO–GO with a weight ratio of 9:1 was prepared. The hybrid filler with different weight percentages ranging from 0.1–0.5 was used to reinforce the epoxy resin. The prepared samples were analyzed using XRD, FTIR, FESEM, TEM, and tensile testing. According to the XRD results and SEM images, the hybrid powder was successfully prepared, and the mechanical testing results showed an improvement in tensile strength in the composite samples. The best composite sample in terms of tensile strength was the one containing 0.3 wt% of hybrid reinforcement, which exhibited a 73% increase in strength compared to the neat resin sample.

In this article, effects of annealing treatment on the evolution of microstructure, tensile properties and electrical resistivity of copper-graphene nanocomposites are investigated. In order to fabricate the nanocomposite, graphene nanopowder was ball-milled after being mixed with copper powder to form a mixture of copper-graphene powder (CuG). Hot rolled copper sheets were used as the matrix of the composite which were annealed prior to accumulative roll bonding (ARB). The nanocomposite was fabricated using 2, 4 and 6 cycles of ARB leading to 20, 40 and 160 multi-layered nanocomposites. Despite increased mechanical strength, the elongation to failure and the electrical conductivity were significantly reduced which were attributed to the high defect density after severe cold deformation and strength-ductility trade-off. The effect of cold deformation on increasing electrical resistivity was so significant that no positive effects of addition of 1% CuG on reducing resistivity was observed but a slight improvement was found in the sample with 2% CuG. However, after annealing at 500 C for 2 h, ductility was fully recovered to the initial value and the electrical resistivity was significantly reduced in the nanocomposite. This was attributed to the fact that a fully recrystallized grain structure was achieved after annealing. Percentage of reinforcing agent and the thickness of the stacking layers were found to determine the final grain size. Electrical conductivity of the nanocomposite was found to significantly improve with annealing. Indeed, the electrical conductivity of the annealed 6ARB-2%CuG composite was higher than the initially annealed copper sheet while the strength and ductility were increased, as well. This determines that the combination of ARB and annealing can be used as an effective method for fabrication of copper-graphene nanocomposites.

Graphene Nanoparticles (GNPs), an upshot of nanotechnology have attracted great interest in diverse research fields including dentistry for their unique properties. Graphene Nanoparticles are cytocompatible and when combined with other compounds, they possess improved synergistic antimicrobial and anti-adherence properties against oral pathogens. The cytotoxicity of graphene in the oral setting has been reported to be very limited in the scientific literature. Current applications of graphene include reinforcing Polymethylmethacrylate (PMMA) for the fabrication of dentures, improving properties of dental luting agents like glass ionomer cement, reinforcing restorative composites and ceramics, and improving osseointegration of titanium dental implants by coating with graphene. This paper reviews the nanoparticle ‘Graphene’ and its potential uses in the field of restorative dentistry.

Numerous researchers have shown interest in the new technique of adding various nanoparticles to elastic materials in an attempt to improve their properties. Physical qualities such as wear resistance, strength, thermal properties, tear limit, and elastic fracture were improved as a result of the atomic scale bonds between the nanoparticles and elastic compounds. These characteristics will in turn lead to high-quality and market-friendly products that can compete in international markets. According to the literature, various nanoscale materials including graphene, calcium carbonate (CaCO3) nanoparticles, aluminum nanoparticles, diamond nanoparticles, nanoclays, and zinc oxide nanoparticles have been widely used in the rubber industry. Development of significant CaCO3 nanoparticle structures has continued to date. Carbon nanotubes are another type of nanoscale that can be employed in the rubber industry. In this paper, the effect of graphene on the mechanical properties of rubber compounds was studied due to the significance of incorporation of graphene into the composites, especially into the rubber compounds. The obtained results demonstrated that mechanical properties including tensile strength, wear resistance, and elongation percentage could be easily enhanced by adding graphene to rubber materials. The authors hope that these enhanced compounds will be applicable to the industrial production.

Considering the widespread use of aluminum composites in various industries and the emergence of nanomaterials such as graphene and boron nitrite (BN) with their unique properties, aluminum-based nanocomposite reinforced by the graphene-BN hybrid was fabricated at different percentages. For this purpose, the graphene-BN hybrid was prepared and subjected to wet milling along with the aluminum powder. The mechanical properties of the final nanocomposite which was consolidated using the spark plasma sintering (SPS) method were examined. Aluminum-based composite specimens containing 1 wt.% graphene–0 wt.% BN (AGB1), 0.95 wt.% graphene–0.05 wt.% BN (AGB2), 0.90 wt.% graphene–0.1 wt.% BN (AGB3), and 0.85 wt.% graphene–0.15 wt.% BN (AGB4) were fabricated and compared with non-reinforced aluminum (AGB0). The hardness values of 48.1, 51.1, 56.2, 54.1, and 43.6 Hv were obtained for AGB0, AGB1, AGB2, AGB3, and AGB4, respectively. Additionally, tensile strengths of these specimens were 67.2, 102.1, 129.5, 123.7, and 114.7 MPa, respectively. According to the results of the hardness and tensile tests, it was revealed that the AGB2 specimen had the highest tensile strength (93% higher than AGB0 and 27% higher than AGB1) and hardness (17% higher than AGB0 and 10% higher than AGB1).

Graphene, a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice, exhibits extraordinary properties that have attracted widespread attention across various scientific disciplines. This paper explores the transformative impact of monolayer graphene in the field of sensor technology, specifically focusing on Graphene Field-Effect Transistors (GFETs) and Graphene Hall Sensors, and their applications in biomedical contexts. The unique combination of mechanical strength, electrical conductivity, and optical transparency in monolayer graphene has positioned it as an ideal material for sensor development. In the biomedical domain, graphene’s biocompatibility and high surface area have opened avenues for applications in drug delivery systems, biosensors, and biomaterials for tissue engineering. The paper delves into the operational principles of GFETs, highlighting their ambipolar electric field effect, reduced short channel effects, and recent advancements in bandgap engineering. GFETs offer versatility in high-frequency electronics, digital electronics, sensing applications, and flexible/wearable electronics. The fabrication process of GFETs involves synthesizing high-quality graphene, transferring it onto substrates, precise patterning, and electrode fabrication. These steps play a crucial role in determining the final performance and application potential of GFETs. Graphene Hall Sensors, another focus of this paper, leverage graphene’s exceptional electronic properties for unparalleled precision in magnetic field detection. The advantages include high sensitivity, low power consumption, and compatibility with flexible substrates. The fabrication process involves synthesizing high-quality graphene, transferring it onto substrates, precise patterning, and final integration steps. The paper concludes by emphasizing the pivotal role of monolayer graphene in advancing sensor technologies, particularly in biomedical applications. The review underscores the potential of graphene-based sensors in enhancing sensitivity, specificity, and overall performance, thereby contributing to advancements in personalized medicine, health monitoring, and environmental sensing.

In this research, zinc oxide quantum dots and graphene nanocomposites were synthesized via two different methods; In the first (direct) method, ZnO-graphene Nanocomposites were made mixing the synthesized zinc oxide and graphene. In the second (indirect) method, zinc nitrate, graphene, and sodium hydroxide were used to made ZnO-graphene Nanocomposites. XRD, FTIR and Raman spectroscopy analyses were used for phase and structural evaluations. The morphology of the nanocomposites w::as char::acterized by SEM. The specific surface area and porosity of the samples were characterized by BET analysis. The optical properties of the samples were investigated by photoluminescence and ultraviolet-visible spectroscopy analyses. Results showed that using graphene, increased the photoluminescence property and shifted the photoluminescence spectrum of the composites towards the visible light spectrum. The photoluminescence of the synthesized graphene-zinc oxide composite, in the visible light region, was closer to white light than that of pure zinc oxide. According to the results of BET test, the nanocomposite synthesized by direct method had a higher surface area (25.7 m2.g-1) and a higher porosity (0.32 cm3.g-1) than the nanocomposite synthesized by the indirect method with a specific surface area of (16.5 m2.g-1) and a porosity of 0.23 cm3.g-1).

Large area fabrication of graphene, as a leading two-dimensional material as well as an allotrope of carbon, is a challenging requirement prior to its preparation for applications. Chemical Vapor Deposition (CVD) is one of the most effective and promising methods for high-scale and high-quality synthesis of graphene. In this study, graphene layers were grown on copper (Cu) sheets using low-pressure CVD technique at 930 °C, 870 °C, and 760 °C. Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Optical Microscopy (OM) and Atomic Force Microscopy (AFM) were employed in this study to investigate the effect of the process temperature on the structural properties, morphology, grain boundaries, continuity, purity, and number of layers. The results from analyses revealed that at higher temperatures, the continuity and quality of the layers and number of grain boundaries were higher and lower, respectively. In contrast, at lower temperatures, the nucleation and discontinuity of the deposited layers were relatively high. The surface roughness of the graphene sheets increased with a decrease in temperature.