Papers by Keyword: Exfoliation

Abstract: Hexagonal boron nitride nanosheets (BNNSs), are among the most prominent layered two-dimensional (2D) nanomaterials due to their superior thermal, electrical, and dielectric properties. However, their strong interlayer bonding limits efficient exfoliation into few-layer structures. In this study, a mixed-solvent strategy based on 1-cyclohexyl-2-pyrrolidone (CHP) and deionized water was developed for rapid and scalable production of BNNSs via sonication-assisted liquid-phase exfoliation (LPE). A CHP/water ratio of 1:20 enabled stable dispersion of exfoliated hBN at a concentration of 1.05 mg/mL, with 56% of the starting material delaminated. Atomic force microscopy (AFM) analysis revealed that 16.8% of the exfoliated product consisted of nanosheets thinner than five layersafter a fast exfoliation. In contrast, exfoliation using IPA/water (3:7) under identical conditions yielded predominantly thick, stacked hBN structures. Spectroscopic and microscopic analyses, including UV–Vis, FTIR, XRD, and Raman, confirmed effective delamination and structural preservation of CHP-exfoliated BNNSs. These results highlight the critical role of solvent composition and demonstrate the superior performance of CHP-based systems as a co-solvent for time-efficient exfoliation. This scalable and safer approach can be adapted for other layered materials and holds strong potential for expanding the use of BNNSs in advanced technological applications.

Abstract: In this work, the liquid phase exfoliation (LPE) method was investigated to produce a large quantity of 2D MoS₂. The introduction of ultrasound into IPA and IPA/DI solutions containing MoS₂ resulted in fragmentation and exfoliation of the MoS₂. The determination of the layers of LPE-MoS₂ was performed by optical microscopy, atomic force microscopy, non-resonant Raman spectroscopy and XRD. Flakes with few layers were detected by AFM and resonant Raman investigations.

Abstract: For the purpose of synthesizing 2D-Material–Magnetic nanocomposites, several new modifications of existing 2D-materials synthesis methods by exfoliation and chemical synthesis from liquid charge are developed. Using them, graphene (G), graphene oxide (GO), reduced graphene oxide (rGO) and hexagonal boron nitride (h-BN) matrix magnetic nanocomposites for the first time are obtained by coating or intercalation their nanoparticles with ferromagnetic iron (Fe) or ferrimagnetic iron oxide – magnetite (Fe₃O₄). These materials are prospective for variety of high tech applications. In particular, h-BN–Fe₃O₄ composite nanoparticles can serve for neutron-capturing boron isotope ¹⁰B effective delivery agents in BNCT (Boron Neutron Capture Therapy) of cancer as they allow the controlling by an external magnetic field targeting to tumor tissue.

Abstract: In this work, graphene was produced by liquid-phase exfoliation of graphite in different organic solvents with addition of picric acid. The graphene was easily produced by one step ultra-sonication of graphite powder in the organic solvents. The addition of picric acid has increased the graphene production yield in most of the solvents tested in this work. Picric acid serves as a “molecular wedge” to intercalate into the edge of graphite, which plays a key role during sonication and significantly improves the production yield of graphene. The products were analyzed by microscopic techniques, including atomic force microscopy (AFM) and scanning electron microscope (SEM). The AFM images indicate that the exfoliation efficiency and amount of graphene increased by addition of picric acid in organic solvents. Moreover, the AFM images also indicate presence of bilayer graphene. SEM analysis also shows that the addition of picric acid into the organic solvent favors the exfoliation process. The produced graphene was also analyzed by XRD, FTIR, Raman and UV-visible spectroscopy. The XRD results illustrate that exfoliation was best achieved in N-methyl-2-pyrrolidone (NMP) as a solvent. FTIR and Raman results indicate that addition of picric acid has slightly defected the produced graphene surface. The amount of graphene concentration was calculated by using Beer Lambert law, and it was observed that the graphene production yield was increased by using picric acid in most of the solvents. The maximum amount of graphene concentration (0.159 mg/ml) was achieved by adding 30 mg of picric acid in NMP.

Abstract: Investigating the influence of process parameters is vital to improve the mechanical properties of nanoparticle reinforced polymer nanocomposites. In this effort, nanocomposites of polypropylene/nanoclay are prepared by the extrusion method. In order to characterize the mechanical behavior of nanocomposites over different compounding ratios, samples are prepared with 5 and 10 wt%. Effect of re-extrusion and PP-g-MA compatibilizer on the tensile performance of nanocomposites is evaluated at different strain rates. XRD evaluation of compounds indicated that re-extrusion is an important factor in increasing the exfoliation degree.

Abstract: By mechanical blending method or melt extrusion method, several kinds of poymers and OMMT were selected with different mixing progress and conditions, and several polymer/OMMT nanocomposites with different substructure morphology were prepared. The properties of polymer/OMMT nanocomposites were investigated. Firstly, several types of OMMT were prepared with different layer spacing, the results of XRD and TEM showed that the OMMT with larger layer spacing would form exfoliation nanocomposites, and then the schemes explained the mechanism. The polyethylene (such as LDPE, HDPE, LLDPE) composited with the same OMMT indicated the influence of different molecular chain structure. Different morphology of PP/OMMT and EPDM/OMMT nano-composites were discussed to find the relationship of shear force effecting structure.

Abstract: In this report, graphene sheets used as reinforcements for improvement of anti-corrosion properties have been synthesized by electrochemical intercalation and exfoliation process. The (001) and (002) plane of graphene sheets at a 2θ angle of 13.2 and 26.13 confirmed by X-ray diffraction pattern. High-resolution TEM confirms 8-12 layers of graphene present in the final products. The as-received graphene sheets have been used as reinforcement with copper matrix to synthesize Cu-Gr nanocomposite by electrodeposition method. The results and investigations of Cu-Gr composite thin films deposited from the bath containing 0.1g/L and 0.5g/L graphene concentrations with acidic copper sulfate solution have been compared. The surface morphology and roughness of composites were studied by SEM, AFM and surface profiler. The presence of graphene in Cu-Gr nanocomposite confirmed by EDS analysis. It was observed that the reinforcement particle has increased the mechanical properties of Cu-Gr composite (by 30%) with the addition to the copper matrix. The corrosion resistance of sample was studied by Tafel extrapolation method in standard borate buffer solution. For nanocomposites of 0.5g/L graphene, the values of Tafel constants are, βa=177.37 mv, βc=138.51 mv, Icorr = 9.3165×10-7Amp/cm², Ecorr = -0.051 volts and corrosion rate 0.01028 mm/a as comparison to the corrosion rate of pure electroplated copper of a value of 0.029 mm/a. The corrosion rate of 0.5g/L Cu-Gr composite was found to be decreased by 2.7 times as compared to pure copper thin films. The structure of the films before and after corrosion was also analyzed to co-relate the electrochemical and structural relationship.

Abstract: Studies and production of anodic exfoliated graphene have been blossoming exponentially to meet the high demand for next generation optoelectronics devices. In this study, the effect of sulfate concentration on the graphene film is presented. The electrochemical exfoliation was conducted using a simple two-electrode system to study on the morphological and optical properties of graphene films using Atomic Force Microscope (AFM), Raman Spectroscopy and Ultraviolet–Visible (UV-Vis) spectrophotometer. Preliminary results show the presence of few layers graphene with nanometer-scale lateral dimension. The study suggests an alternative solution for the large-scale manufacturing capabilities of graphene is feasible

Abstract: The influence of hollow corundum microspheres on mechanical properties and wear resistance of nitrile butadiene rubber (NBR) with the lowest quantity of acrylonitrile (17-19%) have been studied. Results show that the abrasion resistance increased with increase in filler loadings at the two particle sizes investigated. Research of mechanical properties showed that strength at break decreased, while relative elongation at break increased with increase in microspheres loadings. Atomic force microscopy (AFM) was used to perform high-resolution imaging of surfaces of NBR composites. Microspheres exfoliation from NBR matrix at uniaxial stretching was studied with the use of special device compatible with AFM. The obtained AFM images demonstrate stretched fibrils bonded to the surface of microspheres.

Abstract: Polymer-clay nanocomposites (PCNC), are characterized by the high ratio of surface area to volume of the clay nanoparticles which are in the form of clay platelets with very high aspect ratio. This feature provides superior gas barrier properties at very low volume fraction of the nanofiller. Clay platelets introduce discontinuity to flows through the bulk polymer matrix material. The extent of this improvement depends on the success of separation of clay layers during processing which would produce single-layer particles (exfoliation) or several-layer particles (intercalation) through the bulk polymer matrix. This paper discusses the common permeability models used to capture the effects of the clay nanofillers in PCNC. Since these models assume a state of full exfoliation of clay platelets; that is a single phase of the nanofiller, they fall short of representing the actual state as evidenced by experimental works, which confirm the presence of both the intercalated phase and the exfoliated phase. A model that incorporates clay inclusions with different sizes (different thicknesses) is proposed and its implications are assessed.