Abstract:A new strategy to induce superhydrophobicity via introducing hierarchical structure into the polyvinylidene fluoride (PVDF) film was explored in this study. For this purpose nanofibrous composite films were prepared by electrospinning of PVDF and PVDF/graphene blend solution as the main precursors to produce a net-like structure. Various spectroscopy and microscopy methods in combination with crystallographic and wettability tests were used to evaluate the characteristics of the synthesized films. Mechanical properties have been studied using a universal stress-strain test. The results show that the properties of the PVDF nanofibrous film are improved by compositing with graphene. The incorporation of graphene flakes into the fibrous polymer matrix changes the morphology, enhances the surface roughness, and improves the hydrophobicity by inducing a morphological hierarchy. Superhydrophobicity with the water contact angle of about 160° can be achieved for the PVDF/graphene electrospun nanocomposite film in comparison to PVDF pristine film.

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This study aims to investigate a novel technique to improve the yield of liquid phase exfoliation of graphite to graphene sheets. The method is based on the utilization of magnetic FeO nanoparticles as "particle wedge" to facilitate delamination of graphitic layers. Strong shear forces resulted from the collision of FeO particles with graphite particles, and intense ultrasonic waves lead to enhanced exfoliation of graphite. High quality of graphene sheets along with the ease of FeO particle separation from graphene solution which arises from the magnetic nature of FeO nanoparticles are the unique features of this approach. Initial graphite flakes and produced graphene sheets were characterized by various methods including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Zeta potential analysis. Moreover, the effect of process factors comprising initial graphite concentration, FeO nanoparticles concentration, sonication time, and sonication power were investigated. Results revealed that graphene preparation yield and the number of layers could be manipulated by the presence of magnetic nanoparticles.

Experimental and numerical studies were conducted on the performance and capacity of structured packings for mixture separation with very low separation factor. Different formations and conditions of the innovative structured packing PACK-2100 with high surface area were studied to evaluate the main characteristics such as dry pressure drop. In addition, numerical simulation was performed to describe the details of the flow structure in these modified structured packings. Three-dimensional computational fluid dynamics modeling of PACK-2100 allowed for comparing the pressure drop in both laminar and turbulent flow regime. The obtained experimental and numerical data demonstrate the potential contribution of the packing to high-efficiency systems with low separation factor.