Raed Hashaikeh

Fog-harvesting potential of lubricant-impregnated electrospun nanomats.

Hydrophobic PVDF-HFP nanowebs were fabricated by a facile electrospinning method and proposed for harvesting fog from the atmosphere. A strong adhesive force between the surface and a water droplet has been observed, which resists the water being shed from the surface. The water droplets on the inhomogeneous nanomats showed high contact angle hysteresis. The impregnation of nanomats with lubricants (total quartz oil and Krytox 1506) decreased the contact angle hysteresis and hence improved the roll off of water droplets on the nanomat surface. It was found that water droplets of 5 μL size (diameter = 2.1 mm) and larger roll down on an oil-impregnated surface, held vertically, compared to 38 μL (diameter = 4.2 mm) on a plain nanoweb. The contact angle hysteresis decreased from ~95 to ~23° with the Krytox 1506 impregnation.

Nanocrystalline cellulose extraction process and utilization of the byproduct for biofuels production.

Cellulose consists of amorphous and crystalline regions. It is the crystalline regions which may be exploited to produce nanocrystalline cellulose (NCC). In order to extract nanocrystalline cellulose from native cellulose, sulfuric acid hydrolysis is typically used. The amorphous regions of cellulose are hydrolyzed and degraded into soluble products while the crystalline regions remain intact. In an effort to make the NCC extraction process more feasible, a new process was developed to recover and utilize the hydrolyzed regions of cellulose as a byproduct. The acid hydrolyzed amorphous regions were separated and then recovered (regenerated) into solid particles. XRD data revealed that the recovered material is characteristic of cellulose II. Hydrolysis conditions were optimized to maximize the yield of the recovered material and at the same time produce NCC material. Preliminary experiments showed yield values of approximately 61% for the cellulose I crystalline portions and values of about 21.7% for the recovered material (cellulose II). Enzymatic hydrolysis experiments of the recovered material revealed high susceptibility to enzymatic hydrolysis which makes it a promising source for biofuels production.

Modified cellulose morphologies and its composites; SEM and TEM analysis.

The complex, multi-level super molecular architecture of cellulose has been the subject of interest for several decades. The mechanical, physical, and environmental properties of cellulose depend on the molecular, supramolecular and morphological structure of the cellulose. This paper gives a brief overview to micro structural analysis of cellulose, as studied using transmission electron microscopy and scanning electron microscopy. The application of these techniques to study the diverse morphology of cellulose and its composites is illustrated using several examples.

Synthesis and morphology analysis of electrospun copper nanowires

We report the fabrication of copper nanowires (NWs) using electrospinning technique. This processing technique was used successfully to synthesize copper NWs with various morphologies using a precursor composed of copper acetate salt and poly(vinyl) alcohol. The obtained NWs were characterized through high resolution scanning electron microscopy and atomic force microscopy and it was found that their morphology is sensitive to the applied voltage and solution flow rate. Their diameter decreased with increasing voltage and increasing flow rate. Moreover, at higher flow rate and lower voltage, the roughness of NWs became more pronounced. In addition, further improvement in NW morphology may be obtained with appropriate heat treatment. These copper NWs with varying morphologies and microstructures have potential applications in different engineering domains such as electronics, optoelectronics, and catalysis.

Electrospun metallic nanowires: Synthesis, characterization, and applications

Metals are known to have unique thermal, mechanical, electrical, and catalytic properties. On the other hand, metallic nanowires are promising materials for variety of applications such as transparent conductive film for photovoltaic devices, electrodes for batteries, as well as nano-reinforcement for composite materials. Whereas varieties of methods have been explored to synthesize metal nanowires with different characteristics, electrospinning has also been found to be successful for that purpose. Even though electrospinning of polymeric nanofibers is a well-established field, there are several challenges that need to be overcome to use the electrospinning technique for the fabrication of metallic nanowires. These challenges are mainly related to the multi-steps fabrication process and its relation to the structure evolution of the nanowires. In addition to reviewing the literature, this article identifies promising avenues for further research in this area with particular emphasis on the applications that nonwoven metal wires confined in a nano-scale can open.

Facile synthesis of copper oxide nanoparticles via electrospinning

A novel approach for synthesizing copper oxide (CuO) nanoparticles (NPs) through electrospinning is reported. The approach is based on producing rough and discontinuous electrospun nanofibers from a precursor based on copper acetate salt and polyvinyl alcohol (PVA) polymer. Selectively removing the polymeric phase from the fibers produced highly rough CuO nanofibers, which were composed of NPs that are weakly held together in a one-dimensional (1D) manner. Sonication in a suitable liquid under controlled conditions completely disintegrated the nanofibers into NPs, resulting in the formation of uniform CuO NPs suspension. Aberration corrected high resolution transmission electron microscope (HRTEM) showed that the obtained NPs are highly crystalline and nearly sphere-like with a diameter of 30 to 70 nm. Thus, electrospinning, which is a low cost and industrially scalable technique, can also be employed for economic and large scale synthesis of NPs.

Optimum loading level of nanoclay in PLA nanocomposites: Impact on the mechanical properties and glass transition temperature

Biodegradable polymer nanocomposites of poly(lactic acid) and nanoclay (Cloisite 30B) samples were prepared with compositions of 0%, 1%, 2%, 3%, 4%, and 5% (by mass) nanoclay using extrusion followed by injection molding. An exfoliated morphology was observed using x-ray diffraction. The nanocomposites were investigated for their mechanical properties using dynamic mechanical analysis (DMA) and tensile testing. The combination with 3% nanoclay was found to be optimum as a result of having the greatest mechanical strength. The fracture surfaces of the samples were also observed with the help of a scanning electron microscopy, and the images obtained complied with the experimental values attained for the samples, indicating more ductile fractures for those samples with greater mechanical strength. The thermal properties of the composites were studied with the help of differential scanning calorimetry and DMA data, and it was found that the trend followed by the glass transition temperature values obtained by both the methods was the same.

Electrolytic processing of MgO coatings

MgO coating was formed on nickel superalloy substrate. The coating process consisted of two steps: cathodic electrolytic deposition of MgOH, and heat treatment. The heat treatment was necessary to calcinate and to sinter the deposit. The deposit morphology and composition, before and after heat treatment, were studied by X-ray diffraction and the scanning electron microscopy. The influence of deposition parameters on deposition yields and deposit morphology is studied and discussed.

Theoretical and experimental study of direct contact membrane distillation

AbstractDirect contact membrane distillation (DCMD) is characterized as a low-thermal energy process, involving evaporation and a phase change driven by the pressure difference between two fluid channels separated by a hydrophobic membrane. The temperature difference creates a driving pressure between the hot channel (feed) and the cold channel (permeate). This paper demonstrates the performance of the DCMD through high fidelity simulation and experimental observation to reveal a fundamental and qualitative understanding of the spatial distribution of the temperature, mass flux, and heat flux as well as the temperature polarization. The flow model is governed by the Navier–Stokes equations of non-isothermal fluid coupled with the energy equation for the two adjacent channel flow and the middle hydrophobic and porous membrane. The experimental study involved the development of a transparent acrylic DCMD unit operated by two peristaltic pumps where each cycles the feed and the permeate from the correspondin...

Photocatalytic activity of an electrophoretically deposited composite titanium dioxide membrane using carbon cloth as a conducting substrate

This is the first report where a polymer, namely poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP), has been used as a binder together with the electrophoretic deposition process. PVDF–HFP provided mechanical stability and membrane flexibility and, at the same time, eliminated the leaching of the electrophoretically deposited TiO2 particles in the solution during the water treatment process. Electrophoretic deposition of TiO2 particles containing different weight percentages of PVDF–HFP were conducted and the required concentration of PVDF–HFP in the solution to prevent the leaching of TiO2 was established. The obtained material finds applications in photocatalytic water treatment, as investigated under simulated solar light in aqueous solutions using 4-nitrophenol, caffeine, acetaminophen and uracil as target molecules. Results indicated the complete removal of 4-nitrophenol after 24 hours, a degradation percentage above 80% of acetaminophen and uracil and 60% for caffeine. Photodegradation of pre-adsorbed methylene blue (MB) both under simulated solar radiation and visible light was successfully achieved in dry conditions as confirmed by diffusion reflectance spectra.