Browsing by Author "Darwish, Mohamed S. A."
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- ItemControlled Preparation of Thermally Stable Fe-Poly(dimethylsiloxane) Composite by Magnetic Induction Heating(MDPI, 2019-05-07) Al-Harbi, Laila M.; Darwish, Mohamed S. A.; Khowdiary, Manal M.; Stibor, IvanThe most challenging task in the preparation of poly(dimethylsiloxane) composites is to control the curing time as well as to enhance their thermal and swelling behavior. Curing rate can be modified and controlled by a range of iron powder contents to achieve a desired working time, where iron is used as self-heating particles. Iron under alternative current magnetic field (ACMF) is able to generate thermal energy, providing a benefit in accelerating the curing of composites. Three types of iron-Poly(dimethylsiloxane) (Fe-PDMS) composites were prepared under ACMF with iron content 5, 10, and 15 wt %. The curing process was investigated by FTIR, while the morphology and the thermal stability were examined by SEM, DMA, and TGA. The heating’s profile was studied as functions of iron content and induction time. It was found that the time required to complete curing was reduced and the curing temperature was controlled by varying the iron content and induction time. In addition, the thermal stability and the swelling behavior of the prepared composites were enhanced in comparison with the conventional PDMS and thus offer a promising route to obtain thermally stable composites.
- ItemFunctionalized Magnetic Nanoparticles and Their Effect on Escherichia coli and Staphylococcus aureus(Hindawi Publishing Corporation, 2015) Darwish, Mohamed S. A.; Nguyen, Nhung H. A.; Ševců, Alena; Stibor, IvanMagnetite (Fe3O4) nanoparticles were prepared using coprecipitation and subsequently surface-functionalized with 3-aminopropyltriethoxysilane (APTS), polyethylene glycol (PEG), and tetraethoxysilane (TEOS). Nanoparticle morphology was characterized using scanning electron microscopy, while structure and stability were assessed through infrared spectroscopy and zeta potential, respectively. Average size of the nanoparticles analysed by dynamic light scattering was 89 nm, 123 nm, 109 nm, and 130 nm for unmodified magnetite and APTS-, PEG-, and TEOS-modified magnetite nanoparticles, respectively. Biological effect was studied on two bacterial strains: Gram-negative Escherichia coli CCM 3954 and Gram-positive Staphylococcus aureus CCM 3953. Most of modified magnetite nanoparticles had a significant effect on S. aureus and not on E. coli, whereas PEG- magnetite nanoparticles displayed no significant effect on the growth rate of either bacteria.