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Showing 3 results for Emami
Modification of Superhydrophilic, Anti-bacterial Polyurethane Polymer with TiO2 Nanoparticles for Medical Devices
A. Razmjou, F. Noorisafa, N. Emami,
Volume 37, Issue 4 (Journal of Advanced Materials-winter 2019)
Abstract
Polyurethane polymer plays an important role in health care, and it is widely used in medical devices and instruments. However, the low biocompatibility and biofilm formation on the surface can be regarded as a challenging issue. Engineering the wetting capability of the surface is an effective way to increase the biodegradability of polymer surfaces with sufficient bulk properties. In this study, the surface modification of polyurethane sheets by a thin layer of polyethylene glycol and trapping of titanium dioxide nanoparticles were carried out by means of physical and chemical changes on the surface to enhance the biocompatibility. The physicochemical properties of the modified surfaces were determined using fourier-transform infrared (FTIR) spectroscopy , scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and contact angle and free surface energy measurement. The biocompatibility of the modified levels was evaluated using the MTT toxicity test on cervical cancer cells (HeLA), bacterial adhesion, biofilm formation, and the protein absorption assay by the Bradford method. A thin, autoclave able and inexpensive thin layer with a solid and stable roughening structure was created covalently on the surface of the polyurethane plates for biological and medical applications. The results, therefore, showed that apart from antibacterial activity, the modified sample also had the ability to reduce the biofilm formation, such that the maximum biofilm attachment inhibition in the first 24 hours was 94% higher than that of the modified sample.

A New Method for the Experimental Evaluation of High-Temperature Erosion-Corrosion in Fluidized Bed Waste Incineration Conditions
M. Emami, Sh. Hayashi,
Volume 38, Issue 3 (Journal of Advanced Materials-Fall 2019)
Abstract
The outer surface of heat exchanger tubes that work under fluidized bed waste or biomass incineration is exposed to severe high-temperature erosion-corrosion (E-C). To evaluate the behavior and enhance the service life of the tubes, the real service conditions ought to be simulated in the laboratory. In this study a test rig with a fluidized bed of hot sand was designed and manufactured to expose nickel-based SFNi4 alloy to high-temperature E-C. In order to increase the corrosiveness of the environment, the silicon oxide sand was mixed with 0, 0.5 and 1 wt.% of a mixture of NaCl and KCl salts with 1:1 molar ratio. The erosive conditions of the environment were changed by altering air flow rate from 20 to 25 L/min and changing the sand incident angle from 45 to 90 degrees. The rate of material removal was calculated by measuring the thickness of each sample before and after the test. After each experiment, the surface and cross-section of specimens were studied using SEM and EDS analysis. Finally, the optimum E-C parameters to ensure actual industrial conditions were obtained.

High Temperature Erosion- Oxidation Behavior of Nickel- Based Alloys Containing Mo in Fluidized Bed Waste Incineration
M. Emami, S. Hayashi,
Volume 39, Issue 3 (Journal of Advanced Materials-Fall 2020)
Abstract
High-temperature erosion-oxidation behavior of nickel-based alloys containing 0-7 wt.% Mo in fluidized bed waste incineration conditions was studied. A stream of hot condensed air with a flow rate of 25 L/min caused hot silica sand (700 °C) mixed with 0.5 wt.% of chloride salts to hit the specimens for 250 h. By removing the erosive factor, the high-temperature oxidation behavior of the alloys in air and air-chlorine atmospheres was studied at 520 and 560 °C for 100 h. Mass gain measurement due to oxidation followed by thickness loss measurement in the erosion-oxidation tests showed that an increased Mo content led to improved oxidation resistance as a result of reduced scaling rate. However, under simultaneous oxidation and erosion conditions, the lower oxidation rate of the alloy with 7 wt.% Mo caused rapid removal of the protective scale and a reduction in erosion-oxidation resistance of the alloy. Under these conditions, the alloy with 3 wt.% Mo showed the smallest removal rate. Microscopic observations and XRD analysis confirmed formation of Cr2O3/NiCr2O4 scales on the surface.  Mo-free alloy with lowest oxidation resistance showed a higher erosion-oxidation resistance. However, the high oxidation rate of this alloy led to a severe Cr-depletion and internal oxidation in subsurface region.

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