فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 29 (تابستان 1398)

In this research, the cladding process was done using the mechanically alloyed Al-Cr and Al-Cr2O3 powder mixtures by GTAW process on the surface of CK45 steel. After creating the AlCr2 and AlCr2-Al2O3 surface layers, the microstructural and microhardness of the claddings were studied by optical microscopy, scanning electron microscopy and microhardness measurements. In order to evaluate the wear resistance of the claddings, pin-on-disk wear test was done. It was found that after 20 h of MA of Al-Cr powder mixture, Cr(Al) solid solution was formed. XRD analysis of created cladding by this powder mixture indicated the formation of AlCr2 phase. Also the cladding of Al-Cr2O3 powder mixture led to the formation of AlCr2 and Al2O3 phases. The microhardness of both claddings was higher than the base metal. Also the microhardness of AlCr2-Al2O3 cladding reached to about 780 HV. The predominant wear mechanism in wear test of both claddings was micro-cutting abrasive wear. The wear weight loss of AlCr2 cladding was about 0.2 mg, while AlCr2-Al2O3 cladding did not show any weight loss. The friction coefficient of AlCr2-Al2O3 cladding after 200 m of sliding distance was about 0.15 which reached to about 0.35 at longer sliding distances. This increase in friction coefficient of this cladding as compared with AlCr2 cladding was related to the presence of Al2O3 hard particles in this cladding.

Protein coating as an outstanding surface modification strategy can influence the organization of biomolecules in the interface with nanomaterials. In the present study, human serum albumin (HSA) were applied to modify the surface chemistry of single walled carbon nanotubes (SWNTs) and carboxylated SWNTs (CO2-SWNTs). This study was conducted to discover the effect of protein coating on the protein corona composition and biological activity of both SWNT types. Different methodologies were performed in order to characterize the physicochemical properties of both SWNTs after surface modification. The results showed that HSA followed changed the biomolecular organization of SWNTs and CO2-SWNTs coronas . Protein coating also changed the plasmon intensity of both SWNT derivatives which affected the efficacy of their interaction with proteins existed in plasma. Moreover, both SWNTs coronas revealed less cytotoxicity and cellular uptake in comparison to bulk samples. It can be concluded that surface modification of SWNTs with different protein can alter the corona pattern that consequently affect the biological behavior of these nanomaterials.

In this study, polyurethane foam was prepared using various nanostructures including polymer nanofibers, carbon nanotubes, and nickel oxide nanoparticles. Polyurethane, poly (methyl methacrylate) and poly (vinyl alcohol) nanofibers were first fabricated by electrospinning method and added to the foam during the formation of polyurethane foam along with carbon nanotube and nickel oxide nanoparticles. The morphology, mechanical properties and sound absorption behavior of the foam were evaluated using scanning electron microscopy (SEM), Instron an impedance tube. The results indicate that the nanofibers are uniform and free of beads, as well as the presence of these nanofibers within the pores and porosity of the foam. Polyurethane foam reinforced with polymer nanofibers also showed higher compressive strength than pure polyurethane foam. Sound absorption studies of foam showed that the addition of nanostructures improves the sound absorption efficiency of polyurethane foam in the frequency range of 250-610 Hz. Polyurethane foam reinforced with poly (methyl methacrylate) nanofibers and carbon nanotubes as well as nickel oxide nanoparticles exhibits the highest sound absorption at all frequencies, especially at low frequencies.

Because of increasing in consumption of digital printers in home and office uses it is important to recycle these papers in a green and sustainable way. Enzyme deinking is an eco-friendly and effective deinking method. In this paper enzyme deinking of electrophotography papers done with commercial cellulose, cellusoft CR supplied from Novozymes Company. The enzyme was applied in three doses including 2.5, 0.25, and 0.025 U on 15 g recycled oven dry pulp prepared from printed paper. Reaction temperature and time were used at of 30, 45, 60 ˚C and 15, 60, 120 min, respectively.15 treatments were intended for this study. Washing and floatation of pulp carried out after enzyme treatment and then optical properties and reprinting of handsheet was evaluated. Measurement of CIE L*a*b*, reflection and optical density showed that printability and print quality after enzyme deinking is acceptable. Measurement of CIE L*a*b*, reflection and optical density showed that printability and print quality after enzyme deinking is acceptable.

In the present study, the performance of a batch suspension photoreactor has been investigated and compared with a catalytic-membrane photoreactor (PMR) for removal of Basic Violet 16 (BV16) from synthetic effluent. Initially, influence of the effective parameters on the photocatalytic process in the presence of Zinc oxide doped with calcium (ZnO: Ca) such as photocatalyst dosage, pH, temperature, initial dye concentration and aeration was studied. Based on the results, the optimal condition of the process was: Catalyst dosage (0.06 g.L-1), normal pH (5.5), ambient temperature, Dye concentration: 10 mg.L-1 and Aeration: 5.5 L.min-1, respectively. The results showed that the removal efficiency at the high concentrations decreases in the photocatalytic process. This will reveal the need to integrate a system as pre-treatment of input feed prior to the preparation. In this study, a polyvinylidene fluoride-based membrane (PVDF) was used as a pre-purification agent before the batch rector system. The results of the research and the calculation of process efficiency show that PMR has been successful in removal of BV16 dye in the same concentrations and also more than the optimal dye concentration of suspension system. Comparing the kinetc of the reactions, the constant reaction rate in PMR increased by about 14% in comparison of the batch system at the optimal concentration (60%) and above the optimal concentration (30 mg.L-1).

In this research, degradation of ß-carotene in nanostructured lipid carriers was studied employing spectrophotometric method. The effect of ß-carotene concentration, liquid lipid concentration, surfactant concentration and temperature on stability of ß-carotene was investigated. ß-carotene loaded nanostructured lipid carriers were prepared using solvent diffusion method and the samples were kept in darkness at room temperature. The results indicated that the degradation of ß-carotene in nanostructured lipid carriers follows first order kinetics. The stability of ß-carotene increased significantly by increasing the liquid oil concentration. Furthermore, rising the ß-carotene and surfactant concentrations from 1-5 %w/w resulted in climbing of degradation rate constants from 0.00473 and 0.00737 up to 0.01280 and 0.01093 1/h, respectively. ß-carotene retention decreased by Increment of temperature from 5°C to 65°C while further elevating of temperature was led to reverse results. Particle size studies revealed that addition of ß-carotene to nanostructured lipid carriers grows particle size from 38nm to 105 nm. Moreover, liquid lipid concentration had no significant effect on initial particle size of ß-carotene loaded nanostructured lipid carrier.

Hydrogel is a three dimensional water insoluble polymeric network that can absorb body fluids in a biological environment. Its polymer network structure can be formed by chemical cross-linking such as photo-polymerization, enzyme-catalyzed reactions, and physical cross-linking induced by temperature, pH, and ionic interaction. Physical hydrogel is formed by weak secondary interaction. Covalent bonds are normally formed among polymer chains in a chemically crosslinked hydrogel. To synthesize hydrogels, natural and synthetic polymers were applied. Swelling, mechanical and biological properties of the hydrogels are the most important parameters that can be affected on its structure and morphology. The large volume of water that they can absorb and an ability to mimic the extracellular matrix environment are the main reasons for use the hydrogels for many biomedical applications such as tissue engineering, contact lenses, wound healing, and the controlled delivery of therapeutic agents. This review covers the various mechanisms of hydrogel formation, types of hydrogels, their properties and applications in the medicine.