فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 12 (بهار 1394)

Multiple nozzle electrospinning systems can be designed to increase both productivity and thickness for large scale nanofibers production. In the present study describes the results of the experimental investigation and modeling of multiple jets during the electrospinning of polyacrylonitrile (PAN) solutions. Several multiple nozzle electrospinning setups were tested. PAN solutions (15 w/v%) were electrospun varying the number of nozzles between 1 and 4. Nanofiber morphology was observed under a scanning electron microscopy (SEM). With increasing the number of nozzles in the electrospinning setup from 1 to 4, the average nanofibers diameter increased from 223±26 nm to 519±78 nm. The geometrical alignment and number of the nozzles showed significant effects on the average diameter and the divergence angle between jets. The divergence angle enlargement due to the increase of jets number from 2 to 4, made necessary to increase collector dimensions from 20cm×25cm to 40cm×45cm. It indicates that the interaction between the polymer jets from individual nozzles plays a great role in the electrospun nanofibers formation.

Graphene is a two dimentional crystal which made by a monolayer of carbon. It has a special electronic structure, which gives it unusual electronic, mechanical and thermal properties so that made it very useful for using in nanocamposits and even in an electronic industry. Although the graphene is a newfangled material, but these days graphene known as a vanguard of nanotechnology. The graphene oxide which consists of lots of functional groups could easily incorporate in many polymers and composites. Moreover, it is produced from rather cheap materials so it is an appropriate replacement for the most of organic and inorganic fillers. In this report the chemical structure of graphene and graphene oxide, synthesis methods which consist of micro-mechanical exfoliation, epitaxial growth, chemical vapor deposition, electrostatic deposition, upzipping of cabon nano tube and also chemical methods were depicted. So for improving its dispersing behavior in different matrix, different methods of functionalization of graphene were studied. The emphasis of this paper is on the functionalization of graphene surface even by covalancy or noncovalancy bond. Indeed this paper is a review of more than 110 different articles in this field.

In this study, the influence of temperature on the formation of a zirconium-based conversion coating is investigated for the automotive industry. The coated samples were obtained by dipping galvanized steel substrates in a hexafluorozirconic acid based solution. The coating was characterized using scanning electron microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). The protective efficiency of coatings was evaluated by potentiodynamic polarization measurement and salt spray test. The SEM/EDS and AFM analyses revealed that treated galvanized surfaces are covered with nano nodules. According to polarization measurements and salt spray tests all samples treated with the conversion solution had a better corrosion performance in comparison with the blank galvanized sample. From the potentiodynamic polarization experiment, the best anti-corrosion performance occurred when the temperature of solution was considered 25 °C.

Deterioration of lubricants and dressings used in the conservation of historic leathers can alter the aesthetic and structural properties of these objects. Therefore, regarding to values of historical relics, assess the stability of conservation materials will be required before protective interventions. Hence, the heat stability of polyethylene glycol (PEG) and silicone oil were studied as dry and waterlogged leather dressings. Moreover, performance of ascorbic acid (AA) was evaluated as an antioxidant additive for PEG. For this purpose, structural stability of leather dressings and aesthetical changes of treated leathers were investigated by ATR-FTIR spectroscopy and colorimetery technique. The results show that aging process causes to severe oxidation in PEG, whereas ascorbic acid inhibits the change. Color measurement signified an intense color change of the aged PEG and PEG+AA treated leathers. While, silicone oil had a great heat stability and the treated leathers showed minimum color change. Therefore, silicone oil treatment was characterized best than PEG and PEG+AA, due to its high stability and minimum color change in treated leathers.

A series of potassium zinc phosphate (PZP) pigments were synthesized by a co-precipitation method using different mole ratios of KOH:ZnCl2, and were investigated their inhibitive properties in this study.The morphology and phase composition of the pigments were studied by X-ray diffraction (XRD),Fourier transform infrared spectroscopy (FTIR)and scanning electron microscopy (SEM). The concentration of the ions released was measured by an inductivelycoupled plasma mass spectrometry (ICP). Also, the corrosion inhibition action of the pigment extract was studied bypolarization testthrough dipping steel samples in the solution containing extract for different immersion times.The results of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) revealed that the ratio of KOH:ZnCl2 significantly affected the phase composition, the shape and size distribution of the pigments. KZn-2(HPO4)PO4 and KZnPO4are the main phase recognized at low and high KOH:ZnCl2 ratio, respectively. Results showed a decrease in the corrosion current density of the steel panels immersed in the solutions containing PZPs for 24 h. In addition, it was found that PZPs with KZn-2(HPO4)PO4 phase showed greater corrosion inhibition properties than those having KZnPO4 phase.

Abstract: In this research, alpha-cellulose was extracted from Turkmen Sahra cotton waste (linter) under mild conditions. Effect of soda curing with auxiliaries such as sodium sulfide and sodium dithionite were investigated on the final properties of the alpha-cellulose, including degree of polymerization, weight loss and yellowness. Also, influence of bleaching conditions by hydrogen peroxide on the properties of final product was studied. Under mild curing with sodium hydroxide/sodium dithionite, alpha-cellulose containing optimal degree of polymerization (DP), yellowness and weight loss equal to 5755, 24.20 and 8.95%, was achieved respectively, which is higher in DP and lower in yellowness and weight loss in comparison to other similar methods. The product whiteness and DP were achieved to be 52.64 and 5441 respectively after bleaching with 3% (w/w) hydrogen peroxide at 85oC.

Epoxy resin has high capacity in order to properties enhancement. Since, polymer's morphology has a great effect on mechanical properties of polymers, there are many attempt to find relation between mechanical properties and morphology in polymers and it is an interesting area for researchers. To understand the relation between morphology and mechanical properties, knowing deformation mechanism and fracture is necessary. In this paper we aim to investigate the effect of liquid elastomer addition on fracture resistance of epoxy resin. For this purpose, the history of liquid elastomer addition and toughening mechanism have been reviewed.