فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 25 (تابستان 1397)

In this study, surface modification of silk fabrics was done through adsorbing multi-walled carbon nanotubes (MWCNTs) on the silk fabric surface. For this purpose, a simple method of immersing silk in the solution MWCNTs dispersion was used. In order to increase adsorption of activated MWCNTs on the silk fabric surface, citric acid was used as a crosslinking agent in the presence of sodium Hypophosphite as a catalyst. Results of potentiometric measurements showed that electrical conductivity of CNT modified silk fabric increases with the concentration of CNTs in the solution. Washing fastness of the CNT modified samples were assessed by a spectrophotometer just before and after washing out. Brightness was increased for all samples after washing. Scanning electron microscope (SEM) images was used to investigate morphology of fabric surfaces. SEM images represent that, in the same density, accumulation of single-wall carbon nanotubes was more in samples that obtained in presence of citric acid.

In this study, a nanocomposite of ZnV2O6 photo-catalyst hybridized with reduced graphene oxide (rGO) was prepared to degrade Rhodamine B. The ZnV2O6 nanostructures were successfully synthesized via co-precipitation route and the most significant process parameters were optimized during calcination. The structure and morphology were explored in detail using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Graphene oxide was synthesized from natural graphite powder using a modified Hummers method and reduced to graphene-like sheets by removing oxygen functionalities with the recovery of conjugated structure. The self-degradation of RhB is almost negligible, but when ZnV2O6 powders were inserted in the solution, the degradation of RhB increased to 44% after irradiation for 120 min. The ZnV2O6/rGO nanocomposites exhibit a much higher photocatalytic activity towards the photodegradation of dye, indicating that the presence of rGO can suppress charge recombination thanks to the fast interfacial electron transfer between ZnV2O6 particles and rGO sheets.

Magnesium has many benefits, since it has been used in many industries e.g. aerospace, electronics and etc. one of the most important advantages of magnesium is its high solidity, although the corrosion resistance of it is poor. In this study, the Surface modification of Magnesium Alloy AZ31 by conversion coatings based on Praseodymium was performed. The results confirmed the forming of conversion coating on magnesium alloy. Moreover, anti-corrosion performance of treated surface was investigated and according to the results of the tests, an improvement in the corrosion resistance can be observed.

Structure-property relation is of vital importance in developing advanced polymer nanocomposites as well as enhancing their ultimate properties. In this research study, toughening of polylactic acid (PLA) with nanofibrillated cellulose (NFC) was studied and comparison was made between thermal and mechanical properties of systems containing pristine and modified NFC. NFC was modified through two different methods; acetylation of hydroxyl groups and grafting of polyethylene glycol (PEG) onto cellulose chains. Fourier transform infrared spectroscopy , X-ray diffraction , and differential scanning calorimetry were employed to probe into the surface characteristics, thermal properties and crystallinity of NFC/modified NFC, respectively; moreover, SEM imaging was utilized for surface morphology of samples. Subsequently, PLA with modified and unmodified NFC was prepared to evaluate the filler addition effect on toughness. Acetylated NFC has changed the PLA crystallinity degree and rate, which affected the modulus of PLA, as signaled by the changed NFC surface. Particularly, mechanical and toughening behavior of the prepared nanocomposites were analyzed based on tensile measurements which showed an eight-fold rise in toughening along with 18% decrease in modulus of the samples comprising 1 wt.% of acetylated NFC compared to the blank PLA. In the light of the obtained results, it can be inferred that brittle PLA can be toughened by the surface modified NFC. This research study can illuminate the way for future works on the modifications of nano-scale fillers/additives to achieve improved mechanical and thermal properties of PLA.

In this study, a multi nano biosensor was developed for simultaneous detection of carbon dioxide, methane, ethanol and ammonia gas, and its electrochemical response to various concentrations of these gases was studied. In the previous study, GO/PANI nanocomposite was constructed and examined the chemical composition and morphology and its structure by analyzing FT-IR, FE-SEM, HR-TEM and XRD. In this study, we put nanocomposite on silver-coated new electrodes and then, by placing nanoparticles of aluminum oxide, zinc oxide, tin oxide and titanium oxide, different parts of the sensor were compared to Carbon dioxide, Methane, Ethanol and Ammonia are susceptible, then, the response rate and its sensitivity to each of the gases were measured by amprometric tests. The results showed that the sensitivity of the multi nano biosensor is acceptable for sensing these gases. The results of the electrochemical experiments showed that the response of each sensor component is defined as an illuminated 4 equation to a mixture of the four gas discussed. Considering the responses of the four components of this multi nano biosensor simultaneously to the 4-gas mixture, 4 equations are obtained, which can be ascertained by the exact concentration of each of the four measured gases.Of course, these equations are correct until none of the sensors are saturated and there is no other effective gas in the analyte.

In the present study, the combination of cladding and carburization process for reconstructing of gears made of DIN - 25CrMo4 steel was evaluated. Therefore, at fist weld cladding was carried out by using E - 7018-1 basic electrode to compensate the lost thickness. Subsequently, the cladded specimens was subjected to carburization process to increase the hardness and wear resistance of the coating. Microstructural and phase studies indicated that ferrite microstructure of base metal converted to the martensite accompanied with residual austenite and Fe-C carbides such as Fe3C that increased surface hardness ~300. Wear evaluations indicated significant improvement of wearing resistance of carbonized specimens (80% reduction in friction coefficient and 90% reduction in lost weight).the microscopy SEM study of worn surfaces implying a change in the wear mechanism from the two-body scrub bing wear to the cutting mechanism by increasing the volume fraction of the martensitic phase in the carbonized specimens.

This research focuses on the effect of synchronous and asynchronous apply of cross linking agents (CERESOL CPN and DMDHEU (N, N'-dimethylol-4, 5-dihydroxyethylene urea)) and Fluorocarbon (FOBUGARD AF300) on the repellency of the cotton fabric. Then the effect of silica particles on the repellency and durability of the samples was investigated. Silica particles were synthesized with TEOS (Tetraethyl orthosilicate), ethanol and ammonium hydroxide as catalyst which controls particle size of the silica and applied on the samples. Silica particles increase the roughness of the fabric surface and affect water/oil repellency. The optimum values are 6% of CPN and 8% of FOBUGARD AF300 provide oil and water repellency values 6 and 9 respectively. The FESEM and EDX were used for the assessment of morphological properties, size distribution and elemental analysis of fluorocarbon/silica particles coated fabric. Non-synchronous application of crosslinking agent and fluorocarbon resin improves the repellency of the samples. Also, silica particles enhance the durability of the treatment. So that after 5 cycles of washing and heat treatment of samples containing 1% of the synthesized silica particles, the values 6 and 9 were obtained for oil and water repellency, respectively.