ADVANCED MATERIALS AND NOVEL COATINGS
Year:2019 | Volume:8 | Issue:30 |Papers Count:7

In this study, polyurethane nanofibers containing carbon nanotubes modified with metal oxide nanoparticles including copper oxide and chromium oxide were prepared. First, carbon nanotubes were modified by hydrothermally (CNT-CuO-h) and ultrasonically (CNT-CuO-s) synthesized copper oxide nanoparticles, as well as chromium oxide, and then 12% polyurethane solution containing 0. 7% modified carbon nanotube were electrospuned. Morphology and energy dispersive X-ray diffraction (EDX) results indicating the distribution and dispersion of metal oxide nanoparticles on carbon nanotubes, as well as the uniform distribution of bead-free nanofibrous composites. Moreover, structural analysis through Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction patterns (XRD) indicate the modification of carbon nanotube with copper and chromium oxides. Investigation of hydrogen sulfide adsorption on nanofibrous membrane containing modified carbon nanotubes and its comparison with nanofibrous membrane containing carbon nanotubes and activated carbon indicate a significant enhancement in gas adsorption capacity of samples containing carbon nanotubes modified with metal oxides. The results showed that adding only 0. 7% (wt. %) carbon nanotube modified with copper oxide (CNT-CuO-h) to polyurethane nanofiber membranes increases the hydrogen sulfide adsorption capacity and gas breakthrough time by three times.

anodizing due to the significant increase in the surface performance of aluminum and its alloys is an appropriate method in the field of surface engineering. But for the application of this method as much as possible, filling the porosity of this coating is a very effective selection. On the other hand, due to the unique structure of the oxide layer, this layer can also be used to grow a variety of nanowires. In this study, 1070 aluminum anodizing was performed in oxalic acid-sulfuric acid solution. In order to reduce the thickness of the barrier layer, the anodizing voltage was slowly reduced in the last step of anodizing. Microstructure of the coating was studied by means of field emmision scanning electron microscopy (FESEM) images. Subsequently, silver nanowires were grown in the oxid layer by electrochemical deposition method. The result of X-ray diffraction(XRD) test showed that the oxide layer has a non-crystalline structure and silver nanowires has a very high purity. The hardness measurment of the samples showed that the presence of silver reduces the hardness of coating. The wear resistance of the coatings was investigated using a pin on disc test. The growth of silver in the oxid coating resulted in a 55% increase in the wear resistance. The scanning electron microscopy (SEM) images of the wear surfaces showed that this increase is related to silver lubrication nature that have reduced the coefficient of friction of the coating in the presence of these fillers. The effect of these nanowires on the corrosion resistance of anodized aluminum was studied by using electrochemical impedance and polarization tests. The results showed that corrosion behavior was improved slightly in the presence of silver nanowires.

Both physical and mechanical properties of a semi-crystalline polymer are highly related to the crystallization behavior and morphology development during processing. In the present work, non-isothermal crystallization of polypropylene/graphene nanoplatelets (PP/GnPs) nanocomposite fibers containing 0. 1, 0. 5, and 1% GnPs was investigated by differential scanning calorimetry (DSC). The Ozawa and Mo methods were used to fit the primary stage of non-isothermal crystallization of the samples. Moreover, the nucleation activity and the crystallization activation energy of GnPs in the PP matrix were calculated by Dobreva’ s approach and Friedman’ s method, respectively. The results show that the crystallization peak shifted to the lower temperatures with increasing cooling rate. Contrary to Ozawa method, it was observed that Mo approach could describe the non-isothermal crystallization process of PP and PP/GnPs nanocomposite fibers satisfactory. Furthermore, the maximum and minimum nucleation activity was observed for PP/G-0. 1 and PP/G-1 nanocomposite fibers, respectively. Crystallization activation energy decreased in the presence of GnPs, indicating that it is easier for the PP/GnPs to crystallize. Although GnPs work as a nucleating agent, they also act as a barrier to molecular mobility and reduce the growth rate, resulting in a more depressed crystallization for PP/GnPs nanocomposite fibers.

Direct yellow is one of the contaminations in the wastewater, which is dangerous for environmental health. In the present study, Co3O4-ZnO-Ag nanocomposite was synthesized as a photocatalyst using two-stage precipitation method. The synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy, differential thermal and weight loss analysis, and UV-Vis spectroscopy. XRD patterns showed that the size of ZnO crystallites increase with increasing the silver content. SEM micrographs showed that the size of particles in the sample with 3% silver was in the range of 20-300 nm. UV-Vis absorption spectrum of the prepared powders revealed that absorption in the visible region increases by adding metallic Ag. Calculation of the band gap energy indicated that by increasing the Ag content, the band gap energy of the samples decreases. Investigation of photocatalyst behavior for degradation of direct yellow dye exhibited that by adding 3% Ag to Co3O4-ZnO nanocomposite, the degradation efficiency improved from 71% to 89%. However further increase of Ag reduced the degradation kinetics, because Ag nanoparticles act as sites for accumulation of electrons and recombination of electron-hole pair.

Thermoplastic vulcanized (TPVs) with high abrasion resistance based on BR / PP and BR/ Ac-BR/ PP were prepared using melt mixing method under dynamic vulcanization condition. First, the mechanical (tensile strength, elongation at break and abrasion resistance) properties of BR and BR/ Ac-BR compounds were evaluated. The results show that although the abrasion resistance of rubber compound is much higher than pure BR, it has lower tensile strength and elongation at break. TPV samples were then prepared from BR/ PP and BR/ Ac-BR/ PP with a rubber / plastic ratio phase of 70 to 30. The results showed that TPVs based on BR / Ac-BR/ PP in which a finer vulcanized rubber particles are dispersed in the plastic matrix, exhibit higher abrasion resistance and tensile strength. Also, differential temperature scanning calorimetry (DSC) analysis shows a lower crystallinity degree of TPV based on BR/ Ac-BR/ PP, which is due to better dispersion of smaller micro-size of vulcanized rubber particles in PP, promoting better rubber-plastic matrix interaction in TPV. This has also been investigated using scanning electron microscopy (SEM) images of the samples.

Diffuse reflectance spectra of printed cotton/nylon blend fabrics coated with mineral compounds are investigated in near infrared (NIR) and short-wave infrared (SWIR) in order to tune the diffuse reflectance behavior of them with the ones in woodland and desert backgrounds. Cotton/nylon blend fabrics printed with four-color digital pattern were used as the substrate and different concentrations of magnesium oxide and cerium dioxide (MgO and CeO2) with and without citric acid as a cross-linker were loaded on these fabrics using pad-dry-cure method. Coated fabrics were characterized by diffuse reflectance spectroscopy (DRS), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). Adding 1% (w/v) of nanoparticles to fabric could approach the reflection spectrum of fabrics to reflection pattern of forest and desert areas by reducing the reflection trend. Also, adding 6% (w/v) citric acid combined with 1% (w/v) cerium dioxide and magnesium oxide to the fabric could reduce the total reflection at all wavelengths. However, the reduction of reflection intensity of magnesium oxide was higher at all wavelengths. Electron microscopy images also showed that fabrics coated with cerium dioxide had a better dispersion on the surface of fabric and a mean particle size about 50 to 70 nanometers. In contrast, magnesium oxide nanoparticles, when bonded with citric acid, exhibit better adsorption on the fabric but are more likely to agglomerate.

nano-molecularly imprinted polymer (N-MIP) dual-sensor based on a graphene screen-printed electrode was developed for the detection of glycated hemoglobin and cardiac troponin T (cTnT), separately. In order to obtain a biomimetic surface, a conductive copolymer matrix was deposited on the surface of graphene oxide (GO) electrode. The sensor probe was modified via electropolymerization of aniline and carboxylated aniline on the graphene oxide (GO) electrode, in the presence template proteins (cTnT for cardiac troponin T probe and HbA1c for glycated hemoglobin probe) by cyclic voltammetry. The surfaces of both sensors were characterized using cyclic and differential pulse voltammetry (CV), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), quartz crystal microbalance (QCM). The best biomimetic surface nanotexture was obtained at aniline/carboxylatedaniline ratio of 1: 4. The linear ranges of cTnT and HbA1c were from 0. 02 to 0. 09 ng/mL and from 0. 004 to 0. 81 μ g/mL, with detection limits of 0. 008 ng/mL and 4. 3 ng/mL, respectively. The reliability of the M-NIP cTnT and HbA1c sensors was examined by comparing the results with those obtained from HPLC method and It was observed that the results from N-MIP sensors and HPLC had a great correlation.