نشریه علوم و فناوری رنگ
سال دوازدهم شماره 3 (پیاپی 45، پاییز 1397)

The stability of acid treatment solution containing 100 ppm hydrogen peroxide, as a surface activating agent and 1 mM benzothiazole, as a corrosion inhibitor during 12 days of storage was investigated using electrochemical impedance spectroscopy (EIS), polarization test, high resolution scanning electron microscopy (HRSEM) and atomic force microscopy (AFM). The results of EIS and polarization showed that in the presence of H2O2, corrosion resistance is much less than the one contains no H2O2 after aging. According to the results of HRSEM, corrosion products became denser and more porous. Surface roughness increased over aging time and therefore confirmed the previous results. In the following, protective performance of silane sol-gel coating applied on mild steels treated in acid solutions in both fresh and stored conditions was examined using EIS. It was founded the coating resistance decreased during storage. However, the coating on the surface treated by fresh acid solution containing H2O2 had the superior protection compared to the one containing no activating agent.

The main purpose of current research was to investigate the adhesion strength of transparent coatings of thermally modified poplar wood in different mediums before and after accelerated aging. Specimens of 150×100×20 mm were prepared and thermally modified in different mediums (air, steam, steam and press, linseed oil) in 150 and 180 °C. Untreated and modified specimens were coated with acid catalyzed lacquer and nitrocellulose lacquer. Adhesion strength of coatings were analyzed before and after accelerated aging. The results showed that thermal modification in hot air and hot steam, affect positively on coating adhesion strength before and after aging test. The best results observed in hot steam in 150 °C. As temperature of thermal modification elevated, adhesion strength of coatings decreased. Specimens coated with nitrocellulose lacquer had higher adhesion strength. Based on revealed results, it can be concluded that adhesion strength of thermally modified wood depends on coating type, thermal modification medium and aging process.

The increasing application of magnesium alloys in various industries on the one hand and its low corrosion resistance on the other hand, have been a new challenge for researches around the world. In this study, vanadium conversion coating was investigated as a method for protection of AZ31 alloy. In the first section, the importance of surface pretreatment for applying conversion coating was studied. In the second part, the duration of immersion in the solution was investigated and the results showed that the coating reaches to its maximum resistance (8100 Ohm.cm2) in 60 minutes immersion. Then, in the next section, it will be seen how the addition of 1 g/l copper sulphate not only reduced the optimum immersion time to 30 minutes, but also increased the polarization resistance of the coating from 250 to 14300 Ohm.cm2. In addition it is clarified that this significant change is in compliance with the polarization test in which the corrosion current density decreased from 33.4×10-6 to 5.3×10-7 A/cm2. In the final section, the images of the FE-SEM showed that the surface of vanadium conversion coating was inherently cracked. Also, reducing the number of pits and increasing the thickness of compact and uniform layer next to the surface are the reasons of higher corrosion resistance for vanadium conversion coating in the presence of copper sulphate.

M-type substituted strontium hexaferrite nanostructures were synthesized by pechini sol-gel route. The ferrites were investigated by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and performing network analyzer (PNA). In accordance with diffraction patterns, no extra peak was observed for the pure samples. VSM and PNA results showed that the saturation magnetization increased and the dielectric constant decreased with increasing calcination temperature. According to results, the synthesized nanoparticles are suitable for use in high frequency absorbers.

Dyes are stable in the conventional wastewater treatment processes. Use of ozone with persulfate anions and hydrogen peroxide compounds releases active radicals. The aim of study was to determine the effectiveness of hydroxyl and sulfate radicals that activated by ozone molecules in (AB25) decomposition. This study was handled in semi batch Ozonation reactor with one liter volume. In O3/PS process effect of pH, concentration of persulfate, concentration of Ozone and concentration of AB25 parameters and in O3/H2O2 process effect of pH, H2O2, concentration of Ozone and concentration of AB25 parameters were investigated. Synergistic effect of parameters in processes determined. For measurement of AB25 use of DR6000 instrument. The results of study was showed that pH, persulfate anion, Ozone concentration, reaction time and initial concentration parameters in O3/PS process and pH, H2O2, Ozone concentration, reaction time and initial concentration in O3/H2O2 have a significant impact on performance of processes. Highest efficiency of O3/PS process (97/58 %) is in acidic pH. Process efficiency has a direct relationship with increasing of persulfate to a certain extent. Increasing in concentration of pollutant cause reduce of efficiency. Highest efficiency of O3/H2O2 process (98/96 %) is in alkaline pH. Process efficiency has a direct relationship with increasing of H2O2 to a certain limit. Increasing in concentration of pollutant cause reduce of efficiency. Due to the production of active radicals, Ozonation process in presence of persulfate anion and H2O2 is suitable process in removal of resistance pollutant such an ACID BLUE 25 dye.

The molecular and electronic structure of 4-[(4-bromophenyl)diazenyl]-2-ethoxyaniline, (L1), as ligand was calculated by Density Functional Theory (DFT). The bond distances as well as bond and torsion angles in the optimized molecular structure was compared with the already reported X-ray structure determined values. Also, tetrahedral geometry for the Zn(II) complex was proposed with Zn―O and Zn―N bond distances are in accord with those reported for similar N2O2 coordinating complexes. For the optimized free ligand, HOMO is calculated to be π orbital and LUMO is π* orbital and the energy gap of LUMO-HOMO is ~3.25 eV. Whereas, for the optimized [Zn(L1)2]+2 complex, HOMO is predicted to be π(bromophenyldiazophenyl) fragment delocalized on one ligand and LUMO is σ*(Ligand―4s Zn). Moreover, time-dependent density functional theory (TDDFT) calculations were applied to preciously predicting and assigning of the UV-Vis absorption spectra of L1 and [Zn(L1)2] in gas phase. The results showed that the electronic spectra of free ligand is mainly due to π→π* and nb(N=N)→σ*(C―H)ethyl+σ*(N―H) electronic transitions. Strong absorption bands predicted at 426 and 415 nm for [Zn(L1)2]+2 due to π→π* electronic transitions from one ligand to the other one. Accordingly, the color of the [Zn(L1)2]2+ complex was predicted to be yellowish-orange.

Coating of fabrics with spectrally selective nanopigments, in order to manipulate their optical properties, has been introduced in recent years. This method presents a new field in high performance textiles which covers high technological aspects such as UV protective fabrics, Solar cells and cool fabrics as well. One of the most important approaches in prediction of reflectance factor of coated fabrics is based on Discrete Ordinate Method (DOM), namely, Kubelka-Munk or Multi Flux Model, where the fabric is considered as a continuous medium consists of a dispersion of nanopigments. However, ignored surface scattering on interfaces causes considerable error. Geometric optic, on the other hand, is utilized widely for prediction of spectral behavior of particles with very large dimension compared with incident wavelength. The model lacks limitation of DOM but is not appropriate for nanopigments of small diameters. According to the fact that, coated fabrics are systems consists of nano and micron sized materials, a theoretical model is proposed in which radiative properties of micro particles are described using Geometric Optic, and those for nano and submicron sized particles are described using Mie scattering theory. Subsequently, the experimental realization of proposed model has been conducted on Titanium dioxide nanopigments coated on polyester fabrics, and the successful comparison of the proposed model with experimental results confirms its suitability, and introduces a rather new procedure in the field of radiation transfer through mixed beds of elements with extremely different sizes.