ADVANCED MATERIALS AND NOVEL COATINGS
Year:2019 | Volume:7 | Issue:28 |Papers Count:7

In this research, the effects of different parameters such as milling time, leaching, and amounts of magnesium and carbon on the reactions in the CrO3-V2O5-Mg-C powder system were studied during mechanochemical process. The synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), elemental map (X-Map) and transmittance electron microscopy (TEM). Calculation of the adiabatic reaction temperature (Tad = 4259 K) indicates that the reaction is self-propagating high-temperature synthesis (SHS). Based on the X-ray diffraction pattern obtained after 3 minutes of milling, the raw materials reacted together and magnesium oxide, vanadium carbide, chromium carbide and magnesium chromate were produced. The leaching process by hydrochloric acid (HCl) led to the removal of the MgO phase. Increasing the amount of magnesium resulted in the removal of magnesium chromate phase. The addition of carbon led to an increase in the peak intensity of the carbide phases.

This paper investigates the interaction of tetryl on the surface of pure C24, Si-doped C24 and Ge-doped C24 by density functional theory. For this purpose, the structures of tetryl, pure and doped fullerenes and their complexes were optimized geometrically. Then, IR and frontier molecular orbital calculations were implemented on them. The obtained adsorption energies, Gibbs free energy variations, enthalpy changes, and thermodynamic equilibrium constants showed that the interaction of tetryl with pure and doped fullerenes is exothermic, spontaneous, irreversible and experimentally possible. The calculated specific heat capacity values proved the heat sensitivity has declined significantly after adsorption of tetryl on the surface of nanostructure. The N-O and C-O bond lengths and density of tetryl complexes with C24 exhibited the detonation pressure, explosion velocity and energetic features of tetryl have enhanced considerably after its coating on the fullerene. Molecular orbital parameters such as band gap, chemical potential, electrophilicity, chemical hardness, and maximum transferred charge capacity have also been evaluated and the results indicated that the electric conductivity of C24 has decreased after absorbing of tetryl on the surface of nano-adsorbent. Therefore, fullerene can be used as an electroactive sensing material in the construction of novel electrochemical sensors for the detection of tetryl.

PNS is one of the chemical additives that used as a dipersing agents in various applications. Synthesis of this material was done in 2 stage: 1. Sulfonation of naphthalene 2. Polymerization of beta naphthalene sulfonate. The influence of various parameters was studied on synthesis stages of this substance. FTIR and H-NMR were used to identify the chemical structure of synthesized product. Purity of beta naphthalene sulfonate was confirmed by melting point test. Assessment of molecular weight and evaluation of molecular weight was done by preparing GPC photograph and the result was compared by a known comercial grade. The result showed that the increase of formaldehyde and the use of the catalysis during the polymerization reaction lead to increase of the molecular weight. On the other hand when the molar ratio of formaldehyde to naphthalene sulfonate was tripled, PNS didn’ t dissolve in the aqueous media. existente of sodium sulfate as impurities was evaluated by XRD. The use of a mixture of sodium and calcium hydroxide as a neutralizing agents resulted in a partial refuction of sodium sulfate.

This study introduced a novel, nontoxic, scalable, two-step method for the fabrication of nickel-nickel oxide foam/electrochemically reduced graphene oxide (ERGO) electrodes. This procedure included drop cast and graphene oxide (GO) reduction by constant current and pulse current methods. The result of structure was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Electrochemical impedance spectroscopy (EIS) measurements are carried out to study the electrochemical behavior of ERGO/Ni-NiO foam electrodes. SEM images revealed that the wrinkling degree of the synthesized graphene layers increased in pulse current method. The Raman test results showed that the current density pulse method is more efficient in comparison with constant current method. The XRD also showed that the interlayer spacing between the graphene sheets was higher in the pulse current method. The ERGO/Ni-NiO foam fabricated by pulse current method provided the least ESR value, and thus the highest rate charge/discharge process. The desirable electrochemical performance of ERGO/Ni-NiO foam electrode was mainly attributed to its irregular porous structure provided a large specific area, short ion diffusion distances and transport pathways for electrons. High-performance ERGO/Ni-NiO foam hybrid electrode materials made it as a reliable and accessible candidate for application in electrochemical energy storage.

In this study, the effect of cobalt percentage on WC-Co coating properties was investigated. Corrosion behavoiur of coatings was evaluated after immersion in molten zinc. For this purpose, various compositions of WC-Co powder (WC-12Co, WC-17Co and WC-10Co-4Cr) were coated on 316 stainless steel by means of HP/HVOF method. To determine the phases produced during the process of spraying, thickness, porosity and hardness of the coatings, X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester were used. The XRD patterns showed negligible amount of W2C and Co6W6C brittle phases, which indicates very low decarborizing of WC phase. WC-17Co coating showed the highest hardness (1280 Hv). Pin on disk wear test was used at 450 ° C and then wear surfaces were examined by electron microscopy. WC-10Co-4Cr coating showed highest wear resistance. Main wear mechanism of coatings was adhesive wear. Evaluation of corrosion behaviour of coatings and phases produced during immersion in molten zinc was done by SEM and energy dispersive X-ray spectroscopy (EDS). Unlike WC-17Co coating, on the cross section of WC-12Co and WC-10Co-4Cr coatings some cracks were observed which penetrating element to these cracks was aluminum and lead to destruction of these two coatings.

Crystallization behavior of polypropylene/graphene nanoplatelets (PP/GnPs) nanocomposite fiber was studied by means of differential scanning calorimetry. PP/GnPs nanocomposite fibers containing different amounts of GnPs were prepared with and without a compatibilizer, maleic anhydride-grafted polypropylene (PP-g-MA), and then isothermal crystallization kinetics was investigated at different crystallization temperatures by Avrami and Lauritzen-Hoffman equations. The results show that heterogeneous nucleation occurs easily in the presence of GnPs even at higher temperatures and thereby the crystallization rate of PP in the PP/GnPs fiber increased. Moreover, upon inclusion of PP-g-MA, relative crystallinity-time curves shifted to the shorter times. The Avrami equation revealed that although GnPs and PP-g-MA have nucleation effect, the crystal growth of PP is restricted in the PP/PP-g-MA/GnPs nanocomposite fiber, increasing the crystallization half-time. Furthermore, Avrami exponent of approximately 3 for neat PP and 2 for PP/GnPs is consistent with three-dimensional crystal growth process and two-dimensional crystal growth, respectively. According to Lauritzen-Hoffman equation, the nucleation parameter decreased with the addition of GnPs, suggesting that the GnPs act as a nucleating agent and also reduced the interfacial free energy.

The main purpose of this work is to study the physical, mechanical and thermal properties of epoxy based resin modified with acrylonitrile-butadiene-rubber (NBR) nanoparticles. At first, elastomer nanoparticle (ENP) at different content was added to epoxy resin. Then, the morphology of nanocomposite and dispersion condition of elastomer nanoparticles was studied using microscopy techniques including SEM, TEM and AFM. The results showed an acceptable dispersion condition for ENPs in epoxy resin. The tensile and impact strength of nanocomposites as two key parameters were thoroughly investigated. The results depicted two times increase in the amount of toughness besides three times increase in the amount of elongation at break in nanocomposite containing 1. 5wt% of ENP. Thereafter, the specific coating experimnets including adhesion, hardness, impact, bending and water absorption were performed. The adhesion increased and water uptake was reduced while the toughness was enhanced. The best results were obtained in samples containing 1 wt% elastomeric nanoparticles.