فهرست مطالب

  • Volume:4 Issue:2, 2019
  • تاریخ انتشار: 1398/09/10
  • تعداد عناوین: 6
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  • Ali Feiz, Hamed Khosravi *, Esmaeil Tohidlou Pages 59-65
    In the present work, Na+-montmorillonite nanoclay (Na-MMT) was functionalized using 3-aminopropyltrimethoxysilane (3-APTMS) as a coupling agent. The covalent functionalization of MMT was confirmed by Fourier-transform infrared spectroscopy (FT-IR). In the specimen fabrication stage, 5 wt% of pristine MMT or silane-functionalized MMT (f-MMT) were incorporated into an epoxy system and the resultant mixture was applied on an E-glass chopped strand mat (CSM). A significant enhancement in the mechanical behavior (tensile and flexural properties) of CSM/epoxy composite was observed when enhanced with 5 wt% of f-MMT. The addition of 5 wt% of f-MMT enhanced the tensile strength, flexural strength, tensile modulus, and flexural modulus by 18%, 38%, 18%, and 28%, respectively. Compared to the MMT/CSM/epoxy composite, the f-MMT/CSM/epoxy specimen demonstrated 12%, 18%, 11%, and 16% increase, respectively, in the tensile strength, flexural strength, tensile modulus, and flexural modulus. The observed behavior is related to the enhanced interfacial interaction between f-MMT and the epoxy matrix due to the chemical functionalization of MMT.
    Keywords: Na+-montmorillonite nanoclay, Surface functionalization, Epoxy-based composite, mechanical properties, Interfacial bonding
  • Zeynab Shahedi, Yagoub Mansoori * Pages 67-79
    In this study, magnetite nanoparticles were obtained from Fe(II) and Fe(III) salts in an alkaline medium. The nanoparticles were then protected from oxidation by a silica shell formed by the sol-gel method using tetraethoxy orthosilicate (TEOS) in an EtOH/H2O mixture. The synthesized Fe3O4@SiO2-SO3H magnetic nanocatalyst was characterized with Fourier transform infrared (FT-IR) spectroscopy, wide angle X-ray diffraction (WXRD), thermal gravimetric analysis (TGA), energy-dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), Hammett acidity function and pH analysis as well as Brunauer-Emmett-Teller surface area measurement (SBET). Finally, the esterification reaction of phthalic anhydride, mono- and dicarboxylic acids with various alcohols was chosen to show the catalytic activity of the magnetic nanocatalyst. The reaction conditions were optimized and catalyst recovery was also demonstrated. The nanocatalyst was magnetically separated and reused several times without significant loss of activity.
    Keywords: heterogeneous catalyst, Core-shell magnetic solid acid, Esterification
  • Negin Hatami, Sattar Ghader * Pages 81-90
    This paper reports the effect of temperature, presence of impurity (Fe3+), and crystal seed on the induction time of silver nanoparticles. In this study, Ag precipitation was achieved by solution reduction and the experimental induction time was measured by monitoring the absorption of the solution after creation of supersaturation. Experimental induction time was compared to the cluster coagulation models (the Smoluchowski model and its’ variation cluster coagulation model) and the conclusion is that the conventional Smoluchowski coagulation model works better than the modified version.
    Keywords: Silver nanoparticles, Induction time, Cluster coagulation model, coagulation theory
  • Akbar Jafari *, Ali Abolghandi, Arash Gharibi, Mohammad Vahid Khalili, Ali Begheri Pages 91-100

    Blockage is a common problem in many practical silo applications, and vibration seems to be a practical solution to overcome this problem. An experimental setup was developed to observe the effects of different vibrational parameters on vibrator anti-jamming efficiency. The silo was made of transparent plates to provide the possibility of watching the materials inside it. The outlet mass was recorded on a computer via a weighing load cell. The vibrator was installed at different locations on the silo walls to reveal effects of the vibrator position on its efficiency to prevent jamming. Moreover, relevant tests were conducted to reveal the effects of the vibration frequency. A vibrometer instrument with contacting probe was employed to measure the local vibration characteristics. The measured data was used to identify the vibration dimensionless acceleration. It was concluded that the location of the vibrator significantly affects its anti-jamming ability. Furthermore, it was observed that the vibration frequency and acceleration influence the impact of the vibration to prevent the silo jamming to some extent. It was observed that while the vibration does not influence the instant discharge rate it does considerably affects the average rate.

    Keywords: Silo, Vibration, Jamming, Blockage, Discharge
  • Morteza Ziyaadini *, Mir Mahdi Zahedi, Azadeh Dehghan Pages 101-109

    ZnAl2O4 and Sr-doped ZnAl2O4 nanoparticles were synthesized by co-precipitation using ammonia as precipitating agent, followed by thermal treatment at 700°C. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and the Brunauer-Emmett-Teller (BET) were employed to clarify the structure and morphology of the samples. In addition, the presence of Sr in Sr-doped ZnAl2O4 NPs was further evidenced from energy-dispersive X-ray analysis (EDX). The Photocatalytic activity of ZnAl2O4 and Sr-doped ZnAl2O4 nanoparticles were evaluated in the photo-catalytic degradation of 2,4-dichlorophenol (2,4-DCP) in aqueous media under the UV irradiation technique. The effect of various parameters, including catalyst dosage, 2,4-DCP concentration, pH, and temperature, on the degradation of 2,4-DCP was investigated. With 0.6 wt% Sr doped ZnAl2O4 samples after 60 min irradiation, 100% of 2,4-DCP photodegradation was observed in acidic conditions, while with undoped ZnAl2O4 samples only 67% 2,4-DCP was removed upon UV irradiation for 200 min. The reusability of the catalyst was examined under optimized conditions. The results demonstrate that Sr-doped ZnAl2O4 nanoparticles exhibit considerably high catalytic stability with more than 90% degradation after the third catalytic cycle.

    Keywords: Sr-Doped ZnAl2O4 nanoparticles, Photocatalytic degradation, 2, 4-Dichlorophenol
  • Taleb Asadi, Mohammad Ali Ghasemzadeh *, Manoochehr Fadaeian Pages 111-117
    In the present work, a simple, green and efficient procedure for the synthesis of imidazolone derivatives is described via the reaction of oxazolones and different arylamines in the presence of Co3O4@SiO2 nanocomposite as a catalyst under solvent-free conditions at 90°C. The catalyst has been fully analyzed by FT-IR, FE-SEM, EDX, and XRD analysis. The present method offers several advantages such as high yields, short reaction times, mild reaction conditions and recoverability of the catalyst. In addition, the obtained heterocyclic compounds were analyzed by FT-IR and 1HNMR spectroscopy analysis.
    Keywords: Imidazolone, Co3O4@SiO2, Nanocomposite, Oxazolone, Catalyst