فهرست مطالب

  • Volume:14 Issue:4, 2018
  • تاریخ انتشار: 1397/09/05
  • تعداد عناوین: 7
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  • M. A. Aroon orcid , , H. Beheshti, J. Barzin, M. Shariaty, Niassar Pages 251-266
    To fabricate a defect free and high performance mixed matrix membrane (MMM), one approach is the functionalization of inorganic nanofillers (as dispersed phase) in the organic polymer matrix (as continuous phase) to modify the interactions between two phases. For this purpose,, raw multi-walled carbon nanotubes (rMWCNTs) were purified by acid mixture (HNO3/H2SO4; v/v = 1:3) and then the purified MWCNTs (pMWCNTs) were functionalized by low molecular weight chitosan (LMWC) and characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) tests. Functionalized MWCNTs (fMWCNTs) were added to polyethersulfone (PES) solution, and mixed matrix membranes containing different amount of the fMWCNTs in PES matrix were fabricated by immersion precipitation technique. Neat PES and mixed matrix membranes were characterized by differential scanning calorimetry (DSC), Field emission scanning electron microscopy (FESEM) and permeation (using CO2 and CH4 as test gases) experiments. FTIR and XRD experiments confirmed attachment of LMWC on the surface of fMWCNTs. Gas permeation test results revealed that the mixed matrix membrane containing 1 wt.% fMWCNTs (PES/1wt.%fMWCNTs) has the best CO2/CH4 separation performance and this result was confirmed by DSC and FESEM results. Therefore simultaneous purification (by acid mixture) and functionalization (by LMWC) of MWCNTs can be used for fabrication of high performance mixed matrix gas separation membranes.
    Keywords: CO2, CH4, Functionalization, Gas Separation, Mixed Matrix Membrane, MWCNTs
  • B. Divya , Ch. Karthikeyan, M. Rajasimman Pages 267-275
    In the present study, various size of Zinc Oxide Nanoparticles (ZnO NPs) was synthesized via Sol-gel method. The photocatalytic activity of the synthesized ZnO NPs was investigated for the Decolourization of three different colored dyes viz. Congo Red, Acid Blue 9 and Coomassie Brilliant Blue R-250 under UV lamp. Zinc Chloride (Zncl2) and Sodium Hydroxide (NaOH) were used for the chemical synthesis. The SEM and FTIR analysis shows that the synthesized ZnO NPs are crystalline in nature. The synthesized NPs were then checked for its efficiency to decolorize the above same dyes under the condition of 20 mg/L dye and 0.3 g/L of photocatalyst dosage. The investigation results showed that each size of ZnO NPs was able to effectively decolorize the dye solution and the efficiency was found to be 88% for Congo red (CR: 27-29 nm), 73% for Acid Blue 9 (AB: 24-27 nm) and 70% for Coomassie Brilliant Blue R-250 (BB: 29-32 nm). Out of which CR dye oxidation rate was higher than the other dyes and especially BB dye possible to decolorize by using synthesized ZnO NPs. Hence, it was concluded that ZnO NPs by itself is strong enough to decolorize these dye aqueous solutions. Moreover, the photocatalytic activity of NPs on dye was the decisive factor/unique property for dye reduction rather than size and morphology of the ZnO NPs.
    Keywords: Chemical Synthesis, Decolourization, Dye, Photocatalyst, Sol-gel Method, Zinc Chloride
  • R. Marani, A. G. Perri Pages 277-288
    In this paper we propose a simulation study to carry out dynamic analysis of CNTFET-based digital circuit, introducing in the semi-empirical compact model for CNTFETs, already proposed by us, both the quantum capacitance effects and the sub-threshold currents. To verify the validity of the obtained results, a comparison with Wong model was carried out. Our model may be easily implemented both in SPICE and in Verilog-A, obtaining, in this last case, the development time in writing the model shorter, the simulation run time much shorter and the software much more concise and clear than Wong model.
    Keywords: CNTFET, Digital Design, Dynamic Analysis
  • A. Olad , F. Ghazjahaniyan, R. Nosrati Pages 289-296
    In the present work, a fast, green and simple synthesis method for the production of silver nanoparticles (AgNPs) is introduced. Silver nanoparticles are currently among the most widely used man-made nano materials, present in a wide range of consumer products. Green chemistry is characterized by careful planning of chemical synthesis of silver nanoparticles to reduce adverse outcomes. Synthesis of AgNPs was carried out at 100 ◦C temperature using glucose as reducing agent and starch as capping agent. Prepared AgNPs were characterized using transmission electron microscopy, UV-Vis spectrophotometry, Dynamic Light Scattering (DLS) and X-ray Diffraction (XRD) patterns. It was found that the synthesized AgNPs have an average diameter size of 50 nm. Further experiments showed that silver nanoparticles have good antibacterial properties and their production process is capable to scaling up. Due to the using of natural and low-cost materials, the production process is also environmental and eco-friendly.
    Keywords: Glucose, Green Chemistry, Silver Nanoparticle, Starch
  • A. Rezaei Pages 297-306
    One of the several promising new technologies for computing at nano-scale is quantum-dot cellular automata (QCA). In this paper, new designs for different QCA sequential circuits are presented. Using an efficient QCA D flip-flop (DFF) architecture, a 5-bit counter, a novel single edge generator (SEG) and a divide-by-2 counter are implemented. Also, some types of oscillators, a new edge-triggered K-pulse generator (KPG) and a negative pulse generator (NPG) are presented for implementation in QCA. The robust layouts of proposed circuits are designed, implemented and simulated using QCADesigner software without any wire crossing. The fault effects at the output of proposed DFF due to the missing cell defects are analyzed. Also, the robustness of the proposed QCA designs with respect to temperature variations is examined. The proposed designs are compared with the previous QCA works and conventional CMOS technology. The simulation results confirm that the novel QCA architectures work properly and can be simply used in designing of QCA sequential circuits.
    Keywords: Quantum-dot cellular Automata, QCADesigner, Sequential Circuits, Simulation
  • A. Bahramian Pages 307-317
    High transparent conductive indium tin oxide/titanium dioxide (ITO/TiO2) nanostructured thin film is prepared by sol-gel dip-coating technique. This method yielded monodisperse ITO nanoparticles with mean diameter of 12 nm. The atomic composition of the Sn within the ITO structure changed from 0-20 wt.%. Through controlled annealing temperature at 550 oC, the results of four-point probe technique showed that the resistivity of the ITO film depends on the Sn doping ratio, the film thickness and atmospheric conditions applied during annealing. The ITO nanostructured film with thickness of 165 nm containing 8 wt.% Sn atoms annealed under vacuum condition showed a low resistivity of 5.1×10-4 Ω-cm and transparency as high as 90% with wavelengths between 500 and 700 nm. The refractive index and extinction coefficient of the ITO/TiO2 thin film is determined by using the UV-vis spectrophotometer. An optical method is used to determine the band gap of the film. Experimental results showed that the refractive index, extinction coefficient, and band gap was closely on the atmospheric conditions and crystallinity of the ITO nanostructures. The monodispersed ITO nanostructures and its preparation methodology can be used for the fabrication of novel thin films that applied for large-scale integrated opto-electronic devices.
    Keywords: ITO, TiO2 thin film, Nanostructures, Electrical Resistance, Optical Transmittance
  • M. Hadi Soltanabad, M. B. Bagherieh, Najjar , E. Kohan Baghkheirati, , M. Mianabadi Pages 319-325
    In recent years, the world has witnessed an explosion of interest in biogenic synthesis of metallic nanoparticles (NPs), using plant extracts; however, the plant constituents involved in this reaction are poorly characterized. Here, major components of Rosemary (Rosmarinus officinalis L.) leaf extracts were isolated monthly during 2012-2013 and their competences for Ag–conjugated nanoparticle biosynthesis were studied. Formation of Ag/AgCl–NPs was examined using UV-visible spectroscopy and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and Transmission electron microscopy (TEM). Correlation analysis showed that extracts with more protein contents and higher total reducing capacity were more efficient in biosynthesis of Ag/AgCl–NPs. There existed no correlation between total phenolic, ascorbic acid and anthocyanin contents with Ag/AgCl–NPs biosynthesis activity. These results partly explain the mechanisms controlling plant mediated biosynthesis of nanoparticles, with possible applications in standardization of plant materials harvested throughout a year.
    Keywords: Ag, AgCl–NPs Biosynthesis, Antioxidant Activity, FTIR, Nanoparticles, Rosmarinus Officinalis