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    Effects of Additives on Chromium Coating in Trivalent Chromium Bath

    , M.Sc. Thesis Sharif University of Technology Ebrahimi, Ghasem (Author) ; Dolati, Abolghasem (Supervisor)
    In this work, effects of different additives on trivalent Chromium bath and Chromium coating has been investigated. Malonic acid wich had been used as a complexing agent of the bath improved current efficiancy and coating quality obviously. Effects of Magnesum, zinc, Tin, Aluminium sulfates, Molybdic acid, TiO2 nano particles, Sodium hypophospite, formaldehead and mixtures of these compositions on hexavalent Chromium concentration of the bath were also studied. Concentration of Cr6+ ion decreased by 18 ppm due to adding these materials. Using Ti/ TiO2/ RuO2 Anode also could decrease Cr6+ concentration by 78 ppm. Remarkable results had been recorded in current efficiency and coating... 

    Influence of polyaniline synthesis conditions on its capability for removal and recovery of chromium from aqueous solution

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 3 , 2011 , Pages 97-100 ; 10219986 (ISSN) Riahi Samani, M ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology
    Absorptive characteristics of polyaniline synthesized in different solvents were studied. Water and mixture of water with other solvents were implemented for polyaniline synthesis. Synthesized polyanilines in powder shape is used as an adsorbent to remove toxic hexavalent chromium from aqueous solutions. Experiments were conducted in batch mode. Removal mechanism involving polyaniline is the combination of surface adsorption and reduction. The kind of solvent used at synthesizing stage can affect the capacity of produced polyanilines for removal of heavy metals including chromium. Synthesized polyaniline in water had the maximum chromium removal efficiency. The morphology study of... 

    Removal of chromium from aqueous solution using two kinds of polyaniline

    , Article Journal of Environmental Studies ; Volume 36, Issue 55 , 2010 , Pages 91-98 ; 10258620 (ISSN) Riahi Samani, M ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology

    Nano-scale modification of polysulfone membrane matrix and the surface for the separation of chromium ions from water

    , Article Chemical Engineering Journal ; Volume 267 , May , 2015 , Pages 306-316 ; 13858947 (ISSN) Habibi, S ; Nematollahzadeh, A ; Mousavi, S. A ; Sharif University of Technology
    Elsevier  2015
    In this study, aiming at hexavalent chromium removal from aqueous solutions, different strategies were proposed for developing hydrophilic and surface functional polysulfone (PSf) membrane. In addition to PSf membrane, three different types of membranes were prepared by addition of SiO2 nano-particles to the dope solution and/or by deposition of polydopamine (PDA) layer on the surface of the membranes. The membranes (i.e. PSf, PSf/PDA, PSf/SiO2 and PSf/SiO2/PDA) were characterized by different techniques. The membranes' transport properties and the separation performance were studied using a filtration unit operated at a continuous dead-end flow mode. The kinetics and the separation... 

    Influence of pulse parameters on electrocodeposition of Cr-Al2O3 nanocomposite coatings from trivalent chromium bath

    , Article International Heat Treatment and Surface Engineering ; Volume 6, Issue 4 , December , 2012 , Pages 178-184 ; 17495148 (ISSN) Salehi Doolabi, M ; Sadrnezhaad, S. K ; Salehi Doolabi, D ; Asadirad, M ; Sharif University of Technology
    Cr and Cr-Al2O3 coatings were electrodeposited from Cr(III) bath with both pulsating and direct current onto copper substrates. Pulsating current resulted in homogeneous films of higher Al2O3 content and lower particle agglomeration than the direct current. Differences were more tangible at shorter duty cycles and pulse frequencies. Pulsating current improved both microhardness and corrosion resistance. The presence of alumina nanoparticles resulted in greater current efficiency, higher film microhardness and better corrosion resistance. Maximum current efficiency, highest microhardness and densest electrodeposited coatings were achieved at current density of 20 A dm-2, duty cycle of 40% and... 

    Hybrid nano-adsorbent supported carbon dots for removal of chromium from aqueous solution

    , Article Desalination and Water Treatment ; Volume 103 , 2018 , Pages 221-231 ; 19443994 (ISSN) Eslami, A ; Borghei, S. M ; Rashidi, A ; Takdastan, A ; Sharif University of Technology
    Desalination Publications  2018
    In this study, hybrid nano adsorbent supported carbon dots was prepared and used for removing Cr(VI) from aqueous solution. Carbon dots were synthesized from sugarcane molasses under microwave irradiation. Hybrid nano adsorbent was prepared by impregnating carbon dot with H3PO4 in a ratio of 2:1 and introducing 0.01 M FeCl3 into the slurry. The carbon dot hybrid was activated via a conventional thermal method under N2 flow. The physico-chemical properties of the synthesized material were investigated using X–ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption/desorption, and field emission scanning electron microscopy (FESEM). Chromium adsorption was studied... 

    Demo paper: Atomic bonded cross-chain debt

    , Article 3rd IEEE International Conference on Blockchain and Cryptocurrency, ICBC 2021, 3 May 2021 through 6 May 2021 ; 2021 ; 9781665435789 (ISBN) Khajehpour, A ; Bagheri, F ; Abdi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Atomic Bonded Cross-chain Debt (ABCD) is the first non-custodial smart-contract-independent cross-chain atomic bond. Theoretical aspects of ABCD have been presented in the International Conference on Blockchain Technology and Applications (ICBTA) and won the best presentation award. It is the first time a demo of Atomic Bonded Cross-chain Debt is presented. © 2021 IEEE  

    Study of thermal behavior of CrO3 using TG and DSC

    , Article Journal of Thermal Analysis and Calorimetry ; Vol. 116, Issue. 2 , 2014 , pp. 915-921 ; ISSN: 13886150 Sajadi, S. A. A ; Khaleghian, M ; Sharif University of Technology
    Using two techniques of thermogravimetry and differential scanning calorimetry under O2 and N2 gas atmosphere from 25 to 600 °C, the thermal behavior of chromium(VI) oxide CrO3 was investigated. The identity of products at different decomposition steps was confirmed by XRD technique. Both techniques produced similar results supporting the same steps for the compound. The received products were investigated by SEM electron microscope. The form and the size of crystals were investigated. Three distinct energy changes were observed, namely, two endothermic and one exothermic in DSC. The amount of ΔH for each peak is also reported  

    Effects of tungsten on erosion-corrosion behavior of high chromium white cast iron

    , Article Materials Science and Engineering A ; Volume 454-455 , 2007 , Pages 623-628 ; 09215093 (ISSN) Mousavi Anijdan, S. H ; Bahrami, A ; Varahram, N ; Davami, P ; Sharif University of Technology
    In this study, effects of tungsten on wear resistance of high chromium white cast iron with and without tungsten in erosion-corrosion condition have been investigated. At the same time, the comparison between wear resistance of this grade of cast iron and low alloy steels with various contents of Cr which are used in industrial condition (in Sarcheshme Company, the greatest copper production company in the Middle East and with more than 4000 years historical cupper production background) was studied, while, copper concentrates have used for erosion particles. Results show that, because of higher hardness of matrix due to the tungsten, the wear resistance of high chromium cast iron increases.... 

    Pulse Electrodeposition of Chromium Coating From Trivalent Bath and Studying it’s Properties

    , M.Sc. Thesis Sharif University of Technology Araban, Vahid (Author) ; Ghorbani, Mohammad (Supervisor) ; Dolati, Abolghasem (Supervisor)
    Trivalent chromium plating has been known as a very promising technology to replace hexavalent chromium which is so toxic. The coatings obtained from tivalent chromium baths have lower thickness and Hardness and higher corrosion rate in comparison with deposits obtained from hexavalent chromium baths.A few studies on pulse plating of trivalent chromium as an effective way to enhance the coating properties have been published.
    In this research glycine was chosen as complexing agent.The results have shown that in pulse plating at 1 Hz, Duty cycle 50%, peak current density 0/2 A/Cm2 and after 30 minutes, thickness achieves 13 µm which is much greater in comparison with coatings obtained in... 

    A novel screen-printed TiO2 photoelectrochemical sensor for direct determination and reduction of hexavalent chromium

    , Article Electrochemistry Communications ; Volume 61 , 2015 , Pages 110-113 ; 13882481 (ISSN) Siavash Moakhar, R ; Goh, G. K. L ; Dolati, A ; Ghorbani, M ; Sharif University of Technology
    Elsevier Inc  2015
    A novel and simple photoelectrochemical (PEC) sensor to detect Cr(VI) based on screen-printed TiO2 modified with gold nanoparticles is presented. The proposed PEC sensor showed a very low detection limit (S/N = 3) of 0.004 μM, over a wide linear concentration range from 0.01 μM to 100 μM with a high sensitivity of 11.88 μA.μM-1 Cr(VI). Results also indicated good anti-interference and superb recovery in natural media application for Cr(VI) sensing  

    Removal of chromium from aqueous solution using polyaniline - Poly ethylene glycol composite

    , Article Journal of Hazardous Materials ; Volume 184, Issue 1-3 , December , 2010 , Pages 248-254 ; 03043894 (ISSN) Riahi Samani, M ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology
    The adsorption of chromium compounds from solutions by a composite of polyaniline/poly ethylene glycol (PANi/PEG) was investigated in this study. Experiments were conducted in batch mode under various operational conditions including agitation time, solution pH, PANi/PEG dose and initial concentration of chromium salts. Results showed that concentration of PEG at synthesizing stage has a significant effect on the capacity of produced composite for removal of chromium. Morphologically, PANi/PEG composite is closely dependent on the concentration of PEG. Maximum removal of hexavalent chromium was experienced when 2. g/L of PEG was used in synthesis of PANi/PEG. Removal of hexavalent chromium... 

    Synthesis and study of a new class of red pigments based on perovskite YAlO3 structure

    , Article Ceramics International ; Volume 33, Issue 8 , December , 2007 , Pages 1427-1433 ; 02728842 (ISSN) Shirpour, M ; Faghihi Sani, M. A ; Mirhabibi, A ; Sharif University of Technology
    A red pigment has been prepared by substituting chromium ions in aluminum ion sites in YAlO3 perovskite structure. In a first step, effect of various mineralizers on YAlO3 formation has been investigated, which resulted in decrease of formation temperature down to 1400 °C. In the next step, a red pigment corresponding to YAl1-yCryO3 (y = 0.05), has been prepared by heating a mixture containing Y2O3, Al2O3 and Cr2O3 at 1500 °C for 6 h. Later, effect of the doped chromium amount on the pigment redness (a*) has been studied. The highest redness has been obtained when y was 0.04(YAl1-yCryO3). Application of the prepared red pigment in low and high temperature glazes, demonstrated its high... 

    Artificial neural network aided design of a multi-component catalyst for the steam reforming of methanol

    , Article Indian Journal of Chemistry - Section A Inorganic, Physical, Theoretical and Analytical Chemistry ; Volume 44, Issue 1 , 2005 , Pages 64-66 ; 03764710 (ISSN) Jooya, Sh ; Gobal, F ; Sharif University of Technology
    A neural network based on the feed forward back propagation error has been developed for the design and simulation of the catalytic properties of a multi-component system based on Cu-M-Al2O3 (M=Zn,Cr,Zr) for the steam reforming of methanol. Due to the limited size of the data set, cross validation method has to be used to enhance and also evaluate the prediction ability of the network. The best structural organization has been found to include 4,3,6,3 nodes in the input, two hidden layers and the output layer respectively  

    Electroplating and characterization of Cr–Al2O3 nanocomposite film from a trivalent chromium bath [electronic resource]

    , Article Anti-Corrosion Methods and Materials ; Vol 61, No 4, 2014, 205-214 Salehi Doolabi, M. (Mohsen) ; Sadrnezhaad, Khatiboleslam ; Salehi Doolabi, Davood ; Sharif University of Technology
    The main aim of this study was to improve current efficiency and to obtain thicker coatings via aluminum oxide (Al2O3) addition to the chromium (Cr) (III) bath. Design/methodology/approach ‐ Pure Cr and nanocomposite Cr–Al2O3 coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al2O3 content and particle size were investigated. Findings ‐ Current efficiency increased with Al2O3 amount and decreased with Al2O3 particle size. Maximum current efficiency was achieved at 25 A/dm2 for pure Cr and 30 A/dm2 for composite coatings. Al2O3 bath content, current density and stirring rate increased... 

    The effect of the Cr and Mo on the surface accumulation of copper in the electrodeposited Ni-Fe/Cu alloy films

    , Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 127, Issue 1 , 2006 , Pages 17-21 ; 09215107 (ISSN) Ranjbar, M ; Ahadian, M. M ; Iraji Zad, A ; Dolati, A ; Sharif University of Technology
    In the present study, the surface chemical and depth profile composition of the electrodeposited Ni-Fe base alloy layers on the Cu substrates were investigated with compositions of the Ni80-Fe20 (binary) and Ni77-Fe20.7-Cr1.7-Mo0.6 (quaternary) deposits. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) results showed the surface accumulation of copper on the surface layers of binary alloy films in the form of Cu 2O. In the quaternary films, addition of Cr and Mo reduced the amount of the Cu accumulation at the surface, while Cu accumulation was enhanced under air-exposed condition for both alloy films. Depth profiles using the secondary ion mass spectroscopy... 

    The effect of the Cr and Mo on the physical properties of electrodeposited Ni-Fe alloy films

    , Article Journal of Alloys and Compounds ; Volume 386, Issue 1-2 , 2005 , Pages 43-46 ; 09258388 (ISSN) Ghorbani, M ; Iraji zad, A ; Dolati, A ; Ghasempour, R ; Sharif University of Technology
    Ni-Fe and the Ni-Fe-Cr-Mo alloy films were electrodeposited from a chloride solution containing complexing compounds on ITO/glass substrates. AFM studies revealed a spherical structure for the alloy films with roughnesses from 10 up to 50 nm. The Ni-Fe-Cr-Mo alloy films were found to have a fine-grain structure. The quaternary alloy compounds containing up to 4% Cr and 2% Mo showed higher resistivity and little decrease in magnetoresistance (MR) relative to the Ni80Fe20 alloy compound. The MR of the quaternary alloy compounds was decreased for higher Cr and Mo contents. Moreover, the anisotropy (AMR) was also decreased by the addition of Cr and Mo to Permalloy films. Auger studies indicated... 

    Self aligned passivation of Cu in Cu/Cr, Cu/V and Cu/Ta multilayers

    , Article 12th International Conference on Microelectronics, ICM 2000, 31 October 2000 through 2 November 2000 ; Volume 2000-October , 2000 , Pages 209-212 ; 9643600572 (ISBN) Iraji Zad, A ; Vashaei, Z ; Mahdavi, S. M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2000
    We compare Cu/M/SiO2 (M=Cr,V and Ta) multilayers that were deposited on Si substrates. Sample resistance measurements were carried out during annealing in 80% N2+20% H2, N2 and Ar environments. Resistivity measurements, SEM observations, RBS and AES spectroscopies from annealed samples showed good diffusion barrier properties for Cr and V but rather poor properties for Ta buffer layers. This is due to the amorphous nature of Cr films and formation of a continuous Cu overlayer. SEM observation also showed granular structure for Cu/V and Cu/Ta with grain sizes of about 500 and 1000 Å respectively. However, shallow nitrogen implantation in Cu/V samples and DC biasing for Cu/Ta layers during... 

    Influence of deformation during T10 treatment on microstructure/hardness/ electrical conductivity of Cu-Cr alloy produced in nonprotected atmosphere

    , Article Materials Science and Technology ; Volume 25, Issue 10 , 2009 , Pages 1283-1288 ; 02670836 (ISSN) Hosseini, E ; Habibollahzadeh, A ; Erfanmanesh, M ; Mostajabodave, H ; Kazeminezhad, M ; Sharif University of Technology
    Cu-1·5Cr alloy was successfully produced by a new method, composed of alloying via melting in a non-protected atmosphere followed by rapid cooling in a water cooled mould. The effects of deformation magnitude during T10 treatment on microstructure, electrical conductivity and hardness of alloy were also investigated. The results showed that cold work before age hardening treatment, especially in the range of 20-40% deformation, provides optimum electrical and mechanical properties, i.e. electrical conductivity of 70-85% International Annealed Copper Standard (IACS) and hardness of 160-180 HB. In addition, the cold work promotes a useful anisotropy in electrical and mechanical properties of... 

    Properties of Fe-Ni-Cr alloy coatings by using direct and pulse current electrodeposition

    , Article Journal of Alloys and Compounds ; Volume 476, Issue 1-2 , 2009 , Pages 234-237 ; 09258388 (ISSN) Adelkhani, H ; Arshadi, M. R ; Sharif University of Technology
    This paper describes the effects of using direct and pulse current on composition and corrosion resistance of Fe-Ni-Cr alloy coatings. In both direct and pulse current electrodeposition, increasing the current density has a decreasing effect on Fe and Ni and an increasing influence on Cr. In pulse current electrodeposition, duty cycle has a greater effect than frequency on composition of the alloy coating, particularly in the range of 10-50%. In this range, by increasing the duty cycle, Ni decreases, Fe sharply increase and Cr shows an increasing trend. Following a study of the microhardness of coatings, it is determined that the microhardness increases about 1.5 times by pulse current...