Search for: surface-treatment
0.007 seconds

    The investigation of laser shock peening effects on corrosion and hardness properties of ANSI 316L stainless steel

    , Article International Journal of Advanced Manufacturing Technology ; Volume 88, Issue 5-8 , 2017 , Pages 1557-1565 ; 02683768 (ISSN) Ebrahimi, M ; Amini, S ; Mahdavi, S. M ; Sharif University of Technology
    Springer London  2017
    Laser shock peening (LSP) is known as a post processing surface treatment which can improve the mechanical properties of some materials. Shock waves are generated by confining the laser-induced plasma to cause a large pressure shock wave over a significant surface area. In the present study, effects of LSP on the electrochemical corrosion and micro hardness properties of 316L stainless steel alloy were investigated by changing the laser parameters such as the laser spot size, the average number of impacts, and the laser intensity. Since laser parameters do not cover the desired region of LSP, we have to use the proper design of experiment method, in which the D-optimal design of MATLAB was... 

    Enhancement of surface properties and performance of reverse osmosis membranes after surface modification: a review

    , Article Desalination ; Volume 420 , 2017 , Pages 330-383 ; 00119164 (ISSN) Asadollahi, M ; Bastani, D ; Musavi, S. A ; Sharif University of Technology
    Reverse osmosis (RO) membrane process has become the most promising technology for desalination to produce purified water. Among numerous polymeric materials used to fabricate RO membranes, aromatic polyamide thin film composite (TFC) membranes are dominant in commercial RO membrane processes because of their high salt rejection and water permeability as well as their excellent chemical, thermal, and mechanical stability. However, the major hindrance to the effective application of polyamide TFC RO membranes is membrane fouling. Furthermore, polyamide TFC RO membranes have limited stability to chlorine, which is commonly used as disinfect to control membrane biofouling. These two factors... 

    Fouling control mechanism by optimum ozone addition in submerged membrane bioreactors treating synthetic wastewater

    , Article Journal of Environmental Chemical Engineering ; Volume 6, Issue 6 , 2018 , Pages 7294-7301 ; 22133437 (ISSN) Mashayekhi, F ; Hazrati, H ; Shayegan, J ; Sharif University of Technology
    In this paper, the effect of ozone on membrane fouling of membrane bioreactor (MBR) systems was investigated. Sludge specification such as soluble microbial product (SMP), extracellular polymeric substance (EPS), viscosity, particle size distribution (PSD), microscopic observations and sludge volume index (SVI) in presence of ozone were determined. Further, EPS, Fourier-transform infrared (FTIR) analysis, excitation-emission matrix (EEM) fluorescence spectroscopy, and gel permission chromatography (GPC) are considered to determine cake layer characteristics. The results indicated COD removal did not show significant difference with ozonation. Ozone also increases the particle size and... 

    Silver nano-islands on glass fibers using heat segregation method

    , Article Materials Chemistry and Physics ; Volume 113, Issue 1 , 2009 , Pages 63-66 ; 02540584 (ISSN) Sharifi, N ; Taghavinia, N ; Sharif University of Technology
    A new method for fabrication of silver nano-islands on glass fibers using a top-down process is introduced. A thin layer of silver chemically coated on the surface of the glass fibers evolves into silver islands by heat treatment. The effect of the concentration of the initial solution and the temperature were investigated. Segregation was more clearly observed for lower solution concentrations and higher temperatures. The temperature of 500 °C was found optimum where separated islands form. At higher temperatures, the coagulation and burial of silver islands occur. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and diffused reflectance spectroscopy (DRS) were... 

    Effect of oxidizing atmosphere on the surface of titanium dental implant material

    , Article Journal of Bionic Engineering ; Volume 16, Issue 6 , 2019 , Pages 1052-1060 ; 16726529 (ISSN) Khodaei, M ; Alizadeh, A ; Madaah Hosseini, H. R ; Sharif University of Technology
    Springer  2019
    Direct oxidation is a simple and effective method for titanium surface treatment. In this research, a titanium sample was directly oxidized at the high temperature in two different atmospheres, air and pure oxygen, to obtain better atmosphere for titanium surface treatment. The results of the Raman spectroscopy indicated that in both atmospheres, the rutile bioactive phase (TiO2) has been formed on the titanium surface. The results of X-ray diffraction (XRD) also revealed that the surface of oxygen-treated sample was composed of the rutile phase and titanium monoxide (TiO), while at the surface of the air-treated sample, the rutile phase and titanium dioxide had been formed. Further, the... 

    Surface modification of polysulfone ultrafiltration membranes by free radical graft polymerization of acrylic acid using response surface methodology

    , Article Journal of Polymer Research ; Volume 26, Issue 9 , 2019 ; 10229760 (ISSN) Ganj, M ; Asadollahi, M ; Mousavi, S. A ; Bastani, D ; Aghaeifard, F ; Sharif University of Technology
    Springer Netherlands  2019
    In this research, polysulfone (PSf) ultrafiltration (UF) membranes were prepared by a phase inversion method. Surface modification of the PSf membranes was carried out via grafting of acrylic acid as a hydrophilic monomer by free radical graft polymerization initiated by redox reaction. A central composite design (CCD) of response surface methodology (RSM) was applied to design the experiments. The process variables were acrylic acid concentration (CAA), redox system contact time (T1), and acrylic acid polymerization time (T2), while the contact angle (CA), pure water flux (PWF), and flux recovery ratio (FRR) were considered as the responses. Analysis of variance (ANOVA) demonstrated that... 

    Hexagonal core–shell SiO2[–MOYI]Cl–]Ag nanoframeworks for efficient photodegradation of the environmental pollutants and pathogenic bacteria

    , Article Journal of Inorganic and Organometallic Polymers and Materials ; Volume 29, Issue 4 , 2019 , Pages 1314-1323 ; 15741443 (ISSN) Padervand, M ; Asgarpour, F ; Akbari, A ; Eftekhari Sis, B ; Lammel, G ; Sharif University of Technology
    Springer New York LLC  2019
    Hexagonal core–shell SiO2[–MOYI]Cl–]Ag nanoframeworks were synthesized via surface modification of hexagonal silica nanoparticles prepared from perlite (EP) as a cheap and abundant raw material. The prepared samples were well characterized by X-ray diffraction powder (XRD), energy dispersive X-ray (EDX), diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) specific surface area analysis, fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The XRD patterns confirmed that Ag and AgCl crystalline phases were successfully loaded on the surface. The TEM images were also implied that the... 

    Effects of severe plastic deformation on pre-osteoblast cell behavior and proliferation on AISI 304 and Ti-6Al-4V metallic substrates

    , Article Surface and Coatings Technology ; Volume 366 , 2019 , Pages 204-213 ; 02578972 (ISSN) Tevlek, A ; Aydın, H. M ; Maleki, E ; Varol, R ; Unal, O ; Sharif University of Technology
    Elsevier B.V  2019
    In this study, titanium alloy (Ti-6Al-4V) and austenitic stainless steel (AISI 304) biomedical alloys were subjected to surface severe plastic deformation (SSPD) via severe shot peening (SSP) with the conditions of A28-30 Almen intensity. SSP is widely accepted as much more effective than the conventional surface modification techniques since it forms a nano-grain layer with large number of dislocations and grain boundaries. The SSP treatment in this study was led to a very thin rough layer in Ti-6Al-4V titanium alloy compared to that of AISI 304. The thicker layer of AISI 304 was created by twin-twin intersections and a martensite structure transformations. SSP treatment was resulted in a... 

    Improvement of performance and fouling resistance of polyamide reverse osmosis membranes using acrylamide and TiO2 nanoparticles under UV irradiation for water desalination

    , Article Journal of Applied Polymer Science ; Volume 137, Issue 11 , 2020 Asadollahi, M ; Bastani, D ; Mousavi, S. A ; Heydari, H ; Vaghar Mousavi, D ; Sharif University of Technology
    John Wiley and Sons Inc  2020
    The purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results... 

    Oxidation behavior and electrical properties of de-siliconized aisi 430 alloy with mn1.5co1.5o4 coating for solid oxide fuel cell interconnect

    , Article Oxidation of Metals ; Volume 93, Issue 3-4 , 2020 , Pages 401-415 Bakhshi Zadeh, A ; Salmani, S ; Faghihi Sani, M. A ; Abdoli, H ; Jalili, N ; Sharif University of Technology
    Springer  2020
    Abstract: The effect of de-siliconization on the oxidation behavior of AISI 430 stainless steel used for solid oxide fuel cell interconnect application was investigated. De-siliconization treatment was conducted via heating steel parts in an H2 environment. The de-siliconized substrates were then coated with a Mn1.5Co1.5O4 spinel coating, using wet spray method. For comparison, a similar coating process was applied on the as-received AISI 430 stainless steel specimens. Oxidation kinetics of coated interconnects were evaluated at 700, 800 and 900 °C in air. Results showed that the de-siliconization surface treatment decreased oxidation rates, with kinetic rates (g2 cm−4 s−1) of 4.39 × 10−14... 

    CaTiO3/α-TCP coatings on CP-Ti prepared via electrospinning and pulsed laser treatment for in-vitro bone tissue engineering

    , Article Surface and Coatings Technology ; Volume 401 , 2020 Yadi, M ; Esfahani, H ; Sheikhi, M ; Mohammadi, M ; Sharif University of Technology
    Elsevier B.V  2020
    In this study, the in-vitro bone regeneration ability of commercial pure titanium (CP-Ti) surface modified via electrospun polyvinylidene/hydroxyapatite (PVP/HA) masking and subsequent Nd-YAG pulsed laser treatment was investigated. The ratio of HA to PVP played a significant role in achieving a perfect homogenous mask on the CP-Ti. In the laser treatment process, the parameter of area scanning speed (ASS) had an important influence on the final surface morphology. A favorable range was defined for this parameter where these two conditions were satisfied: no PVP remaining and no severe substrate melting. Within a favorable range of ASS, as decreasing ASS exchanged the surface structure from... 

    Efficiency improvement of solar stills through wettability alteration of the condensation surface: An experimental study

    , Article Applied Energy ; Volume 268 , 2020 Zanganeh, P ; Soltani Goharrizi, A ; Ayatollahi, S ; Feilizadeh, M ; Dashti, H ; Sharif University of Technology
    Elsevier Ltd  2020
    The condensation process is of great importance in many heat transfer devices in which a large amount of energy must be transferred. Furthermore, condensation is a crucial part of energy conversion and affects the energy efficiency of thermal desalination plants and solar stills. During the condensation process in solar stills, an essential part of the energy is transferred through the condensation surface to produce fresh water. Therefore, the condensation surface plays a significant role in the working efficiency of solar stills. The wettability of the condensation surface influences the condensation mechanism, which, in turn, affects the efficiency of solar stills. This study aims to... 

    A clustering approach to identify the time of a step change in shewhart control charts

    , Article Quality and Reliability Engineering International ; Volume 24, Issue 7 , 2008 , Pages 765-778 ; 07488017 (ISSN) Ghazanfari, M ; Alaeddini, A ; Akhavan Niaki, S. T ; Aryanezhad, M. B ; Sharif University of Technology
    Control charts are the most popular statistical process control tools used to monitor process changes. When a control chart indicates an out-of-control signal it means that the process has changed. However, control chart signals do not indicate the real time of process changes, which is essential for identifying and removing assignable causes and ultimately improving the process. Identifying the real time of the change is known as the change-point estimation problem. Most of the traditional methods of estimating the process change point are developed based on the assumption that the process follows a normal distribution with known parameters, which is seldom true. In this paper, we propose... 

    Alumina - copper eutectic bond strength: Contribution of preoxidation, cuprous oxides particles, and pores

    , Article 16th International Federation for Heat Treatment and Surface Engineering Congress, Brisbane, QLD, 30 October 2007 through 2 November 2007 ; Volume 32 , 2007 , Pages 90-97 ; 08832900 (ISSN) Ghasemi, H ; Kokabi, A. H ; Faghihi Sani, M. A ; Riazi, Z ; Sharif University of Technology
    The influences of cupric oxide layer thickness, cuprous oxide particles, and pores on mechanical properties and microstructure of alumina-copper eutectic bond have been investigated. The furnace atmosphere in the first stage was argon gas with 2 × 10-6 atm oxygen partial pressure. In the second stage, the furnace atmosphere was same as the first stage unless that in cooling between 900-1000 °C, the hydrogen gas was purged in furnace atmosphere. Finally, in the last stage a vacuum furnace with 5 × 10 -8 atm pressure was chosen for bonding procedure. Peel strength of first stage specimens shows that cupric oxide layer with 320 ± 25 nm thick generates the maximum peel strength (13.1 ± 0.3... 

    Supramolecular polycaprolactone nanocomposite based on functionalized hydroxyapatite

    , Article Journal of Bioactive and Compatible Polymers ; Volume 27, Issue 5 , January , 2012 , Pages 467-480 ; 08839115 (ISSN) Mehmanchi, M ; Shokrollahi, P ; Atai, M ; Omidian, H ; Bagheri, R ; Sharif University of Technology
    SAGE  2012
    Arms bearing ureido-pyrimidinone functional groups with self-association capability (through quadruple hydrogen bonds) were successfully grafted onto hydroxyapatite nanoparticles. The supramolecularly modified nanoparticles (nHApUPy) exhibited enhanced colloidal stability compared to the original hydroxyapatite nanoparticles and were uniformly dispersed in supramolecular polycaprolactone in PCL(UPy)2/HApUPy nanocomposites at different filler loadings. The combined atomic force microscopy, mechanical, and rheological analyses confirmed a high degree of compatibility of HApUPy nanoparticles with the polymer matrix. The temperature dependence of the supramolecular structure in PCL(UPy)2/HApUPy... 

    Study of cemented carbonitrides with nickel as binder: Experimental investigations and computer calculations

    , Article International Journal of Refractory Metals and Hard Materials ; Volume 31 , 2012 , Pages 164-170 ; 02634368 (ISSN) Mohammadpour, M ; Abachi, P ; Parvin, N ; Pourazrang, K ; Sharif University of Technology
    Cobalt is the most common binder in cemented carbides industry. However, there are some interests in use of alternatives. The similarity in properties has made nickel the first choice. In the present work, the effect of initial composition on modern hardmetals containing transition metal carbides/carbonitrides that are called "cemented carbonitrides" with nickel as binder was investigated. Change in quantity of additive carbides and tungsten to carbon (C/W) weight ratio through applying metallic tungsten powder in primary powder mixture had some effects on final hardness, transverse rupture strength, and microstructure of studied alloys. Addition of vanadium carbide not more than 0.2 wt.%,... 

    Palladium nanoparticle deposition onto the WO3 surface through hydrogen reduction of PdCl2: Characterization and gasochromic properties

    , Article Solar Energy Materials and Solar Cells ; Volume 95, Issue 8 , August , 2011 , Pages 2335-2340 ; 09270248 (ISSN) Ranjbar, M ; Fardindoost, S ; Mahdavi, S. M ; Iraji Zad, A ; Tahmasebi G. N ; Sharif University of Technology
    Nowadays, gasochromic Pd/WO3 coatings as optically switchable materials have become more applicable for hydrogen sensors and smart windows. In this study, WO3 films were prepared by Pulsed Laser Deposition (PLD) and spin-coating sol-gel techniques. For deposition of Pd, first a layer of PdCl2 was obtained via a simple drop-drying process by dropping PdCl2 solution onto WO3 substrates and drying them at room temperature. Then Pd nanoparticles were synthesized via hydrogen gas exposure that causes reduction of the PdCl2 layer. According to Scanning Electron Microscope (SEM) observations before hydrogen reduction, many individual nanoparticles or fractal-like constructions of palladium were... 

    Study of nanocrystallization in FINEMET alloy by active screen plasma nitriding

    , Article Journal of Alloys and Compounds ; Volume 491, Issue 1-2 , 2010 , Pages 487-494 ; 09258388 (ISSN) Shivaee, H. A ; Madaah Hosseini, H. R ; Memarzadeh Lotfabad, E ; Roostaie, S ; Sharif University of Technology
    The nanocrystallization process of amorphous Fe73.5Si13.5B9Nb3Cu 1 was investigated by active screen plasma nitriding (ASPN) treatment at temperatures ranging from 410 °C to 560 °C for 3 h in two gas mixtures of 75% N2-25% H2 and 25% N2-75% H2 at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum at the same time and temperatures mentioned above. The structure of the samples was analyzed using various techniques such as X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Microhardness measurements, electrical resistivity and Vibrating Sample Magnetometer (VSM) were used to study mechanical, electrical and magnetic... 

    Self cleaning TiO2 coating on polycarbonate: Surface treatment, photocatalytic and nanomechanical properties

    , Article Surface and Coatings Technology ; Volume 204, Issue 9-10 , 2010 , Pages 1562-1568 ; 02578972 (ISSN) Yaghoubi, H ; Taghavinia, N ; Keshavarz Alamdari, E ; Sharif University of Technology
    A developed route to form TiO2 self cleaning coatings on polycarbonate substrates is reported. TiO2 coatings on plastics may find widespread application in auto and construction industries if possess desired photocatalytic and mechanical properties. A chemical surface treatment method was used to create hydrophilic groups on the surface. X-ray photoelectron spectroscopy showed the treatment led to the oxidation of surface groups. TiO2 deposition was based on wet coating using an anatase sol of TiO2 nanoparticles of 30 nm size. The sol was synthesized using a sol-gel route. A pre-coat of peroxotitanium complex was employed to improve adhesion and inhibit the substrate degradation. The coating... 

    Synthesis and cyto-genotoxicity evaluation of graphene on mice spermatogonial stem cells

    , Article Colloids and Surfaces B: Biointerfaces ; Volume 146 , 2016 , Pages 770-776 ; 09277765 (ISSN) Hashemi, E ; Akhavan, O ; Shamsara, M ; Daliri, M ; Dashtizad, M ; Farmany, A ; Sharif University of Technology
    Elsevier  2016
    The present study analyzed the dose-dependent cyto- and genotoxicity of graphene oxide and reduced graphene oxide on spermatogonial stem cells (SSCs) for the first time. The results showed that graphene oxide significantly increased oxidative stress at concentrations of 100 and 400 μg/ml, while low concentrations did not have a significant effect. In addition, according to the MTT assay, the cell number decreased in high-concentration (100 and 400 μg/ml) graphene oxide-treated samples compared to untreated cells. However, a reduced graphene-treated sample demonstrated a significant increase in cell number. Moreover, microscopic analysis found high concentrations of graphene nanosheets in...