Search for: surface-treatment
Total 74 records
Study on Effects of Short Wood Fibers on Physical and Mechanical Properties of Biodegradable Composite Based on Thermoplastic Starch, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza ; Sayyed Reihani, Morteza
Due to the negative effects of conventional plastics on the enviroment, especially in the packaging sector, extensive efforts have been put to replace these polymers with biodegradable polymers. Starch is one of the biodegradable polymers which has attracted a lot of attentions because of low cost and good processability. Native starch has the form of granule and can be processed to a continuous phase after gelatinization in the presence of a plasticizer. The resulting material is a biodegradable plastic-like material called thermoplastic starch (TPS) which is processed using conventional technologies, but suffers from low mechanical properties and high hydrophilicity. Addition of natural...
“ Nano Oxide Layer Forming on the Surface of Porous Nitinol Shape Memory Alloy for Improving Surface Properties “, M.Sc. Thesis Sharif University of Technology ; Sadrnejhad, Khatiboleslam
In this project ,it has been done different surface treatment on 6 samples of nitinol with 40 % prosity,three of them are anodized by H2SO4 ,Hf, Acetic acid, one of them is treated with plasma spray with TIO2 powder, one of them is putted in the furnace at 700 degrees for an hour, and the last one is bare ; Moreover, these treated samples are putted in Simulated body fluid for 16 days . After this period of time, we analyzed the results. Then the cell adhesion amount of osteo blast cells (MG 63) is measured to these samples by immersing them for 3 days in these cells.The results are investigated by SEM ,XRD(X pertpro produced by Panalitical), XRF(530-XRF-01), AAS( AA240), Roughness measuring...
Developing an Analytical Model for Predicting the Residual Stresses Induced by Shot Peening with Considering the Effect of Initial Surface Treatment, Ph.D. Dissertation Sharif University of Technology ; Farrahi, Gholam Hossein ; Mahmoudi, Amir Hossein
Shot peening is a cold-working process commonly used in industry to improve the fatigue performance, stress corrosion resistance and surface nano-crystallization of metallic parts. This process extends fatigue life via two mechanisms: Preventing the crack growth due to compressive residual stresses and, preventing the crack initiation because of increased material hardness. These mechanisms are the results of the bombardment of the component's surface with small spherical particles. In this research, an analytical model is developed for estimating the residual stress distribution induced by shot peening process. The modifications of the developed analytical model are related to...
Enhanced Electronic Properties in Mesoporous TiO2 Via Passivation Treatment in Perovskite Solar Cells, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza
Perovskite solar cells are the new generation of solar cells, and are mainly introduced in two types of structures.1) planer and 2) mesoscopic structure. The difference between these two structures derives from the absence of mesoporous layer in the planer structures. The mesoporous layer acts as an electron transporting layer, and is mainly a titanium dioxide semiconductor. To apply the mesoporous layer, the preparation of the TiO2 paste is needed.The synthesis of titanium dioxide nanopowder for the preparation of TiO2 paste requires high temperature heat treatment and is not desirable in terms of energy consumption.Another weakness of this layer is the presence of surface defects, which...
hysical and Chemical Surface Modification of Titanium by Nanostructured Materials, and Biological Characterization for Use in Bone Tissue Implants, Ph.D. Dissertation Sharif University of Technology ; Bagheri, Reza ; Vossoughi, Manochehr ; Samadi Kuchaksaraei, Ali
According to human needs and in line with the development of advanced technologies, different biomedical Engineering fields like hard tissue implants are growing rapidly. Despite significant biotechnology Developments in recent years, some problems to the recognition of implants related osseointegration phenomena persist. The deficient osseointegration and implant-associated infections are key issues for the long-term clinical success of titanium and titanium alloy implants, while development of multifunctional surfaces that can simultaneously overcome these problems remains highly challenging. Therefore, the ultimate goal of this paper was to improve bone cell attachment and simultaneously...
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad
In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg)...
The effect of multiple surface treatments on biological properties of Ti-6Al-4V alloy, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 10 , 2014 , p. 4588-4593 ; Amini, P ; Asgari, S ; Sharif University of Technology
In this research, the effect of various surface treatments including laser processing, grit blasting and anodizing on chemical structure, surface topography, and bioactivity of Ti-6Al-4V was investigated. Six groups of samples were prepared by a combination of two alternative laser processes, grit blasting and anodizing. Selected samples were first evaluated using microanalysis techniques and contact roughness testing and were then exposed to in vitro environment. Scanning electron microscopy was used to characterize the corresponding final surface morphologies. Weight measurement and atomic absorption tests were employed for determination of bioactivity limits of different surface...
Chromium carbonitride coating produced on DIN 1.2210 steel by thermo-reactive deposition technique: Thermodynamics, kinetics and modeling, Article Surface and Coatings Technology ; Volume 225 , 2013 , Pages 1-10 ; 02578972 (ISSN) ; Nazari, A ; Khoie, S. M. M ; Khalaj, M. J ; Pouraliakbar, H ; Sharif University of Technology
A duplex surface treatment on DIN 1.2210 steel has been developed involving nitriding and followed by chromium thermo-reactive deposition (TRD) techniques. The TRD process was performed in molten salt bath at 550, 625 and 700°C for 1-14h. The process formed a thickness up to 9.5μm of chromium carbonitride coatings on a hardened diffusion zone. Characterization of the coatings by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicates that the compact and dense coatings mainly consist of Cr(C,N) and Cr2(C,N) phase. All the growth processes of the chromium carbonitride obtained by TRD technique followed a parabolic kinetics. Activation energy (Q) for the...
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) ; Shokrollahi, P ; Atai, M ; Omidian, H ; Bagheri, R ; Sharif University of Technology
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...
The effect of shot peening on fatigue life of welded tubular joint in offshore structure, Article Materials and Design ; Volume 36 , 2012 , Pages 250-257 ; 02641275 (ISSN) ; H-Gangaraj, S. M ; Farrahi, G. H ; Majzoobi, G. H ; Mahmoudi, A. H ; Daghigh, M ; Yari, A ; Moridi, A ; Sharif University of Technology
An offshore structure is exposed to environmental loading and cyclic stress variations throughout its life. This would result in the possibility of fatigue cracking in its members. Cracks in these structures usually initiate around welded areas, then grow progressively from the heat-affected zone to base metal through the thickness of the tubular members. Therefore, fatigue life improvement of offshore structures is of great importance. In this paper, structural analysis of an offshore platform is carried out and the critical joint is specified. The welding process is simulated and the residual stresses due to the welding are determined. Experimental residual stress measurement is carried...
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) ; 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) ; 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...
The effects of combination of severe plastic deformation and Shot Peening surface treatment on fatigue behavior of 6082 aluminum alloy, Article Russian Journal of Non-Ferrous Metals ; Volume 56, Issue 2 , 2015 , Pages 206-211 ; 10678212 (ISSN) ; Irani, M ; Karimi Taheri, A ; Sharif University of Technology
In this paper, the effects of Equal Channel Angular Pressing process (ECAP) followed by Shot Peening process (SP) on the fatigue properties of 6082 aluminum alloy are investigated. Several samples of the alloy are ECAPed and SPed and then their mechanical behavior are characterized using tensile, micro-hardness, and fatigue tests. The results indicate that shot peening and then polishing the specimen after one-pass ECAP is an effective method to improve the fatigue life of the alloy. Moreover, by increasing the number of ECAP passes before shot peening, a local work softening occurs at the subsurface layer, leading to a significant decrease in the fatigue life of the alloy. The results of...
Characterisation of Ni-Ti intermetallic coatings formed on Cp titanium by diffusion treatment, Article International Journal of Surface Science and Engineering ; Volume 9, Issue 1 , 2015 , Pages 43-54 ; 1749785X (ISSN) ; Sohi, M. H ; Ghasemi, H. M ; Vafadar, A. Kh ; Sharif University of Technology
Inderscience Enterprises Ltd 2015
In order to produce a thick near equi-atomic NiTi intermetallic layer on the surface of titanium plate, layers of nickel with thicknesses of 30 μm and 60 μm were electroplated on commercial pure (Cp) titanium and subsequently were heat treated at 850°C and 900°C. The effects of heat treating temperature and the thickness of electroplated nickel on the evolution of the microstructure and mechanical properties were studied. The results confirm the formation of various intermetallic layers in the coatings that substantially affect their hardness. The optimum condition for the formation of a thick NiTi intermetallic layer on the outer surface of the titanium was diffusion treatment of the sample...
Energy aspects and workpiece surface characteristics in ultrasonic-assisted cylindrical grinding of alumina-zirconia ceramics, Article International Journal of Machine Tools and Manufacture ; Volume 90 , 2015 , Pages 16-28 ; 08906955 (ISSN) ; Tawakoli, T ; Akbari, J ; Sharif University of Technology
Ultrasonic assisted grinding is a novel method for improving the grinding process of difficult-to-cut materials. In the present research a novel setup has been designed and manufactured for utilizing ultrasonic vibrations in external cylindrical grinding. The designed ultrasonic head vibrates a rotating workpiece in axial direction. An alumina-zirconia ceramic (AZ90) has been selected as the workpiece material. Energy aspects and workpiece surface characteristics of ultrasonic assisted cylindrical grinding (UACG) and conventional cylindrical grinding (CG) processes have been analytically modeled and corresponding grinding experiments have been performed. The combined kinematics of the...
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) ; 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) ; 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...
Voltammetric studies of Azathioprine on the surface of graphite electrode modified with graphene nanosheets decorated with Ag nanoparticles, Article Materials Science and Engineering C ; Volume 58 , 2016 , Pages 1098-1104 ; 09284931 (ISSN) ; Iraji Zad, A ; Shahrokhian, S ; Sharif University of Technology
By using graphene nanosheets decorated with Ag nanoparticles (AgNPs-G) as an effective approach for the surface modification of pyrolytic graphite electrode (PGE), a sensing platform was fabricated for the sensitive voltammetric determination of Azathioprine (Aza). The prepared AgNPs-G nanosheets were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis and Raman spectroscopy techniques. The electrochemical behavior of Aza was investigated by means of cyclic voltammetry. Comparing to the bare PGE, a remarkable enhancement was observed in the response characteristics of Aza on the surface of the modified electrode (AgNPs-G/PGE) as well as a noticeable...
Modeling of shot-peening effects on the surface properties of a (Tib + Tic)/Ti-6Al-4V composite employing artificial neural networks, Article Materiali in Tehnologije ; Volume 50, Issue 6 , 2016 , Pages 851-860 ; 15802949 (ISSN) ; Zabihollah, A ; Sharif University of Technology
Institute of Metals Technology
Titanium matrix composites (TMCs) have wide application prospects in the field of aerospace, automobile and other industries because of their good properties, such as high specific strength, good ductility, and excellent fatigue properties. However, in order to improve their fatigue strength and life, crack initiation and growth at the surface layers must be suppressed using surface treatments. Shot peening (SP) is an effective surface mechanical treatment method widely used in industry which can improve the mechanical properties of a surface. However, artificial neural networks (ANNs) have been used as an efficient approach to predict and optimize the science and engineering problems. In...
A comprehensive experimental and numerical study on redistribution of residual stresses by shot peening, Article Materials and Design ; Volume 90 , 2016 , Pages 478-487 ; 02641275 (ISSN) ; Ghasemi, A ; Farrahi, G. H ; Sherafatnia, K ; Sharif University of Technology
Elsevier Ltd 2016
Shot peening is one of the most effective surface strengthening treatment technologies in which compressive residual stresses are induced beneath the specimen surface. Effects of various factors on the distribution of residual stress profile induced by shot peening have been investigated by many researchers. However, initial residual stresses are one of the important factors which affect the shot peening residual stress.This study is aimed to present comprehensive numerical and experimental study on the effect of initial residual stresses on the shot peened specimen. Initial residual stresses were induced using a four-point bending rig and grinding. Incremental center hole drilling (ICHD)...