Search for: powders
0.008 seconds
Total 355 records

    Microstructure and compressibility of SiC nanoparticles reinforced Cu nanocomposite powders processed by high energy mechanical milling [electronic resource]

    , Article Ceramics International ; Volume 40, Issue 1, Part A, January 2014, Pages 951–960 Akbarpour, M.R. (Mohammad Reza) ; Salahi, E ; Alikhani Hesari, F ; Simchi, A ; Kim, H. S ; Sharif University of Technology
    Cu/SiC nanocomposite powders with homogeneously distributed nanosize SiC particles were produced by high energy mechanical milling (MM). Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and micro-hardness and density measurements were performed to understand the effects of microstructure and hardness on compaction behavior during MM. The effects of SiC nanoparticle content and mechanical milling time on apparent density (AD) and tap density (TD) of the nanocomposite powders were systematically investigated. The Hausner ratio (HR), defined as TD to AD, were estimated to evaluate friction between the particles. Increasing MM duration and SiC content resulted... 

    Warm compaction of metallic powders

    , Article Advances in Powder Metallurgy: Properties, Processing and Applications ; 2013 , Pages 86-108 ; 9780857094209 (ISBN) Simchi, A ; Nojoomi, A ; Sharif University of Technology
    Warm compaction is a cost saving and effective method for obtaining high performance powder metallurgy (PM) parts. This chapter presents the principles of warm compaction and technical aspects of the process. The green and sintered properties of warm compacted parts are discussed and compared with conventionally (cold) produced compacts. The applications of the process for ferrous and non-ferrous PM parts are presented and future trends are outlined  

    Synthesis of wide band gap nanocrystalline NiO powder via a sonochemical method

    , Article Ultrasonics Sonochemistry ; Volume 19, Issue 4 , 2012 , Pages 841-845 ; 13504177 (ISSN) Mohseni Meybodi, S ; Hosseini, S. A ; Rezaee, M ; Sadrnezhaad, S. K ; Mohammadyani, D ; Sharif University of Technology
    A sonochemistry-based synthesis method was used to produce nanocrystalline nickel oxide powder with ∼20 nm average crystallite diameter from Ni(OH)2 precursor. Ultrasound waves were applied to the primary solution to intensify the Ni(OH)2 precipitation. Dried precipitates were calcined at 320 °C to form nanocrystalline NiO particles. The morphology of the produced powder was characterized by transmission electron microscopy. Using sonochemical waves resulted in lowering of the size of the nickel oxide crystallites. FT-IR spectroscopy and X-ray diffraction revealed high purity well-crystallized structure of the synthesized powder. Photoluminescence spectroscopy confirmed production of a wide... 

    Effect of nanoparticle content on the microstructural and mechanical properties of nano-SiC dispersed bulk ultrafine-grained Cu matrix composites [electronic resource]

    , Article Journal of Materials & Design ; December 2013, Volume 52, Pages 881–887 Akbarpour, M. R ; Salahi, E ; Alikhani Hesari, F ; Kim, H. S ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    In this study, the microstructural and mechanical features of monolithic pure Cu and Cu matrix nanocomposites reinforced with three different fractions (2, 4, and 6 vol%) of SiC nanoparticles (n-SiC) fabricated via a combination of high energy mechanical milling and hot pressing techniques were investigated. The fabricated composites exhibited homogeneous distribution of the n-SiC with few porosities. It was found that the grain refinement, the planar features within the grains, and the lattice strains increase with increase in the n-SiC content. The yield and compressive strengths of the nanocomposites were significantly improved with increases in the n-SiC content up to 4 vol%; then they... 

    Sintering viscosity and sintering stress of nanostructured WC–Co parts prepared by powder injection moulding [electronic resource]

    , Article Journal of Powder Metallurgy ; Februrary 2011, Volume 54, Issue 1, P. 84-88 Simchi, A. (Abdolreza) ; Sharif University of Technology
    The uniaxial viscosity and sintering stress of WC-10Co-0⊙ 9VC (wt-%) were obtained by a loading dilatometer as functions of fractional density (0⊙ 64< ρ< 0⊙ 93) and temperature (1084< T< 1297° C) according to a Newtonian constitutive law commonly used to simulate sintering. The viscosity is suggested to follow In η= a+ Q/RT+ bρ with the values of a= 52⊙ 3±4⊙ 5 and b= 16⊙ 8±0⊙ 2. Q reflects the temperature dependence of η and estimated to be 502±52 kJ mol-1. The sintering stress exhibited almost a constant value in the range of 0·05–0·4 MPa. It is shown that Rahaman's model best fits the experimental results. This paper describes experiments performed on nanostructured WC–Co feedstock to... 

    A comprehensive investigation into the effect of water to cement ratio and powder content on mechanical properties of self-compacting concrete

    , Article Construction and Building Materials ; Vol. 57 , April , 2014 , pp. 69-80 ; ISSN: 09500618 Nikbin, I. M ; Beygi, M. H. A ; Kazemi, M. T ; Vaseghi Amiri, J ; Rabbanifar, S ; Rahmani, E ; Rahimi, S ; Sharif University of Technology
    Self compacting concrete (SCC), as an innovative construction material in concrete industry, offers a safer and more productive construction process due to favorable rheological performance which is caused by SCC's different mixture composition. This difference may have remarkable influence on the mechanical behavior of SCC as compared to normal vibrated concrete (NVC) in hardened state. Therefore, it is vital to know whether the use of all assumptions and relations that have been formulated for NVC in current design codes are also valid for SCC. Furthermore, this study presents an extensive evaluation and comparison between mechanical properties of SCC using current international codes and... 

    High voltage SnO2 varistors prepared from nanocrystalline powders

    , Article Journal of Materials Science: Materials in Electronics ; Volume 21, Issue 2 , 2010 , Pages 199-205 ; 09574522 (ISSN) Shahraki, M. M ; Shojaee, S. A ; Nemati, A ; Sani, M. A. F ; Sharif University of Technology
    In this study, SnO 2-based varistors were prepared from mechanically activated nanocrystalline powders. Nanocrystalline powders were derived by subjecting the initial powders to intensive high-energy activation with different times and ball to powder ratio. The effect of activation parameters on the powder properties and sintering temperature, as well as microstructural, micro-electrical and macro-electrical properties of the final specimens was evaluated. Varistors derived from high-energy mechanical activation exhibit a higher density (98.3% relative density) and more refined microstructure upon sintering at 1,300 °C in comparison varistors prepared from conventional powders. Breakdown... 

    Effects of microsilica percentage amount on structure and compressive strength of reactive powder concrete (RPC)

    , Article Journal of Engineering and Applied Sciences ; Volume 11, Issue 7 , 2016 , Pages 1502-1507 ; 1816949X (ISSN) Khaloo, A ; Azizi, K ; Sharif University of Technology
    Medwell Journals 
    Reactive powder concrete is a new kind of powerful concrete which is called so because of tiny powder and pozzolanic materials as well as a lot of hydraulically active materials used in it and it has been presented by two French scientists in 1994. The aim of this study is to measure the possibility of producing powder concretes using local materials used in Asaluyeh Region. By calculating cement amount, water ratio to cement and optimal percentage of super plasticizer in this article, we start constructing six mix plans with different percentages of microsilica (0, 10, 15, 20, 30 and 40). Results show that 15% mix plan has the highest bending and compressive strength in three conditions of... 

    A ligand and palladium-free avenue for cyanation of aryl Halides: The art of samarium powder in C–C coupling reaction

    , Article ChemistrySelect ; Volume 4, Issue 33 , 2019 , Pages 9618-9621 ; 23656549 (ISSN) Matloubi Moghaddam, F ; Pourkaveh, R ; Gholamtajari, M ; Karimi, A ; Sharif University of Technology
    Wiley-Blackwell  2019
    This is the first study of samarium powder catalyzed cyanation reaction of aryl halides, bearing electron-withdrawing and electron-releasing substituents, in the presence of NaCN to afford corresponding benzonitriles in high yields. This protocol takes the advantage of being done in the absence of additive, ligand and precious transition metals such as palladium. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim  

    Electrophoretic deposition of titanium dioxide nano-powders films in isopropanol as a solvent

    , Article International Journal of Modern Physics B ; Volume 22, Issue 18-19 , 2008 , Pages 2989-2994 ; 02179792 (ISSN) Ghorbani, M ; Roushan Afshar, M ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2008
    In this study, titanium dioxide nano powders were electrophoretically deposited on the stainless steel in Isopropanol and Triethanolamine as a solvent and dispersant, respectively. The effects of deposition parameters including deposition voltage (5 to 20 V) and deposition time (5 to 60 s) on the microstructure and surface topography were examined by scanning electron microscope (SEM) and scanning probe microscope (SPM), respectively. In addition, the effects of these deposition parameters on packing density were investigated. This research revealed that substrate surface is fully covered with increasing deposition voltage and deposition time. Therefore packing density of deposited films is... 

    Investigation on compressibility of Al-SiC composite powders

    , Article Powder Metallurgy ; Volume 51, Issue 3 , 2008 , Pages 217-223 ; 00325899 (ISSN) Hafizpour, H.R ; Simchi, A ; Sharif University of Technology
    The consolidation behaviour of particulate reinforced metal matrix composite powders during cold uniaxial compaction in a rigid die was studied. Al-SiC powder mixtures with varying SiC particle size, ranging from nanoscale (50 nm) to microscale (40 μm), at different volume fractions up to 30% were used. Based on the experimental results, the effect of the reinforcement particles on the densification mechanisms, i.e. particle rearrangement and plastic deformation, was studied using modified Cooper-Eaton equation. It was found that by increasing the reinforcement volume fraction or decreasing its size, the contribution of particle rearrangement on the densification increases while the plastic... 

    Single and double stage sintering of mechanically alloyed powder for nanostructured Ti6Al4V foams usable in cancellous scaffolds

    , Article International Heat Treatment and Surface Engineering ; Volume 7, Issue 1 , 2013 , Pages 43-48 ; 17495148 (ISSN) Sadrnezhaad, S. K ; Aryana, M ; Hassanzadeh Nemati, N ; Alizadeh, M ; Ebadifar, A ; Sharif University of Technology
    Mechanical alloying and sintering were used to fabricate nanostructured Ti6Al4V scaffolds of highly controllable pore geometry and fully interconnected porous network. Elemental powders were milled for different periods of time (10, 20, 30, 40 and 60 h), mixed with 40-60 vol.-% of 200-400 μm cuboidal NaCl, compacted at 500-600 MPa and sintered according to single or double stage heat treatment regimes at 790 and 950°C under vacuum. After sintering, the samples were soaked in distilled water to washout the NaCl. Foamy microstructures were obtained showing well shaped biopores and fragmentary embedded micropores. The shape of initial NaCl was copied into the biopores which had highly... 

    A new computational algorithm for contact friction modeling of large plastic deformation in powder compaction processes

    , Article International Journal of Solids and Structures ; Volume 46, Issue 2 , 2009 , Pages 287-310 ; 00207683 (ISSN) Khoei, A. R ; Biabanaki, S. O. R ; Vafa, A. R ; Yadegaran, I ; Keshavarz, Sh ; Sharif University of Technology
    In this paper, the large deformation frictional contact of powder forming process is modeled based on a new computational algorithm by imposing the contact constraints and modifying the contact properties of frictional slip. A simple and efficient numerical algorithm is presented for imposing the contact constraints and frictional contact properties based on the node-to-surface contact technique to simulate the large deformation contact problem in the compaction process of powder. The Coulomb friction law is used to simulate the friction between the rigid punch and the workpiece by the use of penalty approach. A double-surface cap plasticity model is employed together with the nonlinear... 

    Waste ceramic powder-based geopolymer mortars: effect of curing temperature and alkaline solution-to-binder ratio

    , Article Construction and Building Materials ; Volume 227 , 2019 ; 09500618 (ISSN) Shoaei, P ; Musaeei, H. R ; Mirlohi, F ; Narimani zamanabadi, S ; Ameri, F ; Bahrami, N ; Sharif University of Technology
    Elsevier Ltd  2019
    In this study, the optimum curing temperature and alkaline solution-to-binder (S:B) ratio of geopolymer mortars based on waste ceramic powder (WCP) were investigated. For this purpose, mixes with S:B ratios of 0.4–0.7 were prepared and cured at 60, 75, 90, and 105 °C. The density, compressive and flexural strengths were measured at 3, 7, 14, and 28 days. Higher S:B ratios enhanced the flow of the fresh mortar. The optimum mortar was obtained for S:B ratio of 0.6 and curing temperature of 90 °C. The SEM analysis revealed that the optimal mix had a dense matrix with minimum pores. © 2019 Elsevier Ltd  

    Effect of hydrogen reduction on microstructure and magnetic properties of mechanochemically synthesized Fe-16.5Ni-16.5Co nano-powder

    , Article Journal of Magnetism and Magnetic Materials ; Volume 321, Issue 18 , 2009 , Pages 2729-2732 ; 03048853 (ISSN) Azizi, A ; Yoozbashizadeh, H ; Sadrnezhaad, S. K ; Sharif University of Technology
    Most recent findings on structural and magnetic properties of Fe-Ni-Co nano-powders produced by mechanical alloying and subsequent low-temperature hydrogen reduction are presented in this paper. At 300 rpm, with ball to powder weight ratio of 20, single phase nickel-cobalt ferrite is mechanically synthesized for 50 h. The as-milled powder is then subjected to 1 h hydrogen reduction at 700 °C. Hydrogen reduction results in the formation of Fe-16.5%Ni-16.5%Co nano-powders. The phases of the powders are identified by X-ray diffraction (XRD) utilizing Cu Kα radiation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to study the morphology and the average... 

    Friction Stir Welding of Aluminum to Magnesium Using Alumina and Zinc Powders

    , M.Sc. Thesis Sharif University of Technology Alipour Masoumabad, Saeid (Author) ; Movahedi, Moshtaba (Supervisor) ; Pouranvari, Majid (Supervisor)
    In this work, friction stir welding of aluminum to magnesium sheets using alumina and zinc powders was investigated. A preliminary investigation has been carried out on the joining of aluminum 5052 to AZ61 magnesium alloys and finding the optimum welding parameters. The optimum parameters were found to be with the shoulder diameter, pin diameter, and pin height of 14 mm, 5 mm, and 2.7 mm, respectively, with the travel speed of 60 mm/min and rotating speed of 500 rpm. As regards the main purpose of the using zin and alumina powders are controlling of Al-Mg IMCs formation and benefiting from pinning effect of grain boundaries, hence by adopting preliminary investigations and fixing pervious... 

    Multiphysics Modeling and Magnetic Control of Powder Deposition Process in DMD Method of Additive Manufacturing Technology

    , M.Sc. Thesis Sharif University of Technology Nejati Eghteda, Sina (Author) ; Movahhedy, Mohammad Reza (Supervisor)
    Direct Metal Deposition is one of the methods of Additive manufacturing that has seen the most spread in recent years. In this method metal powder is directed towards the free surface of the workpiece through a nuzzle, and is simultaneously heated to become molten in a melting pool by a laser beam and begins the deposition process. One of the parts that make up a DMD system is powder feeding nuzzle. These nuzzles usually encounter a similar fundamental problem: that the effect of gravity on the stream of metal powder and the carrier fluid causes this stream to deviate from its intended position. To prevent this, nuzzles are usually designed with a fixed downward angle and the angle of the... 

    Comparative assessment of the crystalline structures of powder and bulk human dental enamel by X-ray diffraction analysis

    , Article Journal of Oral Biosciences ; Volume 61, Issue 3 , 2019 , Pages 173-178 ; 13490079 (ISSN) Behroozibakhsh, M ; Hajizamani, H ; Shekofteh, K ; Otadi, M ; Ghavami Lahiji, M ; Faal Nazari, N. S ; Sharif University of Technology
    Japanese Association for Oral Biology  2019
    Objectives: The aim of this study was to assess and compare the crystalline structures of both powder and bulk human dental enamel by X-ray diffraction analysis (XRD). Methods: The buccal surfaces of 60 selected noncarious third molars were divided into two groups of powdered and bulk enamel specimens. To prepare enamel powders, the enamel tissues were ground and powdered manually using a mortar and pestle. For bulk samples, the enamel slabs were sectioned using a low-speed diamond saw. The crystalline structures of samples were analyzed by XRD, and the obtained data were analyzed. The values of the lattice parameters were obtained using the equation of hexagonal crystalline structures. The... 

    Study of the densification of a nanostructured composite powder. part 1: effect of compaction pressure and reinforcement addition

    , Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 580-584 ; 09215093 (ISSN) Abdoli, H ; Farnoush, H ; Salahi, E ; Pourazrang, K ; Sharif University of Technology
    The compressibility behavior of Al-AlN nanostructured composite powder with different amount of reinforcement content was studied. The composite powder was synthesized by blending and high-energy milling process for 25 h. Williamson-Hall method was applied to determine the crystallite size after milling process. To investigate the role of reinforcement particles in consolidation of composite powders, monolithic aluminum powder was examined. Samples were made at different pressures and relationships were established between the compaction pressure and the density of the compacts. The modified Heckel equation was used to assume the pressure effect on yield strength and then was compared with... 

    Contact friction simulation in powder compaction process based on the penalty approach

    , Article Materials and Design ; Volume 29, Issue 6 , 2008 , Pages 1199-1211 ; 02613069 (ISSN) Keshavarz, Sh ; Khoei, A. R ; Khaloo, A. R ; Sharif University of Technology
    Elsevier Ltd  2008
    In this paper, the influence of powder-tool friction on the mechanical properties of the final product is investigated in pressing metal powders. A computational algorithm is presented for simulation of frictional contact in the compaction process of powder. The large deformation finite element (FE) formulation is characterized by the use of penalty approach in which a plasticity theory of friction is incorporated to simulate sliding resistance at the powder-tool interface. The constitutive relations for friction are derived from a Coulomb friction law. A double-surface cap plasticity model is employed together with the nonlinear contact friction behavior in numerical simulation of powder...