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Structural characteristics and desorption properties of nanostructured MgH2 synthesised by high energy mechanical milling [electronic resource]
, Article Journal of Powder Metallurgy ; September 2011, Volume 54, Issue 4 , P.480-483 ; Kaflou, A ; Simchi, A. (Abdolreza) ; Sharif University of Technology
Abstract
The effect of particle size, lattice strain and crystallite size on the hydrogen desorption properties of nanocrystalline magnesium hydride powder was investigated. Commercial MgH2 powder was milled in a Spex 8000M up to 16 h and its structural evolution and desorption characteristics at different time intervals were examined using various analytical techniques. At the early stage of milling, the formation of metastable γ-MgH2 phase was noticed. While the crystallite size gradually decreased to 12 nm with increasing the milling time, the accumulated lattice strain gained a maximum value of 0·9% after 4 h milling. The highest drop in the desorption temperature (∼100°C) was attained at the...
Effect Of Mechanical Milling on the Microstructure Development and Mechanical Properties of Gas-Atomized Al-20Si-5Fe-2Ni Alloy
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor) ; Maddah Hosseini, Hamid Reza (Supervisor)
Abstract
In this work, hypereutectic Al-20Si-5Fe-2Ni powder was prepared by gas atomizing method. The alloy was fabricated by melting of commercially pure metals and re-melting at approximately 200 K above the liquidus temperature. The molten alloy was then atomized by nitrogen at a gas pressure of 0.8 MPa. The nozzle diameter was 3 mm. The aluminum alloy powders were milled under pure Argon atmosphere with a ball to powder ratio of 10:1 in a planetary ball for 12, 24, 36 and 48 hours. The gas-atomized and milled powders were then consolidated by cold sintering method. Microstructure and phase analysis were performed by SEM and XRD technique. Mechanical properties were evaluated by microhardness and...
Fabrication & Characterization of Al-Al3Ti-Al2O3 Nano-composites Based on the Thermal Degradation of Aluminium Titanate & Facile Study on the Correlation between Microstructure & Their Mechanical Properties
, M.Sc. Thesis Sharif University of Technology ; Maddah Hosseini, Hamid Reza (Supervisor)
Abstract
In this study insitu Al-Al3Ti-Al2O3 nanocomposite has been fabricated based on thermal decomposition of tialite (Al2TiO5) precursor in aluminium matrix through powder metallurgy method. Also the effect of high energy mechanical milling and hot extrusion on this procedure has been investigated. In the first step nano-structured tialite were synthesized through citrate sol gel methods. Then, different volume fraction of tialte was mixed with aluminium by high energy vibratory milling. The results of X-ray differaction analysis, scanning electron microscopy and differential thermal analysis showed that mechanical milling can degrade stability of tialite and cause strain-induced decomposition,...
Synthesis of Boron Nitride Quantum Dots Using a Mechanical Milling- Solvothermal Process
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
Boron Nitride Quantum Dots, as a new member of Heavy-metal-free Quantum dots has attracted many attention due to their unique properties. The hyroxylate functionalized BNQDs was synthesized with two steps fabrication approache which were contained mechanical milling and solvothermal process. It has been shown that 12 hours for mechanical milling and 24 hours for solvothermal process would be the most optimum time that produce well disperse functionalized BNQDs . The characterization results have proved that the as-prepared BNQDs have lateral size at around 5 nm with thickness in range of 4-6 layers. Also, it has been demonstrated that OH functional groups can attache into the surface of...
Structural evolution during mechanical milling of nanometric and micrometric Al2O3 reinforced Al matrix composites
, Article Materials Science and Engineering A ; Volume 428, Issue 1-2 , 2006 , Pages 159-168 ; 09215093 (ISSN) ; Simchi, A ; Reihani, S. M. S ; Sharif University of Technology
2006
Abstract
The morphological and microstructural changes during mechanical milling of Al powder mixed with 5 vol% nanoscaled alumina particles (35 nm) were studied. The milling was performed in a planetary ball mill under argon atmosphere for various times up to 24 h. The process was also conducted for Al and Al-5 vol% Al2O3 (1 μm) powders to explore the role of reinforcement nanoparticles on the mechanical milling stages. The results showed that the addition of hard particles accelerate the milling process, leading to faster work hardening rate and fracture of the aluminum matrix. Meanwhile, the structural evolution during mechanical milling of the microcomposite powder occurred faster than that of...
Microstructure and compressibility of SiC nanoparticles reinforced Cu nanocomposite powders processed by high energy mechanical milling
, Article Ceramics International ; Volume 40, Issue 1 PART A , January , 2014 , Pages 951-960 ; ISSN: 02728842 ; Salahi, E ; Alikhani Hesari, F ; Simchi, A ; Kim, H. S ; Sharif University of Technology
Abstract
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...
Structural characteristics and desorption properties of nanostructured MgH2 synthesised by high energy mechanical milling
, Article Powder Metallurgy ; Volume 54, Issue 4 , 2011 , Pages 480-483 ; 00325899 (ISSN) ; Kaflou, A ; Simchi, A ; Sharif University of Technology
2011
Abstract
The effect of particle size, lattice strain and crystallite size on the hydrogen desorption properties of nanocrystalline magnesium hydride powder was investigated. Commercial MgH2 powder was milled in a Spex 8000M up to 16 h and its structural evolution and desorption characteristics at different time intervals were examined using various analytical techniques. At the early stage of milling, the formation of metastable γ-MgH2 phase was noticed. While the crystallite size gradually decreased to 12 nm with increasing the milling time, the accumulated lattice strain gained a maximum value of 0·9% after 4 h milling. The highest drop in the desorption temperature (∼100°C) was attained at the...
Desorption properties of nanostructured MgH2 synthesized by high-energy mechanical milling
, Article European International Powder Metallurgy Congress and Exhibition, Euro PM 2008, Mannheim, 29 September 2008 through 1 October 2008 ; Volume 2 , 2008 , Pages 351-356 ; 9781899072033 (ISBN) ; Simchi, A ; Kaflou, A ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2008
Abstract
The hydrogen desorption properties of nanocrystalline magnesium hydride processed by high-energy mechanical milling was investigated. MgH2 powder was milled for various times (up to 16 h) under a high purity argon atmosphere and the effect of milling on the particle size and morphology, grain refinement, lattice strain, and desorption temperature was studied. It was shown that accumulated lattice strain combined with nanometric grain structure significantly decrease the desorption temperature. The effect of powder particle size was found to be of less importance. The lowest desorption temperature was obtained after 4 h high-energy milling. Nanostructured magnesium hydride with grain size of...
The Synthesis of Iron Aluminide Nano Composite/Alumina by in Situ Procedure Based on Mechanical Alloying and Surveying Some of its Mechanical Characteristics
, M.Sc. Thesis Sharif University of Technology ; Purazaang, Kazem (Supervisor) ; Salahi, Esmail (Supervisor)
Abstract
In this study, first nano structure powders of Fe3AL / Al2o3 by different percentages of reinforcement phases (10, 20 and 50 percent of volume) based on mechanical milling procedure was created. To do so, iron, Al and iron oxide (hematite) pure powder based on special weight percentages mixed with each other and milled in 20 to 100 hour periods based on two different weights of ball toward powder: 10 and 20. Morphological variations, particles sizes and powder densities, lattice strain and phase variations in different timing periods of mechanical milling process was studied by Scanning Electron Microscopy(SEM) , analyzing apparatus of particles sizes by laser , gaseous picnometer and X-ray...
Producing Cu-TiB2 Nano Composite Using Powder Metallurgy Route and Study on its Mechanical and Physical Behavior
, M.Sc. Thesis Sharif University of Technology ; Pourazrang, Kazem (Supervisor) ; Abachi, Parvin (Supervisor)
Abstract
In applications such as high duty sliding contacts and other electrical components requiring good electrical- and thermal-conductivity, proper mechanical wear resistance in combination with arc erosion resistance are required.The Cu/TiB2 nano-composite seems to be a good candidate for such cases. At present work TiB2 nano-particles has been selected as reinforcement, due to its valuable properties, i.e., high melting point (2850 - 2900 °C), low linear CTE (8.10 µmm-1 °C-1), thermal conductivity (60.0 - 120 W/m-K) as well as low specific electrical resistivity (10 - 30 μΩ.cm) and high hardness (25-35 GPa HV). Additionally, there are limited articles which have focused on evaluation of...
“Production of Micro and Nanocomposites of Fe3Al/ZrO2 Via Mechanical Alloying and Surveying of Mechanical Properties”
, M.Sc. Thesis Sharif University of Technology ; Pourazarang, Kazem (Supervisor) ; Salahi, Esmail (Supervisor)
Abstract
In this investigation, nanostructure Fe3Al was produced by mechanical milling initially. Pure iron and aluminum powders were milled with suitable ratio 86Fe-14Al by weight. Milling was done up to 120 h times and with BPR 10 and BPR 20. Morphological changes, powder density and size, phase and structural changes, grain size and lattice strain were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and laser particle size analyzer (LPSA). 40 h mechanical alloying with BPR 20 led to the corresponding intermetallic compound, Fe3Al with a nanocrystalline structure. Therefore Fe3Al/ZrO2 micro and nanocomposite powders were synthesized with manufactured by milling of...
Effect of nanoscaled reinforcement particles on the structural evolution of aluminium powder during mechanical milling
, Article Powder Metallurgy ; Volume 52, Issue 2 , 2009 , Pages 151-157 ; 00325899 (ISSN) ; Kamrani, S ; Simchi, A ; seyed Reihani, M ; Sharif University of Technology
2009
Abstract
This paper presents experimental results on the synthesis of nanostructured aluminium matrix nanocomposite powders by comilling of nanoscaled SiC and Al2O3 particles and micrometric aluminium powder. The effect of the nanometric reinforcement particles on the mechanical milling (MA) process of the soft matrix was studied by scanning electron microscopy, X-ray diffraction (XRD), transmission electron microscopy, laser particle size analyser and standard metallographic techniques. It was found that at the early stage of milling, the nanoparticles are smeared on the surface of the aluminium powder and thus do not significantly contribute in the MA process. As the milling continues, the hard...
Mechanical properties of Al-Al2O3 nanocomposite produced by mechanical milling and powder hot extrusion
, Article European Powder Metallurgy Congress and Exhibition, Euro PM 2007, Toulouse, 15 October 2007 through 17 October 2007 ; Volume 2 , 2007 , Pages 259-264 ; 9781899072293 (ISBN) ; Simchi, A ; Seyed Reihani, S. M ; Simancik, F ; Balog, M ; Csuba, A ; Sharif University of Technology
European Powder Metallurgy Association (EPMA)
2007
Abstract
In the present work, ultrafine-grained Al-5vol.% Al2O3 nanocomposite was synthesized through mechanical milling followed by direct powder extrusion method. The characteristics of the processed nanocomposite were examined by electron microscopy (SEM and TEM), Xray diffraction (XRD), tensile test and Vickers hardness measurement. It was shown that the addition of the reinforcement nanoparticles accelerates the milling process of the aluminum matrix and enhances the grain refinement of the aluminum matrix. An improved mechanical strength as compared with Al-Al2O3 microcompoiste was obtained. A dimple-type fracture mode was observed, which is a clear evidence of micro-deformation. In addition,...
Effect of mechanical milling on carbothermic reduction of magnesia
, Article ISIJ International ; Volume 50, Issue 5 , 2010 , Pages 668-672 ; 09151559 (ISSN) ; Yoozbashizadeh, H ; Askari, M ; Kuwata, N ; Kawamura, J ; Kano, J ; Saito, F ; Kobatake, H ; Fukuyama, H ; Sharif University of Technology
2010
Abstract
A mixture of MgO and graphite with a molar ratio (1:1) was subjected to planetary ball milling for 1, 2, 4, and 8 h with the intention of enhancing carbothermic reduction reaction of MgO during subsequent thermal treatment. Unmilled and milled mixtures were characterized using a combination of X-ray diffraction (XRD) analysis, Raman spectroscopy, scanning electron microscopy (SEM), surface area analysis (SSA), and thermogravimetric analysis (TGA). The reduction reaction of milled samples occurred at lower temperature than that of the unmilled sample. A longer milling time engenders a lower reaction temperature. These results are attributable to the increased interfacial area of the sample...
Microstructural development and mechanical properties of nanostructured copper reinforced with SiC nanoparticles
, Article Materials Science and Engineering A ; Volume 568 , 2013 , Pages 33-39 ; 09215093 (ISSN) ; Salahi, E ; Hesari, F. A ; Yoon, E. Y ; Kim, H. S ; Simchi, A ; Sharif University of Technology
2013
Abstract
Nanostructured Cu and Cu-2. vol% SiC nanocomposite were produced by high energy mechanical milling and hot pressing technique. Microstructure development during fabrication process was investigated by X-ray diffraction, scanning electron microscope, scanning transmission electron microscope, and electron backscatter diffraction techniques. The results showed that the microstructure of copper and copper-based nanoco mposite composed of a mixture of equiaxed nanograins with bimodal and non-random misorientation distribution. The presence of SiC nanoparticles refined the grain structure of the copper matrix while the fraction of low angle grain boundaries was increased. Evaluation of mechanical...
Effect of nanoparticle content on the microstructural and mechanical properties of nano-SiC dispersed bulk ultrafine-grained Cu matrix composites
, Article Materials and Design ; Volume 52 , 2013 , Pages 881-887 ; 02641275 (ISSN) ; Salahi, E ; Alikhani Hesari, F ; Kim, H. S ; Simchi, A ; Sharif University of Technology
Elsevier Ltd
2013
Abstract
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...
Effect of high energy ball milling on compressibility and sintering behavior of alumina nanoparticles
, Article Ceramics International ; Volume 38, Issue 4 , May , 2012 , Pages 2627-2632 ; 02728842 (ISSN) ; Aminzare, M ; Razavi Hesabi, Z ; Aboutalebi, S. H ; Sadrnezhaad, S. K ; Sharif University of Technology
2012
Abstract
The effect of high-energy ball milling on the textural evolution of alumina nanopowders (compaction response, sinter-ability, grain growth and the degree of agglomeration) during post sintering process is studied. The applied pressure required for the breakage of the agglomerates (P y) during milling was estimated and the key elements of compressibility (i.e. critical pressure (P cr) and compressibility (b)) were calculated. Based on the results, the fracture point of the agglomerates decreased from 150 to 75 MPa with prolonged milling time from 3 to 60 min. Furthermore, the powders were formed by different shaping methods such as cold isostatic press (CIP) and uniaxial press (UP) to better...
Preparation of nanostructured high-temperature TZM alloy by mechanical alloying and sintering
, Article International Journal of Refractory Metals and Hard Materials ; Volume 29, Issue 1 , 2011 , Pages 141-145 ; 02634368 (ISSN) ; Malekzadeh, M ; Sadrnezhaad, S. K ; Sharif University of Technology
Abstract
Mechanical milling proceeded by sintering was used to synthesize nanostructured temperature-resistant TZM alloy. Milling under Ar for different times (1, 2, 3, 5, 10, 15, 20, 25, and 30 h) and sintering at 1500, 1600 and 1700 °C for 30, 45, 60 and 90 min resulted in increasing of low-energy grain boundaries (LEGBs) and dispersion of TiC and ZrC with a size of ~ 65 nm in the matrix near LEGBs. Morphology and grain size of the products were determined from scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns, almost precisely. Optimum density of nanostructured TZM alloy ~ 9.95 ± 0.01 g/cm 3 was achieved by sintering at 1700 °C for 90 min
The effect of mechanical milling on the soft magnetic properties of amorphous FINEMET alloy
, Article Journal of Magnetism and Magnetic Materials ; Volume 381 , 2015 , Pages 322-327 ; 03048853 (ISSN) ; Madaah Hosseini, H. R ; Davami, P ; Gjoka, M ; Song, M ; Sharif University of Technology
Elsevier
2015
Abstract
The effect of milling time on the magnetic properties of FINEMET amorphous ribbons has been investigated using X-ray diffraction, Mössbauer spectroscopy, thermo-magnetic measurements, transmission electron microscopy and SQUID magnetometery. Ribbons were melt-spun at a wheel speed of 38 ms-1 and then mechanically milled for different periods up to 45 min. The results showed that the partially crystallization of the amorphous powder occurs during milling. TEM observations confirmed the formation of small volume fraction of the crystalline phase with ∼9 nm crystallite size in the amorphous matrix for the ribbon milled for 45 min. Thermo-magnetic measurements indicated the enhancement of the...
The effect of reinforcement percentages on properties of copper matrix composites reinforced with TiC particles
, Article Journal of Alloys and Compounds ; Volume 676 , 2016 , Pages 120-126 ; 09258388 (ISSN) ; Sharif University of Technology
Elsevier Ltd
Abstract
In this research, copper matrix composites reinforced with different amounts of titanium carbide particles were produced by mechanical milling and in-situ formation of reinforcements. Morphology and size of milled powders were inspected by scanning electron microscopy (SEM) several times during milling process. Changes in lattice parameter, crystallite size, lattice strain, dislocation density and Gibbs free energy changes (due to increasing in dislocation densities and grain boundaries) in different samples (with different TiC particles contents) were studied by X-Ray Diffraction technique with Cu-kα radiation and using Nelson-Riley method and Williamson-Hall equation. Microstructure of...