Nanocomposite Bi(Sb)Te(Se) Materials by Cryogenic Mechanical Alloying and Optimized High Pressure Hot-pressing

2012 ◽  
Vol 1456 ◽  
Author(s):  
Tsung-ta E. Chan ◽  
Rama Venkatasubramanian ◽  
James M. LeBeau ◽  
Peter Thomas ◽  
Judy Stuart ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Hot Pressing ◽  
High Energy ◽  
Structural Features ◽  
Milling Process ◽  
Nanocrystalline Powders ◽  
Full Density ◽  
Seebeck Coefficients ◽  
The Matrix ◽  
Cryogenic Process

ABSTRACTNanocomposite Bi2Te3 based alloys are attractive for their potentially high thermoelectric figure-of-merit (ZT) around room temperature. The nano-scale structural features embedded in the matrix provide more scattering of phonons and can thus reduce the lattice thermal conductivity. To further take advantage of such nanocomposite structures, we focus on the development of nanocrystalline Bi(Sb)Te(Se) powders by high energy cryogenic mechanical alloying followed by an optimized hot pressing process. This approach is shown to successfully produce Bi(Sb)Te(Se) alloy powders with grain size averaging about 9 nm for n-type BiTe(Se) and about 16 nm for p-type Bi(Sb)Te respectively. This cryogenic process offers much less milling time and prevents thermally activated contamination or imperfections from being introduced during the milling process. The nanocrystalline powders are then compacted at optimized pressures and temperatures to achieve full density compactions and preserve the grain sizes effectively. The resulting nano-bulk materials have optimal Seebeck coefficients and are expected to have improved ZT. Thermoelectric properties and microstructure studies by X-ray diffraction and transmission electron microscopy will also be presented and discussed.

Effect of Milling Speed on the Synthesis of In-Situ Cu-25 Vol. % WC Nanocomposite by Mechanical Alloying

2012 ◽  
Vol 59 (2) ◽  
Author(s):  
Nurulhuda Bashirom ◽  
Nurzatil Ismah Mohd Arif
Keyword(s):  
Stainless Steel ◽  
Mechanical Alloying ◽  
Weight Ratio ◽  
High Energy ◽  
Milling Process ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
The Matrix ◽  
Steel Balls

This paper presents a study on the effect of milling speed on the synthesis of Cu-WC nanocomposites by mechanical alloying (MA). The Cu-WC nanocomposite with nominal composition of 25 vol.% of WC was produced in-situ via MA from elemental powders of copper (Cu), tungsten (W), and graphite (C). These powders were milled in the high-energy “Pulverisette 6” planetary ball mill according to composition Cu-34.90 wt% W-2.28 wt% C. The powders were milled in different milling speed; 400 rpm, 500 rpm, and 600 rpm. The milling process was conducted under argon atmosphere by using a stainless steel vial and 10 mm diameter of stainless steel balls, with ball-to-powder weight ratio (BPR) 10:1. The as-milled powders were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD result showed the formation of W2C phase after milling for 400 rpm and as the speed increased, the peak was broadened. No WC phase was detected after milling. Increasing the milling speed resulted in smaller crystallite size of Cu and proven to be in nanosized. Based on SEM result, higher milling speed leads to the refinement of hard W particles in the Cu matrix. Up to the 600 rpm, the unreacted W particles still existed in the matrix showing 20 hours milling time was not sufficient to completely dissolve the W.

Formation of Fe3AlC Base Alloy by Mechanical Alloying and Vacuum Hot Pressing

2007 ◽  
Vol 534-536 ◽  
pp. 189-192 ◽  
Author(s):  
Kazuo Isonishi
Keyword(s):  
Mechanical Alloying ◽  
Hot Pressing ◽  
Base Alloy ◽  
Average Particle Size ◽  
Processing Route ◽  
Full Density ◽  
Second Phase ◽  
Average Particle ◽  
Vacuum Hot Pressing ◽  
Metallurgical Processing

Fabrication of Fe3AlC matrix in-situ composite, reinforced by a FeAl phase, was studied by using the powder metallurgical processing route. Especially, in order to disperse the second phase more finely, we chose the mechanical alloying process. We investigated the microstructural and mechanical properties of the consolidated material. After consolidation by vacuum hot pressing, the compact showed almost full density and consisted of a Fe3AlC matrix and FeAl second phase (average particle size was less than 1μm). The compact showed HV746, which was higher than that of the arc melted Fe3AlC monolithic material, HV650.

SYNTHESIS OF NANO-CRYSTALLINE Cu-Cr ALLOY BY MECHANICAL ALLOYING

2012 ◽  
Vol 05 ◽  
pp. 496-501 ◽  
Author(s):  
S. SHEIBANI ◽  
S. HESHMATI-MANESH ◽  
A. ATAIE
Keyword(s):  
Mechanical Alloying ◽  
Structural Evolution ◽  
High Energy ◽  
Lattice Parameter ◽  
Control Agent ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Nano Crystalline ◽  
High Energy Ball Mill ◽  
Energy Ball

In this paper, the influence of toluene as the process control agent (PCA) and pre-milling on the extension of solid solubility of 7 wt.% Cr in Cu by mechanical alloying in a high energy ball mill was investigated. The structural evolution and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, respectively. The solid solution formation at different conditions was analyzed by copper lattice parameter change during the milling process. It was found that both the presence of PCA and pre-milling of Cr powder lead to faster dissolution of Cr . The mean crystallite size was also calculated and showed to be about 10 nm after 80 hours of milling.

Obtaining of the Ir-Al Nanocrystalline Powders by Mechanical Alloying

2011 ◽  
Vol 672 ◽  
pp. 171-174
Author(s):  
Ionel Chicinaş ◽  
P. Cârlan ◽  
Florin Popa ◽  
Virgiliu Călin Prică ◽  
Lidia Adriana Sorcoi
Keyword(s):  
Mechanical Alloying ◽  
Particle Morphology ◽  
High Energy ◽  
Atomic Ratio ◽  
Planetary Mill ◽  
Nanocrystalline Powders ◽  
Alloy Formation ◽  
X Ray Diffraction ◽  
Chemical Homogeneity ◽  
Diffraction Patterns

The Ir-Al powder in the 1:1 atomic ratio was obtained by high energy mechanical alloying in a Pulverisette 4 Fritch planetary mill. The final product was obtained after 28 h of milling in argon atmosphere. Alloy formation was investigated by X-ray diffraction. After 4 h of milling the new structure of IrAl compound is found in the diffraction patterns. The obtained powders are nanocrystalline with a mean crystallite size of 11 nm after 28 h of milling. The particle morphology and the chemical homogeneity were studied using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX). It was found that the obtained compound present large particles composed by smaller one.

Synthesis of Cathode Materials Fe-Doped NiS2 by Mechanical Alloying for Li/NiS2 Cells

2011 ◽  
Vol 287-290 ◽  
pp. 1428-1432
Author(s):  
Xiao Jing Liu ◽  
Dong Wook Park ◽  
Zhe Zhu Xu ◽  
Sang Dae Kang ◽  
In Shup Ahn ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Cathode Materials ◽  
Lithium Ion ◽  
High Energy ◽  
Milling Process ◽  
High Energy Density ◽  
Tetraethylene Glycol ◽  
Wet Milling ◽  
Powder Particles ◽  
Normal Hexane

In order to synthesize the fine compound iron-doped nickel disulfide (NiS2) with environmentally friendly nickel, sulfur and iron powders, mechanical alloying (MA) was conducted for 8 hrs with SPEX Mill at a speed of 1000 rpm. In this process, stearic acid was added as a kind of process control agents (PCAs) to prevent the excessive cold welding. Meanwhile, for the purpose of getting nanocrystalline of Fe-doped NiS2powder particles to improve the contact areas between the active materials, the wet milling process was also done for 30 hrs with normal hexane (C6H14) as a solvent PCA. The prepared powders were characterized by FE-SEM, XRD, EPMA, EDS and TEM. Finally, the charge/discharge properties of Li/Fe-doped NiS2cells were investigated at room temperature by employing 1 M LiCF3SO3(lithium trifluoromethanesulfonate) dissolved in TEGDME (tetraethylene glycol dimethylether) as the electrolyte. The initial discharge capacity of Li/Fe-doped NiS2cell using wet milled powders as the cathode material is 792 mAh/g, which may indicate its high energy density and good future as cathode materials for lithium-ion batteries.

Zamak 2 Alloy Produced by Mechanical Alloying and Consolidated by Sintering and Hot Pressing

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Flávia Costa da Silva ◽  
Kamila Kazmierczak ◽  
César Edil da Costa ◽  
Júlio César Giubilei Milan ◽  
José Manuel Torralba
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Hot Pressing ◽  
High Energy ◽  
Zinc Alloy ◽  
Stable Phase ◽  
Phase Stabilization ◽  
Near Net Shaping ◽  
Net Shaping ◽  
Additional Phase

The Zamak 2 alloy has the best mechanical properties of the Zamak alloys with respect to the tensile strength, creep resistance, and hardness. Zamak 2 is a commercial material widely used for the manufacturing of mechanical components. The presence of Cu in this alloy (3 wt. %) improves the mechanical properties through the formation of E (CuZn4) precipitates. The powder metallurgy (P/M) has an important direct advantage in the fabricated parts with respect to the finished dimensions or near net shaping due to the additional phase stabilization without heat treatment. However, there are few studies into the production of this zinc alloy via mechanical alloying and the effect of the consolidation technique in terms of the material properties; these research deficiencies led to the development of this work. The powder was analyzed during milling until achieving a steady-state, which occurred after 30 h of milling in a planetary ball mill at 400 rpm. The high-energy milling produces a Zamak 2 alloy powder with a T′ stable phase and with a greater melting point. When consolidated using hot pressing, the hardness increases compared to sintering and casting alloy.

Ti50Fe25Ni25 Amorphous Alloy Prepared by Mechanical Alloying

2011 ◽  
Vol 327 ◽  
pp. 76-80
Author(s):  
Yu Ying Zhu ◽  
Qiang Li ◽  
Yun Hua He ◽  
Ge Wang ◽  
Xing Hua Wang
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Mechanical Alloying ◽  
High Energy ◽  
Structural Features ◽  
Liquid Region ◽  
X Ray Diffraction ◽  
Crystallization Peak ◽  
Activation Energy Of Crystallization ◽  
Amorphous Alloy Powder

A new ternary Ti-based amorphous alloy, Ti50Fe25Ni25, is prepared by the mechanical alloying. The milling is performed in a high-energy planetary ball mill under argon atmosphere. Fully Ti50Fe25Ni25amorphous alloy powder is obtained after milled 160h. The milling speed is 300rpm and the weighs ratio of ball to powder is 10:1. The structural features are studied by X-ray diffraction and field emission scanning electron microscope, and the thermal stability is investigated by a differential scanning calorimeter. The super-cooled liquid region of the amorphous alloy increases from 98K to 119K as the heating rate increasing from 10K/min to 40K/min. The effective activation energy of crystallization is estimated with modified Kissinger’s plot. The initial crystallization activation energyEx1and the first crystallization peakEp1are 155.9KJ/mol and 188.5KJ/mol, respectively.

Study of Nanocrystalline NiAl Alloys Prepared by Mechanical Alloying

2012 ◽  
Vol 329 ◽  
pp. 19-28 ◽  
Author(s):  
M. Gherib ◽  
A. Otmani ◽  
A. Djekoun ◽  
A. Bouasla ◽  
M. Poulain ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Crystallite Size ◽  
Milling Time ◽  
Structural Features ◽  
Milling Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Size Refinement ◽  
20 Nm ◽  
Kinetics Of

Nanostructured Powders of Ni-20wt%Al and Ni-50wt%Al Were Prepared, by Mechanical Alloying under an Argon Atmosphere, from Elemental Ni and Al Powders Using a Planetary Ball Mill (type Fritsch P7) for Different Times (0.5-24h).). Microstructural and Structural Features of the Final Products Were Characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). the Results of the XRD Shows the Formation of the B2 (Ni Al) Phase after 2 Hours of Milling for both Systems. Also Detected Was the Ni3al Phase in Ni80al20after 4 Hours. Crystallite Size Refinement of the Final Product Occurred down to Nanometer Scales when the Milling Time Increased, and Attained 17 Nm in the Ni50al50System and 20 Nm in the other System, at 24 Hours. this Decrease in Crystallite Size Is Accompanied by an Increase in the Interval Level Strain. the Kinetics of Al Dissolution during the Milling Process of Ni50al50System Can Be Described by Two Regimes, Characterised by Different Values of Avrami Parameters which Are Calculated by Using the Johnson–Mehl–Avrami Formalism.

scholarly journals Wear Dry Behavior of the Al-6061-Al2O3 Composite Synthesized by Mechanical Alloying

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1652
Author(s):  
Víctor Hugo Mercado-Lemus ◽  
Cynthia Daisy Gomez-Esparza ◽  
Juan Carlos Díaz-Guillén ◽  
Jan Mayén-Chaires ◽  
Adriana Gallegos-Melgar ◽  
...  
Keyword(s):  
Mechanical Alloying ◽  
Load Transfer ◽  
Wear Behavior ◽  
Aluminum Matrix ◽  
High Energy ◽  
Aluminum Matrix Composite ◽  
Al2o3 Nanoparticles ◽  
Protective Behavior ◽  
Al 6061 ◽  
The Matrix

The present research deals with the comparative wear behavior of a mechanically milled Al-6061 alloy and the same alloy reinforced with 5 wt.% of Al2O3 nanoparticles (Al-6061-Al2O3) under different dry sliding conditions. For this purpose, an aluminum-silicon-based material was synthesized by high-energy mechanical alloying, cold consolidated, and sintered under pressureless and vacuum conditions. The mechanical behavior was evaluated by sliding wear and microhardness tests. The structural characterization was carried out by X-ray diffraction and scanning electron microscopy. Results showed a clear wear resistance improvement in the aluminum matrix composite (Al-6061-Al2O3) in comparison with the Al-6061 alloy since nanoparticles act as a third hard body against wear. This behavior is attributed to the significant increment in hardness on the reinforced material, whose strengthening mechanisms mainly lie in a nanometric size and homogeneous dispersion of particles offering an effective load transfer from the matrix to the reinforcement. Discussion of the wear performance was in terms of a protective thin film oxide formation, where protective behavior decreases as a function of the sliding speed.

Effect of Boron on the Amorphization of Fe-Si Alloys by Mechanical Alloying

2012 ◽  
Vol 730-732 ◽  
pp. 739-744 ◽  
Author(s):  
Petr Urban ◽  
Francisco Gomez Cuevas ◽  
Juan M. Montes ◽  
Jesus Cintas
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Alloy System ◽  
High Energy ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Structural And Phase Transformations ◽  
Transmission Electron ◽  
Energy Ball

The amorphization process by mechanical alloying in the Fe-Si alloy system has been studied. High energy ball milling has been applied for alloys synthesis. X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to monitor the structural and phase transformations through the different stages of milling. The addition of amorphous boron in the milling process and the increase of the milling time were used to improve the formation of the amorphous phase. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of equilibrium intermetallic compounds.

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