scholarly journals Effect of Mechanical Milling and Cold Pressing on Co Powder

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
A. S. Bolokang ◽  
M. J. Phasha ◽  
D. E. Motaung ◽  
S. Bhero
Keyword(s):  
Compaction Pressure ◽  
Milled Powder ◽  
Xrd Analysis ◽  
High Energy ◽  
Lattice Parameter ◽  
Exothermic Peak ◽  
Cold Pressing ◽  
First Order Phase Transition ◽  
Fcc Phase ◽  
First Time

Cold pressing (CP) of the amorphous-like Co powder suppressed most of the XRD peaks, in particular the peak along (100) plane. The DSC curve of unmilled CP Co powder has shown a distinct sharp exothermic peak at 615C°. Upon annealing at 700C°, only the FCC phase with lattice parameter of 3.51 Å was detected by XRD. Our results implied that the exotherm at 615C° corresponds to compaction-pressure-assisted HCP to FCC first-order phase transition. The XRD analysis of 30 h milled powder revealed for the first time the FCC phase with a=3.80 Å. However, due to presence of (100) and (210) peaks, this phase is thought to be FCT with lattice parameters a=b=3.80 and c=3.07 Å. Consequently, the high-energy milling carried out in the current work induced for the first time HCP to FCT transition in Co. Upon CP of milled powder, the lattice parameter a shrunk from 3.80 to 3.75 Å. However, during annealing of the CP milled Co powder at 750C°, the FCT to FCC transition occurred, yielding the FCC phase with a=3.51 Å.

scholarly journals The properties of high-energy milled pre-alloyed copper powders containing 1 wt.% Al

2007 ◽  
Vol 72 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Viseslava Rajkovic ◽  
Dusan Bozic ◽  
Aleksandar Devecerski
Keyword(s):  
Thermal Stability ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Morphological Changes ◽  
Milled Powder ◽  
Copper Matrix ◽  
High Energy ◽  
Lattice Parameter ◽  
Good Thermal Stability ◽  
Before And After

The microstructural and morphological changes of inert gas atomized pre-alloyed Cu-1 wt.% Al powders subjected to hith-energy milling were studied. The microhardness of hot-pressed compacts was measured as a function of milling time. The thermal stability during exposure at 800 ?C and the electrical conductivity of compacts were also examined. During the high-energy milling, severe deformation led to refinement of the powder particle grain size (from 550 nm to about 55 nm) and a decrease in the lattice parameter (0.10 %), indicating precipitation of aluminium from the copper matrix. The microhardness of compacts obtained from 5 h-milled powders was 2160 MPa. After exposure at 800?C for 5 h, these compacts still exhibited a high microhardness value (1325 MPa), indicating good thermal stability. The increase of microhardness and good thermal stability is attributed to the small grain size (270 and 390 nm before and after high temperature exposure, respectively). The room temperature electrical conductivity of compacts processed from 5 h-milled powder was 79% IACS. .

scholarly journals SYNTHESIS OF Cu1.6Bi4.6S8 COMPOUND FOR THERMOELECTRIC APPLICATION

2019 ◽  
Vol 25 (2) ◽  
pp. 86
Author(s):  
Binh Ngoc Duong ◽  
Long Duc Bui
Keyword(s):  
Heat Treatment ◽  
Heating Rate ◽  
Ball Mill ◽  
Milled Powder ◽  
Xrd Analysis ◽  
High Energy ◽  
Starting Mixture ◽  
Heat Treated ◽  
Annealed Powder ◽  
Thermoelectric Application

<p class="AMSmaintext">In this work, Cu<sub>1.6</sub>Bi<sub>4.6</sub>S<sub>8</sub> thermoelectric compound was synthesized using high energy milling and heat treatment. The starting mixture include Cu, Bi and S elemental powders at the stoichiometry ratio of the formula Cu<sub>1.6</sub>Bi<sub>4.6</sub>S<sub>8</sub> were ball milled in a planetary ball mill and heat treated in an electric furnace. The results shown that after 10 hours of milling, a compound identified as Cu<sub>3.21</sub>Bi<sub>4.79</sub>S<sub>9</sub> was formed. The 16h milled powder was heat-treated at 350, 400 and 450ºC for 1 hours at a heating rate of 8 ºC/minute, XRD of the annealed powder reveals that the Cu<sub>3.21</sub>Bi<sub>4.79</sub>S<sub>9</sub> obtained fully transformed into Cu<sub>1.6</sub>Bi<sub>4.6</sub>S<sub>8</sub> after being heat treated at 400ºC. Meanwhile, Bi<sub>2</sub>S<sub>3</sub> was found in the powder being annealed at 350ºC. The 5h milled powder was also annealed at 400ºC for 1 hours at a heating rate of 2 and 8 ºC/minute, XRD analysis show that Cu<sub>1.6</sub>Bi<sub>4.6</sub>S<sub>8</sub> was also formed in the heat-treated powder with the heating rate of 2 ºC/min.</p>

The structural transformation of anatase TiO2 by high-energy vibrational ball milling

1999 ◽  
Vol 14 (3) ◽  
pp. 841-848 ◽  
Author(s):  
Suchitra Sen ◽  
M. L. Ram ◽  
S. Roy ◽  
B. K. Sarkar
Keyword(s):  
Electron Microscopy ◽  
Ball Milling ◽  
Structural Transformation ◽  
Milled Powder ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
First Time ◽  
Pressure Phase

The structural transformation of anatase TiO2 by high-energy vibrational ball milling was studied in detail by different analytical methods of x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This structural transformation involves both phase transition and nanoparticle formation, and no amorphization was observed. The crystallite size was found to decrease with milling time down to nanometer size ∼13 nm and approaching saturation, accompanied by phase transformation to metastable phases, i.e., TiO2(II), which is a high-pressure phase and TiO2(B), which was identified in ball-milled powder reported for the first time in this paper. These phases eventually started transforming to rutile by further milling.

MECHANOCHEMICAL SYNTHESIS OF TIAL3/AL2O3 ULTRAFINE GRAINED COMPOSITE

2008 ◽  
Vol 22 (18n19) ◽  
pp. 2914-2923 ◽  
Author(s):  
M. M. VERDIAN ◽  
S. HESHMATI-MANESH
Keyword(s):  
Ball Milling ◽  
Titanium Oxide ◽  
Milled Powder ◽  
Xrd Analysis ◽  
High Energy ◽  
Reduction Reaction ◽  
High Energy Ball Milling ◽  
X Ray Diffraction ◽  
Ultrafine Grained ◽  
Energy Ball

The TiAl 3/ Al 2 O 3 metal-ceramic composite was synthesized using high energy ball milling, powder compaction and thermal treatment. Micron sized powders of titanium oxide ( TiO 2) and aluminum were subjected to high energy ball milling under an argon protected atmosphere. Milling of this powder mixture although reduced crystallites sizes to a nano scale, did not result in a reaction between the reactants. Further compaction of the milled powder and annealing, paved the way to a reduction reaction and led to the formation of an ultrafine grained composite structure. The reaction appeared to proceed through two-steps. Titanium oxide was first reduced to TiO and later on, TiO was reduced to Ti . The resulting Ti was alloyed with extra Al to produce TiAl 3 intermetallic in which alumina particles were dispersed. Also, mechanical activation was found to reduce the reaction temperature between Al and TiO 2. The morphology and phase composition of the milling products were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis.

Nanoscale Phase Separation Induced by Mechanical Alloying in the Iron-Erbium-Nitrogen System

1990 ◽  
Vol 186 ◽  
Author(s):  
Z. Fu ◽  
H. J. Fecht ◽  
W. L. Johnson
Keyword(s):  
Phase Separation ◽  
Ball Milling ◽  
High Energy ◽  
Lattice Parameter ◽  
Milling Process ◽  
Parameter Analysis ◽  
Nitride Phase ◽  
Nanoscale Phase Separation ◽  
Amorphous Structures ◽  
Fcc Phase

AbstractMetastable phases, including nanocrystalline and amorphous structures, can be prepared by high energy cyclic deformation processes. In the present study, we compare the behavior of a stable congruent melting compound (Fe2Er Laves phase) with a mixture of pure elemental Fe and Er powders subjected to high energy ball milling. X-ray diffraction and transmission electron microscopy reveal similar results in both cases. In the early stages, a nanocrystalline fcc phase with lattice parameter a = 0.484 nm and a grain size of 6 nm is formed together with a bcc Fe-rich phase. Extended milling results in a nanoscale phase separation into Fe-rich and Er-rich crystallites with average grain sizes of 1.8-4 nm. Based on a lattice parameter analysis, the fcc phase was initially thought to be a metastable FeEr3 phase. Further studies revealed nitrogen gas in the milling vial had reacted with the powder during ball milling to produce the cubic ErN phase (“NaCl” structure with a lattice parameter of 0.4836 nm). Our experiments demonstrate that the steel vials for ball milling do not remain hermetically sealed during the milling process and a nitride phase can be formed easily if a catalyst for the dissociation of nitrogen molecules (such as Fe) exists in the system.

Microstructural Evolution during Mechanical Alloying and Hot Pressing of a Powder Blend of Aluminium and 316 Stainless Steel

2006 ◽  
Vol 114 ◽  
pp. 211-218
Author(s):  
A. Samanta ◽  
P.P. Chattopadhyay ◽  
Witold Łojkowski ◽  
Stanislaw Gierlotka ◽  
Hans Jorg Fecht ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Property ◽  
Stainless Steel ◽  
Hot Pressing ◽  
Milled Powder ◽  
Phase Evolution ◽  
Xrd Analysis ◽  
High Energy ◽  
Nanocrystalline Powders ◽  
Powder Blend

The paper examines the phase evolution in blends consisting of different proportions of stainless steel (SS316) and Al (0, 25, 65 and 85 wt. %) powders during high-energy ball milling by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy. An attempt has also been made to study the mechanical property of the bulk samples obtained by hot pressing the ball milled powder blend at suitable a temperature and pressure. The results of microstructural changes and mechanical property and the ability of consolidation of the amorphous/nanocrystalline powders by high-pressure techniques to develop engineering components has been discussed and highlighted.

scholarly journals Mechanochemical Synthesis and Nitrogenation of the Nd1.1Fe10CoTi Alloy for Permanent Magnet

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3854
Author(s):  
Hugo Martínez Sánchez ◽  
George Hadjipanayis ◽  
Germán Antonio Pérez Alcázar ◽  
Ligia Edith Zamora Alfonso ◽  
Juan Sebastián Trujillo Hernández
Keyword(s):  
Mechanochemical Synthesis ◽  
Applied Field ◽  
Volume Fraction ◽  
Synthesis Method ◽  
High Energy ◽  
Direction Parallel ◽  
Best Value ◽  
Heat Treated ◽  
Bcc Phase ◽  
First Time

In this work, the mechanochemical synthesis method was used for the first time to produce powders of the nanocrystalline Nd1.1Fe10CoTi compound from Nd2O3, Fe2O3, Co and TiO2. High-energy-milled powders were heat treated at 1000 °C for 10 min to obtain the ThMn12-type structure. Volume fraction of the 1:12 phase was found to be as high as 95.7% with 4.3% of a bcc phase also present. The nitrogenation process of the sample was carried out at 350 °C during 3, 6, 9 and 12 h using a static pressure of 80 kPa of N2. The magnetic properties Mr, µ0Hc, and (BH)max were enhanced after nitrogenation, despite finding some residual nitrogen-free 1:12 phase. The magnetic values of a nitrogenated sample after 3 h were Mr = 75 Am2 kg–1, µ0Hc = 0.500 T and (BH)max = 58 kJ·m–3. Samples were aligned under an applied field of 2 T after washing and were measured in a direction parallel to the applied field. The best value of (BH)max~114 kJ·m–3 was obtained for 3 h and the highest µ0Hc = 0.518 T for 6 h nitrogenation. SEM characterization revealed that the particles have a mean particle size around 360 nm and a rounded shape.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

Microstructure and superconducting properties of attrition-milled Bi2Sr2CaCu2Ox

1994 ◽  
Vol 9 (2) ◽  
pp. 297-304 ◽  
Author(s):  
J.S. Luo ◽  
H.G. Lee ◽  
S.N. Sinha
Keyword(s):  
Electron Microscopy ◽  
Milled Powder ◽  
High Energy ◽  
Double Layers ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Steel Tank ◽  
Practical Implications

The microstructure and superconducting properties of Bi2Sr2CaCu2Ox (Bi-2212) during high-energy attrition milling were investigated in detail by a combination of x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and magnetization techniques. The starting superconducting powder was milled in a standard laboratory attritor using yttria-stabilized ZrO2 balls and a stainless steel tank. After selected time increments, the milling was interrupted and a small quantity of milled powder was removed for further analysis. It was found that the deformation process rapidly refines Bi-2212 into nanometer-size crystallites, increases atomic-level strains, and changes the plate-like morphology of Bi-2212 to granular submicron clusters. At short milling times, the deformation seems localized at weakly linked Bi-O double layers, leading to twist/cleavage fractures along the {001} planes. The Bi-2212 phase decomposes into several bismuth-based oxides and an amorphous phase after excessive deformation. The superconducting transition is depressed by about 10 K in the early stages of milling and completely vanishes upon prolonged deformation. A deformation mechanism is proposed and correlated with the evolution of superconducting properties. The practical implications of these results are presented and discussed.

Development of Nano-Structure Cu-Ti Alloys by Mechanical Alloying Process

2013 ◽  
Vol 829 ◽  
pp. 168-172 ◽  
Author(s):  
Ahdie Pourfereidouni ◽  
Gholam Hossein Akbari
Keyword(s):  
Milled Powder ◽  
Lattice Parameter ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
Nano Structure ◽  
Cu Alloys ◽  
Ti Alloys ◽  
Alloy Process ◽  
Electrical Conductivities ◽  
Ti Powder

Cu-Ti system with a terminal solution in the Cu-rich portion of equilibrium Cu-Ti phase diagram with a decreasing trend with temperature shows a potential to develop age hardenable alloys with suitable strength and thermal and electrical conductivities. In the present study, the mechanical alloy process has been employed to increase solubility of Ti in Cu matrix to make age hardenable Cu alloys. Cu-Ti powder mixtures with different rations of 1 and 6 wt% of Ti were milled in planetary ball mill for different milling times of 4, 12, 48, 96 and 192 hours. The milled powder mixtures were investigated and characterised by X-ray diffraction (XRD) technique. The results show increasing in lattice parameter of Cu, which indicates that Ti atoms are dissolved in the Cu matrix. Cu crystal sizes showed decreasing trend which were more obvious in the mixture with higher Ti contents. The final crystal sizes were in the range of 17-23 nm after 192 hours of milling.

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