Fully dense Al–Pb nanocomposite bulk samples consolidated from mechanically milled powders

1998 ◽  
Vol 13 (2) ◽  
pp. 249-252 ◽  
Author(s):  
F. Zhou ◽  
H. W. Sheng ◽  
K. Lu
Keyword(s):  
Melting Point ◽  
Mechanical Milling ◽  
Theoretical Density ◽  
Full Density ◽  
Consolidation Process ◽  
Grain Coarsening ◽  
Grain Sizes ◽  
Milled Powders

Powders with a nanostructured mixture of pure Al and Pb phase were produced by mechanical milling of elemental blends of Al and Pb with a composition of Al90Pb10 (wt. %). Under a pressure of 1.5 GPa at 280 °C, the as-milled powders were successfully consolidated into bulk, full-density samples (>99.5% theoretical density) while the average grain sizes of Al and Pb in the compacted samples remain unchanged with respect to those in the as-milled powders. The achievement of the full density without grain coarsening in the consolidation process could be reasonably attributed to melting of the nanometer-sized Pb particles of which the melting point is considerably depressed.

Full-density nanocrystalline Fe–29Al–2Cr intermetallic consolidated from mechanically milled powders

1996 ◽  
Vol 11 (1) ◽  
pp. 72-80 ◽  
Author(s):  
L. He ◽  
E. Ma
Keyword(s):  
Grain Size ◽  
Mechanical Milling ◽  
Hot Forging ◽  
Full Density ◽  
Strengthening Effect ◽  
Practical Applications ◽  
Size Refinement ◽  
Sinter Forging ◽  
Average Grain Size ◽  
Milled Powders

Fe–29Al–2Cr powders with nanoscale grain sizes were produced by mechanical milling of prealloyed intermetallic powders. A consolidation procedure employing high-pressure, low strain rate hot forging (sinter-forging) has been developed to consolidate the powders into full-density compacts. The relative density and average grain size of the compact have been studied as a function of consolidation temperature at constant pressure. Fully dense compacts (>99.5% theoretical density) were produced at a relatively low temperature of 545°C with a pressure of 1.25 GPa. Transmission electron microscopy and x-ray diffraction analysis indicate that the average grain size has been maintained to the order of 30 nm in samples consolidated under these conditions. By using protective Ar atmosphere during mechanical milling and consolidation, contamination of oxygen and carbon in consolidated samples has been controlled to below a small fraction of an atomic percent. Microhardness tests of nanocrystalline Fe–29Al–2Cr samples indicate a significant strengthening effect due to grain size refinement and a monotonic hardness increase with decreasing residual porosity. Our work demonstrates the feasibility of using mechanically milled powders as the source of nanocrystalline materials for the production of fully dense, low-impurity, nanocrystalline bulk samples needed for reliable mechanical property measurements and practical applications.

Microhardness Enhancement in Fully Dense Fe-Based Nanophase Metallic Alloys

1995 ◽  
Vol 400 ◽  
Author(s):  
L. He ◽  
E. Ma
Keyword(s):  
Grain Size ◽  
High Energy ◽  
Metallic Alloys ◽  
Full Density ◽  
Strengthening Effect ◽  
Two Phase ◽  
Grain Sizes ◽  
Sinter Forging ◽  
Interphase Boundaries ◽  
Energy Ball

AbstractNano-grained Fe-29Al-2Cr intermetallic and Fe-Cu two-phase composites have been consolidated to full density from powders produced by high-energy ball milling, using a sinter forging procedure developed recently in our laboratory. Grain sizes remained within nanophase range (<100 nm) after consolidation. Microhardness tests of Fe-29Al-2Cr samples consolidated to different density levels indicate a significant strengthening effect due to nanoscale grain size and a monotonic microhardness increase with decreasing residual porosity. Fully dense Fe-Cu composites exhibit enhanced microhardness as compared with rule-of-mixtures predictions, which may be attributable to interface strengthening at fcc-bcc interphase boundaries.

scholarly journals Nanocomposite of Si/C Anode Material Prepared by Hybrid Process of High-Energy Mechanical Milling and Carbonization for Li-Ion Secondary Batteries

2018 ◽  
Vol 8 (11) ◽  
pp. 2140 ◽  
Author(s):  
Reddyprakash Maddipatla ◽  
Chadrasekhar Loka ◽  
Woo Choi ◽  
Kee-Sun Lee
Keyword(s):  
Electron Microscopy ◽  
Anode Material ◽  
Mechanical Milling ◽  
Coulombic Efficiency ◽  
Electronic Conductivity ◽  
High Capacity ◽  
Lithium Ion ◽  
High Energy ◽  
Particle Size Reduction ◽  
Milled Powders

Si/C nanocomposite was successfully prepared by a scalable approach through high-energy mechanical milling and carbonization process. The crystalline structure of the milled powders was studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Morphology of the milled powders was investigated by Field-emission scanning electron microscopy (FE-SEM). The effects of milling time on crystalline size, crystal structure and microstructure, and the electrochemical properties of the nanocomposite powders were studied. The nanocomposite showed high reversible capacity of ~1658 mAh/g with an initial cycle coulombic efficiency of ~77.5%. The significant improvement in cyclability and the discharge capacity was mainly ascribed to the silicon particle size reduction and carbon layer formation over silicon for good electronic conductivity. As the prepared nanocomposite Si/C electrode exhibits remarkable electrochemical performance, it is potentially applied as a high capacity anode material in the lithium-ion secondary batteries.

Characteristics of nanophase TiAl produced by inert gas condensation

1992 ◽  
Vol 7 (11) ◽  
pp. 2962-2970 ◽  
Author(s):  
H. Chang ◽  
C.J. Altstetter ◽  
R.S. Averback
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
Large Fraction ◽  
Inert Gas ◽  
Full Density ◽  
Indentation Creep ◽  
Small Component ◽  
Grain Sizes ◽  
Transmission Electron ◽  
20 Nm

Nanophase TiAl, with grain sizes in the range of 10–20 nm, was synthesized by magnetron sputtering in an inert gas atmosphere and consolidated, in situ, under vacuum. The properties of the powders and sintered compacts were studied by transmission electron microscopy, scanning electron microscopy, calorimetry, Rutherford backscattering, and x-ray diffraction. Samples compacted at 1.0 GPa at room temperature had a large fraction of amorphous phase, while samples compacted at the same pressure and 250 °C were predominantly the equilibrium γ phase. An enthalpy change of 22 kJ/g-atom was measured during a DSC scan over the temperature range 125–450 °C, which is approximately the range over which crystallization occurs. Nearly full density could be achieved by sintering at 450 °C without significant, concomitant grain growth. The Vickers microhardness of these samples at room temperature and at −30 °C revealed an inverse Hall–Petch relationship at small grain sizes, 10–30 nm, and the usual Hall–Petch behavior at larger grain sizes. A small component of indentation creep was also observed. The maximum hardness is 4 times larger than that of a cast TiAl specimen of the same composition. The Vickers hardness was also observed to decrease rapidly with temperature above 200 °C.

Consolidation of Copper-Copper Nitride Nanocomposite Powders via Warm Extrusion

2008 ◽  
Vol 587-588 ◽  
pp. 177-181
Author(s):  
Vanessa Livramento ◽  
Jose Brito Correia ◽  
Filipe Neves ◽  
Rosa Calinas ◽  
M. Teresa Vieira
Keyword(s):  
Data Storage ◽  
Nitrogen Atmosphere ◽  
Optical Data Storage ◽  
Optical Data ◽  
Composite Powders ◽  
Consolidation Process ◽  
Copper Nitride ◽  
Nanocomposite Powders ◽  
Warm Extrusion ◽  
Milled Powders

Copper nitride films prepared by sputtering have applications such as optical data storage material, insulation barriers in micro electronic devices and coatings for mechanical applications. The present study examines nanocomposites prepared by mechanical alloying of copper with copper nitride under nitrogen atmosphere, at room temperature, in order to establish a comparison with properties of Cu-N sputtered films. The powders were consolidated into bulk samples via warm extrusion at temperatures ranging from 300 to 500°C (0.42-0.64 Tf) after encapsulation without degassing. The as-milled powders and the extruded materials were studied using X-ray diffraction, optical microscopy, scanning and transmission electron microscopy and microhardness measurements. Also, the TEM observation of the extruded sample indicates a mean grain size of about 50 nm. This evidences a higher thermal stability of the as-milled powders and the advantage of using a fast consolidation process, at a relatively low temperature. Therefore, the consolidated material did not show the dramatic softening associated with recrystallization. The consolidation of nanostructured copper-copper nitride composite powders via warm extrusion, without major grain coarsening, was demonstrated.

Ag/YBa2Cu3O7-x Powder Generation by Aerosol Decomposition

1989 ◽  
Vol 169 ◽  
Author(s):  
Toivo T. Kodas ◽  
Altaf H. Carim ◽  
Kevin C. Ott
Keyword(s):  
Melting Point ◽  
Aerosol Particles ◽  
Nitrate Solution ◽  
Metal Nitrate ◽  
Operating Conditions ◽  
Grain Sizes ◽  
Reactor Operating ◽  
Uniform Composition

AbstractYBa2Cu3O7-x (123) powders containing silver have been prepared by aerosol decomposition. Metal nitrate solution droplets were decomposed at temperatures above and below the melting point of the Ag-O eutectic. In both cases, the Ag was present as a separate grain attached to YBa2Cu3O7-x. Individual aerosol particles had dimensions of 50 – 1000 nm. Grain sizes of Ag and 123 crystallites within these particles were 10 to 100 nm. Larger 123 grain sizes could be obtained by varying the reactor operating conditions. The powders provide a source of material for generation of YBa2Cu3O7-x/Ag ceramics with smaller Ag and 123 grain sizes and more uniform composition than can be obtained by other methods.

Mechanochemically synthesized NbC cermets: Part I. Synthesis and structural development

1999 ◽  
Vol 14 (11) ◽  
pp. 4274-4284 ◽  
Author(s):  
B. R. Murphy ◽  
T. H. Courtney
Keyword(s):  
Heat Treatment ◽  
Companion Paper ◽  
Full Density ◽  
Structural Development ◽  
Powder Charge ◽  
Powder Consolidation ◽  
Cu Content ◽  
Grinding Media ◽  
Pure Cu ◽  
Milled Powders

The mechanochemical synthesis of NbC-based cermets is described. Nanocrystalline NbC is synthesized by room-temperature milling of Nb and graphite (or hexane) mixtures. While some structural coarsening occurs during powder consolidation to full density, a nanoscale structure is maintained. Grinding media wear occurs during milling, and milled powders contain Fe from this abrasion. This phase, homogeneously distributed in milled powders, segregates during consolidation and heat treatment, and a cermetlike microstructure results. Copper added to the powder charge yields NbC–Cu or NbC–Cu-Fe cermets. Copper-containing materials have different phase morphologies. In particular, relatively large NbC particles are dispersed in a matrix containing finer NbC and metal particles. Higher Cu-content materials also develop a pure Cu constituent on heat treatment. A companion paper, “Mechanochemically synthesized NbC cermets: Part II. Mechanical properties,” addresses aspects of the mechanical behavior of these materials.

Examination of microstructure evolution and strengthening mechanisms in an aluminum-based hybrid composite prepared through the spark plasma sintering method

2020 ◽  
Vol 117 (6) ◽  
pp. 613
Author(s):  
Mohammad Reza Rezaei ◽  
Alireza Albooyeh ◽  
Hassan Shiraghaei ◽  
Misagh Shayestefar
Keyword(s):  
Yield Strength ◽  
Spark Plasma Sintering ◽  
Hybrid Composite ◽  
Full Density ◽  
Interfacial Region ◽  
Strengthening Mechanisms ◽  
Consolidation Process ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Difference

A bulk hybrid composite to be potentially used as a foam precursor was produced in this study. TiH2 powder particles along with different concentrations of SiC were mixed with pure Al particles and consolidated through the spark plasma sintering (SPS) method. Bulk samples with nearly full density were successfully produced using the SPS method. During the consolidation process, no additional phases were found within the ceramic particles/matrix interfacial region. Using the ceramic TiH2 and SiC particles as the reinforcement cause notably strengthened the pure Al matrix (37% higher yield strength) without adversely affecting the plasticity, helping retain strain to fracture of about 50% for the sample. The yield strength of the samples was quantitatively approximated by examining their strengthening mechanisms via a number of simplified models available in the literature. The analyses found grain boundary and dislocation strengthening to be the most effective mechanisms for enhancing the strength of the samples; it was also found that the difference between the approximated and experimentally obtained overall yield strength was negligible.

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