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. .

Thermal Stability and Properties of Cu-TiB2 Nanocomposites Prepared by Combustion Synthesis and Spark-Plasma Sintering

2007 ◽  
Vol 534-536 ◽  
pp. 1517-1520
Author(s):  
Dae Hwan Kwon ◽  
Thuy Dang Nguyen ◽  
Dina V. Dudina ◽  
Jong Won Kum ◽  
Pyuck Pa Choi ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Ball Milling ◽  
Copper Matrix ◽  
High Energy ◽  
Good Thermal Stability ◽  
Plasma Sintering ◽  
High Temperature Synthesis ◽  
Spark Plasma ◽  
Nanocomposite Powders ◽  
Tib2 Particles

In the present work, Cu-TiB2 nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.%TiB2 powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.%TiB2 composites. TiB2 particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at 650-750°C were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to 950°C for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu-TiB2 composite showed good thermal stability at eleveated temperature.

scholarly journals Microstructure and Enhanced Properties of Copper-Vanadium Nanocomposites Obtained by Powder Metallurgy

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 339 ◽  
Author(s):  
Yong Wang ◽  
Jinguo Wang ◽  
Haohao Zou ◽  
Yutong Wang ◽  
Xu Ran
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Yield Strength ◽  
Grain Boundary ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Copper Matrix ◽  
Dispersion Strengthening ◽  
Annealed Copper ◽  
Grain Boundary Strengthening

Cu-2.4 wt.%V nanocomposite has been prepared by mechanical alloy and vacuum hot-pressed sintering technology. The composites were sintered at 800 °C, 850 °C, 900 °C, and 950 °C respectively. The microstructure and properties of composites were investigated. The results show that the Cu-2.4 wt.%V composite presents high strength and high electrical conductivity. The composite sintered at 900 °C has a microhardness of 205 HV, a yield strength of 404.41 MPa, and an electrical conductivity of 79.5% International Annealed Copper Standard (IACS); the microhardness and yield strength reduce gradually with the increasing consolidation temperature, which is mainly due to the growth of copper grain size. After sintering, copper grain size and V nanoparticle both maintain in nanoscale; the strengthening mechanism is related to grain boundary strengthening and dispersion strengthening, while the grain boundary strengthening mechanism plays the most important role. This study indicates that the addition of small amounts of V element could enhance the copper matrix markedly with the little sacrifice of electrical conductivity.

Preparation of poly(ether ether ketone)-based composite with high electrical conductivity, good mechanical properties and thermal stability

2016 ◽  
Vol 29 (2) ◽  
pp. 205-210 ◽  
Author(s):  
Yu Jin Lin ◽  
Shi Qin ◽  
Bing Han ◽  
Cong Gao ◽  
Shu Ling Zhang
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Electrical Conductivity ◽  
High Electrical Conductivity ◽  
Aryl Ether ◽  
Good Thermal Stability ◽  
Ether Ether Ketone ◽  
Peek Composite ◽  
Poly Ether Ether Ketone ◽  
Ether Ketone

Poly(ether ether ketone)-based (PEEK-based) composites with high electrical conductivity, good mechanical properties, and thermal stability were prepared using multiwall carbon nanotubes (MWCNTs) as a conductive filler and the liquid crystalline copolymer of poly(aryl ether ketone) (FPEDEKKLCP) as a processing aid. The composites were fabricated using melt blending, and the MWCNT/PEEK composites with FPEDEKKLCP exhibited an obvious improvement in the measured electrical conductivity relative to the MWCNT/PEEK composite without FPEDEKKLCP. Moreover, the MWCNT/PEEK composites exhibited good mechanical properties and thermal stability after addition of an appropriate amount of FPEDEKKLCP. This is attributed to the good thermal stability of FPEDEKKLCP, wherein addition of FPEDEKKLCP effectively decreased the melt viscosity of the MWCNT/PEEK composites, accompanied by an improvement in the dispersion of the MWCNTs in the PEEK matrix.

scholarly journals Influence of Microstructure-Evolution Changes on the Dielectric Properties of Strontium Titanate Prepared via Mechanical Alloying

2019 ◽  
Vol 7 (2) ◽  
Author(s):  
Mutia Suhaibah Abdullah ◽  
Dayang Nur Fazliana Abdul Halim ◽  
Jumiah Hassan ◽  
Mansor Hashim ◽  
Alex See ◽  
...  
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Mechanical Alloying ◽  
Dielectric Material ◽  
Perovskite Phase ◽  
Morphological Changes ◽  
Milled Powder ◽  
Sudden Increase ◽  
Common Trend ◽  
Lower Frequency Region

SrTiO3 is a dielectric material of considerable interest. However, the relationships between microstructure and dielectric properties have not been studied in detail. Hence, we have undertaken an extensive experimental work to study the evolution of the dielectric properties against morphological changes of SrTiO3. SrTiO3 was prepared using the mechanical alloying method and samples with nano-sized starting powder were obtained. The milled powder was pressed into pellets and sintered at various temperatures ranging from 500 °C to 1400 °C. XRD studies showed that these ceramics completely formed a perovskite phase at 900 °C. FeSEM studies show the presence of small grain sizes ranging from 120 to 600 nm. Dielectric constant (εr’) and dielectric loss tangent (tan δ) were measured as a function of frequency and correlated with the microstructure. εr’ and tan δ against frequency show a falling trend at the lower frequency region due to the changing interfacial effect. For sintering temperatures 1000 °C to 1100 °C, grain size and XRD peak data show a significant increase with the corresponding increase in εr’, suggesting a sudden increase in the polarizability due to significant increase in crystallinity. With increasing sintering temperature, εr’ increased proportionally with XRD peak and grain size increases, further confirming polarizability and crystallinity relationship. tan δ correlation with microstructure does not have a common trend.

scholarly journals The influence of powder particle size on properties of Cu-Al2O3 composites

2009 ◽  
Vol 41 (2) ◽  
pp. 185-192 ◽  
Author(s):  
V. Rajkovic ◽  
D. Bozic ◽  
M. Popovic ◽  
M.T. Jovanovic
Keyword(s):  
Thermal Stability ◽  
Particle Size ◽  
Grain Size ◽  
Copper Powder ◽  
Average Particle Size ◽  
High Energy ◽  
Average Particle ◽  
Size Refinement ◽  
Al2o3 Particles ◽  
Milled Powders

Inert gas atomized prealloyed copper powder containing 2 wt.% Al (average particle size ? 30 ?m) and a mixture consisting of copper (average particle sizes ? 15 ?m and 30 ?m) and 4 wt.% of commercial Al2O3 powder particles (average particle size ? 0.75 ?m) were milled separately in a high-energy planetary ball mill up to 20 h in air. Milling was performed in order to strengthen the copper matrix by grain size refinement and Al2O3 particles. Milling in air of prealloyed copper powder promoted formation of finely dispersed nano-sized Al2O3 particles by internal oxidation. On the other side, composite powders with commercial micro-sized Al2O3 particles were obtained by mechanical alloying. Following milling, powders were treated in hydrogen at 400 0C for 1h in order to eliminate copper oxides formed on their surface during milling. Hot-pressing (800 0C for 3 h in argon at pressure of 35 MPa) was used for compaction of milled powders. Hot-pressed composite compacts processed from 5 and 20 h milled powders were additionally subjected to high temperature exposure (800?C for 1 and 5h in argon) in order to examine their thermal stability. The results were discussed in terms of the effects of different size of starting powders, the grain size refinement and different size of Al2O3 particles on strengthening, thermal stability and electrical conductivity of copper-based composites.

scholarly journals Characteristics of Cu-Al2O3 composites of various starting particle size obtained by high-energy milling

2009 ◽  
Vol 74 (5) ◽  
pp. 595-605 ◽  
Author(s):  
Viseslava Rajkovic ◽  
Dusan Bozic ◽  
Milan Jovanovic
Keyword(s):  
Particle Size ◽  
Internal Oxidation ◽  
Lattice Distortion ◽  
Copper Matrix ◽  
High Energy ◽  
Lattice Parameter ◽  
Constant Amount ◽  
High Energy Milling ◽  
Al2o3 Composite ◽  
Powder Particles

The powder Cu-Al2O3 composites were produced by high-energy milling. Various combinations of particle size and mixtures and approximately constant amount of Al2O3 were used as the starting materials. These powders were separately milled in air for up to 20 h in a planetary ball mill. The copper matrix was reinforced by internal oxidation and mechanical alloying. During the milling, internal oxidation of pre-alloyed Cu-2 mass %-Al powder generated 3.7 mass % Al2O3 nano-sized particles finely dispersed in the copper matrix. The effect of different size of the starting copper and Al2O3 powder particles on the lattice parameter, lattice distortion and grain size, as well as on the size, morphology and microstructure of the Cu-Al2O3 composite powder particles was studied.

Properties of Copper-Based Composite Reinforced with Al2O3 Particles of Different Size

2014 ◽  
Vol 875-877 ◽  
pp. 318-323
Author(s):  
Viseslava Rajkovic ◽  
Dusan Bozic ◽  
Jelena Stasic ◽  
Milan T. Jovanovic ◽  
Huai Wen Wang
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Synergetic Effect ◽  
Copper Matrix ◽  
High Energy ◽  
Inert Gas ◽  
Al2o3 Powder ◽  
Al Powder ◽  
Al2o3 Particles

Copper matrix was simultaneously reinforced with nano- and micro-sized Al2O3 particles via high-energy milling of the mixture of inert gas-atomized prealloyed Cu-1 wt.% Al powder and 0.6 wt.% commercial Al2O3 powder. At the maximum of microhardness (2400 MPa) the grain size reaches the smallest value as a result of the synergetic effect of nano- and micro-sized Al2O3 particles. The relatively low decrease in microhardness during HTE may be explained by grain growth which is retarded by Al2O3 nano-sized particles precipitated at the grain boundaries.

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.

Fabrication of TiAl Alloy Powders by High-Energy Ball Milling and Low Temperature Sintering

2011 ◽  
Vol 338 ◽  
pp. 60-64 ◽  
Author(s):  
Xiao Ting Liu ◽  
Hui Ping Shao ◽  
Dong Hua Yang ◽  
Zhi Meng Guo ◽  
Ye Ji
Keyword(s):  
Ball Milling ◽  
Tial Alloy ◽  
Morphological Changes ◽  
Phase Particle ◽  
Milled Powder ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Composite Powders ◽  
Different Temperatures ◽  
Energy Ball

Ti/Al(Ti-50at.%Al) composite powders were prepared by high-energy ball milling followed by reaction sintering heat treatment at 550°C ~ 650°C for 2 hours. Mechanical alloying of TiAl had been performed in a high energy plant ball after different milling times and pre-sintered at different temperatures. The particle sizes of Ti/Al powders were analyzed by scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was performed for microstructural characterization. The results show that microstructural and morphological changes of high energy milled powder are studied as a function of milling time. Over 600°C TiAl powders are completely alloyed by being sintered at different temperatures. The powders are mainly composed of γ-TiAl as well as a small amount of AlTi3. The TiAl alloy powders of high energy ball mill/2h and sintered at 650°C/2h get plasma spheroidization. Spheroidizing powders with fine texture, γ-TiAl and AlTi3phase, particle size of 10~40μm are obtained.

Microstructural effects of high-energy grinding on poorly soluble drugs: the case study of efavirenz

2017 ◽  
Vol 32 (S1) ◽  
pp. S135-S140 ◽  
Author(s):  
Elisa Cappelletto ◽  
Luca Rebuffi ◽  
Alberto Flor ◽  
Paolo Scardi
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Mechanical Activation ◽  
Morphological Changes ◽  
Domain Size ◽  
High Energy ◽  
Water Soluble ◽  
Size Reduction ◽  
Dissolution Behavior ◽  
Particle Size Reduction

In this work, a poorly water-soluble drug (efavirenz) was mechanically activated by ball-milling. The effect of the mechanical activation on the dissolution behavior was investigated considering changes in the particle size and morphology. The powder diffraction was used to follow the comminution process, verifying phase compositions, and crystalline domain size. The interplay between domain and grain size was studied in relation to the solubility rate, through specific dissolution tests. Finally, the morphological characterization has allowed to complete the physical–chemical characterization of the milled powders. This study demonstrated that the mechanical activation of the drug leads the particle size reduction and, with a long milling time, morphological changes. The grain size reduction is not always sufficient to increase the solubility: morphology and agglomeration grade play an important role in the dissolution process.

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