Mixture Of Cu Powders Research Articles

Microstructure and thermal stability of nanostructured Cu-7.5vol.%Al2O3 composite powders produced by high energy mechanical milling

Nanostructured Cu-7.5vol.%Al2O3 composite powders were produced from a mixture of Cu powder and Al2O3 nanopowder using two routes of high energy mechanical milling. The milled composite powders were heat treated at 150, 300, 400 and 500°C for 1 hour, respectively, to determine the thermal stability of the microstructure and corresponding micohardness change of the powder particles as a function of the annealing temperature. For the nanocomposite powder produced with 12 hours of milling (Route 1), heat treatment at 150°C did not change the microstructure, increasing the annealing temperature from 150 to 500°C caused the Cu grain sizes to increase due to grain coarsening. For the composite powder produced with 24 hours milling (Route 2), the grain sizes of the Cu matrix also increased due to grain coarsening with increasing the annealing temperature from 150 to 500°C. Average microhardness decreased significantly for both the nanocomposite powders but the degree of grain size increase was smaller with increasing the annealing temperature from 400 to 500°C.

MICROSTRUCTURAL EVOLUTION DURING HIGH ENERGY MECHANICAL MILLING AND HEAT TREATMENT OF Cu-(5,10)vol.%Al2O3 NANOCOMPOSITE POWDERS

Cu -(5-10) vol .% Al 2 O 3 nanocomposite powders were produced from a mixture of Cu powder and Al 2 O 3 nanopowder using a high energy mechanical milling (HEMM) route consisting of two stages. The microstructural evolution of the Cu – Al 2 O 3 nanocomposite powder particles (or granules) produced after first and the second stages of milling was studied using scanning electron microscopy (SEM), transmission electron microcopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray (EDX) mapping. The study confirmed that homogenous dispersion of Al 2 O 3 nanoparticles in the Cu matrix was achieved after the first stage of milling and the relatively large Al 2 O 3 particles were further broken into smaller nanoparticles after the second stage of milling. The milled nanocomposite powders were also heat treated at 150, 300, 400 and 500°C for 1 hour, respectively, to determine the microstructural changes of the powder particles as a function of annealing temperature. It was found that after heat treatment at 150°C, the Cu grain sizes decreased due to recrystallisation, and increasing the annealing temperature to 300°C causes slight coarsening of the Cu grains. Further increasing the annealing temperature to 500°C caused significant coarsening of the Cu grains and the Al 2 O 3 nanoparticles. It also appeared that the coarsening of Cu grains in the composite powder particles after annealing at 500°C become less severe with increasing the volume fraction of Al 2 O 3 particles.

Synthesis and thermal stability of Cu-(2.5-10)vol.%Al2O3nanocomposite powders by high energy mechanical milling

High energy mechanical milling (HEMM) of a mixture of Cu powder and Al2O3 nanopowder has been used to produce Cu-(2.5-10)vol.%Al2O3 nanocomposite powders with a ultrafine grained or nanocrystalline Cu matrix. The microstructure and microhardness of the as-milled powder particles and the thermal stability and microhardness change of the nanocomposite powder particles caused by annealing at temperatures up to 500oC have been studied. It is shown that HEMM can be effectively used to disperse (2.5-10)vol.% Al2O3 nanoparticles into a ultrafine grained or nanocrystalline Cu matrix. Using larger diameter balls or increasing the volume fraction of Al2O3 nanoparticles to 7.5% or higher allows synthesis of Cu-Al2O3 nanocomposite powders with nanocrystalline Cu matrix. Refining the microstructure of the Cu matrix and increasing the volume fraction of Al2O3 nanoparticles in the nanocomposite both increase the thermal stability of the nanocomposite structure.

Consolidation of mechanically alloyed powder mixture of Cu–Zn alloy and graphite

A powder mixture consisting of Cu–29.7at.% Zn alloy and graphite was mechanically alloyed in a planetary ball mill. The supersaturated solid solubility of carbon in the Cu–29.7at.% Zn alloy was determined to be 38.5at.% C (alloy composition: Cu–18.3at.% Zn–38.5at.% C) by the change in lattice parameter of the alloy. Supersaturated Cu–24.2at.% Zn–18.5at.% C alloy powder consolidated by a static compression stress of 1.4 GPa was found to have a relative density of 89.7%, a Vickers hardness of 147.2, and a compressive strength of 1.4 GPa which is equal to the statically consolidated compression stress. Moreover, the supersaturated solid-soluble carbon did not precipitate. When dynamically consolidated by a 93 g projectile at a speed of 38.1 m s −1 (estimated impact compression stress of 2.3 GPa) after static precompression of 0.4 GPa, the alloy powder was found to have a relative density of 93%, a Vickers hardness of 177, and a compressive strength of 2.3 GPa which is equal to the impact compression stress. Supersaturated solid solubility of 18.5at.% C decreased to 15at.% C after impact consolidation. The mechanically alloyed powders can maintain supersaturated solid solubility when consolidated by impact pressure, and especially when consolidated by static pressure.

Crystal growth and characterization of Cu-intercalated misfit-layer compounds.

Single crystals of ${\mathrm{Cu}}_{\mathit{x}}$${\mathrm{CeNb}}_{2}$${\mathrm{S}}_{5}$ (x\ensuremath{\approxeq}0.6) are grown by chemical-vapor-transport reaction of powder mixture of Cu and ${\mathrm{CeNb}}_{2}$${\mathrm{S}}_{5}$. The compound is regarded as a Cu intercalation derivative of a second-stage misfit-layer compound with incommensurate planar intergrowth structure of CeS and ${\mathrm{Cu}}_{\mathit{x}}$(${\mathrm{NbS}}_{2}$${)}_{2}$ layers. Two sublattices for CeS and ${\mathrm{Cu}}_{\mathrm{x}}$(${\mathrm{NbS}}_{2}$${)}_{2}$ layers have a different geometry in the a-b plane although the stacking direction coincides with the c axis. Lattice parameters are ${\mathit{a}}_{1}$=5.80 \AA{}, ${\mathit{b}}_{1}$=5.80 \AA{}, and ${\mathit{c}}_{1}$=17.93 \AA{} for CeS layers and ${\mathit{a}}_{2}$=3.35 \AA{} and ${\mathit{c}}_{2}$=1.93 \AA{} for ${\mathrm{Cu}}_{\mathit{x}}$(${\mathrm{NbS}}_{2}$${)}_{2}$ layers, where ${\mathit{a}}_{1}$=\ensuremath{\surd}3${\mathit{a}}_{2}$. The composite crystals, which are represented by [${\mathrm{Cu}}_{\mathit{x}}$${\mathrm{CeNb}}_{2}$${\mathrm{S}}_{5}$${]}_{\mathit{z}}$[${\mathrm{Cu}}_{\mathit{y}}$${\mathrm{NbS}}_{2}$${]}_{1\mathrm{\ensuremath{-}}\mathit{z}}$, [${\mathrm{Cu}}_{\mathit{x}}$${\mathrm{SmNb}}_{2}$${\mathrm{S}}_{5}$${]}_{\mathit{z}}$[${\mathrm{Cu}}_{\mathit{y}}$${\mathrm{NbS}}_{2}$${]}_{1\mathrm{\ensuremath{-}}\mathit{z}}$, and [${\mathrm{SnNbS}}_{3}$${]}_{\mathit{z}}$[${\mathrm{Cu}}_{\mathit{y}}$${\mathrm{NbS}}_{2}$${]}_{1\mathrm{\ensuremath{-}}\mathit{z}}$, are also grown by a similar method. The single and the composite crystals are, respectively, formed by regular and irregular stacking of Cu and MS (M=Ce, Sm, and Sn) layers. The electronic structures are studied by means of x-ray photoemission spectroscopy and inner-shell-electron energy-loss spectroscopy methods. \textcopyright{} 1996 The American Physical Society.

Homonuclear molybdenum(VI) and heteronuclear molybdenum(VI) copper(II) peroxo complexes containing amino acids

MoO3·H2O reacts with two equivalents of glycylglycine (H2Gg) or aspartic acid (H2Asp) in an excess of aqueous H2O2 at ambient temperature to give [MoO(O2)2-(H2Gg)2(H2O)] (1) and [MoO(O2)2(H2Asp)(H2O)] (2), respectively. An equimolar mixture of Cu powder and MoO3·H2O, on interaction with H2Gg or H2Asp in the presence or absence of H2O2, results in formation of [CuMoO(O2)(Gg)2(H2O)2] (3), [CuMoO2(Gg)2-(H2O)4] (4) and [CuMoO2(Asp)2(H2O)4] (5), respectively. These novel complexes have been characterized by elemental and thermogravimetric analysis, and e.s.r., electronic and i.r. spectral data.

Friction-Assisted Extrusion of Thin Strips Made of copper and Aluminium Composite Material.

The friction-assisted extrusion of thin strips, developed by the authors, was applied to the production of copper and aluminium composite thin strips. The composite thin strips which are claddings with 2 and 3 layers of copper and aluminium and 0.25∼1mm in thickness could be extruded successfully from block metals with the extrusion ratio of 10∼40 and punch pressure ranging from about 0.6 to 1.1 GPa. Composite thin strips which are made of complex phases of copper and aluminium and are 0.05∼1mm in thickness could be extruded directly from the powder mixture of Cu and Al with the extrusion ratio of 5∼200 and the punch pressure of 0.3∼1.2 GPa. The thin strips as extruded from the metal powders showed Vickers hardness HV increasing with the mixture ratio of copper powder and the extrusion ratio within a range from 50 to 240. The tensile strength ST of the thin strips as extruded from composite metal powders was 290 MPa at maximum and was increased to 340 MPa by heat treatment for 1 hour at 400°C.