Particle Size Of Milled Powders Research Articles

Influence of Graphene Content on Sinterability and Physico-Mechanical Characteristics of Al/Graphene Composites Prepared via Powder Metallurgy

The main goal of the present study is to add graphene lubricant to enhance the microstructure and physicomechanical properties of aluminum matrix composites. The proposed composites were prepared by mechanical alloying technique, and the graphene was added with different contents up to 0.8 wt.% as reinforcement. X-ray diffraction analysis and transmission electron microscopy were employed to inspect milled powders' phase changes and particle features (shape and size). The obtained powders were sintered at 400, 500, and 570oC. The microstructure of fired composites was tested by scanning electron microscopy. The physical properties, hardness, compressive strength, strengthening factor, elastic-moduli, and electrical conductivity were also measured. The results displayed that the graphene particles are homogenously distributed through the Al matrix after milling. The particle size of milled powders was about 31.6 nm with an obvious degree of agglomeration. The mechanical properties of sintered composites were affected significantly by sintering temperature and graphene content as dominant factors. The highest obtained microhardness and compressive strengths were 920.8 MPa and 292.1 MPa. They achieved the composite that contains 0.8 wt.% of graphene (AG0.8). Moreover, the conductivity was decreased slightly with the increase of graphene, but it was increased with increasing sintering temperature.

Particle Morphology and Optical Property of Silicate Powder Prepared from Waste Borosilicate Glass by High Energy Ball Milling Process

The aim of this work was focused on the size reduction of waste glass that was obtained from broken beaker glass in the laboratory. The particle size reduction of glass cullet was performed by a high energy ball milling process. Firstly, the obtained beaker glass was smashed into fine particles before the milling process. The milling parameters studied, which had potential effects on the efficiency of the milling process, were rotation speed, milling time and ball sizes. The particle size and morphology of before/after milled silicate powder were evaluated by a particle analyzer and a field emission scanning electron microscope (FE-SEM). It was shown that the particle size of the milled powder had decreased after milling. However, agglomeration occurred after the use of high rotation speeds and longer milling times. Furthermore, functional groups of the milled samples were analyzed by a Fourier transform-infrared (FT-IR) spectrometer. The FTIR spectra of samples of each milled condition displayede similar patterns. Meanwhile, an optical property, the scattering effect of milled samples of different particle sizes, was identified by a luminance meter. The preliminary results suggested that the minimum particle size of the milled glass was reached at 1.33 µm with milling time of 30 min at 500 rpm. Therefore, an increase of light scattering property occurred, and this correspondented to the smaller particle size of milled silicate powder.

Microstructure evolution of Cu-Fe-based immiscible alloys prepared by powder metallurgy

The work is focused on the preparation of bulk immiscible Cu-Fe-based alloys by powder metallurgy. Three samples with chemical composition Cu70Fe30, Cu70Fe15Co15, and Cu50Fe25Co25 were prepared by mechanical alloying and spark plasma sintering (SPS). Microstructure evolution during sintering and the effect of Co on the resulting microstructure and hardness of the bulk samples were evaluated. Despite the immiscibility of Cu with Fe and Co, the FCC supersaturated solid solution was formed upon mechanical alloying. This supersaturated solid solution was decomposed during SPS and fine microstructure, consisting of separated BCC and FCC phases, was formed. The results showed that cobalt influenced the particle size of milled powders as the particle size of Cu70Fe30 alloy was about an order of magnitude higher compared to other alloys. Cobalt also affected the resulting microstructure of bulk samples, however, its effect on the hardness was negligible. It has been shown that powder metallurgy can be used for the preparation of bulk immiscible alloys with the fine microstructure consists of separate phases, which can be individually alloyed by the selected elements, and therefore, powder metallurgy can be considered as a suitable alternative to the more used casting.

Mechanical Alloying and Sintering of a Ni/10wt.%Al2O3 Nanocomposite and its Characterization

A Ni matrix nanocomposite reinforced by 10 wt.% Al2O3 was fabricated by mechanical alloying. The powders mixture was milled up to 24 h in a ball mill. Phase composition and morphology of prepared powders were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. To obtain compact bodies, pressing was applied on the milled powders; then sintered at different temperatures for 1 h in argon atmosphere. Furthermore, the effect of milling time and sintering temperature on microstructure. Physical, mechanical and electrical properties of the sintered nanocomposite specimens were evaluated. The results show decrease of particle size of milled powders (69 nm) as the time increased up to 24 h of milling with a noticeable presence of agglomerates. On the other hand, relative density, microhardness, compressive strength, elastic modulus and electrical conductivity of the sintered samples were found to progressively increase with the increasing of milling time and sintering temperature. Their maximum values were 97.36%, 1137 MPa, 633 MPa, 21.6 GPa and 9.71 × 105 S/m, respectively, for the sample that was milled for 24 h and sintered at 1200 °C. On the other hand, the increasing milling time tended to decrease the fracture strain while it increased with increase of the sintering temperature.

Effect of Carbon Nanotubes as Reinforcement on the Mechanical Properties of Aluminum-Copper-Magnesium Alloy

Elemental powders of Al, Cu, Mg and x wt.% CNT (x: 0-2.5) were blended and milled in the high-energy ball mill for 4 h. Milled powders of Al alloy-CNT composites were subsequently consolidated by upset forging followed by hot extrusion. Even though the particle size of milled powders of Al alloy-CNT composites decreased with the addition of CNT, there is no significant effect on crystallite size. Raman spectra indicated that the nanocrystalline structure of CNT is retained after milling. Yield and ultimate tensile strengths increased with CNT content and Al alloy-2.5 wt.% CNT exhibited an enhancement of 56 and 73%, respectively, when compared to Al alloy in solutionized condition. The improvement in mechanical properties of Al alloy-CNT composites is due to ultra-fine grain size, finer second-phase precipitates and uniform dispersion of CNT.