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Nanocrystalline metals—with grain sizes less than 100 nm— have strengths exceeding those of coarse-grained and even alloyed metals [1,2] . A bulk nanocrystalline Cu-1%Nb alloy was synthesized by an in-situ consolidation mechanical alloying technique. The mechanical behavior of this alloy was investigated by hardness and tensile tests. The nanostructure was investigated by X-ray diffraction and transmission electron microscopy and the fracture surface by scanning electron microscopy. Electrical resistivity was measured using a four-point probe technique. The dilute additives of Nb and the processing conditions induced artifact-free bulk nanocrystalline materials that possess extraordinary high strength, good ductility, and high electrical conductivity. [ABSTRACT FROM AUTHOR]

We have synthesized artifact-free bulk nanocrystalline copper samples with a narrow grain size distribution (mean grain size of 23 nm) that exhibited tensile yield strength about 11 times higher than that of conventional coarse-grained copper, while retaining a 14% uniform tensile elongation. In situ dynamic straining transmission electron microscope observations of the nanocrystalline copper are also reported, which showed individual dislocation motion and dislocation pile-ups. This suggests a dislocation-controlled deformation mechanism that allows for the high strain hardening observed. Trapped dislocations are observed in the individual nanograins. [ABSTRACT FROM AUTHOR]

We report a unique way of using mechanical milling/in situ consolidation at both liquid-nitrogen and room temperature to produce artifact-free nanocrystalline Cu (23 nm) with a narrow grain size distribution. This nanocrystalline Cu exhibits an extraordinarily high yield strength (770 MPa), as predicted from a Hall–Petch extrapolation, along with good ductility (comparable with ∼30% uniform tensile elongation). Possible factors leading to this excellent optimization of strength and ductility are discussed. [ABSTRACT FROM AUTHOR]

Nanocrystalline (nc) Cu and Cu–1% Nb bulk materials are synthesized using a combination of cryogenic and room temperature ball milling. The grain size values of these in situ consolidated Cu and Cu–1% Nb, determined using transmission electron microscopy, are found to be 22 nm and 18 nm, respectively. In this investigation, isochronal heat treatments are performed for 1 h to establish grain size and microstructural changes as a function of temperature. The annealing of nc Cu–1% Nb at a temperature of 1073 K reveals a slight increase in the average grain size from 18 to 45 nm. The grain size of nc Cu, however, increases from 22 nm to about 3 μm after annealing at the same conditions. The present results indicate that solute entrapment plays a major role in thermal stability of the high purity contaminant‐free Cu with the addition of only 1 at% Nb after annealing for 1 h up to a homologous temperature of 0.8. Kinetic stabilization via clustering of Nb atoms on the grain boundaries and the triple junctions is also observed after annealing at high temperature for longer times. [ABSTRACT FROM AUTHOR]

Unconventional treatments can provide a modification to convert ash waste into valuable materials that can be used in various applications. This study focuses on bottom ash (BA) collected from a local incineration plant and characterizes its chemical composition before and after pretreatment by coating with polymers. The toxicity-characteristic leaching procedure (TCLP) was used to identify selected heavy metal leaching after treatment with vinyl-terminated polydimethylsiloxane (PDMS) of different molecular weights. BA coatings were incorporated in two ratios, 0.5% and 1%, by milling to avoid heavy metal leaching. The results showed that all the coating batches had reduced concentrations of copper (Cu), manganese (Mn), and zinc (Zn), whereas the concentrations of chromium (Cr) and cadmium (Cd) showed higher amounts of BAV34 (0.5%) and BAV25 (1%). The treated BA with GP demonstrated percentages of reduction of 70%, 65%, 80%, 75%, 90%, and 80% for Cu, Mn, Ni, Zn, Pb, and Cd, respectively. The milling procedure reduced the particle size of the coated ash. Hydrophobicity was observed in all coating batches compared to untreated BA. The thermogravimetric analysis (TGA) results showed variations between BA and treated BA, which confirmed that PDMS caused surface modification. These features have potential significance for extending the use of coated ash as a sustainable material for construction applications. • The leachability of heavy metal was investigated by Toxicity-characteristic leaching procedures (TCLP). • Coating by PDMS, and milling methods are a potential pretreatment for BA. • Surface modification impacted the hydrophobicity and the leachability of heavy metal. • The best coated formulation was indicated with GP and BV25 (1%) coatings. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical behavior of nanocrystalline materials has been studied extensively for the past few years. Recent studies on artifact-free materials with nanosize grains less than 100nm have been very fruitful. These nanograined metals have exhibited very high strengths with reasonably good ductility. While there have been a large number of studies on hardness and strength characteristics, studies on strain rate sensitivity (SRS) are very limited. We describe here some of our recent work in characterizing SRS as well as activation volumes of nanograined copper using different testing procedures. These tests have been carried out under iso-strain rate and iso-structural conditions. [Copyright &y& Elsevier]