Mechanical properties of nanocrystalline copper produced by solution-phase synthesis
- PDF / 630,419 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 96 Downloads / 226 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Mechanical properties of nanocrystalline copper produced by solution-phase synthesis R. Suryanarayanan, Claire A. Frey, and Shankar M. L. Sastry Materials Science and Engineering Program, Department of Mechanical Engineering, Washington University, St. Louis, Missouri 63130-4899
Benjamin E. Waller, Susan E. Bates, and William E. Buhro Department of Chemistry, Washington University, St. Louis, Missouri 63130-4899 (Received 18 May 1995; accepted 13 October 1995)
Nanocrystalline copper powder was produced by a NaBH4 reduction of CuCl in a simple solution phase room temperature reaction. Uniaxial hot pressing in a closed tungsten die was used to compact powder into dense specimens. Samples were analyzed by x-ray diffraction, precision densitometry, electron microscopy, energy dispersive x-ray analysis, and selected area diffraction. Mechanical properties of the consolidated samples were determined by microhardness measurements, three-point bending of rectangular specimens, and compression tests. Yield strength measured for nanocrystalline Cu in the present work was over two times that reported in literature for Cu with comparable grain size and over five times that of conventional Cu. Restricted grain growth observed in the hot-pressed samples and improved mechanical properties are attributed to the presence of boron. A unique method of obtaining homogeneous in situ nanosized reinforcements to strengthen the grain boundaries in nanocrystalline materials is identified.
I. INTRODUCTION
Extending microstructural refinement to the nanometer regime (1–100 nm) results in significant mechanical property improvements.1–3 The property improvements in nanocrystalline materials have been attributed to the novel characteristics of grain boundaries and dramatic grain refinement. Nanocrystalline materials have a unique structure in that a large fraction of the atoms (5–30%) are located in grain or interphase boundaries.4 Gas-phase condensation was one of the earliest methods used to synthesize nanocrystalline particles,5–7 but several other routes have subsequently been successfully used.8–15 Many of these methods provide new nonequilibrium processing routes to produce conventional materials with refined grain sizes and permit the production of new alloys and composite powders without equilibrium constraints. The major limitation of most of these processes is that the output per day is limited to a maximum of a few grams. Most of the other nanoparticle synthesis techniques, with the exception of a few such as the electrochemical method,9,10 are unsuitable for scale up. In contrast, the chemical route employed in the present work utilizes simple benchtop chemistry generating 20 –30 g per day (two runs per researcher) on a laboratory scale and is amendable to scale up with ease. In order to produce dense compacts for mechanical property measurements, a combination of sintering, uniaxial cold/hot pressing, and cold or hot isostatic pressing is used. The primary requirement of the consolJ
Data Loading...
