ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
Two-nanophase SiC-Zn composites were synthesized under pressure up to 8 GPa at up to1000oC using an high-pressure infiltration method. The advantage of this technique is that in asingle, continuous process the ceramic nanopowder is compressed to form the matrix withnanopores; the nanopores are filled with a liquid secondary phase, (here Zn), which crystallizes asnano-scale grains. The key limitation is that the pores in the infiltrated preform have to stay openduring the entire process. For this reason only powders of very hard ceramic materials can be usedas a matrix. Two types of SiC nanopowders with average crystallite size of 10 nm and 60 nm andaverage particle size of 30 nm and 100 nm, respectively were used. The measurements of porosityof the green compacts prepared from these powders, pressed at 2.5 GPa and 8 GPa at roomtemperature, indicated that open porosity was maintained. The nanocomposites obtained show a“nano-nano” type microstructure with a uniform mixture of SiC and Zn phases. The volumefraction of Zn is 20 % independent of the process conditions and initial powder morphology. Theprocess parameters and powder granularity influenced the crystal size of the secondary phase. Theaverage grain size of Zn varied from 20 to 85 nm and was smaller in the composites obtained withthe finer matrix, under higher pressure and at lower temperature. The microhardness HV02 of SiCZnnanocomposites varied from 6 to 22 GPa and increased with an increase of pressure andtemperature of the infiltration process, and was significantly larger for the finer grained composites
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/22/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.114.257.pdf
