Accession Number : ADA264191


Title :   Processing of Novel Nanoparticle Dispersion Strengthened Ceramics for Improved Mechanical Performance


Descriptive Note : Annual rept. no. 1,


Corporate Author : LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER


Personal Author(s) : Chan, Helen M ; Harmer, Martin P ; Miller, Gary A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a264191.pdf


Report Date : 14 Dec 1992


Pagination or Media Count : 109


Abstract : Nanocomposites have continued to show promise both as structural ceramic materials and as ideal systems in which to design multiphase microstructures. This report focuses on successful techniques for fabricating A1203/SiC nanocomposites, the strengthening obtained by the addition of sub- micron SiC particles to Al203, and the technological advantages of the nanocomposite. Some of the most significant conclusions of this work are: (1) A technique has been developed to reproducibly fabricate fine-grained nanocomposites of A1203 containing 0.15 micrometer SiC particles. (2) It has been confirmed that nanocomposites of A1203 containing 5 vol% 0. 15 micrometer SiC have exceptionally high unindented strengths. A subsequent annealing step improves these unindented strengths to greater than 1 GPa. (3) The strengthening effect appears to be grain size independent: the strengthening does not diminish even after the matrix grain size is coarsened to the level of 60 micrometer. This is in marked contrast to undoped A1203 in which the unindented strengths decrease significantly as the grain size coarsens. (3) The strengthening mechanism in the nanocomposite is believed to arise from machining-induced residual surface stresses. The function of the annealing step is to relax these stresses slightly (as indicated in preliminary x-ray stress measurements) while significantly decreasing the size of the machining flaws.


Descriptors :   *CERAMIC MATERIALS , *PARTICLES , *DISPERSIONS , STRESSES , FUNCTIONS , ANNEALING , MECHANICAL PROPERTIES , CONTRAST , MICROSTRUCTURE , MATERIALS , FINES , SILICON CARBIDES , ALUMINUM OXIDES , RESIDUALS , COMPOSITE MATERIALS , FABRICATION , GRAIN SIZE , X RAYS , STRENGTH(MECHANICS) , PHASE , SURFACES


Subject Categories : Ceramics, Refractories and Glass
      Laminates and Composite Materials
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE