Densification, Microstructure, and Mechanical Properties of ZrC-SiC Ceramics

ZrC-SiC ceramics were fabricated by high-energy ball milling and reactive hot pressing of ZrH2, carbon black, and varying amounts of SiC. The ceramics were composed of nominally pure ZrC containing 0 to 30 vol% SiC particles. The relative density increased as SiC content increased, from 96.8% for nominally pure ZrC to 99.3% for ZrC-30 vol% SiC. As SiC content increased from 0 to 30 vol%, Young\u27s modulus increased from 404 ± 11 to 420 ± 9 GPa and Vickers hardness increased from 18.5 ± 0.7 to 23.0 ± 0.5 GPa due to a combination of the higher relative density of ceramics with higher SiC content and the higher Young\u27s modulus and hardness of SiC compared to ZrC. Flexure strength was 308 ± 11 MPa for pure ZrC, but increased to 576 ± 49 MPa for a SiC content of 30 vol%. Fracture toughness was 2.3 ± 0.2 MPa·m1/2 for pure ZrC and increased to about 3.0 ± 0.1 MPa·m1/2 for compositions containing SiC additions. The combination of high-energy ball milling and reactive hot pressing was able to produce ZrC-SiC ceramics with sub-micron grain sizes and high relative densities with higher strengths than previously reported for similar materials

Tests of enhanced leading order QCD in W boson plus jets events from 1.8 TeV barp p collisions

We present a study of events with W bosons and hadronic jets produced in (p) over barp collisions at a center of mass energy of 1.8 TeV. The data consist of 51400 W-->e nu decay candidates from 108 pb(-1) of integrated luminosity collected using the CDF detector at the Fermilab Tevatron collider. Cross sections and jet production properties have been measured for W+greater than or equal to1 to greater than or equal to4 jet events. The data compare well to predictions of leading-order QCD matrix element calculations with added gluon radiation and simulated parton fragmentation