Elastic properties of hot isostatically pressed magnesium diboride
  Powder of magnesium diboride was hot isostatically pressed using three qualitatively different cycles: cooling under pressure (DMCUP), "standard" cycle with pressure and temperature reduced simultaneously and isothermal presure release. Elastic properties of dense material were measured at normal conditions using resonant ultrasound specroscopy (RUS) method. The highest value of density (2.66 g/cc) and elastic moduli (Young's modulus 273.5 GPa, bulk modulus 143.9 GPa, Poisson's ratio 0.183) correspond to the sample processed using DMCUP cycle. These data agree very well with some theoretical predictions based on quantum mechanics calculations. Effect of lower density on elastic constants is consistent with theoretical approach based on elasticity theory taking into account effect of low porosity. 
V.F. Nesterenko, Y.Gu