3040
E. J. HUBER, JR.,E. L. HEAD,.4KD C. E. HOLLEY, JR.
The Heats of Formation of Zirconium Diboride and Dioxide'
by Elmer J. Huber, Jr., Earl L. Head, and Charles E. Holley, Jr. Unaversity of Calzfornza, Lou d ~ a n 2 . Scmtafic o~ Labolatoiy, Los Alamos, I-eu, llezbco
(ReceaLed June 11, 1964)
The heat of formation of zirconium diboride as determined by oxygen bomb calorimetry on two samples of the inaterial was 4Hf029E = -77.2 st 1.2 kcal. mole. The heat of formation of zirconium dioxide from the combustion of the nietal in oxygen mas AHf02gE= -263.1 i 0.5 kcal./mole.
Introduction Because of their use in high temperature applications, refractory-type coinpounds such as zirconium diboride with a melting point of ca. 3000" are beconiing increasingly important. Values in the literature for heat of formation of this c o i i ~ p o u n d ~vary -~ from -60 to Tinsson, and J. P.McCullough, "Thermochemistry of Boron and Some of Its Compounds," presented at t'he Symposium on Thermodynamics and Thermochemistry, Lund, Sweden, July 18, 1963; E. J. Prosen, W. H. Johnson, and E'. Y. Pergiel, J . Res. Natl. Bur. Std., 62, 43 (1959): and G. L. Gal'chenko, 4.N. Kornilov, B. I. Timofeev, and S. 31. Shuratov, Dokl. Akad. S a u k S S S R , 127, 1016 (1959). (12) A. E. Cameron and E. TVichers, J . Am. Chem. Soc., 84, 4175 (1962). (13) A. D. Mah and B. J. Boyle, ibid., 77, 6512 (1955). (14) D. R. Fredrickson, R. L. Nuttall, H . E . Flotow, and T. N. Hubbnrd, J . P h ~ s Chem., . 67, 1506 (1963). (15) G. L. Humphrey, J . Am. Chem. Soc., 7 6 , 978 (1954).
