Phase Formation and Thermal Conductivity of Zirconium Carbide

Download or read book Phase Formation and Thermal Conductivity of Zirconium Carbide written by Yue Zhou and published by . This book was released on 2021 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This research focused on the synthesis and phase formation of zirconium carbide with different carbon contents, and lattice thermal conductivity of zirconium carbide with different carbon vacancy, hafnium, and oxygen contents. Nominally pure phase ZrC[sub x] was synthesized by solid-state reaction of zirconium hydride (ZrH2) and carbon black at a temperature as low as 1300°C. The powder synthesized at 1300°C was carbon deficient ZrC[sub x]. Carbon stoichiometry of the as-synthesized powders increased as the synthesis temperature increased. As the synthesis temperature increase, the oxygen content of ZrC[sub x] decreased due to the increasing C site occupancy. Low stoichiometry ZrC[sub 0.6] powders were synthesized at 1300°C and 2000°C, and the formed phases were investigated. Carbon vacancy ordered phases were detected by neutron diffraction and selected area electron diffraction. Lattice thermal conductivities of ZrC[sub x] with different carbon contents (x=1.0, 0.75, 0.5) and different hafnium contents (3.125 at% and 6.25 at% were studied theoretically. A combination of first-principles calculations and the Debye-Callaway model was employed to predict the lattice thermal conductivities. Lattice thermal conductivities of all the compositions decreased as temperature increased. Increasing carbon vacancy content reduced the lattice thermal conductivity while increasing the grain size increased the lattice thermal conductivity. Lattice thermal conductivities of ZrC[sub x] also decreased as the content of Hf increased. Carbon vacancies and Hf impurities decreased the phonon transport, thus the lattice thermal conductivity decreased"--Abstract, page iv.