The heat capacity of a characterized, zone-melted sample of zirconium diboride has been measured over the low temperature range by adiabatic calorimetry and found to be of a normal sigmoid shape without transitions or thermal anomalies. The values of the heat capacity at constant pressure (Cp), the entropy (S°), and the Gibbs function (-[G°-H §]/T) are 11.53, 8.59, and 3.25 cal. (g.f.m. °K.) "l, respectively, at 298.15°K.ALTHOUGH in increasing demand as a consequence of technological developments in nuclear reactors, missiles, and other high temperature applications of refractory materials, accurate thermodynamic data on carbides, borides, and related compositions on the group IV elements are relatively rare. The major difficulty is preparing these substances in high-purity, well-characterized states suitable for thermodynamic reference use. This study endeavors to procure reliable thermodynamic data on zirconium diboride (ZrB2) by adiabatic calorimetry. EXPERIMENTAL Cryostat and Technique. Measurements were made in the Mark II adiabatic, vacuum cryostat schematically similar to one previously described ( 20), but modified and improved in several respects to give an instrument of greater compactness, mechanical rigidity, and operating convenience. The cryostat is provided with an economizer, with perforated silver foil discs. This economizer serves as a heat exchanger between the bundle of electrical leads Constantan thermocouples monitor the difference in temperature between calorimeter and shield and between shield and ring. Three separate channels of recording electronic circuitry with proportional, rate, and reset control actions are used for shield control above 50°K. This instrumentation controls temperature to within about a millidegree over the temperature range and makes the uncertainty in the (enameled around it) and the heat capacity of the cold ef-
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.