Thermodynamics Of The Interaction Of Niobium And Tantalum with Oxygen And Nitrogen At Temperatures Near The Melting Point

Download this report (PDF, 1.3 MB, 46 pages)
Report Number: WADD TR 60-655
Author(s): Pemsler, J. Paul
Corporate Author(s): Nuclear Metals, Inc.
Laboratory: Materials Central
Date of Publication: 1961-03
Pages: 46
Contract: AF 33(616)-6627
DoD Project: 7364
DoD Task: 73640
Identifier: AD0262060

Abstract:
The concentration of nitrogen and oxygen present in niobium and tantalum in equilibrium with the pure gas has been determined as a function of pressure at each of three temperatures near the melting point, and in the liquid phase at the melting point. The solubility of nitrogen in niobium is directly proportional to the square root of the pressure (Sievert's Law) up to the solubility limit, where the saturated solution is in equilibrium with Nb2N. The solubility of nitrogen in tantalum shows a negative deviation from Sievert's Law at nitrogen concentrations above 5 atomic percent; beyond the solubility limit saturated solution is converted to Ta2N. The niobium-oxygen and tantalum-oxygen systems obey Sievert's Law up to the solidus point. The temperatures investigated were above the melting points of the metal oxides and no oxide scales were obtained. A curious solubility inversion was noted in the tantalum-oxygen system where the oxygen concentration in equilibrium with a specified pressure of oxygen is lower at 2850 than at 2960°C. Data were used to calculate the partial molar and integral values of the free energy, enthalpy, and entropy of dissociation of solutions of nitrogen in niobium and tantalum and partial molar free energy and enthalpy of dissociation of solutions of oxygen in niobium and tantalum. It was shown that the concentration of hydrogen in equilibrium with metal at high temperature is very low.

Provenance: IIT

Other options for obtaining this report:

Via the Defense Technical Information Center (DTIC):
A record for this report, and possibly a pdf download of the report, exists at DTIC

Via National Technical Report Library:
This report may be available for download from NTRL. Use the Title from this record to locate the item in DTIC Online

Indications of Public Availability
No digital image of an index entry indicating public availability is currently available
The inside cover of this report indicates that it was released for public sale




Export