Title

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

Date

1961

Index Abstract

Contrails and DTIC condensed

Photo Quality

Incomplete

Report Number

WADD TR 60-655

Corporate Author

Nuclear Metals, Inc.

Laboratory

Materials Central

Extent

46

Identifier

AD0262060

Access Rights

OTS

Distribution Classification

1

Contract

AF 33(616)-6627

DoD Project

7364

DoD Task

73640

DTIC Record Exists

Yes

Distribution Change Authority Correspondence

None

Report Availability

Full text available

Date Issued

1961-03

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

Type

report

Publisher

Wright-Patterson Air Force Base, OH : Wright Air Development Division, Air Research and Development Command, United States Air Force

Subject

Niobium

Thermodynamics

Enthalpy

Entropy

High Temperature

Thermochemistry

Tantalum

Phase Studies

Solids

Nitrogen

Gases

Oxygen

Chemical Reactions

Melting

Solubility

Dissociation

Chemical Analysis

Thermionic Emission

Heat Of Reaction

Metals

Measurement

Format

1 online resource

Creator

Pemsler, J. Paul