Fluxoid Pinning by Vanadium Carbide Precipitates in Superconducting Vanadium.
Abstract
The purpose of this investigation is to study fluxoid pinning in a Type II superconductor. Vanadium was chosen as the superconductor to study because it is obtainable in high purity and its microstructure can be readily controlled. The pinning centers are formed by introducing carbon into the vanadium matrix forming vanadium carbide precipitates. The vanadium carbide precipitates are disc-shaped particles whose thickness is only a few atomic layers. The precipitates are likely to be superconducting when H = 0 by reason of the proximity effect. The vanadium carbide precipitates on the (310) habit planes. According to studies with the transmission electron microscope, the particles are uniformly distributed throughout the specimen. The particle size and number density is changed by aging the specimens for fixed amount of time at 350 C. The present results are based on the study of thirty specimens. A 99.95% pure annealed vanadium specimen was used as a control. The other vanadium specimens contain 0.1 atomic percent to 0.6 atomic percent carbon. As a result of metallurgical analysis, the mean diameters of the particles range from less than 100 A to 2613 A and the number density of the pinning centers range from 3.3 x 10 to the 15 power particles/cc to 4.2 x 10 to the 17th power particles/cc. The measurement of the superconducting properties lead to values of the macroscopic pinning force density ranging from 33400 dynes/cc to 3170000 dynes/cc for T - O K.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 30, 1977
- Accession Number
- ADA039522
Entities
People
- Alexander J. Marker Iii
Organizations
- Pennsylvania State University