The sinter forging of the barium-yttrium-copper-oxide superconductor

Thesis/Dissertation · Sat Dec 31 23:00:00 EST 1988

OSTI ID:6948899

Robinson, Q K

Sinter forging typically exhibits components of both densification and deformation, which depends upon temperature, loading conditions and material characteristics. These parameters were investigated to gain a better understanding of the underlying phenomena and mechanisms operating in the sinter forging of the Ba{sub 2}YCu{sub 3}O{sub 6+x} superconductor. The apparatus used allowed variable loading and temperature profiles to be applied to porous compacts. Three linear variable differential transformers (LVDT's) measured axial and radial displacements. Laboratory and commercial superconductor compositions were investigated. Sinter forged compacts were characterized in terms of radial and axial strains, strain rates, density, x-ray diffraction, and optical microscopy. Sinter forging enhanced densification compared to sintering without a load. Densification was non-uniform due to friction at the interface between the sample and the pressurizing rams. Radial density gradients invalidated the use of biaxial dilatometry to measure densification and deformation kinetics. The sample deformation was correlated to densification in the early stages and to creep processes in the final stages of forging. Analysis of grain size corrected axial strain rates indicates deformation was controlled by diffusion in the grain boundary region. Grain growth kinetics increased with applied stress. Increasing the applied stress had a favorable effect on the grain size density trajectory. X-ray diffraction indicated a preferential alignment of the grains with the sinter forge axis. The c-axis distribution was radially symmetric about the forge axis, indicating a fiber-like texture. The degree of orientation increases towards the mid-height but was invariant across the diameter. Applied loads on particle rearrangement in the high porosity stage of sintering was significant in densification and the development of preferred orientation.

• Research Organization: Northwestern Univ., Evanston, IL (USA)
• OSTI ID: 6948899
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
426001 -- Engineering-- Superconducting Devices & Circuits-- (1990-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM NITRIDES
BENCH-SCALE EXPERIMENTS
CHALCOGENIDES
COHERENT SCATTERING
CONTROL
COPPER COMPOUNDS
COPPER OXIDES
DIFFRACTION
FABRICATION
FORGING
MATERIALS WORKING
MICROSCOPY
NITRIDES
NITROGEN COMPOUNDS
OPTICAL MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
SCATTERING
SINTERING
STRAIN RATE
STRESS INTENSITY FACTORS
SUPERCONDUCTORS
TEMPERATURE CONTROL
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
YTTRIUM COMPOUNDS
YTTRIUM OXIDES