Controlled relative humidity storage for high toughness and strength of binderless green pellets

An equation was developed to predict fracture toughness of green powder compacts. The model combines crack tip toughness predicted by Kendall's model with crack tip shielding due to bridging of moisture meniscuses across the crack. The model predicts that crack tip shielding due to moisture sho...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2017-10, Vol.100 (10), p.4442-4449
Main Authors: Cannon, W. Roger, Hoggan, Rita E., Erickson, Arnold, Forsmann, Bryan, O'Brien, Robert C., Lessing, Paul A.
Format: Article
Language:English
Subjects:
absorption/absorbents
Bridging
Cerium oxides
Fracture strength
Fracture toughness
green body
green powder compacts
Humidity
MATERIALS SCIENCE
Mathematical models
Mechanical properties
Moisture
NUCLEAR FUEL CYCLE AND FUEL MATERIALS
Pellets
Powder compacts
pressing
Relative humidity
Shielding
Storage
strength
surrogate nuclear fuel
toughness
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Summary:An equation was developed to predict fracture toughness of green powder compacts. The model combines crack tip toughness predicted by Kendall's model with crack tip shielding due to bridging of moisture meniscuses across the crack. The model predicts that crack tip shielding due to moisture should be dominant. Fracture tests on ceria green pellets verified that storing pellets at a high relative humidity (98% RH) for an extended period of time led to fracture strength more than double those stored at lower RH. However, at lower RH there is no significant increase in fracture strength with increased RH as predicted by the model. The lower strength at low RH is due to insufficient capillary and surface forces but may also be related to the lack of sufficient adsorbed moisture to form bridging meniscuses. The high green strengths achieved by storing pellets at a high RH suggest a method of strengthening green parts without adding binder.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.14982