skip to main content

DOE PAGESDOE PAGES

This content will become publicly available on June 11, 2019

Title: Prediction of continuous porosity gradients in ceramics using ZnO as a model material

Materials with gradient microstructures have a wide range of applications such as cutting tools, armor, and electronic devices. However, it is difficult to predict and control the gradient microstructure during processing. In the present work, a continuous porosity gradient was successfully achieved in ZnO material via spark plasma sintering with a large induced thermal gradient. The porosity is overestimated if isothermal prediction is applied. The current work proposed a more accurate prediction of the porosity by considering the stress-shielding effect caused by the thermal gradient. The shielding effect results from different stress states in the sample due to differential sintering: the hotter side of the specimen experiences a higher strain rate and more shrinkage while the colder side experiences a lower strain rate and less shrinkage simultaneously. Therefore, the axial strains are varied throughout the sample thickness. Using the constituent equations in advanced sintering analysis, the shield stress was calculated to be approximately 13 MPa for the viscoelastic assumption of sintering. To improve the accuracy of predicting porosity gradient, it is necessary to add a load to overcome the shield stress when the materials are sintered with a thermal gradient.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [2]
  1. Colorado State Univ., Fort Collins, CO (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Colorado State Univ., Fort Collins, CO (United States)
  3. Colorado State Univ., Fort Collins, CO (United States); Veloxint, Framingham, MA (Untied States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of the American Ceramic Society
Additional Journal Information:
Journal Volume: 0; Journal Issue: 0; Journal ID: ISSN 0002-7820
Publisher:
American Ceramic Society
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1470854
Alternate Identifier(s):
OSTI ID: 1454901

Cramer, Corson L., Aguirre, Trevor G., Holland, Troy B., and Ma, Kaka. Prediction of continuous porosity gradients in ceramics using ZnO as a model material. United States: N. p., Web. doi:10.1111/jace.15872.
Cramer, Corson L., Aguirre, Trevor G., Holland, Troy B., & Ma, Kaka. Prediction of continuous porosity gradients in ceramics using ZnO as a model material. United States. doi:10.1111/jace.15872.
Cramer, Corson L., Aguirre, Trevor G., Holland, Troy B., and Ma, Kaka. 2018. "Prediction of continuous porosity gradients in ceramics using ZnO as a model material". United States. doi:10.1111/jace.15872.
@article{osti_1470854,
title = {Prediction of continuous porosity gradients in ceramics using ZnO as a model material},
author = {Cramer, Corson L. and Aguirre, Trevor G. and Holland, Troy B. and Ma, Kaka},
abstractNote = {Materials with gradient microstructures have a wide range of applications such as cutting tools, armor, and electronic devices. However, it is difficult to predict and control the gradient microstructure during processing. In the present work, a continuous porosity gradient was successfully achieved in ZnO material via spark plasma sintering with a large induced thermal gradient. The porosity is overestimated if isothermal prediction is applied. The current work proposed a more accurate prediction of the porosity by considering the stress-shielding effect caused by the thermal gradient. The shielding effect results from different stress states in the sample due to differential sintering: the hotter side of the specimen experiences a higher strain rate and more shrinkage while the colder side experiences a lower strain rate and less shrinkage simultaneously. Therefore, the axial strains are varied throughout the sample thickness. Using the constituent equations in advanced sintering analysis, the shield stress was calculated to be approximately 13 MPa for the viscoelastic assumption of sintering. To improve the accuracy of predicting porosity gradient, it is necessary to add a load to overcome the shield stress when the materials are sintered with a thermal gradient.},
doi = {10.1111/jace.15872},
journal = {Journal of the American Ceramic Society},
number = 0,
volume = 0,
place = {United States},
year = {2018},
month = {6}
}