TY - JOUR
T1 - Predicting transformations during reactive flash sintering in CuO and Mn2O3
AU - Murray, Shannon E.
AU - Lin, Yu Ying
AU - Sulekar, Soumitra S.
AU - Gebre, Mebatsion S.
AU - Perry, Nicola H.
AU - Shoemaker, Daniel P.
N1 - Funding Information:
We acknowledge the research support by the Army Research Office under Grant Number W911NF-17-1-0142. SEM acknowledges the support from the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE1144245. YYL and NHP acknowledge the support from the US Army CERL W9132T-19-2-0008.
PY - 2021/1
Y1 - 2021/1
N2 - Reactive flash sintering has been demonstrated as a method to rapidly densify and synthesize ceramic materials, but determining the extent of chemical reactions can be complex since the maximum temperature reached by the sample may be brief in time. The black body radiation (BBR) model has been shown to accurately predict the sample temperature during the steady state of flash (stage III). This work demonstrates situations where the BBR model alone does not accurately predict when a phase transformation will occur. We examine the model reactions of CuO reduction to Cu2O during stage II and Mn2O3 reduction to Mn3O4 in stage III. In CuO, highly resistive samples result in initially localized current flow, a stochastic process resulting in inhomogeneous heating and error in the BBR model during stage II. CuO reduction does not occur in constant heating rate experiments with 6.25 V/mm fields, even though the sample temperature momentarily exceeds the phase transformation temperature. Increased furnace heating to 950°C before application of a field is required to drive the transition. In Mn2O3, the calculated sample temperature of the gauge is less than the transformation temperature, but localized heating at the contact will exceed the transformation temperature, causing the transformation to propagate away from the electrode during stage III. This work demonstrates two forms of inhomogeneity (local, stochastic current flow, and local contact resistance) that result in a complex thermal profile of the sample. This profile should be interrogated to understand reaction kinetics, and can be beneficial when engineered.
AB - Reactive flash sintering has been demonstrated as a method to rapidly densify and synthesize ceramic materials, but determining the extent of chemical reactions can be complex since the maximum temperature reached by the sample may be brief in time. The black body radiation (BBR) model has been shown to accurately predict the sample temperature during the steady state of flash (stage III). This work demonstrates situations where the BBR model alone does not accurately predict when a phase transformation will occur. We examine the model reactions of CuO reduction to Cu2O during stage II and Mn2O3 reduction to Mn3O4 in stage III. In CuO, highly resistive samples result in initially localized current flow, a stochastic process resulting in inhomogeneous heating and error in the BBR model during stage II. CuO reduction does not occur in constant heating rate experiments with 6.25 V/mm fields, even though the sample temperature momentarily exceeds the phase transformation temperature. Increased furnace heating to 950°C before application of a field is required to drive the transition. In Mn2O3, the calculated sample temperature of the gauge is less than the transformation temperature, but localized heating at the contact will exceed the transformation temperature, causing the transformation to propagate away from the electrode during stage III. This work demonstrates two forms of inhomogeneity (local, stochastic current flow, and local contact resistance) that result in a complex thermal profile of the sample. This profile should be interrogated to understand reaction kinetics, and can be beneficial when engineered.
KW - copper/copper compounds
KW - flash sintering
KW - impedance spectroscopy
KW - manganese/manganese compounds
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U2 - 10.1111/jace.17445
DO - 10.1111/jace.17445
M3 - Article
AN - SCOPUS:85091351125
VL - 104
SP - 76
EP - 85
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 1
ER -