TY - JOUR
T1 - Enhancing oxidation resistance of silicon nitride using a Ca2+ stabilizer
AU - Numkiatsakul, Prapassorn
AU - Lee, Tonghun
AU - Kim, Kenneth S.
AU - Kriven, Waltraud M.
N1 - The research was sponsored by the US Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF2020220. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. The XRD, SEM, and TEM experiments were performed at the Frederick Seitz Materials Research Laboratory, Central Research Facilities, at the University of Illinois at Urbana-Champaign.
PY - 2025/3
Y1 - 2025/3
N2 - Silicon nitrides are widely used in ceramic heaters for combustion engines due to their high strength and wear resistance. However, their poor oxidation resistance at elevated temperatures limits their reliability. Oxidation products, such as silica and intermediate compounds from sintering additives, often suffer from microcracks due to phase transformation and volume expansion mismatch during thermo-mechanical cycles. Use of cation dopants to chemically stabilize the transformation of the oxidation front is proposed. This study investigated the effect of Ca2+ treatment on Si3N4 with MgO and Y2O3 sintering aids. The Si3N4 samples were coated with CaO and the phase composition, microstructure, and chemical distribution of the oxidation products were analyzed using XRD, SEM, TEM, STEM, and EDS. The oxidation coupon tests revealed that the CaO coating effectively protected Si3N4 from oxidation at 1300 ºC for 40 h. Moreover, the microstructural analysis showed that CaO coating created more favorable microstructures which reduced oxidation reactions.
AB - Silicon nitrides are widely used in ceramic heaters for combustion engines due to their high strength and wear resistance. However, their poor oxidation resistance at elevated temperatures limits their reliability. Oxidation products, such as silica and intermediate compounds from sintering additives, often suffer from microcracks due to phase transformation and volume expansion mismatch during thermo-mechanical cycles. Use of cation dopants to chemically stabilize the transformation of the oxidation front is proposed. This study investigated the effect of Ca2+ treatment on Si3N4 with MgO and Y2O3 sintering aids. The Si3N4 samples were coated with CaO and the phase composition, microstructure, and chemical distribution of the oxidation products were analyzed using XRD, SEM, TEM, STEM, and EDS. The oxidation coupon tests revealed that the CaO coating effectively protected Si3N4 from oxidation at 1300 ºC for 40 h. Moreover, the microstructural analysis showed that CaO coating created more favorable microstructures which reduced oxidation reactions.
KW - CaO
KW - Cation stabilizers
KW - Oxidation resistance
KW - SiN
KW - Sintering additives
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U2 - 10.1016/j.jeurceramsoc.2024.116977
DO - 10.1016/j.jeurceramsoc.2024.116977
M3 - Article
AN - SCOPUS:85206678470
SN - 0955-2219
VL - 45
JO - Journal of the European Ceramic Society
JF - Journal of the European Ceramic Society
IS - 3
M1 - 116977
ER -