Sol-Gel Activities in the United States, a 1991 Perspective

Uhlmann, D. R.

doi:10.1016/b978-0-444-89344-4.50006-9

Cited by 1 publication

(1 citation statement)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The thermal shock resistance of coated and uncoated samples was examined for temperatures ranging from 500 to 1000"C. CMZP and Mg-doped A12Ti05 coatings should yield an excellent thermal shock resistance since their respective coefficient of thermal expansion (0.1-2 10-G/OC for CMZP and 2-3 10-G/OC for Mg-doped A12Ti05) 89 matches that for Si3N4(3 10-G/oC). The experimental results presented in Table 22 are consistent with the above analysis and the data provided by previous workers.…”

Section: Tilermal Skock Resistancementioning

confidence: 99%

Corrosion resistant coatings for SiC and Si{sub 3}N{sub 4} ceramics

Thierry¹,

Yang²,

Brown³

1998

View full text Add to dashboard Cite

It is the goal of this program to 1) develop coatings for SiC and Si3N4that will enhance their performance as heat exchangers under coal combustion conditions and 2) to conduct an indepth evaluation of the cause and severity of ceramic heat exchanger deterioration and failure under coal combustion conditions. Part 1 Thin film coatings of (C~.GMg0.4)Zr4(P04)G (CMZP) and Mg-stabilized aluminum titanate (Mg-A12Ti05) on dense SiC substrates were investigated using sol-gel coating techniques. The thickness and quality of both CMZP and Mg-A12Ti05 coatings were found to depend on the solution concentration and Iifl rate. Double coatings were applied to obtain homogeneous and crack-free coatings. The quality of double coatings was influenced by different first and second coating thickness. The CMZP coated samples were fired in controlled atmospheres to have the pure CMZP phase. Unhydrolyzed solution of Mg-A12Ti05 was utilized instead of hydrolyzed solution to improve the quality of Mg-A12Ti05 coatings. An aging process was found to improve the quality of CMZP and Mg-A12Ti05 coatings. SiC samples coated with CMZP and Mg-A12Ti05 exhibited good thermal shock resistance and greatly improved the high temperature alkali corrosion resistance. Part 2 Silicon nitride (Si3N4)is a potentially good ceramic material for industrial heat exchangers. However, at elevated temperatures and in coal combustion atmospheres its lifetime is severely reduced by oxidation. To increase its corrosion resistance, the formation of a protective oxidation barrier layer was promoted by the deposition of oxide thin films. Homogeneous and crack-free oxide coatings of CMZP and Mg-doped A12Ti05 were successfully deposited on Si3N4using the sol-gel and dip-coating technique. Coated and uncoated samples were then exposed to a sodium containing atmosphere at 10OO°Cfor 360 hours to simulate typical industrial environment conditions. Structural post-exposure analyses based on weight loss measurements and mechanical tests indicated better corrosion resistance and strength retention for CMZP coated Si3N4compared to as-received and Mg-doped AlzTi05 coated SisN4. This difference was attributed to the protective nature of the corrosion layer which, in the case of CMZP, significantly impeded the inward diffusion of oxygen to the Si3N4surface.

show abstract

Section: Tilermal Skock Resistancementioning

confidence: 99%