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Precipitation Coating of Monazite on Woven Ceramic Fibers: III—Coating without Strength Degradation Using a Phytic Acid Precursor
Author(s) -
Fair Geoff E.,
Hay Randall S.,
Boakye Emmanuel E.,
Morgan Peter E. D.,
Marzke Robert F.,
Sharma Ramesh
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2009.03406.x
Subject(s) - materials science , coating , precipitation , fiber , chemical engineering , composite material , amorphous solid , phytic acid , nucleation , crystallography , biochemistry , chemistry , physics , organic chemistry , meteorology , engineering
Multiple coatings of La‐monazite (LaPO 4 ) were applied to Nextel ™ 610 and 720 oxide fibers using a heterogeneous nucleation and growth coating process with phytic acid solution precursors. The as‐processed coatings were found to be largely amorphous. Coated fibers were heat treated at 1200°C for 1–2 h, whereupon the coatings crystallized to porous LaPO 4 with thin (50–100 nm) layers of AlPO 4 at the fiber–coating interface. Heat‐treated fibers exhibited full strength retention, in marked contrast to fibers coated by precipitation using citric acid precursors as in a previous work. The microstructural evolution of the amorphous coatings was studied as a function of temperature. AlPO 4 forms at the fiber–coating interface between 700° and 800°C, before high‐temperature outgassing of the coating as measured by TGA. NMR spectroscopy was used to study as‐precipitated powders and as‐processed coatings to gain insights into the structural nature of the materials. A possible explanation for the retention of fiber strength through the coating process is proposed and discussed in light of the experimental evidence.