Monazite coatings

FIGURE 7. SEM micrograph showing Nextel 610/monazite/alumina fracture surface. Monazite coatings can be seen on the pulled-out fibers and in the fibertroughs. 

The production of composites containing higher volume fractions of monazite-coated fibers has been somewhat limited and a summary of the relevant work is listed in Table 3. These composites were subjected to mechanical testing, either tensile or flexural, to evaluate the effectiveness of the coatings. 

Monazite coatings were also evaluated in Nextel 312 and 610/aluminosilicate matrix composites [102]. In this case, the monazite coating was deposited using an aqueous slurry (for 312 fabric) or solution (for 610 fabric). Composites containing either fiber type displayed... 

D.-H. Kuo, W. M. Kriven, and T. J. Mackin, Control of Interfacial Properties through Fiber Coatings Monazite Coatings in Oxide-Oxide Composites, J. Am. Ceram. Soc., 80 [12] 2987-2996 (1997). 

T. A. Parthasarathy, E. Boakye, K. A. Keller, and R. S. Hay, Evaluation of Porous Zirconia Silica and Monazite Coatings using Nextel 720 Fiber Reinforced Blackglas Minicomposites, /. Am. Ceram. Soc., 84 [7] 1526-1532(2001). 

The heavy mineral sand concentrates are scmbbed to remove any surface coatings, dried, and separated into magnetic and nonmagnetic fractions (see Separation, magnetic). Each of these fractions is further spHt into conducting and nonconducting fractions in an electrostatic separator to yield individual concentrates of ilmenite, leucoxene, monazite, mtile, xenotime, and zircon. Commercially pure zircon sand typically contains 64% zirconium oxide, 34% siUcon oxide, 1.2% hafnium oxide, and 0.8% other oxides including aluminum, iron, titanium, yttrium, lanthanides, uranium, thorium, phosphoms, scandium, and calcium. 

The thin films of those obtained RPO4 NPs of 2-5 ran in size could be fabricated via spin coating. Therefore, the NEXAFS studies could be carried out (Suljoti et al., 2008). The results show that the light lanthanides tend to form monoclinic monazite phase of 3-5 nm in size and the heavy lanthanides tend to form the tetragonal zircon phase of 3-5 nm in size, while the medium lanthanides tend to form a mixture of the two phases with 2 nm in sizes. 

Segadaes et al. [79] Cooper and Hall [80] and Morgan and Marshall [81] have proposed the use of j3-aluminas, the related magnetoplumbite oxides, micaceous materials, and monazites as interface coatings for ceramic matrix composites. The principle... 

More recently, Morgan and Marshall have suggested that compounds having the monazite crystal structure may be useful oxidation interface coatings. Specifically, they recommend the compound LaP04. Their sol-gel experiments with this compound are encouraging. 

Goettler, R.W., and S. Sambasivan. 1996. Slurry and solution derived monazite fiber coatings for sol-gel oxide matrix CFCC. Presented at the American Ceramic Society 98th Annual Meeting and Exposition (paper no.B-185-96 replacement), April 14-17, 1996, Indianapolis, Indiana. 

Monazites and xenotimes are two classes of weak oxide coatings that satisfy the criteria for crack deflection for the currently available fibers [84, 85]. Of these, monazite (LaP04) has been the most widely studied. 

At the current time, liquid precursor (solution/sol/slurry) coating techniques have been the most successful for the deposition of oxides, such as monazite (LaP04) and porous oxides (carbon-oxide mixtures) onto oxide fiber tows [178, 179, 191, 192]. Atypical fiber coater is shown in Figure 10a [193]. In the coating process, a lighter, immiscible liquid is floated on the surface of the coating precursor. The immiscible liquid is used to remove excess sol from the coated tow and it allows for the coating of individual filaments with... 

K. K. Chawla, H. Liu, J. Janczak-Rusch, and S. Sambasivan, Microstmcture and properties of monazite (LaP04) coated saphikon fiber/alumina matrix composites, J. Eur. Ceram. Soc., 20 551—559 (2000). 

K. A. Keller, T. Mah, E. E. Boakye, T. A. Parthasarathy, and P. Mogilevsky. Evaluation of Dense Monazite Fiber-Coatings in Oxide-Oxide Minicomposites. Presented at the 27th Annual Cocoa Beach Conference Exposition on Advanced Ceramics Composites. Cocoa Beach, FL, January 29, 2003, 2003. 

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