Coatings for Fibers

A newer addition is in-tube SPME that makes use of an open capillary device and can be coupled online with GC, HPLC, or LC/MS. All these techniques and their utilization in pharmaceutical and biomedical analysis were recently reviewed by Kataoka.45 Available liquid stationary fiber coatings for SPME include polydimethylsiloxane (PDMS) and polyacrylate (PA) for extracting nonpolar and polar compounds, respectively. Also in use for semipolar compounds are the co-polymeric PDMS-DVB, Carboxen (CB)-PDMS, Carbowax (CW)-DVB, and Carbowax-templated resin (CW-TPR). A few examples of in-tube SPME extractions from biological matrices are shown in Table 1.19 and drawn from Li and coworkers.166... 

Katzmann. H.A. (1987). Fiber coatings for the fabrication of graphite reinforced magnesium composites. J. Mater. Sci. 22, 144. 

Fiber coating for improved energy absorption capability... 

SPME (Figure 2.48) can be conducted as a direct extraction in which the coated fiber is immersed in the aqueous sample in a headspace configuration for sampling air or the volatiles from the headspace above an aqueous sample in a vial (headspace SPME analyses are discussed elsewhere) or by a membrane protection approach, which protects the fiber coating, for analyses of analytes in very polluted samples [136]. The SPME process consists of two steps (Figure 2.49) (a) the sorbent, either an externally coated fiber or an internally coated tube, is exposed to the sample for a specified period of time (b) the sorbent is transferred to a device that interfaces with an ana-... 

Cladding for optical fibers Coating for magnetic recording tape Coatings for textiles and leather Housings for office machines... 

Cladding for optical fibers Coating for magnetic recording tape Coatings for textiles and leather Housings for office machines Source Brady, R. F., Jr. in Modem Fluoropolymers (Scheirs, J., Ed.), John Wiley Sons, New York, p. 130, 1997 (With permission). 

A.T. Hunt, CCVD Processing of Lanthanum Phosphate and Beta-Alumina Fiber Coatings for Mullite Matrix Composites, Contract DM19561712, NSF SBIR Phase 1 Grant, 1996. 

M.K. Cinibulk et al., Porous yttrium aluminum garnet fiber coatings for oxide composites. J. Am. Ceram. Soc. 85(11), 2703-2710 (2002). 

The trimeric dimethylaluminum amide, [Me2Al(NH2)]2 (19), was originally used as a single source precursor for growth of AIN under LPCVD conditions using a hot walled reactor [192], although subsequent deposition was also demonstrated in a cold walled system [193]. While the films showed promise as fiber coatings for composites, film quality was never demonstrated for electronic applications. 

This section centers on fiber coatings for non-oxide eomposites in which either the fiber or the matrix is a non-oxide ceramic. Although oxide fiber-reinforced composites have been studied, most of the research available in the literature has focused on SiC fiber-reinforced composites. For example, mullite (3Al203-2Si02) fiber-reinforced SiC matrix composites have been fabricated by CVI (chemical vapor infiltration). However, SiC fiber-reinforced SiC matrix (SiC/SiC) composites are superior for the following reasons (1) mullite fiber-reinforced composites do not improve resistance to oxidation, one of the major factors limiting the use of non-oxide composites and (2) SiC fibers have mechanical properties superior to those of mullite fibers. This section will be concerned primarily with SiC fiber-reinforced ceramic composites, which offer the best oxidation resistance of any non-oxide fiber at high temperatures (particularly above 1,100°C [2012°F]). 

FIGURE 6-3 Depth of oxidation of fiber coatings for uniaxial SiC/C/SiC composites with fiber ends exposed. All of the data is for Nicalonreinforced composites made by CVI. Source Luthra, 1994. 

CVD is the most common method of depositing fiber coatings for composite systems because it is a conformal process that can deposit fairly uniform coatings on a wide variety of structures. CVD is perhaps the only method that has been used successfully to provide tough composites with acceptable mechanical properties. A wide variety of coatings have been deposited by CVD, including carbon, BN, silicon-doped BN, Si3N4, and SiC. 

Goettler, R.W. 1996. Oxide fiber coatings for Nextel 610 and Nextel 720 fibers. Presented at the 1996 Conference and Exposition on Composites, Advanced Ceramics, Materials and Structures (paper no. SI-13-96F), January 7-11, 1996, Cocoa Beach, Florida. 

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. 

Goettler, R.W., S. Sambasivan, and V.P. Dravid. 1997a. Isotropic complex oxides as fiber coatings for oxide-oxide CFCC. Ceramic Engineering and Science Proceedings 18(3) 279-286. ... 

Luthra, K.L. 1997b. Oxidation resistant fiber coatings for non-oxide ceramic composites. Journal of the American Ceramic Society 80(12) 3253-3257. 

Misra, A.K. 1994. Current static and future direction of fibers and fiber coatings for MMCs and IMCs. (NASA CP 10146) HiTemp Review 71 1-12. ... 

G.S. Corman and K.L. Luthra, Silicon-Doped Boron Nitride Fiber Coatings for Melt Infiltrated Composites, presented at the 24 annual Conference on Composites, Materials and Stmctures, Cocoa Beach, FL, January 24-28,2000. 

R. W. Goettler, S. Sambasivan, and V. P. Dravid, Isotropic Complex Oxides as Fiber Coatings for Oxide-Oxide CFCC, Ceram. Eng. Sci. Proc., 18 [3] 279-286 (1997). 

Pawliszyn, 1995). In SPME, a phase-coated fiber housed within a syringe is exposed to the sample medium (water or air), allowing the analytes to be adsorbed on the fiber coating. For organic compounds having high partition coefficients, adsorption equilibrium can be attained within minutes. After sample adsorption, the fiber is withdrawn into the needle, which is then inserted into the heated injection port of the GC. The adsorbed analytes are thermally desorbed and analysis proceeds in the same manner as in normal GC/MS analysis. 

Farced, A. S., Schiroky, G. H., and Kennedy, C. R. (1993). Development of BN/SiC duplex fiber coatings for fiber-reinforced aluminia matrix composites fabricated by directed metal oxidation. Ceram. Eng. Sci. Proc. 18 794-801. 

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