Fibers spectroscopy

Knezovich, J. P. Bishop, D. J. Kulp, T. J., et al., Anaerobic Microbial Degradation of Acridine and the Application of Remote Fiber Spectroscopy to Monitor the Transformation Process. Environ. Toxicol. Chem., 1990 pp. 1235-1243. 

Silica fibers - [SPECTROSCOPY, OPTICAL] (Vol 22) -coupling of NLO materials [NONLINEAR OPTICAL MATERIALS] (Vol 17) -use in infrared technology [INFRARED TECHNOLOGY AND RAMAN SPECTROSCOPY - INFRARED TECHNOLOGY] (Vol 14)... 

This article will concern itself only with devices that involve a chemical or biochemical transduction mechanism to generate the analytical information, with the processes occurring in a membrane or layer attached to the probe in such a manner that the analytical information can be accessed electronically from the outside world. This covers sensors that are for single use and for continuous monitoring because the basic chemistry and sensor configuration used are very similar for a particular application. Hence, the article does not cover techniques such as open-cell Fourier transform infrared or remote fiber spectroscopy, which can be used to sense the chemical nature of the environment without involving the use of a bona fide sensor. 

Aerospace struetwes made of composite. As part of the evaluation of the developed ultrasonic spectroscopy system the NSC software was tested on ultrasonic resonance spectra from composite panel samples. Spectra were collected with four different types of damages, and from flawless samples. The damages included a small cut in one of the carbon fiber... 

Ren B, Li W H, Mao B W, Gao J S and Tian Z Q 1996 Optical fiber Raman spectroscopy combined with scattering tunneling microscopy for simultaneous measurements ICORS 96 XVth Int. Conf on Raman Spectroscopy ed S A Asher and P B Stein (New York Wley) pp 1220-1... 

Instrumental Analysis. It is difficult to distiaguish between the various acryhcs and modacryhcs. Elemental analysis may be the most effective method of identification. Specific compositional data can be gained by determining the percentages of C, N, O, H, S, Br, Cl, Na, and K. In addition the levels of many comonomers can be estabhshed usiag ir and uv spectroscopy. Also, manufacturers like to be able to identify their own products to certify, for example, that a defective fiber is not a competitor s. To facihtate this some manufacturers iatroduce a trace of an unusual element as a built-ia label. 

Polyester composition can be determined by hydrolytic depolymerization followed by gas chromatography (28) to analyze for monomers, comonomers, oligomers, and other components including side-reaction products (ie, DEG, vinyl groups, aldehydes), plasticizers, and finishes. Mass spectroscopy and infrared spectroscopy can provide valuable composition information, including end group analysis (47,101,102). X-ray fluorescence is commonly used to determine metals content of polymers, from sources including catalysts, delusterants, or tracer materials added for fiber identification purposes (28,102,103). 

Microscopy (qv) plays a key role in examining trace evidence owing to the small size of the evidence and a desire to use nondestmctive testing (qv) techniques whenever possible. Polarizing light microscopy (43,44) is a method of choice for crystalline materials. Microscopy and microchemical analysis techniques (45,46) work well on small samples, are relatively nondestmctive, and are fast. Evidence such as sod, minerals, synthetic fibers, explosive debris, foodstuff, cosmetics (qv), and the like, lend themselves to this technique as do comparison microscopy, refractive index, and density comparisons with known specimens. Other microscopic procedures involving infrared, visible, and ultraviolet spectroscopy (qv) also are used to examine many types of trace evidence. 

The ease of sample handling makes Raman spectroscopy increasingly preferred. Like infrared spectroscopy, Raman scattering can be used to identify functional groups commonly found in polymers, including aromaticity, double bonds, and C bond H stretches. More commonly, the Raman spectmm is used to characterize the degree of crystallinity or the orientation of the polymer chains in such stmctures as tubes, fibers (qv), sheets, powders, and films... 

More recently, Raman spectroscopy has been used to investigate the vibrational spectroscopy of polymer Hquid crystals (46) (see Liquid crystalline materials), the kinetics of polymerization (47) (see Kinetic measurements), synthetic polymers and mbbers (48), and stress and strain in fibers and composites (49) (see Composite materials). The relationship between Raman spectra and the stmcture of conjugated and conducting polymers has been reviewed (50,51). In addition, a general review of ft-Raman studies of polymers has been pubUshed (52). 

Instrumental Methods for Bulk Samples. With bulk fiber samples, or samples of materials containing significant amounts of asbestos fibers, a number of other instmmental analytical methods can be used for the identification of asbestos fibers. In principle, any instmmental method that enables the elemental characterization of minerals can be used to identify a particular type of asbestos fiber. Among such methods, x-ray fluorescence (xrf) and x-ray photo-electron spectroscopy (xps) offer convenient identification methods, usually from the ratio of the various metal cations to the siUcon content. The x-ray diffraction technique (xrd) also offers a powerfiil means of identifying the various types of asbestos fibers, as well as the nature of other minerals associated with the fibers (9). 

Infrared spectroscopy can also be used incisively to identify the six main varieties of asbestos fibers. Specific absorption bands in the infrared spectmm can be associated with the asbestos fibers, first in the 3600 3700 cm range (specific hydroxyl bands) and, second, in the ranges 600—800 and 900 1200 cm (specific absorption bands for various siUcate minerals (10)). 

FIGURE 12.4 Wide scan x-ray photoelectron spectroscopy (XPS) images of unaged and aged melamine fiber filaments. (From Rajeev, R.S., Bhowmick, A.K., De, S.K., Gong, B., and Bandyopadhyay, S., J. Adh. Set Technol., 16, 1957, 2002. With permission.)... 

Goldman, A. et al.. Fiber laser intracavity absorption spectroscopy of ammonia and hydrogen cyanide in low pressure hydrocarbon flames, Chem. Phys. Lett., 423, 147, 2006. 

---