Fiber quartz

Quartz fibers are made firom natural quartz crystals by softening quartz rods in an oxy-hydrogen flame and drawing rods into filaments. Because high purity quartz crystals are rare, the cost of quartz fibers is considerable higher than that of glass fiber and high silica fibers. 

Quartz filaments have assumed a role as high-temperature resistant fibers, and are produced in considerable quantities for high temperature and corrosion-resistant applications. They are widely used as filtration and insulation materials at temperatures above those of mineral silicate fibers. Quartz and silica fiber RPs are used in jet aircrafts, rocket nozzles, nose cones, and reentry heat shields for spacecraft. 

Information on fibers applicable to different materials of construction and use that relates to compositions, surface treatments, performances, processing, and terminology follows  

Fiber Fiber is a general term used to refer to filamentary materials. Often it is used synonymously with filament, monofilament, whisker, and yarn. It is any material in a form such that it has a 

abaca The plant Musa textiles provides 6 to 12 ft (1.8 to 3.6 m) long fiber bundles used in the manufacture of ropes, cables, and RPs. 

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Gaseous and particulate pollutants are withdrawn isoldnetically from an emission source and collected in a multicomponent sampling train. Principal components of the train include a high-efficiency glass- or quartz-fiber filter and a packed bed of porous polymeric adsorbent resin (typically XAD-2 or polyurethane foam for PCBs). The filter is used to collect organic-laden particulate materials and the porous polymeric resin to adsorb semivolatile organic species (com-... 

For PHg, a variety of different filter methods have been applied, such as Teflon or quartz fiber filters. Before analysis, these filters undergo a wet chemical digestion usually followed by reduction-volatilization of the Hg to Hg(0) and analysis using cold vapor atomic absorbance spectrometry (CVAAS) or cold vapor atomic fluorescence spectrometry (CVAFS). Recently, a collection device based on small qrrartz... 

This Chapter provides information on available certified reference and quahty control materials relevant for use in the measurement of airborne contaminants in occupational hygiene. The majority of measurements made in this area worldwide are solvents, dust (total, respirable), elements, oil mist, quartz, fiber identification (asbestos, man-made fibers), mists and gases. 

Inclusion of inorganic compounds such as graphite, quartz fiber felt, days and metal oxides is another way to modify the porosity of the sol-gel matrices... 

The newest electroscope utilizes a quartz fiber and has many advantages over the gold-leaf type. It is portable, less dependent on position, much smaller in size, and more sensitive. The capacity of the quartz fiber electroscope is about 0.2 pico-farads, and its voltage sensitivity is about one volt per division on the scale. The sensitive element is a fine gold plated quartz fiber mounted on a parallel metal support. Figure 22 illustrates a quartz fiber electroscope. 

Charging causes the quartz fiber to be deflected from the support. 

A fiber optic immunosensor (FOI) has also been reported for detection of PCBs in Aroclors [204]. The quartz fiber surface is coated with PAbs against PCBs and the competitive assay takes place using as fluorescent tracer, an analog of the analyte coupled to 2,4,5-trichlorophenoxybutyrate (TCPB) on the Ab-coated fiber. The LOD achieved is around 10 pg L L... 

In. samples were taken with a small spatula from a 10 cm x 10 cm area, while the 1-6 and 6-12 In. samples were taken using a 2 In. diameter soil core sampler. Air samples were taken at the downwind edge of each bed by running a high volume air sampler with a quartz fiber filter backed with 120 mL of XAD-4 resin for 2 hr. 

Frondel, C. (1985). Systematic compositional zoning in the quartz fibers of agates. Amer. Min. 70 975—979. 

The vane is suspended from a graduated torsion head by a quartz fiber 15 cm. long and 0.002 cm. in diameter. The pressure of the waves rotates the vane. In the experiment the rotation is more than 50 degrees when dry air is flowing through the tube. With the aid of a mirror attached to the vane and a lamp and scale about 60 cm. away the vane can be tmned back to the original position. The amoimt of rotation, of the torsion head which is required to accomplish this is taken as a measure of the intensity of the emergent beam. 

FIGURE 9.61 Surface area normalized gas-particle partition coefficients as a function of liquid vapor pressure for some alkanes and PAHs on urban particulate matter (UPM) and quartz fiber filters (QFF) at 30% RH and 70% RH (adapted from Storey et al., 1995 data for UPM from Yamasaki el al. (1982) and Foreman and Bidle-nian (1990)). 

Filters collect liquid and solid particles by mechanisms including diffusion, impaction, interception, electrostatic attraction, and sedimentation onto the filter while allowing the gas to pass through. The types commonly used in atmospheric particulate collection are membranes, fibrous mats, or porous sheets. Different filter materials are used depending on the particular type of measurement being carried out, including Teflon, quartz fiber, nylon, silver, cellulose filters, glass fibers, and polycarbonate. The characteristics of each are summarized by Chow (1995). 

Stutz, J., and U. Platt, Improving Long-Path Differential Optical Absorption Spectroscopy with a Quartz-Fiber Mode Mixer, Appl. Opt., 36, 1105-1115 (1997). 

Bell (1981) (see also Bell and Bickel, 1981) measured all matrix elements for fused quartz fibers of a few micrometers in diameter with a photoelastic polarization modulator similar to that of Hunt and Huffman (1973) the HeCd (441.6 nm) laser beam was normal to the fiber axes. Advantages of fibers as single-particle scattering samples are their orientation is readily fixed and they can easily be manipulated and stored. Two of the four elements for a 0.96-jtim-radius fiber are shown in Fig. 13.16 dots represent measurements and solid lines were calculated using an earlier version of the computer program in Appendix C. Bell was able to determine the fiber radius to within a few tenths of a percent by varying the radius in calculations, assuming a refractive index of 1.446 + iO.O, until an overall best fit to the measured matrix elements was obtained. 

Figure 13.16 Two of the four matrix elements for a fused quartz fiber of radius 0.96 jam illuminated by light of wavelength 0.4416 /im. The solid curves are calculations, the dots are measurements. From Bell (1981). 

The composition of the carbonaceous species retained by sorption on sampling media has rarely been evaluated. Fung (59) reported that the carbonaceous materials retained by sorption on quartz-fiber filters were relatively polar organic compounds, including phthalate esters and nitrogen-containing heterocyclic compounds. Additional studies of this type would be very helpful. 

Figure 6. A denuder-dual filter system for investigating the organic positive artifact on quartz-fiber filters. (Reproduced with permission from reference...

Table V. Comparison of Organic and Elemental Carbon Analyses With and Without the Quartz-Fiber Filter Denuder (n = 18) ...

Our water-column sampling techniques include in-line filtration using an all-Teflon sampling device with quartz fiber filters (0.7- xm nominal size cutoff) to differentiate between dissolved and particulate phases (21). Particulate concentrations (nanograms per gram) and subsequent calculations of partitioning between particle and aqueous phases (log KD) are based on this particle size division. This fractionation scheme precludes direct estimates of colloidal influences on Hg transport. 

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