Quartz filaments

Quarz-faden, m. quartz thread, quartz filament, -fels, m. quartz rock, quartzite, -fenster, n. quartz window, quarzfrei, a. free from quartz. 

Figure 3a. Boron on quartz filament emerging from broken end (165X)...

Other samples of boron-coated 1.0-mil quartz filament show only two broad diffuse halos. No lines indicating B203 were seen. No positive identification of the material was possible from the data. 

E. Saunders, M. Weinstein, A. I. Mlavsky, Radiant Energy Reactor Technique for the Deposition of SiC onto Quartz Filaments, Proc. Conf. Chemical Vapor Deposition of Refractory Metals, Alloys, and Comp., American Nuclear Society, Hinsdale, IL, 1967, pp. 1X1-21. 

The vapor-pressure measurements were carried out with hexa sublimed in high vacuum. Pressures of 10 to 10 mm. Hg, corresponding to 20 to 85°, were measured with a quartz filament manometer 2, S). At temperatures of 120 to 210° a simple mercury manometer was used, and the vapor pressures were obtained by extrapolating the pressure-time curves plotted in Fig. 1 to time zero. 

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. 

Figure 14. Schematic rod drawing process from quartz preforms. A large diameter siiica preform rod (1) is heated in a circumferentiai heater, i.e., a gas burner, an eiectncal furnace or laser source. (2) the molten jet solidifies and the resulting quartz filament (3) is passed over a sizing device (4) and collected on a winding dmm (5). Redrawn from M. S. Aslanova, Glass fibers, page 34, Khimia Publisher (in Russian), Moscow (1979).

If a film is deposited on the quartz surface, the adhesion of the filaments is due to molecular surface forces in the film material, and the quartz filaments themselves constitute a peculiar kind of dynamometer [87]. The principle of the improved apparatus is shown in Fig. 11.18, The force of interaction between the filaments is measured by reference to the torsional angle of filament 1. 

Knapschinsky, L., Katz, W., Ehmke, B. and Sonntag, H., Interaction forces between crossed quartz filaments in presence of adsorbed poly(vinyl alcohol). Colloid Polym. Sci., 260, 1153-1156 (1982)... 

The experiment was carried out in a reaction cell shown in Fig. 3.3 with inner walls covered by a zinc oxide film having thickness 10 pm [20]. The surface area of the measuring film on the quartz plate was about 1/445 of the total film area on the wall of the vessel. The results of direct experimental measurements obtained when the adsorbent temperature was -196 C and temperature of pyrolysis filament (emitter of H-atoms) 1000°C and 1100°C, are shown on Fig. 3.4. One can see a satisfactory linear dependence between parameters A r (the change in film conductivity) and APh2 (reduction of hydrogen pressure due to adsorption of H-atoms), i.e. relations... 

Fig.4.3. Experimental arrangement for investigation of pyrolysis of molecules by the method of semiconductor sensors 1 - reaction vessel, 2 - quartz slab with a ZnO film (sensor), 3 - filter, 4 - contacts, 5 - incandescent filament, 6 - thermocouple, 7 - cell with a substance, 8 - lamp - manometer, 9 - pin, 10 - flask, 11 - sealing bulkhead, 12 - trap, 13 - thermostat.

Pulse-mode pyrolyzers include resistively-heated electrical filaments or ribbons and radio frequency induction-heated wires [841,842,846,848,849]. The filament or ribbon-type pyrolyzers are simple to construct. Figure 8.45, and typically consist of an inert wire or ribbon (Pt or Pt-Rh alloy) connected to a high-current power supply. Samples soluble in a volatile solvent are applied to the fileutent as a thin film. Insoluble materials are placed in a crucible or quartz tube, heated by a basket-lilce shaped or helical wound filiunent. The coated filament is contained within a low dead volume chamber through which the carrier gas flows, sweeping the pyrolysis products onto the column. The surface temperatui of the filament is raised rapidly from ambient temperature to He equilibrium pyrolysis temperature. This... 

Steinfeld et al. [133] demonstrated the technical feasibility of solar decomposition of methane using a reactor with a fluidized bed of catalyst particulates. Experimentation was conducted at the Paul Scherrer Institute (PSI, Switzerland) solar furnace delivering up to 15 kW with a peak concentration ratio of 3500 sun. A quartz reactor (diameter 2 cm) with a fluidized bed of Ni (90%)/Al2O3 catalyst and alumina grains was positioned in the focus of the solar furnace. The direct irradiation of the catalyst provided effective heat transfer to the reaction zone. The temperature was maintained below 577°C to prevent rapid deactivation of the catalyst. The outlet gas composition corresponded to 40% conversion of methane to H2 in a single pass. Concentrated solar radiation was used as a source of high-temperature process heat for the production of hydrogen and filamentous... 

Incidentally, these different scattering patterns explain why a car headlamp causes more scattering with a quartz-halogen bulb than with a standard tungsten filament, because of their differing wavelengths and power. 

Using Pyrex ampoules with resistively heated tungsten wire or strip filaments, protactinium metal has been prepared on the milligram scale (9,13,15). An improved technique is to use a quartz van Arkel-De Boer bulb with an inductively heated W sphere which solves the previous problem of filament breaking and considerably improves the deposition rate of Pa metal (109). 

Figure 13 shows a photocell used recently for work-function measurements (43). A metal coating inside the cell serves as the anode, and B is the cathode, which may be a metal foil or a film previously evaporated from a filament at C. Also provided at C are a W emitter for bombarding the cathode surface and a Pt electrode for thermally dissociating gas molecules. The monochromatic light which passes through the quartz window Q strikes the cathode B, and its energy can be measured by a calibrated photocell. 

Figure 12.8—Xenon arc lamp used influorimetry. The pressure of xenon in the lamp is in the order of 1 MPa. The lamp, made from a quartz envelope and without a filament, produces polychromatic (white) light whose power is wavelength dependent. (Reproduced by permission of Oriel.)...

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