Coated filaments

Oxyd-chlorid, n. oxychloride, -einschluss, m. oxide inclusion, -faden, m. Elec.) oxide-coated filament, -firms, m. oxide varnish (thickened drying oil). 

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... 

A C.P.D. method was adopted by Bosworth and Rideal (95, 119) to investigate the evaporation of Na from a W filament. Desorption was accompanied by a negative drift in the S.P. when the coated filament was held at a temperature in the range 610° to 795° K., and the resulting S.P.-time curves were converted into coverage-time curves by the use of calibration data previously obtained. The results represent the mutual effect of adsorption and desorption processes on the W filament. Hence, the heat of evaporation E wav iiaay be calculated from the temperature coefficient of... 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

Sie et al. [601—603] analysed silicon and tin in different alloys and steel samples. A sample of the material (1-50 mg) was heated at 600-900° C in a quartz tube, which was then washed with chlorine. Chlorides were trapped in a colum packed with 15% of Kel-F 40 on Haloport F and analysed on the same column at 75°C. With the use of a gas-density balance and PTFE-coated filaments a sensitivity of 50 ppm was obtained for silicon. The analysis time of 15—20 min can be reduced to 10 min. 

As shown in Figure 1, there are two thermal conductivity detectors with Teflon-coated filaments and thermostated at 125 °C. One is located immediately after the catalyst and measures retention volume and surface area. The second detector is located after the analytical column and analyzes feed and product samples. This detector output at maximum... 

W.J. Heffernan, I. Ahmad, R.W. Haskell, A Continuous CVD Process for Coating Filaments with Tantalum Carbide, Proc. 4th Int. Conf. on CVD, The Electrochemical Society, Inc., Princeton, NJ, 1973, pp. 498-508. 

This was the first serious study of the vapour pressure of thoria. Weighed tungsten filaments coated with thoria were in heated in vacuo for a known period and the resultant mass loss determined directly. The brightness temperature of the filament was measured pyrometrically, and corrected to true temperature from a cahbration curve obtained from another thoria-coated filament to which a Mo-W thermocouple was welded. Similar measurements were made using a molybdenum filament, with results indistinguishable from those from tungsten filaments. 

Most modern lamps of this type contain deuterium unijjirc of a low-voltage type in which an, irc is formed between a heated, oxide-coated filament and a metal elecirode (see Figure 1,3 I la). The heated filament provides electrons to maintain a direct current when about 40 V is applied between the filament and the electrode. A regulated power supply is required for constant Intensities. 

In the heat of combustion type there is a catalyst-coated filament that is kept heated at a certain temperature. When the gas sample passes over the filament, it is burned and the heat of combustion changes the filament resistance. This change in resistance also changes the electrical conductivity of the filament. This conductivity is proportional to the concentration of the contaminant in the air. The general practice for calibrating these instruments in industry is to calibrate them with specific gases (for example, methane) and use a table of response factors for other gases. 

Materials used to coat filament bundles - usually contains a coupling agent to to improve the fibre to resin bond, a lubricant to prevent abrasion and a binder to preseve integrity of a filament bundle. 

A composite laminate analysis of the coated filament woimd mbing was carried out using a Fortran program. The catheter was treated as a thin walled cylinder composed of fom layers of material as follows. 

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