Oxygen-carbon tetrafluoride

Tetrafluoroethylene undergoes addition reactions typical of an olefin. It bums in air to form carbon tetrafluoride, carbonyl fluoride, and carbon dioxide (24). Under controlled conditions, oxygenation produces an epoxide (25) or an explosive polymeric peroxide (24). Trifluorovinyl ethers,... 

In the absence of air, TEE disproportionates violently to give carbon and carbon tetrafluoride the same amount of energy is generated as in black powder explosions. This type of decomposition is initiated thermally and equipment hot spots must be avoided. The flammability limits of TEE are 14—43% it bums when mixed with air and forms explosive mixtures with air and oxygen. It can be stored in steel cylinders under controlled conditions inhibited with a suitable stabilizer. The oxygen content of the vapor phase should not exceed 10 ppm. Although TEE is nontoxic, it may be contaminated by highly toxic fluorocarbon compounds. 

The gas escaping at the anode contains about 90 % Fa after the hydrogen fluoride has ]jeen condensed by cooling the remainder consists of oxygen, carbon dioxide, silicon tetrafluoride and carbon fluorides. At an anode current density of 10 A per sq. dm current efficiency equals 95 to 99 per cent. The output of one cell is on the average 1 kg of fluorine per hour. The electrolyte content lasts about one year and then it must be replaced. 

TEE (molecular weight 100.02) is a colorless, tasteless, odorless nontoxic gas [11]. It is stored as a liquid (its vapor pressure at -20°C is 1 MPa) and polymerized usually above its critical temperature of 33.3°C (91.9°E) and below its critical pressure 3.94 MPa (571 psi). The polymerization reaction is exothermic. In the absence of air it disproportionates violently to yield carbon and carbon tetrafluoride. This reaction generates the same amount of energy as an explosion of black powder. The decomposition is initiated thermally therefore, the equipment used in handling and polymerization of TFE has to be without hot spots. The flammability limits are 14% to 43% TFE burns when mixed with air and forms explosive mixtures with air and oxygen. The ignition temperature is 600°C to 800°C (1112°F to 1472°F) [12]. When stored in a steel cylinder it has to be under controlled conditions and with a suit-... 

Oxygen dilluoride reacts rapidly with selected alkenes at low temperatures 40 however, per-fluoroalkenes are less reactive than the corresponding alkylalkenes and require either thermal or ultraviolet activation.41 The oxidation, which is a homogeneous chain reaction,42 of hexa-fluoropropene, tetrafluorocyclopropene, and perfluorobut-2-ene all give a variety of products such as carbon tetrafluoride. carbonyl difluoride, hexafluoroethane, oxiranes, and other oxidation products.41 This reaction is not useful for preparative organic work. 

Urethane acrylate polymer Silica dioxide Carbon tetrafluoride and oxygen plasma Company informationa 0... 

A flow diagram of the chromatographic apparatus with the pressurizing manifold is shown on Fig. 7. The column is pressurized at ambient temperature with the mixture of helium and carbon tetrafluoride to 1000 psi. The valves at either end of the column retain the gas mixture in the column while the pressurizing manifold is evacuated. The pressurized column is then plunged, valves and all, into the liquid-oxygen bath to permit the carbon tetrafluoride to condense uniformly throughout the column bed. After the column... 

F2O Oxygen fluoride, 1 109 F4C Carbon tetrafluoride, 1 34 FeS SuEur(VI) fluoride, 1 121 FeSe Selenium(VI) fluoride, 1 121 FeTe Tellurium(VI) fluoride, 1 121 Fe(CO)4H2 Iron tetracarbonyl dihydride, 2 243... 

Recently, an increasing amount of nitrogen trifluoride is being used in the semiconductor industry as a dry etchant, showing significantly higher etch rates and selectivities when compared to carbon tetrafluoride and mixtures of carbon tetrafluoride and oxygen. 

Carbon tetrafluoride is used as a low temperature refrigerant gas. It is also widely employed by the electronics industry as a dry etchant in microchip manufacture. It is blended with oxygen and used to desmear and etch-back through holes on printed circuit boards. 

Carbon tetrafluoride is considered to be nontoxic. The major hazard of overexposure to carbon tetrafluoride is the exclusion of an adequate supply of oxygen therefore, it should be treated as a simple asphyxiant. 

A commercial 4H-SiC (0001) wafer was used as a specimen. A gas mixture of helium, carbon tetrafluoride and oxygen was used as the reactive gas. Table 19.1 shows the removal rates of both Si- and C faces of the SiC wafer under various experimental conditions. We achieved a high removal rate of 4 gm/min for the Si face and 8 gm/min for the C face. It is shown that the removal rates of the C face are higher than those of the Si face. In most cases, the former are twice the latter. Generally, the oxidative rate of SiC varies with the SiC surface orientation, and the C face is oxidized more rapidly than the Si face. Thus, there is a possibility that oxidation plays a prominent role in the etching of SiC. 

For the diatomic molecules that were studied—nitrogen, oxygen, nitric oxide, and carbon monoxide—the concept of a Coulomb explosion appears to be relevant. The yield of atomic ions is high, 93% to 97%, and the ion kinetic energies of around 7 eV for +1 ions and about twice this value for -1-2 ions are consistent with the Coulomb repulsion model. For the polyatomic molecules the situation is different. The yield of atomic ions drops to 85% for carbon dioxide and to 74% for carbo i tetrafluoride. For excitation of a core to bound state resonance in nitrous oxide, involving the terminal nitrogen atom, the yield of atomie ions is only 63% (Murakami et al. 1986). These molecules do not simply explode following excitation of a core electron. 

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