Carbon tube furnaces

Preparation. Boron carbide is most commonly produced by the reduction of boric oxide with carbon in an electric furnace between 1400 and 2300°C. In the presence of carbon, magnesium reduces boric oxide to boron carbide at 1400—1800°C. The reaction is best carried out in a hydrogen atmosphere in a carbon tube furnace. By-product magnesium compounds are removed by acid treatment. 

In iadustrial production of titanium carbide, pure (99.8%, with minor impurities of Si, Fe, S, P, and alkahes) titanium oxide [13463-67-7] Ti02, iu the dry or wet state is mixed iu 68.5 31.5 ratio with carbon black or finely milled low ash graphite. The dry mixture is pressed iato blocks that are heated iu a horizontal or vertical carbon-tube furnace at 1900—2300°C hydrogen that is free of oxygen and nitrogen serves as protective gas. In the vertical push-type furnaces, the Hberated CO itself provides protection. 

Ct202 and 26 wt % carbon black can be heated in carbon-tube furnaces at 1600°C in the presence of hydrogen, giving a carbide containing 13—13.3 wt % total C and 0.1—0.3 wt % free C. 

Greenwood used the apparatus shown in Fig. 12. VIII J. The main part of the apparatus was the carbon tube furnace with a side-tube for observing through a suitable window by a Wanner p)n ometer ( 16.VIB) the temperature of an inner tube of graphite containing the molten metal. The surface of the metal... 

Carbothermal reduction-nitridation The process was carried out by heating the impregnated SBA-15 slowly in a carbon tube furnace to 1400-1450 °C for 4-6 h under N2 at a flow rate of 600 ml/min. The products are denoted as S-T-t (where T refers to the temperature, t refers to the holding time). Excess carbon was removed by calcining the product in air at 600 °C for 6 h. 

There are many other uses for carbon in laboratories and in industries. Molds and plungers for hot pressing metallic powders are made from carbon, as are laboratory crucibles. It is a resistor in carbon tube furnaces and is used as an inductor in high frequency furnaces. Carbon is used in rocket engines and in heat transfer systems. Graphite is used as a moderator in some nuclear reactor cores. 

The concentrates were subsequently analysed for arsenic using Varian-Techtron AAS atomic absorption spectrophotometer fitted with a Perkin-Elmer HGA 72 carbon furnace, linked to a zinc reductor column for the generation of arsine (Fig. 5.3). A continuous stream of argon was allowed to flow with the column connected into the inert gas line between the HGA 72 control unit and the inlet to the furnace. Calcium sulfate (10-20 mesh) was used as an adsorbent to prevent water vapour entering the carbon furnace. The carbon tube was of 10 mm id and had a single centrally located inlet hole. 

The production of an homogeneous atomic vapour from a sample is achieved by aspirating a solution into a flame or evaporating small volumes in an electrically heated tube furnace or from the surface of a carbon rod. In all cases, the thermal energy supplied must (a) evaporate the solvent and (b) dissociate the remaining solids into their constituent atoms without causing appreciable ionization. 

Two forms of flameless atomizer are in use, i.e. the graphite tube or L Vov furnace and the carbon rod or filament. Of these the first has proved to be the most generally effective and popular. It is widely used in a variety of modifications. In both cases, the temperature is raised rapidly to about 2500 K by the passage of a heavy current for a period of 1-2 minutes. Tube furnaces, which are usually 5 or 10 cm x 3 mm, may be flushed through with argon before vaporizing the sample so as to prevent the formation of... 

Nebulization is inefficient and therefore not appropriate for very small liquid samples. Introducing samples into the plasma in liquid form reduces the potential sensitivity because the analyte flux is limited by the amount of solvent that the plasma will tolerate. To circumvent these problems a variety of thermal and electrothermal vaporization devices have been investigated. Two basic approaches are in use. The first involves indirect vaporization of the sample in an electrothermal vaporizer, e.g. a carbon rod or tube furnace or heated metal filament as commonly used in atomic absorption spectrometry [7-9], The second involves inserting the sample into the base of the... 

Two commercial coal-tar-pitch-based carbon fibres, which were supplied by Osaka Gas Co., Ltd. (Osaka, Japan), have been used as starting materials. In the course of their synthesis, these CFs had been carbonised at different temperatures Tc = 1273 K (Donacarbo S-241) and Tc = 973 K (Donacarbo SL-242). The carbon fibres have been chemically activated with KOH and NaOH (Panreac Chemicals, Barcelona, Spain) at 1023 K under a N2 gas flow. More details concerning the activation conditions can be found elsewhere. Two different kinds of furnaces have been used for the activations. For laboratory synthesis a horizontal tube furnace is used which is capable of activating about 2 g of raw fibres per activation process. For the scale-up production approach an industrial chamber furnace is used. Thereby the amount of initial material could be increased by more than one order of magnitude up to 30 g per activation process. 

The carbon or silica-loaded nanoparticles were treated in a tube-furnace under controlled temperature and atmosphere. A typical protocol involved shell removal by heating at 300°C under 20% O2/N2 for 1 h and calcination at 400°C under 15% H2/N2 for 2 h. The carbon-loaded Au or AuPt nanoparticles are denoted as Au/C or AuPt/C. The silica-loaded AuPt nanoparticles are denoted as AuPt/Si02. 

Monodisperse particles of salts, metals, metal oxides, and carbon have also been generated using electrically heated tube furnaces (e.g., Scheibel and... 

Diethyl ketone was either purchased from the Eastman Kodak Company and redistilled, or prepared by passing propionic acid slowly over a mixture of manganous oxide and clay plate chips in a tube furnace at 420-440° 3 the apparatus was similar to one described in Organic Syntheses When prepared by this method the ketone was distilled, dried over potassium carbonate, and redistilled b.p. 100-101°. 

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