Tammann furnace

The mixture is heated at 1600°C for 15 minutes in a Tammann furnace this is obviously insufficient to bring about complete reaction. The Ti is not completely consumed, but it becomes so brittle that it is readily pulverized in an agate mortar. This fine powder is reheated and the product is then homogeneous. 

The suicides are prepared by fusing or sintering Intimate stoichiometric mixtures of the elements (in powder form). The reaction is carried out in sintered clay or ceramic crucibles, placed in a Tammann furnace under a blanket of Ar. In all three cases the reaction takes place at a relatively low temperature and is highly exothermic therefore, one should work with gram quantities only. 

Sch2] Chemical analysis of compositions of two liquid layers after exposition at certain temperatures and quenching. Tammann furnace, graphite crucibles, electrolytic Fe and Cu. Thermodynamic calculation The liquidus surfaces with the miscibility gap and liquidus isotherms. The melting equilibria in stable and metastable systems. 

Tammann Furnace. An electric high-temperature furnace having a carbon tube as resistor it is used without a protective atmosphere but is sealed to prevent ingress of air (G. Tammann see paper by E. Lowenstein. Z. Anorg. Chem., 154,173, 1926.). 

Figure 6.1. High temperature Tammann type furnace and its application to differential thermal analysis. The supports A act also as connections to the electric supply (typically about 10 volts and several hundred amperes) B upper lid and electric connection to the carbon tubular resistance C the tube C is surrounded by packed granular carbon inside the ceramic insulating filling D ...

The heating element of these furnaces, which were first constructed by Nernst and Tammann, is a carbon tube. Because of their low resistance, they are also called short circuit furnaces. The larger models have foimd wide industrial use. Thus, these furnaces are commercially available. It does not pay to attempt construction of such a imit in the laboratory. The most e q)ensive part is the transformer, needed because of the low resistance of the carbon tube, and this must be purchased in any case. Depending on the size, these units require some 100-1000 amp. at approximately 10 volts. Careful construction of the unit permits easy replace-mait of the carbon tube (whose durability at high temperature is limited). Temperatures of over 2000°C can easily be reached. A reducing atmosphere must always be maintained inside the tube. Should this be undesirable, then protective insert tubes must be provided. For this purpose, alumina can be used iq) to 2000°C. At higher temperatures, only sintered BeO or ThOg is effective MgO is subject to reduction. 

The growing of metal single crystals can be carried out via several methods. Tammann and Bridgman [12] have devised an apparatus for slow solidification of metallic melts. A tube filled with the melt is lowered slowly and at a uniform rate (e.g., by means of a clock mechanism) through a vertical, electrically heated tubular furnace. In order to force the crystallization process to occur at a fixed place and from only one crystallization center, the bottom of the tube is drawn out to a capillary point (Schubnikow Straumanis Cl2]. 

Iwa] Method of quenching the melt in ice water after heating at different temperature over liquidus and investigation of stracture under light microscopy. Tammann carbon resistance furnace, electrolytic Fe and Cu, master alloy with 4.25 mass% C and graphite powder. Isothermal equilibria of two Uquids at 1450 and 1540°C in Fe comer at 0 to 4 mass% C and 0 to 30 mass% Cu... 

Starting materials were electrolyte Fe (99.998%), graphite (99.94%) and eiystallized boron (99.8%). Alloys were melted in a high frequeney or Tammann fumaee. The B and C eontent of the alloys was eonlrolled by wet ehemieal methods. Isothermal reactions were determined on alloys (50 g each) heated in a Mo-wire furnace to preset temperature under argon in Fe- or C-cmeibles. 

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