Tantalum thermal functions

In the case of molten salts, the functional electrolytes are generally oxides or halides. As examples of the use of oxides, mention may be made of the electrowinning processes for aluminum, tantalum, molybdenum, tungsten, and some of the rare earth metals. The appropriate oxides, dissolved in halide melts, act as the sources of the respective metals intended to be deposited cathodically. Halides are used as functional electrolytes for almost all other metals. In principle, all halides can be used, but in practice only fluorides and chlorides are used. Bromides and iodides are thermally unstable and are relatively expensive. Fluorides are ideally suited because of their stability and low volatility, their drawbacks pertain to the difficulty in obtaining them in forms free from oxygenated ions, and to their poor solubility in water. It is a truism that aqueous solubility makes the post-electrolysis separation of the electrodeposit from the electrolyte easy because the electrolyte can be leached away. The drawback associated with fluorides due to their poor solubility can, to a large extent, be overcome by using double fluorides instead of simple fluorides. Chlorides are widely used in electrodeposition because they are readily available in a pure form and... 

One of the prototypes of this behavior is the low-temperature form of tantalum pentoxide, L-Ta20s. The structure of this phase is ill defined, even though it is a stoichiometric oxide, and the room temperature stracture is a function of the prior thermal treatment temperature of the material. Reaction with other oxides, notably WO3, Zr02 and AI2O3, gives rise to solids with a broad oxygen nonstoichiometry. However, each composition appears to generate a uniquely ordered structure, which have been termed infinitely adaptive structures. 

Figure 11. Scheme of one of the microcalorimeters used for the simultaneous measurements of O2 consumption and heat production rates in perfused preparations. The thermal gradient layers (1) are made of semiconductor thermocouples mounted in series on each chamber. The preparation (2) is placed near the upstream extremity of one of the 8-cm long tantalum chambers, so that most of the heat it produces is transmitted to the surrounding aluminium block that functions as a heat sink. The four-way distributor, driven from outside the thermostatic jacket by a torsion bar and a pneumatic valve, directs the effluents of the preparation chamber and the control chamber to the drain, alternately via a jet in front of the O2 cathode (3) or directly (4) every 2 to 5 min. Immediately upstream of the calorimeter chambers, the downstream components of the heat exchangers (5) are wound together, in co-current, in close contact with an extension of the aluminium block (not represented on the drawing) (Reproduced from Reference [70] with permission). 

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