By L. Bartha, E. Lassner, W. -D. Schubert, B. Lux
Non-sag (NS) tungsten is a dispersion-strengthened microalloy with elemental potassium, that is contained as microscopic bubbles within the tungsten lattice. lower than operating stipulations in an incandescent lamp the potassium is a gasoline below excessive strain. those gasoline bubbles basically hinder the recrystallization of the tungsten cord and are liable for the exceptional creep resistance of NS tungsten on the tremendous excessive temperatures of a gleaming lamp filament. greater than ninety% of NS tungsten is used for incandescent lamps. additionally, small quantities are used as defroster heating wires in car windshields and as heating twine coils for aluminium evaporation in metallization purposes. The provided papers take care of the chemical reactions and the chemicals happening alongside the trail from tungsten uncooked fabrics to the ultimate NS tungsten filament; a compendium of current wisdom at the assorted chemical features of NS tungsten manufacture is gifted. it's composed of 9 person papers, every one of them written by way of specialists operating within the box
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11. 12. 13. 14. 15. 16. 17. 18. 19. 20. Effluent-Free Manufacture of Ammonium Paratungstate (APT) by Recycling the Byproducts K. Vadasdi Research Institute for Technical Physics of the Hungarian Academy of Sciences, 1325 Budapest, PO Box 76, Hungary Abstract: Within the framework of a review of the fundamental processes applied for the manufacture of ammonium paratungstate (APT) the main byproducts and wastes generated in these processes and their environmental impact are summarized. A subsidiary process based on the electrodialytic recovery of NaOH for the elimination of the salt byproduct, which is generated in the largest quantities, is outlined together with the main aspects to be taken into account for large-scale industrial implementation.
Lower Mo concentrations afford a higher excess. A detailed study of the efficiency of Mo removal by this method is given in Ref. 25. The remaining Mo concentration after filtration is < 10 mg Mo litre" l . 26 As already mentioned, other elements forming insoluble sulphide compounds are co-precipitated, as there are As, Sb and Bi, which can be found in ore concentrates or Co traces, stemming from cemented carbide scrap. — this conversion in modern plants is exclusively achieved either by solvent extraction (also called liquid ion exchange) or by ion exchange resins.
The chemical reactions taking place seem to be rather complex. A simplified scheme23 is: Na 2 Si0 3 + 2MgS0 4 + 2NaC0 3 - 2MgO. 7H 2 0 kg" 1 W0 3 were added to the 70-80°C hot solution directly after digestion as long as the undissolved gangue material is still contained, which will act as a filter aid. The pH value should range between 9-0 and 9-5 and filtration may be started after 1 h. The second precipitation is performed under equal conditions. Because of poor filtration behaviour of the precipitate, cellulose must be added as a filter aid.