Search results
Results from the WOW.Com Content Network
The majority of aluminium fluoride is produced by treating alumina with hydrogen fluoride at 700 °C: [4] Hexafluorosilicic acid may also be used make aluminium fluoride. [11] H 2 [SiF 6] + Al 2 O 3 + 3 H 2 O → 2 AlF 3 + SiO 2 + 4 H 2 O. Alternatively, it is manufactured by thermal decomposition of ammonium hexafluoroaluminate. [12]
Fluoride mimics the nucleophilic hydroxide ion in these enzymes' active sites. [41] Beryllium fluoride and aluminium fluoride are also used as phosphatase inhibitors, since these compounds are structural mimics of the phosphate group and can act as analogues of the transition state of the reaction. [42] [43]
Often, the metal (such as aluminium, iron, or copper) must be powdered because many metals passivate by forming protective layers of the metal fluoride that resist further fluoridation. [7] The alkali metals can react with fluorine explosively, while the alkaline earth metals react not quite as aggressively.
[citation needed] The metal ions, more noble than aluminium, then undergo a redox reaction, dissolve the surface layer of aluminium and form a deposit there. This intermediate layer of another metal then can be wetted with a solder. One example of such flux is a composition of triethanolamine, fluoroboric acid, and cadmium fluoroborate. More ...
Aluminium (or aluminum in North American English) is a chemical element; it has symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has a great affinity towards oxygen, forming a protective layer of oxide on the surface when exposed to air.
The difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s). Pure cryolite itself melts at 1012 °C (1285 K), and it can dissolve the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis. Substantial energy is still ...
Activated alumina is manufactured from aluminium hydroxide by dehydroxylating it in a way that produces a highly porous material; this material can have a surface area significantly over 200 m 2 /g. The compound is used as a desiccant (to keep things dry by adsorbing water from the air) and as a filter of fluoride , arsenic and selenium in ...
The process produces a quantity of fluoride waste: perfluorocarbons and hydrogen fluoride as gases, and sodium and aluminium fluorides and unused cryolite as particulates. This can be as small as 0.5 kg per tonne of aluminium in the best plants in 2007, up to 4 kg per tonne of aluminium in older designs in 1974.