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| | HAFNIUM FLUORIDE Chemical Properties |
| Melting point | 310°C (subl.) | | Boiling point | 970°C | | density | 7.100 | | solubility | reacts with H2O | | form | Powder | | color | White | | Water Solubility | React with water. | | Sensitive | Moisture Sensitive | | Exposure limits | ACGIH: TWA 2.5 mg/m3; TWA 0.5 mg/m3
NIOSH: IDLH 250 mg/m3; IDLH 50 mg/m3; TWA 0.5 mg/m3 | | CAS DataBase Reference | 13709-52-9(CAS DataBase Reference) |
| | HAFNIUM FLUORIDE Usage And Synthesis |
| Preparation | Hafnium tetrafluoride may be prepared by passing anhydrous hydrogen fluoride over hafnium tetrachloride at 300°C:
HfCl4 + 4HF HfF4 + HCl
Another method of preparation involves thermal decomposition of ammonium fluorohafnate, (NH4)2 HfF6 [16925-24-9] in the absence of air:
(NH4)2 HfF6 HfF4 + 2NH3 + 2HF
Also, HfF4 can be prepared by treating metallic hafnium with 40% aqueous HF. The monohydrate formed may be heated at 350°C for several days under a flow of fluorine and nitrogen to yield anhydrous HfF4.
Hf + 4HF (aq) → HfF4•H2O + 2H2
| | Chemical Properties | Off-white powder | | Physical properties | White monoclinic crystals; refractive index 1.56; density 7.1 g/cm3; sublimes at 970°C. | | Uses | Hafnium(IV) fluoride is used as Vacuum deposition. | | Production Methods | Hafnium tetrafluoride is prepared by careful thermal
decomposition of ammonium fluorohafniate in an oxygen-
free atmosphere or by passing anhydrous hydrogen
fluoride over hafnium tetrachloride at 300℃. Direct synthesis
from the elements is incomplete because the product
merely forms a film on the metal. Ammonium fluorohafniate
can be prepared by crystallization from an aqueous
hydrofluoric acid solution by adding ammonium
fluoride. |
| | HAFNIUM FLUORIDE Preparation Products And Raw materials |
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