Metallurgy-Hf & Nb

1. By Nikhat.S.Hussain
MSc Part II,Paper4
S.I.E.S

2. Properties
Occurence
Extraction
Applications

4. LUSTRE HARD
DENSITY;13.29g/cm
;MP=2200´C;BP=5000´C
2 forms
α-form
β-form

5. Hf + 4HF → HfF₄ + 2H₂ ↑
Hf + AquaRegia → HfCl₄
Resistant to Bases
Hf + 2H₂ 300´C HfH₄

6. 0.002% IN EARTH’S CRUST
ALVITE
MALAEON
CRYTOLITE

7. Zircon
Thiocyanite Arc Furnace CO,SiO2
ZrCN,HfCl4
Cl2 Chlorinating furnace,500 C
ZrCl4,HfCl4
Condenser,100’ C
Condensate crude ZrCl4,HfCl4
H2 Sublimation Residue-FeCl2
Purified (ZrCl4,HfCl4-2-7 %)

8. NH4OH
ZrCl4,HfCl4 mixture H2O
NH4CNS
Solvent (Methyl iso butyl ketone)
Liquid -Liquid Extraction Zirconyl chloride
Hf rich solvent
HCl → Stripping
Hafnyl chloride
H2SO4→ Scrubbing → Solvent recycle
NH4OH→ Precipitation
Heat → Calcining
Hf Oxine

9. Kroll Process
De-Boer or hot wire method

10. Hf(OH)4 cake
Rotary oven → H2O
HfO(OH)2
Electric muffle furnace → H2O
300 C
HfO2
Cl2, → Chlorinator → CO2
Purification Furnace
Resublimed HfCl4
Mg(excess) → Reduction Furnace(850 C)
Hf+MgCl2
Vacuum Distillation furnace
Hf sponge
Arc melting Furnace
Hf metal

11. (Zr +Hf)+H2O+2H2SO4→Hf ppt
+Zr(SO)4+2H2
HfI4→Hf +2I2

12. 1. HfCl4+4Na→Hf+4NaCl
2. HfI4→Hf+2I2
3. HfO2+2Mg→Hf+2MgO
HfO2+4Na→Hf+2Na2O
HfO2+2Ca→Hf+2CaO

13. Applications
Electroni
cs
Control
rods
Special
Glasses
Hf-Ti
alloys –
lamps
Radio
tubes
TV
tubes

15. Discovered:1801 by Charles & Hatchet

16. Hard grey metal
M.P=1927 C
B.P=4925 C
Density=8.5 g/cm3
Superconductor at low temperature

17. 2Nb+air→ Nb
2
O
5
2Nb+5Cl
2
→2NbCl
5
2Nb+N
2
→2NbN
2Nb+H
2
→2NbH
2Nb+3F
2
→2NbF
3
2Nb+5Cl
2
→2NbCl
5
Nb+4HF→NbF
4
+2H
2
↑

18. Minerals
Columbite (Fe,Mn)(Ta,Nb)2O6)
Euxenite (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6)
Pyrochlore (Na,Ca)2Nb2O6(OH,F)
Fergusonite

19. Solvent Extraction
Mineral
Fusion with K
2
CO
3
Extraction with H
2
O
Filtrate Residue
(K
3
[NbO
4
] &K
3
[TaO
4
]) (Insoluble hydroxide of Fe & Mn )
Treated with CO
2
Filter off
Filtration
Filtrate Precipitate
(Nb
2
O
5
& Ta
2
O
5
)
Removed Dissolved in HF acid containing KF
Fractional Crystallisation
Less soluble K
2
TaF
7
More soluble K
2
NbOF
5
Electrolysis

20. Kroll’s Method
2NbCl
5
+5Mg→2Nb+5MgCl
2
→Nb
NbCl
5
+NaCl→Nb-metal
Nb
2
O
5
+Al→Nb-Al alloy→Nb
5NbC+Nb
2
O+→7Nb+5CO

21. Rocket missiles
Optical glass
Air welding rods
Petroleum
equipments
With steel
Nuclear reactor
Gel engines
Electronics

22. General and inorganic chemistry by R.Sarkar