Hf(Atomic number : 72)

1. Introduce

– Metal in the quaternary group with titanium and zirconium in the periodic table

– Hf is mainly obtained as a by-product when producing zirconium from Hf ores (zircon, hafnon, albite) (approximate ratio of zirconium to hafnium is 50:1)

– Has excellent corrosion resistance by reacting with oxygen to form a surface oxide layer

– Hf alloying elements influence : corrosion resistance

* Zr and Hf

– Zr is always accompanied by Hf in nature

– Zr has nearly the same electron and ionic radii as Hf, and other properties such as density, transition temperature, and chemical properties, except for neutron absorption, are nearly identical

– Zr ores typically have 1 to 4 percent of the Zr added as Hf, so commercially available Zr also typically contains 1 to 4 percent Hf

– Zr absorbs very few neutrons, while Hf is a neutron capture agent that absorbs neutrons 600 times better than Zr, so Hf must be removed from the Zr used in reactors
(Zr Hf separation methods)

– (Europe) : Fractional distillation of tetrachloride compounds (extractive distillation)

– (USA) : liquid-liquid extraction method : utilizes the difference in partitioning of thiocyanate-oxides between water and methyl isobutyl ketone solvent

– (Other) : Fractional determination method : utilizes the difference in solubility of K₂ZrF6₆ and K₂HfF₆ in water

2. Properties

– Corrosion resistance, heat resistance, excellent ductility

[Hf Mechanical Properties]

[Hf Physical Properties]

3. Application

– Nuclear submarine control rods, gas turbine blades, plasma cutting equipment electrodes, insulators, blue laser for DVD readers, optical coatings, filaments, electrodes

(1) Gas turbine blades / (2) Plasma cutting equipment electrodes / (3) Filaments / (4) Insulators