Tantalum magnetism

Niobium finds use in the production of numerous stainless steels for use at high temperatures, and Nb/Zr wires are used in superconducting magnets. The extreme corrosion-resistance of tantalum at normal temperatures (due to the presence of an exceptionally tenacious film of oxide) leads to its application in the construction of chemical plant, especially where it can be used as a liner inside cheaper metals. Its complete inertness to body fluids makes it the ideal material for surgical use in bone repair and internal suturing. 

The presence of a few atomic percent of oxygen in tantalum increases electrical resistivity, hardness, tensile strength, and modulus of elasticity, but decreases elongation and reduction of area, magnetic susceptibility, and corrosion resistance to HF . 

Ores of magnetic origin. Tantalum/columbite granites are of economic interest when the columbite content of the ore ranges from 0.001% to 0.01% and the tantalite up to 0.2%. These deposits are most common in Nigeria (Africa). Because they are a low-grade ore, they do not represent significant economic value. 

Throughout the development testwork, emphasis was placed on finding an effective reagent scheme that would produce a bulk concentrate with satisfactory tantalum, niobium and zircon recoveries. The Ta/Nb-Zr separation study concentrated mainly on magnetic separation. The floatability of Ta/Nb and Zr depend on type of collector, modifier and depressant system used. 

In the past, most of the rutile was produced from heavy mineral sands using physical concentration, involving gravity, magnetic separation and electrostatic concentration. The physical preconcentration method cannot be applied to a fine heavy mineral sand or hard ore. In some cases, heavy mineral sand contains zircon, tantalum, niobium and other heavy minerals, where in most cases a flotation method is used. 

Vanadium, niobium and tantalum - All these elements have magnetic nuclei occurring at virtually 100% natural abundance, although the high quadrupole moment of tantalum has tended to restrict investigations to those of compounds with highly symmetric coordination around the metal. 

A magnetic cell separator was constructed on a Si wafer to separate cells that were labeled with paramagnetic beads (FeO nanocrystals 50 nm) from unlabeled ones. The magnetic force was generated from thin magnetized wires (10 pm wide, 0.2 pm thick) formed by depositing a cobalt-chrome-tantalum alloy in pre-etched 0.2-pm-deep trenches. These wires were parallel and were oriented at 45° to the hydrodynamic flow direction of cells [278]. 

---