Hafnium general properties

References 3,18, 32, 58, 59, and 64 are good general references. K. L. Komarek, ed.. Hafnium Physico-Chemical Properties of Its Compounds and Alloys International Atomic Energy Agency, Vieima, 1981. 

Generally, for the chemical engineer not particularly associated with atomic energy, unalloyed zirconium containing hafnium is an appropriate choice for those occasions which require the special corrosion resistant properties exhibited by the metal. 

Zirconium can be a shiny grayish crystal-Uke hard metal that is strong, ductile, and malleable, or it can be produced as an undifferentiated powder. It is reactive in its pure form. Therefore, it is only found in compounds combined with other elements—mosdy oxygen. Zirconium-40 has many of the same properties and characteristics as does hafhium-72, which is located just below zirconium in group 4 of the periodic table. In fact, they are more similar than any other pairs of elements in that their ions have the same charge (+4) and are of the same general size. Because zirconium is more abundant and its chemistry is better known than hafnium s, scientists extrapolate zirconium s properties for information about hafnium. This also means that one twin contaminates the other, and this makes them difficult to separate. 

In this chapter we will review the synthesis, structural aspects, and basic chemical properties of formally divalent and trivalent titanium and zirconium metallocene complexes. We have restricted our coverage to the low-valent bis(rj-cyclopentadienyl) and related metallocenes metal halide complexes and organometallic mixed metal systems will not be discussed here. We have not attempted to present an exhaustive coverage of the field. Rather, our aim has been to describe critically and to evaluate the often confusing chemistry that has been reported for the reactive low-valent titanium and zirconium metallocenes. More general reviews (7) and a book (2) on the organometallic chemistry of titanium, zirconium, and hafnium have been published. 

Osmium is of great interest to mantle geochemists because, in contrast with the geochemical properties of strontium, neodymium, hafnium, and lead, all of which are incompatible elements, osmium is a compatible element in most mantle melting processes, so that it generally remains in the mantle, whereas the much more incompatible rhenium is extracted and enriched in the melt and ultimately in the crust. This system therefore provides information that is different from, and complementary to, what we can learn from... 

There are several complete compilations of the literature concerning zirconium and hafnium that take the reader up to about 1960 62, 344, 420, 558). Since then several reviews of more limited scope have been published, one on the structural aspects of zirconium chemistry 116), and others on the separation of zirconium and hafnium 578), aqueous chemistry 234, 533), and ion-exchange properties of zirconium compounds 29). In general, the data in the present review are drawn from publications since 1960, although references to earlier work are included where necessary to complete the picture. 

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