ASTM Manual on Zirconium and Hafnium: Sponsored by ASTM Committee B on J. H. Schemel Snippet view – ASTM Manual on Zirconium and Hafnium: Sponsored by ASTM Committee B on Reactive and Refractory Metals and Alloys. Front Cover. J. H. Schemel. The ASTM Manual on Zirconium and Hafnium, STP, was prepared for engineers, students, purchasing agents, and others who do not work regularly with.
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Hafnium is a chemical element with symbol Hf and atomic number A lustroussilvery gray, tetravalent transition metalhafnium chemically resembles zirconium and is found in many zirconium minerals.
ASTM Manual on Zirconium and Hafnium – J. H. Schemel – Google Books
Its existence was predicted by Dmitri Mendeleev inthough it was not identified untilby Coster and Hevesy, making it the last stable element to be discovered.
Hafnium is named after Hafniathe Latin name for Copenhagenwhere it was discovered. Hafnium is used in filaments and electrodes. Some superalloys used for special applications contain hafnium in combination with niobiumtitanium mankal, or tungsten. Hafnium’s large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plantsbut at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.
Hafnium is a shiny, silvery, ductile metal that is corrosion -resistant and chemically similar to zircoinum  due to its having the same number of valence electronsbeing in the same group, but also to relativistic effects ; the expected expansion of atomic radii from period 5 to 6 is almost exactly cancelled out by the lanthanide contraction.
The physical properties of hafnium metal samples are markedly affected by zirconium impurities, especially the nuclear properties, as these two elements are among the most difficult to separate because of their chemical similarity. A notable physical difference between these metals is their densitywith zirconium having about one-half the density of hafnium. The nafnium notable nuclear properties of hafnium are its high thermal neutron-capture cross-section and that the nuclei of several different hafnium isotopes readily absorb two or more neutrons apiece.
Hafnium reacts in air to form a protective film that inhibits further corrosion. The metal is not readily attacked by acids but can be oxidized with halogens or it can be burnt in air.
Like its sister metal zirconium, finely divided hafnium can ignite spontaneously in air. The metal is resistant to concentrated alkalis. The chemistry of hafnium and zirconium is so similar that the two cannot be separated on the basis of differing chemical reactions.
The melting points and boiling points of the compounds and the solubility in solvents are the major differences in the chemistry of these twin elements. At least 34 isotopes of hafnium have been observed, ranging in mass number from to The nuclear isomer m2 Hf was at the center of a controversy for several years regarding its potential use as a weapon.
Hafnium is estimated to make up about 5. A major source of zircon and hence hafnium ores is heavy mineral sands ore depositspegmatitesparticularly in Brazil and Malawiand carbonatite intrusions, particularly the Crown Polymetallic Deposit at Mount WeldWestern Australia. A potential source of hafnium is trachyte tuffs containing rare zircon-hafnium silicates eudialyte or armstrongite, at Dubbo in New South WalesAustralia.
Hafnium reserves have been infamously estimated to last under 10 years by one source if the world population increases and demand grows. The heavy mineral sands ore deposits of the titanium ores ilmenite and rutile yield most of the mined zirconium, and therefore also most of the hafnium. Zirconium is a good nuclear fuel-rod cladding metal, with the desirable properties of a very low neutron capture cross-section and good chemical stability at high temperatures. However, because of hafnium’s neutron-absorbing properties, hafnium impurities in zirconium would cause it to be far less useful for nuclear-reactor applications.
Thus, a nearly complete separation of zirconium and hafnium is necessary for their use in nuclear power. The production of hafnium-free zirconium is the main source for hafnium.
The chemical properties of hafnium and zirconium are nearly identical, which makes the two difficult to separate. After zirconium was chosen as material for nuclear reactor programs in the s, a separation method had to be developed.
Liquid-liquid extraction processes with a wide variety of solvents were developed and are still used for the production of hafnium. The end product of the anr is hafnium IV chloride. Further purification is effected by a chemical transport reaction developed by Arkel and de Boer: The hafnium forms a solid coating at the tungsten filament, and the iodine can react with additional hafnium, resulting in a steady turn over.
Due to the lanthanide contraction the ionic radii of hafnium IV 0. Halogens react hafnijm it to maunal hafnium tetrahalides.
Hafnium IV chloride and hafnium IV iodide have some applications in the production and purification of hafnium metal. They are volatile solids with polymeric structures. In his report on The Periodic Law of the Chemical ElementsinDmitri Mendeleev had implicitly predicted the existence of a heavier analog of titanium and zirconium. At the time of his formulation inMendeleev believed that the elements were ordered by their atomic masses and placed lanthanum element 57 in the spot below zirconium.
The exact placement of the elements janual the location zlrconium missing elements was done by determining the specific weight of the elements and comparing the chemical and physical properties. The X-ray spectroscopy done by Henry Moseley in showed a direct dependency between spectral line and effective nuclear charge. This led to the nuclear charge, or atomic number of an element, being used to ascertain its place within the periodic table.
With this method, Moseley determined the number of lanthanides and showed the gaps in the atomic number sequence at numbers 43, 61, 72, and The discovery of the gaps led to an extensive search for the missing elements. Inseveral people claimed the discovery after Henry Moseley predicted the gap in the periodic table for the then-undiscovered element Bury  suggested that element 72 should resemble zirconium and therefore was not part of the rare earth elements group.
These suggestions were based on Bohr’s theories of the atom, the X-ray spectroscopy of Moseley, and the chemical arguments of Friedrich Paneth. Encouraged by o suggestions and by the reappearance in of Urbain’s claims that element 72 was a rare earth element discovered inDirk Coster and Georg von Hevesy were motivated to search for the new element in zirconium ores. Hafnium was separated from zirconium through repeated recrystallization of the double ammonium or potassium fluorides by Valdemar Thal Jantzen and von Hevesey.
Infour predicted elements were still missing from the periodic table: Since rhenium was discovered inhafnium was the last element with stable isotopes to be discovered.
Most of the hafnium produced is used in the manufacture of control rods for nuclear reactors. Several details contribute to the fact that there are only a few technical uses for hafnium: First, the close similarity between hafnium and zirconium makes it possible to use zirconium for most of the applications; second, hafnium was first available as pure metal after the use in the nuclear industry for hafnium-free zirconium in the late s.
Furthermore, the low abundance and difficult separation techniques necessary make it a scarce commodity. The nuclei of several hafnium isotopes can each absorb multiple neutrons. This makes hafnium a good material for use in the control rods for nuclear reactors. Its neutron-capture cross-section is about times that of zirconium. Other elements that are good neutron-absorbers for control rods are cadmium and boron.
Excellent mechanical properties and exceptional corrosion-resistance properties allow its use in the harsh environment of pressurized water reactors. Hafnium is used in alloys with irontitaniumniobiumtantalumand other metals. Small additions of hafnium increase the adherence of protective oxide scales on nickel-based alloys.
It improves thereby the corrosion resistance especially under cyclic temperature conditions that tend to break oxide scales by inducing thermal stresses between the bulk material and the oxide layer. Isotopes of hafnium and lutetium along with ytterbium are also used in isotope geochemistry and geochronological applications, in lutetium-hafnium dating.
Garnet is another mineral that contains appreciable amounts of hafnium to act as a geochronometer. Due to its heat resistance and its affinity to oxygen and nitrogen, hafnium is a good scavenger for oxygen and nitrogen in gas-filled and incandescent lamps.
Hafnium is also used as the electrode in plasma cutting because of its ability to shed electrons into air. This program determined that the possibility of using a nuclear isomer of hafnium the above-mentioned m2 Hf to construct high-yield weapons with X-ray triggering mechanisms—an application of induced gamma emission —was infeasible because of its expense.
Catalog Record: ASTM manual on zirconium and hafnium | Hathi Trust Digital Library
Care needs to be taken when machining hafnium because it is pyrophoric —fine particles can spontaneously combust when exposed to air. Compounds that contain this metal are rarely encountered by most people. The pure metal is not considered toxic, but hafnium compounds should be handled as if they were toxic because the ionic forms of metals are normally at greatest risk for toxicity, and limited animal testing has been done for hafnium compounds.
People can be exposed to hafnium in the workplace by breathing it in, swallowing it, skin contact, and eye contact. From Wikipedia, the free encyclopedia. Pure and Applied Chemistry. Chemical Rubber Zigconium Publishing. Early Days of X-ray Crystallography. Atlantic Europe Publishing Company,p. Lehrbuch der Anorganischen Chemie in German 91— ed. Periodic Table of Elements. Atomic Mass Data Center. The Rock-Forming Minerals, volume 1A: Archived from the original PDF on zircinium Archived from the original on Zirconium and Hafnium” manhal.
United States Geological Survey.
Preparation of Hafnium-Free Zirconia”. Minerals yearbook metals and minerals manul fuels. The first production plants Bureau of Mines. Journal of the Electrochemical Society. Chemistry of the Elements 2nd ed. Bulletin for the History of Zirconiym. Archived from the original pdf on The search for a missing element”. Comptes rendus in French: The Theory of Spectra and Atomic Constitution: Ergebnisse der Exakten Naturwissenschaften 1 in German.
Journal of Chemical Education. Comptes rendus in French.