Hafnium: application and properties

Introduction to this article will allow the reader to find out what hafnium (a chemical element) is, the application of which is widely used by man in a variety of areas of his activity. And also the properties of the chemical and physical nature of matter, the methods of extraction and finding on the planet, the brief history of the discovery of this element will be considered.

What is hafnium

Hafnium is a chemical element of the periodic table. It is in the fourth group, the sixth period, the atomic number is seventy-two. Refers to a simple type of substances, has a high density and refractoriness, the color of the metal is silvery-white. Hafnium can exist in two modifications. Under the influence of a temperature of about 2016 Kelvin, a lattice of the hexagonal type, undergoing allotropic changes, transforms into a state of a body-centered cubic lattice, at room temperature has a crystal lattice of hexagonal syngony.

From item discovery history

The discovery of the element occurred in 1923, committed by Gyorgy De Heshevi and Koster Dirk. They were able to predict the valency and various qualitative characteristics of hafnium, based on the conclusions of N. Bohr, who, in turn, analyzed the work of the Frenchman J. Urben, who believed that he had discovered the Celtic - a new element. However, it turned out later that the mixture of a small amount of hafnium with lutecium and ytterbium was a Keltium.

Niels Bohr, studying this work and using quantum-mechanical calculations, proved that hafnium is an analog of the element at number 71 in PTCA, namely zirconium. Gyorgy De Heshevi and Koster Dirk announced the discovery of a new element of hafnium, named after the city in which the discovery was made, after using the X-ray spectral method, the zircons of Norway and Greenland were repeatedly analyzed. Detection of the similarity of the X-ray lines allowed scientists to announce the discovery of a new x-ray element.

Ways of obtaining and world stocks

Hafnium is in the bark of the earth, but does not have its own mineral, and therefore it is a "satellite" of zirconium. The amount of Hf in ores is about 2.5%, and annual production is about seventy tons. Hafnium is a rather expensive substance, its main locations are concentrated in Australia, South Africa, the United States, India and Brazil. The location of the countries in the order of the transfer corresponds to the places by the number of Hf in the country. It is also worth mentioning that Russia and Ukraine have fairly large reserves of this metal, the bulk of which is concentrated in zirconium, loparite and baddeleyite.

Physical Characteristics

Part of the physical properties of hafnium was mentioned above. You can add to them that this metal, which, taking a finely dispersed state, becomes almost black. Melts at 2233 degrees Celsius, boiling begins at 4603 ^o C. The cross section for the capture of neutrons of the thermal type is very high. Zirconium, in contrast to hafnium, has a cross section level that is three orders of magnitude weaker. While the capture of Hf is 115 bars, in zirconium it is only about 0.2 bar. Hafnium has an analogous level of the specific heat of germanium (Ge) and is anomalous. Peak heat capacity is at the level of 60-80 Kelvin. This can not be explained by any theory related to Hooke forces, which is due to the inability of the Einstein superposition function to provide a curve with a maximum.

Chemical properties

Hafnium has an x-ray resistance much stronger than that of a similar zirconium. The metal itself is quite inert, which is associated with a film of passive oxide that is formed on hafnium. It is best to dissolve Hf in hydrofluoric acid, a mixture of hydrofluoric acid with nitric acid and in royal vodka. At high temperatures, it burns in oxygen, and in the open air begins to oxidize. Can enter into x-ray reactions with halogens. Has hydrophobic properties.

Compounds of two-, three- and four-valent Hf

For this element, the value of valence is variable and, in accordance with the different values of the number of possible x-ties, there are several important compounds of hafnium with other substances.

Divalent hafnium dibromide has a dark green color. At a temperature of 400 degrees Celsius begins the decomposition process with the formation of Hf and HfBr4. In the industry, it is produced by disproportionation in a vacuum of HfBr3 under thermal action.

Trivalent Hf is represented by tribromide (HfBr3) - this substance is black-blue, rather hard. Under the influence of a temperature equal to 400 degrees Celsius, it begins to disproportionate into two components of hafnium tetrabrombites and dibromobids. The production method consists in the reduction of HfBr4 by heating in hydrogen, optionally with the addition of aluminum.

To the compounds of tetravalent hafnium there is a rather large number of compounds, namely HfO2 is its dioxide, and also hydroxide with the x-th formula Hf (OH) 4. There are also tertrachloride (HfCl4), tetrafluoride (HfF4), tetraiodide (HfI4) and the above-mentioned hafnium tetrabomide (HfBr), and there are also hafnium hydrogenphosphates (Hf (HPO4) 2).

Application in everyday life and communication with medicine

Hafnium finds its application in a number of spheres of activity of the human race. This is due to the multitude of qualitative characteristics, properties that make it an indispensable material, a substance in a variety of human industries, military affairs and even in the nuclear industry.

So how is hafnium used? Application in medicine - this is one of many options where you can use the properties of this metal. Since Hf carbides are heavy-duty, practically non-corrosive, they can be used for making cutting objects used by physicians, and they are also used in the manufacture of an X-ray mirror.

An element with exceptional properties of both chemical and physical nature is hafnium. Application in everyday life, he finds as a material in the manufacture of radio technology, radio tubes and television tubes. It is widely used in the metallurgical industry with the aim of making other metals of higher quality physicotechnical and mechanical properties. Hafnium is also used in x-ray engineering, but it is rarely used due to its shortage and more important methods of application.

The use of hafnium in the military craft

How else can you use hafnium? The use in armament is another sphere of human activity, in which it does not do without this element. Oxides, silicides, borides and carbides of hafnium are extremely refractory compounds, for this reason in military craft they can be used as a protective coating. It is also extremely ultra-high-strength, which makes it possible to use Hf and its compounds for the production of parts destined for super-high-speed aircraft and rockets, including space ones.

Since 1998, attempts have been made to create a "hafnium bomb", based on the isomer 187m2Hf. But as a result of research and testing, the idea turned out to be untenable, this is due to the lack of the ability, with current technologies, to achieve the release of excess energy from the core of this isomer.

Other applications of the simple substance Hf

In nuclear power, along with the above-mentioned spheres, but even in even larger quantities, hafnium is also used. Where is this metal used? Because of its ability to neutron capture from Hf, rods for regulation, specialized glass and ceramics are made.

Hafnium has a relatively low performance of the electronic output (3.53 eV) and for this reason it can be used in the production of cathodes and electron guns. In nuclear reactive gas-phase engines, it is possible to find borides and carbides of hafnium, or rather in some structural elements.

Hafnium is used even in the manufacture of thermoelectric type generators and is often found in ionic engines. On the basis of HfO2, dielectrics with a high level of permittivity are created. In the future, it is planned to replace the familiar silicon oxide in microelectronics with HfO2 oxide. This replacement will increase the density of elements in the chip.

In conclusion, it can be said that hafnium, the application of which takes place in many branches of human activity, starting everyday and ending with military and atomic, is an extremely important element. This is a very demanded metal and in nature always accompanies zirconium. The rarity and its features of qualitative characteristics cause a rather high cost.