Familiarization with this article will allow the reader to find out what is hafnium (a chemical element), the use of which is widely used by man in many areas of his activity. And also the properties of the chemical and physical nature of the substance, the methods of extraction and location on the planet will be considered, a brief history of the discovery of this element will be considered.
What is hafnium
Hafnium is a chemical element of the periodic table. Located in the fourth group, sixth period, the atomic number is seventy-two. Refers to a simple type of substance, has a high density and refractoriness, the color of the metal is silver-white. Hafnium can exist in two versions. Under the influence of temperature around 2016, the Kelvin lattice of the hexagonal type, having undergone allotropic changes, goes into the state of a body-centered lattice of a cubic shape, at room temperature it has a crystal lattice of hexagonal syngony.
From the history of the discovery of the element
The discovery of the element occurred in 1923, performed by György de Heshevi and Bonfire 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 Celtium - a new element. However, later it turned out that Celtic was a mixture of a small amount of hafnium with lutetium and ytterbium.
Niels Bohr, studying this work and using quantum-mechanical calculations in his work, proved that hafnium is an analogue of element number 71 in PTCE, namely zirconium. György de Heshevi and Bonfire 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 to repeatedly analyze the zircons of Norway and Greenland. The discovery of the similarity of X-ray lines allowed scientists to announce the discovery of a new x-ray element.
Methods of obtaining and world stocks
Hafnium is in the crust of the earth, but does not have its own mineral, and therefore it is a "satellite" of zirconium. The amount of Hf in the 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 USA, India and Brazil. The location of the countries in the order of listing corresponds to the places according to the amount of Hf in the country. It is also worth mentioning that Russia and Ukraine have rather large reserves of this metal, the bulk of which is concentrated in zircon, loparite and baddeleyite.
Physical characteristic
Part of the physical properties of hafnium has been mentioned above. We can add to them that this metal, which, assuming a finely dispersed state, becomes almost black. It melts at 2233 degrees Celsius, boiling starts at 4603 ° C. The cross section for thermal-type neutron capture is very high. Zirconium, unlike hafnium, has a cross-sectional level three orders of magnitude weaker. While the Hf capture is 115 bar, in zirconium it is only about 0.2 bar. Hafnium has a similar level of heat capacity of germanium (Ge) and is abnormal. The peak heat capacity is at the level of 60-80 Kelvin. This cannot be explained by any theory related to the Guk forces, due to the inability of the Einstein superposition function to provide a curve with a maximum.
Chemical properties
Hafnium has x-resistance is much stronger than that of similar zirconium. The metal itself has a rather large inertness, which is associated with a film of passive type oxides, which is formed on hafnium. Hf is best dissolved in hydrofluoric acid, a mixture of hydrofluoric acid with nitric acid, and in aqua regia. At high temperatures, it burns out in oxygen, and begins to oxidize in the open air. It can enter into x-reactions with halogens. It has hydrophobic properties.
Compounds of trivalent and tetravalent Hf
For this element, the valency value is variable and, in accordance with various values of the number of possible x bonds, there are several important compounds of hafnium with other substances.
The divalent hafnium dibromide has a dark green color. At a temperature of 400 degrees Celsius, the decomposition process begins with the formation of Hf and HfBr4. In industry, HfBr3 is produced by disproportionation in vacuum under thermal influence.
Trivalent Hf is represented by tribromide (HfBr3) - this substance is black and blue, rather solid. Under the influence of a temperature of 400 degrees Celsius, hafnium and dibrombides begin to disproportionate into two components. The production method consists in reducing HfBr4 by heating in hydrogen, possibly with the addition of aluminum.
Compounds of tetravalent hafnium include a fairly large number of compounds, namely HfO2 - its dioxide, as well as hydroxide with the x-formula Hf (OH) 4. There are also tetrachloride (HfCl4), tetrafluoride (HfF4), tetraiodide (HfI4) and the aforementioned hafnium tetrabomide (HfBr), there are also hafnium hydrophosphates (Hf (HPO4) 2).
Home use and connection with medicine
Hafnium finds its application in many spheres of human activity. This is due to the multitude of qualitative characteristics, properties that make it an indispensable material, a substance in many branches of human craft, military affairs, and even in the nuclear industry.
So how is hafnium used? Application in medicine is one of many options where you can use the properties of this metal. Since Hf carbides are heavy-duty, practically not subject to corrosion, they can be used to make cutting items used by doctors, and they are also used in the manufacture of X-ray mirrors.
An element with exceptional properties of both chemical and physical nature is hafnium. It finds application in everyday life as a material in the manufacture of radio equipment, radio tubes and television tubes. It is widely used in the metallurgical industry in order to give other metals better physical, technical and mechanical properties. Hafnium is also used in x-mechanical engineering, but is rarely used due to its shortage and more important methods of application.
The use of hafnium in military craft
How else can hafnium be used? Use in armaments is another area of human activity in which this element cannot be dispensed with. Hafnium oxides, silicides, borides and carbides are extremely refractory compounds, for this reason they can be used as a protective coating in military craft. It is also extremely heat-resistant, which allows the use of Hf and its compounds for the production of parts for ultra-high-speed aircraft and rockets, including space ones.
Since 1998, attempts have been made to create a “hafnium bomb” based on the 187m2Hf isomer. But as a result of research and testing, the idea turned out to be untenable, this is due to the lack of the ability to achieve the release of excess energy from the core of this isomer with current technologies.
Other uses of the simple substance Hf
In nuclear energy, along with the aforementioned areas, but even in even greater quantities, hafnium is also used. Where is this metal used? Because of its ability to capture neutrons, regulation rods, specialized glass and ceramics are made from Hf.
Hafnium has a relatively low electron work function (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, hafnium borides and carbides can be found, and more precisely in some structural elements.
Hafnium is even used in the manufacture of thermionic-type electric generators and is often found in ion engines. Based on HfO2, dielectrics are created having a high level of dielectric constant. In the future, it is planned to replace the usual silicon oxide in microelectronics with HfO2 oxide. This replacement will increase the density of elements in the chip.
In conclusion, we can say that hafnium, the use of which takes place in many branches of human activity, starting everyday and ending with the military and atomic, is an extremely important element. This is a very popular metal and in nature always accompanies zirconium. Rarity and its features of qualitative characteristics determine a rather high cost.