Zirconium dioxide: properties and applications. Zirconium (metal): medicinal properties and uses
Zircon is the most common zirconium mineral. It is found in all types of rocks, but mainly in granites and syenites. In Ginderson County (North Carolina), zircon crystals several centimeters long were found in pegmatites, and crystals weighing kilograms were discovered in Madagascar. Baddeleyite was discovered by Hussac in 1892 in Brazil. The main deposit is located in the Pocos de Caldas region (Brazil). Most large deposits zirconium are located in the USA, Australia, Brazil, and India.
In Russia, which accounts for 10% of the world's zirconium reserves (3rd place in the world after Australia and South Africa), the main deposits are: Kovdorskoe primary baddelite-apatite-magnetite in the Murmansk region, Tuganskoe placer zircon-rutile-ilmenite in the Tomsk region, Central alluvial zircon-rutile-ilmenite in the Tambov region, Lukoyanovskoye alluvial zircon-rutile-ilmenite in the Nizhny Novgorod region, Katuginskoye primary zircon-pyrochlore-cryolite in the Chita region and Ulug-Tanzek primary zircon-pyrochlore-columbite.
Reserves at zirconium deposits in 2012, thousand tons *
| Australia | 21,000.0 |
| South Africa | 14,000.0 |
| India | 3,400.0 |
| Mozambique | 1,200.0 |
| China | 500.0 |
| Other countries | 7,900.0 |
| Total stocks | 48,000.0 |
* US Geological Survey data
In industry, the starting raw materials for the production of zirconium are zirconium concentrates with a mass content of zirconium dioxide of at least 60-65%, obtained by enriching zirconium ores. The main methods for obtaining zirconium metal from concentrate are chloride, fluoride and alkaline processes. The largest zircon producer in the world is Iluka.
Zircon production is concentrated in Australia (40% of production in 2010) and South Africa (30%). The rest of the zircon is produced in more than a dozen other countries. Zircon production increased annually by an average of 2.8% between 2002 and 2010. Major producers such as Iluka Resources, Richards Bay Minerals, Exxaro Resources Ltd and DuPont extract zircon as a by-product during titanium mining. Demand for titanium minerals has not increased at the same rate as zircon in the past decade, so producers have begun to develop and exploit mineral sand deposits with higher zircon content, such as in Africa and South Australia.
* US Geological Survey data
Zirconium has been used in industry since the 30s of the 20th century. Because of high cost its use is limited. Metal zirconium and its alloys are used in nuclear energy. Zirconium has a very small thermal neutron capture cross section and a high melting point. Therefore, metallic zirconium, which does not contain hafnium, and its alloys are used in nuclear energy for the manufacture of fuel elements, fuel assemblies and other structures of nuclear reactors.
Another area of application of zirconium is alloying. In metallurgy it is used as an alloy. A good deoxidizer and denitrogenizer, superior in efficiency to Mn, Si, Ti. Alloying steels with zirconium (up to 0.8%) increases their mechanical properties and machinability. It also makes copper alloys more durable and heat-resistant with a slight loss of electrical conductivity.
Zirconium is also used in pyrotechnics. Zirconium has a remarkable ability to burn in atmospheric oxygen (self-ignition temperature - 250°C) with virtually no smoke emission and with high speed. In this case, the highest temperature for metal combustibles develops (4650°C). Due to high temperature the resulting zirconium dioxide emits a significant amount of light, which is used very widely in pyrotechnics (production of fireworks and fireworks), production chemical sources light used in various areas human activity (torches, flares, flare bombs, FOTAB - photo air bombs; widely used in photography as part of disposable flash lamps until it was replaced by electronic flashes). For use in this area, not only zirconium metal is of interest, but also its alloys with cerium, which provide a significantly higher luminous flux. Powdered zirconium is used in a mixture with oxidizing agents (Berthollet salt) as a smokeless agent in pyrotechnic signal lights and fuses, replacing fulminate of mercury and lead azide. Successful experiments were carried out on the use of zirconium combustion as a light source for pumping a laser.
Another use of zirconium is in superconductors. Superconducting alloy of 75% Nb and 25% Zr (superconductivity at 4.2 K) withstands loads up to 100,000 A/cm2. In the form of a structural material, zirconium is used in the manufacture of acid-resistant chemical reactors, fittings, and pumps. Zirconium is used as a substitute noble metals. In nuclear energy, zirconium is the main material for fuel cladding.
Zirconium has high resistance to biological environments, even higher than titanium, and excellent biocompatibility, due to which it is used to create bone, joint and dental prostheses, as well as surgical instruments. In dentistry, ceramics based on zirconium dioxide is a material for the manufacture of dental prosthetics. In addition, due to its bioinertness, this material serves as an alternative to titanium in the manufacture of dental implants.
Zirconium is used to make a variety of tableware that has excellent hygienic properties due to its high chemical resistance.
Zirconium dioxide (mp 2700°C) is used for the production of refractory materials (bakor - baddeleyite-corundum ceramics). It is used as a substitute for fireclay, as it increases the cycle time in furnaces for melting glass and aluminum by 3-4 times. Refractories based on stabilized dioxide are used in the metallurgical industry for troughs, glasses for continuous casting of steel, crucibles for melting rare earth elements. It is also used in cermets - ceramic-metal coatings that have high hardness and resistance to many chemicals and can withstand short-term heating up to 2750°C. Dioxide is a suppressor of enamels, giving them a white and opaque color. Based on the cubic modification of zirconium dioxide, stabilized with scandium, yttrium, and rare earths, a material is obtained - cubic zirconia (from the Lebedev Physical Institute where it was first obtained), cubic zirconia is used as an optical material with large coefficient refraction (flat lenses), in medicine ( surgical instrument), as a synthetic gemstone (dispersion, refractive index and color play are greater than diamond), upon receipt synthetic fibers and in the production of certain types of wire (drawing). When heated, zirconium dioxide conducts current, which is sometimes used to produce heating elements, stable in air at very high temperatures. Heated zirconium is capable of conducting oxygen ions as a solid electrolyte. This property is used in industrial oxygen analyzers.
Zirconium hydride is used in nuclear technology as a very effective neutron moderator. Zirconium hydride is also used for coating with zirconium in the form thin films by thermal decomposition on various surfaces.
Zirconium nitride material for ceramic coatings, melting point about 2990°C, hydrolyzes in aqua regia. Found application as coatings in dentistry and jewelry.
Zircon, i.e. ZrSiO4 is the main source mineral of zirconium and hafnium. Various rare elements and uranium, which are concentrated in it, are also extracted from it. Zircon concentrate is used in the production of refractories. The high uranium content of zircon makes it a convenient mineral for determining age using uranium-lead dating. Transparent crystals zircon are used in jewelry(hyacinth, slang). When zircon is calcined, bright blue stones called starlite are obtained.
About 55% of all zirconium is used for the production of ceramics - ceramic tiles for walls, floors, and also for the production of ceramic substrates in electronics. About 18% of zircon is used in the chemical industry, and consumption growth in this area is last years on average 11% per year. Approximately 22% of zircon is used for metal smelting, but this direction has not been so popular lately due to the availability of cheaper methods for producing zirconium. The remaining 5% of zircon is used to make cathode tubes, but consumption in this area is falling.
Zircon consumption increased strongly in 2010 to 1.33 million tons, after the global economic downturn in 2009 caused consumption to decline by 18% by 2008. Increased consumption in the ceramics industry, which accounted for 54% of zircon consumption in 2010, especially in China, but also in other emerging economies such as Brazil, India and Iran, was key factor for increased demand for zircon in the 2000s. While in the US and the Eurozone, consumption even decreased. Consumption of zircon in zirconium chemicals, including zirconium dioxide, more than doubled between 2000 and 2010, while the use of zircon for smelting zirconium metal showed a slower growth rate.
According to Roskill, 90% of the world's zirconium metal consumption is used in the production of nuclear reactor components and about 10% in the manufacture of corrosion-resistant and high pressures lining of containers used in production plants acetic acid. According to experts, in the future, the global demand for zirconium metal is expected to increase, since a number of countries (China, India, South Korea and the USA) are planning to build new nuclear power plants.
Zirconium oxide, also known as zirconium dioxide, is used in industrial applications, including medications, fiber optics, waterproof clothing and cosmetics. There is a greater consumption of zirconia materials - zircon flour and fused zirconia due to the rapid increase in ceramic tile production in China. South Korea, India and China are important growth markets for zirconium oxide. According to the zirconium market research report, Asia Pacific represents the largest and fastest growing regional market in the world. Saint-Gobain, based in France, is one of the largest manufacturers of zirconium dioxide.
The largest end use market for zirconium is ceramics, which includes tiles, sanitary product and tableware. Next largest markets, which use zirconium materials, refractory and foundry sectors. Zircon is used as an additive for a wide variety of ceramic products, and it is also used in glass coatings in computer monitors and television panels because the material has radiation-absorbing properties. Zirconium-infused bricks are used as an alternative to basic fused zirconia solutions.
Production and consumption of zircon (ZrSiO4) in the world, thousand tons*
| year | 2008 | 2009 | 2010 | 2011 | 2012 |
| Total production | 1300.0 | 1050.0 | 1250.0 | 1400.0 | 1200.0 |
| China | 400.0 | 380.0 | 600.0 | 650.0 | 500.0 |
| Other countries | 750.0 | 600.0 | 770.0 | 750.0 | 600.0 |
| Total consumption | 1150.0 | 980.0 | 1370.0 | 1400.0 | 1100.0 |
| Market balance | 150.0 | 70.0 | -120.0 | -- | 100.0 |
| COMEX price | 788.00 | 830.00 | 860.00 | 2650.00 | 2650.00 |
* Summary data
The zircon market showed a sharp decline that began in late 2008 and continued through 2009. Manufacturers have cut production volumes to cut costs and stop stockpiling. Consumption began to recover at the end of 2009, accelerated growth in 2010, and continued in 2011. Supplies, especially from Australia, where more than 40% of zirconium ores are mined, have been stagnant for a long time, and other producers were forced to put approximately 0.5 million tons of their reserves on the market during 2008-2010. Market shortages, coupled with declining inventory levels, led to price increases that began in early 2009. By January 2011, Australian zircon premium prices were at record levels after rising 50% since early 2009 and continued to rise further in 2011-2012.
In 2008, prices for zirconium sponge increased due to the rise in price of zircon sand, which is raw material for metal production. Prices industrial grades zirconium increased by 7-8% - to $100/kg, and for metal for nuclear reactors - by 10% - to $70 - $80. At the end of 2008 and the beginning of 2009, there was a slight decline in prices, but only in the second half In 2009, zirconium prices resumed their growth again, and in such a way that average zirconium prices in 2009 were higher than in 2008. In 2012, zirconium prices rose to $110/kg.
Despite more low consumption In 2009, zircon prices did not fall sharply as major producers cut production and lowered inventories. In 2010, production could not keep up with demand, primarily because Chinese imports of zircon increased by more than 50% in 2010 to 0.7 million tons. Demand for zircon is predicted to increase by 5.4% annually until 2015, but production capacity may only increase by 2.3% per year. Additional supply will therefore continue to be limited and prices may continue to rise until new projects come online.
According to a research report published by Global Industry Analysts (GIA), the global zirconium market is expected to reach 2.6 million metric tons by 2017. The report provides sales estimates and forecasts from 2009 to 2017 in various geographic markets including Asia Pacific, Europe, Japan, Canada and the United States.
Growth in the international nuclear energy industry will increase demand for zirconium, as well as increase its production capacity globally. Other growth factors are increasing demand in the Asia-Pacific region as well as in the ceramic tile industry worldwide.
Page 2
In 1945, only 0.07 kg of zirconium was produced in the USA, but since 1948, in connection with work on the creation nuclear reactors Zirconium production increased sharply and after a few years reached several tens of tons.
Deposits of zirconium ore, which is much more widespread in nature than, for example, beryllium, are, according to foreign press reports, in the USA, India, Brazil, Australia, and in a number of African countries. Zirconium production in the USA increased 3 thousand times from 1947 to 1958.
Due to its high anti-corrosion properties, zirconium can be used for the manufacture of parts for chemical equipment, medical instrument and in other areas of technology. However, it is unlikely that the production of zirconium would have reached the modern level so quickly if it had not had another specific property - small cross section absorption of thermal neutrons.
The technology and equipment used to produce hafnium using the Kroll process are essentially the same as those used in the production of zirconium metal. Modifications compared to technological process zirconium production is determined by replacing or changing individual devices, technological operations and varieties starting materials. Here one should keep in mind the greater sensitivity of hafnium tetrachloride to atmospheric moisture, the greater stability of hafnyl chloride and the somewhat greater pyrophoric properties of the freshly obtained metal sponge.
Since hafnium is extracted as a by-product during the production of reactor zirconium, its production increases in proportion to the output of the latter, and by 50 kg of zirconium; approximately 1 kg of hafnium is obtained. Using this calculation and fragmentary information about the production of zirconium in individual. According to the forecast of the US Bureau of Mines, published in 1975, the country's need for hafnium at the turn of the 20th - 21st centuries.
Spectral analysis of zirconium for impurities is largely difficult due to the fact that against the background of the multiline spectrum of zirconium it is difficult to identify weak lines in the spectra of low concentrations of impurities. This method also makes it possible to determine low concentrations of fluorine in metallic zirconium, which is very important in controlling the production of electrolytic zirconium.
Since hafnium is extracted as a by-product when producing reactor zirconium, its production increases in proportion to the output of the latter, with approximately 1 kg of hafnium being obtained per 50 kg of zirconium. Over the current decade (1970 - 1980), the world's nuclear power plant capacity will increase 5 - 8 times, and the production of zirconium and hafnium will increase accordingly. After all, every megawatt of nuclear power plant power requires from 45 to 79 kg of zirconium for the manufacture of pipes and other parts. In addition, 25 - 35% of zirconium tubes in operating reactors must be replaced annually. As a result, already in the mid-70s, approximately the same amount of zirconium will be consumed for these purposes as for new reactors.
Fluoride-sublimation technology for the purification of zirconium tetrafluoride from Al, Ca, Cu, Fe, Mg fluorides was well mastered in the USSR in the 80s at the Pridneprovsky Chemical Plant during the development and development of fluoride extraction technology for the production of nuclear-pure zirconium.
Ca, Cu, Fe, Mg, Th) is in the form of a fluoride composition obtained by sublimation purification of zirconium. For large-scale plasma production zirconium and silicon, the accumulated mass of these wastes can become significant over time; for their processing, plasma and frequency technologies can be used to extract these components in the form of dispersed oxides or metals (see Chap.
When processing 1 ton of zircon and extracting zirconium and silicon from it in the form of fluorides, 4–6 kg of A1 remain in the waste; 0 1 kg Ca; 0 4 kg Si; 1 3 kg Fe; 1 1 kg Mg; 0 3 - 0 4 kg Th; 0 3 - 0 4 kg U; 0 3 kg Ti; those. 8 6 kg of metals, the main part of which (A1, Ca, Cu, Fe, Mg, Th) is in the form of a fluoride composition obtained by sublimation purification of zirconium. In large-scale plasma production of zirconium and silicon, the accumulated mass of these wastes can become significant over time; for their processing, plasma and frequency technologies can be used to extract these components in the form of dispersed oxides or metals (see Chap.
In 1945, only 0.07 kg of zirconium was produced in the United States, but starting in 1948, in connection with work on the creation of nuclear reactors, zirconium production increased sharply and after a few years reached several tens of tons. As a result, the technology for producing zirconium, which was rare a few years ago, is now more advanced than the technology for producing many other metals known and used for decades.
According to the heating principle, vacuum arc furnaces belong to arc furnaces direct action. Vacuum arc furnaces are one of the new types of electrothermal equipment. Their appearance is caused by an increase in the production of zirconium, titanium, molybdenum and some other refractory and chemically active materials.
But even in this case, it cannot be used without preliminary chemical purification (see section 15.5) from the element hafnium, which always accompanies it in nature, and has properties similar to zirconium chemical properties. Hafnium, extracted in the production of reactor grade zirconium, is excellent material for the manufacture of reactor control rods.
Hafnium is in group IV periodic table elements of D.I. Mendeleev and is included in the titanium subgroup. It belongs to the trace elements that do not have their own minerals; in nature accompanies zirconium. Currently, it is obtained as a by-product in the production of zirconium. In terms of chemical and physical properties, hafnium is close to zirconium, but differs significantly from the latter in nuclear properties.
In the chemical industry, molybdenum is used in the form of gaskets and bolts for hot repair (filling) of lined glass tiles vessels used when working with sulfuric acid and acidic media in which hydrogen is released. In products operating in sulfuric acid, molybdenum thermocouples and valves are also used, and molybdenum alloys serve as reactor linings in installations intended for the production of n-butyl chloride by reactions involving hydrochloric and sulfuric acids at temperatures exceeding 170 C. various applications processes that use molybdenum also include processes of liquid-phase hydrochlorination, production of zirconium and ultra-pure thorium.
The fortieth element of the periodic table was discovered in 1783 by a chemist German origin M.G. Klaproth. Zirconium metal purified from impurities was obtained only at the beginning of the 20th century. And although almost 100 years have passed since that moment, the metal still has a number of uncertainties, starting with the origin of its name and ending with its effect on human health. Why has the price per gram of it continued to rise for several decades?
Being in nature
Zirconium in natural conditions occurs only in the form of oxides and silicates. Among them, zircon, eudialyte, and baddeleyite are mainly distinguished. It is worth noting that the metal in deposits is always accompanied by hafnium. This happens due to the similar crystal lattice of metals.
The main share of zirconium minerals is located in the lithosphere. There is an average of 210 grams of zircon per ton of the earth's crust. Zirconium compounds are also found in the composition sea water. But its concentration here is much lower and amounts to 0.05 mg per 1000 liters.
The leaders in the number of zirconium deposits are Australia (zircon), South Africa (baddeleyite), slightly less than the USA, Brazil and India. Russia accounts for 10% of world reserves.
Receipt
Initially, zirconium was isolated from oxides using the “growth” method. The zirconium strip was placed on hot tungsten filaments. Under the influence of temperatures above 2000 ºС, the zirconium metal adhered to the surface of the heater, and the remaining components of the compound burned out.
This method required large quantity electricity and soon the more economical Kroll method was developed. Its essence lies in the preliminary chlorination of zirconium dioxide followed by reduction with magnesium. But the development of methods for producing zirconium did not stop there. After some time, industry began to use even cheaper alkaline and fluoride reduction of zirconium from oxides.
Zirconium e110 composition
Iodide zirconium
Highly flexible and with low performance strength. It is obtained by the iodide method based on the ability of the metal to form compounds with iodine. In this case, harmful impurities are easily separated and pure metal is obtained. Rods are made from zirconium iodide.
Price
The main suppliers of zirconium to the world market are Australia and South Africa. Recently, the preponderance in the export of zircon and zirconium minerals has increasingly leaned towards the Republic of South Africa. The main consumers are the European Union (Italy, France, Germany), China and Japan. Zircon is traded mainly in the form of ferroalloys.
Over the past 10 years, demand for zirconium metal has increased by an average of 5.2% per year. During this time, production capacity managed to rise by a little more than 2%. As a result, there was a constant shortage of zirconium on the world market, which was a prerequisite for increasing its cost.
There are 2 main reasons for the growth in demand for this metal:
- Global expansion of the nuclear industry.
- Active use of zirconium in the production of ceramics.
Also, some experts believe that the increase in zirconium prices was partly influenced by the cessation of baddeleyite mining in Australia.
On Russian market For secondary metal, the cost of zirconium ranges from 450 to 7,500 rubles per kilogram. The purer the metal, the more expensive the price.
Application
The above properties provide zirconium with extensive use in various kinds industries. The following areas are highlighted here:
- In electrical engineering, zirconium alloy with niobium is used as a superconductor. Withstands loads up to 100 kA/cm2. The transition point to the superconducting mode is 4.2 K. Also in radio equipment, electronic circuit boards are coated with zirconium to absorb the released gases. Zirconium filters for X-ray tube radiation are characterized by a high monochrome value.
- In nuclear energy, it is used as a material for the shells of fuel rods (the zone where nuclear fission and heat energy production are directly carried out) and other components of a thermonuclear reactor.
- Metallurgy uses zirconium as an alloying element. This metal is a strong deoxidizer, surpassing both manganese and silicon in this indicator. Adding only 0.5% zirconium to structural metals (steel 45, 30KhGSA) increases their strength by 1.5-1.8 times. In this case, the cutting process is further improved. Zircon is the main component of corundum ceramics. Compared to fireclay, its service life is 3-4 times longer. This refractory material is used in the manufacture of crucibles and troughs of steel furnaces.
- In mechanical engineering, metal serves as a material for products such as pumps and pipe shut-off valves that operate under conditions of exposure to aggressive environments.
- In pyrotechnics, zirconium metals are used to make fireworks and fireworks. This happens due to the absence of smoke during combustion, as well as the release of a significant amount of light energy.
- In the chemical industry, zircon serves as a raw material for cermet - a metal-ceramic coating with increased wear resistance and immunity to acids.
- In optics, cubic zirconia is actively used - processed zircon with additions of scandium and other rare earth metals. Cubic zirconias have a significant refractive angle, which allows them to be used as a material for the production of lenses. In jewelry, cubic zirconia is known as a synthetic substitute for diamond.
- In the military industry, zirconium is used as a filler for tracer bullets and flares.
Physical and chemical properties
Zirconium is a metal that looks like silver. Its density is 6506 kg/m3. Melting point - 1855.3 ºС. Specific heat fluctuates within 0.3 KJ/kg C. This metal does not have high thermal conductivity. Its value is at the level of 21 W/m C, which is 1.9 times lower than that of titanium. The electrical resistance of zirconium is 41-60 μOhm cm and is directly dependent on the amount of oxygen and nitrogen in the metal.
Zirconium has one of the lowest transverse thermal neutron capture rates (0.181 barn). In terms of this parameter, of the currently known metals, it is surpassed only by magnesium (0.060 barn).
Zirconium, like iron, is paramagnetic. His susceptibility to magnetic field increases with increasing temperature.
Pure zirconium does not have high mechanical characteristics. Its hardness is about 70 units on the Vickers scale. The tensile strength is 175 MPa, which is almost 2.5 times lower compared to carbon steel of ordinary quality. Yield strength 55 MPa. Zirconium is a ductile metal with an elastic modulus of 96 MPa.
All of the above mechanical properties are conditional, because their value changes greatly with increasing impurities in the zirconium composition.
Thus, an increase in oxygen content (up to 0.4%) reduces the plasticity of zirconium to such a state that forging and stamping becomes completely impossible. An increase in hydrogen content to 0.001% increases the fragility of zirconium by almost 2 times.
Zirconium is resistant to water and most alkalis and acids. But, like mechanical characteristics, corrosion resistance is directly dependent on metal contamination with elements such as carbon, titanium and aluminum. Metal does not enter chemical reaction with 50% solutions of sulfuric and hydrochloric acid. It reacts with nitric acid only at temperatures above 95 ºС. It is the only metal resistant to alkalis containing ammonia. When the mark passes 780 ºС, active absorption of oxygen by zirconium begins. With nitrogen, these processes proceed more slowly, but the temperature is also lower. Only 600 ºС.
The most active gas in this regard is hydrogen. Its penetration deep into the metal begins already at 145 ºС and is accompanied by such an abundant release of heat that zirconium increases in volume. Zirconium dust is especially fire hazardous due to its ability to spontaneously ignite in air. It is worth noting that this process is reversible. Complete removal hydrogen is carried out on special equipment at a temperature of 800 ºС.
Medicinal properties
As a chemical element, it does not have any effect on the human body. On the contrary, it is one of the most biologically inert materials. According to this indicator, zirconium is ahead of such metals as titanium and stainless steel. The well-known zirconium bracelets, actively advertised in the late 90s, have not proven themselves in real practice. Medical experts have proven that the well-being from their use is a consequence of the Placebo effect.
Although, on the other hand, it is known that wearing zirconium earrings promotes faster healing of the wound after ear piercing.
Zirconium has been used in industry since the 30s of the 20th century. Due to its high cost, its use is limited. The only enterprise, specializing in the production of zirconium in Russia is the Chepetsk Mechanical Plant (Glazov, Udmurtia).
Applications of zirconium dioxide
Highly heated zirconium dioxide emits light so intensely that it can be used in lighting technology. The famous German scientist Walter Hermann Nernst took advantage of this property. The filament rods in the Nernst lamp were made of ZrO2. Hot zirconium dioxide is sometimes used as a light source in laboratory experiments.
In industry, silicate production and metallurgy were the first to use zirconium dioxide. At the beginning of this century, zircon refractories were made that last three times longer than conventional ones. Refractories containing the addition of ZrO2 allow up to 1200 steel melts to be carried out without repairing the furnace. It's a lot.
Zircon bricks have replaced fireclay (a widely used refractory material based on clay or kaolin) in the smelting of aluminum metal, and here's why. Fireclay is fused with aluminum, and slag build-up forms on its surface, which must be periodically cleaned off. But zircon bricks are not wetted by molten aluminum. This allows zircon-lined kilns to operate continuously for ten months.
Significant quantities of zirconium dioxide are consumed in the production of ceramics, porcelain and glass.
The list of industries that need zirconium dioxide could go on and on. But let’s see what the metal zirconium, which was not obtained for so long, was useful for.
Zirconium and metallurgy
The very first consumer of zirconium metal was the ferrous metallurgy. Zirconium turned out to be a good deoxidizing agent. In terms of deoxidizing action, it surpasses even manganese and titanium. At the same time, zirconium reduces the content of gases and sulfur in steel, the presence of which makes it less ductile.
Steels alloyed with zirconium do not lose the required toughness over a wide temperature range; they resist shock loads well. Therefore, zirconium is added to the steel used to make armor plates. This probably takes into account the fact that zirconium additives also have a positive effect on the strength of steel. If a sample of steel not alloyed with zirconium fails at a load of about 900 kg, then steel of the same recipe, but with the addition of only 0.1% zirconium, can withstand a load of 1600 kg.
Non-ferrous metallurgy also consumes significant quantities of zirconium. Here its action is very diverse. Minor additions of zirconium increase the heat resistance of aluminum alloys, and multicomponent magnesium alloys with the addition of zirconium become more corrosion-resistant. Zirconium increases the resistance of titanium to acids. Corrosion resistance of titanium alloy with 14% Zr at 5% hydrochloric acid at 100°C 70 times (!) more than that of commercially pure titanium. Zirconium has a different effect on molybdenum. The addition of 5% zirconium doubles the hardness of this refractory but rather soft metal.
There are other applications for zirconium metal. High corrosion resistance and relative refractoriness have made it possible to use it in many industries. Die dies for the production of artificial fiber, parts for hot fittings, laboratory and medical equipment, catalysts - this is not a complete list of products made from metal zirconium.
However, it was not metallurgy or mechanical engineering that became the main consumers of this metal. Nuclear energy required huge quantities of zirconium.
Application of zirconium in nuclear energy
This metal did not come into use in nuclear technology right away. In order to become useful in this industry, a metal must have a certain set of properties. (Especially if it claims to be a structural material in the construction of reactors.) The main one of these properties is the small cross section for the capture of thermal neutrons. In principle, this characteristic can be defined as the ability of a material to retain and absorb neutrons and thereby prevent the spread of a chain reaction.
The neutron capture cross section is measured in barns. The larger this value, the more neutrons the material absorbs and the more it prevents the development of a chain reaction. Naturally, materials with a minimum capture cross section are selected for the reaction zone of reactors.
For pure metallic zirconium this value is 0.18 barn. Many cheaper metals have capture cross sections of the same order: for tin, for example, it is 0.65 barn, for aluminum - 0.22 barn, and for magnesium - only 0.06 barn. But tin, magnesium, and aluminum are fusible and not heat-resistant; zirconium melts only at 1860°C.
It seemed that the only limitation was the rather high price of element No. 40 (although for this industry there is no need to spare money), but another complication arose.
IN earth's crust zirconium is always accompanied by hafnium. In zirconium ores, for example, its content is usually from 0.5 to 2.0%. A chemical analogue of zirconium (hafnium is located directly below zirconium in the periodic table) captures thermal neutrons 500 times more intense than zirconium. Even minor hafnium impurities greatly affect the course of the reaction. For example, a 1.5% hafnium impurity increases the zirconium capture cross section by 20 times.
The technology was faced with the problem of completely separating zirconium and hafnium. While the individual properties of both metals are very attractive, their combined presence makes the material completely unsuitable for nuclear technology.
The problem of separating hafnium and zirconium turned out to be very difficult - their chemical properties are almost identical due to the extreme similarity in the structure of the atoms. To separate them, complex multi-stage purification is used: ion exchange, multiple precipitation, extraction.
All these operations significantly increase the cost of zirconium, and it is already expensive: the ductile metal (99.7% Zr) is many times more expensive than the concentrate. The problem of economical separation of zirconium and hafnium is still waiting to be solved.
And yet, zirconium became an “atomic” metal.
This is, in particular, evidenced by the following facts. The first American nuclear submarine, the Nautilus, had a zirconium reactor installed. Later it turned out that it was more profitable to make the shells of fuel elements from zirconium, rather than stationary parts of the reactor core.
Nevertheless, the production of this metal is increasing from year to year, and the rate of this growth is unusually high. Suffice it to say that in the decade from 1949 to 1959, world zirconium production increased 100-fold! According to American data, in 1975 the world production of zirconium was about 3000 tons.
Metal zirconium and its alloys, areas of applicationNuclear energy
Zirconium has a very small thermal neutron capture cross section. Therefore, metallic zirconium, which does not contain hafnium, and its alloys are used in nuclear energy for the manufacture of fuel elements, fuel assemblies and other structures of nuclear reactors.
Alloying
In metallurgy it is used as an alloy. A good deoxidizer and denitrogenizer, superior in efficiency to Mn, Si, Ti. Alloying steels with zirconium (up to 0.8%) increases their mechanical properties and machinability. It also makes copper alloys more durable and heat-resistant with a slight loss of electrical conductivity.
Pyrotechnics
Zirconium has a remarkable ability to burn in air oxygen (self-ignition temperature - 250 ° C) with virtually no smoke and at high speed. In this case, the highest temperature for metal combustibles develops (4650 °C). Due to the high temperature, the resulting zirconium dioxide emits a significant amount of light, which is used very widely in pyrotechnics (production of fireworks and fireworks), the production of chemical light sources used in various fields of human activity (torches, flares, flare bombs, FOTAB - photo air bombs). For use in this area, not only zirconium metal is of interest, but also its alloys with cerium (significantly higher luminous flux). Powdered zirconium is used in a mixture with oxidizing agents (Berthollet salt) as a smokeless agent in pyrotechnic signal lights and fuses, replacing fulminate of mercury and lead azide.
Superconductor
Superconducting alloy of 75% Nb and 25% Zr (superconductivity at 4.2 K) withstands loads up to 100,000 A/cm².
Construction material
In the form of a structural material it is used in the manufacture of acid-resistant chemical reactors, fittings, and pumps. Zirconium is used as a substitute for precious metals. In nuclear energy, zirconium is the main material for fuel cladding.
Iron-free zircon is used in the form of various refractories for lining glass melting and metallurgical furnaces. It is also used in the production of building ceramics, enamels and glazes for sanitary products.
Medicine
Zirconium has high resistance to biological environments, even higher than titanium, and excellent biocompatibility, due to which it is used to create bone, joint and dental prostheses, as well as surgical instruments.
In world practice, implant manufacturers use it for the manufacture of plates and screws. stainless steel and titanium alloys.
NIKIET has developed design and technological documentation and mastered the production of implants made of zirconium alloys of the E125 and E110 grades, which are not inferior to the best foreign models. The use of implants made of zirconium alloys provides a number of advantages:
- high corrosion resistance;
- unique biocompatibility, absence allergic reactions, which allows the use of implants without repeated surgery to remove them;
- the material and manufacturing technology provide the required set of strength properties;
- the relatively low density of the alloy makes it possible to produce lightweight implants;
- good plasticity ensures a more precise fit of the implant along the bone contour by bending.
NIKIET produces sets of implants and instruments for bone osteosynthesis and maxillofacial surgery. It included reconstructive plates of 22 types, cortical screws of four sizes for their fastening, drills of three sizes made of tool steel with diamond coating and with stainless steel shanks, as well as a screwdriver made of titanium alloy with a special grip for the screw.
To ensure the production of implants (plates and screws), NIKIET developed a technology and launched the production of blanks (strips and rods) from zirconium alloys.
The high corrosion resistance of zirconium has made it possible to use it in neurosurgery. Zirconium alloys are used to make hemostatic clamps, surgical instruments, and sometimes even threads for suturing during brain operations.
Zirconium is used to make a variety of tableware that has excellent hygienic properties due to its high chemical resistance.
Zirconium compoundsZirconium dioxide (mp 2700 °C). Area of application: production of refractory shells (bacor - baddeleyite-corundum ceramics). It is used as a substitute for fireclay, as it increases the cycle time in furnaces for melting glass and aluminum by 3-4 times. Refractories based on stabilized dioxide are used in the metallurgical industry for troughs, glasses for continuous casting of steel, crucibles for melting rare earth elements. It is also used in cermets - ceramic-metal coatings that have high hardness and resistance to many chemicals and can withstand short-term heating up to 2750 °C. Dioxide is a suppressor of enamels, giving them a white and opaque color. Based on the cubic modification of zirconium dioxide, stabilized by scandium, yttrium, and rare earths, a material is obtained - cubic zirconia (from the Lebedev Physical Institute where it was first obtained), cubic zirconia is used as an optical material with a high refractive index (flat lenses), in medicine (surgical instrument) , as a synthetic jewelry stone (dispersion, refractive index and color play are greater than that of a diamond), in the production of synthetic fibers, and in the production of certain types of wire (drawing). When heated, zirconium dioxide conducts current, which is sometimes used to make heating elements resistant to air at very high temperatures. Heated zirconium is capable of conducting oxygen ions as a solid electrolyte. This property is used in industrial oxygen analyzers.
Zirconium diboride ZrB 2 - cermet. In various mixtures with tantalum nitride and silicon carbide material for the production of cutters. Zirconium metal prices averaged US$120 per kilogram in 2006.
Zirconium carbide (mp 3530 °C) is the most important construction material for solid phase nuclear jet engines.
Zirconium beryllide is extremely hard and resistant to oxidation in air up to 1650 °C, and is used in aerospace technology (engines, nozzles, reactors, radioisotope electric generators).
Zirconium hydride is used as a component rocket fuel, in nuclear technology as a very effective neutron moderator. Zirconium hydride is also used to coat zirconium in the form of thin films using its thermal decomposition on various surfaces.
Zirconium nitride material for ceramic coatings, melting point about 2990 °C, hydrolyzes in aqua regia. Found application as coatings in dentistry and jewelry.
Zirconium is an element of a secondary subgroup of the fourth group of the fifth period of the periodic table chemical elements D.I. Mendeleev, atomic number 40. Denoted by the symbol Zr (lat. Zirconium). The simple substance zirconium (CAS number: 7440-67-7) is a shiny metal of silver-gray color. It has high ductility and is resistant to corrosion. It exists in two crystalline modifications: α-Zr with a hexagonal lattice of the magnesium type, β-Zr with a cubic body-centered lattice of the α-Fe type, transition temperature α↔β 863 °C Zirconium in the free state is a shiny metal. Zirconium, which does not contain impurities, is ductile and can be easily processed hot and cold. One of the most valuable properties of zirconium is its high resistance to corrosion in various environments.