Why Is Zirconium Important in Modern Chemistry?
What is Zirconium?
Zirconium is a durable, ductile, malleable, and lustrous silver-grey metal. It shares some physical properties with titanium. Moreover, Zirconium has extreme resistance to corrosion and heat. Besides, it is lighter than steel and has similar durability like copper.
Furthermore, thin shavings of this metal can ignite in air, spontaneously in higher temperature. The powder of this metal is black, and it is a dangerous fire hazard. Additionally, Zirconium does not dissolve in acids and alkalis.
Physical Properties of Zirconium
1- Zirconium is a hard, grey and shiny metal and it has a flaky surface. Moreover, it has a black or bluish-black like powder. Zirconium is highly flammable in its powder form.
2- Additionally, the zirconium melting point is 1,857°C, i.e. 3,375°F. Its boiling point is 3,577°C, which is 6,471°F, and its density is 6.5 grams per cubic centimetre.
3- Furthermore, at room temperature, this metal displays a hexagonally close-packed crystal structure, i.e. α-Zr. At 863°C, this α-Zr structure converts to β-Zr and remains the same until it reaches its melting point.
4- Another significant physical property of Zirconium is that it is transparent to neutrons. Due to the transparent property, Zirconium is considered as one of the best materials for nuclear power plants.
Since most of the durable materials available on this planet will catch the passing neutron; thus, compounds that can let a neutron pass through, it is an ideal one for a nuclear power plant. Moreover, zircons will not remove any neutrons from a fission reaction.
Zircaloy, which is an alloy of zircon, has been developed for this purpose.
5- As mentioned above, zirconium has a high resistance to heat and corrosion.
Chemical Properties of Zirconium
ZR element is mostly an inactive element. If it is exposed to air, it will react with oxygen and produce a thin layer of zirconium oxide. This layer protects it from any further corrosion. Besides, zircon oxide does not react with water or acid. Additionally, it also does not react with any hot acids.
Natural Occurrence of Zirconium
Zirconium is available in abundance in Earth’s surface. It has a concentration of around 130mg/kg in soil and about 0.0256 μg/L in seawater. However, it is not available as a native metal, which reflects its fundamental unsteadiness with respect to water. Additionally, two very well-known ores of Zirconium are –
Zircon or zirconium silicate
Zirconia or zirconia oxide is known as baddeleyite
This metal is found in almost every country on this planet. Moreover, countries like South Africa, Brazil, Australia, Russia, etc. have a large deposit of this compound. Among all of these countries, Australia and South Africa are the biggest producers of this element.
Isotopes of Zirconium
Isotopes are two or more types of any element. Isotopes differ from each other as per their mass number. Additionally, this mass number portrays the number of neutron and protons present within the nucleus of an element.
Furthermore, there are five natural isotopes of Zirconium, zirconium-90, 91, 92, 94, and 96. Among these isotopes, ZR-94 can undergo double beta decay with its half-life lasting more than 1.10X1017 years. However, this phenomenon has not been witnessed yet experimentally.
On the other hand, Z-96 has a half-life of 2.4X1019 years. Thus, it is the longest-living isotope of Zirconium. Moreover, among all of these natural isotopes, Z-90 is the most common and easily available one. It is almost 51.45% of all Zirconium that is available. Contrarily, Z-96 is the least common one and around 2.80% of the entire zirconium production.
In addition to its natural isotopes, there are 28 artificial isotopes of Zirconium ranging from 78 to 110 according to their atomic mass. Moreover, Z-93 is the longest living artificial isotope with a half-life of 1.53X106 years. Z-110 is the heaviest isotope, and also the most radioactive one. It has an estimated half-life of 30 milliseconds.
Typically, radioactive isotopes above 93 mass number decay via electron emission and the ones below 89 deteriorate by positron emission. However, the only exception here is, Zr-88. It decays due to electron capture.
Additionally, 5 isotopes of Zirconium exists as metastable isomers. These are Zr-83, 85, 89, 91, and Zr-90m1 and Zr-90m2. Among these, Zr-90m2 has the shortest half-life of 131 nanoseconds, and Z-89 has the longest one with 4.161 minutes. Moreover, the zirconium electron configuration is: [Kr] 4d² 5s².
Applications of Zirconium
Some of the prominent Zirconium uses are discussed here.
As a Compound
Zircons are primarily used directly in high-temperature applications. It is a hard and refractory chemical that has high resistance against chemicals. Due to the zirconium properties, it has several applications, and some of them are extremely well-known.
Additionally, they are primarily used as an opacifier, which helps in bringing an opaque and white appearance to ceramic materials. Moreover, owing to chemical resistance, Zirconium is also used in harsh conditions, namely moulds for melted metals.
Moreover, zirconium dioxides (ZrO2) are used in laboratory crucibles. It is used in metallurgical furnaces and as refractory materials. Since Zirconium is so flexible and flexible, it can be sintered in ceramic knives and others. Additionally, zircon and cubic zirconia are used for jewellery. Furthermore, it is a component in certain abrasives like sandpaper and grinding wheels.
As Metals
A small portion of Zirconium is transformed into metal that has very niche applications. As mentioned above, this substance has a high resistance against corrosion, and it is used to produce alloys that are exposed to harsh environments. Some of the prominent examples are light filaments, surgical appliances, watch cases, etc.
Moreover, Zirconium’s high reactivity with oxygen at higher temperatures has been exploited in specific applications like explosive primers, getters in vacuum tubes, etc.
Apart from these, another significant application of Zirconium is in nuclear power plants. As mentioned above, Zirconium’s ability to not to catch electrons during fission makes it a suitable material for nuclear plants. Moreover, cladding for such plants consumes only 1% supply of this compound.
Furthermore, the temperature resisting property of this material helps to produce parts of aeroplanes and space engines. Sections of the rocket and aeroplanes that go through extreme temperature and harsh environment are constructed via metals extracted from Zirconium. Jet engines, vanes, blade, combustors, etc. are protected by a thin ceramic layer. This layer is created by a mixture of zirconia and yttria.
In Postern emission tomography cameras
Zirconium isotope of ZR-89 is used to track and qualify of molecular antibodies with Positron Emission Tomography cameras or PET. This method is known as “immune-PET”. Additionally, this process has reached its peak of technical development. Hence, it is now entering its widespread phase of clinical applications.
Medical usage
This compound is used to produce a wide range of biomedical products. It includes middle-ear ossicular chain reconstruction, knee and hip replacement parts, dental implants and crowns, and many other prosthetic and restorative devices. Additionally, Zirconium is well-known for its ability to bind urea. Thus, it is utilised extensively during the treatment of chronic kidney disease.
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FAQs on Zirconium: Properties, Occurrence, Isotopes & Applications
1. What is Zirconium and what are its basic characteristics?
Zirconium (symbol Zr) is a lustrous, greyish-white transition metal with atomic number 40. It is known for its exceptional durability, malleability, and ductility. Physically, it resembles titanium but is significantly lighter than steel. One of its most valued characteristics is its outstanding resistance to corrosion and heat, making it stable when exposed to most acids, alkalis, and salt solutions.
2. What are the key physical and chemical properties of Zirconium?
Zirconium exhibits several important properties that define its use:
- Physical Properties: It is a strong, shiny, silvery-grey metal with a density of 6.52 g/cm³. It has a high melting point of 1855°C (2128 K). In powdered form, Zirconium can be highly flammable and may ignite spontaneously in air.
- Chemical Properties: Chemically, it is highly unreactive due to the formation of a stable, passive oxide layer on its surface. This layer protects it from corrosion by acids, alkalis, and seawater. It typically exhibits a +4 oxidation state in its compounds.
3. How does Zirconium occur in nature and where is it found?
Zirconium does not occur as a free element in nature. Its principal commercial source is the mineral zircon (ZrSiO₄), a zirconium silicate. Significant deposits of zircon are mined in countries like Australia, South Africa, the USA, Brazil, and India. It is also found in the mineral baddeleyite (ZrO₂), but zircon is the primary source for commercial extraction.
4. What is the electron configuration and atomic number of Zirconium?
The atomic number of Zirconium is 40, meaning a neutral atom has 40 protons and 40 electrons. Its ground state electron configuration is [Kr] 4d² 5s². This configuration places it in Period 5 and Group 4 of the periodic table, establishing it as a d-block transition element.
5. What are the most common applications of Zirconium and its compounds?
Zirconium's unique properties lend it to a wide range of applications:
- Nuclear Industry: Its very low absorption cross-section for thermal neutrons makes it an ideal material for cladding nuclear fuel rods in reactors.
- Chemical Industry: It is used to build corrosion-resistant equipment like pipes, valves, and heat exchangers for handling corrosive chemicals.
- Alloys: It is alloyed with other metals, such as steel, to improve their strength and durability.
- Ceramics: Zirconium dioxide (zirconia) is used to make strong, heat-resistant ceramics, dental implants, and cutting tools.
- Gemstones: The compound cubic zirconia is a popular synthetic gemstone used as a diamond simulant.
6. How many isotopes of Zirconium exist?
Zirconium has five naturally occurring stable isotopes: ⁹⁰Zr, ⁹¹Zr, ⁹²Zr, ⁹⁴Zr, and ⁹⁶Zr. The most abundant of these is ⁹⁰Zr, which constitutes over half (51.45%) of all natural zirconium. In addition to these, scientists have synthesized over 30 artificial radioactive isotopes, with mass numbers ranging from 77 to 114.
7. Why is Zirconium so highly resistant to corrosion?
Zirconium's remarkable resistance to corrosion is not due to its inherent lack of reactivity, but rather to a phenomenon called passivation. When exposed to air or moisture, a very thin, dense, and non-porous layer of zirconium oxide (ZrO₂) instantly forms on its surface. This stable oxide layer acts as a protective barrier, preventing corrosive agents like acids, alkalis, and saltwater from reaching and reacting with the underlying metal.
8. What makes the separation of Zirconium and Hafnium so challenging?
Separating Zirconium (Zr) from Hafnium (Hf) is notoriously difficult because their chemical properties are almost identical. This similarity arises from the lanthanide contraction. Hafnium, which is just below Zirconium in the periodic table, has an atomic radius nearly identical to Zirconium's due to the poor shielding effect of the 4f electrons in the elements preceding it. With similar sizes and the same number of valence electrons, they react in the same way, making their chemical separation a complex and costly process requiring techniques like fractional distillation or ion exchange.
9. Why is Zirconium metal a critical material for the nuclear power industry?
Zirconium is critical for the nuclear industry primarily due to its extremely low thermal neutron absorption cross-section. This means that Zirconium is virtually 'transparent' to the neutrons required to sustain a nuclear fission chain reaction. This property, combined with its high strength and corrosion resistance at high temperatures, makes it the perfect material for cladding (coating) uranium fuel rods. It contains the fuel securely while allowing the essential neutrons to pass through freely, maximising the efficiency of the reactor.
