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Zirconium has symbol Zr and atomic number 40. It is a metal extracted from the oxide mineral baddeleyite and Zirconium silicate. Zirconium is the nineteenth most abundant element in the earths crust, it is more plentiful than lead and copper. It has a good tendency to form metallic salts with good electrical conductivity. Due to these properties, it is used in various structural components of nuclear reactors.
It was discovered in 1789 by a German chemist Martin Heinrich Klaproth. Its metallic powder was made in 1824 by a Swedish Chemist, Jons J. Berzelius. In 1925, the method to purify useable quantities of metal was developed by two Dutch chemists J.H. de Boer and Anton E van Arkel. They also invented a thermal iodide process to thermally decompose Zirconium tetraiodide.
Fundamental properties of Zirconium Oxide:
Zirconia is a highly refractory material. It offers great chemical and corrosion inertness.
High density.
Chemical inertness.
Low thermal conductivity.
Ionic electrical conduction.
Resistance to molten metals.
High hardness.
Wear resistance.
Use temperatures up to 2400 C.
High fracture toughness.
Zirconium dioxide (ZrO2) commonly known as Zirconia, is a natural occurring metal with a monoclinic crystalline structure. It has same features and design as that of alumina, but gives better finish after surface grinding as compared to alumina. Machining Zirconia is much easier than machining alumina in comparison to alumina, its threads, big holes Etc. are easily produced. There are three basic principles that should be followed when machining Zirconia: high feed rates, slow speeds and a flood coolant system using a water soluble oil lubricant.
Manufacturing of Zirconium Oxide:
Absolutely pure products must be used for the production of high quality ceramics, advanced synthesis methods have been developed for high purity of Zirconia.
Raw material used for manufacturing of Zirconia is the mineral Zircon silicate. ZrO2 can be obtained on a large scale by melting coke and lime.
Its manufacturing methods include - reactions in the gas phase, molten salt baths, hydrothermal powder synthesis and sol-gel methods.
The Zirconia powder of particle sizes 0.01 to 0.10m can be obtained by gas phase manufacturing. The powder obtained by this method is further mixed with additives and then green bodies are manufactured by tape casting, dry pressing and slip casting.
After that, the sintering additives remain in the ceramic but the auxiliary substances which are volatile organic compounds are removed from the moulding before the sintering process.
The green body is transmuted into a raw product by sintering method, later polished & grounded as per the application.
The mouldings are endued their actual properties in the sintering process. The ceramic powder contracts by reducing to their specific shape. This is obtained by temperature-dependent diffusion process.
The speed of solid body diffusion can be increased by appropriate selection of sintering additives. If solid body diffusion occurs too slowly, sintering should be done with a liquid phase or under specific pressure.
The sintering process done under high temperatures and pressure increases the production costs of ceramic components.
Typical uses of Zirconium Oxide:
Thread and wire guides.
Hot metal extrusion dies.
Powder compacting dies.
In mill grinding industries.
Used in Oxygen sensors.
Fuel cell membranes.
Precision ball valve and seats.
High temperature induction furnace susceptors.
Rollers and guides for metal tube forming.
Marine pump seals and shaft guides.
Deep well down-hole valve seats.
Machining Zirconia is done through conventional methods as being chemically unreactive element requires unique high technology tools to produce the best quality products.
