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Crucible Materials
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
Zirconia has a combination of high melting point (2715°C) and potential for high strength with a maximum operating temperature of 2400°C depending on grade (Fruehan 1998). Zirconium oxide (ZrO2) occurs naturally as the mineral baddeleyite, commercially used zirconia is generally obtained by processing zircon. Combined with high melting point, the superior resistance to corrosion and erosion makes zirconia an attractive refractory (Bullock et al. 1989). Zirconia is polymorphic. The stable room-temperature phase is monoclinic. Around 1170°C, it transforms to the tetragonal, which is stable up to 2370°C, when it becomes cubic. The tetragonal/monoclinic transformation is associated with a large volume change (~4%). This is the reason why pure zirconia wares break as their temperature changes through this value. To counteract the deleterious effect of phase changes, zirconia may be converted fully to the cubic phase by incorporating small amounts of calcia, magnesia or yttria. The cubic phase then remains stable at all temperatures. Stability, thermal shock resistance and hot load properties are all enhanced in the stabilized zirconia (Fruehan 1998).
Zr, 40]
Published in Alina Kabata-Pendias, Barbara Szteke, Trace Elements in Abiotic and Biotic Environments, 2015
Alina Kabata-Pendias, Barbara Szteke
The oxidation state of zirconium is mainly +4, but it may also be +2 and +3. It occurs in several silicates and its principal source is the mineral zircon, ZrSiO4. Also, baddeleyite (called zirconia), ZrO2, has technological importance and is used as a diamond simulant in jewelry. It is associated with Ti and Hf minerals, and may occur in several minerals, such as pyroxenes, amphiboles, micas, and ilmenites.
Properties of the Elements and Inorganic Compounds
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
mended that where zinc oxide is encountered good ventilation be provided. The commercial price of zinc in January 2002 was roughly 40/lb ($90 kg). Zinc metal with a purity of 99.9999% is priced at about $5/g. Zirconium -- (Syriac, zargun, color of gold), Zr; at. wt. 91.224(2); at. no. 40; m.p. 1855 °C; b.p. 4409 °C; sp. gr. 6.52 (20 °C); valence +2, +3, and +4. The name zircon may have originated from the Syriac word zargono, which describes the color of certain gemstones now known as zircon, jargon, hyacinth, jacinth, or ligure. This mineral, or its variations, is mentioned in biblical writings. These minerals were not known to contain this element until Klaproth, in 1789, analyzed a jargon from Sri Lanka and found a new earth, which Werner named zircon (silex circonius), and Klaproth called Zirkonerde (zirconia). The impure metal was first isolated by Berzelius in 1824 by heating a mixture of potassium and potassium zirconium fluoride in a small iron tube. Pure zirconium was first prepared in 1914. Very pure zirconium was first produced in 1925 by van Arkel and de Boer by an iodide decomposition process they developed. Zirconium is found in abundance in S-type stars, and has been identified in the sun and meteorites. Analyses of lunar rock samples obtained during the various Apollo missions to the moon show a surprisingly high zirconium oxide content, compared with terrestrial rocks. Naturally occurring zirconium contains five isotopes. Thirty-one other radioactive isotopes and isomers are known to exist. Zircon, ZrSiO4, the principal ore, is found in deposits in Florida, South Carolina, Australia, South Africa, and elsewhere. Baddeleyite, found in Brazil, is an important zirconium mineral. It is principally pure ZrO2 in crystalline form having a hafnium content of about 1%. Zirconium also occurs in some 30 other recognized mineral species. Zirconium is produced commercially by reduction of the chloride with magnesium (the Kroll Process), and by other methods. It is a grayish-white lustrous metal. When finely divided, the metal may ignite spontaneously in air, especially at elevated temperatures. The solid metal is much more difficult to ig-
Thermal efficiency enhancement using a ceramic coating on the cylinder liner and the piston head of the IC engine
Published in International Journal of Ambient Energy, 2021
P. Anand, D. Rajesh, M. Shunmugasundaram, I. Saranraj
Zirconium dioxide (ZrO2), sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite (Alkidas 1989). A dopant stabilised cubic structured zirconia, cubic zirconia, is synthesised in various colours for use as a gemstone and a diamond simulant. Zirconia can be found in three crystal structures and it can be seen in Figure 2. These are monolithic (m), tetragonal (t) and cubic (c) structures. The monolithic structure is stable between room temperature and 1170°C while it turns to a tetragonal structure above 1170°C. The tetragonal structure is stable up to 2379°C and above this temperature, the structure turns to cubic structure (Assanis et al. 1991).
Precise U–Pb baddeleyite dating of the Derim Derim Dolerite, McArthur Basin, Northern Territory: old and new SHRIMP and ID-TIMS constraints
Published in Australian Journal of Earth Sciences, 2021
S. Bodorkos, J. L. Crowley, J. C. Claoué-Long, J. R. Anderson, C. W. Magee
Baddeleyite is a valuable U-bearing phase for dating silica-undersaturated magmatic rocks because: (1) unlike zircon, its physical fragility largely precludes its occurrence as an inherited phase, and (2) baddeleyite is relatively resistant to post-crystallisation loss of radiogenic Pb, and thus commonly preserves an unaltered record of the crystallisation age (Heaman & LeCheminant, 1993). However, ion-probe U–Pb dating of baddeleyite presents several difficulties. In addition to the challenges associated with mineral separation, mounting and polishing described above, very slender baddeleyite crystals require the use of a small-diameter primary ion beam, in turn leading to poor counting statistics, especially in crystals poor in U and radiogenic Pb. An additional artefact specific to ion-probe U–Pb dating of baddeleyite is the ‘crystal orientation effect’ (Wingate & Compston, 2000), whereby the calibrated 238U/206Pb varies widely from spot to spot, depending on the local orientation of the target crystal lattice, relative to the primary ion beam. This largely precludes meaningful measurement of 238U/206Pb, restricts ion-probe dating to baddeleyites containing enough radiogenic Pb to use orientation-independent 207Pb/206Pb (i.e. typically Mesoproterozoic or older), and compromises evaluation of isotopic concordance, which is a primary test of the reliability of 207Pb/206Pb dates.