Kinetics of Zircon Synthesis

Ramani, Saradha; Subbarao, E. C.; Gowhale, K. V. G. M.

doi:10.1111/j.1151-2916.1969.tb15853.x

Cited by 23 publications

(12 citation statements)

References 8 publications

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“…It has already been observed that cristobalite does not react with ZrO 2 below a temperature of 1300°C [27]. These results confirm the findings of Ramani et al [27], that ZrO 2 does not react with quartz. According to Itoh [28], zircon starts forming around 1300°C and proceeds exclusively between amorphous silica and tetragonal zirconia.…”

Section: Discussionsupporting

confidence: 86%

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On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

Xia

Yang

et al. 2016

Surface and Coatings Technology

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Thermal barrier coatings (TBCs), such as 7-8 wt.% yttria stabilized zirconia (YSZ), are widely used to reduce the temperature of coated materials. However, when a turbine operates in a harsh environment, for example a volcanic ash attack, sand and ash particles ingested by the engine could be deposited on the TBC surfaces as molten calcium-magnesium-alumino-silicate (CMAS). CMAS melts and penetrates into TBCs at high temperatures, which causes a loss of strain tolerance and results in the premature failure of the top coat. It is recognized that the formation of CMAS is inevitable due to exposing the turbine to sand and ash; therefore, CMAS mitigation solutions are among the top challenges for materials scientists. To some extent, CMAS is the biggest weakness of the traditional 7-8YSZ TBC material. The thermochemical interactions between YSZ and real volcanic ash are investigated in this paper as a means to alleviate the volcanic ash attack by understanding the underlying mechanisms. 7YSZ, 0.5Gd-8YSZ and 3Er-7YSZ powders and free-standing plates were prepared, respectively. The effect of the volcanic ash on the three different samples was investigated using an X-ray diffraction, scanning electron microscopy, a scanning transmission electron microscopy, and a differential scanning calorimetry. The phase transformations and reaction of TBCs materials subjected to a volcanic ash attack were examined and the volcanic ash degradation and mitigation mechanisms were discussed. It was found that rare earth-doped YSZ samples suffered less damage from the volcanic ash attack than the standard 7YSZ. The results demonstrate that rare earth-doped YSZ may be effectively utilized to mitigate a volcanic ash attack.

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Section: Discussionsupporting

confidence: 86%

“…The reaction between ZrO 2 and SiO 2 is very slow at 1250°C [25,26]. It has already been observed that cristobalite does not react with ZrO 2 below a temperature of 1300°C [27]. These results confirm the findings of Ramani et al [27], that ZrO 2 does not react with quartz.…”

Section: Discussionsupporting

confidence: 77%

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

Xia

Yang

et al. 2016

Surface and Coatings Technology

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“…It is worth noting that crystalline ZrSiO4 was not identified in the ZrSi2 oxidation at 1000 °C for 10 hours and 1200 °C for 5 hours even though its formation is preferred as indicated in binary ZrO2-SiO2 phase diagram at either temperature with any composition. However, the phase identification of ZrSiO4 at longer oxidation (1200 °C for 50 hours) and higher temperature oxidation (1400 °C for 5 hours) of ZrSi2 agree with published results that ZrSiO4 formation from a reaction of ZrO2 and SiO2 requires at least 1300°C annealing temperature [50,[54][55][56]. Formation of crystalline ZrSiO4 is a solid state reactionit is hypothesized that Si 4+ cations from amorphous SiO2 diffuse through the highly refractory ZrSiO4 layer and reacts with t-ZrO2 in order to produce new phase and there are no mobile liquid or gas species [50].…”

Section: Kinetic Suppression Of Crystalline Zrsio4 Formationsupporting

confidence: 90%

Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding

Sridharan

Mariani

Bai

et al. 2018

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Zirconium-alloy fuel claddings have been used successfully in Light Water Reactors (LWR) for over four decades. However, under high temperature accident conditions, zirconium-alloys fuel claddings exhibit profuse exothermic oxidation accompanied by release of hydrogen gas due to the reaction with water/steam. Additionally, the ZrO2 layer can undergo monoclinic to tetragonal to cubic phase transformations at high temperatures which can induce stresses and cracking. These events were unfortunately borne out in the Fukushima-Daiichi accident in in Japan in 2011. In reaction to such accident, protective oxidation-resistant coatings for zirconium-alloy fuel claddings has been extensively investigated to enhance safety margins in accidents as well as fuel performance under normal operation conditions. Such surface modification could also beneficially affect fuel rod heat transfer characteristics. Zirconium-silicide, a candidate coating material, is particularly attractive because zirconium-silicide coating is expected to bond strongly to zirconium-alloy substrate. Intermetallic compound phases of zirconium-silicide have high melting points and oxidation of zirconium silicide produces highly corrosion resistant glassy zircon (ZrSiO4) and silica (SiO2) which possessing self-healing qualities. Given the long-term goal of developing such coatings for use with nuclear reactor fuel cladding, this work describes results of oxidation and corrosion behavior of bulk zirconium-silicide and fabrication of zirconium-silicide coatings on zirconium-alloy test flats, tube configurations, and SiC test flats. In addition, boiling heat transfer of these modified surfaces (including ZrSi2 coating) during clad quenching experiments is discussed in detail. Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding DE-NE0008300 Final Report 5 was also confirmed that the theoretical composition coating enhanced oxidation protection and wear resistance. Distinctive oxide layers of ZrSi2 prepared at 1000 °C and 1400 °C in ambient air were subjected to a 3.9 MeV Si 2+ ions irradiation at 305 °C and their radiation responses were characterized and analyzed. Nanocomposite oxides consisting of ZrO2 nanocrystals embedded in amorphous SiO2 matrix formed on ZrSi2 surface after oxidation at 1000 °C. Radiation-induced phase mixing of the oxide phases and amorphization of ZrO2 was observed up to ~ 820 nm in depth, about one-third of the total radiation damaged region (2.5 µm in thickness) as estimated by SRIM calculation. The ion-mixing was facilitated with fine ZrO2 grains (< 25 nm) at low doses (5 to 10 dpa) but not in larger grains (> 30 nm) even at high damage levels (30 to 60 dpa). Qualitative explanation of the ion-mixing of the nanocomposite was proposed with respect to grain size of ZrO2 in SiO2 matrix. Polygonal crystalline ZrSiO4 grains in dual-layered oxide scale on ZrSi2 at 1400 °C were completely amorphized under the ion-irradiation. Given the high corrosion resistance of ZrSiO4 and immobil...

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“…When ZrO 2 , HfO 2 , or a mixture of both, are present during the oxidation of silicon, the formation of a SiO 2 TGO is expected to be accompanied by a parallel reaction between SiO 2 and either ZrO 2 or HfO 2 to form a zirconium or hafnium orthosilicate (ZrSiO 4 ; zircon, or HfSiO 4 ; hafnon) or a mixed Zr x Hf 1-x SiO 4 orthosilicate [15][16][17][18][19][20] . Since these orthosilicates are phase stable at the temperatures at which silicon bond coated EBC systems are used (currently up to 1316°C), and have reported CTE values similar to those of silicon (5.1x10 -6 C -1 for zircon, 3.6x10 -6 C -1 for hafnon) 19,21 , their formation by reaction with SiO 2 in EBC systems would be of significant technological interest 20,22,23 .…”

Section: Author Manuscriptmentioning

confidence: 99%

“…The formation of zircon by the reaction between amorphous (fused) SiO 2 and crystalline t-ZrO 2 has been investigated by Veytizou et al 17 and shown to be rapid at 1300°C. However, above 1200°C crystalline SiO 2 is formed on silicon in the engine environment, and Ramani et al 16 observed a much slower reaction between quartz and tetragonal ZrO 2 at 1300°C. They argued that this was related to the need for a phase…”

Section: Author Manuscriptmentioning

confidence: 99%

Hafnium silicate formation during the reaction of β‐cristobalite SiO₂ and monoclinic HfO₂ particles

Deijkers

Wadley

2020

J Am Ceram Soc

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Kinetics of Zircon Synthesis

Cited by 23 publications

References 8 publications

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding

Hafnium silicate formation during the reaction of β‐cristobalite SiO₂ and monoclinic HfO₂ particles

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Kinetics of Zircon Synthesis

Cited by 23 publications

References 8 publications

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

On the resistance of rare earth oxide-doped YSZ to high temperature volcanic ash attack

Development of Self-Healing Zirconium-Silicide Coatings for Improved Performance Zirconium-Alloy Fuel Cladding

Hafnium silicate formation during the reaction of β‐cristobalite SiO2 and monoclinic HfO2 particles

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Hafnium silicate formation during the reaction of β‐cristobalite SiO₂ and monoclinic HfO₂ particles