On the mechanism of internal oxidation in platinum–zirconium alloys

Undisz, Andreas; Zeigmeister, U.; Rettenmayr, Markus; Oechsle, M.

doi:10.1016/j.jallcom.2006.08.036

Cited by 9 publications

(6 citation statements)

References 17 publications

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“…Where the numerical values of x, y and z are x = −4.0521, y = 0.075 96, z = 42.1046 (−3.807 05, 0.082 47, 37.583 19). The values of S for the thermocouple used in this study are given in table 1.…”

Section: Stabilitymentioning

confidence: 99%

A systematic investigation of the thermoelectric stability of Pt–Rh thermocouples between 1300 °C and 1500 °C

et al. 2018

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By using a simple model to relate the electromotive force drift rate of Pt–Rh thermoelements to dS/dc, i.e. the sensitivity of the Seebeck coefficient, S, to rhodium mass fraction, c, the composition of the optimal pair of Pt–Rh wires that minimizes thermoelectric drift can be determined. The model has been applied to four multi-wire thermocouples each comprising 5 or 7 Pt–Rh wires of different composition. Two thermocouples were exposed to a temperature of around 1324 °C, one thermocouple to around 1492 °C, i.e. the melting points of the Co–C and Pd–C high temperature fixed points, respectively, and one thermocouple to a series of temperatures between 1315 °C and 1450 °C. The duration of exposure at each temperature was several thousand hours. By performing repeated calibrations in situ with the appropriate fixed point during the high temperature exposure, the drift performance has been quantified with high accuracy, entirely free from errors associated with thermoelectric homogeneity. By combining these results it is concluded that the Pt-40%Rh versus Pt-6%Rh is the most stable at the temperatures investigated. A preliminary reference function was determined and is presented.

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Section: Stabilitymentioning

confidence: 99%

A systematic investigation of the thermoelectric stability of Pt–Rh thermocouples between 1300 °C and 1500 °C

et al. 2018

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“…A key reference for this subject is the study of Undisz et al [17], who looked at grain growth with zirconium oxide doped Pt. Internal oxidation of alloys is a well-known process commonly used for generating 'oxide dispersion strengthened' materials.…”

Section: Grain Growthmentioning

confidence: 99%

“…Cold working and heat treatment may help to promote migration of zirconium oxide particles into the grains [27,28]. However, until the work of Undisz et al [17] the formation and distribution of zirconium oxide particles was poorly understood.…”

Section: Grain Growthmentioning

confidence: 99%

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Stability assessment of a new high strength, high temperature Type R and Type S thermocouple

Pearce

Tucker

Rawal

et al. 2020

Meas. Sci. Technol.

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Platinum-rhodium Type R and S thermocouples fail in service because of two main reasons: excessive grain growth in the platinum limb at high temperatures (causing wire breakage) and temperature drift, i.e. deviation of electromotive force (emf) generated over time because of deposition of rhodium oxide on the platinum limb, out of accepted industry tolerances. Finding a solution to the problem is challenging because of the contradictory requirements of strength and narrow permissible emf range: emf is extremely sensitive to any dopants or alloying elements that can be used to improve strength at high temperatures. Johnson Matthey has developed a new thermocouple wire (platinum limb) called 'HTX ™ ' by doping platinum with a small quantity of zirconium which is oxidised during processing to electrically neutral zirconium oxide. Zirconium oxide improves the high temperature strength of platinum wire by restricting the grain growth but does not significantly affect the emf. The result is a wire which has the potential to last many times longer at high temperatures (>1200 °C) than standard platinum wire, whilst still achieving Class 1 tolerance (i.e. ±1 °C at 1000 °C). It also improves the thermoelectric drift characteristics of the thermocouple by counteracting any reduction in emf due to rhodium contamination by an increase in emf as any remaining zirconium is converted to zirconium oxide. We describe an impartial long-term assessment (up to 1500 h) of the thermoelectric stability of the HTX ™ wire by exposure to high temperature with periodic in situ calibration using a Co-C (1324 °C) high temperature fixed point. This yields stability measurements with very high precision.

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“…[15][16][17] On the other hand, a method without the procedure of adding Y 2 O 3 powder has been explored for fabrication of some other ODS alloys, for example, Ni, Cu, Co and Pt based alloys. [18][19][20][21] On the field of Fe based alloy, Schneibel and Shim has fabricated intermetallic compounds (Fe 17 Y 2 and Fe 11 TiY) to characterise the oxidation of Ti and Y in these compounds. 22 However, this method has not been widely used in the fabrication of ODS RAFM steels up to now.…”

Section: Introductionmentioning

confidence: 99%

Segregation and precipitation formation for in situ oxidised 9Cr steel powder

Wang

Liu

et al. 2016

Materials Science and Technology

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Powder and sintered bulk materials of a reduced activation steel with oversaturated Ti and Y are prepared by gas atomisation and sintering. Segregation on both the surface and interior of the powder particles are observed after an thermal treatment. The oxidation of the segregates promotes formation of clusters of large Y oxide crystals and thick continuously distributed Ti oxide layers on the surface of the powder particles. The oxidation also occurs within the powder particles and mainly forms larger Ti oxide dispersoids in the grain boundaries of the powder. The coarsening and aggregation of the oxide dispersoids occur with increasing duration of the thermal treatment. Yttrium is also segregated and precipitated in the grains of the powder particles.

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On the mechanism of internal oxidation in platinum–zirconium alloys

Cited by 9 publications

References 17 publications

A systematic investigation of the thermoelectric stability of Pt–Rh thermocouples between 1300 °C and 1500 °C

A systematic investigation of the thermoelectric stability of Pt–Rh thermocouples between 1300 °C and 1500 °C

Stability assessment of a new high strength, high temperature Type R and Type S thermocouple

Segregation and precipitation formation for in situ oxidised 9Cr steel powder

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