Metal Carbide-Carbon Eutectic and Peritectic Fixed Points as High-Temperature Standards

Sasajima, N.; Yamada, Yoshiro; Wang, Yunfen

doi:10.1109/sice.2006.315281

Cited by 1 publication

(6 citation statements)

References 4 publications

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“…Nevertheless this implies that the phase regions L + WC, WC + FCC-A1 and WC + HCP-A3 are separated by the phase (δ-WC) from the phase region WC + G. See appendices A.2-A. 4.…”

Section: Some Structural Data On the System W-c And On Graphite Gmentioning

confidence: 99%

“…Therefore, the present study aims at a better understanding of the melting and freezing transitions in the peritectic system W-C-X reported in [2][3][4][5][6]. This report just aimed at optimizing the potential applications of this point, given its unique position at the higher end of the range of HTFPs, especially within the context of calibrations, involving interpolation and extrapolation, and comparisons, requiring proven stability.…”

Section: Contextmentioning

confidence: 99%

“…In [4] four cells were compared. Tungsten powder with a nominal purity 99.99% mass fraction, and high purity graphite powder with a nominal purity of 99.9999% were used for the fillings.…”

Section: Nmij-2mentioning

confidence: 99%

“…In section 7.2, it is supposed that corrections have been applied, and the associated uncertainties specified for the thermal inertia [24,25], if any, and the non-uniformity of the furnace [26] as well as for emissivity, temperature drop across the cavity bottom, and the size-of-source effect [27,28]. As to the non-uniformity of the furnace, this is expected not to be a critical issue since W-C-X during the melting or freezing process does not show a well-outlined solid phase [4]. 7.3.7.…”

Section: Liquidus Pointmentioning

confidence: 99%

“…the dependence of the scale of the frozen structure on the freezing rate and its influence on T freeze and, subsequently, T liq , if any, see section 4.4, could be checked for one and the same sample with a given impurity spectrum, to be specified, by means of GDMS (glow discharge mass spectroscopy) or ICP-mass spectroscopy [29]. Structure analysis of the quenched frozen sample has been done for each freezing rate by BSE (back scattered electron imaging), EPMA (electron probe microanalysis) [4], or XRD (x-ray diffraction) [14].…”

Section: Checksmentioning

confidence: 99%

See 4 more Smart Citations

Freezing and melting in the peritectic W–C–X

Bloembergen¹,

Wei²,

Wang³

2018

Metrologia

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The tungsten-carbon (WC) peritectic, with a liquidus temperature near to 3020 K, shows promise as a high-temperature reference fixed point. It appears that the WC phase is a discrete phase with full stoichiometry of the components W and C, in which impurities cannot be dissolved. In this paper we describe the use of Thermo-Calc software to derive the liquidus and solidus temperatures versus the impurity concentration for the impurities V and Si. It is found that the liquidus is univariant, whereas the solidus is invariant. Additionally, the transition curves between the solidus and the liquidus are modeled. The liquid fraction at the liquidus point is found to be less than 1; in contrast, it is unity for metal-carbon eutectics. Measurements are presented for a series of melting and freezing curves for two WC fixed-point cells. The Gibbs phase rule requires segregation of a fourth compound phase, involving the impurity in question, at the solidus point. The observations confirm that during supercooling, impurities are trapped in compound phases consisting of the impurity together with W and/or C, encapsulating the impurity, and resulting in a flat freezing plateau characteristic of the pure system. Finally, an expression for the melting temperature, as a function of the liquid fraction, is derived, spanning the temperature range from an initial melting temperature to the liquidus temperature. Within this range just free impurities are involved.

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“…Nevertheless this implies that the phase regions L + WC, WC + FCC-A1 and WC + HCP-A3 are separated by the phase (δ-WC) from the phase region WC + G. See appendices A.2-A. 4.…”

Section: Some Structural Data On the System W-c And On Graphite Gmentioning

confidence: 99%

Section: Contextmentioning

confidence: 99%

“…In [4] four cells were compared. Tungsten powder with a nominal purity 99.99% mass fraction, and high purity graphite powder with a nominal purity of 99.9999% were used for the fillings.…”

Section: Nmij-2mentioning

confidence: 99%