Carbide, Nitride and Boride Materials Synthesis and Processing

Weimer, Alan W.

doi:10.1007/978-94-009-0071-4

Cited by 254 publications

(4 citation statements)

References 251 publications

(363 reference statements)

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“…The B 2 O 3 melts at relatively low temperature (T = 452°C) and then easily evaporates under high vacuum conditions. [26] The presence of liquid B 2 O 3 also facilitates the process of SiC dissolution/decomposition in accordance to the following reaction [27] :…”

Section: Discussionmentioning

confidence: 98%

Ultra-High Temperature Interaction Between h-BN-Based Composite and Molten Silicon

Polkowski

Sobczak

Polkowska

et al. 2018

Metall Mater Trans A

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Silicon has been recently proposed as a very promising phase change material for applications in latent heat thermal energy storage (LHTES) and conversion systems working at ultra-high temperatures. However, in order to successfully develop such kind of devices, suitable refractories showing low reactivity and non-wetting behavior upon the melting and storing of molten silicon at temperatures much higher than its melting point have to be selected. In our previous work, we have documented that the non-wetting behavior in Si/h-BN system is preserved at temperatures up to 1650°C, with the absence of new reaction products formed at the interface. These findings make hexagonal boron nitride (h-BN) a reasonable first candidate for Si-based LHTES applications. Nevertheless, the rather poor mechanical strength of ''pure'' h-BN ought to be improved in order to enhance the reliability under thermocycling operational conditions and to increase the life period of the device. Therefore, in the present paper, we examine for the first time the interactions at ultra-high temperatures between a high strength commercial h-BN-based composite and molten Si. At temperatures up to 1750°C, the wettability of the h-BN-based composite (h-BN + SiC + ZrO 2) with molten Si is much lower if compared to the pure h-BN counterpart. Additionally, the role of reinforcements (SiC + ZrO 2) and occured microstructural evolution is discussed based on the results obtained by SEM and XRD analyses.

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Section: Discussionmentioning

confidence: 98%

Ultra-High Temperature Interaction Between h-BN-Based Composite and Molten Silicon

Polkowski

Sobczak

Polkowska

et al. 2018

Metall Mater Trans A

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“…melting and evaporation of native B 2 O 3 boron oxide that is introduced during sintering of the h-BN composite. B 2 O 3 melts at T m = 452 • C [21] and under non-oxidizing conditions it quickly evaporates (under atmospheric pressure it starts at 1227 • C, while under vacuum the evaporation takes place at much lower temperatures) [22]. The existence of liquid boron oxide supports a decomposition of SiC particles through the following reaction [22]:…”

Section: Structural Characterization Of Si-32b Alloy/(h-bn+sic+zro 2 ) Sessile Drop Couples After High Temperature Testsmentioning

confidence: 99%

Silicon-Boron Alloys as New Ultra-High Temperature Phase-Change Materials: Solid/Liquid State Interaction with the h-BN Composite

Polkowski

Sobczak

Bruzda

et al. 2019

Silicon

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Silicon-boron alloys have been recently pointed out as novel ultra-high temperature phase change materials for applications in Latent Heat Thermal Energy Storage (LHTES) and conversion systems. One of the emerging challenges related to the development of such devices is a selection of refractories applicable to build a vessel for storing molten Si-B alloys at high temperatures and under consecutive melting/solidification conditions. Previously, it has been documented that hexagonal boron nitride (h-BN) is the only one ceramic showing a non-wettability and limited reactivity with Si-B alloys at temperatures up to 1750 • C, what makes it a good candidate of the first selection for the predicted application. Nevertheless, pure h-BN shows a rather low mechanical strength that could affect a durability of the LHTES vessel. Therefore, the main purpose of this work was to examine high temperature behavior of commercial high strength h-BN composite having a nominal composition of h-BN-24ZrO 2 -6SiC (vol.%) in contact with a solid/liquid eutectic Si-3.2B alloy. Two types of sessile drop experiments were carried out: a step-contact heating up to 1750 • C, and a thermocycling at 1300 − 1450 • C composed of 15 cycles of the alloy melting/solidification. The obtained results showed a lack of wettability in the examined system at temperatures up to 1750 • C. The Si-3.2B alloy presented good repeatability of melting/solidification temperatures in consecutive thermal cycles, which was not affected by the interaction with the h-BN composite. However, due to reactions taking place between the composite's components leading to structural degradation, it is not recommended to increase operational temperature of this material above 1450 • C. Keywords Silicon-boron alloys • Hexagonal boron nitride • Sessile drop method • Latent heat thermal energy storage • AMADEUS project Electronic supplementary material The online version of this article (

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“…It could be explained by the nature of the initial powder, which is composed of aggregates made of smaller particles [52]. The HA powder used in our study could then be defined as a weak material because of its capability to be ground [53]. When a certain value of specific energy is surpassed, the aggregates break rapidly into particles with a much smaller size than the initial aggregates.…”

Section: Stirrer Speed (V R )mentioning

confidence: 98%