Abstract
Silicon has recently been recognized as a potentially attractive phase change material for ultra-high-temperature latent heat thermal energy storage (LHTES) and conversion systems. It has been proposed that the utilization of silicon’s latent heat should drastically increase the performance of LHTES devices in terms of operational temperatures and available energy density. Nevertheless, in order to ensure a high reliability and long lifetime of the system, proper ceramic materials that are able to withstand contact heating and cooling cycles during consecutive melting/solidification steps need to be examined and selected. Previously, we have documented that hexagonal boron nitride (h-BN) is the only ceramic that shows non-wettability and limited reactivity in contact with molten silicon at temperatures up to 1650°C. In this work, we present for the first time the results of experimental research on the performance of a Si/h-BN system upon cycling melting/solidification processes. For this reason, the Si/h-BN couple was subjected to a sessile drop experiment containing 15 cycles of heating/cooling between 1300°C and 1450°C. During the test, temperatures of specific events as well as contact angle values were recorded. After the test, the structure and surface morphology of the solidified Si/h-BN couple were characterized by means of scanning electron microscopy.
Highlights
Latent heat thermal energy storage (LHTES)based devices are utilized to produce electricity by converting heat absorbed/released during phase transformations of a material subjected to cyclic heating/cooling schemes
The performance of a commercial hexagonal boron nitride (hBN) ceramic in contact with silicon upon its cycling melting/solidification was experimentally examined for the first time
The Si/hexagonal boron nitride (h-BN) couple was subjected to a sessile drop experiment containing 15 cycles of heating/cooling between 1300°C and 1450°C
Summary
Latent heat thermal energy storage (LHTES)based devices are utilized to produce electricity by converting heat absorbed/released during phase transformations of a material (a so-called phase change material; PCM) subjected to cyclic heating/cooling schemes. The current and perspective application fields of LHTES devices cover, for example, terrestrial or space solar energy systems.[1,2,3] Very recently, it has been proposed that the introduction of silicon as the PCM should significantly overcome limitations of state-of-theart molten salt-based LHTES systems, both in terms of operational temperatures and available energy density.[2] in order to move the Sibased LHTES system from a designer’s desk to real industrial applications, the performance of ceramics intended to be used for building the PCM container has to be a priori experimentally evaluated. The selected ceramic material should exhibit a non-wetting behavior and a limited degradation (a lack of reactively formed interfacial products due to a direct reaction between Si and contacting refractory). The one reported exception in this field is hexagonal boron nitride (hBN) that shows non-wettability at temperatures up (Published online February 7, 2019)
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