Simultaneous Differential Thermal Analysis and Thermogravimetric Analysis of Si-30B Alloy
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JMEPEG https://doi.org/10.1007/s11665-020-05157-2
Simultaneous Differential Thermal Analysis and Thermogravimetric Analysis of Si-30B Alloy M. Homa
, N. Sobczak, K. Hodor, and S. Gezgin
(Submitted May 20, 2020; in revised form July 16, 2020; Accepted: 7 August 2020) This article focuses on the experimental determination of the transformation temperature of Si-30B alloy in the temperature range of 25-1820 °C in a flowing gas atmosphere (He, 99.9992%) carried out by simultaneous differential thermal analysis and thermogravimetric analysis (DTA–TG) using a graphite container. The DTA curve during heating showed the presence of two critical temperatures, i.e., T = 1380.7 °C and T = 1532.0 °C. The first one corresponds to the melting point of a eutectic system (Si + SiB6). The hightemperature interaction and reactivity between the alloy and the container during DTA–TG test were evaluated by scanning electron microscopy coupled with energy-dispersive x-ray analysis. The results have demonstrated that the graphite container reacts with both liquid silicon and boron dissolved in liquid constituent of the alloy to form SiC and B4C, respectively. Keywords
DTA, graphite container, reactivity, Si-B alloys, TG
1. Introduction Recently, the Si-B alloys have been proposed as phase change materials (Ref 1) for ultra-high-temperature latent heat thermal energy storage (LHTES) because of high theoretical values of the latent heat of both silicon (1800 J/g) and boron (4650 J/g) (Ref 2). However, the ultra-high melting temperatures of Si and B (1414 and 2076 C, respectively) and the presence of high-melting phases in Si-B alloys make experimental estimation of their critical temperatures by containerassisted methods such as differential thermal analysis (DTA) and thermogravimetric analysis (TG) very difficult. Due to the very high reactivity of molten Si with many commercial refractories, such as silica, alumina, magnesia (Ref 3), SiC, Si3N4, AlN (Ref 4) and graphite (Ref 5, 6), and currently not yet recognized interaction of pure Si with refractories at T > 1500 C, the phase transformation analysis using DTA– TG appears to be very challenging. The key factor in these types of measurements is the choice of a suitable container material, which should be non-wettable and non-reactive in contact with liquid metal tested. This article is an invited submission to JMEP selected from presentations at the 73rd World Foundry Congress and has been expanded from the original presentation. 73WFC was held in Krakow, Poland, September 23-27, 2018, and was organized by the World Foundry Organization and Polish FoundrymenÕs Association. M. Homa, ŁUKASIEWICZ Research Network, Krakow Institute of Technology, 73 Zakopian´ska Str., 30-418 Krakow, Poland; N. Sobczak, ŁUKASIEWICZ Research Network - Institute of Precision Mechanics, 3 Duchnicka Str., 01-796 Warsaw, Poland; and Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Str., 30-059 Krakow, Poland; and K. Hodor and S. Gezgin, NETZSCH-Gera¨tebau GmbH, Wittelsbac
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