Interaction Between Liquid Silver and Graphene-Coated SiC Substrate
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JMEPEG https://doi.org/10.1007/s11665-018-3503-7
Interaction Between Liquid Silver and Graphene-Coated SiC Substrate Marta Homa, Natalia Sobczak, Jerzy J. Sobczak, Artur Kudyba, Grzegorz Bruzda, Rafał Nowak, Donatella Giuranno, Katarzyna Pietrzak, and Marcin Chmielewski (Submitted June 9, 2018) Wettability between liquid Ag and graphene-coated SiC single crystal has been investigated by dispensed drop method at T = 970 °C under vacuum accompanied with subsecond recording of the drop/substrate images (100 frames per second) by high-speed high-resolution CCD camera. Non-contact heating method coupled with capillary purification of the Ag drop procedure has been applied. Scanning electron microscopy combined with EDS analysis and scanning probe microscopy combined with Raman spectroscopy techniques has been utilized for microstructure and surface characterization of samples before and after high-temperature wetting tests. Immediately after its detachment from the capillary, the Ag drop showed non-wetting behavior (h > 90°) forming a high contact angle of h = 114°. Surface characterization of the drop surface after wettability tests evidenced the presence of graphene and Si transferred from the substrate to the top of Ag drop. These findings suggest chemical interaction phenomena occurring at the interface. Locally, an intimate contact between liquid Ag and SiC substrate was allowed by the appearance of discontinuities in the graphene layer basically produced by thermomechanical stress. Local dissolution of carbon into liquid Ag and its reorganization (by segregation, nucleation and growth) as secondary graphene layer at the Ag surface was also observed. Keywords
Ag/graphene, Ag/SiC, dispensed drop, sessile drop method, wetting at high temperature
1. Introduction The use of graphene (CGn) as a reinforcement material in metal matrix composites (MMCs) raises hopes of scientists to obtain materials with outstanding functional properties such as high thermal conductivity coupled with low thermal expansion coefficient (Ref 1), particularly useful for aeronautical, aerospace and automobile industries (Ref 1). The group of metals considered potentially applicable as a matrix of graphenecontaining composite materials is Al, Cu and Ag (Ref 1-4). With the exception of Al that easily forms aluminum carbide (Al4C3) (Ref 2), Cu and Ag are non-reactive elements with respect to carbon. Moreover, carbon solubility in these metals at the liquid state is extremely low, showing 90°) showing a contact angle of h = 114° (Fig. 5a). After approximatively 1 min, a scatter in the contact angle values is observed. It was related to an abnormal kinetics (Fig. 5b) with a decrease in the contact angle to a value of h = 110°, which during the second minute of the test, rises again up to a value of h 114°. Holding the couple for 11 min, the value of the contact angle does not change (Fig. 5a). The scatter of data is observed at the t = 12 min of the test and is owing to the spontaneous squeezing of the second Ag drop. By visual observations of the
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