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High-temperature interaction between molten conventional gray cast iron (wt.%: 4.1 C; 1 Si; 0.20 Mn; 0.03 S; 0.04 P, the rest—Fe) and multiphase Al2O3-ZrO2-SiO2 ceramic substrate (wt.%: 51.5 Al2O3, 33.8 ZrO2, 13.3 SiO2, ~ 1 NaO2, 0.15 Fe2O3 + TiO2 + CaO) was examined at a temperature of 1450 °C for 15 min under inert flowing gas atmosphere (Ar, 850-900 hPa) using a sessile drop method coupled with contact heating procedure. Melting, wetting behavior and solidification of gray cast iron sample were continuously recorded with a high-speed high-resolution CCD camera. Under conditions of this study, selected gray cast iron alloy does not wet the Al2O3-ZrO2-SiO2 ceramic forming the final contact angle with average value of θf ~ 135°. The wetting kinetic curve was not smooth and its shape suggests the effect of substrate chemical heterogeneity due to multiphase composition of the substrate material. After the sessile drop test, the solidified drop was easily detached from the ceramic substrate along the drop-side interface showing a lack of bonding between the drop and the substrate. Structural characterization of the drop/substrate couple evidenced the nucleation and growth of graphite at the drop surface and at the drop/substrate interface taken place during solidification and resulting into the formation of discontinuous interfacial graphite layer.

Boron-doped molybdenum silicides have been already recognized as attractive candidates for space and ground ultra-high temperature applications far beyond limits of state-of-the-art nickel based superalloys. In this work, we are exploring a new method for fabricating Mo-Si-B alloys (as coatings or small bulk components) by utilizing a pressure-less reactive melt infiltration approach. The basic assumption of this approach is a synthesis of binary and/or ternary and complex intermetallic phases (silicides, borides, borosilicides), through a direct interaction of Si-B melt with molybdenum . The main purpose of this work, was to examine the effect of temperature and time of Si-B melt interaction on the structure and morphology of the formed reaction products. For this purpose, sessile drop experiments were carried out on the eutectic Si-3.2B (wt%) alloy/Mo couples at temperature varying between 1385-1550{\deg}C and holding time between 10 to 30 minutes. The solidified sessile drop couples were subjected to microstructural characterization by means of light microscopy and scanning electron microscopy analyses performed both at "top-view" and cross-sectioned interfaces. The phases formed within the interaction zone were identified by using TEM/SAED and XRD techniques. It was documented that a thickness of both main product layer (MoSi2+Mo5Si3), as well as boron-rich interlayer increases with raising temperature and time of the Si-B melt interaction with Mo substrates.

The contact heating sessile drop method was applied for a fundamental study concerning the wettability and reactivity of liquid Si-16.2at%Ti (eutectic composition) in contact with Glassy Carbon. The evolution of the contact angle behaviors and spreading kinetics were evaluated at three different temperatures. A strong temperature-dependence was found by analyzing the spreading kinetics in determining the achievement of the equilibrium at the interface. Different spreading stages with different slopes, depending on whether the diffusion of reacting phases (liquid Si and C) through the growing reaction layer (SiC), starts to be the rate-limiting factor. On the contrary, the final contact angle value seems not affected by the temperature. The solidified Si-Ti eutectics/GC samples were examined both at the top of the drop and at the crosssection by SEM/EDS. The presence of C-pockets of dissolution and a SiC layer at the interface, confirmed the reactive nature of the interaction mechanisms. In addition, a thicker layer of SiC at the triple line was detected and most probably responsible for pinning the alloy drop and as a consequence for the final value of contact angle measured (θ ≈ 43°± 2).

The sessile drop method combined with contact heating procedure was applied for the investigation of high-temperature interaction between liquid Gd and Y2O3 substrate. Real-time behavior of Gd sample in flowing inert gas (Ar) atmosphere upon heating to and at temperature of 1362 °C was recorded using high-speed high-resolution CCD camera. The results evidenced that molten Gd wets Y2O3 substrate (the contact angle θ

To properly design and optimize liquid-assisted processes, such as reactive infiltration for fabricating lightweight and corrosion resistant SiC/TiSi2 composites, the extensive knowledge about the interfacial phenomena taking place when liquid Si-rich Si-Ti alloys are in contact with glassy carbon (GC) is of primary importance. To this end, the wettability of GC by two different Si-rich Si-Ti alloys was investigated for the first time by both the sessile and pendant drop methods at T = 1450 °C. The results obtained, in terms of contact angle values, spreading kinetics, reactivity, and developed interface microstructures, were compared with experimental observations previously obtained for the liquid Si-rich Si-Ti eutectics processed under the same operating conditions. As the main outcome, a different Si content did not seem to affect the final contact angle values. Contrarily, the final developed microstructure at the interface and the spreading kinetics were observed as weakly dependent on the composition. From a practical point of view, Si-Ti alloy compositions with a Si content falling in the simple eutectic region of the Si-Ti phase diagram might be potentially used as infiltrating materials of C- and SiC-based composites.

A good thermochemical compatibility of ceramics intended to be applied as a vessel with the preselected phase change materials (PCMs) is crucial regarding development of novel ultra-high temperature latent heat thermal energy storage (LHTES) systems. The selection of proper refractories, that will ensure long life-time and reliable service of the system, should be preceded by the experimental verification of candidate materials upon contact heating/cooling cycles. In this chapter, we focus on the characterization of a solid/liquid interaction between Si-based PCMs and potential container materials under conditions specified by the predicted LHTES application. In this regard, new experimental procedures based on the sessile drop method were developed to examine temperature applicability limits of selected PCM/refractory couples and their thermocycling behavior upon consecutive melting/solidification cycles.

To succeed in the design and optimization of liquid-assisted processes such as reactive infiltration for the fabrication of tailored refractory SiC/ZrSi2 composites, the interfacial phenomena that occur when Si-rich Si-Zr alloys are in contact with glassy carbon (GC) were investigated for the first time by the sessile drop method at T = 1450 &deg, C. Specifically, two different Si-rich Si-Zr alloys were selected, and the obtained results in terms of wettability, spreading kinetics, reactivity, and developed interface microstructures were compared with experimental observations that were previously obtained for the liquid Si-rich, Si-Zr, near-eutectic composition (i.e., Si-10 at.%Zr) that was processed under the same operating conditions. The increase of the Si content only weakly affected the overall phenomena that were observed at the interface. From the practical point of view, this means that even Si-Zr alloys with a higher Si content, with respect to the near eutectic alloy, may be potentially used as infiltrant materials.

The wettability of graphene-coated SiC single crystal (CGn/SiCsc) by liquid Cu (99.99%) was investigated by a sessile drop method in vacuum conditions at temperature of 1100 °C. The graphene layer was produced via a chemical vapor deposition routine using 4H-SiC single crystal cut out from 6″ wafer. A dispensed drop technique combined with a non-contact heating of a couple of materials was applied. The Cu drop was squeezed from a graphite capillary and deposited on the substrate directly in a vacuum chamber. The first Cu drop did not wet the CGn/SiCsc substrate and showed a lack of adhesion to the substrate: the falling Cu drop only touched the substrate forming a contact angle of θ0 = 121° and then immediately rolled like a ball along the substrate surface. After settling near the edge of the substrate in about 0.15 s, the Cu drop formed an asymmetric shape with the right and left contact angles of different values (θR = 86° and θL = 70°, respectively), while in the next 30 min, θR and θL achieved the same final value of ~ 52°. The second Cu drop was put down on the displacement path of the first drop, and immediately after the deposition, it also did not wet the substrate (θ = 123°). This drop kept symmetry and the primary position, but its wetting behavior was unusual: both θR and θL decreased in 17 min to the value of 23° and next, they increased to a final value of 65°. Visual observations revealed a presence of ~ 2.5-mm-thick interfacial phase layer reactively formed under the second drop. Scanning electron microscopy (SEM) investigations revealed the presence of carbon-enriched precipitates on the top surface of the first Cu drop. These precipitates were identified by the Raman spectroscopy as double-layer graphene. The Raman spectrum taken from the substrate far from the drop revealed the presence of graphene, while that obtained from the first drop displacement path exhibited a decreased intensity of 2D peak. The results of SEM investigations and Raman spectroscopy studies suggest that the presence of graphene layer on the SiC substrate suppresses but does not completely prevent chemical interaction between liquid Cu drop and SiC. Both chemical degradation (etching) and mechanical degradation of the graphene layer during drop rolling due to high adhesion of the Cu drop to the SiC substrate are responsible for mass transfer through the 2nd drop/substrate interface that in turn results in significant changes of structure and chemistry of the drop and the interface.

The wetting, reactivity and phase formation at the liquid Ni-Al/TiB2 ceramic interfaces have been investigated at the temperatures close to the Ni-Al liquidus line. The wetting kinetics has been studied by the sessile drop technique utilizing liquid drop dispension and high-speed high-resolution video imaging. It is established that the wetting behavior changes from a non-reactive for the Al-rich melts to a dissolution-reactive for the Ni-rich melts. For the Ni concentration ≥40 at.%, TiB2 precipitates are found in the solidified Ni-Al droplets after the high-temperature interaction of the melts with TiB2 substrates. Besides, new (Al,Ti)Ni3 and (Al,Ti)2Ni21B6 phases are formed due to dissolution of TiB2 ceramic in Ni-rich melts and subsequent solidification. This article is protected by copyright. All rights reserved.

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-24ZrO2-6SiC (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.

Introduction/Purpose SiC is one of the candidates for highly demanding applications because of its outstanding properties. Reactive infiltration of Si-based alloys into C and SiC-C preforms is a valuable costless alternative over other conventional processing techniques. In order to optimize reactive infitration and to tailor the joint microstructures, the knowledge of wetting characteristics, reactivity, surface properties and thermodynamics concerning reacting phases, is a key contribution. Methods Systematic investigation of wetting, reactivity, surface properties and thermodynamics of Si-Ti melts in contact with Glassy-C and HIP-SiC substrates has been carried out. Two Si-Ti alloy compositions, i.e. Si-16Ti eutectics and Si-8Ti hypereutectics (in at %) have been selected. Contact heating and quasi-contact less sessile drop methods have been applied. After experiments, the formed microstructures at the Si-Ti/C and Si-Ti/SiC interfaces have been analysed by OM and SEM-EDS techniques. In addition, surface and bulk properties of the Si-Ti system have been compared with the predicted values calculated by ideal solution and Quasi-Chemical Approximation for regular solution models. Results Interaction phenomena observed at the interfaces are strongly affected by temperature and by the substrate, mainly by the C and Si content, as expected. In agreement with thermodynamics, absence of carbides was detected under the operating conditions applied. Surface and bulk properties are in a good agreement with the theoretical predictions. Conclusions The knowledge of the joining-relevant interfacial properties and reactive mechanisms occuring at the interfaces are crucial to optimize joining processes of C- and SiC-based materials. Tailored interfacial microstructures are key requirements to ensure the joints performance and durability. Acknowledgements This work was supported by National Science Center of Poland in the framework of “SIC-WIN: Reactivity of SI-alloy/C-material system: Wetting vs INfiltration project (G.A. UMO-2016/23/P/ST8/01916), POLONEZ-3. This project received funding under the EU Research and innovation funding programme "Horizon 2020" G.A. no 665778 for the Marie Skłodowska-Curie actions., This work was supported by National Science Center of Poland in the framework of "SIC-WIN: Reactivity of SI-alloy/C-material system: Wetting vs INfiltration project (G.A. UMO-2016/23/P/ST8/01916), POLONEZ-3. This project received funding under the EU Research and innovation funding programme "Horizon 2020" G.A. no 665778 for the Marie Skłodowska-Curie actions.

In this work, Ni50Al50 alloy is taken into consideration as potential brazing material for joining ZrB2 ultra-high temperature ceramic. The results of experimental study on high temperature interfacial phenomena between molten binary Ni50Al50 alloy and polycrystalline ZrB2, are shown. A sessile drop method combined with a capillary purification procedure was applied to investigate the wetting behavior of Ni50Al50/ZrB2 couple during holding for 400 seconds at temperature of 1688{\deg}C (i.e. at T=1.02Tm). It was found that the molten Ni50Al50 rapidly wets and spreads over the surface of ZrB2, while involved reactive infiltration into the solid substrate allowed reaching a final contact angle of ~0{\deg} in 250 sec. The wetting kinetics was much faster than that reported in the literature for Cu, Ag or Au tested at T=1.05Tm. The solidified couple was subjected to SEM/EDS microstructural characterization in order to reveal a course of interfacial phenomena. The results point towards (I) an existence of Ni-enriched Ni-Al/ZrB2 surface interfacial layer; (II) a formation of infiltration zone assisted by reactively formed Al2O3 due to a reaction with Al-rich melt and (III) a partial transfer of ZrB2 phase to Ni50Al50 alloy by a dissolution/precipitation mechanism.

The wetting behavior and reactivity between molten pure Gd and polycrystalline 3YSZ substrate (ZrO2 stabilized with 3 wt% of Y2O3)were experimentally determined by a sessile drop method using a classical contact heating coupled with drop pushing procedure. The test was performed under an inert flowing gas atmosphere (Ar) at two temperatures of 1362?C and 1412?C. Immediately after melting (Tm=1341?C), liquid Gd did not wet the substrate forming a contact angle of ?=141?. The non-wetting to wetting transition (? < 90?) took place after about 110 seconds of interaction and was accompanied by a sudden decrease in the contact angle value to 67?. Further heating of the couple to 1412 ?C did not affect wetting (?=67??1?). The solidified Gd/3YSZ couple was studied by means of optical microscopy and scanning electron microscopy coupled with X-ray energy dispersive spectroscopy. Structural investigations revealed that the wettability in the Gd/3YSZ system is of a reactive nature associated with the formation of a continuous layer of a wettable reaction product Gd2Zr2O7.

The wettability of glassy, microcrystalline and nanocrystalline carbon materials by liquid sulfur is studied by the sessile-drop technique applying the contact heating and drop-dispension procedures. Liquid sulfur shows a good wetting on all examined substrates just after melting, although the contact angle depends on the type and structure of the carbon material. Sulfur drops remain on the surfaces of glassy carbon and electrographite, whereas the liquid infiltrates into the substrates pressed from carbon micro- or nanoparticles. In the latter case, the infiltration rate increases along with decreasing size of particles used for preparation of the substrates, indicating a role of capillarity. The wetting and adhesion in the sulfur-carbon material systems are determined by the van der Waals interactions.

In this work, we used a sessile drop experiment to assess a feasibility of novel processing design engaging liquid-phase assisted fabrication of multi-phase materials from Mo-Si-B system. For this purpose, binary eutectic silicon-boron alloy (Si-3.2B wt%) was subjected to contact heating with polycrystalline molybdenum substrate at temperature up to 1385 °C. It was in-situ observed that molten Si-3.2B alloy wets and rapidly spreads over the Mo surface. After the high temperature test, the solidified couple was subjected to structural characterization by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and X-ray diffraction methods. The obtained results revealed that the direct interaction between examined materials under applied testing conditions results in the reactively formed product layer having a thickness of ∼80 µm. The following structural features were recognized starting from the surface side: (I) the main product layer composed of columnar-like MoSi2 phase and Mo5Si3 phase; (II) an intermediate layer made of MoB and Mo5SiB2 phases. Although these results give the first indication for designing a novel liquid-assisted fabrication method of Mo-Si-B materials, an existence of porosity in the product layer clearly suggests that a further optimization of the process parameters is necessary.

The contact heating (CH) sessile drop and capillary purification (CP) methods were applied for a fundamental study concerning the wettability and reactivity of liquid Si-16.2 at. pct Ti alloy (eutectic composition) in contact with glassy carbon (GC) and SiC at T = 1450 °C under an Ar atmosphere. Different spreading stages with different slopes, depending on the starting conditions of the materials used, where observed. On the contrary, the final contact angle value seemed not affected and the values of θ ≈ 44 deg ± 2 and θ ≈ 42 deg ± 2 where displayed on GC and SiC, respectively. The solidified Si-Ti eutectics/GC and Si-Ti eutectics/SiC samples were examined both at the top of the drop and at the cross section by scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS). The presence of a SiC layer as unique reaction product at the Si-Ti eutectics/GC interface, confirmed that wettability is mainly driven by reactivity. Contrarily, as nonreactive system, at the Si-Ti eutectics/SiC interface a weak dissolution of SiC substrate was detected.

In this work, the effect of boron content on the high temperature wetting behavior in the Si-B alloy/h-BN systems was experimentally examined. For this reason, hypoeutectic, eutectic and hypereutectic Si-B alloys (Si-1B, Si-3.2B and Si-5.7B wt %, respectively) were produced by electric arc melting method, and then subjected to sessile drop/contact heating experiments with polycrystalline h-BN substrates, at temperatures up to 1750°C. Similar to pure Si/h-BN system, wetting kinetics curves calculated on a basis of in-situ recorded drop/substrate images point towards non-wetting behavior of all selected Si-B alloy/h-BN couples. The highest contact angle values of ~150° were obtained for hypoeutectic and eutectic Si-B alloys in the whole examined temperature range.

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 degrees 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 degrees C and 1450 degrees 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.

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 + ZrO2) with molten Si is much lower if compared to the pure h-BN counterpart. Additionally, the role of reinforcements (SiC + ZrO2) and occured microstructural evolution is discussed based on the results obtained by SEM and XRD analyses.

Wetting characteristics of the Al/ZrB2 system were experimentally determined by the sessile drop method with application of separate heating of the ZrB2 and Al samples and combined with in situ cleaning of Al drop from native oxide film directly in vacuum chamber. The tests were performed in ultrahigh vacuum of 10−6 mbar at temperatures 710, 800, and 900 °C as well as in flowing inert gas (Ar) atmosphere at 1400 °C. The results evidenced that liquid Al does not wet ZrB2 substrate at 710 and 800 °C, forming high contact angles (θ) of 128° and 120°, respectively. At 900 °C, wetting phenomenon (θ < 90°) occurs in 29th minute and the contact angle decreases monotonically to the final value of 80°. At 1400 °C, wetting takes place immediately after drop deposition with a fast decrease in the contact angle to 76°. The solidified Al/ZrB2 couples were studied by scanning and transmission electron microscopy coupled with x-ray energy diffraction spectroscopy. Structural characterization revealed that only in the Al/ZrB2 couple produced at the highest temperature of 1400 °C new phases (Al3Zr, AlB2 and α-Al2O3) were formed.

High-temperature interactions of liquid Ti and Ti74.3Al25.7, Ti49.3Al50.7, Ti26.5Al73.5 and Ti3.5Al96.5 (at.%) alloys with TiB2 ceramic are studied using the sessile drop technique. Molten Ti and Ti–Al alloys show a very good wetting of TiB2. A homogeneous TiB layer with a thickness of about 20 μm forms at the Ti/TiB2 interface. An approximately 200-μm-thick layer of densely packed TiB whiskers is observed at the interface of a Ti74.3Al25.7/TiB2 couple. The Ti49.3Al50.7 liquid penetrates the grain boundaries in the TiB2 ceramic and disconnects the grains in the near-interface region. The Ti26.5Al73.5 melt does not disconnect the TiB2 grains, but penetrates the grain boundaries over a distance of about 300 μm from the interface. Ti3.5Al96.5 just fills the pores in the ceramic up to a distance of about 120 μm from the interface.

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.

The wetting behaviour and interfacial interactions between liquid Al and TiB2 ceramic have been studied by the sessile drop technique in the temperature range from 700 to 1400 °C. At about 800 °C, liquid Al starts to wet TiB2 and at about 1000 °C it completely spreads over the ceramic. Al3Ti and Al2O3 are found to be the main phases precipitating at the interface. Starting from 1000 °C, liquid Al either fill pores or penetrates along the grain boundaries of the TiB2 ceramic. Scanning electron microscopy analysis of the interfaces evidences that the TiB2 grains remain intact after the aluminium melt/ceramic interaction even at 1400 °C.

For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism. © The Author(s) 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

In this work, the surface tension and density of Si-Ge liquid alloys were determined by the pendant drop method. Over the range of measurements, both properties show a linear temperature dependence and a nonlinear concentration dependence. Indeed, the density decreases with increasing silicon content exhibiting positive deviation from ideality, while the surface tension increases and deviates negatively with respect to the ideal solution model. Taking into account the Si-Ge phase diagram, a simple lens type, the surface tension behavior of the Si-Ge liquid alloys was analyzed in the framework of the Quasi-Chemical Approximation for the Regular Solutions model. The new experimental results were compared with a few data available in the literature, obtained by the containerless method. (C) 2014 AIP Publishing LLC.

Reactive infiltration of liquid Si-enriched alloys into C- or SiC-based preforms is a viable cost-less alternative to manufacture dense and highly performant SiC-based and MMC composites. In view to design and optimize liquid-assisted processes such as reactive infiltration, fundamental investigations on the interfacial phenomena occurring when the liquid Si-based alloys are in contact with C and SiC substrates, are crucial steps. In this context, targeted wettability studies may provide indications for predicting the key factors strongly influencing the reactive infiltration mechanisms, such as, unexpected interaction phenomena, etc. In particular, such preliminary experience may be helpful in finding the suitable set of operating conditions for fabricating tailored composites via reactive infiltration process. Aiming to “mimic’’ the conventional industrial processes for manufacturing SiC/ZrSi2 refractory composites, the sessile drop method was applied to study the interfacial phenomena occurring at Si-10 % atZr/SiC interfaces over the temperature range of T =1360 °C-1450 °C.

Gd–Ti monotectic alloys were studied in a wide temperature range by the sessile drop technique. The eutectic and monotectic transformations in Gd–Ti alloys upon heating were in situ monitored by a high-speed and high-resolution CCD camera. Our findings suggest that the existing Gd–Ti phase diagram significantly underestimates the monotectic and binodal temperatures in this system. The wetting behavior and the high-temperature interaction of the Gd–Ti melts with yttria and yttria-stabilized zirconia substrates were investigated.