New advanced SiC-based composite materials for use in highly oxidizing environments: Synthesis of SiC/IrSi3

Currently, MMCs with SiC as reinforcement emerge as ideal candidates for long-term stable devices withstanding high temperatures and harsh operating environments which are typical for many industrial sectors, such as energy, aerospace, electronics, catalysis, etc. However, the costly manufacture of such composites is the major restraint to make them marketable. In this paper, highly-dense, nearly-shaped SiC/IrSi3 composites effortless produced at T = 1250 °C under a vacuum by reactive melt infiltration of liquid Si-62 wt%Ir eutectic alloy into bimodal SiCp-C porous preforms, are presented. The replacement of unreacted detrimental Si by a tougher and less oxidizing intermetallic phase (IrSi3) was successfully obtained.The work performed at the University of Alicante was funded by the Spanish “Ministerio de Economía y Competitividad” (Grant MAT2017-86992-R), and action Mobility of Alicante University. The work performed at CNR-ICMATE was supported by National Science Center of Poland through POLONEZ project number UMO-2016/23/P/ST8/01916. This project is carried out under POLONEZ-3 program which has received funding from European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement. No. 665778

Further Development of Testing Procedures for High Temperature Surface Tension Measurements

A new testing procedure combining in one test two methods for surface tension measurements of liquid metals [the pendant drop (PD) and the sessile drop] and carried out in the same device is discussed. The attention is focused on methodological aspects of the PD method due to the novelty of its application for high temperature metallic systems. It has been claimed that under the conditions applied in the present study, this method can be considered as a quasi-containerless one. Surface tension measurements of pure Cu, Ni, Al, and Fe performed using the new procedure are described. To confirm the validity of this procedure, the experimental results are discussed in the framework of the available literature data, particularly those obtained by the containerless methods. © 2013 The Author(s)

The effective oxidation pressure of indium-oxygen system

A theoretical model on oxygen transport at the surface of liquid metals has been validated by dynamic surface tension measurements performed on liquid Indium as test metal. The oxygen contamination conditions have been obtained at different oxygen partial pressures under both low total pressure (Knudsen regime) and inert atmospheric pressure (Fick regime) conditions, confirming that an oxide removal regime occurs under an oxygen partial pressure much higher than the equilibrium one (the "Effective Oxidation Pressure"). Experimental results are reported which give a further insight on the relative importance of the various processes due to the oxygen mass transport between the liquid metal and the gas phase. The critical aspects involved in surface tension measurements of liquid metals, related to the problem of liquid metal-oxygen interactions, are also underlined

Interfacial Phenomena between Liquid Si-rich Si-Zr Alloys and Glassy Carbon

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 °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 work performed at CNR-ICMATE was supported by National Science Center of Poland through POLONEZ project number UMO-2016/23/P/ST8/01916. This project is carried out under POLONEZ-3 program which has received funding from European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement. No 665778. The work performed by JN was funded by the Spanish “Ministerio de Economía y Competitividad” (Grant MAT2017-86992-R) and action Mobility of Alicante University

Improvements in experimental investigation of molten Mg-based materials

In this paper, the experimental performance of a new testing device designed for investigating the high temperature properties of molten Mg is presented. The newly developed device allows examining high temperature wetting behavior and thermophysical properties of molten Mg (and Mg alloys) by using various experimental procedures (e.g. classical sessile drop, pendant drop, dispensed drop and drop sucking). High temperature wettability tests at temperatures up to 1000 °C in an inert gas atmosphere or under high vacuum (up to 10−7 hPa) are now possible. It has been documented that the application of the classical sessile drop method combined with a capillary purification procedure successfully eliminates the problem of magnesium oxidation that traditionally affects obtained results. Selected examples of high temperature experiments carried out for molten Mg in contact with various refractories are presented in order to show a wide range of analytical possibilities of the new device. The results obtained by using the new device are important from both a high theoretical and practical perspective regarding liquid phase assisted fabrication and processing of Mg-based alloys and metal-matrix composites. Keywords: Equipment design, Sessile drop method, Reactivity, Mg composites, Mg alloy

Improved methodological concepts for processing liquid Mg at high temperature

Abstract In this paper, new improvements of methodological concepts upon examining wettability of high vapor pressure liquid metal systems (e.g. Mg-based alloys) in contact with refractory materials, are presented and discussed. In this regard, high-temperature experiments on molten magnesium (Mg) in contact with graphite as a refractory substrate, were performed by utilizing a newly developed testing device and by applying a suitable experimental procedure. The wetting experiments were carried out by the sessile drop method and under identical testing conditions (700 °C/10 min under a protective gas atmosphere). Two different procedures were applied: the classical contact heating (CH) or a newly introduced capillary purification (CP) one. The contact angle behaviors observed under the same conditions were strongly influenced by the applied procedure. Specifically, in the case of using the CH procedure, a presence of native surface oxide layer on the metal surface hinders the observations of melting process, making not possible to experimentally determine the wetting kinetics curve θ=f(t). Contrarily, during the wetting test performed on the Mg/graphite couple by applying the CP procedure, the native surface oxide layer was mechanically removed during the squeezing of the molten Mg through the hole of a capillary. Indeed, an oxide-free squeezed Mg-drop with regular and spherical shape was successfully obtained and dispensed on the graphite substrate. Consequently, the reliable contact angle value around θ=150° for the Mg/graphite system, was measured within the wetting test

The Effect of Boron Content on Wetting Kinetics in Si-B Alloy/h-BN System

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 toward 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. © 2018, The Author(s)

Solid state reactions between SiC and Ir

Reactivity between SiC and Ir as a function of SiC-crystallinity was investigated by diffusion bonding technique under a vacuum and over the temperature range of 1200–1450 °C. As reaction products, various Ir-silicides and free unreacted-C were detected. Reactivity is strongly affected by the temperature and SiC-crystallinity involving a series of interactions, from “no reaction” to “massive exothermic reactions”. In particular, interfacial phenomena are more pronounced by the presence of defects and grain boundaries. Solid state reactions result in formation of fine C-precipitates rearranged in a quasi-periodic microstructure. On the contrary, clustering of highly ordered C-precipitates (C-graphitized) occurs after “massive reactions” take place. A relationship between the degree of graphitization (from 1 to multi-layers of graphene), temperature and SiC crystallinity was found by Raman spectroscopy. 2D-layering phenomenon is enhanced in polycrystalline SiC at high temperature.The work performed at the University of Alicante was funded by the Spanish “Ministerio de Economía y Competitividad” (Grant MAT2017-86992-R), action Mobility of Alicante University. The work performed at CNR-ICMATE was funded by CNR-STM 2016 call (prot. n. AMMCNT-0059260 25/01/2017)

Studio delle proprieta\u27 di superficie di sistemi metallici ad alta temperatura in funzione dell\u27atmosfera di lavoro

No abstract availabl

SiC-IrSi3 for High Oxidation Resistance

SiC is a material with excellent mechanical and thermal properties but with a high production cost. Obtaining SiC by reactive infiltration is an attractive method with a much lower cost than the traditional sintering process. However, the reactive infiltration process presents a serious problem, which is the high residual silicon content, which decreases its applicability. The replacement of silicon with silicides is a widely used alternative. The present investigation shows the good mechanical properties of the SiC-IrSi3 composite material obtained by reactive infiltration of SiC-C preforms with Ir–Si alloys. The thermomechanical analysis shows a high compatibility of silicide with SiC. The presence of the silicide shows a substantial improvement against the oxidation of the SiC-Si composites.The work performed at the University of Alicante was funded by the Spanish Ministerio de Economía y Competitividad (Grant MAT2017-86992-R) and action Mobility of Alicante University. The work performed at CNR-ICMATE was supported by the National Science Center of Poland through POLONEZ project number UMO-2016/23/P/ST8/01916. This project is carried out under POLONEZ-3 program, which has received funding from the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement No. 665778