Fabrication of C/SiC composites by combining liquid infiltration process and spark plasma sintering technique

5 páginas, 4 figuras, 1 tabla.-- El pdf del artículo es la versión post-print.Carbon fibre-reinforced silicon carbide composites (C-SiC) were fabricated combining, for the first time, a liquid infiltration process (LI) of a mesophase pitch doped with silicon carbide nanoparticles followed by reactive liquid silicon infiltration using Spark Plasma Sintering (SPS) technique. A graphitization step was applied in order to improve the effectiveness of the processing. Up to three different morphologies of SiC particles were identified with a noticeable influence on the preliminary oxidation tests carried out. The presence of SiC nanoparticles added to the carbon matrix affects the morphology of the SiC obtained by in situ reaction of silicon and carbon during the LI process by SPS and it leads to an improvement of the material oxidation resistance. The results show that SPS is a promising method to develop C-SiC composites in a short time and with a high efficiency in the liquid silicon infiltration process.This work has been performed within the framework of the Integrated European Project ‘‘ExtreMat’’ (NMP-CT-2004- 500253) and IP-NANOKER (NMP3-CT-2005-515784) with financial support by the European Community and the Spanish Education Ministry (Programa Nacional de Cooperación Internacional de Ciencia y Tecnología, Acciones Complementarias, MAT2004-22787-E). A. Borrell acknowledges the Spanish Ministry of Science and Innovation for her FPI Ph.D. grant BES-2007-15033.Peer reviewe

Thermal curing of mesophase pitch: An alternative to oxidative stabilisation for the development of carbon–carbon composites

[EN] Thermal curing of mesophase pitch was studied as an alternative to oxidative stabilisation for the development of carbon–carbon composites, with the aim of avoiding several problems associated to the oxidative process such as thickness limitations or gradients in the properties of the resultant materials. Carbon fibre preforms densified with the mesophase were submitted to thermal treatments at temperatures between 400 and 475 °C for different periods in order to promote polymerisation and thus avoid exudation of the matrix precursor during carbonisation. Changes induced in the matrix precursor were monitored by thermogravimetric analysis and infrared spectroscopy. The effectiveness of the treatments was evaluated from the porosity of the resultant materials after carbonisation. The highest degree of polymerisation of the matrix precursor was achieved with treatments at 400 °C for 24 h or 475 °C for 5 h, the resultant materials having similar porosity values to those obtained by oxidative stabilisation.This work has been performed within the framework of the Integrated European Project “ExtreMat” (contract NMP-CT-2004-500253) with financial support by the European Community and the Spanish Education Ministry (Programa Nacional de Cooperación Internacional de Ciencia y Tecnología, Acciones Complementarias, MAT2004-22787-E). The authors would like to thank SGL Carbon Group for supplying the carbon fibre preforms.Peer reviewe

Further studies on the use of Raman spectroscopy and X-ray diffraction for the characterisation of TiC-containing carbon–carbon composites

[EN] Raman spectroscopy and X-ray diffraction are used to study the crystalline structure of carbon–carbon and TiC-containing composites. The advantages and drawbacks of these techniques for the characterisation of carbon–carbon composites are analysed in the light of the distribution and arrangement of their components and the microstructural orientation of the supporting matrix. Analyses performed on longitudinal and transverse sections of the composites confirm that the measurements are affected by the orientation of the crystals. The overall crystalline parameters calculated by X-ray diffraction were unequivocally resolved for each single component by means of Raman spectroscopy. A significantly higher degree of order was observed in the TiC-containing matrix as a result of the catalytic graphitisation of the carbon achieved by the addition of titanium. In addition, Raman spectroscopy corroborated that the incorporation of TiC into the carbon matrix does not disrupt the orientation of the graphene planes of the matrix parallel to the fibre axis, a necessary characteristic for achieving an optimum heat transfer through the material.This work has been performed within the framework of the Integrated European Project “ExtreMat” (contract NMP-CT-2004-500253) with financial support from the European Community and the Spanish Education Ministry (MAT2004-22787-E).Peer reviewe

Graphene/alumina (G/Al2O3) composites by Spark Plasma Sintering; a simple, fast and upscalable method

Resumen del póster presentado a la 4th edition of Graphene Conference series, celebrada en Toulouse (Francia) del 6 al 9 de Mayo de 2014.Peer Reviewe

Behaviour of Ti-doped 3D carbon fibre composites under intense thermal shock tests

This paper reports on the development of novel Ti-doped 3D carbon fibre composites (CFCs) and their performance when exposed to transient thermal loads (disruptions) in the electron beam facility JUDITH at different conditions. Depending on the applied load, the CFCs showed three steps of erosion: (i) breaking of PAN fibres with pull out from the surface; (ii) cracking and ablation of pitch fibres close to the interface of PAN/pitch fibre bundles; and (iii) finally, erosion of pitch fibres in the centre of the bundle. The addition of titanium carbide resulted in a significant improvement in thermal shock behaviour of these materials compared with undoped counterparts.The authors would like to thank SGL Carbon Group for supplying the 3D preforms. This work has been performed within the framework of the Integrated European Project ‘ExtreMat’ (contract NMP-CT-2004-500253) with financial support by the European Community.Peer reviewe

Development of titanium-doped carbon–carbon composites

[EN] The development of titanium-doped carbon matrix–carbon fibre reinforced composites (CCCs) via liquid impregnation of carbon fibre preforms using mesophase pitch is studied. Two different approaches for introducing the dopant into the carbon material are investigated. One consists of doping the matrix precursor followed by the densification of the preform with the doped precursor. The second approach consists of doping the porous preform prior to densification with the undoped mesophase pitch. Titanium-doped CCCs with a very fine distribution of dopant (in the nanometric scale) are obtained by adding TiC nanoparticles to the matrix precursor. Thermal decomposition of titanium butoxide on the carbon preform prior to densification yields doped CCCs with higher titanium content, although with larger dopant size. The combination of these two methods shows the best results in terms of dopant content.This work has been performed within the framework of the Integrated European Project “ExtreMat” (contract NMP-CT-2004-500253) with financial support by the European Community and the Spanish Education Ministry (Programa Nacional de Cooperación Internacional de Ciencia y Tecnología, Acciones Complementarias, MAT2004-22787-E). The authors would like to thank Karl Hingst and Sandra Sitter, from SGL Carbon Group, for supplying the carbon fibre performs.Peer reviewe

Influence of titanium carbide on the interlaminar shear strength of carbon fibre laminate composites

The potential use of carbon fibre laminate composites is limited by the weak out-of-plane properties, especially delamination resistance. The effect of incorporating titanium carbide to the mesophase pitch matrix precursor of carbon fibre laminate composites on interlaminar shear strength is studied both on carbonised and graphitised composites. The presence of titanium carbide modifies the optical texture of the matrix from domains to mosaics in those parts with higher concentrations and it contributes to an increase of fibre/matrix bonding. This fact produces an increase of the interlaminar shear strength of the material and changes the fracture mode.This work has been performed within the framework of the Integrated European Project “ExtreMat” (contract NMP-CT-2004-500253) with financial support by the European Community and the Spanish Education Ministry (Programa Nacional de Cooperación Internacional de Ciencia y Tecnología, Acciones Complementarias, MAT2004-22787- E).Peer reviewe

Graphene for tough and electroconductive alumina ceramics

A simple, fast and upscalable method is described to produce graphene/alumina (G/Al2O3) composites by spark plasma sintering (SPS) with a significant improvement on both mechanical and electrical properties of monolithic Al2O3. Graphene oxide (GO) was mixed with Al2O3 using a colloidal method obtaining an excellent dispersion of GO in the alumina matrix. The material was consolidated by SPS that allowed, in one-step, the in situ reduction of the GO during the sintering process. A detailed Raman analysis was found to be very useful to study the orientation of the graphene in the composite and to evaluate and optimise its thermal reduction. Graphene platelets acted as elastic bridges avoiding crack propagation and providing this material with a crack bridging reinforcement mechanism. A very low graphene loading (0.22wt%) led to a 50% improvement on the mechanical properties of the alumina and to an increase of the electrical conductivity up to eight orders of magnitude. © 2013 Elsevier Ltd.Authors would like to thank the support of contract 14.B25.31.0012.Peer Reviewe

Wear behavior of graphene/alumina composite

In the present work, the dry sliding behavior of a graphene/alumina composite material was studied against alumina in air. The tests were carried out in a reciprocating wear tester with an applied load of 20 N, a sliding speed of 0.06 m s−1 and a sliding distance of up to 10 km. Under the testing conditions, the graphene/ceramic composite showed approximately half the wear rate and a 10% lower friction coefficient than the monolithic alumina. It has been found that this behavior is related to the presence of graphene platelets adhered to the surface of friction that form a self-lubricating layer which provides enough lubrication in order to reduce both wear rate and friction coefficient, as compared to the alumina/alumina tribological system.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) under the Project MAT2012-38645. The Ministry of Education of the Russian Federation supported this work by Contract no. 14.577.21.0089, unique identifier of contract RFMEFI57714X0089.. Anton Smirnov has been supported by JAE-Pre Programme 2010.Peer Reviewe

Reducing cement consumption in mortars by waste-derived hydrochars

Waste-derived hydrochars are presented for the first time as promising materials to reduce the consumption of natural resources and the carbon footprint of the cement industry, while eliminating waste and sequestering a high amount of carbon in civil infrastructures. Rice husk (RH) and stabilized organic waste from a mixed municipal waste mechanical-biological treatment plant (SOW) were subjected to hydrothermal carbonization at 200 °C for 2 h and the resulting hydrochars were thoroughly evaluated as cement substitutes in fresh and hardened mortars. Compared to the control, mortars with 1.25–5 wt% of cement replaced by hydrochar from stabilized organic fraction caused a decrease in compressive strength of about 50–60% at 28 days of curing, while flexural strength was diminished by about 38–47%. The use of rice husk-derived hydrochar led to a reduction of 32–47% in compressive strength and of 22–34% in flexural strength. With compressive and flexural strengths of 27–41 and 3.31–4.92 MPa, respectively, blended mortars (28 days) display good prospects for use in plastering, rendering, masonry, partition panels and low-load paving. On the other hand, substituting 5 wt% of cement by hydrochar decreases the thermal conductivity and increases electrical resistivity of the mortar by 25–30%, which enhances thermal insulation properties and potential durability. This approach opens a new avenue for large-scale application of biowaste hydrochars as secondary raw materials for sustainable construction.Funding from the European Regional Development Fund (ERDF) through project CEMOWAS2 (SOE2/P5/F0505)-INTERREG V SUDOE 2017 and from the Plan de Ciencia, Tecnología e Innovación (PCTI) 2018-2022 del Principado de Asturias and the ERDF (project IDI/2021/000037) is gratefully acknowledged. CINN acknowledges the financial support received from FICYT (IDI/2021/000106). Michael M. Santos thanks the University of Beira Interior and the Spanish National Research Council (CSIC) for the Erasmus+ internship award. This study was carried out with the support of COGERSA for obtaining and managing the SOW sample and of the company DACSA for supplying the rice husk. The assistance of the INCAR-CSIC library service led by Luis Gutiérrez Fernández-Tresguerres is highly appreciated.Peer reviewe