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SiC composites by spark plasma sintering technique
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ScienceDirect Journal of the European Ceramic Society 34 (2014) 903–913
Feature Article Joining of C/SiC composites by spark plasma sintering technique Stefano Rizzo a , Salvatore Grasso b , Milena Salvo a,∗ , Valentina Casalegno a , Michael J. Reece b , Monica Ferraris a b
a Department of Applied Science and Technology, Institute of Materials Physics and Engineering, Corso Duca degli Abruzzi 24, 10129 Torino, Italy School of Engineering & Materials Science and Nanoforce Technology Ltd., Queen Mary University of London, Mile End Road, London E1 4NS, UK
Received 24 July 2013; received in revised form 19 October 2013; accepted 21 October 2013 Available online 19 November 2013
Abstract CVD–SiC coated C/SiC composites (C/SiC) were joined by spark plasma sintering (SPS) by direct bonding with and without the aid of joining materials. A calcia-alumina based glass–ceramic (CA), a SiC + 5 wt% B4 C mixture and pure Ti foils were used as joining materials in the non-direct bonding processes. Morphological and compositional analyses were performed on each joined sample. The shear strength of joined C/SiC was measured by a single lap test and found comparable to that of C/SiC. © 2013 Elsevier Ltd. All rights reserved. Keywords: Joining; C/SiC composites; Spark plasma sintering
1. Introduction Ceramic matrix composites (CMC), e.g. SiC/SiC, C/SiC and C/C, are being considered as the primary candidates for components and subsystems in the field of satellite (nearsun) missions, defence, aerospace missions (e.g. body flaps, nose cones, wings, leading edges, turbine components) and for terrestrial/industrial applications under extreme environmental conditions (e.g. valves, shaft sleeves for pump sliding bearings, heat exchangers, nuclear plant components, etc.).1–3 A critical issue for a wider use of CMC is the development of inexpensive, reliable and user-friendly joining methods to assemble large components into more complex structures.4 There are many possible techniques for joining CMC to themselves and to dissimilar materials: diffusion bonding;5 transient eutectic phase methods such as nano-infiltration and transient eutectic-phase (NITE);6 transient liquid-phase diffusion bonding;7 pressure-less glass–ceramic joining;8–10 solid state displacement reactions;11 adhesive and preceramic polymer routes;12,13 reaction forming;14 brazing.15 Brazing is the most commonly used joining and integration method for CMC
∗
Corresponding author. Tel.: +390110904706. E-mail address: [email protected] (M. Salvo).
0955-2219/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jeurceramsoc.2013.10.028
and extensive research on brazing of CMC for their joining and integration has been done by Singh and his group at NASA.16–18 High temperature brazing alloys are based on gold, nickel and copper and are often used for joining CMC to cobalt, titanium alloys and nickel-based superalloys.19 TiZrNiCu, Ni and Ag–Cu–Ti have been used as filler to join C/SiC to Ti–6Al–4V.20 Whatever the joining process is, the joined interfaces need to be thermodynamically stable: reactions and diffusion of species from the joining material and the CMC can affect the quality of the joints and their performance in service.21 Furthermore, the coefficient of thermal expansion (CTE) of CMC is lower than that of most metals and considerable residual stress is generated in the joint during the cooling process or when exposed to high temperature environments, thus leading to cracks or failure of the joints. In order to deal with the CTE mismatch between CMC and brazing alloys, several options have been proposed: different layers with a gradually changing CTE from CMC to the metal alloy;22 compliant metallic layers (e.g. Cu); composite brazing alloys obtained by adding short fibres or particles to the brazing alloy.22,23 Selecting the optimal braze filler metal for brazing CMC to metals is not easy because the application requires a high brazing temperature (high thermal load in operation predicted), while the prevention of high joining stresses should require a low brazing temperature. Moreover, the wetting of CMC often
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requires the addition of active elements (i.e. Ti, Cr . . .), but the formation of brittle intermetallic phases based on these elements must be avoided. The CMC employed in this study consist of carbon fibre reinforced SiC matrix composites coated with a chemical vapour deposited (CVD) layer of SiC. The aim of this work is to investigate the effectiveness of using spark plasma sintering (SPS)24 to join CMC. The SPS has recently been employed to achieve high quality joint25 .The intrinsic advantages of SPS as a joining process for CMC, especially if the materials are electrically conductive, are: – localized heating generated by joule heating; – low energy consumption due to both the rapid processing and the localized heating; – limited deformation of the joined parts; – both the rapid heating and short processing time allow highly controllable reaction of interlayer formed between the joined materials. The effect of the electric field has been reported to enhance the diffusivity by electro migration phenomena,26 thus promoting migration of ions trough the joining interface. The joining by SPS represents a novelty in the field of composites. Several works on SPS as a manufacturing technique for SiC based composites have been published in the last few years.27–31 In the field of materials joining, research has focused on metal-to-metal, ceramic-to-ceramic or ceramic-tometal joints32–34 using conventional techniques, but at present there is still a lack of scientific experience on joining of composites by SPS. Direct bonding and three different types of joining materials (a metal, a glass–ceramic and a ceramic powder mixture) were tested by SPS in order to have an overview of this technique for joining C/SiC. If the use of a joining material cannot be avoided, several options can be proposed to join C/SiC. The first choice would be using SiC as joining material in order to maintain the same thermo-mechanical properties of the composite matrix. However, both the direct bonding process and the use of SiC as joining material need high temperature, high pressure and long processing time. In this work, SPS was used to obtain a quick and effective direct bonding between C/SiC and a sound SiC based joint by using a typical SiC sintering aid (B4 C). The room temperature electrical and thermal conductivity of C/SiC composite is 0.5 × 104 S/m and 135 W/m K,35 which is comparable to the constitutive graphite of the SPS mould (6 × 104 S/m and 70 W/m K). The lower electrical conductivity of C/SiC compared to graphite results in a preferential current across the SPS moulds, however according to modelling results up to 10% of the total current might still able to flow across the sample, in particular at the joined region where there is initially a contact resistance that will lead to a favourable increase in Joule heating.36 In addition the high thermal conductivity of C/SiC compared to graphite allowed an even temperature homogenization during heating/cooling.
The choice of a CaO–Al2 O3 glass–ceramic (CA) as joining material have been discussed in:8,37,38 CA was designed to have a suitable wettability and CTE towards SiC based materials; CA can be almost completely crystallized after a pressure-less joining process, thus providing a potential high temperature resistant joining material, also suitable in a neutron environment.8,37 SPS was used here as an alternative joining technique for CA based joints, which is able to provide a localized quick heating of the joined region. Titanium was chosen as a joining material for C/SiC because of its refractory properties and well known reactivity with SiC. Ti–SiC system finds use in the joining of ceramics and metals because the interfacial reaction provides good bonding effects.39 Halbig et al. developed a SiC joining technology, where titanium interlayers were used to form diffusion bonds between CVD–SiC substrates.40 Ti–SiC and Ti–C reactions can limit the joint thermodynamic stability and must be carefully controlled. The reaction products between Ti and SiC are very brittle with the exception of TiC and Ti3 SiC2 .41 Furthermore, coherent phase boundaries have been found between SiC and Ti3 SiC2 , thus leading to very good adhesion of this ternary phase on the SiC. The main purpose of this paper is to explore the influence of pressure, surface and intermediate joining materials used for bonding C/SiC by SPS. Since SPS involves rapid heating rates, a direct comparison with other bonding techniques is difficult. These results can be useful in order to define the SPS joining processing window, the intermediate joining materials and to guide future research. In this study CVD–SiC coated C/SiC composites have been used because oxidation protected C/SiC is the final status of C/SiC for most of the applications and the coating deposition is directly performed by the manufacturer (MT Aerospace, Germany).
2. Experimental CVD–SiC coated C/SiC composites used in this study were manufactured in disk shaped samples with diameter of 20 mm and height of 5 mm by MT Aerospace (Germany).42 C/SiC were joined by SPS technique (SPS-HP D 25, FCT HP, Germany) using joining materials or by direct bonding. Specimens joined by direct bonding were hand polished up to 3 m diamond slurry in order to reduce roughness and maximize the contact surface. The as received samples were ultrasonically cleaned in acetone. Before inserting the samples in a graphite mould (hollow die, diameter of 2 cm) an interlayer was interposed between the materials to be joined. The temperature was probed by an optical pyrometer installed on the top side of the SPS machine. This configuration allowed a precise measurement of the sample temperature. According to experimental/modelling results, the temperature was measured by an optical pyrometer focused at 4 mm from the sample top surface, as detailed in Ref. [43]. All SPS joining process parameters are summarized in Table 1. All the joining surfaces were ultrasonically cleaned to remove dust particles, grease and any other contaminants.
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Table 1 SPS processing conditions used to join C/SiC and apparent shear strengths of joined and not joined C/SiC measured with a single-lap mechanical test. (DB = direct bonding). SPS conditions Temperature (◦ C) C/SiC–CA C/SiC–Ti (30 m) C/SiC–Ti (130 m) C/SiC–SiC + B4 C C/SiC–DB C/SiC as received C/SiC–1480 C/SiC–1700 C/SiC–1900
Joined 1480 1700 1700 1900 1900 Not joined – 1480 1700 1900
Apparent shear strength (MPa)
Heating rate (◦ C/min)
Dwell time (min)
Pressure (MPa)
50 150–200 150–200 150–200 150–200
10 3 3 3 3
0 60 60 60 60
12.1; 14.1 19.8; 9.5; 27.1; 13.0 (17.3 ± 7.8) 21.6; 18.3 18.2 5.6; 11.2
– 50 150–200 150–200
– 10 3 3
– 0 60 60
15.4; 5.3 15.5; 13.8 24.6; 19.6 11.3; 16.1
The following joining materials were used: – Ti foil – Calcia-alumina glass–ceramic – SiC + 5 wt% B4 C powder mixture 2.1. Titanium as joining material C/SiC–Ti–C/SiC sandwiches were heated by SPS between 150 and 200 ◦ C/min, with a dwell time of 3 min and a pressure of 60 MPa in vacuum atmosphere. The maximum temperature was set at 1700 ◦ C. To investigate the effect of the Ti foil thickness, 30 m and 130 m Ti foils were used (Ti Foil 99.6%, Goodfellow). 2.2. Calcia-alumina glass–ceramic as joining material C/SiC composites were joined using CaO–Al2 O3 (49.7 CaO, 50.3 Al2 O3 wt%) glass–ceramic, which is referred to as CA here forth. The joining material was designed, prepared, and characterized as described in Refs. [8,37]. The CA was synthesized by melt/quenching: the powdered raw products were melted in a platinum–rhodium crucible in air at 1750 ◦ C for 30 min, then the glass was poured onto a brass plate and subsequently powdered and sieved. Sandwich-like joined samples were produced by depositing the glass slurry at room temperature on the surface of composites. The slurry was a mixture of glass powder (powder size between 38 and 75 m) dispersed in ethanol. Samples joined by CA slurry (0.8 mg/mm2 ) were heated by SPS to 1480 ◦ C for 10 min, a minimal pressure (a 25 g tungsten disk was put on the top of the SPS mould to keep samples in place) and cooled at 50 ◦ C/min in an argon atmosphere. 2.3. SiC ± 5 wt% B4 C mixture as joining material C/SiC composites were joined using a mixture of SiC + 5 wt% B4 C powders at 1900 ◦ C, 3 min, 60 MPa. The powder mixture was prepared in a rotary mill starting from silicon carbide (UF 10, H.C. Starck) and boron carbide (H.C. Starck HD 20) powders.
In order to understand the effect of SPS on C/SiC mechanical strength, some as received C/SiC discs samples, hereinafter defined as not joined, were SPSed under identical processing conditions used to join them. Joined C/SiC, as received C/SiC and C/SiC after the same SPS treatments used for the joining processes (1700 ◦ C, 3 min, 60 MPa; 1480 ◦ C, 10 min, a minimal pressure; and 1900 ◦ C, 3 min, 60 MPa), were tested at room temperature by the single lap test (SL) adapted from ASTM D1002-05.44 Two samples for each joining processes were tested and four samples for C/SiC joined by Ti, 30 m thick. The disk shaped C/SiC (joined and not joined) were cut with a diamond blade into rectangular shaped samples suitable for mechanical tests (about 7 × 12 × 8 mm3 ). Polished cross-sections and fracture surfaces were analysed by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM–FEI, QUANTA INSPECT 200, EDS–EDAX PV 9900) and micro X-ray diffraction (Rigaku D/MAX Rapid microdiffractometer, X-ray generator settings fixed at 40 kV and 20 mA, Cu K␣ incident radiation with ˚ with a spot detector of 30 m2 . λ = 1.54 A) 3. Results and discussion The ideal joining technology is a direct bonding between the two identical substrates to be joined: in this case the thermomechanical properties of the substrates are not affected by the presence of a joining material in between. Fig. 1 shows the polished cross-sections of C/SiC specimens joined by direct bonding (DB) and by non-direct bonding (CA glass–ceramic, SiC + 5 wt% B4 C and Ti foil). Cracks in the CVD–SiC coating are visible in all joined samples and are due to the thermal expansion coefficient mismatch between SiC coating and C/SiC substrate. Consistently, cracks propagate through the SiC-based joined area in the direct bonded and in the SiC + B4 C bonded samples, but they seem to be absent in the glass–ceramic and in the Ti-foil joining materials (Fig. 1). In particular, C/SiC joined by DB and SiC + 5 wt% B4 C (1900 ◦ C, 3 min, 60 MPa) produced continuous interfaces, but many cross-sectional cracks propagated from the CVD–SiC coating through the joint area
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Fig. 1. Scanning electron microscopy of polished cross-sections of C/SiC specimens joined by SPS: direct bonding (a), SiC powder + 5 wt% B4 C (b), CA glass–ceramic (c) and Ti 130 m (d). (a) and (b) secondary electron images; (c) and (d) backscattered electron images.
(Fig. 1a and b); no cracks were observed along SiC/joint interfaces. C/SiC joined by CA glass–ceramic (1480 ◦ C, 10 min, no pressure) showed a homogenous joint area without cracks, Fig. 1c. The cracks in the CVD–SiC coating did not propagate through the CA and the interfaces between the glass–ceramic and the CVD SiC layer are continuous. The joining mechanism in the case of CA is based on fast heating typical of SPS which produces a decrease in the viscosity of CA. This allows the joining of C/SiC by CA, which acts as an adhesive. The same process occurs with conventional heating,8,37,38 but takes longer time, typically 30–60 min for samples of the size used in the current study. Interfacial reactions between CA and CVD–SiC with gaseous or other products have never been observed.38 Ti joined C/SiC were produced using Ti foils of 30 and 130 m thickness. Fig. 1d shows the cross-section of C/SiC joined by a 130 m thick Ti foil. The cracks in the CVD–SiC coating did not propagated in the pore free joint area. Fig. 2a shows a magnification image of the cross-section of the titanium based joint (130 m Ti foil) C/SiC sample and the fracture surface after mechanical testing (Fig. 2b). The interface CVD–SiC/titanium based joint is dense and defect free: Fig. 2c shows the perfect adhesion of the joint which follows the nanoroughness of the CVD–SiC. Micro-XRD analysis on the fracture surface (square area in Fig. 2b) showed the formation of Ti3 SiC2
(Fig. 3b), whereas SiC comes from the CVD SiC layer deposited on C/SiC. Gottseling et al.41 investigated the reaction products between SiC and Ti after an annealing time of 2 h: for temperatures lower than 1500 ◦ C, Ti3 SiC2 is predominantly formed, while TiSi2 and TiC are secondary products. The thermal decomposition of Ti3 SiC2 in a vacuum furnace up to 1500 ◦ C has been investigated by Zheng et al.45 They demonstrated that the decomposition of Ti3 SiC2 to titanium carbide starts at 1300 ◦ C in a vacuum furnace, the higher the holding temperature, the larger is the volatilization of Si. The presence of Ti3 SiC2 in the joining area after the heat treatment by SPS at 1700 ◦ C under vacuum might be explained by the very short dwell time (3 min) at high temperature. EDS element maps of cross-sections Ti joined C/SiC are shown in Fig. 4a and b (130 and 30 m Ti foil, respectively). Silicon, titanium and carbon are mostly homogeneously dispersed in the joint areas. A Ti–Si–C based phase (most likely Ti3 SiC2 , as also detected by micro-XRD) is the main reaction product. A depletion of silicon is evident at the centre of the joints (red arrows in Fig. 4a and b) where a higher concentration of C has been revealed thus indicating the formation of a titanium carbide. The presence of titanium carbide at the centre of the joints may be due to the faster diffusion of C compared to that of Si.46
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Fig. 2. Scanning electron microscopy (backscattered electron images) of cross-sections (a), fracture surface after mechanical test (b) and particular of the interface (c) of C/SiC joined by SPS with Ti (130 m foil). Highlighted area: micro-XRD analysis zone (Fig. 3). (a) and (b): secondary electron images; (c): backscattered electron image.
Only by using a 130 m thick titanium foil, the formation of a silicon rich phase (probably TiSi2 ) was detected in the joint region, as indicated by the white arrows in Fig. 4a. The formation of the titanium silicide phase has been already observed by Gottselig et al.41 if thick titanium layers were used. The presence of titanium silicide, which is not detected by the micro-XRD in Fig. 3b, suggests the incomplete reaction as in47 : 7TiC + 2TiSi2 → 3 Ti3 SiC2 + SiC
Fig. 3. Micro-XRD on the fracture surfaces of C/SiC joined by SPS with (a) Ti (30 m foil), highlighted area in Fig. 2 and (b) Ti (130 m foil).
Ti3 SiC2 phase has been already identified as ideal intermediate joining material for SiC matrix composites as reported by Dong et al.48 However unlike the previous investigation where Ti3 SiC2 was used as starting material,48 we report the in situ reactive formation of Ti3 SiC2 phase in the joining interlayer. By using a 30 m thick Ti foil the formation of the brittle titanium silicide phase did not occur (Fig. 4b) and the main phase is again the Ti–Si–C based phase (most likely Ti3 SiC2 ) with the presence of titanium carbide at the centre of the joint. MicroXRD on this fracture surface (Fig. 3a) did not detect anything other than SiC and C, most likely due to the thinner joined area than that investigated in Fig. 3b. It is worth noting that the very rapid SPS heating (100 ◦ C/min) and very short dwelling time allowed the formation of Ti3 SiC2 phase which is metastable at temperature of 1700 ◦ C.49 Typically other techniques such as hot pressing are not suitable to obtain this phase, thus to control the chemistry of the joined interfaces. The aim of this work was to provide preliminary results on the potential of SPS to join SiC-based CMC (C/SiC). It was not possible to do a complete mechanical characterization of joined composites. The amount of C/SiC necessary for standard interlaminar shear strength tests on CMC and for standard shear strength tests on joined CMC was unavailable. It was then decided to do some comparative tests on joined and not-joined
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Fig. 4. Compositional elements map of C/SiC joined by SPS with Ti foil 130 m (a) and Ti foil 30 m (b) at 1700 ◦ C, 3 min, vacuum, 60 MPa. Backscattered electron images. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 5. (a) Relationship between SPS temperature and apparent shear strength of C/SiC composites and (b) that of joined C/SiC.
C/SiC. An apparent shear strength can be obtained from this test, which is able to give preliminary comparative information among several samples tested with the same set-up and size. For the same reasons as above, only two samples for each joining processes were tested, and four samples only for C/SiC joined by Ti (30 m foil), which gave the most promising results. With the aim of evaluating the effect of the SPS process on the mechanical strength of the C/SiC composites, the same mechanical tests were also performed on not joined C/SiC after the same heat treatments used for the joining processes (Table 1 and Fig. 5). The apparent shear strength of two direct bonded C/SiC samples were 5.6 and 11.2 MPa: these values seem lower than those of the not joined C/SiC after heat treatment at 1900 ◦ C. However, the SPS direct bonding of a CMC is for sure a very promising result, in particular for extreme applications when the presence of a joining material must be avoided. The only value measured for C/SiC joined by SiC + 5 wt% B4 C was 18.2 MPa, with the failure occurred by delamination in the composite; this is a result to be confirmed, but encouraging when an application requires the use of a SiC based joining material. The apparent shear strength of CA joined C/SiC was about 13 MPa, comparable with the strength of the not joined C/SiC after heat treatment at 1480 ◦ C, 10 min (Table 1). The failure occurred close or inside the joining area. The apparent shear strength of CA joined SiC/SiC (CVD–SiC coated SiC/SiC) obtained by a pressure-less technique based on deposition of a CA slurry between two SiC/SiC then heating at 1500 ◦ C, 1 h, was measured between 28 and 33 MPa;37 the factor of two is due to the different mechanical properties of the two composites (C/SiC and SiC/SiC) since both processes have been done at the same temperature and without or with only a minimal pressure applied. It must be noted that SPS has been an effective joining technique with only a minimal pressure applied, just when a viscous joining material was used (glass–ceramic): in all other cases it gave unsatisfactory results when used without applying any pressure during joining.
The apparent shear strength of C/SiC joined by a 30 m thick Ti foil is 17 ± 7.8 MPa (four samples) and about 20 MPa for the 130 m thick foil (two samples). These values are comparable to the apparent shear strength of the not joined C/SiC after heat treatment at 1700 ◦ C, 3 min, 60 MPa (Table 1), the same one used to join C/SiC by Ti foils. The fracture always occurred by delamination in the composite joined by a 30 m Ti foil, as it is shown in Fig. 6, where the two fracture surfaces clearly show the typical composite structure. In the samples joined by the thicker Ti foil (130 m) most of the fracture surface is CVD–SiC and C/SiC as in Fig. 2b. A possible explanation for the different fractures could be the presence of a brittle silicon rich phase (white arrows in Fig. 4a) in the joined area obtained by using a 130 m thick titanium. Due to the presence of this phase, cracks can form within the joining material and propagate across the CVD–SiC and the below C/SiC. Further investigations will be performed to determine the joint thickness vs. mechanical strength relationship for these samples. As received C/SiC shows an interlaminar failure at 15.4 and 5.3 MPa (on two samples), mostly unchanged after SPS at 1480 ◦ C; on the contrary, it seems to improve after SPS at 1700 ◦ C, (about 20 and 25 MPa measured on two samples), whereas at 1900 ◦ C mechanical properties seem to slightly decrease again (Table 1 and Fig. 5). However, the overall apparent shear strength is not affected by the presence of joining materials. Due to the low inter laminar shear strength (ILSS) of these composites and their porosity, the fracture propagates inside the C/SiC in most of cases; for this reason, the apparent shear strengths of the joined C/SiC are comparable. They are also comparable with the apparent shear strength of the non-joined C/SiC heated at the same SPS conditions. More samples should be tested to find a convincing explanation for this evidence, possibly by using standard tests for the measurement of interlaminar shear strength of CMC. At this stage of the research, a possible beneficial densification of the composite due to SPS at 1700 ◦ C with a pressure of 60 MPa can be supposed, together with a detrimental thermal
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Fig. 6. Sketch and macrograph of the fracture propagation and surfaces of C/SiC joined by SPS with Ti (foil 30 m) after mechanical test.
degradation of the whole composite at 1900 ◦ C and 60 MPa of pressure. To summarize these obtained results, – SPS was successfully used to join C/SiC with and without joining materials, – the role of pressure was found to be essential, – SPS can be used with a minimal applied pressure with a glass–ceramic as joining material, – all SPS joined samples showed comparable mechanical properties with not joined ones subjected to same SPS process. The joining mechanism with CA and Ti is similar using SPS and conventional heating. In both cases the joining materials are heated to the liquid phase. However, the mechanism of direct bonding and the joining with the SiC + 5 wt% B4 C mixture is different, it is based on the diffusion bonding. The SPS technique increases the diffusion rate at interfaces because of localized heating, thus leading to a continuous interface and a dense joining area in a very short time. Furthermore, in the case of electrically conductive interlayers (i.e. Ti) the electric field might accelerate the diffusion reaction as reported in Ref. [50]. Therefore, the main advantage of SPS technique consists in the rapid heating rate and a shorter dwelling time (3 min) in comparison with conventional heating (typically 30–60 min).
(SiC + B4 C) or directly bonded without any additional joining material. Investigation on the SPS joints morphology revealed several promising features. Most joined composites showed a sound joined area free from defects or porosity. Glass–ceramic system joined with a minimal applied pressure joining conditions confirmed a perfect wettability on C/SiC, continuous interfaces and absence of voids. Samples were mechanical tested at room temperature with single-lap test configurations in order to estimate the apparent shear strength of the joint on a comparative basis. All joined composites presented comparable strength in comparison with not joined ones subjected to same SPS process. The most promising results were obtained by SPS joining C/SiC with a 30 microns Ti foil at 1700 ◦ C for 3 min under 60 MPa of pressure, which gave a Ti–Si–C phase with titanium carbide in the middle of the joined area and with an apparent shear strength of 17.3 ± 7.8 MPa. The formation of a Ti–Si phase was found only with a thicker Ti foil (130 microns). In conclusion, SPS process has been demonstrated as an effective joining technique for C/SiC and it might be considered on as a novel technique for joining ceramic composites by a localized, current-assisted technique, almost pressure-less when viscous joining materials are used. Acknowledgements
4. Conclusion The potential of the SPS technique applied to C/SiC composite joining has been demonstrated in this work. SPS is a very promising method for rapid, localized heating and potentially almost pressure-less joining of composite materials. C/SiC have been joined using different materials like a metal (Ti), a glass–ceramic system (CA), a ceramic powder mixture
The authors would like to thank Dr Karin E. Handrick (MT Aerospace) for the helpful discussion. The research leading to these results has received funding from the European Union’s Seventh Framework Programme managed by REA—Research Executive Agency http://ec.europa.eu/research/rea and it participates in a Marie Curie Action (GlaCERCo GA 264526).
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References 1. Schmidt S, Beyer S, Immich H. Ceramic matrix composites: a challenge in space-propulsion technology applications. Int J Appl Ceram Tech 2005;2:85–96. 2. Naslain R. Design, preparation and properties of non-oxide CMCs for application in engines and nuclear reactors: an overview. Compos Sci Technol 2004;64:155–70. 3. Sommers A, Wang Q, Han X, T’Joen C, Parkd Y, Jacobi A. Ceramics and ceramic matrix composites for heat exchangers in advanced thermal systems: a review. Appl Ther Eng 2010;30:1277–91. 4. Fareed AS, Copper CC. Joining techniques for fiber-reinforced ceramic matrix composites. Ceram Eng Sci Proc 1999;20:61–70. 5. Cockeram BV. Flexural strength and shear strength of silicon carbide to silicon carbide joints fabricated by a molybdenum diffusion bonding technique. J Am Ceram Soc 2005;88:1892–9. 6. Hinoki T, Eiza N, Son S, Shimoda K, Lee J, Kohyama A. Development of joining and coating technique for SiC and SiC/SiC Composites utilizing NITE processing. Ceram Eng Sci Proc 2005;26:399–405. 7. Li JL, Xiong JT, Zhang FS. Transient liquid-phase diffusion bonding of twodimensional carbon–carbon composites to niobium alloy. Mater Sci Eng, A 2008;483–484:698–700. 8. Katoh Y, Kotani M, Kohyama A, Montorsi M, Salvo M, Ferraris M. Microstructure and mechanical properties of low activation glass–ceramic joining and coating for SiC/SiC composites. J Nucl Mater 2000;283–287:1262–6. 9. Ferraris M, Salvo M, Casalegno V, Ciampichetti A, Smeacetto F, Zucchetti M. Joining of machined SiC/SiC composites for thermonuclear fusion reactors. J Nucl Mater 2008;375:410–5. 10. Ferraris M, Salvo M, Casalegno V, Han S, Katoh Y, Jung HC, Hinoki T, Kohyama A. Joining of SiC-based materials for nuclear energy applications. J Nucl Mater 2011;417:379–82. 11. Henager CH, Shin Y, Blum Y, Giannuzzi LA, Kempshall BW, Schwarz SM. Coatings and joining for SiC and SiC-composites for nuclear energy systems. J Nucl Mater 2007;367–370:1139–43. 12. Salvo M, Rizzo S, Casalegno V, Handrick K, Ferraris M. Shear and bending strength of SiC/SiC joined by a modified commercial adhesive. Inter J Appl Ceram Tech 2012;9:778–85. 13. Lewinsohn CA, Colombo P, Reimanis I. Stresses occurring during joining of ceramics using preceramic polymers. J Am Ceram Soc 2001;84: 2240–4. 14. Singh M. Design, fabrication and characterization of high temperature joints in ceramic composites. Key Eng Mater 1999;415:164–5. 15. Ikesoji TT. Brazing of carbon–carbon (C/C) composites to metals. In: Editor Sekulic DP, editor. Advances in brazing: science, technology and applications. Cambridge, UK: Woodhead Publishing; 2013. p. 395–417. 16. Singh M, Asthana R. Brazing of advanced ceramic composites: issues and challenges. Ceram Trans 2007;198:9–14. 17. Singh M, Matsunaga T, Lin HT, Asthana R, Ishikawa T. Microstructure and mechanical properties of joints in sintered SiC fiber-bonded ceramics brazed with Ag–Cu–Ti alloy. Mater Sci Eng A 2012;557: 69–76. 18. Singh M, Asthana R, Shpargel T. Brazing of carbon–carbon composites to Cu-clad molybdenum for thermal management applications. Mater Sci Eng A 2007;452-453:699–704. 19. Asthana R, Singh M. Active metal brazing of advanced ceramic composites to metallic systems. In: Sekulic DP, editor. Advances in brazing: science, technology and applications. Cambridge, UK: Woodhead Publishing; 2013. p. 323–60. 20. Xiong JH, Huang JH, Zhang H, Zhao XK. Brazing of carbon fibre reinforced SiC composite and TC4 using Ag–Cu–Ti active brazing alloy. Mater Sci Eng A 2012;527:1096–101. 21. Mergia K. In: Cuppoletti J, editor. Joining of Cf/C and Cf/SiC Composites to metals, nanocomposites with unique properties and applications in medicine and industry. Rijeka, Croatia: InTech; 2011., ISBN 978-953-307351-4 http://www.intechopen.com/books/nanocomposites-with-uniqueproperties-and-applications-inmedicine-and-industry/joining-of-cf-c-andcf-sic-composites-to-metals
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22. Yousefiani A, Comfort JM, Vollmer J, Hand M. Joined composite structures with graded coefficient of thermal expansion for extreme environment applications. In: Patent application U.S. 0266870 A1.; 2009. 23. Blugan G, Kuebler J, Bissig V, Janczak-Rusch J. Brazing of silicon nitride ceramic composite to steel using SiC-particle-reinforced active brazing alloy. Ceram Int 2007;33:1033–9. 24. Grasso S, Sakka Y, Maizza G. Electric current activated/assisted sintering (ECAS): a review of patents 1906–2008. Sci Technol Adv Mater 2009;10:053001. 25. Pinc WR, Di Prima M, Walker LS, Wing ZN, Corral EL. Spark plasma joining of ZrB2 –SiC composites using zirconium–boron reactive filler layers. J Am Ceram Soc 2011;94:3825–32. 26. Munir ZA, Anselmi-Tamburini U, Ohyanagi M. The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method. J Mater Sci 2006;41:763–77. 27. Centeno A, Rocha VG, Borrell A, Blanco C, Fernández A. Fabrication of C/SiC composites by combining liquid infiltration process and spark plasma sintering technique. Ceram Int 2012;38:2171–5. 28. Luo Y, Li S, Pan W, Li L. Fabrication and mechanical evaluation of SiC–TiC nanocomposites by SPS. Mater Lett 2004;58:150–3. 29. Guillard F, Allemand A, Lulewicz JD, Galy J. Densification of SiC by SPS-effects of time, temperature and pressure. J Eur Ceram Soc 2007;27: 2725–8. 30. Wang HJ, Jin ZH, Miyamoto Y. Ti3 SiC2 /Al2 O3 composites prepared by SPS. Ceram Int 2003;29:539–42. 31. Magnant J, Pailler R, Le Petitcorps Y, Maillé L, Guette A, Marthe J, Philippe E. Fiber-reinforced ceramic matrix composites processed by a hybrid technique based on chemical vapor infiltration, slurry impregnation and spark plasma sintering. J Eur Ceram Soc 2013;33:181–90. 32. Miriyev A, Stern A, Tuval E, Kalabukhov S, Hooper Z, Frage N. Titanium to steel joining by spark plasma sintering (SPS) technology. J Mater Process Tech 2013;213:161–6. 33. Liu L, Ye F, Zhou Y, Zhang Z, Hou Q. Fast bonding ␣-SiAlON ceramics by spark plasma sintering. J Eur Ceram Soc 2010;30:2683–9. 34. Ozaki K. Joining of ceramic/cermet to metal by spark plasma sintering. Met Powder Rep 1998;53:35. 35. Papenburg U, Pfrang W, Kutter G, Mueller C, Kunkel B, Deyerler M, Bauereisen S. Optical and optomechanical ultra-lightweight C/SiC® components. In: SPIE conference on optical manufacturing and testing. 1999. p. 0277-786. 36. Maizza G, Grasso S, Sakka Y. Moving finite-element mesh model for aiding spark plasma sintering in current control mode of pure ultrafine WC powder. J Mater Sci 2009;44:1219–36. 37. Ferraris M, Salvo M, Isola C, Appendino Montorsi M, Kohyama A. Glass–ceramic joining and coating of SiC/SiC for fusion applications. J Nucl Mater 1998;258-263:1546–50. 38. Ferraris M, Salvo M, Rizzo S, Casalegno V, Han S, Ventrella A, Hinoki T, Katoh Y. Torsional shear strength of silicon carbide components pressurelessly joined by a glass–ceramic. Int J Appl Ceram Tech 2012;9: 786–94. 39. Choi SK, Chandrasekaran M, Brabers MJ. Interaction between titanium and SiC. J Mater Sci 1990;25:1957–64. 40. Halbig MC, Singh M, Tsuda H. Integration technologies for silicon carbide-based ceramics for micro-electro-mechanical systems-lean direct injector fuel injector applications. Int J Appl Ceram Tech 2012;9: 677–87. 41. Gottselig B, Gyarmati E, Naoumidis A, Nickel H. Joining of ceramics demonstrated by the example of SiC/Ti. J Eur Ceram Soc 1990;6: 153–60. 42. http://en.wikipedia.org/wiki/Ceramic matrix composite. 43. Grasso S, Hu C, Kim B, Maizza G, Sakka Y. Effects of pressure application method on transparency of SPSed alumina. J Am Ceram Soc 2011;94:1405–9. 44. Ferraris M, Ventrella A, Salvo M, Avalle M, Pavia F, Martin E. Comparison of shear strength tests on AV119 epoxy-joined carbon/carbon composites. Composites Part B 2010;41:182–91. 45. Zeng J, Ren S, Lu J. Phase evolution of Ti3 SiC2 annealing in vacuum at elevated temperatures. Int J Appl Ceram Tech 2013;10:527–39.
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46. Naka M, Feng JC, Schuster JC. Phase reaction and diffusion path of the SiC/Ti system. Metall Mater Trans A 1997;28:1385–90. 47. Gan GY, Chen JC, Sun JL, Zhou XL, Chen XH. Estimation of the Gibbs free energies of intermetallic compounds for Ti–Si–C ternary system. J Kunming Univ Sci Technol 2002;27:1–8. 48. Dong H, Li S, Teng Y, Ma W. Joining of SiC ceramic-based materials with ternary carbide Ti3 SiC2 . Mater Sci Eng, B 2011;176:60–4.
49. Wang Q, Hu C, Huang Q, Cai S, Sakka Y, Grasso S. Synthesis of highpurity Ti3 SiC2 by microwave sintering. Int J Appl Ceram Tech 2013;1–8, http://dx.doi.org/10.1111/ijac.12065. 50. Munir Z, Anselmi-Tamburini U, Ohyanagi M. The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method. J Mater Sci 2006;41:763–77.
Dr Stefano Rizzo is a research fellow in Department of Applied Science and Technology at Politecnico di Torino, Italy. He obtained his MSc in Materials Engineering in 2006 at Politecnico di Torino with a thesis concerning metal nanoclusters in silica thin layers. In 2008, he received a Master of Science in Materials for micro and nano technology from Institute for Advanced Study of Pavia, Italy. His academic and research interests include joining and coating of high-temperature ceramics, composites and metals; characterization of glass systems for nuclear and aerospace applications; recycling of biomass ash in building materials.
Dr Salvatore Grasso joined the School of Material Science and engineering (SEMS) at Queen Mary university of London in 2011 as experienced researcher in ceramics processing. Dr Grasso Salvatore performed his doctoral work (2008-2011) at the University of TsukubaNIMS (National Institute for material Science) Japan. Dr Grasso’s research work was been mainly focused on Spark Plasma Sintering (SPS) and other Electric Current Assisted Sintering Techniques. His work aimed to elucidate the unknown mechanisms involved in SPS and identify the critical parameters in SPS processing. At present he has published more than 40 papers in peer-reviewed Journals and 8 patents, he delivered 8 invited talks in international conferences.
Prof Milena Salvo PhD on Materials Engineering with a thesis concerning the joining of ceramic matrix composites for high temperature and thermonuclear fusion applications (Politecnico di Torino, Italy). She is Associate Professor of Materials Science and Technology at Politecnico di Torino. She is part of the “Glasses, ceramics and composites” research group (www.composites.polito.it). Her academic and research interests include glasses, glass-ceramics, ceramics and composites for energy production, joining and coating of advanced materials and waste management. She is co-author of 80 peer-reviewed journal publications and 3 patents in the field of advanced ceramics and composites.
Dr Valentina Casalegno carried out her Ph.D in Materials Engineering at Politecnico di Torino, Department of Material Science and Chemical Engineering and she obtained her PhD degree in 2006 after defending a thesis on the “Joining of composites materials for nuclear fusion applications”. Since 2002, she has been working in the Department of Materials Science and Chemical Engineering at the Politecnico di Torino. Her research activity focuses on design, fabrication and characterization of joining materials and joints for advanced ceramic composites and ceramic/metal components. Actually she is involved as post-doc researcher at Politecnico di Torino in many international and Italian scientific projects regarding joining of ceramics and ceramic composites for special applications and nuclear environment. She is author and co-author of several international papers and 1 PCT patent.
Prof Mike Reece Prof of Functional Ceramics, Head of the Functional Nanomaterials Group at Queen Mary University London (QMUL). His work at QMUL has focused on the understanding the electromechanical properties of ferroelectric, ferroelastic and piezoelectric ceramics. He has set-up the first spark plasma sintering (SPS) furnace in the UK. The focus of his research in this area is to produce new structural and functional materials, including ceramics for extreme environments. This includes nanostructured, textured and metastable materials. A long term objective of his work is commercialise materials prepared by SPS through knowledge transfer and spin-outs. He is the Director of Nanoforce Technology Ltd, a spin-out company of QMUL, which was funded as part of the DTI Micro- and Nano-technology Network. He is a Royal Society Industry Fellow (2011-2015) and Editor of Advances in Applied Ceramics. He is a visiting professor at the Shanghai Institute of Ceramics and Xi’an Xiaotong University.
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Prof Monica Ferraris is Professor of Materials Science and Technology at the Politecnico di Torino, Torino, Italy. She received a M.S. in Solid State Chemistry in 1985 from the University of Torino, Italy. In 1985, M. Ferraris joined the Italian Telecom Research Centre (CSELT-Torino) to work on fluoride glasses for ultra low loss optical fibers. In 1990 she moved to Fiat Research Centre (CRF-Torino) where she worked on metal and ceramic matrix composites for automotive applications. She joined Politecnico di Torino in 1991, where she is now Professor of Materials Science and Technology and group leader (http://www.composites.polito.it). Her academic and research interests include glasses, ceramics and composites for energy production, photonics, biomedical applications and waste management. She has over one hundred peer-reviewed journal publications and patents in these areas. Ferraris is a member of the Engineering Ceramics Division of The American Ceramic Society since 1995.
ScienceDirect Journal of the European Ceramic Society 34 (2014) 903–913
Feature Article Joining of C/SiC composites by spark plasma sintering technique Stefano Rizzo a , Salvatore Grasso b , Milena Salvo a,∗ , Valentina Casalegno a , Michael J. Reece b , Monica Ferraris a b
a Department of Applied Science and Technology, Institute of Materials Physics and Engineering, Corso Duca degli Abruzzi 24, 10129 Torino, Italy School of Engineering & Materials Science and Nanoforce Technology Ltd., Queen Mary University of London, Mile End Road, London E1 4NS, UK
Received 24 July 2013; received in revised form 19 October 2013; accepted 21 October 2013 Available online 19 November 2013
Abstract CVD–SiC coated C/SiC composites (C/SiC) were joined by spark plasma sintering (SPS) by direct bonding with and without the aid of joining materials. A calcia-alumina based glass–ceramic (CA), a SiC + 5 wt% B4 C mixture and pure Ti foils were used as joining materials in the non-direct bonding processes. Morphological and compositional analyses were performed on each joined sample. The shear strength of joined C/SiC was measured by a single lap test and found comparable to that of C/SiC. © 2013 Elsevier Ltd. All rights reserved. Keywords: Joining; C/SiC composites; Spark plasma sintering
1. Introduction Ceramic matrix composites (CMC), e.g. SiC/SiC, C/SiC and C/C, are being considered as the primary candidates for components and subsystems in the field of satellite (nearsun) missions, defence, aerospace missions (e.g. body flaps, nose cones, wings, leading edges, turbine components) and for terrestrial/industrial applications under extreme environmental conditions (e.g. valves, shaft sleeves for pump sliding bearings, heat exchangers, nuclear plant components, etc.).1–3 A critical issue for a wider use of CMC is the development of inexpensive, reliable and user-friendly joining methods to assemble large components into more complex structures.4 There are many possible techniques for joining CMC to themselves and to dissimilar materials: diffusion bonding;5 transient eutectic phase methods such as nano-infiltration and transient eutectic-phase (NITE);6 transient liquid-phase diffusion bonding;7 pressure-less glass–ceramic joining;8–10 solid state displacement reactions;11 adhesive and preceramic polymer routes;12,13 reaction forming;14 brazing.15 Brazing is the most commonly used joining and integration method for CMC
∗
Corresponding author. Tel.: +390110904706. E-mail address: [email protected] (M. Salvo).
0955-2219/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jeurceramsoc.2013.10.028
and extensive research on brazing of CMC for their joining and integration has been done by Singh and his group at NASA.16–18 High temperature brazing alloys are based on gold, nickel and copper and are often used for joining CMC to cobalt, titanium alloys and nickel-based superalloys.19 TiZrNiCu, Ni and Ag–Cu–Ti have been used as filler to join C/SiC to Ti–6Al–4V.20 Whatever the joining process is, the joined interfaces need to be thermodynamically stable: reactions and diffusion of species from the joining material and the CMC can affect the quality of the joints and their performance in service.21 Furthermore, the coefficient of thermal expansion (CTE) of CMC is lower than that of most metals and considerable residual stress is generated in the joint during the cooling process or when exposed to high temperature environments, thus leading to cracks or failure of the joints. In order to deal with the CTE mismatch between CMC and brazing alloys, several options have been proposed: different layers with a gradually changing CTE from CMC to the metal alloy;22 compliant metallic layers (e.g. Cu); composite brazing alloys obtained by adding short fibres or particles to the brazing alloy.22,23 Selecting the optimal braze filler metal for brazing CMC to metals is not easy because the application requires a high brazing temperature (high thermal load in operation predicted), while the prevention of high joining stresses should require a low brazing temperature. Moreover, the wetting of CMC often
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requires the addition of active elements (i.e. Ti, Cr . . .), but the formation of brittle intermetallic phases based on these elements must be avoided. The CMC employed in this study consist of carbon fibre reinforced SiC matrix composites coated with a chemical vapour deposited (CVD) layer of SiC. The aim of this work is to investigate the effectiveness of using spark plasma sintering (SPS)24 to join CMC. The SPS has recently been employed to achieve high quality joint25 .The intrinsic advantages of SPS as a joining process for CMC, especially if the materials are electrically conductive, are: – localized heating generated by joule heating; – low energy consumption due to both the rapid processing and the localized heating; – limited deformation of the joined parts; – both the rapid heating and short processing time allow highly controllable reaction of interlayer formed between the joined materials. The effect of the electric field has been reported to enhance the diffusivity by electro migration phenomena,26 thus promoting migration of ions trough the joining interface. The joining by SPS represents a novelty in the field of composites. Several works on SPS as a manufacturing technique for SiC based composites have been published in the last few years.27–31 In the field of materials joining, research has focused on metal-to-metal, ceramic-to-ceramic or ceramic-tometal joints32–34 using conventional techniques, but at present there is still a lack of scientific experience on joining of composites by SPS. Direct bonding and three different types of joining materials (a metal, a glass–ceramic and a ceramic powder mixture) were tested by SPS in order to have an overview of this technique for joining C/SiC. If the use of a joining material cannot be avoided, several options can be proposed to join C/SiC. The first choice would be using SiC as joining material in order to maintain the same thermo-mechanical properties of the composite matrix. However, both the direct bonding process and the use of SiC as joining material need high temperature, high pressure and long processing time. In this work, SPS was used to obtain a quick and effective direct bonding between C/SiC and a sound SiC based joint by using a typical SiC sintering aid (B4 C). The room temperature electrical and thermal conductivity of C/SiC composite is 0.5 × 104 S/m and 135 W/m K,35 which is comparable to the constitutive graphite of the SPS mould (6 × 104 S/m and 70 W/m K). The lower electrical conductivity of C/SiC compared to graphite results in a preferential current across the SPS moulds, however according to modelling results up to 10% of the total current might still able to flow across the sample, in particular at the joined region where there is initially a contact resistance that will lead to a favourable increase in Joule heating.36 In addition the high thermal conductivity of C/SiC compared to graphite allowed an even temperature homogenization during heating/cooling.
The choice of a CaO–Al2 O3 glass–ceramic (CA) as joining material have been discussed in:8,37,38 CA was designed to have a suitable wettability and CTE towards SiC based materials; CA can be almost completely crystallized after a pressure-less joining process, thus providing a potential high temperature resistant joining material, also suitable in a neutron environment.8,37 SPS was used here as an alternative joining technique for CA based joints, which is able to provide a localized quick heating of the joined region. Titanium was chosen as a joining material for C/SiC because of its refractory properties and well known reactivity with SiC. Ti–SiC system finds use in the joining of ceramics and metals because the interfacial reaction provides good bonding effects.39 Halbig et al. developed a SiC joining technology, where titanium interlayers were used to form diffusion bonds between CVD–SiC substrates.40 Ti–SiC and Ti–C reactions can limit the joint thermodynamic stability and must be carefully controlled. The reaction products between Ti and SiC are very brittle with the exception of TiC and Ti3 SiC2 .41 Furthermore, coherent phase boundaries have been found between SiC and Ti3 SiC2 , thus leading to very good adhesion of this ternary phase on the SiC. The main purpose of this paper is to explore the influence of pressure, surface and intermediate joining materials used for bonding C/SiC by SPS. Since SPS involves rapid heating rates, a direct comparison with other bonding techniques is difficult. These results can be useful in order to define the SPS joining processing window, the intermediate joining materials and to guide future research. In this study CVD–SiC coated C/SiC composites have been used because oxidation protected C/SiC is the final status of C/SiC for most of the applications and the coating deposition is directly performed by the manufacturer (MT Aerospace, Germany).
2. Experimental CVD–SiC coated C/SiC composites used in this study were manufactured in disk shaped samples with diameter of 20 mm and height of 5 mm by MT Aerospace (Germany).42 C/SiC were joined by SPS technique (SPS-HP D 25, FCT HP, Germany) using joining materials or by direct bonding. Specimens joined by direct bonding were hand polished up to 3 m diamond slurry in order to reduce roughness and maximize the contact surface. The as received samples were ultrasonically cleaned in acetone. Before inserting the samples in a graphite mould (hollow die, diameter of 2 cm) an interlayer was interposed between the materials to be joined. The temperature was probed by an optical pyrometer installed on the top side of the SPS machine. This configuration allowed a precise measurement of the sample temperature. According to experimental/modelling results, the temperature was measured by an optical pyrometer focused at 4 mm from the sample top surface, as detailed in Ref. [43]. All SPS joining process parameters are summarized in Table 1. All the joining surfaces were ultrasonically cleaned to remove dust particles, grease and any other contaminants.
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Table 1 SPS processing conditions used to join C/SiC and apparent shear strengths of joined and not joined C/SiC measured with a single-lap mechanical test. (DB = direct bonding). SPS conditions Temperature (◦ C) C/SiC–CA C/SiC–Ti (30 m) C/SiC–Ti (130 m) C/SiC–SiC + B4 C C/SiC–DB C/SiC as received C/SiC–1480 C/SiC–1700 C/SiC–1900
Joined 1480 1700 1700 1900 1900 Not joined – 1480 1700 1900
Apparent shear strength (MPa)
Heating rate (◦ C/min)
Dwell time (min)
Pressure (MPa)
50 150–200 150–200 150–200 150–200
10 3 3 3 3
0 60 60 60 60
12.1; 14.1 19.8; 9.5; 27.1; 13.0 (17.3 ± 7.8) 21.6; 18.3 18.2 5.6; 11.2
– 50 150–200 150–200
– 10 3 3
– 0 60 60
15.4; 5.3 15.5; 13.8 24.6; 19.6 11.3; 16.1
The following joining materials were used: – Ti foil – Calcia-alumina glass–ceramic – SiC + 5 wt% B4 C powder mixture 2.1. Titanium as joining material C/SiC–Ti–C/SiC sandwiches were heated by SPS between 150 and 200 ◦ C/min, with a dwell time of 3 min and a pressure of 60 MPa in vacuum atmosphere. The maximum temperature was set at 1700 ◦ C. To investigate the effect of the Ti foil thickness, 30 m and 130 m Ti foils were used (Ti Foil 99.6%, Goodfellow). 2.2. Calcia-alumina glass–ceramic as joining material C/SiC composites were joined using CaO–Al2 O3 (49.7 CaO, 50.3 Al2 O3 wt%) glass–ceramic, which is referred to as CA here forth. The joining material was designed, prepared, and characterized as described in Refs. [8,37]. The CA was synthesized by melt/quenching: the powdered raw products were melted in a platinum–rhodium crucible in air at 1750 ◦ C for 30 min, then the glass was poured onto a brass plate and subsequently powdered and sieved. Sandwich-like joined samples were produced by depositing the glass slurry at room temperature on the surface of composites. The slurry was a mixture of glass powder (powder size between 38 and 75 m) dispersed in ethanol. Samples joined by CA slurry (0.8 mg/mm2 ) were heated by SPS to 1480 ◦ C for 10 min, a minimal pressure (a 25 g tungsten disk was put on the top of the SPS mould to keep samples in place) and cooled at 50 ◦ C/min in an argon atmosphere. 2.3. SiC ± 5 wt% B4 C mixture as joining material C/SiC composites were joined using a mixture of SiC + 5 wt% B4 C powders at 1900 ◦ C, 3 min, 60 MPa. The powder mixture was prepared in a rotary mill starting from silicon carbide (UF 10, H.C. Starck) and boron carbide (H.C. Starck HD 20) powders.
In order to understand the effect of SPS on C/SiC mechanical strength, some as received C/SiC discs samples, hereinafter defined as not joined, were SPSed under identical processing conditions used to join them. Joined C/SiC, as received C/SiC and C/SiC after the same SPS treatments used for the joining processes (1700 ◦ C, 3 min, 60 MPa; 1480 ◦ C, 10 min, a minimal pressure; and 1900 ◦ C, 3 min, 60 MPa), were tested at room temperature by the single lap test (SL) adapted from ASTM D1002-05.44 Two samples for each joining processes were tested and four samples for C/SiC joined by Ti, 30 m thick. The disk shaped C/SiC (joined and not joined) were cut with a diamond blade into rectangular shaped samples suitable for mechanical tests (about 7 × 12 × 8 mm3 ). Polished cross-sections and fracture surfaces were analysed by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM–FEI, QUANTA INSPECT 200, EDS–EDAX PV 9900) and micro X-ray diffraction (Rigaku D/MAX Rapid microdiffractometer, X-ray generator settings fixed at 40 kV and 20 mA, Cu K␣ incident radiation with ˚ with a spot detector of 30 m2 . λ = 1.54 A) 3. Results and discussion The ideal joining technology is a direct bonding between the two identical substrates to be joined: in this case the thermomechanical properties of the substrates are not affected by the presence of a joining material in between. Fig. 1 shows the polished cross-sections of C/SiC specimens joined by direct bonding (DB) and by non-direct bonding (CA glass–ceramic, SiC + 5 wt% B4 C and Ti foil). Cracks in the CVD–SiC coating are visible in all joined samples and are due to the thermal expansion coefficient mismatch between SiC coating and C/SiC substrate. Consistently, cracks propagate through the SiC-based joined area in the direct bonded and in the SiC + B4 C bonded samples, but they seem to be absent in the glass–ceramic and in the Ti-foil joining materials (Fig. 1). In particular, C/SiC joined by DB and SiC + 5 wt% B4 C (1900 ◦ C, 3 min, 60 MPa) produced continuous interfaces, but many cross-sectional cracks propagated from the CVD–SiC coating through the joint area
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Fig. 1. Scanning electron microscopy of polished cross-sections of C/SiC specimens joined by SPS: direct bonding (a), SiC powder + 5 wt% B4 C (b), CA glass–ceramic (c) and Ti 130 m (d). (a) and (b) secondary electron images; (c) and (d) backscattered electron images.
(Fig. 1a and b); no cracks were observed along SiC/joint interfaces. C/SiC joined by CA glass–ceramic (1480 ◦ C, 10 min, no pressure) showed a homogenous joint area without cracks, Fig. 1c. The cracks in the CVD–SiC coating did not propagate through the CA and the interfaces between the glass–ceramic and the CVD SiC layer are continuous. The joining mechanism in the case of CA is based on fast heating typical of SPS which produces a decrease in the viscosity of CA. This allows the joining of C/SiC by CA, which acts as an adhesive. The same process occurs with conventional heating,8,37,38 but takes longer time, typically 30–60 min for samples of the size used in the current study. Interfacial reactions between CA and CVD–SiC with gaseous or other products have never been observed.38 Ti joined C/SiC were produced using Ti foils of 30 and 130 m thickness. Fig. 1d shows the cross-section of C/SiC joined by a 130 m thick Ti foil. The cracks in the CVD–SiC coating did not propagated in the pore free joint area. Fig. 2a shows a magnification image of the cross-section of the titanium based joint (130 m Ti foil) C/SiC sample and the fracture surface after mechanical testing (Fig. 2b). The interface CVD–SiC/titanium based joint is dense and defect free: Fig. 2c shows the perfect adhesion of the joint which follows the nanoroughness of the CVD–SiC. Micro-XRD analysis on the fracture surface (square area in Fig. 2b) showed the formation of Ti3 SiC2
(Fig. 3b), whereas SiC comes from the CVD SiC layer deposited on C/SiC. Gottseling et al.41 investigated the reaction products between SiC and Ti after an annealing time of 2 h: for temperatures lower than 1500 ◦ C, Ti3 SiC2 is predominantly formed, while TiSi2 and TiC are secondary products. The thermal decomposition of Ti3 SiC2 in a vacuum furnace up to 1500 ◦ C has been investigated by Zheng et al.45 They demonstrated that the decomposition of Ti3 SiC2 to titanium carbide starts at 1300 ◦ C in a vacuum furnace, the higher the holding temperature, the larger is the volatilization of Si. The presence of Ti3 SiC2 in the joining area after the heat treatment by SPS at 1700 ◦ C under vacuum might be explained by the very short dwell time (3 min) at high temperature. EDS element maps of cross-sections Ti joined C/SiC are shown in Fig. 4a and b (130 and 30 m Ti foil, respectively). Silicon, titanium and carbon are mostly homogeneously dispersed in the joint areas. A Ti–Si–C based phase (most likely Ti3 SiC2 , as also detected by micro-XRD) is the main reaction product. A depletion of silicon is evident at the centre of the joints (red arrows in Fig. 4a and b) where a higher concentration of C has been revealed thus indicating the formation of a titanium carbide. The presence of titanium carbide at the centre of the joints may be due to the faster diffusion of C compared to that of Si.46
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Fig. 2. Scanning electron microscopy (backscattered electron images) of cross-sections (a), fracture surface after mechanical test (b) and particular of the interface (c) of C/SiC joined by SPS with Ti (130 m foil). Highlighted area: micro-XRD analysis zone (Fig. 3). (a) and (b): secondary electron images; (c): backscattered electron image.
Only by using a 130 m thick titanium foil, the formation of a silicon rich phase (probably TiSi2 ) was detected in the joint region, as indicated by the white arrows in Fig. 4a. The formation of the titanium silicide phase has been already observed by Gottselig et al.41 if thick titanium layers were used. The presence of titanium silicide, which is not detected by the micro-XRD in Fig. 3b, suggests the incomplete reaction as in47 : 7TiC + 2TiSi2 → 3 Ti3 SiC2 + SiC
Fig. 3. Micro-XRD on the fracture surfaces of C/SiC joined by SPS with (a) Ti (30 m foil), highlighted area in Fig. 2 and (b) Ti (130 m foil).
Ti3 SiC2 phase has been already identified as ideal intermediate joining material for SiC matrix composites as reported by Dong et al.48 However unlike the previous investigation where Ti3 SiC2 was used as starting material,48 we report the in situ reactive formation of Ti3 SiC2 phase in the joining interlayer. By using a 30 m thick Ti foil the formation of the brittle titanium silicide phase did not occur (Fig. 4b) and the main phase is again the Ti–Si–C based phase (most likely Ti3 SiC2 ) with the presence of titanium carbide at the centre of the joint. MicroXRD on this fracture surface (Fig. 3a) did not detect anything other than SiC and C, most likely due to the thinner joined area than that investigated in Fig. 3b. It is worth noting that the very rapid SPS heating (100 ◦ C/min) and very short dwelling time allowed the formation of Ti3 SiC2 phase which is metastable at temperature of 1700 ◦ C.49 Typically other techniques such as hot pressing are not suitable to obtain this phase, thus to control the chemistry of the joined interfaces. The aim of this work was to provide preliminary results on the potential of SPS to join SiC-based CMC (C/SiC). It was not possible to do a complete mechanical characterization of joined composites. The amount of C/SiC necessary for standard interlaminar shear strength tests on CMC and for standard shear strength tests on joined CMC was unavailable. It was then decided to do some comparative tests on joined and not-joined
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Fig. 4. Compositional elements map of C/SiC joined by SPS with Ti foil 130 m (a) and Ti foil 30 m (b) at 1700 ◦ C, 3 min, vacuum, 60 MPa. Backscattered electron images. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Fig. 5. (a) Relationship between SPS temperature and apparent shear strength of C/SiC composites and (b) that of joined C/SiC.
C/SiC. An apparent shear strength can be obtained from this test, which is able to give preliminary comparative information among several samples tested with the same set-up and size. For the same reasons as above, only two samples for each joining processes were tested, and four samples only for C/SiC joined by Ti (30 m foil), which gave the most promising results. With the aim of evaluating the effect of the SPS process on the mechanical strength of the C/SiC composites, the same mechanical tests were also performed on not joined C/SiC after the same heat treatments used for the joining processes (Table 1 and Fig. 5). The apparent shear strength of two direct bonded C/SiC samples were 5.6 and 11.2 MPa: these values seem lower than those of the not joined C/SiC after heat treatment at 1900 ◦ C. However, the SPS direct bonding of a CMC is for sure a very promising result, in particular for extreme applications when the presence of a joining material must be avoided. The only value measured for C/SiC joined by SiC + 5 wt% B4 C was 18.2 MPa, with the failure occurred by delamination in the composite; this is a result to be confirmed, but encouraging when an application requires the use of a SiC based joining material. The apparent shear strength of CA joined C/SiC was about 13 MPa, comparable with the strength of the not joined C/SiC after heat treatment at 1480 ◦ C, 10 min (Table 1). The failure occurred close or inside the joining area. The apparent shear strength of CA joined SiC/SiC (CVD–SiC coated SiC/SiC) obtained by a pressure-less technique based on deposition of a CA slurry between two SiC/SiC then heating at 1500 ◦ C, 1 h, was measured between 28 and 33 MPa;37 the factor of two is due to the different mechanical properties of the two composites (C/SiC and SiC/SiC) since both processes have been done at the same temperature and without or with only a minimal pressure applied. It must be noted that SPS has been an effective joining technique with only a minimal pressure applied, just when a viscous joining material was used (glass–ceramic): in all other cases it gave unsatisfactory results when used without applying any pressure during joining.
The apparent shear strength of C/SiC joined by a 30 m thick Ti foil is 17 ± 7.8 MPa (four samples) and about 20 MPa for the 130 m thick foil (two samples). These values are comparable to the apparent shear strength of the not joined C/SiC after heat treatment at 1700 ◦ C, 3 min, 60 MPa (Table 1), the same one used to join C/SiC by Ti foils. The fracture always occurred by delamination in the composite joined by a 30 m Ti foil, as it is shown in Fig. 6, where the two fracture surfaces clearly show the typical composite structure. In the samples joined by the thicker Ti foil (130 m) most of the fracture surface is CVD–SiC and C/SiC as in Fig. 2b. A possible explanation for the different fractures could be the presence of a brittle silicon rich phase (white arrows in Fig. 4a) in the joined area obtained by using a 130 m thick titanium. Due to the presence of this phase, cracks can form within the joining material and propagate across the CVD–SiC and the below C/SiC. Further investigations will be performed to determine the joint thickness vs. mechanical strength relationship for these samples. As received C/SiC shows an interlaminar failure at 15.4 and 5.3 MPa (on two samples), mostly unchanged after SPS at 1480 ◦ C; on the contrary, it seems to improve after SPS at 1700 ◦ C, (about 20 and 25 MPa measured on two samples), whereas at 1900 ◦ C mechanical properties seem to slightly decrease again (Table 1 and Fig. 5). However, the overall apparent shear strength is not affected by the presence of joining materials. Due to the low inter laminar shear strength (ILSS) of these composites and their porosity, the fracture propagates inside the C/SiC in most of cases; for this reason, the apparent shear strengths of the joined C/SiC are comparable. They are also comparable with the apparent shear strength of the non-joined C/SiC heated at the same SPS conditions. More samples should be tested to find a convincing explanation for this evidence, possibly by using standard tests for the measurement of interlaminar shear strength of CMC. At this stage of the research, a possible beneficial densification of the composite due to SPS at 1700 ◦ C with a pressure of 60 MPa can be supposed, together with a detrimental thermal
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Fig. 6. Sketch and macrograph of the fracture propagation and surfaces of C/SiC joined by SPS with Ti (foil 30 m) after mechanical test.
degradation of the whole composite at 1900 ◦ C and 60 MPa of pressure. To summarize these obtained results, – SPS was successfully used to join C/SiC with and without joining materials, – the role of pressure was found to be essential, – SPS can be used with a minimal applied pressure with a glass–ceramic as joining material, – all SPS joined samples showed comparable mechanical properties with not joined ones subjected to same SPS process. The joining mechanism with CA and Ti is similar using SPS and conventional heating. In both cases the joining materials are heated to the liquid phase. However, the mechanism of direct bonding and the joining with the SiC + 5 wt% B4 C mixture is different, it is based on the diffusion bonding. The SPS technique increases the diffusion rate at interfaces because of localized heating, thus leading to a continuous interface and a dense joining area in a very short time. Furthermore, in the case of electrically conductive interlayers (i.e. Ti) the electric field might accelerate the diffusion reaction as reported in Ref. [50]. Therefore, the main advantage of SPS technique consists in the rapid heating rate and a shorter dwelling time (3 min) in comparison with conventional heating (typically 30–60 min).
(SiC + B4 C) or directly bonded without any additional joining material. Investigation on the SPS joints morphology revealed several promising features. Most joined composites showed a sound joined area free from defects or porosity. Glass–ceramic system joined with a minimal applied pressure joining conditions confirmed a perfect wettability on C/SiC, continuous interfaces and absence of voids. Samples were mechanical tested at room temperature with single-lap test configurations in order to estimate the apparent shear strength of the joint on a comparative basis. All joined composites presented comparable strength in comparison with not joined ones subjected to same SPS process. The most promising results were obtained by SPS joining C/SiC with a 30 microns Ti foil at 1700 ◦ C for 3 min under 60 MPa of pressure, which gave a Ti–Si–C phase with titanium carbide in the middle of the joined area and with an apparent shear strength of 17.3 ± 7.8 MPa. The formation of a Ti–Si phase was found only with a thicker Ti foil (130 microns). In conclusion, SPS process has been demonstrated as an effective joining technique for C/SiC and it might be considered on as a novel technique for joining ceramic composites by a localized, current-assisted technique, almost pressure-less when viscous joining materials are used. Acknowledgements
4. Conclusion The potential of the SPS technique applied to C/SiC composite joining has been demonstrated in this work. SPS is a very promising method for rapid, localized heating and potentially almost pressure-less joining of composite materials. C/SiC have been joined using different materials like a metal (Ti), a glass–ceramic system (CA), a ceramic powder mixture
The authors would like to thank Dr Karin E. Handrick (MT Aerospace) for the helpful discussion. The research leading to these results has received funding from the European Union’s Seventh Framework Programme managed by REA—Research Executive Agency http://ec.europa.eu/research/rea and it participates in a Marie Curie Action (GlaCERCo GA 264526).
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References 1. Schmidt S, Beyer S, Immich H. Ceramic matrix composites: a challenge in space-propulsion technology applications. Int J Appl Ceram Tech 2005;2:85–96. 2. Naslain R. Design, preparation and properties of non-oxide CMCs for application in engines and nuclear reactors: an overview. Compos Sci Technol 2004;64:155–70. 3. Sommers A, Wang Q, Han X, T’Joen C, Parkd Y, Jacobi A. Ceramics and ceramic matrix composites for heat exchangers in advanced thermal systems: a review. Appl Ther Eng 2010;30:1277–91. 4. Fareed AS, Copper CC. Joining techniques for fiber-reinforced ceramic matrix composites. Ceram Eng Sci Proc 1999;20:61–70. 5. Cockeram BV. Flexural strength and shear strength of silicon carbide to silicon carbide joints fabricated by a molybdenum diffusion bonding technique. J Am Ceram Soc 2005;88:1892–9. 6. Hinoki T, Eiza N, Son S, Shimoda K, Lee J, Kohyama A. Development of joining and coating technique for SiC and SiC/SiC Composites utilizing NITE processing. Ceram Eng Sci Proc 2005;26:399–405. 7. Li JL, Xiong JT, Zhang FS. Transient liquid-phase diffusion bonding of twodimensional carbon–carbon composites to niobium alloy. Mater Sci Eng, A 2008;483–484:698–700. 8. Katoh Y, Kotani M, Kohyama A, Montorsi M, Salvo M, Ferraris M. Microstructure and mechanical properties of low activation glass–ceramic joining and coating for SiC/SiC composites. J Nucl Mater 2000;283–287:1262–6. 9. Ferraris M, Salvo M, Casalegno V, Ciampichetti A, Smeacetto F, Zucchetti M. Joining of machined SiC/SiC composites for thermonuclear fusion reactors. J Nucl Mater 2008;375:410–5. 10. Ferraris M, Salvo M, Casalegno V, Han S, Katoh Y, Jung HC, Hinoki T, Kohyama A. Joining of SiC-based materials for nuclear energy applications. J Nucl Mater 2011;417:379–82. 11. Henager CH, Shin Y, Blum Y, Giannuzzi LA, Kempshall BW, Schwarz SM. Coatings and joining for SiC and SiC-composites for nuclear energy systems. J Nucl Mater 2007;367–370:1139–43. 12. Salvo M, Rizzo S, Casalegno V, Handrick K, Ferraris M. Shear and bending strength of SiC/SiC joined by a modified commercial adhesive. Inter J Appl Ceram Tech 2012;9:778–85. 13. Lewinsohn CA, Colombo P, Reimanis I. Stresses occurring during joining of ceramics using preceramic polymers. J Am Ceram Soc 2001;84: 2240–4. 14. Singh M. Design, fabrication and characterization of high temperature joints in ceramic composites. Key Eng Mater 1999;415:164–5. 15. Ikesoji TT. Brazing of carbon–carbon (C/C) composites to metals. In: Editor Sekulic DP, editor. Advances in brazing: science, technology and applications. Cambridge, UK: Woodhead Publishing; 2013. p. 395–417. 16. Singh M, Asthana R. Brazing of advanced ceramic composites: issues and challenges. Ceram Trans 2007;198:9–14. 17. Singh M, Matsunaga T, Lin HT, Asthana R, Ishikawa T. Microstructure and mechanical properties of joints in sintered SiC fiber-bonded ceramics brazed with Ag–Cu–Ti alloy. Mater Sci Eng A 2012;557: 69–76. 18. Singh M, Asthana R, Shpargel T. Brazing of carbon–carbon composites to Cu-clad molybdenum for thermal management applications. Mater Sci Eng A 2007;452-453:699–704. 19. Asthana R, Singh M. Active metal brazing of advanced ceramic composites to metallic systems. In: Sekulic DP, editor. Advances in brazing: science, technology and applications. Cambridge, UK: Woodhead Publishing; 2013. p. 323–60. 20. Xiong JH, Huang JH, Zhang H, Zhao XK. Brazing of carbon fibre reinforced SiC composite and TC4 using Ag–Cu–Ti active brazing alloy. Mater Sci Eng A 2012;527:1096–101. 21. Mergia K. In: Cuppoletti J, editor. Joining of Cf/C and Cf/SiC Composites to metals, nanocomposites with unique properties and applications in medicine and industry. Rijeka, Croatia: InTech; 2011., ISBN 978-953-307351-4 http://www.intechopen.com/books/nanocomposites-with-uniqueproperties-and-applications-inmedicine-and-industry/joining-of-cf-c-andcf-sic-composites-to-metals
911
22. Yousefiani A, Comfort JM, Vollmer J, Hand M. Joined composite structures with graded coefficient of thermal expansion for extreme environment applications. In: Patent application U.S. 0266870 A1.; 2009. 23. Blugan G, Kuebler J, Bissig V, Janczak-Rusch J. Brazing of silicon nitride ceramic composite to steel using SiC-particle-reinforced active brazing alloy. Ceram Int 2007;33:1033–9. 24. Grasso S, Sakka Y, Maizza G. Electric current activated/assisted sintering (ECAS): a review of patents 1906–2008. Sci Technol Adv Mater 2009;10:053001. 25. Pinc WR, Di Prima M, Walker LS, Wing ZN, Corral EL. Spark plasma joining of ZrB2 –SiC composites using zirconium–boron reactive filler layers. J Am Ceram Soc 2011;94:3825–32. 26. Munir ZA, Anselmi-Tamburini U, Ohyanagi M. The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method. J Mater Sci 2006;41:763–77. 27. Centeno A, Rocha VG, Borrell A, Blanco C, Fernández A. Fabrication of C/SiC composites by combining liquid infiltration process and spark plasma sintering technique. Ceram Int 2012;38:2171–5. 28. Luo Y, Li S, Pan W, Li L. Fabrication and mechanical evaluation of SiC–TiC nanocomposites by SPS. Mater Lett 2004;58:150–3. 29. Guillard F, Allemand A, Lulewicz JD, Galy J. Densification of SiC by SPS-effects of time, temperature and pressure. J Eur Ceram Soc 2007;27: 2725–8. 30. Wang HJ, Jin ZH, Miyamoto Y. Ti3 SiC2 /Al2 O3 composites prepared by SPS. Ceram Int 2003;29:539–42. 31. Magnant J, Pailler R, Le Petitcorps Y, Maillé L, Guette A, Marthe J, Philippe E. Fiber-reinforced ceramic matrix composites processed by a hybrid technique based on chemical vapor infiltration, slurry impregnation and spark plasma sintering. J Eur Ceram Soc 2013;33:181–90. 32. Miriyev A, Stern A, Tuval E, Kalabukhov S, Hooper Z, Frage N. Titanium to steel joining by spark plasma sintering (SPS) technology. J Mater Process Tech 2013;213:161–6. 33. Liu L, Ye F, Zhou Y, Zhang Z, Hou Q. Fast bonding ␣-SiAlON ceramics by spark plasma sintering. J Eur Ceram Soc 2010;30:2683–9. 34. Ozaki K. Joining of ceramic/cermet to metal by spark plasma sintering. Met Powder Rep 1998;53:35. 35. Papenburg U, Pfrang W, Kutter G, Mueller C, Kunkel B, Deyerler M, Bauereisen S. Optical and optomechanical ultra-lightweight C/SiC® components. In: SPIE conference on optical manufacturing and testing. 1999. p. 0277-786. 36. Maizza G, Grasso S, Sakka Y. Moving finite-element mesh model for aiding spark plasma sintering in current control mode of pure ultrafine WC powder. J Mater Sci 2009;44:1219–36. 37. Ferraris M, Salvo M, Isola C, Appendino Montorsi M, Kohyama A. Glass–ceramic joining and coating of SiC/SiC for fusion applications. J Nucl Mater 1998;258-263:1546–50. 38. Ferraris M, Salvo M, Rizzo S, Casalegno V, Han S, Ventrella A, Hinoki T, Katoh Y. Torsional shear strength of silicon carbide components pressurelessly joined by a glass–ceramic. Int J Appl Ceram Tech 2012;9: 786–94. 39. Choi SK, Chandrasekaran M, Brabers MJ. Interaction between titanium and SiC. J Mater Sci 1990;25:1957–64. 40. Halbig MC, Singh M, Tsuda H. Integration technologies for silicon carbide-based ceramics for micro-electro-mechanical systems-lean direct injector fuel injector applications. Int J Appl Ceram Tech 2012;9: 677–87. 41. Gottselig B, Gyarmati E, Naoumidis A, Nickel H. Joining of ceramics demonstrated by the example of SiC/Ti. J Eur Ceram Soc 1990;6: 153–60. 42. http://en.wikipedia.org/wiki/Ceramic matrix composite. 43. Grasso S, Hu C, Kim B, Maizza G, Sakka Y. Effects of pressure application method on transparency of SPSed alumina. J Am Ceram Soc 2011;94:1405–9. 44. Ferraris M, Ventrella A, Salvo M, Avalle M, Pavia F, Martin E. Comparison of shear strength tests on AV119 epoxy-joined carbon/carbon composites. Composites Part B 2010;41:182–91. 45. Zeng J, Ren S, Lu J. Phase evolution of Ti3 SiC2 annealing in vacuum at elevated temperatures. Int J Appl Ceram Tech 2013;10:527–39.
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46. Naka M, Feng JC, Schuster JC. Phase reaction and diffusion path of the SiC/Ti system. Metall Mater Trans A 1997;28:1385–90. 47. Gan GY, Chen JC, Sun JL, Zhou XL, Chen XH. Estimation of the Gibbs free energies of intermetallic compounds for Ti–Si–C ternary system. J Kunming Univ Sci Technol 2002;27:1–8. 48. Dong H, Li S, Teng Y, Ma W. Joining of SiC ceramic-based materials with ternary carbide Ti3 SiC2 . Mater Sci Eng, B 2011;176:60–4.
49. Wang Q, Hu C, Huang Q, Cai S, Sakka Y, Grasso S. Synthesis of highpurity Ti3 SiC2 by microwave sintering. Int J Appl Ceram Tech 2013;1–8, http://dx.doi.org/10.1111/ijac.12065. 50. Munir Z, Anselmi-Tamburini U, Ohyanagi M. The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method. J Mater Sci 2006;41:763–77.
Dr Stefano Rizzo is a research fellow in Department of Applied Science and Technology at Politecnico di Torino, Italy. He obtained his MSc in Materials Engineering in 2006 at Politecnico di Torino with a thesis concerning metal nanoclusters in silica thin layers. In 2008, he received a Master of Science in Materials for micro and nano technology from Institute for Advanced Study of Pavia, Italy. His academic and research interests include joining and coating of high-temperature ceramics, composites and metals; characterization of glass systems for nuclear and aerospace applications; recycling of biomass ash in building materials.
Dr Salvatore Grasso joined the School of Material Science and engineering (SEMS) at Queen Mary university of London in 2011 as experienced researcher in ceramics processing. Dr Grasso Salvatore performed his doctoral work (2008-2011) at the University of TsukubaNIMS (National Institute for material Science) Japan. Dr Grasso’s research work was been mainly focused on Spark Plasma Sintering (SPS) and other Electric Current Assisted Sintering Techniques. His work aimed to elucidate the unknown mechanisms involved in SPS and identify the critical parameters in SPS processing. At present he has published more than 40 papers in peer-reviewed Journals and 8 patents, he delivered 8 invited talks in international conferences.
Prof Milena Salvo PhD on Materials Engineering with a thesis concerning the joining of ceramic matrix composites for high temperature and thermonuclear fusion applications (Politecnico di Torino, Italy). She is Associate Professor of Materials Science and Technology at Politecnico di Torino. She is part of the “Glasses, ceramics and composites” research group (www.composites.polito.it). Her academic and research interests include glasses, glass-ceramics, ceramics and composites for energy production, joining and coating of advanced materials and waste management. She is co-author of 80 peer-reviewed journal publications and 3 patents in the field of advanced ceramics and composites.
Dr Valentina Casalegno carried out her Ph.D in Materials Engineering at Politecnico di Torino, Department of Material Science and Chemical Engineering and she obtained her PhD degree in 2006 after defending a thesis on the “Joining of composites materials for nuclear fusion applications”. Since 2002, she has been working in the Department of Materials Science and Chemical Engineering at the Politecnico di Torino. Her research activity focuses on design, fabrication and characterization of joining materials and joints for advanced ceramic composites and ceramic/metal components. Actually she is involved as post-doc researcher at Politecnico di Torino in many international and Italian scientific projects regarding joining of ceramics and ceramic composites for special applications and nuclear environment. She is author and co-author of several international papers and 1 PCT patent.
Prof Mike Reece Prof of Functional Ceramics, Head of the Functional Nanomaterials Group at Queen Mary University London (QMUL). His work at QMUL has focused on the understanding the electromechanical properties of ferroelectric, ferroelastic and piezoelectric ceramics. He has set-up the first spark plasma sintering (SPS) furnace in the UK. The focus of his research in this area is to produce new structural and functional materials, including ceramics for extreme environments. This includes nanostructured, textured and metastable materials. A long term objective of his work is commercialise materials prepared by SPS through knowledge transfer and spin-outs. He is the Director of Nanoforce Technology Ltd, a spin-out company of QMUL, which was funded as part of the DTI Micro- and Nano-technology Network. He is a Royal Society Industry Fellow (2011-2015) and Editor of Advances in Applied Ceramics. He is a visiting professor at the Shanghai Institute of Ceramics and Xi’an Xiaotong University.
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Prof Monica Ferraris is Professor of Materials Science and Technology at the Politecnico di Torino, Torino, Italy. She received a M.S. in Solid State Chemistry in 1985 from the University of Torino, Italy. In 1985, M. Ferraris joined the Italian Telecom Research Centre (CSELT-Torino) to work on fluoride glasses for ultra low loss optical fibers. In 1990 she moved to Fiat Research Centre (CRF-Torino) where she worked on metal and ceramic matrix composites for automotive applications. She joined Politecnico di Torino in 1991, where she is now Professor of Materials Science and Technology and group leader (http://www.composites.polito.it). Her academic and research interests include glasses, ceramics and composites for energy production, photonics, biomedical applications and waste management. She has over one hundred peer-reviewed journal publications and patents in these areas. Ferraris is a member of the Engineering Ceramics Division of The American Ceramic Society since 1995.