B. Riccardi et al./Fusion Engineering and Design 51-52(2000)11-22 the textile stage, metallic brazing, homogeneous shear strength, measured by means of an almost joining by preceramic polymers, joining by glass pure shear test were obtained for a joining sin- and glass ceramic tered a-SiC (40 MPa). Concerning SiC Sic com a brazing alloy series for joining 2-and 3-d posites(SEP CERASEP N3-1)the best results SiC/SiC composites has been developed at CEa were obtained using SR 350 silicone resin with Grenoble and named Brasic" [20]. This brazing Al/Si powders used as additives(31.6 MPa maxi compound is composed of low activation elements mum) with pyrolysis carried out at 1200oC and was conceived to work at elevated tempera Ferraris and Salvo [22] from Politecnico of tures and to be compatible with SiC. In partices o the use of pure silicon giving a room temperature Turin developed a joining technology based on the brazing system contain a sufficient amount silicon to prevent reaction with the SiC substrate. shear strength of 22 MPa. Encouraging results promote good wetting and to induce some infiltra- were also obtained using a glass ceramic phase to tion in the composites. Silicon is associated with join SiC CMCs [22]: in this case a 33 MPa shear reactive elements to improve the joining strength. strength were reached at room temperature Glass By using different alloys and compositions(Brasic and glass ceramic compound were also used for H2 and V2 or V3)and brazing in vacuum or in an coating SIC/SiC CMCs. The formulation was re- inert atmosphere it was possible to control the cently optimised in order to give a coating with infiltration of the alloy. USing Brasic V3 and reduced neutron activation (M. Ferraris, Pol carrying out the joining at 1300C in a neutral technic of Turin, personal communication, 1999) atmosphere a sound joint was obtained with aa double layer coating was set up: the first con- perfect filling of the joint gap but no infiltration sists of a glass ceramic phase stable at 800C and of the composite(Fig. 6). For this joint a shea the second consists of a glassy phase which is able perature and about 100 MPa at 800 C. The main about 1100 r crack appearance when heated to strength of 174 MPa was obtained at room tem to self heal aft limitation of the method rely on the free Si con- tent and the open high porosity of the composite This low activation brazing alloy can in principle 7. Conclusions be used for coating SiC/SiC c An homogeneous joining technique has been A specific R&D effort on SiCr/SiC composites developed by ENEA and Padua University [21 is currently ongoing in order to support the use of This technique is based on the application of a the material for FPRs. Significant higher effort preceramic polymer which pyrolysed at high tem both on the theoretical aspects, such as modelica perature to provide an adhesive bonding lay tion and analyses, and on expe riment consisting of a silicon oxi-carbide phase. Relevar ufacturing aspects will be required overt the next Sicdsic improvement and to establish its vance for use as a structural material in in-vessel SiC/SiC On the theoretical side activities include the development of the TaURo blanket conceptual BraSic V3 design with the double objective of:(i) improving behavioural modelisation and results interpreta- tion al nd (ii) supplying useful guidelines for the Sic/SiC material development and characterisation in or der to relax some critical issues concerning the manufacturing of complex shapes. In this respect Fig. 6. Sicy Sic composite brazed joint with a BraSiC v3 alloy the production of small scale mock ups aimed at Q-no infiltration of the composite is observed reproducing the main features of the blanket de20 B. Riccardi et al. / Fusion Engineering and Design 51–52 (2000) 11–22 the textile stage, metallic brazing, homogeneous joining by preceramic polymers, joining by glass and glass ceramic. A brazing alloy series for joining 2- and 3-D SiC/SiC composites has been developed at CEA Grenoble and named Brasic® [20]. This brazing compound is composed of low activation elements and was conceived to work at elevated tempera￾tures and to be compatible with SiC. In particular the brazing system contain a sufficient amount of silicon to prevent reaction with the SiC substrate, promote good wetting and to induce some infiltra￾tion in the composites. Silicon is associated with reactive elements to improve the joining strength. By using different alloys and compositions (Brasic H2 and V2 or V3) and brazing in vacuum or in an inert atmosphere it was possible to control the infiltration of the alloy. Using Brasic V3® and carrying out the joining at 1300°C in a neutral atmosphere a sound joint was obtained with a perfect filling of the joint gap but no infiltration of the composite (Fig. 6). For this joint a shear strength of 174 MPa was obtained at room tem￾perature and about 100 MPa at 800°C. The main limitation of the method rely on the free Si con￾tent and the open high porosity of the composite. This low activation brazing alloy can in principle be used for coating SiCf /SiC composites. An homogeneous joining technique has been developed by ENEA and Padua University [21]. This technique is based on the application of a preceramic polymer which pyrolysed at high tem￾perature to provide an adhesive bonding layer consisting of a silicon oxi-carbide phase. Relevant shear strength, measured by means of an almost pure shear test were obtained for a joining sin￾tered a-SiC (40 MPa). Concerning SiCf /SiC com￾posites (SEP CERASEP® N3-1) the best results were obtained using SR 350 silicone resin with Al/Si powders used as additives (31.6 MPa maxi￾mum) with pyrolysis carried out at 1200°C. Ferraris and Salvo [22] from Politecnico of Turin developed a joining technology based on the use of pure silicon giving a room temperature shear strength of 22 MPa. Encouraging results were also obtained using a glass ceramic phase to join SiC CMCs [22]: in this case a 33 MPa shear strength were reached at room temperature. Glass and glass ceramic compound were also used for coating SiC/SiC CMCs. The formulation was re￾cently optimised in order to give a coating with reduced neutron activation (M. Ferraris, Poly￾technic of Turin, personal communication, 1999). A double layer coating was set up: the first con￾sists of a glass ceramic phase stable at 800°C and the second consists of a glassy phase which is able to self heal after crack appearance when heated to about 1100°C. 7. Conclusions A specific R&D effort on SiCf /SiC composites is currently ongoing in order to support the use of the material for FPRs. Significant higher effort both on the theoretical aspects, such as modelisa￾tion and analyses, and on experimental and man￾ufacturing aspects will be required overt the next several years in order to achieve the necessary SiCf /SiC improvement and to establish its rele￾vance for use as a structural material in in-vessel FPR components. On the theoretical side activities include the development of the TAURO blanket conceptual design with the double objective of: (i) improving behavioural modelisation and results interpreta￾tion and (ii) supplying useful guidelines for the material development and characterisation in or￾der to relax some critical issues concerning the manufacturing of complex shapes. In this respect the production of small scale mock ups aimed at reproducing the main features of the blanket de￾Fig. 6. SiCf /SiC composite brazed joint with a BraSiC V3 alloy Q — no infiltration of the composite is observed