SiC-based sandwich material for Flow Channel Inserts in DCLL blankets: Manufacturing, characterization, corrosion tests

Abstract

h i g h l i g h t s • A wide range of porous SiC materials with different properties were produced. • The produced 50% porous SiC has k ≈ 5 W/m K at 700 • C and ≈ 3 10 −5 S/m at 550 • C. • The produced 50% porous SiC has a flexural strength in the range 50-80 MPa. • A 200 m dense CVD-SiC coating offers reliable protection against static PbLi corrosion. a b s t r a c t Flow Channel Inserts (FCIs) are key elements in a DCLL blanket concept for DEMO, since they provide the required thermal insulation between the He cooled structural steel and the hot liquid PbLi flowing at ≈700 • C, and the necessary electrical insulation to minimize MHD effects. In this work a SiC-based sandwich material is proposed for FCIs, consisting of a porous SiC core covered by a dense CVD-SiC layer. A method to produce the porous SiC core is presented, based on combining a starting mixture of SiC powder with a spherical carbonaceous sacrificial phase, which is removed after sintering by oxidation, in such a way that a microstructure of spherical pores is achieved. Following this technique, a porous SiC material with low thermal and electrical conductivities, but enough mechanical strength was produced. Samples were covered by a 200 m thick CVD-SiC coating to form a SiC-sandwich material. Finally, corrosion tests under static PbLi were performed, showing that such a dense layer offers a reliable protection against static PbLi corrosion.

Controlling the electrical resistivity of porous silicon carbide ceramics and their applications: A review

“…The electrical resistivity of porous SiC ceramics is affected by their porosity. Porous SiC ceramics exhibit a room temperature electrical resistivity of the order of 10 –1 –10 6 Ω·cm 30,31,37,41,57,76–79 . For example, the electrical resistivities of porous SiC ceramics sintered with 10 vol.% AlN‐Y 2 O 3 and 7wt.% Y 2 O 3 –La 2 O 3 are 1.3 × 10 –1 Ω·cm at 30.3% porosity 31 and 5.3 × 10 1 Ω·cm at 9.9% porosity, 37 respectively.…”

“…Porous SiC ceramics exhibit a room temperature electrical resistivity of the order of 10 -1 -10 6 Ω⋅cm. 30,31,37,41,57,[76][77][78][79] For example, the electrical resistivities of porous SiC ceramics sintered with 10 vol.% AlN-Y 2 O 3 and 7wt.% Y 2 O 3 -La 2 O 3 are 1.3 × 10 -1 Ω⋅cm at 30.3% porosity 31 and 5.3 × 10 1 Ω⋅cm at 9.9% porosity, 37 respectively. The electrical resistivity of ceramics generally increases with an increase in the porosity.…”

Development, Characterization, and Testing of a SiC-Based Material for Flow Channel Inserts in High-Temperature DCLL Blankets

“…10), although some damages of the dense coating occurred during dismantling the samples after the experiment. Details of these results can be found in [15].…”

“…To characterize the material's behavior against hot PbLi corrosion, two different experiments have been conducted. First, porous samples coated with a ∼200-µm CVD-SiC layer were tested under static PbLi at 700 °C for 1000 h [15]. A second corrosion experiment has been recently performed, testing a new batch of coated samples under flowing PbLi at ∼10 cm/s and 550 °C for 850 h; in order to study the possible influence of the presence of a magnetic field in the corrosion phenomena, some samples were subjected to a 1.8-2 T magnetic field during the experiment.…”

Effects of Composite Sintering Additives: Al(OH)3+Y2O3+CaF2 on the Performance of Porous Mullite Oxide-Bonded SiC Ceramics

“…Porous silicon carbide (SiC) ceramics are promising materials in fields of filters for diesel particulate and molten metals, membrane and catalyst supports, heat exchangers, gas purifiers, high-temperature insulators and wave absorption materials [1][2][3][4][5][6][7][8][9][10] due to their low density, high corrosion resistance, good chemical stability, high thermal shock resistance, low coefficient of thermal expansion and high specific strength at both room and elevated temperatures [11][12][13][14][15]. However, the highly covalent character of Si-C bond makes it very difficult to be sintered.…”