Studies on the coating of fuel particles for the ‘dragon’ reactor experiment

Silver Diffusion in Silicon Carbide Coatings

“…The formation of these microstructural defects could be inherent from the deposition process itself because the coatings are not produced under constant deposition conditions because the temperature, residence time, and the surface area/volume ratio change as the substrate cycles trough out the bed. For example, during the deposition of SiC the particles follow a cyclic pattern in which the substrate goes in and out of the deposition zone travelling through areas with a temperature gradient of up to 500°C between the nozzle and the hot zone depending on the design of the coater 23–26 . These changes in temperature, residence time and surface area/volume ratio can have a huge impact on the gas maturation of the intermediate species and affect the homogeneous and heterogeneous reactions, resulting in the formation of different microstructures or textures 27,28 .…”

Effect of coating temperature on properties of the SiC layer in TRISO-coated particles

“…Characteristics of the coating layer depend largely on the FBCVD conditions such as the gas flow rate, concentration of the coating gas, coating temperature, etc. [4][5][6][7][8][9][10][11]. Among the deposition parameters, the coating temperature is particularly important to determine the properties of the SiC layer.…”

SiC, from Amorphous to Nanosized Materials, the Exemple of SiC Fibres Issued of Polymer Precursors

“…gives rise to a variety of preparation routes leading to monoliths, films, fibres, composites, crystal,…, from the amorphous state to the single crystal, including nanomaterials (Gough & Kern, 1967;Parlier & Colomban, 1996;Naslain, 2004). The mix of atomic orbital led to an intermediate electric behaviour between that of carbon (a semi-metal) and silica (an insulator), the electronic gap is intermediate (2-3 eV) and the material is a semiconductor.…”

“…They can be regarded as consisting of stacked bi-layers. The availability of volatile/liquid silanes led to the preparation of SiC materials in various forms (McDiarmid, 1961;Fritz et al, 1965;Gough & Kern, 1967;Learn & Khan, 1970;Corriu & Lanneau, 1970;Kumar & Litt, 1988;Schmidt et al, 1991): films/coatings (Rynders et al, 1991), fibres (a SiC coating is deposited on a carbon fibre core (Hurwitz et al, 1991;Tanaka et al, 1995;idem, 1996;Popovska et al, 1997), monoliths and fibre-reinforced composites (Yajima et al, 1980;Tanaka & Kurachi, 1988;Bouillon et al, 1991 a & b;Monthioux et al, 1990;idem, 1991;Delplancke et al, 1991;Lee & Yano, 2004). The growth rate was slow and for the preparation of thick monoliths or composites weeks are required with sometimes an intermediate machining of the parts in order to avoid the closure of the porosity that occurs at the sample surface, avoiding the completion of the core densification.…”