Emission characteristics of ultrafine particles from bare and Al₂O₃ coated graphite for high temperature applications

Graphite is employed as structural material and fuel block in high temperature reactors (HTRs) due to its favourable properties at high temperatures. The performance of graphite at high temperature becomes a key input to the technology aiming towards its utilization in HTRs. An important issue of concern is the modifications in its structural characteristics due to postulated air ingress conditions, which needs to be addressed for ensuring safe operations. Under air ingress conditions, oxidation of graphite results in significant weight loss, usually above a threshold temperature termed as 'transition temperature'. Limited information is available defining the characteristics of aerosol particles generated above the transition temperature. The HTAF at IIT-BHU was commissioned to address such aerosol related issues. Fig. represents the experimental setup used in HTAF for studying the particle generation features in the given context. In these experiments, transition temperature for high density isotropic ultrafine grain graphite specimens (99.96 % carbon content by weight) was obtained as ∼ 600 °C