19 Non-metallic building materials for the purpose of use in the fields of aerospace, aviation and aeronautics, namely, non-metallic trays formed of carbon, non-metallic grates composed primarily of carbon, non-metallic hearths composed primarily of carbon, non-metallic plates composed primarily of carbon, and non-metallic spacers composed primarily of carbon; structured composite materials, essentially with a ceramic matrix, for the purpose of use in the fields of aerospace, aviation and aeronautics, namely, non-metallic trays formed of carbon, non-metallic grates composed primarily of carbon, non-metallic hearths composed primarily of carbon, non-metallic plates composed primarily of carbon, and non-metallic spacers composed primarily of carbon; carbonaceous composite materials, essentially with a ceramic matrix, for the purpose of use in the fields of aerospace, aviation and aeronautics, namely, non-metallic trays composed primarily of carbon composite material, non-metallic grates composed primarily of carbon composite material, non-metallic hearths composed primarily of carbon composite material, non-metallic plates composed primarily of carbon composite material, and non-metallic spacers composed primarily of carbon composite material; composite materials with a ceramic matrix, for the purpose of use in the fields of aerospace, aviation and aeronautics, namely, non-metallic trays formed of carbon, non-metallic grates composed primarily of carbon, non-metallic hearths composed primarily of carbon, non-metallic plates composed primarily of carbon, and non-metallic spacers composed primarily of carbon