NOVELTY - A capsule (100) comprises a cylindrical mechanism; a closed end (106); a sealed end (104); fill tube(s) having an opening; a first reinforcement component coupled to the closed end; and a second reinforcement component coupled to the sealed end. The cylindrical member has a material (108) thickness and a first Young's modulus and a first yield strength. The material thickness is capable of deformation upon a change of a first state to a second state of a material. The two reinforcement mechanisms can maintain a cylindrical shape of the cylindrical mechanism free from deformation.    USE - Capsule for processing materials in supercritical fluids at high pressure and high temperature (claimed), or growing crystals of gallium nitride, aluminum nitride, indium nitride, indium-gallium-nitride, aluminum-gallium-nitride, or aluminum-indium-gallium-nitride for manufacture of bulk or patterned substrates. The bulk or patterned substrates can be used for optoelectronic devices, lasers, light emitting diodes, solar cells, photodetectors, and integrated circuits, transistor devices, other device structures, photoelectrochemical water splitting and hydrogen generation.    ADVANTAGE - The capsule can improve the reliability and robustness of capsule filling, handling, and processing at high pressure and high temperature, increasing yields and decreasing overall process costs.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for processing materials in supercritical fluids within a capsule at high pressure and high temperature, comprising:    (A) loading material(s) into an interior volume of the capsule;    (B) attaching a lid with a fill tube onto the open end of the capsule to seal the lid to the capsule; and    (C) purging the interior of the capsule of air, moisture, and other contaminants.    DESCRIPTION OF DRAWING(S) - The drawing is a sectional diagram of a capsule device for supercritical fluids.    Capsule (100)    Sealed end (104)    Closed end (106)    Material (108)    Solvent (112)