Pressure vessel

A pressure vessel for processing at least one material in an a supercritical fluid, the pressure vessel comprising:

• a)a capsule for containing said at least one material and said supercritical fluid in a substantially air-free environment, wherein said capsule has at least one wall, a closed end, and a sealed end defining a chamber therein for containing said at least one material and said supercritical fluid, and wherein said capsule is self-pressurizing;
• b)a pressure transmission medium for maintaining an outer pressure on said capsule, said pressure transmission medium surrounding said capsule;
• c)a heating system for heating said capsule, said heating system comprising at least one heating element insertable in said pressure transmission medium such that said at least one heating element is proximate to said capsule, at least one temperature sensor disposed proximate to said capsule for measuring a temperature of said capsule, and a wattage control system electrically connected to said at least one heating element and said at least one temperature sensor, wherein said wattage control system provides power to said at least one heating element and controls said temperature;
• d)a restraint to contain and hold in place said capsule, said pressure transmission medium, and said at least one heating element, wherein said restraint maintains said capsule, said pressure transmission medium, and said at least one heating element at a constant pressure;
• and
• e)at least one seal for preventing escape of said pressure transmission medium, said at least one seal being disposed between said restraint and said pressure transmission medium.

A method of using a pressure vessel to process at least one material at high temperature and high pressure in the presence of a supercritical fluid, the method comprising the steps of:

• a)providing a sealed capsule containing the at least one material and a solvent that forms a supercritical fluid, wherein the capsule is self-pressurizing;
• b)providing a pressure vessel comprising a restraint for containing the sealed capsule, a pressure transmission medium disposed within the pressure vessel, and at least one heating element disposed within the pressure transmission medium and electrically coupled to a wattage control system;
• c)disposing the sealed capsule within the pressure transmission medium such that the sealed capsule is proximate to the at least one heating element;
• d)placing the pressure vessel containing the pressure transmission medium, the sealed capsule, and the at least one heating element in a press;
• e)pressurizing the press to apply a predetermined pressure to the pressure vessel, the pressure transmission medium, the sealed capsule, and the at least one heating element;
• f)providing electrical power from the wattage control system to the at least one heating element, thereby heating the sealed capsule to a predetermined temperature, wherein the solvent contained within the sealed capsule becomes a supercritical fluid and wherein the supercritical fluid generates a predetermined pressure within the sealed capsule;
• and
• g)counterbalancing the predetermined pressure within the sealed capsule by maintaining an equivalent pressure with the restraint and transmitting the equivalent pressure through the pressure transmission medium, wherein the at least one material is processed at high temperature and high pressure in the presence of a supercritical fluid.

A method of processing at least one material at high temperature and high pressure in the presence of a supercritical fluid, the method comprising the steps of:

• a)providing a sealed capsule containing the at least one material and a solvent that forms a supercritical fluid, wherein the capsule is self-pressurizing;
• b)providing a pressure vessel comprising a restraint, a pressure transmission medium disposed within the restraint, and at least one heating element disposed within the restraint;
• c)disposing the sealed capsule within the pressure transmission medium such that the sealed capsule is proximate to the at least one heating element;
• d)heating the sealed capsule to a predetermined temperature by providing electrical power to the at least one heating element, wherein the solvent contained within the sealed capsule becomes a supercritical fluid and wherein the supercritical fluid generates a predetermined pressure within the sealed capsule;
• and
• e)counterbalancing the predetermined pressure within the sealed capsule by applying a pressure to the restraint, wherein the at least one material reacts with the supercritical fluid within the sealed capsule.

A metal nitride single crystal, wherein the metal nitride single crystal is formed by:

• enclosing a metal nitride source material and a solvent within a sealed capsule that is self-pressurizing;
• disposing the sealed capsule within a pressure vessel comprising a restraint, a pressure transmission medium disposed within the restraint, and at least one heating element disposed within the restraint;
• heating the sealed capsule to a predetermined temperature, wherein the solvent contained within the sealed capsule becomes a supercritical fluid and generates a predetermined pressure within the sealed capsule;
• and counterbalancing the predetermined pressure within the sealed capsule by applying a pressure to the restraint;
• wherein the metal nitride source material reacts with the supercritical fluid within the sealed capsule to form a metal nitride single crystal at high temperature and high pressure.