Supercritical fluid molecular spray thin films and fine powders

A method for forming a fine powder of a solid material, comprising:

• forming a supercritical solution including a supercritical fluid solvent and a dissolved solute of a solid material;
• rapidly expanding the supercritical solution through an orifice of a predetermined length and diameter to produce a particulate spray of the material and vaporized solvent;
• discharging the spray into a low pressure region to form a powder of the solid material therein;
• and
• selecting and maintaining a temperature of the supercritical solution in relation to a two-phase expansion temperature of the solvent to control a liquid solvent content of the molecular spray and thereby determine a porosity characteristic of the powder.

A method for forming a solid material into one of a thin film and a powder, comprising:

• forming a supercritical solution containing a supercritical fluid solvent and a dissolved solute of the solid material in a predetermined concentration and at an elevated pressure;
• discharging the supercritical solution through a short orifice into a region of lower pressure so as to rapidly expand the solution to produce a molecular spray of the solid material and solvent;
• varying at least one of the elevated pressure, the solute concentration, and the pressure of the low pressure region so as to control one of the rate of deposition of solute and the extent of nucleation of molecules of the solute in the low pressure region;
• and
• varying the solution temperature to control porosity of the film or powder.

A method for forming a solid material into one of a thin film and a powder, comprising:

• selecting a solvent having, in a liquid phase, a limited solubility of said solid material and, in a supercritical fluid state, an increased solubility of the solid material;
• forming a supercritical solution containing the solvent in a supercritical fluid state and a dissolved solute of the solid material in a predetermined concentration and at an elevated pressure;
• discharging the supercritical solution through a common, short orifice into a region of lower pressure so as to rapidly expand the solution to produce a molecular spray of the solid material and solvent;
• and
• varying at least one of the elevated pressure, the solute concentration, and the pressure of the low pressure region so as to control one of the rate of deposition of solute and the extent of nucleation of molecules of the solute in the low pressure region.