Abstract: In accordance with one aspect of the present invention, a process for forming a specific reactive element barrier on a titanium and aluminum containing substrate is provided. The process includes creating a dry air atmosphere with a concentration of water vapor below about 750 ppm at a temperature above about 550° C. contiguous to a surface of the substrate on which the barrier layer is to be formed. The temperature is maintained above 550° C. and the water vapor concentration is maintained below about 100 ppm while the water vapor in the dry air atmosphere is reacted with specific reactive elements at the substrate surface. The reaction forms a specific reactive element oxide barrier layer which is strongly bonded to the substrate surface. The barrier layer includes an aluminum oxide layer at the substrate/barrier layer interface and a second oxide layer at a barrier layer/atmosphere interface.

Abstract: In accordance with one aspect of the present invention, a process for forming a specific reactive element barrier on a titanium and aluminum containing substrate is provided. The process includes creating a dry air atmosphere with a concentration of water vapor below about 750 ppm at a temperature above about 550° C. contiguous to a surface of the substrate on which the barrier layer is to be formed. The temperature is maintained above 550° C. and the water vapor concentration is maintained below about 100 ppm while the water vapor in the dry air atmosphere is reacted with specific reactive elements at the substrate surface. The reaction forms a specific reactive element oxide barrier layer which is strongly bonded to the substrate surface. The barrier layer includes an aluminum oxide layer at the substrate/barrier layer interface and a second oxide layer at a barrier layer/atmosphere interface.

Abstract: A titanium aluminide substrate (4) is vulnerable to air oxidation, limiting the use of this substrate in a variety of industrial applications, including the aircraft and aerospace industries. A bilayer reactive barrier (2) is formed on a titanium aluminide substrate. The barrier layer includes an &agr;-Al2O3 layer (6) from the reaction of oxygen from the disassociation of water with alumina in a gaseous and water vapor atmosphere at high temperatures and low oxygen concentration. During the process, titanium migrates through the &agr;-Al2O3 to a gas/barrier layer surface (14) and is oxidized to form a Ti2O3 layer (8). A surface of the Ti2O3 layer is subsequently oxidized to form a TiO2 layer (12). In this manner, a triple layer barrier is formed in which the immersible TiO2 and &agr;-Al2O3 are separated by Ti2O3. The three layers are bonded to each with a bond strength greater than 4500 kPa.

Abstract: A substrate material to be coated with either a nitride, carbide, or oxide contains a small percent of a specific reactive element, like titanium, which forms very stable nitrides, carbides, or oxides. The material also contains larger percentages of elements, such as chromium, which form less-stable nitrides, carbides, or oxides. When the substrate material is immersed in a process medium which contains reactants, such as nitrogen, carbon, or oxygen, at a chosen elevated temperature and concentration, the less-stable nitrides, carbides, or oxides are reduced and cannot form a coating on the material surface. Thus, only a very stable nitride, carbide, or oxide can form a strong, adherent coating.

Abstract: An alloy has less stable oxides, e.g. nickel oxide, chromium oxide, and iron oxide on a surface (FIG. 1 ). The material has specific reaction elements such as titanium and aluminum in a relatively low concentration throughout the alloy. At an elevated temperature, the surface of the alloy is subject to a fluid which reduces the nickel, chromium, and iron oxides and the aluminum or titanium adjacent the surface reduces components of the fluid (FIG. 2 ). The alloy is maintained at the elevated temperature in the presence of the fluid until a barrier film of the specific reactive elements is formed. In one embodiment, the working fluid is a gaseous fluid of hydrogen or an inert gas with water vapor. The hydrogen of the water vapor reduces the less stable oxides and the oxygen oxidizes the specific reaction elements. In another embodiment, the working fluid is a liquid metal other than lithium which carries oxygen.

Abstract: A permeation barrier is maintained on inner surfaces of a Stirling engine, particularly the heat tubes, by maintaining a preselected concentration of dopant gas in the working gas, e.g. hydrogen. A dopant gas (10) is adsorbed on a sorbent (1) in a dopant cartridge or enclosure (2). The amount of gas adsorbed, the quantity of sorbent, and the permeability of a permeable window (3) are selected such that a preselected partial pressure of the dopant is maintained in the hydrogen. In a diffusion cell (FIGS. 1 and 2) an equilibrium partial pressure of the dopant gas is maintained by diffusion through the porous window. In a flow-through cell (FIGS. 3-5) the hydrogen or working gas is circulated through the sorbent. A fraction of the adsorbtion sites on the sorbent may be left open to adsorb excess water vapor from the hydrogen. In a trap cell (FIGS. 9 and 10) water vapor is removed from the working gas as the working gas is pumped by a compressor into a high pressure storage reservoir (59).

Abstract: A closed loop apparatus for spraying coolant against the back of a radiation target. The coolant is circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material is disposed between the bubble and the surface of the liquid coolant which is below the bubble at a predetermined level. In a second embodiment no inert gas is used, the bubble consisting of vapor produced when the coolant is sprayed against the target.

Abstract: A closed loop apparatus for spraying coolant against the back of a radiation target. The coolant is circulated through a closed loop with a bubble of inert gas being maintained around the spray. Mesh material is disposed between the bubble and the surface of the liquid coolant which is below the bubble at a predetermined level. In a second embodiment no inert gas is used, the bubble consisting of vapor produced when the coolant is sprayed against the target.

Abstract: There is disclosed a method of forming a continuous, thin film of stoichiometric metal hydride such as titanium dihydride, titanium dideuteride, or titanium ditritide on a substrate which may be of metal, glass or the like. The substrate is first cleaned, both chemically and by off-sputtering in a vacuum chamber. In an ultra-high vacuum system vapor deposition by a sublimator or vaporizer first coats a cooled shroud disposed around the substrate with a thin film of hydride forming metal which getters any contaminant gas molecules. A shutter is then opened to allow hydride forming metal to be deposited as a film or coating on the substrate.After the hydride forming metal coating is formed, a deuterium or other hydrogen isotopes are bled into the vacuum system and diffused into the metal film or coating to form a hydride of metal film. Higher substrate temperatures and pressures may be used if various parameters are appropriately adjusted.