Abstract: A coated metal heat pipe, method of joining the heat pipe to a block of fissionable uranium, and the fissionable block with one or more embedded heat pipes are provided for use in a nuclear space reactor. The heat pipe wall is composed of a nickel-based alloy, stainless steel, or refractory metal. A sandwich of successive copper, molybdenum and copper layers cover the heat pipe. This interface manages the shear stresses from differential thermal expansions of the core and heat pipe materials. The molybdenum also serves as a uranium diffusion barrier. After inserting each coated heat pipe into openings in the block of fissionable material, a hydraulic ram, hot isostatic press, or other means apply selected external heat and pressure in an inert environment to complete the metallurgical bond, where the copper interface layers are brought up to a near liquidus temperature.

Abstract: An integrated multi-layer metal insulation structure thermally isolates an interior system from external environments more than 1200° C. Three or more refractory metal sheet layers are separated from one another by respective standoffs, where refractory metal comprises any elemental or alloy metal with a melting point more than 1600° C. Each standoff is in the form of a skeletal cage framework of refractory metal ribs with cells between the ribs. Successive interlayers are offset from one another to shunt the heat transfer laterally at each sheet layer. The ribs may have cutouts and the cells may be partially open. Each crate standoff limits thermal transfer from one sheet layer to the next to less than 2.5 W/mK, including the cells restricting air flow to substantially eliminate convective heat transfer and the skeletal cage framework creating a tortuous thermal path that lowers conductive heat transfer to less than 5% of environmental exposure.

Abstract: A solid-state bonding method sandwiches an intermediate layer between a pair of refractory metal members, e.g., of niobium, tantalum, and alloys, to form a composite bonding assembly. This sandwiching can be repeated with multiple refractory metal members. The intermediate layer is substantially uniform of at most 75 ?m thickness and composed of a material that is soluble and diffusive in the refractory metal members, e.g., of iron, nickel, cobalt, chromium, silicon, or carbon. Compressive pressure is applied, and the assembly is heated to a specified elevated temperature of at least 1280° C. The applied pressure and elevated temperature are maintained until the intermediate layer has dissolved surface oxides and asperities in the refractory metal members and has completely diffused into the refractory metal to create a seamless refractory metal bond. The pressures and temperatures needed are much lower than those required in direct diffusion bonding of refractory metals.

Abstract: A solid-state bonding method sandwiches an intermediate layer between a pair of refractory metal members to form a composite bonding assembly. This sandwiching can be repeated with multiple refractory metal members. The intermediate layer is substantially uniform of at most 75 ?m thickness and composed of a material that is soluble and diffusive in the refractory metal members, such as any of carbon, silicon, chromium, iron, cobalt, and nickel. Compressive pressure is applied, and the assembly is heated to a specified elevated temperature of at least 1280° C. The applied pressure and elevated temperature are maintained until the intermediate layer has dissolved surface oxides and asperities in the refractory metal members and has completely diffused into the refractory metal to create a seamless refractory metal bond. The pressures and temperatures needed are much lower than those required in direct diffusion bonding of refractory metals.

Abstract: A thermally conductive composite material, a thermal transfer device made of the material, and a method for making the material are disclosed. Apertures or depressions are formed in aluminum or aluminum alloy. Plugs are formed of thermal pyrolytic graphite. An amount of silicon sufficient for liquid interface diffusion bonding is applied, for example by vapor deposition or use of aluminum silicon alloy foil. The plugs are inserted in the apertures or depressions. Bonding energy is applied, for example by applying pressure and heat using a hot isostatic press. The thermal pyrolytic graphite, aluminum or aluminum alloy and silicon form a eutectic alloy. As a result, the plugs are bonded into the apertures or depressions. The composite material can be machined to produce finished devices such as the thermal transfer device. Thermally conductive planes of the thermal pyrolytic graphite plugs may be aligned in parallel to present a thermal conduction path.

Abstract: A heat pipe device and a corresponding method in which micro-channel embedded pulsating heat pipes are incorporated into a substrate. A volume of fluid in a vacuum is introduced into a micro-channel which will become slugs of liquid. Heating of the contents of the micro-channel at an evaporator region (heat source) will cause vaporization within the micro-channel and cooling at a heat sink will cause condensation within the micro-channel, acting to both drive fluid flow within the micro-channel and efficiently transfer heat. Such devices could be used in a number of different configurations, including one as a stacked set of micro-channel embedded substrates.

Abstract: A heat pump device and method in which micro-channel embedded pulsating heat pumps are incorporated into a substrate. A volume of fluid in a vacuum is introduced into a micro-channel which will become slugs of liquid. Heating of the contents of the micro-channel at an evaporation (heat source) will cause vaporization within the micro-channel and cooling at a heat sink will cause condensation within the micro-channel, acting to both drive fluid flow within the micro-channel and efficiently transfer heat. Such devices could be used in a number of different configuration, including as a stacked set of micro-channel embedded substrates.

Abstract: A method for joining metal parts in which an aluminum rich surface is produced on a first metal part by selective removal of the beryllium component of a beryllium-aluminum alloy, as by said etching. The aluminum rich surface may then be joined to another aluminum rich surface by a brazing.