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Capillography of Mats of Nanofibers

These mats can be the basis of small devices and instruments. Capillography (from the Latin capillus, “hair”, and the Greek graphein, “to write”) is a recently conceived technique for forming mats of nanofibers into useful patterns. The concept was inspired by experiments on carpetlike mats of multiwalled carbon nanotubes. Capillography may have the potential to be a less-expensive, less- time-consuming alternative to electron- beam lithography as a means of nanoscale patterning for the fabrication of small devices and instruments.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Electron-Beam Welding of Superalloys at High Temperatures

Strain age cracks can be prevented. Electron-beam welding at high temperatures has been found to be a suitable process for joining structural components made by casting certain superalloys. This process can be used in the fabrication of superalloy parts that must withstand high operating temperatures. Examples of such parts include exhaust ducts of advanced aerospace engines and end caps on turbine buckets.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Software for Optimized Flattening From 3D to 2D

Manufacturing considerations can be taken into account in designing minimally wasteful 2D patterns. A computer program offers enhanced capabilities for calculating two-dimensional (2D) patterns needed to construct specified three-dimensional (3D) surfaces to within acceptably close approximations, with minimal waste of sheet material. Examples of complexly shaped sheet-material items that could be designed by use of this program include aircraft fuselages, hulls of ships, clothing, and automotive bodies.

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Photolithographic Fine Patterning of Difficult-To-Etch Metals

Copper is used as a liftoff material. A process that includes photolithography, liftoff, etching, and sputter deposition has been developed to enable the fabrication of thin, finely patterned layers of gold, platinum, and other difficultto- etch materials in advanced miniature sensors and associated electronic circuitry. Heretofore, photolithography has been used in conjunction with liftoff and etching to produce finely detailed structures in easy-to-etch materials. The present process is needed because conventional photolithography cannot be used to pattern difficult-to-etch materials and the alternative processes heretofore available for patterning difficult-to-etch materials are limited to spatial resolution of about 0.005 in. (≈0.13 mm) or coarser.

Posted in: Manufacturing & Prototyping, Briefs, TSP

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Heat Transfer Analysis for Optimizing Solar Cell Casting Equipment

Finite element analysis was used to develop a miniature furnace to cast the solar cell wafers. Solar Power Industries’ (SPI) current annual production capacity for processing polycrystalline silicon feedstock into completed solar cells has grown to 40 megawatts, with plans to increase capacity to 250 megawatts over the next several years. SPI’s solar cell manufacturing process consists of three main steps:   Ingot and Wafer Production—High-quality silicon feedstock (containing specific quantities of dopants such as boron in order to alter electrical properties) is melted and solidified inside a directional solidification furnace to cast polycrystalline silicon ingots. The ingots are cut into rectangular blocks with a square cross-section, and then the blocks are sawed into thin multicrystalline wafers. Cell Production — The wafers are etched to remove surface damage caused by sawing. The wafers are then processed in a series of steps to produce photovoltaic cells. Module Assembly — Individual cells are connected by soldering to flat wires. Strings of cells are then joined to parallel connector wires and laminated to produce a solar module.

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Fabricating Large-Area Sheets of Single-Layer Graphene by CVD

Such sheets are components for high-speed digital and RF electronics for defense and commercial communications. This innovation consists of a set of methodologies for preparing large area (>1 cm2) domains of single-atomic-layer graphite, also called graphene, in single (two-dimensional) crystal form. To fabricate a single graphene layer using chemical vapor deposition (CVD), the process begins with an atomically flat surface of an appropriate substrate and an appropriate precursor molecule containing carbon atoms attached to substituent atoms or groups. These molecules will be brought into contact with the substrate surface by being flowed over, or sprayed onto, the substrate, under CVD conditions of low pressure and elevated temperature. Upon contact with the surface, the precursor molecules will decompose. The substituent groups detach from the carbon atoms and form gas-phase species, leaving the unfunctionalized carbon atoms attached to the substrate surface. These carbon atoms will diffuse upon this surface and encounter and bond to other carbon atoms. If conditions are chosen carefully, the surface carbon atoms will arrange to form the lowest energy single-layer structure available, which is the graphene lattice that is sought.

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Improved Probe for Evaluating Compaction of Mold Sand

Sand is not perturbed during switching among different measurement positions. A nominally stationary tubular probe denoted a telescopic probe has been developed as an improved alternative to a prior movable probe used to evaluate the local degree of compaction of mold sand. The prior movable probe consists mainly of a vertically oriented tube with screen vents at its lower end. The upper end is connected to a source of constant airflow equipped with a pressure gauge. The probe is inserted vertically to a desired depth in a sand-filled molding flask and the back pressure at the given rate of flow of air is recorded as a measure of the degree of partial impermeability and, hence, of the degree of compaction of sand in the vicinity of the probe tip.

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