Materials

Making Plant-Support Structures From Waste Plant Fiber

Environmentally benign, biodegradable structures for supporting growing plants can be made in a process based on recycling of such waste plant fiber materials as wheat straw or of such derivative materials as paper and cardboard. Examples of structures that can be made in this way include plant plugs, pots, planter-lining mats, plant fences, and root and shoot barriers. No chemical binders are used in the process. First, the plant material is chopped into smaller particles. The particles are leached with water or steam to remove material that can inhibit plant growth, yielding a fibrous slurry. If the desired structures are plugs or sheets, then the slurry is formed into the desired shapes in a pulp molding subprocess. If the desired structures are root and shoot barriers, pots, or fences, then the slurry is compression-molded to the desired shapes in a heated press. The processed materials in these structures have properties similar to those of commercial pressboard, but unlike pressboard, these materials contain no additives. These structures have been found to withstand one growth cycle, even when wet.

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Polyimides From a-BPDA and Aromatic Diamines

These polyimides have low color and high mechanical properties. Polymers having low color and a favorable combination of other properties, including high glass-transition temperature (Tg) and high mechanical properties (strength, tensile modulus, and toughness) will find use in a variety of terrestrial and space applications. Some of the space applications will be in thin films used as membranes on antennas, solar concentrators, coatings on second-surface mirrors, solar sails, sunshades, thermal and optical coatings, and multi-layer thermal insulation blankets. Depending upon the application, the film will be required to exhibit a unique combination of such properties as resistance to degradation by ultraviolet light, visible light, and electrons; low color and/or low solar absorptivity; resistance to tearing and/or wrinkling during packaging and deployment; and high mechanical properties (e.g. high strength, stiffness, and toughness). Recently developed polyimides having several of these desired properties are described below.

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Generating Aromatics From CO2 on Mars or Natural Gas on Earth

The terrestrial version may make it economical to recover some natural-gas deposits. “Methane to aromatics on Mars” (“METAMARS”) is the name of a process originally intended as a means of converting Martian atmospheric carbon dioxide to aromatic hydrocarbons and oxygen, which would be used as propellants for spacecraft to return to Earth. The process has been demonstrated on Earth on a laboratory scale. A truncated version of the process could be used on Earth to convert natural gas to aromatic hydrocarbon liquids. The greater (relative to natural gas) density of aromatic hydrocarbon liquids makes it more economically feasible to ship them to distant markets. Hence, this process makes it feasible to exploit some reserves of natural gas that, heretofore, have been considered as being “stranded” too far from markets to be of economic value.

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Cleaning Carbon Nanotubes by Use of Mild Oxygen Plasmas

Mildness of the plasmas is the key to cleaning without destruction. Experiments have shown that it is feasible to use oxygen radicals (specifically, monatomic oxygen) from mild oxygen plasmas to remove organic contaminants and chemical fabrication residues from the surfaces of carbon nanotubes (CNTs) and metal/CNT interfaces. A capability for such cleaning is essential to the manufacture of reproducible CNT-based electronic devices.

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Designing Cure Cycles for Matrix/Fiber Composite Parts

This methodology enables production of void-free laminates. A methodology has been devised for designing cure cycles to be used in the fabrication of matrix/fiber composite parts (including laminated parts). As used here, “cure cycles” signifies schedules of elevated temperature and pressure as functions of time, chosen to obtain desired rates of chemical conversion of initially chemically reactive matrix materials and to consolidate the matrix and fiber materials into dense solids. Heretofore, cure cycles have been designed following an empirical, trial-and-error approach, which cannot be relied upon to yield optimum results. In contrast, the present methodology makes it possible to design an optimum or nearly optimum cure cycle for a specific application.

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Combustion Synthesis of Ca3(PO4)2 Net-Shape Surgical Implants

More-biocompatible materials are produced in fewer processing steps. ASelf-propagating high-temperature combustion synthesis (SHS) is the basis of a method of making components of porous tricalcium phosphate [Ca3(PO4)2] and related compounds in net sizes and shapes for use as surgical implants that are compatible with bone. Ca3(PO4)2-based materials are among those preferred for use in orthopedic, restorative, and reconstructive surgery. As explained below, the SHS method offers advantages over prior methods of manufacturing Ca3(PO4)2-based surgical implants.

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Thermally Stable Piezoelectric and Pyroelectric Polymers

Neither mechanical nor solvent treatment is necessary for orientation of polymer molecules. A class of thermally stable piezoelectric and pyroelectric polymers, and an improved method of making them, have been invented. These polymers can be used as substrates for a wide variety of electro- mechanical transducers, sensors, and actuators.

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