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Alternating-Composition Layered Ceramic Barrier Coatings

These coatings are expected to be more durable, relative to prior thermal/environmental barrier coatings. Ceramic thermal and environmental barrier coatings (T/EBCs) that contain multiple layers of alternating chemical composition have been developed as improved means of protecting underlying components of gas-turbine and other heat engines against both corrosive combustion gases and high temperatures. A coating of this type (see figure) is configured using the following layers: An outer, or top oxide layer that has a relatively high coefficient of thermal expansion (CTE) and serves primarily to thermally protect the underlying coating layers and the low-CTE ceramic substrate structural material (the component that is ultimately meant to be protected) from damage due to exposure at the high temperatures to be experienced in the application; An inner, or bottom silicon-containing/ silicate layer, which is in contact with the substrate, has a low CTE and serves primarily to keep environmental gases away from the substrate; and Multiple intermediate layers of alternating chemical composition (and, hence, alternating CTE).

Posted in: Briefs, TSP

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Using ALD To Bond CNTs to Substrates and Matrices

CNT-based field emitters could be made more durable. Atomic-layer deposition (ALD) has been shown to be effective as a means of coating carbon nanotubes (CNTs) with layers of Al2O3 that form strong bonds between the CNTs and the substrates on which the CNTs are grown. It should also be possible to form strong CNT/ substrate bonds using other coating materials that are amenable to ALD — for example, HfO2, Ti, or Ta. Further, it has been conjectured that bonds between CNTs and matrices in CNT/matrix composite materials could be strengthened by ALD of suitable coating materials on the CNTs.

Posted in: Briefs

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Omniscient Code Generation for 8-, 16- and 32-bit Microcontrollers

C-language programs are usually developed by teams of engineers who are often geographically dispersed, leading to redundant code and inconsistent variable declarations between modules. Traditional compilation technology compiles each module separately with no regard for what goes on in the other modules and with no information about how pointers, stacks, variables and functions are used throughout the whole program. Traditional compilers tend to over-allocate memory space for pointers, stacks and registers. They are unable to fully exploit the wide variety of memory maps, and register and stack configurations available in today’s microcontrollers. All too often, the programmer must resort to manual optimizations that compromise portability (Figure 1).

Posted in: Articles, Articles

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Laptop Refrigerator



Posted in: Blog

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New Mineral



Posted in: Blog

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Creating Patterned Multispectral Filters

In recent years the explosion in demand for multispectral imaging has coupled with the industry’s insatiable need for weight reduction, thereby greatly increasing the demand for more sophisticated approaches to producing optical filters that are used in these systems. One method to meet the challenge of reducing the weight of a multispectral system is to eliminate beam-splitting optics and multiple detectors by patterning a filter array on a single substrate, or directly on the CCD itself.

Posted in: Articles

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Drew Feustel, Astronaut, Johnson Space Center, Houston, TX

Astronaut Drew Feustel is scheduled to fly aboard the Space Shuttle Discovery when it makes what is projected to be the final manned mission to service the Hubble Space Telescope. Feustel will perform three of the five spacewalks planned for that mission.

Posted in: Who's Who

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