Materials

Liquid Coatings for Reducing Corrosion of Steel in Concrete

Structures could be protected more easily and less expensively. Inorganic coating materials are being developed to slow or stop corrosion of reinforcing steel members inside concrete structures. It is much simpler and easier to use these coating materials than it is to use conventional corrosion-inhibiting systems based on impressed electric currents. Unlike impressed electrical corrosion-inhibiting systems, these coatings do not require continuous consumption of electrical power and maintenance of power-supply equipment. Whereas some conventional systems involve the use of expensive arc-spray equipment to apply the metallic zinc used as the sacrificial anode material, the developmental coatings can be applied by use of ordinary paint sprayers.

Posted in: Materials, Briefs

Read More >>

Processable Polyimides Containing APB and Reactive End Caps

Properties can be tailored through choice of proportions of dianhydrides and APB. Imide copolymers that contain 1,3-bis (3- aminophenoxy) benzene (APB) and other diamines and dianhydrides and that are terminated with appropriate amounts of reactive end caps have been invented. The reactive end caps investigated thus far include 4-phenylethynyl phthalic anhydride (PEPA), 3-amino- phenoxy-4'- phenylethynyl benzophenone (3-APEB), maleic anhydride (MA), and 5-norbornene-2,3-dicarboxylic anhydride [also known as nadic anhydride (NA)]. The advantage of these copolyimides terminated with reactive groups, relative to other polyimides terminated with reactive groups, is a combination of (1) higher values of desired mechanical-property parameters and (2) greater ease of processing into useful parts.

Posted in: Materials, Briefs

Read More >>

Rod/Coil Block Copolyimides for Ion-Conducting Membranes

Lithium cells and fuel cells could function over wider temperature ranges. Rod/coil block copolyimides that exhibit high levels of ionic conduction can be made into diverse products, including dimensionally stable solid electrolyte membranes that function well over wide temperature ranges in fuel cells and in lithium-ion electrochemical cells. These rod/coil block copolyimides were invented to overcome the limitations of polymers now used to make such membranes. They could also be useful in other electrochemical and perhaps some optical applications, as described below.

Posted in: Materials, Briefs

Read More >>

Scandia-and-Yttria-Stabilized Zirconia for Thermal Barriers

These compositions offer thermal stability greater than that of yttria-stabilized zirconia. Zirconia stabilized with both scandia and yttria in suitable proportions has shown promise of being a superior thermal-barrier coating (TBC) material, relative to zirconia stabilized with yttria only. More specifically, a range of compositions in the zirconia/scandia/yttria material system has been found to afford increased resistance to deleterious phase transformations at temperatures high enough to cause deterioration of yttria- stabilized zirconia.

Posted in: Materials, Briefs

Read More >>

Switching and Rectification in Carbon-Nanotube Junctions

Research shows promise for nanoscale electronic devices. Figure 1. Symmetric and Asymmetric Carbon-Nanotube Multiterminal carbon-nanotube junctions are under investigation as candidate components of nanoscale electronic devices and circuits. Three-terminal "Y" junctions of carbon nanotubes (see Figure 1) have proven to be especially interesting because (1) it is now possible to synthesize them in high yield in a controlled manner and (2) results of preliminary experimental and theoretical studies suggest that such junctions could exhibit switching and rectification properties.

Posted in: Materials, Briefs

Read More >>

Environmentally Safer, Less Toxic Fire-Extinguishing Agents

Water droplets would be microencapsulated in flame-retardant polymers. Fire-extinguishing agents comprising microscopic drops of water micro- encapsulated in flame-retardant polymers have been proposed as effective, less toxic, non-ozone- depleting, non-global- warming alternatives to prior fire-extinguishing agents. Among the prior fire-extinguishing agents are halons (various halocarbon fluids), which are toxic and contribute both to depletion of upper- atmospheric ozone and to global warming. Other prior fire-extinguishing agents are less toxic and less environmentally harmful but, in comparison with halons, are significantly less effective in extinguishing fires.

Posted in: Materials, Briefs

Read More >>

Multiaxial Temperature- and Time-Dependent Failure Model

This model should be applicable to a variety of materials. A temperature- and time-dependent mathematical model predicts the conditions for failure of a material subjected to multiaxial stress. The model was initially applied to a filled epoxy below its glass-transition temperature, and is expected to be applicable to other materials, at least below their glass-transition temperatures. The model is justified simply by the fact that it closely approximates the experimentally observed failure behavior of this material: The multiaxiality of the model has been confirmed (see figure) and the model has been shown to be applicable at temperatures from —20 to 115 °F (–29 to 46 °C) and to predict tensile failures of constant-load and constant-load-rate specimens with failure times ranging from minutes to months.

Posted in: Materials, Briefs

Read More >>

White Papers

What They Didn’t Teach You in Engineering School About Heat Transfer
Sponsored by Mentor Graphics
Spherical Plain Bearing
Sponsored by AST Bearings
Is There an Easy Way to Cut the Cost of EWIS Compliance?
Sponsored by Mentor Graphics
Improving Absorption Measurements through Light Source Selection
Sponsored by Ocean Optics
Identification of Circuit Card Assembly Contamination Using NIR Spectroscopy
Sponsored by Ocean Optics
Introduction to Hypervisor Technology
Sponsored by Curtiss-Wright Controls Embedded Computing

White Papers Sponsored By: