Materials & Coatings

CO2 Sensors Based on Nanocrystalline SnO2 Doped With CuO

Miniature CO2 sensors could be mass-produced inexpensively. Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases.

Posted in: Briefs, TSP

Read More >>

Nanolaminate Mirrors With Integral Figure-Control Actuators

A report discusses the development of thin-shell curved mirrors comprised of metallic multilayer nanolaminate substrates that contain integral inplane actuators for controlling surface figure with micron-level precision. These mirrors, intended for incorporation into scientific imaging systems, would have areal mass densities of

Posted in: Materials, Briefs, TSP

Read More >>

Diaminobenzoquinones as Corrosion-Inhibiting Additives

Protection can extend beyond edges of paints to adjacent unpainted areas. Non-polymeric N,N´-di-N-hydrocarbyl- 2,5-diamino-1,4-benzoquinones (where the hydrocarbyl substituents are alkyl or aryl) have been found to be useful as corrosion-inhibiting additives for paints and other conventional coating materials that are applied to steel and other metals. Prior coating additives made from reactions of benzoquinones with diamines are polymeric. Such polymers are expensive and difficult to make. Moreover, being polymers, they cannot diffuse much and hence are believed not to protect uncoated areas of metal against corrosion. In contrast, when used in proper concentrations, the present non-polymeric diaminobenzoquinones provide enhanced protection that extends somewhat from the edges of coats into uncoated areas — an important advantage in situations in which there are imperfections (e.g., gaps, scratches, and blisters) in coats of paint.

Posted in: Materials, Briefs, TSP

Read More >>

Fluorinated Alkyl Carbonates as Cosolvents in Li-Ion Cells

These solvents offer advantages with respect to performance and safety. Partially fluorinated alkyl carbonate liquid compounds have been found to be excellent electrolyte cosolvents for rechargeable lithium-ion electrochemical cells. The benefits afforded by these and other ingredients of electrolyte solutions in rechargeable Li-ion cells have been investigated in continuing research directed toward extending the range of practical operating temperatures of the cells (from +40 °C down to –40 °C, and possibly even as low as –60 °C). Fluorinated solvents were perceived to be especially attractive in that they will result in inherently safer cells, due to their low flammability. This research at earlier stages was reported in a number of previous NASA Tech Briefs articles; namely, “Update on Electrolytes for Low-Temperature Lithium Cells” (NPO-20407), Vol. 24, No. 1, (January 2000), page 56; “Lithium Alkoxide Electrolyte Additives for Lithium-Ion Cells” (NPO- 20607), Vol. 25, No. 6 (June, 2001), page 52; “Aliphatic Ester Electrolyte Additives for Lithium-Ion Cells” (NPO-20601), Vol. 25, No. 6 (June, 2001), page 53; “Ethyl Methyl Carbonate as a Cosolvent for Lithium-Ion Cells” (NPO-20605), Vol. 25, No. 6 (June, 2001), page 53; and “Alkyl Pyrocarbonate Electrolyte Additives for Li-Ion Cells” (NPO-20775), which precedes this article.

Posted in: Materials, Briefs, TSP

Read More >>

Alkyl Pyrocarbonate Electrolyte Additives for Li-Ion Cells

Beneficial properties of films that form on carbon anodes are enhanced. Alkyl pyrocarbonates have been found to be useful as electrolyte additives for improving the low-temperature performances of rechargeable lithium-ion electrochemical cells. The beneficial effects of these and other additives have been investigated, along with various electrolyte formulations, in continuing research directed toward extending the range of practical operating temperatures from the present lower limit of –20 °C down to –40 °C, and even lower if possible. This research at earlier stages was reported in a number of NASA Tech Briefs articles; namely, “Update on Electrolytes for Low-Temperature Lithium Cells” (NPO-20407), Vol. 24, No. 1, (January 2000), page 56; “Lithium Alkoxide Electrolyte Additives for Lithium-Ion Cells” (NPO-20607), Vol. 25, No. 6 (June 2001), page 52; “Aliphatic Ester Electrolyte Additives for Lithium-Ion Cells” (NPO-20601), Vol. 25, No. 6 (June 2001), page 53; and “Ethyl Methyl Carbonate as a Cosolvent for Lithium-Ion Cells” (NPO-20605), Vol. 25, No. 6 (June 2001), page 53.

Posted in: Materials, Briefs, TSP

Read More >>

Chevrel Phases as Potential Thermoelectric Materials

Scattering of phonons by loosely bound atoms reduces thermal conductivity. Crystalline phases of compounds of general composition (Cuw, CuxFey, or Tiz)Mo6Se8 [where w

Posted in: Materials, Briefs, TSP

Read More >>

Improved Conversion Coating for Protection of Metals

This method is an environmentally friendly alternative to older processes.A simple, cost effective, environmentally friendly conversion-coating process has been developed for protecting a variety of metals against wear and corrosion and to increase adhesion of paints. This process results in the deposition of a thin, adherent coats of iron phosphate on treated metal substrates. This process is expected to supplant the environmentally hazardous chromate-based conversion- coating process heretofore used in the automotive and aerospace industries. It is also expected to supplant a process in which bearing races made of 440C stainless steel are pretreated with tricresyl phosphate.

Posted in: Materials, Briefs

Read More >>

White Papers

Serial Fabrics Improve System Design
Sponsored by Pentek
Liquid Silicone Rubber Takes the Heat
Sponsored by Proto Labs
Achieving Better Adhesion with Proper Surface Preparation
Sponsored by master bond
Reverse Engineering
Sponsored by Servometer
Next-Generation, Miniature High Voltage Power Modules
Sponsored by EMCO High Voltage
Avionics Reliability – Thermal Design Considerations
Sponsored by Mentor Graphics

White Papers Sponsored By: