Materials & Coatings

Spray CVD for Making Solar-Cell Absorber Layers

Spray CVD combines the advantages of metalorganic CVD and spray pyrolysis. Spray chemical vapor deposition (spray CVD) processes of a special type have been investigated for use in making CuInS2 absorber layers of thin-film solar photovoltaic cells from either of two subclasses of precursor compounds: [(PBu3) 2Cu(SEt)2In(SEt)2] or [(PPh3)2Cu(SEt)2 In(SEt)2] . CuInS2 is a member of the class of chalcopyrite semiconductors described in the immediately preceding article. [(PBu3)2Cu(SEt)2In(SEt)2] and [(PPh3)2 Cu(SEt)2In(SEt)2] are members of the class of single-source precursors also described in the preceding article.

Posted in: Briefs, TSP, Materials

Read More >>

Making Ternary Quantum Dots From Single-Source Precursors

Relative to a prior process, this process is simpler and safer. A process has been devised for making ternary (specifically, CuInS2) nanocrystals for use as quantum dots (QDs) in a contemplated next generation of highefficiency solar photovoltaic cells. The process parameters can be chosen to tailor the sizes (and, thus, the absorption and emission spectra) of the QDs.

Posted in: Briefs, TSP, Materials

Read More >>

Increasing Durability of Flame-Sprayed Strain Gauges

Low-oxygen heat treatments and internal platinum oxygen-diffusion barriers extend lifetimes. Thermally sprayed dielectric ceramic coatings are the primary means of attaching strain and temperature gauges to hot-section rotating parts of turbine engines. As hot-section temperatures increase, lifetimes of installed gauges decrease, and seldom exceed one hour above 2,000 °F ( ≈1,100 °C). Advanced engine components are expected to operate at temperatures approaching 2,200 °F ( ≈1,200 °C), and the required high-temperature lifetime is 10 hours minimum.

Posted in: Briefs, Materials

Read More >>

Multifunctional, High-Temperature Nanocomposites

Electrical and thermal conductivities increase with proportions of nanotubes. In experiments conducted as part of a continuing effort to incorporate multifunctionality into advanced composite materials, blends of multi-walled carbon nanotubes and a resin denoted “PETI-330” (wherein “PETI” is an abbreviation for “phenylethynyl- terminated imide”) were prepared, characterized, and fabricated into moldings. PETI-330 was selected as the matrix resin in these experiments because of its low melt viscosity (<10 poise at a temperature of 280 °C), excellent melt stability (lifetime >2 hours at 280 °C), and high temperature performance (>1,000 hours at 288 °C). The multi-walled carbon nanotubes (MWCNTs), obtained from the University of Kentucky, were selected because of their electrical and thermal conductivity and their small diameters. The purpose of these experiments was to determine the combination of thermal, electrical, and mechanical properties achievable while still maintaining melt processability.

Posted in: Briefs, TSP, Materials

Read More >>

Multilayer Impregnated Fibrous Thermal Insulation Tiles

Temperature rises are limited by transpiration cooling. The term “secondary polymer layered impregnated tile” (“SPLIT”) denotes a type of ablative composite-material thermal- insulation tiles having engineered, spatially non-uniform compositions. The term “secondary” refers to the fact that each tile contains at least two polymer layers wherein endothermic reactions absorb considerable amounts of heat, thereby helping to prevent overheating of an underlying structure. These tiles were invented to afford lighter-weight alternatives to the reusable thermal-insulation materials heretofore variously used or considered for use in protecting the space shuttles and other spacecraft from intense atmospheric- entry heating. Tiles of this type could also be useful on Earth as relatively lightweight components of fire-retardant structures.

Posted in: Briefs, TSP, Materials

Read More >>

Accounting for Uncertainties in Strengths of SiC MEMS Parts

Fracture strength of a part can be predicted as one statistical distribution. A methodology has been devised for accounting for uncertainties in the strengths of silicon carbide structural components of microelectromechanical systems (MEMS). The methodology enables prediction of the probabilistic strengths of complexly shaped MEMS parts using data from tests of simple specimens. This methodology is intended to serve as a part of a rational basis for designing SiC MEMS, supplementing methodologies that have been borrowed from the art of designing macroscopic brittle material structures.

Posted in: Briefs, TSP, Materials

Read More >>

Lithium Dinitramide as an Additive in Lithium Power Cells

This inorganic additive appears to act as a superior SEI promoter. Lithium dinitramide, LiN(NO2)2 has shown promise as an additive to nonaqueous electrolytes in rechargeable and non-rechargeable lithium-ion-based electrochemical power cells. Such non-aqueous electrolytes consist of lithium salts dissolved in mixtures of organic ethers, esters, carbonates, or acetals. The benefits of adding lithium dinitramide (which is also a lithium salt) include lower irreversible loss of capacity on the first charge/discharge cycle, higher cycle life, lower self-discharge, greater flexibility in selection of electrolyte solvents, and greater charge capacity.

Posted in: Briefs, Materials

Read More >>

White Papers

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.