Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Synthesis and Characterization of Zr2SC Ceramics

Abstract: MAX-phase Zr2SC ceramics were synthesized by hot pressing mixtures containing ZrH2, carbon or ZrC, and ZrS2, WS2, or FeS2 as sulfur sources. The Zr2SC synthesized with FeS2 had a typical MAX-phase laminated structure, good thermal shock resistance, thermal stability to 2100 °C, and were readily machineable. The flexural strength was about 250 MPa up to 800 °C. The thermal expansion coefficient was 8.8 × 10−6/°C in the 25–2000 °C-temperature range, thermal conductivity was 38 W/m-K at 100 °C and about 30 W/m-K at 1100 °C, and specific heat at temperatures from 100 to 1100 °C ranged from 0.4 to 0.5 kJ/kg °C. Load–deflection curves exhibited plastic deformation from RT to 2066 °C. The sample deflection at fracture demonstrated significant dependence on temperature with a minimum at 1510 °C. In arc heater testing at 2150 °C for 23 s, the material developed an adherent, protective scale.

The effect of fluid loading on radiation efficiency

Abstract: The metric “radiation efficiency,” used to estimate a panel’s radiated acoustic power from a measure of its normal velocity, is typically derived under the condition of very light fluid loading. This paper shows that efficiencies calculated in this manner can significantly overestimate the radiated power when the condition of light fluid loading is not met, as can be the case for steel plates in water. It is also shown that, when fluid loading is not light, a baffled semi-infinite plate is not a good model for an interior support. Numerical results are presented for radiation efficiencies calculated for steel plates in water, and are compared to those calculated under the assumption of vanishing fluid loading.

Overcharge and thermal destructive testing of lithium metal oxide and lithium metal phosphate batteries incorporating optical diagnostics

Abstract: Lithium batteries have a tendency to fail violently under adverse conditions leading to the rapid venting of gas. Overcharge, thermal heating, and a combination of the two conditions are applied here to investigate the gas venting process. A test chamber has been constructed with data recordings including chamber pressure and temperature, battery voltage, current, and surface temperature as functions of time throughout the charging and failure processes. High-speed imaging and schlieren flow visualization are used to visualize the gas venting process. A direct comparison between lithium iron phosphate based K2 26650 and lithium nickel manganese cobalt oxide LG 18650 cells is made through a test series of the three failure methods. Failure under thermal, overcharge, and thermal-overcharge conditions are generally similar in terms of the gas venting process, but are observed to have increasingly energetic failures. The thermal-overcharge abuse condition demonstrates an ability to reconnect via internal short circuit even after an initial electrical failure seen as the refusal to accept charge. This reconnection is associated with a secondary, more energetic failure which can produce weak shock pressure waves.