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Experimental Methods for Predicting Material Interactions with Plasmas

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: Develop new experimental methods to evaluate material-plasma interactions to advance material response models. 

DESCRIPTION: At hypersonic velocities above M ~ 7, the flow fields near vehicle bodies become dissociated and ionize, forming significant levels of plasma. These conditions can exist for portions of the flight trajectory for a variety of vehicles including space re-entry, hypersonic vehicles, and missiles. The shock wave at the nose of the vehicle and viscous boundary layers are significant sources of free electrons. The plasma can be further compounded by the ejection of ablating materials into the flow field that can alter the chemistry and density of the resulting plasma. From the boundary layer near the vehicle, the plasma flows into near body recirculation regions that are just behind the vehicle and then into the trailing wake region. The plasma around vehicles traveling at high Mach can impact the material response to the environment. The influence of the ions can impact the radiative and absorption characteristics of the material that it interacts with. Ground based tests that contain dissociated ions (i.e. arcjets and inductively coupled plasmatrons) have been shown to impact the oxidation and ablation properties of materials to a greater extent relative to those that do not (burner rigs, oxyacetylene torches, laser heating, etc). Vehicle designers rely on these ground tests to predict properties of the emerging materials of interest such as ultra-high temperature (UHT) carbides and borides. However, the disparity of testing methods introduce difficultly in the ability to isolate the impact of the plasma and dissociated species on the material and thus predict how they will behave in flight. High temperature catalytic effects of the parent material and of the material as it changes in response to its environment are not well-understood and often ignored in the evaluation of the material response. The objective of this effort is to develop and validate new techniques to test UHT materials in high temperature (>1600 deg. C) exposures both with and without dissociated ions of oxygen and nitrogen. Furthermore, the development of diagnostic tools to evaluate the chemical species in the flow field to understand the interaction between the material and flow field is required. 

PHASE I: Develop a candidate ground based test facility and show the ability to produce environments containing chemical species relevant to high Mach flight such as dissociated oxygen or dissociated nitrogen that can impinge upon or in some way react with a heated material sample. Temperatures are expected to exceed 1600 deg. C. Initial tests of a candidate material would illustrate the use of non-contact diagnostics to describe temperature and characterize material changes during environmental exposure. 

PHASE II: Further develop test and diagnostic facilities proving capability on a suite of materials. Develop a database of material-environment interactions that will be utilized to develop materials models that can predict material performance under environments for a range of temperatures and concentration of ionized gas species. 

PHASE III: Finalize the development of the test facility, diagnostic tools, and materials models that can be made available for the materials test community to perform relevant ground test operations. 

REFERENCES: 

1: Bond, J.W. "Plasma Physics and Hypersonic Flight", Journal of Jet Propulsion, 28 [4] 1958, pp. 228-235.

2: Monteverde, F.

3:  Savino, R. "Stability of ultra-high-temperature ZrB2–SiC ceramics under simulated atmospheric re-entry conditions", Journal of the European Ceramic Society, 27 [16] 2007, pp. 4797-4805.

KEYWORDS: Plasma, Ultra High Temperature Materials, Composites 

CONTACT(S): 

Carmen Carney (RXCC) 

(937) 255-9154 

carmen.carney.1@us.af.mil 

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