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Controlled Plasma Reactor for Bulk Production of Extended Solid Materials

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: To develop and demonstrate a controlled low temperature plasma reactor capable of large scale, high volume production of extended solid materials with precisely engineered chemical and physical properties. 

DESCRIPTION: Extended solids are polymorphs/phases of otherwise simple molecules (e.g., CO2, H2, N2, N(H)x, CN) that are typically formed under ultrahigh pressure conditions (e.g., >10 GPa) where strong intermolecular bonding and tight crystal packing can be induced, which results in dramatic changes in physical, mechanical, and functional properties. Examples include superior structural (high strength, high thermal conductivity), energetic (propellant) and functional (e.g. ferroelectric, magnetic, optical) properties. The high pressures currently required to produce these materials is the major hurdle for large quantity productions and limit the per-reaction-yield to, at most, the microgram scale. However, the Army is currently developing new fabrication methods using advanced plasma techniques that permit access to these ultrahigh pressure polymorphs/phases without the experimental conditions which are currently required. Plasma-enhanced chemical vapor deposition reactors, which deposit the new material directly onto a substrate from the gas phase, have demonstrated viability [1]. The resulting material can manually be removed from the substrate after completion of the experiment and collected for follow-on testing and evaluation. However, existing laboratory-scale systems are disadvantageous in that the resultant product varies from batch to batch and, in general, such designs have low deposition rates. These limitations lead to low overall yields as a result of both the limited reactor dimensions and high degrees of user involvement in processing (reactor setup and taking down, deposit removal, and ex-situ characterizations) [2-4]. Moreover, the ability to fabricate the vast array of potential extended solid materials is predicated on precision control of the plasma parameters, such that they mimic the complex processes otherwise occurring in the high-pressure multistep synthesis and stabilization strategies. In order to acquire large-scale quantities of promising materials with high purity, the new plasma reactors must demonstrate significant advancements in the deposition rate, understanding of kinetics, and overall yield with satisfactory reproducibility, precision, with minimal human interference. Several technical barriers must also be overcome for large scale production including, but not limited to, variations in the gas flow kinetics, substrate material, and control of other environmental conditions. Current plasma deposition research efforts have primarily centered on the discovery of novel materials and plasma chemistries. In contrast, relatively little effort is devoted to bridging the scales from small-area deposition to large quantity production of materials with homogenous properties. It is not clear that techniques for plasma coatings can successfully translate to material production, which is the focus of this effort. The key issue (problem) has been the lack of knowledge on the significantly more complicated engineering formulations and process design necessary for scale-up, rather than the fundamental scientific understanding beyond the lab scale. The development and demonstration of a controlled low temperature plasma reactor capable of large scale, high volume production of extended solid materials (10s of grams to kilograms per day) with precisely engineered chemical and physical properties could widely advance Army systems. The commercialization of the plasma reactor for the manufacture of extended solids would be pervasive. 

PHASE I: Develop a conceptual design for a system that maximizes the deposition rate. This should be accomplished through control of the temperature and plasma power during the deposition process. Tunability of the system is also required and while this is dependent on electrode design and gas pressure, parameters should be on the 3-5 kV/mm range or sufficient to reach breakdown voltages in gases similar to nitrogen and air. The electrode and deposition temperatures must remain between 0 and 30°C, while deposition rates should be a minimum of 400 mg per 8 hours, with larger amounts preferred. The conceptual design will address the issues of reproducibility and user support while providing an avenue for further scalability. The focus in this phase is to identify the hurdles that prevent large scale production and address them with appropriate solutions. 

PHASE II: Application of conceptual design to generate larger scale quantities. Specifically, the concepts explored in Phase I should be practically implemented with a prototype reactor and demonstrate the uniformity and quantity of the produced material. The reactor should be capable of production ranging from a minimum of 20 grams to hundreds of grams of material in a period of 8 hours while maintaining the controls in the material properties that are identified in Phase I. In-situ diagnostics should be included in the design to monitor the deposition conditions and plasma phase chemistry should allow for increased automation tuning of deposited material, releasing the operator from constant monitoring of plasma conditions. 

PHASE III: Technology will be transferred to the Army. Commercialization of the design should be pursued. Potential commercial avenues include carbon sequestration and novel chemical synthesis. Successful production of large amounts of material provides avenues to plasma assisted chemical synthesis not currently available. 

REFERENCES: 

1: U. Kogelschatz. Dielectric-barrier Discharges: Their History, Discharge Physics, and Industrial Applications, Plasma Chem. and Plasma Process. 23 (2003) 1 (46 pp).

2:  R. Geiger and D. Staack. Analysis of solid products formed in atmospheric non-thermal carbon monoxide plasma, J. Phys. D: Appl. Phys. 44 (2011) 274005 (13 pp).

3:  I. Belov, S. Paulussen, A. Bogaerts. Appearance of a conductive carbonaceous coating in a CO2 dielectric barrier discharge and its influence on the electrical properties and the conversion efficiency, Plasma Sources Sci. Technol. 25 (2016) 015023 (13 pp).

4:  I. Belov, J. Vanneste, M. Aghaee, S. Paulussen, A. Bogaerts. Synthesis of micro- and nanomaterials in CO2 and CO dielectric barrier discharge, Plasma Process. Polym. 2016, DOI: 10.1002/ppap.201600065

KEYWORDS: Plasma, Energetic Material, High Voltage, Scale-Up, Dielectric Barrier Discharge, Glow Plasma Discharge, Manufacturing Process, Manufacturing Materials, Manufacturing Efficiency 

CONTACT(S): 

Timothy Jenkins 

(410) 306-1902 

timothy.a.jenkins51.civ@mail.mil 

Chi-Chin Wu 

(410) 306-1905 

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