Graphene Reinforced Glassy Carbon Particle Beam Windows

Secondary particle beams require beam windows that isolate the target (usually in air) from the primary particle beam vacuum. Advanced beam window solutions are needed that can withstand anticipated increases in beam power and intensity that will result in higher thermal shock on the window and increased oxidative erosion rates on the air-side caused by increased temperatures. Carbon-based windows, in particular glassy carbon windows are of interest to minimize interaction with the beam. The attractive properties of glassy carbon are: 1. Low atomic number 2. Low thermal expansion 3. High strength and low young’s modulus 4. Low gas permeability and low outgassing for ultrahigh vacuum use. The one liability of glassy carbon is its low thermal conductivity, nominally 5 W/mK, which will exacerbate temperature rise, oxidation, and thermal shock concerns as beam powers increase. TA&T proposes development of graphene reinforced glassy carbon (GRGC) composites to increase the thermal conductivity and address this Achilles heel of glassy carbon. The intrinsic thermal conductivity of graphene is among the highest measured for any material and is in the range 2,000 – 4,000 W/mK. Graphene as a reinforcing phase has been shown to increase the thermal conductivity of the matrix material by up to two orders of magnitude. For beam windows this would substantially increase heat spreading away from the beam zone of the window and improve thermal shock resistance, and reduce maximum temperature and air-side oxidation of the window. Increased thermal conductivity would also improve the effectiveness of edge-cooling schemes to minimize temperature increase.
In the Phase I effort graphene oxide (GO) particles will be dispersed into glassy carbon precursor resin and formed into thin layers to promote alignment of the graphene platelettes to maximize in-plane thermal conductivity. Thin layers of GO/resin composite will be stacked and laminated and hot pressed to form graphene reinforced glassy carbon window blanks. The experimental work will determine the effect of graphene concentration on the mechanical properties (flexure strength), and thermal (thermal conductivity). The results of Phase I will be used in Phase II to optimize GRGC properties. The optimized properties will be used to design, fabricate and test particle beam windows at a selected DOE particle beam user facility in Phase II. In addition to enabling improved windows for high energy particle beam experiments, the reinforced glassy carbon material will find various other applications such as thruster bodies for rocket propulsion, more durable carbon-based electrodes for electrochemistry applications, bi-polar plates for advanced batteries, catalyst support structures, and structural bio-implants. Key Words: carbon-based beam windows, high energy physics, glassy carbon, graphene, graphene oxide, thermal conductivity, high strength, thermal shock resistance