Stanford, Victoria L.

DOE OSTI2021

Effect of pressure on TATB and LX-17 thermal decomposition

Thermal decomposition of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) and its formulation LX-17 is studied at pressures from 0.1 to 7 MPa for both isothermal heating at 340 K and ramped heating at 1 to 6 K min -1 . Conditions that eliminate self-heating are thoroughly explored to avoid experimental artifacts. The increase in pressure accelerates the rate of decomposition by only about 10 %, but it substantially increases the enthalpy of the reaction, presumably because of longer volatile product residence times in the heated zone. The narrowness of the decomposition profile and the acceleratory phase during isothermal pyrolysis are consistent with a multistep autocatalytic mechanism, and the lack of a significant pressure effect suggests that the autocatalytic species have low volatility. The apparent activation energy is about 210 kJ/mol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Polyphosphonates as ionic conducting polymers

Polyphosphonates, a class of polymers with the generic formula –[P(R)(X)–OR'O] n –, exhibit a high degree of modularity due to the range of R, R', and X groups that can be incorporated. As such, these polymers may be designed with a polyethylene oxide (PEO) backbone (R' group) and employed as solid polymer electrolytes (SPEs). Two PEO-containing polyphosphonate analogs (R = Ph; X = S or Se) were doped with LiPF 6 and their conductivities were measured. Conductivities were similar (X = S) to or exceeding (X = Se) those of standard PEO systems (just below 10 -4 S/cm at 100°C). Binding models for Li + were generated using 31 P{ 1 H}NMR titration experiments. Binding of Li + by these polyphosphonates followed a positive cooperativity model, and varying the X group (S or Se) affected the observed cooperativity (Hill coefficient = 1.73 and 4.16, respectively). The presence of Se also leads to an increase in conductivity as temperature is raised above the T g , which is likely an effect of reduced Columbic interactions. Finally, because of their modularity and ease with which cation binding can be evaluated using 31 P{ 1 H} NMR titration experiments, polyphosphonates offer a unique approach for the modification of Li + ion battery technology.

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