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The thermal properties of CL-20 explosive in the bulk and confined in controlled pore glass matrices to nanoscale dimensions were studied using dynamic differential scanning calorimetry. The decomposition reaction of the CL-20 was found to be accelerated in 12-nm-diameter pores compared to the bulk CL-20 with the onset of the decomposition occurring 16–24 °C lower and a fourfold to sevenfold larger reaction rate constant. The total heat of decomposition was found to be independent of pore size and heating rate, and the average activation energy for all samples was found to be 160 ± 7 kJ mol−1.

The structural recovery of amorphous glassy materials is nonlinear and nonexponential, and the relaxation process can be described by the phenomenological Tool–Narayanaswamy–Moynihan and Kovacs–Aklonis–Hutchinson–Ramos models. The nonlinearity parameter x in these models can be determined by several methods, including inflectional analysis, time–temperature superposition, and a new modified temperature-jump method, the latter a modification of the two-step Lagasse et al.’s method. The activation energy ∆h/R can also be determined by the first two methods. In this paper, the applicability of these methods for determining x and ∆h/R is analyzed using simulated structural recovery data as a function of aging time, after cooling at high rates such as those obtainable experimentally using Flash DSC. The results indicate that the activation energy obtained by the time–temperature superposition method is slightly better than that estimated by the inflectional analysis method. The results also indicate that the nonlinearity parameter x can be obtained by the inflectional analysis method for β = 1.0 and for low x and high β. On the other hand, the new modified temperature-jump method works for a broader range of x and β.

The thermal properties of bulk and nanoconfined HMX were studied using differential scanning calorimetry in dynamic scanning mode at rates ranging from 0.3 to 100 °C/min. At the slowest heating rates, decomposition occurs in the solid phase; at intermediate heating rates, it starts in the solid phase, melts, and finishes with a faster rate of reaction in the liquid state; and at the highest heating rates, the decomposition is entirely in the liquid phase. The activation energy decreases with conversion and is highest for 12 nm-diameter pores. The decomposition reaction is accelerated for nanoconfined HMX compared to the bulk with the onset of decomposition decreased by 1–5 °C in 50 nm-diameter pores and by 4–11 °C in 12 nm-diameter pores. The kinetics of decomposition is well described by a first-order autocatalytic reaction model with the reaction rate constants increasing with nanoconfinement. In addition, the reaction rate constant is one order of magnitude higher in the melt state than in the solid state.

Novel ionic liquids (ILs) were designed and synthesized to contain aromatic groups on the imidazolium cation that non-covalently interact with graphene surfaces. This route enables the dispersion of pristine graphene without covalent functionalization or an additive stabilizer; such dispersions are stable against aggregation and display high concentration values. We find that ILs without these aromatic groups are less effective in graphene dispersion, and the dispersed graphene concentration increases with increasing interaction between the cation and graphene surface. Density functional theory (DFT-D3) calculations support the experimental observations and provide a foundation for predictive modeling of IL design for optimal graphene dispersions.

Here we demonstrate through experiment and simulation the polymer-assisted dispersion of inorganic 2D layered nanomaterials such as boron nitride nanosheets (BNNSs), molybdenum disulfide nanosheets (MoS2), and tungsten disulfide nanosheets (WS2), and we show that spray drying can be used to alter such nanosheets into a crumpled morphology. Our data indicate that polyvinylpyrrolidone (PVP) can act as a dispersant for the inorganic 2D layered nanomaterials in water and a range of organic solvents; the effectiveness of our dispersion process was characterized by UV-vis spectroscopy, microscopy and dynamic light scattering. Molecular dynamics simulations confirm that PVP readily physisorbs to BNNS surfaces. Collectively, these results indicate that PVP acts as a general dispersant for nanosheets. Finally, a rapid spray drying technique was utilized to convert these 2D dispersed nanosheets into 3D crumpled nanosheets; this is the first report of 3D crumpled inorganic nanosheets of any kind. Electron microscopy images confirm that the crumpled nanosheets (1–2 μm in diameter) show a distinctive morphology with dimples on the surface as opposed to a wrinkled, compressed surface, which matches earlier simulation results. These results demonstrate the possibility of scalable production of inorganic nanosheets with tailored morphology.

We demonstrate three different techniques (dialysis, vacuum filtration, and spray drying) for removal of dispersants from liquid-exfoliated graphene. We evaluate these techniques for elimination of dispersants from both the bulk liquid phase and from the graphene surface. Thermogravimetric analysis (TGA) confirms dispersant removal by these treatments. Vacuum filtration (driving by convective mass transfer) is the most effective method of dispersant removal, regardless of the type of dispersant, removing up to ∼95 wt.% of the polymeric dispersant with only ∼7.4 wt.% decrease in graphene content. Dialysis also removes a significant fraction (∼70 wt.% for polymeric dispersants) of un-adsorbed dispersants without disturbing the dispersion quality. Spray drying produces re-dispersible, crumpled powder samples and eliminates much of the unabsorbed dispersants. We also show that there is no rapid desorption of dispersants from the graphene surface. In addition, electrical conductivity measurements demonstrate conductivities one order of magnitude lower for graphene drop-cast films (where excess dispersants are present) than for vacuum filtered films, confirming poor inter-sheet connectivity when excess dispersants are present.