Next Generation Energy Storage: An Examination of Lignin-based Carbon Composite Anodes for Sodium Ion Batteries through Modeling and Simulation

The current energy market relies heavily on fossil fuel sources; however, we are amidst a momentous shift towards wind, solar, and water based renewable energies. Large-scale energy storage allows renewable energy to be stored and supply the grid with consistent energy despite changing weather conditions. Improvements to large-scale energy storage in terms of cost, safety, and sustainability are crucial to wide-scale adoption. A promising candidate for large-scale energy storage are sodium-ion batteries using hard carbon anodes. Sodium is globally available, cheaper, and more sustainable than lithium, but requires a different anode structure. A sustainable hard carbon anode with excellent Li-ion performance has been manufactured from lignin, a byproduct of the paper and bio-ethanol industries. The carbon composite generated from lignin is composed of nanoscale crystallites dispersed in an amorphous graphene matrix whose structure is highly dependent on manufacturing process; however, the sodium-ion storage mechanisms for these lignin-based hard carbons are not well known. The purpose of the following work is to elucidate the Na-ion storage mechanisms for these lignin-based hard carbons and develop process-structure-property-performance (PSPP) relationships for them so an optimal Na-ion anode can be manufactured. To this end, reactive molecular dynamics simulations of lignin-based carbon composites were conducted with both lithium and sodium to compare the binding energies and mechanisms as well as their respective diffusive properties. It was found that lithium-ions prefer to localize in the hydrogen dense interfacial regions of the carbon composites while sodium prefer to adsorb to the surfaces of graphene fragments as well as the outer faces and edge-intercalation positions of the crystallites. At higher porosity, sodium shows a tendency to aggregate in the porous regions along curved planes of graphene, which gives the Na-ions the highest diffusion rate of all systems studied. To aid in determining the PSPP relationships of LBCCs, synchrotron x-ray scattering was performed, and models were created and refined using the Hierarchical Decomposition of the Radial Distribution Function (HDRDF) technique and software (now highly generalized). PSPP relationships with respect to processing temperature were quantitatively and qualitatively determined for the lignin-based carbon composites

An Experimental And Computational Investigation Of The Mechanical, Structural, And Hydrothermal Properties Of Mesoporous Materials

Periodic mesoporous materials have tunable pore sizes and high surface to volume ratios. Some of the most anticipated applications are those that call for energy harvesting in extreme environments, and these materials have a great structural stability to withstand the harsh conditions. In this work, the structural properties of mesoporous materials SBA-15 silica and Al-SBA-15 aluminosilica have been investigated by pressure dependent in situ small angle x-ray scattering (SAXS) using a diamond anvil cell (DAC) up to ~12 GPa in pressure. Hydrothermal measurements were also made in this manner to near supercritical water/steam conditions (to 255 °C and ~ 114 MPa) using the DAC. Analysis of the pressure dependent SAXS data yielded bulk modulus values of 12.0 +- 3.0 GPa and 34.7 +- 6.5 GPa for the SBA-15 silica and Al-SBA-15 aluminosilica respectively. The hydrothermal DAC experiment produced results detailing a small net swelling of 1-2% of the pore walls from the dissolution of water into the network structure. The Al-SBA-15 shows significantly greater hydrothermal stability than the SBA-15 silica. In addition, classical molecular dynamics simulations were performed on a series of silica and charge uncompensated aluminosilica amorphous glasses with varying percentage porosity, chemical composition, and onset of pressure at varying temperatures. The simulations were conducted from two types: 1) onset of pressure at the computer-glass transition temperature, and, 2) onset of pressure at room temperature. Within each type, simulations were varied by percentage porosity (0% to 60%) and by aluminum cation percentage (0% to 33%.) These simulations show a decrease in bulk modulus with respect to increasing percentage porosity that follows an exponential decay curve. This is consistent with experimental data from randomly porous materials. The bond angle analysis shows a unique bimodal distribution of Al-O-Al bond angles from the charge uncompensated aluminosilica. This is caused by edge sharing of adjacent tetrahedra due to local charge imbalance created by the substitution of the Al3+ ions

Whose Heritage?: Public Symbols of the Confederacy

This report compiles the collective history of memorials and monuments to Confederate soldiers in the Civil War, and provides a list of all known monuments, parks, schools, roads, and municipalities honoring Confederate military figures

Metabolically stabilized long-circulating PEGylated polyacridine peptide polyplexes mediate hydrodynamically stimulated gene expression in liver

A novel class of PEGylated polyacridine peptides was developed that mediate potent stimulated gene transfer in the liver of mice. Polyacridine peptides, (Acr-X) n-Cys-polyethylene glycol (PEG), possessing 2-6 repeats of Lys-acridine (Acr) spaced by either Lys, Arg, Leu or Glu, were Cys derivatized with PEG (PEG 5000 kDa) and evaluated as in vivo gene transfer agents. An optimal peptide of (Acr-Lys) 6-Cys-PEG was able to bind to plasmid DNA (pGL3) with high affinity by polyintercalation, stabilize DNA from metabolism by DNAse and extend the pharmacokinetic half-life of DNA in the circulation for up to 2 h. A tail vein dose of PEGylated polyacridine peptide pGL3 polyplexes (1 g in 50 l), followed by a stimulatory hydrodynamic dose of normal saline at times ranging from 5 to 60 min post-DNA administration, led to a high level of luciferase expression in the liver, equivalent to levels mediated by direct hydrodynamic dosing of 1 g of pGL3. The results establish the unique properties of PEGylated polyacridine peptides as a new and promising class of gene delivery peptides that facilitate reversible binding to plasmid DNA, protecting it from DNase in vivo resulting in an extended circulatory half-life, and release of transfection-competent DNA into the liver to mediate a high-level of gene expression upon hydrodynamic boost. \ua9 2011 Macmillan Publishers Limited All rights reserved

Studies of the mechanical and extreme hydrothermal properties of periodic mesoporous silica and aluminosilica materials

In order to assess the suitability of mesoporous materials for applications in energy harvesting/storage processes occurring under extreme conditions, their mechanical, thermal and hydrothermal properties need to be fully investigated. In this study, the bulk mechanical and extreme hydrothermal properties of periodic mesoporous SBA-15 type silica and SBA-15 type aluminosilica (Al-SBA-15) were investigated using in situ small angle x-ray scattering (SAXS). In situ SAXS measurements were made on dry mesoporous SBA-15 silica and Al-SBA-15 aluminosilica samples as a function of pressure (at room temperature) to ∼ 12 GPa and on the same mesoporous materials under extreme hydrothermal conditions (to 255 °C and ∼114 MPa) using the diamond anvil cell (DAC). The analyses of the high-pressure SAXS data indicate that the mesoporous Al-SBA-15 aluminosilica has substantially greater bulk mechanical stability (isothermal bulk modulus κ = 34.7(4.5) GPa) than the mesoporous SBA-15 silica (κ = 12.0(3.0) GPa). Our molecular dynamics (MD) simulations are able to accurately model the bulk mechanical stability properties of mesoporous SBA-15 silica but underestimate the same properties of Al-SBA-15 aluminosilica. Analysis of the in situ SAXS data measured under extreme hydrothermal conditions indicates swelling of the pore walls due to water incorporation that is more significant in mesoporous Al-SBA-15 aluminosilica (∼2x) than in SBA-15 silica. In addition, the Al-SBA-15 aluminosilica clearly exhibits superior hydrothermal stability compared to SBA-15 silica under the extreme experimental temperature and pressure conditions