In the ternary system CsCl – NaCl – H2O, at a temperature of 298.15 K, a double salt with the stoichiometric formula CsCl∙2NaCl∙2H2O(cr) is known to be formed. This double salt and the anhydrous CsCl(cr) are the end-members of a solid solution. For the pure double salt, the solubility constant was determined. The obtained value was applied to calculate the solubility diagram also of the quaternary system CsCl – NaCl – KCl – H2O and the quaternary-reciprocal system Cs+, Na+ || Cl−, SO42− – H2O. The solubility constant together with a solid solution between CsCl·2NaCl·2H2O(cr) and CsCl(cr) were implemented in THEREDA, which extends the applicability of the existing cesium dataset.

For the polythermal Pitzer dataset of the hexary system of oceanic salts (Na+, K+, Mg+2, Ca+2, Cl-, SO4-2 - H2O) including acids and hydroxides the data selection is documented in detail in the report “THEREDA - Thermodynamische Referenzdatenbasis” (Altmaier et al. 2011, https://www.grs.de/de/aktuelles/publikationen/grs-265-thereda-thermodynamische-referenzdatenbasis-abschlussbericht). The present short communication supplements this report by the numerical values of all temperature coefficients.

<p dir="ltr">Energetic materials contain microstructural defects like cracks, voids, grain boundaries, and interfaces which act as nucleation sites for ignition and detonation when shocked. Finite element (FE) models are currently unable to capture explicit microstructure with voids, cracks, and randomly oriented grains with representative mechanics, thermal conduction, and reactivity that exhibit the full shock to detonation transition (SDT). Modern computational efforts seek to accurately model material response while also balancing efficiency and speed. Work presented in this thesis will highlight all of these microstructural features, investigate mechanical and thermal response of each microstructure, connect these results to what is observed in other experimental and computational work, and bring computational modeling even closer to an efficient model that contains all processes necessary to replicate SDT.</p><p dir="ltr">In energetic materials (EM), voids are irregular in shape, but most computational work has focused on circular void collapse behavior. However, geometries that contain irregularities or corners are more likely to act as initiation sites due to stress concentrations. Validation and calibration of void simulations with experimental lengthscales and loading conditions is still limited. Plus, pore collapse modeling efforts at low impact velocities do not model fracture, and it is known that cracks cause more extreme temperatures than pores.</p><p dir="ltr">Other microstructure characteristics like cracks and grains have sub-micrometer length scale, and influence the mechanical and thermal response of materials under extreme conditions. However, approximations and coarse-graining must be applied to continuum FE simulations to fit length and timescales required to capture phenomena such as detonations that occur at a millimeter scale. With the use of machine learning (ML), numerical models can be trained on results of small-scale microstructure simulations and applied to larger length and time-scale simulations. The ML model follows Microstructure-Informed Shock-induced Temperature net (MISTnet) model and is trained upon stress, strain, temperature, pressure, and slip data and includes crystal plasticity, fracture, friction, an equation of state, and heat conduction. The ML model is able to predict temperature fields behind the shock, concentrations at grain boundaries, and the influence of grain orientation.</p><p dir="ltr">Accurate temperature values are extremely important to modeling EM because thermal hot spots (HS) are the main cause of ignition. Critical HS cause the chemical reactions which transition the shock front into a detonation, but many continuum models do not include chemistry in their framework. A 1-step Arrhenius reaction model is added to FE mechanics model to investigate the relationship HS have on the run to detonation (RTD).</p>

<p dir="ltr">Insights from research into the natural photosynthetic processes are applied to inform the rational design of inorganic catalysts. The study of these synthetic systems – artificial photosynthesis – will lead towards the development of a device able to absorb light, convert and store the energy in the form of chemical bonds. The water-splitting reaction, a bottleneck of the photosynthetic process, is a key barrier to overcome in this endeavor. Thus, the focused study of water-oxidation catalysts able to facilitate this difficult reaction is performed, in order to develop a green-energy solution in the form of an artificial photosynthesis system.</p>

The THEREDA model has been extended by phases and species formed within the title system. A temperature range of 0 °C to 100 °C is considered. Most of the solubility products, Pitzer parameters and association constants were adapted from the model of Königsberger et al. (Königsberger, E., Königsberger, L.-C., Gamsjäger, H.: Low-temperature thermodynamic model for the system Na2CO3−MgCO3−CaCO3−H2O. Geochim. Cosmochim. Acta, 63, (1999), pp. 3105–3119, DOI 10.1016/S0016-7037(99)00238-0). Literature on solubility data of carbonates of magnesium and calcium is critically evaluated. As far as experimental solubility data were available, they were compared with model calculations. The data comprise the minerals magnesite (MgCO3), nesquehonite (MgCO3∙3H2O), lansfordite (MgCO3∙5H2O), hydromagnesite (4MgCO3∙Mg(OH)2∙4H2O), dypingite (4MgCO3∙Mg(OH)2∙5H2O), calcite (CaCO3), aragonite (CaCO3), vaterite (CaCO3), ikaite (CaCO3∙6H2O), dolomite (MgCO3∙CaCO3), huntite (3MgCO3∙CaCO3), magnesian calcite (solid solution between CaCO3 and MgCO3), eitelite (Na2CO3·MgCO3), pirssonite (Na2CO3·CaCO3·2H2O), gaylussite (Na2CO3·CaCO3·5H2O), natrite (Na2CO3), thermonatrite (Na2CO3·H2O), Na2CO3·7H2O, natron (Na2CO3·10H2O), nahcolite (NaHCO3), wegscheiderite (Na2CO3·3NaHCO3) and trona (Na2CO3·NaHCO3·2H2O). There are minerals known as artinite (MgCO3∙Mg(OH)2∙3H2O) or barringtonite (MgCO3·2H2O), for which no solubility data exist. The literature survey also covers geochemical observations on the existence of carbonate minerals, laboratory investigations on the decomposition, formation and conversion as well as spectral and XRD characterization of carbonate phases. For important minerals, such as magnesite or hydromagnesite, the uncertainty of the solubility constants is large. The added Pitzer parameters, concern the binary cation - carbonate, cation - hydrogen carbonate and the ternary interactions, including mixing parameters of the anions HCO3-, CO32- and OH-. Mixing parameters of these anions with chloride or sulfate are not considered in this work. From the data situation and the modelling results, conclusions are drawn with respect to future experimental work to obtain more reliable equilibrium data.

<p>Additive manufacturing of gun propellants is an emerging and promising field which addresses the limitations of conventional manufacturing techniques. Gun propellants are manufactured using wetted extrusion, which uses volatile solvents and dies of limited and constant geometries. On the other hand, additive techniques are faced with the challenges of maintaining the gun propellant’s energetic content as well as its structural integrity during high pressure combustion. The work presented in this thesis demonstrates the feasibility of producing functioning gun propellant grains using vibration-assisted 3D printing, a novel method which has been shown to extrude extremely viscous materials such as clays and propellant pastes. At first, the technique is compared to screw-driven additive methods which have been used in printing gun propellant pastes with slightly lower energetic content. In chapter two, diethylene glycol dinitrate (DEGDN), a highly energetic plasticizer, was investigated due to its potential to replace nitroglycerin in double base propellants with high nitroglycerin content. A novel isoconversional method was applied to analyze its decomposition kinetics. The ignition and lifetime values of diethylene glycol dinitrate were obtained using the new isoconversional method, in order to assess the safety of using the plasticizer in a modified double base propellant. In chapter three, a modified double base propellant (M8D) containing DEGDN was additively manufactured using VAP. The printed strands had little to no porosity, and their density was nearly equal to the theoretical maximum density of the mixture. The strands were burned at high pressures in a Crawford bomb and the burning was visualized using high speed cameras. The burning rate equation as a function of the M8D propellant as a function of pressure was obtained. Overall, this work shows that VAP is capable of printing highly energetic gun propellants with low solvent content, low porosity, with high printing speeds, and which have consistent burning characteristics at high pressures. </p>

This report documents the selection of thermodynamic data for lead and lead compounds. Except for elemental lead, it is restricted to lead in the oxidation state +II (plumbous lead). Besides formation constants and, in part, enthalpies of formation and standard entropies, interaction coefficients for the correction of activity coefficients following the Pitzer formalism are provided. Aqueous complexes of lead with chloride, sulphate, and hydroxide are explicitly accounted for in the Pitzer model. Wherever possible, the validity of selected data is tested by recalculating experimental data. The presented data set is valid for 298.15K only.