Feasibility Study and Demonstration of an Aluminum and Ice Solid Propellant

Aluminum-water reactions have been proposed and studied for several decades for underwater propulsion systems and applications requiring hydrogen generation. Aluminum and water have also been proposed as a frozen propellant, and there have been proposals for other refrigerated propellants that could be mixed, frozen in situ, and used as solid propellants. However, little work has been done to determine the feasibility of these concepts. With the recent availability of nanoscale aluminum, a simple binary formulation with water is now feasible. Nanosized aluminum has a lower ignition temperature than micronsized aluminum particles, partly due to its high surface area, and burning times are much faster than micron aluminum. Frozen nanoscale aluminum and water mixtures are stable, as well as insensitive to electrostatic discharge, impact, and shock. Here we report a study of the feasibility of an nAl-ice propellant in small-scale rocket experiments. The focus here is not to develop an optimized propellant; however improved formulations are possible. Several static motor experiments have been conducted, including using a flight-weight casing. The flight weight casing was used in the first sounding rocket test of an aluminum-ice propellant, establishing a proof of concept for simple propellant mixtures making use of nanoscale particles

On the use of solid-state 45 Sc NMR for structural investigations of molecular and silica-supported scandium amide catalysts

International audienc

The D-HMQC MAS-NMR technique: An efficient tool for the editing of through-space correlation spectra between quadrupolar and spin-1/2 (³¹P, ²⁹Si, ¹H, ¹³C) nuclei

The D-HMQC (dipolar heteronuclear multiple-quantum coherence) technique is a recently developed NMR pulse sequence particularly suitable for the investigation of spatial proximity between quadrupolar and spin-1/2 nuclei. Compared to the cross-polarisation magic-angle spinning technique applied to a quadrupolar nucleus, D-HMQC does not require time-consuming optimisations and exhibits on the quadrupolar spin a better robustness to irradiation offset and to Cq values and radiofrequency field. Furthermore, the high robustness to irradiation offset makes of the D-HMQC sequence the technique of choice for the structural characterisation of materials especially at high magnetic field. We show here how the D-HMQC can be easily implemented and optimised to give access to the structural analysis of silicate-, phosphate-, carbon- and proton-containing materials. An emphasis will be on describing the most popular dipolar recoupling schemes that can be used in that sequence and providing their advantages and drawbacks

Chapter 4. Two-dimensional Methods for Half-integer Quadrupolar Nuclei

International audienc

Calcium phosphates and hydroxyapatite. Solid-state NMR experiments and first-principles calculations

Various calcium phosphates and hydroxyapatite (HAp) have been fully characterized by one- and two-dimensional solid-state nuclear magnetic resonance (NMR) experiments and first principles calculations of NMR parameters, such as chemical shift anisotropy (CSA) and electric field gradient tensors for all nuclei. Such compounds act as useful biocompatible materials. The projector augmented wave (PAW) and gauge including PAW methods allowed the complete assignment of spectra, including (1)H magic-angle spinning (MAS) spectra for which ultimate resolution is not attained experimentally. (1)H CSA tensors and orientation of the principal axes systems have been also discussed. (17)O parameters have been calculated for a large variety of oxo-bridges and terminal oxygen atoms, including P-O-Si fragments characteristic for silicophosphate phases. The (delta(iso), C (Q)) sets of values allowed the clear distinction between the various oxygen atoms in a calculated (17)O 3-quantum MAS experiment. Such an approach should be of great help for the description of interfaces in complex materials, in terms of structure and chemical composition

Thermophysical Properties of Te-based II-VI Semiconductors: Reduced Algorithms for Thermal Diffusivity Determination

This paper presents methodologies for measuring the thermal diffusivity using the difference between temperatures measured at two, essentially independent, locations. A heat pulse is applied for an arbitrary time to one region of the sample; either the inner core or the outer wall. Temperature changes are then monitored versus time. The thermal diffusivity is calculated from the temperature difference versus time. No initial conditions are used directly in the final results