Neutral and Cation-Free LTA-Type Aluminophosphate (AlPO₄) Molecular Sieve Membrane with High Hydrogen Permselectivity

Neutral and Cation-Free LTA-Type Aluminophosphate (AlPO4) Molecular Sieve Membrane with High Hydrogen Permselectivit

Nanoparticle Precursor into Polycrystalline Bi₂Fe₄O₉: An Evolutionary Investigation of Structural, Morphological, Optical, and Vibrational Properties

Mullite-type Bi₂Fe₄O₉ was synthesized using a polyol-mediated method. X-ray powder diffraction (XRD) revealed that the as-synthesized sample is nanocrystalline. It transformed into a rhombohedral perovskite-type BiFeO₃ followed by a second transformation into mullite-type Bi₂Fe₄O₉ during heating. Each structural feature, from as-synthesized into crystalline phase, was monitored through temperature-dependent XRD in situ. The locally resolved high resolution transmission electron micrographs revealed that the surface of some heated samples is covered by 4–13 nm sized particles which were identified from the lattice fringes as crystalline Bi₂Fe₄O₉. XRD and Raman spectra demonstrate that the nucleation of both BiFeO₃ and Bi₂Fe₄O₉ might simultaneously commence; however, their growth and ratios are dependent on temperature. The diffuse UV/vis reflectance spectra showed fundamental absorption edges between 1.80(1) and 2.75(3) eV. A comparative study between the “derivation of absorption spectrum fitting method” (DASF) and the Tauc method suggests Bi₂Fe₄O₉ to be a direct band gap semiconductor

DataSheet1_Optimizing lunar regolith beneficiation for ilmenite enrichment.docx

Over the past few years, the international space industry has focused extensively on advancing technologies to enable prolonged human space exploration missions. The primary limiting factor for these endeavors is the spacecraft’s capacity to transport and store essential supplies from Earth to support human life and mission equipment throughout the mission’s duration. In-situ resource utilization (ISRU) is the preferred solution for this challenge. Previous lunar missions have identified the presence of oxygen within the lunar regolith, which is an important resource for human space exploration missions. Oxygen is present in many different minerals within the lunar regolith out of which, ilmenite provides the highest yield of oxygen per unit mass using hydrogen reduction. However, the distribution of ilmenite is neither high nor uniform throughout the lunar surface and therefore, needs beneficiation, which is an important intermediate step for ilmenite-based oxygen production. A regolith beneficiation testbed was developed at DLR Bremen which is a TRL 4 level representation of the technology. The testbed has multiple process parameters that can be adjusted to produce the desired feedstock. This work focuses on the optimization of this testbed to produce a feedstock with higher ilmenite content than the input regolith. The testbed comprises three beneficiation techniques, viz. gravitational, magnetic and electrostatic beneficiation that work sequentially to produce the desired feedstock. The optimized parameter configuration achieved up to three-fold increase in the ilmenite grade relative to the input with about 32 wt% of the total ilmenite being recovered in the enriched output. These experiments have highlighted other underlying factors that influenced the experimental research such as the design of testbed components, system residuals and limited availability for Off-the-shelf components. The observations made from these experiments have also provided insights into the further development of the technology. The work has thus produced evidence for the effectiveness of the beneficiation testbed in producing an enriched feedstock while outlining avenues for future improvements.</p

Morphotropy and Temperature-Driven Polymorphism in A₂Th(AsO₄)₂ (A = Li, Na, K, Rb, Cs) Series

A new alkaline thorium arsenate family was obtained and systematically investigated. The structures of A₂Th­(AsO₄)₂ (A = Li, Na, K, Rb, Cs) were determined from single crystal X-ray diffraction data. Li₂Th­(AsO₄)₂ and either isostructural K₂Th­(AsO₄)₂ and Rb₂Th­(AsO₄)₂ crystallize in the monoclinic crystal system. Na₂Th­(AsO₄)₂ and Cs₂Th­(AsO₄)₂ crystallize in the orthorhombic and tetragonal crystal systems, respectively. Li₂Th­(AsO₄)₂ consists of [Th­(AsO₄)₂]^2– layers with Li atoms in the interlayer space. The rest of the compounds are based on 3D frameworks. Differences in local environments of ThO₈ coordination polyhedra are described in relation to the symmetry. Despite different local environments of ThO₈ coordination polyhedra and different structural symmetry, underlying nets of A₂Th­(AsO₄)₂ (A = Na, K, Rb, Cs) were shown to be the same. Single-crystal and powder Raman spectra were measured, and bands are assigned. DSC measurements showed phase transitions in K₂Th­(AsO₄)₂ and Rb₂Th­(AsO₄)₂, which were studied using high-temperature powder X-ray diffraction (HT-PXRD). The data of HT-PXRD demonstrates two high-temperature polymorphic modification of K₂Th­(AsO₄)₂ and only one for the isotypic Rb₂Th­(AsO₄)₂. The phase transitions in both K and Rb phases are reversible