Influence of Fluorine Content in Apatite–Mullite Glass-Ceramics

The nucleation and crystallization of a series of glasses based on 4.5SiO₂·3Al₂O₃·1.5P₂O₅·(5 − z )CaO · z CaF₂ with a Ca:P ratio corresponding to apatite were studied. In these glasses, the objective was to investigate the influence of fluorine content and z was varied from 3 to 0. All the glasses studied crystallized to fluorapatite (FAP) and mullite with the exception of the glass containing no fluorine, which crystallized to β-tricalcium phosphate (Ca₃(PO₄)₂) and anorthite (CaAl₂Si₂O₈). Glasses that contained sufficient fluorine to form FAP bulk nucleated to give FAP without a nucleation hold. Thermal gravimetric analysis demonstrated a significant weight loss corresponding to the crystallization of mullite, which increased with the fluorine content of the glass and also with decreased particle size. The loss was attributed to volatile SiF₄. The glass transition temperature decreased with increased fluorine content of the glass.     

Molten Salt Synthesis of Bi4(V0.85Co0.15)2O11−δ (BICOVOX) Ceramic Powders

Cobalt (15 at.%)-doped bismuth vanadate, Bi₄(V_0.85Co_0.15)₂O_11−δ (BICOVOX) is known to have high oxygen ion conduction. However, the conductivity is highly anisotropic due to its layered structure. In this paper, we report the synthesis of BICOVOX powders with platelet habit by molten salt synthesis using a NaCl–KCl eutectic mixture as the reaction medium. The effects of treatment temperature and time on the morphology and phase content of the BICOVOX powders were investigated. By this method, it is possible to synthesize powders with platelets of major face dimension ∼50 μm and aspect ratio (major face dimension to thickness) as high as 15.     

Novel process for biodiesel by reactive absorption

Process integration and intensification is increasingly applied also in the biodiesel production, as shown by recent research papers. This study takes previous work on reactive separation processes for biodiesel production to a new level by proposing an innovative technology based on reactive absorption using solid acid catalysts. This is a major step forward since reactive absorption offers significant benefits over reactive distillation, such as: reduced capital investment and operating costs due to the absence of the reboiler and condenser, higher conversion and selectivity as no products are recycled in the form of reflux or boil-up vapors, as well as no occurrence of thermal degradation of the products due to a lower temperature profile in the column. Rigorous simulations embedding experimental results were performed in AspenTech AspenONE engineering suite to design this novel reactive absorption process and evaluate the technical and economical feasibility. The main results are given for a plant producing 10 ktpy biodiesel from waste vegetable oil with high free fatty acids content, using solid acids as green catalysts. This innovative process eliminates all conventional catalyst-related operations, and efficiently uses the raw materials and the reactor volume in an integrated setup that allows significant savings in CapEx and OpEx of the plant.     

Ligand-directed immobilization of proteins through an esterase 2 fusion tag studied by atomic force microscopy

Atomically flat mica surfaces were chemically modified with an alkyl trifluoromethyl ketone, a covalent inhibitor of esterase 2 from Alicyclobacillus acidocaldarius, which served as a tag for ligand-directed immobilization of esterase-linked proteins. Purified NADH oxidase from Thermus thermophilus and human exportin-t from cell lysates were anchored on the modified surfaces. The immobilization effectiveness of the proteins was studied by atomic force microscopy (AFM). It was shown that ligand-esterase interaction allowed specific attachment of exportin-t and resulted in high-resolution images and coverage patterns that were comparable with immobilized purified protein. Moreover, the biological functionality of immobilized human exportin-t in forming a quaternary complex with tRNA and the GTPase Ran-GTP, and the dimension changes before and after complex formation were also determined by AFM.     

Advanced Postirradiation Characterization of Nuclear Fuels Using Pulsed Neutrons

Methods for postirradiation characterization of bulk (cm³) irradiated materials or even spent nuclear fuels are sparse due to their extremely radioactive nature. While several methods exist to characterize smaller volumes (<?1 mm³) of such samples, selecting these volumes from larger samples is challenging. X-ray-based methods are prohibitive due to the strong γ-radiation from the sample flooding the detectors. Neutron-based methods available in the proximity of irradiation reactors allow for thermal neutron radiography or computed tomography using a small reactor source, but one cannot assess isotope distributions or microstructural features such as phases, texture, or strain from diffraction measurements due to flux limitations. We present herein a pathway to provide pulsed neutron characterization of bulk irradiated samples using time-of-flight neutron diffraction for microstructural characterization and energy-resolved neutron imaging for assessment of isotopic densities and distributions. Ultimately, laser-driven pulsed neutron sources may allow deployment of these techniques pool-side at irradiation reactors.

     

On the Room-Temperature Mechanical Properties of an Ion-Irradiated TiZrNbHfTa Refractory High Entropy Alloy

JOM - Refractory high-entropy alloys (RHEAs) are potential candidate materials for use in next-generation nuclear reactors due to their excellent mechanical performance at high temperatures. Here,...     

Multiscale, Multiphysics Numerical Modeling of Fusion Welding with Experimental Characterization and Validation

Various physical interfacial phenomena occur during the process of welding and influence the final properties of welded structures. As the features of such interfaces depend on physics that resolve at different spatial scales, a multiscale and multiphysics numerical modeling approach is necessary. In a collaborative research project Modeling of Interface Evolution in Advanced Welding, a novel strategy of model linking is employed in a multiscale, multiphysics computational framework for fusion welding. We only directly link numerical models that are on neighboring spatial scales instead of trying to link all submodels directly together through all available spatial scales. This strategy ensures that the numerical models assist one another via smooth data transfer, avoiding the huge difficulty raised by forcing models to attempt communication over many spatial scales. Experimental activities contribute to the modeling work by providing valuable input parameters and validation data. Representative examples of the results of modeling, linking and characterization are presented.