Study on the fluorination of dysprosium oxide by ammonium bifluoride for the preparation of dysprosium fluoride

In this report, dysprosium fluoride (DyF3) - a material for the preparation of dysprosium (Dy) metal was prepared by the fluorination of dysprosium oxide (Dy2O3) by ammonium bifluoride (NH4HF2) reagent. The effect of reaction time and temperature on the formation of dysprosium fluoride salt has been studied. The phase composition and crystal structure of the obtained products were analysed by X-ray diffraction (XRD). Thermal analysis techniques were applied to determine the temperature range of the fluorination. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) was used for external morphology observation and chemical elemental composition analysis. The results showed that the high purity phase of DyF3 was formed at the conditions: reaction time and temperature of >1 h and >350oC, respectively. The product is available for the preparation of Dy metal by metallothermic reduction.

Modeling the Optical Properties of a Polyvinyl Alcohol-Based Composite Using a Particle Swarm Optimized Support Vector Regression Algorithm

We developed particle swarm optimization-based support vector regression (PSVR) and ordinary linear regression (OLR) models for estimating the refractive index (n) and energy gap (E) of a polyvinyl alcohol composite. The n-PSVR model, which can estimate the refractive index of a polyvinyl alcohol composite using the energy gap as a descriptor, performed better than the n-OLR model in terms of root mean square error (RMSE) and mean absolute error (MAE) metrics. The E-PSVR model, which can predict the energy gap of a polyvinyl alcohol composite using its refractive index descriptor, outperformed the E-OLR model, which uses similar descriptor based on several performance measuring metrics. The n-PSVR and E-PSVR models were used to investigate the influences of sodium-based dysprosium oxide and benzoxazinone derivatives on the energy gaps of a polyvinyl alcohol polymer composite. The results agreed well with the measured values. The models had low mean absolute percentage errors after validation with external data. The precision demonstrated by these predictive models will enhance the tailoring of the optical properties of polyvinyl alcohol composites for the desired applications. Costs and experimental difficulties will be reduced.

Dysprosium Oxide-Supported CaO for Thermochemical Energy Storage

A novel CaO-based material supported with Ca3Al2O6 and Dy2O3 was found to show excellent performance as a thermochemical energy storage material for use in solar thermal power plants. It retains a carbonation conversion capacity of 82.7% for a period of 40 cycles, as well as exothermic heats of reaction of 582.2 kJ kg−1, up to seven times greater than other materials found in the literature. The improved performance was attributed to the greater prevention of sintering and retention of high surface area by the addition of two inert supports: Ca3Al2O6 and Dy2O3. Long-term effectiveness of the novel material was also evaluated by using a sintering model. It retains an energy storage utilization of 6.2 kg kWh−1 after 30 years of cycling, while commercial limestone would require 81 tons kWh−1 equivalent. Limestone requires replacement every six thermal cycles, making it impractical for real thermochemical energy storage implementation. The extra cost associated with the addition of supports in this CaO-based material is justified by the long-term durability, which would imply a reduction in the overall capital and operational expenditure of the plant.

New Class of Efficient T2 Magnetic Resonance Imaging Contrast Agent: Carbon-Coated Paramagnetic Dysprosium Oxide Nanoparticles

Nanoparticles are considered potential candidates for a new class of magnetic resonance imaging (MRI) contrast agents. Negative MRI contrast agents require high magnetic moments. However, if nanoparticles can exclusively induce transverse water proton spin relaxation with negligible induction of longitudinal water proton spin relaxation, they may provide negative contrast MR images despite having low magnetic moments, thus acting as an efficient T2 MRI contrast agent. In this study, carbon-coated paramagnetic dysprosium oxide (DYO@C) nanoparticles (core = DYO = DyxOy; shell = carbon) were synthesized to explore their potential as an efficient T2 MRI contrast agent at 3.0 T MR field. Since the core DYO nanoparticles have an appreciable (but not high) magnetic moment that arises from fast 4f-electrons of Dy(III) (6H15/2), the DYO@C nanoparticles exhibited an appreciable transverse water proton spin relaxivity (r2) with a negligible longitudinal water proton spin relaxivity (r1). Consequently, they acted as a very efficient T2 MRI contrast agent, as proven from negative contrast enhancements seen in the in vivo T2 MR images.