AB_(2)-type rare earth-based compounds with C-15 structure:Looking for reversible hydrogen storage materials

AB_(2)-type(A=rare earth,B=transition metal)intermetallic compounds with C15 structure can easily absorb large amount of hydrogen,showing their potential use as hydrogen storage materials.The crucial problem hindering their application is hydrogen induced amorphization(HIA),which leads to the irreversible hydrogen sorption process.The stability of the AB_2 Laves phase compounds,the structural properties,the hydrogenation properties and the controlling factors of HIA are discussed in this review.Comparing with other factors,the atomic radii ratio r_A/r_B is the most important one influencing the HIA.Multi-element substitution is an efficient way to suppress or limit HIA and may enable AB_2 compounds to be suitable for hydrogen storage.

Ab initio molecular dynamics study on the local structures in Ce_(70)Al_(30) and La_(70)Al_(30) metallic glasses

Ab initio molecular dynamics simulations were performed to investigate the effect of similar elements on the shortto medium-range atomic packing features in Ce70Al30 and La70Al30 glass-forming alloys. 4 f electrons of Ce element in Ce70Al30 alloy were properly treated in electronic calculations. The local atomic structures in both alloys are qualitatively similar. However, the local environments of Al atoms in Ce70Al30 alloy show fluctuation with temperature in the cooling process, which could result from 4 f electrons of Ce elements. Surprisingly, the medium-range atomic packing features of Al atoms in both MGs are quite different, although Ce and La elements are similar. These findings are useful for understanding the enhanced glass-forming ability by similar element substitution in RE-based MGs from a medium-range structure perspective.

Effect of Precipitation on the Hardness of Ternary Metallic Glass

The present study reports effects of annealing treatment on the hardness of Ce75Al23Si2 rare earth-based metallic glasses (REMG). Then specimens were annealed at 100°C, 200°C, 250°C, 270°C, and 290°C five different temperatures for 30 minutes. After that, three different characteristic methods, including microindentation, X-ray Diffraction (XRD), and scanning electrical microscope (SEM) were conducted on the as received REMG sample and five annealed samples. XRD data demonstrate that the crystallization occurs in the sample at the annealing temperature as low as 200°C. The microindentation measurement shows that hardness of the REMG sample does not change at all before crystallization occurs in the sample and increases with the annealing temperature in the range of 200°C to 290°C. The average crystal size in the annealed samples was estimated using Debye-Scherrer equation to be 28-42 nm, in consistent with the SEM observation, indicating that nano-crystalline domains may give rise to the enhancement of hardness.

A Comprehensive Review on Mechanisms and Applications of Rare-Earth Based Perovskite Nanocrystals

Rare earth(RE)ions,with abundant 4f energy level and unique electronic arrangement,are considered as substitutes for Pb^(2+)in perovskite nanocrystals(PNCs),allowing for partial or complete replacement of lead and minimizing environmental impact.This review provides a comprehensive overview of the characteristics of RE-doped PNCs,including up-conversion luminescence,down-conversion luminescence,and quantum confinement effects,etc.Additionally,RE doping has been found to effectively suppress defect formation,reduce nonradiative recombination,enhance photoluminescence quantum yield(PLQY),and even allow for controlling over the morphology of the nanocrystals.The review also highlights the recent advancements in lead-free RE-based perovskites,especially in the case of Eu-based perovskites(CsEuBr_(3) and CsEuCl_(3)).Furthermore,it briefly introduces the applications of PNCs in various fields,such as perovskite solar cells(PSCs),luminescent solar concentrators(LSCs),photodetectors(PDs),and light-emitting diodes(LEDs).A systematic discussion on the luminescence mechanisms of RE-doped PNCs and lead-free RE-based perovskites is provided,along with an outlook on future research directions.The ultimate goal of this review is to provide guidance for the development of RE-based perovskite optoelectronic devices.

Fluorescent nanoparticles for chemical and biological sensing

Fluorescent nanoparticles (NPs), including quantum dots (QDs), dye-doped NPs, and rare earth-based NPs, etc., have been a major focus of research and development during the past decade. The impetus behind such endeavors can be attributed to their unique chemical and optical properties, such as bright fluorescence, high photostability, large Stocks shift and flexible processability. The introduction of fluorescent NPs into analytical chemistry has opened up new venues for fluorescent analysis. In this review, we focus on the developments and analytical applications of fluorescent NPs in the chemical and biological sensing of pH, ions, organic compounds, small biological molecules, nucleic acids, proteins, virus and bacteria. The review also points out the in vitro and in vivo imaging application of fluorescent NPs at the cell and body levels. Meanwhile, the ad- vantages of NPs brought field of sensing and signal transductions are also discussed.

Observation of table-like magnetocaloric effect and large refrigerant capacity in Nd_(6)Fe_(13)Pd_(1-x)Cu_(x) compounds

The table-like magnetocaloric effect is significant for the magnetic refrigeration applications above 20 K based on the Ericsson cycle.Herein,we prepared a series of Nd_(6)Fe_(13)Pd_(1-x)Cu_(x)(x=0.05,0.1,0.15)compounds by the arc-melting method.These compounds show the single crystalline phase in the tetragonal Nd_(6)Fe_(13)Si-type structure with the space group I4/mcm.A magnetic phase transition from ferromagnetism to antiferromagnetism and a metamagnetic transition from the antiferromagnetic state to the ferromagnetic state are observed in each of the compounds.The compounds exhibit table-like magnetocaloric effects with large refrigerant capacities.A constantΔSM in a temperature span of 40 K in the Nd_(6)Fe_(13)Pd_(0.85)Cu_(0.15) compound are observed.For a field change of 0–5 T,the peak values of–ΔS_(M) for the Nd_(6)Fe_(13)Pd_(0.95)Cu_(0.05),Nd_(6)Fe_(13)Pd_(0.90)Cu_(0.10),and Nd_(6)Fe_(13)Pd_(0.85)Cu_(0.15) compounds are estimated to be 4.8,4.6 and 4.4 J/(kg·K)with corresponding refrigerant capacity values of 323,331 and 316 J/kg,respectively.The obtained table-like magnetocaloric effects with large refrigerant capacities as well as fairly small thermal and magnetic hysteresis deem these series of compounds good candidates for single-phase magnetic refrigeration based on the Ericsson cycle.