Synthesis of high‐purity high‐entropy metal diboride powders is critical to implementing their extensive applications. However, the related studies are rarely reported. Herein we first theoretically studied the synthesis possibility of high‐purity high‐entropy diboride powders, namely (Hf0.25Ta0.25Nb0.25Ti0.25)B2 (HTNTB), via boro/carbothermal reduction by analyzing the thermodynamics of the possible chemical reactions and then successfully synthesized the high‐purity and superfine HTNTB powders via boro/carbothermal reduction for the first time. The as‐prepared powders exhibited low‐oxygen impurity content of 0.49 wt% and small average particle size of 260 nm. Meanwhile, they possessed good single‐crystal hexagonal structure of metal diborides and high‐compositional uniformity from nanoscale to microscale. This work will open up a new research field on the synthesis of high‐purity high‐entropy metal diboride powders.
Polymer‐derived ceramic (PDC) route has been widely used to fabricate various ceramics or ceramic‐matrix composites in recent years. However, the synthesis of high‐entropy ceramics via PDC route has rarely been reported until now. Herein, we successfully synthesized a class of high‐entropy carbides, namely (Hf0.25Nb0.25Zr0.25Ti0.25)C (HEC‐1), via PDC route. The polymer‐derived HEC‐1 ceramics consisted of numerous superfine particles with the average particle size ~800 nm. Meanwhile, they possessed a rock‐salt structure of metal carbides and high‐compositional uniformity from nanoscale to microscale. In addition, the as‐obtained HEC‐1 ceramics had a low oxygen impurity content of 0.51% and a low free carbon impurity content of 2.56%. This work will open up a new research field on the fabrication of high‐entropy ceramics or high‐entropy ceramic‐matrix composites via PDC route.
High-entropy ceramics (HECs) are gaining significant interest due to their huge composition space, unique microstructure, and adjustable properties. Previously reported studies focus mainly on HECs with the multi-cationic structure, while HECs with more than one anion are rarely studied. Herein we reported a new class of HECs, namely highentropy alumino-silicides (Mo 0.25 Nb 0.25 Ta 0.25 V 0.25)(Al 0.5 Si 0.5) 2 (HEAS-1) with multi-cationic and-anionic structure. The formation possibility of HEAS-1 was first theoretically analyzed from the aspects of thermodynamics and lattice size difference based on the first-principles calculations and then the HEAS-1 were successfully synthesized by the solid-state reaction at 1573 K. The as-synthesized HEAS-1 exhibited good single-crystal hexagonal structure of metal alumino-silicides and simultaneously possessed high compositional uniformity. This study not only enriches the categories of HECs but also will open up a new research field on HECs with multi-cationic and-anionic structure.
BackgroundToo fast or slow weight gain in infancy is bad for health in later life. In this study, we aim to investigate the optimal weight gain pattern during the first 2 y of life for term small-for-gestational-age (SGA) infants.MethodWe employed data from a longitudinal, community-based cohort study on the growth and development of SGAs collected between 2004 and 2010 in Shanghai, China.Latent class growth analysis (LCGA) was applied to identify weight gain patterns among 3004 SGAs. BMI curves for each latent class from 1 mo to 5 y were produced through mixed-effects regression analysis. Multivariable regression was performed to examine the association between various classes and adverse outcomes (overweight/obesity/ malnutrition) during 2–5 y.ResultFive weight gain patterns aged 0–2 y of 3004 term SGAs were identified and labeled as follows--class 1: excessively rapid catch-up growth (10.7%); class 2: rapid catch-up growth (19.7%); class 3: appropriate catch-up growth (55.7%); class 4: slow catch-up growth (10.2%); class 5: almost no catch-up growth (3.7%). A decreasing age at adiposity rebound (AR) and an increasing BMI value were observed from class 5 to 1. Class 1 and 2 showed an early appearance of AR (< 4 y). SGAs in class 1 and 2 had a higher BMI in 2–5 y of life. After adjustment for potential confounding variables, class 1 and 2 were found to have an increased risk of being overweight/ obese. At the same time, we found the risk of malnutrition was especially prominent among SGAs in classes 4 and 5.ConclusionOur results suggest that for term SGA infants, catch-up growth that crossing two centile levels, that is, from < 10th to the interval between 25th and 50th (ΔWAZ> 1.28) in the first several months, along with on track growth and maintenance at a median level by age 2 may be the optimal catch-up growth trajectory, minimizing risk of childhood adverse health outcomes.
High-entropy nanomaterials have been arousing considerable interest in recent years due to their huge composition space, unique microstructure, and adjustable properties. Previous studies focused mainly on high-entropy nanoparticles, while other high-entropy nanomaterials were rarely reported. Herein, we reported a new class of high-entropy nanomaterials, namely (Ta0.2Nb0.2Ti0.2W02Mo0.2)B2 high-entropy diboride (HEB-1) nanoflowers, for the first time. The formation possibility of HEB-1 was first theoretically analyzed from two aspects of lattice size difference and chemical reaction thermodynamics. We then successfully synthesized HEB-1 nanoflowers by a facile molten salt synthesis method at 1473 K. The as-synthesized HEB-1 nanoflowers showed an interesting chrysanthemum-like morphology assembled from numerous well-aligned nanorods with the diameters of 20-30 nm and lengths of 100-200 nm. Meanwhile, these nanorods possessed a single-crystalline hexagonal structure of metal diborides and highly compositional uniformity from nanoscale to microscale. In addition, the formation of the as-synthesized HEB-1 nanoflowers could be well interpreted by a classical surface-controlled crystal growth theory. This work not only enriches the categories of high-entropy nanomaterials but also opens up a new research field on the high-entropy diboride nanomaterials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.