Tuning effect of silicon substitution on magnetic and high frequency electromagnetic properties of R2Fe17 and their composites

In this work, we report the tuning effect of the Si substitution on the magnetic and high frequency electromagnetic properties of R₂Fe₁₇ compounds and their paraffin composites. It is found that the introduction of Si can remarkably improve the magnetic and electromagnetic properties of the R₂Fe₁₇ compounds, making the R₂Fe_17–xSi_x-paraffin composites excellent microwave absorption materials (MAMs). By introducing the Si element, their saturation magnetizations decrease slightly, while much higher Curie temperatures are obtained. Furthermore, better impedance match is reached due to the decrease of the high-frequency permittivity ε′ by about 40%–50%, which finally enhances the performance of the microwave absorption. The peak frequency (f_RL) of the reflection loss (RL) curve moves toward high frequency domain and the qualified bandwidth (QB, RL ≤ ?10 dB) increases remarkably. The maximum QB of 3.3 GHz (12.0–15.3 GHz) is obtained for the Sm_1.5Y_0.5Fe₁₅Si₂-paraffin composite (d = 1.0 mm) and the maximum RL of ?53.6 dB is achieved for Nd₂Fe₁₅Si₂-paraffin composite (d = 2.2 mm), both surpassing most of the reported MAMs. Additionally, a distinguished dielectric microwave absorption peak is observed, which further increases the QB in these composites.     

添加纳米Y2O3的ODS-HT9钢的显微结构和性能

为了研究纳米Y₂O₃对HT9钢的显微结构和力学性能的影响，采用粉末冶金工艺，制备了纳米Y₂O₃含量为0.1%~0.9%的ODS-HT9钢样品，测定了样品的抗拉强度、伸长率、维氏硬度等力学性能，利用透射电子显微镜（TEM）观察和分析了样品中纳米Y₂O₃颗粒的分布状况、形状和相结构，利用扫描电子显镜（SEM）观察了样品拉伸断口的形貌。研究表明，球磨和热压烧结后，纳米Y₂O₃颗粒能够均匀地分布于基体中，相结构和形状未发生明显变化。弥散分布的纳米Y₂O₃硬质颗粒，具有明显的弥散强化作用，导致ODS-HT9钢的抗拉强度和维氏硬度随Y₂O₃含量的增加而显著增加，伸长率显著降低。Y₂O₃含量低于0.7%时，样品以韧性断裂为主，进一步增加含量，断裂方式将由韧性断裂转变成脆性断裂。纳米Y₂O₃含量为0.3%~0.5%的ODS-HT9钢，抗拉强度达到了913~936 MPa，伸长率为10.7%~11.2%，具有良好的综合力学性能。本文研究结果有助于ODS-HT9钢高温性能的研究及其在反应堆中的实际应用。      

SPS反应烧结HfB2复合材料的制备和性能

针对HfB2陶瓷材料难烧结和韧性差等问题,选择ZrC粉、Si粉和C粉为烧结助剂,借助ZrC-Si-C间的原位反应生成ZrSi2和SiC,促进HfB2陶瓷的烧结,并提高HfB2陶瓷的综合力学性能。结果表明,HfB2与烧结助剂的混合粉体经放电等离子烧结(SPS)在1600℃保温10 min和40 MPa的压力条件下制备出相对密度为96.6 1%的HfB2-ZrSi2-SiC复合材料,所制样品的硬度、抗弯强度和断裂韧性均随着烧结助剂ZrC-Si-C含量的增加呈现先上升后降低的趋势。当ZrC-Si-C添加量为10%时所制备样品的综合力学性能最好,其硬度值为26.80±1.2 GPa、抗弯强度为504±40 MPa、断裂韧性值为4.66±0.21 MPa·m1/2。     

Self-assembled core-shell polydopamine@MXene with synergistic solar absorption capability for highly efficient solar-to-vapor generation

As a renewable and environment-friendly technology for seawater desalination and wastewater purification, solar energy triggered steam generation is attractive to address the long-standing global water scarcity issues. However, practical utilization of solar energy for steam generation is severely restricted by the complex synthesis, low energy conversion efficiency, insufficient solar spectrum absorption and water extraction capability of state-of-the-art technologies. Here, for the first time, we report a facile strategy to realize hydrogen bond induced self-assembly of a polydopamine (PDA)@MXene microsphere photothermal layer for synergistically achieving wide-spectrum and highly efficient solar absorption capability (≈ 96% in a wide solar spectrum range of 250–1,500 nm wavelength). Moreover, such a system renders fast water transport and vapor escaping due to the intrinsically hydrophilic nature of both MXene and PDA, as well as the interspacing between core-shell microspheres. The solar-to-vapor conversion efficiencies under the solar illumination of 1 sun and 4 sun are as high as 85.2% and 93.6%, respectively. Besides, the PDA@MXene photothermal layer renders the system durable mechanical properties, allowing producing clean water from seawater with the salt rejection rate beyond 99%. Furthermore, stable light absorption performance can be achieved and well maintained due to the formation of ternary TiO2/C/MXene complex caused by oxidative degradation of MXene. Therefore, this work proposes an attractive MXene-assisted strategy for fabricating high performance photothermal composites for advanced solar-driven seawater desalination applications.

     

Fabrication of ultrafast temperature-responsive nanofibrous hydrogel with superelasticity and its 'on–off' switchable drug releasing capacity

The temperature-responsive bulky hydrogel with fast response rate and satisfactory mechanical property has fascinating application potential in many aspects, such as the implantable macroscale controlled drug release carrier for post-surgical therapy; however, creating such a smart hydrogel was proven extremely challenging. Here a novel type of temperature-responsive bulky hydrogel with ultrafast response rate and super compressible elasticity was fabricated by the fibrous freeze-shaping technique using shortened temperature-responsive polymer based electrospun hollow nanofibers as building blocks, followed by heat treatment for endowing the hydrogel with high stability in water. Because the hydrogel has hierarchical porous structure and its constituent nanofibers have hollow structure, which are beneficial to diffusion of its embodied water during temperature-induced volume phase transition, its temperature-response time is less than 30 s. In addition, the hierarchical porous structure benefits dissipation of the compression stress exerted on the hydrogel. Fluorescein isothiocyanate (FITC)-dextran as a model biomacromolecular drug, was loaded into the shells of the hollow nanofibers during coaxial electrospinning, and the ultimately obtained nanofibrous hydrogel can release its loaded FITC-dextran in a 'on–off' switchable fashion in response to temperature alternation between 15 and 47°C. Cell cytotoxicity test results demonstrate that the temperature-responsive nanofibrous hydrogel is biocompatible.     

Protein from Hylocereus polyrhizus protects MRC-5 cells against hydrogen peroxide (H2O2)-induced damage

Food Science and Biotechnology - The cytoprotective and potential molecular mechanisms of Hylocereus polyrhizus protein (RFPP) were investigated on the hydrogen peroxide (H2O2)-triggered damage in...