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2D transition metal carbides and nitrides (MXenes) have gained much interest in microwave absorption. However, the high conductivity of MXenes results in inferior absorption performance. To solve this problem, Cellulose nanofiber (CNF) is compounded with MXenes to build membranes with biomimetic structures. CNF not only contributes to adjusting the electromagentic parameters, but also enhances the microwave attenuation and regulates the absorption band. In this work, nacre-like and loofah-like carbonized CNF/MXenes membranes were successfully prepared. The self-assembly of CNF and MXene avoids the impedance mismatch, and the biomimetic structures enhance conductive loss, polarization loss and multiple reflection. The results show that nacre-like carbonized CNF/MXene membrane (CCM) exhibits absorbing performance with the minimum reflection loss (RLmin) of −42.2 dB and the Effective absorption band (EAB) of 7.12 GHz. Meanwhile, the absorption peaks are mainly concentrated on X-band. Further, as the morphology changes to porous layers, the RLmin of loofah-like CCM increases to −63.8 dB, whose EAB is 7.32 GHz at 2.5 mm, and the main absorption peaks shift to Ku-band. Besides, the possible absorption mechanism of biomimetic composite membranes has been expounded. This work provides a versatile strategy for CNF/MXene composite membrane with biomimetic structures on excellent and tunable microwave absorption performance.

Although metal chalcogenides have been widely utilized as microwave absorbers, it remains a challenge for them to achieve efficient and broadband absorption performance with low filler content. Herein, a series of rime-like carbon paper@Bi2S3 hybrid structures are manufactured by a facile one-step solvothermal process, whose morphology and microwave absorption properties also can be easily adjusted by the dosage control of raw materials. The Bi2S3 clusters are grown densely on the surface of carbon paper fibers, like the rime in winter. The collocation of carbon paper and Bi2S3 is beneficial to impedance matching and synergistically enhances microwave absorption capability based on various attenuation mechanisms, including interfacial/dipolar polarization loss, conduction loss, and multiple reflection. At a low filler content (only 5 wt%), the optimal reflection loss among these composites is −56.63 dB at 8.84 GHz with 3.3 mm thickness, and the broadest efficient absorption bandwidth is 7.32 GHz with a thickness of 2.4 mm, covering the whole Ku band. By adjusting the thickness, the total covered frequency range reaches 13.36 GHz (83.5% of 2–18 GHz). The as-prepared materials have unique microstructure and exhibit strong and broadband absorption performance with thin thickness and low filler content, enlightening future exploration of metal chalcogenides on high-quality microwave absorbers.

Covalent triazine-based frameworks (CTFs) have been considered as new promising candidates for host materials in lithium–sulfur batteries (LSBs). However, few people have focused on the molecular structure design of the building units of the CTFs to improve the sulfur loading contents and electrochemical performance, whereas the different types, contents of functional groups, and molecular lengths largely dominate the battery’s performance. Herein, we purposefully designed and synthesized N, O-containing CTFs (NO-CTF-1 and NO-CTF-2) by the N, O-containing building units for LSB electrodes and explored the influence of heteroatoms (N and O) on the polysulfide redox conversion reactions in detail. N and O heteroatoms with extra pair of electrons in NO-CTFs can interact with the strong Lewis acid of terminal Li atoms in lithium polysulfides. The unique pore structure and the fast heterogeneous nucleation process of Li2S accelerate the conversion of lithium polysulfides in a working battery. As a result, NO-CTF-1 delivers a high reversible capacity of 1250 mA h g−1 at 0.1 C, an outstanding cycling stability with a capacity retention of 92% at 0.5 C (300 cycles), and an excellent rate performance of up to 678 mA h g−1 at 2 C. This work provides a new insight into the LSB electrode materials to rationally design the building unit of CTFs and inspires the exploration of the effect of nitrogen, oxygen, and other heteroatoms on the heterogeneous nucleation of Li2S.

A spinning disk reactor is a promising contacting device used in the synthesis of nanoparticles through reactive precipitation. The synthesis performance depends on the flow characteristics of the liquid film on the reactor. Using a glycerol–water solution as the experimental medium, this study examined the three distinct zones of the radial velocity profile and the formation of hydraulic jump through laser Doppler velocimetry and volume-of-fluid methods. The results showed that as the inlet Reynolds number increases, the inertial effect dominates farther out and pushes the three zones outwards, a wider acceleration zone is obtained, and the pouring diameter does not affect the synchronisation zone. At higher rotational speeds, the centrifugal effect dominates even at a smaller radius, and the three zones move inwards, leading to a wider synchronisation zone. The hydraulic jump generally occurs at lower rotational speeds, higher viscosity, or smaller pouring diameter. At higher inlet Reynolds number or lower speeds, the jump region expands and migrates outwards. Although the pouring diameter can determine whether the jump occurs, it only slightly affects the location of the jump. The synchronisation and jump radii can be predicted using the radial length scale factor. The Nusselt model was modified by incorporating a correction term, and a regression model was proposed to predict the maximum film height.