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Abstract Polyvinyl chloride (PVC) is the world’s third-most widely manufactured thermoplastic, but has the lowest recycling rate. The development of PVC-like plastics that can be depolymerized back to monomer contributes to a circular plastic economy, but has not been accessed. Here, we develop a series of chemically recyclable plastics from the reversible copolymerization of cyclic anhydride with chloral. The copolymerization is highly efficient through the anionic or cationic mechanism under mild conditions, yielding polyesters with tunable structure and properties from multiple commercial monomers. Notably, these polyesters manifest mechanical properties comparable to PVC and polystyrene. Meanwhile, such polyesters are flame-retardant like PVC due to high chloride content. Of significance, these polyesters can be depolymerized back to starting monomers at high temperatures owing to the reversibility of the copolymerization, leading to a circular economy. Overall, the readily available monomers, simple synthesis, advantageous performance, and practical recyclability make the polymers promising for applications.

Abstract Corynespora cassiicola is a highly diverse fungal pathogen that commonly occurs in tropical, subtropical, and greenhouse environments worldwide. In this study, the isolates were identified as C. cassiicola, and the optimum growth and sporulation were studied. The phenotypic characteristics of C. cassiicola, concerning 950 different growth conditions, were tested using Biolog PM plates 1–10. In addition, the strain of C. cassiicola DWZ from tobacco hosts was sequenced for the using Illumina PE150 and Pacbio technologies. The host resistance of tobacco Yunyan 87 with different maturity levels was investigated. In addition, the resistance evaluation of 10 common tobacco varieties was investigated. The results showed that C. cassiicola metabolized 89.47% of the tested carbon source, 100% of the nitrogen source, 100% of the phosphorus source, and 97.14% of the sulfur source. It can adapt to a variety of different osmotic pressure and pH environments, and has good decarboxylase and deaminase activities. The optimum conditions for pathogen growth and sporulation were 25–30 °C, and the growth was better on AEA and OA medium. The total length of the genome was 45.9 Mbp, the GC content was 51.23%, and a total of 13,061 protein-coding genes, 202 non-coding RNAs and 2801 and repeat sequences were predicted. Mature leaves were more susceptible than proper mature and immature leaves, and the average diameter of diseased spots reached 17.74 mm at 12 days. None of the tested ten cultivars exhibited obvious resistance to Corynespora leaf spot of tobacco, whereby all disease spot diameters reached > 10 mm and > 30 mm when at 5 and 10 days after inoculation, respectively. The phenotypic characteristics, genomic analysis of C. cassiicola and the cultivar resistance assessment of this pathogen have increased our understanding of Corynespora leaf spot of tobacco.

Development of strategies to toughen HfB2 ceramic, improve their mechanical properties is the key to promote their applications in extreme thermal environments. This study explores a kind of self-toughening method of HfB2 ceramic by incorporation the highly crystalized multi-branched HfB2 microrods. The multi-branched HfB2 microrods were synthesized by sol–gel process and carbothermal reduction, exhibiting length of 6–13 μm and diameter of 0.60–1.50 μm, respectively. Detailed analysis of the formation mechanism of HfB2 microrods reveals that the HfB2 multi-branched structure is a collaborative consequence of orientation attachment mechanism and reactive templates growth, in which process monoclinic HfO2 crystals transform into crystalized HfO2 microrods at ∼1000 °C, and worked as template to induce one-dimensional HfB2 microrods. Furthermore, spark plasma sintering experiments show that the optimal mechanical properties were attained by 6 wt% addition of HfB2 microrods, comparing with HfB2 ceramics free of self-toughening agent, the hardness and fracture toughness of self-toughened HfB2 ceramic improved by 8.82 % and 81.91 % respectively, demonstrating the effectiveness of self-toughening of the microrods without sacrificing the hardness of HfB2 ceramic. Thus, it can be seen that the work has important reference value for the synthesis of HfB2 powder with different morphologies and the toughening of HfB2 ceramics.

To enhance the wear resistance of carburized M50NiL steel, this study introduces a method for refining the grains in carburized layer to a micro/nano-scale. The method involves extending the carburization time to ensure the formation of large M7C3 carbides at grain boundaries, and adjusting the quenching temperature to facilitate the particle-stimulated nucleation (PSN). The process promoted the recrystallization of the residual austenite (RA), together with the subgrains unexpectedly discovered, successfully achieving the grain refinement. In this paper, the formation mechanism of recrystallization and subgrains are discussed based on interfacial energy model and first principles calculation. The results indicate that recrystallization is driven by the release of energy at the interface between M7C3 carbides and the matrix during quenching, while the formation of subgrain boundaries is due to the reduction of fault energy in the RA, which caused by the increase of C content, promotes the dislocation movement and entanglement. Furthermore, the effects on hardness and wear resistance of micro/nano-crystalline region (MNCR) were investigated. The results show that MNCR after complete carburizing heat treatment has abundant dispersed carbides and refined martensite, which led to an approximate 15HV1 increase in the hardness, and exhibited nearly a 50% reduction in wear loss.

In this paper, a high-yield Hf-modified SiHfBOC ceramic precursor was developed, and a high-pressure assisted impregnation pyrolysis method was proposed to achieve the preparation of 3D PyC–Cf/SiHfBOC composites. This high-pressure assisted impregnation method significantly improves impregnation filling effect of the precursor in and between fiber bundles compared to dozens of traditional impregnation cycles. After undergoing just 9 precursor infiltration pyrolysis (PIP) cycles, the composites achieved relative density of approximately 90% and density of 1.64 g/cm3. The critical temperature difference of the 3D PyC–Cf/SiHfBOC composites after the shock of room temperature (RT)–1000 ℃ is as high as 650 ℃, which is twice that of traditional ceramic materials, showing good thermal shock resistance. Under the effect of Hf modification, a dense HfO2–SiO2 oxide layer (thickness of 93 μm) was formed in situ on the surface of the 3D PyC–Cf/SiHfBOC composites, effectively preventing further erosion of the composite matrix by high-temperature oxidation gas. Even in the ultra-high-temperature oxygen-containing environment at 1800 ℃, it still exhibits an excellent non-ablative result (with a linear ablation rate of 0.83×10−4 mm/s). This work not only enriches the basic research on lightweight ultra-high-temperature ceramic composites converted from Hf ceramic precursors, but also provides strong technical support for their applications in ultra-high-temperature non-ablative thermal protection materials for high-speed aircraft.

Abstract Our society is pursuing chemically recyclable polymers to accelerate the green revolution in plastics. Here, we develop a recyclable polyester library from the alternating copolymerization of aldehyde and cyclic anhydride. Although these two monomer sets have little or no thermodynamic driving force for homopolymerization, their copolymerization demonstrates the unexpected alternating characteristics. In addition to readily available monomers, the method is performed under mild conditions, uses common Lewis/Brønsted acids as catalysts, achieves the facile tuning of polyester structure using two distinct monomer sets, and yields 60 polyesters. Interestingly, the copolymerization exhibits the chemical reversibility attributed to its relatively low enthalpy, which makes the resulting polyesters perform closed-loop recycling to monomers at high temperatures. This study provides a modular, efficient, and facile synthesis of recyclable polyesters using sustainable monomers.

As the percentage of lithium-ion batteries as in a system for storing energy gradually rises, accidents brought by the deterioration of battery performance continue to occur. The solution to guaranteeing the steady operation of this system is learning how to precisely forecast the lithium-ion batteries’ remaining useful life (RUL). A prediction framework that combines elements of incremental capacity analysis (ICA) and electrochemical impedance spectroscopy (EIS) is proposed to address issues of RUL. The framework initially examines the charging and discharging features of the battery before establishing a mapping association between fusion features and RUL using convolutional neural network (CNN) and improved long short-term memory network (ILSTM). The parameters of the improved particle swarm optimization algorithm (IPSO) are optimized to build the IPSO-CNN-ILSTM model by modifying updating rules of the inertia weight and learning factor of the particle swarm optimization (PSO) algorithm to improve its optimization ability. Lastly, numerical outcomes of the NASA PCoE datasets confirm this method’s applicability and efficacy.

Abstract Polyesters with both cyclic topology and chemical recyclability are attractive. Here, the alternating copolymerization of cyclic anhydride and o‐phthalaldehyde to synthesize a series of cyclic and recyclable polyesters are reported for the first time. Besides readily available monomers, the copolymerization is carried out at 25 °C, uses common Lewis/Brønsted acids as catalysts, and achieves high yields within 1 h. The resulting polyesters possess well‐defined alternating sequences, high‐purity cyclic topology, and tunable structures using distinct two monomer sets. Of interest, the copolymerization manifests obvious chemical reversibility as revealed by kinetic and thermodynamic studies, making the unprecedented polyesters easy to recycle to their distinct two monomers in a closed loop at high temperatures. This work furnishes a facile and efficient method to synthesize cyclic polyesters with closed‐loop recyclability.

Validamycin, is classified as an environmentally friendly fungicide. It has high efficacy with little associated pollution risk, and it has been used in China on tobacco for many years especially during leaf spot season. To understand changes in microbial communities and functional aspects of the tobacco phyllosphere after exposure to validamycin, the chemical was sprayed on tobacco leaves during brown spot epidemic periods caused by Alternaria alternata, and asymptomatic and symptomatic leaves of tobacco were sampled at different times (0 day before, 5, 10, and 15 days after application). The fungal and bacterial population diversity and structure were revealed using Illumina NovaSeq PE250 high-throughput sequencing technology, and Biolog-ECO technology which analyzes the metabolic differences between samples by using different carbon sources as the sole energy source. The results showed that the microbial community structure of both asymptomatic and symptomatic tobacco leaves changed after the application of valproate, with the microbial community structure of the asymptomatic tobacco leaves being more strongly affected than that of the symptomatic leaves, and the diversity of bacteria being greater than that of fungi. Phyllosphere fungal diversity in asymptomatic leaves increased significantly after application, and bacterial abundance and diversity in both asymptomatic and symptomatic leaves first increased and then decreased. Validamycin treatment effectively reduced the relative abundance of Alternaria, Cladosporium, Kosakonia, and Sphingomonas in leaves showing symptoms of tobacco brown spot, while the relative abundance of Thanatephorus, Pseudomonas, and Massilia increased significantly after application. Furthermore, the ability to metabolize a variety of carbon sources was significantly reduced in both types of leaves after validamycin application, and both types had a weaker ability to metabolize α-Ketobutyric Acid after application. This study reveals phyllosphere micro-ecological changes in symptomatic and asymptomatic tobacco leaves during different periods after validamycin application and the effects on the metabolic capacity of phyllosphere microorganisms. It can provide some basis for exploring the effect of validamycin on the control of tobacco brown spot.

A two-step brazing process was successfully employed to join MgF2 ceramic and TA15 alloy using eutectic Ag28% (in mass fraction) Cu alloy and Bi2O3B2O3ZnO (BBZ) glass as fillers, by introducing a 100 μm thick GH4169 interlayer. Multiscale characterization revealed that interdiffusion and reaction occurred at the joint interfaces. As a result, a reliable joint system consisting of TA15/TiCu/TiCu2Al/Ag(s,s) + Cu(s,s)/TiCu2Al/TiCu Ni + Ag-rich layer/GH4169/nano-oxide layer/glass/Mg3(BO3)F3+MgO + MgF2 reaction layer/MgF2 was formed. The GH4169-interlayer exhibited adaptive compatibility though its interaction with AgCu and BBZ glass fillers, effectively accommodating strong interface bonding and thermal mismatch stress between TA15 and MgF2 substrates. It shows an excellent shear strength (32 MPa, at room temperature) as well as thermal cycling stability without any cracking or spallation observed after the 20 thermal shock cycles between room temperature and 300 °C. It provides valuable insights into designing highly reliable ceramic/metal joints that demonstrate superior stability and adaptability in specific applications.

The difficulty of reducing the diameter of lutetium oxide (Lu2O3) continuous fibers below 50 μm not only limits the flexibility of the sample but also seriously affects their application and development in high-energy lasers. In this work, a Lu-containing precursor with high ceramic yield was used as raw material, fiberized into precursor fibers by dry spinning. The pressure-assisted water vapor pretreatment (PAWVT) method was creatively proposed, and the effect of pretreatment temperature on the ceramization behavior of the precursor fibers was studied. By regulating the decomposition behavior of organic components in the precursor, the problem of fiber pulverization during heat treatment was effectively solved, and the Lu2O3 continuous fibers with a diameter of 40 μm were obtained. Compared with the current reported results, the diameter was reduced by about 50%, successfully breaking through the diameter limitation of Lu2O3 continuous fibers. In addition, the tensile strength, elastic modulus, flexibility, and temperature resistance of Lu2O3 continuous fibers were researched for the first time. The tensile strength and elastic modulus of Lu2O3 continuous fibers were 373.23 MPa and 31.55 GPa, respectively. The as-obtained flexible Lu2O3 continuous fibers with a limit radius of curvature of 3.5–4.5 mm had a temperature resistance of not lower than 1300 ℃, which established a solid foundation for the expansion of their application form in the field of high-energy lasers.

Abstract Ultra-high temperature ceramics (UHTCs) are generally referred to the carbides, nitrides, and borides of the transition metals, with the Group IVB compounds (Zr & Hf) and TaC as the main focus. The UHTCs are endowed with ultra-high melting points, excellent mechanical properties, and ablation resistance at elevated temperatures. These unique combinations of properties make them promising materials for extremely environmental structural applications in rocket and hypersonic vehicles, particularly nozzles, leading edges, and engine components, etc. In addition to bulk UHTCs, UHTC coatings and fiber reinforced UHTC composites are extensively developed and applied to avoid the intrinsic brittleness and poor thermal shock resistance of bulk ceramics. Recently, highentropy UHTCs are developed rapidly and attract a lot of attention as an emerging direction for ultra-high temperature materials. This review presents the state of the art of processing approaches, microstructure design and properties of UHTCs from bulk materials to composites and coatings, as well as the future directions.

In this study, the effect of microstructure under various dose rates of plasma immersion ion implantation on 8Cr4Mo4V steel has been investigated for crystallite size, lattice strain and dislocation density. The phase composition and structure parameters including crystallite size, dislocation density and lattice strain have been investigated by X-ray diffraction (XRD) measurements and determined from Scherrer’s equation and three different Williamson–Hall (W-H) methods. The obtained results reveal that a refined crystallite size, enlarged microstrain and increased dislocation density can be obtained for the 8Cr4Mo4V steel treated by different dose rates of ion implantation. Compared to the crystallite size (15.95 nm), microstrain (5.69 × 10−3) and dislocation density (8.48 × 1015) of the dose rate of 2.60 × 1017 ions/cm2·h, the finest grain size, the largest microstrain and the highest dislocation density of implanted samples can be achieved when the dose rate rises to 5.18 × 1017 ions/cm2·h, the effect of refining is 26.13%, and the increment of microstrain and dislocation density are 26.3% and 45.6%, respectively. Moreover, the Williamson–Hall plots are fitted linearly by taking βcosθ along the y-axis and 4sinθ or 4sinθ/Yhkl or 4sinθ(2/Yhkl)1/2 along the x-axis. In all of the W-H graphs, it can be observed that some of the implanted samples present a negative and a positive slope; a negative and a positive slope in the plot indicate the presence of compressive and tensile strain in the material.

This paper studies the trajectory tracking control of a class of multi-agent systems, in which, each agent is expressed by a nonlinear discrete-time unknown dynamics and can interact with its neighbors via the history outputs of its neighbors. In order to tackle each unknown dynamics, based on its neighbors' and its own history I/O data and neural network, an approximate model is established by the direct data-driven method. Using the neighbors' history information and the reference trajectory, the decentralized adaptive indirect data-driven control is designed; then, the feedback gain matrix online is designed and adjusted by measured output data and previous estimates. For each agent, this is an adaptive control process of prediction, estimation, and adjustment, which needs to solve some nonlinear optimization problems online, can surmount the negative effects of the modeling errors caused by neural networks, and is the key to making each agent output asymptotically track the given reference trajectory. The convergence analysis shows that the applied method is effective and feasible.

This paper studies the decentralized adaptive tracking control problem for a class of discrete-time multi-agent systems with unknown parameters and high-frequency gains using multi-model method. Each agent is strong coupling with its neighbors by the historical outputs. All agents are interacted either directly or indirectly. In the face of uncertainties, the projection algorithm as a normal adaptive method is adopted. In order to improve quality of identification, the multi-model method is taken to identify unknown parameters and high-frequency gains using switching sets of the multiple parameters' and high-frequency gains' estimates, and the index switching functions. Using the certainty equivalence principle, the control law for the hidden leader agent is designed by the desired reference signal; the control law for each follower agent is devised by neighbors' historical outputs. Moreover, the proposed decentralized adaptive control laws can guarantee the following performances of the system: (1) the leader agent tracks the reference trajectory and each follower agent follows the average value of its neighborhood historical outputs; (2) the synchronization of all the follower agents to the leader agent is achieved; (3) all the agents track the reference trajectory, and the closed-loop system eventually achieves strong synchronization. Finally, simulations validate the effectiveness on improving control performance of multi-model adaptive algorithm by comparing with the projection algorithm.

Four kinds of sugar (glucose, fructose, sucrose, and maltose) were selected as carbon precursors, and corresponding dense carbon products were prepared using a novel hydrogel carbonization method. The carbonization processes of sugar–polyacrylamide (sugar–PAM) hydrogels were studied in detail. The molecular structures in the raw materials were analyzed by proton nuclear magnetic resonance spectroscopy (1H NMR). Samples prepared at different temperatures were characterized by thermogravimetry analysis (TGA) and Fourier-transform infrared (FTIR) spectroscopy. The morphology and microstructure of sugar-derived carbons were confirmed by field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicated that the sugar solution was surrounded by PAM with a three-dimensional network structure and formed hydrogels in the initial stage. The sugar solution was considered to be separated into nanocapsules. In each nanocapsule, sugar molecules could be limited within the hydrogel via walls formed by PAM chains. The hydroxyl group in the sugar molecules connected with PAM by the hydrogen bond and intermolecular force, which can strengthen the entire hydrogel system. The self-generated pressure of hydrogel constrains the foam of sugar during the heat treatment. Finally, dense carbon materials with low graphitization instead of porous structure were prepared at 1200 °C.

In model free adaptive control (MFAC), a virtual equivalent dynamic linearized model is built. The linearization length constants (LLCs) of the virtual equivalent dynamic linearized model are selected by the practitioner based on experience. In this paper, the optimal LLCs are investigated, and compact model free adaptive control (CMFAC) is introduced for a class of unknown discrete-time nonlinear systems. Compared with MFAC, the proposed CMFAC does not need to consider the values of LLCs, and the optimal LLCs are decided by the desired tracking error of systems. Simulation experiments are taken, and the simulation results indicate that the proposed control algorithm is effective and can achieve asymptotic tracking.

Abstract Rhenium dichalcogenides (ReX2, X = S or Se) are catalysts that have great promise for the photoenhanced hydrogen evolution reaction (PE‐HER) because of their unique physiochemical properties. However, the catalytic performance is still restricted by their low concentration of electrocatalytic activity sites and poor injection of hot electrons. Herein, dual‐enhancement in ReSe2 nanosheets (NSs) with high concentration of active sites and efficient use of hot electrons is simultaneously achieved with moderate Mo doping. Contributions from exposed catalytically active sites, improved electrical conductivity, and enhanced solar spectral response are systematically investigated. Superior PE‐HER catalytical performance is obtained in Re0.94Mo0.06Se2, which has more catalytically active sites and optimized band structure than other Re1−xMoxSe2 samples. Here, it is demonstrated that only doping can reduce the overpotential (η10) from 239 to 174 mV at −10 mA cm−2 (Δ1η10 = 65 mV). Then, η10 is further improved to 137 mV under simulated AM 1.5 sun illumination (Δ2η10 = 37 mV). The total improvement (Δη10) toward PE‐HER is 102 mV (Δ1η10 + Δ2η10 = 102 mV) in optimal Re0.94Mo0.06Se2. This work presents a new perspective for researching high‐efficiency photoenhanced HER ReSe2‐based electrocatalysts and other layered transition metal dichalcogenides.

Abstract Several-millimeter long SiC nanowires (NWs) with unique optical properties, excellent thermal stability and flexible nanomechanical properties were synthesized using a simple method with silicon and phenolic resin as the raw materials. The SiC NWs displayed special optical properties that were attributed to their large size and Al-doping. They displayed broad green emission at 527.8 nm (2.35 eV) and purple emission concentrated at 438.9 nm (2.83 eV), in contrast to the other results, and the synthesized SiC NWs could also remain relatively stable in air up to 1000 °C indicating excellent thermal stability. The Young’s moduli of the SiC NWs with a wide range of NW diameters (215–400 nm) were measured using an in situ nanoindentation method with a hybrid scanning electron microscopy/scanning probe microscopy (SEM/SPM) system for the first time. The results suggested that the values of the Young’s modulus of the SiC NWs showed no clear size dependence, and the corresponding Young’s moduli of the SiC NWs with diameters of 215 nm, 320 nm, and 400 nm were approximately 559.1 GPa, 540.0 GPa and 576.5 GPa, respectively. These findings provide value and guidance for studying and understanding the properties of SiC nanomaterials and for expanding their possible applications.

Abstract Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels’ applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stability and electric conductivities via hydrothermal reduction and supercritical ethanol drying. Annealing at 1500 °C resulted in slightly increased thermal conductivity and further improvement in mechanical properties, oxidation temperature and electric conductivity of the graphene aerogel. The large BET surface areas, together with strong mechanical properties, low thermal conductivities, high thermal stability and electrical conductivities made these graphene aerogels feasible candidates for use in a number of fields covering from batteries to sensors, electrodes, lightweight conductor and insulation materials.

Abstract ZrB2–SiC–Cf composites containing 20–50 vol% short carbon fibers were hot pressed at low sintering temperature (1450 °C) using nanosized ZrB2 powders, in which the fiber degradation was effectively inhibited. The strain-to-failure values of such composites increased with increasing fiber content, and the value for the composite with 50 vol% Cf was even more than 3 times higher than that of the composite with 20 vol% Cf. Furthermore, the composite exhibited non-brittle fracture mode when the fiber content was above 30 vol%, and the thermal shock critical temperature difference of the composite with 30 vol% Cf was up to 727 °C, revealing excellent thermal shock resistance of this composite. Additionally, ZrB2–SiC–Cf composites displayed good oxidation resistance when the fiber content was below 40 vol%, suggesting that this method provides a promising way for preparation of high-performance ZrB2–SiC–Cf composites at low temperature.