Porous bulk superhydrophobic nanocomposites for extreme environments

Robust superhydrophobic materials providing protections from harsh weather events such as hurricanes, high temperatures, and humid/frigid conditions have proven challenging to achieve. Here, we report a porous bulk nanocomposite comprising carbon nanotube (CNT)-reinforced polytetrafluoroethylene (PTFE). The nanocomposites are prepared using a templated approach by infusing a CNT/PTFE dispersion into a sponge followed by thermal annealing and decomposition of the sponge template. Importantly, an excess accretion of CNT/PFFE particle mixture on the sponge resulted in nanocomposites with unique and hierarchical porous microstructure, featuring nanochannels near the surface connected to microscale pores inside. The superhydrophobic nanocomposite could resist liquid jets impacting at a velocity of �85.4 m s1 (Weber number of �202,588) and exhibits excellent high-temperature resistance as well as mechanochemical robustness. The porous nanocomposites display excellent icephobicity both with and without infusion with polydimethylsiloxane/silicone oil. These properties should facilitate exploitation as stiff/strong structural polymeric foams used in a variety of fields

Stitching Repair for Delaminated Carbon Fiber/Bismaleimide Composite Laminates

Due to the excellent mechanical properties and heat resistance, bismaleimide matrix composite materials have been widely used in aircraft. However, they are susceptible to low-energy impacts, such as bird hits, gravel, tools falling, etc., which can easily result in delamination. The delamination can significantly reduce the compression performance of composites and become a potential hazard for aircraft in service. In this paper, a stitching method developed from the Z-pin manufacturing process was proposed to repair delaminated laminates. Firstly, the delaminated area was stitched by fiber bundles that were pre-impregnated with glue. Then, the fiber bundles threading through the laminate become the pins after the curing process, thus producing the bridging effect between delaminated layers. As a result, the in-plane compressive properties of the laminate are enhanced. The parameters, including the size, number, and position of the stitching hole, for the stitching repair were optimized, and the factors affecting the repair effect were discussed through both finite element analysis and experiments. The results showed that for a carbon fiber/bismaleimide composite plate with a circular delamination roughly 30 mm in diameter, the in-plane compressive strength can be recovered from 54.45% to 84.23% of the pristine plate, and the modulus was fully recovered

Effect of molecular structure of polyurethane elastomer on damping and mechanical properties

In order to obtain polyurethane elastomer (PUE) for reducing the vibration and noisy in deep-water environments, toluene diisocyanate (TDI), polypropylene glycol 2000 (PPG2000) and triethanolamine (TEA) were selected as raw materials, and the effects of hard segment content, R value and synthesis route on damping property and compression modulus of PUE were explored. Results reveal that the tanδ of PUE could be decreased with the increase of hard segment content, while the compression modulus increases. With the increase of R value, Tg increases, the compression modulus first increases and then decreases, reaching a peak when R=2. The prepolymer process and one-step process have little effect on the tanδ, but the compression modulus of PUE synthesized by prepolymer process is obviously greater than that of one-step process, which is more in line with the requirements of high damping/strong pressure resistance. It was observed that the compression modulus of PUE can be effectively improved by increasing the stiffness of molecular chain, the degree of hydrogen bonding and the uniformity of hard segment micro region distribution, but for damping property have a negative impact

Protocol for preparation of highly durable superhydrophobic bulks with hierarchical porous structures

Summary: Superhydrophobic surfaces face challenges in comprehensive durability when used in extreme outdoor environments. Here, we present a protocol for preparing nanocomposite bulks with hierarchical structures using the template technique. We describe steps for using hybrid nanoparticles of polytetrafluoroethylene and multi-walled carbon nanotube to fill inside and dip on the polyurethane (PU) foam. We then detail procedures for its removal by sintering treatment. The extra accretion layer on the PU foam surface was highlighted to construct hierarchical porous structures.For complete details on the use and execution of this protocol, please refer to Wu et al.1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics

Improving Yield and Water Productivity of Rainfed Summer Maize in Smallholder Farming: A Case Study in Hebei Province, China

Because of the strong competition for a limited resource of water and demand for food production, understanding yield and water productivity (WP) potentials and exploitable gaps in the current production of intensively rainfed maize (Zea mays L.) is essential on the regional scale in China. In this study, we conducted 411 site–year on-farm trials to assess the actual yield and WP of rainfed summer maize and its yield and WP potentials in Hebei Province, China. Each on-farm trial contained detailed information of three different treatments: no fertilizer application (CK), current farmers’ practices (FP, depending on local farmer field fertilization management), and optimum fertilizer application (OPT, depending on soil testing and balanced fertilization). Results revealed that the yield and WP of rainfed summer maize in Hebei Province were 7635 kg ha−1 and 20.7 kg ha−1 mm−1, respectively, and the yield and WP potentials were 12,148 kg ha−1 and 32.0 kg ha−1 mm−1, respectively. Thus, the farmers attained 62.8% of the yield potential and 64.7% of the WP potential. A wide variation was observed in terms of the yield and WP across various types of farming. Compared with high-yield and high-WP (HYHW) farming, in low-yield and low-WP (LYLW) farming, the yield decreased by 24.9% and WP decreased by 44.4%. Nitrogen fertilizer application rate and rain were the most significant factors for yield and WP gaps among farmers, respectively. Other factors, such as solar radiation (tSola), soil available phosphorus content (AP), potassium fertilizer application rate, and grass-referenced evapotranspiration from planting to maturity (ET0), contributed the most to the variations in the yield and WP. Scenario analysis indicated that the optimization of fertilization levels from current to optimal for each farming could increase the yield and WP by 9.7% and 14.8%, respectively; closing gaps between the farming groups and achievement of the standard of HYHW farming by all farmers could increase the yield and WP by 14.8% and 35.5%, respectively; and achieving the yield and WP potentials could increase the yield and WP by 59.1% and 54.8%, respectively. These findings provided farming-based evidence that optimal nutrient management, advanced and climate-adapted agronomy practices, and higher soil fertility are essential for future maize production

Impact of Abdominal Obesity on Thyroid Auto-Antibody Positivity: Abdominal Obesity Can Enhance the Risk of Thyroid Autoimmunity in Men

Background. The interrelation between obesity and autoimmune thyroid diseases is complex and has not been confirmed. The aim of the present study was to observe the relationship between thyroid autoimmunity and obesity, especially abdominal obesity, in a large population. Methods. A total of 2253 residents who had lived in Xinjiang for more than 3 years were enrolled. Serum thyroid hormone concentration, thyroid autoantibodies, lipid parameters, Weight, height, and waist and hip circumference were measured. Results. The prevalence of thyroid peroxidase antibody (TPOAb) and/or thyroglobulin antibody (TgAb) positive was 32.1% (21.2% in men and 37% in women, P<0.01). Compared with women, men had significantly higher TG levels, waist circumference, and hip circumference levels (P<0.01), while women showed higher TSH, TPOAb, and TgAb levels (P<0.01). The prevalence of overweight and obesity was 71.1% in men and 63.5% in women. Men had a higher prevalence of abdominal obesity than women (56.6% in men and 47.6% in women, P<0.01). TPOAb correlates positively with waist circumference (r = 0.100, P<0.05) in men. Binary logistic analysis showed that TPOAb positivity had increased risks of abdominal obesity in men, and the OR was 1.1044 (95% CI 1.035, 1.151, P<0.05). Conclusion. Our results indicate that men had higher lipid levels, thicker waist circumference, and higher prevalence of overweight, obesity, and abdominal obesity. Abdominal obesity is a risk factor for TPOAb positivity in men, suggesting that abdominal obesity can enhance the risk of thyroid autoimmunity in men

Application, development, and challenges of stealth materials/structures in next-generation aviation equipment

Accessing the electromagnetic spectrum is the essence of modern warfare, which is determined by the detection direction, the airframe structure, and the material. Modern aviation equipment with a long strike range, penetration, and strong sensing and rapid decision-making capabilities is the key to capturing spectrum access. The development of penetration detection can promote the application of stealth materials/structures in next-generation aviation equipment, though the design of component-level stealth structures is constrained by aerodynamic efficiency, maneuverability, and preparation processes. Panel-level stealth material/structure design provides new avenues for the development of next-generation aviation equipment. This paper reviews the key advances and future challenges for stealth materials/structures. The main content focuses on the detection technology and application of stealth materials/structures in aviation equipment and the challenges posed by stealth materials/structures in terms of aviation equipment maintenance. Furthermore, this study addresses the opportunities and development tendencies of stealth materials/structures

Integrated multi-omics analysis reveals insights into Chinese forest musk deer (Moschus berezovskii) genome evolution and musk synthesis

Among the artiodactyls, male animals belonging to the Family Moschidae have a unique tissue, the musk gland, with the capability of musk synthesis. However, the genetic basis of musk gland formation and musk production are still poorly understood. Here, musk gland tissues from two juvenile and three adult Chinese forest musk deer (Moschus berezovskii) were utilized to analyze genomic evolution events, evaluate mRNA profiles and investigate cell compositions. By performing genome reannotation and comparison with 11 ruminant genomes, three expanded gene families were identified in the Moschus berezovskii genome. Transcriptional analysis further indicated that the musk gland displayed a prostate-like mRNA expression pattern. Single-cell sequencing revealed that the musk gland is composed of seven distinguishable cell types. Among them, sebaceous gland cells and luminal epithelial cells play important roles in musk synthesis, while endothelial cells master the regulation of cell-to-cell communication. In conclusion, our study provides insights into musk gland formation and the musk-synthesizing process

Improving mechanical properties of high-temperature resistant carbon fiber/phthalonitrile composites via surface modification: a comparative study on modification methods

The interfacial bonding is of essential importance for the mechanical properties of high-temperature resistant carbon fiber/phthalonitrile composite materials. To promote the interfacial adhesion of carbon fiber/phthalonitrile composites, three surface modification methods, namely HP302 sizing, diazotization modification, and oxidation-diazotization modification, were applied and compared. The results showed that the de-sizing treatment barely affected the mechanical properties of the composites. Both re-sizing with HP302 agent and diazotization modification improved the mechanical properties, while the mechanical properties were drastically decreased via the oxidation-diazotization modification. Among these surface modification methods, the diazotization treatment derived the best mechanical properties of carbon fiber/phthalonitrile composites both at room and high temperature. Specifically, the flexural strengths were 345 MPa (RT), 525 MPa (300°C), and 442 MPa (400°C), which were 47%, 302%, and 281% higher than those of the pristine composites. The interlaminar shear strengths were 33 MPa (RT), 26 MPa (300°C), and 27 MPa (400°C), which were all over twofold than those of the original counterparts.</p