Remarkable progress has been made in surface icephobicity in the recent years. The mainstream standpoint of the reported antiicing surfaces yet only considers the ice–substrate interface and its adjacent regions being of static nature. In reality, the local structures and the overall properties of ice–substrate interfaces evolve with time, temperature and various external stimuli. Understanding the dynamic properties of the icing interface is crucial for shedding new light on the design of new anti-icing surfaces to meet challenges of harsh conditions including extremely low temperature and/or long working time. This article surveys the state-of-the-art anti-icing surfaces and dissects their dynamic changes of the chemical/physical states at icing interface. According to the focused critical ice–substrate contacting locations, namely the most important ice–substrate interface and the adjacent regions in the substrate and in the ice, the available anti-icing surfaces are for the first time re-assessed by taking the dynamic evolution into account. Subsequently, the recent works in the preparation of dynamic anti-icing surfaces (DAIS) that consider time-evolving properties, with their potentials in practical applications, and the challenges confronted are summarized and discussed, aiming for providing a thorough review of the promising concept of DAIS for guiding the future icephobic materials designs.

Reference: Zhuo, Y., Xia, Z., Qi, Y., Sumigawa, T., Wu, J., Šesták, P., Lu, Y., Håkonsen, V., Li, T., Wang, F., Chen, W., Xiao, S., Long, R., Kitamura, T., Li, L., He, J., Zhang, Z., Simultaneously Toughening and Stiffening Elastomers with Octuple Hydrogen Bonding. Adv. Mater. 2021, 33, 2008523. https://doi.org/10.1002/adma.202008523

Gel materials have drawn great attention recently in the anti-icing research community due to their remarkable potential for reducing ice adhesion, inhibiting ice nucleation, and restricting ice propagation. Although the current anti-icing gels are in their infancy and far from practical applications due to poor durability, their outstanding prospect of icephobicity has already shed light on a new group of emerging anti-icing materials. There is a need for a timely review to consolidate the new trends and foster the development towards dedicated applications. Starting from the stage of icing, we first survey the relevant anti-icing strategies. The latest anti-icing gels are then categorized by their liquid phases into organogels, hydrogels, and ionogels. At the same time, the current research focuses, anti-icing mechanisms and shortcomings affiliated with each category are carefully analysed. Based upon the reported state-of-the-art anti-icing research and our own experience in polymer-based anti-icing materials, suggestions for the future development of the anti-icing gels are presented, including pathways to enhance durability, the need to build up the missing fundamentals, and the possibility to enable stimuli-responsive properties. The primary aim of this review is to motivate researchers in both the anti-icing and gel research communities to perform a synchronized effort to rapidly advance the understanding and making of gel-based next generation anti-icing materials.

Carbon sulfur nanothreads (CSNTs) mainly composed of two chiral long alkane chains have been recently fabricated from thiophene by a pressure-induced phase transition in low-temperature, but their mechanical properties remain unexplored. Here, the critical roles of morphology and temperature on the tensile characteristics of CSNTs are for the first time examined using molecular dynamic simulations with a first-principles-based ReaxFF forcefield. It is revealed that CSNTs exhibit high tensile Young's modulus, high tensile strength and excellent ductility, and their tensile properties are morphology and temperature dependent. Morphologically, atomic arrangement with various configurations makes every CSNTs possess unique mechanical properties. Thermally, as temperature varies from 1 to 1500 K, CSNTs become mechanically weakened. In comparison with conventional diamond nanothreads (DNTs) and carbon nitride nanothreads (CNNTs), CSNTs show distinct axial elongation mechanisms, with relatively insignificant changes in chemical bond orders and bond length in the skeleton prior to the final rupture. Instead, the stretching of bond angle and dihedral angle mainly contribute to the global axial elongation, while the torsional deformation is limited due to their perfect global symmetry in the configuration. This study provides fundamental insights into the mechanics of ultra-thin CSNT structures.

The manuscript demonstrates the direct transgranular to intergranular fracture transition process controlled by hydrogen-influenced plasticity, by scrutinizing the tensile responses of Ni Σ5(210)[001] GB with varied hydrogen concentration using atomistic modeling. Compared with the Σ3 coherent twin GB which traps nearly no H atoms, H will form an atmosphere at the Σ5 GB due to the high trapping energy and excess volume and induce a higher initial local stress. In the case without H, less stress is built up at the Σ5 GB region during deformation, which leads to transgranular fracture. In contrast, H suppresses the stress-releasing ability of the Σ5 GB, which causes a local stress concentration and promotes local plasticity on the GB. This further leads to early dislocation emission, severe twinning evolution, increased number of vacancies and thus enhanced nanovoiding on the GB. The growth of nanovoids with H finally completes the transgranular to intergranular-fracture transition. These findings enrich our knowledge of hydrogen-induced intergranular fracture at the microscale.

A new paper published in Materials Science and Engineering A

The microstructure and crystallographic orientation-dependent nanomechanical characteristics of an additively manufactured (AM-ed) high-entropy alloy (HEA) were investigated by aid of nanoindentation and SEM. Furthermore, the effect of heat treatment on AM-ed HEA was explored by comparing with as-printed HEA. Interestingly, it is found that the grain {101} has the highest hardness and elastic modulus, whereas the creep resistance of grain {111} is the greatest, with the indicators of the creep mechanism showing lattice diffusion is the dominant mechanism. Heat treatment in the current study can increase the hardness and elastic modulus but decrease the creep resistance slightly. This work elucidates the grain orientation dependence on nanomechanical properties and the role of heat treatment, and sheds light on the nanoscale creep behavior and the corresponding creep mechanisms in the AM-ed HEA.

The local structure and heat transfer properties (thermal conductivity and interfacial conductance) in model semi-crystalline polyethylene (PE) are studied by non-equilibrium molecular dynamics. Three different force fields with different levels of detail (all-atom, all-atom with constraints, and united-atom) are compared. We find that the structure of the model PE is significantly influenced by the choice of force field. The united-atom force field results in a reduced overall crystallinity and an over-idealized organization of the polymer chains, compared to the all-atom force fields. We find that thermal transport properties are not greatly influenced when structural effects are taken into consideration, and our results suggest that united-atom models can be used to study heat transfer properties of model PE, with decreased computational cost.

The experimental method and setup for determining the heat transfer coefficient under CO2 condensation is developed and validated. Condensation heat transfer coefficient of CO2 on smooth surfaces of Cu, Al and stainless steel as well as hierarchical surfaces of Cu based micro and nanostructures have been investigated. It is found that the heat transfer coefficient increases with increasing the saturation pressure and increased surface area. The best of the structured surfaces resulted in a heat transfer coefficient 66% higher than that of the unstructured surface.

Nanoparticles hold promising potentials in enhanced oil recovery. The mechanics of nanoparticles interacting with different components in confined nanochannels still awaits in-depth clarification. In the current work, atomistic modeling and molecular dynamics simulations were utilized to investigate three different nanoparticle dispersion patterns in nanochannels with trapped oil droplets, namely nanoparticles favoring in water, in oil, and in both phases. The special focus of this study is to detail the local pressure in the nanochannels induced by the injections of nanoparticles. The results reveal the key effects of different nanoparticles on altering the atomistic mechanics in the complex nanofluid system and shed light on the rational design and selection of nanoparticles in practice. Particularly, the local pressure in the three-phase contact area triggered by hydrophilic nanoparticles was found to feature the famous structural disjoining pressure, which supplied supporting evidences to the former continuum medium based analytical study from the atomistic level for the first time. 

Current synthetic elastomers suffer from the well‐known trade‐off between toughness and stiffness. By a combination of multiscale experiments and atomistic simulations, a transparent unfilled elastomer with simultaneously enhanced toughness and stiffness is demonstrated. The designed elastomer comprises homogeneous networks with ultrastrong, reversible, and sacrificial octuple hydrogen bonding (HB), which evenly distribute the stress to each polymer chain during loading, thus enhancing stretchability and delaying fracture. Strong HBs and corresponding nanodomains enhance the stiffness by restricting the network mobility, and at the same time improve the toughness by dissipating energy during the transformation between different configurations. In addition, the stiffness mismatch between the hard HB domain and the soft poly(dimethylsiloxane)‐rich phase promotes crack deflection and branching, which can further dissipate energy and alleviate local stress. These cooperative mechanisms endow the elastomer with both high fracture toughness (17016 J m⁻²) and high Young's modulus (14.7 MPa), circumventing the trade‐off between toughness and stiffness. This work is expected to impact many fields of engineering requiring elastomers with unprecedented mechanical performance.

News: No ice, ice, baby!