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The linkages among carbon, renewable energy, and electricity markets are gradually strengthening. In order to prevent risk transmission among markets, this paper uses the TVP-VAR-DY (Time-Varying Parameter–Vector Auto Regression–Dynamic) model to analyze the dynamic risk spillover effects and network structure of risk transmission among carbon, renewable energy, and electricity markets. The empirical results show that there are significant asymmetric spillover effects among carbon, renewable energy, and electricity markets. The total spillover index shows that spillover effects among carbon, renewable energy, and electricity markets are time-varying, especially during unexpected events. Besides, the net spillover index indicates that the spillover effects are bidirectional, asymmetric, and time-varying. Finally, under the influence of unexpected events, the network structures of risk transmission among carbon, renewable energy, and electricity markets are heterogeneous. Compared to the Russia-Ukraine conflict, the COVID-19 pandemic has a more significant impact on these markets. [ABSTRACT FROM AUTHOR]

To investigate the variations in price volatility spillover effects on different time scales across the LME, SMM, and Chinese spot nickel markets. This study uses data from the London Metal Exchange (LME), Shanghai Nonferrous Metals (SMM) nickel daily closing prices, and Chinese nickel daily market prices from April 1, 2015, to September 30, 2022, to categorize the above three markets' yield series into four-time scales: very short, short, medium, and long term. The multivariate BEKK-GARCH approach is then used to analyze the spillover effects at different time scales. The study's findings reveal that (1) the LME, SMM, and spot nickel prices are all impacted by external shocks and inherent volatility at all time scales; (2) at the very short time scale, there is a two-way volatility spillover effect between the SMM nickel and the other two markets, in addition, a one-way volatility spillover effect between the LME and spot nickel price; (3) at the short time scale, the volatility spillover effect between the LME and spot nickel price disappears; (4) at the medium-term time scale, there is no volatility spillover effect between the LME, SMM, and spot nickel price; (5) at the long-term time scale, the SMM has a volatility spillover effect on spot nickel price. [ABSTRACT FROM AUTHOR]

High-temperature ablation is a common failure phenomenon that limits the service life of the transmission parts on heavy-duty machines used in heavy load, high temperature, high shock conditions due to in-sufficient supply of lubricating oil and grease. Traditional self-lubricating coatings prepared by inorganic, organic or organic-inorganic hybrid methods are prone to be oxidated at high temperatures to lose their friction reducing function, so that it is difficult to meet the engineering requirements of high-temperature lubrication. We design viscoelastic polymer coatings by a high-temperature self-lubricating and wear-resistant strategy. Polytetrafluoroethylene (PTFE, Tm = 329 °C) and polyphenylene sulfide (PPS, Tg = 84 °C, Tm = 283 °C) are used to prepare a PTFE/PPS polymer alloy coating. As the temperature increases from 25 to 300 °C, the PTFE/PPS coating softens from glass state to viscoelastic state and viscous flow state, which is owing to the thermodynamic transformation characteristic of the PPS component. Additionally the friction coefficient (µ) decreased from 0.096 to 0.042 with the increasing of temperature from 25 to 300 °C. The mechanism of mechanical deformation and surface morphology evolution for the PTFE/PPS coating under the multi-field coupling action of temperature (T), temperature-centrifugal force (T-Fω), temperature-centrifugal force-shearing force (T-Fω-Fτ) were investigated. The physical model of "thermoviscoelasticity driven solid-liquid interface reducing friction" is proposed to clarify the self-lubricating mechanism determined by the high-temperature viscoelastic properties of polymers. The high-temperature adjusts the viscosity (η) of the coating, increases interface slipping and intensifies shear deformation (τ), reducing the friction coefficient. The result is expected to provide a new idea for designing anti-ablation coatings served in high temperature friction and wear conditions. [ABSTRACT FROM AUTHOR]

Exploiting a renewable and inexpensive electrochemical catalyst for hydrogen evolution reaction (HER) has attracted great attentions recently. In this study, a MOF catalyst CdS@PCN-224(Ni) was fabricated using CdS quantum dots (QDs) and unique PCN-224(Ni) by a simple hydrothermal method. Due to synergetic effect of the CdS QDs and bimetallic porphyrin MOF structure, the special catalyst showed a great electrocatalytic activity with a low overpotential of 120 mV and a current density of 10 mA/cm2 with a Tafel slope of 90.8 mV/dec, which is approaching to that of the Pt/C (42.8 mV/dec). The double-layer capacitances (Cdl) of CdS@PCN-224(Ni) are 9.75 mF/cm2 which is distinctly superior to that of the PCN-224 (2.33 mF/cm2). Even more to the point, this innovative electrochemical catalyst has a wonderful durability in acid solution, which means it could reach a sustainable utilization. In conclusion, the high activity and low-cost catalyst could be a promising candidate for HER devices in acid media. [ABSTRACT FROM AUTHOR]

Dense colloidal suspensions are processed in a wide variety of industries. Challenges for pumping suspensions and slurries at high concentrations include shear thickening and dilation, which can have deleterious consequences. These systems are shear sensitive close to the jamming point, meaning that a significant increase in high shear viscosity can be observed with just a few percent change in volume fractions. Therefore, accurate and rapid determination of the jamming point can greatly aid formulation. Typically, conventional rheometry identifies the jamming point by a time-consuming process, whereby multiple flow curves of suspensions of different volume fraction are measured and extrapolated to the volume fraction where the viscosity diverges. We present an alternative approach for rapid, one-step, experimental determination of the jamming point for aqueous suspensions. The procedure monitors the shear stress under constant shear stress or shear rate as the sample is dewatered using immobilization cell rheometry, until the viscosity diverges. The method is validated by comparing the results of this work with conventional rheometry for a model suspension. Then it is applied to examine the effect of grafting a short-chain polymer to particles, comprising an industrial suspension of silica-coated titania. Polymeric coating of the particles increases the jamming concentration and mitigates shear thickening, qualitatively consistent with predictions from simulations. [ABSTRACT FROM AUTHOR]

Bionic self-cleaning surfaces with well-ordered polymer nano-fibers are firstly fabricated by disturbing crystallization during one-step coating-curing process. Orderly thin (100 nm) and long (5-10 μm) polymer nano-fibers with a certain direction are fabricated by external macroscopic force ( F) interference introduced by H gas flow, leading to superior superhydrophobicity with a water contact angle (WCA) of 170° and a water sliding angle (WSA) of 0-1°. In contrast, nano-wires and nano-bridges (1-8 μm in length/10-80 nm in width) are generated by 'spinning/stretching' under internal microscopic force ( F) interference due to significant temperature difference in the non-uniform cooling medium. The findings provide a novel theoretical basis for controllable polymer 'bionic lotus' surface and will further promote practical application in many engineering fields such as drag-reduction and anti-icing. [ABSTRACT FROM AUTHOR]

Surface behaviors of superhydrophobic polymer coating applied in severe engineering environment are firstly systematically investigated. The PTFE/PPS (Polytetrafluoroethylene/Polyphenylene sulfide) coating still possess good superhydrophobicity after natural ice and snow covering for 10 day due to its micrometer-nanometer-scale binary structure (MNBS) with long-term stability. Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) are used to characterize the morphology, chemical components and wetting properties of the coating, respectively. Surprisingly, the PTFE nano-fibers on most micro-scale papillae of the original coating were 'chemical-etched' and then 'secondary-constructed' to form nano-spheres/papules by HSO under 'accelerated simulated acid rain' condition (pH = 0.3). It is firstly found that chemical-etching by simulated acid rain only result in the 'secondary-construction' of MNBS structure. However, the laboratory weathering tests indicated that light-etching by the light with specified wavelength (UV, about 300-400 nm) can lead to both the 'secondary-construction' of MNBS structure and the change of surface chemical composition/groups on the superhydrophobic coatings. This thesis clarifies the long-term stability and surface behaviors of the superhydrophobic polymer coating under severe engineering condition, and will provide significant theoretical guidance for superhydrophobic polymer coating as anti-ice/frost engineering material. [ABSTRACT FROM AUTHOR]

The ability to dictate the motion of microscopic objects is an important challenge in fields ranging from materials science to biology. Field-directed assembly drives microparticles along paths defined by energy gradients. Nematic liquid crystals, consisting of rod-like molecules, provide new opportunities in this domain. Deviations of nematic liquid crystal molecules from uniform orientation cost elastic energy, and such deviations can be molded by bounding vessel shape. Here, by placing a wavy wall in a nematic liquid crystal, we impose alternating splay and bend distortions, and define a smoothly varying elastic energy field. A microparticle in this field displays a rich set of behaviors, as this system has multiple stable states, repulsive and attractive loci, and interaction strengths that can be tuned to allow reconfigurable states. Microparticles can transition between defect configurations, move along distinct paths, and select sites for preferred docking. Such tailored landscapes have promise in reconfigurable systems and in microrobotics applications. Nematic liquid crystals have a rich energy landscape which can define elastic fields to guide colloidal assembly. Here the authors show controllable trapping of colloidal particles by placing them in a system with wavy walls which are exploited to obtain stable, metastable and unstable equilibria. [ABSTRACT FROM AUTHOR]