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In this work, poly(ionic liquid) (PIL)-containing block copolymers (BCPs), poly(ethylene oxide)-b-poly(1-((2-acryloyloxy)ethyl)-3-docosylimidazolium) with different counterions (PEO-b-P(AOEDIm-X), ...

While the regulation of surface oxygen vacancy (VO) of ceria is an effective methodology to construct solid frustrated Lewis pairs (FLPs), the intrinsic properties and potential applications of solid FLPs are not well-demonstrated. Herein, we present a theoretical study on the formation rules and dynamic behaviors of FLPs on CeO2(110) and their performance on nonoxidative conversion of methane. The density functional theory studies show that the formation of solid FLPs on CeO2(110) is dependent on the number of oxygen vacancies (VOs). The FLPs constructed by three or more VOs are stable in thermodynamics, whereas the FLPs containing few VOs (i.e., VO monomer and VO dimer) are less stable but can be dynamically formed via thermal fluctuation and reactant-adsorption, as observed by ab initio molecular dynamics simulations. Hence, the general existence of FLPs on reduced CeO2(110) surface under reaction conditions is revealed. Calculations on methane activation show that FLPs are active for C–H bond breaking...

In the present work, we found that single-walled carbon nanotubes (SWCNTs) could be straightened by poly(9,9-dioctylfluorene) (PFO) chains with both α- and β-conformations in different solvents. UV–vis and PL spectroscopic studies confirm that there exists π-π interaction between SWCNTs and PFO. SWCNTs are helically wrapped by the adsorbed PFO chains, which is different from the coaxial interaction between SWCNTs and poly(3-hexylthiophene) (P3HT). More stretched PFO β-conformers have a stronger interaction with SWCNTs, and the interactions between SWCNTs and PFO slightly improve the conjugation length of β-conformers in turn. We proposed that the straightening of SWCNTs by adsorbed rigid conjugated polymers is irrespective of interaction mode between them.

Manipulating droplet dynamics is of great importance in condensation heat transfer enhancement. Cavity topography was believed to be able to regulate droplet merging and self-removal via Laplace force imbalance by the cavity wall and the effect of spatial confinement and isolation. However, the size effect of the microcavity on the droplet dynamics behavior, droplet size distribution and condensation heat transfer performance are not sufficiently understood. In this paper, hierarchical microcavity-arrayed superhydrophobic surfaces with a nominal cavity diameter of 20, 35, 50 and 70 μm were fabricated. Condensation experiments were first carried out in the atmosphere under an optical microscope, and then in pure steam in a self-designed environmental chamber at 4000 Pa. Local dynamic behaviors and time-lapsed evolutions of droplets during condensation were observed. Droplet size distribution and jumping rate were statistically analyzed using ImageJ software. It was proved the smaller cavity size of 20 μm is beneficial to facilitate condensate droplet jumping and increase the density of small droplets. The surface coverage ratio on the microcavity-arrayed superhydrophobic surfaces was only half of that on the hydrophobic surface at steady state. Enhancement of pure steam condensation heat transfer can be realized by effectively regulating droplet dynamics using microcavity topographies at limited subcooling degrees.

Steam condensation heat transfer was studied over a honeycomb-like microporous superhydrophobic surface under various pressures, in order to elucidate the effects of pressure on the jumping-droplet condensation behaviors. The condensing pressure was varied from 4 kPa to 13 kPa, based on the typical operating conditions of condensers in power plants. Stable coalescence-induced droplet jumping was realized on the honeycomb-like superhydrophobic surface over this range of pressure, leading to a great enhancement on the condensation heat transfer as compared to that on the common hydrophobic surface, especially at small degrees of subcooling (e.g., < 10 K). The frequency and number of jumping droplets were observed to decrease at lower pressures because of the less amount of condensate produced, and at higher degrees of subcooling due to the occurrence of surface flooding. The increasing condensing pressure was found to lead to a later onset of surface flooding. The results indicated that the honeycomb-like superhydrophobic surface has a great potential for industrial condensation equipment operating at multiple pressures owing to its superior performance and facile fabrication.

The efficiency of dropwise condensation heat transfer has been improved significantly by the development of superhydrophobic surfaces, which are usually fabricated by coating a thin superhydrophobic layer on different kinds of substrates (e.g., different metals/alloys). However, the effects of the thermal conductivity of the substrate on condensation heat transfer over such superhydrophobic surfaces remain unclear. In this paper, we investigated experimentally the condensation heat transfer and droplet dynamics on honeycomb-like superhydrophobic (HCLS) surfaces with hierarchical microporous structures, fabricated by an electrochemical method on four metallic substrates with different thermal conductivities, i.e., copper, brass H96, brass H65 and stainless steel SS316. We observed spontaneous droplet jumping on all these HCLS surfaces at a relatively low degree of subcooling. We also demonstrated the interplay between the substrate thermal conductivity and condensation heat transfer performance during the flooding condensation transition (FCT) by numerical simulations. In the jumping-droplet condensation and flooding condensation regimes, the condensation heat flux and heat transfer coefficient were found to be almost unchanged for different substrates. However, the substrate with a higher thermal conductivity leads to a higher condensation heat transfer coefficient as well as a higher droplet departure frequency at moderate degrees of subcooling, indicating the synergistic effect between the substrate thermal conductivity and droplet dynamics during FCT. The substrate thermal conductivity-mediated droplet dynamics enables a way for further enhancing condensation heat transfer on the HCLS surfaces.

Manipulating dropwise condensation is of critical importance in enhancing liquid-gas phase change heat transfer. In addition to experimental investigations, theoretical modeling is also helpful in understanding the process of heat transfer in dropwise condensation. It has been over half a century since the very first theoretical model for dropwise condensation heat transfer. The essence of integrating the droplet heat transfer and droplet distribution is deeply rooted and long-lasting appreciated. In recent decades, the high-ended micro/nano-fabrication of the superhydrophobic textured surface has motivated both dropwise and jumping-droplet condensation heat transfer. Efforts have been made to understand and predict dropwise condensation or jumping-droplet condensation heat transfer by different models. However, the transient and random characteristics of self-propelled droplet jumping or sliding make it hard to establish a universal heat transfer model for all surfaces. In this review, we summarized the existing theoretical models for the multimode dropwise condensation on the smooth hydrophobic and textured superhydrophobic surfaces, including models for individual droplet heat transfer and droplet size distribution, to highlight the status-of-the-art. Comparisons with the experimental data under various conditions were provided. Some of the authors’ reflections were also presented, which are hoped to bring as many inspirations as possible to advances in the modeling work in the future.

In the present work, the evaporation-induced interfacial self-assembly behavior of an amphiphilic conjugated polymer, poly(3-hexylthiophene)-b-poly(acrylic acid) (P3HT-b-PAA), at the oil–water interface is explored. Novel 2D nanotapes of P3HT-b-PAA are prepared via the interfacial self-assembly. It is inferred that P3HT segments adopt a special conformation at the oil–water interface, which facilitates the packing of alkyl side chains and π–π interaction. The UV-vis spectrum further confirms that the ordering degree of P3HT segments is increased while transmission IR and Raman spectroscopic studies suggest that the P3HT chains adopt a more planar conformation at the oil–water interface. It is proposed that the formation of the nanotapes is driven by the ordered packing of the P3HT chains at the oil–water interface. Finally, the packing model of the P3HT chains inside the nanotapes is roughly proposed.

In this paper, a high-performance large-scale flexible heater based on graphene and silver particles is described. The graphene-based heater can be integrated into various systems without having to be too selective about the substrate used. When silver particles are mixed with graphene, the sheet resistance is greatly reduced to 158.7 Ω sq−1. A time-dependent temperature profile under an applied voltage of 18 V exhibits a steady-state temperature of up to 220 °C within 5 s. The high steady-state temperature and ultrafast response time are superior to those of most of the existing heaters. The infrared pictures show a uniform temperature distribution whether the graphene-based heater is flat or curved. Therefore, with the advantages of a low driving voltage, high steady-state temperature, ultrafast response and excellent flexibility, the graphene-based heater is expected to be a promising potential candidate for various wearable heating applications.

Over the past decade, reports of graphene-based devices have increased exponentially due to the superior characteristics and unique advantages that graphene introduces. However, the cost-effective growth and patterning of graphene is always a challenge for large-scale graphene-based device applications. Here we report a universal method based on one-step laser scribing technology for quick synthesis and patterning of large-scale multi-layer graphene films from graphene oxide films using a 650 nm commercial laser on arbitrary substrates. Moreover, by tuning the laser power, three distinct regions are found: growth, transition and etch regions. SEM, optical microscopy, Raman spectroscopy, electrical conductance testing, and transmittance measurements confirm the presence of three such regions. These tests show that the reduction of GO happens at low power and the gasification of LSG into CO2 happens at high power. Furthermore, a theoretical model is established to analyse the thickness changes under different laser power. This laser processing method could significantly simplify the processing steps and reduce the cost for the fabrication of graphene-based devices. This work also demonstrates promising applications for scalable manufacturing of graphene-based devices using one-step laser processing at standard temperature and pressure.

Steam condensation was studied experimentally over a honeycomb-like microporous superhydrophobic surface, as fabricated by electrodeposition method, under various condensing pressures. The condensing pressure was varied from 4 kPa to 13 kPa, based on the typical operating conditions of condensers in coal-fired power plants. Over this range of pressure, stable coalescence-induced condensate droplet jumping was realized on the honeycomb-like surface with hierarchical micro-/nanostructures, leading to a significantly enhanced condensation heat transfer over that on a smooth hydrophobic surface at low degrees of subcooling (

In the present work, composite single crystals (CSCs) composed of poly (L-lactic acid) (PLLA) homopolymer and poly (L-lactic acid)-b-polystyrene (PLLA-b-PS) block copolymers (BCPs) were prepared by solution co-crystallization. The effects of crystallization temperature (Tc), mass ratio of BCP/homopolymer and PS block length on the morphology and growth habit of the CSCs were investigated. Particularly, parallelogram CSCs with four {110} crystal planes as edges tend to be formed at a low Tc and a small BCP/homopolymer mass ratio for the BCP with a short PS block. The parallelogram shape of the crystals indicates the growth rates along four {110} crystal planes are different in two directions. It is proposed that the folded surface free energy is reduced after incorporation of PLLA-b-PS BCP into the crystals, leading to accelerated growth and concave surface structure along the long side direction. The chain folding of the PLLA block in the CSCs was also discussed. It is found that, in order to match the chain folding of PLLA homopolymer, the PLLA block in the BCPs adopts more chain folds in the CSCs than that in the single crystals formed by neat BCPs.

Steam condensation is a ubiquitous phenomenon of phase change that can be encountered in various industrial applications. In practice, the presence of non-condensable gases (NCG) is often inevitable, which can severely deteriorate condensation heat transfer by accumulating in the vicinity of the condensing surface as an additional thermal resistance. In this work, steam condensation heat transfer on a honeycomb-like microporous superhydrophobic surface, which has already been shown to lead to stable coalescence-induced droplet jumping with high heat flux, was studied with NCG concentrations up to ~28%. The superhydrophobic surface, having a nominal pore diameter of ~20 μm, was prepared by a rapid, cost-effective and highly scalable electrodeposition method over the outer surface of thin copper tubes. Condensation experiments were conducted in a visualized vacuum chamber maintaining at a constant pressure of 9.5 kPa. Significant enhancements of condensation heat transfer at the various NCG concentrations were exhibited on such superhydrophobic surface over a wide range of subcooling up to ~35 K, due to the successful realization of droplet jumping in spite of the presence of NCG. The adsorption of NCG into the micropores was elucidated to be a partial reason for prohibition of condensate flooding at relatively high degrees of subcooling.

Strain sensors have been widely used in the fields of wearable devices, robot arms, medical sensing, bio-sensing, artificial skin and so on, but the existing strain sensors have some shortcomings such as a limited gauge factor (GF) or strain range. We fabricate a novel and flexible strain sensor with high performance based on self-locked overlapping graphene sheets (SOGS) which can be used for wearable devices. Polydimethylsiloxane (PDMS) is used to lock the overlapping graphene sheets, and then the graphene can be stretched and achieve an ultrahigh GF. In addition, a new theory is put forward to explain the GF changes with strain range for the SOGS strain sensor. In this work, graphene oxide (GO) film is reduced to reduced GO (rGO) by a laser. Then, the SOGS and electrodes are encapsulated by PDMS. The SOGS strain sensor has a high GF up to 400 and strain range over 7.5%, and this SOGS strain sensor achieves a balance between high sensitivity and large strain range compared with other existing strain sensors. Furthermore the theoretical equation based on the new theory agrees well with the experimental results. And this strain sensor can be used in many applications because of its high sensitivity. Some applications of the SOGS strain sensors are demonstrated for the detection of various human motions and human sounds. The SOGS strain sensor can exhibit great potential in wearable electronics because of its good balance between high sensitivity and large strain.

Co3O4/Nitrogen-doped graphene (Co3O4/NG) composites were synthesized by a simple hydrothermal method. The Co3O4/NG composites show a better electrochemical performance than the Co3O4/graphene (Co3O4/G) composite. The specific capacitance of Co3O4/NG electrode is 428 F/g (290 F/g for Co3O4/G electrode) at a current density of 1 A/g. As the current density was increased from 1 to 8 A/g, the capacitance of Co3O4/NG still retained 57%, significantly larger than that of Co3O4/G (40%). Moreover, over 94% of the original capacitance was maintained after 500 cycles (72% for Co3O4/G electrode), indicating a good cycle stability of Co3O4/NG electrode materials.

A combination process was developed in laboratory scale including microwave (MW) coagulation and iron/carbon micro-electrolysis (Fe/C ME) in series for treatment of heavy oil produced water (HOPW) with high concentrations of oil and chemical oxygen demand and high corrosion rates. The effects of coagulant dosage, MW irradiation time, settling time, and Fe:C mass ratio on the actual treatment results were investigated. The use of MW irradiation brought some benefits including enhancing oil removal, reducing coagulation consumption, shortening settling time and lowering corrosion rate. During the 30-day continuous treatment period, the Fe-based metallic glasses/activated carbon (MGs/AC) ME system exhibited high performance stability, whereas the iron shavings/AC ME system had good performance for only 8 days. The total reduction percentages of oil, suspended solids and corrosion rate were 95.5%, 98.3% and 96.5%, respectively, in the combined MW coagulation-MGs/AC ME system, and the corrosion rate of the treated HOPW was only 0.025 mm/year. The quality parameters of the treated heavy oil produced water (HOPW) could completely meet the requirements of the C1 grade in the SY/T 5329-1994 standard for wastewater reinjection in oilfields. Moreover, the biodegradability of the HOPW was greatly improved after treatment, creating favorable conditions for subsequent biological treatment if not reinjection.

There is a growing demand for flexible electronic devices. In particular, strain sensors with high performance have attracted more and more attention, because they can be attached on clothing or human skin for applications in the real-time monitoring of human activities. However, monitoring human-body motions that include both subtle and intensive motions, and many strain sensors cannot meet the diverse demands simultaneously. In this work, a silver nanoparticles (Ag NPs) bridged graphene strain sensor is developed for simultaneously detecting subtle and intensive human motions. Ag NPs serve as many bridges to connect the self-overlapping graphene sheets, which endows the strain sensor with many excellent performances. Because of the high sensitivity, with a large gauge factor (GF) of 475 and a strain range of >14.5%, high durability of the sensor has been achieved. Besides, the excellent consistency and repeatability of the fabrication process is verified. Furthermore, the model for explaining the working mechanism of the strain sensor is proposed. Most importantly, the designed wearable strain sensor can be applied in human motion detection, including large-scale motions and small-scale motions.

In this paper, we fabricate a graphene film heater through laser reduction on graphene oxide, which is a two-step process. The electrothermal performance of the graphene heater can be adjusted by the laser energy density. While the applied voltage is 18 V, the graphene heater reaches a steady-state temperature of 247.3 °C within 20 s. After the graphene heater is folded in half 100 times, its output temperature remains to be precisely controlled by the input power and the temperature distribution is uniform. In addition, the flexibility of the graphene heater is superior to a heater based on a commercial indium tin oxide film. It's worth noting that the graphene heater can be fabricated with desired shapes directly and easily, which is rare among the reported film heaters. In consideration of the high performance of the graphene film heater, we demonstrate its three application scenarios: portable warmers applied in medical infusion apparatus, flexible custom-shaped heaters for special requirements and displays.

To model the stress-strain relation of frozen soil under different temperatures, an elasto-plastic constitutive model coupling with temperature variable was proposed. Under axisymmetric condition, elastic strain was calculated by the K-G model coupling with temperature. The plastic strain was calculated by using the DP yield criterion, associated flow rule and isotropic hardening law. All of the elastic and plastic parameters are related to the temperature variable. The simulated results show that the proposed model can predict the deformation behavior of frozen soil under different temperatures.

Coalescence-induced jumping of condensate droplets has been studied as an emerging mode for enhanced condensation heat transfer. However, the spontaneous droplet jumping phenomenon usually disappears at relatively higher degrees of subcooling due to the increase of nucleation density of condensate droplets. In this Letter, we show that self-propelled droplet jumping condensation can be realized surprisingly on a hierarchical porous superhydrophobic surface, having pores of the size of ∼20 μm with nanoscale dendritic structures, which was fabricated via a facile electrochemical deposition method. Droplet jumping condensation was always able to be sustained on this surface, making it never flooded even at elevated subcooling up to ∼20 K, although the intensity of droplet jumping degraded gradually with increasing the subcooling. It was hypothesized that the presence of microscale ridges among the pores, where nucleating droplets tended to appear and grow over the nano-structures on the ridge tips, serve as spatial separation barriers that prevent the surfaces from nucleation-density-modulated flooding at relatively high degrees of subcooling. As compared to conventional dropwise condensation on a smooth hydrophobic surface, significant heat transfer enhancement was able to attain for subcooling up to ∼7 K. The fabrication of this hierarchical porous superhydrophobic surface was deemed to be rapid, scalable, and highly-adaptive for curved surfaces on metallic bulk materials, e.g., copper tubes, with a great potential for industrial condensation applications.

The temperature field and stress field of laser welding were simulated by "ansys" analysis soft of finite element for different thickness aluminum alloy plate. The results show that quasi steady state temperature field were formed after laser act on aluminum alloy plate for a certain time. Because heating volume of thin plate is small than one of thickness plate under the same amount of heat input, thin plate has greater grads of temperature and melting pool size. Distribution law of heat stress is similarity with common melt welding. However. heat stress filed area and its peak value of thin plate is greater than one of thickness plate.

In this paper, TiH2-47Al-5Nb (at.%) and TiH2-47Al-7Nb(at.%) alloys were mixed and synthesized using TiH2, Al and Nb powders. The composition and morphology evolution of the mixed powder were systematically investigated during high energy ball milling. The results show obvious that structure change of the particle during milling, and amorphous, TiAl, Ti3Al and Ti2Al phases at nanoscale are formed. The addition of Nb shows an active influence on the decomposition of TiH2and formation of TiAl-intermetallics. Compare with Ti-Al system alloy, the forming process of TiAl-intermetallics for TiH2-Al-Nb system alloy is different and slower. Ti2Al metastable phase formed after ball milling for 15 h in our experiments.

In this paper, low-voltage, large-strain flexible electrothermal actuators (ETAs) based on laser-reduced graphene oxide (LRGO)/Ag particle composites were fabricated in a simple and cost-efficient process. By adding Ag particles to the LRGO, the sheet resistance decreased effectively. Under a driving voltage of 28 V, the actuator obtained a bending angle of 192° within 6 s. Besides, the bending deformation could be precisely controlled by the driving voltage ranging from 10° to 192°. Finally, a gripper composed of two actuators was demonstrated to manipulate a piece of polydimethylsiloxane block. With the advantages of low-voltage, fast-response, and easy-to-manufacture, the graphene based ETAs have a promising application in soft robotics and soft machines.

Metal oxide-based resistive random access memory (RRAM) has attracted a lot of attention for its scalability, temperature robustness, and potential to achieve machine learning. However, a thick oxide layer results in relatively high program voltage while a thin one causes large leakage current and a small window. Owing to these fundamental limitations, by optimizing the oxide layer itself a novel interface engineering idea is proposed to reduce the programming voltage, increase the uniformity and on/off ratio. According to this idea, a molybdenum disulfide (MoS2 )-palladium nanoparticles hybrid structure is used to engineer the oxide/electrode interface of hafnium oxide (HfOx )-based RRAM. Through its interface engineering, the set voltage can be greatly lowered (from -3.5 to -0.8 V) with better uniformity under a relatively thick HfOx layer (≈15 nm), and a 30 times improvement of the memory window can be obtained. Moreover, due to the atomic thickness of MoS2 film and high transmittance of ITO, the proposed RRAM exhibits high transparency in visible light. As the proposed interface-engineering RRAM exhibits good transparency, low SET voltage, and a large resistive switching window, it has huge potential in data storage in transparent circuits and wearable electronics with relatively low supply voltage.

In this paper, we have developed a high-performance graphene electrothermal actuator (ETA). The fabrication method is easy, fast, environmentally friendly, and suitable for preparing both large-size and miniature graphene ETAs. When applied with the driving voltage of 65 V, the graphene ETA achieves a large bending angle of 270° with a fast response of 8 s and the recovery process costs 19 s. The large bending deformation is reversible and can be precisely controlled by the driving voltage. A simple robotic hand prepared by using a single graphene ETA can hold the object, which is more than ten times the weight of itself. By virtue of its large-strain, fast response, and easy-to-manufacture, we believe that the graphene ETA has tremendous potential in extensive applications involving biomimetic robotics, artificial muscles, switches, and microsensors in both macroscopic and microscopic fields.

In this paper, a flexible, simple-preparation, and low-cost graphene-silk pressure sensor based on soft silk substrate through thermal reduction was demonstrated. Taking silk as the support body, the device had formed a three-dimensional structure with ordered multi-layer structure. Through a simple and low-cost process technology, graphene-silk pressure sensor can achieve the sensitivity value of 0.4 kPa − 1, and the measurement range can be as high as 140 kPa. Besides, pressure sensor can have a good combination with knitted clothing and textile product. The signal had good reproducibility in response to different pressures. Furthermore, graphene-silk pressure sensor can not only detect pressure higher than 100 kPa, but also can measure weak body signals. The characteristics of high-sensitivity, good repeatability, flexibility, and comfort for skin provide the high possibility to fit on various wearable electronics.

In this paper, a flexible heater based on anisotropic laser-reduced graphene oxide (LRGO) is established. Attributing to precision and shape design of laser processing and excellent adhesion of graphene oxide, the LRGO-based heater can be microminiaturized with custom patterns and integrated on various substrates, which is what the existing film heaters cannot do and can be widely used for wearable heating devices, flexural warming systems in medical science, and light deicing equipment and heaters for aero vehicles. The electrothermal performance of the anisotropic LRGO is investigated systematically through a series of experiments including Raman spectra, SEM, white-light interferograms, IV testing, and infrared thermography. The electrothermal performance of the LRGO with the parallel aligned direction is better than the LRGO with the vertical aligned direction. The electrothermal performance can be improved greatly through radiating repeatedly. The saturated temperature and heating rate of the LRGO ra...