Silk fibroin-based biopolymer composite binders with gradient binding energy and strong adhesion force for high-performance micro-sized silicon anodes

Micro-sized silicon anodes have shown much promise in large-scale industrial production of high-energy lithium batteries.However,large volume change(>300%)of silicon anodes causes severe particle pulverization and the formation of unstable solid electrolyte interphases during cycling,leading to rapid capacity decay and short cycle life of lithium-ion batteries.When addressing such issues,binder plays key roles in obtaining good structural integrity of silicon anodes.Herein,we report a biopolymer composite binder composed of rigid poly(acrylic acid)(PAA)and flexible silk fibroin(SF)tailored for micro-sized silicon anodes.The PAA/SF binder shows robust gradient binding energy via chemical interactions between carboxyl and amide groups,which can effectively accommodate large volume change of silicon.This PAA/SF binder also shows much stronger adhesion force and improved binding towards high-surface/defective carbon additives,resulting in better electrochemical stability and higher coulombic efficiency,than conventional PAA binder.As such,micro-sized silicon/carbon anodes fabricated with novel PAA/SF binder exhibit much better cyclability(up to 500 cycles at 0.5 C)and enhanced rate capability compared with conventional PAA-based anodes.This work provides new insights into the design of functional binders for high-capacity electrodes suffering from large volume change for the development of nextgeneration lithium batteries.

Direct measurement and theoretical prediction model of interparticle adhesion force between irregular planetary regolith particles

Interparticle adhesion force has a controlling effect on the physical and mechanical properties of planetary regolith and rocks.The current research on the adhesion force of planetary regolith and rock particles has been primarily based on the assumption of smooth spherical particles to calculate the intergranular adhesion force;this approach lacks consideration for the adhesion force between irregular shaped particles.In our study,an innovative approach was established to directly measure the adhesion force between the arbitrary irregular shaped particles;the probe was modified using simulated lunar soil particles that were a typical representation of planetary regolith.The experimental results showed that for irregular shaped mineral particles,the particle size and mineral composition had no significant influence on the interparticle adhesion force;however,the complex morphology of the contact surface predominantly controlled the adhesion force.As the contact surface roughness increased,the adhesion force gradually decreased,and the rate of decrease gradually slowed;these results were consistent with the change trend predicted via the theoretical models of quantum electrodynamics.Moreover,a theoretical model to predict the adhesion force between the irregular shaped particles was constructed based on Rabinovich’s theory,and the prediction results were correlated with the experimental measurements.

Adhesion forces for water/oil droplet and bubble on coking coal surfaces with different roughness

Surface roughness plays a significant role in floatability of coal.In the present paper,coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements.The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness.The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning.Maximum adhesion forces between water and surfaces were 111.70,125.48,and 136.42μN when the roughness was 0.23,0.98,and 2.79 μm,respectively.In contrast,under a liquid environment,the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water.Maximum adhesion forces of increasing roughness were 97.14,42.76,and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48,145.84,and 121.02 lN between oil droplet and surfaces,respectively.Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.

Influence of atomic force microscope(AFM) probe shape on adhesion force measured in humidity environment

In micro-manipulation, the adhesion force has very important influence on behaviors of micro-objects. Here, a theoretical study on the effects of humidity on the adhesion force is presented between atomic force microscope （AFM） tips and substrate. The analysis shows that the precise tip geometry plays a critical role on humidity depen- dence of the adhesion force, which is the dominant factor in manipulating micro-objects in AFM experiments. For a blunt （paraboloid） tip, the adhesion force versus humidity curves tends to the apparent contrast （peak-to-valley corrugation） with a broad range. This paper demonstrates that the abrupt change of the adhesion force has high correla- tion with probe curvatures, which is mediated by coordinates of solid-liquid-vapor contact lines （triple point） on the probe profiles. The study provides insights for further under- standing nanoscale adhesion forces and the way to choose probe shapes in manipulating micro-objects in AFM experiments.

Variation of Surface Adhesion Force During the Formation of OTS Self-assembled Monolayer Investigated by AFM

Variation of the surface adhesion force during the formation of octadecyl trichlorosilane (OTS) self-assembled monolayer on a glass substrate surface was investigated by atomic force microscope (AFM). The research shows that the hydrophobicity and the adhesion force of the sample surface increases gradually while the substrate surface is covered by OTS molecules as the reaction proceeds. After 15min reaction, a close-packed and smooth OTS self-assembled monolayer could form on the glass substrate surface with an advancing contact angle of 105° and an interfacial energy of 55.79mJ·m-2.

MEASUREMENT OF ADHESION FORCES IN AIR WITH THE VIBRATION METHOD

The vibration method represents a practical method for the measurement of adhesion forces and adhesion force distributions. This method causes sinusoidally alternating stresses and yields detachment and contact forces between particles and substrate of the same order of magnitude. Alternating contact forces of the vibration method can cause an adhesion force intensification through flattening of asperities. The measuring principle of the vibration method and the analysis of experimental results are described in the article. Normal adhesion forces (pull-off forces) are measured using the vibration method and the colloidal probe technique. The results of both methods show good agreement for small particle sizes. The influence of the detachment force direction is shown by comparing tangential and normal adhesion forces measured using particle reentrainment in a turbulent air flow and the vibration method, respectively. The surface roughness of the substrate and the relative humidity are shown to significantly influence the measured adhesion forces. For the calculation of the adhesion forces, an approach by Rabinovich was combined with approximations of plastic micro asperity flattening. The Rabinovich approach accounts for roughness effects on the van der Waals force by incorporating the rms roughness of the interacting surfaces, rms-values of the particles and substrates were measured with atomic force microscopy at different scanning areas.

Effect of dilute acid treatment on adhesion properties of Longmaxi black shale

Properties of shale in an acid environment are important when acid or CO2 is injected into geologic formations as a working fluid for enhanced oil and gas recovery,hydraulic fracturing and reduced fracture initiation pressure.It has previously been shown that acid fluids can enhance the formation conductivity and decrease the hardness of shale.However,less is known about the effect of dilute acid on the adhesion properties of shale.In the study,shale samples are characterized in detail with advanced analysis.Adhesion properties of shale via dilute acid treatment were revealed by atomic force microscopy(AFM)for the first time.Results indicate that acid treatment can greatly enhance adhesion forces of the shale surface.After acid treatment,the average adhesion forces show a platform-like growth with an increase in loading force.Through analysis of results from AFM,scanning electron microscopy,and X-ray diffraction,we affirm that the enhanced adhesion forces are mainly from increased specific surface area and reduced elastic modulus.The results presented in this work help understand the adhesion properties of shale oil/gas present in an acidic environment,which have great significance in unconventional resources development.

Discrete element method for adhesion properties evaluation of deep-sea sediment from macro and micro perspectives

The adhesion between the mining machine and the deep-sea sediments will significantly affect the driving performance of the mining machine in the deep-sea environment.When the mining machine and the deep-sea sediment interaction simulation was carried out,the accuracy of the particle interaction parameters will directly affect the simulation results.This study proposed a method to systematically calibrate the interaction parameters between deep-sea sediment and grouser through the combination of experiment and simulation.The uniaxial compression test and macro adhesion test and corresponding discrete element numerical simulation were carried out,modifying the contact parameters until the simulation results are close to the experimental results.Then the micro-parameters of the JKR adhesion contact model were back calibrated with the test results,and the contact parameters between soil particle-soil particle and soil particle-metal are calibrated.Besides,the adhesion test shows that the adhesion forces were ranked in the order of 5052<STi80<TA2<TC4 under the same surface roughness,which indicates the aluminum alloy 5052 has the best anti-adhesion performance.The relationship between surface adhesion force and microscopic contact parameters was studied by discrete element numerical simulation,and the result shows that the coefficient of static friction and the coefficient of rolling friction has little effect on adhesion force.While it is mainly affected by the coefficient of restitution and surface energy,the surface adhesion force tends to decrease with the increase of the coefficient of restitution and increase with the growth of surface energy.The obtained parameters of soil particle to soil particle and soil particle to metal affecting the adhesion can contribute to the design optimization for the grouser of mining machines to decrease surface adhesion and enhance its movability and mining efficiency.

Efficient Preparation of Nanoparticle-Reinforced Nickel-based Composite Coating with Highly Preferred(220)Orientation

Nanoparticle-reinforced metal matrix composite coatings have significant potential in mechanical part surface strengthening owing their excellent mechanical properties.This paper reports a phenomenon in which the grain orientation gradually evolves to(220)as the deposition current density increases when preparing nanoparticle-reinforced nickel-based composite coatings through jet electrodeposition(JED).During the preparation of the Ni-SiC composite coatings,the deposition current density increased from 180 A/dm2 to 220 A/dm2,and TC(220)gradually increase from 41.4%to 97.7%.With an increase of TC(220),the self-corrosion potential increases from−0.575 to−0.477 V,the corrosion current density decreases from 9.52μA/cm^2 to 2.76μA/cm^2,the diameter of the corrosion pits that after 10 days of immersion in a 3.5 wt%NaCl solution decreases from 278–944 nm to 153–260 nm,and the adhesion of the coating increases from 24.9 N to 61.6 N.Compared a conventional electrodeposition(CED),the Ni-SiC composite coating using JED has the advantages of a smooth surface morphology,high corrosion resistance,and strong adhesion,which are more obvious with an increase in TC(220).

Analysis of Mechanical Adhesion Climbing Robot Design for Wind Tower Inspection

Maintenance of wind turbine farms is a huge task,with associated significant risks and potential hazard to the safety and well-being of people who are responsible for carrying the tower inspection tasks.Periodic inspections are required for wind turbine tower to ensure that the wind turbines are in full working order,with no signs of potential failure.Therefore,the development of an automated wind tower inspection system has been very cnucial for the overall performance of the renewable wind power generation industry.In order to determine the life span of the tower,an investigation of robot design is discussed in this paper.It presents how a mechanical spring-loaded climbing robot can be designed and constructed to climb and rotate 360°around the tower.An adjustable circular shape robot is designed that allows the device to fit in different diameters of the wind generator tower.The rotational module is designed to allow the wheels to rotate and be able to go in a circular motion.The design further incorporates a suspension that allows the robot to go through any obstacle.This paper also presents a finite element spring stress analy sis and Simulink control system model to find the optimal parameters that are required for the wind tower climbing robot.

A MODEL FOR COMPUTATIONAL INVESTIGATION OF ELASTO-PLASTIC NORMAL AND TANGENTIAL CONTACT CONSIDERING ADHESION EFFECT

With the rapid development of Micro-Electro-Mechanical System(MEMS),we enter a field in which the surface effects have dominated many of the micro-scale phenomena,and the adhesive contact is one of the focuses.In this paper,a feasible model for finite element computation is presented via a macroscopic and microscopic combination approach,in which the adhesive forces are simulated by some non-linear spring elements considering the softening stage.Two basic problems concerning the adhesion effect were considered;through specific quantitative analysis,the results show a consistency with the current elastic continuum theories of adhesion and a brief investigation into the effects of adhesion on plastic deformation and tangential contact will be carried out as well.

Numerical Analysis of the Adhesive Forces in Nano-Scale Structure

Nanohairs, which can be found on the epidermis of Tokay gecko＇s toes, contribute to the adhesion by means of van der Waals force, capillary force, etc. This structure has inspired many researchers to fabricate the attachable nano-scale structures. However, the efficiency of artificial nano-scale structures is not reliable sufficiently. Moreover, the mechanical parameters related to the nano-hair attachment are not yet revealed qualitatively. The mechanical parameters which have influence on the ability of adhesive nano-hairs were investigated through numerical simulation in which only van der Waals force was considered. For the numerical analysis, finite element method was utilized and van der Waals force, assumed as 12-6 Lennard-Jones potential, was implemented as the body force term in the finite element formulation.

FPGA Implementation of Extended Kalman Filter for Parameters Estimation of Railway Wheelset

It is necessary to know the status of adhesion conditions between wheel and rail for efficient accelerating and decelerating of railroad vehicle.The proper estimation of adhesion conditions and their real-time implementation is considered a challenge for scholars.In this paper,the development of simulation model of extended Kalman filter(EKF)in MATLAB/Simulink is presented to estimate various railway wheelset parameters in different contact conditions of track.Due to concurrent in nature,the Xilinx®System-on-Chip Zynq Field Programmable Gate Array(FPGA)device is chosen to check the onboard estimation ofwheel-rail interaction parameters by using the National Instruments(NI)myRIO®development board.The NImyRIO®development board is flexible to deal with nonlinearities,uncertain changes,and fastchanging dynamics in real-time occurring in wheel-rail contact conditions during vehicle operation.The simulated dataset of the railway nonlinear wheelsetmodel is tested on FPGA-based EKF with different track conditions and with accelerating and decelerating operations of the vehicle.The proposed model-based estimation of railway wheelset parameters is synthesized on FPGA and its simulation is carried out for functional verification on FPGA.The obtained simulation results are aligned with the simulation results obtained through MATLAB.To the best of our knowledge,this is the first time study that presents the implementation of a model-based estimation of railway wheelset parameters on FPGA and its functional verification.The functional behavior of the FPGA-based estimator shows that these results are the addition of current knowledge in the field of the railway.

Surface physicochemical properties of semi-anthracitic coal from Painan-Sumatra during air oxidation

Painan coals of West Sumatra were selected as semi-anthracitic coal sample for studying the physicochemical properties such as measurement, evaluation and description of the changes of surface characteristic of coal sample and their oxidation in the atmospheric air at a temperature ranging from 105 to 400 ℃ for 30 min. Several methods are adopted to analyze and discuss several phenomena of the oxidized Painan coal surface during oxidation process for the change in the physicochemical properties as determined by Atomic Force Microscope （AFM）, contact angle, Fourier Transform Infrared Spectroscopy （FTIR）, Thermogravimetric and Differential Thermal Analysis （TG-DTA） analyses as well as other supporting analytical equipment. AFM analyses revealed some changes in adhesion force and surface morphology with more adhesion force available between 0.6 and 8.6 nN on polished coal surfaces due to the increased oxidation temperature. The study revealed that the extent of hydrophobicity of coal surface decreased with the increased of oxidation temperature expressed as contact angles at about 80° and 20°. Another phenomenon occurred during the experiment was hydrophilicity index of coal surface increase at approximately 1.3 and 2.9. Oxidation of coal that occurred with increased temperature also indicated an increase in oxygen content from 3.8% to 22.9 wt%. Increased oxygen functional group also noted that oxidation of coal took place during the treatment. We also found that oxidation treatment also affected the combustion properties of coal： decreasing ignition temperature between 452.9 and 317.6, lowering the reactivity of coal at maximum combustion rate temperature, and reflecting their char characteristics as burnt out, ranging from 652.3 to 648.5 ℃.

Quantitative analysis on resistant forces at oil-surfactant-rock interfaces with dynamic wettability characterization

Adhesion of oil at rock surface plays an important role in the liberation of oil from micro-/nano-pores,especially for heavy oil that has extremely high viscosity.Although molecular dynamics simulation is widely used to study the interfacial interaction for some specific oil-water-rock systems,experimental measurements provide more realistic and reliable evidence.In this work,we propose a dynamic wettability characterization method to indirectly measure resistant forces at oil-surfactant-rock interfaces,including frictional force,wettability hysteresis force,and viscous force,which are parallel with the oil-solid interface.The adhesive force,which is normal to the oil-solid interface is calculated through measurement of work of adhesion.The results show that work of adhesion instead of contact angle can better describe the adhesion of oil at solid surface.The effect of surfactant concentration on work of adhesion is different for water-wet and oil-wet surfaces.Moreover,average viscous forces are calculated through force analysis on oil drops moving along solid surface in different surfactant environments.It is found that viscous force has a magnitude comparable to the frictional force during the movement,while the wettability hysteresis force is negligible.On the other hand,the adhesive force calculated from the work of adhesion is also comparable to the viscous force.Therefore,both the resistant forces parallel with and normal to the oil-solid interface should be minimized for the liberation of oil from rock surface.This work proposes a simple method to evaluate the wetting capability of different surfactants and measure the adhesive force between heavy oil and rock surfaces indirectly,which provides insight into the adhesion of heavy oil at rock surface and would be valuable for the development of surfactant-based oil recovery methods.

Exploration of the enhanced performances for silk fibroin/sodium alginate composite coatings on biodegradable Mg-Zn-Ca alloy

To expand the future clinic applications of biodegradable magnesium alloy,polymer coatings with excellent biocompatibility are the keys to solve the local alkalinity and rapid hydrogen release.Natural-organic silk fibroin provides an approach to fabricate a protective coating on biomedical Mg-Zn-Ca alloy,however,the adhesion force and mechanical properties of the coating on substrates are ought to be further improved without any chemical conversion/intermediate layer.Hereby,based on VUV/O;surface activation,a hybrid of silk fibroin and sodium alginate is proposed to enhance the adhesion force and mechanical properties of the composite coatings on hydrophilic Mg-Zn-Ca alloy surfaces.Various mass ratios of sodium alginate addition were investigated to achieve the optimum coating strategy.The nanoscratch test and nanoindentation test confirmed that the adhesion force was tripled and mechanical properties index was significantly improved when the mass ratio of silk fibroin/sodium alginate was 70/30 compared to pure silk fibroin or sodium alginate coatings.Meanwhile,the corrosion rate of the coated Mg-Zn-Ca alloy was significantly delayed with the addition of sodium alginate,resulting in a reaction layer during corrosion process.Furthermore,the mechanisms for both adhesion and corrosion processes were discussed in detail.Our findings offer more possibilities for the controllable surface performance of degradable metals.

Self-healing elastomer modified proppants for proppant flowback control in hydraulic fracturing

To address proppant flowback issues during post-fracturing treatments and production,self-healing elastomer modified proppants(SMPs)are proposed.Owing to their inherent self-aggregation behavior,the SMPs can aggregate together spontaneously to prevent proppant flowback and increase the pack porosity.It is noteworthy that the SMPs have a firm and dry self-healing elastomer(SE)coating,making their storage,transport and use as conventional proppants possible.The SE synthesized through polymerization is rich in amidogens and carbonyl groups as characterized by Fourier transform infrared spectroscopy and the proton nuclear magnetic resonance.Thermal and thermomechanical properties of the SE coating are revealed by the thermogravimetric analysis,the differential scanning calorimetry and the rheological tests.The self-aggregation behavior of the SMPs is demonstrated by the adhesion force tests.The reversible hydrogen bonding interactions in SE coating contribute to the self-aggregation behavior of the SMPs,which is revealed by the thixotropy test and the FTIR analysis at different temperatures.With the self-aggregation behavior,the crushed proppants can aggregate in situ to form a stable structure again and therefore reduce the threat of narrowing down the fracture and proppant flowback,which has an important practical significance during oil and gas production.

Effect of protein on PVDF ultrafiltration membrane fouling behavior under different pH conditions： interface adhesion force and XDLVO theory analysis

To further detem3ine the fouling behavior of bovine serum albumin （BSA） on different hydrophilic PVDF ultrafiltration （UF） membranes over a range of pH values, self-made atomic force microscopy （AFM） colloidal probes were used to detect the adhesion forces of membrane-BSA and BSA BSA, respectively. Results showed that the membrane-BSA adhesion interaction was stronger than the BSA-BSA adhesion interaction, and the adhesion force between BSA-BSA-fouled PVDF/PVA membranes was similar to that between BSA-BSA-fouled PVDF/PVP membranes, which indicated that the fouling was mainly caused by the adhesion interaction between membrane and BSA. At the same pH condition, the PVDF/PVA membrane-BSA adhesion force was smaller than that of PVDF/ PVP membrane-BSA, which illustrated that the more hydrophilic the membrane was, the better antifouling ability it had. The extended Derjaguin-Landau-Verwey Overbeek （XDLVO） theory predicts that the polar or Lewis acid-base （AB） interaction played a dominant role in the interracial free energy ofmcmbrane-BSA and BSA BSA that can be affected by pH. For the same membrane, the pH values of a BSA solution can have a significant impact on the process of membrane fouling by changing the AB component of free energy.

Effects of Substrate Hydrophobicity/Hydrophilicity on Height Measurement of Individual DNA Molecules

Effects of substrate hydrophobicity/hydrophilicity on height measurement of individual ds-DNA molecules are investigated with tapping mode atomic force microscopy （TMAFM） and vibrating mode scanning polarization force microscopy （VSPFM）. The measured heights of ds-DNA on hydrophobic highly oriented pyrolytic graphite （HOPG） are remarkably less than those on hydrophilic bare mica and Ni^2＋ treated mica in both TMAFM and VSPFM. By analysing the results, we propose that the hydrophobicity/hydrophilicity of substrate can greatly influence the height measurement of DNA molecules.

Silver Film Growth on Glass Ceramic by Radio Frequency Magnetron Sputtering

Thin silver films are deposited by radio frequency magnetron sputtering on glass ceramic at room temperature.Variations of sputtering power,bios voltage and power density are carried out for each deposition,then parts of as-deposited samples are subjected to annealing at 600 ℃ within a vacuum chamber.Structural properties are studied by X-ray diffraction(XRD),scanning electron microscope(SEM)and laser scanning confocal microscope(LSCM).It is shown that structural properties have a strong dependency on sputtering power and annealing temperature.Electrical contact resistance measured by a four point probe instrument is directly affected by the thickness of films.It is also found that the film conductivity,especially in thinner films,is improved by the increasing grain size.Finally,the film adhesion is observed by scratch tests.And the adhesive ability deposited by radio frequency magnetron sputtering shows a better performance than that produced by traditional methods.