固-液界面接触角测定实验的课程思政设计

固液界面接触角的测定是一个重要的物理化学实验,本案例结合特殊润湿性材料可处理含油废水这一科研进展,将其改进为一个融入课程思政元素的综合创新实验,不仅能提升学生的学习兴趣,还能引导学生学会理论联系实际,利用所学专业知识来保护自然、治理环境,培养学生的社会责任感和专业自豪感,有助于达成创新型人才培养目标。

超疏水表面的制备及其在含油废水处理中的应用——一个物理化学综合创新实验

以较前沿的科研成果为基础设计了一个物理化学综合创新实验。通过该实验,学生不仅可以了解油污染水环境问题,加深对润湿性一般理论的理解,还可以掌握超疏水材料的制备、接触角表征以及超疏水/超亲油材料对含油废水进行处理的操作和方法。实验融入了较多的课程思政元素,通过引导学生利用课堂学习的表面化学理论知识解决含油废水处理问题,培养学生的社会责任感、专业自豪感、严谨的科学思维和创新能力。

Magnetically enhancing diffusion for dendrite-free and long-term stable lithium metal anodes

Lithium metal batteries are promising devices for the next-generation energy storage due to their ultrahigh theoretical specific capacity and extremely low electrochemical potential.Their inherent problem is the formation of lithium dendrites in cycling,which has induced safety concerns for almost half a century.After understanding the formation mechanism of branching structures,we propose to suppress lithium dendrites by adopting external magnetic fields to induce diffusion enhancement at the interface of the anode,thus attenuating concentration gradient there and reducing the driving force for the formation of dendritic structures.The diffusion coefficient of lithium ions is dependent on the strength of magnetic fields,confirming the effectiveness of magnetic fields in improving Li^(+) diffusion.After employing the magnetic field of0.8 T,the concentration gradients at the growth front becomes nearly half of the control case,which leads to a dendrite-free lithium deposition up to the high current density of 10 mA cm^(-2).Both the Cu|LiCoO_(2) batteries and the symmetric Li | Li coin cells show a long-term stable cycling at high current densities under the assistance of magnetic field.This diffusion enhanced technique promises a facile and general approach to suppress dendritic structures in secondary batteries,which may help to develop quick charging strategies.

Bi@C nanosphere anode with Na^(+)-ether-solvent cointercalation behavior to achieve fast sodium storage under extreme low temperatures

The low ion transport is a major obstacle for low-temperature(LT)sodium-ion batteries(SIBs).Herein,a core-shell structure of bismuth(Bi)nanospheres coated with carbon(Bi@C)is constructed by utilizing a novel Bi-based complex(1,4,5,8-naphthalenetetracarboxylic dianhydride as the ligand)as the precursor,which provides an effective template to fabricate Bi-based anodes.At-40℃,the Bi@C anode achieves a high capacity,which is equivalent to 96%of that at 25℃,benefitting from the core-shell nanostructured engineering and Na^(+)-ether-solvent cointercalation process.The special Na+-diglyme cointercalation behavior may effectively reduce the activation energy and accelerate the Na+diffusion kinetics,enabling the excellent low-temperature performance of the Bi@C electrode.As expected,the fabricated Na_(3)V_(2)(PO_(4))_(3)//Bi@C full-cell delivers impressive rechargeability in the ether-based electrolyte at-40℃.Density functional theory calculations and electrochemical tests also reveal the fast reaction kinetic mechanism at LT,thanks to a much lower diffusion energy barrier(167 meV)and a lower reaction activation energy(32.2 kJ mol^(-1))of Bi@C anode in comparison with that of bulk Bi.This work provides a rational design of Bi-based electrodes for rechargeable SIBs under extreme conditions.

Dominant role of wettability in improving the specific capacitance

Here we report a strategy to enhance the energy density of supercapacitors by increasing the utilization rate of the specific surface area(SSA)via wettability improvement. The nonporous gold(NPG) film is used as the electrodes and the ionic liquid [EMIM]BF4 is the electrolyte. When the electrode is coated by paraffin, an increase of the contact angle leads to a remarkable reduction of the specific capacitance. While when acetonitrile is added into the electrolyte, the contact angle is decreased and the utilization rate of SSA is improved, which results in an increase of the specific capacitance. The addition of isopropyl acetate into the electrolyte leads to a further increase of the specific capacitance. To generalize the role of the wettability in improving the energy density, a carbon-based electrode is evaluated in the solution of potassium hydroxide. An addition of propyl alcohol into the potassium hydroxide solution leads to an increase of the specific capacitance, as well as a long-term stability of the supercapacitor. The role of conductivity in this study is excluded by designing experiments. This paper highlights the significance of wettability in determining the specific capacitance, showing an alternative to improve the energy density of supercapacitors.

High-precision stress determination in photoelasticity

Stress separation is usually achieved by solving differential equations of equilibrium after parameter determination from isochromatics and isoclinics.The numerical error resulting from the stress determination is a main concern as it is always a function of parameters in discretization.To improve the accuracy of stress calculation,a novel meshless barycentric rational interpolation collocation method(BRICM)is proposed.The derivatives of the shear stress on the calculation path are determined by using the differential matrix which converts the differential form of the equations of equilibrium into a series of algebraic equations.The advantage of the proposed method is that the auxiliary lines,grids,and error accumulation which are commonly used in traditional shear difference methods(SDMs)are not required.Simulation and experimental results indicate that the proposed meshless method is able to provide high computational accuracy in the full-field stress determination.

The role of diffusion in the nucleation of calcium carbonate

Nucleation widely exists in nature,from cloud formation to haze generation.The classical nucleation theory(CNT)was created to describe the nucleation process,but it fails to predict many experimental phenomena due to the short consideration of nanoscale phenomena and macroscale dynamics.Although the attachment and detachment of monomers are considered in the developed model of nucleation,the diffusion of chemicals in the bulk is not valued as supersaturation in the nucleation process so far.Here we employ simulation and experimental approaches to investigate how the diffusion of ions affects the nucleation of calcium carbonate.The diffusion of ions is regulated by the viscosity of solvents and the sonication imposed on the solution.It is found that the nucleation rates increased exponentially with the diffusion coefficient of ions,which is beyond the prediction of CNT.This abnormal finding might be ascribed to the involvement of cluster aggregation in the nucleation of calcium carbonate.This study highlights the significance of chemical diffusion in the nucleation process,which may help to revise the nucleation theory and develop solutions for the rational synthesis of materials,as well as for the control of air pollution.

Phase-field modeling of faceted growth in solidification of alloys

A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.

Effects of Bovine Embryos at Different Developmental Stages on Bisection Effect

[Objectives]This study was conducted to explore the effects of embryos at different developmental stages on the bisection effect of embryos,improve the efficiency of bovine embryo bisection,and facilitate the application of embryo bisection technology in cattle breeding.[Methods]The effects of two different bisection solutions on the bisection of morulae and blastocysts in vitro were explored.The morulae and blastocysts produced in vitro from cattle that developed to the 6th to 8th d were bisected by hands,and demi-embryos were cultured in vitro.Their development was observed.[Results]Morulae were bisected in PBS solution and PBS+0.2 mol/L sucrose,and the success rates of bisection were 50%and 95.2%,respectively.The success rate of bisecting morulae in PBS+0.2 mol/L sucrose was significantly higher than that in PBS(P<0.05),while the development rate of the bisected demi-embryos had no significant difference between the two(53.3%,52.4%)(P>0.05).The success rates of blastocyst bisection in PBS solution and PBS+0.2 mol/L sucrose were 51.6%and 95.1%,respectively.The success rate of blastocyst bisection in PBS+0.2 mol/L sucrose was significantly higher than that in PBS(P<0.05),while the development rate of the bisected demi-embryos had no significant difference between the two(50.0%,56.4%)(P>0.05).[Conclusions]There were no significant differences between the success rates of bisecting bovine morulae and blastocysts in PBS+0.2 mol/L sucrose,which were both significantly better than those in pure PBS bisection solution,proving that PBS+0.2 mol/L sucrose bisection solution is suitable for bovine embryo bisection.

Research on Key Technology of Efficient Production of Bovine Embryos

[Objectives]This study was conducted to explore the effects of three different splitting fluids on the bisection effects of bovine morulae and blastocysts.[Methods]With the help of a micromanipulator,the morulae and blastocysts that were routinely produced in the body from the 6 th to the 8 th d were divided into half-embryos in vitro to observe their development,and the half-embryos with a restored morphology and a blastocyst trophoblast were selected.[Results]The success rates of bisection of morulae in PBS+0.2 mol/L sucrose and PBS+5%PVP were significantly higher than that in PBS(P<0.05),and the values in the three liquids were 95.7%,97.2% and 50%,respectively,while the blastocyst development rates and of half-embryos and the pregnancy rates of transplantation were not significantly different(P>0.05).When blastocysts were bisected in PBS+0.2 mol/L sucrose and PBS+5% PVP,the success rates of bisection were significantly higher than that of PBS(P<0.05),and the values in the three liquids were 96.8%,95.5% and 50.0%,respectively,while the development rates of half-embryos and the pregnancy rates of transplantation were not significantly different(P>0.05).The development rate of half-embryos bisected from blastocysts was significantly higher than that of morulae.[Conclusions]This study improves the efficiency of bovine embryo bisection,which is beneficial to the application of embryo bisection technology in cattle breeding.

Anisotropic lattice Boltzmann-phase-field modeling of crystal growth with melt convection induced by solid-liquid density change

Density change is ubiquitous in phase transformation, and it can induce melt convection which strongly influences the crystal growth. Here, an anisotropic lattice Boltzmann-phase-field method was extended to predict the dendritic growth under the shrinkage or expansion melt convection by density change induced. A novel LB equation with an anisotropic coefficient was constructed to model the advancement of ordering parameter, coupling with the passive scalar LB equation for convective and diffusive heat transfer during phase transition. We studied dendritic growth and shape selection with melt convection induced by density change in crystal growth. Results show that the melt convection induced by density change affects strongly the dendritic growth. The shrinkage flow results in a higher tip velocity while the expansion flow leads to a slower one. Predicted Péclet number with respect to the relative density change was compared with an analytical solution. Moreover, the modified selection parameter has been verified by numerical simulations.

Light doping of tungsten into copper-platinum nanoalloys for boosting their electrocatalytic performance in methanol oxidation

Coupling the bi-functional mechanism with compressive lattice strain might be an effective way to boost the electrocatalysis of platinum(Pt)-based nanoparticles for methanol oxidation reaction(MOR).This strategy weakens the chemisorption of poisoning CO-like intermediates generated during MOR on the active Pt sites by lowering their d-band center.In this context,we herein report the synthesis of ternary copper-tungsten-platinum(CuWPt)nanoalloys with light doping of W element by simply co-reducing their precursors at elevated temperature.In this ternary alloy system,the presence of only small amount of W element not only weakens the chemisorption of CO-like intermediates by lowering the Pt d-band center through compressive lattice strain,but also cleans the active Pt sites by“hydrogen spillover effect”,endowing the as-prepared CuWPt nanoalloys at an appropriate Cu/W/Pt ratio with good activity for MOR.In specific,the ternary CuWPt alloy nanoparticles at a Cu/W/Pt molar ratio of 21/4/75 show a specific activity of 2.5 mA·cm^(−2)and a mass activity of 2.11 A·mg^(−1)with a better durability,outperforming those ternary CuWPt alloy nanoparticles at other Cu/W/Pt ratios,binary CuPt alloys and commercial Pt/C catalyst as well as a large number of reported Pt-based electrocatalysts.In addition,a single direct methanol fuel cell(DMFC)assembled using ternary CuWPt nanoalloys as anodic catalysts shows a power density of 24.3 mW·cm^(−2)and an open-circle voltage of 0.6 V,also much higher than those of the single DMFC assembled from commercial Pt/C catalysts.

Multifunctional silver film with superhydrophobic and antibacterial properties

Material properties are strongly dependent on material structure. The large diversity and complexity of material structures provide significant opportunities to improve the properties of the materials, expanding their applications. Here, we discuss the fabrication of a multifunctional silver film prepared by controlling the nucleation and growth of silver particles. Silver films with high hydrophobicity and antibacterial activity were fabricated by adopting an electrochemical approach. The dependence of the hydrophobic and antibacterial properties on the size and shape of the silver particles was first investigated. Small-sized silver particles exhibited a high antibacterial rate, while a porous silver film composed of dendritic particles showed a significant hydrophobic activity. By regulating the reaction time, current density, and silver salt concentration, a silver film with a contact angle of 150.9° and an antibacterial rate of 54.7% was synthesized. This study demonstrates that finding a compromise between different material structures is a suitable wav to fabricate multifunctional devices.

Developing hierarchical CdS/NiO hollow heterogeneous architectures for boosting photocatalytic hydrogen generation

The hierarchical binary CdS/NiO hollow heterogeneous architectures(HHAs)with p–n heterojunction are constructed by a facile microwave-assisted wet chemical process for high-efficient photocatalytic hydrogen evolution reaction(HER)from water.The as-designed CdS/NiO HHAs are composed of hexagonal n-type CdS nanoparticles with a size in the range of 20–40 nm attaching to cubic p-type NiO hollow microspheres(HMSs)which are aggregates of porous nanoplates with a thickness of about 20 nm.The photocatalytic water splitting over CdS/NiO HHAs is significantly increased under simulated solar irradiation,among which the most active sample of CdS/NiO-3(the mass ratio of CdS to NiO is 1:3)exhibits the fastest photocatalytic HER rate of 1.77 mmol∙g^(−1)∙h^(−1),being 16.2 times than that of pure CdS.The boosted photocatalytic HER could be attributed to the synergistic effect on the proportional p–n heterojunction with special hierarchical hollow and porous morphology,an enhancement of visible light absorption,and an improvement of photoinduced charge separation as well as the photo-stability given by the composite heterojunction.This work shows a viable strategy to design the heterojunction with special morphology for the efficient hydrogen generation by water splitting utilizing solar energy.

In Situ Investigation of Dynamic Silver Crystallization Driven by Chemical Reaction and Diffusion

Rational synthesis of materials is a long-term challenging issue due to the poor understanding on the formation mechanism of material structure and the limited capability in controlling nanoscale crystallization.The emergent in situ electron microscope provides an insight to this issue.By employing an in situ scanning electron microscope,silver crystallization is investigated in real time,in which a reversible crystallization is observed.To disclose this reversible crystallization,the radicals generated by the irradiation of electron beam are calculated.It is found that the concentrations of radicals are spatiotemporally variable in the liquid cell due to the diffusion and reaction of radicals.The fluctuation of the reductive hydrated electrons and the oxidative hydroxyl radicals in the cell leads to the alternative dominance of the reduction and oxidation reactions.The reduction leads to the growth of silver crystals while the oxidation leads to their dissolution,which results in the reversible silver crystallization.A regulation of radical distribution by electron dose rates leads to the formation of diverse silver structures,confirming the dominant role of local chemical concentration in the structure evolution of materials.

Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering. If we look at crystallization at the atomic level, crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice. Diffusion can be a rate determining step for the growth of crystals. In this paper, we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced. The diffusion effect is studied in a specially designed three-cell reactor. Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concen- tration gradient in the reaction cell, thus promoting the formation of cubic calcite particles. The reaction rate is regulated by temperature. Increase of reaction rate favors the formation of needle-like aragonite particles. When diffusion and reaction play joint roles in the reaction system, their compromise dominates the formation of products, leading to a mixture of cubic and needle-like particles with a controllable ratio. Since diffusion and reaction are universal factors in the preparation of materials, the finding of this paper could be helpful in the controlled synthesis of other materials.

Spherical Particles Growth with Dynamic Oscillation during Lithium Electrodeposition

In this paper,the spherical particles growth during lithium electrodeposition was investigated by directly solving the governing equations based on the Landau transformation method.The basic growth kinetic characteristics of a spherical particle during electrodeposition was studied.Predicted results show that the dynamic oscillation of the growth velocity occurs during the spherical particle growth.It was found from numerical simulations that applied electrical potential difference,electrolyte concentration,and diffusion coefficient are 3 main factors influencing the spherical growth and the existence of the dynamic oscillation state of the growth velocity during electrodeposition.The increase in both the applied electrical potential difference and the electrolyte concentration can lead to the increase of the growth velocity of the spherical particle,while the growth velocity is independent of the diffusion coefficient.Moreover,it was found that the wavelength and the amplitude of the dynamic oscillation of the growth velocity can be influenced by the applied electrical potential difference,the electrolyte concentration,and the diffusion coefficient.We determined that the dynamic competition between electrochemical reactions and ion transport in the electrodeposition is the reason for the existence of the oscillation of the growth velocity.