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Dynamic Bubble Behaviour during Microscale Subcooled Boiling

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Chinese Physics Letters 2005年第11期22卷 2881-2884页

作者：王昊彭晓峰 David M. Christopher laboratory of phase-change and Interracial transport phenomena Department of Thermal Engineering Tsinghua University Beijing 100084

Bubble cycles, including initiation, growth and departure, are the physical basis of nucleate boiling. The present investigation, however, reveals unusual bubble motions during subcooled nucleate boiling on microwires 25 or 100μm in diameter. Two types of bubble motions, bubble sweeping and bubble return, are observed in the experiments. Bubble sweeping describes a bubble moving back and forth along the wire, which is motion parallel to the wire. Bubble return is the bubble moving back to the wire after it has detached or leaping above the wire. Theoretical analyses and numerical simulations are conducted to investigate the driving mechanisms for both bubble sweeping and return. Marangoni flow from warm to cool regions along the bubble interface is found to produce the shear stresses needed to drive these unusual bubble movements.

关键词： Dynamic Bubble Behaviour during Microscale Subcooled Boiling

KTN thin films prepared by pulsed laser deposition on transparent single crystal quartz(100)

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Science China(Physics,Mechanics & Astronomy) 2005年第1期48卷 33-43页

作者： WANG Xiaodong, PENG Xiaofeng & ZHANG Duanming laboratory of phase change and interfacial transport phenomena, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China Department of Physics, Huazhong University of Science and Technology, Wuhan 430074, China laboratory of phase change and interfacial transport phenomena Department of Thermal Engineering Tsinghua University Beijing China Department of Physics Huazhong University of Science and Technology Wuhan China

Using the Sol-Gel method to produce the KTN ultrafine powder and the sintering technique with K2O atmosphere to prepare KTN ceramics as the targets instead of the KTN single crystal, highly oriented KTN thin films were produced on the transparent single crystal quartz (100) by the pulsed laser deposition (PLD). Since the thermal stress sustained by the quartz is relatively small, the limit temperature of the quartz substrates(300℃) is much lower than that of the P-Si substrates (560℃); the prepared thin film is at amorphous state. Increasing the pulsed laser energy density in the process incorporated with annealing the film after deposition at different temperatures converts the amorphous films into crystal. The optimal pulsed laser energy density and annealing temperature were 2.0 J/cm2 and 600℃, respectively. A discussion was made to understand the mechanism of film production at relatively low substrate temperature by PLD and effects of the annealing temperatures on the forming of the perovskite phase, and optimal conditions for the orientation of the crystal grain.

关键词： PLD technology, KTN thin film, single crystal quartz, pulsed energy density, annealing, perovskitephase.

Contact Angle Hysteresis and Hysteresis Tension on Rough Solid Surface

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Chinese Journal of Chemical Engineering 2004年第5期12卷 615-621页

作者：王晓东彭晓峰王补宣 laboratory of phase change and interfacial transport phenomena Department of Thermal Engineering Tsinghua University Beijing 100084 China

Observation and measurement were conducted to investigate contact angle andits hysteresis on rough surface. The experimental results indicate that the increase in solidsurface roughness enlarges advancing contact angle and decreases receding contact angle, resultingin enhanced hysteresis. It was observed that when Young''s contact angle θ_Y < 90°, as theroughness of solid surface increased the extent of the decrease in receding contact angle exceededthat of the increase in advancing contact angle. Based on the experimental observations, the conceptof hysteresis tension was introduced to describe the contact angle hysteresis behavior on roughsolid surface. The model provides a thoughtful understanding of the physical nature of contact anglehysteresis, in particular an instructive description of the influence of surface roughness on thehysteresis. The prediction of the model is found in quite good agreement with the experimentalobservation and measurement.

关键词： contact angle hysteresis roughness hysteresis tension sessile drop

ADSORPTION OF NANO-PARTICLES ON BUBBLE SURFACE IN NANO-PARTICLE SUSPENSION

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China Particuology 2005年第4期3卷 208-212页

作者： Buxuan Wang Chunhui Li Xiaofeng Peng laboratory of phase-change and interfacial transport phenomena Department of Thermal Engineering Tsinghua UniversityBeijing 100084 P. R. China

The adsorption of nano-particles on bubble surface is discussed for saturated boiling on thin wire of nano-particle suspensions. Owing to the decrease of surface tension for suspensions, the nano-particles tend to adsorb on the bubble surface to decrease the Gibbs free energy for stability, and meanwhile the velocity of nano-particles would be smaller than that of bubble growth. The long-range van der Waals force existing between “water particles” and nano-particles is considered the attractive force between the nano-particles and the bubble surface. Thus, the nano-particles would attach on the bubble surface if the particle-surface distance is smaller than its critical value. The distribution of nano-particles on the bubble surface and in the adjacent region is also investigated.

关键词： nano-particle suspension attachment critical distance

Effects of carbon content on the microstructure and tensile properties of a low-density steel

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International Journal of Minerals,Metallurgy and Materials 2025年第2期32卷 391-401页

作者： Yongxuan Shang Mingyu Fan Shuyong Jiang Zhongwu Zhang Key laboratory of Superlight Materials and Surface Technology Ministry of EducationCollege of Materials Science and Chemical EngineeringHarbin Engineering UniversityHarbin 150001China State Key laboratory of Metal Material for Marine Equipment and Application Iron&Steel Research Institute of Ansteel Group CorporationAnshan 114009China

Carbon can change the phase components of low-density steels and influence the mechanical *** this study,a new method to control the carbon content and avoid the formation ofδ-ferrite by decarburization treatment was *** microstructural changes and mechanical characteristics with carbon content induced by decarburization were systematically ***-Jaoul(C-J)analysis was employed to examine the work hardening characteristics during the tensile *** decarburization by heat treatments,the carbon content within the austenite phase decreased,while Mn and Al were almost unchanged;this made the steel with full austenite transform into the austenite and ferrite dual ***,(Ti,V)C carbides existed in both matrix phase and the mole fraction almost the *** addition,the formation of other carbides *** loss induced a decrease in strength due to the weakening of the carbon solid *** the steel with the single austinite,the deformation mode of austenite was the dislocation planar glide,resulting in the formation of *** the dual-phase steel,the deformation occurred by the dislocation planar glide of austenite first,with the increase in strain,the cross slip of ferrite took place,forming dislocation cells in *** the late stage of deformation,the work hardening of austinite increased rapidly,while that of ferrite increased slightly.

关键词： low-density steels carbon content decarburization strengthening mechanisms work hardening behavior

Kinetics of hydrate formation using gas bubble suspended in water

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Science China Chemistry 2002年第2期45卷 208-215页

作者：马昌峰陈光进郭天民 High Pressure Fluid phase Behavior & Property Research laboratory School of Chemical Engineering University of Petroleum Beijing China

An innovative experimental technique, which was devised to study the effects of temperature and pressure on the rate of hydrate formation at the surface of a gas bubble suspended in a stagnant water phase, was adapted in this work. Under such conditions, the hydrate-growth process is free from dynamic mass transfer factors. The rate of hydrate formation of methane and carbon dioxide has been systematically studied. The measured hydrate-growth data were correlated by using the molar Gibbs free energy as driving force. In the course of the experiments, some interesting surface phenomena were observed.

关键词： hydrate formation, kinetics, suspended gas bubble, methane, carbon dioxide.

Cobalt-embedded 3D conductive honeycomb architecture to enable high-sulphur-loading Li-S batteries under lean electrolyte conditions

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Nano Research 2022年第9期15卷 8091-8100页

作者： Hui Pan Zhibin Cheng Jan Fransaer Jiangshui Luo Michael Wübbenhorst laboratory for Soft Matter and Biophysics Department of Physics and AstronomyKU LeuvenLeuven 3001Belgium Fujian Key laboratory of Polymer Materials College of Chemistry and Materials ScienceFujian Normal UniversityFuzhou 350007China Department of Materials Engineering KU LeuvenLeuven 3001Belgium Lab of Electrolytes and phase change Materials College of Materials Science and EngineeringSichuan UniversityChengdu 610065China

High sulphur loading and lean electrolyte conditions are important to achieve the high theoretical energy density of lithiumsulphur(Li-S)***,serious problems such as low sulphur utilization and fast capacity fade are typically experienced under low electrolyte/sulphur(E/S)ratios and high sulphur loading *** address these issues,a cobaltcontaining three-dimensional conductive honeycomb(Co@N-HPC)is proposed in this work as a material for sulphur *** good electrical conductivity and high density of catalytic sites of(Co@N-HPC)allow fast redox kinetics of lithium polysulfide(LiPS)in high-sulphur-loading *** addition,the hierarchical structure and good wettability by the electrolyte of Co@NHPC facilitates electrolyte penetration and LiPS conversion,leading to a high utilization of sulphur under lean electrolyte ***,at a current density of 0.2 C,a volumetric capacity of 1,410 mAh·cm^(−3)was attained with a sulphur loading of 5.1 mg·cm^(−2)and an E/S ratio of 5μL·mg^(−1).This work provides ideas for the development of lean electrolyte Li-S batteries with a high sulphur loading.

关键词： honeycomb architecture cobalt nanoparticles high sulphur loading lean electrolyte lithium-sulphur battery

Multiple Equilibria in a Land–Atmosphere Coupled System

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Journal of Meteorological Research 2018年第6期32卷 950-973页

作者： Dongdong LI Yongli HE Jianping HUANG Lu BI Lei DING Key laboratory for Semi-Arid Climate change of the Ministry of Education College of Atmospheric Sciences Lanzhou University

Many low-order modeling studies indicate that there may be multiple equilibria in the atmosphere induced by thermal and topographic ***,most work uses uncoupled atmospheric model and just focuses on the multiple equilibria with distinct wave amplitude,i.e.,the high-and low-index ***,a low-order coupled land–atmosphere model is used to study the multiple equilibria with both distinct wave phase and wave *** model combines a two-layer quasi-geostrophic channel model and an energy balance *** truncated spectral expansions are used and the results show that there may be two stable equilibria with distinct wave phase relative to the topography:one(the other)has a lower layer streamfunction that is nearly in(out of)phase with the topography,i.e.,the lower layer ridges(troughs)are over the mountains,called ridge-type(trough-type)*** wave phase of equilibrium state depends on the direction of lower layer zonal wind and horizontal scale of the *** multiple wave phase equilibria associated with ridge-and trough-types originate from the orographic instability of the Hadley circulation,which is a pitch-fork *** with the uncoupled model,the land–atmosphere coupled system produces more stable atmospheric flow and more ridge-type equilibrium states,particularly,these effects are primarily attributed to the longwave radiation *** upper layer streamfunctions of both ridge-and trough-type equilibria are also characterized by either a high-or low-index flow ***,the multiple wave phase equilibria associated with ridge-and trough-types are more prominent than multiple wave amplitude equilibria associated with high-and low-index types in this study.

关键词： multiple equilibria land–atmosphere coupling wave phase longwave radiation stability

System-size effect on the friction at liquid-solid interfaces

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Applied Mathematics and Mechanics(English Edition) 2020年第3期41卷 471-478页

作者： Liang ZHAO Jiajia SUN Xian WANG Li ZENG Chunlei WANG Yusong TU College of Physical Science and Technology Yangzhou UniversityYangzhou 225009Jiangsu ProvinceChina School of Physics and Electronics Nanning Normal UniversityNanning 530023China Division of interfacial Water and Key laboratory of interfacial Physics and Technology Shanghai Institute of Applied PhysicsChinese Academy of SciencesShanghai 201800China

The friction at the liquid-solid interfaces is widely involved in various phenomena ranging from nanometer to micrometer scales. By the molecular dynamic(MD)simulation, the friction properties of liquid-solid interfaces at the molecular level are calculated via the Green-Kubo relation. It is found that the system size will influence the value of the friction coefficient, especially for the solid surfaces with the larger polar charge. The value of the friction coefficient decreases with the increase in the system size and converges at large system sizes. The large polar charge will lead to a significant friction coefficient. However, the diffusion of water molecules on this surface is almost a constant, indicating that the diffusion coefficient seems to be independent of the system size and polar charge. This work provides insights for the selection of the system size in modeling the frictional properties of hydrophobic/hydrophilic surfaces.

关键词： Green-Kubo relation liquid-solid interface system-size effect friction coefficient