Article
Chemistry, Physical
Yasemin Keskin, Ozhan Unverdi, Dogan Erbahar, Ismet Inonu Kaya, Cem Celebi
Summary: The friction coefficients of single-layer epitaxial graphene grown on Si-terminated and C-terminated faces of SiC substrate were measured using FFM under ambient conditions. The results showed that the friction coefficient of graphene on the C-terminated face of SiC is about two times smaller than on its Si-terminated face. The observed difference in friction coefficients cannot be solely attributed to the roughness of the graphene layers.
Article
Nanoscience & Nanotechnology
Senjiang Yu, Yongjie Guo, Huihua Li, Chenxi Lu, Hong Zhou, Lingwei Li
Summary: This study reports on the controllable heterogeneous wrinkles in template-modulated thickness-gradient metal films sputter-deposited on polydimethylsiloxane substrates. The surface performances are well controlled by the wrinkle arrays achieved by adjusting the deposition time, copper grid period, template shape, and lifting height.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
Xinchang Wang, Yu Qiao, Karin Larsson, Fanghong Sun
Summary: In this study, H-, O-, OH-, and F-terminated N-doped diamond surfaces were calculated using density functional theory, revealing that the N dopant has different effects depending on its position and the terminating species. The adsorption energy is decreased when the N dopant is in the first carbon layer, while it is slightly increased when in the second carbon layer. Oxygen shows the highest reactivity to attacks, and N dopants have slight influences on the reactivity of adjacent adsorbates.
MATERIALS CHEMISTRY AND PHYSICS
(2021)
Article
Materials Science, Coatings & Films
Yueling Yu, Yi Ma, Xianwei Huang, Yuxuan Song, Taihua Zhang, Congda Lu
Summary: By annealing at different temperatures, the density, hardness, and elastic modulus of the PTFE film can be increased, while the room-temperature creep resistance is improved. Meanwhile, the elastic recovery ratio during scratch testing decreases with higher annealing temperatures.
SURFACE & COATINGS TECHNOLOGY
(2021)
Article
Chemistry, Physical
Yanan Zhao, Wandong Xing, Fanyan Meng, Haozhi Sha, Yunbo Yu, Xingqiao Ma, Rong Yu
Summary: The study shows that steps at the (111) surface of CeO2 are highly reducible, with simultaneous loss of surface and subsurface oxygen observed. The outermost Ce atoms in the Ce-terminated surface exhibit negligible relaxation compared to the O-terminated surface.
APPLIED SURFACE SCIENCE
(2021)
Article
Oceanography
Allison Ho, Sophia Merrifield, Nick Pizzo
Summary: Observations from CDIP moored buoys off the coast of Florida show that tidal currents can modify wave heights by up to 25% and shift peak periods by up to a second. A case study at Fernandina Beach reveals that surface waves become steeper on following tidal currents and less steep on opposing tidal currents, with the largest modulations in the long-period swell band. Theoretical and numerical simulations confirm these findings and suggest that knowledge of tidal currents and water-depth variations can accurately predict wave-height variations. Rating: 8/10.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2023)
Article
Engineering, Chemical
Lixia Huo, Jinshan Guo, Fahu Yang, Changou Pan, Hanjun Hu, Kaifeng Zhang, Hui Zhou, Peng Liu
Summary: A novel high-performance lubricating oil was developed through esterification, which exhibited ultralow friction and excellent wear-reduction performance.
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
(2022)
Article
Materials Science, Multidisciplinary
Zhenxi Zhang, Guomin Yu, Zhongrong Geng, Pei Tian, Kexin Ren, Wenchao Wu, Zhenbin Gong
Summary: In this study, a solid lubricating film with ultralow friction coefficient and good electrical conductivity was prepared using hydroxylated CNTs through electrophoretic deposition, and the structural evolution of CNT films acting as lubricants was investigated. It was found that the electric resistance decreased significantly with the increase of deposited CNT film thickness, and the friction coefficient was reduced as well.
DIAMOND AND RELATED MATERIALS
(2021)
Article
Agriculture, Multidisciplinary
Xuefeng Song, Fei Dai, Xuekun Zhang, Huhu Chen, Fengwei Zhang, Wuyun Zhao
Summary: This study examines the impact of inclination angles and depths of ridger on the quality of ridge forming in the Northwest of China's rain-fed agriculture. The results demonstrate that the resistance of ridger increases with the increase of inclination angles and depths. The height of the ridges is significantly influenced by these factors, with the depth of ridger directly proportional to the height of the ridges. The study also reveals that the soil disturbance is stronger in small ridges compared to large ridges, with the soil within a range of 30-90 mm from the surface being most susceptible to disturbance. These findings contribute to a deeper understanding of the rotary tillage ridging process and the factors influencing the quality of ridge forming.
COMPUTERS AND ELECTRONICS IN AGRICULTURE
(2023)
Article
Nanoscience & Nanotechnology
Chenxi Li, Eliezer F. Oliveira, Abhijit Biswas, Anand B. Puthirath, Xiang Zhang, Atin Pramanik, Elias J. Garratt, Mahesh R. Neupane, Bradford B. Pate, Anthony Glen Birdwell, Tony G. Ivanov, Tanguy Terlier, Robert Vajtai, Pulickel M. Ajayan
Summary: Diamond surface functionalization has attracted significant research interest, particularly H-termination due to its ability to enhance surface conductivity. This study focused on exploring the attachment of different functional groups, such as nitrogen and sulfur heteroatoms, on the diamond surface and their impact on electronic structure. The functionalized diamond surfaces were found to possess higher conductivity than H-terminated diamonds and showed a downshift in the conduction band minimum and valence band maximum, indicating a reduced bandgap. These findings suggest the potential of heteroatom functionalizations on diamond surfaces for various electronic applications.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Physical
Linxia Bi, Xiaona Li, Yinglin Hu, Junyi Zhang, Xiao Wang, Xuecheng Cai, Tongde Shen, Renwei Liu, Qing Wang, Chuang Dong, Peter K. Liaw
Summary: In this study, a series of high-entropy alloy films were prepared by radio frequency magnetron sputtering, and systematic investigations were conducted on their microstructure, mechanical properties, and resistivity-temperature behavior. The addition of V did not alter the crystal structure of the films, but enhanced their homogeneity and instability.
APPLIED SURFACE SCIENCE
(2021)
Article
Engineering, Mechanical
Jing Shi, Wanrong Wang, Jinzhu Yang, Xiaoyu Cao, Junyan Zhang, Chengbing Wang
Summary: The study found that the friction coefficient of H-FLC film is negatively correlated with rotational speed, reaching ultra-low friction at 500 rpm. Detailed nano structure evolution research indicates that the odd carbon ring fraction at the sliding interface is the key to H-FLC's low friction, with rearranged pentagonal and heptagonal carbon rings enhancing the fullerene-like carbon content. This work corroborated the significant role of rehybridization at the frictional interface in achieving ultra-low friction of H-FLC.
TRIBOLOGY INTERNATIONAL
(2021)
Article
Engineering, Chemical
Antai Liu, Changqi Yan, Fuqiang Zhu, Haifeng Gu, Suijun Gong
Summary: The experimental results showed that the liquid film thickness was affected by both gas phase velocity and liquid phase velocity, with the effect of gas phase velocity gradually decreasing as its speed increases in annular flow. The interfacial friction factor was significantly influenced by liquid phase velocity at low gas phase velocity but this impact decreased with increasing gas phase velocity. Existing correlations for the parameters showed a large deviation between predicted and experimental results, leading to the proposal of new correlations for the parameters.
CHEMICAL ENGINEERING RESEARCH & DESIGN
(2021)
Article
Engineering, Mechanical
Febin Cyriac, Xin Yi Tee, Sendhil K. Poornachary, Pui Shan Chow
Summary: The study found that organic friction modifiers (OFMs) can reduce friction under heavy loads, low sliding speeds, and high temperatures, forming a boundary lubrication film containing OFM. While the adsorption of OFM on the metal surface did not directly correlate with surface coverage and tribofilm thickness, the reduction in friction mechanism may involve other localized processes at the interface.
Article
Chemistry, Physical
Qiye Guan, Hejin Yan, Yongqing Cai
Summary: MXenes, as promising materials for catalytic and nanoelectronic applications, have limitations in interlayer adhesion and environmental disturbances. This study explores the surface passivation and exfoliation of MXenes through polymers, revealing the effects of different monomers on adsorption and charge transfer. The results show that specific functional groups and polymer types have significant effects on the properties of MXenes.
CHEMISTRY OF MATERIALS
(2022)
Article
Engineering, Mechanical
Yazhuo Liu, Chung-Yuen Hui, Wei Hong
Summary: This study investigates the role of friction in cutting soft materials and reveals that the slicing motion diverts the friction force towards the horizontal direction, minimizing its contribution in resisting the cutting process in the vertical plane. The presence of friction reduces energy barrier of crack opening and promotes cutting by enabling sliding and facilitating the development of local tension.
EXTREME MECHANICS LETTERS
(2021)
Article
Materials Science, Multidisciplinary
Chung-Yuen Hui, Bangguo Zhu, Rong Long
Summary: We compare different theories on the steady state growth of a Mode I crack in linear viscoelastic solids and test these theories against experimental data. Realistic constitutive models are used in the analytical solutions, and new results such as the strain field near the crack tip and the investigation of the viscoelastic trumpet shape and size are presented.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2022)
Article
Multidisciplinary Sciences
Yong Zheng, Takahiro Matsuda, Tasuku Nakajima, Wei Cui, Ye Zhang, Chung-Yuen Hui, Takayuki Kurokawa, Jian Ping Gong
Summary: Double-network gels are tough soft materials with two elastic networks, where the large crack resistance is attributed to the internal damage zone formed ahead of the crack tip by the rupturing of the brittle network. The size of the necking zone decreases with higher solvent viscosity, leading to reduced fracture toughness of the material, highlighting the role of stretchable network dynamics triggered by brittle network rupture. This discovery adds an important missing piece to the fracture mechanism of this unique material.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Multidisciplinary Sciences
Chung-Yuen Hui, Fan Cui, Alan Zehnder, Franck J. Vernerey
Summary: This article compares two physically-based constitutive models for describing the behavior of polymer networks consisting of a mixture of chemical and physical cross-links. These two models, developed independently by different research groups using different mathematical formulations, can accurately predict the time-dependent behavior of a poly(vinylalcohol) dual cross-link hydrogel. Experimental data supports the equivalence of the models under specific conditions, while also highlighting the advantages and disadvantages of each approach in applications.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2021)
Article
Chemistry, Physical
Zezhou Liu, Hao Dong, Anand Jagota, Chung-Yuen Hui
Summary: This study proposes a numerical scheme for solving lubrication problems that does not require iteration, and is stable, efficient, and automatic. Experimental results are in excellent agreement with the numerical solution.
Article
Engineering, Chemical
Haibin Wu, Anand Jagota, Chung-Yuen Hui
Summary: In this study, we investigate the lubricated sliding of a rigid cylinder on a viscoelastic half space with a single characteristic retardation time using a numerical scheme. Our results show that the total friction force can be decomposed into viscoelastic and hydrodynamic components. We find that the viscoelastic component can be well approximated by the dry limit, while the hydrodynamic component can be approximated by a modification of the elastic limit. We also examine the effects of parameters on the hydrodynamic pressure, film thickness, and friction coefficient.
Article
Engineering, Chemical
Nichole Moyle, Hao Dong, Haibin Wu, Constantine Y. Khripin, Chung-Yuen Hui, Anand Jagota
Summary: Controlling the lubricated sliding friction of compliant contacts is crucial in mechanical and biological systems. In this study, a structured two-phase material composed of a plastic mesh embedded in a compliant elastomer matrix was developed. The results showed that the embedded mesh structure exhibited increased lubricated sliding friction under specific conditions. Simulations suggested that the difference in lubrication regimes between the structured sample and the unstructured control was caused by areas of high contact pressure induced by the increased local contact stiffness near the embedded mesh.
Article
Polymer Science
Jingwen Zhao, Jingyi Guo, Costantino Creton, Chung Yuen Hui, Tetsuharu Narita
Summary: Mechanical reinforcement of hydrogels is crucial in gel science. Dual cross-linked hydrogels with both chemical and transient cross-links exhibit enhanced mechanical properties compared to chemically cross-linked gels alone. This study investigates the effect of the ratio of chemical and transient cross-links on chain dynamics using model dual poly(vinyl alcohol) cross-linked gels. The results suggest that the characteristic time of network relaxation increases with decreasing concentration of transient cross-linkers, and the characteristic time distribution gradually transitions from Maxwell-like to Rouse-like relaxation.
Article
Materials Science, Multidisciplinary
Chung-Yuen Hui, Bangguo Zhu, Matteo Ciccotti
Summary: This article investigates stress concentration in sharp corners or wedge structures and explores the changes caused by considering large deformation. The study found that, under large deformation, the stress field differs from the predictions of linear elasticity and does not exhibit oscillations.
INTERNATIONAL JOURNAL OF FRACTURE
(2022)
Article
Physics, Multidisciplinary
Xuechen Shi, Zezhou Liu, Luyi Feng, Tiankai Zhao, Chung-Yuen Hui, Sulin Zhang
Summary: The study investigates the elastocapillary effect at cell-matrix contacts and its impact on tissue morphogenesis, wound healing, and cancer metastasis. By observing cell colonies indenting soft hydrogels, the researchers propose a two-step traction force microscopy to separate active cell traction from interfacial stresses. The study provides a foundation for understanding elastocapillarity-induced mechanobiological processes in cells and tissues.
Article
Engineering, Mechanical
Haibin Wu, Constantine Khripin, Anand Jagota, Chung-Yuen Hui
Summary: It has been discovered that lubricated friction can be enhanced by the periodic variation of near-surface stiffness. In this study, we simulated the lubricated sliding of a rigid cylinder on a substrate with a periodic variation in mechanical stiffness. The results show that increasing the variation of near-surface stiffness can significantly increase the friction force. This research provides insight into the mechanism of friction enhancement and can guide the design of surfaces to control friction during lubricated sliding.
EXTREME MECHANICS LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Haibin Wu, Chung -Yuen Hui, Anand Jagota
Summary: This paper investigates the problems in elasto-hydrodynamic lubrication when one of the contacting bodies is elastically soft. A numerical method is developed to solve both normal indentation and transient sliding lubrication problems, avoiding the difficulties of converging iterative methods.
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
(2023)
Article
Engineering, Mechanical
Jikun Wang, Kunpeng Cui, Bangguo Zhu, Jian Ping Gong, Chung-Yuen Hui, Alan T. Zehnder
Summary: Relaxation experiments were conducted on single edge notch tension (SENT) and T shape specimens made of various polyampholyte (PA) hydrogels. These specimens have the common feature of containing regions with high and low stress/strain, allowing us to investigate the load transfer mechanisms between permanent and dynamic networks of different strengths, which are related to viscoelastic behavior. PA gels exhibit non-linear viscoelasticity, with time-dependent behavior controlled by the breaking and reforming of ionic bonds in the dynamic network. Contrary to the prediction of linear viscoelastic theory, the displacement and strain fields during stress relaxation change in a complex manner depending on the strength of the dynamic bonds and the observation time window. These experimental findings are explained by a non-linear viscoelastic model. Additional physical insights are obtained by studying the non-linear rheology of dynamic bonds or stickers. Our results demonstrate that modifying the strength of dynamic bonds can control the load transfer between networks.
EXTREME MECHANICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Hao Dong, Nichole Moyle, Haibin Wu, Constantine Yuri Khripin, Chung-Yuen Hui, Anand Jagota
Summary: Lubricated contacts in soft materials are common in various applications. The transition between elasto-hydrodynamic lubrication (EHL) and mixed lubrication (ML) regimes governs the minimum sliding friction achievable. Previous belief held that the transition occurs when the thickness of the lubricant layer is comparable with the amplitude of surface roughness, but this study found that the transition can occur when the thickness of the liquid layer is much larger than the height of the asperities. Direct visualization showed the formation of wave-like surface wrinkles triggering the transition to the mixed regime.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Sairam Pamulaparthi Venkata, Kunpeng Cui, Jingyi Guo, Alan T. Zehnder, Jian Ping Gong, Chung-Yuen Hui
Summary: A finite strain nonlinear viscoelastic constitutive model is used to study the uniaxial tension behavior of chemical polyampholyte (PA) gel, cross-linked by chemical and physical bonds. Material parameters in the model are obtained by least squares optimization and showed good agreement with experimental results.