Zhiping Xu

Zhiping Xu
Tsinghua University | TH · Department of Engineering Mechanics

PhD

About

242
Publications
83,208
Reads
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12,208
Citations
Citations since 2016
119 Research Items
9505 Citations
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201620172018201920202021202205001,0001,500
201620172018201920202021202205001,0001,500
201620172018201920202021202205001,0001,500
Introduction
My general research interests include the physics of synthetic materials and living systems, the mechanical behaviors and transport processes of materials with complex microstructures.
Additional affiliations
December 2015 - present
Tsinghua University
Position
  • Professor
May 2010 - December 2015
Tsinghua University
Position
  • Professor (Associate)
September 2008 - May 2010
Massachusetts Institute of Technology
Position
  • PhD Student
Education
September 2002 - August 2007
Tsinghua University
Field of study
  • Engineering Mechanics
September 1998 - August 2002
Tsinghua University
Field of study
  • Engineering Mechanics

Publications

Publications (242)
Method
Full-text available
Unraveling the morphological complexity of two-dimensional macromolecules allows researchers to design and fabricate high-performance, multifunctional materials. Here, we present a protocol based on statistical learning to resolve morphological complexity utilizing geometrical, topological, and physical features extracted from the strain energy hea...
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Composites combining the polymer and inorganic phases are ubiquitous in nature and the industry. The relationship between interfacial molecular structures and their mechanical performance is a critical issue to be addressed in practical applications. Structural and mechanical properties of the polymer-inorganic interfaces are investigated by molecu...
Article
The anisotropic fracture toughness G(θ) is an intrinsic feature of graphene and is fundamental for fabrication, functioning, and robustness of graphene-based devices. However, existing results show significant discrepancies on the anisotropic factor, i.e., the ratio between zigzag (ZZ) and armchair (AC) directions, G_{ZZ}/G_{AC}, both qualitatively...
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The two-dimensional nature of graphene offers a number of interesting mechanical properties. Amongst these, fracture toughness has received substantial interest, yet computational works have not reached a consensus regarding anisotropy in its fracture energy when graphene is loaded in armchair or zigzag directions. Here, we resolve the steps involv...
Article
Graphene nanoporous membranes are the ultimate ultrathin nanoporous membranes and have enormous potential applications due to efficient heat and mass transfer that is limited only by interfacial evaporation kinetics. Developing such membranes requires fundamental understanding of evaporation at the single-pore level, which has remained largely unex...
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Thermoplastic polymers and composites are ubiquitous in the industry for their reshaping and fusing capabilities at elevated temperatures. The quality of heat-fused thermoplastic interfaces is of great concern for adhesion, coating, and welding applications, especially those between dissimilar materials. Kinetic evolution of the microstructures def...
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2D macromolecules, such as graphene and graphene oxide, possess a rich spectrum of conformational phases. However, their morphological classification has only been discussed by visual inspection, where the physics of deformation and surface contact cannot be resolved. We employ machine learning methods to address this problem by exploring samples g...
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Structural superlubricity is a theoretical concept stating that the friction force is absent between two rigid, incommensurate crystalline surfaces. However, elasticity of the contact pairs could modify the lattice registry at interfaces by nucleating local slips, favoring commeasure. The validity of structural superlubricity is thus concerned for...
Article
Artificial muscles are materials or devices producing work under external stimuli. Recently-developed twisted-filament artificial muscles share a two-step process of triggered rotation or contraction, that are, volumetric expansion and tension-torsion coupling. Various actuating mechanisms such as thermal expansion, electrochemical cues, solvents a...
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Although layered van der Waals (vdW) materials involve vast interface areas that are often subject to contamination, vdW interactions between layers may squeeze interfacial contaminants into nanopockets. More intriguingly, those nanopockets could spontaneously coalesce into larger ones, which are easier to be squeezed out the atomic channels. Such...
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Two-dimensional (2D) crystals provides a material platform to explore the physics and chemistry at the single-atom scale, where surface characterization techniques can be applied straightforwardly. Recently there have been emerging interests in engineering materials through structural deformation or transformation. The strain field offers crucial i...
Preprint
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Two-dimensional materials and their multilayers or heterostructures are promising candidates for optoelectronic devices. Their performance such as the transient current can be remarkably modified under irradiation since the atoms are extremely exposed. This effect, however, still lacks theoretical understanding. Using real-time time-dependent densi...
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Abstracct Efforts to obtain high-strength graphene sheets by near-room-temperature assembly have been frustrated by the misalignment of graphene layers, which degrades mechanical properties. While in-plane stretching can decrease this misalignment, it reappears when releasing the stretch. Here we use covalent and π–π inter-platelet bridging to perm...
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Miniaturized or microscale generators that can effectively convert weak and random mechanical energy into electricity have significant potential to provide solutions for the power supply problem of distributed devices. However, owing to the common occurrence of friction and wear, all such generators developed so far have failed to simultaneously ac...
Article
Carbon sp2 building blocks such as graphene and carbon nanotubes hold great promises for structural and functional applications due to their intriguing material properties, which, unfortunately, fail to be upscaled into fibers or films as their macroscopic assemblies. The loss in performance originates from material imperfection and microstructural...
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The past 2 decades have witnessed the explosion of research on two-dimensional (2D) materials, where notable efforts have been made in the synthesis and design of a wide spectrum of applications. To understand their mechanical properties and responses triggered by deformation, the prerequisites for reliable applications under realistic service cond...
Article
Engineering strain and interlayer registry in 2D crystals have been demonstrated as effective controls of their properties. Separation of domains with different interlayer registries in graphene bilayer has been reported, but the pattern control of strained solitons has not yet been achieved. We show here that, by pulling a graphene bilayer apart,...
Article
Single-particle irradiation is a typical condition in space applications, which could be detrimental for electronic devices through processes such as single-event upset or latch-up. For functional devices made of few-atom-thick monolayers that are entirely exposed to the environment, the irradiation effects could be manifested through localized or...
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Intrinsic graphene features semi-metallic characteristics that limit its applications in electronic devices, whereas graphene nanoribbons (GNRs) are promising semiconductors owing to their bandgap-opening feature. However, the controllable mass-fabrication of high-quality GNR arrays remains a major challenge. In particular, the in situ growth of GN...
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One of the most celebrated achievements in polymer physics is the finding of simple scaling laws that correlate molecular behaviors with molecular size. Scaling relations of 2D macromolecules between the conformation and size have been extensively investigated in theory. However, in contrast to their 1D counterparts, the fundamental correlation of...
Article
Quantifying the intrinsic mechanical properties of one-dimensional nanostructures such as nanotubes and nanowires is technically challenging due to their extremely small sizes and large aspect ratios. In comparison with direct tensile measurements, displacement responses of an end-clamped rod under transverse loads are more significant and more fea...
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Monolayer hexagonal boron nitride can serve in optoelectronics or as a dielectric in graphene and other two-dimensional (2D) electronics due to its ultra-wide band gap. As there is no center of symmetry, monolayer hexagonal boron nitride (h-BN) also shows piezoelectricity. However, these applications require h-BN to sustain large uniform elastic de...
Article
Previous studies indicate that 2D materials such as graphene, WS2 and MoS2 deposited on oxidized silicon substrate are susceptible to aging due to the adsorption of airborne contamination. As a result, their surfaces become more hydrophobic. However, it is not clear how ubiquitous such a hydrophobisation is, and the interplay between the specific a...
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The sp2 nature of graphene endows the hexagonal lattice with very high theoretical stiffness, strength and resilience, all well-documented. However, the ultimate stretchability of graphene has not yet been demonstrated due to the difficulties in experimental design. Here, directly performing in situ tensile tests in a scanning electron microscope a...
Preprint
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Self-limiting oxidation of nanowires has been previously described as a reaction- or diffusion-controlled process. In this letter, the concept of finite reactive region is introduced into a diffusion-controlled model, based upon which a two-dimensional cylindrical kinetics model is developed for the oxidation of silicon nanowires and is extended fo...
Article
Understanding irradiation effects is crucial for risk management in space science as well as technological development in material processing, imaging, and radiotherapy. The single-particle event is a stepping stone to this complicate, multiscale problem, which finds relevance in low-dose irradiation where long-term effects are usually concerned. U...
Article
Out-of-plane deformation patterns, such as buckling, wrinkling, scrolling, and folding, formed by multilayer van der Waals materials have recently seen a surge of interest. One crucial parameter governing these deformations is bending rigidity, on which significant controversy still exists despite extensive research for more than a decade. Here, we...
Article
Direct chemical vapor deposition (CVD) growth of high quality graphene on dielectric substrates holds great promise for practical applications in electronics and optoelectronics. However, graphene growth on dielectrics always suffers from the issues of inhomogeneity and/or poor quality owing to the absence of metal catalysts. Here, we firstly revea...
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Fabrication of highly ordered and dense nanofibers assemblies is of key importance for high-performance and multi-functional material and device applications. In this work, we design an experimental approach in silico, where shear flow and solvent evaporation are applied to tune the alignment, overlap of nanofibers, and density of the assemblies. M...
Article
Hybrid membranes with nanoconfined ionic liquid (IL) have demonstrated promising potential for CO2 separation, while the trade-off between their permeance and selectivity is still an obstacle. In this work, an IL is confined in the 2D nanochannels (nanoslits) between graphene oxide (GO) nanosheets to form a GO-supported IL membrane (GO-SILM). By ap...
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Graphene-derived macroscopic assemblies feature hierarchical nano- and microstructures that provide numerous routes for surface and interfacial functionalization achieving unconventional material properties. We report that the microstructural hierarchy of pristine chemically modified graphene films, featuring wrinkles, delamination of close-packed...
Preprint
With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require the functionality of a biological ion channel, graphene provides a promising solid-state alternative, due to its atomic thinness and mechanical strength. Here, we dem...
Article
Graphene oxide (GO) has shown enormous potential applications in improving crop yield and soil cultivation quality. However, in heavy metal contaminated soil, the effect of GO on heavy metals and the indirect toxicity of GO to plants remain unclear. In this work, we reveal the GO-promoted cadmium (Cd) uptake by rice in a Cd-contaminated soil system...
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This study demonstrates that enzymatic reaction rate can be increased significantly by targeted heating on the microenvironment around enzyme, while maintaining the reaction system at environmental temperature. Enzyme molecules are covalently attached on the surface of Fe3O4@reduced graphite oxide (rGO). Under visible light irradiation, the reactio...
Article
With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require the functionality of a biological ion channel, graphene provides a promising solid-state alternative, due to its atomic thinness and mechanical strength. Here, we dem...
Article
Converting natural graphite to high-performance graphene films is very attractive due to graphite's abundance. However, this conversion is challenging to do inexpensively and under ambient conditions. One of the major challenges is how to design the interface between adjacent graphene nanosheets to integrate high strength, high toughness, and high...
Article
Though pristine graphene exhibits remarkable mechanical and electronic properties, many electromechanical applications may come from chemically doping it with heteroatoms. The goal is to tune the atomic lattice and, in turn, modulate the electronic band structure of graphene – that may also affect the mechanical responses of the graphene sheet. Par...
Article
Understanding molecular processes of evaporation at the liquid-vapor interfaces is of critical importance for development of phase-change-related applications. The interfacial behaviors are defined by liquid-vapor equilibrium following thermodynamic rules, while the process through nanopores can be modulated by spatial confinement and intermolecula...
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The self‐assembly into highly ordered pattern is a universal phenomenon with unprecedented natural properties. However, the nonequilibrium processes in complex systems demand rigorous molecular formation mechanism, which are highly important for fundamental research. Herein, a large‐scale formation of highly self‐assembly hierarchical hexagonal bor...
Article
Selective transport of liquids is an important process in the energy and environment industry. The increased energy consumption, as well as the demands of clean water and fossil fuels have urged the development of high-performance membrane technologies. Nanoscale channels with the critical size for molecular sieving and atomistically-smooth walls f...
Article
Fast and controllable water transport in microchannels implicates multifarious applications. A combination of stimuli‐responsive asymmetrical changes in the geometry and gradient in the surface wettability offers the possibility to accelerate the transport and realize controllability. Herein, we introduce a meters‐long sunlight‐powered reconfigurab...
Article
Fast and controllable water transport in microchannels implicates multifarious applications. A combination of stimuli‐responsive asymmetrical changes in the geometry and gradient in the surface wettability offers the possibility to accelerate the transport and realize controllability. Herein, we introduce a meters‐long sunlight‐powered reconfigurab...
Article
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Two types of electrospun polyoxymethylene nanofibers with rough and smooth surface morphologies [rough fibers (RFs) and smooth fibers (SFs), respectively] were successfully prepared via the control of the electrospinning voltages. Mechanical tensile tests showed that the RF nonwoven mats exhibited a much higher elongation (440%) than the SFs (180%)...
Article
Diffusion of lithium atoms in the silicon anode is a key process for the lithiation and de-lithiation steps in lithium-ion batteries. The relationship between atomic structures of silicon, in forms of crystals and glasses, and the diffusivity of lithium atoms are thus of critical importance to assess the performance of batteries using silicon as th...
Article
Recently experimental studies of selective ion transport across nanoporous membranes or through single nanochannels have unveiled interesting behaviors of dissolved ions under nanoconfinement. However, the exploration was limited by the resolution of experimental characterization. In this work, we present an atomistic simulation based study, showin...
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The past three decades have witnessed the explosion of nanoscience and technology, where notable research efforts have been made in synthesizing nanomaterials and controlling nanostructures of bulk materials. The uncovered mechanical behaviors of structures and materials with reduced sizes and dimensions pose open questions to the community of mech...
Article
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Membrane separation of CO2 from H2, N2 or CH4 has economic benefits. However, the trade-off between selectivity and permanence in membrane separation is challenging. Here, we prepared a high-performance CO2-philic membrane by confining the [BMIM][BF4] ionic liquid to the nanochannels in a laminated graphene oxide membrane. Nanoconfinement causes th...
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Two-dimensional transition metal dichalcogenides (TMDs) have attracted lots of interest because of their potential for electronic and optoelectronic applications. Atomically thin TMD flakes were believed capable to scroll into nanoscrolls (NSs) with distinct properties. However, limited by mechanical strength and chemical stability, production of h...
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Precisely controlled size of nanoscale fluidic channels plays a critical role in resolving the permeation-selectivity trade-off in separation and filtration applications, where highly efficient gas separation and water desalination are targeted. Inspired by natural nacre where the spacing between mineral platelets changes upon tension as fractured...
Article
Growing large-area single-crystal monolayers is the holy grail of graphene synthesis. In this work, the efficiency of graphene growth and the quality of their continuous films are explored through the time evolution of individual domains and their surface coverage on the substrate. Our phase-field modeling results and experimental characterization...
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Superfast water transport discovered in graphitic nanoconduits, including carbon nanotubes and graphene nanochannels, implicates crucial applications in separation processes and energy conversion. Yet lack of complete understanding at the single-conduit level limits development of new carbon nanofluidic structures and devices with desired transport...