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Unconventional superconductivity in magic-strain graphene superlattices

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arXiv

arXiv 2024年

作者： Ji, Qingxiang Li, Bohan Christensen, Johan Wang, Changguo Kadic, Muamer National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150001 China IMDEA Materials Institute Calle Eric Kandel 2 Getafe Madrid28906 Spain Université de Franche-Comté Institut FEMTO-ST CNRS Besançon25000 France

Extensive investigations on the Moiré magic-angle have been conducted in twisted bilayer graphene, unlocking the mystery of unconventional superconductivity and insulating states. In analog to magic angle, here we demonstrate the new concept of magic-strain in graphene systems by judiciously tailoring mechanical relaxation (stretch and compression) which is easier to implement in practice. We elucidate the interplay of strain-induced effects and delve into the resulting unconventional superconductivity or semimetal-insulator transition in relaxation-strained graphene, going beyond the traditional twisting approach. Our findings reveal how relaxation strain can trigger superconducting transitions (with an ultra-flat band at the Fermi level) or the semimetal-insulator transition (with a gap opening at the K point of 0.39 eV) in both monolayer and bilayer graphene. These discoveries open up a new branch for correlated phenomena and provide deeper insights into the underlying physics of superconductors, which positions graphene as a highly tunable platform for novel electronic applications. © 2024, CC BY.

关键词： Strain relaxation

Surface-Enhanced P-Type Transparent Conducting Cui−Ga2o3 Films with High Hole Transport Performance and Stability

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SSRN 2024年

作者： Xue, Ruibin Gao, Gang Yang, Lei Xu, Liangge Zhang, Yumin Zhu, Jiaqi National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150080 China Center of Analysis Measurement Harbin Institute of Technology Harbin150001 China Zhengzhou Research Institute Harbin Institute of Technology Zhengzhou450046 China Key Laboratory of Micro-systems and Micro-structures Manufacturing Ministry of Education Harbin Institute of Technology Harbin150080 China

CuI is a wide bandgap p-type transparent conductor with promising optoelectronic properties. However, conventional CuI films prepared through the iodination of Cu films exhibit rough surface, poor stability and excessively high hole concentration, hindering its application. Herein, we introduce CuI−Ga2O3 composite films as a substitution to overcome the shortcomings of pure CuI. During the iodination process, Ga2O3 hinders the mobility of CuI grain boundaries, resulting in small grain size and low surface roughness. After the charge re-equilibrium between Ga2O3 and CuI, the hole concentration in the films decreased by an order of magnitude. The interface effect of Ga2O3 at the grain boundaries of CuI, increases the hole mobility by 5 times and the conductivity by 53%. The ultra-wide band gap of Ga2O3 enhances the transmittance of CuI films in short wavelength region. Ga2O3 serves to passivate the grain boundaries of CuI, preventing the oxidation of CuI and the loss of iodine, consequently improving the stability of the films. This work deepens the understanding of the failure and hole transport mechanisms of CuI films. © 2024, The Authors. All rights reserved.

关键词： Stability

Micro and nanolattice fabrication using projection micro litho stereo exposure additive manufacturing techniques and synchrotron X-ray 3D imaging-based defect characterization

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science China(Technological sciences) 2020年第4期63卷 561-570页

作者： HU WenXia LIU LiWu WU WenWang XI Li LENG JinSong FANG DaiNing Institute of Advanced Structure Technology Beijing Institute of TechnologyBeijing 100081China Department of Astronautical Science and Mechanics Harbin Institute of TechnologyHarbin 150001China National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology(HIT)Harbin 150080China Department of Mechanical Engineering Massachusetts Institute of TechnologyCambridge MA 02139USA

Synchrotron radiation X-ray micro-computed tomography(SR-μCT)is a 3D imaging technique that is widely employed for the characterization of defects in advanced materials and *** this study,we characterize several typical defects in octettruss and re-entrant 3D lattice structures by using SR-μ*** 3D micro-lattice structures are manufactured using projection micro litho stereo exposure(PμLSE)additive manufacturing *** as-fabricated 3D lattice samples are characterized using optical microscopy,and subsequently,by SR-μ*** more,a statistical analysis is performed to characterize the surface roughness and internal defects qualitatively,whereby the statistical geometrical parameters of struts along different directions and strut joints are analyzed and ***,several typical defects are identified:(1)holes at the joints of the strut and irregular diameter deviations of the strut in the octet-truss lattice structure;(2)irregular diameter variations,bulges,dislocations,grooves,accumulations,and torsion in the re-entrant lattice *** of these defects are related to the building direction,the weight of the structure,bubbles,dust,and impurities during the PμLSE additive manufacturing process.

关键词： synchrotron radiation X-ray additive manufacturing lattice structures defect characterization

Cold Sintering: A Promising in Situ Resource Utilisation Strategy to Densify Lunar Regolith Simulants for Construction Applications

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SSRN 2023年

Sintering lunar regolith simulants as building materials is an effective method to establish long-term lunar bases. However, the high energy consumption of conventional thermal sintering is a challenge for energy-scarce lunars. The cold sintering process (CSP), which densifies ceramics with the assistance of transient solvent, offers a solution to overcome the aforementioned problems. Utilizing the CSP at 150 °C, 200 MPa, and 15 wt% 10 mol NaOH for 90 min, the density and compressive strength of the samples reached 2.44 g/cm3 and 207 MPa, respectively. The energy consumption of CSP equipment is only 0.86 kW·h, which is 6.66 times lower than that of conventional thermal sintering (5.73 kW·h). Furthermore, the compressive strength of the samples after three cool-heat cycles temperature between -196 °C and 150 °C was 205 MPa, indicating that the samples maintained high reliability in a simulated lunar environment. This excellent performance is attributed to the NaOH solution dissolving the oxide clusters on the particle surface, and the precipitation-generated glass phase connecting adjacent particles, making the particles consolidated and densified. Therefore, the cold sintering process presents promising prospects for the energy-efficient fabrication of lunar construction materials with excellent mechanical strength and durability. © 2023, The Authors. All rights reserved.

关键词： Energy utilization

An experimental study of ultra-high temperature ceramics under tension subject to an environment with elevated temperature,mechanical stress and oxygen

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science China(Technological sciences) 2019年第8期62卷 1349-1356页

作者： HAN XinXing XU ChengHai JIN Hua XIE WeiHua MENG SongHe National Key Laboratory of Science and Technology for National Defence on Advanced Composites in Special Environments Harbin Institute of Technology

Ultra-high temperature ceramic(UHTC) composites are widely used in high-temperature environments in aerospace applications. They experience extremely complex environmental conditions during service, including thermal, mechanical and chemical loading. Therefore, it is critical to evaluate the mechanical properties of UHTCs subject to an environment with elevated temperature, mechanical stress and oxygen. In this paper, an experimental investigation of the uniaxial tensile properties of a ZrB_2-SiC-graphite subject to an environment with a simultaneously elevated temperature, mechanical stress and oxygen is conducted based on a high-temperature mechanical testing system. To improve efficiency, an orthogonal experimental design is used. It is suggested that the temperature has the most important effect on the properties, and the oxidation time and stress have an almost equal effect. Finally, the fracture morphology is characterized using scanning electron microscopy(SEM), and the mechanism is investigated. It was concluded that the main fracture mode involved graphite flakes pulling out of the matrix and crystalline fracture, which indicates the presence of a weak interface in the composites.

关键词： ultra-high temperature ceramics environment with elevated temperature mechanical stress and oxygen uniaxial tensile strength orthogonal experimental design

Bio-Inspired Robust and Highly Thermal Conductive Bnns/Pbo Nanofiber Films with Excellent Thermal Stability, Wear Resistance, and Adjustable Photothermal Properties

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SSRN 2023年

作者： Sun, Tingting Cao, Wenxin Zhao, Kechen Wang, Xiaolei Wang, Zhuochao Gao, Ge Ye, Zhijie Zhao, Kunlong Su, Zhenhua Dai, Bing Zhang, Mingfu Han, Jiecai Zhu, Jiaqi National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150080 China Zhengzhou Research Institute Harbin Institute of Technology Zhengzhou450000 China Key Laboratory of Micro-Systems and Micro-Structures Manufacturing Ministry of Education Harbin Institute of Technology Harbin150080 China

We present electrically insulating composite films inspired by the nacre lamellar structure to address heat dissipation challenges in miniaturized electronic devices. These films comprise poly-p-phenylene benzodiazole (PBO) nanofibers reinforced with boron nitride nanosheets (BNNS). To mimic the nacre composition, we uniformly deposited polydopamine (PDA) nanoparticles on the hydroxylated BNNS (BNNS-OH), creating a "brick-mortar" structure. Through computational and experimental analyses, we confirmed enhanced interfacial interaction between the BNNS and PBO nanofiber, facilitated by hydrogen bonding and delocalized π–π* conjugation induced by PDA. This study provided optimal thermal conductivity enhancement of per unit, achieving in-plane thermal conductivity of 45.15 W/(m·K) at only 37.5wt.% of BNNS@PDA. The composite film demonstrates a high tensile strength (104.9 MPa), thermal stability (T5% = 670.03 °C), low thermal expansion (2.29 ppm/K), low dielectric loss (tanδ = 0.03), and low wear rate (6.85×10-11 m3 N-1 m-1). Moreover, the PDA-functionalized BNNS/PBO nanofiber composite films exhibits a tunable photothermal conversion performance. Under 1064 nm laser irradiation (0.5 W/mm2 for 120 s), the BNNS@PDA/PBO nanofiber composite films film exhibits a temperature increase of about 70 °C. The multifunctionality and the excellent heat dissipation, scratch resistance, and photothermal conversion efficiency of the composite film emphasize its application potential in heat dissipation in electronic devices, hot-swappable optical modules, and photothermal therapy. © 2023, The Authors. All rights reserved.

关键词： Nanofibers

Simulation Analysis of A Cable-Driven Astronaut on-Orbit Physical Exercise Equipment

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Simulation Analysis of A Cable-Driven Astronaut on-Orbit Phy...

International Conference on Autonomous Robots and Agents, ICARA

作者： Lailu Li Lixun Zhang Bing Wang Da Song National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin China College of Mechanical and Electrical Engineering Harbin Engineering University Harbin China School of Mechanical Engineering Northeast Electric Power University Jilin China

It has been proved by aerospace medicine that physical exercises are the most effective countermeasure to eliminate the negative influence brought by microgravity when astronauts carry out space exploration missions. A cable-driven astronaut on-orbit physical exercise equipment (CAPE) is proposed in this paper, and to verify its feasibility and performance: First, the cable-driven astronaut on-orbit physical exercise equipment was introduced. Second, the force analysis of the CAPE-assisted deep squat was conducted, and the cable tension distribution strategy was established. Third, the simulation study was carried out by utilizing Matlab. The results demonstrate that the deep squat conducted by the CAPE is smooth and steady, the cable tension distribution strategy is accurate, astronaut can realize deep squat during a space trip with the assistance of CAPE.

关键词： Analytical models Presses Power cables Distribution strategy Real-time systems Space exploration Reliability

One-Pot Preparation of MXene/SPUA Hollow Microsphere and its Electromagnetic Absorbing Properties

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SSRN 2022年

作者： An, Boyuan Zhang, Dongjie Liu, Yuyan Fan, Zhimin Tan, Huifeng Xie, Zhimin National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Center for Composite Materials and Structures Harbin Institute of Technology Harbin150001 China MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical Engineering Harbin Institute of Technology Harbin150001 China

Ti3C2Tx (MXene) has potential applications in electromagnetic (EM) absorbing due to its excellent electrical properties. Generally, the MXene hollow core-shell structure is obtained by the template method for EM absorbing. However, due to the need of post-processing such as high-temperature carbonization, this will lead to the oxidation of MXene. Here, we propose a one-pot method to prepare MXene/SPUA hollow microspheres through the emulsion polymerization to avoid this defect. The flocculation method was used to increase the content of MXene in the SPUA shell. UV spectrum and SEM proved the high content of MXene in the shell and the acquisition of regular microspheres with the introduction of arabic gum. Remarkably, the MXene/SPUA hollow microspheres with K2SO4 flocculant achieve a RLmin of -18dB with a corresponding EAB of 4 GHz. While the RLmin of microspheres without K2SO4 flocculant all > -10 dB. In addition, we also found the MXene/SPUA hollow microsphere with regular spherical structure has better EM absorbing performance. It is reasonable to consider that MXene/SPUA microspheres are more compatible with polymer matrix. At the same time, MXene/SPUA hollow microspheres have nonmagnetic particles, they are particularly suitable for applications in fields with limited magnetic properties, such as medical and health care. © 2022, The Authors. All rights reserved.

关键词： Microspheres

Microstructure and Properties of (Diamond + Tic) Reinforced Ti6al4v Titanium Matrix composites Manufactured by Directed Energy Deposition

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SSRN 2023年

作者： Wang, Jiandong Tang, Lang Xue, Yu Zhao, Ziang Ye, Zhijie Cao, Wenxin Zhu, Jiaqi Jiang, Fengchun Key Laboratory of Superlight Materials & Surface Technology Ministry of Education College of Materials Science and Chemical Engineering Harbin Engineering University Harbin150001 China National Key Laboratory of Science and Technology Advanced Composites in Special Environments Harbin Institute of Technology Harbin150080 China Yantai Graduate School of Harbin Engineering University Yantai264006 China

In this study, (diamond + TiC) reinforced Ti6Al4V titanium matrix composites (DT-TMCs) are fabricated using the directed energy deposition (DED) technique to enhance the hardness, wear resistance, and thermal conductivity of the Ti6Al4V alloy. The phase composition, microstructure, microhardness, wear resistance, and thermal conductivity of the composites are investigated. The findings demonstrate that the DT-TMCs consist of diamond, in-situ formed TiC (including eutectic TiC and primary TiC), α-Ti and β-Ti. The formation of in-situ TiC is attributed to the partial dissolution of the diamond into the Ti6Al4V matrix during directed energy deposition. The superior hardness of in-situ TiC, compared to that of Ti6Al4V alloy, plays a pivotal role in enhancing the overall hardness of the DT-TMCs. Owing to the high hardness and excellent thermal conductivity of diamond, the wear resistance and thermal conductivity of the DT-TMCs are superior to those of the unmodified Ti6Al4V alloy. With an increase in diamond volume fraction from 0% to 15%, the microhardness of the DT-TMCs raises from 333.99 HV0.2 to 438.15 HV0.2, while the wear rate decreases from 207.514 × 10-5 mm³·N-1m-1 to 2.256 × 10-5 mm³·N-1m-1 and thermal conductivity increases from 6.686 W·m-1·K-1 to 13.613 W·m-1·K-1. Additionally, the in-situ TiC exhibits superior thermal conductivity compared to the Ti6Al4V alloy, which also contributes to the improved thermal conductivity of the DT-TMCs. © 2023, The Authors. All rights reserved.

关键词： Wear resistance