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Molecular Dynamics Simulation of a New Inhomogeneous Concentration Distribution Model Based on Frictional Behavior of Fenicrcocu High-Entropy Alloy

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SSRN 2023年

作者： Qiu, Jiezheng Xu, Zhonghai Song, Jieren Hu, Chunxing Miao, Linlin He, Xiaodong National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150080 China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering Mechanics Tsinghua University Beijing100084 China Shenzhen STRONG Advanced Materials Research Institute Co. Ltd Shenzhen518000 China

High entropy alloys (HEA) have excellent mechanical properties and wear properties, and they have a powerful role in wear materials. In this study, molecular dynamics (MD) method was used to investigate the friction and wear properties of FeNiCrCoCu high-entropy alloy. Firstly, the effects of cutting speed, cutting depth, cutting environment temperature and alloy concentration on the frictional behavior were explored by analyzing friction coefficient, the stress distribution and dislocation in the wear model of FeNiCrCoCu high-entropy alloy. The results show that an increase in friction velocity leads to the formation of more high-temperature regions, and the temperature in these regions mainly diffuses perpendicular to the friction direction. During the friction process, the increase of the friction environment temperature will lead to local stress concentration phenomenon and the appearance of low-stress areas. In addition, based on the above research on the friction mechanism of FeNiCrCoCu high-entropy alloy, a new model based on the concentration distribution is proposed. Through the analysis of its wear degree, it is found that the structure can effectively reduce the wear situation of the material, the reason is that the model can effectively impede the movement of dislocation lines and improve the wear resistance of the alloy. It is great significance to improve the frictional wear performance of the alloy structure. © 2023, The Authors. All rights reserved.

关键词： Molecular dynamics

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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

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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

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Thermal Stress and Assembling Parameters Evolution of CMC Bolted Joint under Transient Thermal Loads

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Journal of Harbin Institute of technology(New Series) 2021年第3期28卷 1-8页

作者： Shuyuan Zhao Zhengyu Li Zeliang Pu Xinyang Sun Wenjiao Zhang National Key Laboratory of Science and Technology for National Defense on Advanced Composites in Special Environments Harbin Institute of TechnologyHarbin 150080China School of Aeronautics and Astronautics Harbin Institute of TechnologyHarbin 150001China Engineering College Northeast Agricultural UniversityHarbin 150030China

Ceramic matrix composite(CMC) and superalloy bolted joints have exhibited great potential for high temperature hot structure application in hypersonic aircraft. In service conditions, the thermal expansion mismatch between CMC and superalloy plates will cause complex thermal stress and strain distributions at hole-edge areas and assembly parameters changes of the joints under elevated temperatures. These effects might lead to early damage of joint structure, which will endanger the structural integrity and load carrying capacity of aircraft components. In the present study, transient heat transfer and thermo-structural analysis of C/SiC composite and superalloy bolted joint were carried out by using a commercial FEA software ABAQUS. The stress distributions at hole-edge areas, pre-load loosening, and variation of bolt-hole clearance of CMC bolted joints under transient temperature rises were discussed for better understanding of high temperature structural behaviors. Results showed that pre-load declined with the increase of imposed hot side temperature, due to the thermal expansion mismatch between CMC and superalloy. The bolt-hole clearance for the composite plate decreased, whereas the clearance for the superalloy plate increased with the rise of temperature.

关键词： ceramic matrix composite heat transfer thermal stress pre-load bolt-hole clearance

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Unconventional Superconductivity in Magic-Strain Graphene Superlattices

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SSRN 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 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 0.39eV 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, The Authors. All rights reserved.

关键词： Graphene

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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

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Insight into Pyrolysis Behavior of Silicone-Phenolic Hybrid Aerogel Through Thermal Kinetic Analysis and Reaxff Md Simulations

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SSRN 2022年

作者： Xiao, Jie Zhang, Hanqi Gao, Xu Wang, Hongyue Fang, Guodong Wang, Bing Hong, Changqing Meng, Songhe National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150001 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing210094 China

Phenolic aerogel matrix nanocomposites are modified to improve their thermal stability, flame retardancy, and oxidation resistance, while the pyrolysis behavior will become more complex. Herein, the pyrolysis behavior of silicone-phenolic hybrid aerogel, as the pyrolyzable component of the nanocomposites, was investigated by thermal analysis experiments (TG-MS and TG-FTIR), kinetic studies (isoconversional methods and distributed activation energy model (DAEM)), and reactive force field molecular dynamics (ReaxFF MD) simulations. Experimentally, it was found that the main product of silicone-phenolic hybrid aerogel during the first decomposition stage is CH4, which was also validated by ReaxFF MD simulation. The main product CH4 was predominantly formed by hydrogen extraction reaction from silicone aerogel. The main decomposition products and pyrolysis kinetics of silicone-phenolic hybrid aerogel were analyzed by a combination of the multi-DAEM and ReaxFF MD simulations. The five-pseudo-components DAEM was utilized to reveal the decomposition of silicone-phenolic hybrid aerogel in five stages, which were in good agreement with the experimental conversion rates. The rearrangement of the Si-O-Si backbone of silicone aerogel at elevated temperatures forms silica-like species with flame retardance and antioxidant performance. This study can provide reliable guidance for the characterization and design of phenolic aerogel matrix nanocomposites and the selection of antioxidant modifiers. © 2022, The Authors. All rights reserved.

关键词： Pyrolysis

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The compatibility of polylactic acid and polybutylene succinate blends by molecular and mesoscopic dynamics

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International Journal of Smart and Nano Materials 2020年第1期11卷 24-37页

作者： Cheng Lin Liwu Liu Yanju Liu Jinsong Leng Department of Astronautic Science and Mechanics Harbin Institute of Technology(HIT)HarbinPeople’s Republic of China National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology(HIT)HarbinPeople’s Republic of China

The compatibility of polylactic acid(PLA)/polybutylene succinate(PBS)blends was studied by molecular dynamics and mesoscopic dynamics,which is a controversial issue in *** simulation models of PLA/PBS with different composition ratios(100/0,90/10,80/20,70/30,60/40,0/100)were *** radial distribution function,hydrogen bond,free energy density,order parameter and iso-density surface morphology of the PLA/PBS systems were simulated and *** to the formation of hydrogen bonds and van der Waals bonds between different elements of PLA chains and PBS chains,the PLA/PBS blends exhibit good compatibility at all composition ratios.

关键词： Compatibility molecular dynamics simulation radial distribution function PLA PBS

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Mxene Nanohybrids Assembled with Phytic Acid-Modified Uio-66 Toward Mechanically Reinforced, Fire-Resistant and Smoke-Suppressed Epoxy composites

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SSRN 2024年

作者： Gong, Kaili Yin, Lian Wu, Zilong Zhou, Keqing Yu, William W. School of Chemistry and Chemical Engineering Ministry of Education Key Laboratory of Special Functional Aggregated Materials Shandong Key Laboratory of Advanced Organosilicon Materials and Technologies Shandong University Jinan250100 China School of Engineering China University of Geosciences Wuhan430074 China State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology Beijing10029 China Qingdao University of Science and Technology China

Given the good structural and compositional characteristics, there are considerable trends towards optimizing the architectures of two-dimensional materials to work for high-performance flame-retardant polymeric materials. Herein, considering the promising features of Ti3C2Tx MXene, phytic acid-modified UIO-66 (PA-UIO) was self-assembled onto MXene nanosheets (MXene/PA-UIO) using electrostatic interactions. The resulting nanohybrids presented good interfacial interactions and dispersion in epoxy matrix, opening up the possibility of simultaneously improving the mechanical and flame-retardant properties of the composites. Consequently, epoxy composites with 2 wt% MXene/PA-UIO achieved elevated mechanical properties and enhanced thermal properties, reflected by the increased storage modulus and tensile strength, as well as the declined rate of mass loss (Rmax, 28.3% reduction rate). Also, the addition of MXene/PA-UIO nanohybrids led to the drops in peak heat release rate (PHRR), peak smoke production rate (PSPR), peak CO production rate (PCOP) and peak CO2 production rate (PCO2P) of 32.0%, 36.5%, 33.8% and 38.6% respectively, compared to those of pure epoxy. Meanwhile, a smoke factor (SF) with 47% drop rate was obtained, accompanied by significantly decreased gas-phase products, verifying the superior heat-reducing, smoke-suppressing and toxic fume-attenuating effects of the nanohybrids. The synergistic effects between MXene and PA-UIO realized the "3-in-1" fire-safety epoxy nanocomposites in mechanical properties, flame retardancy and smoke/toxic fume-suppressing effects. The performance enhancement was mainly attributed to the dehydration charring of phosphorus-containing acid, catalytic charring of transition metal derivatives, quenching effects of phosphorus radicals and dilution of non-flammable gases, as well as the barrier effects of the nanosheets. © 2024, The Authors. All rights reserved.

关键词： Tensile strength

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Diamond Single Crystal-Polycrystalline Hybrid Microchannel Heat Sink Strategy for Directional Heat Dissipation of Hot Spots in Power Devices

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SSRN 2022年

作者： Hao, Xiaobin Liu, Benjian Li, Yicun Zhao, Jiwen Zhang, Sen Wen, Dongyue Liu, Kang Dai, Bing Han, Jiecai Zhu, Jiaqi National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of Technology Harbin150080 China Key Laboratory of Micro-systems and Micro-structures Manufacturing Ministry of Education Harbin150080 China

Aiming at the hot spots heat dissipation in power integrated circuits and challenging growth problems of large size single crystal diamond, a novel heat sink strategy is proposed, based on a diamond single crystal-polycrystalline hybrid microchannel for directional heat dissipation of hot spots. We conducted numerical simulations to investigate the effects of fluid flow rate, hot spot heat flux density, hot spot sizes and single crystal diamond sizes on the heat dissipation performance of the hybrid heat sink. A comparison of performances with a Si-polycrystalline diamond hybrid microchannel and polycrystalline diamond heat sink is made. Results show that, the heat dissipation performance of the diamond single crystal-polycrystalline hybrid microchannel radiator is improved by 35.9% and 8.4% compared with the other two types of heat sink, respectively. On this basis, a simple and fast preparation scheme of hybrid heat sink is proposed and preliminary growth experiments are carried out. The heat dissipation scheme proposed in this study is a promising route, which is expected to improve the performance and stability of power devices through efficient directional heat dissipation, and will further promote the application of diamond materials in the field of heat dissipation. © 2022, The Authors. All rights reserved.

关键词： Heat sinks

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