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Effect of high temperature on compression property and deformation recovery of ceramic fiber reinforced silica aerogel composites

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Science China(Technological Sciences) 2017年第11期60卷 1681-1691页

作者： lyu shuangqi YANG XiaoGuang SHI DuoQi QI HongYu JING Xin LI ShaoLin School of Energy and Power Engineering Beihang UniversityBeijing 100191China Collaborative Innovation Center for Advanced Aero-engine Beijing 100191China

Ceramic fiber reinforced silica aerogel composites are novel insulation materials in the thermal protection field for hypersonic vehicles. Before the aerogel composites are applied in load-bearing structures, it is necessary to investigate their mechanical properties including load-bearing and deformation recovery capabilities. High temperature from service conditions will have important effects on the mechanical properties of thermal protection materials. In this paper, compression tests including loading and unloading stages were conducted for ceramic fiber reinforced silica aerogel composites at room temperature and elevated temperatures(300℃, 600℃ and 900℃). Influences of thermal exposure to high temperature and high temperature service environment on the compression property and deformation recovery were both investigated. Scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FT-IR) and X-ray diffraction(XRD) were applied to help understand the mechanisms of mechanical property variations. The experimental results show that the compression modulus and strength both increase with the increasing thermal exposure temperature and testing temperature,but the deformation recovery capability decreases. The micro structure changes caused by thermal sintering are considered as the main reason for the property *** flow and matter transport due to high temperature resulted in the fusion of aerogel particles. This made the particle skeleton thicker and stronger, which led to higher stiffness and strength of the composites. However, matrix cracks induced by the formation and fracture of larger pores made unrecoverable deformation more serious. In the tests at elevated temperatures,the aggregation of aerogel particles in a fused state got more severe because of the addition of mechanical load. As a result, the degradation of deformation recovery capability became more significant.

关键词： aerogel composites high temperature deformation recovery thermal exposure thermal protection sintering

A physically-based representative stress methodology for predicting stress rupture life of Ni-based DS superalloy

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Chinese Journal of Aeronautics 2023年第6期36卷 174-185页

作者： Jia HUANG Zhenzhuo HE shuangqi lyu Xiaoguang YANG Duoqi SHI Yantao SUN Yongzhao lyu Zhizhong FU Guolei MIAO Jianan SONG School of Aeronautics and Astronautics Central South UniversityChangsha 410083China Aviation Engineering College Civil Aviation University of ChinaGuanghan 618307China School of Energy and Power Engineering Beihang UniversityBeijing 100083China Beijing Aeronautical Engineering Technical Research Center Beijing 100076China Chengdu Holy Industry&Commerce Corp.LTD Pengzhou 611936China School of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China

Smooth and three types of U-shape single-edge notched plate specimens adopted to experimentally investigate stress rupture behavior of Ni-based Directionally Solidified(DS)superalloy at 850℃ exhibit notch weakening effect and multi-source cracking initiation near the notch ***,stress rupture behavior of smooth and V-shape notched round bars at 1040℃ revealed by Li et al indicates notch strengthening effect and creep micro-holes originating mostly from the central portion.A combined creep-viscoplastic constitutive model is employed to analyze the distribution of stress,strain and stress Triaxial Factor(TF)near the notch *** different stress distribution and creep restraint between asymmetric notched plate specimens and symmetric notched round bars are the main reasons for the corresponding failure ***,a good qualitative relationship exists between TF value and stress rupture life of notched ***,the area with maximum TF value(TF_(max))is highly consistent with creep damage initiation ***,based on the distribution characteristics of the initial tensile loading,a representative stress method independent of time-changing creep load at the location of TF_(max) is conducted for life *** predicted results of both smooth and notched plate specimens and round bars agrees well with the experimental results.

关键词： Creep Life model Ni-based superalloy Notched round bar Single edge notch

采用数字图像相关方法的莫来石纤维增强气凝胶复合材料力学试验

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复合材料学报 2015年第5期32卷 1428-1435页

作者：吕双祺石多奇杨晓光孙燕涛冯坚北京航空航天大学能源与动力工程学院北京100191 先进航空发动机协同创新中心北京100191 国防科学技术大学航天科学与工程学院新型陶瓷纤维及其复合材料国防科技重点试验室长沙410073

基于V型缺口试样双轨剪切法设计了面内剪切试验方案,开展了莫来石纤维增强气凝胶复合材料的室温面内剪切和弯曲性能试验,采用数字图像相关方法对试样表面的位移场和应变场进行测量,并分析了力学行为和破坏模式。结果表明:设计的试验方... 详细信息

基于V型缺口试样双轨剪切法设计了面内剪切试验方案,开展了莫来石纤维增强气凝胶复合材料的室温面内剪切和弯曲性能试验,采用数字图像相关方法对试样表面的位移场和应变场进行测量,并分析了力学行为和破坏模式。结果表明:设计的试验方案可以在测试区域获得均匀的剪切应变场,适用于莫来石纤维增强气凝胶复合材料的面内剪切性能测试。试验获得的面内剪切模量和强度分别为248 MPa和0.95 MPa,弯曲模量和强度分别为294 MPa和2.08 MPa。面内剪切载荷下,试样的裂纹萌生于缺口尖端附近,并沿两缺口连线方向扩展。根据弯曲正应变场的分布特点,发现试样中性层与几何对称面不重合,验证了该材料拉压模量不同的性质。采用数字图像相关方法获得的中性层位置和理论计算值比较接近,相对误差在10%左右。

关键词：气凝胶复合材料面内剪切破坏模式数字图像相关方法中性层

Macro-micro behaviors and failure mechanism of frozen weakly cemented mudstone

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1337-1347页

作者： Xianzhou lyu Jijie Du Hao Fu Dawei lyu Weiming Wang College of Earth Science and Engineering Shandong University of Science and TechnologyQingdao266590China College of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao266590China

Understanding the mechanical properties and multiscale failure mechanism of frozen soft rock is an important prerequisite for the construction safety of tunnels,artificially frozen ground and other infrastructure in cold *** this study,the triaxial compression test are performed on mudstone in the weakly cemented soft rock strata in the mining area of western China,and the mechanical characteristics and failure mechanism of weakly cemented mudstone are systematically investigated under the combined action of freezing and ***,the quantitative relationship between the microstructural parameters and the macroscopic strength and deformation parameters is established based on fractal ***,the failure mechanism of frozen weakly cemented mudstone is revealed on both micro- and *** results show that temperature and confining pressure significantly affects the elastic modulus and peak strength of weakly cemented *** decreasing temperature,the compressive strength increases,while the corresponding peak strain decreases *** the deformation curve,the plastic deformation stage is shortened,and the brittle fracture feature at the post-peak stage is more prominent,and the elastic modulus correspondingly increases with decreasing *** low-temperature conditions,most of the weakly cemented mudstone undergoes microscopic shear failure along the main fracture *** micro-fracture morphology characteristics of weakly cemented mudstone under different temperatures are quantified via the fractal dimension,and an approximately exponential relationship can be obtained among the fractal dimension and the temperature,compressive strength and elastic modulus.

关键词： Weakly cemented mudstone Artificial freezing Mechanical properties Linkage destruction mechanism Fractal dimension

Amorphous hybrid tungsten oxide–nickel hydroxide nanosheets used as a highly efficient electrocatalyst for hydrogen evolution reaction

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Nano Research 2024年第4期17卷 2499-2508页

作者： Chao lyu Chenghai Dai Yiwei Tan State Key Laboratory of Materials-Oriented Chemical Engineering School of Chemistry and Chemical EngineeringNanjing Tech UniversityNanjing 211816China

There are more challenges for alkaline hydrogen evolution reaction(HER)via simultaneously expediting the electron-coupled water dissociation process(Volmer step)and the following electrochemical H_(2) desorption(Heyrovsky step).Hybrid amorphous electrocatalysts are highly desirable for efficient hydrogen evolution from water-alkali electrolyzers due to the bifunctionality for the different elementary steps of HER and optimal interactions with water molecules and the reactive hydrogen intermediates(Had).Herein,the synthesis of amorphous hybrid ultrathin(tungsten oxide/nickel hydroxide)hydrate(a-[WO_(3)/Ni(OH)_(2)]·0.2H_(2)O)nanosheets on nickel foam(NF)for efficient alkaline HER is *** structural and composition features of a-[WO_(3)/Ni(OH)_(2)]·0.2H_(2)O are characterized in *** resulting a-[WO_(3)/Ni(OH)_(2)]·0.2H_(2)O/NF electrocatalyst with the synergistic effect of both hybrid components for the HER elementary steps shows greatly improved the activity and durability for the HER with a low overpotential of-41 and-163 mV at-10 and-500 mA·cm^(-2),respectively,a Tafel slope as low as-72.9 mV·dec^(-1),and long-term stability of continuous electrolysis for at least 150 h accompanying by inappreciable overpotential change in 1 M *** the hybrid a-[WO_(3)/Ni(OH)_(2)]·0.2H_(2)O,Ni(OH)_(2) and WO_(3) moieties are separately responsible for accelerating dissociative adsorption of water and weakening Had adsorption strength,which is beneficial to the improvement of the alkaline HER activity.

关键词： amorphous nanomaterial bimetallic electrocatalyst tungsten oxide ultrathin nanosheet hydrogen evolution reaction

Tunable polarization holographic gratings obtained by varying the ratio of intensities of the recording beams

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Photonics Research 2024年第4期12卷 749-754页

作者： HONG CHEN ZIYAO lyu CHANGSHUN WANG State Key Laboratory of Advanced Optical Communication Systems and Networks School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Space-Ground Integrated Information Technology Beijing Institute of Satellite Information EngineeringBeijing 100095China

Polarization holography has been extensively applied in many fields, such as optical science, metrology, and biochemistry, due to its property of polarization modulation. However, the modulated polarization state of diffracted light corresponds strictly to that of incident light one by one. Here, a kind of tunable polarization holographic grating has been designed in terms of Jones matrices, and intensity-based polarization manipulation has been realized experimentally. The proposed tunable polarization holographic grating is recorded on an azobenzene liquid-crystalline film by a pair of coherent light beams with orthogonal polarization states and asymmetrically controlled intensities. It is found that the diffracted light can be actively manipulated from linearly to circularly polarized based on the light intensity of the recording holographic field when the polarization state of incident light keeps constant. Our work could enrich the field of light manipulation and holography.

关键词： holographic recording Polarization

Pre-combustion mercury removal with co-production of hydrogen via coal electrolysis

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Journal of Environmental Sciences 2024年第2期136卷 382-389页

作者： Xiang lyu Runming Tao Tianyu Zhang Chemical and Biomolecular Engineering Department Ohio University165 Stocker CenterAthensOH45701USA Electrification and Energy Infrastructures Division Oak Ridge National LaboratoryOak RidgeTN37831USA Beijing Key Lab for Source Control Technology of Water Pollution College of Environmental Science and EngineeringBeijing Forestry UniversityBeijing 100083China Engineering Research Center for Water Pollution Source Control&Eco-remediation College of Environmental Science and EngineeringBeijing Forestry UniversityBeijing 100083China

Pre-combustion mercury removal via coal electrolysis was performed and investigated on a bench-scale coal electrolytic cell(CEC)systemically,and factorial design was used to determine the effect of different operating conditions(coal particle size,operating temperature,operating cell voltage,and flow rate of slurry)on the percentage of mercury removal,percentage of ash removal,and dry heating value *** results showed that the operating cell voltage,as well as the interaction between operating cell voltage and coal particle size,are significant factors in the percentage of mercury *** is no significant factor in the percentage of ash removal and the dry heating value change,but the coal could be purified while keeping the dry heating value almost constant after electrolysis.A co-product of hydrogen could be produced during coal electrolysis with 50%lower energy consumption compared with water ***,a mechanism for mercury removal in coal was *** facts indicate that coal electrolysis is a promising method for precombustion mercury removal.

关键词： Pre-combustion mercury removal Coal electrolysis Ash removal Dry heating value Hydrogen production

Challenges and opportunities in rare cancer research in China

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Science China(Life Sciences) 2024年第2期67卷 274-285页

作者： Jianxin Xue Qunyan lyu Division of Thoracic Tumor Multimodality Treatment Cancer CenterWest China HospitalSichuan UniversityChengdu 610041China National Natural Science Foundation of China Beijing 100085China

Cancer is one of the major public health challenges in *** cancers collectively account for a considerable proportion of all *** lack of awareness of rare cancers among healthcare professionals and the general public,the typically complex and delayed diagnosis,and limited access to clinical trials are key *** years have witnessed an increase in funding for research related to rare cancers in *** this review,we provide a comprehensive overview of rare cancers and summarize the status of research on rare cancers in China and overseas,including the trends of funding and *** also highlight the challenges and perspectives regarding rare cancers in China.

关键词： rare cancers basic research clinical research preclinical model funding scheme

Single transmembrane GPCR modulating proteins:neither single nor simple

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Protein & Cell 2024年第6期15卷 395-402页

作者： Meng Wang Jianjun lyu Chao Zhang Department of Plastic and Reconstructive Surgery Shanghai Ninth People’s HospitalShanghai Jiao Tong University School of MedicineShanghai 200011China Hubei Topgene Research Institute of Hubei Topgene Biotechnology Co. LtdEast Lake High-Tech Development ZoneWuhan 430205China Fundamental Research Center Shanghai Yangzhi Rehabilitation Hospital (Shanghai Sunshine Rehabilitation Center)Tongji UniversityShanghai 200092China

The discovery of G-protein coupled receptor(GPCR)accessory proteins has fundamentally redefined the pharmacological concept of GPCR signaling,demonstrating a more complex molecular basis for receptor specificity on the plasma membrane and impressionable downstream intracellular *** accessory proteins not only contribute to the proper folding and trafficking of receptors but also exhibit selectable receptor preferences.

关键词： specificity GPCR neither