Crack initiation is an essential stage of fatigue process due to its direct effect on fatigue failure.However,for titanium alloys in high-temperature high cycle fatigue(HCF),the crack initiation mechanisms remain uncl...Crack initiation is an essential stage of fatigue process due to its direct effect on fatigue failure.However,for titanium alloys in high-temperature high cycle fatigue(HCF),the crack initiation mechanisms remain unclear and the understanding for the defect sensitivity is also lacking.In this study,a series of fatigue tests and multi-scale microstructure characterizations were conducted to explore the high-temperature failure mechanism,and the coupled effect of temperature and defect on TC17 titanium alloy in HCF.It was found that an oxygen-rich layer(ORL)was produced at specimen surface at elevated temperatures,and brittle fracture of ORL at surface played a critical role for surface crack initiation in HCF.Besides,internal crack initiation with nanograins at high temperatures was a novel finding for the titanium alloy.Based on energy dispersive spectroscopy,electron backscatter diffraction and transmission electron microscope characterizations,the competition between surface and internal crack initiations at high temperatures was related to ORL at surface and dislocation resistance in inner microstructure.The fatigue strengths of smooth specimens decreased at elevated temperatures due to the lower dislocation resistance.While the fatigue strengths of the specimens with defect were not very sensitive to the temperatures.Finally,a fatigue strength model considering the coupled effect of temperature and defect was proposed for TC17titanium alloy.展开更多
A neural network is applied to high-quality 3-D seismic data during micro-seismic facies analysis to perform the waveform analysis and training on single reflection events. Modeled seismic channels are established and...A neural network is applied to high-quality 3-D seismic data during micro-seismic facies analysis to perform the waveform analysis and training on single reflection events. Modeled seismic channels are established and the real seismic channels are classified. Thus, a distribution of micro-seismic facies having a high precision over a fiat surface was acquired. This method applied to existing geological data allows the distribution of areas rich in coal bed methane to be clearly defined. A distribution map of the micro-seismic facies in the research area is shown. The data accord well with measured methane con- tents, indicating that the analysis using micro-seismic facies is reliable and effective. This method could be applied to coal bed methane exploration and is of great importance to future exploration work and to an increase in the drilling success rate.展开更多
Defect-rich,highly porous two-dimensional carbon nanosheets(CNS) have attracted tremendous research interests in catalysis and environmental purification and other fields,because of their unique micromorphology,chemic...Defect-rich,highly porous two-dimensional carbon nanosheets(CNS) have attracted tremendous research interests in catalysis and environmental purification and other fields,because of their unique micromorphology,chemical stability and high specific surface area.Herein,in this work,we report a new solution to synthesize an ultrathin two-dimensional CNS with rich defects and abundant pores via two-step etching the Ti_(3)AlC_(2)with the help of I2and NaOH.The CNS thickness,specific surface area and pore volume could be all tunable by adding the amount of I2.And the highest specific surface area and pore volume of the synthesized 2D CNS can be achieved 1134.4 m^(2)/g and 0.80 cm^(3)/g,with a thickness of only 0.64 nm and a yield of 35.9%.When employed as the anodes for lithium-ion batteries,the synthesized CNS anodes exhibit good cycling and rate capabilities.This work provides a novel and facile strategy for synthesizing highly porous and defective 2D carbon materials with good lithium storage properties.展开更多
Coal samples taken from the Taiyuan Formation in the Hequ area, China, for this study are typical cutinite-rich coals.The petrology and geochemistry of the samples were analyzed using microscopic examination, proximat...Coal samples taken from the Taiyuan Formation in the Hequ area, China, for this study are typical cutinite-rich coals.The petrology and geochemistry of the samples were analyzed using microscopic examination, proximate and ultimate analysis,rock pyrolysis, and gas chromatography-mass spectrometry(GC-MS). The cutinites in Haochuan(HC) coals are predominantly of the thin-walled type, whereas those in the Jingzigou(JZG) coals are predominantly thick-walled. The variable thickness of cutinites in different coals is related to the environment in which the coal-forming plants grew. Compared with typical Ⅲ kerogens, HC and JZG bituminous coals are characterized by high volatile matter yields and hydrogen contents due to the elevated hydrogen-rich cutinite content. Pyrolysis data indicate that these cutinite-rich coals can be expected to generate commercial liquid and gaseous hydrocarbons. Pristane(Pr) and phytane(Ph) are both abundant in the samples, with the Pr/Ph ratios for both the HC and JZG coals being >3.0, indicating moderate maturity and oxic peat depositional conditions. The C>>C>Cnormalized relative abundance of regular steranes is consistent with a dominant contribution from higher plants.Abundant hopanes in the coals also suggest a substantial organic matter input from bacteria, which are common inhabitants of peat and coal. Palynology studies indicate that pteridophytes are likely to be the most common coal-forming plants. A gymnosperm contribution is also indicated by the presence of tetracyclic diterpenes. Massive accumulations of cuticles as cutinite in coal are rare and account for only a small proportion of coals worldwide. However, cutinite-rich coals are found in the northern margin of the North China Craton, in the Taiyuan Formation. The accumulation of cutinite in this area is the result of distinctive peat deposition conditions. Frequent marine transgression was an important contributing factor.展开更多
基金financially supported by the National Natural Science Foundation of China(No.91860112)the International Postdoctoral Exchange Fellowship Program(China)。
文摘Crack initiation is an essential stage of fatigue process due to its direct effect on fatigue failure.However,for titanium alloys in high-temperature high cycle fatigue(HCF),the crack initiation mechanisms remain unclear and the understanding for the defect sensitivity is also lacking.In this study,a series of fatigue tests and multi-scale microstructure characterizations were conducted to explore the high-temperature failure mechanism,and the coupled effect of temperature and defect on TC17 titanium alloy in HCF.It was found that an oxygen-rich layer(ORL)was produced at specimen surface at elevated temperatures,and brittle fracture of ORL at surface played a critical role for surface crack initiation in HCF.Besides,internal crack initiation with nanograins at high temperatures was a novel finding for the titanium alloy.Based on energy dispersive spectroscopy,electron backscatter diffraction and transmission electron microscope characterizations,the competition between surface and internal crack initiations at high temperatures was related to ORL at surface and dislocation resistance in inner microstructure.The fatigue strengths of smooth specimens decreased at elevated temperatures due to the lower dislocation resistance.While the fatigue strengths of the specimens with defect were not very sensitive to the temperatures.Finally,a fatigue strength model considering the coupled effect of temperature and defect was proposed for TC17titanium alloy.
基金supported financially by the National Key Project(No. 2008ZX05035-005-003)the National Basic Research Program of China (No. 2009CB219603)
文摘A neural network is applied to high-quality 3-D seismic data during micro-seismic facies analysis to perform the waveform analysis and training on single reflection events. Modeled seismic channels are established and the real seismic channels are classified. Thus, a distribution of micro-seismic facies having a high precision over a fiat surface was acquired. This method applied to existing geological data allows the distribution of areas rich in coal bed methane to be clearly defined. A distribution map of the micro-seismic facies in the research area is shown. The data accord well with measured methane con- tents, indicating that the analysis using micro-seismic facies is reliable and effective. This method could be applied to coal bed methane exploration and is of great importance to future exploration work and to an increase in the drilling success rate.
基金financially supported by the National Natural Science Foundation of China (No. 51902036)Natural Science Foundation of Chongqing Science & Technology Commission (No. cstc2019jcyj-msxm1407)+4 种基金Natural Science Foundation of Jiangsu Province (No. BK20200047)Natural Science Foundation of Chongqing Technology and Business University (No. 1952009)the Science and Technology Research Program of Chongqing Education Commission (Nos. KJQN201900826 and KJQN201800808)the Venture & Innovation Support Program for Chongqing Overseas Returnees (Nos. CX2021046 and CX2018129)the Innovation Group of New Technologies for Industrial Pollution Control of Chongqing Education Commission (No. CXQT19023)。
文摘Defect-rich,highly porous two-dimensional carbon nanosheets(CNS) have attracted tremendous research interests in catalysis and environmental purification and other fields,because of their unique micromorphology,chemical stability and high specific surface area.Herein,in this work,we report a new solution to synthesize an ultrathin two-dimensional CNS with rich defects and abundant pores via two-step etching the Ti_(3)AlC_(2)with the help of I2and NaOH.The CNS thickness,specific surface area and pore volume could be all tunable by adding the amount of I2.And the highest specific surface area and pore volume of the synthesized 2D CNS can be achieved 1134.4 m^(2)/g and 0.80 cm^(3)/g,with a thickness of only 0.64 nm and a yield of 35.9%.When employed as the anodes for lithium-ion batteries,the synthesized CNS anodes exhibit good cycling and rate capabilities.This work provides a novel and facile strategy for synthesizing highly porous and defective 2D carbon materials with good lithium storage properties.
基金supported by the National Natural Science Foundation of China (Grant No. 42073069)。
文摘Coal samples taken from the Taiyuan Formation in the Hequ area, China, for this study are typical cutinite-rich coals.The petrology and geochemistry of the samples were analyzed using microscopic examination, proximate and ultimate analysis,rock pyrolysis, and gas chromatography-mass spectrometry(GC-MS). The cutinites in Haochuan(HC) coals are predominantly of the thin-walled type, whereas those in the Jingzigou(JZG) coals are predominantly thick-walled. The variable thickness of cutinites in different coals is related to the environment in which the coal-forming plants grew. Compared with typical Ⅲ kerogens, HC and JZG bituminous coals are characterized by high volatile matter yields and hydrogen contents due to the elevated hydrogen-rich cutinite content. Pyrolysis data indicate that these cutinite-rich coals can be expected to generate commercial liquid and gaseous hydrocarbons. Pristane(Pr) and phytane(Ph) are both abundant in the samples, with the Pr/Ph ratios for both the HC and JZG coals being >3.0, indicating moderate maturity and oxic peat depositional conditions. The C>>C>Cnormalized relative abundance of regular steranes is consistent with a dominant contribution from higher plants.Abundant hopanes in the coals also suggest a substantial organic matter input from bacteria, which are common inhabitants of peat and coal. Palynology studies indicate that pteridophytes are likely to be the most common coal-forming plants. A gymnosperm contribution is also indicated by the presence of tetracyclic diterpenes. Massive accumulations of cuticles as cutinite in coal are rare and account for only a small proportion of coals worldwide. However, cutinite-rich coals are found in the northern margin of the North China Craton, in the Taiyuan Formation. The accumulation of cutinite in this area is the result of distinctive peat deposition conditions. Frequent marine transgression was an important contributing factor.
