Reduction of graphene oxide （GO） is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of ...Reduction of graphene oxide （GO） is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders the development of practical applications. Here, we present a strategy for real-time repair of the newborn vacancies with carbon radicals produced by thermal decomposition of a suitable precursor. The sheet conductivity of thus-obtained single-layer graphene was raised more than six-fold to 350-410 S/cm （whilst retaining 〉96% transparency）. X-ray photoelectron spectroscopy （XPS） and Raman spectroscopy revealed that the conductivity enhancement can be attributed to the formation of additional sp2-C structures. This method provides a simple and efficient process for obtaining highly conductive transparent graphene films.展开更多
When two-dimensional graphene is exfoliated from three-dimensional highly oriented pyrolytic graphite （HOPG）, ripples or corrugations always exist due to the intrinsic thermal fluctuations. Surface-grown graphenes a...When two-dimensional graphene is exfoliated from three-dimensional highly oriented pyrolytic graphite （HOPG）, ripples or corrugations always exist due to the intrinsic thermal fluctuations. Surface-grown graphenes also exhibit wrinkles, which are larger in dimension and are thought to be caused by the difference in thermal expansion coefficients between graphene and the underlying substrate in the cooling process after high temperature growth. For further characterization and applications, it is necessary to transfer the surface-grown graphenes onto dielectric substrates, and other wrinkles are generated during this process. Here, we focus on the wrinkles of transferred graphene and demonstrate that the surface morphology of the growth substrate is the origin of the new wrinkles which arise in the surface-to-surface transfer process; we call these morphology- induced wrinkles. Based on a careful statistical analysis of thousands of atomic force microscopy （AFM） topographic data, we have concluded that these wrinkles on transferred few-layer graphene （typically 1-3 layers） are determined by both the growth substrate morphology and the transfer process. Depending on the transfer medium and conditions, most of the wrinkles can be either released or preserved. Our work suggests a new route for graphene engineering involving structuring the growth substrate and tailoring the transfer process.展开更多
Inspired by nature,a superhydrophobic and magnetic melamine sponge(BFSM-MF)was fabricated by a one-step dip-coating method.Aiming at replacing nano-Fe_(3)O_(4) particles with a complex preparation process and high cos...Inspired by nature,a superhydrophobic and magnetic melamine sponge(BFSM-MF)was fabricated by a one-step dip-coating method.Aiming at replacing nano-Fe_(3)O_(4) particles with a complex preparation process and high cost,the commercial and cheap Fe_(3)O_(4) originated from magnetite was employed as a magnetic substance.To acquire superhydrophobicity,the hierarchical mirco/nano-sized structure with low surface energy was mainly contributed by bonding hydrophobic Fe_(3)O_(4) and graphene with silicone resin onto the surface of the melamine sponge.The results demonstrated that the water and oil static contact angle values of BFSM-MF were 160°and 0°,revealing that BFSM-MF was superhydrophobic and super-oleophilic.Moreover,the self-cleaning ability,magnetic-driven oil absorption ability and continuous oil–water separation performance of BFSM-MF have also been evaluated.As expected,BFSM-MF possessed magnetic-driven oil absorption ability and the oil–water separation efficiency for light oil reaches 98%±1%.In addition,the adsorption capacity and recycling performance of diff erent organic solvents were systematically investigated.Therefore,the development of biomimetic,fluorine-free and superhydrophobic foam with magnetic-driven eff ect has potential application value in marine oil spill treatment and separation of domestic oil pollution.展开更多
Crash occurrence is a complex phenomenon,and crashes associated with pedestrians and bicyclists are even more complex.Furthermore,pedestrian-and bicyclist-involved crashes are typically not reported in detail in state...Crash occurrence is a complex phenomenon,and crashes associated with pedestrians and bicyclists are even more complex.Furthermore,pedestrian-and bicyclist-involved crashes are typically not reported in detail in state or national crash databases.To address this issue,developers created the Pedestrian and Bicycle Crash Analysis Tool(PBCAT).However,it is labour-intensive to manually identify the types of pedestrian and bicycle crash from crash-narrative reports and to classify different crash attributes from the textual content of police reports.Therefore,there is a need for a supporting tool that can assist practitioners in using PBCAT more efficiently and accurately.The objective of this study is to develop a framework for applying machine-learning models to classify crash types from unstructured textual content.In this study,the research team collected pedestrian crash-typing data from two locations in Texas.The XGBoost model was found to be the best classifier.The high prediction power of the XGBoost classifiers indicates that this machine-learning technique was able to classify pedestrian crash types with the highest accuracy rate(up to 77%for training data and 72%for test data).The findings demonstrate that advanced machine-learning models can extract underlying patterns and trends of crash mechanisms.This provides the basis for applying machine-learning techniques in addressing the crash typing issues associated with non-motorist crashes.展开更多
基金This work was supported by the National Natural Science Foundation of China （Grants Nos. 50802003, 20973013, 51072004, 50821061, and 20973006） and Ministry of Science and Technology of the people＇s Republic of China （Grants Nos. 2007CB936203, 2006CBP32602, and 2009CB929403）.
文摘Reduction of graphene oxide （GO） is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders the development of practical applications. Here, we present a strategy for real-time repair of the newborn vacancies with carbon radicals produced by thermal decomposition of a suitable precursor. The sheet conductivity of thus-obtained single-layer graphene was raised more than six-fold to 350-410 S/cm （whilst retaining 〉96% transparency）. X-ray photoelectron spectroscopy （XPS） and Raman spectroscopy revealed that the conductivity enhancement can be attributed to the formation of additional sp2-C structures. This method provides a simple and efficient process for obtaining highly conductive transparent graphene films.
基金The research was supported by the Natural Science Foundation of China （Grants Nos. 51072004, 50802003, 20973013, and 50821061） and the Ministry of Science and Technology of China （Grants Nos. 2007CB936203, 2009CB29403, 2011CB933003, and 2011CB921903）.
文摘When two-dimensional graphene is exfoliated from three-dimensional highly oriented pyrolytic graphite （HOPG）, ripples or corrugations always exist due to the intrinsic thermal fluctuations. Surface-grown graphenes also exhibit wrinkles, which are larger in dimension and are thought to be caused by the difference in thermal expansion coefficients between graphene and the underlying substrate in the cooling process after high temperature growth. For further characterization and applications, it is necessary to transfer the surface-grown graphenes onto dielectric substrates, and other wrinkles are generated during this process. Here, we focus on the wrinkles of transferred graphene and demonstrate that the surface morphology of the growth substrate is the origin of the new wrinkles which arise in the surface-to-surface transfer process; we call these morphology- induced wrinkles. Based on a careful statistical analysis of thousands of atomic force microscopy （AFM） topographic data, we have concluded that these wrinkles on transferred few-layer graphene （typically 1-3 layers） are determined by both the growth substrate morphology and the transfer process. Depending on the transfer medium and conditions, most of the wrinkles can be either released or preserved. Our work suggests a new route for graphene engineering involving structuring the growth substrate and tailoring the transfer process.
基金supported by the National Natural Science Foundation of China(Grant No.52005050)Foundation of State Key Laboratory of Automotive Simulation and Control(Grant No.20201105).
文摘Inspired by nature,a superhydrophobic and magnetic melamine sponge(BFSM-MF)was fabricated by a one-step dip-coating method.Aiming at replacing nano-Fe_(3)O_(4) particles with a complex preparation process and high cost,the commercial and cheap Fe_(3)O_(4) originated from magnetite was employed as a magnetic substance.To acquire superhydrophobicity,the hierarchical mirco/nano-sized structure with low surface energy was mainly contributed by bonding hydrophobic Fe_(3)O_(4) and graphene with silicone resin onto the surface of the melamine sponge.The results demonstrated that the water and oil static contact angle values of BFSM-MF were 160°and 0°,revealing that BFSM-MF was superhydrophobic and super-oleophilic.Moreover,the self-cleaning ability,magnetic-driven oil absorption ability and continuous oil–water separation performance of BFSM-MF have also been evaluated.As expected,BFSM-MF possessed magnetic-driven oil absorption ability and the oil–water separation efficiency for light oil reaches 98%±1%.In addition,the adsorption capacity and recycling performance of diff erent organic solvents were systematically investigated.Therefore,the development of biomimetic,fluorine-free and superhydrophobic foam with magnetic-driven eff ect has potential application value in marine oil spill treatment and separation of domestic oil pollution.
文摘Crash occurrence is a complex phenomenon,and crashes associated with pedestrians and bicyclists are even more complex.Furthermore,pedestrian-and bicyclist-involved crashes are typically not reported in detail in state or national crash databases.To address this issue,developers created the Pedestrian and Bicycle Crash Analysis Tool(PBCAT).However,it is labour-intensive to manually identify the types of pedestrian and bicycle crash from crash-narrative reports and to classify different crash attributes from the textual content of police reports.Therefore,there is a need for a supporting tool that can assist practitioners in using PBCAT more efficiently and accurately.The objective of this study is to develop a framework for applying machine-learning models to classify crash types from unstructured textual content.In this study,the research team collected pedestrian crash-typing data from two locations in Texas.The XGBoost model was found to be the best classifier.The high prediction power of the XGBoost classifiers indicates that this machine-learning technique was able to classify pedestrian crash types with the highest accuracy rate(up to 77%for training data and 72%for test data).The findings demonstrate that advanced machine-learning models can extract underlying patterns and trends of crash mechanisms.This provides the basis for applying machine-learning techniques in addressing the crash typing issues associated with non-motorist crashes.
