This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current dens...This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm^2 has been obtained for diodes with AlAs barriers of ten monolayers, and an Ino.53Ga0.47As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.展开更多
Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs fur...Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.展开更多
The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E ...The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E 1050-12.The Creality Ender-3,a 3D printer,was used for printing the honeycomb structures,and polylactic acid(PLA)material was employed for their construction.The organic,inorganic,and polymeric compounds within the composites were identified using fourier transformation infrared(FTIR)spectroscopy.The structure and homogeneity of the samples were examined using a field emission scanning electron microscope(FESEM).To determine the sound absorption coefficient of the 3D printed honeycomb structure,numerous samples were systematically developed using central composite design(CCD)and analysed using response surface methodology(RSM).The RSM mathematical model was established to predict the optimum values of each factor and noise reduction coefficient(NRC).The optimum values for an NRC of 0.377 were found to be 1.116 wt% carbon black,1.025 wt% aluminium powder,and 3.151 mm distance between parallel edges.Overall,the results demonstrate that a 3Dprinted honeycomb structure filled with nanofillers is an excellent material that can be utilized in various fields,including defence and aviation,where lightweight and acoustic properties are of great importance.展开更多
Steve Pennycook is a pioneer in the application of high-resolution scanning transmission electron microscopy(STEM)and in particular the use of annular dark-field(ADF)imaging.Here we show how a general framework for 4D...Steve Pennycook is a pioneer in the application of high-resolution scanning transmission electron microscopy(STEM)and in particular the use of annular dark-field(ADF)imaging.Here we show how a general framework for 4D STEM allows clear links to be made between ADF imaging and the emerging methods for reconstructing images from 4D STEM data sets.We show that both ADF imaging and ptychographical reconstruction can be thought of in terms of integrating over the overlap regions of diffracted discs in the detector plane.This approach allows the similarities in parts of their transfer functions to be understood,though we note that the transfer functions for ptychographic imaging cannot be used as a measure of information transfer.We also show that conditions of partial spatial and temporal coherence affect ADF imaging and ptychography similarly,showing that achromatic interference can always contribute to the image in both cases,leading to a robustness to partial temporal coherence that has enabled high-resolution imaging.展开更多
The mechanism of the shear band formation in the high cold rolled BCC metal is analyzed. Based on the plastic deformation theory, the shear distribution in the deformed grain is calculated by using the Taylor constrai...The mechanism of the shear band formation in the high cold rolled BCC metal is analyzed. Based on the plastic deformation theory, the shear distribution in the deformed grain is calculated by using the Taylor constraint model and the Bishop ＆ Hill maximum work principle. Results show that when the rolling direction （RD） is parallel to a certain direction of a grain, the large localized shear occurs on one slip plane, thus generating microbands in the grain because of the high localized shear strain. The angle between the RD and the shear band is about 30°. The plate-like structure of the microband is formed because of the dislocation double cross slip. The transmission electron microscope （TEM） observation of the microband in the cold rolled BCC metal confirms the formation mechanism of the microband.展开更多
The present study deals with the rapid green synthesis of silver nanoparticles using fresh leaves of Cymbopogan Citratus(Lemongrass). Silver nanoparticles were formed within 8～10 minutes by microwave irradiation usin...The present study deals with the rapid green synthesis of silver nanoparticles using fresh leaves of Cymbopogan Citratus(Lemongrass). Silver nanoparticles were formed within 8～10 minutes by microwave irradiation using aqueous solution of Ag NO3(1 m M) with fresh leaves extract of Cymbopogan Citratus. The synthesized silver nanoparticles were characterized by using UV-visible spectrophotometer analysis, nanoparticle tracking analyzer, transmission electron microscope and energy dispersive X-ray spectra. The antibacterial activity of these nanoparticles was studied against multiple drug resistant hospital isolates of E.coli, S.aureus,P.mirabilis and hospital isolates of S. typhi, K.pnuemoniae. Also, the antifungal activity of these nanoparticles was studied against C.albicans(hospital isolate) and A.niger(NCIM 616). The synergistic effect of silver nanoparticles along with antibiotics was also studied against multiple drug resistant hospital isolates and found to be effective. The extracellular synthesis of Silver nanoparticles using leaves of Cymbopogan Citratus appears to be rapid and eco-friendly.展开更多
In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosi...In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.展开更多
The secondary electron emission yields of materials depend on the geometries of their surface structures.In this paper,a method of depositing vertical graphene nanosheet(VGN)on the surface of the material is proposed,...The secondary electron emission yields of materials depend on the geometries of their surface structures.In this paper,a method of depositing vertical graphene nanosheet(VGN)on the surface of the material is proposed,and the secondary electron emission(SEE)characteristics for the VGN structure are studied.The COMSOL simulation and the scanning electron microscope(SEM)image analysis are carried out to study the secondary electron yield(SEY).The effect of aspect ratio and packing density of VGN on SEY under normal incident condition are studied.The results show that the VGN structure has a good effect on suppressing SEE.展开更多
Polyhydroxyalkanoates（PHAs）were synthesized in activated sludge using three types of carbon sources（sodium acetate,sodium propionate and sodium butyrate）,and their characterization were studied.It was shown that t...Polyhydroxyalkanoates（PHAs）were synthesized in activated sludge using three types of carbon sources（sodium acetate,sodium propionate and sodium butyrate）,and their characterization were studied.It was shown that the content of PHA synthesized by microorganisms in activated sludge were different.The biggest synthetic amount up to 36.7% of VSS was obtained when sodium acetate was used as carbon source.The polymer yield was lower when using sodium propionate as the carbon source than when using others,with25.1% of VSS,while resulted in an increase of hydroxyvalerate（HV）units produced.The structure and thermal properties of extracted biopolymers were analyzed by scanning electron microscope（SEM）,Fourier transform infrared spectroscopy（FTIR）and themogravimetry（TG）.展开更多
An investigation on the discharge characteristic of a dielectric barrier discharge （DBD） device was carried out using bare and ZnO-coated alumina dielectric layer in atmospheric pressure air. Highly conductive ZnO f...An investigation on the discharge characteristic of a dielectric barrier discharge （DBD） device was carried out using bare and ZnO-coated alumina dielectric layer in atmospheric pressure air. Highly conductive ZnO film was first deposited on the alumina surface, and the characteristics of the dielectric barrier discharge were examined and compared. Experimental result shows that discharge behavior was definitely improved in the case of ZnO-coated dielectric barrier discharge. Relevant explanation is offered to describe its discharge physics.展开更多
Fe-Cr ferritic/martensitic(F/M)steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies.In this study,a widely-used ferritic/martensitic steel,T91 steel,was irradiated by ...Fe-Cr ferritic/martensitic(F/M)steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies.In this study,a widely-used ferritic/martensitic steel,T91 steel,was irradiated by 196-MeV Kr^(+)ions at 550℃.To reveal the irradiation mechanism,the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope(TEM).With increasing dose,the defects gradually changed from black dots to dislocation loops,and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations.When many dislocation loops of primary a0/2<111>type with high migration interacted with other defects or carbon atoms,it led to the production of dislocation segments and other dislocation loops of a0<100>type.Lots of defects accumulated near grain boundaries in the irradiated area,especially in the high-dose area.The grain boundaries of martensite laths acted as important sinks of irradiation defects in T91.Elevated temperature facilitated the migration of defects,leading to the accumulation of defects near the grain boundaries of martensite laths.展开更多
Recent advances in the ultrafast transmission electron microscope （UTEM）, with combined spatial and temporal resolutions, have made it possible to directly visualize the atomic, electronic, and magnetic structural d...Recent advances in the ultrafast transmission electron microscope （UTEM）, with combined spatial and temporal resolutions, have made it possible to directly visualize the atomic, electronic, and magnetic structural dynamics of materials. In this review, we highlight the recent progress of UTEM techniques and their applications to a variety of material systems. It is emphasized that numerous significant ultrafast dynamic issues in material science can be solved by the integration of the pump-probe approach with the well-developed conventional transmission electron microscopy （TEM） techniques. For instance, UTEM diffraction experiments can be performed to investigate photoinduced atomic-scale dynamics, including the chemical reactions, non-equilibrium phase transition/melting, and lattice phonon coupling. UTEM imaging methods are invaluable for studying, in real space, the elementary processes of structural and morphological changes, as well as magnetic-domain evolution in the Lorentz TEM mode, at a high magnification. UTEM electron energy-loss spectroscopic techniques allow the examination of the ultrafast valence states and electronic structure dynamics, while photoinduced near-field electron microscopy extends the capability of the UTEM to the regime of electromagnetic-field imaging with a high real space resolution.展开更多
The early risk of internal contaminated accumulation of 147Pm is in blood cells and endothelial cells, especially in red blood cells. Then 147Pm is selectively deposited in ultrastructure of liver cells, such as in nu...The early risk of internal contaminated accumulation of 147Pm is in blood cells and endothelial cells, especially in red blood cells. Then 147Pm is selectively deposited in ultrastructure of liver cells, such as in nucleus, nucleolus, rough endoplasmic reticulum, mitochondria and microbodies. Dense tracks also appear in mitochondria and lysosome of pedal cells within renal corpuscle, and so does in nucleus as well as in mitochondria and microbodies of epicyte of kidney near-convoluted tubule. With the prolongation of observing time, 147Pm is selectively and steadily deposited in subcellular level of organic component for bone. Substantial amount of 147Pm is taken up into the nuclear fraction of osteoclasts and osteoblasts. Particularly, in organelles 147Pm is mainly accumulated in rough endoplasmic reticulum and in mitochondria.Autoradiographic tracks especially localize in combined point between Golgi complex and transitive vesicle of rough endoplasmic reticulum. In addition, numerous 147Pm deposited in collagenous fibre within interstitial of bone cells is hardly excreted.展开更多
Sr0.6 Ba0.4 Nb2 O6 micro-rods are prepared by the molten-salt method with K2 SO4,KCl-K2 SO4,and KCl as fluxes.It reveals that the Sr0.6 Ba0.4 Nb2 O6 synthesized with KCl as a flux exhibits a single phase with tetragon...Sr0.6 Ba0.4 Nb2 O6 micro-rods are prepared by the molten-salt method with K2 SO4,KCl-K2 SO4,and KCl as fluxes.It reveals that the Sr0.6 Ba0.4 Nb2 O6 synthesized with KCl as a flux exhibits a single phase with tetragonal tungsten bronze structure.The measurement of X-ray diffraction indicates that the Sr0.6 Ba0.4 Nb2 O6 micro-rods synthesized at 1 300℃are anisotropic.The morphology of the powers is examined by transmission electron microscope.It reveals that the length-diameter ratio of Sr0.6 Ba0.4 Nb2 O6 micro-rods increases with increasing annealing temperature from 900℃to 1 300℃.At 1 300℃,the rod possesses a large length-diameter ratio of 8∶1.Moreover,the analysis of the piezoelectric properties of single micro-rods using apiezo-response force microscope indicates that the domains of the material are arranged along its radial direction.展开更多
The TiO2-Mn-TiO2multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the mag...The TiO2-Mn-TiO2multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the magnetic behaviours of these films are characterised with x-ray diffraction, transmission electron microscope （TEM）, vibrating sample magnetometer, and superconducting quantum interference device （SQUID）. It is shown that the multi-film consists of a mixture of anatase and rutile TiO2 with an embedded Mn nano-film. It is found that there are two turning points from ferromagnetic phase to antiferromagnetic phase. One is at 42 K attributed to interface coupling between ferromagnetic Mn3O4 and antiferromagnetic Mn2O3, and the other is at 97 K owing to the interface coupling between ferromagnetic Mn and antiferromagnetic MnO. The samples are shown to have ferromagnetic behaviours at room temperature from hysteresis in the M-H loops, and their ferromagnetism is found to vary with the thickness of Mn nano-film. Moreover, the Mn nano-film has a critical thickness of about 18.5 nm, which makes the coercivity of the multi-film reach a maximum of about 3.965 × 10^-2 T.展开更多
The Al–C–N films are deposited on Si substrates by using a dense plasma focus（DPF） device with aluminum fitted central electrode（anode） and by operating the device with CH_4/N_2 gas admixture ratio of 1：1. XRD ...The Al–C–N films are deposited on Si substrates by using a dense plasma focus（DPF） device with aluminum fitted central electrode（anode） and by operating the device with CH_4/N_2 gas admixture ratio of 1：1. XRD results verify the crystalline Al N（111） and Al_3CON（110） phase formation of the films deposited using multiple shots. The elemental compositions as well as chemical states of the deposited Al–C–N films are studied using XPS analysis, which affirm Al–N, C–C, and C–N bonding. The FESEM analysis reveals that the deposited films are composed of nanoparticles and nanoparticle agglomerates. The size of the agglomerates increases at a higher number of focus deposition shots for multiple shot depositions. Nanoindentation results reveal the variation in mechanical properties（nanohardness and elastic modulus）of Al–C–N films deposited with multiple shots. The highest values of nanohardness and elastic modulus are found to be about 11 and 185 GPa, respectively, for the film deposited with 30 focus deposition shots. The mechanical properties of the films deposited using multiple shots are related to the Al content and C–N bonding.展开更多
文摘This paper reports that InAs/In0.53Ga0.47As/AlAs resonant tunnelling diodes have been grown on InP substrates by molecular beam epitaxy. Peak to valley current ratio of these devices is 17 at 300K. A peak current density of 3kA/cm^2 has been obtained for diodes with AlAs barriers of ten monolayers, and an Ino.53Ga0.47As well of eight monolayers with four monolayers of InAs insert layer. The effects of growth interruption for smoothing potential barrier interfaces have been investigated by high resolution transmission electron microscope.
基金finically supported by the National Key Research and Development Program of China (Grant No. 2016YFB0100100)Strategic Priority Research Program of Chinese Academy of Sciences (CAS, Grant No. XDA09010101)Ningbo Key Science and Technology Projects "Industrial Application Development of Graphene" (Grant No. 2014S10008)
文摘Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.
文摘The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties,utilizing an impedance tube setup in accordance with ASTM standard E 1050-12.The Creality Ender-3,a 3D printer,was used for printing the honeycomb structures,and polylactic acid(PLA)material was employed for their construction.The organic,inorganic,and polymeric compounds within the composites were identified using fourier transformation infrared(FTIR)spectroscopy.The structure and homogeneity of the samples were examined using a field emission scanning electron microscope(FESEM).To determine the sound absorption coefficient of the 3D printed honeycomb structure,numerous samples were systematically developed using central composite design(CCD)and analysed using response surface methodology(RSM).The RSM mathematical model was established to predict the optimum values of each factor and noise reduction coefficient(NRC).The optimum values for an NRC of 0.377 were found to be 1.116 wt% carbon black,1.025 wt% aluminium powder,and 3.151 mm distance between parallel edges.Overall,the results demonstrate that a 3Dprinted honeycomb structure filled with nanofillers is an excellent material that can be utilized in various fields,including defence and aviation,where lightweight and acoustic properties are of great importance.
基金funding from the European Research Council(ERC)under the European Union’s Horizon 2020 Research and Innovation Programme via Grant Agreement No.802123-HDEM(TJP)from the UK Engineering and Physical Sciences Research Council(EPSRC)via grant EP/M010708/1(PDN).
文摘Steve Pennycook is a pioneer in the application of high-resolution scanning transmission electron microscopy(STEM)and in particular the use of annular dark-field(ADF)imaging.Here we show how a general framework for 4D STEM allows clear links to be made between ADF imaging and the emerging methods for reconstructing images from 4D STEM data sets.We show that both ADF imaging and ptychographical reconstruction can be thought of in terms of integrating over the overlap regions of diffracted discs in the detector plane.This approach allows the similarities in parts of their transfer functions to be understood,though we note that the transfer functions for ptychographic imaging cannot be used as a measure of information transfer.We also show that conditions of partial spatial and temporal coherence affect ADF imaging and ptychography similarly,showing that achromatic interference can always contribute to the image in both cases,leading to a robustness to partial temporal coherence that has enabled high-resolution imaging.
文摘The mechanism of the shear band formation in the high cold rolled BCC metal is analyzed. Based on the plastic deformation theory, the shear distribution in the deformed grain is calculated by using the Taylor constraint model and the Bishop ＆ Hill maximum work principle. Results show that when the rolling direction （RD） is parallel to a certain direction of a grain, the large localized shear occurs on one slip plane, thus generating microbands in the grain because of the high localized shear strain. The angle between the RD and the shear band is about 30°. The plate-like structure of the microband is formed because of the dislocation double cross slip. The transmission electron microscope （TEM） observation of the microband in the cold rolled BCC metal confirms the formation mechanism of the microband.
基金Pravara Institute of Medical Sciences,Loni,Ahmednagar(MS),India for the financial support
文摘The present study deals with the rapid green synthesis of silver nanoparticles using fresh leaves of Cymbopogan Citratus(Lemongrass). Silver nanoparticles were formed within 8～10 minutes by microwave irradiation using aqueous solution of Ag NO3(1 m M) with fresh leaves extract of Cymbopogan Citratus. The synthesized silver nanoparticles were characterized by using UV-visible spectrophotometer analysis, nanoparticle tracking analyzer, transmission electron microscope and energy dispersive X-ray spectra. The antibacterial activity of these nanoparticles was studied against multiple drug resistant hospital isolates of E.coli, S.aureus,P.mirabilis and hospital isolates of S. typhi, K.pnuemoniae. Also, the antifungal activity of these nanoparticles was studied against C.albicans(hospital isolate) and A.niger(NCIM 616). The synergistic effect of silver nanoparticles along with antibiotics was also studied against multiple drug resistant hospital isolates and found to be effective. The extracellular synthesis of Silver nanoparticles using leaves of Cymbopogan Citratus appears to be rapid and eco-friendly.
基金funded by the National Natural Science Foundation of China (Grant No.11972018)sponsored by the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry (Grant No. 6141B012858)。
文摘In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.
基金supported by the National Natural Science Foundation of China(Grant No.11975163)。
文摘The secondary electron emission yields of materials depend on the geometries of their surface structures.In this paper,a method of depositing vertical graphene nanosheet(VGN)on the surface of the material is proposed,and the secondary electron emission(SEE)characteristics for the VGN structure are studied.The COMSOL simulation and the scanning electron microscope(SEM)image analysis are carried out to study the secondary electron yield(SEY).The effect of aspect ratio and packing density of VGN on SEY under normal incident condition are studied.The results show that the VGN structure has a good effect on suppressing SEE.
基金Supported by the National Science&Technology Pillar Program During the 12th Five-Year Plan Period(2014BAC28B01)Beijing Natural Science Foundation(8112012)
文摘Polyhydroxyalkanoates（PHAs）were synthesized in activated sludge using three types of carbon sources（sodium acetate,sodium propionate and sodium butyrate）,and their characterization were studied.It was shown that the content of PHA synthesized by microorganisms in activated sludge were different.The biggest synthetic amount up to 36.7% of VSS was obtained when sodium acetate was used as carbon source.The polymer yield was lower when using sodium propionate as the carbon source than when using others,with25.1% of VSS,while resulted in an increase of hydroxyvalerate（HV）units produced.The structure and thermal properties of extracted biopolymers were analyzed by scanning electron microscope（SEM）,Fourier transform infrared spectroscopy（FTIR）and themogravimetry（TG）.
基金supported by Anhui Provincial Natural Science Foundation of China(No.11040606M27)
文摘An investigation on the discharge characteristic of a dielectric barrier discharge （DBD） device was carried out using bare and ZnO-coated alumina dielectric layer in atmospheric pressure air. Highly conductive ZnO film was first deposited on the alumina surface, and the characteristics of the dielectric barrier discharge were examined and compared. Experimental result shows that discharge behavior was definitely improved in the case of ZnO-coated dielectric barrier discharge. Relevant explanation is offered to describe its discharge physics.
基金Project supported by Guangdong Major Project of Basic and Applied Basic Research(Grant No.2019B030302011)the National Natural Science Foundation of China(Grant Nos.U2032143,11902370,and 52005523)+2 种基金the International Science and Technology Cooperation Program of Guangdong Province,China(Grant No.2019A050510022)the China Postdoctoral Science Foundation(Grant Nos.2019M653173 and 2019TQ0374)the Heavy Ion Research Facility of Lanzhou(HIRFL).
文摘Fe-Cr ferritic/martensitic(F/M)steels have been proposed as one of the candidate materials for the Generation IV nuclear technologies.In this study,a widely-used ferritic/martensitic steel,T91 steel,was irradiated by 196-MeV Kr^(+)ions at 550℃.To reveal the irradiation mechanism,the microstructure evolution of irradiated T91 steel was studied in details by transmission electron microscope(TEM).With increasing dose,the defects gradually changed from black dots to dislocation loops,and further to form dislocation walls near grain boundaries due to the production of a large number of dislocations.When many dislocation loops of primary a0/2<111>type with high migration interacted with other defects or carbon atoms,it led to the production of dislocation segments and other dislocation loops of a0<100>type.Lots of defects accumulated near grain boundaries in the irradiated area,especially in the high-dose area.The grain boundaries of martensite laths acted as important sinks of irradiation defects in T91.Elevated temperature facilitated the migration of defects,leading to the accumulation of defects near the grain boundaries of martensite laths.
基金Project supported by the National Basic Research Program of China(Grant No.2015CB921300)the National Key Research and Development Program of China(Grant Nos.2016YFA0300300,2017YFA0504703,and 2017YFA0302900)+3 种基金the National Natural Science Foundation of China(Grant Nos.11604372,11474323,and 11774391)the”Strategic Priority Research Program(B)”of the Chinese Academy of Sciences(Grant No.XDB07020000)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant No.ZDKYYQ20170002)the financial support of the Hundred Talent Program B from CAS
文摘Recent advances in the ultrafast transmission electron microscope （UTEM）, with combined spatial and temporal resolutions, have made it possible to directly visualize the atomic, electronic, and magnetic structural dynamics of materials. In this review, we highlight the recent progress of UTEM techniques and their applications to a variety of material systems. It is emphasized that numerous significant ultrafast dynamic issues in material science can be solved by the integration of the pump-probe approach with the well-developed conventional transmission electron microscopy （TEM） techniques. For instance, UTEM diffraction experiments can be performed to investigate photoinduced atomic-scale dynamics, including the chemical reactions, non-equilibrium phase transition/melting, and lattice phonon coupling. UTEM imaging methods are invaluable for studying, in real space, the elementary processes of structural and morphological changes, as well as magnetic-domain evolution in the Lorentz TEM mode, at a high magnification. UTEM electron energy-loss spectroscopic techniques allow the examination of the ultrafast valence states and electronic structure dynamics, while photoinduced near-field electron microscopy extends the capability of the UTEM to the regime of electromagnetic-field imaging with a high real space resolution.
文摘The early risk of internal contaminated accumulation of 147Pm is in blood cells and endothelial cells, especially in red blood cells. Then 147Pm is selectively deposited in ultrastructure of liver cells, such as in nucleus, nucleolus, rough endoplasmic reticulum, mitochondria and microbodies. Dense tracks also appear in mitochondria and lysosome of pedal cells within renal corpuscle, and so does in nucleus as well as in mitochondria and microbodies of epicyte of kidney near-convoluted tubule. With the prolongation of observing time, 147Pm is selectively and steadily deposited in subcellular level of organic component for bone. Substantial amount of 147Pm is taken up into the nuclear fraction of osteoclasts and osteoblasts. Particularly, in organelles 147Pm is mainly accumulated in rough endoplasmic reticulum and in mitochondria.Autoradiographic tracks especially localize in combined point between Golgi complex and transitive vesicle of rough endoplasmic reticulum. In addition, numerous 147Pm deposited in collagenous fibre within interstitial of bone cells is hardly excreted.
基金supported by the National Natural Science Foundation of China(No.11475086)
文摘Sr0.6 Ba0.4 Nb2 O6 micro-rods are prepared by the molten-salt method with K2 SO4,KCl-K2 SO4,and KCl as fluxes.It reveals that the Sr0.6 Ba0.4 Nb2 O6 synthesized with KCl as a flux exhibits a single phase with tetragonal tungsten bronze structure.The measurement of X-ray diffraction indicates that the Sr0.6 Ba0.4 Nb2 O6 micro-rods synthesized at 1 300℃are anisotropic.The morphology of the powers is examined by transmission electron microscope.It reveals that the length-diameter ratio of Sr0.6 Ba0.4 Nb2 O6 micro-rods increases with increasing annealing temperature from 900℃to 1 300℃.At 1 300℃,the rod possesses a large length-diameter ratio of 8∶1.Moreover,the analysis of the piezoelectric properties of single micro-rods using apiezo-response force microscope indicates that the domains of the material are arranged along its radial direction.
基金supported by the Innovation Foundation of Beijing University of Aeronautics and Astronautics for PhD Graduates,China(Grant No.292122)the Equipment Research Foundation of China (Grant No.373974)
文摘The TiO2-Mn-TiO2multilayers are successfully grown on glass and silicon substrates by alternately using radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and the magnetic behaviours of these films are characterised with x-ray diffraction, transmission electron microscope （TEM）, vibrating sample magnetometer, and superconducting quantum interference device （SQUID）. It is shown that the multi-film consists of a mixture of anatase and rutile TiO2 with an embedded Mn nano-film. It is found that there are two turning points from ferromagnetic phase to antiferromagnetic phase. One is at 42 K attributed to interface coupling between ferromagnetic Mn3O4 and antiferromagnetic Mn2O3, and the other is at 97 K owing to the interface coupling between ferromagnetic Mn and antiferromagnetic MnO. The samples are shown to have ferromagnetic behaviours at room temperature from hysteresis in the M-H loops, and their ferromagnetism is found to vary with the thickness of Mn nano-film. Moreover, the Mn nano-film has a critical thickness of about 18.5 nm, which makes the coercivity of the multi-film reach a maximum of about 3.965 × 10^-2 T.
文摘The Al–C–N films are deposited on Si substrates by using a dense plasma focus（DPF） device with aluminum fitted central electrode（anode） and by operating the device with CH_4/N_2 gas admixture ratio of 1：1. XRD results verify the crystalline Al N（111） and Al_3CON（110） phase formation of the films deposited using multiple shots. The elemental compositions as well as chemical states of the deposited Al–C–N films are studied using XPS analysis, which affirm Al–N, C–C, and C–N bonding. The FESEM analysis reveals that the deposited films are composed of nanoparticles and nanoparticle agglomerates. The size of the agglomerates increases at a higher number of focus deposition shots for multiple shot depositions. Nanoindentation results reveal the variation in mechanical properties（nanohardness and elastic modulus）of Al–C–N films deposited with multiple shots. The highest values of nanohardness and elastic modulus are found to be about 11 and 185 GPa, respectively, for the film deposited with 30 focus deposition shots. The mechanical properties of the films deposited using multiple shots are related to the Al content and C–N bonding.
