Direct strain mapping from high resolution transmission electron microscopy images is possible for coherent structures. At proper imaging conditions the intensity peaks in the image have a constant spatial relationshi...Direct strain mapping from high resolution transmission electron microscopy images is possible for coherent structures. At proper imaging conditions the intensity peaks in the image have a constant spatial relationship with the projected atom columns. This allows the determination of the geometry of the projected unit cell without comparison with image simulations. The fast procedure is particularly suited for the analysis of large areas. The software package LADIA is written in the PV-WAVE code and provides all necessary tools for image processing and analysis. Image intensity peaks are determined by a cross-correlation technique, which avoids problems from noise in the low spatial frequency range. The lower limit of strain that can be detected at a sampling rate of 44 pixels/nm is≈2%.展开更多
High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important t...High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.展开更多
Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM)....Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM). As-deposited films were observed to be a mixed structure of a few ultrafine epsilon-Fe2-3N particles existing in the amorphous matrix. it was found that the structure-relaxation in the amorphous occurred at 473 K, and the ultrafine grains began to grow at the higher annealing temperatures. The transition of the amorphous to epsilon-Fe2-3N was almost completed at 673 K. It is considered that the formation of the ideal epsilon-Fe3N is originated from the ordering of the nitrogen atoms during the annealing in vacuum. On the other hand, gamma'-phase (Fe4N) was seen to precipitation of epsilon-phase at 723 K. Two possible modes are proposed in the precipitation of gamma'-phase, depending on the heating rate and crystallographic orientation relationships, i.e. [121](epsilon)//[001](gamma), (2(1) over bar0$)(epsilon)//(110)(gamma) and [100](epsilon)//[110](gamma), (001)(epsilon)//(111)(gamma). In addition, alpha-Fe particles were observed to form from the gamma'-phase at high temperatures. We assumed that these structural changes are due to the diffusion of nitrogen and iron atoms during the annealing, except for the case of the precipitation of the gamma'-phase as depicted above. The results obtained in this work are in a good agreement with the assumption.展开更多
Stacking structure and defects in SiGe/P Si infrared detector were studied by using localization high resolution electron microscopy (HREM). The photosensitive region in the detector consists of 3 P + Si 0.65 Ge 0.35 ...Stacking structure and defects in SiGe/P Si infrared detector were studied by using localization high resolution electron microscopy (HREM). The photosensitive region in the detector consists of 3 P + Si 0.65 Ge 0.35 layers and 2 UD Si (undoped Si) layers. The interface between Si 0.65 Ge 0.35 and UD Si is not sharp and has a transition zone with non uniform contrast. The misfit stress of interface is distributed gradiently along the normal direction of the interface. Therefore the crystal defects and serious lattice deformations on the interface have not been found. A defect area with a shape of inverted triangle exists in the edge of photosensitive region. The main types of the defects in the area are stacking faults and microtwins. The stacking faults are on (111), and the thickness of the most microtwins is less than 4 interplanar spacing and the twin plane is (111). The Si 0.65 Ge 0.35 and UD Si layers on amorphous SiO 2 layer consist of polycrystals grown by random nucleation, and are in wave.展开更多
The microstructures and defects of various aged Sm( Co, Fe,Cu,Ti)_7 alloys have been observed in several orientations by using high resolution electron microscopy.Experimental results indicate that the alloy is compo...The microstructures and defects of various aged Sm( Co, Fe,Cu,Ti)_7 alloys have been observed in several orientations by using high resolution electron microscopy.Experimental results indicate that the alloy is composed of Sm2(Co,Fe,Cu,Ti)_(17)(2:17) phase with a small amount of titanium and Sm(Co,Fe,Cu)5,(1:5) phase.The 2:17 phase is rich in iron and the 1.5 phase is rich in copper.At aging stages corresponding to the peak magnetic coercivity,the alloy has a cellular-like microstructure with fine cells of the 2:17 phase surrounded by thin boundaries of the 1:5 phase.The average size of the cells is about 33 nm.The orientation relationship of [0001]_(2:17)/[0001]1:5 and(1210)_(2:17)/(0110)_(1:5) has been found in this alloy.The high resolution images show coherence between 2:17 phase and 1:5 phase and very small mismatch in some phase boundaries.The cells of 2:17 phase are full of microtwins with twin plane perpendicular to caxis.The cells of 2:17 phase rapidly grow up,when the aging temperature rises and aging time prolongs.For the alloy aged at 850℃, the 2:17 phase and 1:5 phase transform from cellular-like into striplike microstructure,and a few of twin boundaries can be seen in the 2:17 phase.Besides the twin boundaries,antiphase boundaries are sometimes observed in the 2:17 phase of the alloy aged at 800℃,for 10 h.展开更多
The microstructures of the grain boundary phases in Fe-Ni-Co-Nb-Ti superalloy have been studied by high resolution electron microscopy (HREM).Besides the Laves phase,three other grain boundary phases have been found a...The microstructures of the grain boundary phases in Fe-Ni-Co-Nb-Ti superalloy have been studied by high resolution electron microscopy (HREM).Besides the Laves phase,three other grain boundary phases have been found and analyzed. The ε phase particles are needle-like with some stacking faults along the(0001) direction. The dominant phase at the grain boundaries is the orthorhombic phase that is also rod-like. High reselution image also confirms the existence of the triclinic phase at the grain boundaries that is irregular and scarce.展开更多
Revealing the underlying correlations between microscopic structures and the fundamental physicochemical properties is essential for designing better functional materials.Cryogenic electron microscopy(cryo-EM)techniqu...Revealing the underlying correlations between microscopic structures and the fundamental physicochemical properties is essential for designing better functional materials.Cryogenic electron microscopy(cryo-EM)techniques have emerged as an essential tool for obtaining high-resolution images of beam-sensitive materials and studying properties at low temperatures for materials science.In this perspective,we compare and present the similarities and differences in cryo-EM workflows for biomolecules and materials,and briefly enumerate several scenarios of cryo-EM applications in materials science.Finally,we point out the current challenges of cryo-EM and potential directions for its future development.This perspective aims to shed light on the application of cryo-EM in materials science and provide useful guidance.展开更多
文摘Direct strain mapping from high resolution transmission electron microscopy images is possible for coherent structures. At proper imaging conditions the intensity peaks in the image have a constant spatial relationship with the projected atom columns. This allows the determination of the geometry of the projected unit cell without comparison with image simulations. The fast procedure is particularly suited for the analysis of large areas. The software package LADIA is written in the PV-WAVE code and provides all necessary tools for image processing and analysis. Image intensity peaks are determined by a cross-correlation technique, which avoids problems from noise in the low spatial frequency range. The lower limit of strain that can be detected at a sampling rate of 44 pixels/nm is≈2%.
基金Supported by Startup Fund for Youngman Research at SJTU(SFYR at SJTU)National Basic Research Program of China(Grant No.2011CB012904)China Postdoctoral Science Foundation(Grant No.2013M541517)
文摘High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.
文摘Iron-nitride films were prepared by reactive sputtering, and the effect of annealing treatment on the structures was investigated by means of in-situ electron microscopy and high resolution electron microscopy (HREM). As-deposited films were observed to be a mixed structure of a few ultrafine epsilon-Fe2-3N particles existing in the amorphous matrix. it was found that the structure-relaxation in the amorphous occurred at 473 K, and the ultrafine grains began to grow at the higher annealing temperatures. The transition of the amorphous to epsilon-Fe2-3N was almost completed at 673 K. It is considered that the formation of the ideal epsilon-Fe3N is originated from the ordering of the nitrogen atoms during the annealing in vacuum. On the other hand, gamma'-phase (Fe4N) was seen to precipitation of epsilon-phase at 723 K. Two possible modes are proposed in the precipitation of gamma'-phase, depending on the heating rate and crystallographic orientation relationships, i.e. [121](epsilon)//[001](gamma), (2(1) over bar0$)(epsilon)//(110)(gamma) and [100](epsilon)//[110](gamma), (001)(epsilon)//(111)(gamma). In addition, alpha-Fe particles were observed to form from the gamma'-phase at high temperatures. We assumed that these structural changes are due to the diffusion of nitrogen and iron atoms during the annealing, except for the case of the precipitation of the gamma'-phase as depicted above. The results obtained in this work are in a good agreement with the assumption.
文摘Stacking structure and defects in SiGe/P Si infrared detector were studied by using localization high resolution electron microscopy (HREM). The photosensitive region in the detector consists of 3 P + Si 0.65 Ge 0.35 layers and 2 UD Si (undoped Si) layers. The interface between Si 0.65 Ge 0.35 and UD Si is not sharp and has a transition zone with non uniform contrast. The misfit stress of interface is distributed gradiently along the normal direction of the interface. Therefore the crystal defects and serious lattice deformations on the interface have not been found. A defect area with a shape of inverted triangle exists in the edge of photosensitive region. The main types of the defects in the area are stacking faults and microtwins. The stacking faults are on (111), and the thickness of the most microtwins is less than 4 interplanar spacing and the twin plane is (111). The Si 0.65 Ge 0.35 and UD Si layers on amorphous SiO 2 layer consist of polycrystals grown by random nucleation, and are in wave.
基金sponsored by the National Basic Research Program of China(973 Program)under grant no.2015CB351905the National Natural Science Foundation of China(no.61504019)+3 种基金China Postdoctoral Science Foundation(no.2015M580783)Scientific Research Start-up Foundation of University of Electronic Science and Technology of China(Y02002010301082)the Technology Innovative Research Team of Sichuan Province of China(no.2015TD0005)the Fundamental Research Funds for the Central Universities of China(no.ZYGX2015J140)
文摘The microstructures and defects of various aged Sm( Co, Fe,Cu,Ti)_7 alloys have been observed in several orientations by using high resolution electron microscopy.Experimental results indicate that the alloy is composed of Sm2(Co,Fe,Cu,Ti)_(17)(2:17) phase with a small amount of titanium and Sm(Co,Fe,Cu)5,(1:5) phase.The 2:17 phase is rich in iron and the 1.5 phase is rich in copper.At aging stages corresponding to the peak magnetic coercivity,the alloy has a cellular-like microstructure with fine cells of the 2:17 phase surrounded by thin boundaries of the 1:5 phase.The average size of the cells is about 33 nm.The orientation relationship of [0001]_(2:17)/[0001]1:5 and(1210)_(2:17)/(0110)_(1:5) has been found in this alloy.The high resolution images show coherence between 2:17 phase and 1:5 phase and very small mismatch in some phase boundaries.The cells of 2:17 phase are full of microtwins with twin plane perpendicular to caxis.The cells of 2:17 phase rapidly grow up,when the aging temperature rises and aging time prolongs.For the alloy aged at 850℃, the 2:17 phase and 1:5 phase transform from cellular-like into striplike microstructure,and a few of twin boundaries can be seen in the 2:17 phase.Besides the twin boundaries,antiphase boundaries are sometimes observed in the 2:17 phase of the alloy aged at 800℃,for 10 h.
文摘The microstructures of the grain boundary phases in Fe-Ni-Co-Nb-Ti superalloy have been studied by high resolution electron microscopy (HREM).Besides the Laves phase,three other grain boundary phases have been found and analyzed. The ε phase particles are needle-like with some stacking faults along the(0001) direction. The dominant phase at the grain boundaries is the orthorhombic phase that is also rod-like. High reselution image also confirms the existence of the triclinic phase at the grain boundaries that is irregular and scarce.
基金supported by the National Key Research and Development Program of China(grant no.2022YFB2502200)the National Natural Science Foundation of China(NSFC,grant nos.52172257 and 22005334)+2 种基金the Natural Science Foundation of Beijing,China(grant no.Z200013),the China Postdoctoral Science Foundation(grant no.2023M743739)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(CPSF,grant no.GZC20232939)the Chinese Academy of Sciences Youth Interdisciplinary Team.
文摘Revealing the underlying correlations between microscopic structures and the fundamental physicochemical properties is essential for designing better functional materials.Cryogenic electron microscopy(cryo-EM)techniques have emerged as an essential tool for obtaining high-resolution images of beam-sensitive materials and studying properties at low temperatures for materials science.In this perspective,we compare and present the similarities and differences in cryo-EM workflows for biomolecules and materials,and briefly enumerate several scenarios of cryo-EM applications in materials science.Finally,we point out the current challenges of cryo-EM and potential directions for its future development.This perspective aims to shed light on the application of cryo-EM in materials science and provide useful guidance.
