TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack...TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack propagation of a notched investment cast TiAl specimens in tension under incremental loading conditions. The whole process of crack initiation, propagation and failure during tensile deformation was observed and characterized. The results show that the fracture mechanism was sensitive to not only the microcracks near the notched area but also lamellar orientation to loading axis. The high tensile stress leads to the new microcracks nucleate along lamellar interfaces of grains with favorable orientation when local stress intensity reaches the toughness threshold of the material. Thus, both plasticity and high tensile stress are required to cause notched TiAl failure.展开更多
The observation on crack initiation and propagation of surface inclusion Al2O3 in seeded PM Rene95 was conducted by SEM in-situ tension test. The results show that the cracks often initiate at the inclusion/matrix int...The observation on crack initiation and propagation of surface inclusion Al2O3 in seeded PM Rene95 was conducted by SEM in-situ tension test. The results show that the cracks often initiate at the inclusion/matrix interface vertical to the applied stress direction, and easily propagate along the interface into the matrix. The interface of inclusion/matrix is just mechanically bounded on the base of SEM observation. The weak bonding of inclusion/matrix interface and stress concentration around inclusions are the main reasons of the matrix/inclusion interface debonding and local plastic deformation under the tensile loading in the in-situ tension test. Surface inclusion does not definitely lead to the failure of in-situ tension test. But the early surface crack initiation caused by ceramic inclusion is critically harmful to the LCF property of PM Rene95 superalloy, which can't be ignored.展开更多
The strengthening effect of a Zn alloy reinforced by SiC particulate was examined. Based on the results of SEM in-situ fracture observation and stress field analysis by finite element method, it is believed that the r...The strengthening effect of a Zn alloy reinforced by SiC particulate was examined. Based on the results of SEM in-situ fracture observation and stress field analysis by finite element method, it is believed that the reinforcing effect of this composite is due to the combination of strain and stress hardening in the matrix.展开更多
The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatme...The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatment had significant effect on the change curves of contact angle of Chinese fir wood due to the change curves of contact angle became more centralized and orderly after the specimens heat treated at 180 ℃. Compared with the untreated wood, the contact angle in-creased from 51＆#176; to 124＆#176; after 4 h treatment, and hydroxyl absorbance of hy-drophilic functional groups decreased from 2.08 to 1.63, while carbonyl absorbance from 0.92 to 0.62. The surface roughness has not significant influence on the con-tact angle. Heat treatment of the Chinese fir caused surface morphological change, which produced hol owed-out phenomenon. The increased surface contact angle caused by heat treatment can be used for outdoor and sauna facilities.展开更多
High density packaging is developing toward miniaturization and integration, which causes many difficulties in designing, manufacturing, and reliability testing. Package-on-Package （POP） is a promising three-dimensi...High density packaging is developing toward miniaturization and integration, which causes many difficulties in designing, manufacturing, and reliability testing. Package-on-Package （POP） is a promising three-dimensional high- density packaging method that integrates a chip scale package （CSP） in the top package and a fine-pitch ball grid array （FBGA） in the bottom package. In this paper, in-situ scanning electron microscopy （SEM） observation is carried out to detect the deformation and damage of the PoP structure under three-point bending loading. The results indicate that the cracks occur in the die of the top package, then cause the crack deflection and bridging in the die attaching layer. Furthermore, the mechanical principles are used to analyse the cracking process of the PoP structure based on the multi-layer laminating hypothesis and the theoretical analysis results are found to be in good agreement with the experimental results.展开更多
The hydrophobic aggregation of ultrafine kaolinite in cationic surfactant suspension was investigated by sedimentation test,zeta potential measurement and SEM observation. SEM images reveal that kaolinite particles sh...The hydrophobic aggregation of ultrafine kaolinite in cationic surfactant suspension was investigated by sedimentation test,zeta potential measurement and SEM observation. SEM images reveal that kaolinite particles show the self-aggregation of edge-face in acidic media,the aggregation of edge-face and edge-edge in neutral media,and the dispersion in alkaline media due to electrostatic repulsion. In the presence of the dodecylammonium acetate cationic surfactant and in neutral and alkaline suspension,the hydrophobic aggregation of face-face is demonstrated. The zeta potential of kaolinite increases with increasing the concentration of cationic surfactant. The small and loose aggregation at a low concentration but big and tight aggregation at a high concentration is presented. At pH=7 alkyl quarterly amine salt CTAB has the best hydrophobic aggregation among three cationic surfactants,namely,dodecylammonium acetate,alkyl quarterly amine salts 1227 and CTAB.展开更多
Leaf cuticle analysis has long been a powerful tool for fossil plant identification,systematics,and palaeoclimatological recon-struction.In recent decades the application of stomatal frequency data that are relied on ...Leaf cuticle analysis has long been a powerful tool for fossil plant identification,systematics,and palaeoclimatological recon-struction.In recent decades the application of stomatal frequency data that are relied on precise calculation of stomata on plant fossil cuticles to reconstruct ancient atmospheric CO_(2)concentration made the preparation of cuticular membrane with sufficient size a critical technique in palaeoclimatological research.However,for plants with originally thin and fragile cuticles,e.g.,most deciduous plants,conventional techniques sometimes fail to obtain cuticular membranes with sufficient size,or sometimes unable to recover any.This has largely hampered the usage of fossil cuticle analysis in palaeobotanical and palaeo-climatological research.Here,we describe a new method using clear nail polish as a medium to"strengthen"the originally thin and fragile cuticles prior to maceration procedures.We demonstrate the method by using middle Eocene Metasequoia fossils that were notorious for the difficulty of recovering large-sized clean cuticular membranes due to their thin and fragile nature.Metasequoia,with well-documented and widely-distributed fossil records since the Late Cretaceous and with a living repre-sentative,114.glyptostroboides,as a comparative reference,bas been widely used as a model genus for the study of evolution of plants,palaeoclimatological reconstruction,and plant adaptation to climate changes.But its deciduous habit produces thin cuticles and makes the preparation of clean cuticular membranes a tedious process.The new method successfully allows us to recover its delicate cuticular membranes with sufficient sizes for SEM observation and stomatal frequency analysis.展开更多
基金Project(51001040)supported by the National Natural Science Foundation of ChinaProject(200802130014)supported by Specialized Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(HIT.NSRIF.2010116)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(HITQNJS 2009022)supported by Development Program for Outstanding Young Teachers in Harbin Institute of Technology
文摘TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack propagation of a notched investment cast TiAl specimens in tension under incremental loading conditions. The whole process of crack initiation, propagation and failure during tensile deformation was observed and characterized. The results show that the fracture mechanism was sensitive to not only the microcracks near the notched area but also lamellar orientation to loading axis. The high tensile stress leads to the new microcracks nucleate along lamellar interfaces of grains with favorable orientation when local stress intensity reaches the toughness threshold of the material. Thus, both plasticity and high tensile stress are required to cause notched TiAl failure.
基金This work was financially supported by the National Nature Science Foundation of China (No.59871007)PM Rene95 materialofferi
文摘The observation on crack initiation and propagation of surface inclusion Al2O3 in seeded PM Rene95 was conducted by SEM in-situ tension test. The results show that the cracks often initiate at the inclusion/matrix interface vertical to the applied stress direction, and easily propagate along the interface into the matrix. The interface of inclusion/matrix is just mechanically bounded on the base of SEM observation. The weak bonding of inclusion/matrix interface and stress concentration around inclusions are the main reasons of the matrix/inclusion interface debonding and local plastic deformation under the tensile loading in the in-situ tension test. Surface inclusion does not definitely lead to the failure of in-situ tension test. But the early surface crack initiation caused by ceramic inclusion is critically harmful to the LCF property of PM Rene95 superalloy, which can't be ignored.
基金This project is supported by the National Natural Science Foundation of China(No.59971017).
文摘The strengthening effect of a Zn alloy reinforced by SiC particulate was examined. Based on the results of SEM in-situ fracture observation and stress field analysis by finite element method, it is believed that the reinforcing effect of this composite is due to the combination of strain and stress hardening in the matrix.
基金Supported by Science and Technology Programs of Liangqing District of Nanning City(201304A)Science and Technology Program of Guangxi University(XJZ120270)~~
文摘The aim of this study was investigate the effects of heat treatment on the contact angle of Chinese fir, and the indicators affecting the change of contact an-gle change. It was determined that the duration of treatment had significant effect on the change curves of contact angle of Chinese fir wood due to the change curves of contact angle became more centralized and orderly after the specimens heat treated at 180 ℃. Compared with the untreated wood, the contact angle in-creased from 51＆#176; to 124＆#176; after 4 h treatment, and hydroxyl absorbance of hy-drophilic functional groups decreased from 2.08 to 1.63, while carbonyl absorbance from 0.92 to 0.62. The surface roughness has not significant influence on the con-tact angle. Heat treatment of the Chinese fir caused surface morphological change, which produced hol owed-out phenomenon. The increased surface contact angle caused by heat treatment can be used for outdoor and sauna facilities.
基金Projects supported by the National Natural Science Foundation of China(Grant Nos.11072124 and 11272173)the National Basic Research Program of China(Grant No.2010CB631006)the State Key Laboratory of Advanced Metals and Materials, China(Grant No.2010ZD-04)
文摘High density packaging is developing toward miniaturization and integration, which causes many difficulties in designing, manufacturing, and reliability testing. Package-on-Package （POP） is a promising three-dimensional high- density packaging method that integrates a chip scale package （CSP） in the top package and a fine-pitch ball grid array （FBGA） in the bottom package. In this paper, in-situ scanning electron microscopy （SEM） observation is carried out to detect the deformation and damage of the PoP structure under three-point bending loading. The results indicate that the cracks occur in the die of the top package, then cause the crack deflection and bridging in the die attaching layer. Furthermore, the mechanical principles are used to analyse the cracking process of the PoP structure based on the multi-layer laminating hypothesis and the theoretical analysis results are found to be in good agreement with the experimental results.
基金Project(2005CB623701) supported by the Major State Basic Research Development Program of China
文摘The hydrophobic aggregation of ultrafine kaolinite in cationic surfactant suspension was investigated by sedimentation test,zeta potential measurement and SEM observation. SEM images reveal that kaolinite particles show the self-aggregation of edge-face in acidic media,the aggregation of edge-face and edge-edge in neutral media,and the dispersion in alkaline media due to electrostatic repulsion. In the presence of the dodecylammonium acetate cationic surfactant and in neutral and alkaline suspension,the hydrophobic aggregation of face-face is demonstrated. The zeta potential of kaolinite increases with increasing the concentration of cationic surfactant. The small and loose aggregation at a low concentration but big and tight aggregation at a high concentration is presented. At pH=7 alkyl quarterly amine salt CTAB has the best hydrophobic aggregation among three cationic surfactants,namely,dodecylammonium acetate,alkyl quarterly amine salts 1227 and CTAB.
基金supported by CAS/SAFEA International Partnership Program for Creative Research Teams,the Pilot Project of Knowledge Innovation of CAS(Grant No.KZCX2-YW-105)National Basic Research Program of China(Grant No.2006CB806400)National Natural Science Foundation of China(Grant Nos.40402002,40872011)
文摘Leaf cuticle analysis has long been a powerful tool for fossil plant identification,systematics,and palaeoclimatological recon-struction.In recent decades the application of stomatal frequency data that are relied on precise calculation of stomata on plant fossil cuticles to reconstruct ancient atmospheric CO_(2)concentration made the preparation of cuticular membrane with sufficient size a critical technique in palaeoclimatological research.However,for plants with originally thin and fragile cuticles,e.g.,most deciduous plants,conventional techniques sometimes fail to obtain cuticular membranes with sufficient size,or sometimes unable to recover any.This has largely hampered the usage of fossil cuticle analysis in palaeobotanical and palaeo-climatological research.Here,we describe a new method using clear nail polish as a medium to"strengthen"the originally thin and fragile cuticles prior to maceration procedures.We demonstrate the method by using middle Eocene Metasequoia fossils that were notorious for the difficulty of recovering large-sized clean cuticular membranes due to their thin and fragile nature.Metasequoia,with well-documented and widely-distributed fossil records since the Late Cretaceous and with a living repre-sentative,114.glyptostroboides,as a comparative reference,bas been widely used as a model genus for the study of evolution of plants,palaeoclimatological reconstruction,and plant adaptation to climate changes.But its deciduous habit produces thin cuticles and makes the preparation of clean cuticular membranes a tedious process.The new method successfully allows us to recover its delicate cuticular membranes with sufficient sizes for SEM observation and stomatal frequency analysis.
