Single crystals of two liquid crystal compounds, 5-{[4＇-（（（pentyl）oxy）-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO5） and 5-{[（4＇-nonyloxy-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO9）, have been prepared b...Single crystals of two liquid crystal compounds, 5-{[4＇-（（（pentyl）oxy）-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO5） and 5-{[（4＇-nonyloxy-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO9）, have been prepared by solution growth technique. The morphologies and structures of A3EO5 and A3EO9 crystals were investigated by wide angle X-ray diffraction （WXRD）, atom force microscope （AFM） and transmission electron microscope （TEM）. In contrast to the same series of compounds which have a longer alkyl tail, 5-{[（4＇-heptoxy-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO7）, 5-{[（4＇-heptoxy-4-biphenylyl）oxy]carbonyl}-1-pentyne （A3E＇O7） and A3EO9, A3EO5 shows strikingly different crystalline behavior. The former three compounds have only one crystal form, whereas A3EO5 exhibits polymorphism. Specifically, A3EO5 crystals grown from toluene solution show two crys- tal forms. The first one is crystal I which adopts a monoclinic P112/m space group with unit cell parameters of a= 5.79A, b=8.34A, c=43.92/k, y=96°, and the other one is crystal II which adopts a monoclinic P112 space group with unit cell parameters of a=5.55A, b=7.38A, c=31.75 ]k, y=94°. When using dioxane as the solvent to grow A3EO5 crystal, we can selectively obtain crystal Ⅰ. A3EO5 melt-grown crystals also have two crystal forms which derive from crystal I and crystal Ⅱ, respectively. The different crystalline behavior of the compounds should correlate with their different electron dipole moment resulting from the different length of alkyl tail.展开更多
A nickel-based single crystal superalloy containing Re and Ru was cast in a directional solidification furnace.The single crystal specimens after standard heat treatment were grit blasted with different pressures and ...A nickel-based single crystal superalloy containing Re and Ru was cast in a directional solidification furnace.The single crystal specimens after standard heat treatment were grit blasted with different pressures and then heat treated at 1100°C for 4 hunder vacuum condition.The evolution of recrystallized microstructure and its effect on the tensile properties at 850 and 980°C were investigated.After heat treatment,the cellular microstructure was observed,and the thickness of the cellular recrystallization zone increases with the increase in grit blasting pressure.The appearance of the cellular structure undermines the tensile properties.Both the tensile strength and elongation decrease with increasing the thickness of the cellular structure.The recrystallized grain boundaries can act as the channels for the crack initiation and propagation during tensile test.The low bearing capacity of recrystallized layers and the local stress concentration resulting from the notch effect of cracking were the main reasons for the decrease of tensile properties.展开更多
Specific surface free energy (SSFE) of natural calcium fluorapatite from the same mother rock and synthesized barium chlorapatite from the same lot was determined using contact angle of water and formamide droplets, c...Specific surface free energy (SSFE) of natural calcium fluorapatite from the same mother rock and synthesized barium chlorapatite from the same lot was determined using contact angle of water and formamide droplets, compared with grown length of crystal face (h). The experimentally obtained SSFEs have different values even for the same index faces of the different crystals. The SSFEs also have wide distribution for each face of crystals. Observed SSFE is considered to be not only the SSFE of ideally flat terrace face, but also includes the contribution of strep free energy. Though the crystals we experimentally obtained were growth form, the relationship between SSFE and h was almost proportional, which looks like satisfying Wulff’s relationship qualitatively. The slope of SSFE versus h line shows the driving force of crystal growth, and the line for larger crystal has less steep slope. The driving force of crystal growth for larger crystal is smaller, which also means that the chemical potential is larger for larger crystal. The individuality of crystals for the same lot can be explained by the difference of the chemical potential of each crystal.展开更多
Electron spin resonance （ESR） in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 10^18 cm^-...Electron spin resonance （ESR） in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 10^18 cm^-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 （nitrogen impurity atom occupying C site in diamond lattice） is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.展开更多
Bi2Te3single crystals were prepared by the solid-state reaction method. The effect of the vacuum on the growth of Bi2Te3 single crystals was studied with varying the oxygen content by controlling the air pressure in t...Bi2Te3single crystals were prepared by the solid-state reaction method. The effect of the vacuum on the growth of Bi2Te3 single crystals was studied with varying the oxygen content by controlling the air pressure in the silica tube. High quality Bi2Te3 single crystals have been obtained and there is no influence on the growth by an extremely small amount of oxygen in a high vacuum at 1.0 × 10^-3Pa. As the air pressure is increased at 1.0 × 10^-2Pa, oxygen only mainly impacts on the growth of the surface for the prepared samples. Micron-sized rod-like structure and flower-like clusters are observed on the surface. For the samples prepared at 1.0 × 10^-1Pa, x-ray diffraction data show that the yellow part on the surface is Bi2TeO5, while the Bi2Te3 single crystal is still the major phase as the inside part. More interestingly, various crystal morphologies are observed by scanning electron microscope for Bi2Te3 near the boundary between Bi2Te3 and Bi2TeO5.Possible growth mechanisms for Bi2Te3 with different morphologies are discussed in detail.展开更多
The step pattern of single crystal growth and the morphology at equilibrium state of(Mn, Fe)S on the wall of micro-voids in ZG25 cast steel have been observed using scanning electron microscope.The face-centred cubic(...The step pattern of single crystal growth and the morphology at equilibrium state of(Mn, Fe)S on the wall of micro-voids in ZG25 cast steel have been observed using scanning electron microscope.The face-centred cubic(Mn,Fe)S single crystal at equilibrium state is shown to be tetrakaidecahedron consisted of eight{111}planes and six{100}planes,and is a typical example of the O_h—m3m cubic crystal system.展开更多
In this paper, the modified slip/fracture activation model has been used in order to understand the mechanism of ductile-brittle transition on the R-plane of sapphire during ultra-precision machining by reflecting dir...In this paper, the modified slip/fracture activation model has been used in order to understand the mechanism of ductile-brittle transition on the R-plane of sapphire during ultra-precision machining by reflecting direction of resultant force. Anisotropic characteristics of crack morphology and ductility of machining depending on cutting direction were explained in detail with modified fracture cleavage and plastic deformation parameters. Through the analysis, it was concluded that crack morphologies were mainly determined by the interaction of multiple fracture systems activated while, critical depth of cut was determined by the dominant plastic deformation parameter. In addition to this, by using proportionality relationship between magnitude of resultant force and depth of cut in the ductile region, an empirical model for critical depth of cut was developed.展开更多
Single crystals of head-to-tail poly（3-hexylthiophene）s have been grown through the method of isothermal solution crystallization. Electron diffraction in combination with powder X-ray diffraction revealed the cryst...Single crystals of head-to-tail poly（3-hexylthiophene）s have been grown through the method of isothermal solution crystallization. Electron diffraction in combination with powder X-ray diffraction revealed the crystal structure, a= 1.52 nm, b = 3.36nm, c = 1.56 nm and α = β= γ= 90°.展开更多
Polyurethane elastomers are segmented co-polymers of alternating hard and soft segments which are based on various low molecular weight polyesters, polyethers or polybutadienes that are terminated with hydroxyl groups...Polyurethane elastomers are segmented co-polymers of alternating hard and soft segments which are based on various low molecular weight polyesters, polyethers or polybutadienes that are terminated with hydroxyl groups. The hard segments consist of diisocyanates and chain extenders or cross-linking agents which can be diols展开更多
It is well known that in biomineralization, the inorganic solids crystallized in the presence of organic phases, which are generally recognized as additives and matrix, leading to the crystal morphology modification. ...It is well known that in biomineralization, the inorganic solids crystallized in the presence of organic phases, which are generally recognized as additives and matrix, leading to the crystal morphology modification. However, the synergy effects of both soluble additive and insoluble matrix on regulating the morphology of synthetic single-crystals are less studied. Here, we examine the morphological revolution of calcite single crystals induced by the additive, citrate（CIT）, or/and the matrix, agarose gel network. The agarose gel matrix is inert to the crystal morphology in the sense that the agarose gelgrown calcite crystals maintain in characteristic rhombohedra. In contrast, CIT additives are active in crystal morphology modification and crystals begin to exhibit curved rough surfaces when grown in solution with the concentration of CIT coated Au nanoparticles（[CIT-Au NPs]） of more than 2.25 mg/mL.Interestingly, once agarose gel and CIT-Au NPs are simultaneously introduced, the curved morphological feature emerges at a much lower [CIT-Au NPs] of around 0.2 mg/mL. Increasing the gel concentrations further reduce the [CIT-Au NPs] needed to trigger calcite morphological modification, suggesting that the gel networks reduce the CIT diffusion and thereby enhance the kinetic effects of CIT on crystallization. As such, this work may have implications for understanding the mechanism of hierarchical biominerals construction and provide rational strategy to control single-crystal morphologies.展开更多
In the typical air polluted city of Shijiazhuang, single inhalable particle samples in non-heating period, heating period, dust storm days, and snowy days were collected and detected by SEM/EDS （scanning electron mic...In the typical air polluted city of Shijiazhuang, single inhalable particle samples in non-heating period, heating period, dust storm days, and snowy days were collected and detected by SEM/EDS （scanning electron microscopy and energy dispersive X-ray spectrometry）. The particle morphology was characterized by the 6 shape clusters, which are： irregular square, agglomerate, sphere, floccule, column or stick, and unknown, by quantitative order. The irregular square particles are common in all kinds of samples; sphere particles are more, and column or stick are less in winter samples; in the wet deposit samples, agglomerate and floccule particles are not found. The surface of most particles is coarse with fractal edge, which can provide suitable chemical reaction bed in the polluted atmospheric environment. New formed calcium crystal is found to demonstrate the existence of neutralized reaction, explaining the reason for the high SO2 emission and low acid rain frequency in Shijiazhuang. The three sorts of surface patterns of spheres are smooth, semi-smooth, and coarse, corresponding to the element of Si-dominant, Si-Al-dominant, and Fe-dominant, The soot particle is present as floccule with average size around 10 μm, considerably larger than the former reported results, but wrapped or captured with other fine particles to make its appearance unique and enhance its toxicity potentially. The new formed calcium crystal, the 3 sorts of sphere surface patterns, and the unique soot appearance represent the single inhalable particle＇s morphology characteristics in Shijiazhuang City.展开更多
Large size C_(70) single crystals with the dimension of more than 5 mm are grown from the vapor phase by controlling nucleation. X-ray diffraction and electron diffraction confirm that in the C_(70)single crystal a ...Large size C_(70) single crystals with the dimension of more than 5 mm are grown from the vapor phase by controlling nucleation. X-ray diffraction and electron diffraction confirm that in the C_(70)single crystal a phase of the hexagonal close-packed (hcp) structure coexists with a minor face-center-cubic (fcc) phase at room temperature. The morphologies and their formation mechanism of the C_(70) single crystals are investigated by means of scanning electron microscopy and optical microscopy. The influence of growth conditions on the morphologies of C_(70) single crystals is discussed.展开更多
ZnO single crystal was used as the substrate to study the effect of ZnO crystal plane polarity on the morphology and structure of CH_3NH_3PbI_3（MAPbI_3） perovskite film and carrier transport properties,which is mean...ZnO single crystal was used as the substrate to study the effect of ZnO crystal plane polarity on the morphology and structure of CH_3NH_3PbI_3（MAPbI_3） perovskite film and carrier transport properties,which is meaningful for improving ZnO-based perovskite solar cell. It is found that perovskite thin film has small grain size（about 190 nm） and high coverage rate on the O-face of ZnO single crystal,and the dominant exposed crystal plane of perovskite film is（110） plane. While the MAPbI_3 thin film has large grain size（about 1.03 μm） and low coverage rate on the Zn-face,and the（022） plane is dominantly exposed for the perovskite film. The injection of photogenerated electrons from MAPbI_3 film into the O-face of ZnO single crystal is faster and more effective than that to Zn-face. It is supposed that O-face is more suitable for ZnO single crystal based perovskite cell fabrication than Zn-face.展开更多
文摘Single crystals of two liquid crystal compounds, 5-{[4＇-（（（pentyl）oxy）-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO5） and 5-{[（4＇-nonyloxy-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO9）, have been prepared by solution growth technique. The morphologies and structures of A3EO5 and A3EO9 crystals were investigated by wide angle X-ray diffraction （WXRD）, atom force microscope （AFM） and transmission electron microscope （TEM）. In contrast to the same series of compounds which have a longer alkyl tail, 5-{[（4＇-heptoxy-4-biphenylyl）carbonyl]oxy}-1-pentyne （A3EO7）, 5-{[（4＇-heptoxy-4-biphenylyl）oxy]carbonyl}-1-pentyne （A3E＇O7） and A3EO9, A3EO5 shows strikingly different crystalline behavior. The former three compounds have only one crystal form, whereas A3EO5 exhibits polymorphism. Specifically, A3EO5 crystals grown from toluene solution show two crys- tal forms. The first one is crystal I which adopts a monoclinic P112/m space group with unit cell parameters of a= 5.79A, b=8.34A, c=43.92/k, y=96°, and the other one is crystal II which adopts a monoclinic P112 space group with unit cell parameters of a=5.55A, b=7.38A, c=31.75 ]k, y=94°. When using dioxane as the solvent to grow A3EO5 crystal, we can selectively obtain crystal Ⅰ. A3EO5 melt-grown crystals also have two crystal forms which derive from crystal I and crystal Ⅱ, respectively. The different crystalline behavior of the compounds should correlate with their different electron dipole moment resulting from the different length of alkyl tail.
基金funded by the Assembly Pre-research Foundation Program of China(140A18040115HK51248)
文摘A nickel-based single crystal superalloy containing Re and Ru was cast in a directional solidification furnace.The single crystal specimens after standard heat treatment were grit blasted with different pressures and then heat treated at 1100°C for 4 hunder vacuum condition.The evolution of recrystallized microstructure and its effect on the tensile properties at 850 and 980°C were investigated.After heat treatment,the cellular microstructure was observed,and the thickness of the cellular recrystallization zone increases with the increase in grit blasting pressure.The appearance of the cellular structure undermines the tensile properties.Both the tensile strength and elongation decrease with increasing the thickness of the cellular structure.The recrystallized grain boundaries can act as the channels for the crack initiation and propagation during tensile test.The low bearing capacity of recrystallized layers and the local stress concentration resulting from the notch effect of cracking were the main reasons for the decrease of tensile properties.
文摘Specific surface free energy (SSFE) of natural calcium fluorapatite from the same mother rock and synthesized barium chlorapatite from the same lot was determined using contact angle of water and formamide droplets, compared with grown length of crystal face (h). The experimentally obtained SSFEs have different values even for the same index faces of the different crystals. The SSFEs also have wide distribution for each face of crystals. Observed SSFE is considered to be not only the SSFE of ideally flat terrace face, but also includes the contribution of strep free energy. Though the crystals we experimentally obtained were growth form, the relationship between SSFE and h was almost proportional, which looks like satisfying Wulff’s relationship qualitatively. The slope of SSFE versus h line shows the driving force of crystal growth, and the line for larger crystal has less steep slope. The driving force of crystal growth for larger crystal is smaller, which also means that the chemical potential is larger for larger crystal. The individuality of crystals for the same lot can be explained by the difference of the chemical potential of each crystal.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50372007 and 50572007, Russian Fund for Basic Research under Grant Nos 06-02-39031 and 07-03-00956, and Belarus Republic Foundation for Basic Research under Grant No F05-281.
文摘Electron spin resonance （ESR） in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 10^18 cm^-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 （nitrogen impurity atom occupying C site in diamond lattice） is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10904013 and 11274060)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK2009260 and BK20141329)the Scientific Research Staring Foundation for the Returned Overseas Chinese Scholars,Ministry of Education of China
文摘Bi2Te3single crystals were prepared by the solid-state reaction method. The effect of the vacuum on the growth of Bi2Te3 single crystals was studied with varying the oxygen content by controlling the air pressure in the silica tube. High quality Bi2Te3 single crystals have been obtained and there is no influence on the growth by an extremely small amount of oxygen in a high vacuum at 1.0 × 10^-3Pa. As the air pressure is increased at 1.0 × 10^-2Pa, oxygen only mainly impacts on the growth of the surface for the prepared samples. Micron-sized rod-like structure and flower-like clusters are observed on the surface. For the samples prepared at 1.0 × 10^-1Pa, x-ray diffraction data show that the yellow part on the surface is Bi2TeO5, while the Bi2Te3 single crystal is still the major phase as the inside part. More interestingly, various crystal morphologies are observed by scanning electron microscope for Bi2Te3 near the boundary between Bi2Te3 and Bi2TeO5.Possible growth mechanisms for Bi2Te3 with different morphologies are discussed in detail.
文摘The step pattern of single crystal growth and the morphology at equilibrium state of(Mn, Fe)S on the wall of micro-voids in ZG25 cast steel have been observed using scanning electron microscope.The face-centred cubic(Mn,Fe)S single crystal at equilibrium state is shown to be tetrakaidecahedron consisted of eight{111}planes and six{100}planes,and is a typical example of the O_h—m3m cubic crystal system.
基金supported by the NSF under grant No. CMMI-1844821。
文摘In this paper, the modified slip/fracture activation model has been used in order to understand the mechanism of ductile-brittle transition on the R-plane of sapphire during ultra-precision machining by reflecting direction of resultant force. Anisotropic characteristics of crack morphology and ductility of machining depending on cutting direction were explained in detail with modified fracture cleavage and plastic deformation parameters. Through the analysis, it was concluded that crack morphologies were mainly determined by the interaction of multiple fracture systems activated while, critical depth of cut was determined by the dominant plastic deformation parameter. In addition to this, by using proportionality relationship between magnitude of resultant force and depth of cut in the ductile region, an empirical model for critical depth of cut was developed.
基金This work was financially supported by the Special Funds for Major State Basic Research Projects (No. 2002CB613400) by the National Natural Science Foundation of China (Nos. 90301008, 20474064, and 20521415).
文摘Single crystals of head-to-tail poly（3-hexylthiophene）s have been grown through the method of isothermal solution crystallization. Electron diffraction in combination with powder X-ray diffraction revealed the crystal structure, a= 1.52 nm, b = 3.36nm, c = 1.56 nm and α = β= γ= 90°.
基金Project supported by the National Natural Science Foundation of China.
文摘Polyurethane elastomers are segmented co-polymers of alternating hard and soft segments which are based on various low molecular weight polyesters, polyethers or polybutadienes that are terminated with hydroxyl groups. The hard segments consist of diisocyanates and chain extenders or cross-linking agents which can be diols
基金supported by the 973 Program (No. 2014CB643503)the National Natural Science Foundation of China (Nos. 51625304, 51461165301)
文摘It is well known that in biomineralization, the inorganic solids crystallized in the presence of organic phases, which are generally recognized as additives and matrix, leading to the crystal morphology modification. However, the synergy effects of both soluble additive and insoluble matrix on regulating the morphology of synthetic single-crystals are less studied. Here, we examine the morphological revolution of calcite single crystals induced by the additive, citrate（CIT）, or/and the matrix, agarose gel network. The agarose gel matrix is inert to the crystal morphology in the sense that the agarose gelgrown calcite crystals maintain in characteristic rhombohedra. In contrast, CIT additives are active in crystal morphology modification and crystals begin to exhibit curved rough surfaces when grown in solution with the concentration of CIT coated Au nanoparticles（[CIT-Au NPs]） of more than 2.25 mg/mL.Interestingly, once agarose gel and CIT-Au NPs are simultaneously introduced, the curved morphological feature emerges at a much lower [CIT-Au NPs] of around 0.2 mg/mL. Increasing the gel concentrations further reduce the [CIT-Au NPs] needed to trigger calcite morphological modification, suggesting that the gel networks reduce the CIT diffusion and thereby enhance the kinetic effects of CIT on crystallization. As such, this work may have implications for understanding the mechanism of hierarchical biominerals construction and provide rational strategy to control single-crystal morphologies.
文摘In the typical air polluted city of Shijiazhuang, single inhalable particle samples in non-heating period, heating period, dust storm days, and snowy days were collected and detected by SEM/EDS （scanning electron microscopy and energy dispersive X-ray spectrometry）. The particle morphology was characterized by the 6 shape clusters, which are： irregular square, agglomerate, sphere, floccule, column or stick, and unknown, by quantitative order. The irregular square particles are common in all kinds of samples; sphere particles are more, and column or stick are less in winter samples; in the wet deposit samples, agglomerate and floccule particles are not found. The surface of most particles is coarse with fractal edge, which can provide suitable chemical reaction bed in the polluted atmospheric environment. New formed calcium crystal is found to demonstrate the existence of neutralized reaction, explaining the reason for the high SO2 emission and low acid rain frequency in Shijiazhuang. The three sorts of surface patterns of spheres are smooth, semi-smooth, and coarse, corresponding to the element of Si-dominant, Si-Al-dominant, and Fe-dominant, The soot particle is present as floccule with average size around 10 μm, considerably larger than the former reported results, but wrapped or captured with other fine particles to make its appearance unique and enhance its toxicity potentially. The new formed calcium crystal, the 3 sorts of sphere surface patterns, and the unique soot appearance represent the single inhalable particle＇s morphology characteristics in Shijiazhuang City.
基金Project supported by the National Natural Science Foundation of China (Grant No. 59772026)
文摘Large size C_(70) single crystals with the dimension of more than 5 mm are grown from the vapor phase by controlling nucleation. X-ray diffraction and electron diffraction confirm that in the C_(70)single crystal a phase of the hexagonal close-packed (hcp) structure coexists with a minor face-center-cubic (fcc) phase at room temperature. The morphologies and their formation mechanism of the C_(70) single crystals are investigated by means of scanning electron microscopy and optical microscopy. The influence of growth conditions on the morphologies of C_(70) single crystals is discussed.
基金supported by the National Natural Science Foundation of China(Nos.91333207,61427901 and U1505252)
文摘ZnO single crystal was used as the substrate to study the effect of ZnO crystal plane polarity on the morphology and structure of CH_3NH_3PbI_3（MAPbI_3） perovskite film and carrier transport properties,which is meaningful for improving ZnO-based perovskite solar cell. It is found that perovskite thin film has small grain size（about 190 nm） and high coverage rate on the O-face of ZnO single crystal,and the dominant exposed crystal plane of perovskite film is（110） plane. While the MAPbI_3 thin film has large grain size（about 1.03 μm） and low coverage rate on the Zn-face,and the（022） plane is dominantly exposed for the perovskite film. The injection of photogenerated electrons from MAPbI_3 film into the O-face of ZnO single crystal is faster and more effective than that to Zn-face. It is supposed that O-face is more suitable for ZnO single crystal based perovskite cell fabrication than Zn-face.
