The oligomerization of light olefins is considered a green production technology.Currently,the application of mordenite in isoamylene oligomerization faces two main challenges:low dimerization selectivity and poor sta...The oligomerization of light olefins is considered a green production technology.Currently,the application of mordenite in isoamylene oligomerization faces two main challenges:low dimerization selectivity and poor stability.In this work,a series of different SiO_(2)/Al_(2)O_(3) ratio mordenite are synthesized by utilizing hexamethyleneimine(HMI)as the organic structure directing agent,and it turns out that the rod-like zeolite with the ratio of SiO_(2)/Al_(2)O_(3)=14 exhibits the higher dimerization selectivity.The incorporation of TPOAC optimizes the pore structure and acid site distribution of the rod-like zeolite,which enables the samples to not only exhibit a conversion rate of isoamylene over 88.30% within 12 h,while maintaining good dimerization selectivity.These findings provide a promising approach for improving the efficiency and sustainability of olefin oligomerization processes.展开更多
The introduction of concept of the three domains of isotactic polypropylene（iPP） by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behav...The introduction of concept of the three domains of isotactic polypropylene（iPP） by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behaviors and consequent properties. To further understand the physical nature of the melt structures, the crystalline structures of i PP after thermal treatment in the three domains are systematically investigated. It is found that after treated at different domains the crystal morphologies, including the sizes and birefringence of spherulitic, the proportion of radial and tangential lamellae, etc., have distinctly different features. Our study reveals that the ＂nuclei＂ at domain II compose of locally ordered chains and the induced memory effect could not be erased under annealing treatment, while the ＂nuclei＂ at domain III compose of crystal fragments, which will aggregate under annealing process. Based on our results, highly schematic diagrams are proposed to illustrate the probable physical characteristics of the melt structures at the three different domains.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
In this study, the isothermal crystallization kinetics and crystalline morphology of poly（butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate）（PBAC）, which refers to a copolyester containing a non-planar rin...In this study, the isothermal crystallization kinetics and crystalline morphology of poly（butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate）（PBAC）, which refers to a copolyester containing a non-planar ring structure, were investigated by differential scanning calorimetry and polarized optical microscopy, and compared with those of neat poly（butylene 1,4-cyclohexanedicarboxylate）（PBC）. The results indicate that the introduction of butylene adipate（BA） unit into PBAC did not change the intrinsical crystallization mechanism. But, the crystallization rate and ability, and equilibrium melting temperature of PBAC copolymers were reduced. All PBC and PBAC copolymers could only form high density of nucleation from melt at given supercooling, while no Maltese cross or ring-banded spherulites could be observed. PBAC copolymers with a high amount of BA unit became amorphous after quenching with liquid nitrogen from melt, while PBC and PBAC copolymers with a low amount of BA unit could still form a large amount of nuclei under the same treatment.展开更多
Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studi...Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro,pore to macro.Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel.Aqueous phase tests were performed by controlling the concentration of calcium(Ca)to magnesium(Mg)ratio to vary from 1.00:0 to 0:1.00.The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates.As the magnesium content increases,the crystal morphology of precipitates changes from calcite to Mg-calcite,vaterite,rosette and nesquehonite.Cementation effect in the Ca-rich group is superior to that in the Mgrich group.In terms of unconfined compressive strength of the treated sand,the contribution of Mg is much less significant in Mg-rich groups.The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed.All samples exhibited strength improvement after biotreatments.Among all the four groups,the EICP 1-phase group with Ca:Mg of 0.90:0.10 and 0.75:0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa,respectively.展开更多
Suspended particulate substances were sampled in the eastem equatorial Pacific in water column from surface to near bottom in five stations in 2005, from which 868 barite crystals were recovered. The barite crystals w...Suspended particulate substances were sampled in the eastem equatorial Pacific in water column from surface to near bottom in five stations in 2005, from which 868 barite crystals were recovered. The barite crystals were examined under scanning electron microscopy. About 61% of the total barites crystals contained detectable Sr by energy dispersive X-ray spectrometry. Barite crystals could be classified into four groups based on their morphology： 1） bladed; 2） ovoid or rounded; 3） arrow-like; and 4） irregularly shaped. The arrow-like barite crystals in natural environment has never been reported before. In addition, about a half of the studied crystals showed features of dissolution as cavities or holes inside of the crystals or around their edges. We found that differential dissolution of barite crystals is consequence of heterogeneous Sr distribution in barite crystals. Our results would help in understanding the biogeochemical processes of marine barite formation and preservation in seawater and marine sediments.展开更多
In order to theoretically study the growth morphology of dihydroxylammonium 5,5’-bistetrazole-1,1’-dio late(TKX-50)crystal in different solvent systems,crystal–solvent models were established,and then molecular dyn...In order to theoretically study the growth morphology of dihydroxylammonium 5,5’-bistetrazole-1,1’-dio late(TKX-50)crystal in different solvent systems,crystal–solvent models were established,and then molecular dynamics(MD)methods were adopted as a means to simulate particle motion.Modified attachment energy(MAE)model was employed to calculate the growth morphology of TKX-50.The simulation results demonstrate that COMPASS force field and RESP charge are suitable for molecular dynamics simulation of TKX-50.The morphologically dominant growth surfaces of TKX-50 in vacuum are(020),(011),(11–1),(100)and(120),respectively.In water(H_(2)O)and N,N-dimethylformamide(DMF)solvents,the(11–1)face is the largest in the habit face,the growth rate of(020)face becomes faster.With the increase of temperature,the aspect ratios of TKX-50 crystal in DMF solvent increase,and the areas of the(120)faces decrease.In ethylene glycol/H_(2)O mixed solvent system with volume ratio of 1/1,aspect ratio of TKX-50 is relatively small.In formic acid/H_(2)O mixed solvents with different volume ratios(1/4,1/3,1/2,1/1 and 2/1),aspect ratio of TKX-50 is relatively small when volume ratio is 1/2.展开更多
Adding Na_(2)CO_(3) to the NaHCO_(3) cooling crystallizer, using the common ion effect to promote crystallization and improve product morphology, is a new process recently proposed in the literature. However, the mech...Adding Na_(2)CO_(3) to the NaHCO_(3) cooling crystallizer, using the common ion effect to promote crystallization and improve product morphology, is a new process recently proposed in the literature. However, the mechanism of the impact of Na_(2)CO_(3)on the crystal morphology is still indeterminate. In this work, the crystallization of NaHCO_(3)in water and Na_(2)CO_(3)–NaHCO_(3) aqueous solution was investigated by experiments and molecular dynamics simulations(MD). The crystallization results demonstrate that the morphology of NaHCO_(3) crystal changed gradually from needle-like to flake structure with the addition of Na_(2)CO_(3). The simulation results indicate that the layer docking model and the modified attachment energy formula without considering the roughness of crystal surface can obtain the crystal morphology in agreement with the experimental results, but the lower molecules of the crystal layer have to be fixed during MD. Thermodynamic calculation of the NaHCO_(3) crystallization process verifies that the common ion effect from Na^(+)and the ionization equilibrium transformation from CO_(3)^(2-) jointly promote the precipitation of NaHCO_(3) crystal. The radial distribution function analysis indicates that the oxygen atoms of Na_(2)CO_(3) formed strong hydrogen bonds with the hydrogen atoms of the(0 1 1) face, which weakened the hydration of water molecules at the crystal surface, resulting in a significant change in the attachment energy of this crystal surface. In addition, Na+and CO_(3)^(2-) are more likely to accumulate on the(011) face,resulting in the fastest growth rate on this crystal surface, which eventually leads to a change in crystal morphology from needle-like to flake-like.展开更多
In this work, a liquid-gas heterogeneous microreactor was developed for investigating continuous crystallization of dolutegravir sodium(DTG), as well as revealing reaction kinetics and mixing mechanism with 3-min data...In this work, a liquid-gas heterogeneous microreactor was developed for investigating continuous crystallization of dolutegravir sodium(DTG), as well as revealing reaction kinetics and mixing mechanism with 3-min data acquisition. The reaction kinetics models were established by visually recording the concentration variation of reactants over time in the microchannel via adding pH-sensitive fluorescent dye. The mixing intensification mechanism of liquid-gas flow was quantified through the fluorescent signal to indicate mixing process, demonstrating an outstanding mixing performance with a mixing time less than 0.1 s. Compared with batch crystallization, continuous synthesis of dolutegravir sodium using liquid-gas heterogenous microreactor optimizes crystal distribution size, and successfully modifies the crystal morphology in needle-like habit instead of rod-like habit. The microreactor continuous crystallization can run for 5 h without crystal blockage and achieve D90 of DTG less than 30 μm. This work provides a feasible approach for continuously synthesizing dolutegravir sodium, and can optimize the existing pharmaceutical crystallization.展开更多
Important crystal faces that dominate the crystal morphology of royal demolition explosive （RDX） in vacuum were analyzed with the attachment energy （AE） method. Molecular dynamics （MD） simulations were used to c...Important crystal faces that dominate the crystal morphology of royal demolition explosive （RDX） in vacuum were analyzed with the attachment energy （AE） method. Molecular dynamics （MD） simulations were used to calculate the interaction energies between these crystal faces and different solvent molecules for an attachment energy correction. Growth habits in the presence of different solvents were generated. The results showed that some crystal faces in solutions became morphologically more important than that in vacuum while others became less important. Thus, crystal shape and surface property changed a lot with the variation of crystal faces. The results from calcula- tion were in agreement with those from the re-crystallization experiment, which indicated that cyclohexanone （CH） was a promising solvent to modify the crystal morphology of RDX for obtaining products with regular shape and high purity, while butyrolactone （BL） played a great role in improving the surface electrostatic property of RDX.展开更多
Lanthanum magnesium hexaaluminate（LaMgAl（11）O（19）, LMA） was prepared at different temperatures by solid-state reaction. Phase compositions and crystal morphologies of specimens synthesized at different temperatu...Lanthanum magnesium hexaaluminate（LaMgAl（11）O（19）, LMA） was prepared at different temperatures by solid-state reaction. Phase compositions and crystal morphologies of specimens synthesized at different temperatures were investigated using X-ray diffraction（XRD）, scanning electron microscopy（SEM）. It was observed that the crystalline grain size of LMA was not only dependent on the preparation temperature but also on its powder morphology. In the temperature range of 1300 e1550℃, LMA showed platelet grain and the average crystalline grain size increases with the increase in temperature. At1600℃, if the powder was sintered for two times, the equiaxed grain could be found with the decrease in grain space, resulting in the reduction of the crystalline grain size. Styles of specimens（powder or disk） might have no obvious influence on morphologies and sizes of LMA crystalline grains which were synthesized with the well-dispersed raw material mixtures. The synthesis temperature played a key role in influencing the free space for the formation and growth of crystalline grains.展开更多
We studied cocrystal of bis(8-quinolinolato) copper(II) (CuQ<sub>2</sub>) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), which change dramatically crystal shape in a moment by adding press on crystal face. S...We studied cocrystal of bis(8-quinolinolato) copper(II) (CuQ<sub>2</sub>) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), which change dramatically crystal shape in a moment by adding press on crystal face. Single crystal was prepared by dissolving CuQ<sub>2</sub> and TCNQ in chloroform by evaporation of the solution at ambient conditions. We investigated about crystal structure and morphological change properties. We proclaim that this phenomenon is solid phase transition to Form I from Form II, it is caused by pressure on the crystal face (001) of Form II and the crystal expansion direction is the side face (100). We take note of the common structure between polymorph and explain that this transition occurs by the structure like dominoes falling. We obtained a correlation between molecular level structure change and macroscopic shape changes.展开更多
To elucidate the regulation mechanism of catalyst geometry structure to diamond growth,we establish three catalyst modes with different structures.The simulation results show that with the decrease of the protruding h...To elucidate the regulation mechanism of catalyst geometry structure to diamond growth,we establish three catalyst modes with different structures.The simulation results show that with the decrease of the protruding height of the catalyst,the low-temperature region gradually moves toward the center of the catalyst,which causes the distribution characteristics of the temperature and convection field in the catalyst to change.The temperature difference in vertical direction of the catalyst decreases gradually and increases in the horizontal direction,while the catalyst convection velocity has the same variation regularity in the corresponding directions.The variation of temperature difference and convection velocity lead the crystal growth rate in different crystal orientations to change,which directly affects the crystal morphology of the synthetic diamond.The simulation results are consistent with the experimental results,which shows the correctness of the theoretical rational analysis.This work is expected to be able to facilitate the understanding of catalyst structure regulation mechanism on diamond morphology and the providing of an important theoretical basis for the controllable growth of special crystal shape diamond under HPHT process.展开更多
The crystal morphology of zinc lactate trihydrate in the absence or presence of impurities(viz.succinic acid,L-malic acid and D-malic acid)is investigated by molecular simulation based on surface docking model and COM...The crystal morphology of zinc lactate trihydrate in the absence or presence of impurities(viz.succinic acid,L-malic acid and D-malic acid)is investigated by molecular simulation based on surface docking model and COMPASS force field.Combing simulation results with our previous experimental results,it is found that the solvent mainly has an inhibition effect on the(0 0 2)surface,and succinic acid impurity will inhibit the growth of(0 0 2)and(0 1 1)surfaces while two enantiomers of malic acid impurity will inhibit the(0 0 2)and(1 0 0)surfaces,which are in good agreement with the experimental results.展开更多
Cuprous oxides with different morphologies were formed on F-doped tin oxide （FTO） covered glass substrates by potentiostatic deposition of cupric acetate. The effects of CTAB and Cl- on the crystal morphologies of c...Cuprous oxides with different morphologies were formed on F-doped tin oxide （FTO） covered glass substrates by potentiostatic deposition of cupric acetate. The effects of CTAB and Cl- on the crystal morphologies of cuprous oxide were studied. Different crystal morphologies of cuprous oxides were obtained by the change of the concentrations of CTAB and Cl. The flowerlike and cubic morphologies of Cu2O crystals were obtained when using higher concentration of CTAB and KCl, respectively. Photoelectrochemical properties of the Cu2O thin films prepared in the system were also studied.展开更多
Tantalum pentoxide reacts actively with concentrated NaOH solution under hydrothermal conditions at 180 ℃. In the reaction between NaOH solution and Ta2O5, the structure and composition of the tantalates depend on th...Tantalum pentoxide reacts actively with concentrated NaOH solution under hydrothermal conditions at 180 ℃. In the reaction between NaOH solution and Ta2O5, the structure and composition of the tantalates depend on the reaction time, and the structure evolution results in a remarkable change in light absorption. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) diffused reflection spectrum were used to characterize various properties of the obtained solid products. At 180 ℃, the reaction proceeds rapidly. With the increase of time, the reflection peaks of unreacted Ta2O5 in the XRD patterns becomes weaker and weaker. Pure NaTaO3 is obtained after 60 min, which is well crystallized with a uniform cubic morphology.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
The intergranular cracking face is smooth and Iransgranular cracking fracture shows trace of cleavage. It is hard to .tirol characteristic rhombus in the dense small crystals. As measured by SEM, the particle size of ...The intergranular cracking face is smooth and Iransgranular cracking fracture shows trace of cleavage. It is hard to .tirol characteristic rhombus in the dense small crystals. As measured by SEM, the particle size of microcrystalline magnesite originating in Sichuan - Tibet is uniform, most grains range in 2 -4 μm. Three-dimensional （ 3D ） crystal morphology assumes cubic or column.展开更多
The research on morphology of mineral crystals in China includes classical goniometry of 100 minerals such as hsianghualite, orthobrannerite, jamesonite and bertrandite and surface microtopography of 20 minerals such ...The research on morphology of mineral crystals in China includes classical goniometry of 100 minerals such as hsianghualite, orthobrannerite, jamesonite and bertrandite and surface microtopography of 20 minerals such as wolframite and diamond, among which 5 new minerals and 34 uranium minerals were discovered and measured by Chinese mineralogists. These have enriched mineralogy and crystal morphology and strengthened the study of information of morphological genesis.展开更多
基金supported by the National Natural Science Foundation of China(21776505)。
文摘The oligomerization of light olefins is considered a green production technology.Currently,the application of mordenite in isoamylene oligomerization faces two main challenges:low dimerization selectivity and poor stability.In this work,a series of different SiO_(2)/Al_(2)O_(3) ratio mordenite are synthesized by utilizing hexamethyleneimine(HMI)as the organic structure directing agent,and it turns out that the rod-like zeolite with the ratio of SiO_(2)/Al_(2)O_(3)=14 exhibits the higher dimerization selectivity.The incorporation of TPOAC optimizes the pore structure and acid site distribution of the rod-like zeolite,which enables the samples to not only exhibit a conversion rate of isoamylene over 88.30% within 12 h,while maintaining good dimerization selectivity.These findings provide a promising approach for improving the efficiency and sustainability of olefin oligomerization processes.
基金financially supported by the National Natural Science Foundation of China(Nos.21174032 and 21574029)China National Petroleum Corporationthe beam time provided by beamline BL16B1 of Shanghai Synchrotron Radiation Facility(Z14sr0051)
文摘The introduction of concept of the three domains of isotactic polypropylene（iPP） by Wittmann and Lotz et al. is an important advance in understanding the influence of the melt structures on the crystallization behaviors and consequent properties. To further understand the physical nature of the melt structures, the crystalline structures of i PP after thermal treatment in the three domains are systematically investigated. It is found that after treated at different domains the crystal morphologies, including the sizes and birefringence of spherulitic, the proportion of radial and tangential lamellae, etc., have distinctly different features. Our study reveals that the ＂nuclei＂ at domain II compose of locally ordered chains and the induced memory effect could not be erased under annealing treatment, while the ＂nuclei＂ at domain III compose of crystal fragments, which will aggregate under annealing process. Based on our results, highly schematic diagrams are proposed to illustrate the probable physical characteristics of the melt structures at the three different domains.
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.
基金financially supported by the National Natural Science Foundation of China(No.51503217)Zhejiang Province Public Welfare Project(No.2017C31081)+1 种基金the Open Project Program of MOE Key Laboratory of Macromolecular Synthesis and Functionalization,Zhejiang University(No.2016MSF001)Youth Innovation Promotion Association CAS(No.2017339)
文摘In this study, the isothermal crystallization kinetics and crystalline morphology of poly（butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate）（PBAC）, which refers to a copolyester containing a non-planar ring structure, were investigated by differential scanning calorimetry and polarized optical microscopy, and compared with those of neat poly（butylene 1,4-cyclohexanedicarboxylate）（PBC）. The results indicate that the introduction of butylene adipate（BA） unit into PBAC did not change the intrinsical crystallization mechanism. But, the crystallization rate and ability, and equilibrium melting temperature of PBAC copolymers were reduced. All PBC and PBAC copolymers could only form high density of nucleation from melt at given supercooling, while no Maltese cross or ring-banded spherulites could be observed. PBAC copolymers with a high amount of BA unit became amorphous after quenching with liquid nitrogen from melt, while PBC and PBAC copolymers with a low amount of BA unit could still form a large amount of nuclei under the same treatment.
基金supported by the National Parks Board,Singapore,and the Cities of Tomorrow R&D programme(Grant No.COT-V1-2020-4)by Ministry of National Development and National Research Foundation,Singapore.
文摘Microbial induced carbonate precipitation(MICP)and enzyme induced carbonate precipitation(EICP)processes can be affected by many factors.The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro,pore to macro.Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel.Aqueous phase tests were performed by controlling the concentration of calcium(Ca)to magnesium(Mg)ratio to vary from 1.00:0 to 0:1.00.The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates.As the magnesium content increases,the crystal morphology of precipitates changes from calcite to Mg-calcite,vaterite,rosette and nesquehonite.Cementation effect in the Ca-rich group is superior to that in the Mgrich group.In terms of unconfined compressive strength of the treated sand,the contribution of Mg is much less significant in Mg-rich groups.The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed.All samples exhibited strength improvement after biotreatments.Among all the four groups,the EICP 1-phase group with Ca:Mg of 0.90:0.10 and 0.75:0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa,respectively.
基金Supported by the China Ocean Mineral Resources R&D Association(Mas,DYXM-115-02-1-13,DYXM-115-01-3-04)
文摘Suspended particulate substances were sampled in the eastem equatorial Pacific in water column from surface to near bottom in five stations in 2005, from which 868 barite crystals were recovered. The barite crystals were examined under scanning electron microscopy. About 61% of the total barites crystals contained detectable Sr by energy dispersive X-ray spectrometry. Barite crystals could be classified into four groups based on their morphology： 1） bladed; 2） ovoid or rounded; 3） arrow-like; and 4） irregularly shaped. The arrow-like barite crystals in natural environment has never been reported before. In addition, about a half of the studied crystals showed features of dissolution as cavities or holes inside of the crystals or around their edges. We found that differential dissolution of barite crystals is consequence of heterogeneous Sr distribution in barite crystals. Our results would help in understanding the biogeochemical processes of marine barite formation and preservation in seawater and marine sediments.
基金supported by Fundamental Research Program of Shanxi Province(20210302123055)and(201801D221035).
文摘In order to theoretically study the growth morphology of dihydroxylammonium 5,5’-bistetrazole-1,1’-dio late(TKX-50)crystal in different solvent systems,crystal–solvent models were established,and then molecular dynamics(MD)methods were adopted as a means to simulate particle motion.Modified attachment energy(MAE)model was employed to calculate the growth morphology of TKX-50.The simulation results demonstrate that COMPASS force field and RESP charge are suitable for molecular dynamics simulation of TKX-50.The morphologically dominant growth surfaces of TKX-50 in vacuum are(020),(011),(11–1),(100)and(120),respectively.In water(H_(2)O)and N,N-dimethylformamide(DMF)solvents,the(11–1)face is the largest in the habit face,the growth rate of(020)face becomes faster.With the increase of temperature,the aspect ratios of TKX-50 crystal in DMF solvent increase,and the areas of the(120)faces decrease.In ethylene glycol/H_(2)O mixed solvent system with volume ratio of 1/1,aspect ratio of TKX-50 is relatively small.In formic acid/H_(2)O mixed solvents with different volume ratios(1/4,1/3,1/2,1/1 and 2/1),aspect ratio of TKX-50 is relatively small when volume ratio is 1/2.
基金supported by the National Natural Science Foundation of China (21878143)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)。
文摘Adding Na_(2)CO_(3) to the NaHCO_(3) cooling crystallizer, using the common ion effect to promote crystallization and improve product morphology, is a new process recently proposed in the literature. However, the mechanism of the impact of Na_(2)CO_(3)on the crystal morphology is still indeterminate. In this work, the crystallization of NaHCO_(3)in water and Na_(2)CO_(3)–NaHCO_(3) aqueous solution was investigated by experiments and molecular dynamics simulations(MD). The crystallization results demonstrate that the morphology of NaHCO_(3) crystal changed gradually from needle-like to flake structure with the addition of Na_(2)CO_(3). The simulation results indicate that the layer docking model and the modified attachment energy formula without considering the roughness of crystal surface can obtain the crystal morphology in agreement with the experimental results, but the lower molecules of the crystal layer have to be fixed during MD. Thermodynamic calculation of the NaHCO_(3) crystallization process verifies that the common ion effect from Na^(+)and the ionization equilibrium transformation from CO_(3)^(2-) jointly promote the precipitation of NaHCO_(3) crystal. The radial distribution function analysis indicates that the oxygen atoms of Na_(2)CO_(3) formed strong hydrogen bonds with the hydrogen atoms of the(0 1 1) face, which weakened the hydration of water molecules at the crystal surface, resulting in a significant change in the attachment energy of this crystal surface. In addition, Na+and CO_(3)^(2-) are more likely to accumulate on the(011) face,resulting in the fastest growth rate on this crystal surface, which eventually leads to a change in crystal morphology from needle-like to flake-like.
基金supported by the Natural Science Foundation of the Science and Technology Commission of Shanghai Municipality(No.19ZR1472200)National Natural Science Foundation of China(No.22178072)。
文摘In this work, a liquid-gas heterogeneous microreactor was developed for investigating continuous crystallization of dolutegravir sodium(DTG), as well as revealing reaction kinetics and mixing mechanism with 3-min data acquisition. The reaction kinetics models were established by visually recording the concentration variation of reactants over time in the microchannel via adding pH-sensitive fluorescent dye. The mixing intensification mechanism of liquid-gas flow was quantified through the fluorescent signal to indicate mixing process, demonstrating an outstanding mixing performance with a mixing time less than 0.1 s. Compared with batch crystallization, continuous synthesis of dolutegravir sodium using liquid-gas heterogenous microreactor optimizes crystal distribution size, and successfully modifies the crystal morphology in needle-like habit instead of rod-like habit. The microreactor continuous crystallization can run for 5 h without crystal blockage and achieve D90 of DTG less than 30 μm. This work provides a feasible approach for continuously synthesizing dolutegravir sodium, and can optimize the existing pharmaceutical crystallization.
文摘Important crystal faces that dominate the crystal morphology of royal demolition explosive （RDX） in vacuum were analyzed with the attachment energy （AE） method. Molecular dynamics （MD） simulations were used to calculate the interaction energies between these crystal faces and different solvent molecules for an attachment energy correction. Growth habits in the presence of different solvents were generated. The results showed that some crystal faces in solutions became morphologically more important than that in vacuum while others became less important. Thus, crystal shape and surface property changed a lot with the variation of crystal faces. The results from calcula- tion were in agreement with those from the re-crystallization experiment, which indicated that cyclohexanone （CH） was a promising solvent to modify the crystal morphology of RDX for obtaining products with regular shape and high purity, while butyrolactone （BL） played a great role in improving the surface electrostatic property of RDX.
基金Project supported by the National Natural Science Foundation of China(51501137)National University of Defense Technology,and Wuhan University of Technology
文摘Lanthanum magnesium hexaaluminate（LaMgAl（11）O（19）, LMA） was prepared at different temperatures by solid-state reaction. Phase compositions and crystal morphologies of specimens synthesized at different temperatures were investigated using X-ray diffraction（XRD）, scanning electron microscopy（SEM）. It was observed that the crystalline grain size of LMA was not only dependent on the preparation temperature but also on its powder morphology. In the temperature range of 1300 e1550℃, LMA showed platelet grain and the average crystalline grain size increases with the increase in temperature. At1600℃, if the powder was sintered for two times, the equiaxed grain could be found with the decrease in grain space, resulting in the reduction of the crystalline grain size. Styles of specimens（powder or disk） might have no obvious influence on morphologies and sizes of LMA crystalline grains which were synthesized with the well-dispersed raw material mixtures. The synthesis temperature played a key role in influencing the free space for the formation and growth of crystalline grains.
文摘We studied cocrystal of bis(8-quinolinolato) copper(II) (CuQ<sub>2</sub>) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), which change dramatically crystal shape in a moment by adding press on crystal face. Single crystal was prepared by dissolving CuQ<sub>2</sub> and TCNQ in chloroform by evaporation of the solution at ambient conditions. We investigated about crystal structure and morphological change properties. We proclaim that this phenomenon is solid phase transition to Form I from Form II, it is caused by pressure on the crystal face (001) of Form II and the crystal expansion direction is the side face (100). We take note of the common structure between polymorph and explain that this transition occurs by the structure like dominoes falling. We obtained a correlation between molecular level structure change and macroscopic shape changes.
基金Project supported by the National Natural Science Foundation of China(Grant No.11804305)the Natural Science Foundation of Chongqing,China(Grant No.cstc2019jcyj-msxmX0391)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission,China(Grant No.KJ201901405)the Open Project of State Key Laboratory of Superhard Materials,Jilin University,China(Grant No.201912).
文摘To elucidate the regulation mechanism of catalyst geometry structure to diamond growth,we establish three catalyst modes with different structures.The simulation results show that with the decrease of the protruding height of the catalyst,the low-temperature region gradually moves toward the center of the catalyst,which causes the distribution characteristics of the temperature and convection field in the catalyst to change.The temperature difference in vertical direction of the catalyst decreases gradually and increases in the horizontal direction,while the catalyst convection velocity has the same variation regularity in the corresponding directions.The variation of temperature difference and convection velocity lead the crystal growth rate in different crystal orientations to change,which directly affects the crystal morphology of the synthetic diamond.The simulation results are consistent with the experimental results,which shows the correctness of the theoretical rational analysis.This work is expected to be able to facilitate the understanding of catalyst structure regulation mechanism on diamond morphology and the providing of an important theoretical basis for the controllable growth of special crystal shape diamond under HPHT process.
基金Supported by the Shanghai Commission of Science and Technology(06SR07108)the OpenProject of State Key Laboratory of Chemical Engineering(08C08)
文摘The crystal morphology of zinc lactate trihydrate in the absence or presence of impurities(viz.succinic acid,L-malic acid and D-malic acid)is investigated by molecular simulation based on surface docking model and COMPASS force field.Combing simulation results with our previous experimental results,it is found that the solvent mainly has an inhibition effect on the(0 0 2)surface,and succinic acid impurity will inhibit the growth of(0 0 2)and(0 1 1)surfaces while two enantiomers of malic acid impurity will inhibit the(0 0 2)and(1 0 0)surfaces,which are in good agreement with the experimental results.
基金Funded by the Scientific and Technological Developing Scheme of Jilin Province (20100550)
文摘Cuprous oxides with different morphologies were formed on F-doped tin oxide （FTO） covered glass substrates by potentiostatic deposition of cupric acetate. The effects of CTAB and Cl- on the crystal morphologies of cuprous oxide were studied. Different crystal morphologies of cuprous oxides were obtained by the change of the concentrations of CTAB and Cl. The flowerlike and cubic morphologies of Cu2O crystals were obtained when using higher concentration of CTAB and KCl, respectively. Photoelectrochemical properties of the Cu2O thin films prepared in the system were also studied.
基金The work was financially supported by the National Natural Science Foundation of China(No.50472034),Natural Science Foundation of Hebei Province(No.E2005000048)and SpecializedResearch Fund for the Doctoral Program of Higher Education(No.20050080006).
文摘Tantalum pentoxide reacts actively with concentrated NaOH solution under hydrothermal conditions at 180 ℃. In the reaction between NaOH solution and Ta2O5, the structure and composition of the tantalates depend on the reaction time, and the structure evolution results in a remarkable change in light absorption. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-Vis) diffused reflection spectrum were used to characterize various properties of the obtained solid products. At 180 ℃, the reaction proceeds rapidly. With the increase of time, the reflection peaks of unreacted Ta2O5 in the XRD patterns becomes weaker and weaker. Pure NaTaO3 is obtained after 60 min, which is well crystallized with a uniform cubic morphology.
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.
文摘The intergranular cracking face is smooth and Iransgranular cracking fracture shows trace of cleavage. It is hard to .tirol characteristic rhombus in the dense small crystals. As measured by SEM, the particle size of microcrystalline magnesite originating in Sichuan - Tibet is uniform, most grains range in 2 -4 μm. Three-dimensional （ 3D ） crystal morphology assumes cubic or column.
文摘The research on morphology of mineral crystals in China includes classical goniometry of 100 minerals such as hsianghualite, orthobrannerite, jamesonite and bertrandite and surface microtopography of 20 minerals such as wolframite and diamond, among which 5 new minerals and 34 uranium minerals were discovered and measured by Chinese mineralogists. These have enriched mineralogy and crystal morphology and strengthened the study of information of morphological genesis.
