The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace（BF） slag was studied using confocal scanning laser microscopy（CSLM）. Results showed that perovskite was the primary ...The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace（BF） slag was studied using confocal scanning laser microscopy（CSLM）. Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O^2-, when Ti2O3 was involved in the formation of perovskite.展开更多
Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was de...Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was deve- loped. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size.展开更多
In this paper, the saturated solution crystallization method is proposed to promote the formation of hydrate by means of the known similarities between the hydrate formation process and the crystallization process. In...In this paper, the saturated solution crystallization method is proposed to promote the formation of hydrate by means of the known similarities between the hydrate formation process and the crystallization process. In this method,adding the second phase crystals was used to replace the spontaneous formation of hydrate crystal nuclei to form hydrate.The effects of saturated Na_2SO_4, MgSO_4, NH_4HCO_3 and CuSO_4 solutions on the formation rates of natural gas hydrate and gas storage capacity were investigated. The results showed that the saturated solution had an influence on the hydrate formation process. Under the given experimental conditions, the saturated Na_2SO_4 solution showed a highest increase in the hydrate formation rate, and the average hydrate formation rate in its presence was 11.8 times higher than that obtained in the deionized water. Moreover, the largest formation rate of gas hydrates observed in the saturated Na_2SO_4 solution was 386 times bigger than that in the deionized water, and the gas storage capacity increased by 10 times. In addition, the average hydrate formation rate in the saturated Mg SO_4 solution was faster than that in water by 20 times. The largest formation rate of gas hydrates in the saturated MgSO_4 solution was 165 times faster than that obtained in the deionized water, and the gas storage capacity increased by 6.2 times. The saturated NH_4HCO_3 and saturated CuSO_4 solutions also influenced the formation process of hydrate. Therefore, the crystallization method of saturated solution can be used to achieve a highefficiency preparation of natural gas hydrates, which provides theoretical guidance for the storage of natural gas in the form of hydrate.展开更多
The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pil...The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pilot batch reactor. This article presents a method for the determination of nucleation and crystal growth rates of calcium carbonate by following two macroscopic parameters: the mass production rate by precipitation and the specific surface area. The results give a constant nucleation rate around 4 × 1015m-3 ·s-1 and a decreasing crystal growth rate between 0.2 and 2 × 10-10 m·s-1. It also provides the main characteristics of the monoparticle size distributions (i.e. the mean particle sizes and in situ coefficient of variation) in the agglomerates, which cannot be obtained by other known methods. For the carbonation carried out in this work, the mean mass particle size at the end of the reaction is about 300 nm and the coefficient of variation of 0.28 indicates a narrow particle size distribution of the monoparticles.展开更多
A mathematical expression of the crystal growth rate during crystallization of the amorphous alloys was derived from the micromechanism of crystallization newly developed by the authors. Thus, the satisfactory explana...A mathematical expression of the crystal growth rate during crystallization of the amorphous alloys was derived from the micromechanism of crystallization newly developed by the authors. Thus, the satisfactory explanation of the experimental results obtained by Nunogaki et al., Heimendahl et al. and the authors might be found. It seems also to be modelled with the expression for the crystal growth and the crystal size influenced by time during the crystallization of amorphous Ni-P alloy foil at in situ heating. Based on the expression, the factors influencing the crystal growth rate, such as temperature, time and microstructure of amorphous alloys have been discussed.展开更多
In order to study the effect of the withdrawing rate on carbide morphology,MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s.The carb...In order to study the effect of the withdrawing rate on carbide morphology,MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s.The carbide morphologies were investigated by scanning electron microscopy(SEM),and the electron probe microanalysis(EPMA) was used to characterize the carbide composition.The results indicate that the solidification rate is the important factor governing MC carbide growth morphology,size and distribution,composition and growth mechanism.With the increase of withdrawing rate,nodular,rod-like,Chinese script types of carbide morphology are observed.For the low withdrawing rate,with the increase of withdrawing rate,the carbide size becomes larger.For the case of dendritic interface,the carbide size becomes smaller with refinement of dendrites as withdrawing rate increases.The volume fraction of carbides increases with the withdrawing rate increasing.展开更多
Numerical models of trajectories of small aerosol spheres relative to oblate spheroids were used to determine ice crystal scavenging efficiencies. The models included the effects of aerodynamic flow about the ice part...Numerical models of trajectories of small aerosol spheres relative to oblate spheroids were used to determine ice crystal scavenging efficiencies. The models included the effects of aerodynamic flow about the ice particle, gravity, aerosol particle inertia and drag and electrostatic effects. Two electric configurations of the ice particle were investigated in detail. The first applied a net charge to the ice particle, of magnitude equal to the mean thunderstorm charge distribution, while the second applied a charge distribution, with no net charge, to the ice particle to model the electric multipole charge distribution. The results show that growing ice crystals with electric multipoles are better scavengers than single ice crystals with net thunderstorm charges, especially in the Greenfield gap (0.1 to 1.0 um), and that larger single crystals are better scavengers than smaller single crystals. The results also show that the low density ice crystals are more effective scavengers with net charges than they are with charge distribution.展开更多
A theoretical model is developed using statistical rate theory to determine the rate of molecular transport across the interface of a growing spherical zeolite crystal. The model is expressed in terms of the interface...A theoretical model is developed using statistical rate theory to determine the rate of molecular transport across the interface of a growing spherical zeolite crystal. The model is expressed in terms of the interface concentration. Two model constants appear in the expression for the equilibrium exchange rate. In order to validate the model, zeolite crystallization is investigated for a system for which experimental data exist. The model constants were first established using the measured growth rates at a specific temperature. Then the model was used to predict the growth rate at other temperatures.展开更多
We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light s...We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.展开更多
The compressive and tensile strain rate sensitivities of polycrystalline and single crystal NiAl have been evaluated at 877 ℃ which is well above DBTT. Samples were prepared to specific sizes by hot press consolidati...The compressive and tensile strain rate sensitivities of polycrystalline and single crystal NiAl have been evaluated at 877 ℃ which is well above DBTT. Samples were prepared to specific sizes by hot press consolidation of appropriate powder sizes and minimizing past consolidation thermal exposures. NiAl single crystals were grown in the [100]orientation using a modified Bridgeman technique. The yield and tensile strength of polycrystalline NiAl as a function of grain size generally follows a Hall-Petch type relationship . A tensile strain rate effect was found at strain rate of 1 to 10-4 sec-1. The strain rate sensitivity coefficient, m,in the equation of σ = Kε is in the range of 0. 10 to 0. 13. The highest strain rate (1 sec-1) resulted in significantly higher strengths and little or no observed ductility. Compressive strain rate testing al strain rate of 10-5to 10-2 sec-1 and at temperature of 1050°to 1250°K was conducted both for polycrystalline and for single crystal NiAl. The calculated stress exponents and the activation energy for creep were compared with the reference data.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51090383)the Fundamental Research Funds for the Central Universities of China(No.CDJZR12130049)
文摘The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace（BF） slag was studied using confocal scanning laser microscopy（CSLM）. Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O^2-, when Ti2O3 was involved in the formation of perovskite.
文摘Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was deve- loped. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size.
基金the Program for Liaoning Excellent Talents in University (LJQ2014038)the Natural Science Foundation of Liaoning Province (201602470)
文摘In this paper, the saturated solution crystallization method is proposed to promote the formation of hydrate by means of the known similarities between the hydrate formation process and the crystallization process. In this method,adding the second phase crystals was used to replace the spontaneous formation of hydrate crystal nuclei to form hydrate.The effects of saturated Na_2SO_4, MgSO_4, NH_4HCO_3 and CuSO_4 solutions on the formation rates of natural gas hydrate and gas storage capacity were investigated. The results showed that the saturated solution had an influence on the hydrate formation process. Under the given experimental conditions, the saturated Na_2SO_4 solution showed a highest increase in the hydrate formation rate, and the average hydrate formation rate in its presence was 11.8 times higher than that obtained in the deionized water. Moreover, the largest formation rate of gas hydrates observed in the saturated Na_2SO_4 solution was 386 times bigger than that in the deionized water, and the gas storage capacity increased by 10 times. In addition, the average hydrate formation rate in the saturated Mg SO_4 solution was faster than that in water by 20 times. The largest formation rate of gas hydrates in the saturated MgSO_4 solution was 165 times faster than that obtained in the deionized water, and the gas storage capacity increased by 6.2 times. The saturated NH_4HCO_3 and saturated CuSO_4 solutions also influenced the formation process of hydrate. Therefore, the crystallization method of saturated solution can be used to achieve a highefficiency preparation of natural gas hydrates, which provides theoretical guidance for the storage of natural gas in the form of hydrate.
文摘The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pilot batch reactor. This article presents a method for the determination of nucleation and crystal growth rates of calcium carbonate by following two macroscopic parameters: the mass production rate by precipitation and the specific surface area. The results give a constant nucleation rate around 4 × 1015m-3 ·s-1 and a decreasing crystal growth rate between 0.2 and 2 × 10-10 m·s-1. It also provides the main characteristics of the monoparticle size distributions (i.e. the mean particle sizes and in situ coefficient of variation) in the agglomerates, which cannot be obtained by other known methods. For the carbonation carried out in this work, the mean mass particle size at the end of the reaction is about 300 nm and the coefficient of variation of 0.28 indicates a narrow particle size distribution of the monoparticles.
文摘A mathematical expression of the crystal growth rate during crystallization of the amorphous alloys was derived from the micromechanism of crystallization newly developed by the authors. Thus, the satisfactory explanation of the experimental results obtained by Nunogaki et al., Heimendahl et al. and the authors might be found. It seems also to be modelled with the expression for the crystal growth and the crystal size influenced by time during the crystallization of amorphous Ni-P alloy foil at in situ heating. Based on the expression, the factors influencing the crystal growth rate, such as temperature, time and microstructure of amorphous alloys have been discussed.
基金Projects(50771081, 50931004) supported by the National Natural Science Foundation of ChinaProject(2010CB631202) supported by the National Basic Research Program of China
文摘In order to study the effect of the withdrawing rate on carbide morphology,MC-type carbide in single crystal superalloy AM3 was systematically investigated with sample growth rates from 3.5 μm/s to 500 μm/s.The carbide morphologies were investigated by scanning electron microscopy(SEM),and the electron probe microanalysis(EPMA) was used to characterize the carbide composition.The results indicate that the solidification rate is the important factor governing MC carbide growth morphology,size and distribution,composition and growth mechanism.With the increase of withdrawing rate,nodular,rod-like,Chinese script types of carbide morphology are observed.For the low withdrawing rate,with the increase of withdrawing rate,the carbide size becomes larger.For the case of dendritic interface,the carbide size becomes smaller with refinement of dendrites as withdrawing rate increases.The volume fraction of carbides increases with the withdrawing rate increasing.
文摘Numerical models of trajectories of small aerosol spheres relative to oblate spheroids were used to determine ice crystal scavenging efficiencies. The models included the effects of aerodynamic flow about the ice particle, gravity, aerosol particle inertia and drag and electrostatic effects. Two electric configurations of the ice particle were investigated in detail. The first applied a net charge to the ice particle, of magnitude equal to the mean thunderstorm charge distribution, while the second applied a charge distribution, with no net charge, to the ice particle to model the electric multipole charge distribution. The results show that growing ice crystals with electric multipoles are better scavengers than single ice crystals with net thunderstorm charges, especially in the Greenfield gap (0.1 to 1.0 um), and that larger single crystals are better scavengers than smaller single crystals. The results also show that the low density ice crystals are more effective scavengers with net charges than they are with charge distribution.
文摘A theoretical model is developed using statistical rate theory to determine the rate of molecular transport across the interface of a growing spherical zeolite crystal. The model is expressed in terms of the interface concentration. Two model constants appear in the expression for the equilibrium exchange rate. In order to validate the model, zeolite crystallization is investigated for a system for which experimental data exist. The model constants were first established using the measured growth rates at a specific temperature. Then the model was used to predict the growth rate at other temperatures.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10674051 and 10811120010)the Program for Innovative Research Team of the Higher Education of Guangdong, China (Grant No 06CXTD005)
文摘We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.
文摘The compressive and tensile strain rate sensitivities of polycrystalline and single crystal NiAl have been evaluated at 877 ℃ which is well above DBTT. Samples were prepared to specific sizes by hot press consolidation of appropriate powder sizes and minimizing past consolidation thermal exposures. NiAl single crystals were grown in the [100]orientation using a modified Bridgeman technique. The yield and tensile strength of polycrystalline NiAl as a function of grain size generally follows a Hall-Petch type relationship . A tensile strain rate effect was found at strain rate of 1 to 10-4 sec-1. The strain rate sensitivity coefficient, m,in the equation of σ = Kε is in the range of 0. 10 to 0. 13. The highest strain rate (1 sec-1) resulted in significantly higher strengths and little or no observed ductility. Compressive strain rate testing al strain rate of 10-5to 10-2 sec-1 and at temperature of 1050°to 1250°K was conducted both for polycrystalline and for single crystal NiAl. The calculated stress exponents and the activation energy for creep were compared with the reference data.
