A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys...A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.展开更多
In the present investigation, the microstructures and growth morphology of Mg32（Al,Zn）49 Frank-Kasper phase in rapidly solidified Mg32Al17Zn32 temary alloys were studied in detail. The samples were characterised by ...In the present investigation, the microstructures and growth morphology of Mg32（Al,Zn）49 Frank-Kasper phase in rapidly solidified Mg32Al17Zn32 temary alloys were studied in detail. The samples were characterised by X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, field-emission scanning electron microscopy （FE-SEM） and energy dispersive spectrum （EDS）. The results show that the microstructures mainly consist of Mg3e（Al,Zn）49 Frank-Kasper phase and interdendritic Mg-rich O-phase. Under rapid solidification condition, Mg32（Al,Zn）49 Frank-Kasper phase reveals a perfect faceted dendritic characteristic in the shape of a three-fold symmetric microstructure with doublet tips in the axes direction. Observations for fracture surfaces show that the growth morphology of Mg32（Al,Zn）49 grains was truncated cubic, and its growth mechanism was also discussed.展开更多
Crystal shape distribution, i.e. the multidimensional size distribution of crystals, is of great importance to their down-stream processing such as in filtration as well as to the end-use properties including the diss...Crystal shape distribution, i.e. the multidimensional size distribution of crystals, is of great importance to their down-stream processing such as in filtration as well as to the end-use properties including the dissolution rate and bioavailability for crystalline pharmaceuticals. Engineering crystal shape and shape distribution requires knowledge about the growth behavior of different crystal facets under varied operational conditions e.g. supersaturations. Measurement of the facet growth rates and growth kinetics of static crystals in a crystallizer without stirring has been reported previously. Here attention is given to study on real-time characterization of the 3D facet growth behavior of crystals in a stirred tank where crystals are constantly moving and rotating. The measurement technique is stereo imaging and the crystal shape reconstruction is based on a stereo imaging camera model. By reference to a case study on potash alum crystallization, it is demonstrated that the crystal size and shape distributions (CSSD) of moving and rotating potash alum crystals in the solution can be reconstructed. The moving window approach was used to correlate 3D face growth kinetics with supersaturation (in the range 0.04 - 0.12) given by an ATR FTIR probe. It revealed that {100} is the fastest growing face, leading to a rapid reduction of its area, while the {111} face has the slowest growth rate, reflected in its area continuously getting larger.展开更多
Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too ...Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2001800)the National Natural Science Foundation of China(Grant No.21978298)+2 种基金the Natural Science Foundation of Shaanxi Province in China(Grant No.2020JM-111)Applied Basic Research Key Project of Yunnan,China(Grant No.202002AB080001-1)Henan Youth Talent Promotion Project.China(Grant No.2020HYTP019)。
文摘A regularization of the surface tension anisotropic function used in vapor-liquid-solid nanowire growth was introduced into the quantitative phase-field model to simulate the faceted growth in solidification of alloys.Predicted results show that the value of δ can only affect the region near the tip,and the convergence with respect to δ can be achieved with the decrease of δ near the tip.It can be found that the steady growth velocity is not a mo no tonic function of the cusp amplitude,and the maximum value is approximately at ε=0.8 when the supersaturation is fixed.Moreover,the growth velocity is an increasing function of supersaturation with the morphological transition from facet to dendrite.
基金the National Natural Science Foundation of China (No. 50571081)the Aeronautical Science Foundation of China (No. 04G53042) for their financial support
文摘In the present investigation, the microstructures and growth morphology of Mg32（Al,Zn）49 Frank-Kasper phase in rapidly solidified Mg32Al17Zn32 temary alloys were studied in detail. The samples were characterised by X-ray diffraction analysis （XRD）, scanning electron microscopy （SEM）, field-emission scanning electron microscopy （FE-SEM） and energy dispersive spectrum （EDS）. The results show that the microstructures mainly consist of Mg3e（Al,Zn）49 Frank-Kasper phase and interdendritic Mg-rich O-phase. Under rapid solidification condition, Mg32（Al,Zn）49 Frank-Kasper phase reveals a perfect faceted dendritic characteristic in the shape of a three-fold symmetric microstructure with doublet tips in the axes direction. Observations for fracture surfaces show that the growth morphology of Mg32（Al,Zn）49 grains was truncated cubic, and its growth mechanism was also discussed.
文摘Crystal shape distribution, i.e. the multidimensional size distribution of crystals, is of great importance to their down-stream processing such as in filtration as well as to the end-use properties including the dissolution rate and bioavailability for crystalline pharmaceuticals. Engineering crystal shape and shape distribution requires knowledge about the growth behavior of different crystal facets under varied operational conditions e.g. supersaturations. Measurement of the facet growth rates and growth kinetics of static crystals in a crystallizer without stirring has been reported previously. Here attention is given to study on real-time characterization of the 3D facet growth behavior of crystals in a stirred tank where crystals are constantly moving and rotating. The measurement technique is stereo imaging and the crystal shape reconstruction is based on a stereo imaging camera model. By reference to a case study on potash alum crystallization, it is demonstrated that the crystal size and shape distributions (CSSD) of moving and rotating potash alum crystals in the solution can be reconstructed. The moving window approach was used to correlate 3D face growth kinetics with supersaturation (in the range 0.04 - 0.12) given by an ATR FTIR probe. It revealed that {100} is the fastest growing face, leading to a rapid reduction of its area, while the {111} face has the slowest growth rate, reflected in its area continuously getting larger.
基金Financial support from the following projects and organisa- tions are acknowledged： the China One Thousand Talent Scheme, the National Natural Science Foundation of China （NNSFC） under its Major Research Scheme of Meso-scale Mechanism and Control in Multi-phase Reaction Processes （project reference： 91434126）, the Natural Science Foundation of Guangdong Province （project reference： 2014A030313228）, the UK Engineering and Physical Sciences Research Council （EPSRC） for the projects of Shape （EP/C009541） and StereoVision （EP/E045707）, and the Technology Strategy Board （TSB） for the project of High Value Manufacturing CGM （TP/BD059E）.
文摘Crystal morphology is known to be of great importance to the end-use properties of crystal products, and to affect down-stream processing such as filtration and drying. However, it has been previously regarded as too challenging to achieve automatic closed-loop control. Previous work has focused on controlling the crystal size distribution, where the size of a crystal is often defined as the diameter of a sphere that has the same volume as the crystal. This paper reviews the new advances in morphological population balance models for modelling and simulating the crystal shape distribution （CShD）, measuring and estimating crystal facet growth kinetics, and two- and three-dimensional imaging for on-line characterisation of the crystal morphology and CShD. A framework is presented that integrates the various components to achieve the ultimate objective of model-based closed-loop control of the CShD. The knowledge gaps and challenges that require further research are also identified.
