Effect of rutile crystal shapes on its settlement

The effect of rutile crystal shapes on its settlement in a modified slag was studied by theoretical analysis,FactSage simulation,X-ray diffraction and scanning electron microscopy.The results show that the settling velocities of spherical rutile crystals are faster than those of other shapes of rutile crystals under the same volume conditions,and the shape transformation of rutile crystals from rod to sphere can be achieved by adding titanium slag to Ti-bearing blast furnace slag.The volume fractions of the rutile crystals in the upper and lower parts of the modified slag are 30%and 71%when the added titanium slag increases to 278 g,indicating that rutile settling is obvious.Due to the rutile settling,half shaker sorting task is saved,and the recovery rate of TiO2 is significantly increased.The TiO2 content of rutile is greater than 93%,and the total content of CaO and MgO is less than 0.4%,meeting the requirements for the raw materials of titanium white in the chloride process.

Relationship between Colored Microstructure under Polarized Light and Shape Recovery Characteristics on the Thermomechanical Cycled CuAlNi Single Crystals

The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAlNi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the βphase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.

First-principles thermodynamics of metal-oxide surfaces andinterfaces:A case study review

An important step for achieving the knowledge-based design freedom on nano-and interfacial materials is attained by elucidating the related surface and interface thermodynamics from the first principles so as to allow engineering the microstructures for desired properties through smartly designing fabrication processing parameters.This is demonstrated for SnO2 nano-particle surfaces and also a technologically important Ag-SnO2 interface fabricated by in-situ internal oxidation.Based on defect thermodynamics,we first modeled and calculated the equilibrium surface and interface structures,and as well corresponding properties,as a function of the ambient temperature and oxygen partial pressure.A series of first principles energetics calculations were then performed to construct the equilibrium surface and interface phase diagrams,to describe the environment dependence of the microstructures and properties of the surfaces and interfaces during fabrication and service conditions.The use and potential application of these phase diagrams as a process design tool were suggested and discussed.

Observation and Analysis of Gypsum Particleboard using SEM

The microstructures of gypsum board and gypsum particleboard were observed by SEM. The effects of retarder and waterproof agent on the shape and the average dimension of the gypsum crystal were discussed. The mechanism was investigated as well. Four typical instances, i e, the gypsum crystal shape, the gypsum combined with particles on the particles surface, the gypsum combined with particles on the wood cross section and the gypsum combined with particles inside the wood cell cavity were selected and observed. Furthermore, the agglomeration and cementation mechanism between gypsum and particle were studied.

Deep learning-based on-line image analysis for continuous industrial crystallization processes

In situ microscopic imaging is a useful tool in monitoring crystallization processes,including crystal nucleation,growth,aggregation and breakage,as well as possible polymorphic transition.To convert the qualitative information to be quantitative for the purpose of process optimization and control,accurate analysis of crystal images is essential.However,the accuracy of image segmentation with traditional methods is largely affected by many factors,including solid concentration and image quality.In this study,the deep learning technique using mask region-based convolutional neural network(Mask R-CNN)is investigated for the analysis of on-line images from an industrial crystallizer of 10 m^(3) operated in continuous mode with high solid concentration and overlapped particles.With detailed label points for each crystal and transfer learning technique,two models trained with 70,908 and 7,709 crystals respectively are compared for the effect of training data amount.The former model effectively segments the aggregated and overlapped crystals even at high solid concentrations.Moreover,it performs much better than the latter one and traditional multi-scale method both in terms of precision and recall,revealing the importance of large number of crystals in deep learning.Some geometrical characteristics of segmented crystals are also analyzed,involving equivalent diameter,circularity,and aspect ratio.

Measurement, modelling, and closed-loop control of crystal shape distribution： Literature review and future perspectives

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.

Mechanism and inhibition of trisodium phosphate particle caking： Effect of particle shape and solubility

We investigated the influence of particle shape and solubility on the caking behavior of trisodium phosphate by considering the adhesion free energy and crystal bridge theory. Caking of trisodium phosphate during the drying process under static conditions is a two-step process： adhesion followed by crystal bridge formation between particles. The adhesion free energy plays an important role in adhesion. Trisodium phosphate particles cannot adhere to each other and cake when the adhesion free energy is greater than a critical value, which varies with particle shape. Compared with granular particles, cylindrical particles have larger contact area between particles, which results in more crystal bridges forming and a higher caking ratio. Thus, the critical value is about 100 mJ/m^2 for cylindrical particles, but 60 mJ/m^2 for granular particles at 25 ℃. Concerning the solubility, when particles are similar shapes and soluble in the rinsing liquid, the caking ratio has a linear relationship with adhesion free energy. However, if the particles are insoluble in the rinsing liquid, caking can be completely prevented regardless of adhesion free energy because no crystal bridges form during the growth process. Hence, caking of trisodium phosphate particles could be inhibited by screening rinsing liquids, and optimizing the particle shape and size distribution.

Tadpole-shaped Au nano-particles fabricated by laser fragmentation of Au nano-spheres in liquid

Tadpole-shaped Au nano-particles with controllable tails are successfully fabricated by simply using laser fragmentation of separated Au nano-spheres in liquid. The optimum laser power densities（1.5–3 GW∕cm-2） can enable part of the individual Au nano-sphere to be re-melted, released, and ultra-rapidly recondensed/crystallized on the outside of the original region. We find that the length of the tail in a tadpole-shaped Au nano-particle significantly increases from about 10 to 25 nm by increasing the laser power density. Benefiting from the unique structural features, the localized surface plasmon resonance（LSPR） absorption spectra of the tadpole-shaped Au nano-particles become broader by increasing the tail length. Moreover, the LSPR absorption band also exhibits a noticeable red shift from about 520 to 650 nm. Our results provide a convenient and valuable strategy to fabricated novel anisotropic-shaped nano-structures with fascinating properties.

Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering. If we look at crystallization at the atomic level, crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice. Diffusion can be a rate determining step for the growth of crystals. In this paper, we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced. The diffusion effect is studied in a specially designed three-cell reactor. Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concen- tration gradient in the reaction cell, thus promoting the formation of cubic calcite particles. The reaction rate is regulated by temperature. Increase of reaction rate favors the formation of needle-like aragonite particles. When diffusion and reaction play joint roles in the reaction system, their compromise dominates the formation of products, leading to a mixture of cubic and needle-like particles with a controllable ratio. Since diffusion and reaction are universal factors in the preparation of materials, the finding of this paper could be helpful in the controlled synthesis of other materials.

Modes of Grain Selection in Spiral Selector during Directional Solidification of Nickel-base Superalloys

The modes of grain selection in spiral selector were investigated by both a ProCAST simulation and experimental confirmation.The results show that the efficiency of grain selection in starter block is associated with the geometry shape.At the early stage of grain selection,the optimization of grain orientation is dominated by competitive grain growth,but the optimization of grain orientation in starter block is gradually dominated by geometry shape at the later stage of grain selection.Besides,the spiral part could also optimize the orientation of the selected single crystal when the initial angle is large enough,and the single crystal selection in spiral parts with different pitch lengths and initial angles is dominated by different modes.The simulation results agree well with experimental ones.

Spatial beam shaping by quartz crystal piano-convex lens

Based on the optical activity of quartz crystal, we proposed a scheme for shaping the spatial intensity distribution of a linearly polarized laser beam by utilizing a quartz crystal piano-convex lens in combination with a polarizer. The intensity profile of the shaped laser beam can be easily switched from one profile to another by controlling the polarization direction of the incident laser beam.