Porosity Distribution Simulation and Impure Inclusion Analysis of Porous Crystal Layer Formed via Polythermal Process

In this work, we investigated the porosity distribution and separation property of the porous crystal layer formed via the polythermal process. The proposed porosity distribution model, considering both the cooling profile and the crystal settling effect, provided simulative results that met the MRI analysis experimental results with suitable agreement. Significant porosity variation from the top to the bottom of the crystal layer (ϕ from 0.75 to 0.55 under rapid cooling profile) was detected. Meanwhile, the vertical supersaturation degree gradient induced by the fluid fluctuation could impact nucleation and crystal growth kinetic along with crystal particle settling. The resulting crystal layer possessed various impurity inclusion conditions. Under a moderate cooling profile (0.4 K·min−1), the volume fraction of closed pores against overall pores decreased from 0.75 to 0.36. The proposed model and experimental analysis approach were demonstrated to be helpful for porosity distribution simulation and impure inclusion analysis of layer crystallization.

A digital workflow from crystallographic structure to single crystal particle attributes for predicting the formulation properties of terbutaline sulfate

A detailed inter-molecular (synthonic) analysis of terbutaline sulfate, an ionic addition salt for inhalation drug formulation, is related to its crystal morphology, the surface chemistry of the habit faces and hence to its crystal surface energy.

Toward Understanding of the Effect of Nucleation Temperature on Porous Structure of Micro-Mesoporous Composite Molecular Sieves and Related Crystallization Mechanism

Although micro-mesoporous composite molecular sieves have received significant attention due to their desirable properties, they still lack systematic studies on their crystallization process to achieve controllable synthesis of composite molecular sieves. In this study, a series of Y/SBA-15 micro-mesoporous composite molecular sieves with different porous structures were synthesized by tuning nucleation temperature, based on epitaxial growth on the outer surface of the Y-type crystal particle. All composite molecular sieves were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Moreover, the effect of nucleation temperature on the structure of composite molecular sieves was investigated, while the crystallization mechanism was also explored. Furthermore, the performance of the molecular sieves on isomerization of n-pentane was investigated, the results suggested that the isomerization selectivity was positively correlated with regularity degree of the mesoporous porous structure, where the highest isomerization reached 95.81%. This work suggests that nucleation temperature plays a key role in structures of micro-mesoporous composite molecular sieves, providing a solid basis for the further development of functional composite molecular sieves.

Preparation and spectroscopic study of a water-soluble NaYF4:Yb3+/Er3+@NaGdF4 crystal particle and its application in bioimaging

Water-soluble, magnetic and up-conversion luminescent NaYF4:Yb3+/Er3+@NaGdF4 core–shell particles were prepared directly by the hydrothermal method.

Effect of Crystal Modifiers and Dispersants on Paraffin-Wax Particles in Petroleum Fluids

Summary Petroleum fluids from shale light-oil and gas/condensate reservoirs generally have a high content of normal paraffins. Paraffin-wax deposition is among the challenges in shale gas and oil production and in offshore flow assurance. Low-dosage chemical additives can be effective in paraffin-wax mitigation because of their high efficiency and economics. These additives are divided into broad categories of crystal modifiers and dispersants with vastly different molecular structures and mechanisms in wax-crystal-particle stabilization and wetting. This investigation focuses on the understanding of the differences in the aggregate size and morphology of chemical additives, and it centers on (1) wax-particle sedimentation from diluted petroleum fluids in vial tests, (2) wax-crystal-particle-size distributions and morphology by dynamic light scattering (DLS) and polarized-light microscopy, and (3) the wetting state from the effect of water. In two of the three petroleum-fluid samples used in this work, there is no visible precipitation at the bottom of the vials at temperatures below the wax-appearance temperature (WAT). The microscopic image of fluids along the length of the tube shows that the wax-particle size and intensity increase from top to bottom. To observe precipitation, we dilute the crude with a hydrocarbon such as n-heptane. The sedimentation of wax is then observed. The petroleum fluids used in this work have very low asphaltene content, and there is no complication from asphaltene precipitation. Our study shows that a small amount of crystal modifier and dispersant can reduce crystal-particle size to the submicron scale, and change the crystal morphology. We investigate the differences in the mechanisms of dispersants and crystal modifiers in bulk. Water, which is often coproduced with petroleum fluids, can increase the effectiveness of dispersants significantly by altering the wetting state of the wax-particle surface. Such enhancement is not found in crystal modifiers. Both additives affect the rheology of petroleum fluids.

Preliminary study on the growth mechanism of zircon whiskers prepared via non-hydrolytic sol-gel method combined with carbon black as reducing agent

Zircon whiskers were prepared at 700?C via non-hydrolytic sol-gel method combined with carbon black as reducing agent, Si(OC2H5)4 (TEOS) and ZrCl4 as precursors and LiF as mineralizer. The whiskers were characterized and their growth mechanism was discussed. The results show that the introduction of carbon black is beneficial for the preferential axial growth of zircon crystals into whiskers. The diameter and aspect ratio of zircon whiskers are 30-40 nm and 6-15, respectively. The zircon whiskers grow along the [001] direction, which is c-axis oriented. The growth mechanism is revealed to be the screw dislocation mechanism with the mass transport mainly from the zircon crystal particle matrix.