NaxScF3+x nanocrystals with controllable shapes were synthesized in the oleic acid/1-octadecene (OA/OD) coprecipitation reaction system. By adjusting the volume ratio of the solvents, well-defined NaxScF3+x nanopolyhedrons, nanoplates, nanorods, and nanospheres with different sizes and phases could be selectively obtained. The as-prepared NaxScF3+x nanocrystals were well characterized and investigated. Based on the results obtained, it was found that the solvents influenced significantly the growth process of the NaxScF3+x nanocrystals. A change in the nucleus formation rate and the responsible crystal planes leads to different morphologies of the resulting nanocrystals. Further investigation on the upconversion (UC) luminescence of the Yb/Er codoped NaxScF3+x nanocrystals showed that NaxScF3+x nanostructures could serve as host matrices to give strong UC luminescence. In addition, their different phases and morphologies were responsible for the diverse luminescence intensity.

Novel roughness-controlled mannitol/LB Agar microparticles were synthesized by polymorphic transformation and self-assembly method using hexane as the polymorphic transformation reagent and spray-dried mannitol/LB Agar microparticles as the starting material. As-prepared microparticles were characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction spectra (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Andersen Cascade Impactor (ACI). The XRD and DSC results indicate that after immersing spray-dried mannitol/LB Agar microparticles in hexane, β-mannitol was completely transformed to α-mannitol in 1 h, and all the δ-mannitol was transformed to α form after 14 days. SEM shows that during the transformation the nanobelts on the spray-dried mannitol/LB Agar microparticles become more dispersed and the contour of the individual nanobelts becomes more noticeable. Afterward, the nanobelts self-assemble to nanorods and result in rod-covered mannitol/LB Agar microparticles. FTIR indicates new hydrogen bonds were formed among mannitol, LB Agar, and hexane. SEM images coupled with image analysis software reveal that different surface morphology of the microparticles have different drug adhesion mechanisms. Comparison of ACI results and image analysis of SEM images shows that an increase in the particle surface roughness can increase the fine particle fractions (FPFs) using the rod-covered mannitol microparticles as drug carriers. Transformed microparticles show higher FPFs than commercially available lactose carriers. An FPF of 28.6 ± 2.4% was achieved by microparticles transformed from spray-dried microparticles using 2% mannitol(w/v)/LB Agar as feed solution. It is comparable to the highest FPF reported in the literature using lactose and spray-dried mannitol as carriers.

Surface modification of pollen-shape hydroxyapatite (HA) carriers is achieved using surface etching technique. Characterization of HA carriers before and after etching are performed by scanning electron microscopy (SEM), Carr’s compressibility index (CI), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Four surface etching temperatures are tested but only the particles etched at 40 and 50 °C are found satisfactory. Proper surface etching allows a reduction of the petal-like structure on the particle surface and improves the crystallinity of the particles. While the reduction of petal-like structure decreases the emitted dose (ED) of the drug particles, an increase in fine particle fraction (FPF) can be attained owing to the improvement in drug liberation. An increase in the air flow rate, however, decreases the significance of particle surface morphology and the difference in FPF among the use of different carrier particles diminishes. Surface etching technique is found to have good potential as an economical process to improve dry powder inhalation efficiency through surface modification.

Carbon dioxide reforming of methane to synthesis gas was studied over Ni/ZrO2–SiO2 catalyst under different pretreatment atmospheres. Characterization using powder X-ray diffraction, H2 temperature-programmed reduction, H2 temperature-programmed hydrogenation, TG/DTA, XPS, Raman spectra and transmission electron microscopy techniques revealed that gas atmospheres employed in the catalyst pretreatment have a significant influence on the catalytic performance. The helium-pretreated catalyst was found to be the most suitable catalyst for this application, showing the improved catalytic performance. More specifically, helium pretreatment facilitated the generation of well-distributed active metal sites while the heterogeneity of Ni components upon H2 pretreatment degraded catalytic activity of metal sites considerably. Pretreatment under CO atmosphere resulted in the formation of carbon encapsulated metal species thus causing catalyst deactivation severely. Inefficient reduction under CH4 activation and the presence of a great amount of carbonaceous species, disfavor the production of synthesis gas during the dry reforming.Graphical abstractThe influence of various pretreatment gas atmospheres on catalytic properties was investigated over ZrO2–SiO2 supported Ni catalyst for CO2 reforming of CH4. The sequence of final catalytic activity is as follows: He-pretreated > H2 pretreated > CH4 pretreated > CO pretreated. Highlights► Ni/ZiO2–SiO2 is an effect catalyst for CO2 dry reforming of methane. ► Various reduction atmospheres result in different catalytic properties. ► Helium is the best to hinder metal sintering and carbon deposition. ► CO atmosphere results in encapsulating carbon and Ni agglomeration. ► Inefficient reduction under CH4 was observed for Ni nanoparticles.

Submerged gas injection into liquids is a widely applied processing technique. The main objective of the current study was to determine the effects of orifice angle and orifice surface roughness on the bubbling-to-jetting regime transition in a bubble column. The bubbling behaviors at single-orifice distributors were investigated over a wide range of orifice gas velocities. The pressure fluctuations in the plenum and high-speed image sequence of the bubble emerging process at the orifice were recorded in experiments. Both orifice angle and orifice surface roughness were found to have significant effects on the regime-transition velocity between the bubbling and jetting regimes. Models were also developed by incorporating those available in the literature with the experimental results obtained in the current study.

Liquid weeping at the orifices of a gas distributor plate is one problem commonly encountered in bubble column operations. The effect of orifice surface roughness on the liquid weeping phenomenon in a bubble column is investigated over a superficial orifice gas velocity range of 143−703 cm/s. High-speed images of the bubbling and liquid weeping process are analyzed using a computer-aided image analysis algorithm. Pressure fluctuation in the plenum is also monitored. The liquid weeping rate is found to decrease with an increase in orifice surface roughness at low superficial orifice gas velocities while it increases with an increase in surface roughness at high superficial orifice gas velocities. Analysis indicates that the orifice surface roughness affects liquid weeping indirectly by changing the bubbling behaviors at the orifice. At low superficial orifice gas velocities, an increase in orifice surface roughness reduces the bubble size at bubble detachment. The reduction in pressure fluctuation in the plenum thus decreases the liquid weeping rate. On the other hand, as the superficial orifice gas velocity is approaching the bubbling/jetting regime transition, an increase in orifice surface roughness increases the transition velocity and hence the liquid weeping rate increases. Nonetheless, a modification of the orifice surface roughness is a viable solution to the liquid weeping problem in industrial bubble columns.

The direct imaging technique has been a common technique for size distribution measurement in multiphase systems. A statistical reconstruction method was developed in a previous study to determine the actual size distribution from image size measurements. The method accounts for the change in magnification scale within the depth-of-field (DOF) of the imaging device. It is anticipated that the DOF will reduce at high object concentrations. Since accurate DOF information is necessary for the application of the reconstruction method, the effect of object concentration on the DOF is examined in this study. A DOF model is developed to predict the DOF under various object concentrations. The applicability of the DOF model in the statistical reconstruction method is verified experimentally. A theoretical analysis is also performed to discuss the effect of having objects whose image sizes are larger than the maximum viewable limit of the imaging device.

The wall effect on the settling of cylindrical particles in the inertial regime is revisited. This study covers particle Reynolds number from 600 to 16 100 and particle-length-to-diameter ratios (l/d) from 4 to 21. The wall factor (Ut/Ut,∞) is found to decrease initially as the particle-to-column diameter ratio (d/D) increases. When the wall effect becomes significant, Ut/Ut,∞ starts to increase with an increase in d/D due to a change of the particle orientation during settling. After Ut/Ut,∞ reaches a maximum, it decreases to 0 when d/D increases to 1. A semiempirical model is developed to predict the wall effect of settling of cylindrical particles over the whole range of d/D. The model shows good prediction to the experimental results and matches the wall factor models developed for spherical particles when l/d approaches 1.

Understanding the phenomenon of liquid weeping requires knowledge of the bubbling and weeping cycle. Hence, an image analysis algorithm is developed and subsequently coupled with high-speed imaging techniques to examine the different stages in the bubbling and weeping cycle automatically. The bubbling and weeping cycle is studied under various operating conditions, using the developed algorithm, coupled with high-speed imaging techniques and the pressure fluctuation measurement. The effect of orifice angle (where the orifice angle is a measure of the orifice taperness) on the liquid weeping rate is evaluated over a range of superficial orifice gas velocities and justified with the aid of the developed algorithm, coupled with high-speed imaging techniques. A gas distributor plate with negative angle orifices is recommended for improved operation of industrial bubble column reactors over the range of superficial orifice gas velocities considered in this study, because it substantially decreases the liquid weeping rate.

Pollen-shape (spiked sphere) hydroxyapatite (HA) particles for drug carrier application are studied. The particle shape and size effect on flow characteristics and deposition are assessed. The pollen-shape HA particles are synthesized to have comparable size as typical carrier particles with mean diameter of 30–50 μm and effective density less than 0.3 g/cm3. The flow behaviors of HA and commonly used lactose (LA) carrier particles are characterized by the Carr's compressibility index (CI). The HA particles have lower CI than the LA particles for the same size range. The flow fields of HA and LA carrier particles are measured in an idealized inhalation path model using particle image velocimetry (PIV) technique. The particle streamlines indicate that a large portion of particles may deposit at the bending section due to inertial impaction and gravitational deposition. The flow field result shows that HA particles give smaller separation regions than the LA particles for the same size range. The pollen-shape HA particles are found to be able to follow the gas flow in the model and minimize undesired deposition. Deposition result confirms the bending section to have the most deposition. Deposition is found to be a function of particle properties. An empirical correlation is derived for the deposition efficiency of the pollen-shape particles as a function of particles Stokes number.

Direct imaging is a technique commonly used in the study of particle, bubble, and droplet size distribution in a dynamic system. Objects such as particles, bubbles, and droplets can be present at various distances from the imaging device when images are captured. Hence, the location of the object will need to be known in order to determine the actual size of an individual object. However, the location of the object cannot be determined from a single image. A single calibration scale defined at the focusing plane is normally used for the determination of all the object sizes from images. When the focus is close to the imaging device, the change in magnification with location is large. The size distribution obtained from the use of a single calibration scale would thus give a considerable deviation from the actual size distribution. In this study, a statistical method is proposed to reconstruct the actual object size distribution from the experimental object size distribution obtained from images using a single calibration scale defined at the focusing plane. Experiments are performed to validate the accuracy of the proposed method on the particle size distribution determination in a settling system. The stability of the proposed method is also analyzed theoretically for imaging devices with different depth-of-field (DOF), focusing location, and change in magnification with distance.

In this study, the drug delivery performance of pollen-shape hydroxyapatite (HA) carriers is assessed and compared with conventional lactose (LA) carriers. Budesonide (Bd) is used as the model drug. Three drug mixing ratios of 2:1, 10:1 and 45:1 (carrier:drug, w/w) are used. The attachment of the drug with the carrier is characterized by sieving test. It is found that the drug content in the blends with HA particles is higher than the blends with LA. In vitro inhalation experiments are also conducted in an Andersen cascade impactor (ACI) equipped with a Rotahaler® at gas flow rates of 30 and 60 L/min. The HA blends show high emitted dose (ED) of 82–90% at 30 L/min while the LA blends are observed to have ED of 69–82% at the same conditions. The high emission of the HA blends also allows high fine particle fraction (FPF) of 10–18% while the FPF of the LA blends are 3–15%. At a gas flow rate of 60 L/min, all the HA and LA blends show compatible ED (83–95% for HA blends and 82–84% for LA blends) and FPF (19–41% for HA blends and 21–34% for LA blends).