Suspensions of monodisperse spherical particles under shear flow were simulated using a solid-liquid two-phase model based on coupled lattice Boltzmann method (LBM) and discrete element method (DEM). Evaluating the shear stresses due to the viscous behavior of the bulk fluid, the hydrodynamic interaction between particles and fluid, and the physical contact between particles, the contribution of each factor to the suspension viscosity was investigated. The results showed that in the range of low to moderate particle volume fractions, the viscosity of suspensions is mainly determined by the action of the fluid, and that the contribution of particle contact increases with increasing particle volume fraction. In particular, the flow behavior of dense suspensions should be viewed not as a fluid motion but as the motion of a group of particles. From these results, in order to predict and control the rheological properties of particle suspensions, it is important to understand that the main factors increasing viscosity vary with the concentration range of interest.
In this study, we investigated milling characteristics of sulfide solid electrolytes (SEs) for all-sold-state lithium ion batteries (ASSLIBs). Subsequently, we employed the milled SEs as guest particles for dry coating of cathode active material (AM), and examined the influence of SE size distribution on ASSLIB performance. Our finding revealed that SE particles have unique milling characteristics, in which coalescence of milled fine particles occurs simultaneously with size reduction by milling. The dry coating experiments confirmed that the use of milled SEs (guest particles) resulted in more uniform coating of the AM (host particles) with SE, leading to significant improvement in the performance of ASSLIB (630% increase in capacity as compared to unmilled SEs). However, when SEs were excessively milled, the SE coating layer exhibited non-uniform morphology, resulting in lower battery performance (15% decrease in capacity). Consequently, our results highlighted that there is an optimal milling condition for SE guest particle for the dry coating.
The Sustainable Development Goals were adopted by the United Nations in 2015. Technologies that realize an economically low-carbon society are attracting attention of the international community. Regarding powder processing technology and device development, we will introduce examples of technological development that contribute to the achievement of the SDGs (Sustainable Development Goals).
The photoluminescence (PL) intensities of Li-Ta-Ti-O:Mn4+ red phosphors were successfully improved under various oxygen partial pressures in an air-pressure control atmosphere furnace (APF). The Mn phosphors were synthesized using an APF and a conventional electric furnace (EF) with the composition formula Li1.33Ta0.67Ti0.33O3 as the host material. The effects of oxygen partial pressure on the Mn4+ ratio and crystal structure for the PL intensity were investigated. As a result, the PL intensity was enhanced under high oxygen partial pressure, showing about 2.6 times higher than the phosphor synthesized by EF.
Alginate capsules for encapsulating probiotics were synthesized under mild conditions without using harmful chemicals. When alginate capsules were synthesized using glucono-δ-lactone while suppressing the rapid pH drop of the inner water phase, it was possible to encapsulate living lactic acid bacteria. It was also found that coating the alginate capsule surface with chitosan improved the protective effect of the encapsulated lactic acid bacteria. Furthermore, culturing the encapsulated bacteria inside the capsules increased the number of living bacteria to meet the minimum recommended level for probiotic effect. Finally, we demonstrated that almost all encapsulated bacteria were released within 60 minutes in simulated intestinal fluid. From the above, it was suggested that the chitosan-coated alginate capsules synthesized in this study can be used as capsules for encapsulating probiotics.
SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is a single-stranded RNA virus which causes COVID-19 (coronavirus disease 2019). SARS-CoV-2 invade a human airway epithelium cell through binding of its Spike (S)-protein to ACE2 (angiotensin converting enzyme 2). Approved anti-inflammatory drugs and a viral RNA-dependent RNA polymerase (RdRp) inhibitor underdevelopment for other disease were repositioned for the COVID-19 treatment. Furthermore, neutralization antibodies targeting the S-protein and antiviral drugs of RdRp or 3CL protease inhibitors were newly developed within only 3 years. The innovations of the drug discovery and development, including regulation, realized the rapid release of drugs to the market.
Comminution process is widely used in industry to produce fine particles. We developed a mathematical model of comminution in order to analyze particle size reduction in an impact pulverizer. In our model, it is assumed that parameter a, which represents particle breakage modes, depends on both impact velocity and size of the particles. To obtain that dependence, particle-size distribution was measured experimentally before and after the breakage using a jet-mill. We implemented the mathematical model into the simulation based on computational fluid dynamics (CFD) and discrete phase model (DPM). It was confirmed that the simulation results coincide with the experimental ones in a rotary mill. Therefore, we conclude that it is important to consider the dependence of impact velocity as well as particle size on the breakage modes.
In various fields, most raw materials are in a granular state: their bulk properties are therefore of interest. The discrete element method (DEM) is frequently used to determine these properties. As numerous particles can be simulated by DEM, and particle shapes affect bulk properties, effective modeling of realistic particle shapes is required. In this study, two types of DEM simulations were compared: one using real ore particle shape, and one using particle shape computed by spherical harmonic-based principal component analysis. We confirmed the latter to successfully reproduce the bulk properties (repose angle, porosity, and coordination number) of the former.
Hematite (α-Fe2O3) nanoparticles were synthesized by a solvent-free homogeneous precipitation method using urea hydrolysis via dry mechanical treatment of urea and ferric nitrate nonahydrate for activation. This novel method consists of high-energy ball milling of the raw materials and subsequent heating of the activated liquid precursor, which can provide smaller-sized nanoparticles than conventional methods. The milling and heating conditions were systematically investigated in detail. It was found that the hematite formation can be promoted by milling ferric nitrate nonahydrate and urea simultaneously under dry conditions even when relatively gentle milling and heating treatments were employed. The hematite nanoparticles had a similar crystallite size and particle diameter regardless of the conditions. This method can contribute to large-scale environmentally-friendly synthesis of fine hematite nanoparticles.
Xylitol raw powder exhibits strong aggregation during storage, making it difficult to form fluidized bed and low compressibility. In this study, fluidized bed could be formed by co-milled with xylitol and fumed silica, and tabletability could also be improved by granulation with hydroxypropyl cellulose (HPC-L). To further improve the compressibility of xylitol, cellulose nanofiber (CN) was applied as a binder. As methods for adding CN, we investigated 1-step granulation method in which CN were added to the HPC-L binder solution and 2-step granulation method in which cellulose nanofibers are sprayed onto xylitol granules. In the 1-Step method, there was an optimum amount of CN. Addition of excess CN caused troubles during granulation and decreased the compressibility. In the 2-step method, the surfaces of xylitol granules were coated with CN. As a result, compressibility of the xylitol granules could be improved by only slight addition (13 ppm in xylitol) of CN.
The Mahalanobis-Taguchi system (MTS) is one of the multi-variate analyses which can classify data by correlations among multi-variables. The MTS has significant advantage of applying a cause analysis which provides effective variable combinations to upgrade the accuracy of the classification. In this study, droppings, which were extruded from Japanese rhinoceros beetle larva were selected to classify into male/female based on their shape-related features using the MTS. Based on the cause analysis, the projected area/Feret’s diameter (A/F) and solidity were the best variable combination which all the larval droppings were classified into male/female. Both the variable has surface roughness-related factors with size effect (A/F) without size effect (solidity). The MTS has the great ability to classify from the powders’ minor difference and will be an effective tool for particle design in the near future.
Wheel sliding, which may occur during rainy weather, is a severe problem faced by railways. The re-adhesion control method is an effective countermeasure; however, it cannot entirely prevent wheel sliding. Therefore, an increasing number of rail vehicles are equipped with a device that jets a small amount of ceramic particles toward the contact area between the wheel and rail to improve the wheel adhesion. However, no method exists to monitor the flow state of the particles in the jetting device. Therefore, we developed monitoring methods focusing on the electrostatic charging of particles passing through the device and conducted experiments using corundum and silica sands. The experimental results verified that two methods, that is, those used to analyze the electrical signals detected by the device and their integration values, are adequate to discriminate the flow state. Furthermore, we evaluated the electrostatic characteristics of the monitoring system and considered it for practical applications.
While the Discrete Element Method (DEM) is expected to evaluate wet grinding performance of bead mills, the conventional DEM requires high computational cost because it has the limitation of the time step size for stable computation. In addition, the simulation of wet grinding process requires additional cost to consider the interaction between beads and fluids by using such as CFD-DEM coupling techniques. This study proposes an analysis system for evaluating wet grinding performance of bead mills with less computational cost. Our proposed system adopts the Impulse-Based DEM (IB-DEM) which can use large time step size, the wall model by using the Sign Distance Function (SDF) which flexibly represents complicated shape walls, and the simple modeling of fluid force which can reduce computational cost. We verify our proposed system by comparing the numerical results with experimental results of bead mills with different shapes of rotors.
Continuous crystallization is the next step of manufacturing especially at the production of pharmaceutical ingredients. We have developed small-scale continuous taylor-vortex crystallizer that is suitable for research in laboratory. But there was a problem that rotating inner cylinder at high-speed range causes much frictional heat and it raises the temperature of the solution, that may spoil the effort of controlling characteristics of crystals. So, we have developed new taylor-vortex crystallizer that has inner cooling system. We conducted several examinations of anti-solvent crystallization of glycine, which aims to obtain unstable crystal polymorph of glycine continuously. The new crystallizer showed the advantage of crystallizing unstable crystal polymorph.
The ABC powder used for a fire extinguisher shows high flowability. The evaluation about a flowability of such powder was very difficult and was not able to show the difference in the property by the measurement of the existing repose angle. Then, in this study, we considered about a new evaluation method of the powdery flowability indicating the high flowability using ABC powder. That rotated a cylindrical container after the tapping, and an angle when powder collapsed was measured and was named the rotational collapse angle. As a result, the rotational collapse angle was able to clarify a flowable difference for high flowable powders such as the ABC powder. Furthermore, it was found that the rotational collapse angle could determine with the right and wrong of the emission test of the fire extinguisher beforehand.
Mechanical synthesis of lithium titanate hydrate (LHTO: Li1.81H0.19Ti2O5·xH2O) in liquid phase was investigated using a bead mill. LHTO has layered crystal structure which leads to form thin plate particles. As starting materials, lithium hydroxide which was dissolved in water and titanium dioxide nanoparticles were used. As bead media, 0.3, 0.5 and 1 mm diameter of zirconia balls were employed. At least some amount of LHTO was formed at each bead size condition. In cases of 0.3 and 0.5 mm beads, crystallization of LHTO looked not to proceed after some hours. After 5 hours, the most crystallized LHTO was synthesized at 1 mm beads. Some of observed particles showed thin plate shape but the greater part of particles were fine particles in the obtained powder. It was supposed that synthesized LHTO particles were broken faster than crystals of LHTO grew up since small bead media performed high grinding ability.
A granular soil conditioner with several millimeter diameters was prepared using scallop shell powder by pan granulator. The scallop shell powder was classified using a vibrating sieve to adjust the angle of repose for the granulation. As a result, the scallop shell granules with controlled size were prepared by adjusting the process parameters of the granulation such as the pan angle and the rotational speed. In addition, the amount of lignin (binder for the granulation) was adjusted to be 4 wt.% to attain the enough strength for the assumed compressive stress during the storage. Lastly the acidity correction of the obtained scallop shell granules had a low immediate effect and a high persistence compared with that of the scallop shell powder.
This paper describes separation performance of newly developed forward cyclones with 7 kinds of size and structure. The forward cyclones have 2 or 4 tangential-air-inlets, a dust pot and a flow receiver for fine particles. Our previous study showed that the cyclones had sharp size separation performance for PM2.5 but did not clarify the mechanism. Size separation characteristics of the cyclones were evaluated using a pair of optical particle counters with test aerosols of standard polystyrene latex particles ranging from 1 to 6 μm in diameter. Also swirling flow in the cyclone was observed by tracer powder. Measured data, such as 50% cut-off aerodynamic diameter at flow conditions of each cyclone, were used to estimate the flowrate branching off the dust pot. Ranging from 3 to 30 percent of total flowrate were passed to the dust pot before flow throughout the cyclone. The flow caused sharp centrifugal separation to the aerosol particles introduced into the cyclone. Smallest the cyclone (bore diameter was 10 mm) covered samplings for PM2.5 fraction of ambient aerosols at 3 L/min and respirable particle faction (PM4) at work environments at 1.7 L/min. Largest the cyclone (bore diameter was 90 mm) fitted to a high-volume air sampler of which flowrate ranged from 150 to 600 L/min, showed the same performance as the smallest one.
The sustained-release formulations consist of many components, such as the active pharmaceutical ingredient, excipient, binder, lubricant, and polymer, leading to the complex dissolution process. The objective of this study is the elucidation of the rate-determining step in the dissolution process by direct optical observation. The composite particles of hydroxypropyl methylcellulose (HPMC) and brilliant blue FCF (model drug) were prepared, and the direct observation of the dissolution process and image analysis were conducted. The decrease in particle size and the penetration of solvent into the particles during the dissolution process had little impact on the sustained-release performance. On the other hand, the diffusion rate of the model drug in the HPMC gel strongly depended on the type of HPMC, suggesting that the rate-determining step in the dissolution process of the sustained-release formulations using HPMC would be the drug diffusion process in the polymer gel in the particles.
In the field of non-equilibrium science, the Liesegang phenomenon is well-known as a particle formation process involving the diffusion of precursor chemicals. From a chemical engineering perspective, our research group had previously applied this method to synthesize metal nanoparticles and found that when Au ions diffuse unidirectionally into a gel containing a reductant, bands of Au nanoparticles are formed in a striped pattern. However, metal species other than Au have not yet been investigated. In this study, we synthesized nanoparticles of other metal species (Pt and Pd) using a similar process and compared the results with those of the Au nanoparticles to clarify the particle formation mechanism. The findings showed that the band patterns that were formed vary according to the metal species. Furthermore, the bands formed in each metal species were reproduced by using a mathematical model capable of representing the diffusion of ions and the formation of particles.