Discrete Element Method (DEM) has been widely utilized to analyze various granular physics, although it faces computational load issues due to complex calculations on particle collisions. The Soft Sphere Model, which considers the overlap depth between particles as elastic deformation and calculates contact forces based on repulsive and frictional forces, has been conventionally employed in many applications. In contrast, the Hard Sphere Model, which calculates post-collision particle velocities using the conservation of momentum and the coefficient of restitution, is used in systems where the frequency of particle collisions is low. However, this Hard Sphere Model cannot handle multi-body contacts, making it unsuitable for dense particle conditions. This study developed a modified model based on the conventional Hard Sphere Model for particle collisions, capable of retrospectively calculating multi-body contacts by tracing the collision history. In addition, the study considered the parallelization of the modified Hard Sphere Model to improve computational efficiency.

The eutectic mixture of gallium and indium is a type of liquid metal due to its melting point below room temperature. Hence, it exhibits high electrical and thermal conductivities, fluidity and deformability. Recently, liquid metal–polymer hybrids and composites have been developed, enabling access unique electrical and thermal properties. However, there are still limited easy and robust strategies to prepare those composites due to the high surface tension of liquid metals. Herein, it has been demonstrated that surface modification of liquid metal microparticles with organic surfactants prevents the coalescence of the particles and affords powderized liquid metal microparticles. Liquid metal–polymer composites can be prepared through simple methods, such as mixing and solution processes.

For titanium suboxides such as Ti₂O₃, Ti³⁺ on the particle surface is facilely oxidized to Ti⁴⁺ by exposure to air. When Ti³⁺ inside the particle as well as on the surface is oxidized, the entire structure of the particle transforms into TiO₂. In this study, in order to suppress the oxidation inside the particles and the resulting structural change, the effect of incorporating foreign metals that are tolerant to oxidation into Ti₂O₃ was investigated. Ti₂O₃ incorporating foreign metals was synthesized by the reduction of TiO₂ incorporating the foreign metals with TiH₂. In this way, Ti₂O₃ samples incorporating 5 mol% Al, V, and Cr were successfully obtained. The incorporation of these foreign metals significantly increased the onset temperature for oxidation of Ti₂O₃, demonstrating the effect of suppressing the oxidation by the incorporation of foreign metals. The incorporation of foreign metals was also effective in improving the catalytic activity and stability of Ti₂O₃ in the reverse water–gas shift (RWGS) reaction.

In the present study, we attempted to produce inhaled high-dose dry powder formulations for an active pharmaceutical ingredient (API) with poor aqueous solubility using several additives by spray freeze drying (SFD) and spray drying (SD) techniques. Scanning electron microscopy revealed that the SFD powders composed of 50% API were highly porous and spherical microparticles with diameters of 5–15 μm, the SFD powders composed of 90% API were aggregates constructed with submicron-sized primary particles, and the SD powders composed of 50% API were corrugated microparticles with diameters of 0.5–5 μm. Toxicity assessment using an air–liquid interface-cultured cell layer confirmed the relatively high safety of the additives used. Particle size distribution measurements clarified that both the SFD and SD powders could be efficiently dispersed in air using an inhalation device, whereas the SFD powders had higher air dispersibility than the SD powders. Aerosol performance evaluation demonstrated that the SFD powders composed of 90% API achieved the fine particle fraction (FPF) of approximately 50%, enabling the maximum possible amount of API to be delivered to the lungs through inhalation.

There is a need for the effective use of wood resources, which are recyclable. In this study, we propose a method for manufacturing products of various shapes from wood resources by mixing wood with a natural binder made from sucrose and citric acid, and then molding it through thermal-assisted flow. The effects of the heating temperature and time during molding, as well as the particle size, on the moldability of wood powder and the strength of the molded products were evaluated using capillary flow tests. By optimizing the heating temperature, time, and particle size, the fluidity of the wood powder was increased. In addition, the higher the temperature during the flow test, the higher the strength of the extruded material. Based on the results of the flow test, an injection molding and back extrusion test were conducted, and it was successful in obtaining a container-shaped molded product. Based on the above results, the appropriate heating conditions and particle sizes of wood powder mixed with natural binders were clarified for application in wood powder molding.

The present study developed a new route for fabricating ceramic hollow particles by a template method using ceramic coating via chemical vapor deposition (CVD). The CaCO₃ templates were coated with silica layers using a rotary CVD technique, and the hollow particles of silica were formed by removing the templates via acid treatment. The effects of the silica deposition duration by CVD on the microstructure, specific surface area, and pore structure of the silica hollow particles were investigated. The silica hollow particles had 10–30 nm thick silica shells with angular morphologies inherited from those of the templates. The specific surface area of the silica hollow particles increased from 75 to 466 m²/g as the deposition time decreased from 240 to 60 min. Additionally, the preparation of titania hollow particles was demonstrated using CaCO₃ templates coated with titania layers via rotary CVD.

We focused on cyclodextrin-metal-organic frameworks (CD-MOFs) as a novel carrier for inhalable microparticles. CD-MOFs have garnered attention in pharmaceutical fields owing to their high biodegradability and safety. Particles produced by spray-drying were found to successfully achieve a high loading of levofloxacin (LVFX) compared to the antisolvent crystallization method. Furthermore, a significantly higher delivery rate to the lungs was observed when comparing particles prepared via spray-drying with those prepared using the antisolvent crystallization method. Additionally, aiming for the design of inhalable combination drugs, particles were prepared via spray-drying with 4-aminosalicylic acid and isoniazid. These particles demonstrated the formulation of cocrystals, enabling the simultaneous local delivery of drugs with different properties to the lungs.

In this study, we investigated the effect of kneading on particle dispersion in aqueous carbon slurries used for the manufacture of lithium-ion battery anodes. Kneading, a method involving the preparation of slurry with a high particle concentration followed by dilution, is traditionally recognized as a technique to enhance particle dispersion. To evaluate this process, slurries with varying particle concentrations during kneading were prepared, and their characteristics were analyzed. Our findings revealed contrasting effects depending on the type of carbon material. For acetylene black slurries, increasing the particle concentration during kneading reduced the relative viscosity and improved particle dispersion. However, in graphite slurries, the addition of carboxymethyl cellulose (CMC) and subsequent kneading resulted in particle agglomeration. These results indicate that kneading does not always enhance dispersion and may, under certain conditions, even lead to agglomeration. This study highlights the need to reevaluate the conventional approach to kneading, suggesting that the process parameters should be carefully optimized to suit the specific materials and applications.

Transparent ceramics have been used in various fields such as HID lamps, optical lenses, lasers and phosphors. In recent years, our research group reported that the optically stimulated luminescence properties of transparent ceramics prepared by spark plasma sintering showed superior luminescence properties compared to those of single crystals. In this study, we focused on bromide-transparent ceramics and investigated the effects of differences in sintering conditions on the optical and optically stimulated luminescence properties. By optimizing the sintering conditions for bromides such as LiBr, NaBr, KBr, RbBr, and CsBr, we have successfully developed the transparent ceramics. Regarding optically stimulated luminescence properties, the Eu-doped CsBr showed high sensitivity to X-rays and performance comparable to commercial products.

We have developed an airflow plasma reactor for hydrophilic treatment of 3 μm PE powder. In the R&D, we designed and manufactured an air flow plasma reactor and evaluated its production capacity and processing capability. The PE powders enable hydrophilization in an extremely short period of time by ensuring uniform dispersion in the airflow. On the other hand, the reactor with an electrode inserted inside the reactor was found to have problems in terms of continuous processing, such as blockage due to particle adhesion and particle melting at the electrode. Therefore, a new helical plasma reactor without electrodes inside was developed to solve the problems, and continuous treatment was realized by using the helical plasma reactor.

In this study, we synthesized porous crystals (^FPMOF_3D) of fused porphyrins using an extended π-conjugated system. These crystals exhibit volume contraction through the photothermal effect of near-infrared (NIR) irradiation and return to their original state when the NIR irradiation ceases. Furthermore, we proposed the construction of porous nanoreactors that enable efficient material circulation by taking advantage of this property. The ^FPMOF_3D crystals demonstrated effective substrate uptake, conversion, and product release within the pores by leveraging the thermal energy produced through NIR absorption. Moreover, through the development of a synthesis method, the crystals were successfully miniaturized to yield a fine powder sample while preserving their functional properties. These findings underscore the potential for the advancement of NIR-driven reactors and in vivo applications.

This study aims to develop functional metal sulfide materials with nanoscale crystalline grain structures using a shock solidification technology based on cylindrical compaction with explosives. Compared with metals and ceramics, which have traditionally been the subject of explosive shock solidification, metal sulfides are characterized by their brittleness and low melting points. In this study, the slowest detonation velocity explosive, PAVEX, was used. The expansion of the explosive gas was employed to drive a metal tube at high velocity, causing it to impact a sample container at high speed, thereby generating shock waves utilized for powder compaction. In the case of Ni fine powder, densification and particle refinement were achieved under a shock pressure of approximately 19 GPa, resulting in significantly increased hardness. On the other hand, for CuFeS₂ fine powder, decomposition reactions occurred under pressures of around 9.8 GPa, and the desired microstructure control was not achieved. However, the formation of a high-pressure phase, cubanite CuFe₂S₃, was confirmed. These findings suggest the potential for novel phase synthesis in metal sulfides, and indicate promising prospects for future applications.

Zinc oxide (ZnO) is widely used in cosmetics as a UV protection agent to shield the human body from ultraviolet (UV) radiation. However, its low acid resistance poses a challenge, as it tends to degrade on the weakly acidic human skin. In this study, titanium dioxide/zinc oxide (TiO₂/ZnO) composite particles were synthesized using a flame aerosol process to enhance the acid resistance of ZnO. The synthesized particles exhibited a uniform distribution of titanium and zinc atoms within each particle, indicating titanium dioxide existing in an amorphous state. Acid resistance evaluation through a sulfuric acid drop test confirmed that the elution of Zn²⁺ was suppressed, and the acid resistance of ZnO improved upon compositing with TiO₂. Furthermore, increasing the amount of TiO₂ in the composite further enhanced the acid resistance. These TiO₂/ZnO composite particles demonstrated potential for application as UV protection agents in sunscreen cosmetics due to their broad UV absorption properties.

In this research, near-monodispersed iron oxide nanoparticles were synthesized using the alkaline-treated hydrothermal method under various conditions. Machine learning, specifically support vector regression (SVR), was employed with the hydrothermal temperature, time, ammonia solution amount, and Ole/M ratio as explanatory variables, and CV values as the response variable. The experimental results showed a CV value of 11.4% under conditions of hydrothermal temperature 220°C, hydrothermal time 24 hours, ammonia solution amount 3.00 mL, and Ole/M ratio 1.00. SVR was performed to estimate the relationship between CV values and experimental conditions. However, the obtained CV value was 25% which was higher than expected. To address this, a new evaluation index that combines particle size and CV value was introduced for estimation, however, the predicted value did not exceed the actual measured value. Finding conditions that yield lower CV values is challenging with the current method. On the other hand, the CeO₂ nanoparticles synthesized using the alkaline-treated hydrothermal method showed a broader particle distribution. This highlights the importance of selecting appropriate initial materials. As a next step, further exploration of synthesis conditions near the lowest CV, validation of the experimental results, and refinement of the dataset will be conducted.

This research explores a novel approach to achieve spontaneous demulsification of Pickering emulsions by leveraging the exchange reaction between particles adsorbed on emulsion droplets and surfactants. Surfactant-adsorbed films typically create two-dimensional liquid-like film (expanded film) with low surface coverage, which is unable to fully exclude adsorbed particles from the emulsion surface. Therefore, to realize spontaneous demulsification of a Pickering emulsion, the surface phase transition to a two-dimensional solid-like film (condensed film) of surfactants on the droplet surface was utilized. This phase transition successfully realized spontaneous demulsification of silica-stabilized Pickering emulsions upon cooling.

This study focused on utilizing two types of hydrogel particles (microgels) with distinct surface properties to precisely control interparticle interactions in aqueous environments and construct unique particle assemblies. The effects of electrostatic attraction and steric repulsion on the structural formation of assemblies were investigated in detail by systematically varying particle and salt concentrations. The findings revealed that raspberry-like aggregates formed at low salt concentrations, while medium salt concentrations maintained a uniform dispersion state, and high salt concentrations led to random aggregation. Furthermore, it became possible to directly observe swollen structures using fluorescence microscopy by utilizing fluorescently labeled microgels. This approach enhances the simplicity and efficiency of structural analysis for real-time observations of particle dynamics and assembly behavior. The results provide critical insights into controlling interparticle interactions and offer a foundational methodology for designing functional materials and achieving precise structural control at the nanoscale, with potential applications in material science and biological fields.

In this study, fine-grained Zn samples with excellent mechanical properties were prepared via spark plasma sintering (SPS) using fine Zn powder and heat treatment. The as-sintered sample prepared by SPS exhibited fine grain size and random crystallographic texture. Moreover, heat treatment induced recrystallization and reduced the dislocation density in the vicinity of the grain boundaries of the as-sintered samples. Mechanical testing revealed superior properties in the sintered and heat-treated samples, with the sample heat-treated at 650 K demonstrating an exceptional elongation exceeding 80%. The remarkable mechanical performance is linked to the initial microstructural characteristics and dynamic recrystallization (DRX) occurring during deformation. These findings suggest that the combination of SPS and heat treatment is an effective strategy for enhancing the mechanical properties of Zn, presenting potential applications in advanced materials and biomaterials.

This study provides fundamental insights into improving the moldability of rice batter. To clarify the effects of amylose content and molecular weight on batter properties, three experiments were conducted. First, rice flours with varying amylose contents were blended, and their bread-making properties were evaluated. The results revealed that higher amylose content increased the storage modulus (G’) during heating, thereby enhancing the bread’s expansion ratio. Second, the viscoelastic properties of natural starches were measured. Adding amylose to glutinous rice starch significantly increased G’ in the temperature range of 25°C to 65°C. Third, enzymatically synthesized amylose with different molecular weights was employed to assess viscoelasticity. High-molecular-weight amylose markedly improved G’ in the same temperature range as the second experiment, showing a clear dependence on amylose concentration. These results demonstrate that G’ during heating plays a crucial role in the expansion properties of rice flour dough, and this characteristic is determined by both amylose content and its molecular weight.

Polymer particles are widely used in various fields, such as paintings. When the particles were adsorbed on the substrate by electrostatic force, it was important to develop techniques for removing the particles from the substrate. We used 2,2’-azobis(2-methylbutyronitrile) (V-59) as a foaming agent to make the particles desorbed from the substrate. First, polystyrene particles with positive charges were prepared by soap-free emulsion polymerization. Second, V-59 was added to the polymer colloid solution to encapsulate V-59 by the polystyrene particles. The particles were adsorbed on the mica substrate with negative charges. Finally, the mica substrates were heated in water to emit the nitrogen gas generated by the decomposition of V-59 inside the polymer particles adsorbed on the mica surface. To evaluate the desorption efficiency of this method, the mica coated with adsorbed particles was observed using SEM to calculate the surface coverage from the SEM images. The desorption ratio increased with the amount of V-59 inside the polystyrene particles. Therefore, the nitrogen gas emitted from V-59 inside the particles played an important role in removing the particles from the mica surface. This removal method is environmentally friendly because it does not involve the use of organic solvents.

Understanding the local flow behavior in a hopper container is important to improve particle discharge flow rate from the hopper. In this study, DEM simulations were used to analyze the effect of discharge flow rate from a hopper container on a spatial particle velocity distribution in the container. The Hamaker constant, friction angle, and particle density were varied to change the discharge flow rate. As the discharge flow rate increased, fast and slow flow regions became distinct, and spatially asymmetric local flow was observed. In addition, the difference in average particle velocity between the zones near the wall and the center of the container decreased. From the results, the particles in each zone did not flow at a constant velocity, and instead, fast-flowing discharged regions appeared randomly at each zone, and switched frequently between these zones. In addition, these trends were similar regardless of the particle properties. Thus, the results suggested that the same guidelines could be used to control flow behavior to improve the discharge flow rate, without considering the differences in particle properties.

Organic semiconductors have many advantages: abundant resources, tunable functionality by molecular design, and easy coating process. In particular, n-type organic semiconductors have been in high demand owing to their requirement for complementary metal-oxide-semiconductor (CMOS) circuits. However, n-type organic semiconductors have lower electron mobility than inorganic and p-type semiconductors. Achieving an electron mobility of 1 cm²/Vs in n-type transistors would enable the fabrication of CMOS in combination with conventional p-type semiconductors. In the current work, we focused on the significant influence of the molecular arrangement of n-type organic semiconductors on their electron mobility and aimed to control their molecular arrangement.

Tablets are formed by compressing powder filled in a die using upper and lower punches. Although the tableting process seems apparently simple, tableting failures, such as capping, may occur depending on the tableting conditions. However, due to the unclear mechanism of capping, the tableting conditions have been traditionally determined by trial and error by skilled engineers. Thus, we attempted to develop novel capping prediction methods by measuring die wall pressure which is a key factor influencing capping. This approach could contribute to earlier detection of capping occurrence. Furthermore, it enhances our understanding of the tableting process.

Cocrystals have attracted attention as a promising approach to enhance drug concentration in water. Our study explores formation of pharmaceutical cocrystals using fatty acids as a safe medium and their role in controlling drug concentration. In this study, calculations of the Gibbs energy change and experiments on cocrystal formation revealed that the ability of solvents to form cocrystals is attributed to the stability of the drug and coformer in the solvent.

To apply the spray freeze granulation drying technique for nitride fabrication, we prepared silicon nitride slurries using a mixture of tert-butyl alcohol and cyclohexane as a solvent and attempted to understand the internal structural changes of the slurries by observing their freezing behavior. In addition, the ceramics were prepared using granules obtained via the spray freeze granulation drying method. It was found that the microstructures of the freeze-dried bodies differed depending on the solvent mixture ratio and the structure of the organic additive.

The development of metal oxide supports with porous structure and high electrical conductivity has attracted considerable interest for diverse applications, including polymer electrolyte fuel cells (PEFCs) and water electrolysis. Among these supports, iridium oxide-titanium oxide (Ir–IrO₂/TiO₂) particles stand out due to their unique properties. In this study, we synthesized a porous catalyst support consisting of titanium oxide particles with a low loading of iridium–iridium oxide species (Ir–IrO₂) using a flame aerosol process. We examined the effect of annealing these flame-made Ir–IrO₂/TiO₂ particles to boost their electrical conductivity. Prior to annealing, a spherical morphology with a porous structure, and the Ir–IrO₂ species were amorphous but uniformly covered the TiO₂ surface. After annealing at 750°C, the Ir–IrO₂/TiO₂ particles retained their spherical morphology and porous structure, demonstrating their excellent thermal stability. By increasing the annealing temperature to 750°C, the electrical conductivity of Ir–IrO₂/TiO₂ particles improved significantly, rising from 1.05 S/cm before annealing to 1.85 S/cm, demonstrating the effectiveness of annealing treatment in enhancing conductivity. These findings provide valuable insights into optimizing the performance of catalysts for various applications.