Dust collectors with bag filters are widely used to remove hazardous aerosols in work environments. Package type dust collectors, which include a fan and motor, differ in a wide variety of ways, such as the inner structure, the filter media, methods for cleaning collected dust, and flow control methods. In this study we focus on the performance of dust collectors for respirable dust fraction, which can reach the lung alveoli and cause pneumoconiosis. We surveyed the actual situation of dust collectors at worksites by means of light scattering photometers with PM2.5 cyclones, measured the details of performance of a typical dust collector using common test dust (Atomite) in a laboratory, and then tested the collection efficiency of the filter samples with and without dust load. The test aerosols for the filter samples were generated by the nebulization of standard monodisperse particles (Polystyrene latex particles, 0.6 to 3 μm). The penetration measured by photometers with PM2.5 cyclones approximated the performance of dust of 1.2 μm in nominal size. We propose the test methods at worksites and the filter media of bag filters in confirming the performance of dust collectors.

Particle size of raw materials is one of the most important factors in granulation, a general particle processing method. Especially in the case of granulation of multiple materials, component uniformity depends on the particle size. Therefore, pulverizing raw materials to a smaller particle size before granulation is often selected as a preprocessing method. Currently, there is a direct granule producing apparatus, which produces granules direct from a suspension of raw materials. The granules produced from this apparatus have unique features such as content uniformity, spherical shape, and high content yield due to less addition of excipients. From these features, the granules have advantages-such as ease to swallow and downsizing of final dosage form if they used for drugs. Here, we describe the necessity of raw material pulverization by confirming the correlation between particle size of the pulverized raw material and component uniformity of the granules produced by direct granule producing apparatus.

This article provides a brief overview of liquid-liquid phase separation fundamentals. First we discuss thermodynamic factors that drive spontaneous phase separation from homogeneous binary liquid mixtures. Next we introduce some mathematical models for chemical potentials in non-equilibrium state and intermolecular frictions to derive the governing equation for phase separations. Following classical Cahn-Hilliard theory, we show how the linear stability analysis gives the critical wavelength, at which the growth rate of concentration fluctuation shows a maximum. Finally, we discuss possibilities to utilize phase separation structures as a template to assemble/deposit/stratify solid particles on a solid surface.

Because of thermal stability, tunable porosity and modifiable surface, mesoporous silica is a promising material in catalysis, drag delivery and environmental applications. These industrial potentials could be enhanced by compounding mesoporous silica with Fe₃O₄ nano-particles, since its para-magnetism brings about the spatial mobility controlled under magnetic field. For the present research work, tetraethylorthosilicate was hydrolyzed and poly-condensed over the self-assembled surfactant micelles in the presence of Fe₃O₄ nano-particles in order to embed it in mesoporous silica SBA-15. Under the acidic condition caused by an aqueous solution of FeCl₃, the poly-condensates were formed into the well-ordered hexagonal arrays of one-dimensional channels without dissolution of Fe₃O₄ nano-particles. This was the first successful synthesis of SBA-15 in which Fe₃O₄ nano-particles were embedded. On the other hands, another approach where SBA-15 was synthesized over Fe₃O₄ coated with amorphous silica in HCl aqueous solution ended in failure because the coated silica could not prevent Fe₃O₄ from dissolving in HCl aqueous solution. For the SBA-15/Fe₃O₄ composite prepared successfully, a quaternary alkyl-ammonium salt was grafted in order to prove the catalytic application.

A scale-up method of a low drug content mixing process in a V-type blender was proposed. Acetaminophen was used for the model drug, and the low drug mixing experiment was conducted using three scales of V-type blenders under the same fill level and Froude (Fr) number. However, the uniformity of mixtures could not correspond with the mixing time or the total revolution number. To find the optimum scale-up factor, discrete element method (DEM) simulations of three different scales of V-type blender mixing were conducted, and the total travel distance of particles under the different scales was calculated. The uniformity of drug content obtained from the scale-up experiments was well correlated with the mixing time determined by the total travel distance. It was found that the scale-up DEM simulation based on the travel distance of particle was valid for the low drug content mixing scale-up processes.

Plate penetration into dry granular materials is numerically studied using a large-scale discrete element method (DEM). To investigate the effects penetration angle on the interactions between particles and the plate, the simulations with the different angles from 0 (vertical penetration) to 60 degree are compared. The results show that the drag force acting on the plate increases with a decrease in the penetration angle. For all cases, the formation of shear bands from the plate tip to the free surface in the bed is confirmed. The analysis of energy consumption in the bed shows that most of the energy input to the bed by the plate is locally dissipated by sliding frictions between particles in shear bands. As the penetration angle decreases, the amount of energy dissipation due to the friction increases in the shear bands formed near the plate tip.

Controlling flow behavior of micro food powder in the mixer is important for improving the efficiency of premix powder production. Four important factors (particle diameter, particle diameter distribution, particle shape, adhesion force) which could influence the flow behavior in the mixer were examined by several experiments and Distinct Element Method simulations. The experiments and simulations showed that the particle diameter, particle diameter distribution and particle shape had little effect on the flow behavior of the food powder in the rotating drum, while the adhesive force had a very large effect. On the basis of this finding, we proposed a simple adhesion model for representing the behavior of micro food powder in the mixer. It was found that the flow behavior of several kinds of food powder can be represented by the proposed model.

Toward industrial applications of commercialized carbon nanotubes (CNT), fully utilizing the intrinsic CNT properties is challenging due to the quality deterioration and the uncontrolled states through dispersion processes in matrices. Therefore we propose a predispersion step of CNTs prior to distributing them into matrices, clarifying the unravelling effect of CNT powders by various liquids with different viscosities like alcohols, silicone oils, ionic liquid, ketone, hydrocarbons, aprotic polar solvents, and water. Regardless of solvent polarity, liquids with higher viscosities led to more unravelled CNT particles, reaching up to an approximately ten thousand times higher particle number than one before the dispersion.

Herein we report a new grinding method to obtain fine particles having high specific surface area which is difficult to realize a conventional dry grinding. Several inorganic carbonates and metal oxides have been studied. Planetary ball milling under dry conditions and subsequent water addition realize the particles with a crystallite size and equivalent size of the specific surface area in the nanometer range. The equivalent size could be down to 25–136 nm using our method except TiO₂. Regarding ground TiO₂ sample, 47 nm in the equivalent size was successfully obtained via adding KOH solution and washing process. From the view point of solubility, we proposed the mechanism for the equivalent size down to nanometer range.

In this study, the effect of multivalent ions on ionic crosslinking of polyelectrolytes adsorbed on particle was investigated. Ammonium polycarboxylate, one of the typical polyelectrolytes, was used as a dispersant. Zinc oxide and titanium oxide was used as sample powder. A well-dispersed slurry was prepared by adding polyelectrolytes as the dispersant beforehand. Thereafter, multivalent cations were added to the slurry to convert it from liquid to a gel-like consistency, which was caused by the ionic crosslinking of polyelectrolytes adsorbing on the surface of the particles. It was found that the ionic radius of adding multivalent cation has an influence on the strength of the gel. It was also shown that this method was effective for prevention of density segregation during sedimentation.

Functional nanoparticle syntheses by thermal plasmas are reviewed. The advantages of thermal plasmas, such as high enthalpy, high chemical reactivity, and rapid quenching capability, have brought the advances and demands in plasma processing. Recent researches by DC arc, multiphase AC arc, and induction thermal plasma are summarized. Metal, intermetallic compounds, oxide, nitride, and boride nanoparticles are successfully synthesized by thermal plasma method. In particular, nanomaterial synthesis for the utilization in lithium-ion battery are summarized. Attractive nanomaterials related to cathode, anode, and electrolyte are successfully synthesized by thermal plasmas. High-productivity of the nanoparticles by thermal plasmas for industrial utilization can be achieved by improving energy efficiency and solving electrode erosion issue.

This paper shows the effect of the agglomeration control on the catalytic activity for oxygen evolution reaction (OER). In this study, (Ca_0.5Sr_0.5)RuO₃ (CSRO) catalyst was selected as the bi-functional catalyst for OER and oxygen reduction reaction (ORR). The sol-gel derived CSRO particle was mixed with the carbon nano-particle in the tetrahydrofuran (THF) based solution under the various pH condition to prepare the ink for the air electrode of rechargeable metal-air battery. The microstructure of the air electrode was designed by controlling the electrostatic repulsion force of the CSRO catalyst particles in the ink. As a result, the surface area of the air electrode increased with increasing the electrostatic repulsion force of the CSRO catalyst particle, resulting in the enhancement of the OER activity. From these results, we concluded that the agglomeration control of the catalyst particle in the ink is one of the key factors to enhance the catalytic activities of the electrocatalysts.

High-speed fabrication of colloidal crystal films composed of polystyrene particles was attempted by electrophoretic deposition. Flat, uniform colloidal crystal films were fabricated on ITO-coated glass or PET sheet substrates in several minutes by using an optimum ratio of a mixed solvent of water and ethanol. The obtained colloidal crystal films exhibited structural color predicted from the particle size. The structural color of the colloidal crystals immobilized by immersing silicone elastomer changed to different colors when the interlayer spacing was changed due to the swelling/shrinkage by dropping organic solvents or applying tensile stress on the films. Such structural color changes were applicable for a simple sensor to visualize strain.

Vat photopolymerization is an additive manufacturing process that is used to fabricate highly accurate three-dimensional (3D) ceramics. However, with this process, it is difficult to mold powders, such as carbides and TiO₂, which absorb light of a certain wavelength from the light source used. In this study, we investigated the fabrication of low conductivity Al₂O₃-ZrO₂-TiO₂ ceramics, a kind of electro-static discharge countermeasure ceramics, by digital light processing type vat photopolymerization. Slurries having a solid concentration of 35 vol%, in which Al₂O₃, ZrO₂, and TiO₂ ceramic powders were dispersed in a photocurable resin, were prepared. The influence of TiO₂ concentration on the photocurability and laminate properties were investigated. The results showed that as the TiO₂ concentration increased, the light irradiation energy required for molding increased. By carefully investigating the molding conditions at a laminating pitch of 25 μm, we could prepare dense and low conductivity Al₂O₃-ZrO₂-TiO₂ 3D complex shape ceramics.

It is important to reveal fault structures and stress states in accretionary prisms for understanding the building and releasing of seismic energy as they control the generation of great earthquakes and tsunami. Here we show the evolution process of three-dimensional fault structures on sandbox simulations using a discrete element method (DEM). To realize the real-scale sandbox simulation, we developed state-of-the-art techniques in high performance parallel computing methods for the DEM, and then performed the largest DEM simulation in the world using up to 1.9 billion particles with similar grain size of real sand for identifying the three-dimensional fault structure. The DEM simulations reproduced the undulation of fault structures similar to those found commonly in nature. In addition, the characteristic grain motion was found near the frontal fault before beginning the uplift event of sand bed, which could be a precursor of tectonic events behind accretionary prism formation.

For large scale use of renewable energy, hydrogen society is necessary to overcome supply and demand mismatch in time and space. Polymer-electrolyte fuel cells (PEFCs) represent a superior system that exhibits high-efficiency, offering better power generation, meeting the desired levels of demand. However, in order to facilitate widespread use of fuel cells, cost and lifetime problems must be resolved. We are systematically designing and developing new materials from the molecular level to the device level. In the fuel cell systems, different components such as membrane, catalysts, and catalyst layer share significant functions and work in a well-coordinated manner, and hence, the total cell system must be optimized for the best performance. The systematic design and developing approaches concerning electrocatalysts for PEFCs are proposing.

A new simulation model to deal with metal powders was developed. The feature of the proposed model is to express plastic deformation behavior of metal powders. The model is based on Advanced Distinct Element Method (ADEM), which can represent deformation behaviors of elastic materials. The change of the proposed model from ADEM is interaction force of primary particles. In order to confirm the validity of the new model, compression tests and drop tests have been carried out in experiment and simulation. In compression tests, test tablets were thinly stretched and the deformation was maintained. In drop tests, a dimple was formed on the tablet when an iron ball collides. Characteristic behaviors of metal material such as stretching the tablets and forming a dimple were also confirmed in simulation. Therefore, it is identified that the proposed model could express the behavior of metal material.

A new model for estimating macroscopic permittivity was proposed to predict dispersion states of filler particles in a particulate composite material. In the model, the estimation targets are random packed composite materials. The composite materials were represented as a cluster of unit cells. The unit cells were connected by a proposed layer structure model. The macroscopic permittivity was estimated by calculating a synthetic capacity of the cluster.

The proposed model was validated by comparisons between estimated and measured macroscopic permittivity of several particulate composite materials. In addition, it was identified that the proposed model could estimate the permittivity more accuracy than an existing theoretical equation’s one due to considering the effects for the dispersion states of filler particles. Furthermore, it was indicated that the proposed model could also estimate the dispersion states of filler particles by the measured permittivity. The applicability of the method was confirmed by comparisons between estimated and experimental dispersion states of filler particles.

The uptake of nanoparticles (NPs) into biological cells with rigid cell walls is poorly understood. Interestingly, the authors demonstrated that positively charged polystyrene NPs were taken into yeast cells in the physiological saline. However, the polystyrene NPs are not suitable for carrier NPs due to their low biodegradability. In this study, we evaluated the uptake of biodegradable poly(lactic-co-glycolic) acids (PLGA) NPs into the yeast cells. As a result, PLGA NPs were taken into yeast cells regardless of their surface potentials. The yeast cells were alive after the uptake of negatively charged NPs, whereas the cell viability for the positively charged NPs was low. In addition, the experiments using endocytosis inhibitors suggested that the uptake of PLGA NPs was different from the conventional endocytosis. These experimental results strongly suggested that the negatively charged PLGA NPs are suitable for the delivery of useful substances to eukaryotic cells with cell walls.

Monolayer films composed of ordered particle arrays exhibit unique optical properties, which lead to various potential applications like sensors and antireflective coatings. In this study, we investigated particle deposition processes by using a drag coating technique based on convective self-assembly. Unlike micron-sized particles, 300-nm particles formed submonolayers instead of monolayers. Hence, we modified the technique and demonstrated that reversed dragging, introduction of a film blade, and periodic change in deposition speed dramatically improved the particle deposition process to cover the entire substrate surface uniformly with a monolayer of ordered particle arrays. Furthermore, our modified drag coating process produced monolayers of particles with different sizes of 570, 120, 45, and 27 nm. Thus, our technique is simple and versatile, and is applicable to a wide particle size ranging from microns to tens of nanometers.