Hosokawa Powder Technology Foundation ANNUAL REPORT
Annual Report of Hosokawa Powder Technology
Foundation founded for the purpose to contribute to the
promotion and advancement of powder technology Annual Report of Hosokawa Powder Technology Foundation, which was
founded in December, 1991 for the purpose to contribute to the promotion and
advancement of powder technology, includes the report of the business contents
and present status of the foundation in each fiscal year as well as the
research reports submitted by the awardees supported by the foundation. The
details of the activities of the foundation are opened in its homepage on the
website(http://www.kona.or.jp/en/index.html).
In this study, a numerical simulation model was developed in conjunction with X-ray CT (computed tomography) images of actual facemasks in order to clarify the behavior of submicron-sized particles in the facemask microstructure. It was found that the presence of large pores inside the microstructure caused streamlines to curve near the facemask domain, and particles accompanying the streamlines were more likely to be collected on the pore surface. Although the presence of pores results in a decrease in a pressure drop and the collection efficiency, the above effect suppresses the decrease in the collection efficiency and thus improves the performance (quality factor) of the facemask.
In this study, we numerically
investigated the collection behavior of submicron particles within the
microstructure of a facemask. After obtaining the three-dimensional structure
of a commercially available facemask using X-ray CT image analysis, simulations
of aerosol filtration through the obtained microstructure were performed. The
results showed that when there was a local coarse and dense structure and
relatively large pores within the microstructure, particles were more likely to
be collected at the surface of the pores, resulting in a high-quality factor.
The mechanical reliability of products must be assured for scaling up and production of complex-shaped components by spark plasma sintering (SPS) of spray-dried granules. The evolution of morphologies of pores and defects, which control the mechanical strength, is investigated by using synchrotron X-ray multiscale tomography during SPS of alumina granules at 1300°C. While large defects arising from the hierarchical granule packing structure cannot be removed by pressureless sintering, crack-like defects and branched rodlike defects are almost eliminated by SPS at stresses higher than 30 and 50 MPa, respectively. But, small ellipsoidal porous regions, which may arise from aggregates or dimples of granules, cannot be removed even at a pressure of 50 MPa. A very large defect is also found by using micro-CT. It is supposed that this defect is formed from a large void in loosely packed granules. The shrinkage of large voids and the elimination of crack-like defects are explained by the theoretical prediction based on the continuum theory of sintering.
The mechanical
reliability of products must be assured for scaling up and production of
complex-shaped components by spark plasma sintering (SPS) of spray-dried granules.
The evolution of morphologies of pores and defects, which control the
mechanical strength, is investigated by using synchrotron X-ray multiscale
tomography during SPS of alumina granules at 1300 °C. While large defects arising from
the hierarchical granule packing structure cannot be removed by pressureless
sintering, crack-like defects, and branched rodlike defects are almost
eliminated by SPS at stresses higher than 30 and 50 MPa,
respectively.
All-solid-state lithium-ion batteries are promising next-generation secondary batteries, primarily because of their superior safety. In their production process, it is necessary to achieve large contact interfaces between the particles and improve particle fluidity. The particle shape of the solid electrolyte plays a key role in addressing these requirements. Li3PS4 (LPS) is synthesized in the liquid phase and offers the advantages of cost-effectiveness and production scalability. However, the mechanisms controlling particle size and shape have not yet been revealed. In this study, we synthesized LPS particles in the liquid phase using a hot stirrer and an ultrasonic homogenizer to investigate the effects of reaction temperature and impact force on the reaction time and particle shape. We successfully synthesized shape-controlled particles with high ionic conductivity by combining different synthesis methods. This study provides valuable data for optimizing the synthesis conditions to attain specific particle shapes and sizes.
In all-solid-state batteries, the particle shape of
the solid electrolyte plays an important role in increasing the contact
interface and improving flowability. This study investigated the effects of
reaction temperature and impact force on reaction time and particle shape in
the liquid phase synthesis of Li3PS4 (LPS) particles. By
using a hot stirrer, LPS particles were successfully synthesized much faster
than conventional synthesis methods. Furthermore, it was demonstrated that the
particle shape of LPS was determined by the impact energy during the reaction
process.
Porous structures are increasingly getting attentions in developing environmental catalysts, such as three-way catalysts (TWC), due to their ability to improve catalyst performance without changing their composition. This study explored various template-to-TWC mass ratios to create an optimal interconnected nanoporous structure while maintaining the catalyst morphology. This optimized sample was then investigated to compare CO oxidation performance with nanoparticles and aggregate structures. The results demonstrated that the nanoporous structure improved CO oxidation efficiency by 50% compared with other structures. This improvement is attributed to the better diffusion of reactants within the interconnected porous structures of the nanoporous sample. These findings highlight the critical role of nanoporous structures in enhancing the effectiveness of environmental catalysts.
To enhance the gas purification efficacy
of three-way catalysts (TWC), macroporous TWC particles were synthesized using
an aerosol process with the assistance of a polymer template particles (polystyrene
latex). The results indicated that the large pore size of the macroporous
structure facilitated gas diffusion within the structures. On the other hand,
the presence of aggregates and nanoparticle structures within the TWC particles
reduced this diffusion capability. Therefore, the improved diffusion
capabilities of the macroporous structures led to superior CO oxidation
performance compared to other configurations.
Several types of metal–organic frameworks (MOFs) exhibit S-shaped adsorption isotherms due to their structural expansions. These materials are obtained as powder samples and require molding for industrial use; however, molding the samples with polymer binders reportedly made the S-shape less distinct. Our previous study elucidated this mechanism: the polymers inhibited the volume expansion of MOFs in the pellets. In this study, we molded two types of flexible MOFs exhibiting different volume expansion ratios and compared their adsorption behaviors. We concluded that a flexible MOF with a smaller volume expansion suppresses the smeared effect when in pellet form.
Several
metal–organic frameworks (MOFs) exhibit S-shaped adsorption isotherms due to
their structural transition. The unique behavior makes flexible MOFs promising
materials to renovate the conventional energy-wasting processes. The use of
flexible MOFs in an adsorption column requires molding; however, a typical
molding method significantly reduces the adsorption performance. This is mainly
because the volume expansion of flexible MOFs upon structural transition is
inhibited in molds. This paper aims to compare the adsorption behaviors on the
molds with two flexible MOFs that show different ratios of volume expansion and
to investigate the effect of the expansion on the adsorption behavior.