Hosokawa Powder Technology Foundation ANNUAL REPORT
Online ISSN : 2189-4663
ISSN-L : 2189-4663
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Research Grant Report
  • Yoshihiko ARAO
    2018 Volume 26 Pages 20-24
    Published: 2018
    Released: May 31, 2019
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    We have found new process for mass production of high-aspect ratio nanosheets. In liquid-phase exfoliation, layered materials are gradually fragmented by shear force. During the fragmentation, active species are generated at the edge. In general, these active species lead to agglomeration of the nanoparticles. In this study, we added small amount of salts, and the salts can react with the activated edge. The chemical bonded salt enhances the negative charging of nanosheets, and this contributes the exfoliation of layered material in incompatible solvent such as water, alcohol, and acetone and so on. The aspect ratio of nanosheets is also improved by adding salt. This finding will pave the way for the effective usage of nanosheet dispersion.

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  • Shingo ISHIHARA
    2018 Volume 26 Pages 25-31
    Published: 2018
    Released: May 31, 2019
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    A new simulation approach using Advanced Distinct Element Method (ADEM) was proposed to predict the compression behavior and the characteristic of the compact. Relationship between compression load and compressive strength of compact have been analyzed. The breakage behavior and discrete motion of particles during compression was simulated by ADEM. ADEM parameters represent the property of samples, it was determined to fit the experimental results of load-displacement curve obtained by single particle compression test. Internal structure of compact was measured by X-ray CT imaging, information of particle breakage and density distribution was obtained. High density compact could make as a result of high compression load, on the other hand, compressive strength of compact decrease when the compression load was much high. There was optimum condition to obtain the tough compact. Simulation analysis could visualize the compression behavior of compact, fine powder ratio suggest the optimum compression load for powder compact.

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  • Miki INADA
    2018 Volume 26 Pages 32-35
    Published: 2018
    Released: May 31, 2019
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    12CaO·7Al2O3 (C12A7) is composed of cationic cages in which various anions are incorporated. Conventionally, most of reported C12A7 were synthesized by solid state reaction at high temperature above 1200°C using starting reagents such as CaCO3 and γ-Al2O3. This strict heating condition causes the undesirable problems such as increase of the C12A7 particle size and decrease of specific surface area (SSA). Liquid phase process is one of the potential methods of synthesis of C12A7 fine particles with high SSA, which does not require high temperature for heat treatment. In this study, C12A7 porous particles were synthesized from 3CaO·Al2O3·6H2O (hydrogarnet) as precursor prepared by liquid phase process. The synthesized C12A7 were cubic-shaped particles with porous surfaces and the SSA reached the maximum at 55 m2/g.

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  • Tomohiro IWASAKI
    2018 Volume 26 Pages 36-40
    Published: 2018
    Released: May 31, 2019
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    The effects of particle diameter and aggregation of magnetic nanoparticles as heating mediator on the induction heating of magnetic fluids in an alternating magnetic field have been studied experimentally and numerically. As a model magnetic material, magnesium zinc ferrite nanoparticles, which are biocompatible and have excellent induction heating properties, were used. The magnesium zinc ferrite nanoparticles were synthesized via mechanochemical treatment of the precursor, followed by aging. The water-based magnetic fluids consisting of the magnesium zinc ferrite nanoparticles with different diameters were prepared using aqueous solutions including citrate ion and nonionic surfactant as anti-aggregating agent. The magnetic fluids that the nanoparticles were well dispersed showed a relatively large temperature increase rate. On the other hand, when the nanoparticles aggregated at low pH conditions, the temperature increase rate reduced, which was also numerically confirmed. The results demonstrated that not only the particle diameter but also the aggregation/dispersion conditions could be the important factors controlling the induction heating properties.

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  • Shu YIN
    2018 Volume 26 Pages 41-45
    Published: 2018
    Released: May 31, 2019
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    In this research, the synthesis of tungsten-based infrared shielding materials such as tungsten bronze and tungsten sub-oxide was carried out by an environment-friendly soft chemical process. The nano- and microstructure was also controlled in order to improve their infrared shielding functionality. Furthermore, their composites with photocatalyst nanoparticles were also prepared to realize the multifunctionality of photocatalytic materials. Also the photocatalyst thin films were synthesized by using the functional composite particle materials. It is expected that the multi-functionality consists of visible light transparency, ultraviolet rays/infrared light shielding and environmental purification effects can be realized. The concept of the present research can be applied to various photocatalyst materials. The photocatalytic composite materials imparted with infrared light shielding functionality show great potential on novel building material applications, and are expected to be applied as multifunctional smart window materials.

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  • Hiroyuki USUI
    2018 Volume 26 Pages 46-52
    Published: 2018
    Released: May 31, 2019
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    We prepared Na-ion battery anodes of Nb-doped rutile TiO2 and indium phosphide (InP) without conductive additive and binder by using an aerosol process in which active material powders are sprayed onto current collector substrates and are strongly adhered to form film electrodes. In the evaluation for the electrode comprised of Nb-doped TiO2 synthesized by a hydrothermal method, a better charge-discharge performance was obtained for Nb-doped TiO2 with a higher ratio of crystallite size to particle size. Among various binary phosphide electrodes, the InP anode showed a good performance next to an Sn4P3 anode which has been developed by the authors. The nanostructure analysis of the electrode active material suggests that the phase separation of InP occurred during its sodiation to form elemental In and P, and that InP anode showed good performance because metallic In phase relaxed a stress from P phase and compensated a poor electronic conductivity of Na3P phase.

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  • Tomoyuki OKUDA
    2018 Volume 26 Pages 53-59
    Published: 2018
    Released: May 31, 2019
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    For application of functional nanocrystals (nPTX) composed of paclitaxel (PTX) and polyethylene glycol derivatives with sustained release and pulmonary retention abilities to inhalation therapy, nPTX-loaded dry powders were newly produced by spray freeze drying (SFD) and their utility as inhaled formulations was investigated in the present study. The nPTX-loaded SFD powders produced with leucine as an excipient were demonstrated to allow reconstruction of nPTX with almost the same particle size distribution, sustained PTX release ability, and anticancer activity as the original ones after their dissolution and to have high aerosol performance for pulmonary delivery through inhalation. Furthermore, the nPTX-loaded SFD powders were clarified to show both more prolonged retention of PTX and milder irritation in the lungs after pulmonary delivery, compared with Taxol, a conventional liquid formulation of PTX. After dissolution of the nPTX-loaded SFD powders on the respiratory epithelium, reconstituted nPTX were found to be rapidly transferred to the lung tissue, followed by prolonged pulmonary retention. In therapeutic evaluation with lung metastasis mice, the nPTX-loaded SFD powders were suggested to exhibit anticancer effects in the lungs after pulmonary delivery. These results strongly indicate that the nPTX-loaded SFD powders are promising to apply to inhalation therapy against lung cancer.

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  • Kazunori KADOTA
    2018 Volume 26 Pages 60-65
    Published: 2018
    Released: May 31, 2019
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    A synergistic study on computational fluid dynamics (CFD) simulation and sample preparation with highly branched cyclic dextrin (HBCD) as an excipient matrix for dry powder inhaler formulations were performed. The fine particles with HBCD were prepared by spray-drying. HBCD formulations had the highest drug content in terms of both isoniazid and rifampicin. Larger surface areas were obtained for SDPs of HBCD than those of other sugars. Regarding inhalational properties, HBCD formulations had higher emitted dose and fine-particle fractions than formulations of all other sugars tested. Our results confirm the feasibility of the formulation of hydrophilic and hydrophobic drug substances into a single-dosage preparation for pulmonary delivery using HBCD as an excipient. CFD analysis revealed that high inhalation performance was related to the true density and particle size of SDPs. The results on CFD simulations made a prediction about the particle behavior or deposition in pulmonary airways.

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  • Takanori KIGUCHI
    2018 Volume 26 Pages 66-72
    Published: 2018
    Released: May 31, 2019
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    Recently, HfO2-based novel phase without spatial symmetry, which is interesting ferroelectric material as Pb-free and non-perovskite-type structure. HfxZr1 – xO2 (x = 0–1) (HZO) thin films are one of the representative materials with the orthorhombic phase Pca21 in the wide compositional range. We have attempted and realized the epitaxial growth of HZO thin films with the orthorhombic phase Pca21 using solid-state epitaxy with ion-beam sputtering followed by rapid thermal annealing. We have also described the nanoscale morphology and the domain structure of orthorhombic (Pca21) and coexisting monoclinic (P21/c) phases in HZO thin films using the aberration-corrected scanning transmission electron microscopy. These results indicate that two effects, the solute and the elastic constraint effects, are necessary for the stabilization of the orthorhombic phase.

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  • Kenya KUWAGI
    2018 Volume 26 Pages 73-79
    Published: 2018
    Released: May 31, 2019
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    Nowadays a vibration is often utilized in various industrial powder processes. When a vibration is added to a powder bed, the particles move like a fluid. Various powder flow patterns appear, depending on vibration conditions, including frequency and amplitude. The flow pattern is also affected by particles size, bed size, and aspect ratio. In order to examine the effect of powder amount and container shape on the convective flow of powder in a vibrated powder bed, both numerical simulation based on the discrete element method (DEM) and the Positron Emission Particle Tracking (PEPT) measurement were conducted. The obtained results indicate that the convective velocity of powder is independent of the column size under the present conditions. Then an equation to estimate convective velocity was derived from the simulated results. From the equation, it is conjectured that the convective velocity strongly depends on the vibration amplitude. The average velocities obtained using this equation were compared to the values measured using PEPT. When the frequency was less than 90 Hz and dimensionless acceleration was greater than 5, good agreement between the estimated and measured values was obtained.

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  • Murino KOBAYAKAWA
    2018 Volume 26 Pages 80-84
    Published: 2018
    Released: May 31, 2019
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    The plate drag in dry granular materials was simulated using a large-scale discrete element method (DEM). The effect of initial packing volume fraction of the materials on the drag force acting on the plate was examined. The results show that the force averaged in a steady state increases approximately linearly with the volume fraction. In addition, a volume fraction-dependent oscillation occurs in the force: at lower initial fraction, the force reaches an approximately constant value as the plate advances, while at higher initial fraction, the drag force has a larger amplitude oscillation. The observed force behavior is consistent with that obtained experimentally in previous studies. The analysis of local volume fraction in the materials during the drag shows that at the higher initial fraction, a clear shear band (slip surface), reaching from the plate tip to the free surface, is observed but not at the lower initial fraction. The force oscillations are attributed to the consecutive appearing and disappearing of the shear bands.

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  • Daisuke SUZUKI
    2018 Volume 26 Pages 85-88
    Published: 2018
    Released: May 31, 2019
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    Water-swollen hydrogel microspheres, microgels, are expected to be useful in various applications including coating, sensor, and carrier of drug delivery system. Until now, various types of functional microgels, such as core-shell microgels and hollow microgels, have been reported, anisotropic microgels, whose physicochemical structures are not homogeneous, remains to be studied. Therefore, in this study, our group tried to prepare such new types of hydrogel microspheres by modification of homogeneous polymeric microspheres at the interfaces.

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  • Hirokazu SETO
    2018 Volume 26 Pages 89-93
    Published: 2018
    Released: May 31, 2019
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    In this research, a novel particle counter, in which particles were detected by spectral characteristics of metal mesh device with periodic through holes of several micrometers, was developed. When the solution of latex particle with larger than the hole was passed through the metal mesh device, the infrared transmittance of the metal mesh device changed as the concentration of latex particle increased. A linear relationship between the concentration of particle and the change in the transmittance of infrared was confirmed. On the other hand, the infrared transmittance of the metal mesh device did not change, because the metal mesh device did not collect a small latex particle. The metal mesh device could collect and detect only latex particle with larger than the hole in the coexistence of small latex particle with 10 times higher concentration. It is expected that size distribution of particle can be measured by lamination of the metal mesh devices with different hole diameters.

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  • Toshihiro SERA
    2018 Volume 26 Pages 94-99
    Published: 2018
    Released: May 31, 2019
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    In this study, we developed the platform of numerical simulation to predict the particle deposition for drug delivery system (DDS) in lung. In particular, we focused on conducting airways and alveolar regions. In conducting airways, we proposed an averaged airway model design based on four healthy subjects and numerically evaluated its effectiveness for predicting the airflow and particle transport through an airway. It is necessary to use the individual model to obtain the particle deposition rate and distribution in detail, however the direct-averaged model may be useful for predicting the individual airflow and particle transport on a macroscopic scale. In alveolar regions, the deformation during respiration should be not ignored, and previously, the alveolar deformation is assumed to be homogenous self-similar. In this study, we reconstructed the heterogeneous realistic alveolar deformation by the image-based morphing and evaluated the particle transport. Compared from under the homogenous deformation, the particles under the heterogeneous deformation were transported and deposited widely in alveolar region.

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  • Kazuo TANAKA
    2018 Volume 26 Pages 100-104
    Published: 2018
    Released: May 31, 2019
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    Water-soluble networks containing the coumarin luminophore were prepared with polyhedral oligomeric silsesquioxane (POSS), and interaction with various particles was investigated. In particular, the relationships between optical properties of the dye in the networks and chemical composition as well as size of particles were evaluated. The POSS networks were constructed from octaammonium POSS by substituting with the coumarin derivative followed by connecting with succinic acid. From the optical measurements, we found that the coumarin-modified POSS and POSS networks showed bimodal emission spectra in aqueous solutions and changed the intensity ratio depending on their concentrations. The yellow emission of the POSS networks was influenced by coexistence of specific types of particles. The emission bands in the blue region were enhanced in the presence of polystyrene particles (PSPs) and poly(lactic acid) particles (PLAPs), meanwhile significant changes were hardly observed by adding the silica particles. Moreover, PSPs or PLAPs with the diameter no less than 1 μm slightly affected optical properties of the networks.

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  • Kazuho NAKAMURA
    2018 Volume 26 Pages 105-109
    Published: 2018
    Released: May 31, 2019
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    The performance of cake filtration depends on the pressure drop due to the permeation of liquid through cake layer. The size of gaps between particles in cake layer dominates the pressure drop. In this study a novel characterization method for the size of gaps based on the thickness of electric double layer around particles was developed and the results were compared with conventional methods based on hydraulic diameter Dh and capillary diameter Dp. The effects of size and morphology of particles were studied with PMMA latex particles, JIS powder (KANTO loam, sodium bicarbonate), PbSO4, Zn(OH)2. The specific cake resistance, αAV, decreased with the decrease in the average particle size. Dh and Dp were decreased with the decrease in D50. These results showed the smaller particles will make smaller gaps in cake layer. The Dsp could be determined by the analysis of the dependence of streaming potential of cake layer on electric conductivity. Dsp showed almost same trends for particles as Dh and Dp while the absolute value of Dsp showed 1/6~1/10 smaller than Dh and Dp. This result shows the Dsp is useful for the characterization of the size of gaps in cake layer.

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  • Tadachika NAKAYAMA
    2018 Volume 26 Pages 110-113
    Published: 2018
    Released: May 31, 2019
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    As a method of mixing ceramic particles, ball milling, jet mill, stirring such as Cyclomix®, mixing, shear type mixer, etc. have been conventionally used. Although these can be mixed very efficiently, problems of contamination have been pointed out. On the other hand, in our laboratory, we have developed a method to control the movement of ceramic particles with an electric field. Therefore, in this research, we examined whether particle mixing could be performed without causing contamination using an electric field.

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  • Yasuya NAKAYAMA
    2018 Volume 26 Pages 114-119
    Published: 2018
    Released: May 31, 2019
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    The drift motion of a particle under an external electric field, which is termed electrophoresis, is originated from the coupling between the responses of the particle and the ions in the electric double layer surrounding the particle. Since the response of the ions varies as the level of the external field, physics of nonlinear response in the electrophoresis has not been understood. We investigate the nonlinear electrophoretic response of a particle in a salt-free medium. Hydrodynamic equations for the dynamics of ionic distribution and solvent flow are directly solved by the smoothed profile method in order to clarify the response of the electric double layer to the external field. The electrophoretic mobility turns out to first increase and then saturate with an increase of the strength of the external field. These two different nonlinear electrophoretic responses are found to originate from the gradual counterion stripping and the change in electroosmotic flow due to the asymmetrized ionic distribution of the electric double layer.

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  • Tomonori FUKASAWA
    2018 Volume 26 Pages 120-124
    Published: 2018
    Released: May 31, 2019
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    The knowledge of the agglomerates formation from fine particles in the fluidized bed is essential in the powder handling. It is known that fine particles exhibit the unique agglomeration behavior. In this study, the effects of particle properties on the agglomerate formation in the vibrating fluidized bed were investigated using custom-made apparatus. ZnO, TiO2 rutile, and TiO2 anatase powder were used as tested powders. The formation mechanism of agglomerates in the vibrating fluidized bed was clarified by the observation using a high-speed camera. In addition, changes in powder layer height and pressure loss were measured. Based on the obtained results, changes in agglomerate size were calculated using Ergun equation, and agglomerate formation was evaluated.

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  • Cathy E. McNAMEE
    2018 Volume 26 Pages 125-129
    Published: 2018
    Released: May 31, 2019
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    Information about the physical properties of the air/water interface has been obtained by measuring the forces between an air/water interface and a particle (probe) in the water with the Monolayer Particle Interaction Apparatus. A silica particle was modified to be positive charge by using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride. The effect of the pH of the water on the forces was measured by adding HCl or NaOH to the water. The presence of a salt on the force curves was determined by adding NaCl to the water. In the absence of NaCl, the water surface was determined from the force curves to be positively charged at pH 2.0 and negatively charged for pH ≥ 3.0. The charges of interfaces for the pH 2.0 and pH ≥ 3.0 solutions were explained by the adsorption of H+ and OH ions, respectively, to the air/water interface. The surface of a 10 mM NaCl solution was seen from the force curves to be negatively charged at pH 2.0–7.0 and positively charged at pH 9.0. The addition of NaCl to the water therefore caused the charge pH 2.0 and pH 9.0 water surfaces to reverse. This charge reversal is explained by the specific adsorption of Na+ and Cl ions to the OH and H+ ions, respectively, that are at the air/water interfaces.

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  • Ryo MURAKAMI
    2018 Volume 26 Pages 130-134
    Published: 2018
    Released: May 31, 2019
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    Colloidal particles can be irreversibly adsorbed at fluid interfaces, such as oil-water and air-water interfaces. The particle adsorption leads to stabilization of dispersed systems of two immiscible fluids and particle-stabilized, that is, Pickering-type emulsions and foams can be prepared. These materials show some unique properties as a result of adsorption of the particles at the fluid-fluid interface. One of the striking phenomena is that liquid drops can be dispersed in air with the liquid-air surfaces coated by liquid-repellent particles. When the liquid is water, a water-in-air material, named dry water, is produced by aerating water in the presence of very hydrophobic particles. The dry water is a free-flowing powder which can contain significant quantities of water as micrometer-sized drops. Emulsions with water-continuous phase have been also powderized by following the same method. The prepared materials are regarded as oil-in-water-in-air (o/w/a) materials (powdered o/w emulsions). To prepare the powdered o/w emulsions efficiently, it has been shown that the extent of creaming of the oil droplets has to be suppressed. It is expected that, by applying the strategy used to stabilize the powdered o/w emulsions, air-in-water-in-air (a/w/a) materials (powdered aqueous foams) can be prepared. One of the difficulties to prepare the powdered aqueous foams is the significant density difference between air and water, which could enhance the extent of creaming of air bubbles during the preparation and leads to their disappearance due to coalescence. We have reduced the extent of creaming by increasing the viscosity of the water phase and enhanced the preparation of powdered aqueous foams.

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  • Ryoichi YAMAMOTO
    2018 Volume 26 Pages 135-139
    Published: 2018
    Released: May 31, 2019
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    One of the biggest problems when computational approaches are applied for novel engineering targets is that the software often does not support necessary inter-particle force models or boundary conditions needed to reproduce proper situations. Many previous simulation studies are based mostly on scientific and academic interests or focusing only on whether already known experimental results are correctly reproduced or whether the reliability of the model is acceptable. This prevents computational approaches to be used as an effective tool to develop new materials and processes. In this project, we aimed to enhance the applicability and functionality of a colloid simulator KAPSEL, which has been developed by ourselves. Specifically, we have achieved the following points.

    1) DLVO model was implemented as an interparticle force model for efficiently simulating charged particle dispersions with thinner electric double layer compared to the particle diameter.

    2) The simulation code is parallelized so that more realistic larger-scale systems can be simulated.

    3) The external-electric-field induced anisotropic interaction between like-charged colloidal particles is calculated.

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  • Tetsu YONEZAWA
    2018 Volume 26 Pages 140-144
    Published: 2018
    Released: May 31, 2019
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    We report here the preparation of metal/metal oxide core-shell particles as phase-change materials (PCM) which work as a latent heat storage system. In this study, silica-coated tin nanoparticles have been prepared. Sn nanoparticles were distributed inside for enhancing the thermal cyclic stability. After immersing the solution of Sn precursor, silica matrix was treated by hydrogen thermal reduction to obtain Sn@p-SiO2 nanoparticles. The porous silica matrix effectively prevented the coalescence or sintering of the Sn nanoparticles. The product did not show considerable changes in melting behavior up to 100th cycle of a freeze–melt cycle test.

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