Takashi Ogi - Academia.edu (original) (raw)

Papers by Takashi Ogi

ACS Applied Nano Materials

KONA Powder and Particle Journal

The development of energy storage devices providing high energy and power densities and long-term... more The development of energy storage devices providing high energy and power densities and long-term stability will play an important role in the future utilization of sustainable energy sources. Numerous efforts have been devoted to achieving these requirements, especially the design of advanced electrode materials. For this reason, there is growing interest in the innovation of new carbon-based materials with enhanced electrochemical performance. Nanostructured carbon spheres (CSs) have attracted significant attention due to their prominent properties, such as high surface area, excellent electrical conductivity, tunable porosity, and surface functionality. This review offers a comprehensive overview into the recent advances of nanostructured CSs within the last five years, focusing on synthetic strategies for producing carbon particles with precisely controlled morphologies and interior structures, as well as the potential applications of these particles as high-performance electrode materials in rechargeable batteries and supercapacitors. The challenges and perspectives on future research directions are highlighted, focusing on the controlled synthesis and functionalization of nanostructured CSs with tunable structures and properties that are well-suited to practical applications. This review is intended to serve as a helpful resource to researchers involved in the fabrication of new CS materials and the development of methods to control their structure and morphology.

Hosokawa Powder Technology Foundation ANNUAL REPORT

The production of carbon-based materials with controllable shapes and structures from biomass in ... more The production of carbon-based materials with controllable shapes and structures from biomass in accordance with sustainable development goals is of high interest and encouraged. In this work, the carbon spheres were successfully fabricated via a spray drying method followed by the carbonization process, using Kraft lignin as the carbon source and potassium hydroxide (KOH) as the activation agent. The spherical carbon particles could be precisely controlled from dense to hollow sphere by varying the KOH concentration. In addition, the produced carbon has a high specific surface area (2424.8 m 2 g-1) and could be used as active electrode materials for supercapacitors.

Journal of Materials Chemistry C

High-density submicron-sized FeNi particles prepared by a spray pyrolysis route exhibit high magn... more High-density submicron-sized FeNi particles prepared by a spray pyrolysis route exhibit high magnetic characteristics and enhance the powder core performance indicated by the improvement of the DC bias characteristic value.

Data for hysteresis curves shown in Figure 5, Figure 6, and Figure 7.

Indonesian Journal of Science and Technology, 2021

The unique structure of Magnéli phases TiOx renders them effective for the electrochemical applic... more The unique structure of Magnéli phases TiOx renders them effective for the electrochemical applications. This work demonstrates a synthesis of carbon-coated Magnéli phases TiOx (TiOx@C) nanoparticles from 3-aminophenol and rutile titania (TiO2) nanoparticles as a support for platinum (Pt) electrocatalyst. 3-aminophenol was polymerized and carbonized on the surface of TiO2 nanoparticles respectively in a microwave hydrothermal reactor and a tubular furnace. Reduction of the carbon-coated TiO2 (TiO2@C) into TiOx@C was performed in hydrogen atmosphere at 800-1050 °C. The carbon coating effectively prevented TiO2 nanoparticles from sintering, resulted in TiOx@C sizes from 50 to 100 nm. Single-phase Ti4O7 core, which has the highest theoretical electrical conductivity among the Magnéli phases, was obtained from reduction of TiO2@C at 1000 °C. for 10 min C/Ti4O7-supported Pt exhibited an electrochemical surface area of 46 m2 mgPt-1 at 15% Pt loading, slightly higher than that reported for...

Japan Geoscience Union, 2014

Aerial observations were conducted over the East China Sea in October 2009 (autumn), December 201... more Aerial observations were conducted over the East China Sea in October 2009 (autumn), December 2010 (winter) and March 2012 (spring). The base airport was Goto Fukue Airport in Fukue Island, Nagasaki, Japan. The flights were performed between Fukue Island and the southern offing of Jeju Island and the flight altitudes were 500, 1000, 2000 and 3000 metres. The concentration ratios of particulate nitrate (NO3(p)) to inorganic total nitrate (T.NO3) were less than 0.5 in most of the flights except under high concentrations of dust particles (Kosa) or trans-boundary air pollutants. Most of the NO3(p) would be comprised of NaNO3 formed by the reaction of gaseous nitric acid (HNO3(g)) with sea salt aerosols during the observations in autumn and winter, with the exceptions of October 17 and December 11, when high concentrations of Kosa were transported. In the spring observation, the fraction of NaNO3 in NO3(p) was low and a large part of NO3(p) would be originated from reactions of HNO3(g) ...

重金属、希少金属を使用することなく、また、特殊な付活剤を使用することなく、高い発光強度を示し、また、発光スペクトルのピークトップを調整し、色彩を変えることができるＭ－Ｃ－Ｎ－Ｏ系蛍光体を提供する... more 重金属、希少金属を使用することなく、また、特殊な付活剤を使用することなく、高い発光強度を示し、また、発光スペクトルのピークトップを調整し、色彩を変えることができるＭ－Ｃ－Ｎ－Ｏ系蛍光体を提供する。また、これを用いた環境適合性の高いポリマー分散液、無機ＥＬ素子、発光素子、蛍光管などを提供する。 本発明に係るＭ－Ｃ－Ｎ－Ｏ系蛍光体は、IIIＢ族元素（Ｍ）、炭素（Ｃ）、窒素（Ｎ）及び酸素（Ｏ）元素からなるものである。このＭ－Ｃ－Ｎ－Ｏ系蛍光体において、炭素（Ｃ）元素の含有量を変化させることにより色彩を変化させる。そして、このＭ－Ｃ－Ｎ－Ｏ系蛍光体を用いてポリマー分散液、無機ＥＬ素子、発光素子、蛍光管を構成する。

Magnetic wires in highly dense arrays, possessing unique magnetic properties, are eagerly anticip... more Magnetic wires in highly dense arrays, possessing unique magnetic properties, are eagerly anticipated for inexpensive and scalable fabrication technologies. This study reports a facile method to fabricate arrays of magnetic wires directly assembled from well-dispersed α<i>″</i>-Fe₁₆N₂/Al₂O₃ and Fe₃O₄ nanoparticles with average diameters of 45 nm and 65 nm, respectively. The magnetic arrays with a height scale of the order of 10 mm were formed on substrate surfaces, which were perpendicular to an applied magnetic field of 15 T. The applied magnetic field aligned the easy axis of the magnetic nanoparticles (MNPs) and resulted in a significant enhancement of the magnetic performance. Hysteresis curves reveal that values of magnetic coercivity and remanent magnetization in the preferred magnetization direction are both higher than that of the nanoparticles, while these values in the perpendicular direction are both lower. Incensement in the magnetic property for arrays made from spindle-shape α<i>″</i>-Fe₁₆N₂/Al₂O₃ nanoparticles is higher than that made from cube-like α<i>″</i>-Fe₁₆N₂/Al₂O₃ ones, owing to the shape anisotropy of MNPs. Furthermore, the assembled highly magnetic α<i>″</i>-Fe₁₆N₂/Al₂O₃ arrays produced a detectable magnetic field with an intensity of approximately 0.2 T. Although high-intensity external field benefits for the fabrication of magnetic arrays, the newly developed technique provides an environmentally friendly and feasible approach to fabricate magnetic wires in highly dense arrays in open environment condition.

Arabian Journal of Chemistry, 2021

Abstract As the second most abundant bio-resource and as a byproduct of lignocellulose material p... more Abstract As the second most abundant bio-resource and as a byproduct of lignocellulose material processing, alkali lignin has to become a quantitative issue due to its difficulties to handle. On the other hand, lignin has high natural carbon contents, so it has the potential to act as a precursor for carbon materials. However, many previous researchers do three steps to transform it into high porous carbon: precipitation by reducing the alkaline compound, calcination to transform it into carbon, and carbon activation by adding alkaline compound again. In this study, the porous carbon material from alkali lignin in a one-step process for use as an electrode in supercapacitor and electrocatalyst is examined. The evaporation and especially carbonation temperature are studied to obtain the high porous carbon. After varying calcination temperatures, the carbon material's characterization was investigated to examine porosity, morphology, crystallinity, specific electrocapacity, and Oxygen Reduction Reaction (ORR) electrocatalyst activity. The carbon derived from Na-lignin via calcination at 700 °C had the highest electrocapacity of 168.29 F/g. The electron transformed number is 2.23, indicating that the carbon derived from Na-lignin via calcination is promising for an electrode agent of supercapacitor and electrocatalyst for ORR.

Magnesium is a promising hydrogen storage material but requires an efficient catalyst to enhance ... more Magnesium is a promising hydrogen storage material but requires an efficient catalyst to enhance the sluggish kinetics of its hydrogen desorption/absorption reactions. Niobium catalysts have been shown to accomplish this, but the effective factors for catalysis on hydrogen desorption/absorption of Mg are not well understood. In order to investigate these aspects, various types of Nb oxides were synthesized and mixed with Mg, and their catalytic properties were investigated. The spray pyrolysis synthesis of Nb oxides at different temperatures produced homogeneous spherical particles with different degrees of crystallinity, while Nb oxide particles synthesized by simple calcination of ammonium niobium oxalate were nonuniform. These Nb oxides show significant catalytic activities for the hydrogen desorption/absorption of Mg, with amorphous oxides being more effective catalyst precursors than crystalline precursors. Metastable, amorphous Nb oxide is more easily converted to the reduced state, which is the catalytically active state for the reactions. In addition, Nb in the deactivated sample is in the oxidized state compared with the initially activated sample, and the catalytically active (reduced) state is recovered by reactions with hydrogen. Based on these findings, it is concluded that the chemical state of Nb is an important factor in catalyzing the desorption/absorption of hydrogen by Mg, and the catalytically active state can be preserved without further treatments.

Advanced Powder Technology, 2019

Hexagonal cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles are well known as near-infrared (NI... more Hexagonal cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles are well known as near-infrared (NIR) 31 shielding materials. However, one of the critical issues for industrial applications involves a pho-32 tochromic instability, i.e., a blue color change of this material under ultraviolet (UV) irradiation. This color 33 change is attributed to the formation of H x WO 3 phase through doping of H + ions into Cs-deficient sites 34 present at the surface of Cs 0.32 WO 3 nanoparticles. Therefore, a new approach was adopted to prevent 35 the color change by synthesizing a Cs 0.32 WO 3 nanoparticle with less Cs-deficient sites using spray pyrol-36 ysis followed by heat treatment and short-time milling. The Cs 0.32 WO 3 nanoparticles of spray pyrolysis 37 route exhibited an improved photochromic stability under UV irradiation compared to those synthesized 38 through a solid-state-reaction route. Detailed analysis using atomic resolution transmission electron 39 microscopy revealed that the Cs 0.32 WO 3 nanoparticles of spray pyrolysis route retain Cs ions up to a 40 depth of less than 1 nm from the surface. This work demonstrates that the less-Cs-deficient Cs 0.32 WO 3 41 nanoparticles are beneficial to improve the photochromic stability. 42

Journal of the Society of Powder Technology, Japan, 2019

Advanced Powder Technology, 2018

Highly crystalline and hexagonal single-phase cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles... more Highly crystalline and hexagonal single-phase cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles were 33 successfully synthesized by a flame-assisted spray pyrolysis followed by annealing under a reducing 34 gas atmosphere. The resulting Cs 0.32 WO 3 nanoparticles featured a pure hexagonal Cs 0.32 WO 3 phase with 35 a high crystallinity and homogeneous chemical composition. Unlike conventional methods, the proposed 36 process in this paper has several advantages, including a short reaction time and the ability to yield prod-37 ucts with high purity and good energy efficiency. Furthermore, the Cs 0.32 WO 3 nanoparticles produced in 38 this research showed a remarkable near-infrared shielding ability with a 97.7% cutoff at 1500 nm.

Advanced Powder Technology, 2018

The metastable state hexagonal-tungsten oxide (h-WO 3) has been attracting attention over the pas... more The metastable state hexagonal-tungsten oxide (h-WO 3) has been attracting attention over the past dec-32 ade because of its high reactivity that arises from the hexagonal channels in its crystal structure. 33 Simplification of the process used to synthesize h-WO 3 is an important step to facilitate the industrial 34 applications of this material. In this study, we addressed this challenge by developing a spray pyrolysis 35 process to synthesize highly crystalline h-WO 3. The ratio of the monoclinic to the hexagonal phase 36 was controlled by adjusting the segregation time. Single-phase h-WO 3 nanorods were synthesized using 37 a carrier gas flow rate of 1 L/min, which was equivalent to a segregation time of 18.4 s. The ability of the 38 h-WO 3 nanorods to adsorb nitrogen and carbon dioxide was evaluated to confirm the presence of hexag-39 onal channels in the crystal structure.

Bioresource technology, 2016

Adsorption performance in the biosorption of tungsten using Escherichia coli cells can be signifi... more Adsorption performance in the biosorption of tungsten using Escherichia coli cells can be significantly improved by using cell suspensions that have been heat-treated at ⩽100°C. In the case of E. coli cells suspension heated at 100°C, the aqueous tungsten ions concentration rapidly decreased from 0.8mmol/L to practically zero within 1h. This biosorption time is much shorter than that of non-heat treated E. coli cells (7h). Furthermore, the adsorption saturation amount for cells heat-treated at 100°C was significantly increased up to 1.62mmol-W/g-E. coli compared to the unheated E. coli cells case (0.62mmol-W/g-E. coli). Determination of the surface potential and surface structure along with quantitative analyses of free amino acids of heat-treated E. coli cells were also carried out and revealed that heated cells have a high zeta potential and express a higher concentration of amino acids on the cell surface.

AIChE Journal, 2017

Nanostructured particles (clusters) with complex and periodic topography at the microscopic scale... more Nanostructured particles (clusters) with complex and periodic topography at the microscopic scale show unique structural patterns. Hence, good properties should be obtained when the surface topography of such clusters, especially those containing nanoparticles (NPs) of different sizes, can be carefully tuned. The coffee-ring structure is one of the most interesting structures for catalyst and photonic crystal applications or porous particle molds. Here, well-defined clusters with a coffeering structure were prepared by spray drying. The complexity of the NP distribution in the resulting two-and threecomponent systems is discussed. A better understanding of how finite groups of different NPs self-organize in a moving droplet to form a confined geometry may aid in controlling the structure of matter at multiple length scales. Interestingly, the configuration of the large microsphere clusters was found to be influenced by the presence of the small particles, which formed a ring-like structure.

Gold Bulletin, 2010

We report a simple and rapid process for the roomtemperature synthesis of gold nanoparticles usin... more We report a simple and rapid process for the roomtemperature synthesis of gold nanoparticles using tannic acid, a green reagent, as both the reducing and stabilising agent. We systematically investigated the effect of pH on the size distribution of nanoparticles synthesized. Based on induction time and-potential measurements, we show that particle size distribution is controlled by a fine balance between the rates of reduction (determined by the initial pH of reactants) and coalescence (determined by the pH of the reaction mixture) in the initial period of growth. This insight led to the optimal batch process for size-controlled synthesis of 2-10 nm gold nanoparticles-slow addition (within 10 minutes) of chloroauric acid into tannic acid.

ACS Applied Nano Materials

KONA Powder and Particle Journal

The development of energy storage devices providing high energy and power densities and long-term... more The development of energy storage devices providing high energy and power densities and long-term stability will play an important role in the future utilization of sustainable energy sources. Numerous efforts have been devoted to achieving these requirements, especially the design of advanced electrode materials. For this reason, there is growing interest in the innovation of new carbon-based materials with enhanced electrochemical performance. Nanostructured carbon spheres (CSs) have attracted significant attention due to their prominent properties, such as high surface area, excellent electrical conductivity, tunable porosity, and surface functionality. This review offers a comprehensive overview into the recent advances of nanostructured CSs within the last five years, focusing on synthetic strategies for producing carbon particles with precisely controlled morphologies and interior structures, as well as the potential applications of these particles as high-performance electrode materials in rechargeable batteries and supercapacitors. The challenges and perspectives on future research directions are highlighted, focusing on the controlled synthesis and functionalization of nanostructured CSs with tunable structures and properties that are well-suited to practical applications. This review is intended to serve as a helpful resource to researchers involved in the fabrication of new CS materials and the development of methods to control their structure and morphology.

Hosokawa Powder Technology Foundation ANNUAL REPORT

The production of carbon-based materials with controllable shapes and structures from biomass in ... more The production of carbon-based materials with controllable shapes and structures from biomass in accordance with sustainable development goals is of high interest and encouraged. In this work, the carbon spheres were successfully fabricated via a spray drying method followed by the carbonization process, using Kraft lignin as the carbon source and potassium hydroxide (KOH) as the activation agent. The spherical carbon particles could be precisely controlled from dense to hollow sphere by varying the KOH concentration. In addition, the produced carbon has a high specific surface area (2424.8 m 2 g-1) and could be used as active electrode materials for supercapacitors.

Journal of Materials Chemistry C

High-density submicron-sized FeNi particles prepared by a spray pyrolysis route exhibit high magn... more High-density submicron-sized FeNi particles prepared by a spray pyrolysis route exhibit high magnetic characteristics and enhance the powder core performance indicated by the improvement of the DC bias characteristic value.

Data for hysteresis curves shown in Figure 5, Figure 6, and Figure 7.

Indonesian Journal of Science and Technology, 2021

The unique structure of Magnéli phases TiOx renders them effective for the electrochemical applic... more The unique structure of Magnéli phases TiOx renders them effective for the electrochemical applications. This work demonstrates a synthesis of carbon-coated Magnéli phases TiOx (TiOx@C) nanoparticles from 3-aminophenol and rutile titania (TiO2) nanoparticles as a support for platinum (Pt) electrocatalyst. 3-aminophenol was polymerized and carbonized on the surface of TiO2 nanoparticles respectively in a microwave hydrothermal reactor and a tubular furnace. Reduction of the carbon-coated TiO2 (TiO2@C) into TiOx@C was performed in hydrogen atmosphere at 800-1050 °C. The carbon coating effectively prevented TiO2 nanoparticles from sintering, resulted in TiOx@C sizes from 50 to 100 nm. Single-phase Ti4O7 core, which has the highest theoretical electrical conductivity among the Magnéli phases, was obtained from reduction of TiO2@C at 1000 °C. for 10 min C/Ti4O7-supported Pt exhibited an electrochemical surface area of 46 m2 mgPt-1 at 15% Pt loading, slightly higher than that reported for...

Japan Geoscience Union, 2014

Aerial observations were conducted over the East China Sea in October 2009 (autumn), December 201... more Aerial observations were conducted over the East China Sea in October 2009 (autumn), December 2010 (winter) and March 2012 (spring). The base airport was Goto Fukue Airport in Fukue Island, Nagasaki, Japan. The flights were performed between Fukue Island and the southern offing of Jeju Island and the flight altitudes were 500, 1000, 2000 and 3000 metres. The concentration ratios of particulate nitrate (NO3(p)) to inorganic total nitrate (T.NO3) were less than 0.5 in most of the flights except under high concentrations of dust particles (Kosa) or trans-boundary air pollutants. Most of the NO3(p) would be comprised of NaNO3 formed by the reaction of gaseous nitric acid (HNO3(g)) with sea salt aerosols during the observations in autumn and winter, with the exceptions of October 17 and December 11, when high concentrations of Kosa were transported. In the spring observation, the fraction of NaNO3 in NO3(p) was low and a large part of NO3(p) would be originated from reactions of HNO3(g) ...

重金属、希少金属を使用することなく、また、特殊な付活剤を使用することなく、高い発光強度を示し、また、発光スペクトルのピークトップを調整し、色彩を変えることができるＭ－Ｃ－Ｎ－Ｏ系蛍光体を提供する... more 重金属、希少金属を使用することなく、また、特殊な付活剤を使用することなく、高い発光強度を示し、また、発光スペクトルのピークトップを調整し、色彩を変えることができるＭ－Ｃ－Ｎ－Ｏ系蛍光体を提供する。また、これを用いた環境適合性の高いポリマー分散液、無機ＥＬ素子、発光素子、蛍光管などを提供する。 本発明に係るＭ－Ｃ－Ｎ－Ｏ系蛍光体は、IIIＢ族元素（Ｍ）、炭素（Ｃ）、窒素（Ｎ）及び酸素（Ｏ）元素からなるものである。このＭ－Ｃ－Ｎ－Ｏ系蛍光体において、炭素（Ｃ）元素の含有量を変化させることにより色彩を変化させる。そして、このＭ－Ｃ－Ｎ－Ｏ系蛍光体を用いてポリマー分散液、無機ＥＬ素子、発光素子、蛍光管を構成する。

Magnetic wires in highly dense arrays, possessing unique magnetic properties, are eagerly anticip... more Magnetic wires in highly dense arrays, possessing unique magnetic properties, are eagerly anticipated for inexpensive and scalable fabrication technologies. This study reports a facile method to fabricate arrays of magnetic wires directly assembled from well-dispersed α<i>″</i>-Fe₁₆N₂/Al₂O₃ and Fe₃O₄ nanoparticles with average diameters of 45 nm and 65 nm, respectively. The magnetic arrays with a height scale of the order of 10 mm were formed on substrate surfaces, which were perpendicular to an applied magnetic field of 15 T. The applied magnetic field aligned the easy axis of the magnetic nanoparticles (MNPs) and resulted in a significant enhancement of the magnetic performance. Hysteresis curves reveal that values of magnetic coercivity and remanent magnetization in the preferred magnetization direction are both higher than that of the nanoparticles, while these values in the perpendicular direction are both lower. Incensement in the magnetic property for arrays made from spindle-shape α<i>″</i>-Fe₁₆N₂/Al₂O₃ nanoparticles is higher than that made from cube-like α<i>″</i>-Fe₁₆N₂/Al₂O₃ ones, owing to the shape anisotropy of MNPs. Furthermore, the assembled highly magnetic α<i>″</i>-Fe₁₆N₂/Al₂O₃ arrays produced a detectable magnetic field with an intensity of approximately 0.2 T. Although high-intensity external field benefits for the fabrication of magnetic arrays, the newly developed technique provides an environmentally friendly and feasible approach to fabricate magnetic wires in highly dense arrays in open environment condition.

Arabian Journal of Chemistry, 2021

Abstract As the second most abundant bio-resource and as a byproduct of lignocellulose material p... more Abstract As the second most abundant bio-resource and as a byproduct of lignocellulose material processing, alkali lignin has to become a quantitative issue due to its difficulties to handle. On the other hand, lignin has high natural carbon contents, so it has the potential to act as a precursor for carbon materials. However, many previous researchers do three steps to transform it into high porous carbon: precipitation by reducing the alkaline compound, calcination to transform it into carbon, and carbon activation by adding alkaline compound again. In this study, the porous carbon material from alkali lignin in a one-step process for use as an electrode in supercapacitor and electrocatalyst is examined. The evaporation and especially carbonation temperature are studied to obtain the high porous carbon. After varying calcination temperatures, the carbon material's characterization was investigated to examine porosity, morphology, crystallinity, specific electrocapacity, and Oxygen Reduction Reaction (ORR) electrocatalyst activity. The carbon derived from Na-lignin via calcination at 700 °C had the highest electrocapacity of 168.29 F/g. The electron transformed number is 2.23, indicating that the carbon derived from Na-lignin via calcination is promising for an electrode agent of supercapacitor and electrocatalyst for ORR.

Magnesium is a promising hydrogen storage material but requires an efficient catalyst to enhance ... more Magnesium is a promising hydrogen storage material but requires an efficient catalyst to enhance the sluggish kinetics of its hydrogen desorption/absorption reactions. Niobium catalysts have been shown to accomplish this, but the effective factors for catalysis on hydrogen desorption/absorption of Mg are not well understood. In order to investigate these aspects, various types of Nb oxides were synthesized and mixed with Mg, and their catalytic properties were investigated. The spray pyrolysis synthesis of Nb oxides at different temperatures produced homogeneous spherical particles with different degrees of crystallinity, while Nb oxide particles synthesized by simple calcination of ammonium niobium oxalate were nonuniform. These Nb oxides show significant catalytic activities for the hydrogen desorption/absorption of Mg, with amorphous oxides being more effective catalyst precursors than crystalline precursors. Metastable, amorphous Nb oxide is more easily converted to the reduced state, which is the catalytically active state for the reactions. In addition, Nb in the deactivated sample is in the oxidized state compared with the initially activated sample, and the catalytically active (reduced) state is recovered by reactions with hydrogen. Based on these findings, it is concluded that the chemical state of Nb is an important factor in catalyzing the desorption/absorption of hydrogen by Mg, and the catalytically active state can be preserved without further treatments.

Advanced Powder Technology, 2019

Hexagonal cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles are well known as near-infrared (NI... more Hexagonal cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles are well known as near-infrared (NIR) 31 shielding materials. However, one of the critical issues for industrial applications involves a pho-32 tochromic instability, i.e., a blue color change of this material under ultraviolet (UV) irradiation. This color 33 change is attributed to the formation of H x WO 3 phase through doping of H + ions into Cs-deficient sites 34 present at the surface of Cs 0.32 WO 3 nanoparticles. Therefore, a new approach was adopted to prevent 35 the color change by synthesizing a Cs 0.32 WO 3 nanoparticle with less Cs-deficient sites using spray pyrol-36 ysis followed by heat treatment and short-time milling. The Cs 0.32 WO 3 nanoparticles of spray pyrolysis 37 route exhibited an improved photochromic stability under UV irradiation compared to those synthesized 38 through a solid-state-reaction route. Detailed analysis using atomic resolution transmission electron 39 microscopy revealed that the Cs 0.32 WO 3 nanoparticles of spray pyrolysis route retain Cs ions up to a 40 depth of less than 1 nm from the surface. This work demonstrates that the less-Cs-deficient Cs 0.32 WO 3 41 nanoparticles are beneficial to improve the photochromic stability. 42

Journal of the Society of Powder Technology, Japan, 2019

Advanced Powder Technology, 2018

Highly crystalline and hexagonal single-phase cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles... more Highly crystalline and hexagonal single-phase cesium tungsten bronze (Cs 0.32 WO 3) nanoparticles were 33 successfully synthesized by a flame-assisted spray pyrolysis followed by annealing under a reducing 34 gas atmosphere. The resulting Cs 0.32 WO 3 nanoparticles featured a pure hexagonal Cs 0.32 WO 3 phase with 35 a high crystallinity and homogeneous chemical composition. Unlike conventional methods, the proposed 36 process in this paper has several advantages, including a short reaction time and the ability to yield prod-37 ucts with high purity and good energy efficiency. Furthermore, the Cs 0.32 WO 3 nanoparticles produced in 38 this research showed a remarkable near-infrared shielding ability with a 97.7% cutoff at 1500 nm.

Advanced Powder Technology, 2018

The metastable state hexagonal-tungsten oxide (h-WO 3) has been attracting attention over the pas... more The metastable state hexagonal-tungsten oxide (h-WO 3) has been attracting attention over the past dec-32 ade because of its high reactivity that arises from the hexagonal channels in its crystal structure. 33 Simplification of the process used to synthesize h-WO 3 is an important step to facilitate the industrial 34 applications of this material. In this study, we addressed this challenge by developing a spray pyrolysis 35 process to synthesize highly crystalline h-WO 3. The ratio of the monoclinic to the hexagonal phase 36 was controlled by adjusting the segregation time. Single-phase h-WO 3 nanorods were synthesized using 37 a carrier gas flow rate of 1 L/min, which was equivalent to a segregation time of 18.4 s. The ability of the 38 h-WO 3 nanorods to adsorb nitrogen and carbon dioxide was evaluated to confirm the presence of hexag-39 onal channels in the crystal structure.

Bioresource technology, 2016

Adsorption performance in the biosorption of tungsten using Escherichia coli cells can be signifi... more Adsorption performance in the biosorption of tungsten using Escherichia coli cells can be significantly improved by using cell suspensions that have been heat-treated at ⩽100°C. In the case of E. coli cells suspension heated at 100°C, the aqueous tungsten ions concentration rapidly decreased from 0.8mmol/L to practically zero within 1h. This biosorption time is much shorter than that of non-heat treated E. coli cells (7h). Furthermore, the adsorption saturation amount for cells heat-treated at 100°C was significantly increased up to 1.62mmol-W/g-E. coli compared to the unheated E. coli cells case (0.62mmol-W/g-E. coli). Determination of the surface potential and surface structure along with quantitative analyses of free amino acids of heat-treated E. coli cells were also carried out and revealed that heated cells have a high zeta potential and express a higher concentration of amino acids on the cell surface.

AIChE Journal, 2017

Nanostructured particles (clusters) with complex and periodic topography at the microscopic scale... more Nanostructured particles (clusters) with complex and periodic topography at the microscopic scale show unique structural patterns. Hence, good properties should be obtained when the surface topography of such clusters, especially those containing nanoparticles (NPs) of different sizes, can be carefully tuned. The coffee-ring structure is one of the most interesting structures for catalyst and photonic crystal applications or porous particle molds. Here, well-defined clusters with a coffeering structure were prepared by spray drying. The complexity of the NP distribution in the resulting two-and threecomponent systems is discussed. A better understanding of how finite groups of different NPs self-organize in a moving droplet to form a confined geometry may aid in controlling the structure of matter at multiple length scales. Interestingly, the configuration of the large microsphere clusters was found to be influenced by the presence of the small particles, which formed a ring-like structure.

Gold Bulletin, 2010

We report a simple and rapid process for the roomtemperature synthesis of gold nanoparticles usin... more We report a simple and rapid process for the roomtemperature synthesis of gold nanoparticles using tannic acid, a green reagent, as both the reducing and stabilising agent. We systematically investigated the effect of pH on the size distribution of nanoparticles synthesized. Based on induction time and-potential measurements, we show that particle size distribution is controlled by a fine balance between the rates of reduction (determined by the initial pH of reactants) and coalescence (determined by the pH of the reaction mixture) in the initial period of growth. This insight led to the optimal batch process for size-controlled synthesis of 2-10 nm gold nanoparticles-slow addition (within 10 minutes) of chloroauric acid into tannic acid.