Graphene quantum dots (GQDs) are interesting in nanoelectronics because of their unique optical and electrical properties due to quantum confinement and edge effects. For their fabrication methods by the chemical or mechanical cutting of carbon materials, however, it is difficult to control the size and structure of the GQDs. In the present study, nickel (Ni) nanoparticles with clean surfaces were used as catalysts and templates, and nanometer-sized graphene was prepared by metal-catalyzed graphitization of an amorphous carbon (a-C) films. The a-C films deposited on the Ni nanoparticles at room temperature were studied by transmission electron microscopy (TEM) and Raman spectroscopy. In the Raman spectrum obtained from the a-C film on the Ni nanoparticles, two broad peaks of G and D modes appeared at 1582 and 1388 cm–1, respectively, which was different from a typical Raman spectrum of the a-C film. High-resolution TEM observation showed that the a-C film around the Ni nanoparticles was spontaneously transformed into disordered graphitic layers without heat treatment. The present results suggest that clean surfaces of Ni nanoparticles exhibit high catalytic activity and reduce the graphitization temperature of a-C, and may lead to a bottom-up approach to fabricate GQDs.
The generation and transport of solid particle clusters by a vortex ring launched into quiescent water are explored. A vortex ring launcher, composed of a cylinder and a piston, is mounted at the bottom of a water tank. Polyacetal particles are placed on a mesh stretched near the cylinder outlet. The number of particles is 100, the mean diameter and density are 1.52 mm and 1417 kg/m3 respectively. The water in the cylinder is discharged vertically upward into the tank by the piston to launch the particle-laden vortex ring. Such two-phase flows of the Reynolds number Re based on the piston velocity and the cylinder diameter at 6500, 7500 and 13000 are investigated. The particles are entrained just after the launch of the vortex ring of Re = 7500 and 13000. The resultant particle cluster is transported by the convection of the vortex ring. The water velocity on the vertical cross-section of the vortex ring lessens due to the particles, resulting in the reduction of the circulation of the vortex ring. The reduction is larger for the lower Re.
We have been preparing nanocomposite particle which is microparticle containing drug nanoparticles by using 2-solution mixing type spray nozzle. The two passages (carrier-based aqueous solution & organic solution of poorly water-soluble drug) are used in the spray drying equipped with 2-solution mixing type spray nozzle. In the nozzle, the drug solution was mixed with aqueous solution and the drug nano-core is produced by changing the solubility of drug (i.e. anti-solvent effect). Before the drug is crystallized completely, the solution is spray-dried, and drug-nanocomposite particles are obtained. Down-sizing of drug particle is useful method to increase the surface area of drug particle, resulting in the improvement of drug dissolution. Additionally, the 2-solution mixing type spray nozzle is useful in the point of cost and productivity. In this study, in order to extend the application of 2-solution type nozzle, the nano-matrix microparticle was prepared. Sodium chloride-based nano-matrix microparticle was prepared successfully. The nano-porous microparticle has light property and has large void in microparticles. So, this is useful for the inhalation formulation. Eventually, the sodium chloride-based nano-matrix microparticle is promising inhalation against cystic fibrosis.
The effect of atmospheric-pressure plasma jet treatment in conjunction with fine particle peening (FPP) on the generation of a TiO2 layer on pure titanium was investigated. Compared with the TiO2 layer generated using conventional FPP, the layer generated using plasma-assisted FPP was observed to have a uniform and thick surface. Scratch and friction wear evaluation test results revealed that the layer generated with plasma assistance exhibited superior abrasion resistance. These advantages are attributed to the promotion of adhesion of each particle during the plasma treatment. In addition, the layer generated with plasma assistance exhibited superior biocompatibility.
It is necessary to increase the Seebeck coefficient S and electrical conductivity σ, and reduce the thermal conductivity κ of the material for improving the performance of thermoelectric conversion material that directly converts thermal energy to electric energy using the Seebeck effect. As a design guideline for improving the performance, realization of PBET (Phonon Blocking Electron Transmitting) characteristic has been proposed. In this study, we fabricated a composite sintered body of ZnO-based thermoelectric material composed of powder which is modulated and doped carrier, and investigated to improve the performance by realizing PBET characteristic. A powder sample in which the surface of Zn0.98Al0.02O powder is coated with ZnO nanoparticles was prepared using a particle complexing apparatus and sintered by hot pressing to produce Zn0.98Al0.02O-ZnO composite sintered body. In this composite, despite containing low electrical conductivity ZnO particle, some degree of electrical conductivity was obtained due to the modulation doping phenomenon, and reduction of κ by ZnO nanoparticle layer was observed, but dimensionless figure of merit of ZT was not improved.
Gas-stimuli-triggered stability-controllable gold nanoparticles (AuNPs) were successfully developed. The gas-stimuli responsive poly(2-diethylaminoethyl methacrylate) (PDEAEMA) layers were grafted from the AuNPs by the surface-initiated atom transfer radical polymerization of DEAEMA with Br-functionalized AuNPs. The successful synthesis of PDEAEMA-g-AuNPs was confirmed by DLS and XPS. In addition, the obtained PDEAEMA-grafted AuNPs had a reversible colloidal stability with CO2/N2 as a gentle gas-stimuli. Furthermore, the transfer across the immiscible interface between water and organic solvent has been successfully demonstrated by decreasing the colloidal stability of PDEAEMA-g-AuNPs in aqueous medium, resulting in the successful collection of AuNPs using organic solvent from aqueous-phase.
Recently, development of lead-free piezoelectric materials has been receiving great attention because of environmental issues. Among several ferroelectric oxides, BaTiO3 has been attractive as a potential candidate. In this study, we studied the processing of nonreducible BaTiO3-based ceramics for multilayer piezoelectric actuator devices using base metal internal electrodes. Reduction-resistant BaTiO3-based ceramics were fabricated by appropriately modifying the chemical composition in Mn-doped (Ba,Ca)TiO3 ceramics. To improve their electrical properties, grain-oriented ceramics were also prepared by the reactive templated grain growth method using platelike BaTiO3 and CaTiO3 particles. The electrical properties of the BaTiO3-based ceramics, sintered in the reducing atmosphere (oxygen partial pressure below 0.1 Pa), were markedly improved as a result of fabricating grain-oriented samples. Here, we have achieved an effective piezoelectric constant of approximately 570 pm/V and electrical properties (especially insulation resistance) which make it possible to apply to piezoelectric actuators.
In recent years, hydroxyapatite (HAp) is expected as no-minor metal catalyst for reduction of VOC gas as a cause of air pollution. Hydroxyl groups of HAp would be eliminate by the heat treatment and trapped electron occurs on the surface. Trapped electron generates oxygen radical and promotes oxidative decomposition of VOC gas. And also, we have considered that it is able to eliminate hydroxyl groups by lower energy using microwave for the heating method. Microwave absorption property depends on its material, but also crystallization. In this study, the correlation between “microwave absorption and heating properties” and “crystallization of HAp” were investigated using planetary ball mill.
In the present research project, the long-range attractive interactions between solvophobic surfaces in liquid media were studied by the density functional theory (DFT) for inhomogeneous fluids, which is computationally very efficient compared with molecular simulations. The results from our DFT calculations have revealed the relationship between the onset point of solvophobic attraction and the thermodynamic state of a bulk liquid.
A measurement system of the high-frequency resistance (HFR) and drying surface displacement of catalyst inks (slurries) under the drying process, which is to fabricate catalyst layer of polymer electrolyte fuel cells, was constructed and the measurement of the catalyst inks with the different ionomer to carbon (I/C) ratio were demonstrated. A self-made four-terminal micro-electrodes chip was fabricated and used for the HFR measurement. The drying surface displacement measurement was also conducted at the same time by using a laser displacement meter. The catalyst ink with lower I/C showed larger resistance at the beginning of the drying because proton concentration in the ink is low. The lower I/C inks also showed drastic resistance drop at the earlier time. Both the resistance decrease and film thickness decrease of the higher I/C ink occurred at the same time. This result indicates that I/C ratio affect the stability of the catalyst ink.
Spherical crystallization enables the fusion of pharmaceutical downstream manufacturing process by direct preparation of crystal agglomerates of active pharmaceutical ingredients (APIs) with improved crystal handling properties, the concept of which is suitable for effective pharmaceutical manufacturing. However, batch operation for spherical crystallization would be difficult to optimize the scale-up for large scale production because the phenomenon of spherical crystallization is complicated compared with conventional crystallization. The continuous spherical crystallization of salbutamol sulfate and fenofibrate as a model API was developed using a mixed-suspension, mixed-product removal (MSMPR) crystallizer. We demonstrated the continuous spherical crystallization of salbutamol sulfate and fenofibrate using MSMPR and the continuous production over 24 h. The controlling process conditions such as residence time during crystallization affected the characterization of spherical agglomeration of APIs. In the case of water soluble APIs such as salbutamol sulfate, the use of a large amount of organic solvent (antisolvent) would be issue for commercial production. The application of a solvent recycling system for reuse of the antisolvent in the single-stage MSMPR crystallizer was also demonstrated. In the MSMPR crystallizer, 90% of the mother liquor was recycled during the continuous spherical crystallization of salbutamol sulfate by optimizing the rate of each stream.
Fast oxygen (O2) reduction at high positive potential is essential to obtain effective green energy conversion systems. Here, in an attempt to develop a desirable O2 reduction biocathode for fuel cells using laccase (Lac), we modify the surface of single-walled carbon nanotubes (SWCNTs) with various biosurfactants (SC: sodium cholate, SD: sodium deoxycholate, CHAPS: 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonate, BIGCHAP: N,N-bis(3-D-gluconamidopropyl)cholamide) to obtain fast direct electron transfer from the SWCNTs to Lac, resulting in O2 reduction starting from a potential close to the redox equilibrium potential of the oxygen/water couple. Heterogeneous direct electron transfer reaction was reached to 3000 s–1 of the T1 Cu site of Lac with a SC-SWCNT interface, and that the electron transfer rate is very sensitive to the side-chain structure of the steroid-type biosurfactant. The ko of Lac adsorbed on SC-SWCNTs is more than 10 times larger than that on SD-SWCNTs. The investigation using CHAPS- and BIGCHAP-SWCNT electrodes also indicated that the side chain has an important role in directing Lac molecular orientation, which influences direct electron transfer of Lac with SWCNTs.
Enhancement of the effective thermal conductivity of the packed bed was studied by making bridges of high thermal conductive material between particles. The advantage of this method is the effect of the thermal additive on the gas permeability of packed bed can be reduced. As a preliminary investigation, heat transfer enhancement of packed bed of spherical alumina particles was studied. As a result, the effective thermal conductivity was increased by about 5 times as high as that of the original non-treated packed bed. Pressure drop on introduction of airflow was increased by only 20% as high as that of the non-treated packed bed. This result implies that effect of heat transfer enhancement on the gas permeability is relatively small. Effect of the bridge between particles on the heat transfer was numerically studied. As the simplest case, heat transfer between two particles in contact was studied. Based on the results, heat transfer rate between the particles was considerably improved by the bridge with the small volume fraction. Comparing between experiments and calculations, increase in the density of the bridge is essential for the further improvement of the effective thermal conductivity.
Various global changes in the life environments, such as global warming, are now bringing about an outbreak due to unknown infectious viruses, such as new type influenza virus, SARS (Severe Acute Respiratory Syndrome), MERS (Middle East Respiratory Syndrome) corona virus, and Dengue or Zika virus, etc., which have been urgent global issues to develop their rapid detection techniques to prevent a spread of infection beforehand. Furthermore, health damages caused by norovirus, E. coli O157, and Salmonella bacteria have been frequently occurring, therefore, it is also demanded to develop their rapid detection methods for establishing safe and secure food society. In this study, we report recent experimental results of surface functionalization of graphite-encapsulated metal nanoparticles fabricated by DC arc discharge and the highly-sensitive detection of various viruses and bacteria using antibody-immobilized magnetic nanoparticles. We also present the results on highly-sensitive Cu ion detection from aqueous solution by using amino-functionalized Au nanoparticles prepared by one-step DC arc discharge.
Europium sulfide nanocrystals are magneto-optical semiconductors with degenerate 4f orbitals between conduction band (5d orbitals of europium) and valence band (3p orbitals of sulfur). They are well known to induce large magneto-optical effect (i.e., Faraday rotation) by optical electron transition from 4f to 5d orbitals under magnetic field and expected to be used as materials for visible-light security ink of next generation. In this study, we synthesized luminescent Eu2+-included CaS nanocrystals to investigate the effects on magneto-optical properties using nanosized EuS-CaS crystal field at the first time.
Small bodies in the Solar System are composed of granular materials such as dust and collisional debris. They have experienced accumulation and destruction due to collision. The most porous small bodies at present have porosity higher than 80% and it could have been even higher in the earlier stage. Granular layer at the impact point is compacted due to compression. On the other hand, porosity of the location far from the impact point can also change by fluidization due to collision-induced vibration. In this study, uniaxial pressure was applied to the granular layers of different constituent particles and the change of porosity was investigated. As a result, it was shown that there was a pressure range where the initial porosity was kept almost constant, and above that, the porosity decreased with increasing pressure. This threshold was taken as the “yield strength” of the granule layer, and the average force acting between the individual particles was estimated. This force took a value between the theoretical values of rolling frictional force and sliding frictional force acting between particles. In addition, it was shown that particles with smaller sliding friction force tended to be compressed more easily.
We have investigated a steering method to maintain the orientation of active matter that moves by spontaneously breaking the symmetry in a homogenous field. When PVA gel particles loaded with Pt are introduced in a hydrogen peroxide solution, they moves in different directions. In the presence of a concentration gradient of Ag+, they exhibit a positive chemotaxis, whereas in the presence of a concentration gradient of Pb2+, they exhibit a negative chemotaxis. We utilize this chemotactic motion for safe, feasible and reproducible methods to simulate the dynamical features of escape panic.
A technique for the in-situ adsorption of polymer particles on carbon nanotubes was developed. First, the surfaces of carbon nanotubes (CNTs) were coated with poly(N-vinyl acetamide) (PNVA) to give them hydrophilicity with good dispersion stability in water due to a steric effect between the hydration layers. Second, the hydrophilic CNTs were covered with polymethyl methacrylate (PMMA) particles bearing positive charges—synthesized using cationic initiator—through electrostatic interactions. These polymers were prepared by soap-free emulsion polymerization. The in-situ adsorption of PMMA particles on surface CNTs were attributed to the hydration layers of the modified CNTs, and electrostatic interactions between PMMA particles and the modified CNTs. A method for synthesizing composite polymer particles with CNTs was developed, and the particles’ mechanical properties were evaluated. The surfaces of CNTs were modified by acids to increase their hydrophilicity. Then, a Pickering emulsion was formed using liquid benzyl methacrylate monomer and the modified CNTs. The surface charge of the modified CNTs greatly influenced the surface coverage and size of the composite particles. When untreated CNTs were added to the monomer phase, the mechanical properties of the composite polymer particles were successfully improved because the incorporated CNTs worked well as fillers.
During grinding operations, ball mills emit high levels of vibration and sound. The vibration and sound relate to internal state and operation condition of mills. In this study, we develop a simulation model for operating ball mills to characterize the relationship between the internal states and the vibration and sound of the mill. The motion of the balls is calculated based on the discrete-element method. Simultaneously, collision force between the balls and the mill wall are calculated. The collision force is used as the input for a vibration analysis of the mill wall by the finite-element method. After that, assuming that there are many point sound sources on the surface of the mill, radiated sound is calculated from the vibration of the mill wall. The model can estimate the influence of operation condition on radiated sound and can clarify the relation between internal state and radiated sound.
Particle flowability can be improved by admixing particles smaller than the main particles. However, the mechanism by which this technique improves flowability has not yet fully understood. In the present study, we focused on vibrating discharge particle flowability as one of the type of flowabilities, and we investigated the effects of the main particle roughness created by adhesions of admixed particles on improving the flowability. The main and admixed particles were 41.4, 60.8 μm and 8, 104 nm in diameters, respectively. The main and admixed particles were mixed for various mass ratios, and discharge particle flow rates for the mixed particles were measured. We captured SEM images from 2 different directions and obtained 3-dimensional surface roughnesses by an image analysis software. We calculated RMS roughness values and conducted Fourier Transform analysis for the obtained 3-dimensional surface roughness. As a result, the improving trends of vibrating discharge particle flowability differed from those of compression particle flowability. Furthermore, the main particle roughness conditions showing the most improvement were as follows. RMS roughness value were around 0.1 μm and roughness wavelength were around 3.2 μm.
We have synthesized hybrid magnetic nanoparticle for future magnetic hyperthermia application. So far, there has been a lot of reports concerning to magnetic nanoparticles covered with silica. Among almost all previous reports, base has been used as the catalyst for hydrolysis of tetraethyl orthosilicate (TEOS). However, base catalyst brings about a nucleophilic reaction to form monodispersed particles and porous bulk materials. On the other hand, acid catalyst brings about an electrophilic reaction to form fiber, dense bulk or thin films. Therefore, from the point of principal, acid catalyst is considered to be suitable. In this work, we synthesized magnesium ferrite nanoparticles covered with silica thin layer. We have examined crystal structure, microstructure, particle size distribution, chemical stability and hyperthermia properties of the hybrid particles.
In wet powder handling processes, it is of paramount importance to accurately estimate the viscous force acting on particles. In the present work, Direct Numerical Simulation (DNS) of a pendular liquid bridge formed between two particles is performed using the Volume of Fluid (VOF) method and the normal and tangential viscous forces exerted on the particle are investigated. The DNS results are compared with the viscous force models based on the Reynolds lubrication theory in literature to highlight the limitations of the models. New and more accurate models are then proposed which can be easily implemented in Discrete Element Method (DEM) framework.