Toyokazu Yokoyama

Monitoring particle fluidization in a fluidized bed granulator with an acoustic emission sensor

A high-frequency (140 kHz) acoustic emission (AE) sensor with narrow-band receptors was developed and applied in monitoring the particle fluidization in a fluidized bed granulator. In particle fluidization processes, the impact and the friction of the fluidized particles on the wall of fluidized beds produce AE waves. By calibrating an AE sensor at various fluidization conditions with several uniform, spherical granules, the measurement of mean AE amplitudes can be used to monitor fluidization phenomena. It was found that there are direct correlations between the mean AE amplitude, dimensionless excess gas velocity, and dimensionless bed height. The AE sensor can be applied to detect the onset of unstable fluidization due to the increase of moisture content in the fluidized bed.

Design and evaluation of poly(DL-lactic-co-glycolic acid) nanocomposite particles containing salmon calcitonin for inhalation.

Salmon calcitonin, for the treatment of calcium homeostasis and bone remodeling, was used as a model peptide drug and adsorbed on the surface of biodegradable polymeric poly(dl-lactic-co-glycolic acid) (PLGA) nanospheres. Subsequently, the nanospheres were treated using lyophilizer and loaded onto inhalable carrier using Mechanofusion to obtain nanocomposite particles suitable for inhalation. The physicochemical properties and in vitro inhalation properties of the nanocomposite particles were investigated. The pulmonary distribution and pharmacological effect were also evaluated in male Wistar rats. The results showed that the drug loading efficiency of salmon calcitonin on PLGA nanospheres were exceeding 96% (w/w). Inhalation efficiency of the lyophilized PLGA nanospheres was largely improved after they were loaded on the surface of inhalable carrier. Over 50% (w/w) of the lyophilized PLGA nanospheres could be deposited in the alveoli section after intratracheal administration to male Wistar rats, while a rapid elimination rate of the lyophilized nanospheres from the lung was found in pulmonary distribution study. The in vivo pharmacological study showed that the nanocomposite particles exhibited superior hypocalcemic action over salmon calcitonion solution and the lyophilized nanospheres. It suggested that the Mechanofusion(TM) technique can impart improved inhalation properties to the lyophilized nanospheres for pulmonary delivery of therapeutic peptide drugs.

Microscopic analysis on the consolidation process of granule beds

The effect of deformation properties of individual granules on the consolidation process of granule beds was investigated. Four kinds of alumina granules were used as sample materials for the tests. The consolidation process of granule beds was examined using a uniaxial compression tester, and the deformation behavior of a single granule under the compressive force was investigated with a diametral microcompression testing machine. The deformation curve of a single granule was characterized by the yield value and the breakage force, which were correlated with the consolidation starting stress of the granule bed. As a result, it was found that the yield value of a single granule was proportional to the compressive force between granules, which was calculated by applying Rumpfs equation for the granule bed at the consolidation starting stress.

Development of a split-type tensile-strength tester and analysis of mechanism of increase of adhesion behavior of inorganic fine powder bed at high-temperature conditions

To analyze the phenomenon of the increase in cohesive force between fine particles under elevated temperature conditions, a new split-type tensile-strength tester of powder beds for high temperature was developed. Fused silica glass with low thermal expansion coefficient was used as the material for the suspended cell of a commercial split-type tensile-strength measuring device at room temperature. The powder samples used were pure fine silica and two kinds of fly ash powders collected in a pulverized coal (PC) combustion and a pressurized fluidized coal combustion systems. Under conditions of relatively low temperatures below 1000 K, the adhesive force of all powders increased gradually in proportion to the temperature. Rapid increases of tensile strength of both fly ash powder beds were observed in the high-temperature range (above 1100 K). Based on the results of thermo-mechanical analysis (TMA), it was estimated that a viscous flow sintering mechanism controlled this rapid increase phenomenon of adhesive behavior of ash powders at high-temperature conditions above 1100 K. On the other hand, using FT-IR analysis, it was demonstrated that the increase of the van der Waals force with the change of surface molecular structure controlled the stickiness of pure silica and both ash powders at relatively low-temperature conditions below 1000 K.

Design and evaluation of inhalable chitosan-modified poly (dl-lactic-co-glycolic acid) nanocomposite particles

The aim of this study was to investigate two types of chitosan-modified poly (DL-lactic-co-glycolic acid) (PLGA) nanocomposite particles containing salmon calcitonin for pulmonary delivery, which were obtained using spray drying fluidized bed granulation (Agglomaster™) and dry powder coating techniques (Mechanofusion™), respectively. The physicochemical properties, pulmonary distribution, pulmonary clearance rate as well as in vivo hypocalcemia actions of the two types of nanocomposite particles were investigated. As indicated by scanning electron micrographs, soft matrix nanocomposite particles and soft ordered nanocomposite particles were produced by Agglomaster™ and Mechanofusion™, respectively. Both forms of chitosan-modified PLGA nanocomposite particles exhibited a high inhalation efficiency, i.e. more than 50% of the two types of nanocomposite particles could be deposited in the deep lung of male Wistar rats. However, the chitosan-modified PLGA nanocomposite particles designed by Agglomaster™ exhibited superior properties to those obtained by Mechanofusion™ with respect to the redispersibility of fine particles in aqueous liquid, the pulmonary retention time and pharmacological effects. In addition, compared with non-modified PLGA nanocomposite particles, the chitosan-modified PLGA nanocomposite particles obtained by Agglomaster™ exhibited enhanced pulmonary absorption of salmon calcitonin via the lung. The findings in this study suggest that the spray drying fluidized bed granulation technique is superior to the dry powder coating technique for producing chitosan-modified dry powder formulations containing salmon calcitonin for inhalation. This can be attributed to the avoidance of aggregation of chitosan-modified PLGA nanocomposite particles when using Agglomaster™ rather than Mechanofusion™.

Characterizing the effect of surface morphology on particle-wall interaction by the airflow method

Abstract Particle-wall interaction has been studied by the airflow method. The particles used were micrometer-size polymethyl methacrylate (PMMA) spheres treated with an additive, i.e. nanometer-size TiO 2 , Al 2 O 3 or SiO 2 particles. The method for the treatment was dry particle coating based on mechanofusion or simple mixing through shaking manually. The surface morphology of the PMMA particles was modified by changing the species of additives, its concentration and the treatment method. The particles after treatment were dispersed on the surface of a flat metal piece and an experiment on particle entrainment was carried out in an airflow channel to evaluate particle-wall interaction. Relationships between particle entrainment efficiency and air velocity, which corresponds to the distribution of the particle-wall interaction force, were obtained under various conditions, showing that the particle-wall interaction force tends to decrease with the increase in the concentration of added nanoparticles. Furthermore, analysis of the experimental results showed that the main factor affecting the particle-wall interaction force was the actual surface morphology of the particles after treatment.

BASIC PROPERTIES AND MEASURING METHODS OF NANOPARTICLES

Publisher Summary This chapter presents an introduction to nanoparticles and their properties. Nanoparticles are ultrafine particles in the size of nanometer order. The characteristics of nanosized magnetic substance are deviated from the bulk ones. One of major reasons for the unique properties of the nanoparticles different from the bulk material is the increase in specific surface area with micronization of particle, influencing their properties like the solution and reaction rates of the particles. For nanoparticles, the number of atoms, ions, or molecules making up the particle becomes larger on the surface rather than within the particle. For this reason, a number of unique characteristics specific to nanoparticles appear. These characteristics give strong effects not only to quantum size effect specific to nanoparticles but also to phenomena relating to powder handling such as adhesion and coagulation. Magnetic characteristics such as saturation magnetization decrease proportionally with size reduction of magnetic substance. Optical property of nanoparticle is greatly different according to whether the nanoparticle is insulator, semiconductor, or metal. The optical properties of nanoparticles are measured with spectrometry systems that are generally used for ordinary powder particles. The electrical properties such as dielectric and ferroelectric properties are the intrinsic independent of the shape and size. However, it is very difficult to estimate the electrical properties of the nanoparticles. The dielectric constant of nanoparticles can be estimated by analyzing the phonon modes of Raman spectra.

Effect of mechanical stirring of YBaCuO mixed powder during heat treatment on superconductive properties

This paper deals with a new apparatus for the simultaneous processing of mechanical stirring and calcining of superconductive powder materials to achieve a simpler process for the fabrication of superconductive oxides. As the first step, the change of the mechanical motion of a powder bed at elevated temperature was visualized by use of a transparent mixing tube. Consequently, it was possible to analyze the effect of temperature on the dynamic motion of the powder bed. From the analysis, it was found that there was less increase in cohesiveness of mixed powder of Y2O3, BaCO3 and CuO below 400°C. Above this temperature, the cohesiveness increased considerably, which produces a negative effect of mechanical stirring. Furthermore, the powder calcined in the tumbling bed at the lowering temperature step of calcining showed better superconductive properties than that calcined in the fixed bed.