Special Issue
New Aspects of Particulate Meterials
I. Separation and Handling
Review
Regarding on the recent fine particle separation technology
Shinichi ITO(Mineral Processing Div., Materials Processing Dept., NIRE)
Abstract
Separation technology has been developed for ore separation technology. The minimum particle size which is processed by the ore separation technology, has been increased due to demand which means that various types of ore become poor as time passes. This paper reviewes such recent fine particle separation technologies as electrostatic separation, wet magnetic separation, flotation, liquid-liquid extraction, selective flocculation, agglomeration and gravity separation.
Key words : Separation technology, Fine particles
(Language:Japanese)
Review
A review of the theory of stability of dispersed systems
Hiroki YOTSUMOTO (Mineral Processing Div., Materials Processing Dept., NIRE)
Abstract
The development of theoretical analysis for dispersed systems has been reviewed mainly focusing on the DLVO theory and the finding of non-DLVO forces. In aqueous dispersion, the DLVO theory can predict the stability of many hydrophobic dispersed systems. However, the aqueous dispersion of metal oxides with high electrolyte concentration is more stable than predicted by the theory in spite of the small electrostatic repulsion due to the high electrolyte concentration. Aqueous suspension of silica is, on the contrary, more stable than predicted by the theory at low electrolyte concentrations. It is now recognized that such anomalous stability is due to a "hydration force" not considered in the DLVO theory. The theory also fails to explain the low stability of the dispersion of highly hydrophobic particles. It has been found that there is a very strong attraction between hydrophobic surfaces separated by a thin water film. The attractive force is now called a "hydrophobic
force," and is thought to be responsible for the low stability of hydrophobic dispersion. It is, therefore, concluded that a more precise prediction of the stability of dispersion requires an extended DLVO theory where the hydration and hydrophobic forces are incorporated in it.
The discrepancy between the DLVO theory and coagulation kinetics has been also mentioned here. Although it is a serious problem, it may be removed in the future through the refinement of both the DLVO theory and the kinetics theory.
Key words : DLVO theory, hydration force, hydrophobic force, dispersion, stability
(Language:Japanese)
Review
Micro-manipulation of Small Particles Using The Radiation Pressure of Laser Light
Shigeki KOYANAKA(Materials Handling and Characterization Div., Materials Processing Dept., NIRE)
Abstract
Radiation pressure based on the law of conservation of momentum is produced on small particles in a converged laser light. Micro-manipulation of small particles is possible using laser radiation pressure. In this report, the production mechanism and analytical theory of laser radiation pressure on small particles are discussed. Micro-manipulation methods of small particles using laser radiation pressure are classified and applications for fundamental research and industries are also reviewed.
Key words : Radiation pressure, Laser light, Small particles, Micro-manipulation
(Language:Japanese)
II. Synthesis
Review
Recent Development of Researches on the Synthesis of Fine Particles Using Solution Techniques
Mikio KOBAYASHI(Rare Metals Div., Materials Processilg Dept., NIRE)
Abstract
Fine particles have a lot of attention for many application fields. Since the precise contol of shape, component and structure is very important to improve the performance of fine particles, the recent development on the control of factors above in the synthesis of fine particles using solution techniques has been investigated. The forced hydrolysis, the "gel-sol" method, the precipitation from homogeneous solution, the alkoxide hydrolysis, the reverse micelle method, the microemulsion method and precipitation stripping have been reviewed. The separation of nucleation stage and growth atage and no aggregation of particles are essential to the preparation of monodispersed particles. In case of the gel-sol method the monodispersed fine particles are synthesized from the very condensed starting solutions. The microemulsion method and precipitation stripping are posibly hopeful as the integrated process of separation and synthesis.
Key words : fine particles, solution technique, monodisperse
(Language:Japanese)
Review
Plasma Synthesis of Fine Particles
- Topics in International Symposia on Plasma Chemistry -
Nobuyuki KIKUKAWA(Siliceous Materials Div., Materials Processing Dept., NIRE)
Abstract
Recent works on plasma synthesis of fine particles are reviewed. Papers submitted to these two international symposia on plasma chemistry (1993, 1995) are mainly surveyed. Promising topics including SiC, nanocomposites, fullerenes, SiO2, double oxides, particle modification and spheroidization are shown.
Key words : plasma, fine particles, review, SiC, nanocomposites, fullerenes, SiO2, double oxides, particle modification, spheroidization
(Language:Japanese)
Technical Report
Control of the shape and the composition of Eu-Y co-precipitates prepared from homogeneous aqueous solutions : preparation of the precursors of Eu-doped Y oxide phosphor
Yoshihiro NISHISU and Mikio KOBAYASHI(Rare Metals Div., Materials Processing Dept., NIRE)
Abstract
The synthesis of fine multicomponent particles from a homogeneous solution containing rare-earths (yttrium, europium) and urea was studied. The needle-like crystalline precipitate was obtained at 77 ûÃ from a solution containing europium. Fine spherical particles of amorphous precipitate were obtained from a solution containing yttrium at 77 ûÃ, and from another solution containing yttrium and/or europium at 97 ûÃ. The yield of rare-earths depended on the reaction temperature (30-99 %). The ratio of yttrium to europium in the precipitate corresponded to that of the initial solution. The average size of the particles was related to the ratio of yttrium to europium in the initial solutions. The fine particles of the precipitate containing yttrium and europium can possibly be used as starting materials for the fabrication of red phosphors by calcination.
Key words : multicomponent particle, homogeneous aqueous solution, rare-earths
(Language:Japanese)
Original paper
Synthesis of Y-Fe-O Ultrafine Particles Using Inductively Coupled Plasma
- Inluences of precursor forms on products -
Masami SUGASAWA, and Nobuyuki KIKUKAWA(Silliceous Materials Div., Materials Processing Dept. NIRE)
Nobuhiro ISHIKAWA, Naoyuki KAYANO, and Takayasu KIMURA(Shibaura Institute of Technology)
Abstract
Using a thermal plasma evaporation method in which powder or liquid precursors containing some metal elements are supplied to the plasma in order to evaporate and co-condense, various metal oxides of multi-components can be synthesized as ultrafine particles or thin film.
When a co-precipitated powder with a Y/Fe molar ratio of 1 : 1.9 was supplied to an RFAr-O2 plasma generated under certain conditions, the ferro- or ferri- magnetic compound in Y-Fe-O system, having an XRD pattern not registered in the JCPDS, was observed in the synthesized powder.
Therefore, so as to synthesize this new phase as a pure single phase, powder and liquid precursors with various Y/Fe ratios were supplied to plasma, and the influences of precursor forms regarding the products were studied. As a result, it was found that the powders prepared by the amorphous citric gel method were suitable for synthesizing the new phase almost as a pure single phase in the powder state with good crystallinity and with some large primary particles.
Key words : Thermal plasma evaporation method, Co-precipitated powder, Y-Fe-O system New phase, Amorphous citric gel method
(Language:Japanese)
III. Measurement
Review
Size Analysis of Fine Particulate Materials
Shigehisa ENDOH(Materials Handling and Characterization Div., Materials Processing Dept., NIRE)
Abstract
Particle size measurement techniques are mainly classified into the geometric method, dynamic method and optical method. In this report, the characteristics of the measurements are reviewed. Statistical problems in an image analysis are discussed. The characteristics of photo-extinction centrifugal sedimentation are shown. Optical techniques are classified on the basis of the interaction between particles and light and its characteristics are described. The effect of the refractive index is discussed. Nobel acoustic techniques by which the particles size is detected in a highly concentrated suspension are introduced.
Key words : Particle size analysis, Image analysis, Light diffraction, Photo-extinction.
(Language:Japanese)
Review
Optical Motion Analysis of Fine Particles for Multiphase Flows
Hiroyoki HATANO(Advanced Combustion Systems Div., Theramal Energy and Combustion Engineeing Dept., NIRE)
Katsumi TSUCHIYA(Department of Chemical Science and Technology, The University of Tokushima)
Abstract
The optical motion analysis methods for fine particles in a dense gas-solid multiphase flow are explained. Since the light does not reach the inside of the dense particle phase, the usage of an optical system has been limited for the dense system. In this report, we have mainly introduced fiber optics which has been widely applied to the gas-solid fluidized bed ; the basic probe structures, characteristics of the obtained signals, the data processing techniques and the range of applicability. Also, we have provided an image analysis which has been recently developed in the dense multiphase field.
Key words : Optical fiber probe, Reflective type, Penetrative type, Data processing, Image analysis
(Language:Japanese)
IV. Report on Survey Project for Particulate Material Researchhes
Technical Report
Research project on the development of particulate materials for envir onment
Hitoshi OHYA(Materials Handling and Characterization Div., Materials Processing Dept., NIRE)
Masami SUGASAWA(Siliceous Materials Div., Materials Processing Dept., NIRE)
Yoshihiro NISHISU(Rare Metals Div., Materials Processing Dept., NIRE)
Abstract
A research project was carried out in 1996 to develop new particulate materials as ecomaterials.
Three researchers visited universities and institutes in Europe at first.
We had laboratory tours, exchanged information and gave our presentations to discuss the direction in our research field.
American and Dutch researchers were invited to give their ideas and discussions together with us. Very interesting ideas and results could be obtained.
We were able to obtain our opinions on the direction and organization of our research work.
Key words : particulate materials, ecomaterials, advanced research organization
(Language:Japanese)
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