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Ceramic Raw Materials Laboratory
has been carrying out researches on the area of new materials technology,
mainly on development of porous materials. By controlling chemical compositions,
pore and grain size distributions, surface properties, of inorganic materials
in mesoscopic scale, basic research is under going on the design and processing
technologies of advanced ceramic materials for applications in the field
of chemical reaction, catalysis support, ceramic filter, humidity controlling
building materials, and so on.
It is well known that inorganic
nanotubes with mesopore (mainly imogolite: Al2O3.SiO2.nH2O)
have good rheological, adsorptive, and surface properties caused by unique
structural, morphological, and functional groups on the surface.
Present researches are as follows; 1. Study on the synthesis technology
of inorganic nanotubes are carried out by using hydrothermal synthesis,
homogeneous precipitation method, and so on. 2. Study on the arraying
technology of the nanotube and mesopores. 3. Observations on the
uniqueness of the rheology and catalytic properties of the materials.
4. Application of the material to ceramics and environment tunings will
be investigated.
(Joint research with Geological
Survey of Japan )
Recent Results
1) Starting solution was prepared by mixing
tetraethyl orthosilicate and aluminum chloride and NaOH was added until
pH 5.0 followed by 100°C aging for 5 days. Imogolite was
synthesized from the dilute tetrasodium monosilicate solution less than
5mmol/l. However, at higher titration speed than 0.1ml/min, bohemite
(g-AlOOH) was coprecipitated. 2) Starting
solution was prepared by mixing tetrasodium monosilicate and aluminum chloride
and NaOH was added until pH 5.0. Imogolite was synthesized
from the dilute tetrasodium monosilicate solution less than 5mmol/l.
However, no effect of titration speed was observed. 3) Rapid mixing
method was developed, therefore simple and easy synthesis of imogolite
can be achieved.
(For geochemical research, please look at the
home
page of Geological Survey of Japan)
Sectional View of the Inorganic Nanotube (Imogolite)
1. Study on the synthesis technology of inorganic macromolecules with mesopores is carried out by using hydrothermal synthesis, precipitation method, and so on. 2. Study on the arraying technology of the macromolecules and mesopores. 3. Observations on the uniqueness of the photo- and radiation-chemical reactions of organic molecules in the mesoscopic materials. 4. Applications for reaction control and environment tuning are investigated. (Joint research with Excited Molecule Lab., Chemistry Dep.)
Recent Results
1. In the study on synthesis technology of inorganic macromolecules with mesopores, fumed silica and quaternary ammonium salts were used as the starting materials for the hydrothermal synthesis at 100°C for 7 days. After quenching, washing, and decomposition of ammonium salts by heating at 600°C for 6h, the specific surface area of the materials increased from 965 to 1344m2/g and the pore size increased from 2.1 to 3.2nm with an increase in the carbon chain length from C10 to C16. In the case of 5% titanium added synthesis, the specific surface area of the materials increased from 540 to 863m2/g and the pore size increased from 2.0 to 2.7nm with an increase in the carbon chain length from C10 to C16. For the results of the photo- and radiation-chemical reaction, please look at the home page of Exited Molecule Lab. .
Our new life style has asked eagerly to develop the high quality and high functional materials instead of the conventional agents. The present group has been attempting to develop new multi-functional materials (as humidity control materials, deodorizer, filler, and so on) derived from clay minerals and other inorganic materials by using cation exchange reaction and surface modification. The development of antibacterial and antifungal agents is studied as one of them. By using the present technique, it is possible to prepare more systematically an agent with desired functions and will be opened some new application fields for inorganic materials.
Recent Results
Montmorillonite intercalated with silver chelate of 2-(4-thiazolyl)-benzimidazole and quaternary ammonium cations (n-dodecyltrimethylammonium and hexadecylpyridinium ) that has antibacterial and antifungal activities was prepared by cation exchange reaction. The resulting material was subjected to antibacterial and antifungal properties and its structure was observed before and after heating up to 400°C. Minimum inhibitory concentration tests showed that the sample has strong antibacterial and antifungal activities except with that of fungi of Aspergillus niger. Loss of antibacterial activities, after heating at 250°C, had occurred only in quaternary ammonium cations intercalated montmorillonite. The specimen was stable up to 200°C and eventually decomposed at 400°C resulting in fine silver particles which is having significant antibacterial activities against bacteria of Escherichia coli and Staphylococcus aureus. The diameter of silver particles was 20-40nm, and did not change with increase in temperature up to 400°C. Three cations intercalated in montmorillonite showed their characteristic individual activity, however, no synergetic activity was observed in each intercalant.
Basic research on the development of a breathing wall which is safe from earthquakes, healthy for people with allergies, comfortable without dampness, and energy saving without using electricity is carried out using natural and synthetic materials. In this project, three sub theme have been conducted; 1. Technology for design and characterization of mesoporosity and chemistry of humidity control materials, 2. Synthesis technology for the basic component of the breathing wall, 3. Water-repellent and antibacterial treatment technology of the wall materials. (Joint project with three private enterprises)
Recent Results
The water vapor adsorption-desorption properties of sepiolite, diatomite, and selectively leached kaolin were measured by DTG, DSC and a gas adsorption isotherm analyzer to develop a humidity control material in living environments. Based on the Kelvin's capillary condensation theory, suitable pore diameters for the adsorption of water vapor at 40 and 70% of relative humidity were calculated to be 3.2 and 7.4 nm, respectively. Wakkanai diatomite, relatively pure sepiolite, and selectively leached kaolin have suitable pore diameters and high water adsorbability, and were considered as candidates for humidity control materials. The shaping and firing of mesoporous-powder made by a selective leaching method was studied in order to develop a humidity control building material. The specific surface area, total pore volume, pore size distribution, and amount of water vapor adsorbed on fired bodies were measured to evaluate the humidity controlling properties. The amount of water vapor adsorbed on fired bodies was less than that on raw powders. However, the decrease in the amount of water vapor adsorbed at the relative humidity, in the range between 0 and 60%, was larger than that in the range between 60 and 90%. It was found that the enlargement of the pore radius of selectively leached samples by firing was an important factor for the design of humidity control material. To increase anti stain and anti deterioration properties of the selectively reached kaolin and the diatomaceous ceramics, surface fractal dimension (roughness index) and contact angle of water droplet was examined for these ceramics. It was found out that the latter ceramics have high fractal dimension and good water-repellent property.
High performance inorganic film processing technology is asked to produce environmental purification filters, gas separation membrane, ion sensor , thin film condenser , etc. However, because of the complicated chemical compositions and structures of functional inorganic materials, the production of inorganic films with preferred orientation have needed sophisticated method. In this study, we are basically investigating the possibilities to develop the simple processing for inorganic functional films.
Recent Results
Hydrotalcite group particles
were dispersed and hydrophobiced by the intercalation of an organic molecule
and spread on the surface of water in mono-molecular level. The film
was stacked on a glass plate by using Langumuir-Brodgett method.
Good flat film was obtained in mono molecular level proofed by atomic force
microscope.
Recently, industrial demands for sepiolite (Mg8Si12O30(OH)4(H2O)4.8H2O) have increased, utilizing its porous and fibrous properties, for example, carriers for catalyst, deodorant material, humidity conditioning material, and rheological agent. To meet the industrial demands for high purity sepiolite, focussed on the low grade sepiolitic ores mainly containing carbonate, pH controlling purification technology to dissolve the carbonate without any harmful effects on the sepiolite have been investigated.
Recent Results
Controlled addition of acid to dolomitic sepiolite
was successfully applied to the purification of low grade sepiolite.
The main control factor is the rate of addition of the acid, i.e. it must
be slow enough to keep the solution in the special region on the solubility
diagram of pH vs. Mg concentration.
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