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Field Assisted Sintering Group

It has been recently revealed that the sintering densification process assisted by extraneous fields, such as electric field, magnetic field and stress field, can significantly reduce the sintering temperature and time in functional ceramic materials. For instance, the application of electric field and stress can highly enhance the sintering densification rate of ceramics, resulting in the reduction of sintering temperature and time required for production of dense polycrystalline ceramics. Even transparent ceramics can be quickly produced by employing the field-assisted sintering process. The research of our group focuses on the development of new synthesis method effectively employing the extraneous fields in order to produce novel functional ceramic materials.

Objective

Optical and electrical ceramic materials are produced by using spark plasma sintering; SPS (pulsed electric current-assisted sintering) and flash sintering apparatus. We investigate the sintering behavior and microstructural development of ceramic materials under the controlled extraneous fields systematically varying major processing parameters. Based on theoretical analysis and microstructural observation/analysis, the role of the fields on the microstructure and properties of functional ceramics is characterized. We also join the SIP project regarding densification of coating layers.


Facilities

"Schematic of SPS furnace. Compacted powder in a carbon die is set in the chamber, and stress and pulsed current are applied through carbon punches. Specimen temperature is measured by a pyrometer or thermocouple." Image

Schematic of SPS furnace. Compacted powder in a carbon die is set in the chamber, and stress and pulsed current are applied through carbon punches. Specimen temperature is measured by a pyrometer or thermocouple.


"Heated specimen and carbon die in the SPS furnace. The specimen is directly heated by the pulsed current." Image

Heated specimen and carbon die in the SPS furnace. The specimen is directly heated by the pulsed current.


"Schematic of flash sintering apparatus. Electric field is applied to the green compact, and electric current and field strength are monitored during sintering experiments. The dimension of the specimen is is-situ measured by a CCD camera." Image

Schematic of flash sintering apparatus. Electric field is applied to the green compact, and electric current and field strength are monitored during sintering experiments. The dimension of the specimen is is-situ measured by a CCD camera.


Together with common processing equipments, SPS and flash sintering apparatus are used for our researches. We can measure various optical, electrical, mechanical properties, as well as microstructures in ceramic materials. Unique instruments for new sintering processing are also going to be developed in our group.  


Selected Recent Results

"Flash sintering of Y2O3 ceramics, which is a promising optical material with environment-resistant property. The sintering time for full densification is reduced by 1/1000 by flash sintering process." Image

Flash sintering of Y2O3 ceramics, which is a promising optical material with environment-resistant property. The sintering time for full densification is reduced by 1/1000 by flash sintering process.


"Hydroxyapatite can be densified by SPS even at the sintering temperature of 800°C (left). By employing SiC die, transparent fully-densified hydroxyapatite can be obtained at the same temperature (right)." Image

Hydroxyapatite can be densified by SPS even at the sintering temperature of 800°C (left). By employing SiC die, transparent fully-densified hydroxyapatite can be obtained at the same temperature (right).


"Appearance of the (Y₀.₉₅-xGdxEu₀.₀₅)₂O₃ transparent ceramics vacuum sintered at 1700ºC for 4h. Compared with GE product, it has the significant advantages of higher transmittance, lower sintering temperature, and finer microstructure." Image

Appearance of the (Y₀.₉₅-xGdxEu₀.₀₅)₂O₃ transparent ceramics vacuum sintered at 1700ºC for 4h. Compared with GE product, it has the significant advantages of higher transmittance, lower sintering temperature, and finer microstructure.


In order to elucidate mechanisms of the densification and functions of ceramics under extraneous fields, it is necessary to make clear the relationship between the mass transport and fields through theoretical/experimental investigation on mass transport phenomena and microstructural development during sintering. We have succeeded the developments of new transparent ceramics and fluorescent body by field-assisted sintering techniques. 


Group Leader

"Byungnam KIM" Image

Byungnam KIM


Inquiry about this page

Field Assisted Sintering Group
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JAPAN
E-Mail: KIM.Byung-Nam=nims.go.jp(Please change "=" to "@")
National Institute for Materials Science (NIMS)
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JAPAN
TEL.+81-(0)-29-859-2000
FAX.+81-(0)-29-859-2029