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Rapid sintering of silicon nitride foams decorated with one-dimensional nanostructures by intense thermal radiation
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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2014 (English)In: Science and Technology of Advanced Materials, ISSN 1468-6996, E-ISSN 1878-5514, Vol. 15, no 4, 045003Article in journal (Refereed) Published
Abstract [en]

Silicon nitride foams were prepared by direct foaming and subsequent rapid sintering at 1600 °C. The intense thermal radiation generated under the pressureless spark plasma sintering condition facilitated necking of Si3N4 grains. The prepared foams possessed a porosity of ~80 vol% and a compressive strength of ~10 MPa, which required only ~30 min for the entire sintering processes. Rapid growth of one-dimensional SiC nanowires from the cell walls was also observed. Thermodynamic calculations indicated that the vapor–liquid–solid model is applicable to the formation of SiC nanowires under vacuum.

Place, publisher, year, edition, pages
2014. Vol. 15, no 4, 045003
Keyword [en]
silicon nitride, foam, spark plasma sintering, nanowire, thermodynamics
National Category
Ceramics
Research subject
Materials Chemistry
Identifiers
URN: urn:nbn:se:su:diva-109796DOI: 10.1088/1468-6996/15/4/045003OAI: oai:DiVA.org:su-109796DiVA: diva2:767403
Available from: 2014-12-01 Created: 2014-12-01 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Rapid sintering of ceramics by intense thermal radiation
Open this publication in new window or tab >>Rapid sintering of ceramics by intense thermal radiation
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sintering is an important processing step for obtaining the necessary mechanical stability and rigidity of ceramic bulk materials. Both mass and heat transfer are essential in the sintering process. The importance of radiation heat transfer is significantly enhanced at high temperatures according to the well-known Stefan-Boltzmann’s law. In this thesis, we modified the pressure-less spark plasma sintering set-up to generate intense thermal radiation, aiming at rapid consolidation of ceramic bulk materials. This approach was named as “Sintering by Intense Thermal Radiation (SITR)” as only thermal radiation contributed.

Firstly, the heat and mass transfer mechanisms during the SITR process were studied by choosing zirconia ceramics as references. The results revealed that the multiple scattering and absorption of radiation by the materials contributed to the heat diffusion. The observed enhanced densification and grain growth can be explained by a multiple ordered coalescence of zirconia nanocrystals using high heating rates.

Secondly, the temperature distribution during the SITR process was investigated by both numerical simulation and experimental verifications. It showed that the radiator geometry, sample geometry and radiating area were influencing factors. Besides, the change of material and geometry of the radiators resulted in an asymmetric temperature distribution that favored the formation of SiC foams. The foams had gradient structures with different open porosity levels and pore sizes and size distributions.

Finally, ceramic bulk materials were successfully fabricated by the SITR method within minutes. These materials included dense and strong ZrO2 ceramics, Si3N4 foams decorated with one-dimensional nanostructures, and nasal cavity-like SiC-Si3N4 foams with hierarchical heterogeneities. Sufficient densification or formed strong necks were used for tailoring these unique microstructures. The SITR approach is well applicable for fast manufacture of ceramic bulk materials because it is clean and requires low energy consumption and properties can be controlled and tuned by selective heating, heating speed or temperature distribution.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2016. 98 p.
Keyword
Sintering, sintering by intense thermal radiation, spark plasma sintering, heat transfer, mass transfer, scattering, coalescence, densification, grain growth, numerical simulation, porous ceramic, foaming, nanostructure, hierarchical heterogeneities, permeability
National Category
Materials Engineering Ceramics
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-124131 (URN)978-91-7649-325-0 (ISBN)
Public defence
2016-02-12, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.

 

Available from: 2016-01-20 Created: 2015-12-14 Last updated: 2017-02-20Bibliographically approved

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