| 1. |
- de Moraes, Elisangela Guzi, et al.
(author)
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Silicon nitride foams from emulsions sintered by rapid intense thermal radiation
- 2015
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In: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 35:12, s. 3263-3272
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Journal article (peer-reviewed)abstract
- Open cell Si3N4 foams were fabricated by an emulsification process and subsequent sintering. Emulsification took place in an aqueous environment by using octane as alkane phase and a surfactant as stabilizer. Effects of different octane concentrations (50 vol% and 70 vol%) and stirring velocities (700 rpm and 1000 rpm) on porosity and pore size distribution were investigated. The shaped foams were pressureless sintered at 1600 degrees C inside a modified SPS set-up. Si3N4 foams decorated with SiC nanowires and with an average cell size of 8-41 mu m and total porosity of 80-86 vol% were obtained. The compressive strength ranged from 2.0 MPa up to 9.9 MPa. Both the foaming and sintering processes contributed to the development of different microstructures.
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| 2. |
- Li, Duan, et al.
(author)
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Preparation of nasal cavity-like SiC-Si3N4 foams with a hierarchical pore architecture
- 2015
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In: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:35, s. 27891-27900
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Journal article (peer-reviewed)abstract
- Rigid SiC-Si3N4 foams with hierarchical porosity were prepared through protein-based gel-casting followed by radiant sintering in a modified spark plasma sintering (SPS) set-up. The porous bodies sintered at 1500-1700 degrees C for only 10 minutes achieved a compressive strength of 15-21 MPa while keeping a porosity of 60-70 vol%. Gradient porous structures, with pore sizes ranging between 1 to 100 mm, were intersected by the growth of hybrid SiC and Si3N4 nanowires inside the pores resulting in a nasal cavity-like appearance. Gas permeability at room temperature (25 degrees C) and 600 degrees C was evaluated. Darcian permeabilities and non-Darcian permeabilities of all the prepared foams at room temperature fell within (0.354-1.55) x 10(-12) m(2) and (1.60-6.33) x 10(-8) m, respectively. Measurement of the Darcian and non-Darcian permeabilities at 600 degrees C were much higher, at 1.71 x 10(-11) m(2) and 2.68 x 10(-7) m, respectively. The microstructure, stability, gas flow properties and the green synthesis route reveal the potential of these ceramic foams to be used as industrial PM filters for airborne pollutions.
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| 3. |
- Li, Duan, et al.
(author)
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Rapid sintering of silicon nitride foams decorated with one-dimensional nanostructures by intense thermal radiation
- 2014
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In: Science and Technology of Advanced Materials. - : Informa UK Limited. - 1468-6996 .- 1878-5514. ; 15:4
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Journal article (peer-reviewed)abstract
- 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.
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| 4. |
- Li, Duan, et al.
(author)
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Structural study of disordered SiC nanowires by three-dimensional rotation electron diffraction
- 2014
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In: Materials Research Express. - : IOP Publishing. - 2053-1591. ; 1:4
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Journal article (peer-reviewed)abstract
- The structure of disordered SiC nanowires was studied by using the three-dimensional rotation electron diffraction (RED) technique. The streaks shown in the RED images indicated the stacking faults of the nanowire. High-resolution transmission electron microscopy imaging was employed to support the results from the RED data. It suggested that a 2H polytype is most possible for the nanowires.
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