| 1. |
- Shen, Minhao, et al.
(författare)
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Effects of exposure time and printing angle on the curing characteristics and flexural strength of ceramic samples fabricated via digital light processing
- 2020
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 46:15, s. 24379-24384
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Tidskriftsartikel (refereegranskat)abstract
- The development of photosensitive slurries for additive manufacturing has attracted great interest due to their correlation with the final properties of the fabricated parts. This paper focus on the printing quality control in digital light processing (DLP) 3D printing of advanced ceramics. Systematic experiments were performed to assess the effects of the exposure time and printing angle on the three-point bending strength of the fabricated samples. The exposure time affected the bending strength of the printed zirconia ceramic dramatically. When the weak exposure time is 1 s and the strong exposure time is 13 s, the average bending strength can reach 580 MPa while Weibull modulus can reach 8.84. Meanwhile, the printing angle also affected the bending strength mechanical sample printed at 45 degrees exhibits the worst performance.
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| 2. |
- Zhao, W., et al.
(författare)
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Bending Strength of 3D-Printed Zirconia Ceramic Cellular Structures
- 2019
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Ingår i: IOP Conference Series. - : Institute of Physics Publishing.
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Konferensbidrag (refereegranskat)abstract
- Cellular structure has been applied in lightweight engineering application because of its high specific strength, high modulus and low relative density. Here we used 3Y-TZP ceramic to realize two typical cellular structures, Kelvin and Octet-truss, through a novel digital light processing (DLP) 3D printing method. The strut size was changed systematically to generate structures with porosities in the range of 10% ∼ 80% and the bending strength of these structures were investigated and analyzed by three-point bending test.
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| 3. |
- Zhao, Weiming, et al.
(författare)
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Mechanical properties of zirconia octet truss structures fabricated by DLP 3D printing
- 2020
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Ingår i: Materials Research Express. - : IOP PUBLISHING LTD. - 2053-1591. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- Zirconia ceramic octet-truss structures with various strut size and unit cell numbers were successfully fabricated through a DLP-based 3D printing method. The mechanical properties and energy absorption capacity under compressive load were investigated systematically. The sides of all cubes are 10 mm, the strut size was changed from 0.25 mm to 2 mm, cells number was in the range of 1(1 x 1 x 1)-125(5 x 5 x 5). It has been seen that the relative density, compressive strength and energy absorption increases with the increase of strut size when cell numbers remain the same. It can be concluded that the strength and energy absorption were affected by the relative density, strut size and the stacking mode of the unit cells. So far, with this study, a high compressive strength of 75.3 MPa and a reasonably good energy absorption of 6.76 x 10(5)J m(-3)can be achieved at a relative density of 48.57%.
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| 4. |
- Aimable, Anne, et al.
(författare)
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Synthesis and Sintering of ZnO Nanopowders
- 2017
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Ingår i: TECHNOLOGIES. - : MDPI AG. - 2227-7080. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders' nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv(50)similar to 60 nm, easily redispersable) by using a continuous Segmented Flow Tubular Reactor (SFTR), which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a "scale-out" concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 degrees C and 1100 degrees C, and Spark Plasma Sintering (SPS) at 900 degrees C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 degrees C, while also limiting the grain growth, thus leading to a nanostructured material.
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| 5. |
- Bu, Junfu, et al.
(författare)
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Transport properties of BaZr0.5Ce0.3Y0.2O3-δ proton conductor prepared by spark plasma sintering
- 2016
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 42:3, s. 4393-4399
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Tidskriftsartikel (refereegranskat)abstract
- Dense BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) proton conductors were prepared by a spark plasma sintering method. Their conductivities were determined in different atmospheres: dry air, wet N2 and wet H2. Moreover, the potential electronic conductivity contribution to the total conductivity was also identified by testing their total conductivities at different oxygen partial pressures (1-10-24 atm) in combination with an XPS analysis. It is found that the prepared dense BZCY532 ceramics are good proton conductors at 600 °C. In addition, the Ce3+ concentration in the dense BZCY532 ceramics is around 3.5 atm% of the total Ce element, and the electronic contribution to the total conductivity can be neglected after a postheat treatment.
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| 6. |
- Buscaglia, Maria Teresa, et al.
(författare)
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Fe2O3@BaTiO3 Core−Shell Particles as Reactive Precursors for the Preparation of Multifunctional Composites Containing Different Magnetic Phases
- 2010
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 22:16, s. 4740-4748
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Tidskriftsartikel (refereegranskat)abstract
- Well-designed reactive precursors and templates allow for careful control of solid-state reactions at the nanoscale level, thus enabling the fabrication of materials with specific microstructures and properties. In this study, Fe2O3@BaTiO3 core−shell particles have been used as precursors for the in situ fabrication of multifunctional composites containing a dielectric/ferroelectric phase and two magnetic phases with contrasting coercivities (Fe2O3/Fe3O4, BaFe12O19/Ba12Fe28Ti15O84). The formation of new magnetic phases occurs during sintering or post-annealing via reaction between BaTiO3 and Fe2O3. The starting powders have been prepared using a multistep process that combines colloidal chemistry methods and a solid-state reaction. The nature and the amount of the magnetic phases and, consequently, the final magnetic properties of the composite can be controlled by varying the relative amount of Fe2O3 (30 or 50 vol %), the densification method (conventional or spark plasma sintering), and the processing temperature. The composites show constricted magnetic hysteresis loops with a coercivity of 0.1−2.5 kOe and a saturation magnetization of 5−16 emu/g. Composites obtained from powders containing 30 vol % Fe2O3 show, at temperatures of 20−80 °C and frequencies between 10 kHz and 1 MHz, a relative dielectric constant of 50 and dielectric losses of <10%.
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| 7. |
- Buscaglia, M. T., et al.
(författare)
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Ferroelectric properties of dense nanocrystalline BaTiO3 ceramics
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:9, s. 1113-1117
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Tidskriftsartikel (refereegranskat)abstract
- Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro-para phase transition with a maximum permittivity of approximate to1100 at 390 K and 1 kHz. The local ferroelectric switching behaviour was investigated by piezoresponse force microscopy. Typical piezoelectric hysteresis loops were recorded at different positions of the sample. The present results provide experimental evidence for polarization switching at the local scale, indicating that the critical grain size for the disappearance of ferroelectric behaviour in dense, bulk BaTiO3 nanocrystalline ceramics is below 50 nm.
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| 8. |
- Buscaglia, M. T., et al.
(författare)
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High dielectric constant and frozen macroscopic polarization in dense nanocrystalline BaTiO3 ceramics
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:6
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical models for small ferroelectric particles predict a progressive decrease of the Curie temperature, spontaneous lattice strain, and polarization until the critical size corresponding to transition to the cubic phase and disappearance of ferroelectricity is reached. In contrast, the behavior of nanocrystalline BaTiO3 ceramics with a grain size of approximate to 30 nm is dominated by extrinsic effects related to the grain boundaries which mask the expected downscaling of properties. While the noncubic crystal structure, the high dielectric constant (approximate to 1600) and the variation of permittivity with temperature suggest a ferroelectric behavior, very slim, and nearly linear polarization hysteresis loops are observed. Evidence for the existence of a ferroelectric domain structure with domains extending over several grains and of polarization switching at local scale is given by piezoresponse force microscopy. The suppression of macroscopic ferroelectric hysteresis and switching originates from a frozen domain structure stable under an external field owing to the effects exerted by the grain boundaries, such as the clamping of the domain walls and the hindrance of polarization switching. Furthermore, the depolarization field originated by the low-permittivity nonferroelectric grain boundaries can cause a significant reduction of polarization. If the grain size is small enough, the ceramic is expected to undergo a "phase transition" to a polar phase with nonswitchable polarization. The BaTiO3 ceramics with grain size of 30 nm investigated in the present study are deemed to be close to this transition.
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| 9. |
- Buscaglia, M. T., et al.
(författare)
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Synthesis of BaTiO3 core-shell particles and fabrication of dielectric ceramics with local graded structure
- 2006
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 18:17, s. 4002-4010
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Tidskriftsartikel (refereegranskat)abstract
- The coating of BaTiO3 particles with a different perovskite and the subsequent consolidation to dense ceramics retaining a radial composition gradient within the single grains are presented and discussed. A shell of SrTiO3 or BaZrO3 was directly grown on the surface of BaTiO3 spherical templates suspended in aqueous solution by means of a precipitation process making use of inorganic precursors. The overall composition and the particle size can be tailored over a wide range. Densification of the resulting core-shell particles was realized using spark plasma sintering or conventional sintering. Dense ceramics with locally graded structure can be only obtained by a careful choice of the sintering conditions, that is, controlling the interdiffusion between core and shell. The final materials show strongly modified dielectric properties in comparison to both the parent compounds and the homogeneous solid solutions. The proposed approach is generic and suggests a new avenue to create functional and structural polycrystalline materials with locally graded structure by the controlled sintering of core-shell particles.
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| 10. |
- Buscaglia, V., et al.
(författare)
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Nanostructured barium titanate ceramics
- 2004
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Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 148:1, s. 24-27
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Tidskriftsartikel (refereegranskat)abstract
- Dense nanocrystalline ceramics can be obtained starting from non-agglomerated nanopowders and using low-temperature sintering processes. The preparation and the properties of Barium Titanate (BaTiO3) ceramics and thick films are reported: ceramics were prepared by Spark Plasma Sintering (SPS) at 800 degreesC of nanopowders produced by a wet chemical process, while films were fabricated by airflow deposition (AD) of mixed fine and coarse powders at room temperature followed by isothermal firing. Ferroelectric ordering was found in both the ceramics and the sintered films by a.c. impedance. The transition from ferroelectric to paraelectric state was broadened over a wide temperature range with Curie-Weiss parameters strongly depressed in comparison to coarse-grained ceramics.
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