| 1. |
- Zhao, W., et al.
(author)
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Bending Strength of 3D-Printed Zirconia Ceramic Cellular Structures
- 2019
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In: IOP Conference Series. - : Institute of Physics Publishing.
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Conference paper (peer-reviewed)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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| 2. |
- Aimable, Anne, et al.
(author)
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Synthesis and Sintering of ZnO Nanopowders
- 2017
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In: TECHNOLOGIES. - : MDPI AG. - 2227-7080. ; 5:2
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Journal article (peer-reviewed)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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| 3. |
- Bu, Junfu, et al.
(author)
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Transport properties of BaZr0.5Ce0.3Y0.2O3-δ proton conductor prepared by spark plasma sintering
- 2016
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In: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 42:3, s. 4393-4399
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Journal article (peer-reviewed)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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| 4. |
- Cao, C., et al.
(author)
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Optimization of Curing Behavior of Si3N4 UV Resin for Photopolymerization 3D Printing
- 2019
-
In: IOP Conference Series. - : Institute of Physics Publishing.
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Conference paper (peer-reviewed)abstract
- Silicon nitride (Si3N4) ceramics are widely used in mechanical and thermal management applications due to their excellent properties. To overcome the difficulties in traditional Si3N4 ceramic forming techniques, it is interesting to see the possibility of making complex-shaped silicon nitride ceramic component with novel 3D printing methods. In this study, we aim to study the effect of photo-initiators on the curing behavior of pre-formulated Si3N4 ceramic UV resin suspension. To elucidate the potential multi-factor interactions, a statistic experiment design was implemented in a sequence of screening and optimization by using Modde software. It was found that the kinds of photo-initiators, total amount of initiators and the mixture ratio between initiators have a great influence on the curing properties of silicon nitride UV ceramic resin. Based on these results, a formula was selected based on the criterion of using least amount photo-initiator while reaching the highest curing thickness.
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| 5. |
- Cheng, Z., et al.
(author)
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Ink-jet printed BNT thin films with improved ferroelectric properties via annealing in wet air
- 2018
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In: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 44:9, s. 10700-10707
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Journal article (peer-reviewed)abstract
- In this work, an ink-jet printing process based on the sol-gel route was applied to prepare lead-free ferroelectric Na0.5Bi0.5TiO3(BNT) thin films for the first time. Dense and crack-free films with perovskite structure were obtained from a modified precursor solution through multiple printing and pyrolysis processes. The ferroelectric, dielectric and electrical properties were significantly affected by the annealing temperature and atmosphere. The film annealed at 670 °C in wet air showed a high remnant polarization of 24.7 μC/cm2 with a low coercive field of 263 kV/cm, the dielectric constant and loss were 185 and 0.1 at 10 kHz, respectively. It was found that wet air was an alternative to reduce oxygen vacancies and enhance properties of ferroelectric films, which can be explained by the defect chemical reaction between water and oxygen vacancies. X-ray photoelectron spectroscopy(XPS) confirmed the decrease of oxygen vacancies after annealing with water presence, with a formation of Ohmic conduction mechanism dominated by charged hydroxyl groups.
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| 6. |
- Dong, H., et al.
(author)
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Effect of powder characteristics on the thermal conductivity and mechanical properties of Si 3 N 4 ceramics sintered by Spark plasma sintering
- 2019
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In: Journal of materials science. Materials in electronics. - : Springer-Verlag New York. - 0957-4522 .- 1573-482X. ; 30:8, s. 7590-7599
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Journal article (peer-reviewed)abstract
- The effect of powder characteristics on the thermal conductivity and mechanical properties of silicon nitride (Si 3 N 4 ) ceramics were investigated systematically by using two α-Si 3 N 4 powders as raw materials and using MgSiN 2 or MgO + Y 2 O 3 as sintering additives. The Si 3 N 4 ceramics with a higher density were obtained by α-Si 3 N 4 powders with lower oxygen content and impurities and using none-oxide sintering additive MgSiN 2 . The α–β phase transformation completely taken place in all the specimen at 1750 °C. The specimens sintered by powders with lower levels of oxygen and impurities show higher mechanical properties than other specimens. The Y 2 O 3 and MgO sintering additives lead to higher flexural strength and fracture toughness than MgSiN 2 . The Vickers’ hardness is just the opposite. The thermal conductivity value of powders with lower oxygen content is higher than that of the materials prepared by the other type of powder at the same conditions. The effects of the Si 3 N 4 particle size, native oxygen and impurities on the thermal conductivity of resultant materials were discussed in detail. This work demonstrates that the improvement in thermal conductivity of Si 3 N 4 can be obtained by using none-oxide sintering additive MgSiN 2 and the Si 3 N 4 powder with lower oxygen content, and impurities.
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| 7. |
- Gao, S., et al.
(author)
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Mechanical Properties of ZrO2 Honeycomb Sandwich Structures by 3D Printing
- 2019
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In: IOP Conference Series. - : Institute of Physics Publishing.
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Conference paper (peer-reviewed)abstract
- Honeycomb sandwich structures were widely used in lightweight design. However, the difficulties with the fabrication process actually highly limit their practical usage, especially for ceramic materials. In this paper, 3 mol% yttria-stabilized ZrO2 (3Y-TZP) honeycomb sandwich structures with square and hexagonal cell were prepared successfully by using digital light processing (DLP) printing method. With a base material density of >6.02g/cm3, square/hexagonal honeycomb sandwich structures with structural density of 42.89%-66.24% were achieved by modifying unit cell wall thickness. It can be concluded that square honeycomb cell is preferred for getting higher bending strength at the same structural density.
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| 8. |
- Ren, Yanan, et al.
(author)
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3DOM-NiFe2O4 as an effective catalyst for turning CO2 and H2O into fuel (CH4)
- 2018
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In: Journal of Sol-Gel Science and Technology. - : SPRINGER. - 0928-0707 .- 1573-4846. ; 88:3, s. 489-496
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Research review (peer-reviewed)abstract
- Three-dimensional ordered macroporous NiFe2O4 (3DOM-NFO) powder was synthesized through the direct templating method combined with the sol-gel combustion technique. Polymethyl methacrylate (PMMA) spheres with different sizes were used as the hard templates. In order to understand the effect of PMMA spheres mean size on the structure and catalytic activity of synthesized 3DOM-NFO, the detailed characterization of the material was carried out by XRD, SEM, BET, XPS, UV-VIS, and DRS techniques. Direct hydrogeneration production of CH4 from CO2 and H2O was used to evaluate the catalysis performance of 3DOM-NFOs. The production of CH4 evolution can reach 1040.8mol/g at 350 degrees C and ambient pressure when 300nm template was used. It was concluded that the specific surface area and moderate concentration of oxygen vacancies are the crucial factors affecting the catalysis properties. Reasonably high turnover number of 0.244 and high CH4 conversion efficiency of 0.897% were obtained in this study. 3DOM-NFO can be a promising catalyst for hydrocarbon fuel production by directly using CO2 and H2O as the safe and cheap feedstocks. [GRAPHICS] .
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| 9. |
- Shen, M., et al.
(author)
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Mechanical Properties of ZrO2 TPMS Structures Prepared by DLP 3D Printing
- 2019
-
In: IOP Conference Series. - : Institute of Physics Publishing.
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Conference paper (peer-reviewed)abstract
- Compressive strength is one of the most important mechanical properties for cellular ceramics. But the dependence of compressive strength of highly porous cellular ceramic structures on porosity remains unclear due to the limit of available methods for making such strong structures based on specific structural designs. In this paper, the TPMS structures, namely P-cell, and neovius structure, were prepared based on the DLP 3D printing technology. Samples with various unit cells were fabricated with zirconia. The relative density of the sintered samples exceeds 99%. The effects of cell number on the compressive strength and deformation of the model were investigated. Samples with similar relative densities exhibited comparable mechanical property in aspect of compressive strength. It is very interesting that the cell number eventually only influence the total strain.
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| 10. |
- Stuer, Michael, et al.
(author)
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Comparison of apparent activation energies for densification of alumina powders by pulsed electric current sintering (spark plasma sintering) and conventional sintering-toward applications for transparent polycrystalline alumina
- 2017
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In: Journal of Materials Research. - : CAMBRIDGE UNIV PRESS. - 0884-2914 .- 2044-5326. ; 32:17, s. 3309-3318
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Journal article (peer-reviewed)abstract
- In the quest for high real in-line transmittances for transparent polycrystalline alumina (PCA), we need defect free processing. One of the biggest advances in producing high density defect free ceramics over recent years has been the advent of spark plasma sintering (SPS) or pulsed electric current sintering. The production of PCA with high transmittances >60% has been demonstrated, but the mechanisms behind this fast, pressure aided sintering method are still much debated. Here, we investigate the sintering of doped a-alumina powders using traditional and pulsed electric current dilatometry. We demonstrate that at the final sintering stage, there is no major difference in the sintering mechanisms between conventional sintering and SPS sintering. High densification rates occurring in SPS are shown to be related to powder reorientation at the very early sintering stage and viscous-flow dominated densification in the intermediate sintering cycle. This paper clarifies what parameters in the processing-sintering domain have to be improved for even higher real in-line transmittances for PCA.
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