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| Author(s): |
Ana Gabriela Storion
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT) |
| Defense date: | 2023-03-03 |
| Examining board members: |
Eliria Maria de Jesus Agnolon Pallone;
Adilson Luiz Chinelatto;
Eduardo Bellini Ferreira;
Vânia Trombini Hernandes;
Raphael Euclides Prestes Salem
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| Advisor: | Eliria Maria de Jesus Agnolon Pallone; Sylma Carvalho Maestrelli |
| Abstract | |
Alternative techniques to conventional sintering have been studied for controlling microstructure and grain growth, besides lower energy consumption. Among such techniques flash sintering stands out, providing fast shrinkage and densification in seconds. It applies to several materials, such as ZnO, an n-type semiconductor used in many electronic and optoelectronic devices. Despite numerous advances, flash sintering still faces some scientific challenges to overcome for its viability in industrial applications. To contribute to the advances in this scientific field, the present work aimed to evaluate the flash sintering parameters on ZnO microstructural homogeneity and application possibilities. During the parameterization step, it was possible to analyze the ideal process conditions, such as electrical and thermal parameters and material preparation. Subsequently, the influence of forming methods and the consequent density gradients formed in ZnO specimens on densification and microstructure when sintered via flash sintering was evaluated for the first time in the literature. The results indicated that the green density distribution generated during forming should be considered a decisive factor when evaluating specimens submitted to flash sintering. Also, flash sintering was investigated when coupled with thermal insulation with an alumina blanket (TIFS). The results showed that TIFS provided a more homogeneous microstructure, reducing the difference in grain size between the core and the surface of the specimen. TIFS, besides providing a 450°C decrease in the flash event onset temperature, was also able to achieve an estimated temperature during stage III only 100°C lower than that achieved for flash sintering under the same conditions, evidencing energy savings of up to 78% with the insulation process, compared to the uninsulated flash sintering experiments. The present work also aimed to evaluate the performance of flash-sintered ZnO when applied as a photocatalyst, since it may present great potential for application in the production of samples with refined microstructure, improving the surface reactivity. It was possible to prepare specimens with high porosity and sufficient integrity to be submitted to flash sintering. The results of the photocatalytic tests of the flash-sintered specimens were promising compared to the conventional-sintered ones, demonstrating the potential application of this alternative sintering route in the processing of photocatalysts. (AU) | |
| FAPESP's process: | 18/11143-0 - Influence of flash sintering parameters on ZnO densification and microstructure |
| Grantee: | Ana Gabriela Storion |
| Support Opportunities: | Scholarships in Brazil - Doctorate |