Electrospinning as a tool for fabricating functional ceramics
Prof. dr. ir. J.E. ten Elshof
Ceramic micro and nanomaterials have gained interest by the research community during last decade. They have contributed to improved performance in the fields of catalysis, biomedicine, energy and electronics. Amongst these ceramic materials, nanofibers have shown good potential; their large aspect ratio enhances several material properties.
This PhD thesis focuses on the development of novel functional ceramic fibers and nanochannels. Different materials were fabricated, characterized and tested in different applications.
The ceramic nanofibers and nanochannels have been fabricated by combining two techniques: electrospinning and sol-gel processing. The goal of this thesis is to investigate the influence of the fabrication process of different ceramic nanofibers on their properties, and subsequently to explore their potential in different fields of application.
In order to be able to tune the materials’ microstructure and properties, the process of preparing ceramic nanofibers by electrospinning was studied. The role of the solution properties on the process was thoroughly investigated as it controls most of the process and determines the feasibility of producing fibers. It was demonstrated that the fiber diameter, morphology and alignment can be modified. The possibility of preparing nanotubes is also shown. Such understanding was essential to design materials in order to enhance their performance in different fields of application.
A flexible ceramic consisting of a 3% Yttrium Stabilized Zirconia non-woven mat of fibers was designed to be used as scaffold for bone regeneration. Although that ceramic material is inherently rigid and bioinhert, it was proven that it can be turned into flexible and offered an improved bioresponse towards osteogenesis when shaped into nanofibers. Similarly, the possibility of shaping β tri calcium phosphate, a well-known bioactive material for bone regeneration into nanofibers, has been demonstrated. The final grain size in the resulting nanofibers was smaller than reported elsewhere, which is thought to be caused by the fibrous morphology.
Ceramic nanofibers also showed potential to be applied in the field of electronics. The fabrication of aligned ZnO nanofibers, and the semiconducting and photoelectric properties were studied in field effect transistor and UV detector applications. It was proven that electrospinning can be used for rapid fabrication of large area electronic devices.
A novel method to fabricate porous ceramics with controlled catalyst deposition is also presented. Polymer nanofibers were used to template ceramic materials and form nanochannels. 3% Yttrium Stabilized Zirconia / Ni cermet was chosen a model material to be used in the field of solid oxide fuel cells. Nevertheless, the same method can be extended to other fields.
In conclusion, it can be stated that ceramic nanofibers offer a promising alternative in different fields of application. However, the scaling and commercialization still remains a challenge.