Ceramic materials are widely known for their high temperature resistance, chemical stability, and high mechanical and electrical properties. Ceramic materials come in a variety of forms, including nanoparticles (0D), nanofibers (1D), thin films or coatings (2D) and bulk ceramics (3D).
In recent years, electrospinning for ceramic materials has attracted interest for its ability to produce ceramic nanofibers with unique properties.
Electrospinning with ceramic materials
In the ceramic materials context, and because they are not amenable to direct dissolution, the electrospinning process to obtain ceramic nanofibers typically involves the incorporation of a ceramic precursor into a polymeric solution (using a polymer with a high capacity to be stably processed by electrospinning). The main steps for obtaining ceramic nanofibers are:
Preparation of the polymer solution: since a solution made only with ceramic precursors does not have sufficient viscosity to form a jet during the electrospinning process (and viscosity is one of the essential parameters in the electrospinning process), a compatible polymer is usually added. The choice of polymer and ceramic precursor, as well as their concentration and ratio, depends on the desired properties of the final ceramic nanofibers. Another option is to use the sol-gel process, which includes a polymerization step.
Electrospinning process: the solution is loaded into a syringe (in the case of laboratory-scale electrospinning equipment), and a high voltage is applied between the needle and the collector. The electric field causes the solution to form what is known as a Taylor cone at the tip of the needle, which in turn generates a jet. This jet is stretched and, as it travels between emitter and collector, the solvent evaporates, and solidified nanofibers are generated. At this point, the ceramic precursor is embedded in the polymer nanofibers.
Heat treatment (post-processing): electrospun ceramic nanofibers are often subjected to calcination treatment in the form of post pyrolysis, hydrothermal and carbothermal processes. These treatments remove the polymer, so that the resulting nanofibers are composed exclusively of the ceramic material. These treatments also remove the polymer, so that the resulting nanofibers are composed exclusively of the ceramic material.
Ceramic materials and precursors
There are several ceramic materials that have been successfully processed by electrospinning, allowing the number of applications to continue to grow. Examples of ceramic materials include oxides (e.g. TiO2, ZnO, SiO2), carbides (e.g. SiC), nitrides (e.g. BN), and composites. The choice of ceramic precursor influences the properties of the resulting nanofibers, such as their mechanical strength, electrical conductivity and thermal stability.
Composite fibers combining polymers with ceramic materials are attracting a lot of interest. These composites often have improved mechanical, thermal or electrical properties compared to their individual components.
Polymer-ceramic composites: by carefully selecting polymers and ceramic precursors, researchers create composites that exploit the desirable properties of both components. The electrospinning technique can generate nanofibers from polymer-ceramic composites. These composites have applications in a wide range of fields, from aerospace to electronics.
Carbon-ceramic composites: electrospinning has played a key role in producing carbon-ceramic composites. These materials show improved mechanical and thermal stability, making them suitable for high temperature applications.
Ceramic nanofibers applications with electrospinning
Some of their applications include:
- Catalysis: ceramic nanofibers, with their high surface area, are an excellent platform for catalytic applications. Catalysis tests performed on electrospun ceramic nanofibers show increased activity and stability, making them valuable for industrial applications.
- Sensors: electrospun ceramic nanofibers are being investigated for use in sensors due to their high surface area to volume ratio. They can be used in gas and moisture sensors, and in biosensors, as they have a high sensitivity to changes in the environment.
- Energy storage: ceramic nanofibers play a key role in energy storage devices such as lithium-ion batteries and supercapacitors. Their unique structure facilitates fast charge/discharge cycles, improving the performance of these devices. Electrospinning nanofiber membranes usually generates high energy density and good electronic transfer. This is why electrospinning is also emerging in energy-related applications.
- Tissue engineering: In the biomedical field, ceramic nanofibers are being investigated for tissue engineering applications. These fibers can provide a scaffold that replicates the extracellular matrix, promoting cell adhesion and growth. Electrospinning is one of the techniques being explored most recently in the field of tissue engineering.
- Filtration: the high porosity and small pore size of ceramic nanofibers produced by electrospinning make them suitable for certain filtration applications. They have been successfully employed in air and water filtration systems, demonstrating their ability and efficiency to separate particles.
Challenges and sustainability
Among the main challenges in obtaining ceramic nanofibers is achieving a homogeneous distribution of the ceramic precursor within the polymer matrix, as this is critical for the formation of uniform ceramic nanofibers. Researchers are currently facing challenges related to phase separation during the electrospinning process to improve the overall quality of the nanofibers.
On the other hand, researchers are exploring the use of eco-friendly ceramic precursors with the aim of developing sustainable methods for large-scale production while reducing environmental impact.
Electrospinning has emerged as a particularly suitable technique for producing ceramic nanofibers due to its low cost, ease of preparation of the solution containing the ceramic precursor and the polymer, and its ability to generate solid and hollow nanofibers. The properties of nanofibers obtained by electrospinning are superior to their bulk equivalent due to their low weight, as well as their porous structure and high surface area.
The applications of ceramic nanofibers are broad, ranging from catalysis and energy storage to tissue engineering. The unique properties exhibited by ceramic nanofibers continue to drive innovation in various fields. Ongoing research is addressing challenges related to dissolution formulation, phase separation and process scale-up. More sustainable alternatives and eco-friendly applications are also being explored, ensuring the continued growth of electrospinning in the field of ceramic materials.
At Bioinicia Group, we have experience in the processing of some ceramic materials by electrospinning. Also, some of our customers, users of Fluidnatek electrospinning equipment, are specialists in ceramic applications with electrospinning nanofibers, with a positive and satisfactory result of the use of Fluidnatek technology for electrospinning and electrospraying.
References B. Sahoo et al., “Electrospinning of functional ceramic nanofibers”, Open Ceramics 11 (2022) 100291.  H. Esfahani et al., “Electrospun Ceramic Nanofiber Mats Today: Synthesis, Properties, and Applications”, Materials 2017, 10, 1238.