**4. Conclusions**

*Nanofibers - Synthesis, Properties and Applications*

**3.8 Other applications**

fuel cycle [84].

of single-phase ceramic nanofibers at high temperatures, which limit their practical use. The fabricated SiZrOC nanofibers exhibited excellent high-temperature stability (~1200°C in Ar) and low thermal conductivity (~0.1392 W m−1 K−1 at 1000°C in N2). The unique combination of amorphous SiOC and ZrO2 nanocrystals offered a novel strategy to produce high-performance thermal insulation materials. While the multi-phase interfaces and the ZrO2 nanocrystals created thermal transfer barriers to reduce the heat transfer, the SiOC phase effectively suppressed radiative heat transfer [26]. Zhang et al. [82] produced ultra-strong, superelastic, and high temperature resistant, lamellar multiarc structured ceramic nanofibrous aerogels by combining ZrO2 − Al2O3 nanofibers with Al(H2PO4)3 matrices. The resulting ZrO2 − Al2O3 nanofibrous aerogels displayed a recovery of 90%, compression strength of more than 1100 kPa, temperature-invariant superelasticity, and high fatigue resistance, thermal insulation performance with low thermal conductivity (0.0322 W m−1 K−1), and temperature resistance up to 1300°C [82]. Peng et al. [80] fabricated yttria-stabilized zirconia mixed silica (YSZ/SiO2) nanofibers by the electrospinning method. The use temperature of the nanofibers increased by nearly 300°C and their maximum strength reached 5.9 ± 0.8 MPa. The YSZ/SiO2 nanofibers, showing good thermal insulation performance and hydrophobic properties,

were suggested for use as high-temperature insulation materials [80].

CNFs have been intensely investigated and applied in many different applications since their first production in 2002. There is still an ever-growing interest in the field with emerging applications that influence different aspects of life. Apart from the above discussed applications, ceramic nanofibers are also utilized in separation of nuclear waste and recycling of nuclear fuels. Liu et al. [84] electrospun TiO2 nanofibers with high porosity and functionalized the membranes with silver nanoparticles and nanocrystal metal organic frameworks to capture gases of interest in order to recycle nuclear and industrial waste. These ceramic nanofiber materials showed high porosity, loading capacity, permeability, stability in extreme conditions and were effective in recycling of nuclear waste back into the

Ramaseshan and Ramakrishna [85] produced zinc titanate ceramic nanofibers by electrospinning technology using polyvinylpyrrolidone as a binder for use as catalysts for the detoxification of chemical warfare agents, which are known to react with metal oxides (Mg, Al, Fe, Ti, Zn, Cr, Cu, Mn, etc.) and detoxify them into nontoxic harmless by-products. The zinc titanate nanofibers were found to be effective in decontamination of agents, such as dimethyl methyl phosphonate and chloroethyl ethyl sulfide. The extent of detoxification was measured and the products of reaction of zinc titanate against the simulants were found to be relatively harmless. The nanofibers obtained were suggested to replace conventional-activated carbon by electrospun ceramic nanofibers for face masks and protective clothing [85]. Abdo et al. [86] fabricated titanium dioxide (TiO2) and carbon nanofibers by electrospinning technique followed by calcination process and utilized these nanofibers to reinforce magnesium matrix composites. When 5 wt.% TiO2 nanofibers were added the ultimate compressive strength increased to 281 MPa, which was about 12.4% higher than the pure Mg. As a result of the addition of carbon nanofibers into magnesium matrix composites, hardness increased to 64.4% with slight

CNFs were also utilized in development of highly sensitive and reliable capacitive pressure sensors. Using flexible TiO2 ceramic nanofibrous networks, Fu et al. [87] developed a capacitive pressure sensor and studied the capacitance-to-pressure

**70**

sacrifice in the mechanical properties [86].

The development of ceramic nanofibers has attracted a significant interest over the recent years. Among different production techniques such as magnetron sputtering, solution blowing, laser spinning, chemical vapor deposition, template synthesis, phase separation, hydrothermal treatment; electrospinning enabled the production of uniform CNFs with high surface areas, very small diameters, extremely long length, and small pore size. Ceramic nanofibers became indispensable materials in many applications. In this chapter, electrospun ceramic nanofibers are reviewed with an emphasis on their applications in tissue engineering, gas sensors, water remediation, batteries, catalyst supports/catalysts, electromagnetic interference shielding and thermal insulation materials. Although there has been a lot of progress since their first production, there is still a lot to be explored regarding their production, and properties, and there is a great potential for their uses in many different fields.
