Examining Scanning Electron Image of a Nonwoven Composite Consisting of Carbon and Ceramic
On Bayreuth Universityscientists present a new electrospun weave featuring an extraordinary combination of very low thermal conductivity and high electrical conductivity.
It is now feasible to separate thermal and electrical conductivity with a material idea that is easy to implement.
The nonwovens consist of carbon and silicon based ceramics through an electrospinning process and are of interest for technological applications, for example in energy technology and electronics. They can be profitably produced and processed on an industrial scale.
In general, high electrical conductivity is associated with high thermal conductivity, and low thermal conductivity corresponds to low electrical conductivity. But in some high-tech industries, there is increasing interest in multifunctional materials that integrate good electricity together with low heat transport.
Although many strategies such as conjugated polymers, solid inorganic materials and alloys have been developed in materials, obtaining very low thermal conductivity along with high electrical conductivity is still a great difficulty for adaptable and collapsible materials.
At the University of Bayreuth, a research group has come up with a breakthrough idea to overcome this difficulty. The new electrospun weave consists of silicon and carbon-based ceramics and comprises sea island-type nanostructured fibers with diameters ranging between 500 and 600 nm.
Each fiber consists of a carbon matrix in which the nano-sized ceramic phase is homogeneously distributed. The particles develop small “islands” in the “sea” of the carbon matrix and have opposite and complementary effects.
The presence of a carbon matrix allows electron transport within the fiber and hence high electrical conductivity, while the nano-sized silicon-based ceramics help prevent heat energy from spreading easily.
This is due to the presence of interfaces between the nano-sized ceramics and because the carbon matrix is very high, while the pores of nonwovens appear to be very small. As a result, there is a strong scattering of phonons, which are considered to be the smallest physical vibrational units activated by thermal energy. Constant directed heat flow does not occur.
The peculiar combination of very low current electrical and thermal conductivity has been emphasized in comparison with more than 3,900 materials of all types, such as carbon, ceramics, natural materials, metals, glasses, synthetic polymers, and some composites. Electron transport and thermal energy insulation are highly coupled in the new electrospun composite fiber material compared to other materials.
Our electrospun nonwovens incorporate very interesting multifunctional properties that are typically distributed among different classes of materials: high electrical conductivity, the familiar thermal insulation of polymeric foams, and the non-combustible and heat-resistant characteristics of ceramics.
Xiaojian Liao, Postdoctoral Researcher, Macromolecular Chemistry, Bayreuth University
Liao added, “The fibers are based on the concept of simple materials, and are made from commercial polymers.”
“We believe that our new fiber is suitable for several application areas: for example, in energy management, battery-powered electromobility, smart textiles or aerospace, said Professor Dr. Seema Agarwal, professor of macromolecular chemistry at Bayreuth University and one of the co-authors of the new study.
At the University of Bayreuth, an interdisciplinary team with expertise in ceramics, polymers, physical chemistry, electrospinning and electron microscopy, helped make this work possible.
Interdisciplinary Collaboration on the Bayreuth Campus
Collaborations are carried out by various research centers for Bayreuth scientists in the development of new materials and important preliminary studies: the Bavarian Institute of Polymers (BPI), the Bayreuth Center for Colloids and Interfaces (BZKG), the Bavarian Geo Institute (BGI), and the Bavarian Center for Battery Technology (BayBatt).
Liao, X., et al. (2023) Extremely low thermal conductivity and high electrical conductivity of sustainable carbonceramic electrospun nonwovens. Science Advances. doi.org/10.1126/sciadv.ade6066.