In my master’s thesis, I investigate a dielectric composite material in which conductive particles are incorporated into an organic insulating matrix. The material is a percolative composite consisting of cellulose nanofibrils (CNF) as the matrix—the structural framework of the sample—and a filler composed of two-dimensional MXene materials (titanium carbide, Ti₃C₂Tₓ). Titanium carbide Ti₃C₂Tₓ belongs to the class of novel 2D transition-metal carbides, nitrides, and carbonitrides, commonly referred to as MXenes. Due to their outstanding electrochemical properties, hydrophilicity, and metallic-range electrical conductivity, MXenes are of considerable interest for applications in two-dimensional electronics.
Since a strong influence of the MXene incorporated into the matrix on the dielectric properties of the overall sample is expected, the dielectric response of samples with different concentrations of MXene filler was measured as part of the research presented in this master’s thesis. The samples were prepared by solution-based synthesis from cellulose and MXene solutions. Following synthesis, the samples were pressure-filtered, dried at room temperature, and subsequently compressed under elevated pressure for one day. The dielectric properties of nine samples were investigated: one control sample and eight experimental samples containing different fractions of MXene monolayers. The samples containing MXene monolayers are being investigated for the first time using dielectric spectroscopy methods, following previous successful investigations of systems containing multiple layers, which exhibited an enhanced dielectric response. Due to promising theoretical predictions, their geometrical structure, and polarization mechanisms that enhance the dielectric response in composite samples containing monolayers, the response of such materials was investigated.
The samples were measured using a Novocontrol Alpha High-Resolution Analyzer, which operates based on the Wheatstone bridge principle and measures the capacitance and conductance of the samples. The dielectric constant (ε) and specific electrical conductivity (σ) were calculated from the measurements. The influence of the weight fraction of the MXene filler on the enhancement of the dielectric response of such samples was systematically investigated. The results showed that the cellulose nanofibril–MXene monolayer composite exhibits an enhanced dielectric response with increasing weight percentage of the conductive filler. The increase in the dielectric response is attributed to polarization at the interfaces between the two material components. For the sample with the highest conductive filler content, the dielectric constant is almost three times higher than that of the sample with the lowest filler concentration. The specific electrical conductivity also increases by nearly one order of magnitude at the highest filler content; however, the material remains strongly insulating. Materials with a high dielectric constant are used to enhance electric fields in capacitors and are particularly useful in applications where an electrical response is converted into a mechanical one, such as piezoelectric devices. For such applications, the properties of the materials investigated in this work are highly promising, as they may enable an equal or greater mechanical response to be achieved using a lower electric field.
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