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MXenes are a group of two-dimensional materials that are promising for many applications, including as film electrode supercapacitors. When synthesizing such materials, special attention is paid to the conditions for obtaining the MAX phase, the chemical, morphological and structural features of which determine the functional properties of the final product. In this study, the Ti3AlC2 precursor is proposed to be obtained using a technologically simple and accessible method of synthesis in molten salt. This method allows reducing the reaction temperature and creating an antioxidant atmosphere. Ti3C2Tx MXene electrode films are produced by the easily scalable blade coating method without a binder. The synthesized materials were studied by X-ray phase analysis and scanning electron microscopy. Electrochemical testing of Ti3C2Tx film electrodes was carried out in a three-electrode configuration in aqueous solutions of 1M H2SO4, 6M KOH, 1M LiOH and 1M Na2SO4 electrolytes. The maximum specific capacity value for Ti3C2Tx MXene binder-free film electrode supercapacitors is obtained in 1M H2SO4 electrolyte (480 F g−1 at a scan rate of 1 mV s−1). The simple, low-cost and scalable production technology and promising electrochemical characteristics of the Ti3C2Tx MXene binder-free film electrode make it an excellent candidate for new-generation supercapacitors. [ABSTRACT FROM AUTHOR]

Three-phase polymer composites are promising materials for creating electronic device components. The qualitative and quantitative composition of such composites has a significant effect on their functional, in particular dielectric properties. In this study, ceramic filler K2Ni0.93Ti7.07O16 (KNTO) with Ag coating as conductive additive (0.5, 1.0, 2.5 wt.%) was introduced into the polyvinylidene difluoride (PVDF) polymer matrix in amounts of 7.5, 15, 22.5, and 30 vol.%. to optimize the dielectric constant and dielectric loss tangent. The filler was characterized by X-ray phase analysis, Fourier-transform infrared spectroscopy and Scanning electron microscopy methods. The dielectric constant, dielectric loss tangent, and conductivity of three-phase composites KNTO@Ag-PVDF were studied in comparison with two-phase composites KNTO-PVDF in the frequency range from 102 Hz to 106 Hz. The dielectric constant values of composites containing 7.5, 15, 22.5, and 30 vol.% filler were 12, 13, 17.4, 19.2 for pure KNTO and 13, 19, 25, 31 for KNTO@Ag filler (2.5 wt.%) at frequency 10 kHz. The dielectric loss tangent ranged from 0.111 to 0.340 at a filler content of 7.5 to 30 vol.%. A significantly enhanced balance of dielectric properties of PVDF-based composites was found with K2Ni0.93Ti7.07O16 as ceramic filler for 1 wt.% of silver. Composites KNTO@Ag(1 wt.%)-PVDF can be applied as dielectrics for passive elements of flexible electronics. [ABSTRACT FROM AUTHOR]

The development of new electrode materials for electrochemical systems for various purposes is a significant and in-demand task of scientific research. Layered transition metal carbides and nitrides, known as MXenes, show great potential for use as electrodes in electrochemical energy storage devices operating in aqueous electrolytes. In this work, a multilayer Ti3C2Tx MXene was obtained from a Ti3AlC2 precursor and studied as the electrode material of a symmetrical supercapacitor with an aqueous LiCl electrolyte. The formation of the MXene structure was confirmed by the data from X-ray phase analysis and scanning electron microscopy. The X-ray diffraction pattern showed the disappearance of the main reflections related to the Ti3AlC2 phase and the shift of the reflection peak (002) from 9.4° to 6.7°, which indicated successful etching of the Al layers from the Ti3AlC2 precursor. At electrolyte concentrations of 1, 5, 10, and 20 M, the supercapacitors demonstrated high specific capacitances of 105, 120, 126, and 151 F·g−1 at a scan rate of 5 mV·s−1. In addition, an increase in the LiCl concentration contributed to the expansion of the potential window from 0.7 to 1 V. It was shown that the contribution of the surface capacitance to the total capacitance of the electrode is about 40% and depends little on the scan rate. In addition, the symmetrical supercapacitor with 5 M electrolyte showed good cyclic stability with capacitance retention of 88% over 10,000 cycles. The parameters of the main components of the physical processes of supercapacitors based on Ti3C2Tx were determined by the method of impedance spectroscopy. [ABSTRACT FROM AUTHOR]

In this paper, LixCa(1−x)Cu3Ti4O12 (LCCTO) solid solutions were successfully synthesized. XRD diagrams showed that dopant acceptor Li+ cations, in a concentration range of x = 0.01–0.10, were successfully merged into CCTO structure. It was found that doping with low concentrations of lithium (x < 0.05) inhibited grain growth during annealing; however, for x > 0.05, the grain growth process resumed. Permittivity and dielectric losses of obtained LCCTO ceramics were analyzed by the means of impedance spectroscopy in a frequency range from 10−1 to 106 Hz. It was revealed that acceptor doping with lithium at an appropriate concentration of x = 0.05 allowed to obtain ceramics with a permittivity level of ε′ = 3 × 104 and low dielectric losses tanδ < 0.1 at 1 kHz. Further addition of lithium in a concentration range of x = 0.075–0.10 led to a sharp decline in permittivity and an increase in dielectric losses. It was discovered that lithium addition to CCTO ceramics drastically decreased grain boundary resistivity from 115 MΩ·cm to 5–40 MΩ·cm at x = 0.01–0.10. Using Havriliak–Negami equation, the relaxation times for grain dipoles and grain boundary dipoles were found to be ranging from 0.8 × 10−6 to 1.7 × 10−6 s and from 0.4 × 10−4 to 7.1 × 10−4 s, respectively. The developed materials can be used in the manufacture of Multilayer Ceramic Capacitors (MLCC) as a dielectric. [ABSTRACT FROM AUTHOR]

In this work we have synthesized Ti3C2TX MXene powder and studied its structure. Composite electrochemical coatings (CECs) of Ni-Ti3C2TX MXene were obtained from a sulfate– chloride bath in the galvanostatic regime. The microstructure of CEC was researched using X-ray phase analysis and scanning electron microscopy methods. It has been established that a Ni–Ti3C2TX MXene CEC microhardness rises by about 1.80 times compared with electrolytic Ni without a dispersed phase. For corrosion research, different corrosive media is applied. The corrosion–electrochemical behavior of Ni–Ti3C2TX MXene CECs by the chronovoltamperometry method in 0.5 M H2SO4 solution has been investigated. Trials in 3.5% NaCl have shown that Ti3C2TX MXene inclusion into the matrix of the electrochemical Ni results in a decrease in the corrosion rate by 1.60–1.75 times. These effects are due to the addition of Ti3C2TX MXene into the nickel matrix and the formation of CECs with a strengthening fine-grained structure. [ABSTRACT FROM AUTHOR]

In this study, we report the effect of intercalation of dimethyl sulfoxide (DMSO) and urea molecules into the interlayer space of Ti3C2Tx MXene on the dielectric properties of poly(vinylidene fluoride) (PVDF)/MXene polymer nanocomposites. MXenes were obtained by a simple hydrothermal method using Ti3AlC2 and a mixture of HCl and KF, and they were then intercalated with DMSO and urea molecules to improve the exfoliation of the layers. Then, nanocomposites based on a PVDF matrix loading of 5–30 wt.% MXene were fabricated by hot pressing. The powders and nanocomposites obtained were characterized by using XRD, FTIR, and SEM. The dielectric properties of the nanocomposites were studied by impedance spectroscopy in the frequency range of 102–106 Hz. As a result, the intercalation of MXene with urea molecules made it possible to increase the permittivity from 22 to 27 and to slightly decrease the dielectric loss tangent at a filler loading of 25 wt.% and a frequency of 1 kHz. The intercalation of MXene with DMSO molecules made it possible to achieve an increase in the permittivity up to 30 at a MXene loading of 25 wt.%, but the dielectric loss tangent was increased to 0.11. A discussion of the possible mechanisms of MXene intercalation influence on the dielectric properties of PVDF/Ti3C2Tx MXene nanocomposites is presented. [ABSTRACT FROM AUTHOR]

Some solid solutions with the chemical composition KxFeyTi8-yO16 (KFTO) and a hollandite-like structure were successfully synthesized by modified sol–gel method. The obtained powders were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The ceramic pellets based on KFTO powders were obtained by compressing and sintering at 1080 °C for 4 h. The sinters were characterized by X-ray and impedance spectroscopy. XRD results show that KFTO powders have a mono-phase tetragonal structure at x = 1.4–1.8 and y = 1.4–1.6. However, it was recognized that the hollandite-like phase could be broken during sintering to form TiO2 and Fe2TiO5 crystals distributed throughout the volume of the ceramics. A frequency dependency of dielectric properties for the sinters was studied by impedance spectroscopy. It was found that an increase in the TiO2 (rutile) phase during the sintering contributes to a decrease in dielectric losses. At the same time, the KFTO ceramics with reduced content of potassium had increased permittivity. The contribution of electron-pinned defect dipoles (EPDD) and internal barrier layer capacitance (IBLC) in the permittivity of the obtained ceramics was estimated using the Havriliak–Negami equation. It is shown that the KFTO ceramics have the polydisperse characteristic of dielectric relaxation. The observed grain and grain boundary dipole relaxation times were 1.03 × 10−6 to 5.51 × 10−6 s and 0.197 to 0.687 s, respectively. [ABSTRACT FROM AUTHOR]

New three-phase composites, destined for application as dielectrics in the manufacturing of passive elements of flexible electronics, and based on polymer (PVDF) matrix filled with powdered ceramics of the hollandite-like (KFTO(H)) structure (5.0; 7.5; 15; 30 vol.%) and carbon (MWCNT) additive (0.5; 1.0; 1.5 wt.% regarding the KFTO(H) amount), were obtained and studied by XRD, FTIR and SEM methods. Chemical composition and stoichiometric formula of the ceramic material synthesized by the sol–gel method were confirmed with the XRF analysis data. The influence of the ceramic and carbon fillers on the electrical properties of the obtained composites was investigated using impedance spectroscopy. The optimal combination of permittivity and dielectric loss values at 1 kHz (77.6 and 0.104, respectively) was found for the compositions containing K1.6Fe1.6Ti6.4O16 (30 vol.%) and MWCNTs (1.0 wt.% regarding the amount of ceramic filler). [ABSTRACT FROM AUTHOR]

In this work, polymer matrix composites with the compositions PTFE/KFTO(H) and PTFE/KFTO(H)@CB and with filler volume fractions of 2.5, 5.0, 7.5, 15, and 30% (without and with carbon modification at a content of 2.5 wt.% regarding ceramic material) were produced by calendering and hot pressing and studied using FTIR, SEM, and impedance spectroscopy methods. Ceramic filler (KFTO(H)) was synthesized using the sol–gel Pechini method. Its structure was investigated and confirmed by the XRD method with following Rietveld refinement. The carbon black (CB) modification of KFTO(H) was carried out through the calcination of a mixture of ceramic and carbon materials in an argon atmosphere. Afterwards, composites producing all the components' structures weren't destroyed according to the FTIR results. The effect of carbon additive at a content of 2.5 wt.% relating to ceramic filler in the system of polymer matrix composites was shown, with permittivity increasing up to ε' = 28 with a simultaneous decrease in dielectric loss (tanδ < 0.1) at f = 103 Hz for composites of PTFE/KFTO(H)@CB (30 vol.%). [ABSTRACT FROM AUTHOR]

Polymethyl methacrylate/hollandite‐like copper doped potassium titanate high‐k ceramics composites with different filler content (20–60 vol.%) are prepared by simple method of mixing of the polymer solution and ceramics dispersion followed evaporation of the solvent and hot pressing. The particle morphology and size are estimated by SEM. The composites obtained are studied by XRD, FTIR, and TGA methods. The influence of the additive and the concentration of hollandite‐like copper doped potassium titanate high‐k ceramics on dielectric properties (permittivity, conductivity, dielectric loss tangent) are investigated at frequency range from 10−1 to 106 Hz. It is shown that the increasing of ceramics concentration cause the increasing of main dielectric characteristics, namely permittivity up to 40 and dielectric loss up to 0.13 at 60 vol.% of filler and 0.1 Hz. Conductivity percolation threshold for PMMA/KCTO(H) composites was estimated (vc = 0.0773 vol. [20.9 wt. %]). Experimental data on permittivity are compared with different theoretical models (Lichtenecker's model and the Effective Medium Theory model). [ABSTRACT FROM AUTHOR]