Search Results (18)

Polymer-matrix composites with ceramic fillers have various applications, one of which is the modification of the electric field. For this purpose, in this work, high-permittivity silicone composites with different polarization titanates were produced by mechanical mixing. The ceramic fillers chosen were CaCu₃Ti₄O₁₂, K_xFe_yTi_8−yO₁₆, and BaTiO₃ powders with high permittivity values and uniformly distributed in the polymer volume. Ceramic powders were studied by X-ray phase analysis and scanning electron microscopy methods. The proportion of ceramic powder was 25 wt.%. In parallel, composites were prepared with the addition of 25 wt.% glycerin. The functional properties of silicone composites were studied using the following parameters: the electrical strength and permittivity. The addition of all types of ceramic fillers, both together and without glycerin, led to a decrease in electrical strength (below 15 kV·mm⁻¹); the exception is the sample with the CCTO without glycerin (about 28 kV·mm⁻¹). The permittivity and the dielectric loss tangent of the composites increased as a result of the addition of fillers, especially noticeable in combination with glycerol in the low-frequency region. The obtained results are in good agreement with the literature data and can be used in the field of insulation in a high-permittivity layer to equalize equipotential fields. Full article

Polymer and ceramic-based composites offer a unique blend of desirable traits for improving dielectric permittivity. This study employs an empirical approach to estimate the dielectric permittivity of composite materials and uses a finite element model to understand the effects of permittivity and filler concentration on mechanical and electrical properties. The empirical model combines the Maxwell-Wagner-Sillars (MWS) and Bruggeman models to estimate the effective permittivity using Barium Titanate (BT) and Calcium Copper Titanate Oxide (CCTO) as ceramic fillers dispersed in a Polydimethylsiloxane (PDMS) polymer matrix. Results indicate that the permittivity of the composite improves with increased filler content, with CCTO/PDMS emerging as the superior combination for capacitive applications. Capacitance and energy storage in the CCTO/PDMS composite material reached 900 nF and 450 nJ, respectively, with increased filler content. Additionally, increased pressure on the capacitive model with varied filler content showed promising effects on mechanical properties. The interaction between BT filler and the polymer matrix significantly altered the electrical properties of the model, primarily depending on the composite’s permittivity. This study provides comprehensive insights into the effects of varied filler concentrations on estimating mechanical and electrical properties, aiding in the development of real-world pressure-based capacitive models. Full article

The many pollutants detected in water represent a global environmental issue. Emerging and persistent organic pollutants are particularly difficult to remove using traditional treatment methods. Electro-oxidation and sulfate-radical-based advanced oxidation processes are innovative removal methods for these contaminants. These approaches rely on the generation of hydroxyl and sulfate radicals during electro-oxidation and sulfate activation, respectively. In addition, hybrid activation, in which these methods are combined, is interesting because of the synergistic effect of hydroxyl and sulfate radicals. Hybrid activation effectiveness in pollutant removal can be influenced by various factors, particularly the materials used for the anode. This review focuses on various organic pollutants. However, it focuses more on pharmaceutical pollutants, particularly paracetamol, as this is the most frequently detected emerging pollutant. It then discusses electro-oxidation, photocatalysis and sulfate radicals, highlighting their unique advantages and their performance for water treatment. It focuses on perovskite oxides as an anode material, with a particular interest in calcium copper titanate (CCTO), due to its unique properties. The review describes different CCTO synthesis techniques, modifications, and applications for water remediation. Full article

Recently, scientists have been facing major obstacles in terms of improving the performances of dielectric materials for triboelectric nanogenerators. The triboelectric nanogenerator (TENG) is one of the first green energy technologies that can convert random mechanical kinetic energy into electricity. The surface charge density of TENGs is a critical factor speeding up their commercialization, so it is important to explore unique methods to increase the surface charge density. The key to obtaining a high-performance TENG is the preparation of dielectric materials with good mechanical properties, thermal stability and output performance. To solve the problem of the low output performance of PI-based triboelectric nanogenerators, we modified PI films by introducing nanomaterials and designed a new type of sandwich-shaped nanocomposite film. Herein, we used polyimide (PI) with ideal mechanical properties, excellent heat resistance and flexibility as the dielectric material, prepared an A-B-A sandwich structure with PI in the outer layer and modified a copper calcium titanate/polyimide (CCTO/PI) storage layer in the middle to improve the output of a TENG electrode. The doping amount of the CCTO was tailored. The results showed that at 8 wt% CCTO content, the electrical output performance was the highest, and the open-circuit voltage of CCTO/PI was 42 V. In the TENG, the open-circuit voltage, short-circuit current and transfer charge of the prepared sandwich-structured film were increased by 607%, 629% and 672% compared to the TENG with the PI thin film, respectively. This study presents a novel strategy of optimizing dielectric materials for triboelectric nano-generators and has great potential for the future development of high output-performance TENGs. Full article

This paper reports a detailed study of crystal structure and dielectric properties of ruthenium-substituted calcium-copper titanates (CaCu₃Ti_4−xRu_xO₁₂, CCTRO). A series of three samples with different stoichiometry was prepared: CaCu₃Ti_4−xRu_xO₁₂, x = 0, 1 and 4, abbreviated as CCTO, CCT3RO and CCRO, respectively. A detailed structural analysis of CCTRO samples was done by the Rietveld refinement of XRPD data. The results show that, regardless of whether Ti⁴⁺ or Ru⁴⁺ ions are placed in B crystallographic position in AA’₃B₄O₁₂ (CaCu₃Ti_4−xRu_xO₁₂) unit cell, the crystal structure remains cubic with $Im\overline{3}$ symmetry. Slight increases in the unit cell parameters, cell volume and interatomic distances indicate that Ru⁴⁺ ions with larger ionic radii (0.62 Å) than Ti⁴⁺ (0.605 Å) are incorporated in the CaCu₃Ti_4−xRu_xO₁₂ crystal lattice. The structural investigations were confirmed using TEM, HRTEM and ADF/STEM analyses, including EDXS elemental mapping. The effect of Ru atoms share in CaCu₃Ti_4−xRu_xO₁₂ samples on their electrical properties was determined by impedance and dielectric measurements. Results of dielectric measurements indicate that one atom of ruthenium per CaCu₃Ti_4−xRu_xO₁₂ unit cell transforms dielectric CCTO into conductive CCT3RO while preserving cubic crystal structure. Our findings about CCTO and CCT3RO ceramics promote them as ideal tandem to overcome the problem of stress on dielectric-electrode interfaces in capacitors. Full article

A novel calcium copper titanate (CaCu₃Ti₄O₁₂)–polyvinylidene fluoride composite (CCTO@PVDF) with Cu-deficiency was successfully prepared through the molten salt-assisted method. The morphology and structure of polymer composites uniformly incorporated with CCTO nanocrystals were characterized. At the same volume fraction, the CCTOs with Cu-deficiency displayed higher dielectric constants than those without post-treatment. A relatively high dielectric constant of 939 was obtained at 64% vol% CCTO@PVDF content, 78 times that of pure PVDF. The high dielectric constants of these composites were attributed to the homogeneous dispersion and interfacial polarization of the CCTO into the PVDF matrix. These composites also have prospective applications in high-frequency regions (10⁶ Hz). The enhancement of the dielectric constant was predicted in several theoretical models, among which the EMT and Yamada models agreed well with the experimental results, indicating the excellent distribution in the polymer matrix. Full article

A surface acoustic wave (SAW), device composed of polymer and ceramic fillers, exhibiting high piezoelectricity and flexibility, has a wide range of sensing applications in the aerospace field. The demand for flexible SAW sensors has been gradually increasing due to their small size, wireless capability, low fabrication cost, and fast response time. This paper discusses the structural, thermal, and electrical properties of the developed sensor, based on different micro- and nano-fillers, such as lead zirconate titanate (PZT), calcium copper titanate (CCTO), and carbon nanotubes (CNTs), along with polyvinylidene fluoride (PVDF) as a polymer matrix. The piezocomposite substrate of the SAW sensor is fabricated using a hot press, while interdigital transducers (IDTs) are deposited through 3D printing. The piezoelectric properties are also enhanced using a non-contact corona poling technique under a high electric field to align the dipoles. Results show that the developed passive strain sensor can measure mechanical strains by examining the frequency shifts of the detected wave signals. Full article

In this paper, we examined the dielectric properties of CaCu₃Ti₄O₁₂ (CCTO) ceramics fabricated by various routes and discussed the most important conditions affecting their dielectric behavior. We prepared feedstock powder using a molten salt route and compared it with a commercial powder. Both powders were sintered using SPS. For some samples, annealing was applied after sintering. Other samples were obtained by high-pressure forming and conventional sintering, using both powders. Phase composition, porosity and microhardness were evaluated in comparison with the literature. The results showed that a sintering temperature just below or equal to 1000 °C should be set for the SPS process. However, the best dielectric characteristics were obtained in samples prepared by high-pressure forming and conventional sintering, which showed a relative permittivity of 22,000 and a loss tangent of 0.13 at 1 MHz. Full article

Integrating nano- to micro-sized dielectric fillers to elastomer matrices to form dielectric composites is one of the commonly utilized methods to improve the performance of dielectric elastomer actuators (DEAs). Barium titanate (BaTiO₃) is among the widely used ferroelectric fillers for this purpose; however, calcium copper titanate CaCu₃Ti₄O₁₂ (CCTO) has the potential to outperform such conventional fillers. Despite their promising performance, CCTO-based dielectric composites for DEA application are studied to a relatively lower degree. Particularly, the composites are characterized for a comparably small particle loading range, while critical DEA properties such as breakdown strength and nonlinear elasticity are barely addressed in the literature. Thus, in this study, CCTO was paired with polydimethylsiloxane (CH₃)₃SiO[Si(CH₃)₂O]_nSi(CH₃)₃ (PDMS), Sylgard 184, to gain a comprehensive understanding of the effects of particle loading and size on the dielectric composite properties important for DEA applications. The dielectric composites’ performance was described through the figures of merit (FOMs) that consider materials’ Young’s modulus, dielectric permittivity, and breakdown strength. The optimum amounts of the ferroelectric filler were determined through the FOMs to maximize composite DEA performance. Lastly, electromechanical testing of the pre-stretched CCTO-composite DEA validated the improved performance over the plain elastomer DEA, with deviations from prediction attributed to the studied composites’ nonlinearity. Full article

Dielectric elastomer (DE) is a type of electric field type electroactive polymer material that can produce greater deformation under the action of an electric field and has a faster recovery speed. It has the advantages of high energy density, large strain, low quality, and commercialization, and has become the most widely concerned and researched electroactive polymer material. In this study, copper calcium titanate (CCTO) particles with a large dielectric constant were selected as the filling phase, and a silicone rubber (PDMS) with better biocompatibility and lower elastic modulus was used as the matrix to prepare CCTO/PDMS, which is a new type of dielectric elastomer material. The structure of the dielectric elastomer is analyzed, and its mechanical properties, dielectric properties, and driving deformation are tested. Then, KH550, KH560, and KH570 modified CCTO is used in order to improve the dispersibility of CCTO in PDMS, and modified particles with the best dispersion effect are selected to prepare dielectric elastomer materials. In addition, mechanical properties, dielectric properties, and driving deformation are tested and compared with the dielectric elastomer material before modification. The results show that as the content of CCTO increases, the dielectric constant and elastic modulus of the dielectric elastomer also increase, and the dielectric loss remains basically unchanged at a frequency of 100 Hz. When the filling amount reaches 20 wt%, the dielectric constant of the CCTO/PDMS dielectric elastomer reaches 5.8 (100 Hz), an increase of 120%, while the dielectric loss at this time is only 0.0038 and the elastic modulus is only 0.54 MPa. When the filling amount is 5 wt%, the dielectric elastomer has the largest driving deformation amount, reaching 33.8%. Three silane coupling agents have been successfully grafted onto the surface of CCTO particles, and the KH560 modified CCTO has the best dispersibility in the PDMS matrix. Based on this, a modified CCTO/PDMS dielectric elastomer was prepared. The results show that the improvement of dispersibility improves the dielectric constant. Compared with the unmodified PDMS, when the filling content is 20 wt%, the dielectric constant reaches 6.5 (100 Hz). Compared with PDMS, it has increased by 150%. However, the improvement of dispersion has a greater increase in the elastic modulus, resulting in a decrease in its strain parameters compared with CCTO/PDMS dielectric elastomers, and the electromechanical conversion efficiency has not been significantly improved. When the filling amount of modified CCTO particles is 5 wt%, the dielectric elastomer has the largest driving deformation, reaching 27.4%. Full article

Pollutant emissions from vehicles form major sources of metallic nanoparticles entering the environment and surrounding atmosphere. In this research, we spectrochemically analyse the chemical composition of particle matter emissions from in-use diesel engine passenger vehicles. We extracted diesel particulate matter from the end part of the tail pipes of more than 70 different vehicles. In the laboratory, we used the high-resolution laser-induced breakdown spectroscopy (LIBS) spectrochemical analytical technique to sensitively analyse chemical elements in different DPM samples. We found that PM is composed of major, minor and trace chemical elements. The major compound in PM is not strictly carbon but also other adsorbed metallic nanoparticles such as iron, chromium, magnesium, zinc and calcium. Besides the major elements in DPM, there are also minor elements: silicon, nickel, titan, potassium, strontium, molybdenum and others. Additionally, in DPM are adsorbed atomic trace elements like barium, boron, cobalt, copper, phosphorus, manganese and platinum. All these chemical elements form the significant atomic composition of real PM from in-use diesel engine vehicles. Full article

Zn-doped calcium copper titanate (CCTO) was successfully synthesized by rapid laser sintering of sol-gel derived precursors without the conventional long-time heat treatment. The structural, morphological, and crystalline properties were characterized, and the performances of dielectrics and impedance were measured and discussed. The X-ray diffractometer results show that Zn-doped CCTO is polycrystalline in a cubic structure, according to the doping ratio of Ca(Cu₂Zn)Ti₄O₁₂. Electron microscopy showed that Zn-doped CCTO has a denser microstructure with better uniformness with shrunken interplanar spacing of 2.598 nm for the plane (220). Comparing with undoped CCTO, the permittivity almost remains unchanged in the range of 10²–10⁶ Hz, demonstrating good stability on frequency. The electrical mechanism was investigated and is discussed through the impedance spectroscopy analysis. The resistance of grain and grain boundary decreases with rising temperature. Activation energies for the grain boundaries for Zn- doped CCTO were calculated from the slope for the relationship of ln $\sigma$ versus 1/T and were found to be 0.605 eV, smaller than undoped CCTO. This synthesis route may be an efficient and convenient approach to limit excessive waste of resources. Full article

Calcium copper titanate (CCTO) ceramics were successfully synthesized using a rapid laser reactive sintering method without conventional long heat treatment times. The microstructure, dielectric properties, and impedance spectroscopy results for CCTO sintered at laser power rates of 25–85 W were investigated in detail. The X-ray diffractometry results showed that prepared CCTO is polycrystalline in a cubic structure with high purity. Scanning electron microscopy showed that CCTO sintered at 85 W has a dense microstructure with an average grain size of 30 nm. The dielectric permittivity of CCTO ceramics increased with increasing laser power over the entire frequency range and achieved a value of almost 10⁵ in the low-frequency region. The dielectric permittivity maintained almost constant values from 10² Hz to 10⁷ Hz, with lower dielectric loss (~0.1) from 10³ Hz to 10⁶ Hz, demonstrating good frequency stability. The impedance spectroscopy study showed that grain and grain boundary resistance decreased with rising laser power based on two parallel Resistor-Capacitance (RC) equivalent circuits in series. The activation energies for the grain boundaries were calculated from the impedance using the slope of ln $\sigma$ versus 1/T and were found to be in the range of 0.53–0.63 eV. CCTO synthesized by rapid laser reactive sintering is competitive for practical applications. Full article

The formulation of a high dielectric permittivity ceramic/polymer composite feedstock for daylight vat photopolymerization 3D printing (3DP) is demonstrated, targeting 3DP of devices for microwave and THz applications. The precursor is composed of a commercial visible light photo-reactive polymer (VIS-curable photopolymer) and dispersed titanium dioxide (TiO₂, TO) ceramic nano-powder or calcium copper titanate (CCT) micro-powder. To provide consistent 3DP processing from the formulated feedstocks, the carefully chosen dispersant performed the double function of adjusting the overall viscosity of the photopolymer and provided good matrix-to-filler bonding. Depending on the ceramic powder content, the optimal viscosities for reproducible 3DP with resolution better than 100 µm were η_(TO) = 1.20 ± 0.02 Pa.s and η_(CCT) = 0.72 ± 0.05 Pa.s for 20% w/v TO/resin and 20% w/v CCT/resin composites at 0.1 s⁻¹ respectively, thus showing a significant dependence of the “printability” on the dispersed particle sizes. The complex dielectric properties of the as-3D printed samples from pure commercial photopolymer and the bespoke ceramic/photopolymer mixes are investigated at 2.5 GHz, 5 GHz, and in the 12–18 GHz frequency range. The results show that the addition of 20% w/v of TO and CCT ceramic powder to the initial photopolymer increased the real part of the permittivity of the 3DP composites from ε’ = 2.7 ± 0.02 to ε’_(TO) = 3.88 ± 0.02 and ε’_(CCT) = 3.5 ± 0.02 respectively. The present work can be used as a guideline for high-resolution 3DP of structures possessing high-ε. Full article

In order to develop high-performance dielectric materials, poly(arylene ether nitrile)-based composites were fabricated by employing surface-hydroxylated calcium copper titanate (CCTO) particles. The results indicated that the surface hydroxylation of CCTO effectively improved the interfacial compatibility between inorganic fillers and the polymer matrix. The composites exhibit not only high glass transition temperatures and an excellent thermal stability, but also excellent flexibility and good mechanical properties, with a tensile strength over 60 MPa. Furthermore, the composites possess enhanced permittivity, relatively low loss tangent, good permittivity-frequency stability and dielectric-temperature stability under 160 °C. Therefore, it furnishes an effective path to acquire high-temperature-resistant dielectric materials for various engineering applications. Full article