Publications by authors named "Jan Macutkevic"

This study examines how various nanofillers impact thermal conductivity, dielectric characteristics, and electromagnetic interference (EMI) shielding potential of bio-based and biodegradable poly(butylene succinate-co-adipate) (PBSA). TiO, NiFeO, FeO, and FeO were selected as fillers for nanocomposites at 4-50 vol.% (12-81 wt.

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This work presents the dielectric and ultrasonic properties of polydimethylsiloxane (PDMS) nanocomposites filled with titanium dioxide nanoparticles. The dielectric study was performed over a very broad range of frequencies (20 Hz-3 THz). The dielectric permittivity was almost frequency-independent in all the composites at room temperature over the whole range of measurement frequencies, and the dielectric losses were very low under these conditions (less than 2).

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Article Synopsis
  • * Experimental results indicate that the inclusion of BTO alters the dielectric properties of the composites and affects the temperature at which a dielectric anomaly occurs in the PDMS matrix.
  • * The composites exhibit piezoelectric behavior, generating measurable voltage signals under ultrasonic stress, making them promising candidates for use in efficient, lead-free nanogenerators that convert mechanical vibrations into electrical energy.
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Bulk polylactic acid (PLA)/multiwall carbon nanotube (MWCNT) composites were prepared and investigated in wide frequency ranges (20 Hz-1 MHz and 24-40 GHz). It was determined that the percolation threshold in bulk PLA/MWCNT composites is close to 0.2 vol.

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To address the ever-increasing electromagnetic interference (EMI) pollution, a hybrid filler approach for novel composites was chosen, with a focus on EMI absorbance. Carbon nanofiller loading was limited to 0.6 vol.

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We present studies on the microwave properties, electrical resistivity, and low-frequency (10 Hz-20 kHz) noise characteristics in the temperature range of 78 K to 380 K of composite materials made from bisphenol A-based epoxy resin and carbon fiber felts. Two types of carbon fibers were used, derived from polyacrylonitrile or regenerated cellulose. We show that these structures are suitable for electromagnetic shielding applications, especially in the direction parallel to the carbon fibers.

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Article Synopsis
  • - Researchers are working on developing biodegradable materials to replace traditional fossil-fuel plastics used for ESD, AS, and EMI shielding, which contribute to plastic pollution.
  • - They used different carbon-based nanofillers (like graphene and carbon nanotubes) in the biodegradable polymer poly(butylene succinate-co-adipate) to create composites with varying nanoparticle loadings.
  • - Tests showed that these composites, particularly with multi-walled carbon nanotubes, had enhanced strength and conductivity, making them suitable for electromagnetic interference applications.
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Ceramic composites with nanoparticles are intensively investigated due to their unique thermal, mechanic and electromagnetic properties. In this work, dielectric properties of phosphate ceramics with round silver nanoparticles of various sizes were studied in the wide frequency range of 20 Hz-40 GHz for microwave shielding applications. The percolation threshold in ceramics is close to 30 wt.

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Polymer composites with electrically conductive inclusions are intensively developed for microwave shielding applications, where lightweight and elastic coatings are necessary. In this paper, dielectric properties of hybrid polyethylene composites containing cobalt nanoparticles and multi-wall carbon nanotubes (MWCNT) were investigated in the wide frequency range of 20-40 GHz for electromagnetic shielding applications. The percolation threshold in the hybrid system is close to 6.

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Polymer composites containing carbon nanofillers are extensively developed for electromagnetic shielding applications, where lightweight and flexible materials are required. One example of the microwave absorbers can be thermoplastic fibers fabricated from copolyamide hot melt adhesives and 7 wt% of multi-walled carbon nanotubes, as presented in this paper. A broadband dielectric spectroscopy confirmed that the addition of carbon nanotubes significantly increased microwave electrical properties of the thin (diameter about 100 μm) thermoplastic fibers.

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Article Synopsis
  • Researchers created composite materials with high levels of a specific ferroelectric compound (0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3) mixed into phosphate-bonded ceramics under varying pressures.
  • All samples displayed a consistent distribution of the active ferroelectric phase and maintained thermal stability up to 900 K.
  • The study found that the density of these composites varies in a non-linear way with pressure, with increased density leading to higher dielectric permittivity and strong piezoelectric properties.
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  • Polymer matrix composites filled with carbon nanoparticles, such as onion-like carbon (OLC), have varying electrical properties influenced by the size and distribution of the particles in the epoxy resin matrix.
  • The study examines the electrical resistivity and voltage fluctuations in these composites at temperatures from 78 to 380 K, highlighting different electrical transport mechanisms that occur at varying temperatures.
  • Results show that smaller particles (40 nm) lead to quasi one-dimensional electrical transport, while larger particles (220-250 nm) exhibit higher dimensionality; additionally, the conductivity of smaller particle composites is more affected by thermal expansion of the matrix.
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  • The study examined the dielectric and electric properties of epoxy composites containing carbon-coated nickel (Ni@C) and multi-walled carbon nanotubes (MWCNTs) across various temperatures and frequencies.
  • Key findings revealed that the electrical percolation threshold for Ni@C alone was between 10-15 vol.%, making it suitable for electromagnetic shielding applications above this threshold.
  • The research also discovered that a specific concentration of Ni@C (0.2 vol.%) in hybrid composites significantly enhanced conductivity compared to MWCNT-only composites, with electrical transport mechanisms varying with temperature and composite type.
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The composite material filled with nano-sized BaTiO3 and Fe3O4 was designed and studied. The aluminium phosphate ceramics was used as a matrix. The XRD analysis demonstrates only the crystalline structure of the fillers used.

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Polymer composites containing nanocarbon fillers are under intensive investigation worldwide due to their remarkable electromagnetic properties distinguished not only by components as such, but the distribution and interaction of the fillers inside the polymer matrix. The theory herein reveals that a particular effect connected with the homogeneity of a composite manifests itself in the terahertz range. Transmission time-domain terahertz spectroscopy was applied to the investigation of nanocomposites obtained by co-extrusion of PLA polymer with additions of graphene nanoplatelets and multi-walled carbon nanotubes.

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  • - The study focused on the electrical and magnetotransport properties of nanocrystalline tin dioxide films, analyzing performance across temperatures from 4 to 300 K and under magnetic fields up to 8 T.
  • - The films were created using reactive DC magnetron sputtering of tin with subsequent temperature annealing, and their rutile structure was confirmed through X-ray diffraction analysis.
  • - The findings included explanations of resistance and negative magnetoresistance using a model that incorporates quantum corrections, revealing that the weak localization in the films exhibited a three-dimensional character based on the evaluated electron dephasing length.
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The polymeric adhesive used for the bonding of thermoplastic and thermoset composites forms an insulating layer which causes a real problem for lightning strike protection. In order to make that interlayer electrically conductive, we studied a new group of electrically conductive adhesives based on hot melt copolyamides and multi-walled carbon nanotubes fabricated by the extrusion method. The purpose of this work was to test four types of hot melts to determine the effect of their viscosity on the dispersion of 7 wt % multi-walled carbon nanotubes and electrical conductivity.

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  • The study examined the dielectric properties of BaCaTiO ceramics (with x = 0.17) across a frequency range from 20 Hz to 53 GHz, revealing a ferroelectric phase transition near 339 K.
  • It was found that the distribution of relaxation times showed characteristics typical of an order-disorder ferroelectric transition, while below 200 K, relaxation times followed the Arrhenius law.
  • The results indicated that as frequency increased, the temperature at which the imaginary part of dielectric permittivity peaked shifted significantly, which was linked to the dynamics of titanium ions, and the paper discusses the transition from ferroelectric to relaxor behavior in these ceramics.
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  • - The study examines the electrical properties of epoxy composites mixed with multi-walled carbon nanotubes (MWCNTs) and manganese ferrite (MnFeO), focusing on how varying these materials affects conductivity across temperatures and frequencies.
  • - Results reveal that while low MWCNT concentrations with MnFeO can boost conductivity significantly, high MWCNT levels lead to reduced conductivity as MnFeO increases, indicating an optimal concentration for enhanced performance.
  • - The findings suggest that at lower temperatures, electric transport depends on electron tunneling, while at higher temperatures, it relies on matrix conductivity, with implications for future improvements in polymer composites using multiple nanoinclusions.
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  • The study examined the electromagnetic properties of carbon gels with varying bulk densities over a frequency range of 20 Hz to 36 GHz, revealing high dielectric permittivity and electrical conductivity, especially around 129 Hz.
  • As frequency increased, both properties decreased, though still remained notable in the microwave range.
  • The research indicates that while higher bulk densities enhance dielectric permittivity and conductivity, the best microwave absorption occurs at lower densities, suggesting potential applications for electromagnetic coatings due to their stability and unique characteristics.
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  • The study explores the dielectric properties of epoxy composite materials enhanced with fixed amounts of multi-walled carbon nanotubes (MWCNT) and varying concentrations of magnesium oxide (MgO) nanoparticles.
  • The results showed that adding up to 2 vol.% of MgO significantly increased the direct current (DC) conductivity compared to composites without MgO, with an optimal concentration of 0.46 vol.% leading to notable conductivity improvements.
  • The findings suggest that manipulating MgO concentrations can effectively control the electrical transport and electromagnetic properties of the composites, while also providing a method to investigate the distribution of MWCNT within the material.
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Electromagnetic shielding is a topic of high importance for which lightweight materials are highly sought. Porous carbon materials can meet this goal, but their structure needs to be controlled as much as possible. In this work, cellular carbon monoliths of well-defined porosity and cell size were prepared by a template method, using sacrificial paraffin spheres as the porogen and resorcinol-formaldehyde (RF) resin as the carbon precursor.

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  • The study explores the dielectric properties of PMMA composites filled with multiwalled carbon nanotubes (MWCNT) that have different outer diameters.
  • It finds that composites with thicker nanotubes have a lower percolation threshold and higher dielectric permittivity below this threshold.
  • The research highlights that the temperature dependence of the dielectric permittivity is influenced by beta relaxation in the PMMA matrix, with thicker nanotubes increasing the energy barrier for PMMA molecular rotation.
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