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Materials containing benzocyclobutene units with low dielectric constant and good thermostability prepared from star-shaped molecules
摘要： With the development of ultralarge-scale integrated circuits, polymers with low dielectric constant and high thermal stability have aroused great interest. We prepared two novel bridged siloxane-based benzocyclobutene (BCB) star-shaped monomers, tetrakis[dimethyl siloxy-4-(10,10-dimethyl-10-ethyl silicon)-benzocyclobutene] (TDSDES-BCB) and tetrakis(hexamethyl siloxane vinyl-benzocyclobutene) (THSV-BCB), and the corresponding resins were obtained by curing. The structures of TDSDES-BCB and THSV-BCB were confirmed by 1H-NMR, 13C-NMR, and 29Si-NMR spectra and time-of-flight mass spectrometry analysis. The curing behavior of these monomers was investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry. The dielectric constant of cured TDSDES-BCB is only 2.43 at 10 MHz (that of THSV-BCB is 2.46). In addition, these resins display high thermal stability: the 5 wt % weight loss temperature of cured TDSDES-BCB is about 467 °C (454 °C for THSV-BCB resin). The excellent low dielectric property is attributable to the free volume created by the star-shaped structure and crosslinked network structure of BCB after curing.
关键词： thermosets,structure–property relationships,resins,dielectric properties,thermal properties
更新于2025-09-23 15:22:29
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Polydiacetylene capacitive artificial nose
摘要： Polydiacetylenes are a class of conjugated polymers exhibiting unique color and fluorescence properties and employed as useful sensing vehicles. Here we demonstrate for the first time that the dielectric properties of polydiacetylenes can be exploited for vapor sensing. Specifically, electrodes coated with polydiacetylenes, embedded within a porous polyvinylpyrrolidone (PVP) matrix, exhibit significant capacitance transformations upon exposure to different vapors. The capacitive response of the polydiacetylene/PVP films depended upon both the structures of the diacetylene monomers, and the extent of ultraviolet irradiation (i.e. polymerization), underscoring a unique sensing mechanism affected by conjugation, structure, and dielectric properties of the polydiacetylene/polymer matrix. Importantly, the variability of polydiacetylene structures allow vapor identification through an array-based pattern recognition (i.e. artificial nose). This study opens new avenues for applications of polydiacetylene systems, particularly pointing to their dielectric properties as powerful sensing determinants.
关键词： polydiacetylene,polyvinylpyrrolidone,artificial nose,dielectric properties,capacitive vapor sensing
更新于2025-09-23 15:22:29
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Nano-structural investigations of porous silica coated carbonaceous spheres and dielectric properties of its organosilicone hybrid film
摘要： In this research, a series of carbonaceous spheres samples were synthesized by hydrothermal carbonization of glucose and cyclodextrin, and coated with mesoporous silica. The unique nano-structure of such carbonaceous spheres samples was fully characterized by DLS, XRD, SEM, TEM, Raman spectroscopy and infrared spectroscopy techniques. Such carbonaceous spheres samples were then blended with organosilicone in order to prepare a series of hybrid films. The influence of the added silica coated carbonaceous spheres on the dielectric property of these hybrid film samples was thoroughly investigated. The results indicate that the silica coated carbonaceous spheres are amorphous and have a typical core-shell structure. Such nano-structure and aggregation behavior in the organosilicone matrix can introduce more interfaces into the hybrid organosilicone film samples, and have notably affected the dielectric property of the hybrid organosilicon film samples. The dielectric constant and dielectric loss of the hybrid film samples could be kept relatively low if the introduced interfaces were blurred enough to avoid the interfacial polarity.
关键词： Carbonaceous spheres,Films,Nanostructure,Dielectric properties,Silicones
更新于2025-09-23 15:22:29
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Interface Modulation of Core-Shell Structured BaTiO3@polyaniline for Novel Dielectric Materials from Its Nanocomposite with Polyarylene Ether Nitrile
摘要： The core-shell structured polyaniline-functionalized-BaTiO3 (BT@PANI) nanoparticles with controllable shell layer thicknesses are developed via in-situ aniline polymerization technology and characterized in detail. The results prove that the PANI shell layer with the adjustable and controllable thicknesses of 3–10 nm are completely stabilized on the surface of the BaTiO3 core. In addition, the BT@PANI nanoparticles are regarded as the hybrid nanofillers to prepare PEN/BT@PANI nanocomposite films with a PEN matrix. The research results indicate that the surface functionalized nanoparticles facilitate the compatibility and dispersibility of them in the PEN matrix, which improves the properties of the PEN/BT@PANI nanocomposites. Specifically, the PEN/BT@PANI nanocomposites exhibit thermal stability, excellent permittivity-frequency, and dielectric properties-temperature stability. Most importantly, the energy density of nanocomposites is maintained at over 70% at 180 °C compared with that at 25 °C. All these results reveal that a new way to prepare the high-performance PEN-based nanocomposites is established to fabricate an energy storage component in a high temperature environment.
关键词： dielectric properties,in-situ polymerization,nanoparticles,nanocomposites
更新于2025-09-23 15:22:29
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High dielectric and breakdown properties achieved in ternary BaTiO3/MXene/PVDF nanocomposites with low-concentration fillers from enhanced interface polarization
摘要： Although high permittivity is achieved in barium titanate (BT) filled polymer nanocomposites, severely reduced insulation and breakdown properties are frequently found due to overload and agglomeration of BT nanoparticles with ultrahigh specific area. To simultaneously realize high permittivity and breakdown strength, in this work, unfunctionalized 2D Ti3C2 MXene nanosheets with 2 wt % weight concentration were introduced to prepare ternary BT/MXene/polymer nanocomposites by solution cast process. Employing low-concentration conductive MXene instead of high-concentration ferroelectric BT could lead to significant improvement of permittivity of ternary composites, ascribed to remarkably increased interface types and enhanced interface polarization. In comparison to binary BT/polymer composites, ternary composites could have slightly improved dielectric loss and conductivity as well as gracefully reduced breakdown strength, attributed to finely retained high interface compatibility and filler dispersion. Ternary composite containing 8 wt % BT and 2 wt % MXene had a permittivity of 77, loss of 0.15 at 100 Hz and breakdown strength of 220 MV m-1. This work might open the door to large-scale fabrication of promising composites with high permittivity and breakdown strength under low filler loading (~ 10 wt %).
关键词： B. Composites,A. Films,C. Dielectric properties,D. Carbides
更新于2025-09-23 15:22:29
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Tissue-mimicking materials for breast phantoms up to 50 GHz
摘要： Millimeter (mm)-wave imaging has been recently proposed as a new technique for breast cancer detection, based on the significant dielectric contrast between healthy and tumor tissues. Here we propose a procedure to fabricate, electromagnetically characterize and preserve realistic breast tissue-mimicking phantoms for testing mm-wave imaging prototypes. Low-cost, non-toxic and easy-to-produce mixtures made of sunflower oil, water and gelatin were prepared and their dielectric properties were for the first time measured in the [0.5-50] GHz frequency range using a coaxial probe kit. Different oil and gelatin percentages were tested. An alternative recipe based on a waste-oil hardener was also proposed. Finally, water and sunflower oil were investigated as preservation media. The mixtures electromagnetic properties were in good agreement with those of human breast ex vivo samples. By changing the ingredient concentrations or using different solidifying agents it was possible to mimic different tissue types. Besides, we show that sunflower oil represents an effective preservation medium for the developed materials. The first breast phantom mimicking a tumor mass into healthy tissues up to 50 GHz was also successfully fabricated. Results demonstrated the potential of the designed recipes to mimic breast tissues with different biological characteristics.
关键词： microwave imaging,breast phantoms,breast cancer,dielectric properties,millimeter waves,cancer screening
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Proposal of Millimeter-Wave Adaptive Glucose-Concentration Estimation System Using Complex-Valued Neural Networks
摘要： This paper presents a novel approach for glucose concentration detection using a complex-valued neural network (CVNN) based on microwave transmission characteristics. The method leverages the dielectric properties of glucose solutions, which vary with concentration, to train a neural network that accurately predicts glucose levels from S-parameter measurements. Experimental results demonstrate high accuracy and robustness across a range of concentrations from 0 to 300 mg/dL.
关键词： complex-valued neural network,dielectric properties,glucose detection,S-parameters,microwave sensing
更新于2025-09-23 15:22:29
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Effect of Particles Size on Dielectric Properties of Nano-ZnO/LDPE Composites
摘要： The melt blending was used to prepare 3 wt% ZnO/low density polyethylene (ZnO/LDPE) nanocomposites in this article. The effect of different inorganic ZnO particles doping on the dielectrical property and crystal habit of LDPE matrix was explored. The nanoparticles size was 9 nm, 30 nm, 100 nm, and 200 nm respectively. Scanning electron microscope (SEM) was used to characterize ZnO nanoparticles whereas differential scanning calorimetry (DSC) was used to make thermal characterization of the samples. Besides, the AC (alternating current), DC (direct current) breakdown characteristics and electrical conductivity of the nanocomposites was studied in this article. The experimental results showed that nano-ZnO/LDPE composites had the advantages such as small crystal size, high crystallization rate and crystallinity owing to nano-ZnO particles doping, when doping nano-ZnO particles size was 30 nm, the ZnO/LDPE nanocomposite crystallinity crest value 39.77% appeared. At the mean time, the DC and AC breakdown field strength values of composites were 138.0 kV/mm and 340.4 kV/mm respectively. They were the maximal values which improved 8.24% and 13.85% than LDPE. The AC breakdown field strength of samples decreased with specimen thickness increase. The DC breakdown field strength of LDPE and ZnO/LDPE composites were greater than AC breakdown field strength. From the conductivity experimental result it could be seen that when the experimental temperature and electric field intensity rose, the current density and conductivity of ZnO/LDPE composites increased with the enlargement of ZnO particles size. But the values were less than which of LDPE.
关键词： particles size,LDPE,dielectric properties,ZnO
更新于2025-09-23 15:22:29
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Bond theory, Terahertz spectra and dielectric studies in donor-acceptor (Nb-Al) substituted ZnTiNb <sub/>2</sub> O <sub/>8</sub> system
摘要： As a donor and acceptor separately, Nb5+ and Al3+ are used to substitute Ti4+ in the ixiolite ZnTiNb2O8 system for the first time. The dielectric responses in the terahertz range of this system are initially studied based on the data from terahertz time-domain transmitted spectroscopy. Combined with ligand field theory, the formation of a secondary phase of ZnAl2O4 is reasonably explicated. Then, the origins of the lower dielectric loss and the terahertz wave absorption coefficient are determined to be the high chemical bond covalency and effective phase control. For the composition of ZnTi0.85(Al0.5Nb0.5)0.15Nb2O8 sintered at 1180 °C, a low dielectric loss (< 5×10-3 @ 0.5 THz) and absorption coefficient (< 10 cm-1 @ 0.5 THz) are obtained, which make this kind of material propitious for developing terahertz dielectric devices.
关键词： complex chemical bond theory,covalency,microwave and terahertz,dielectric properties,donor-acceptor substituted
更新于2025-09-23 15:22:29
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Investigations on structural, optical and dielectric properties of Mn doped ZnO nanoparticles synthesized by co-precipitation method
摘要： Mn doped ZnO (ZnO:Mn) nanopowders with Mn:ZnO ratio from 0 to 3% were successfully synthesized by co-precipitation method. Their structural, optical, dielectric and conducting properties were investigated. All samples crystallize in the hexagonal wurtzite structure. The change in lattice parameters, bond length and preferential crystalline orientation for Mn doped ZnO samples indicates Mn2+ ions incorporation in ZnO lattice. Both micro-strain and dislocation density decrease due to doping whereas the average crystallite size increases suggesting the improvement of crystalline quality. The optical transmission in the visible region was improved as a result of doping. The observed decrease in ac conductivity (??????) with increasing Mn content is associated with the increase of defects amount. Cole-Cole plots of all samples were fitted to a circuit consisting in a parallel combination of a resistance and a constant phase element (CPE).
关键词： conductivity,optical properties,Mn doped ZnO,dielectric properties,XRD
更新于2025-09-23 15:21:21