Search

Low expansion Li2O-Al2O3-SiO2 (LAS) glass-ceramics were prepared using sintering method. The effect of ZnO partially substitution for Li2O on the microstructure, sintering behavior, crystallization behavior and properties of LAS glass-ceramics was investigated. The results show that the substitution of ZnO for Li2O reduces the initial crystallization temperature of LAS glass-ceramics, leading to significant amount of Li2Al2 Si3O10 phase precipitating out after holding at 800 °C for 10 min, which hinders the sintering shrinkage of glass. In contrast, the LAS glass-ceramics without ZnO exhibits slower crystallization at 800 °C, which is beneficial for sintering densification process. When the sintering temperature is 1 100 °C, the main crystalline phase present in glass-ceramics is identified as β-spodumene. The coefficient of thermal expansion of glass-ceramics without ZnO is 1. 747 x 10-6 K-1, the flexural strength is 138. 4 MPa, the dielectric constant is 3. 52 and the dielectric loss is 0. 0016. [ABSTRACT FROM AUTHOR]

The objective of this study is to enhance the dielectric properties of biocomposite films through the fabrication of biaxially oriented films (BO) and the incorporation of silver-coated microcrystalline cellulose (Ag/MCC). The silver coating was used in concentrations ranging from 0.2 to 2% using an environmentally friendly method. The dielectric constant and dielectric loss of all sample were measured in the frequency range from 103 to − 106 Hz. The sample containing 0.6% silver on microcrystalline cellulose (0.6Ag/MCC) demonstrated the highest dielectric constant, measured 64. Subsequently, biocomposite films were produced by utilizing 0.6%Ag/MCC at different ratios (1–5 phr) through a one-step cast film twin-screw extruder. The sample with the highest dielectric constant was PLA-0.6Ag/MCC4, which increased from 3 (PLA) to 37. Furthermore, biaxially oriented films were successfully prepared using a film biaxial stretching machine, achieving a thickness of 70 μm. This technique can significantly improve their dielectric properties, surpassing those of unstretched films. The improvement in dielectric properties can be attributed to the reorganization of molecular chains, promoting a more orderly arrangement and increases crystallinity. Therefore, the resultant biocomposite and biaxially oriented film demonstrate exceptional dielectric properties, rendering them suitable for dielectric applications such as capacitor dielectric films. [ABSTRACT FROM AUTHOR]

In this work, non-stoichiometric Li2(1+x)Mg3Ti4O12 (LxMTO, x = 0.00–0.05) ceramics with excess lithium were prepared through a simple reaction sintering route to suppress lithium volatilization. According to the characterization of the phase composition and microscopic morphology of the pellets, single-phase LxMTO ceramics with a good microstructure were obtained. Excess lithium effectively inhibited the volatilization and optimized the morphology of the ceramics. A trend in relative density with an initial increase followed by a steep decrease was a predominant observation with the change in dielectric properties. The permittivity of the samples was dominated by the relative density and distortion of the [TiO6] octahedron structure caused by Li+. The dielectric loss primarily originated from the refraction loss and scattering generated by pores, and the grain boundaries also contributed to the loss in the quality factor. Ultimately, at 1220°C, the Li2.08Mg3Ti4O12 ceramics exhibited excellent microwave dielectric properties: εr = 17.83, Q×f = 69,823 GHz and τf = −18.19 ppm/°C. [ABSTRACT FROM AUTHOR]

The effect of boron doping on dielectric properties was examined using β-SrTa2O6:xEu3+ (x = 1.5 mol%, 3 mol%, 5 mol%, 10 mol%), β-SrTa2O6:xEu3+, yB3+ (x = 1.5 mol%, 3 mol%, 5 mol%, 10 mol%, y = 10 mol%) and BaTa2O6:xEu3+, yB3+ (x = 10 mol%, y = 0 mol%, 5 mol%, 15 mol%, 30 mol%, 50 mol%, 70 mol%, 100 mol%) tungsten bronze ceramics produced by the solid-state reaction method. X-ray diffraction (XRD) results of all the β-SrTa2O6 and BaTa2O6 samples showed that they retained a single-phase structure. In scanning electron microscopy (SEM) examinations, the presence of boron promoted grain growth and agglomeration in the β-SrTa2O6 grains, while the increased boron concentration led to grain elongation in addition to grain growth in the BaTa2O6 grains. The dielectric results for the β-SrTa2O6:xEu3+ and β-SrTa2O6:xEu3+, yB3+ series showed that increased Eu3+ caused a decrease in the dielectric constant (ε′) and dielectric loss (tan δ), whereas the increasing B3+ presence for the BaTa2O6:xEu3+, yB3+ series led to an increase in the dielectric constant and a decrease in dielectric loss. The increase in tetragonality for BaTa2O6:xEu3+, yB3+ ceramics was correlated with a higher ferroelectric Curie temperature. [ABSTRACT FROM AUTHOR]

A low dielectric polyimide/polyimide microsphere (PI/PM) composite film was constructed by thermal imidization of polyamic acid from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA) in the presence of porous PM. The PM particles with particle size of about 2 μm were prepared via the solvothermal method using 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) and ODA as monomers through thermal imidization. Due to the favorable compatibility between the porous PM and PI matrix, the mechanical properties, thermal stability, and dielectric properties of the obtained composite films were significantly improved. The PI/PM composite films had a tensile strength of 44.18–64.32 MPa, and the corresponding elongation at break of 6.21%–11.7%. Furthermore, the thermogravimetric temperatures of T5% were 538.9–563.7°C. The dielectric constants of the composite films at 1 MHz were 2.59–3.68, and the corresponding dielectric loss were only 0.0119–0.00405. Thus, the combination of excellent mechanical properties, high thermal stability, extremely low dielectric constant, and dielectric loss make the composite films ideal for deployment as high‐performance materials for 5G applications. Highlights: Low dielectric polyimide composite film was prepared by thermal imidization of polyamic acid in the presence of porous polyimide microspheres.Porous polyimide microspheres were prepared by thermal using the imidization solvothermal method.Low dielectric polyimide composite film with good comprehensive properties. [ABSTRACT FROM AUTHOR]

In high‐frequency applications such as 5G‐6G communication, internet of things, automotive radar, and automated driver‐assistance systems, substrate materials excel as insulating layers owing to their superior dielectric properties. However, traditional methods for material development are often laborious and costly. To overcome these limitations, we employed molecular dynamics (MD) simulations to predict the dielectric properties of these materials at frequencies exceeding 107 Hz. Specifically, we selected thermosetting polyphenylene oxide (m‐PPO) as the resin matrix and combined it with three crosslinking agents, respectively: triallyl cyanurate, triallyl isocyanurate, and trimethylallyl isocyanurate. Our overarching goal is to provide comprehensive insights into the development and enhancement of materials critical for high‐frequency electronic devices. We anticipate that this methodology will be widely adopted for the development of advanced substrate materials across various applications, with the objective of effectively screening crosslinkers. Highlights: Developed a simulation method to efficiently explore material scenarios for high‐frequency applications.Studied the dielectric properties of m‐PPO combined with three crosslinking agents at high frequencies.Successfully predicted dielectric properties using MD simulations. [ABSTRACT FROM AUTHOR]

The use of solid waste such as ceramic sludge, ceramic rollers, and magnesite was studied to obtain cheap refractory ceramics at temperatures of 1300 °C based on XRF, XRD SEM, EDX, bending strength, and dielectric properties. The prepared samples were examined. The results showed that the significant crystalline phases formed were mullite, spinel, and corundum. They also showed that mullite hindered the formation of cordierite and enhanced spinel formation. With increased cordierite content, the microstructure varied from fine grained to coarse grained. Bending strength increased with increasing mullite content and bulk density, ranging from 10.80 to 13.50 MPa. Bulk density increased with the increase in mullite content and sintering temperature and ranged from 1.99 to 1.94 g/cm3, while the percentage of porosity and water absorption decreased and ranged from 29.40 to 38.83, respectively. To examine the effect of the produced phases on the dielectric characteristics, the permittivity (ε′), dielectric loss (ε″), and AC conductivity (σac) were measured in the frequency range of 10−1 Hz to 106 Hz. As the concentration of cordierite increased, there was a noticeable drop in ε′ from 35.6 to 8.2 and σac from 10−8 s/cm to around 10−11 s/cm and high values of resistivity from 108 cm/s to about 1010 cm/s, suggesting that this material might be an excellent insulator. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: Magnetic Resonance Elastography (MRE) allows the non-invasive quantification of tumor biomechanical properties in vivo. With increasing incidence of brain metastases, there is a notable absence of appropriate preclinical models to investigate their biomechanical characteristics. Therefore, the purpose of this work was to assess the biomechanical characteristics of B16 melanoma brain metastases (MBM) and compare it to murine GL261 glioblastoma (GBM) model using multifrequency MRE with tomoelastography post processing. Methods: Intracranial B16 MBM (n = 6) and GL261 GBM (n = 7) mouse models were used. Magnetic Resonance Imaging (MRI) was performed at set intervals after tumor implantation: 5, 7, 12, 14 days for MBM and 13 and 22 days for GBM. The investigations were performed using a 7T preclinical MRI with 20 mm head coil. The protocol consisted of single-shot spin echo-planar multifrequency MRE with tomoelastography post processing, contrast-enhanced T1- and T2- weighted imaging and diffusion-weighted imaging (DWI) with quantification of apparent diffusion coefficient of water (ADC). Elastography quantified shear wave speed (SWS), magnitude of complex MR signal (T2/T2*) and loss angle (j). Immunohistological investigations were performed to assess vascularization, blood-brain-barrier integrity and extent of glucosaminoglucan coverage. Results: Volumetric analyses displayed rapid growth of both tumor entities and softer tissue properties than healthy brain (healthy: 5.17 ± 0.48, MBM: 3.83 ± 0.55, GBM: 3.7 ± 0.23, [m/s]). SWS of MBM remained unchanged throughout tumor progression with decreased T2/T2* intensity and increased ADC on days 12 and 14 (p<0.0001 for both). Conversely, GBM presented reduced j values on day 22 (p=0.0237), with no significant alterations in ADC. Histological analysis revealed substantial vascularization and elevated glycosaminoglycan content in both tumor types compared to healthy contralateral brain. Discussion: Our results indicate that while both, MBM and GBM, exhibited softer properties compared to healthy brain, imaging and histological analysis revealed different underlying microstructural causes: hemorrhages in MBM and increased vascularization and glycosaminoglycan content in GBM, further corroborated by DWI and T2/T2* contrast. These findings underscore the complementary nature of MRE and its potential to enhance our understanding of tumor characteristics when used alongside established techniques. This comprehensive approach could lead to improved clinical outcomes and a deeper understanding of brain tumor pathophysiology. [ABSTRACT FROM AUTHOR]

The rapid development of new proton conductors based on metallo-hydrogen-bonded organic frameworks (MHOFs) and rational regulation of their performance are highly desired for proton exchange membrane fuel cells. As we all know, hydrogen bonds are an indispensable part of proton conduction as conducting mediators. However, the effect of hydrogen bonds, especially the number of hydrogen bonds, on proton conductivity is not yet clear. Herein, we focus on clarifying the relationship between proton conductivity and the number of hydrogen bonds in MHOFs. To this end, two MHOFs with analogous host-framework structures and different hydrogen-bonded networks, [Ni(HCi)2(NH3)4] (Ni–Ci–NH3) and [Ni(HCi)2(H2O)4] (Ni–Ci–H2O) (H2Ci = 1H-indazole-5-carboxylic acid), were designed by controlling coordination states between the same metal ion and different hydrogen bond donors and act as targeting models to study their proton-conducting properties. Notably, Ni–Ci–NH3 shows a high proton conductivity of 6.22 × 10−4 S cm−1 for the powder sample at ∼97% relative humidity (RH) and 303 K, which is superior to that of Ni–Ci–H2O (1.62 × 10−4 S cm−1) under the same condition. The difference in proton conductivity at ∼97% RH is closely related to the number of hydrogen bonds, as evidenced by water adsorption, water contact angle and dielectric loss measurements. Furthermore, frequency- and temperature-varied dielectric constant curves indicate that their proton transfer processes follow the Grotthuss proton-hopping mechanism. Meanwhile, a good correlation between the number of hydrogen bonds and activation energy was obtained, i.e. the more the number of hydrogen bonds, the lower the activation energy. This work contributes to the further understanding of the essential role of hydrogen bonds in the proton conductivity and proton transfer mechanisms. [ABSTRACT FROM AUTHOR]

AbstractPolymer-based composites are highly regarded as favorable candidate materials for dielectrics in high-energy-density capacitors, owing to their exceptional flexibility and fast charge-discharge capabilities. Recently, multilayer-structured polymer composites have gained significant attention as a promising solution for energy storage and dielectric applications, offering a combination of high energy density and low dielectric loss. These polymer multilayer films, comprising two or more layers synthesized through specific fabrication processes, have presented extensive uses in various applications, including packaging and optical materials, such as oxygen barrier, holographic anti-counterfeiting, and optical sensing, due to their versatile and tunable functionalities. The distinctive chemical composition and structural design of these layers, whether symmetrically or gradient distributed, endow these dielectric composites with superior integrated electric properties. This review provides a comprehensive overview of fabrication methods and strategies employed in the latest advancements in dielectric multilayer-structured polymers for energy storage applications. It delves into the design and manufacturing techniques of advanced multilayer composites, highlighting the diverse strategies utilized to enhance energy performance, such as polarization manipulation, electric field distribution control, interfacial modification, and geometric confinement of interfaces within both organic and organic/inorganic multilayer-structured composites. Lastly, this review addresses the current challenges and future prospects in the development of multilayer composites with enhanced energy storage performance. [ABSTRACT FROM AUTHOR]

ABSTRACT Low‐temperature densification of alumina using calcium vanadate (CaV2O6, CV) having a similar dielectric constant as a liquid‐forming additive has been studied. The alumina‒CV composites containing 20‒40 vol.% CV achieve ∼94% of theoretical density at low temperatures of 1100°C‒900°C by liquid‐phase sintering. A reduction in the average size of grains from .87 to .42 µm with a surge in CV amount from 20 to 40 vol.% is observed. The permittivity decreases from 9.2 to 8.90, and the dielectric loss increases from 2.154 × 10‒3 to 4.761 × 10‒3 when the amount of CV in the alumina‒CV composite rises from 20 to 40 vol.%. The temperature coefficient of resonance frequency, thermal expansion coefficient, and thermal conductivity of the alumina‒CV composites are observed in the ranges of ‒54 to ‒72 ppm °C‒1, 6.94‒7.32 ppm °C‒1, and 13.78‒8.02 W m‒1 K‒1, respectively. The compatibility of the composites with Ag for low‐temperature co‐fired ceramics (LTCC) application is established through co‐sintering and energy‐Dispersive X‐ray spectroscopy line spectra analysis. The low‐temperature densification, acceptable range of dielectric and thermal properties, and silver compatibility make the alumina‒CV composite a candidate for LTCC application. [ABSTRACT FROM AUTHOR]

The phase engineering of the polarization interface is of great significance in modifying dielectric loss in electromagnetic wave (EMW) attenuation process, but hard to conduct in a complex hybrid system. Herein, a twin‐phase of β/γ‐MoCx@CN with matched Fermi level and closed work function properties in lightweight MoCx nanoflower is constructed, facilitating electron transport withdraw enhanced conductivity and polarization. Moreover, the EMW multiple dissipations among the β/γ‐MoCx@CN polarization interface is promoted, displaying better matched impedance. It delivered a remarkable minimum reflection loss (RLmin) of −74.2 dB at the thickness of 1.5 mm, which far beyond the single phased β‐MoCx@CN, γ‐MoCx@CN and reported MoCx‐based EMW absorbers. The radar cross‐section (RCS) map of β/γ‐MoCx@CN is simulated, showing a brilliant maximum reduction value of 13.6 dB m2 at the theta angle of 30°. This work presented an excellent sample of atomic‐level manipulation of interfacial polarization in dielectric MoCx EMW absorption materials. [ABSTRACT FROM AUTHOR]

In one dimensional Ca 3 Co 2 O 6 , the magnetic frustration could result in partially disordered antiferromagnetic state. The Ca 3 Co 2 O 6 thus presents spin freezing and slow relaxation at low temperature. In this investigation, magnetic Cr3+-dopants were chosen to substitute the Co3+ cations and a series of Ca 3 Co 2- x Cr x O 6 ceramics were synthesized. Their magnetoelectric properties were characterized. The results manifest that the introduced Cr3+ cations situate in the CoO 6 octahedral centers and they could increase the lattice volume slightly. The antiferromagnetic coupling between Cr3+ and the adjacent Co3+ could reduce the frustration. The doped-Ca 3 Co 2- x Cr x O 6 compounds display a slower magnetic dynamic behavior. The Cr3+ substitution also has great impact on the dielectric properties of Ca 3 Co 2 O 6. The slower response of the freezing spin in Cr3+ doped-Ca 3 Co 2 O 6 makes the dielectric anomaly (anomaly Ⅰ) around the freezing temperature weakens with increasing Cr3+. Additionally, the introduced Cr3+ dopant not only increases the dielectric permittivity but also decreases the dielectric loss greatly. Cr3+ cation is a good candidate for improving the dielectric properties of Ca 3 Co 2 O 6. Magnetodielectric measurement reflects the effectiveness of magnetic field on manipulating the electric dipole of Ca 3 Co 2 O 6. For spin frustrated materials, electric measurement is proved to be an effective method on characterizing the subtle variation of the magnetic structure. [ABSTRACT FROM AUTHOR]

A series of Zr4+-Co2+ substituted U-type hexaferrites (Ba 4 Zn 2 Fe 36-2x Zr x Co x O 60 (0.0 ≤ x ≤ 1.0, having Δx = 0.25)) were synthesized via sol-gel auto-combustion method. The samples were sintered at 1200 ° C for 6 h. The impact of Zr–Co substitution on phase, structure, morphology, and dielectric behavior were investigated through XRD, FTIR, SEM, XPS and VNA. XRD studies shows that the U-type hexaferrite phase has been developed and the increase in lattice constants (a & c), cell volume, c/a ratio, and percentage porosity was observed. Sample with x = 0.25 exhibited the smallest crystallite size (34.5 nm). The existence of signature metal-oxygen vibrational bands for hexaferrites was observed by FTIR spectra. SEM analysis reflects that the substitution produces a significant effect on morphology and grain size of the samples. X-ray photoelectron spectra (XPS) of sample x = 1.0 confirmed the chemical and elemental composition. The dielectric constant, dielectric loss, and ac conductivity increases with increasing frequency and decreases with Zr–Co substitution. The lowest reflection loss of R L = −64.5 dB (with MW absorption >99.9 %) was observed for the composition x = 0.5 with pellet thickness of 1.73 mm at 1.05 GHz frequency. Due to the improved bandwidth and better absorption, these hexaferrites can be used in microwave and high frequency applications. [ABSTRACT FROM AUTHOR]

The structural analysis and microwave dielectric characteristics of ionic-modified tri-rutile Ni 0·5 Sn 0·5 TaO 4 ceramics, focusing on ionic non-stoichiometry and substitution strategies, were systemically studied in this work. A tri-rutile solid solution was unequivocally identified via X-ray diffraction, Raman scatting spectra analysis, and transmission electron microscopy characterization under [110] direction. The unit cell of the tri-rutile structure experiences a contraction primarily due to the compression of the [M2O6] octahedron. An excess of Ni content and the incorporation of (Al 1/2 Nb 1/2)4+ complex cations notably halved the grain size. Conversely, deliberate Sn deficiency led to enlarged grain sizes; however, grain boundaries blurred when the deficiency exceeded 0.03 mol. The microwave dielectric properties are intricately linked to structural characteristics and sintering behavior. Ionic polarizabilities and bulk density predominantly affect the ε r value, while grain growth governs variations in the Q × f value. The distortion of [M2O6] octahedra primarily influences the τ f value. All measured τ f values demonstrated exceptional temperature stability within the range of -5 ∼ +5 ppm/°C. Notably, the Ni 0·5 Sn 0·47 TaO 4 ceramic displayed outstanding microwave dielectric characteristics: ε r = 21.9, Q × f = 45,055 GHz (at f = 10.7 GHz), and τ f = -2.07 ppm/°C post-sintering at 1425 °C, rendering it ideal for applications in extreme environmental conditions. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) based microwave dielectric composite has been widely used because of its adjustable dielectric constant and low dielectric loss, but its low thermal conductivity can not meet the heat dissipation requirements of high-power microwave devices. Therefore, it is of great significance to develop microwave dielectric composites with high thermal conductivity and low loss. In order to obtain microwave composite materials with high thermal conductivity and low losses, schistose Al 2 O 3 /PTFE (S-A/PTFE) composites and globular Al 2 O 3 /PTFE (G-A/PTFE) composites were successfully prepared. It is compared whether S-A can combine with PTFE more fully than G-A, which can promote the dielectric properties and thermal conductivity of Al 2 O 3 /PTFE composites. Surprisingly, the S-A/PTFE composites demonstrate higher thermal conductivity, lower thermal expansion and hygroscopic properties. The S-A/PTFE composites can deliver a high thermal conductivity of 0.986 W/m K. Composite substrates with 53 wt% S-A filler exhibits excellent performance, which specifically show credible dielectric constant (ε r = 4.01) and admissible dielectric loss (tanδ = 0.0014 at 10 GHz). Furthermore, the composite substrate shows a similar thermal expansion coefficient to copper, and lower water absorption rate (0.05 %). The relationship between dielectric constant of composite and filler was predicted by different theoretical modeling methods. [ABSTRACT FROM AUTHOR]

Advancements in electronics and digitization have led to concerns about electromagnetic interference (EMI), necessitating effective EMI shielding measures. This study investigates the electromagnetic wave absorption properties of La n+1 Ni n O 3n+1 (n = 1, 2, 3) Ruddlesden-popper (RP) phases. While a single phase, La 2 NiO 4 , was obtained for n = 1, mixed phases of La 3 N 2 O 7-δ /La 4 Ni 3 O 10-δ were observed for n = 2 and 3. Electron paramagnetic resonance spectroscopy revealed superparamagnetic behavior for La 2 NiO 4 and multi-resonance peaks for La 3 Ni 2 O 7-δ , suggesting increased surface defects. La 3 Ni 2 O 7-δ exhibited enhanced absorption properties, with a minimum reflection loss of −19.4 dB and a broader (less than −10 dB) bandwidth covering 4.2 GHz (X-band) at a thickness of 1.4 mm, attributed to optimal conductivity, magnetic resonance, eddy current losses, and synergistic dielectric loss. The sample with n = 2 demonstrates potential for EMI absorption and electrostatic discharge (ESD) applications. [ABSTRACT FROM AUTHOR]

In this study, inorganic binders are prepared and successfully applied as alternatives to Li 2 MoO 4 for room-temperature fabrication of binder – SrTiO 3 composites. The inorganic compounds Na 2 MoO 4 , Na 2 WO 4 , Na 2 SiO 3 , and MgSO 4 , were used as binding phases (15 vol%) in the room-temperature fabricated composite systems, resulting in pellets with relative density (ρ = 83–88 %) and dielectric properties applicable in radio and microwave (MW) frequency ranges. The relative permittivity values of the as-prepared binder – SrTiO 3 composites varied from 68 – 124 at 1 MHz and between 67 – 129 in the MW frequency range. The dielectric losses exhibited a range of 0.0029 – 0.0142 at 1 MHz, with corresponding Q × f values ranging from 689 – 1335 GHz. The microstructure, binder – SrTiO 3 interactions, and thermal behavior of the binders and composites were studied using SEM, XRD, and TG analysis. This study provides valuable insights into the use of inorganic binders to fabricate binder – SrTiO 3 composite systems, which could have significant implications in various fields, including electronics and telecommunications, owing to their enhanced properties. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the synthesis, structural analysis, and microwave dielectric characteristics of ZnZrNb2O8 ceramics, prepared via solid-state reaction method and subjected to sintering at temperatures ranging from 1,000°C to 1,200°C for 4 h. X-ray diffraction (XRD) analysis confirms the successful formation of ZnZrNb2O8 phase, with a monoclinic wolframite phase. Scanning electron microscopy (SEM) investigations unveil microstructural features such as grain size and porosity, reveals material's morphological details. Dielectric properties conducted in the microwave frequency regime show a correlation between dielectric constant (εr) and relative density of the ceramics. Importantly, the ceramics exhibited a suitable dielectric constant and low dielectric loss, indicative of their suitability for microwave applications. Remarkably, ZnZrNb2O8 ceramics sintered at 1,150°C for 4 h exhibit excellent microwave dielectric properties (εr = 27.2, Q × f = 54,500 GHz, and τf = -60 ppm/°C). These findings underscore the potential of ZnZrNb2O8 ceramics as advanced materials for high-frequency applications, including filters, resonators, and other microwave devices, thus contributing significantly to the advancement of next-generation telecommunications technologies. [ABSTRACT FROM AUTHOR]

Theoretically, separating the positive and negative charge centers of the chain segments of dielectric elastomers (DEs) is a viable alternative to the conventional decoration of chain backbone with polar handles, since it can dramatically increase the dipole vector and hence the dielectric constant (ε′) of the DEs while circumvent the undesired impact of the decorated polar handles on the dielectric loss (tan δ). Herein, a novel and universal method is demonstrated to achieve effective separation of the charge centers of chain segments in homogeneous DEs by steric hindrance engineering, i.e., by incorporating a series of different included angle‐containing building blocks into the networks. Both experimental and simulation results have shown that the introduction of these building blocks can create a spatially fixed included angle between two adjacent chain segments, thus separating the charge center of the associated region. Accordingly, incorporating a minimal amount of these building blocks (≈5 mol%) can lead to a considerably sharp increase (≈50%) in the ε′ of the DEs while maintaining an extremely low tan δ (≈0.006@1 kHz), indicating that this methodology can substantially optimize the dielectric performance of DEs based on a completely different mechanism from the established methods. [ABSTRACT FROM AUTHOR]

Transition metal oxides have been widely used in microwave-absorbing materials, but how to improve impedance matching is still an urgent problem. Therefore, we introduced urea as a polymer carbon source into a three-dimensional porous structure modified by Co3O4 nanoparticles and explored the influence of different heat treatment temperatures on the wave absorption properties of the composite. The nanomaterials, when calcined at a temperature of 450 °C, exhibited excellent microwave absorption capabilities. Specifically, at an optimized thickness of 9 mm, they achieved a minimum reflection loss (RLmin) of −97.3 dB, accompanied by an effective absorption bandwidth (EAB) of 9.83 GHz that comprehensively covered both the S and Ku frequency bands. On the other hand, with a thickness of 3 mm, the RLmin was recorded as −17.9 dB, with an EAB of 5.53 GHz. This excellent performance is attributed to the multi-facial polarization and multiple reflections induced by the magnetic loss capability of Co3O4 nanoparticles, the electrical conductivity of C, and the unique three-dimensional structure of diatomite. For the future development of bio-based microwave absorption, this work provides a methodology and strategy. [ABSTRACT FROM AUTHOR]

Herein, a simple strategy for fabricating amorphous Co2FeGe nanoflakes by tuning the milling time with mechanical alloying method to enhance the microwave absorption capabilities is presented. These alloys exhibit soft magnetic properties characterized by high saturation magnetization and low coercivity. The enhancement of polarization and resonance effects, leading to improved magnetic and dielectric loss, is attributed to the refinement of crystalline size and the substantial aspect ratio of flaky particles. The minimum reflection loss reaches −48.6 dB at 4.92 GHz with an effective absorption bandwidth of 2.88 GHz in the C‐band. Due to its high Curie temperature, Co2FeGe exhibits considerable potential for maintaining highly efficient microwave absorption capabilities under high‐temperature conditions, thereby providing a novel perspective and technical means for the development of new high‐temperature‐resistant, high‐performance microwave‐absorbing materials. This is expected to play a significant role in future high‐temperature electronic countermeasure systems. [ABSTRACT FROM AUTHOR]

Although the physical properties of a structure, such as stiffness, can be determined using some statical tests, the identification of damping parameters requires a dynamic test. In general, both theoretical prediction and experimental identification of damping are quite difficult. There are many different techniques available for damping identification, and each method gives a different damping parameter. The dynamic indentation method, rheometry, atomic force microscopy, and resonant vibration tests are commonly used to identify the damping of materials, including soft materials. While the viscous damping ratio, loss factor, complex modulus, and viscosity are quite common to describe the damping of materials, there are also other parameters, such as the specific damping capacity, loss angle, half-power bandwidth, and logarithmic decrement, to describe the damping of various materials. Often, one of these parameters is measured, and the measured parameter needs to be converted into another damping parameter for comparison purposes. In this review, the theoretical derivations of different parameters for the description and quantification of damping and their relationships are presented. The expressions for both high damping and low damping are included and evaluated. This study is considered as the first comprehensive review article presenting the theoretical derivations of a large number of damping parameters and the relationships among many damping parameters, with a quantitative evaluation of accurate and approximate formulas. This paper could be a primary resource for damping research and teaching. [ABSTRACT FROM AUTHOR]

Curved support can significantly change the electronic structure of a metal single‐atom (M‐SA) and thereby fine tune its intrinsic physicochemical properties. However, constructing asymmetrically coordinated M‐SAs on highly curved supports remains challenging. Here, an efficient strategy driven by the different thermal decomposition rates of two polymers is proposed to create Turing surface with highly curved stripes on hollow carbon spheres (HCSs) for anchoring asymmetrically coordinated Fe‐N3S1 moieties. Experimental and theoretical calculation results reveal that asymmetric Fe‐N3S1 atoms and the strain of Fe─N bonds induced by the highly curved Turing surface efficiently break the symmetric distribution of the charge around the Fe atoms and significantly enhance the dielectric loss of the HCSs, thereby synergistically improving the electromagnetic wave absorption property. Remarkably, the film constructed with Fe‐N3S1‐anchored HCSs and natural rubber exhibits a wide effective absorption bandwidth of 7.68 GHz at a filling ratio of 6%. Moreover, the film also possesses excellent hydrophobicity, frost‐resistant ability, adhesiveness, flexibility, stretchability, and heat‐dispersion ability, which expand its practical applications into various environments. This work provides insights into the synergistic effects of asymmetrically coordinated configurations and curved supports of M‐SAs on their dielectric properties and offers a new method for the preparation of multifunctional films. [ABSTRACT FROM AUTHOR]

The development of high-power piezoelectric ceramics with superior piezoelectric properties and broad temperature usage ranges is vital for the thriving progress of electromechanical applications. However, achieving high piezoelectricity, high mechanical quality factor, and temperature stability often presents a trade-off. In this study, we present an advanced ceramic material with excellent high-power piezoelectric properties and superior temperature stability. The piezoelectric coefficient d 33 reaches 348 pC N−1, the electromechanical coupling factor k p is 54%, the mechanical quality factor Q m is 1501, the dielectric loss tanδ is 0.35%, and the d 33 variation is less than 10% within 25–210 °C in 0.05Pb(Mg1/3Nb2/3)O 3 -0.05Pb(Mn 1/3 Sb 2/3)O 3 -0.9Pb 0.95 Sr 0.05 (Zr 0.48 Ti 0.52)O 3 ceramic. The excellent piezoelectricity is attributed to the enhancement of intrinsic ionic displacement and reversible domains wall motion because of symmetry-conforming short-range distribution of oxygen vacancy, while the high Q m is a result of increased domain size and oxygen vacancy. The outstanding temperature stability is related to the stable non-180°domains structure due to the oxygen vacancy pinning effect. These properties hold great potential for advanced applications, particularly for piezoelectric high-power applications requiring constant d 33 over a broad temperature range. [ABSTRACT FROM AUTHOR]

The exploration of energy harvesting encompasses a wide array of sources, with a specific focus on recovering mechanical and magnetic energy from overlooked outlets, driving current research endeavours. In this study, we developed highly flexible Magneto-Mechano-Electric (MME) harvesters by combining poly(vinylidene fluoride) (PVDF)/barium calcium zirconium titanate (BCT-BZT) composite films with metglas. The flexible piezoelectric polymer-ceramic composite films were fabricated using a solvent casting technique. The high piezoelectric BCT-BZT fillers were synthesized through a sol-gel reaction route. A thorough analysis was carried out on these composites to evaluate their structural, functional, microstructural, and dielectric properties. The composite film loaded with 20 wt% BCT-BZT filler achieved a 78 % β-phase with a significant enhancement in the dielectric properties, resulting in a high permittivity∼40 and low dielectric loss. Employing these films, we engineered nanogenerators capable of converting mechanical energy into electrical energy, yielding an output voltage of 11 V. Thereafter, to harvest mechanical and stray magnetic fields, we developed a MME generator comprising a magnetic Metglas layer and PVDF-BCT-BZT composite and achieved an output voltage of 3.3 V with a power density of 85 μW/m2 when subjected to an AC magnetic field of 5 Oe. Furthermore, the MME generator has demonstrated the ability to charge various capacitors showcasing its potential for usage in self-powered, non-contact, and implantable devices. [ABSTRACT FROM AUTHOR]

Forsterite was synthesized with MgCO 3 and SiO 2 powders using a solid-state method at 1200–1300°C. The ceramic specimen with the highest forsterite phase content was sintered with the ZrO 2 sintering aid at mass fractions of 0.5, 1.0, and 1.5 wt% at 1400°C for 4 h. The dielectric constant and loss tangent were also measured via the waveguide method at 8–12 GHz. The formation of enstatite and cristobalite was minimized through precise synthesis temperature control. Phase measurement by the Rietveld method showed that specimen F28 contained more than 99.8% forsterite. It was found that ZrO 2 reduced the pore volume percent and increased the density even at low mass fractions. A liquid phase on the grain boundaries was demonstrated. The solid ceramic specimen F28-15Z showed a dielectric constant of 6.5 and high quality factor of 189000. [ABSTRACT FROM AUTHOR]

The (Ba 0 · 95 Ca 0.05) (Ti 0 · 95 Zr 0.05) 1-x (Zn 1/3 Nb 2/3) x O 3 BCZTxZN compounds, were created using the widely adopted solid-state method. To assess the impact of (Zn, Nb: ZN) co-substitution ions we studied the structural, vibrational, and dielectric characteristics of BCZT. The phase purity was validated by conducting Rietveld refinement of XRD data, indicating the coexistence of orthorhombic and tetragonal phases at ambient temperature in the (Ba 0 · 95 Ca 0.05) (Ti 0 · 95 Zr 0.05) 0.975 (Zn 1/3 Nb 2/3) 0.025 O 3 (BCZT25ZN) composition. Furthermore, Raman spectroscopy confirmed the observed transitions. The presence of Zn2+ and Nb5+ ions resulted in a decrease in cell parameters and cell volume. The real part of the dielectric constant and the tangent loss (tan δ) exhibited values of approximately 3380 and 0.031, respectively, for the sample (Ba 0 · 95 Ca 0.05)(Ti 0 · 95 Zr 0.05) 0.95 (Zn 1/3 Nb 2/3) 0.05 O 3 (BCZT50ZN), obtained by substituting ZN in Ba 0 · 95 Ca 0 · 05 Ti 0 · 95 Zr 0 · 05 O 3. Incorporation of ZN into Ba 0 · 95 Ca 0 · 05 Ti 0 · 95 Zr 0 · 05 O 3 presents promising prospects for using the material in various device applications, including energy storage capacitors, sensors, and actuators. [ABSTRACT FROM AUTHOR]

As the flight speed of aircraft continues to increase, high-temperature wave-transparent materials for radomes or antenna windows face great challenges. The shortage of new high-performance wave-transparent materials is limiting the improvement of aircraft performance. In this work, dielectric and mechanical properties of RE 2 SiO 5 (RE = Ho, Er, Tm, Yb, and Lu) were investigated to explore their application as high-temperature wave-transparent materials. RE 2 SiO 5 (RE = Ho, Er, Tm, Yb, and Lu) ceramics possess relatively low dielectric constant and it is insensitive to the RE species. For the dielectric loss, they gradually decrease as the radius of rare earth ions decreases. In addition, RE 2 SiO 5 (RE = Ho, Er, Tm, Yb, and Lu) possesses good mechanical properties with high hardness and relatively low reduced modulus, and hardness is insensitive to the rare earth ion radii while the reduced modulus increases with the RE3+ ions radius decreases. They are larger than those of fused silica, the most used traditional high-temperature wave-transparent material. The results provide important material selection and optimization guidelines for RE 2 SiO 5 as the candidate for next-generation high-temperature wave-transparent materials. [ABSTRACT FROM AUTHOR]

Barium borosilicate (BBS) glass is a potential three-dimensional system packaging and sensor cover material. In this study, we prepared glass samples with different SiO 2 /B 2 O 3 ratios based on the revised model of Dell and Bray and discussed the effect of boron anomaly on dielectric and thermal properties through Raman spectroscopy. The results indicate that the [BO 4 ] tetrahedrons are beneficial in reducing the dielectric constant and dielectric loss to a certain extent, while the improvement in the coefficient of thermal expansion (CTE) is attributed to the depolymerization of the glass network by the [BO 3 ] triangles. After the disappearance of the boron anomaly, a certain amount of dielectric performance is sacrificed in exchange for an increase in the CTE. When the substitution rate of B 2 O 3 for SiO 2 reaches 15.12 mol%, the CTE of the sample increases to 8.43 × 10−6/°C, in addition, the dielectric constant and dielectric loss decrease to 4.90 and 0.0071 (@1 GHz), respectively. In summary, this work provides a suitable method for preparing glass with a high coefficient of expansion and low dielectric loss to address the thermal mismatch effect of different materials in electronic packaging systems. [ABSTRACT FROM AUTHOR]

Tunable dielectric materials, serving as key components in microwave electronic application, require both high dielectric tunability and low dielectric loss. However, the trade-off between dielectric tunability and dielectric loss restricts the improvement of the overall dielectric tunability properties. In the present study, we proposed an effective approach to benefit both high tunability and low dielectric loss, i.e., improving intrinsic dielectric response from the lattice polarization and restricting the extrinsic dielectric response from the domain motions at the same time. Experimentally different acceptor dopants were employed, including the introduction of K at the A-site and Mn, Fe and Co at the B-site. On one hand, the different acceptor dopants could adjust the Curie temperature and consequently resulting in the enhanced intrinsic dielectric response at room temperature. On the other hand, the employment of acceptor dopant could introduce the oxygen vacancies and form the acceptor-oxygen vacancy dipoles which may restrict the reorientation of microdomains, resulting in the decrease of extrinsic dielectric response. Herein, both enhanced tunability and reduced dielectric loss were achieved in acceptor doped BZT ceramics at ambient temperature (27 °C). In particular, Fe doped BZT ceramics achieved both high dielectric tunability of 93.8 % and low dielectric loss of 0.0038. Such performance is competitive with that of previous reported dielectric tunable materials. In addition, the dielectric tunability of Fe doped BZT ceramics maintained over 60 % within the wide temperature range from −20 °C to 60 °C. [ABSTRACT FROM AUTHOR]

A range of new fluorine‐containing copolyarylates were successfully produced through interfacial polymerization using hexafluorobisphenol A (BPAF) featuring a symmetric trifluoromethyl group structure, bisphenol B (BPB), and two acyl chloride monomers as raw materials. The results indicated that the synthesized amorphous copolyarylates exhibited good solubility, with number average molecular weights (Mn) of 19,000–44,000 g/mol, weight average molecular weights (Mw) of 66,000–159,000 g/mol, and intrinsic viscosities of 0.66–1.19 dL/g. The thermal stability of copolyarylates increased with the increase of BPAF monomer content (0~100%), which was manifested by the linear increase of glass transition temperature (Tg) from 201.6 to 237.1°C, and the increase of 5% thermogravimetric weight loss temperature (T5%) from 474.1 to 491.5°C. The tensile strength of copolyarylates ranged from 52.63 to 59.93 MPa, the tensile modulus ranged from 1102.08 to 1502.84 MPa, and the elongation at break ranged from 32.0 to 75.5%. In addition, the copolyarylates had good dielectric properties with a dielectric constant of 2.58–3.75 at 107 Hz and a dielectric loss tangent of 0.021–0.028. [ABSTRACT FROM AUTHOR]

Poly(silylene arylether arylacetylene) (PSEA) resin is a promising material for preparing an advanced wave‐transparent composite because of excellent thermal stability and good dielectric properties. Herein, a novel poly(silylene arylether arylacetylene) resin with trifluoromethyl groups (PSEAF) was synthesized by Grignard coupling reaction, and the effects of the incorporation of trifluoromethyl groups on various properties of PSEAF resin and quartz fiber reinforced composites were investigated. Compared to PSEA, the PSEAF resin exhibits better solubility and processability, and lower apparent activation energy for curing reactions. After thermal curing reactions, the PSEAF resin converts to an amorphous crosslinked network with the temperature at 5% weight loss (Td5) around 470 °C. The cured PSEAF resin possesses improved mechanical properties and dielectric properties. The flexural strength arrives at 64.4 MPa, and the dielectric constant (ε) and dielectric loss (tanδ) at 30 MHz are 2.75 and 4.3 × 10−3, respectively. Besides, the quartz fiber reinforced PSEAF composite simultaneously shows ε of 3.3, theoretical wave transmittance |T|2 of 91.4% at 7 GHz, and flexural strength of 350 MPa. [ABSTRACT FROM AUTHOR]

Highlights In this paper, the carboxylic acid modifier 2,3,4,5‐tetrafluorobenzoic acid (F4C) was used to modify the BaTiO3 (BT) nanoparticles, which acted as a coupling agent. The modified BT(F4CBT) nanoparticles, polyvinylidene fluoride (PVDF), and polymethylmethacrylate (PMMA) were used to make the modified nanocomposite films: PVDF/PMMA‐F4C‐BaTiO3 nanocomposite films. The unmodified BT nanoparticles were used to make the unmodified nanocomposite films: PVDF/PMMA‐BaTiO3 nanocomposite films. The modification effect of the F4C resulted in an increase in the amount of β‐phase and γ‐phase, a decrease in the amount of α‐phase, and a decrease in the overall crystallinity of the PVDF‐based nanocomposite films. The dielectric constant of the PVDF/PMMA‐F4C‐BaTiO3 nanocomposite films reached a maximum value of 16.7 at a frequency of 100 Hz at 4 wt% F4C, which was 40.3% higher than that of the unmodified PVDF/PMMA‐BaTiO3 films. The F4C content of 2 wt% PVDF/PMMA‐F4C‐BaTiO3 nanocomposite films showed the lowest dielectric loss of 0.055, which was 56.7% lower than the unmodified PVDF/PMMA‐BaTiO3 films. The breakdown strength of the PVDF/PMMA‐F4C‐BaTiO3 nanocomposite films increased and then decreased with the increase of the F4C content, and the highest breakdown strength was 2800 kV/cm at 4 wt% F4C, which was 55.6% higher than the unmodified PVDF/PMMA‐BaTiO3 films. The charging density of the PVDF/PMMA‐F4C‐BaTiO3 nanocomposite films reached a maximum value of 20.65 J/cm3 at 4 wt% F4C content, which was 394% higher than the unmodified PVDF/PMMA‐BaTiO3 films. Modification of ceramic nanoparticles with carboxylic acid coupling agent. The dielectric properties of the modified nanocomposite film were significantly improved. Maximum polarization and charge/discharge density were greatly improved by coupling agent modification. [ABSTRACT FROM AUTHOR]

Microwave heating provides a rapid method for the heterogeneous nucleation of noble metal particles on perovskite support materials for electrocatalytic purposes. To succeed, dielectric tuning of perovskite materials becomes fundamental. Herein, the dielectric engineering of the BaMnO3 perovskite system is carried out through the use of B‐site doping to give BaTi0.5Mn0.5O3. Using a combination of atomic‐scale imaging and electron energy loss spectroscopy (EELS), the preferential filling of the M1 and M3 B‐sites with Mn and Ti ions in the 12R‐rhombohedral perovskite structure is established. While the addition of Ti in the BaMnO3 system has no detrimental effects on the presence of the oxygen reduction reaction (ORR) active Mn3+ states at the surface, it does alter the dielectric constant and loss tangent, thus facilitating the heterogeneous nucleation of Pt nanoparticles on BaTi0.5Mn0.5O3 via rapid microwave heating. Higher Pt loading regimes are found to increase the size and aggregation of the nucleated particles, thus reducing their ORR activity. Therefore, lower Pt loading not only reduces costs but improves overall activity. This work represents future possibilities for the dielectric engineering of perovskite and similar support materials to aid in the quick and easy formation of stable noble metal‐support catalytic systems. [ABSTRACT FROM AUTHOR]

This study explores the impact of crystallite size on the opto-dielectric properties of LiCu0.5Fe2-yCeyO4 (y = 0.0, 0.01, 0.02, 0.03, 0.04) nanospinel ferrites (NSFs) synthesized via sol–gel auto-combustion. X-ray diffraction (XRD) analysis confirmed the crystalline nature and phase purity, revealing variations in crystallite size within the nanoscale range. Fourier-transform infrared spectroscopy (FTIR) provided insights into chemical bonding, affirming the composition and structure reliability. Morphological characterization via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the nanostructure, highlighting the influence of crystallite size on particle morphology, shape, and size distribution. Energy-dispersive X-ray spectroscopy (EDX) verified the presence of expected elements, with elemental composition offering spatial distribution insights. Inductively coupled plasma (ICP) analysis quantified elemental concentrations, focusing on Li, Cu, Fe, and Ce. Optical properties, including UV–vis absorption spectra, were measured to assess band gap energies. Dielectric measurements across a range of frequencies provided insights into the pure Li-Cu NSFs and Ce3+ doped Li-Cu NSFs dielectric response, revealing variations in dielectric constant and loss tangent with changing crystallite size. The findings highlighted the significant role of crystallite size in modulating both energy band gap and dielectric properties, essential for applications in high-frequency, photonics, electronics, and sensor technologies. [ABSTRACT FROM AUTHOR]

Tow-level system (TLS) loss in amorphous dielectric materials has been intensively studied at millikelvin temperatures due to its impact on superconducting qubit devices and incoherent detectors. However, the significance of TLS loss in superconducting transmission lines at liquid helium temperatures remains unclear. This study investigates TLS loss in amorphous SiO 2 at liquid helium temperatures (about 4 K) within a frequency range of 130–170 GHz, using niobium microstrip and coplanar waveguide resonators. Our results demonstrate notable power and temperature dependence of dielectric loss, with the dielectric loss and quasiparticle loss exchanging dominance at around 4 K. These findings are consistent with TLS models and provide crucial insight for the design of superconducting devices operating at liquid helium temperatures. [ABSTRACT FROM AUTHOR]

Compounding multiple single-component materials in a reasonable and economical way is the key to prepare wave-absorbing materials. Using a straightforward hydrothermal and in-situ oxidative polymerization method, NiSe2@PANI composites were created. PANI forms a cladding structure on NiSe2, increasing contact area and improving interfacial loss, while the addition of PANI lowers relative density and enhances electrical conductivity. NiSe2 mass fractions of 30%, 50%, and 70% in the composites were obtained by changing the mass ratio of NiSe2 to polyaniline, resulting in three distinct types of composite samples. These samples were then subjected to various test procedures to evaluate their characteristics and wave absorption ability. The NP-2 sample with a 50% mass fraction was found to have good attenuation ability and impedance matching conditions. Dielectric loss with a tiny amount of magnetic loss makes up the loss mechanism. At a matching thickness of 2.5 mm, the RLmin value is −49.95 dB and the EAB value is 1.84 GHz. Additionally, the RL value also reaches −40.67 dB at a thickness of 4.5 mm. NP-2 samples exhibit a high absorption capacity at thin thicknesses and a low density, with an EAB frequency of 3.28 GHz. This indicates that NiSe2@PANI composites can meet the requirements for wave-absorbing material manufacturing, which include thin thickness, light weight, wide bandwidth, and high wave-absorbing capacity. This study provides a meaningful reference for lightweight and high-performance wave-absorbing materials. [ABSTRACT FROM AUTHOR]

Highlights Increasing miniaturization and integration of microelectronic devices have led to an unprecedented attention on heat dissipation and signal transmission of electronic equipment. However, the mostly used method to enhance the thermal conductivity of polymers by adding thermally conductive fillers usually results in the increase of dielectric constant (Dk). It was still challenging to synergistically achieve low Dk and high thermal conductivity of polymer‐matrix composites. Herein, hydroxylated boron nitride nanosheet (BNNS‐OH) with a high yield of 35.67% was prepared by the liquid ultrasonic exfoliation under the assistance of sodium cholate (SC), and grafted with (1H,1H,2H,2H‐perfluorodecyl) trimethoxy silane to prepare fluorinated boron nitride nanosheets (F‐BNNS), which can uniformly disperse in liquid silicone rubber (LSR) and reduce the Dk of LSR composites. The thermal conductivity of LSR composites with 20 wt% F‐BNNS reached 0.489 W·m−1·K−1, showing an increase of 307.35% in comparison with pure LSR (0.12 W·m−1·K−1). Meantime, the Dk of as‐obtained LSR/F‐BNNS (20 wt%) composites is reduced from 3.4 to 2.6, and the dielectric loss (Df) is less than 0.012. The facile and rational design of fluorinated BNNS offers a new insight for the high‐end electronic packaging materials. A new method of exfoliation and fluorinated treatment of h‐BN was proposed. The LSR composites achieved an ultralow Dk of 2.63 via fluorinated BNNS. Thermal conductivity of LSR composites increased by 307.35% than pure LSR. [ABSTRACT FROM AUTHOR]

To facilitate future pasteurization experiments utilizing microwave energy, the dielectric properties of five dried fruits — almond (Prunus dulcis), cashew nut (Anacardium occidentale), pistachio (Pistacia vera), peanut (Arachis hypogea L.) and walnut (Juglans regia) were investigated at room temperature (28∘C). Samples were taken in powder form to investigate the effect of increased surface-to-volume ratio on their dielectric properties, as applicable in the case of nanomaterials. The measurements were conducted at four different frequencies (3.30, 7.50, 9.30and 14.70GHz) in the microwave spectrum by using the two-point method and a MATLAB program was used for solving the transcendental equation to obtain values of dielectric constant and loss factor. The findings revealed a decreasing trend in the values of dielectric constant of the five dried fruits as the frequency increased. However, no consistent trend was observed for the dielectric loss factor of the fruits with increasing frequency. Further, the penetration depth of electromagnetic waves in all the five dry fruit samples was observed to decrease as the frequency increased. On comparing results for dielectric parameters of dry fruits in powder form with those of whole fruit kernels, no definite trends are observed for ε′ and ε″, but the penetration depth is found to decrease when the sample is taken in powder form. [ABSTRACT FROM AUTHOR]

Dielectric constant (ε′) and dielectric loss factor (ε′′) of gluten-free grains viz., Finger millet, Amaranth and Buckwheat in powder form were measured at room temperature (22∘C) at frequency 9.76GHz for different moisture content samples. The method used was the Two-Point method which is based on the transmission line technique. Microwaves were employed to investigate dielectric properties and their moisture dependence. The results showed that dielectric constant and dielectric loss of Gluten-free grains increase with the increase in moisture content. It shows that for higher moisture there are more free molecules in comparison to bound water molecules. This work can be an effective guide in designing a moisture meter for gluten-free grains. [ABSTRACT FROM AUTHOR]

The dielectric properties of a material determine its response of the material to the Electromagnetic field (EM field). It comprises dielectric constant (ε′), which is the ability to store energy of EM fields, and dielectric loss (ε′′) which is the amount of dissipated Electromagnetic energy in the form of heat. Dielectric properties are affected by various factors such as frequency, temperature, bulk density, moisture content, etc. Dielectric constant and dielectric loss were determined in this study for milk powders viz. Whole Milk Powder, Skim Milk Powder, and Infant Milk Powder at various microwave frequencies (5.68, 7.45, 10.25GHz). The method used to determine dielectric properties is the Two-point Method which is implemented on a microwave bench. It became apparent that when frequency increases dielectric constant decreases and dielectric loss first decreases and then increases. It was also observed that the fat content can have an impact on the milk powders’ dielectric properties. [ABSTRACT FROM AUTHOR]

The influence of isovalent substitution at B-site by Ge4+ on the dielectric constant and dielectric losses of (Na 0.5 Bi 0.5)TiO 3 has been experimentally investigated. The compositions (Na 0.5 Bi 0.5)(Ti 1-x Ge x)O 3 (x (mol) = 0.00, 0.01, 0.03, and 0.05) were fabricated using the solid-state reaction (SSR) method, with a sintering temperature of 1150 °C for 3 h in air. Rietveld refinement revealed that the phases had a rhombohedral structure and belong to the R 3c space group. Ge4+ substitution inhibits grain growth and improves dielectric properties, with optimized permittivity. Simultaneously, dielectric losses are reduced at both room temperature and elevated temperatures. At room temperature and 1 kHz, it is approximately (tan(δ) ≈ 0.17) for x = 0.03, which is significantly lower than that of NBT (tan(δ) ≈ 0.61), reaching a minimum of 0.02 at 310 °C and 1 MHz. Leakage current is also optimized after Ge4+ modification. Modelling of Nyquist diagrams using an electrical model indicated two contributions: grains and grain boundaries. These results suggest that Ge4+ substitution in the NBT compound could open new possibilities for its application in the manufacturing of capacitors with improved properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Synthesis of two‐dimensional (2D) titanium carbide (Ti3C2Tx), with the name of MXene, by etching Ti3AlC2 (MAX) for different times 20 (v/v) % hydrofluoric acid (HF) at 40 °C was carried out. The influences of time, temperature and source of MAX on the synthesis of MXene were researched. The MXenes produced were characterized by fourier‐transform ınfrared (FT‐IR) spectroscopy technique, energy dispersive x‐ray spectroscopy (EDX), scanning electron microscopy (SEM), x‐ray diffraction (XRD) and thermogravimetry (TG) instruments. Above 390 °C, MXene layers were considerably oxidizing and forming anatase and rutile phases of TiO2 under air atmosphere. The resistance of MAX and MXene was 3.6 Ω and 116 Ω, respectively. However, the resistance of the residual part of MXene heated to 620 °C considerably increased to 17850 Ω. This behavior is another important piece of evidence showing that the MXene crystal structure has changed significantly and transformed into a new chemical structure containing anatase and rutil titanium oxide (TiO2). The dielectric loss (ϵ") and alternating conductivity (δac) of the MAX and MXenes were determined from their impedance measurements. The ϵ" and δac values of MXene were compared with those of MAX. Direct curent conductivities of MAX and MXene produced for 24 h were found to be 0.016 S/cm and 0.0023 S/cm, respectively. [ABSTRACT FROM AUTHOR]

Flexible microwave absorber (MAR), vital in advanced applications such as wearable electronics and precision devices, are highly valued for their lightweight, exceptional electromagnetic waves (EWs), and ease of fabrication. However, optimizing the electromagnetic parameters of microwave absorption materials (MAMs) to enhance absorption ability and expand effective absorption broadband (EAB, reflection loss (RL) <−10 dB) is a considerable challenge. Herein, a permittivity‐attenuation evaluation diagram (PAED) is constructed using parameter scanning based on the Materials Genome Initiative to determine the ideal electromagnetic parameters and thickness, optimize absorption efficiency, and obtain highly efficient absorbers. Guided by the PAED, a multilayer MAR consisting of a "matching‐absorption‐reflection layer" and a dielectric loss gradient aligned with the direction of EWs propagation is developed. This design significantly enhances the EWs penetration and ensures effective absorption, attributed to the well‐matched impedance and attenuation characteristics. As anticipated, the microwave absorption of the absorber (density = 0.063 g cm−3) is optimized, with an RL of −34 dB at d = 4 mm and an EAB covering the entire X‐band (8.2–12.4 GHz). This study presents a novel approach for establishing a material database for MAMs and developing high‐performance absorbers characterized by thinness, lightness, broad operational frequency range, and robust absorption capacity. [ABSTRACT FROM AUTHOR]

Glycinium oxalate (GO) and Bis(glycinium) oxalate (BGO) crystals are successfully grown using the slow evaporation solution growth technique. Following their growth, the crystals are subjected to a series of acoustic shock pulses. The effects of these shock pulses on the structural, optical, dielectric, and morphological properties of the crystals are comprehensively analyzed using various characterization techniques, including powder X‐ray diffraction (XRD), UV‐Visible spectroscopy, dielectric spectroscopy, and optical microscopy. Structural analysis through XRD reveals shifts in diffraction peak positions, indicating structural deformations. Fourier transform infrared spectroscopy analysis assesses the chemical stability of GO and BGO under shocked conditions. UV‐Visible spectroscopy shows alterations in optical transmission with successive shock pulses, attributed to structural and surface defects. Dielectric properties are investigated over a frequency range from 1 Hz to 1 MHz, revealing variations in dielectric constant and loss tangent, which provide insights into the electrical behavior of the materials under normal and shocked conditions. Optical and scanning electron microscopy examine surface morphology, visualizing defects induced by the shock pulses. This study highlights the significant impact of shock pulses on the structural properties, optical transmission, dielectric properties, and surface morphology of GO and BGO crystals, offering valuable information on their resilience under dynamic conditions and potential applications. [ABSTRACT FROM AUTHOR]

This article provides reports on the method of surface functionalization modification of graphene nanosheets (GNPs) and aluminum nitride (AlN) through polydopamine and silane coupling agents, respectively. This modification achieves excellent dielectric performance of polyvinylidene fluoride (PVDF) composites by ensuring the uniform dispersion of fillers within the matrix. The synergistic effect between surface‐modified GNPs and AlN is conducive to increasing polar PVDF crystals and promoting interface polarization. The prepared PVDF/GNPs/AlN composites exhibit a dielectric constant as high as 45 with a dielectric loss of only 0.044. Meanwhile, the enhanced interface compatibility of composite materials, to a certain extent, reduces interface thermal resistance and forms an effective thermal conduction network, which enhances the heat dissipation capability of electronic devices and presents potential application in the dielectric energy storage. [ABSTRACT FROM AUTHOR]

The advancement of crystalline growth and characterization tools allows us to investigate novel nonlinear optical substances suitable for photonic applications. Bis-(4-aminopyridine)-zinc(II) acetate (B4AZA), a metal–organic crystal was produced in this study using the slow evaporation procedure at room temperature. Analytical studies such as X-ray crystallography, Fourier transform infrared (FT-IR), UV–visible (UV–Vis), fluorescence, second harmonic generation (SHG), and dielectric tests were used to characterize the as-grown B4AZA crystals. According to the solubility data, the sample has a positive temperature coefficient of solubility. The crystallographic findings show that the B4AZA crystallized in a monoclinic structure with the P21/n space group. Molecular vibrations and functional groups in the substance were determined using the FT-IR technique. The UV–Vis absorbance and transmittance spectra have shown the wide transparency and minimum absorbance of the B4AZA in the near UV and entire visible regions of the electromagnetic spectrum. The bandgap of the B4AZA has been calculated using the Tauc relation and found to be 4.32 eV. The fluorescence spectra have shown a prominent emission peak at 584 nm with an excitation wavelength of 280 nm. The larger Stokes shift found in the fluorescence spectra is advantageous for practical applications. The SHG study revealed that the powdered B4AZA samples generated a second harmonic output. The dielectric test revealed frequency-dependent changes in the dielectric constant and loss factor. Both the dielectric constant and the loss factor decrease exponentially as frequency increases, reaching low values at higher frequencies. The experimental results illustrate the suitability of the B4AZA crystals for photonic applications. [ABSTRACT FROM AUTHOR]