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The addition of Mg generally enhances the high-temperature stability and reliability of BaTiO 3 -based multilayer ceramic capacitors (MLCCs). Herein, a series of Mg-doped BaTiO 3 -based ceramics and ultra-thin MLCCs were successfully fabricated, and the coherent and semi-coherent interface has been observed in samples. Based on the density functional theory (DFT) calculations, the improvement in temperature stability is due to changes in the coherent interface and electronic structure that promote the formation of polar nano-regions (PNRs) and induce relaxation behavior. Based on the atomic displacement, it is found that the excess substitution released the coherent stresses in the form of defects and formed semi-coherent interfaces. The reliability degradation of MLCCs is mainly due to the evolution of the semi-coherent interfaces. This work points out an avenue to obtain high-temperature stability and high reliability in BaTiO 3 -based MLCCs. [ABSTRACT FROM AUTHOR]

The residual stress relaxation behaviour in low-cycle fatigue brings uncertainty to accurately predict fatigue life. Therefore, establishing the residual stress relaxation model for the welded structure is critical. In this paper, the residual stress is simulated through Abaqus finite element software (6.14). The residual stress relaxation model related to the magnitude of cyclic loading and the number of cycles is proposed. Furthermore, the residual stress relaxation model is applied to predict low-cycle fatigue life. Finally, the simulation results are validated by experimental data obtained using the reliable neutron diffraction method, and a good agreement is observed. [ABSTRACT FROM AUTHOR]

A series of unfilled tungsten bronze Ca 0.5 (Sr 0.5 Ba 0.5) 2 Nb 5- x Sb x O 15 (CSBNS x) ceramics were synthesized by traditional solid-phase method to investigate the relationship between energy storage performances (ESPs) and structural changes including the lattice distortion and structural modulation. The Sb5+ substitution prompted the crystal structure to evolve from tetragonal P 4 bm to orthorhombic Ama 2 and then to tetragonal P 4/ mbm symmetry. The appearance of incommensurate Ama 2 structure and the polar nanoregions were the main factors for the stronger relaxation behavior. Moreover, the effectively enhanced bulk and grain boundary resistivity were conducive to the increase of breakdown field E b. The P - E loops become more elongated and the T c peak moved towards lower temperatures. Ultimately, an excellent recoverable energy density (W rec , 2.38 J/cm3), energy storage efficiency (η , 85%), power density (P D , 200.9 MW/cm3) and current density (C D , 1545.6 A/cm2) were achieved simultaneously for CSBNS 0.2 ceramics. The excellent ESPs make the CSBNS 0.2 show considerable potential in high-power capacitor applications. [ABSTRACT FROM AUTHOR]

We have studied the magnetic relaxation behavior of a two-dimensional Ising ferromagnet by Monte Carlo simulation. Our primary goal is to investigate the effects of the system's geometry (area preserving), boundary conditions and dynamical rules on the relaxation behavior. The Glauber and Metropolis dynamical rules have been employed. The systems with periodic and open boundary conditions are studied. The major findings are the exponential relaxation and the dependence of relaxation time (τ) on the aspect ratio R (length over breadth having fixed area). A power law dependence (τ ∼ R − s ) has been observed for larger values of aspect ratio (R). The exponent (s) has been found to depend linearly (s = a T + b) on the system's temperature (T). The transient behaviors of the spin-flip density have been investigated for both surface and bulk/core. The size dependencies of saturated spin-flip density significantly differ for the surface and the bulk/core. Both the saturated bulk/core and saturated surface spin-flip density was found to follow the logarithmic dependence f d = a + b log (L) with the system size. The faster relaxation was observed for open boundary condition with any kind (Metropolis/Glauber) of dynamical rule. Similarly, Metropolis algorithm yields faster relaxation for any kind (open/periodic) of boundary condition. [ABSTRACT FROM AUTHOR]

Dielectric materials with large dielectric constants are increasingly used in electronics. In this study, dense (Sb 0.5 Lu 0.5) x Ti 1- x O 2 ceramics with strong electron-pinning clusters were prepared using a solid-state reaction. (Sb 0.5 Lu 0.5) 0.99 Ti 0.01 O 2 exhibited a giant dielectric constant of 1.51 × 104 and an ultralow dielectric loss of 0.004 at room temperature (RT). This ceramic also exhibited excellent frequency, temperature, and DC bias stabilities (RT–250 °C, 20 Hz–5 MHz, 0–32 V) owing to the high grain boundary resistance and strong electron-pinning effect. XPS, impedance spectroscopy, and relaxation behavior analysis revealed that electron-pinning, internal barrier layer, and electrode effects resulted in excellent dielectric behavior. This study demonstrates that the construction of defect clusters with strong electron-pinning effects is an effective method for obtaining giant dielectric ceramics with ultralow loss and temperature/DC bias stability. [ABSTRACT FROM AUTHOR]

The purpose of this work is twofold: the manufacturing of functionalized graphene (f-GNF) epoxy nanocomposite and time-dependent thermomechanical characterization of epoxy and nanocomposite. To accomplish these purposes, f-GNF-epoxy nanocomposites are produced for two different graphene fractions (0.1 and 0.5 wt%) using the non-covalent functionalization and three roll milling (3RM) dispersion techniques. Dynamic Mechanical Analysis (DMA) is performed to determine temperature-dependent viscoelastic properties. Quasi-static compression, creep and relaxation tests are conducted at two different temperature values: 65°C and 120°C. As expected, experimental results revealed that the elasticity modulus and yield stress decrease with increasing temperature. It is also determined that the reinforcing effect of graphene reduces with increasing temperature. An important conclusion revealed, through the compression, creep, and relaxation test results that graphene has no reinforcing effect at 120°C but has a weakening effect on total thermo-mechanical behavior. [ABSTRACT FROM AUTHOR]

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BCZT ceramics are considered to be a promising material due to the presence of its morphotropic phase boundary (MPB). However, most of the research on this material is focused on piezoelectric properties, and there is still a lack of research on energy storage properties. Here, a component represented as BiMeO3 [Me = (Li1/2Nb1/2)3+] with a similar structure as BCZT was introduced into ceramics to improve the energy storage properties. The phase composition changes, relaxation behavior, and energy storage properties of the samples were carefully investigated. The improved relative densities brought about by the introduction facilitate the increase in bulk resistance, thus increasing the break-down field strength. Due to the addition of BLN, the Curie temperature drops substantially below room temperature. Under the influence of phase composition and polar nano-regions (PNRs), BCZT ceramics exhibit slim hysteresis loops. In BCZT‒0.12BLN, the recoverable energy density can reach 2.06 J/cm3 and efficiency can stay in 80.5% at the same time. This proposed BCZT ceramic still has great research potential as an energy storage material. [ABSTRACT FROM AUTHOR]

An environmentally-friendly synthesis route and low-cost starting materials are more appropriate for the production of ceramic materials at the industry level. With this concern we prepared the La 2/3 Cu 3 Ti 4 O 12 (LCTO), which is isostructural of CaCu 3 Ti 4 O 12 (CCTO), using the low-cost TiO 2 instead of a high-cost of titanium source (titanium isopropoxide or titanium chloride) using a low-cost wet-chemical route. Although, there are lots of synthetic methods reported for LCTO fabrication in terms of duration, cheap reagents, energy consumption, feasibility, etc. The present method is far better than the others. The prepared ceramic samples were sintered at 1050 °C/12 h and studied their structural, morphology and impedance, and modulus studies for further confirmation. The prepared LCTO ceramic shows the pure phase with the cubic type of morphology. The homogenous distribution of all the elements was observed through dispersive X-ray analysis. X-ray photoelectron spectroscopy studies revels that La is in +3 oxidation state, Cu is in a +2 oxidation state, and Ti is multiple (+3 and + 4) oxidation state. The LCTO ceramic displayed the very high dielectric constant (∼3852) and dielectric loss (0.322), at 1 kHz and at room temperature. Calculated the activation energy using the impedance and modulus data and it shows the superior to that of CCTO ceramic synthesized by the same method. The prepared samples exhibited Debye-type relaxation, which is evoked from the impedance and modulus studies. The calculated optical energy bandgap of LCTO (2.06 eV) is found to be lesser than that of the well-known structure of perovskites (BaTiO 3 (3.28 eV), PbTiO 3 (3.18 eV), LiNbO 3 (3.78 eV) and BiFeO 3 (2.67 eV) as well as structure of spinel CoCr 2 O 4 (3.10 eV) and LuFe 2 O 4 (2.18 eV)) materials. [Display omitted] • La 2/3 Cu 3 Ti 4 O 12 (LCTO) synthesized via the earthly abounded with low-cost solid TiO 2. • La-, and Cu-nitrates as starting materials via novel low cost auto flame chemical route. • We have extensively studied the conductivity, impedance and modulus of LCTO. • The scaling behavior of Zʹʹ and Mʹʹ shows ideal Debye-type relaxation. • Optical energy bandgap of LCTO (2.06 eV) is less than (BaTiO 3 (3.28 eV). [ABSTRACT FROM AUTHOR]

Although BiFeO 3 –BaTiO 3 -based lead-free ceramics have attracted much attention in recent years as a high temperature piezoelectrics, their d 33 value is still difficult to exceed 200 pC/N through conventional methods. In this work, a novel (0.7-x)BiFeO 3 -0.3BaTiO 3 -xLa(Mg 2/3 Nb 1/3)O 3 (x = 0–0.005) ternary system was reported to own excellent room-temperature piezoelectric constant (d 33) ∼216 pC/N and high Curie temperature (480 °C) at x = 0.003 simultaneously. It reveals that the compositions undergo an obvious phase transition from ferroelectric (FE) rhombohedral (R) phase to relaxor pseudo-cubic (PC) phase via an R–PC morphotropic phase boundary (MPB). More importantly, piezoelectric nonlinear Rayleigh analysis and S-E/P-E curves suggest that the significantly enhanced domain dynamics due to the coexistence of macrodomain and nanodomain can be observed in the x = 0.003 sample. The synergy of these two effects induce the improved d 33 value observed in the x = 0.003 sample. In addition, the compositions exhibit the inhibition of defect dipoles and the improvement of the high temperature resistivity, leading to the excellent thermal stability with sensitivity coefficients ƞ less than ± 5% in the annealing temperature range of 25–400 °C. The present work provides a guideline for the subsequent design of high-temperature lead-free ceramics. [ABSTRACT FROM AUTHOR]

Nanoparticles, when incorporated into polymer matrices, can improve the intrinsic properties of composite materials. These materials possess fascinating properties and find widespread applications in bioengineering, medicine, aerospace, and electronics. However, the impact of nanoparticle surface heterostructures on composite systems is not fully understood. To bridge this gap, composite hydrogels (HRCs) are developed using rough‐surfaced raspberry‐like colloidal (RC) particles. It is hypothesized that the surface roughness of nanoparticles can significantly affect their adsorption, motion, and interfacial forces when interacting with polymeric networks, thereby influencing the macroscopic properties of HRCs. The properties of HRCs are compared with those of composite hydrogels containing smooth‐surfaced particles (HSCs) to isolate the effect of surface roughness. The results show that the nano‐surface heterogeneities of nanoparticles dictate the macroscopic properties of HRC hydrogels. It is found that HRCs exhibit much greater mechanical and adhesive properties compared to HSCs and control hydrogel without nanoparticles. As identified by the relaxation behavior, the enhanced frictional drag of interstitial fluid due to surface roughness, combined with the strong interaction of polymer network components dynamically linked by rough‐surfaced RC particles, is responsible for these improvements. These findings can guide the design and fabrication of new nanocomposites, including hydrogels, for various applications. [ABSTRACT FROM AUTHOR]

A low-temperature sintering strategy was realized for preparing 0.21Bi(Ni0.5Ti0.5)O3-0.05BiFeO3-0.74Pb(Zr0.5Ti0.5)O3 (0.21BNT-0.05BF-0.74PZT) ceramics by conventional ceramic processing by adding low melting point BiFeO3 and additional sintering aid LiBO2. Pure perovskite 0.21BNT-0.05BF-0.74PZT ceramics are prepared at relatively low sintering temperatures, and their structure presents tetragonal distortion that is affected slightly by the sintering temperature. The 1030 °C sintered samples have high densification accompanied by relatively large grains. All ceramics have excellent dielectric performance with a relatively high temperature of dielectric constant maximum, and present an apparent relaxation characteristic. A narrow sintering temperature range exists in the 0.21BNT-0.05BF-0.74PZT system, and the 1030 °C sintered 0.21BNT-0.05BF-0.74PZT ceramics exhibit overall excellent electrical performance. The high-temperature conductivity can be attributed to the oxygen vacancies' conduction produced by the evaporation of Pb and Bi during sintering revealed by energy dispersive X-ray measurement. [ABSTRACT FROM AUTHOR]

The environment‐friendly materials exhibiting colossal permittivity play an increasingly important role in the electronics industry. In this work, (Tb0.5Ta0.5)xTi1−xO2 (x = 0, 0.005, 0.01, 0.02, and 0.04) ceramics with new defect clusters were fabricated to enhance the dielectric response. Significantly, all ceramic samples exhibit large dielectric constants (εr > 104), whereas the ceramic with x = 0.005 exhibits an ultralow loss (tan δ) of about 0.008 at room temperature and 1 kHz. The origins of its excellent dielectric properties were revealed by XRD, X‐ray photoelectron spectroscopy, and dielectric response analysis, which were mainly caused by defective dipoles associated with oxygen vacancies (VO⋅⋅$V_{\rm{O}}^{\centerdot \centerdot }$). These defective dipoles limiting the long‐range hopping of electrons lead to the electron pinning effect. Additionally, the frequency spectrum under DC bias and conductivity behavior suggests that grain boundary and electrode effects also contribute to the dielectric constant. This study not only explores the dielectric response properties of a new giant dielectric (Tb0.5Ta0.5)xTi1−xO2 ceramics but also offers a candidate material suitable for ceramics capacitors. [ABSTRACT FROM AUTHOR]

In this paper, < 001 > -oriented ternary NBT-BY-STO textured ceramics were prepared by tape casting technique based on composition design and orientation engineering strategies. The introduction of BY greatly reduces the grain size and increases the breakdown field strength, resulting in the improvement of the energy storage density. The relaxation behavior and saturation polarization of the ceramics were enhanced by < 001 > -orientation engineering, and so significantly increased energy storage density and energy storage efficiency. Finally, the energy storage performance of NBT-based ceramics was improved obviously. When x = 0.3, the energy storage density reached 5.34 J/cm3, and the energy storage efficiency was 83.91%. The prepared textured ceramics have excellent temperature, frequency stability and charge-discharge characteristics. Therefore, < 001 > -oriented ternary textured ceramics prepared in this paper is a potential dielectric material for pulse powder device, and this strategy of optimizing the energy storage performance also provides guidance of energy storage performance regulation for dielectric energy storage materials. [ABSTRACT FROM AUTHOR]

Abstract Nanoparticles, when incorporated into polymer matrices, can improve the intrinsic properties of composite materials. These materials possess fascinating properties and find widespread applications in bioengineering, medicine, aerospace, and electronics. However, the impact of nanoparticle surface heterostructures on composite systems is not fully understood. To bridge this gap, composite hydrogels (HRCs) are developed using rough‐surfaced raspberry‐like colloidal (RC) particles. It is hypothesized that the surface roughness of nanoparticles can significantly affect their adsorption, motion, and interfacial forces when interacting with polymeric networks, thereby influencing the macroscopic properties of HRCs. The properties of HRCs are compared with those of composite hydrogels containing smooth‐surfaced particles (HSCs) to isolate the effect of surface roughness. The results show that the nano‐surface heterogeneities of nanoparticles dictate the macroscopic properties of HRC hydrogels. It is found that HRCs exhibit much greater mechanical and adhesive properties compared to HSCs and control hydrogel without nanoparticles. As identified by the relaxation behavior, the enhanced frictional drag of interstitial fluid due to surface roughness, combined with the strong interaction of polymer network components dynamically linked by rough‐surfaced RC particles, is responsible for these improvements. These findings can guide the design and fabrication of new nanocomposites, including hydrogels, for various applications.

Tools and products used in everyday life are regularly exposed to dynamic, cyclical stress. These stresses are particularly significant in the case of polymers, as their viscoelastic behavior means that creep can be considerable even at room temperature. Therefore, polymer components are often tested for maximum deformation rather than for maximum load-bearing capacity. Basic material testing methods are tensile, compression, and flexure tests, which are excellent for determining the material properties of the bulk material. However, in some cases, it is more appropriate to investigate surface mechanical properties. The ideal method for this is the depth-sensing indentation test. This method has been widely applied to polymers in the last ten years, but cyclic tests are rare, and creep is not considered in this type of indentation test. In the case of cyclical tests, temperature dependence is not fully examined, either. This paper presents the results of cyclic indentation tests on photopolymer specimens produced by additive manufacturing with the use of a dynamic mechanical analyzer with a unique indentation clamp. We performed the tests at three temperatures to investigate the influence of temperature on cyclic indentation tests. The test results show the variation of deformation between cycles and the significant effect of temperature.

• The novel piezoelectric ceramics of 0.36BiScO 3 -0.64PbTiO 3 -1 wt% Sb 2 O 5 - x wt% Nb 2 O 5 were prepared by solid-state reaction approach. • The sample with x = 1.0 demonstrates the optimal properties, including a giant d 33 of 498 pC/N (10.7 % higher than pure BS-PT ceramics), a high t c of 392 °C, a high depolarization temperature of 362 °C and a large remanent polarization of 52.7 μC/cm2 (55.9 % higher than pure BS-PT ceramics). • The enhanced ferroelectric and piezoelectric properties are attributed to a relaxation behavior originated from the formation of polar nanoregions and reduced concentration of oxygen vacancy. Here, novel ferroelectric ceramics of Sb/Nb co-doped 0.36BiScO 3 -0.64PbTiO 3 (BS-PT-Sb 2 O 5 - x Nb 2 O 5) of complex perovskite structure are reported with compositions near the morphotropic phase boundary (MPB) where the dominant monoclinic and tetragonal phases coexist. Excitingly, the incorporation of Sb/Nb dopants leads to a remarkable enhancement in both ferroelectric and piezoelectric properties. Notably, the sample with x = 1.0 demonstrates the optimal properties, boasting a giant piezoelectric coefficient (d 33) of 498 pC/N (10.7 % higher than pure BS-PT ceramics), a high Curie temperature (T c) of 392 °C, a high depolarization temperature of 362 °C and a large remanent polarization of 52.7 μC/cm2 (55.9 % higher than pure BS-PT ceramics). The enhanced ferroelectric and piezoelectric properties are ascribed to a relaxation behavior originating from the formation of polar nanoregions (PNRs) and reduced concentration of oxygen vacancy. The result provides an opportunity to elucidate the relationship between relaxation behavior and electrical properties, offering prospects for substantially improving the performance of piezoelectric ceramics. [Display omitted] [ABSTRACT FROM AUTHOR]

A low-temperature sintering strategy was realized for preparing 0.21Bi(Ni0.5Ti0.5)O3-0.05BiFeO3-0.74Pb(Zr0.5Ti0.5)O3 (0.21BNT-0.05BF-0.74PZT) ceramics by conventional ceramic processing by adding low melting point BiFeO3 and additional sintering aid LiBO2. Pure perovskite 0.21BNT-0.05BF-0.74PZT ceramics are prepared at relatively low sintering temperatures, and their structure presents tetragonal distortion that is affected slightly by the sintering temperature. The 1030 °C sintered samples have high densification accompanied by relatively large grains. All ceramics have excellent dielectric performance with a relatively high temperature of dielectric constant maximum, and present an apparent relaxation characteristic. A narrow sintering temperature range exists in the 0.21BNT-0.05BF-0.74PZT system, and the 1030 °C sintered 0.21BNT-0.05BF-0.74PZT ceramics exhibit overall excellent electrical performance. The high-temperature conductivity can be attributed to the oxygen vacancies’ conduction produced by the evaporation of Pb and Bi during sintering revealed by energy dispersive X-ray measurement.

The synthesis of novel Na 1/2 Er 1/2 Cu 3 Ti 4 O 12 (NECTO) ceramics using conventional solid-state methods and their characterization as well as their dielectric properties were investigated at various temperatures of sintering. SEM results revealed an increase in average grain size with sintering temperature. The sintered NECTO sample at 1080 °C exhibited good frequency stability and a higher dielectric constant (ε ′) of about 6 × 103 at 1 kHz. It is found that the sintering temperature correlates with the dielectric constant, and it agrees with the IBLC model. Additionally, the sample displayed a dielectric loss (tanδ) of less than 0.08 throughout a wide range of frequencies. Particularly, the sintered sample at 1060 °C for 10 h had a significantly low tanδ of 0.06 and exhibited a ε ′ of roughly 3.19 × 103 at 1 kHz. A significant decrease in tanδ with increased R gb was observed, suggesting that reduced grain boundary resistance could minimize the dielectric loss. Moreover, optimizing the sintering temperature enhanced the temperature stability of NECTO ceramics. [Display omitted] • Na 1/2 Er 1/2 Cu 3 Ti 4 O 12 ceramics synthesized via solid-state method. • Grain growth enhances dielectric properties. • Charge states of ions consistent across sintering temperatures. • Highest ε ′ over 6.13x10³ at 1080 °C, low tanδ of 0.06. • Correlation of heterogeneous microstructure and dielectric properties. [ABSTRACT FROM AUTHOR]

Dielectric properties of six bi-cyclohexyl phenyl compounds (3ccp-f, 3ccp-ff, 3ccp-fff, 5ccp-f, 5ccp-ff, 5ccp-fff) have been investigated. The compounds exhibit broad range of temperatures in nematic phase. Only one strong absorption process is observed in the absorption spectra; for clarity spectra only at some selected temperatures are presented. In each case relaxation frequencies are found to increase with temperature. The relaxation behavior is a result of Cole-Cole type process, the complex dielectric permittivity was fitted with the modified Cole-Cole equation to get the actual values of relaxation frequency (fc) and symmetric distribution parameter (α). [ABSTRACT FROM AUTHOR]

0. 7BiFeO3 -0. 3BaTiO3 + x% Sb2O3 (mass fraction) ceramics (BFO-BTO + xSb, x = 0. 00 ~ 0. 20) were synthesized by the conventional solid state reaction method, and the effect of Sb2O3 doping on the crystalline phase structure, dielectric, conductive, piezoelectric and ferroelectric properties of BFO-BTO ceramics was investigated, along with doping mechanism. The results indicate that Sb doping change the crystal structure from a pesodocubic lattice to a rhombohedral lattice. Sb substitution for B site increases ferroelectric relaxation, decreases dielectric loss at high temperature, and also lowers the Curie temperature. The conductive characteristics demonstrate that Sb doping changes the concentration of V×O and Fe2+, and decreases the conductivity, without changing the conductive mechanism with oxygen vacancy as the dominant carrier. BFOBTO + xSb ceramics exhibit optimum electric properties at x = 0. 05: d33 = 213 pC/ N, kp = 28. 8%, Qm = 38, Tc = 520 ℃, Pr = 24. 7 μC/ cm². [ABSTRACT FROM AUTHOR]

A series of 0.75Ba (1− x) La 2 x /3 TiO 3 -0.25Bi(Mg 0.5 Ti 0.5)O 3 (x = 0–0.2) ceramics have been synthesized by doping La 2 O 3 into 0.75BaTiO 3 -0.25Bi(Mg 0.5 Ti 0.5)O 3 (0.75BT-0.25BMT), and their structure and dielectric properties investigated. Upon characterizing the structural properties, the single-phase perovskite structure is identified for all the samples and the long-range order of 0.75BT-0.25BMT is verified to be further destroyed with the addition of La 2 O 3. Moreover, it is found that the density of 0.75BT-0.25BMT can be improved by doping with La 2 O 3 , which also promotes the grain growth. Regarding the dielectric properties, the peak shifting effect induced by La3+ improves the permittivity-temperature stability of 0.75BT-0.25BMT remarkably by strengthening its relaxation behavior. Among all the samples, 0.75Ba 0.8 La 0.4/3 TiO 3 -0.25Bi(Mg 0.5 Ti 0.5)O 3 shows the most outstanding permittivity-temperature stability with ε r = 572 ± 15% (compared with ε r at 25 °C) over the temperature range −70°C–238 °C at 1 kHz, which is notably better than that of 0.75BT-0.25BMT (−4°C–58 °C) and satisfies the specification of the X9R multilayer ceramic capacitor (MLCC). Our work provides one promising option for selecting an alternative dielectric material in terms of permittivity-temperature stability, which advances the development of the X9R MLCC. [ABSTRACT FROM AUTHOR]

In this work, we developed a novel system of isovalent Zr4+ and donor Nb5+ co-doped CaCu 3 Ti 4 O 12 (CCTO) ceramics to enhance dielectric response. The influences of Zr4+ and Nb5+ co-substituting on the colossal dielectric response and relaxation behavior of the CCTO ceramics fabricated by a conventional solid-phase synthesis method were investigated methodically. Co-doping of Zr4+ and Nb5+ ions leads to a significant reduction in grain size for the CCTO ceramics sintered at 1060 °C for 10 h. XRD and Raman results of the CaCu 3 Ti 3.8-x Zr x Nb 0.2 O 12 (CCTZNO) ceramics show a cubic perovskite structure with space group Im -3. The first principle calculation result exhibits a better thermodynamic stability of the CCTO structure co-doped with Zr4+ and Nb5+ ions than that of single-doped with Zr4+ or Nb5+ ion. Interestingly, the CCTZNO ceramics exhibit greatly improved dielectric constant (~105) at a frequency range of 102–105 Hz and at a temperature range of 20–210 °C, indicating a giant dielectric response within broader frequency and temperature ranges. The dielectric properties of CCTZNO ceramics were analyzed from the viewpoints of defect-dipole effect and internal barrier layer capacitance (IBLC) model. Accordingly, the immensely enhanced dielectric response is primarily ascribed to the complex defect dipoles associated with oxygen vacancies by co-doping Zr4+ and Nb5+ ions into CCTO structure. In addition, the obvious dielectric relaxation behavior has been found in CCTZNO ceramics, and the relaxation process in middle frequency regions is attributed to the grain boundary response confirmed by complex impedance spectroscopy and electric modulus. Image 1 • A novel type of CaCu 3 Ti 3.8-x Zr x Nb 0.2 O 12 ceramics were successfully fabricated by a solid-state reaction process. • CaCu 3 Ti 3.8-x Zr x Nb 0.2 O 12 ceramics sintered at 1060 °C for 10 h show a very small grain size of 0.86 ~ 2.05 μm. • Extremely enhanced giant dielectric response of CaCu 3 Ti 4 O 12 is achieved by co-doping Zr4+ and Nb5+ ions. • CaCu 3 Ti 3.8-x Zr x Nb 0.2 O 12 ceramics exhibit obvious dielectric relaxation behavior. [ABSTRACT FROM AUTHOR]

In the pre-forming process of uncured prepreg laminates with hot press, the compaction stress is an important parameter that affects the performance and quality of the final product. Therefore, it is necessary to explore the compaction response of the prepreg during manufacturing processes. In this study, the compression and relaxation viscoelastic behaviors of uncured prepreg laminates were investigated in different temperatures, displacements, velocities, and thicknesses. The results show that the power law model and the fractional viscoelastic model could accurately describe the compression and relaxation behaviors, respectively. The theoretical fitting curves match very well with experimental data at each condition and the R-squared value is greater than 0.95. The effect mechanism of compression and relaxation viscoelastic behaviors is analyzed and the obtained results could provide a reference for the process of hot press-forming and numerical simulation.

The relaxation behavior of two lignins (Alcell organosolv, OSL, and hydroxypropyl modified Kraft, ML) and bio-based thermoplastic polyurethane (TPU) blends have been studied by Differential scanning calorimetry (DSC), Dynamic-mechanical analysis (DMA) and Dielectric relaxation spectroscopy (DRS). The effect of blending on the glass and local relaxation processes as a function of composition, frequency, and temperature has been assessed. The dielectric spectra were resolved into dipolar relaxations as well as conductive processes for differing blend compositions. Characteristic relaxation times, activation energies and dielectric relaxation strengths of lignin/ x TPU blends were also investigated. It was found that blending suppresses the α-relaxation process of the blends compared to virgin TPU. On the other hand, while the position of the β-relaxation was not influenced by blending, a reduction of the activation energies, E a , of this process was observed in the lignin/ x TPU blends. Finally, changes are observed in the conductivity behavior of both blends, with conductivity processes more favorable for the OSL/ x TPU blends. [ABSTRACT FROM AUTHOR]

Relaxation behavior of natural fiber reinforced polymer composites exists in both solid and molten state and profoundly affects the control and optimization of processing parameters and dimensional accuracy of final products. The aim of this study was to establish an experimental estimating method to characterize relaxation behavior of polymer composite with traditional torque rheometer and investigate the effects of fiber concentration, dimension, and processing parameters on the relaxation behavior. Relaxation time of hemp fiber reinforced polypropylene composite were obtained by fitting the experimental torque data and corelated to the buckling deformation of packaging boxes manufactured by injection with the same injection parameters. The results show that all the increasing concentration of hemp fiber, higher rotor speed, and higher temperature can significantly decrease the relaxation time and result in a stable and better dimensional accuracy of injection packaging boxes. The finer fibers with the same weight concertation can bring an obvious reduction in relaxation time and buckling deformation. The proposed method for estimating relaxation behavior of polymer composite is a feasible and cost-effective way to investigate the viscoelastic properties of polymer composites close to the real processing conditions. And it can be widely used in optimization of processing parameters and performance of polymer composite products. [ABSTRACT FROM AUTHOR]

Fiber-reinforced composites are the materials of choice in numerous advanced applications in the fields such as automotive, aerospace, and marine as compared to conventional engineering materials. In this context, the influence of reinforcement architecture on the static mechanical performance of composite leaf spring was investigated. Reinforcement in the form of E-Glass chopped fibers, uni-directional (UD), bi-directional (2D) woven, and 3D orthogonal woven preforms were used to prepare composite leaf spring with identical fiber volume fraction and composite processing conditions. Composite leaf springs were analyzed for tensile properties, load-deflection behavior, strain rate sensitivity, hysteresis behavior (Damping), and relaxation behavior. Performance of 3D woven-based composite leaf spring was significantly better than chopped, UD, and 2D counterparts in terms of energy absorption, strain rate sensitivity, hysteresis damping (energy dissipation), and relaxation behavior. Overall 3D composite leaf spring shows a high potential for leaf spring application. [ABSTRACT FROM AUTHOR]

In electrified vehicle applications, understanding the battery characteristics is of great importance as it is the state-of-art principal energy source. The key battery parameters can be identified by one of the robust and nondestructive characterization techniques, such as electrochemical impedance spectroscopy (EIS). However, relaxing the battery cell before performing the EIS method is crucial for the characterization results to be standardized. In this study, the three most common and commercially available lithium-ion technologies (NMC/graphite, LFP/graphite, NCA/LTO) are investigated at 15–45 °C temperature, in the range of 20–80% state of charge (SoC) and in fresh and aged state of health (SoH) conditions. The analysis shows that the duration of the relaxation time before impedance measurement has an impact on the battery’s nonlinear behavior. A rest time of 2 h can be proposed, irrespective of battery health condition, considering neutral technology-based impedance measurement. An impedance growth in ohmic and charge transfer characteristics was found, due to aging, and the effect of rest periods was also analyzed from an electrochemical standpoint. This experimental data was fitted to develop an empirical model, which can predict the nonlinear dynamics of lithium technologies with a 4–8% relative error for longer rest time.

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A new Dy Na complex [DyIIINaI(CH 3 CO 2) 2 (DMF) 3 (H 6 C8A)]·4DMF (1 , DMF = N , N -dimethylformamide, H 8 C8A = p - tert -butylcalix[8]arene) was obtained and it was characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction analyses, PXRD and magnetic properties. In 1 , one DyIII and one NaIII were linked by two O atoms from two CH 3 CO 2 − and the two metal ions were enclosed into a H 8 C8A. The remaining coordination sites of the DyIII and NaI ions were occupied by three O atoms from three DMF coordinated molecules. The DyIII ion in 1 adopts eight coordinate with a triangular dodecahedron. Magnetic property studies indicated complex 1 show slow magnetic relaxation behavior under 1000 Oe applied dc field. Additionally, the orientation of the anisotropy axis for the DyIII in 1 was estimated by Magellan program and the anisotropic axis is aligned along Dy1-O2 bond with an angle of 12.608°. A novel DyIII-NaI complex was obtained, in which two metal ions are enclosed into a nearly planar Calix[8]arene ligand. Magnetic investigation revealed that the complex almost exhibits a pure quantum tunneling of magnetization behavior with the τQTM in the range of 0.0008–0.0018 s. Unlabelled Image • A thought that regulates the relaxation behavior of Dy(III)-based complexes in a Calix[8]arene was provided. • A new DyIII-NaI complex was reported, with two metal ions enclosed into a nearly planar Calix[8]arene • The orientation of the anisotropic axis of DyIII in 1 was estimated by Magellan. [ABSTRACT FROM AUTHOR]

Highlights • Applied an extra current excitation to reduce polarization voltage. • Analyzed parametric sensitivity of current excitation to model parameters. • Developed a method to determine the parameters for the current excitation. • Shortened the test time due to the active polarization voltage reduction. • Validated the feasibility and superiority with experiments. Abstract The correlation between state of charge (SoC) and open-circuit voltage (OCV) is a crucial characteristic parameter in many aspects of the battery management system (BMS). However, it is a challenging task to obtain the accurate SoC-OCV correlation with a high test efficiency. In this paper, an improved OCV characterization test is proposed to actively reduce the polarization voltage. Based on the third-order equivalent circuit model (ECM), two sets of current pulses are applied to accelerate the convergence of the battery terminal voltage, thus the test time is effectively shortened compared to the conventional incremental OCV characterization test. Furthermore, the parametric sensitivity of the imposed current excitation to battery model parameters is analyzed. Subsequently, the parametric determination method for the imposed current excitation is provided. Experiments are conducted on a lithium-ion polymer battery to prove the feasibility of the proposed test procedure. Comparison with the conventional OCV characterization test further demonstrated the superiority of the proposed test procedure. [ABSTRACT FROM AUTHOR]

Abstract The composite films of Poly (vinyl alcohol) (PVA) and Reduced graphene oxide (RGO) with 1 wt%, 1.5 wt% and 2 wt% loading of RGO using solution mixing have been prepared via evaporative casting technique. For this purpose, RGO has been chemically synthesized using modified Hummer's method and characterized using UV–Visible absorption, Fourier Transform Infrared (FTIR) spectroscopy and Transmission electron Microscopy (TEM). Further, the chemical interaction of PVA chains with RGO has been revealed using FTIR spectroscopy. The variation in dielectric parameter (εʹ and εʹʹ) with frequency has been studied at different temperatures (320 K–400 K) in order to epitomize the dielectric relaxation behavior in the prepared composite films. The values of εʹ and εʹʹ have been found to increase with rise in temperature and loading of RGO. The almost linear variation in ac conductivity (ϭ ac) with frequency at each studied temperature suggests the observation of universal power law in these composites. However, the slope of these curves was found to decrease with rise in temperature suggesting the Correlated Barrier Hopping (CBH) model as charge transport mechanism in these composites. The non-symmetric shape of electric modulus (M″) variation indicate the existence of non-Debye type of relaxation. The relaxation time (τ) determined from M″ variation with frequency is found to be decreased with rise in temperature. This elucidates the transition of long range to short range mobility of charge carriers with rise in temperature. Further, as an effect of increase in RGO concentration in composites, increase in τ has been found depicting their use in energy storage applications where materials with longer discharging time are required. Highlights • PVA-RGO composite films have been prepared via solution mixing evaporating technique. • FTIR spectra reveal that interaction between PVA chain and RGO layer is through H-bonding. • Temperature dependent dielectric behavior of these PVA-RGO composite films has been studied. • The dielectric relaxation process is well depicted through dielectric modulus. • Non symmetric peaks in dielectric modulus indicates non debye type relaxation process. [ABSTRACT FROM AUTHOR]

Abstract The preforming process of fiber fabrics in liquid composite molding presents remarkable viscoelastic behaviors, and gives significant effect on the overall mechanical properties of composite components. Thus, here, a unified viscoelastic model to predict the compression and relaxation viscoelastic behaviors in preforming process for the carbon fiber fabrics with binder is originally proposed. The physical meaning of each model parameter is rationally defined. Experiments for typical carbon fiber fabrics are conducted to validate the proposed model. The theoretical curves match well with the experimental measurements, and the correlation factors for different contents of binder are larger than 0.9, demonstrating the proposed model can well capture the stress evolution. Besides, we clearly reveal that in compression, the elastic stress is the main stress, and the viscoelastic stress is very small. Elastic modulus increases non-linearly and rapidly with the loading time. As the content of the binder increases, the elastic modulus gradually decreases due to the binder layer. For the relaxation stage, the total stress relaxation ratio is enlarged, while the elastic stress relaxation ratio is reduced, indicating the addition of binder can significantly improve the relaxation ability of the fabrics. The relationship of delay time τ : τ 0 w t < τ 4 w t < τ 8 w t < τ 12 w t is experimentally confirmed, and is consistent with the theoretical prediction, suggesting the increasing binder enlarges the relaxation time. The proposed theoretical model here provides an approach to understand the viscoelastic responses in preforming process. [ABSTRACT FROM AUTHOR]

Malaria, COVID-19, and other infectious diseases have been prevalent worldwide. The development of simpler, low cost and more sensitive isothermal genetic diagnostic methods will enable it to contribute to infectious disease measures. In this study, the improvement of the sensor will be aimed at detecting infectious diseases rapidly by combining the isothermal genetic diagnostic methods and the piezoelectric biosensor. The device of the piezoelectric biosensor using quartz is big and quartz is costly. In this study, the piezoelectric polymer (PVDF) biosensor was proposed since it can detect the biopolymer at a low frequency, and is not costly. The issues for the β-PVDF signal transducer sensor were extracted based on the investigation of the output properties of the sensor. To enhance the sensibility and temperature characteristics of β-PVDF issues, barium titanate (BaTiO 3 , BT)/PVDF composites were applied to the piezo biosensor. The relaxation behavior was shifted towards the low frequency due to the immobilization of the avidin on the piezoelectric sensor. Hence, the detection of avidin immobilization was feasible by the relaxation process of the β-PVDF sensor. The dipole and interface polarizations were created in the BT/PVDF composite due to the formation of the BT/PVDF/BT heterointerface in the self-assembly BT aggregates. The relaxation behavior of the BT/PVDF composite signal transducer sensor from room temperature to 338 K was verified. The sensibility and the temperature characteristics were improved. It is expected to use the biosensor with the BT/PVDF piezoelectric composite material for general biopolymer detection. [Display omitted] • It was possible to detect immobilized avidin using the relaxation process of the β-PVDF signal transducer biosensor at a low frequency. • The sensibility and temperature characteristics of the BaTiO 3 /PVDF composite biosensor were enhanced due to the self-assembly BaTiO 3 aggregates. [ABSTRACT FROM AUTHOR]

It is a promising method to obtain desirable damping materials by introducing dangling chains used as additional relaxation components. Regrettably, the strict condition of introducing dangling chains limits its application to saturated polymer or low unsaturated degree polymer, for example butyl rubber (IIR). Hence, we propose a simple yet effective method to obtain desirable IIR based damping composites by blending with miscible polyisobutylene (PIB) oligomers as additional relaxation components in this study. As expected, the damping property of IIR is easily controlled by tuning the chain length of PIB oligomers. The effects of PIB oligomers with different chain length on the molecular motions and damping mechanism of IIR were characterized by dynamical mechanical analysis and 2D correlation dynamic mechanical spectroscopy (2DC-DMS). The damping improvement of IIR was ascribed to the additional relaxation generated by introducing PIB oligomers and the movement of sub-Rouse modes and Rouse modes. It seems a universal method to enhance damping property by using miscible polymer oligomers as additional relaxation component. Furthermore, this method may give some inspirations for preparing polymer matrix specially used for damping composites. [ABSTRACT FROM AUTHOR]

Dielectric, ferroelectric and ferromagnetic properties of (1-x)Ba Ca0.01Zr0.02Ti0.98O3 (BCZT)-xBiFeO3 (BFO) (x = 0.00, 0.05, 0.10, 0.15) ceramics have been investigated. X-ray diffraction and Raman data documented the tetragonal-to-pseudocubic phase transformation with increasing the concentration of BFO and the formation of BFO when the composition with x = 0.15 was sintered at 1100°C. Correspondingly, the samples showed a high temperature at permittivity maxima along with a weak frequency dispersion feature. Surprisingly, the composition with x = 0.15 exhibited weak ferroelectric and good magnetic properties with 2Mr~0.60 emu/g, 2Hc ~0.36 kOe. [ABSTRACT FROM AUTHOR]

The linear and nonlinear magnetizations of LaTbMnO at low temperatures were reported in detail. The temperature dependence of magnetization shows peaks at 50, 100 and 150 K, respectively. When LaMnO is Tb-doped, its magnetic structure exhibits a canted antiparallel spin order. This is different from classical antiferromagnetic (AFM) in which the relaxation behavior takes place at about 150 K. At 50 K, Tb-doped LaMnO exhibits canonical spin glass behavior, arising from the competition of exchange and super-exchange between spins. The peak at 100 K shows neither spin glass behavior nor canted AFM behavior. Its peak value increases with frequency increasing, and the transition temperature of the peak shifts to higher temperatures with frequency increasing. The study of aging behavior at 100 K shows a periodical variable metastability, which is ascribed to the competition between ferromagnetic (FM)-, AFM- and sinusoidal-order interactions. This work should shed a light on understanding the complex magnetic structure of the perovskite oxides. [ABSTRACT FROM AUTHOR]

The temperature-deformation-time dependences of the physical and mechanical characteristics of polymer glass based on polymethylmethacrylate necessary for the strength calculation of glazing were experimentally determined. The calculation of the residual and temperature stresses in a glazing element made of VOS-2 heat-resistant copolymer glass was performed. Ways to decrease the stresses that occur under operation by developing materials with decreased values of the elastic modulus and the temperature coefficient of linear expansion were proposed. The work was performed within complex research trend 15.4 [1] Optical Materials and Glazing Materials ('Strategic Trend of Development of Materials and Technologies for Their Processing for the Period to 2030'). [ABSTRACT FROM AUTHOR]

The relaxation behavior of a series of solvent free polyurethane model networks with variable cross-link density prepared based on different commercial diols and a diisocyanate containing component are studied by differential scanning calorimetry (DSC), dynamic-mechanical analysis (DMA) and dielectric relaxation spectroscopy (DRS). A systematic decrease of the calorimetric glass temperature T g as well as of the softening temperatures T α DMA and T α DRS from relaxation methods is observed with increasing length of the diol sequences between neighbored diisocyanate units acting as cross-linker. This trend is explained based on an internal plasticization of the polymeric network by long, highly mobile diol units containing an increasing fraction of methylene sequences. Cold crystallization effects are only indicated for the longest diol sequence under investigation. This is understood as a consequence of a large fraction of methylene sequences in combination with weaker geometrical constraints. Two secondary relaxations, β and γ , are observed in the glassy state for all amorphous samples at low temperatures by dielectric spectroscopy indicating the existence of localized motions in the polyurethane networks. Below T g these relaxation processes are practically unaffected by changes in the length of the diol units and the softening behavior of the polymeric model networks. Interrelations between secondary β relaxation and cooperative α dynamics are indicated. An onset of the dielectric α relaxation strength Δε α is observed for all amorphous polyurethane networks. A linear extrapolation of Δε α vs. 1/T gives onset temperatures T on which are in good agreement with αβ crossover temperatures T αβ being the temperature where the difference between α and β relaxation times τ α − τ β approaches a minimum. This finding supports an onset of the cooperative α motions in the αβ crossover region as reported in the previous literature for many other glass forming materials. [ABSTRACT FROM AUTHOR]