Loss Tangent Values Research Articles

The Electrical Conductivity Mechanisms and Dielectric Properties of Multiphase Co-synthesized CuV2O6–MnV2O6

AbstractMany research studies on photodegradation, energy storage applications, and biosensing have focused on single and mixed Cu and Mn divanadates (MV2O6, M2+ = Cu2+ and/or Mn2+). In this work, MV2O6 was synthesized, and its electrical conductivity and dielectric properties were studied. The electrical and dielectric properties were investigated in a frequency range of 0.1-300 kHz and a temperature range of 298 K to 573 K. The results indicate that the DC conductivity, AC conductivity, dielectric constant, dielectric loss factor, and loss tangent of the investigated materials increase with temperature, which support the contribution of grains and grain boundaries to the electrical properties. The materials exhibit non-Debye type relaxation, as indicated by the progression of the relaxation frequency. As frequency increases, the activation energy of AC conduction decreases, indicating that hopping conduction is the dominant mechanism. In all samples, the DC conduction activation energy is higher than the AC conduction activation energy. The circuit model was used to estimate the relaxation times. The results revealed remarkable dielectric characteristics, notably higher dielectric loss tangent values at frequencies below 1 kHz. Consequently, these materials can be used as electromagnetic attenuation absorbers. Graphical Abstract

Impact of preacidification on the functionality and insoluble calcium levels of Low-Moisture Part-Skim Mozzarella made from high-casein milk

The use of low-concentration factor ultrafiltered (LCF-UF) milk for cheesemaking has become popular in recent years. Research on using LCF-UF milk to make low-moisture part-skim (LMPS) Mozzarella manufacture is limited due to concerns about the negative impact of the higher casein content on functional properties, such as melt and stretch. Pre-acidification (PA) (reflects acid added to milk before the addition of the starter culture) has been used in low-fat and nonfat Mozzarella cheeses to lower calcium levels and improve their texture and melting properties. We explored the use of PA to reduce the insoluble calcium content of cheese (calcium that is a crosslinking material for the casein proteins) and its impact on the functionality of LMPS Mozzarella made from high casein (4.2%) milk. Seven vats of LMPS Mozzarella, with a control (no PA), 2 pH values for PA (6.40 and 6.00) and 3 different acidification methods (use of acetic, citric, or carbonic acid from carbon dioxide) were evaluated for their impact on solubilization of colloidal calcium phosphate during LMPS manufacture. Composition, proteolysis, microstructural and functional changes in the LMPS cheeses were monitored during 90 d of refrigerated storage. All cheeses had similar composition except for the cheese made with milk PA with carbonic acid, which had a lower fat-in-dry matter probably due to foaming observed in this sample during the gas sparging. The cheese made with milk PA with citric acid to pH 6.00 had the lowest amount of total and insoluble calcium compared with other cheeses at all steps during cheese manufacture and storage, likely due to the calcium chelating ability of citric acid. The cheese that was made with milk PA with citric acid to pH 6.40 had a trend of slightly lower (not significant) total and insoluble calcium during cheese manufacture compared with other cheeses that were made with milk PA to pH 6.40. The pH value in all the cheeses remained similar throughout 90 d of storage, whereas the cheese that was made with milk PA with citric acid to pH 6.00 had the lowest pH values during storage. Treatment significantly (P < 0.05) impacted instrumental hardness, the maximum loss tangent during heating, the melting temperature and the storage modulus values measured at 70°C. Proteolysis was not impacted by treatment suggesting that typical aging should occur. Cheese that was PA with citric acid to pH 6.00 initially had lower maximum loss tangent values and higher hardness, possibly due to the lower pH value of this cheese. The performance of cheeses on pizza was assessed using Sensory Spectrum® method and quantitative descriptive analysis. The PA of cheese milk with citric acid helped to reduce the insoluble Ca level and at 30 and 90 d of storage, these cheeses had lower first chew hardness, lower chewiness, and lower strand thickness values compared with other cheeses. The use of PA could help improve the functionality of LMPS Mozzarella made from milk high in casein with citric acid being the most efficient in dissolving the insoluble calcium from casein.

Exploring the dielectric loss of Martian regolith in the frequency domain using Zhurong radar data

Martian regolith is one of the primary science objectives of Mars exploration missions. The Rover Penetrating Radar carried by Zhurong rover allows for high-resolution subsurface imaging and in-situ measurements of Martian regolith dielectric properties, which are crucial to advance our understanding of Martian geology and hydrological evolution. While earlier studies have derived dielectric constants for the shallow subsurface, further characterization of subsurface materials requires the determination of attenuation properties. In this study, we applied the centroid-frequency shift method to explore the attenuation property of the Martian regolith in the frequency domain. Lateral attenuation variation was analyzed in detail by integrating subsurface radargram and navigation terrain images. The results show that, within a depth of ∼4 m, the attenuation of radar signal for Zhurong subsurface material is equal to a loss tangent of 0.0079, with a standard deviation of 0.001. Based on the loss tangent value, dielectric permittivity and ground characterization, we preclude the possibility that the regolith is predominantly igneous materials. The lateral variation of the attenuation property could likely be attributed to changes in the proportion of duricrusts, which are heterogeneously distributed along the rover traverse. Our findings offer valuable information for understanding the Martian regolith and its evolution, serving as a important reference for future Mars sample return missions.

Unveiling the structural, optical, electrical, and ferromagnetic properties of Ca2+ doped mixed spinel ferrites for switching field high-frequency device applications

In this paper, the calcium-doped nickel-zinc nano-ferrites [Ni0.5Zn0.5CaxFe2-xO4; x = 0.00, 0.10, and 0.30] were prepared using the chemical co-precipitation synthesis route and studied for switching field high-frequency device applications. The structural analysis has been completed by analyzing X-ray diffraction (XRD) patterns. The Rietveld refined XRD patterns confirmed the formation of cubic spinel structure of Ca2+ substituted nickel-zinc ferrites. The detection of metal-oxygen bonds present at A and B lattice sites has been unveiled by Fourier transform infrared (FTIR) spectroscopy. The morphological studies obtained through FESEM (Field emission scanning electron microscopy) analysis showed a reduction in the particle size from 70 nm to 53 nm when the concentration of Ca2+ ions in Ni-Zn ferrites was increased. Energy dispersive spectra (EDS) confirmed the presence of elements present in the prepared composition. The structure of a cubic spinel-shaped unit cell has been verified from three active prominent Raman modes (A1g, A2g, and T2g). Diffuse-reflectance spectroscopy (DRS) exhibits the increment in the bandgap values (from 1.55 eV to 1.63 eV) which helps fabricate highly efficient photovoltaic devices. The ferroelectric measurements yielded a rise in polarization values from 1.461 μC/cm2 to 18.228 μC/cm2 for 10 % Ca2+ ion substitution. The tangent loss values declined from 24 to 3 in Ni-Zn ferrites upon substituting Ca2+ ions. The Vibrating sample Magnetometer (VSM) technique found the increment in the saturation magnetization (Ms) values from 34.724 emu/g to 54.662 emu/g on substituting up to 30 % Ca2+ ions in Ni-Zn ferrites. These obtained results support the material in switching field distribution for high-frequency applications. The results exhibited that the prepared samples can be applicable for switching devices, filters, and microwave absorption devices. The results revealed the maximum frequency between 12 and 18 GHz which is useful for Ku band absorption.

Improved Temperature Sensitivity of the Microwave and Radiofrequency Properties of the Ceramic Matrix Li2LaNbTiO7

This study presents experimental investigations and numerical simulations of the microwave (MW) dielectric and evaluation of the electrical properties in the radiofrequency region (RF). The ceramic matrix Li2LaNbTiO7 (LLNT) is obtained through the solid‐state reaction method. The synthesis of LLNT is confirmed using the X‐ray diffraction technique. In the complex impedance spectroscopy study, permittivity (ε′r) and loss tangent (tanδ) values are analyzed at room temperature. The study of the conductivity spectrum at different temperatures demonstrates that the conduction process is thermally activated, presenting a value of 0.65 eV for the activation energy. Numerical simulations are employed to evaluate the behavior of the LLNT matrix as dielectric resonator antennas (DRA), whereas this ceramics demonstrated a reflection coefficient of less than −10 dB at the resonant frequency, achieving a gain of 3.71 dBi, a bandwidth of 144 MHz and a radiation efficiency greater than 97%. The results indicate that the LLNT matrix would be a promising candidate for RF and MW operating devices.

Electromagnetic Characterization of EAC-1A and JSC-2A Lunar Regolith Simulants.

The development of devices for the in situ resource utilization (ISRU) of lunar surface powder (regolith) by means of microwaves needs regolith simulants with electromagnetic properties similar to the lunar regolith. This document deals with the measurement of complex permittivity and dielectric loss tangent of the aforementioned simulants at ambient temperature from 400 MHz to 20 GHz, performing measurements using two lunar dust simulants, EAC-1A and JSC-2A, resulting, on the one hand, in permittivity values of ε'=-0.0432f+4.0397 for the EAC-1A lunar dust simulant and ε'=-0.0432f+4.0397 for the JSC-2A simulant, and on the other hand, in loss tangent values of tanδe=-0.0015f+0.0659 for the EAC-1A powder and tanδe=-0.0039f+0.1429 for the JSC-2A powder. In addition, further studies are carried out taking into account the humidity of the samples and their densities at room temperature. The obtained results are applicable for comparing the measured values of EAC-1A and JSC-2A between them and with other previously measured simulants and real samples. The measurements are carried out by applying two different nonresonant techniques: Open-Ended Coaxial Probe (OECP) and transmission line. For this purpose, the DAK and EpsiMu commercial kits are used, respectively.

Tailoring Bi1−x−yBaxFeyFeO3 for desired properties: insights into structural, dielectric, and magnetic responses

In present study, samples of Bi1−x−yBaxFeyFeO3 have been synthesized, where x = 0.15, y = 0; x = 0.10, y = 0.10; and x = 0.15, y = 0.10 utilizing a swift two-stage solid-state reaction method. X-ray diffraction (XRD) data has been Rietveld refined to evaluate the structural parameters. Micro-strain is also calculated using Williamson Hall method. Temperature (300 K to 660 K) dependent measurements of the dielectric constant have been conducted at various frequencies (100 kHz, 500 kHz, and 1000 kHz). The dielectric constant (ε′) rises as the temperature increases. Two dielectric anomalies around 450 K and 613 K have been noticed in ε′ versus T curves for all the samples which might be related with defect dipoles and the magnetic transition respectively. Further, an insignificant value of loss tangent (0.2) specifically at around 300 K is a signal of small leakage current in the samples. The source of high dielectric constant is discussed by considering the structural distortions in the ceramics. A clear hysteresis loop has been observed for all the samples which is a sign of collapse of antiferromagnetic nature of BiFeO3. Further, in case of co-doped samples, almost a saturation in magnetization with magnetization value 5.9718 emu g−1 has been noticed in hysteresis curve indicating a major contribution of ferromagnetic interaction. Enhancement in the net magnetization is briefly discussed by considering the ferromagnetic type direct interaction among Fe3+ ions and suppressing the anti-ferromagnetic type super exchange interaction.

Lanthanum Substituted Mg-Zn Ferrite Nanostructures: A Comprehensive Study of Cation Distribution, Structural, Morphological, Optical, Magnetic, Dielectric, and Electromagnetic Traits

The sol-gel auto-combustion (SC) procedure was utilised to fabricate lanthanum-doped Mg-Zn nanostructures with the chemical composition, Mg0.6Zn0.4LaxFe2-xO4, (x = 0, 0.05, 0.10). X-ray diffraction showed nanocrystalline and single-phase of Mg-Zn nanostructures. The morphological traits showed formation of irregular and aggregated grains. Fourier transform infrared spectroscopy detected the formation of two characteristic band positions that fall within the range of 400 to 600 cm−1 and may occur because of stretching vibration within metal-oxygen (M-O) cations located at interstitial positions. From the M-H loops, the excellent values of magnetic factors, such as the saturation magnetization (Ms), rentivity (Mr), and coercivity (Hc) ranging from 35.30 to 44.79 emu g−1, 1.40 to 3.75 emu g−1, and 11.56 to 41.42 Oe were obtained. The loss tangent (tan δ) was observed to be miniscule for all of the samples due to which they can be useful for electronic applications. However, the initial values of the real permeability ( μ′ ) was high and it decreases until 4 GHz, after which it acquires a constant value for rest of frequency range. However, observed low values of the magnetic loss tangent (tan δ μ ) were due to the large grain size and the high densification of the samples.

Ca doped Y2/3Cu3Ti4O12: Structure and dielectric properties

In this study, we systematically examined the structure and dielectric properties of Y2/3-xCa3x/2Cu3Ti4O12 (x = 0.0, 0.05, 0.10, 0.15, and 0.20). X-ray diffraction (XRD) analysis revealed that the structure of all ceramics conformed to the CaCu3Ti4O12 ceramics database, specifically with JCPDS No. 75–2188, and no impurity phases were detected. The conducted experiments revealed a notable rise in the dielectric constant at elevated concentrations of Ca doping, ranging from 104 to 105. Conversely, the loss tangent values, lower than those of Y2/3Cu3Ti4O12, exhibited a decrease from 0.533 to 0.333 as x increased from 0 to 0.20. Synchrotron radiation, based on X-ray photoelectron spectroscopy, was employed to investigate the valence states of Ti and Cu ions. This observation is directly linked to the presence of oxygen vacancies within the lattice. Impedance spectroscopy analysis unveiled two distinct electrical states within the Ca-doped Y2/3Cu3Ti4O12 system. The first part corresponds to the semiconductive nature exhibited by the grain, while the subsequent part pertains to the insulative characteristics observed at the grain boundary. The remarkable dielectric permittivity observed in Ca-doped Y2/3Cu3Ti4O12 system ceramics can be attributed to the existence of a heterogeneous microstructure comprising semiconducting grains and insulating grain boundaries. The presence of Cu+ and Ti3+ ions could potentially account for the semiconductive state observed within the grains of Y2/3Cu3Ti4O12 ceramics.

Comparison of 5G‐IoT antenna performance by using four distinct dielectric materials to verify their efficiencies

SummaryThe characterization of four different materials, Taconic (D1), FR4 (D2), Lab material (D3), and Created material (D4) using the ring resonator technique, is presented in this study along with a comparison of antenna performance using standard and measured dielectric constant ( ) and loss tangent ( ) values. This article discussed the comparison of antenna performances on four distinct dielectric materials to verify their efficiencies. Standard values of for the reported materials are 2.20, 4.40, 2.33, and 10.45 for D1, D2, D3, and D4, respectively, with corresponding values of 0.0009, 0.02, 0.0012, and 0.00032. The and for the materials D1, D2, D3, and D4 are calculated as 2.10, 4.56, 2.51, and 9.89 and 0.00094, 0.01927, 0.0013, and 0.0003025, respectively, using a ring resonator. The materials are utilized as the substrate for a printed single layer Y‐Shape 5G‐IoT antenna in order to validate the measured results. According to the findings of this study, the measurement of using the resonator approach exhibited errors of 4.54%, 3.63%, 7.82%, and 5.33%, respectively, while the has errors of 04.44%, 03.65%, 08.33%, and 5.47% for materials D1, D2, D3, and D4, respectively. The outcomes of this work include the numerical calculation of the and of four materials and the validation of the measured values using a Y‐Shape 5G‐IoT antenna in the millimeter‐wave 5G frequency bands. Additionally, the values calculated mathematically are compared with the values obtained from the conventional ring resonator.

Water absorption in artificial composites: Curse or blessing?

ObjectivesThis study evaluated the impact of mutable water uptake on the durability of mechanical properties and the long-term reliability of artificial composites. MethodsThree resin-based CAD/CAM restorative materials (CRMs) were investigated in three-point bending tests to calculate flexural strength (FS), modulus of elasticity (ME), modulus of resilience (MR), modulus of toughness (MT), and elastic recovery (ER). All specimens (n = 180) were stored under the same conditions and tested in four subsets (n = 15 per material) that were respectively withdrawn after repeated thermocycling (5000 cycles; 5–55 °C, H2O) and repetitive drying (7 d; 37 °C, air). For every specimen, weight differences were determined per storage condition. Likewise, loss tangent data were separately recorded via dynamic mechanical analysis to reliably assess damping characteristics. ResultsRepeated thermocycling always induced weight increase and a concurrent significant loss in all mechanical properties except for MT and ER of a polymethylmethacrylate-based CRM. Drying consistently provoked weight loss and raised mechanical properties to initial values. Weight increase, however, enhanced loss tangent values and accordingly distinct damping characteristics, whereas weight decrease markedly lowered damping properties. SignificanceWater uptake repeatedly induced a decrease in common mechanical properties but concurrently increased damping behavior. Invertible equilibrium processes were found with no evidence for permanent material degradation.

Microstructural and dielectric properties of civil construction ceramic waste sintered at various temperatures

This study investigates the dielectric properties of ceramic waste derived from roof tiles and bricks commonly used in civil construction. The materials were analyzed by grinding them into a fine powder, followed by producing of cylindrical samples through uniaxial pressing on a steel matrix. The samples were sintered at temperatures of 1000 °C, 1050 °C, and 1100 °C to analyze the effect of temperature on the electrical characteristics of the ceramics. XRD and SEM analyses were performed to evaluate microstructural parameters and coalescence behavior. The dielectric characterization aimed to obtain the real relative electrical permittivity with average values of 2.85, 3.56, and 3.65, correlated with apparent porosity levels of 30.74 %, 20.54 %, and 9.11 %, and the loss tangent of 7.5 × 10−5, 3.9 × 10−5, and 12 × 10−5, respectively. The loss tangent values are lower than those obtained in commercial dielectrics from 1 to 6 GHz frequency range. The dielectric characteristics of samples manufactured from ceramic waste from bricks and tiles can serve as sustainable alternatives to produce dielectric resonator antennas (DRA), applicable to fifth-generation wireless communication devices in the sub-6GHz band.

Influence of Ni2+ ions on structural, spectral and dielectric properties of Sr–Co spinel ferrites synthesized by sol-gel auto-combustion route

Nickel substituted Sr–Co nano spinel ferrites with composition Sr0.5-xNixCo0.5Fe2O4 (0.0, 0.1, 0.2, and 0.3) were prepared with the help of a sol-gel auto combustion route. The prepared materials were sintered at 800 for four and a half hours. Analysis of XRD confirmed that the material is composed of a cubic spinel structure with a single phase, and its space group is Fd-3m. Rietveld refinement of X-ray diffraction data was done for all prepared compositions using FULLPROF software. As the composition under study contains more nickel than lattice constant, crystalline size, X-ray density, and bulk density decrease. The dielectric properties were observed about frequency. The dielectric properties revealed that dielectric loss, dielectric constant, and ac conductivity decrease with increasing the Ni2+ content. The activation energy (ΔE) was calculated from the slope of Arrhenius plots. The ΔE found in the range of 0.580–0.096 eV. The analysis of XPS was carried out to examine the elemental state of annealed samples. The prepared material is suitable for employment in applications involving high frequencies because the Ni-doped Sr–Co ferrites with the greatest Ni2+ concentration have the lowest dielectric loss, dielectric constant, and tangent loss value.

Compact high-Q Ka-band sapphire distributed Bragg resonator

In a class of high quality (Q-) factor dielectric resonators with low radiative losses, including popular whispering-gallery mode (WGM) resonators with high azimuthal mode numbers, due to high confinement of modal field in dielectric, the Q-factor is limited by the value of inverse dielectric loss tangent of dielectric material. Metal enclosures necessary for device integration only marginally affect the Q-factor while eliminating the residual radiative loss and allowing the optimization of input and output coupling. While very high Q-factors ∼200000 are available in sapphire WGM resonators in X-band, at millimeter wave frequencies increasing dielectric loss limits the Q-factor to much smaller values, e.g. ∼50000 and ∼25000 for quasi-TE and quasi-TM modes, correspondingly, at 36 GHz. The use of distributed Bragg reflection (DBR) principle allows to push modal energy outside dielectric while also isolating it from Joule losses in metallic enclosure walls. Very high Q∼600000&amp;gt;tgδ has been demonstrated in X-band [C. A. Flory and R. C. Taber, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 44, 486–495 (1997).] at the expense of impractically large dimensions. In this work, we report on the assembly and testing of a compact Ka-band sapphire distributed Bragg reflector cavity characterized with Q-factor seven times larger than one predicted by the material’s dielectric loss at the frequency of interest. An intrinsic Q-factor of ∼200000 is demonstrated at 36 GHz for the lowest order TM-mode of a sapphire DBR. The resonator has 50 cm3 volume, smaller than previously demonstrated DBRs.

High aspect ratio Na–Co-oxide ceramic filler composites with novel electrical and dielectric properties

Polymer composites with high aspect ratio Na–Co oxide ceramic filler – polymer matrix was investigated in this study. They demonstrate high dielectric permittivity, low dielectric loss tangent values which is useful for capacitive field grading and reversible voltage dependent electrical conductivity properties under an applied electric field which can be utilized for resistive field grading. These unique properties are useful for electrical stress control applications in power components. This study employs novel ceramic platelets as the varistor filler component in a polymer composite form, introducing a new class of materials to the world of electrical stress control technology. By minimizing the amount of varistor filler material required to very low levels (15 wt%), it is possible to develop lightweight non-linear dielectric composites that not only exhibit improved electrical characteristics but also make processing easier and open up new design space for making various components for electrical power applications. By utilizing novel NaxCoO2 (x < 1) ceramic fillers in composite form, we aim to contribute to the development of innovative nonlinear dielectric composites that can enhance the performance and processibility of various power system components under various working environments.

Improvement in the dielectric, magnetic, ferroelectric, and magnetoelectric coupling attributes of BaTiO3/CoNb0.02Fe1.98O4 composite systems

The search for new materials and compositions, in which the phenomena of ferrimagnetism and ferroelectricity are closely coupled, is of great technological interest. In the present study, composite systems of (BaTiO3)(100-x)%/(CoNb0·02Fe1·98O4)x% where x = 0, 2, 5, 10, 20, and 100% were produced. Initially, BaTiO3 (BTO) was made by sol-gel combustion approach and CoFe1·98Nb0·02O4 (CoFeNbO) was made by hydrothermal method. Both compounds were then combined via solid-state reaction route to form the composite systems. According to X-ray diffraction, the pristine BTO and CoNbFeO display tetragonal and cubic structures, respectively, and all composite systems consisted of the cubic phase for BTO and spinel phase for CoNbFeO. Scanning electron microscopy showed a decrease in grain size (from 0.552 μm to 0.194 μm) and porosity (from 18.65% to 4.57%) as the CoNbFeO content increases from x = 0 to x = 20%, respectively. The influence of magnetic CoNbFeO content on the magnetic, ferroelectric, magnetoelectric coefficient, electric, and dielectric properties of composite systems has been investigated. The ferromagnetic and ferroelectric natures of diverse composite systems are reflected via the registered M-H and P-E loops at ambient temperature. A steady increase in magnetic parameters such as saturation magnetization and remanent magnetization is observed as the spinel ferrite CoNbFeO content increases. Similarly, the values of the electric coercivity increased from 1.65 kV/cm for x = 0% to 3.99 kV/cm for x = 20%. The frequency-dependent dielectric and electrical measurements were also investigated at various temperatures. By raising the measurement temperature, the dielectric polarization was found to increase for composite systems with x > 2%. Interestingly, the tangent loss was reduced for different composite systems in comparison to pristine BTO and CoNbFeO materials. The lowest tangent loss values were noticed for x = 5% composite system. All composite systems revealed good magnetoelectric coupling with coupling coefficient magnitudes up to a maximum value of ∼22.5 mV/cm.Oe, indicating that they can be potential candidates for use in advanced multifunctional electric devices.

The effect of physical compatibilization and dynamic vulcanization on the properties of thermoplastic vulcanizates derived from polypropylene and natural rubber blends

This interesting study investigated the effect of Maleic Anhydride-grafted-Polypropylene/Epoxidized Natural Rubber (PP-g-MA/ENR) as a compatibilizing agent (CA) on the properties of a 30/70 Polypropylene/Natural Rubber PP/NR blends. The effect of dynamic vulcanization with sulfur-donors (i.e.: Tetramethyl thiuram disulfide (TMTD) and 4,4 Dithiodimorpholine (DTDM)) which were used as vulcanizing agents was also reported. Several formulations of TPVs with different concentrations of CA (from 5 to 15 phr) were prepared by mixing in the molten state using a Haake Rheocord 90. The structural analysis of dual compatibilizer was examined by FTIR spectroscopy. The rheological behavior was examined using Haake Rheocord 90. The mechanical properties were determined by the tensile measurements. The dynamic mechanical thermal properties were investigated by DMA. A morphological examination was conducted using SEM Microscopy, respectively. FTIR analysis confirmed reactions between the MA group in PP-g-MA and the epoxy groups in ENR, resulting in ENR-grafted PP with an ester and acid-based linkage. The Haake plastograms revealed a proportional increase in the final mixing torque value with the increasing content of CA. The mechanical results exhibited higher values in terms of tensile strength and Young’s modulus for the TPVs containing CA compared to un-compatibilized ones. The compatibilized TPV blends exhibited a noteworthy increase in storage modulus and a notable decrease in loss tangent values with the CA concentration increased. Furthermore, the TPVs show two distinct-phase morphologies. That is, the TPV with CA showed the presence of smaller vulcanized rubber particles dispersed within the PP matrix, a phenomenon that becomes more pronounced with higher CA contents.

A Comprehensive Study of Structural, Thermal, and Dielectric Properties of Melt-Processed Polypropylene/Ni0.9Zn0.1Fe2O4 Nanocomposites

This article explores the processing of structural, thermal, and dielectric properties of polypropylene (PP) polymer nanocomposites modified with Ni0.9Zn0.1Fe2O4. The PP/Ni0.9Zn0.1Fe2O4 nanocomposites are manufactured by the melt-processing method using a Brabender Polyspeed B. The XRD and FTIR structural investigations assure good incorporation of Ni0.9Zn0.1Fe2O4 into the PP matrix. It should be noted that adding Ni0.9Zn0.1Fe2O4 NPs to the PP polymer matrix enhances the polymer’s thermal stability. Utilizing the Coats–Redfern model, kinetic thermodynamic parameters such as activation energy (Ea), enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG*) are deduced from TGA data. The dielectric results showed an increase in ε′ with the introduction of nanoparticles into the PP matrix. As the content of Ni0.9Zn0.1Fe2O4 NPs in these nanocomposite films increases, the loss tangent values decrease at higher frequencies while increasing at lower frequencies. The estimated εs and ε∞ of PP nanocomposites using Cole–Cole plots reveal an improvement when NPs are added to PP. We believe that the proposed work suggests a relevant step towards the practical application of PP/Ni0.9Zn0.1Fe2O4 nanocomposites.

Simultaneous Formation of Polyhydroxyurethanes and Multicomponent Semi-IPN Hydrogels.

This study introduces an efficient strategy for synthesizing polyhydroxyurethane-based multicomponent hydrogels with enhanced rheological properties. In a single-step process, 3D materials composed of Polymer 1 (PHU) and Polymer 2 (PVA or gelatin) were produced. Polymer 1, a crosslinked polyhydroxyurethane (PHU), grew within a colloidal solution of Polymer 2, forming an interconnected network. The synthesis of Polymer 1 utilized a Non-Isocyanate Polyurethane (NIPU) methodology based on the aminolysis of bis(cyclic carbonate) (bisCC) monomers derived from 1-thioglycerol and 1,2-dithioglycerol (monomers A and E, respectively). This method, applied for the first time in Semi-Interpenetrating Network (SIPN) formation, demonstrated exceptional orthogonality since the functional groups in Polymer 2 do not interfere with Polymer 1 formation. Optimizing PHU formation involved a 20-trial methodology, identifying influential variables such as polymer concentration, temperature, solvent (an aprotic and a protic solvent), and the organo-catalyst used [a thiourea derivative (TU) and 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU)]. The highest molecular weights were achieved under near-bulk polymerization conditions using TU-protic and DBU-aprotic as catalyst-solvent combinations. Monomer E-based PHU exhibited higher Mw¯ than monomer A-based PHU (34.1 kDa and 16.4 kDa, respectively). Applying the enhanced methodology to prepare 10 multicomponent hydrogels using PVA or gelatin as the polymer scaffold revealed superior rheological properties in PVA-based hydrogels, exhibiting solid-like gel behavior. Incorporating monomer E enhanced mechanical properties and elasticity (with loss tangent values of 0.09 and 0.14). SEM images unveiled distinct microstructures, including a sponge-like pattern in certain PVA-based hydrogels when monomer A was chosen, indicating the formation of highly superporous interpenetrated materials. In summary, this innovative approach presents a versatile methodology for obtaining advanced hydrogel-based systems with potential applications in various biomedical fields.

A coupled electromagnetic and heat transfer model for casket designing for efficient microwave heating: An insight from theoretical analysis, Multiphysics simulation, and experimental investigations

Microwave heating is extensively used in several industries due to its advantageous capabilities such as volumetric heating, reduced processing time and less energy consumption as compared to conventional heating. Refractory casket insulation is primarily used in microwave heating systems for the purposes of insulation and effective microwave transmission. This investigation aims to provide knowledge and insights for selecting suitable high-temperature refractory insulating casket materials, particularly focusing on three different types: dense alumina, dense alumina-silica, and porous alumina-silica casket. The investigation involves evaluating the microwave transmission efficiency (PTC) and insulation resistance capability of the three casket materials concerning their dielectric and thermophysical properties at varying temperatures. Among three casket materials, porous alumina-silica casket showed a significantly lower values of dielectric constant (1.50 to 1.68), loss tangent (0.000086–0.00318) and thermal conductivity (0.26 W/m·K to 0.50 W/m·K) over the entire temperature range. Consequently, the porous alumina-silica casket exhibited superior insulation and PTC (0.9997 to 0.9876) during microwave heating. The heating phenomenon of each casket material has been established. The COMSOL Multiphysics model was used to analyze the microwave heating behavior of SiC susceptor with varying casket composition and geometry under similar parameters for the first time. A higher heating rate was observed by COMSOL simulation for the porous alumina-silica (58.8 °C/ min) casket than dense alumina-silica (22.31 °C/ min) and dense alumina (9.63 °C/min) casket during microwave heating of SiC susceptor at 1200 W, 1500 s. The COMSOL simulation data were corroborated with experimental results. The study serves a general guideline to select an appropriate casket material for any microwave processing.