Materials

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12 pages, 2199 KiB

Open AccessArticle

Enhancement of Magneto-Induced Modulus by the Combination of Filler and Plasticizer Additives-Based Magnetorheological Elastomer

by Muntaz Hana Ahmad Khairi, Ervina Efzan Mhd Noor, Ubaidillah Ubaidillah, Siti Aishah Abdul Aziz, Saiful Amri Mazlan, Siti Maisarah Ahmad Tarmizi and Nur Azmah Nordin

Materials 2022, 15(18), 6396; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15186396 - 15 Sep 2022

Cited by 5 | Viewed by 1245

Abstract

Filler additive is used to provide superior bonding in rubber matrix to enhance the storage modulus of magnetorheological elastomer (MRE). However, the magneto-induced modulus is reduced as the initial storage modulus increases. Therefore, this paper aims to increase the magneto-induced modulus and maintain [...] Read more.

Filler additive is used to provide superior bonding in rubber matrix to enhance the storage modulus of magnetorheological elastomer (MRE). However, the magneto-induced modulus is reduced as the initial storage modulus increases. Therefore, this paper aims to increase the magneto-induced modulus and maintain the initial storage modulus by combining filler and plasticizer additives. Both types of additives have different functions, where cobalt ferrite (CoFe₂O₄) is capable of enhancing the maximum storage modulus and silicone oil (SO) reduces the initial storage modulus. Thus, four MRE samples have been fabricated using (a) no additive, (b) CoFe₂O₄, (c) SO, and (d) a combination of CoFe₂O₄ and SO. The sample’s hardness and magnetic properties were investigated via Durometer Shore A and Vibrating Sample Magnetometer (VSM), respectively. Furthermore, the rheological properties of MRE samples in terms of storage modulus were investigated upon the frequency and magnetic field sweep using a rheometer. The results demonstrated that the storage modulus of the MRE samples has increased with increasing the oscillation frequency from 0.1 to 50 Hz. Interestingly, the combination of additives has produced the largest value of magneto-induced modulus of 0.90 MPa as compared to other samples. Furthermore, their initial storage modulus was in between samples with SO (lowest) and without additive (highest). Therefore, fundamental knowledge in adding the combination of additives can offer solutions for a wide range of stiffness in MR device applications such as vibration and noise control devices, sensing devices, and actuators. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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15 pages, 4796 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Bi₂O₃ and Fe₂O₃ Impurity Phases in BiFeO₃ Perovskite Materials on Some Electrical Properties in the Low-Frequency Field

by Cristian Casut, Iosif Malaescu, Catalin Nicolae Marin and Marinela Miclau

Materials 2022, 15(14), 4764; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15144764 - 07 Jul 2022

Cited by 2 | Viewed by 1722

Abstract

Pure bismuth ferrite (BFO) and BFO with impurity phases (Bi₂O₃ or Fe₂O₃) were synthesized by the hydrothermal method. Complex dielectric permittivity (ε) and electrical conductivity (σ) were determined by complex impedance measurements at different frequencies (200 [...] Read more.

Pure bismuth ferrite (BFO) and BFO with impurity phases (Bi₂O₃ or Fe₂O₃) were synthesized by the hydrothermal method. Complex dielectric permittivity (ε) and electrical conductivity (σ) were determined by complex impedance measurements at different frequencies (200 Hz–2 MHz) and temperatures (25–290) °C. The conductivity spectrum of samples, σ(f), complies with Jonscher’s universal law and the presence of impurity phases leads to a decrease in the static conductivity (σ_DC); this result is correlated with the increased thermal activation energy of the conduction in impure samples compared to the pure BFO sample. The conduction mechanism in BFO and the effect of impurity phases on σ and ε were analyzed considering the variable range hopping model (VRH). Based on the VRH model, the hopping length (R_h), hopping energy (W_h) and the density of states at the Fermi level (N(E_F)) were determined for the first time, for these samples. In addition, from ε(T) dependence, a transition in the electronic structure of samples from a semiconductor-like to a conductor-like behavior was highlighted around 465–490 K for all samples. The results obtained are useful to explain the conduction mechanisms from samples of BFO type, offering the possibility to develop a great variety of electrical devices with novel functions. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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14 pages, 2249 KiB

Open AccessArticle

Investigating the Impact of Cu²⁺ Doping on the Morphological, Structural, Optical, and Electrical Properties of CoFe₂O₄ Nanoparticles for Use in Electrical Devices

by Shahroz Saleem, Muhammad Irfan, Muhammad Yasin Naz, Shazia Shukrullah, Muhammad Adnan Munir, Muhammad Ayyaz, Abdullah Saeed Alwadie, Stanislaw Legutko, Jana Petrů and Saifur Rahman

Materials 2022, 15(10), 3502; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15103502 - 13 May 2022

Cited by 17 | Viewed by 1903

Abstract

This study investigated the production of Cu²⁺-doped CoFe₂O₄ nanoparticles (CFO NPs) using a facile sol−gel technique. The impact of Cu²⁺ doping on the lattice parameters, morphology, optical properties, and electrical properties of CFO NPs was investigated for [...] Read more.

This study investigated the production of Cu²⁺-doped CoFe₂O₄ nanoparticles (CFO NPs) using a facile sol−gel technique. The impact of Cu²⁺ doping on the lattice parameters, morphology, optical properties, and electrical properties of CFO NPs was investigated for applications in electrical devices. The XRD analysis revealed the formation of spinel-phased crystalline structures of the specimens with no impurity phases. The average grain size, lattice constant, cell volume, and porosity were measured in the range of 4.55–7.07 nm, 8.1770–8.1097 Å, 546.7414–533.3525 Å³, and 8.77–6.93%, respectively. The SEM analysis revealed a change in morphology of the specimens with a rise in Cu²⁺ content. The particles started gaining a defined shape and size with a rise in Cu²⁺ doping. The Cu_0.12Co_0.88Fe₂O₄ NPs revealed clear grain boundaries with the least agglomeration. The energy band gap declined from 3.98 eV to 3.21 eV with a shift in Cu²⁺ concentration from 0.4 to 0.12. The electrical studies showed that doping a trace amount of Cu²⁺ improved the electrical properties of the CFO NPs without producing any structural distortions. The conductivity of the Cu²⁺-doped CFO NPs increased from 6.66 × 10⁻¹⁰ to 5.26 × 10⁻⁶ ℧ cm⁻¹ with a rise in Cu²⁺ concentration. The improved structural and electrical characteristics of the prepared Cu²⁺-doped CFO NPs made them a suitable candidate for electrical devices, diodes, and sensor technology applications. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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16 pages, 45567 KiB

Open AccessArticle

Temperature Dependent on Mechanical and Rheological Properties of EPDM-Based Magnetorheological Elastomers Using Silica Nanoparticles

by Rusila Zamani Abdul Rashid, Nurul Azhani Yunus, Saiful Amri Mazlan, Norhasnidawani Johari, Siti Aishah Abdul Aziz, Nur Azmah Nordin, Muntaz Hana Ahmad Khairi and Mohd Aidy Faizal Johari

Materials 2022, 15(7), 2556; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15072556 - 31 Mar 2022

Cited by 5 | Viewed by 1662

Abstract

Temperature is one of the most influential factors affecting the performance of elastomer matrix in magnetorheological elastomer (MRE). Previous studies have utilized silica as a reinforcing filler in polymer composite and as a coating material in MRE to improve the thermal stability of [...] Read more.

Temperature is one of the most influential factors affecting the performance of elastomer matrix in magnetorheological elastomer (MRE). Previous studies have utilized silica as a reinforcing filler in polymer composite and as a coating material in MRE to improve the thermal stability of the base material. However, the usage of silica as an additive in the thermal stability of MRE has not been explored. Thus, in this study, the effect of silica as an additive on the temperature-dependent mechanical and rheological properties of ethylene propylene diene monomer (EPDM)-based MREs was investigated by using 30 wt.% carbonyl iron particles (CIPs) as the main filler, with different contents of silica nanoparticles (0 to 11 wt.%). The microstructure analysis was examined by using field-emission scanning electron microscopy (FESEM), while the thermal characterizations were studied by using a thermogravimetric analyzer and differential scanning calorimetry. The tensile properties were conducted by using Instron Universal Testing Machine in the absence of magnetic field at various temperatures. Meanwhile, the rheological properties were analyzed under oscillatory loadings in the influence of magnetic field, using a rotational rheometer at 25 to 65 °C. The results revealed that the temperature has diminished the interfacial interactions between filler and matrix, thus affecting the properties of MRE, where the tensile properties and MR effect decrease with increasing temperature. However, the presence of silica capable improved the thermal stability of EPDM-based MRE by enhancing the interactions between filler and matrix, thus reducing the interfacial defects when under the influence of temperature. Consequently, the incorporation of silica nanoparticles as an additive in EPDM-based MRE requires more exploration, since it has the potential to sustain the properties of MRE devices in a variety of temperature conditions. Thus, the study on the temperature-dependent mechanical and rheological properties of MRE is necessary, particularly regarding its practical applications. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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15 pages, 5587 KiB

Open AccessArticle

Electric and Dielectric Properties in Low-Frequency Fields of Composites Consisting of Silicone Rubber and Al Particles for Flexible Electronic Devices

by Alexandrina Teusdea, Iosif Malaescu, Paula Sfirloaga and Catalin Nicolae Marin

Materials 2022, 15(6), 2309; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15062309 - 21 Mar 2022

Cited by 3 | Viewed by 1681

Abstract

Understanding the electrical conduction and dielectric polarization properties of elastomer-based composites is important for the design of flexible and elastic electronic devices and circuits. Five samples were manufactured by mixing silicone rubber (RTV-530) with Al particles in different volume fractions, x equal to [...] Read more.

Understanding the electrical conduction and dielectric polarization properties of elastomer-based composites is important for the design of flexible and elastic electronic devices and circuits. Five samples were manufactured by mixing silicone rubber (RTV-530) with Al particles in different volume fractions, x equal to 0%, 0.5%, 1%, 2.5% and 5.1%. Using the complex impedance measurements, the electric modulus, M, the electrical conductivity, σ, and the dielectric permittivity, ε, over the frequency range 100 Hz–200 kHz were analyzed. The electrical conductivity spectrum, σ(f), follows the Jonscher universal law and the DC conductivity of the samples, σ_DC, increases from 2.637·10⁻⁸ S/m to 5.725·10⁻⁸ S/m, with increasing x from, 0 to 5.1%. The conduction process was analyzed in terms of Mott’s variable-range-hopping (VRH) model. The hopping distance of the charge carriers, R_h decreases with increasing x, from 7.30 nm (for x = 0) to 5.92 nm (for x = 5.1%). The frequency dependence of permittivity, ε(f) = ε′(f) − iε″(f), reveals a relaxation process with the maximum of ε″(f) shifting from 301 Hz to 385 Hz and values of ε′(f) increasing with the increase of x. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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7 pages, 2058 KiB

Open AccessEditor’s ChoiceArticle

Tunable Planar Hall Effect in (Ga,Mn)(Bi,As) Epitaxial Layers

by Tomasz Andrearczyk, Janusz Sadowski, Jerzy Wróbel, Tadeusz Figielski and Tadeusz Wosinski

Materials 2021, 14(16), 4483; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14164483 - 10 Aug 2021

Cited by 6 | Viewed by 1576

Abstract

We have thoroughly investigated the planar Hall effect (PHE) in the epitaxial layers of the quaternary compound (Ga,Mn)(Bi,As). The addition of a small amount of heavy Bi atoms to the prototype dilute ferromagnetic semiconductor (Ga,Mn)As enhances significantly the spin–orbit coupling strength in its [...] Read more.

We have thoroughly investigated the planar Hall effect (PHE) in the epitaxial layers of the quaternary compound (Ga,Mn)(Bi,As). The addition of a small amount of heavy Bi atoms to the prototype dilute ferromagnetic semiconductor (Ga,Mn)As enhances significantly the spin–orbit coupling strength in its valence band, which essentially modifies certain magnetoelectric properties of the material. Our investigations demonstrate that an addition of just 1% Bi atomic fraction, substituting As atoms in the (Ga,Mn)As crystal lattice, causes an increase in the PHE magnitude by a factor of 2.5. Moreover, Bi incorporation into the layers strongly enhances their coercive fields and uniaxial magneto-crystalline anisotropy between the in-plane ⟨110⟩ crystallographic directions in the layers grown under a compressive misfit strain. The displayed two-state behaviour of the PHE resistivity at zero magnetic field, which may be tuned by the control of applied field orientation, could be useful for application in spintronic devices, such as nonvolatile memory elements. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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13 pages, 3456 KiB

Open AccessEditor’s ChoiceArticle

Behaviors of Electromagnetic Wave Propagation in Double-Walled Carbon Nanotubes

by Ayse Nihan Basmaci

Materials 2021, 14(15), 4069; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14154069 - 21 Jul 2021

Cited by 5 | Viewed by 1594

Abstract

In this study, behaviors of electromagnetic wave propagation in a double-walled carbon nanotube (DWCNT) are investigated theoretically. For this purpose, the effects of carbon nanotube’s inner and outer tubes’ material property parameters (μ, ε) on electromagnetic wave propagation are discussed. [...] Read more.

In this study, behaviors of electromagnetic wave propagation in a double-walled carbon nanotube (DWCNT) are investigated theoretically. For this purpose, the effects of carbon nanotube’s inner and outer tubes’ material property parameters (μ, ε) on electromagnetic wave propagation are discussed. The effects of interaction between the carbon nanotube’s inner and outer tubes on the electromagnetic wave propagation are defined. Nonlocal effects of the DWCNT on electromagnetic wave propagation are examined. Besides, the electromagnetic wave propagation frequencies are specifically investigated, taking the DWCNT’s nonlocal effects and material property parameters (ε, µ) into account. When the wavenumber, k, is greater than 1.8 × 10¹⁰, the frequencies of the fundamental mode and the second mode converge to 3.554 × 10⁸ Hz. Additionally, the electromagnetic wave propagation frequencies decrease with the increase of the DWCNT’s nonlocal parameter (ν) and decrease with material parameter (D). Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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13 pages, 4131 KiB

Open AccessArticle

Magnetic and Transport Properties of New Dual-Phase High-Entropy Alloy FeRhIrPdPt

by Kohei Baba, Naoki Ishizu, Terukazu Nishizaki and Jiro Kitagawa

Materials 2021, 14(11), 2877; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14112877 - 27 May 2021

Cited by 8 | Viewed by 2521

Abstract

High-entropy alloys (HEAs) are broadly explored from the perspective of mechanical, corrosion-resistance, catalytic, structural, superconducting, magnetic properties, and so on. In magnetic HEAs, 3d transition metals or rare-earth elements are well-studied compositional elements. We researched a magnetic HEA containing Fe combined with [...] Read more.

High-entropy alloys (HEAs) are broadly explored from the perspective of mechanical, corrosion-resistance, catalytic, structural, superconducting, magnetic properties, and so on. In magnetic HEAs, 3d transition metals or rare-earth elements are well-studied compositional elements. We researched a magnetic HEA containing Fe combined with 4d and 5d transition metals, which has not been well investigated, and found a new dual-phase face-centered-cubic (fcc) HEA FeRhIrPdPt. The structural, magnetic, and transport properties were evaluated by assuming that FeRhIrPdPt is a mixture of FeRh₄, FeIr₄, FePd₄, and FePt₄, all with the fcc structure. The dual-phase is composed of a Rh- and Ir-rich main phase and a Pd- and Pt-rich minor one. FeRh₄ and FeIr₄ show spin freezings at low temperatures, while FePd₄ and FePt₄ are ferromagnetic. Two magnetic features can characterize FeRhIrPdPt. One is the canonical spin-glass transition at 90 K, and the other is a ferromagnetic correlation that appears below 300 K. The main and minor phases were responsible for the spin-glass transition and the ferromagnetic correlation below 300 K, respectively. Full article

(This article belongs to the Special Issue Advances in Electromagnetic Properties of Magnetic Materials)

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