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Keywords = thermo-magnetic properties

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21 pages, 5366 KiB  
Article
Multifaceted Analysis of Pr2Fe16.75Ni0.25 Intermetallic Compound: Crystallographic Insights, Critical Phenomena, and Thermomagnetic Behavior near Room Temperature
by Jihed Horcheni, Hamdi Jaballah, Sirine Gharbi, Essebti Dhahri and Lotfi Bessais
Magnetochemistry 2025, 11(8), 65; https://doi.org/10.3390/magnetochemistry11080065 - 31 Jul 2025
Viewed by 78
Abstract
The alloy Pr2Fe16.75Ni0.25 has been examined to investigate its structural properties, critical behavior, and magnetocaloric effects. Rietveld’s refinement of X-ray diffraction patterns has revealed a rhombohedral structure with an R3¯m space group. Pr2Fe [...] Read more.
The alloy Pr2Fe16.75Ni0.25 has been examined to investigate its structural properties, critical behavior, and magnetocaloric effects. Rietveld’s refinement of X-ray diffraction patterns has revealed a rhombohedral structure with an R3¯m space group. Pr2Fe16.9Ni0.25 also demonstrates a direct magnetocaloric effect near room temperature, accompanied by a moderate magnetic entropy change (ΔSMmax = 5.5 J kg−1 K−1 at μ0ΔH=5 T) and a broad working temperature range. Furthermore, the Relative Cooling Power (RCP) is approximately 89% of the widely recognized gadolinium (Gd) for μ0ΔH=2 T. This compound exhibits a commendable magnetocaloric response, on par with or even surpassing that of numerous other intermetallic alloys. Critical behavior was analyzed using thermo-magnetic measurements, employing methods such as the modified Arrott plot, critical isotherm analysis, and Kouvel-Fisher techniques. The obtained critical exponents (β, γ, and δ) exhibit similarities to those of the 3D-Ising model, characterized explicitly by intermediate range interactions. Full article
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21 pages, 9209 KiB  
Article
Effects of Exchange, Anisotropic, and External Field Couplings on a Nanoscale Spin-2 and Spin-3/2 System: A Thermomagnetic Analysis
by Julio Cesar Madera, Elisabeth Restrepo-Parra and Nicolás De La Espriella
Magnetochemistry 2025, 11(7), 56; https://doi.org/10.3390/magnetochemistry11070056 - 30 Jun 2025
Viewed by 289
Abstract
In this research, an analysis of the thermomagnetic properties of a nanoscale spin-2 and spin-3/2 system is conducted. This system is modeled with as a quasi-spherical Ising-type nanoparticle with a diameter of 2 nm, in which atoms with spin-2 and spin-3/2 configured in [...] Read more.
In this research, an analysis of the thermomagnetic properties of a nanoscale spin-2 and spin-3/2 system is conducted. This system is modeled with as a quasi-spherical Ising-type nanoparticle with a diameter of 2 nm, in which atoms with spin-2 and spin-3/2 configured in body-centered cubic (BCC) lattices interact within their relevant nanostructures. To determine the thermomagnetic behaviors of the nanoparticle, numerical simulations using Monte Carlo techniques and thermal bath class algorithms are performed. The results exhibit the effects of exchange couplings (J1,J2), magnetocrystalline anisotropies (D3/2,D2), and external magnetic fields (h) on the finite-temperature phase diagrams of magnetization (MT), magnetic susceptibility (χT), and thermal energy (kBT). The influences of the exchange, anisotropic, and external field parameters are clearly reflected in the compensation, hysteretic, and pseudocritical phenomena presented by the quasi-spherical nanoparticle. When the parameter reflecting ferromagnetic second-neighbor exchanges in the nanosphere (J2) increases, for a given value of the external magnetic field, the compensation (Tcomp) and pseudocritical (Tpc) temperatures increase. Similarly, in the ranges 0<J24.5 and 15h15 at a specific temperature, an increase in J2 results in the appearance of exchange anisotropies (exchange bias) and and increased hysteresis loop areas in the nanomodel. Full article
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16 pages, 5770 KiB  
Article
Effect of Aging on Superelastic Response in [001]-Oriented Single Crystals of FeNiCoAlTiNb Shape-Memory Alloys
by Li-Wei Tseng and Wei-Cheng Chen
Materials 2025, 18(12), 2842; https://doi.org/10.3390/ma18122842 - 16 Jun 2025
Viewed by 399
Abstract
In this study, the effect of aging heat treatment on the superelastic properties and microstructure of [001]-oriented Fe41Ni28Co17Al11.5Ti1.25Nb1.25 (at.%) single crystals was investigated using the cyclic superelastic strain test and a transmission [...] Read more.
In this study, the effect of aging heat treatment on the superelastic properties and microstructure of [001]-oriented Fe41Ni28Co17Al11.5Ti1.25Nb1.25 (at.%) single crystals was investigated using the cyclic superelastic strain test and a transmission electron microscope (TEM). The TEM results reveal that the average precipitate size is around 3–5 nm in the 600 °C/24 h samples, 6–8 nm in the 600 °C/48 h samples, and 10–12 nm in the 600 °C/72 h samples. The results indicate that precipitate size increases as aging time increases from 24 to 72 h. EDS analysis results show decreased Fe and increased Ni when the analyzed line crosses the precipitate region. The diffraction pattern results show that the precipitate has an L12 crystal structure. The thermo-magnetization curves of single crystals under the three aging conditions (600 °C/24 h, 600 °C/48 h, and 600 °C/72 h) show that the values of the transformation temperatures increased from 24 to 72 h. Magnetization was saturated at 140 emu/g under the magnetic field of 7 Tesla. When increasing the magnetic field from 0.05 to 7 Tesla, the transformation temperatures rose. The results indicate that magnetic fields can activate martensitic transformation. From the results of the superelasticity test at room temperature, [001]-oriented FeNiCoAlTiNb single crystals aged at 600 °C for 24, 48, and 72 h presented recoverable strains of 3%, 5.1%, and 2.6%, respectively. Digital image correlation (DIC) results of the aged samples show that two martensite variants were activated during the superelasticity test. The two variants form corresponding variant pairs (CVPs) and improve the recoverable strain of superelasticity. Although maximum recoverable strain was obtained for the 600 °C/48 h samples, the samples show poor cyclic stability at room temperature after applying the 6% strain. According to the DIC results, the retained martensite, which is pinned by dislocations, was observed after the test. The irrecoverable strain was attributed to the residual martensite. For the 600 °C/72 h samples, the large size of the precipitates poses an obstacle to dislocation transformation and formation. The dislocations increase the stress hysteresis width and stabilize the martensite, causing poor recoverability. Full article
(This article belongs to the Special Issue Technology and Applications of Shape Memory Materials)
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16 pages, 3514 KiB  
Article
The Role of Convection and Size Effects in Microhotplate Heat Exchange: Semiconductor and Thermomagnetic Gas Sensors
by Alexey Vasiliev, Alexey Shaposhnik, Oleg Kul and Artem Mokrushin
Sensors 2025, 25(9), 2830; https://doi.org/10.3390/s25092830 - 30 Apr 2025
Viewed by 444
Abstract
The analysis of the influence of microhotplate size on the convective heat exchange of gas sensors is presented. Usually, the role of convection in the heat exchange of gas sensors is not considered in thermal simulation models because of the complexity of the [...] Read more.
The analysis of the influence of microhotplate size on the convective heat exchange of gas sensors is presented. Usually, the role of convection in the heat exchange of gas sensors is not considered in thermal simulation models because of the complexity of the convection process. As a result, the contribution of this process to the overall heat loss of sensors remains without detailed analysis. We analyzed convection issues in two groups of gas sensors: semiconductor and thermocatalytic (calorimetric) sensors and, on the other hand, in the oxygen sensors of the thermomagnetic type. It is demonstrated that there is a critical size leading to the formation of convective heat exchange flow. Below this critical value, only thermal conductivity of ambient air, IR (infrared) radiation from the heated microhotplate surface, and thermal conductivity of the microhotplate-supporting elements should be considered as channels for heat dissipation by the microhotplate, and the contribution of free convection can be neglected. The expression for the critical size contains only fundamental constants of air, dcr~4·ν·Dg3, where ν is the kinematic viscosity of air, D is the diffusion coefficient, and g is the acceleration of free fall, dcr~0.5 cm. Therefore, if the size of the microhotplate d <<dcr, the influence of convection heat exchange can be neglected. Similar results were obtained in the analysis of the behavior of thermal magnetic sensors of oxygen, which use paramagnetic properties of molecular oxygen for the determination of O2 concentration. In this case, the critical size of the sensor is also of significance; if the size of the magnetic sensor is much below this value, the oxygen concentration value measured with such a device is independent of the orientation of the sensor element. The results of the simulation were compared with the measurement of heat loss in micromachined gas sensors. The optimal dimensions of the sensor microhotplate are given as a result of these simulations and measurements. Full article
(This article belongs to the Special Issue Recent Advances in Sensors for Chemical Detection Applications)
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22 pages, 7080 KiB  
Article
A Thermo–TDR Sensor for Simultaneous Measurement of Unfrozen Water Content and Thermal Conductivity of Frozen Soil
by Panting Liu, Simao Fan, Qingyi Mu, Qifan Zhang, Linlin Tang, Jine Liu, Fuqing Cui, Zhiyun Liu and Xuna Wang
Sensors 2025, 25(7), 2155; https://doi.org/10.3390/s25072155 - 28 Mar 2025
Viewed by 400
Abstract
Due to increasing human engineering activities in cold regions, the precise measurement of frozen soil’s physical property parameters has become particularly important. Traditional measurements of thermal conductivity and unfrozen water content of frozen soil are usually tested separately, leading to errors in accurately [...] Read more.
Due to increasing human engineering activities in cold regions, the precise measurement of frozen soil’s physical property parameters has become particularly important. Traditional measurements of thermal conductivity and unfrozen water content of frozen soil are usually tested separately, leading to errors in accurately understanding the dynamic variation law of permafrost’s hydrothermal parameters in the near-phase transition zone. To address this, a multi-sensor fusion technology–thermo time domain reflectometry (thermo-TDR) sensor was designed and optimized for measuring the unfrozen water content and thermal conductivity of frozen soil. Three-dimensional thermal and electromagnetic numerical models were developed to analyze and validate the design parameters of the proposed sensor. Furthermore, a corresponding validation experiment was carried out to confirm the usability and accuracy of the designed sensor. The results show that (1) under the optimized probe parameters, the deviation between the theoretical thermal conductivity and the numerical preset value is 2.94%, verifying the accuracy of the sensor in thermal physical testing. (2) With a 10 mm probe spacing design, the test area of the thermo-TDR significantly increased, and the skin effect coefficient reached 25.54%, satisfying the electromagnetic design requirements of the TDR method. (3) The designed thermo-TDR sensor realizes the simultaneous measurement of unfrozen water and thermal conductivity of frozen soil, and the experimental results present a good consistency with that of the nuclear magnetic resonance (NMR) and transient planar heat source methods. (4) Additionally, due to the drastic changes in the soil’s physical properties due to the probe’s heating process, testing errors of the thermo-TDR sensor will significantly increase in the near-phase transition range, especially in the range of −2~−1 °C. Full article
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30 pages, 586 KiB  
Article
A Comparative Study of Differential Quadrature Methods for METE Nanobeam Vibrations
by Waleed Mohammed Abdelfattah
Algorithms 2025, 18(2), 64; https://doi.org/10.3390/a18020064 - 25 Jan 2025
Viewed by 741
Abstract
This study investigates the use of three different quadrature schemes, as well as an iterative quadrature methodology, to analyze vibrations in magneto-electro-thermo-elastic nanobeams. Individual MATLAB programs for each method are developed with the goal of minimizing errors in comparison to accurate findings, as [...] Read more.
This study investigates the use of three different quadrature schemes, as well as an iterative quadrature methodology, to analyze vibrations in magneto-electro-thermo-elastic nanobeams. Individual MATLAB programs for each method are developed with the goal of minimizing errors in comparison to accurate findings, as well as determining the execution time for each strategy. This study shows that the Discrete Singular-Convolution Differential Quadrature Method with a Regularized Shannon Kernel (DSCDQM-RSK) and specified parameters produces the best accurate and efficient results for this particular situation. A subsequent parametric study is carried out to determine the effect of various factors on the vibrated nanobeam, including boundary conditions, material types, linear and nonlinear elastic foundation properties, nonlocal parameters, length-to-thickness ratios, external electric and magnetic potentials, axial forces, and temperature variations. Important discoveries include insights into the relationship between fundamental frequency, linear elastic foundation features, axial loads, external magnetic fields, temperature fluctuations, and material types. According to this study, these findings could be critical in the development of sophisticated nanostructures made from magneto-electro-thermo-elastic materials for use in a variety of electromechanical applications. This would entail utilizing nanobeams’ unique properties in applications such as sensors, resonators, and transducers for nanoelectronics and biology. Full article
(This article belongs to the Section Algorithms for Multidisciplinary Applications)
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16 pages, 14456 KiB  
Article
Microstructure and Thermal Cyclic Behavior of FeNiCoAlTaB High-Entropy Alloy
by Li-Wei Tseng, Wei-Cheng Chen, Yi-Ting Hsu and Chih-Hsuan Chen
Materials 2025, 18(2), 387; https://doi.org/10.3390/ma18020387 - 16 Jan 2025
Viewed by 630
Abstract
This study investigates the grain morphology, microstructure, magnetic properties and shape memory properties of an Fe41.265Ni28.2Co17Al11Ta2.5B0.04 (at%) high-entropy alloy (HEA) cold-rolled to 98%. The EBSD results show that the texture intensities of [...] Read more.
This study investigates the grain morphology, microstructure, magnetic properties and shape memory properties of an Fe41.265Ni28.2Co17Al11Ta2.5B0.04 (at%) high-entropy alloy (HEA) cold-rolled to 98%. The EBSD results show that the texture intensities of the samples annealed at 1300 °C for 0.5 or 1 h are 2.45 and 2.82, respectively. This indicates that both samples were formed without any strong texture. The grain morphology results show that the grain size increased from 356.8 to 504.6 μm when the annealing time was increased from 0.5 to 1 h. The large grain size improved the recoverable strain due to a reduction in the grain constraint. As a result, annealing was carried out at 1300 °C/1 h for the remainder of the study. The hardness decreased at 24 h, then increased again at 48 h; this phenomenon was related to the austenite finish temperature. Thermo-magnetic analysis revealed that the austenite finish temperature increased when the samples were aged at 600 °C for between 12 and 24 h. When the aging time was prolonged to 48 h, the austenite finish temperature value decreased. X-ray diffraction (XRD) demonstrated that the peak of the precipitates emerged and intensified when the aging time was increased from 12 to 24 h at 600 °C. From the three-point bending shape memory test, the samples aged at 600 °C for 12 and 24 h had maximum recoverable strains of 2% and 3.6%, respectively. The stress–temperature slopes of the austenite finish temperature were 10.3 MPa/°C for 12 h and 6 MPa/°C for 24 h, respectively. Higher slope values correspond to lower recoverable strains. Full article
(This article belongs to the Special Issue Future Trends in High-Entropy Alloys (2nd Edition))
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15 pages, 11668 KiB  
Article
Analysis of the Properties of Anticorrosion Systems Used for Structural Component Protection in Truck Trailers
by Wojciech Skotnicki and Dariusz Jędrzejczyk
Materials 2024, 17(24), 6303; https://doi.org/10.3390/ma17246303 - 23 Dec 2024
Viewed by 875
Abstract
The article compares the properties of coatings (cataphoretic, hot-dip zinc, and thermo-diffusion zinc) applied to steel components used in the automotive industry. The research focused on the analysis of corrosion resistance, hardness measurements, and tribological properties conducted on steel guides used in trailer [...] Read more.
The article compares the properties of coatings (cataphoretic, hot-dip zinc, and thermo-diffusion zinc) applied to steel components used in the automotive industry. The research focused on the analysis of corrosion resistance, hardness measurements, and tribological properties conducted on steel guides used in trailer and truck body structures as well as fasteners (M12 × 40 bolts). The base surfaces were cleaned chemically. Corrosion resistance was tested in a salt chamber, while coating thickness was measured using the magnetic induction method. Coating hardness (HV 0.02) was assessed with a microhardness tester, and tribological properties were tested under dry friction conditions. The results showed that the zinc coatings demonstrated corrosion resistance far superior to paint coatings. Full article
(This article belongs to the Special Issue Metal Coatings for Wear and Corrosion Applications (Second Edition))
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20 pages, 8068 KiB  
Article
Preparation and Performance Study of Composite Aramid Paper for High-Frequency Working Conditions
by Xiaonan Li, Tong Qin, Wenxu Zhang, Hong Wang, Yanhong Chen, Kangle Li, Qing Wang and Yibo Wang
Nanomaterials 2024, 14(23), 1880; https://doi.org/10.3390/nano14231880 - 22 Nov 2024
Viewed by 1133
Abstract
When the power converter connects to the high-frequency transformer breaks through the bottleneck and reaches a frequency of 100 kHz or even higher, the high-frequency transformer’s inter-turn insulation faces more serious high-frequency discharge and high-temperature problems. In order to improve the service performance [...] Read more.
When the power converter connects to the high-frequency transformer breaks through the bottleneck and reaches a frequency of 100 kHz or even higher, the high-frequency transformer’s inter-turn insulation faces more serious high-frequency discharge and high-temperature problems. In order to improve the service performance of oil-immersed high-frequency transformer insulation paper, composite K-BNNS particles are prepared by ultrasonic stripping, heat treatment, and thermomagnetic stirring. Then, K-BNNS particles are mixed with PMIA (polymeric m-phenylenediamine solution) slurry to produce composite aramid paper. And the effects of K-BNNS particles with different contents on the thermal conductivity, dielectric properties, partial discharge properties, and mechanical properties of aramid paper are explored. It can be found that, when the addition of composite particles (K-BNNS) is 10%, the comprehensive performance of composite aramid paper is the best. Compared with Nomex paper, the in-plane and through-plane thermal conductivity of composite insulating paper F-10 increased by 668.33% and 760.66%, respectively. Moreover, the high-frequency breakdown voltage increased by 48.73% and the tensile strength increased by 2.49%. The main reason is that the composite particles form a complete thermal conductive network in the aramid paper matrix and a large number of hydrogen bonds with the matrix, which enhances the internal interface bonding force of the material and changes the charge transport mechanism. Full article
(This article belongs to the Special Issue Functional Polymer and Ceramic Nanocomposites)
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21 pages, 5255 KiB  
Article
Influence of Hydration and Temperature on the NaxCO2 Based Transducer Voltage
by George-Claudiu Zărnescu, Esmaeil Jalali Lavasani, Lucian Pîslaru-Dănescu and Ioan Stamatin
Micromachines 2024, 15(11), 1334; https://doi.org/10.3390/mi15111334 - 31 Oct 2024
Viewed by 1152
Abstract
This paper presents an experimental approach to maximizing the voltage generated by NaxCoO2 and improving the overall efficiency of the p-type thermoelectric leg by doping with Na up to x = 0.88. Two samples with different geometries were tested, each [...] Read more.
This paper presents an experimental approach to maximizing the voltage generated by NaxCoO2 and improving the overall efficiency of the p-type thermoelectric leg by doping with Na up to x = 0.88. Two samples with different geometries were tested, each measured with and without an additional magnetic field applied in the direction of the temperature gradient. The properties of sodium cobaltite in response to hydration were explored, at temperatures between 300 and 380 K. Water injection boosted the current and power up to 75–100 µW at a temperature of 350–360 K. This power boost can be attributed to an electron-ion fluid flow pattern maintained by the longitudinal thermomagnetic effect and by water molecules forming hydrogen bonds with oxygen atoms in the CoO2 layers, inside the material. An electronic circuit was designed to boost the voltage to the desired level, for three or more sodium cobaltite samples mounted in parallel, and to store the energy in a supercapacitor. The output voltage and resistivity change of sodium cobaltite samples can be readily used as a humidity and temperature-sensing element in a transducer when paired with an appropriate electronic conditioning scheme. Full article
(This article belongs to the Special Issue Energy Conversion and Storage Devices: Materials and Applications)
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18 pages, 2792 KiB  
Article
A First-Principles Study of the Structural and Thermo-Mechanical Properties of Tungsten-Based Plasma-Facing Materials
by Jie Peng, Yichen Qian and David Cereceda
Metals 2024, 14(10), 1197; https://doi.org/10.3390/met14101197 - 21 Oct 2024
Cited by 4 | Viewed by 1782
Abstract
Tungsten (W) and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high [...] Read more.
Tungsten (W) and tungsten alloys are being considered as leading candidates for structural and functional materials in future fusion energy devices. The most attractive properties of tungsten for the design of magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. Despite these relevant features, there is a lack of understanding of how the structural and mechanical properties of W-based alloys are affected by the temperature in fusion power plants. In this work, we present a study on the thermo-mechanical properties of five W-based plasma-facing materials. First-principles density functional theory (DFT) calculations are combined with the quasi-harmonic approximation (QHA) theory to investigate the electronic, structural, mechanical, and thermal properties of these W-based alloys as a function of temperature. The coefficient of thermal expansion, temperature-dependent elastic constants, and several elastic parameters, including bulk and Young’s modulus, are calculated. Our work advances the understanding of the structural and thermo-mechanical behavior of W-based materials, thus providing insights into the design and selection of candidate plasma-facing materials in fusion energy devices. Full article
(This article belongs to the Special Issue Advanced Characterization and Testing of Nuclear Materials)
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15 pages, 4386 KiB  
Article
POSS and PAG Dual-Containing Chemically Amplified Photoresists by RAFT Polymerization for Enhanced Thermal Performance and Acid Diffusion Inhibition
by Haimeng Yu, Shaoshuai Liu, Haiyan Fu, Zepeng Cui, Liangshun Zhang and Jia Tian
Appl. Sci. 2024, 14(17), 7722; https://doi.org/10.3390/app14177722 - 2 Sep 2024
Cited by 3 | Viewed by 5060
Abstract
A random copolymer (PTBM), utilized as deep ultra-violet (DUV) photoresist, was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization with tert-butyl methacrylate (tBMA), methyl methacrylate (MMA), triphenylsulfonium p-styrenesulfonate (TPS-SS), and functional poly (sesquicarbonylsiloxanes) (POSS-MA) as the monomer components, and 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl]pentanoic acid [...] Read more.
A random copolymer (PTBM), utilized as deep ultra-violet (DUV) photoresist, was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization with tert-butyl methacrylate (tBMA), methyl methacrylate (MMA), triphenylsulfonium p-styrenesulfonate (TPS-SS), and functional poly (sesquicarbonylsiloxanes) (POSS-MA) as the monomer components, and 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl]pentanoic acid (CDSPA) as the RAFT reagent. Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR) proved successful synthesis. Ultraviolet absorption spectroscopy (UV) analysis verified the transparency of the polymer in the DUV band. RAFT polymerization kinetics showed that the polymerization rate conformed to the first-order kinetic relationship, and the polymerization process exhibited a typical controlled free radical polymerization behavior. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and static thermo-mechanical analysis (TMA) showed that the incorporation of POSS groups improved the thermal properties of the copolymer. According to scanning electron microscopy (SEM) images, the copolymerization of photoacid monomers (TPS-SS) resulted in photoresist copolymers exhibiting good resistance to acid diffusion and low roughness. Full article
(This article belongs to the Section Applied Thermal Engineering)
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17 pages, 2885 KiB  
Article
A Non-Relativistic 2D Quantum System and Its Thermo-Magnetic Properties with a Generalized Pseudo-Harmonic Oscillator
by Haifa I. Alrebdi, Akpan N. Ikot, Ridha Horchani and Uduakobong S. Okorie
Mathematics 2024, 12(17), 2623; https://doi.org/10.3390/math12172623 - 24 Aug 2024
Cited by 1 | Viewed by 1086
Abstract
In this work, we examine the thermo-magnetic characteristics and energy spectra of a system exposed to both magnetic and Aharonov–Bohm (AB) fields with the existence of an interaction potential that is pseudo-harmonic. Explicit calculations of the eigen-solutions are performed with the expanded Nikiforov–Uvarov [...] Read more.
In this work, we examine the thermo-magnetic characteristics and energy spectra of a system exposed to both magnetic and Aharonov–Bohm (AB) fields with the existence of an interaction potential that is pseudo-harmonic. Explicit calculations of the eigen-solutions are performed with the expanded Nikiforov–Uvarov formalism. The confluent Heun function is used to represent the equivalent wave functions. If the AB and magnetic fields are gone, quasi-degeneracy in the system’s energy levels is shown by a numerical analysis of the energy spectrum. Additionally, we provided a visual representation of how the AB and magnetic fields affected the system’s thermo-magnetic characteristics. Our results show a strong dependence of thermo-magnetic properties on temperature, screening parameters, external magnetic fields, and AB fields. Full article
(This article belongs to the Section E4: Mathematical Physics)
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21 pages, 7675 KiB  
Article
Analysis of Structural Changes of pH–Thermo-Responsive Nanoparticles in Polymeric Hydrogels
by Lazaro Ruiz-Virgen, Miguel Angel Hernandez-Martinez, Gabriela Martínez-Mejía, Rubén Caro-Briones, Enrique Herbert-Pucheta, José Manuel del Río and Mónica Corea
Gels 2024, 10(8), 541; https://doi.org/10.3390/gels10080541 - 20 Aug 2024
Cited by 6 | Viewed by 2002
Abstract
The pH- and thermo-responsive behavior of polymeric hydrogels MCcoMA have been studied in detail using dynamic light scattering DLS, scanning electron microscopy SEM, nuclear magnetic resonance (1H [...] Read more.
The pH- and thermo-responsive behavior of polymeric hydrogels MCcoMA have been studied in detail using dynamic light scattering DLS, scanning electron microscopy SEM, nuclear magnetic resonance (1H NMR) and rheology to evaluate the conformational changes, swelling–shrinkage, stability, the ability to flow and the diffusion process of nanoparticles at several temperatures. Furthermore, polymeric systems functionalized with acrylic acid MC and acrylamide MA were subjected to a titration process with a calcium chloride CaCl2 solution to analyze its effect on the average particle diameter Dz, polymer structure and the intra- and intermolecular interactions in order to provide a responsive polymer network that can be used as a possible nanocarrier for drug delivery with several benefits. The results confirmed that the structural changes in the sensitive hydrogels are highly dependent on the corresponding critical solution temperature CST of the carboxylic (–COOH) and amide (–CONH2) functional groups and the influence of calcium ions Ca2+ on the formation or breaking of hydrogen bonds, as well as the decrease in electrostatic repulsions generated between the polymer chains contributing to a particle agglomeration phenomenon. The temperature leads to a re-arrangement of the polymer chains, affecting the viscoelastic properties of the hydrogels. In addition, the diffusion coefficients D of nanoparticles were evaluated, showing a closeness among with the morphology, shape, size and temperature, resulting in slower diffusions for larger particles size and, conversely, the diffusion in the medium increasing as the polymer size is reduced. Therefore, the hydrogels exhibited a remarkable response to pH and temperature variations in the environment. During this research, the functionality and behavior of the polymeric nanoparticles were observed under different analysis conditions, which revealed notable structural changes and further demonstrated the nanoparticles promising high potential for drug delivery applications. Hence, these results have sparked significant interest in various scientific, industrial and technological fields. Full article
(This article belongs to the Special Issue Gel-Based Materials: Preparations and Characterization (2nd Edition))
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15 pages, 4729 KiB  
Article
Differentiation between Hydrolytic and Thermo-Oxidative Degradation of Poly(lactic acid) and Poly(lactic acid)/Starch Composites in Warm and Humid Environments
by Victoria Goetjes, Jan-Christoph Zarges and Hans-Peter Heim
Materials 2024, 17(15), 3683; https://doi.org/10.3390/ma17153683 - 25 Jul 2024
Cited by 4 | Viewed by 1923
Abstract
For the application of poly(lactic acid) (PLA) and PLA/starch composites in technical components such as toys, it is essential to know their degradation behavior under relevant application conditions in a hydrothermal environment. For this purpose, composites made from PLA and native potato starch [...] Read more.
For the application of poly(lactic acid) (PLA) and PLA/starch composites in technical components such as toys, it is essential to know their degradation behavior under relevant application conditions in a hydrothermal environment. For this purpose, composites made from PLA and native potato starch were produced using twin-screw extruders and then processed into test specimens, which were then subjected to various one-week ageing processes with varying temperatures (23, 50, 70, 90 °C) and humidity levels (10, 50, 75, 90%). This was followed by mechanical characterization (tensile test) and identification of degradation using Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance spectroscopy (NMR). With increasing temperature and humidity, there was a clear degradation of the PLA, which could be reduced or slowed down by adding 50 wt.% starch, due to increased crystallinity. Hydrolysis was identified as the main degradation mechanism for PLA and PLA/starch composites, especially above the glass transition temperature, with thermo-oxidative degradation also playing a subordinate role. Both hydrolytic degradation and thermo-oxidative degradation led to a reduction in mechanical properties such as tensile strength. Full article
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