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Measured reflection coefficient S11 of microstrip antennas prototypes of (a) Ch-based films (0-80% of SPIONs); (b) Col-based films (0-80% of SPIONs); and (c) BC-based films (0-80% of SPIONs). (d) Variation of operation frequency in function of the composition of microstrip substrate.
Source publication
Magneto-dielectric composites are interesting advanced materials principally due to their potential applications in electronic fields, such as in microstrip antennas substrates. In this work, we developed superparamagnetic polymer-based films using the biopolymeric matrices chitosan (Ch), cellulose (BC) and collagen (Col). For this proposal, we syn...
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... prototypes of circular microstrip antennas ( Figure 8) were developed with a patch diameter of 13 mm in a rectangular substrate of 30 × 25 mm 2 , which was chosen according to devices operating at around 5.0 GHz. The results of reflection coefficient (S11) measurements are shown in Figure 9. S11 spectra for all samples showed minimal S11 values below −10 dB, which are required for a good antenna operation. ...
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... prototypes of circular microstrip antennas ( Figure 8) were developed with a patch diameter of 13 mm in a rectangular substrate of 30 × 25 mm 2 , which was chosen according to devices operating at around 5.0 GHz. The results of reflection coefficient (S 11 ) measurements are shown in Figure 9. S 11 spectra for all samples showed minimal S 11 values below −10 dB, which are required for a good antenna operation. ...
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... there might be some contribution of error patch cutting in these shifts. Figure 9d shows fo values of antennas versus composition of their respective substrates in the composite film. Interestingly, it is possible to adjust the operation frequency of microstrips with the In circular microstrip antennas with thin substrates, two factors significantly affect f o , a and ε , where f o is inversely proportional to √ ε . ...
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... there might be some contribution of error patch cutting in these shifts. Figure 9d shows f o values of antennas versus composition of their respective substrates in the composite film. Interestingly, it is possible to adjust the operation frequency of microstrips with the substrate content. ...
Citations
... As can be seen in Table 5, this puts the substrate's dielectric constant in line with previous studies. Since Wi-Fi signals come in two distinct frequency bands: 2.4 GHz (2400-2484 MHz) and 5 GHz (4915-5875 MHz), the proposed composite can work as a 5 GHz Wi-Fi antenna substrate [73]. Moreover, the value of return loss of the proposed antenna is on par with other works, showing good impedance matching (VSWR < 1.5) [74]. ...
Here, the eligibility of silicone rubber‐nanoceramic composites as flexible substrates for sub‐6 GHz 5G antennas is investigated. Two different composites are prepared using the solution mixing method, namely mono and hybrid composites. The reflection and transmission coefficient (S‐parameters) of composites are measured using a rectangular waveguide‐based transmission line technique in conjunction with a Vector Network Analyzer (VNA) at C‐band frequencies (4–8 GHz). The Nicolson–Ross–Weir (NRW) algorithm is adopted to extract the complex permittivity and loss tangent of the material under test. Due to the synergetic effect, the silicone rubber hybrid composite (0.12BiVO4+0.12LaNbO4) exhibits the advantage of a lowered loss tangent while retaining a good dielectric constant at 5.78 GHz. A rectangular microstrip patch antenna is designed and simulated with CST software using 0.12BVO/0.12LNO/0.76SR composite as a substrate. Moreover, based on the simulation, the antenna with the proposed substrate has acceptable performance at 5.78 GHz with the return loss, directivity, and gain of −25.05 dB, 5.46 dBi and 2.74 dBi, respectively. As a result, the composite material's ability to act as a suitable substrate for a 5 GHz Wi‐Fi antenna is confirmed.
... It has been revealed that this low-cost marine co-product can contribute to the development of many commercial products with high added value. Generally, all industrial applications are concerned, from pharmaceuticals to agroalimentary, including the environment, agriculture, textile, printing, and cosmetics [18][19][20]. ...
Chitosan, which is a derivative of chitin, is particularly popular due to its biodegradable and renewable nature. However, the properties of chitosan can be inconsistent due to the extraction process and its natural origin, which poses a challenge to its use in composite materials as a matrix. The properties of chitosan can be tuned by controlling the degree of deacetylation (the extent to which acetyl groups are removed from chitin to form chitosan) and molecular weight. This paper presents a detailed study on the extraction and characterization of chitosan from shrimp shells. The structural thermal and mechanical characterization were studied using several techniques: Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry. The intrinsic viscosity and deacetylation degree were determined using various methods. The results showed an average degree of deacetylation of 77%. The chitosan films exhibited a high tensile strength of 43.9 MPa and an elongation at break of 3.14%. The thermal analysis revealed that the films had a glass transition temperature of 88 °C and a maximum thermal degradation temperature of 320 °C. The findings of this research could contribute to the development of chitosan-based materials with improved properties, leading to its wider adoption in the future for composite matrix application. The simple and efficient method used for the extraction and purification of chitosan from shrimp shells makes it a cost-effective and eco-friendly alternative to synthetic polymers.
... The composites' biomaterials, which contain chitosan, hydroxyapatite, and/or carbon nanotubes, [15,16] have potential applications in regenerative medicine due to their properties in promoting bone osteogenesis, while the sponges based on chitosan and alginate favors the differentiation of multipotent stromal cells [17]. Composite materials with collagen and chitosan or the biomimetic magnetic structures covered by composites that contain collagen, chitosan, hydroxyapatite, and magnetic particles, such as Fe 2 O 3 or CoFe 2 O 4 , have promising medical applications [18][19][20], due to their ability to enhance the regeneration of damaged tissues or bones, with or without the influence of a magnetic field [18][19][20] [21,22]. ...
Raw materials, such as collagen and chitosan, obtained from by-products from the food industry (beef hides and crustacean exoskeletons), can be used to obtain collagen–chitosan composite biomaterials, with potential applications in regenerative medicine. Functionalization of these composite biomaterials is a possibility, thus, resulting in a molecule with potential applications in regenerative medicine, namely clotrimazole (a molecule with antibacterial, antifungal, and antitumor activity), at a mass ratio (collagen–chitosan–clotrimazole) of 1:1:0.1. This functionalized composite biomaterial has great potential for application in regenerative medicine, due to the following properties: (1) it is porous, and the pores formed are interconnected, due to the use of a mass ratio between collagen and chitosan of 1:1; (2) the size of the formed pores is between 500–50 μm; (3) between collagen and chitosan, hydrogen bonds are formed, which ensure the unity of composite biomaterial; (4) the functionalized bio-composite exhibits in vitro antimicrobial activity for Candida albicans, Staphylococcus aureus, and Staphylococcus aureus MRSA; for the latter microorganism, the antimicrobial activity is equivalent to that of the antibiotic Minocycline; (5) the proliferation tests performed on a standardized line of normal human cells with simple or composite materials obtained by lyophilization do not show cytotoxicity in the concentration range studied (10–500) μg/mL.
... However, the Fe3O4-HA nanocomposite was found to have inferior magnetic properties compared to Fe3O4 NPs. This can be explained by the presence of non-magnetic material [39]. Therefore, the HA component does not affect the magnetic nature of the composite. ...
Hydroxyapatite (HA) is a bioceramic very similar to the mineral component of bones and teeth. It is well established that osteoblasts grow better onto HA-coated metals than on metals alone. Herein, the preparation of a new system consisting of magnetite (Fe3O4) and HA functionalized with oleic acid and simvastatin (SIMV), and incorporated in chitosan (CHI) scaffolds, was undertaken. HA was synthesized by the hydrothermal method, while Fe3O4 was synthesized by co-precipitation. The polymer matrix was obtained using a 2% CHI solution, and allowed to stir for 2 h. The final material was freeze-dried to produce scaffolds. The magnetic properties remained unchanged after the formation of the composite, as well as after the preparation of the scaffolds, maintaining the superparamagnetism. CHI scaffolds were analyzed by scanning electronic spectroscopy (SEM) and showed a high porosity, with very evident cavities, which provides the functionality of bone growth support during the remineralization process in possible regions affected by bone tissue losses. The synthesized composite showed an average particle size between 15 and 23 nm for particles (HA and Fe3O4). The scaffolds showed considerable porosity, which is important for the performance of various functions of the tissue structure. Moreover, the addition of simvastatin in the system can promote bone formation.
Use of microwave (MW) energy as an alternate to high temperature treatment during material synthesis is gaining much attention as it offers the advantages of being faster and economical than other heating methods. A comprehensive study of structure, magnetization, and polarization behaviour of Cobalt (Co) doped Fe3O4 thin films, prepared by means of microwave assisted sol-gel method is performed. Co doped (0-10wt%) sols are prepared after irradiating them at MW power of 1000W. Phase analysis is confirmed using XRD where Fe3O4 phase persisted with Co concentrations of 0-6wt%. Higher concentration results in the appearance of cobalt oxide phase. Magnetic and transport properties are strongly affected by the presence of Co ions. Co doped Fe3O4 films show anisotropic behaviour with high saturation magnetization obtained for 6wt% Co doped Fe3O4 thin films, i.e. ∼125 emu/g. Verwey transition is observed for thin films with low dopant concentration while no sharp transition in magnetization behaviour is observed for higher dopant concentration. High frequency anomaly in dielectric analysis is observed at high frequencies for Co doped Fe3O4 thin films. Negative values of magneto-dielectric coefficient show coupling of magnetic and dielectric behaviour at room temperature.
The size and shape dependent tunable electromagnetic (EM) properties of magnetite – Fe3O4 nanoparticles makes them an attractive material for various future electronics and biomedical device applications such as tunable attenuators, miniaturized isolators and circulators, RF antennas, EM shielding, and biomedical implants etc. The strategic design of RF devices requires specific dielectric and magnetic properties according to the applications, which in turn depends on the size and shape of the particles. At nanoscale, iron oxide’s magnetic and dielectric properties are very different from its bulk properties and can be tuned and enhanced by utilizing different synthesis approaches. In this chapter, we summarize electromagnetic properties of magnetite (Fe3O4) nanomaterials such as, complex permeability, complex permittivity, magnetic and dielectric loss tangents, saturation magnetization, temperature dependence, and ferromagnetic resonance; and how these properties can be optimized by varying different synthesis parameters. Finally, Fe3O4 nanocomposites will be explored by using different synthesis approaches for implementation of RF and microwave applications and we will conclude the chapter with future recommendations.
Ba5Li2W3O15 (BLWO) electroceramics with different amounts of lithium carbonate (10–15%) were synthesized using the solid-state route. Powder x-ray diffraction (PXRD) and Raman spectroscopy showed the presence of the BaWO4 (BWO) phase in the samples. The excess lithium in the BLWO matrices contributed to an increase in the BWO phase and improved the thermal stability. Images obtained by scanning electron microscopy (SEM) showed grains without a well-defined morphology and with a low porosity. The dielectric properties in the microwave (MW) range for the dielectric resonator based on BLWO were analysed by the Hakki–Coleman and Silva–Fernandes–Sombra methods. The near-zero temperature coefficient of resonant frequency (6.59 ppm°C−1) was obtained for the sample synthesized with 15% Li2CO3. Numerical studies based on the coefficient of reflection (S11) and impedance values of the BLWO-based dielectric resonator antennas (DRA) were also conducted. They agreed well with the experimental results, which indicates that this material can be applied as an antenna device in the MW range.
In the present communication, the simultaneous co-immobilization by covalent binding of lipase A from Candida antarctica (CALA) and lipase B from Candida antarctica (CALB) in glutaraldehyde (GLU) activated chitosan (CHI) was optimized using the Taguchi method. Under optimized conditions (pH 9, 5 mM, 6:1 (protein load/g of support and 1 hour), it was possible to reach 80.00 ± 0.01% for the immobilization yield (IY) and 46.01 ± 0.35 U /g for the activity of the derivative (AtD); in this case, load protein and ionic strength were the only statistically significant parameters and, therefore, those that most influenced the immobilization process. Furthermore, at pH 7, CALA-CALB-CHI had a half-life 2-6 times longer than the mixture of CALA and CALB for a temperature range of 50-80 °C. CALA-CALB showed the highest activity at pH 7, whereas CALA-CALB-CHI, except at pH 7, was more active than the soluble lipase mixture in the pH range (5-9), especially at pH 9. CHI, CHI-GLU, and CALA-CALB-CHI were characterized by X-ray powder diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Thermogravimetry (TGA), and Energy Dispersive Spectroscopy (EDS), proving the immobilization of CALA and CALB in chitosan. CALA-CALB-CHI derivative evaluated in the kinetic resolution of halohydrins acetates rac-2-bromo-1-(2-chlorophenyl) ethyl acetate (2a) and rac-2-chloro-1-(2,4-dichlorophenyl) ethyl acetate (2b), to produce the corresponding halohydrins 3a-b, which are intermediates in the synthesis of the drugs chlorprelanine (antiarrhythmic) and luliconazol (antifungal), respectively. (S)-bromohydrin 3a was obtained with 79% enantiomeric excess (ee), whereas (S)-chlorohydrin 3b produced with 98% ee, conversion of 46% and E > 200. Additionally, molecular docking was performed to elucidate the hydrolysis interaction reaction between β-halohydrin acetates and lipases CALA-CALB.
Electrical and electronic device applications of the hybrid nanocomposite materials are primarily identified from their frequency dependent dielectric properties. In this context, herein, we report the complex dielectric permittivity of poly(vinylalcohol)(PVA)/montmorillonite(MMT) and PVA/poly(vinylpyrrolidone)(PVP)/MMT nanocomposites with varying MMT nanoclay amounts up to 10 wt% and the frequency from 1 MHz to 1 GHz, in order to address their nanodielectric uses in biodegradable electronic devices operative at ultrahigh frequencies. These melt compounded prepared hybrid polymer nanocomposites (PNCs) showed an increase in dielectric permittivity by about 20% at 1 MHz when the MMT concentration was increased, and a gradual decrease with the rise in frequency which revealed their nanofiller concentration and frequency tunable nanodielectric behaviour. The PVA/MMT nanocomposites have high dielectric permittivity as compared to that of the (PVA/PVP)/MMT nanocomposites confirming that the dielectric properties of these PNCs can also be controlled by considering an appropriate composition polymer blend matrix.
