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1.
《Ceramics International》2022,48(4):4886-4896
Recent studies show that the chemical composition and shape of magnetic nanoparticles (NPs) play an important role in their properties. In particular, the bimagnetic NPs display useful and in many cases, more interesting properties than single-phase NPs. In this work, we prepared Fe3O4 and CoFe2O4 cube-like NPs and bimagnetic hard/soft (CoFe2O4/Fe3O4) and soft/hard (Fe3O4/CoFe2O4) nanocomposites (core/coating) using a facile and eco-friendly co-precipitation method that allows the synthesis of the cube-like NPs at temperatures near room temperature. The phase purity and the crystallinity of the NPs with a spinel structure were confirmed by the X-ray diffraction and infrared spectra techniques. Transmission electron microscopy (TEM) images revealed that the NPs have a cubic-like shape with an average dimension of 20 nm. Energy dispersive X-ray analysis, Mössbauer spectroscopy and SQUID magnetic measurements indicated the co-existence of Fe3O4 and CoFe2O4 phases in nanocomposites. In addition, the hysteresis loops exhibited a single-phase behavior in the nanocomposites that indicates there is a good exchange-coupling interaction between the hard and soft magnetic phases. The CoFe2O4/Fe3O4 nanocomposites presented a larger saturation magnetization than the CoFe2O4 NPs that is effective for their use in magnetic hyperthermia. Finally, we studied the hyperthermia properties of samples in an alternating magnetic field with a frequency of 276 kHz and field amplitude of 13.9 kA/m. Our results showed that magnetic hyperthermia efficiency simultaneously depends on the composition of samples along with magnetic anisotropy and saturation magnetization. 相似文献
2.
《Ceramics International》2016,42(12):13755-13760
Sol-gel synthesis of novel MnxGa1−xFe2O4 (x=0–1) magnetic nanoparticles (MNP's) was studied. An inverse spinel crystalline structure was identified for all samples. Magnetization saturation values (Ms) were in the range of 21.4–42.6 emu/g, while coercive field (Hc) was less than 27.4 Oe in all cases. Selected compositions of MnxGa1−xFe2O4 (x=0.6, 0.8) showed nanoparticles with near-spherical morphology and average size of 15 nm. Magnetic induction curves indicate that a suspension concentration of MNP's equal or higher than 4.5 mg/mL was sufficient to reach the temperature required for hyperthermia treatment (>43 °C) in less than 10 min. The incorporation of Mn ions into the crystalline structure led to an increase of the magnetic response of the MNP's when an alternate magnetic field was applied, requiring a shorter time of exposition and a low dose of MNP's, which make these nanoparticles potential candidates for magnetic hyperthermia. 相似文献
3.
《Ceramics International》2021,47(19):27462-27468
As a common flux agent, B2O3–CuO was introduced into Li2TiO3 system to reduce the sintering temperature for the requirements of LTCC applications. The optimal mass ratio of CuO to B2O3 was innovatively explored. When the mass ratio of CuO to B2O3 increased to 1.2:1.0, excellent microwave dielectric properties were obtained in LTMF<ZN0.892+CB1.2 ceramic of εr = 13.23, Q × f = 62,749 GHz, τf = -2.48 ppm/°C and the sintering temperature was reduced from 1300 to 930 °C. In a wide temperature range, the sample still maintain high temperature stability of |τf| < 5 ppm/°C (-40–120 °C). Based on the LTMF<ZN0.892+CB1.2 substrate, a millimeter wave microstrip antenna resonated at 30.12 GHz was designed with a considerably high radiation efficiency of 93.94% and a signal gain of 4.87 dB. Comprehensive microwave dielectric properties make LTMF<ZN0.892+CB1.2 become a candidate material for LTCC applications. 相似文献
4.
《Ceramics International》2023,49(15):25170-25178
Polymer-based magnetoelectric (ME) nanocomposites exhibit a low ME effect and high bias field at room temperature, which severely limits their application in flexible wearable sensors. To overcome these obstacles, Zn-doped magnetic nanoparticles of CoZnxFe2-xO4 (x = 0, 0.1, 0.2, and 0.3) were prepared by an auto-combustion method in this work. The obtained magnetostrictive curves imply that Zn element doping can improve greatly the piezomagnetic coefficient of magnetic nanoparticles, and among the tested materials, CoZn0.1Fe1.9O4 has the largest piezomagnetic coefficient. Composite films of poly(vinylidene fluoride-trifluoroethylene) and CoZn0.1Fe1.9O4 (P(VDF-TrFE)/CoZn0.1Fe1.9O4) were prepared by spin coating. The maximum ME voltage coefficient of P(VDF-TrFE)/CoZn0.1Fe1.9O4 composite film with a filler weight concentration of 10 wt% is 87.9 mV cm−1 Oe−1 with a bias field of 1050 Oe and a resonance frequency of 46 kHz, which is the highest value reported in the literature of 0–3 type polymer-based ME composite films at present. To evaluate the composite films for application in magnetic sensors, the ME output voltage was measured at a bias field of 1050 Oe with increasing AC magnetic field, demonstrating a good linear relationship with linearity of 0.999. These results indicate that the piezomagnetic coefficient of magnetic materials is an the important factor for the great enhancement of the ME voltage coefficient. This work provides a new approach for the synthesis of more effective polymer-based ME nanocomposites for potential applications in smart wearables. 相似文献
5.
In this paper we studied the structural, dielectric, magnetic and magnetoelectric properties of (x)BaTiO3–(1 ? x)Co0.6Zn0.4Fe1.7Mn0.3O4 particulate composite series where x = 0.50, 0.60 and 0.70. BaTiO3–Co0.6Zn0.4Fe1.7Mn0.3O4 composite has the advantage of being non-toxic and environmental friendly from the point of view of device fabrication. High ME voltage coefficients were obtained in the whole series with the highest value of αE ~ 73 mV/cm Oe achieved in sample x = 0.50 containing equal mole fractions of both the component phases. This value of αE is an order of magnitude higher than that of particulate sintered BaTiO3–CoFe2O4 composites (~2–4 mV/cm Oe). Dielectric characteristics for these samples indicated two anomalies: (i) one at low temperature close to ferroelectric to paraelectric transition temperature of pure BaTiO3 and (ii) another at higher temperature related to the magnetic transition in ferrite, a characteristic dielectric feature of composite sample. 相似文献
6.
《Ceramics International》2022,48(1):578-586
The controlled and stable crystal structure, reduction in Curie temperature and semiconducting nature of oxide materials are the key factors for magnetoelectrical applications. Therefore, Co0.6Mn0.4GdxFe2-xO4 where x = 0, 0.033, 0.066 and 0.10 were synthesized to analyse the structural, morphological, magnetic, and electrical properties using a sol-gel autocombustion approach. The X-ray diffraction pattern reveals that the cubic crystallite size decreases with increasing smaller content of Gd3+ oxides without any secondary phase. Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) study explain the complete morphology, agglomeration and dense structure of rare earth-doped Gd oxide in the mixed Co–Mn spinel ferrite nanoparticles. Fourier transform infrared spectra confirms the formation of a spinel structure with absorption bands below 1000 cm?1. The magnetic analysis shows that the saturation magnetization (59.20 emu/g - 49.71 emu/g) and coercivity (985.21 Oe – 254.11 Oe) of the synthesized samples decreased with increasing content of Gd3+ ions. The increase in DC conductivity with increasing temperature verifies the semiconducting nature of the synthesized samples, and a higher DC conductivity of the Co0.6Mn0.4Gd0.10Fe1.90O4(CMGF3) samples was observed at approximately 0.0362 S/cm at 973 K temperature. 相似文献
7.
《Ceramics International》2023,49(16):26568-26577
How to synchronously reduce eddy current loss and hysteresis loss still remains a challenge for achieving low core loss of soft magnetic composite (SMC). In-situ surface oxide effectively combines the formation of insulating layer and the release of internal stress during the molding process. In this study, FeSiAl SMC has been fabricated by powder metallurgy method with in-situ oxidated FeSiAl powder, in which FeSiAl powder are covered by outer Fe3O4 insulating layer and inter super-thin Al2O3/SiO2 hybrid layer. Fe3O4 layer alleviates dilution magnetic effect, ensuring high saturated magnetization and effective permeability. The super-thin Al2O3/SiO2 hybrid layer enhances electrical resistance, reducing eddy loss. Effects of the in-situ oxidation time on insulating layer and soft magnetic performances of SMC are investigated in detail. Synchronous reduction of eddy current loss and hysteresis loss is achieved through high resistance accompanied with proper insulating layer thickness and low coercive force provided by the special microstructure. For powder with 90 min oxidation at 500 °C, core loss of SMC is low up to 64 mW/cm3 at 50 mT and 100 kHz and 363 mW/cm3 at 100 mT and 100 kHz, while the permeability is kept at 50 until 1100 kHz and is stable until 140 °C. Meanwhile, DC bias performance reaches 51.2% at 100 Oe applied field and Q value is 104.8 at 400 kHz. 相似文献
8.
High-performance 0.9Al2O3-0.1TiO2 microwave dielectric ceramics prepared by digital light processing
《Ceramics International》2023,49(1):126-133
In this work, the 0.9Al2O3-0.1TiO2 ceramic sample with good microwave dielectric properties and complex structures can be well fabricated by digital light processing (DLP). A relationship between dispersant content and rheological behavior of 0.9Al2O3-0.1TiO2 slurry was explored. When dispersant content was 3.0 wt%, 0.9Al2O3-0.1TiO2 slurry with high solid loading (50 vol%) and low viscosity (2.9 Pa s) could be obtained. 0.9Al2O3-0.1TiO2 ceramic parts with high accuracy were fabricated successfully by adding 3.0 wt% photoinitiator under 600 mJ/cm2 exposure energy. With the increase of sintering temperature from 1400 °C to 1600 °C, relative density, dielectric constant (εr), and quality factor (Q × f) of 0.9Al2O3-0.1TiO2 ceramic sample increased first and then decreased, and all reached the maximum value at 1550 °C due to the uniformity and densification of microstructures. The temperature coefficient of resonant frequency (τf) value showed an almost monotonous increase, changing from negative to positive, and near-zero τf value at 1550 °C. In addition, 0.9Al2O3-0.1TiO2 ceramic samples sintered at 1550 °C fabricated by DLP method presented much better microwave dielectric properties: εr = 11.30 ± 0.02, Q × f = 35,345 ± 143 GHz (@~12 GHz), τf = 2.16 ± 0.21 ppm/°C than that of by dry pressing method: εr = 11.16 ± 0.11, Q × f = 30,195 ± 257 GHz (@~12 GHz), τf = 4.45 ± 0.13 ppm/°C, especially the Q × f value achieved a 17% increase. Accordingly, DLP technique, which has advantages of producing relatively high properties and complex geometry of microwave dielectric ceramics as well as without extra high-cost mold, greatly satisfies application requirements. 相似文献
9.
《Ceramics International》2023,49(1):918-932
The structural transformation, ferro-paraelectric and magnetic ordering induced dielectric phase transitions, multiferroic properties, relaxation and conduction mechanisms of (Gd1-xBax)(Fe1-xTix)O3 ceramics with different compositions (x = 0.0–0.4) have systematically been investigated. The chemical route is adopted for material synthesis. Rietveld refinement reveals the structural transformation from orthorhombic to mixed phase (coexistence of orthorhombic and tetragonal phase) for x > 0.2. The analysis of the FESEM micrographs suggests a decrease in average grain size with the increase in BT in the composition. Dielectric anomalies are explained based on ferroelectric-paraelectric phase transition of BaTiO3, polarization induced by a spin reorientation, and antiferromagnetic ordering of GdFeO3. The multiferroic properties of all the samples are studied from P-E, M-H, and magneto-electric plots. The improved magnetic properties in compositions x = 0.1–0.3, make them suitable candidates for spintronic devices. The maximum magneto-electric coupling coefficient of 4.77 mV/cm?Oe in the composition x = 0.3, makes it very much suitable for application in magnetoelectric coupling devices. 相似文献
10.
《Ceramics International》2017,43(4):3879-3884
The purpose of the research was to improve the intrinsic magnetic properties of strontium ferrite by substituting lanthanum and cobalt for strontium and iron. The salt-assisted ultrasonic spray pyrolysis (SA-USP) following calcination process were used to from La-Co substituted strontium ferrite particles (LaxSr1-xFe12-yCoyO19), and their compositional dependent magnetic properties systemically investigated. All the samples were calcined at 1050 °C for 1 h in an air atmosphere to yield single-phased hexagonal particles several hundred nanometers to microns in size. A saturation magnetization of 70.76 emu/g and a coercivity 7265 Oe were obtained at a composition of La0.25Sr0.75Fe11.75Co0.25O19. The amount of Co was reduced to obtain an optimized saturation magnetization of 71.40 emu/g and a coercivity of 7572 Oe at a composition of La0.25Sr0.75Fe11.8Co0.2O19. 相似文献
11.
The article reports on low-temperature high-rate sputtering of hydrophilic transparent TiO2 thin films using dc dual magnetron (DM) sputtering in Ar + O2 mixture on unheated glass substrates. The DM was operated in a bipolar asymmetric mode and was equipped with Ti(99.5) targets
of 50 mm in diameter. The substrate surface temperature Tsurf measured by a thermostrip was less than 180 °C for all experiments. The effect of the repetition frequency fr was investigated in detail. It was found that the increase of fr from 100 to 350 kHz leads to (a) an improvement of the efficiency of the deposition process that results in a significant
increase of the deposition rate aD of sputtered TiO2 films and (b) a decrease of peak pulse voltage and sustaining of the magnetron discharge at higher target power densities.
It was demonstrated that several hundreds nm thick hydrophilic TiO2 films can be sputtered on unheated glass substrates at aD = 80 nm/min, Tsurf < 180 °C when high value of fr = 350 kHz was used. Properties of a thin hydrophilic TiO2 film deposited on a polycarbonate substrate are given. 相似文献
12.
《Journal of Industrial and Engineering Chemistry》2014,20(6):3970-3974
Fe3O4 nanoparticles were synthesized via a simple surfactant-free sonochemical reaction. Room temperature synthesis without using inert atmosphere is the novelty of this work. The effect of different parameters on the morphology of the products was investigated. The magnetic properties of the samples were also investigated using an alternating gradient force magnetometer. Fe3O4 nanoparticles exhibit a ferromagnetic behavior with a saturation magnetization of 66 emu/g and a coercivity of 39 Oe at room temperature. For preparation magnetic nanocomposite, Fe3O4 nanoparticles were added to the polyvinyl alcohol (PVA). Nanoparticles can enhance the thermal stability and flame retardant property of the PVA matrix. 相似文献
13.
Yi-Cheng Liou Chao-Yang Shiue Min-Hang Weng 《Journal of the European Ceramic Society》2009,29(6):1165-1171
TiO2 added NiNb2O6 ceramics produced using a reaction-sintering process were investigated. Pure columbite NiNb2O6 could be obtained without TiO2 addition. With 30 and 40 mol% TiO2 addition, a phase with the same structure of Ni0.5Ti0.5NbO4 formed. Grain growth is easier in pellets with 30 and 40 mol% TiO2 addition than in the NiNb2O6 pellets. Microwave dielectric properties: ?r = 20.7, Q × f = 19,800 GHz (at 9 GHz) and τf = ?31.9 ppm/°C were obtained for NiNb2O6 pellets sintered at 1300 °C/2 h. ?r around 45, Q × f = 5400–7700 GHz (at 6 GHz) and τf ~ 73 ppm/°C were obtained in pellets with 30 mol% TiO2 addition. ?r around 50, Q × f = 3800–5700 GHz (at 6 GHz) and τf ~ 99 ppm/°C were obtained in pellets with 40 mol% TiO2 addition. 相似文献
14.
《Ceramics International》2023,49(19):30924-30936
Rare earth ion substitution is one of the most important methods for adjusting the magnetic properties of M-type hexagonal ferrites; however, the regularity of these phase formations has rarely been studied. In this work, La substituted Sr hexaferrite LaxSr1-xO·nFe2O3 (La-SrM, 4.9 ≤ n ≤ 6.0, 0 ≤ x ≤ 0.6) was prepared using the traditional ceramic method. The effects of the Fe/Sr molar ratio (n), calcining temperature, and La3+ substitution (x) on SrM phase formation, the crystalline structure, and magnetic properties were investigated. With an increase of x up to a maximum value of 0.5–0.6, a higher calcining temperature is required to form the single M-phase of La-SrM samples. However, the optimal n values of single-phase La-SrM samples differ as the La substitution varies: when x = 0.1, n = 5.5–6.0; x = 0.2, n = 5.5–5.9; x = 0.3, 0.4 and 0.5, n = 5.7–5.8. The magnetic measurements show that La0.2Sr0.8O·5.8Fe2O3 has the highest specific saturation magnetization (σs), which is 2.2% higher than that of unsubstituted SrM (SrO·6Fe2O3), while the anisotropic field (HA), the anisotropic constant (K1), and Neel point (TN) of La3+ substituted SrM decreased. Detailed structure analyses were conducted to explain the changes in magnetic properties. Fe3+ in the spin-up 2a sublattice of LaxSr1-xO·5.8Fe2O3 decreased by approximately 5% from 98.5% (x = 0) to 93.85% (x = 0.4) with an increase in x. Additionally, a small amount of Fe3+ was reduced to Fe2+ in the spin-down 4f2 sublattice with the maximum reduction amount of 4.13% reached at x = 0.2, thereby improving σs. The decrease in the bond angle of (4f1) Fe3–O2–Fe5 (12k), (2a) Fe1–O4–Fe3 (4f1), and (4f1) Fe3–O4–Fe5 (12k) lead to the weakening of Fe–O–Fe superexchange of La-SrM so that HA, K1, and Tn decreased with increasing values of x. This work lays a solid foundation for the study of process regulation and ion substitution of permanent magnet ferrite. 相似文献
15.
Magnesium-substituted lithium ferrite of different composition (Li0.5Fe2.5−xMgxO4−δ) were prepared for x = 0.0–1.0 by conventional ceramic technique. The crystal structure characterization and morphology were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). Initial permeability and quality factor were measured in the frequency range of 1 kHz to 100 MHz. The permeability decreased gradually from μ (f = 10 MHz) = 34.0 for Li0.5Fe2.5O4 to μ (f = 10 MHz) = 11.5 for Li0.5Fe1.5Mg1.0O4. Electrical conductivity measurements were carried in the range of 250–700 °C in air. The maximum electrical conductivity, σ700 °C = 0.1274 S/cm has been found to be for Li0.5Fe2.5O4 specimen. With increasing Mg-substituted content, the decreased in the electrical conductivity. 相似文献
16.
Shielding properties of copper-doped NiZn ferrites in the frequency range 1 MHz–1.8 GHz, were explored. Samples of composition CuxNi0.4?xZn0.6Fe2O4 with x=0.0, 0.1, 0.2, 0.3 and 0.4, were prepared by the ceramic method. Powders and pellets were sintered at 1100 °C for 2 h. The effect of compositional variation on structural, dielectric and magnetic properties was investigated in order to relate them with the attenuation behavior. X-ray diffraction measurements confirmed the formation of a spinel structure at the selected sintering temperature. The addition of copper promotes grain growth, increases the samples density and modifies saturation magnetization, permeability and permittivity in the explored frequency range. As the reflection loss absolute values (|RL|) for all the samples are above 35 dB, they can all be considered as shielding materials. The optimum attenuation was observed for x=0.2, reaching a maximum |RL| of almost 60 dB at 10 MHz with an attenuation bandwidth of at least 3 MHz. 相似文献
17.
Mei Guo Gang Dou Shuping Gong Dongxiang Zhou 《International Journal of Applied Ceramic Technology》2013,10(5):857-865
The influence of BaCu(B2O5) (BCB) on densification, phases, microstructure and microwave dielectric properties of ZnNb2O6–xTiO2 (x = 1.70–1.90) composite ceramics have been investigated. Undoped ZnNb2O6–1.8TiO2 ceramics sintered at 1200°C exhibit temperature coefficient of resonant frequency (τf) ~9.25 ppm/°C. When BaCu(B2O5) was added, the sintering temperature of the ZnNb2O6–1.8TiO2 composite ceramics was effectively reduced to 950°C. The results indicated that the permittivity and Q × f were dependent on the sintering temperature and the amounts of BaCu(B2O5). Addition of 3.0 wt% BaCu(B2O5) in ZnNb2O6–1.8TiO2 ceramics sintered at 950°C showed excellent dielectric properties of εr = 40.9, Q × f = 12,200 GHz (f = 5.015 GHz) and τf = +0.3 ppm/°C. 相似文献
18.
《Journal of the European Ceramic Society》2006,26(10-11):1933-1936
Bi2O3–TiO2 composites are known to possess attractive microwave dielectric properties. However, producing LTCC analogues with equally promising dielectric properties is problematic. Here, we show that judicious choice of both TiO2 starting powders and dopants can produce composites with excellent properties. Three TiO2 powders were evaluated: 1 μm-anatase, 1 μm-rutile and a nanosized (30 nm) mixture of 75–25 anatase-rutile. The best dielectric properties were obtained by using uncalcined nanosized anatase/rutile with Bi2O3 powder. By doping this Bi2O3–TiO2 powder mixture with 0.112 wt.% CuO dielectric properties of Q × f = 9000 GHz, ɛr = 80 and τf = 0 ppm/K (at 300 K) were obtained at a sintering temperature of 915 °C. 相似文献
19.
《Ceramics International》2020,46(6):7089-7098
In this study, series of hard/soft SrTb0.01Tm0.01Fe11.98O19/AFe2O4 (where A = Co, Ni, Zn, Cu and Mn) composites were fabricated via a single-pot citrate sol-gel approach. The structure, morphology and magnetic properties of prepared composite samples were investigated via X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM - TEM) and vibrating sample magnetometer (VSM). The XRD analysis of all composite samples showed the co-existence of both hard (Sr hexaferrite) and soft (spinel ferrites) ferrite phases with minor impurity. TEM micrographs displayed well-distinguished particles of SrM and AFe2O4 with different symmetry. The magnetic M − H hysteresis loops were performed at room temperature (RT; T = 300 K) and low temperature (T = 10 K) using VSM instrument. The magnitudes of various magnetic parameters including saturation magnetization (Ms), squareness ratio (SQR = Mr/Ms), remanence (Mr) and coercivity (Hc) were determined. M − H loops revealed smoothed curves and the dM/dH versus H curves exposed only a single peak, indicating that the exchange-coupling effect was accomplished in one-step. Moreover, the various composites showed relatively high Ms, Mr, and Hc values. The obtained results revealed the occurrence of exchange-coupling effect among soft and hard magnetic phases. The magnetic properties of various hard/soft SrTb0.01Tm0.01Fe11.98O19/AFe2O4 composites (where A = Co, Ni, Zn, Cu and Mn) were evaluated also by ZFC-FC magnetization measurements with respect to different soft phases. A peak temperature in ZFC curves occurred for various prepared composites. This peak is attributed to competition of the movement of magnetic domain walls and thermal activation. The present study offers a simple but efficient route for the fabrication of exchange-coupled nanocomposites with the chemical formula SrFe11.98Tb0.01Tm0.01O19/AFe2O4 (where A = Co, Ni, Zn, Cu and Mn) having controllable magnetic properties. It was found that the SrTb0.01Tm0.01Fe11.98O19/CoFe2O4 composite sample displayed the strongest exchange-coupling behavior among the different prepared composite products. 相似文献
20.
Single-phase Bi4NdTi3Fe0.7Ni0.3O15 polycrystalline samples were synthesized following a multicalcination procedure. The sample exhibited multiferroic property at room temperature, which was demonstrated by the ferroelectric (2Pr=8.52 μC/cm2, 2Ec=89 kV/cm at applied electric field 110 kV/cm) and magnetic (2Mr=388 m emu/g, 2Hc=689 Oe at applied magnetic field 1.04 T) hysteresis loops. More importantly, magnetoelectric coupling effect is observed from measurements of electrical properties not only under small but also under large electric signal when an external magnetic field is applied. The present results suggest a new candidate for a room temperature multiferroic material with magnetoelectric coupling effect. 相似文献