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1.
Nanocrystalline Ni1?xZnxFe2O4 (0 ≤ x ≤ 1.0) powder with grain size of 30 nm was prepared using the spraying‐coprecipitation method. The obtained nanocrystalline Ni1?xZnxFe2O4 powder was sintered using conventional and microwave sintering techniques. The results show that the microstructure and magnetic properties of the sintered samples are obviously improved by microwave sintering of nanocrystalline Ni1?xZnxFe2O4 ferrite powder. The initial permeability of Ni1?xZnxFe2O4 ferrite increases with the increase in zinc concentration, although its resonance frequencies shift from high frequency to low frequency. The maximum initial permeability for microwave‐sintered Ni0.4Zn0.6Fe2O4 ceramic obtained at the temperature of 1170°C for 30 min reaches up to 360.9, and its resonance frequency is ~10 MHz. It may be attributed to the nanocrystalline Ni1?xZnxFe2O4 raw powder as well as the microwave sintering process, which results in a synergistic effect on improvement of the microstructure and magnetic properties.  相似文献   

2.
《Ceramics International》2017,43(7):5427-5433
(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4 powder was synthesized by a solid state reaction. Then, Ni0.4Zn0.6Fe2O4 was grown on the (Mg0.95Zn0.05)(Ti0.8Sn0.2)O4 particles in a hydrothermal environment to form a core-shell structure. (1-x)(Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4@xNi0.4Zn0.6Fe2O4 composite ceramics were sintered at 1200 °C with these powders. XRD, SEM, TEM analyses indicated that high dense core-shell ceramics without any foreign phase were obtained. Different types of sharp interfaces were self-assembled owing to the minimization of direct elastic energy in the hydrothermal environment. The composites enjoy good magnetic and dielectric properties, especially, good microwave dielectric properties with high saturation magnetization when the ferrite content is 0.3–0.5. The results provided a powerful experimental basis for the sensor and transducer.  相似文献   

3.
The cobalt-zinc ferrite (CZF) nanomaterials were prepared by citrate-gel method, and further calcined at 600°C. The single-phase cubic spinel structure of CZF was confirmed using the X-ray diffraction pattern. The average crystallite size was found to be in the range of 22-29 nm. The surface morphology was examined using the scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average particle size of Co0.6Zn0.4Fe2O4 was determined to be 19 nm using TEM study which is supporting the average crystallite size measured from the X-ray diffraction studies. The Fourier-transform infrared spectra revealed the two strong absorption bands in the series of ferrites between 4500 and 500 cm−1 and these are responsible for the characteristic of spinel ferrites. The presence of elements Cu, Zn, and Co of CZF was confirmed by the elemental spectral signals of energy dispersive spectroscopy. At room temperature, the magnetic measurements of pure ZnFe2O4 and Co0.6Zn0.4Fe2O4 were evaluated based on hysteresis curves (M-H curves). The results expressed that the addition of nonmagnetic Zn2+ ions increases the magnetic behavior in the mixed CZF samples. The antimicrobial activity of the ZnFe2O4 and Co0.6Zn0.4Fe2O4 nanoferrites was tested against harmful microbes.  相似文献   

4.
《Ceramics International》2023,49(20):33099-33110
In this study, spinel Ni0.5Zn0.5Fe2O4 doped with transition metal ions as well as rare-earth ions Ni0.4Zn0.4M′0.2Fe2O4 (M′ = Cu, Dy, Gd and Lu) and M″0.5Zn0.5Fe2O4 (M″ = Ni, Mn and Co) are developed using the sol-gel auto-combustion route, and the role of substitution on electromagnetic properties is investigated. The powder X-ray diffraction accompanied by Rietveld refinement signifies a single-phase spinel ferrite that belongs to Fd-3m space group for all the compositions. Rietveld refinement confirms that doped Cu2+, Dy3+, Gd3+ and Lu3+ ions are at random distribution between spinel tetrahedral and spinel octahedral sites against their preferential occupancy. The saturation magnetisation (MS) of Ni0.5Zn0.5Fe2O4 (MS = 50.5 emu/g) increased with partial doping showing MS = 60.08 emu/g for transition-metal doped Ni0.4Zn0.4Cu0.2Fe2O4 and MS = 109.7 emu/g for rare-earth doped Ni0.4Zn0.4Dy0.2Fe2O4, which was the highest among all the doped compositions. Doping enhances the dielectric permittivity of Ni0.5Zn0.5Fe2O4 from 4.2 to 6.5 for Ni0.4Zn0.4Cu0.2Fe2O4 and 7.7 for Ni0.4Zn0.4Dy0.2Fe2O4. Further, the reflection coefficient (RL) of all the doped compositions of Ni0.4Zn0.4M′0.2Fe2O4 (M′ = Cu, Dy, Gd and Lu) was less than −8 dB (85% absorption) throughout the frequency band of 8–12 GHz with an optimum material thickness of 3.5 mm. Transition metal ion doped Ni0.4Zn0.4Cu0.2Fe2O4 resulted in further improvement of its absorption characteristics of the incident EM waves with reflection coefficient (RL) less than −10 dB (between 84.15% and 90%) between 10 and 12 GHz at a material thickness of 3.5 mm in the X-band frequency range.  相似文献   

5.
Ni0.5Zn0.5Fe2O4 powders were prepared by a novel molten-salt synthesis method. The effects of calcination processes of the powders on their sintering behaviors were investigated. Compared with the synthesis by traditional solid-state reaction, the proposed molten-salt method can significantly reduce the synthesis temperature of Ni0.5Zn0.5Fe2O4 from 800 to 550°C below, and the prepared powders have relatively high sintering activity at low temperature, which can thus decrease the sintering temperature. However, the abnormal growth of grains is easy to occur during sintering, thus resulting in uneven grain size. In particular, during the molten-salt synthesis, the holding time for calcination is a dominant factor affecting the activity and crystallization degree of the resultant powders. From the point of view of increasing the density of sintered bodies, the optimal conditions for synthesizing Ni0.5Zn0.5Fe2O4 powder by the proposed molten-salt synthesis is 400°C for 6 h. In addition, the saturate magnetization of the finally obtained ferrite ceramics has nothing to do with the preparation processes, while their coercivity depends on their densification and grain size caused by their different processing routes.  相似文献   

6.
《Ceramics International》2016,42(14):15585-15591
(x)Ni0.4Zn0.6Fe2O4+(1−x)Ba0.6Sr0.4TiO3 composite ceramics with x=0.6, 0.7, 0.8, 0.9 and 1 were synthesized by solid state reaction method. The high dense composites have only two phases, i.e., Ni0.4Zn0.6Fe2O4 and Ba0.6Sr0.4TiO3. The permittivity ε′ of the composites decreases slightly with the frequency increasing from 3 MHz to 1 GHz. The permittivity ε′′ of the composites also shows a little increase with frequency in the 3 MHz–1 GHz range. The permeability displays a relaxation resonance within the 3 MHz–1 GHz frequency range. The permeability μ′ increases while the cut-off frequency decreases with the Ni0.4Zn0.6Fe2O4 concentration, obeying the Snoek's law μifr=constant. The permittivity ε′ of the composites decreases with Ni0.4Zn0.6Fe2O4 concentration. The composites have a relatively higher ε′ than the pure Ni0.4Zn0.6Fe2O4 at 1–10 GHz. In the frequency range of 1–10 GHz, the magnetic permeability μ′ reaches its maximum and μ′′ shows a minimum for the composite with x=0.6 in all ceramics. The permeability μ′ of the composites decreases with dc magnetic field at 1–10 GHz. The permeability shows a domain wall resonance, and the resonance frequency shifts to high frequency with the dc magnetic field. The permittivity was also influenced by the dc magnetic field due to a magnetodielectric effect.  相似文献   

7.
《Ceramics International》2021,47(20):28764-28769
Ni0.7Zn0.3A0.05Fe1.95O4 (A = La, Ce, and Nd) powders were obtained by the sol-gel combustion technique. The phase composition, microstructure, and electromagnetic properties of La3+, Ce3+, and Nd3+ substituted Ni0.7Zn0.3Fe2O4 were investigated. Compared with the Ni0.7Zn0.3Fe2O4 ferrite, the saturation magnetization of substituted Ni0.7Zn0.3Fe2O4 powders decreases due to the reduction of the super-exchange interaction by the substitution of La3+, Ce3+, and Nd3+at the Fe site. Furthermore, the enhanced dielectric constant of the substituted Ni0.7Zn0.3Fe2O4 ferrites prompts to the formation of good impedance matching and thereby improving the microwave absorption performance. The best reflection loss of Ni0.7Zn0.3Ce0.05Fe1.95O4 ferrite is −17.5 dB at 13.8 GHz, and the corresponding absorption bandwidth (RL ≤ 5 dB) can be achieved 10.9 GHz. These results suggested that the Ni0.7Zn0.3Ce0.05Fe1.95O4 ferrite is a potential composite for electromagnetic applications, particularly for broadband microwave absorption.  相似文献   

8.
《Ceramics International》2015,41(8):9843-9848
Ni0.4Zn0.6Fe2O4 powders were prepared by combustion synthesis with different amount of NaClO4. Phases, particle size and magnetic properties of the powders and annealed powders were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and vibrating sample magnetism (VSM). The excess content of NaClO4 offered significant advantages with respect to the size, morphology and magnetic properties of the powders. After annealing, sub-micro ferrite spherical powders with spinel phase in a range of 500–800 nm can be obtained. With the increase of the NaClO4 content, the saturation magnetization of the powders shows a maximum value at 68.8 emu/g when w=0.4, whereas the coercivity stayed nearly constant. The maximum saturation of annealed powders by combustion synthesis is much higher than the range reported in the literature.  相似文献   

9.
《Ceramics International》2022,48(3):3059-3069
In this work, an ultralight nanocomposite of graphene oxide aerogels as a matrix and nickel-zinc ferrite (Ni0.7Zn0.3Fe2O4) nanoparticles as a second phase for the absorption of electromagnetic waves in the frequency of 1–18 GHz were fabricated by the hydrothermal - freeze-drying method. α-Al2O3 nanoparticles were used for further impedance matching for applications in electromagnetic wave absorption. XRD, SEM, EDS, and VNA analyses were used to characterize the sample. The effects of the amount of Ni0.7Zn0.3Fe2O4 (NZF) nanoparticles (GO: NZF volume percent ratio = 5:1 and 2:1) on the absorption of electromagnetic waves were investigated.  相似文献   

10.
Nano-powders of Ni–Fe and Al2O3 were made from NiO and FeAl powders by high-energy ball milling. Nanocrystalline 5Ni0.6Fe0.4–Al2O3 composite was consolidated by high frequency induction heated sintering (HFIHS) method within 2 min from mechanically alloyed powders of Al2O3 and Ni–Fe. The average grain size and mechanical properties of the composite were investigated.  相似文献   

11.
To solve the heavy mass problem of the traditional spinel ferrite using as the microwave absorber, the CoxZn(1?x)Fe2O4 (= 0.2, 0.4, 0.6, 0.8) ferrite nanofibres were synthesized by electrospinning method. The phase composition, morphology, and electromagnetic properties were analyzed. The results showed that all the as‐prepared CoxZn(1?x)Fe2O4 ferrites exhibited the homogeneous nanofibrous shape. The saturation magnetization and coercivity were enhanced by tuning the Co2+ content. The electromagnetic loss analysis indicated that the Co0.6Zn0.4Fe2O4 ferrite nanofiber performed the strongest microwave attenuation ability. The microwave absorbing coating containing 15 wt% of Co0.6Zn0.4Fe2O4 ferrite nanofiber showed the reflection loss less than ?10 dB in the whole X‐band and 80% of the Ku‐band frequencies. Meanwhile, the surface density was only 2.4 Kg/m2.  相似文献   

12.
《Ceramics International》2022,48(6):7533-7549
(1-x)SrFe10Al2O19/(x)Co0.6Zn0.4Fe2O4-(SFAO/CZFO) hard/soft nanocomposite ferrite materials were synthesized by ‘one-pot’ self-propagating combustion route. The co-existence of the two magnetic phases were confirmed by XRD, FESEM, EDS and VSM. The prepared nanocomposite samples were also characterized by TGA/DSC, Raman spectroscopy and VNA. Exchange coupling between the hard and the soft magnetic grains was observed by determining the switching field distribution (SFD) curve. As a result of the competing effects of exchange interaction and dipolar interaction, magnetic parameters were observed to be sensitive to the incorporation of soft magnetic phase into the nanocomposite. Results showed that with the inclusion of soft magnetic phase, exchange coupling behaviour between the hard and the soft ferrite phases had significant influence on the microwave absorption capacity of the samples. Related electromagnetic parameters and impedance matching ratio of the nanocomposite system were discussed. A minimum reflection loss of ?42.9 dB with an absorber thickness of 2.5 mm was attained by the nanocomposite (90 wt%)SrFe10Al2O19/(10 wt %)Co0.6Zn0.4Fe2O4 at a matching frequency of 11.45 GHz. This assured the candidacy of SrFe10Al2O19/Co0.6Zn0.4Fe2O4 nanocomposite as a promising microwave absorption material in the X-band (8–12 GHz).  相似文献   

13.
《Ceramics International》2020,46(7):8884-8890
Complex three-dimensional nanosheet structure of ZnxFeyO was prepared by highly stable co-sputtering oblique angle deposition. Scanning electron microscopy was employed to observe surface morphology evolution of ZnxFeyO with different Fe concentrations. X-ray diffraction was employed to analyze compositions of ZnO, ZnFe2O4, and ZnFe2O4/Fe2O3 with Fe doping. Furthermore, specific nanostructures of ZnxFeyO decreased band gap and increased visible-light absorption ability. The ZnFe2O4/Fe2O3 sample exhibited higher photocatalytic efficiency than those of other films for the degradation of methylene blue. Addition of Fe led to the enhancement of photoelectrochemical properties of ZnFe2O4/Fe2O3 compared to pure ZnO and Fe2O3, and photocurrent response of ZnFe2O4/Fe2O3 was ~10 times than that of pure ZnO at constant potential of −0.2 V (vs. Ag/AgCl).  相似文献   

14.
The melamine salt of 5,5‐dimethyl‐1,3,2‐dioxaphos‐phorinane‐2‐oxide‐2‐hydroxide (IFR100) was used as an intumescent flame retardant in flame‐retarded polypropylene (PP). As a synergistic agent, nano‐Mn0.4Zn0.6Fe2O4 was incorporated into the PP/IFR100 composite at different proportions. The synergistic effects of nano‐Mn0.4Zn0.6Fe2O4 were studied by the limiting oxygen index (LOI) test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). The synergistic effect of the nano‐Mn0.4Zn0.6Fe2O4 additive with IFR100 was clearly observed by LOI. The TGA results showed that nano‐Mn0.4Zn0.6Fe2O4 improved the thermal stability of the PP/IFR100 system above 400°C. On the basis of the FTIR and XRD results, it was evident that nano‐Mn0.4Zn0.6Fe2O4 efficiently promoted the formation of a charred layer containing phosphocarbonaceous structures. The SEM micrographs indicated that nano‐Mn0.4Zn0.6Fe2O4 strengthened the structure of the char layer remaining after combustion. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers  相似文献   

15.
Sea bed logging is new technique for the detection of hydrocarbon reservoir. Magnitude of EM waves is important for the detection of deep target hydrocarbon reservoir below 4000 m from the sea floor. A new aluminium based EM transmitter is developed and NiZn (Ni0.8Zn0.2Fe2O4) ferrite with and with out multiwall carbon nano tubes (MWCNTs) polymer composites as magnetic feeders are used in a scaled tank. Nickel zinc ferrite plays an important role in many applications due to its best magnetic properties. Nanocrystalline NiZn (Ni0.8Zn0.2Fe2O4) ferrite and novel Ni0.8Zn0.2Fe2O4-MWCNTs composites were prepared by sol-gel route. The samples were sintered at 750-950 °C and were characterized by XRD, FESEM, HRTEM and Raman spectroscopy. Single phase of Ni0.8Zn0.2Fe2O4 having [3 1 1] major peak was obtained by sol-gel method at 750 °C and 950 °C. FESEM micrographs show that grain size increases with the increase of sintering temperature and ranges from 24 to 60 nm. FESEM and HRTEM results showed coating of Ni0.8Zn0.2Fe2O4 on MWCNTs and show better morphology at the sintering temperature of 750 °C. The magnetic properties measured from impedance vector network analyzer showed that sample (Ni0.8Zn0.2Fe2O4-MWCNTs) sintered at 750 °C have higher initial permeability (20.043), Q-factor (50.047), and low loss factor (0.0001) as compared Ni0.8Zn0.2Fe2O4-MWCNTs sintered at 950 °C. Due to better magnetic properties, Sample (Ni0.8Zn0.2Fe2O4-MWCNTs sintered at 750 °C) composites were used as magnetic feeders for the EM transmitter. It was found that magnitude of EM waves from EM transmitter increased up to 243% by using Ni0.8Zn0.2Fe2O4-MWCNTs polymer composites.  相似文献   

16.
Magnetoelectric composite ceramics of spinel ferrite Ni0.5Zn0.5Fe2O4 (NZFO) with high magnetic permeability and tetragonal perovskite Pb(Zr0.48Ti0.52)O3 (PZT) with high piezoelectric constant were synthesized by common solid state reaction method. XRD and SEM showed that high dense composite ceramics without any foreign phases were obtained. The ceramics showed excellent dielectric and magnetic properties, which were stable in a large frequency range. The dielectric peak became wider with the ferrite content in the permittivity spectrum with temperature. With the increase in the ferrite content, the magnetic Curie temperature shifted to higher temperature and closed to that of the pure ferrite. In addition, the magnetoelectric coefficient enhanced as the increase in the ferrite content. The properties of the composite ceramics could be adjusted by the ferrite content. These research results provided a powerful experimental basis for the sensor and transducer in microelectronic and microwave devices.  相似文献   

17.
The structural and dielectric properties of SHS-produced yNi1 − x Cd x Fe2O4 + (1 − y)Ba0.8Sr0.2TiO3 (x = 0.2, 0.4, 0.6; y = 15, 30, 45%) magnetoelectric composites were characterized by XRD, SEM, and resistivity/dielectric measurements. SEM images reveal that SHS reaction can produce two pure phases simultaneously. The grown Cd-substituted nickel ferrite grains were well dispersed in a BST matrix. A decrease in resistivity with temperature shows the semiconducting nature of synthesized samples. The dielectric results demonstrated an attractive response of dielectric constant to frequency and temperature. The Curie temperature of about 480°C was observed in the Ni0.4Cd0.6Fe2O4 + Ba0.8Sr0.2TiO3 composite.  相似文献   

18.
The as-prepared Ni0.5Zn0.5Fe2O4 powders fabricated directly from the solution of metal nitrates by the refluxing method were testified by the analysis of XRD, TEM, SAED and HRTEM. XRD pattern indicated that obtained Ni0.5Zn0.5Fe2O4 powders were single phase with spinel structure, TEM analysis showed that the powders with cubic shape were uniform in particle size of about 10-20 nm. Ceramics prepared by the as-synthesized Ni0.5Zn0.5Fe2O4 powders sintered at various temperatures between 950 °C and 1150 °C for 2 h were observed by SEM technique, which indicated that the Ni0.5Zn0.5Fe2O4 ferrites can almost be sintered to theoretic density at 1100 °C for 2 h, lower by at least about 200 °C compared with those ferrites prepared by the conventional oxide method. The relative magnetic loss tanδ/μi of the ceramic samples sintered at the temperature 1050 °C was measured to be of the order of 10− 4-10− 5 in the frequency range from 1 MHz to 10 MHz, and the threshold frequency of the ferrites was 77.2 MHz.  相似文献   

19.
《Ceramics International》2022,48(3):3417-3425
Zn-doped nickel ferrite nanoparticles (ZnxNi(1-x)Fe2O4) were synthesized using the co-precipitation technique. The structural and compositional studies of the ZnxNi(1-x)Fe2O4 nanoparticles revealed their face-centred cubic spinel structure and an appropriate amount of Zn doping in nickel ferrite nanoparticles, respectively. The morphological analysis had been carried out to obtain the particle size of the synthesized nanoparticles. The magnetic studies revealed the superparamagnetic nature of the ZnxNi(1-x)Fe2O4 nanoparticles, and the maximum magnetization of 30 emu/g for the Zn0.2N0.8Fe2O4 sample. The M ? H curves were fitted with the Langevin function to obtain the magnetic particle diameter of ZnxNi(1-x)Fe2O4 nanoparticles. The electrical conduction in ZnxNi(1-x)Fe2O4 nanoparticles was explained through the Verway hopping mechanism. The Zn0.2N0.8Fe2O4 nanoparticle exhibited a higher electrical conductivity of 42 μS/cm and surface charge of ?29/7 mV due to the enhanced hopping of Fe3+ ions in the octahedral sites. Owing to this nature, they were identified as the suitable candidates in the applications such as thermoelectrics, hyperthermia, magnetic coating and for the preparation of conducting ferrofluids.  相似文献   

20.
《Ceramics International》2022,48(7):9090-9098
Here we introduce a controllable route for the efficient synthesis of Zn0.6Ni0.3Cu0.1Fe2O4 ferrite glass-ceramic with enhanced electromagnetic wave (EMW) absorbing performance. By adding a certain amount of Zn, Ni, Cu and Fe oxides into the SiO2–Al2O3–B2O3–CaO-R2O glass system, the microstructure of three-dimensional dendritic ferrites combined with amorphous SiO2-rich phase is constructed through a high-temperature melt and quenching route. The good EMW absorption performance is attributed to the unique combination of amorphous glass and spinel ferrite, which improves the impedance matching of the material and absorbs EMW by the dielectric loss and magnetic loss. Moreover, the dendritic ferrite crystal phase is compounded with the SiO2-rich amorphous phase to form grain boundaries and crystal-amorphous interfaces, which enhances the interfacial polarization and builds multiple transmission-absorption mechanisms. The results show that the reflection loss peak value of the glass-ceramics containing 60 wt% Zn0.6Ni0.3Cu0.1Fe2O4 spinel is ?42.16 dB with the sample thickness of 2 mm, and the effective absorption band range (reflection loss ≤ -10 dB) is 3.76 GHz (13.6–17.36 GHz) at 1.5 mm. This approach presents a scalable and low-cost solution that may be applied to the design of high-efficiency EMW consumption components in the future.  相似文献   

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