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1.
In the present study, synthesis of different rare earth (RE) doped cobalt ferrite nanoparticles was done via facile sol-gel auto-combustion method using four different RE metal ions: Eu, Gd, Dy and Nd. The RE substituted cobalt ferrite nanoparticles were then characterized using FT-IR, powder XRD, HR-TEM, SAED, EDX, VSM and DRS techniques. From the characterization results, a significant variation in the structural, magnetic and optical properties of pure cobalt ferrite was observed with the introduction of different RE metal ions. This change in the properties was emerged due to the distortion of the ferrite crystal lattice due to replacement of smaller ionic radii Fe3+ ions with the comparatively larger ionic radii RE3+ metal ions. The catalytic activity of the fabricated RE doped cobalt ferrite nanoparticles was studied for the photo-Fenton degradation of cationic and anionic dyes. Under visible light irradiation, the as prepared RE doped nanoparticles exhibited great enhancement in the photo-Fenton degradation of dye molecules as compared to pure cobalt ferrite nanoparticles. The enhancement in the degradation rate was ascribed to the generation of defects in the crystal lattice, lower crystallite size and reduced band gap energy values which facilitated the facile transfer of photo-generated holes and electrons. Best catalytic results were obtained for CoNd0.08Fe1.92O4 for SO dye (k?=?2.23?×?10?1 min?1) which were found to be around 9 times higher than the pure cobalt ferrite nanoparticles (k?=?0.23?×?10?1 min?1).  相似文献   

2.
《Ceramics International》2021,47(20):28240-28251
The gadolinium substituted cobalt ferrite (CoFe1.9Gd0.1O4) nanoparticles and CoFe1.9Gd0.1O4/Polyaniline (PANI) microwave absorber were synthesized by sol-gel auto combustion technique using lemon juice and in-situ polymerization method respectively. X-ray patterns confirmed the formation of single phase cubic structure. The crystallite size of the synthesized CoFe1.9Gd0.1O4 nanoparticles are within the range of 15–68 nm. The saturation magnetization of CoFe1.9Gd0.1O4 ferrite/Polyaniline (PANI) composite was reduced due to nonmagnetic PANI. The reflection loss for microwave absorbing properties of CoFe1.9Gd0.1O4 ferrite nanoparticles and CoFe1.9Gd0.1O4/PANI nanocomposite were investigated and minimum value of reflection loss was found to be −16.85 dB at 13.52 GHz for nanoparticles of thickness 2.5 mm and −25.59 dB at 11.92 GHz for CoFe1.9Gd0.1O4/PANI nanocomposite of thickness 2.0 mm) respectively. The prepared samples have low density, high surface resistivity and enhanced attenuation constant. The nanocomposite exhibits excellent absorption performance over a broad band range in the radar band.  相似文献   

3.
《Ceramics International》2016,42(10):11958-11965
The aim of this study is to synthesize and assess the potential applications of rare earth doped cobalt ferrite nanoparticles in cancer treatment through hyperthermia.The synthesis of CoFe2−xRExO4 (where RE=Yb, Dy, Gd and x=0.01–0.3) through the co-precipitation method is presented. The composition and properties of the nanoparticles where investigated and evaluated in correlation with their heat generating capability. The XRD and EDX analysis indicated phase separation for high rare earth content with the appearance of Gd2O3 and Dy2O3 secondary phases, which leads to unwanted changes in the nanoparticles' magnetic properties and consequently of the specific absorption rate. All the nanoparticles present functional group belonging to the surfactant as determined by FT-IR and Raman. Magnetic and specific adsorption rate measurement suggest increases in saturation magnetization and SAR value in doped ferrites, compared to CoFe2O4 with as much as 26% and 15% for Dy doped and Gd doped samples respectively.  相似文献   

4.
《Ceramics International》2020,46(10):16196-16209
In this study, pure cobalt ferrite (CoFe2O4) nanoparticles and europium doped CoFe2O4 (CoFe2−xEuxO4; x = 0.1, 0.2, 0.3) nanoparticles were synthesized by the precipitation and hydrothermal approach. The impact of replacing trivalent iron (Fe3+) ions by trivalent rare earth europium (RE-Eu3+) ions on the microstructure, optical and magnetic properties of the produced CoFe2O4 nanoparticles was studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra exposed the consistency of a single cubic phase with the evidence of Eu2O3 phases for x ≥ 0.2. FTIR transmittance spectra showed that, the all investigated samples have three characteristic metal-oxygen bond vibrations corresponding to octahedral B-site (υ1 and υ2) and tetrahedral A-site (υ3) around 415 cm−1, 470 cm−1 and 600 cm−1 respectively. XRD and energy dispersive X-ray spectroscopy studies affirmed the integration of RE-Eu3+ ions within CoFe2O4 host lattice and decrease of average crystals size from 13.7 nm to 4.7 nm. Transmission electron microscopy (TEM) analysis showed the crucial role played by RE-Eu3+ added to CoFe2O4 in reducing the particle size below 5 nm in agreement with XRD analysis. High resolution-TEM (HR-TEM) analysis showed that the as-synthesized spinel ferrite, i.e., CoFe2−xEuxO4, nanoparticles are single-crystalline with no visible defects. In addition, the HR-TEM results showed that pure and doped CoFe2O4 have well-resolved lattice fringes and their interplanar spacings matches that obtained by XRD analysis. Magnetic properties investigated by the vibrating sample magnetometer technique illustrated transformation of magnetic state from ferromagnetic to superparamagnetic at 300 K resulting in introducing RE-Eu3+ in CoFe2O4 lattice. At low temperature (~5 K) the magnetic order was ferromagnetic for both pure and doped CoFe2O4 samples. Substitution of Fe3+ ions in CoFe2O4 nanoparticles with RE-Eu3+ ions optimizes the sample nanocrystals size, cation distribution and magnetic properties for many applications.  相似文献   

5.
《Ceramics International》2019,45(16):20165-20171
The influence of rare earth (RE = Dy, Gd, Yb) ion doping on the structural, magnetic and optical properties of cobalt ferrite thin films was studied. CoFe2-xRExO4 (x = 0.01; 0.03; 0.05; 0.1; 0.2; 0.3) films were obtained by pulsed laser deposition on silicon substrates. The X-ray diffraction and Raman spectroscopy results on the bulk materials, which were used as targets during deposition, revealed the formation of residual phases as the concentration of RE dopant was increased. However, the annealed thin films presented diffraction lines and vibrational modes corresponding only to cobalt ferrite. A lower crystallinity of the deposited samples was observed when higher RE concentrations were used. Due to the substitution of Fe by RE elements which possess large ionic radii, the lattice parameter of the thin films presented a monotonous increase. The magnetic response of the nanostructures was correlated to the magnetic moment of the RE dopant and to the structural properties of the films. The optical bandgaps derived from the reflectance spectra presented an increasing trend as the Yb and Dy concentrations were augmented.  相似文献   

6.
《Ceramics International》2017,43(2):2113-2122
The influence of the CoFe2O4 nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe2O4/(100−x)SiO2 nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe2O4 nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 °C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe2O4 nanoparticles have spherical shapes and size in the 6–35 nm range. The Mössbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe2O4 nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix.  相似文献   

7.
Highly crystalline single phase spherical and monodisperse cobalt ferrite (CoFe2O4) nanoparticles (NPs) with uniform shape and size distribution have been synthesized by one pot-rapid sonochemical method. The effect of different solvents, such as aqueous, alcoholic, and a mix of water/ethanol in 1:1 volume ratio on the shape, size, and crystalline structure of CoFe2O4 NPs were studied using X-ray diffraction, transmission electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. The size of CoFe2O4 nanoparticle was controlled in the range from 20 to 110 nm based on the solvent medium used in the synthesis process. Furthermore, the evolution from spherical to cubic morphology of cobalt ferrite NPs is achieved by simply changing the solvent medium from aqueous to alcoholic medium. The magnetic properties of all the synthesized CoFe2O4 NPs were studied by vibrating sample magnetometer (VSM) at room temperature. The magnetization value was found to be particle size dependent, and high magnetization (Ms) of 92.5 emu/g was obtained for the CoFe2O4 NPs sample synthesized in a mixed solution of water and ethanol. A possible reaction mechanism for the formation of cobalt ferrite NPs by the sonochemical technique was discussed. The facile method adopted in our study appears to be a promising route for synthesis of highly crystalline nanoparticles within short times and without the need for using any calcination process.  相似文献   

8.
《Ceramics International》2023,49(12):20104-20117
In this study, a multifunctional textile profiting from photocatalytic activity, magnetic, and antibacterial properties was generated through decorating polyester fabric with cobalt ferrite (CoFe2O4) nanoparticles using the co-precipitation technique. The X-ray diffraction (XRD) results supported the successful decoration of fabrics with CoFe2O4 magnetic nanoparticles. Field emission electron scanning microscopy (FESEM) images accompanied by energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the morphology, dispersion, and chemical structure of particles on the surface. The mean particle size of cobalt ferrite was measured to be approximately 40 nm. Vibrating sample magnetometer (VSM) results confirmed the ferrimagnetic behavior of the decorated fabrics with saturation magnetization (Ms) and coercivity (Hc) of 1.8 emu/g and 1902 Oe, respectively. The UV–vis diffuse reflectance spectrum (DRS) and photoluminescence (PL) data indicated the appropriate performance under visible light irradiation and postponed electron-hole recombination of the decorated fabric, respectively. The maximum MB degradation efficiency of 97% after 180 min of visible light illumination was obtained. The active species trapping analyses indicated that hydroxyl radicals (OH) were the effective species in the photocatalytic degradation mechanism. The decorated sample with the best photocatalytic activity revealed more than 99% reduction in the number of colonies against gram-negative and gram-positive bacteria after 24 h contact time, which validated its excellent potential for antibacterial applications. Outstanding photocatalytic and antibacterial characteristics of the decorated textile with cobalt ferrite nanoparticles turn it into promising composite material for self-cleaning purposes.  相似文献   

9.
In the present work, we reported a facile synthesis of cobalt ferrite (CoFe2O4) nanoparticles in the presence of L-cysteine (Lys). The morphology and size of samples were characterized by SEM and TEM. The successful coating of Lys on the surface of CoFe2O4 was confirmed by XRD, XPS and TGA. The investigation of magnetic properties showed that both bare CoFe2O4 and Lys-coated CoFe2O4 nanoparticles exhibited room-temperature superparamagnetic behavior. The results of MTT experiments revealed insignificant cytotoxicity of Lys-coated CoFe2O4 nanoparticles even after 24?h incubation. More importantly, Lys-coated CoFe2O4 nanoparticles displayed an excellent drug loading capacity and a pH-sensitive drug release behavior. In summary, the prepared Lys-coated CoFe2O4 nanoparticles demonstrated a promising application potential in controlled drug delivery.  相似文献   

10.
Nanocomposite fibers made from polyacrylonitrile (PAN) containing carbon nanotubes (CNTs) and cobalt ferrite (CoFe2O4) nanoparticles were fabricated by electrospinning. The 10–25 nm CoFe2O4 nanoparticles were made by a simple hydrothermal process. Characterization by X‐ray diffraction confirmed that the CNTs and the CoFe2O4 nanoparticles were successfully incorporated into the PAN matrix. Scanning electron microscopy showed nanocomposite fibers with regular morphologies. Transmission electron microscopy revealed the internal distribution of the CNTs and CoFe2O4 nanoparticles. The nanocomposite fibers exhibited effective electromagnetic interference shielding attenuation of about 3.9 dB. Magnetic measurement using a vibrating sample magnetometer showed saturation magnetization of 4.7 emu g−1, thus this property can be accurately tailored by adjusting the loading of CoFe2O4 nanoparticles. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers  相似文献   

11.
The use of renewable resource is a strategic opportunity to meet growing demands of eco-friendly materials. The present study reports the synthesis of castor-oil-based polyurethane (COPU), and its nanocomposites with CoFe2O4 and AgFeO2 via sonication technique. Formation of the nanocomposite was confirmed by IR analysis while UV–visible studies revealed encapsulation of the ferrite particles by COPU. The interaction between COPU, AgFeO2, CoFe2O4, and their nanocomposites with bovine serum albumin (BSA) was also investigated by fluorescence spectroscopy which revealed static quenching of BSA through complex formation. The quenching rate for COPU was determined to be 1.98?×?104?LM?1 while for pure CoFe2O4 and AgFeO2, it was found to be 3?×?104?LM?1 and 3.2?×?104?LM?1, respectively. The interaction of BSA particularly with silver and cobalt ferrite nanoparticles within COPU matrix was found to be promising. It was found that by controlling the loading of ferrite in COPU matrix, desired binding could be achieved.  相似文献   

12.
Yan-Qiu Chu 《Electrochimica acta》2004,49(27):4915-4921
Spinel cobalt ferrite (CoFe2O4) thin films have been fabricated by 355 nm reactive pulsed laser deposition on stainless steel substrates. XRD and SEM analyses showed that the CoFe2O4 films exhibited a polycrystalline structure and were composed of nanoparticles with an average size of 80 nm. At 1C rate, the initial irreversible capacity of polycrystalline CoFe2O4 film electrode cycled between 0.01 and 3.0 V reached 1280 mAh/g. After 20 cycles, the reversible discharge capacities decreased and sustained about 610 mAh/g. The diffusion coefficient of Li ion for CoFe2O4 films was determined by ac impedance method, and the average value was estimated to be 1.1 × 10−13 cm2/S. Based on ex situ XRD, SEM and XPS data, the electrochemical mechanism of CoFe2O4 film with lithium upon cycling was proposed. During the first discharge, the amorphization process of CoFe2O4 film electrode is accompanied with the reduction of Co2+ and Fe3+ into metal Co and Fe, respectively, and then the reversible oxidation/reduction processes of Co, Fe and Li2O take place in the subsequent charge/discharge cycles.  相似文献   

13.
Cobalt–zinc ferrite nanoparticles (NPs) substituted with three different metals, Co0.5Zn0.5RexFe2-xO4 (RE = Ce, Dy, and Y; 0.00?≤?x?≤?0.05) were prepared hydrothermally. Fourier Transform-Infrared (FT-IR) Spectroscopy, X-ray powder diffraction (XRD), Field-Emission Scanning Electron Microscope (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDX) and Vibrating Sample Magnetometry (VSM) analyzed the products. The formation of cubic phase of spinel Co-Zn ferrite NPs were confirmed through XRD, FT-IR and FE-SEM techniques. The structural investigation of NPs by XRD revealed that the lattice parameter "a" decreases with the introduction of the RE in the ferrite structure by the substitution of Fe3+ by RE ions. The different magnetic parameters of Co0.5Zn0.5RexFe2-xO4 (RE = Ce, Dy, and Y; 0.00?≤?x?≤?0.05) NPs such as the saturation magnetization, coercivity, remanence, and magnetic moment were calculated and discussed in relation to structure and microstructure properties. M (H) hysteresis curves indicated that the samples exhibit superparamagnetic nature at room temperature. A slight improvement in the magnetization was obtained especially for the Ce- and Y-substituted Co0.5Zn0.5Fe2O4 (CZF) NPs at a certain RE level. However, the case Dy-substituted CZF products showed a sharp decrease in the magnetization with x?>?0.01. The results are mostly ascribed to the substitution of smaller Fe3+ ions with larger RE3+ ions.  相似文献   

14.
The Ce3+‐, Ho3+‐, and Sm3+‐ single and co‐doped oxyfluoride silicate glasses for light emitting diodes are studied. These glasses were prepared by melt quenching method and their optical and structural properties were investigated by absorption spectra, photoluminescence spectra, Commission International de I'Eclairage chromaticity coordinates, X‐ray diffraction, and Fourier transform infrared spectra. It is found that the introduction of Al2O3 in glass composition can improve the emissions of Ho3+ and Sm3+. While the presence of B2O3 has the adverse effect and can suppress the emissions of Ho3+ and Sm3+. With substituting Na2O for CaO in the glass compositions, CaF2 crystals can be formed during the melt quenching process. We find the formation of CaF2 crystals can change the emission behavior of Ho3+ and Sm3+ ions. White light emissions can be achieved in the glasses and the luminescence colors can be tuned by varying the concentrations of the doped rare‐earth ions and the composition of glass matrix. The Ce3+‐, Ho3+‐, and Sm3+‐doped oxyfluoride silicate glasses presented here demonstrate promising applications in the fields of light emitting diodes.  相似文献   

15.
《Ceramics International》2015,41(7):8623-8629
Samarium doped Mn–Zn ferrite nanoparticles of composition Mn0.5Zn0.5SmxFe2−xO4 (0≤x≤0.5) have been synthesized by a chemical co-precipitation method for developing low Curie temperature stable ferrofluid. These samples were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Electron Paramagnetic Resonance (EPR) spectroscopy and search coil method analytical techniques for their structural, morphological and magnetic properties. X-ray diffraction patterns confirmed the formation of crystalline single spinel phase of as grown nanoparticles. Lattice parameter and lattice strain increases with the increase in Sm3+ content. SEM images revealed the presence of ultrafine particles and their agglomerated structures in higher Sm3+ ions concentration analogues. The stoichiometry of the final product agreed well with the initial substitution composition as evidenced by EDS data. Electron paramagnetic resonance (EPR) spectra proved the ferromagnetic nature of nanoparticles. The magnetic measurements by search coil method showed superparamagnetism for x=0, 0.1 the samples with saturation magnetization of 23.95 emu/g for Mn0.5Zn0.5Fe2O4 sample which increases with rise in Sm3+ ions content. The results are explained and correlated with the structural, morphological and magnetic properties for developing stable kerosene based ferrofluid by using these nanoparticles.  相似文献   

16.
Here we prepared porous silicon oxynitride (Si2N2O) ceramics by reaction sintering of SiO2 and Si3N4 using five different rare-earth oxides (RE2O3, RE = Lu, Yb, Y, Sm, and La) as sintering aids. The influences of RE2O3 on the formation, densification, microstructure, and mechanical properties of Si2N2O ceramics have been investigated in detail. The results have indicated that with the increase in RE ionic radius, the formation temperature of Si2N2O decreases, and the densification process could be promoted by RE2O3 with larger RE3+ ionic radius. In addition, microstructures and mechanical properties are highly dependent on the RE2O3 additives. With the increase in RE3+ ionic radius, Si2N2O changes from platelike crystals to elongated crystals. The samples doped with La2O3 and Sm2O3 with elongated crystals exhibit higher flexural strength and higher Vickers hardness.  相似文献   

17.
Magnetic nanoparticle composite with a cobalt ferrite (CoFe2O4, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.  相似文献   

18.
《Ceramics International》2016,42(6):7360-7365
Y2O3 stabilized ZrO2 (YSZ) has been considered as the material of choice for thermal barrier coatings (TBCs), but it becomes unstable at high temperatures and its thermal conductivity needs to be further reduced. In this study, 1 mol% RE2O3 (RE=La, Nd, Gd, Yb) and 1 mol% Yb2O3 co-doped YSZ (1RE1Yb–YSZ) were fabricated to obtain improved phase stability and reduced thermal conductivity. For 1RE1Yb–YSZ ceramics, the phase stability of metastable tetragonal (t′) phase increased with decreasing RE3+ size, mainly attributable to the reduced driving force for t′ phase partitioning. The thermal conductivity of 1RE1Yb–YSZ was lower than that of YSZ, with the value decreasing with the increase of the RE3+ size mainly due to the increased elastic field in the lattice, but 1La1Yb–YSZ exhibited undesirably high thermal conductivity. By considering the comprehensive properties, 1Gd1Yb–YSZ ceramic could be a good potential material for TBC applications.  相似文献   

19.
《Ceramics International》2017,43(12):9145-9152
The decomposition of succinate type precursors obtained by a modified sol-gel method using cobalt and iron nitrates, 1,4-butanediol and tetraethylorthosilicate, followed by the formation of single phase cobalt ferrite embedded in the silica matrix by annealing at 400–1100 °C was studied. The thermal analysis indicated the formation temperature of succinate type precursors, while the Fourier transform infrared spectroscopy (FT-IR) data confirmed the formation of the precursors in the pores of silica matrix. The formation of CoFe2O4 was investigated by X-ray diffraction and FT-IR, the size and shape of the nanoparticles by transmission electron microscopy, while the resulted microstructures by scanning electron microscopy. The crystallinity and crystallites size increased with the annealing temperature. The hysteresis loops revealed a direct relationship between annealing temperature and saturation magnetization in constant coercive field. The particle size of ferrite powders is critically dependent on the annealing temperature.  相似文献   

20.
《Ceramics International》2017,43(4):3797-3803
High surface area cobalt ferrite (CoFe2O4) powders were synthesized by solution combustion method. The dependence of the adiabatic temperature and the released gases during combustion reaction on the fuel content and cobalt precursor type, cobalt nitrate and cobalt acetate, was thermodynamically calculated. Thermal analysis, infrared spectroscopy, X-ray diffractometry, nitrogen adsorption–desorption, electron microscopy and vibrating sample magnetometer were used for investigation of the phase evolution, surface areas, morphology and magnetic properties of the synthesized CoFe2O4 powders. The specific surface area decreased from 285.4 to 35.7 m2/g with increasing of fuel to oxidant molar ratio, ϕ, from 0.5 to 1.25 for the cobalt nitrate precursor, while the maximum surface area of 182.1 m2/g was attained at ϕ=1 for the cobalt acetate precursor. The synthesized CoFe2O4 powders from the cobalt nitrate precursor exhibited the higher saturation magnetization and coercivity on account of the higher purity and crystallinity.  相似文献   

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