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Oxide Nanoparticles in Heterogeneous Catalysis
Published in Varun Rawat, Anirban Das, Chandra Mohan Srivastava, Heterogeneous Catalysis in Organic Transformations, 2022
Garima Sachdeva, Jyoti Dhariwal, Monika Vats, Varun Rawat, Manish Srivastava, Anamika Srivastava
Spinel cobalt ferrite nanoparticles were synthesized using both sonochemical and co-precipitation methods without any capping agent and surfactant. A reusable catalyst was employed for the Knoevenagel condensation reaction of aldehydes with ethyl cyanoacetate in aqueous ethanol under mild reaction conditions [79]. The excellent yield of desired Knoevenagel products was obtained in a short period of time with 5 mol% of the catalyst. It has been found that the NPs showed stability in both ethanol and aqueous solvent systems and can be stored for months without any stabilizer; no agglomeration was observed.
Low temperature rapid sol–gel auto-combustion synthesis and structural, morphological and magnetic study of nickel substituted cobalt nano ferrites
Published in Phase Transitions, 2021
Ravindra N. Chikhale, S. A. Kanade, Pushpinder G. Bhatia
Spinel ferrites have face-centered cubic (FCC) closed packed structure containing 32 oxygen (O2−) ions, 8 divalent (M2+) ions (Co2+, Ni2+, Fe2+, Zn2+, Mn2+) and 16 trivalent ions (Fe3+). They consist of two sublattices, the tetrahedral (A) site and the octahedral (B) site. The 8 metal ions occupy the tetrahedral (A) site while 16 metal ions occupy the octahedral (B) site. Cobalt and nickel ferrites are the most widely investigated materials having an inverse spinel structure. Cobalt ferrite (CoFe2O4) has a high coercivity, high saturation magnetization and high Curie temperature [5,6]. Cobalt ferrite is highly magnetostrictive and shows large magneto-crystalline anisotropy. Thus it is an important metal oxide system for magnetic recording media [7]. Due to preferential perpendicular magnetization, maximum perpendicular magnetic anisotropy, and orientation of magnetic easy axis the cobalt ferrite has numerous applications [8]. Cobalt ferrite is also an important ferrimagnetic material with high magnetization at room temperature. This material has a unique application in magnetic spin filters [9]. Nickel ferrite (NiFe2O4) has low coercivity, low saturation magnetization and small magneto-crystalline anisotropy. Both materials have large electrical resistivity [10].
Adsorptive removal of cesium ions from aqueous solutions using synthesized Prussian blue/magnetic cobalt ferrite nanoparticles
Published in Particulate Science and Technology, 2020
Mohamed R. Hassan, Mohamed I. Aly
XRD measurement is utilized in the characterization of cobalt ferrite composite. The XRD patterns of as-prepared cobalt ferrite can be indexed to the CoFe2O4 spinel with Fd3m space group (JCPDS No. 22-1086) (Klug and Alexander 1974). Peaks at 30.1°, 35.4°, 43.5°, 57.1°, and 62.7° in (Figure 1), are the main five diffraction characteristic peaks of CoFe2O4, which represents the cubic spinel structure. (Figure 2) shows SEM for the synthesized CoFe2O4. A relatively large area of uniformly distributed parallel nanoparticles grains was observed, with the tendency for accumulation and cohesion. The reason for the cohesion of CoFe2O4 grains may be due to the magnetic attractive forces between them (Ding et al. 2015).
Nonlocal and magneto effects on dispersion characteristics of Love-type waves in piezomagnetic media
Published in Waves in Random and Complex Media, 2022
Cobalt Ferrite is a well-known hard magnetic material with high coercivity, high electromagnetic performance, excellent chemical stability, mechanical hardness, and moderate saturation magnetization. These properties make nanoparticles suitable for the electronic components used in computers, magnetic cards and recording devices such as audio and videotape, high-density digital recording disks, etc.The vast application of nano ferrites in permanent magnets, ferrofluids, storage devices, targeted drug delivery and other uses, has attracted much attention in their way of synthesizing these nano materials.Terfenol-D is an alloy and is a magnetostrictive material. It has the highest magnetostriction of any alloy and it expands and contracts in a magnetic field. It bears a large magnetostriction force, high energy density, low sound velocity, and a low Young's modulus. In its most pure form, it also has low ductility and a low fracture resistance. It has wide application in magnetomechanical sensors, actuators, and acoustic and ultrasonic transducers, due to its high energy density and large bandwidth capabilities, e.g. in the SoundBug device.Compared with piezoelectric sensors, the piezomagnetic sensor has simple structure, large output power, convenient manufacture, low cost, strong signal and good anti-interference performance. In piezomagnetic sensor signal amplifier circuit is simple without charge amplifier, and is suitable for static and dynamic force measurement. Experimental data is stable and can be directly measured with general wire.The force-sensitive film is the most stable and sensitive one among the current piezomagnetic force-sensitive films. To achieve high performance and sensitivity in sensors, a thin film of piezomagnetic material embedded on a substrate is adopted.