@article { ISI:000313149800004, title = {Enhancement in the magnetostriction of sintered cobalt ferrite by making self-composites from nanocrystalline and bulk powders}, journal = {ACS Applied Materials \& Interfaces}, volume = {4}, number = {12}, year = {2012}, month = {DEC}, pages = {6421-6425}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Sintered polycrystalline cobalt ferrite is a potential magnetostrictive smart material for applications as sensors and actuators. A novel concept of enhancing the magnetostrictive strain of sintered cobalt ferrite by making self-composites from nanosized and bulk powders with different particle sizes of the same material as components is reported. The self-composites give higher magnetostriction coefficient and strain derivative when compared to the sintered products obtained from the individual powders. The individual components give a maximum magnetostriction up to similar to 310 ppm, whereas up to similar to 370 ppm is obtained for a two-component system consisting of powders of two different sizes. On the other hand, a three-component self-composite made from starting powders of 3 nm, 40 nm and \>1 mu m give very high magnetostriction of similar to 400 ppm at 800 kA/m, suitable for making devices.

}, keywords = {Cobalt ferrite, Magnetostriction, Nanocrystalline, self-composite, Sintering}, issn = {1944-8244}, doi = {10.1021/am302053q}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000324099300024, title = {High magnetostriction coefficient of Mn substituted cobalt ferrite sintered from nanocrystalline powders and after magnetic field annealing}, journal = {Current Applied Physics}, volume = {13}, number = {8}, year = {2013}, month = {OCT}, pages = {1697-1701}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Magnetostriction characteristics of Mn substituted cobalt ferrite, CoFe2-xMnxO4 (0 \<= x \<= 0.3), sintered from nanocrystalline powders of average particle size of similar to 4 nm have been studied. Larger value of magnetostriction at lower magnetic field is achieved after substitution of Mn for Fe. The maximum value of magnetostriction coefficient is not much affected and the slope of the magnetostriction is increased with increasing Mn content. Higher maximum value of magnetostriction coefficient (lambda) of 234 ppm comparable to that of the unsubstituted composition with larger strain derivative (d lambda/dH) is obtained for x = 0.2 in CoFe2-xMnxO4. The magnetostriction coefficient is increased to 262 ppm with further enhancement in the strain derivative after annealing the sintered compact at 300 degrees C in a magnetic field of 400 kA/m for 30 min. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Cobalt ferrite, Magnetic field annealing, Magnetostriction, Mn substitution, Nanocrystalline}, issn = {1567-1739}, doi = {10.1016/j.cap.2013.06.030}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000324311200017, title = {Influence of initial particle size on the magnetostriction of sintered cobalt ferrite derived from nanocrystalline powders}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {346}, year = {2013}, month = {NOV}, pages = {96-102}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The role of initial particle size on the magnetostriction coefficient of sintered cobalt ferrite derived from nanocrystalline powders is studied. Nanoparticles of cobalt ferrite with different sizes in the range 3-80 nm are synthesized by an autocombustion method using metal nitrates and glycine. It has been observed that the initial particle size of the starting powders has a strong influence on the magnetostrictive behavior of sintered cobalt ferrite. Highest magnetostrictive strain and strain derivative are obtained for sintered ferrite derived from nanoparticles of size \< 5 nm. The results show that higher magnetostriction coefficient for sintered cobalt ferrite can be achieved by compacting nanocrystalline particles of very small size. (C) 2013 Elsevier B.V. All rights reserved.

}, keywords = {Cobalt ferrite, magnetic properties, Magnetostriction, Microstructure, Nanocrystalline, Particle size}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2013.07.016}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000341165000020, title = {High magnetostriction parameters for low-temperature sintered cobalt ferrite obtained by two-stage sintering}, journal = {Journal of Magnetism and Magnetic Materials}, volume = {371}, year = {2014}, month = {DEC}, pages = {121-129}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

From the studies on the magnetostriction characteristics of two-stage sintered polycrystalline CoFe2O4 made from nanocrystalline powders, it is found that two-stage sintering at low temperatures is very effective for enhancing the density and for attaining higher magnetostriction coefficient. Magnetostriction coefficient and strain derivative are further enhanced by magnetic field annealing and relatively larger enhancement in the magnetostriction parameters is obtained for the samples sintered at lower temperatures, after magnetic annealing, despite the fact that samples sintered at higher temperatures show larger magnetostriction coefficients before annealing. A high magnetostriction coefficient of similar to 380 ppm is obtained after field annealing for the sample sintered at 1100 degrees C, below a magnetic field of 400 kA/m, which is the highest value so far reported at low magnetic fields for sintered polycrystalline cobalt ferrite. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Cobalt ferrite, Magnetostriction, Two-stage sintering}, issn = {0304-8853}, doi = {10.1016/j.jmmm.2014.07.013}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000329554400013, title = {Studies on the effect of sintering conditions on the magnetostriction characteristics of cobalt ferrite derived from nanocrystalline powders}, journal = {Journal of the European Ceramic Society}, volume = {34}, number = {3}, year = {2014}, month = {MAR}, pages = {677-686}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

The effect of sintering conditions on the magnetostriction characteristics of sintered cobalt ferrite derived from nanocrystalline powders is studied. It is observed that the magnetostriction coefficient as well as the slope of the magnetostriction as a function of field depends on the microstructure of the sintered product. There is a direct correlation between the magnetostriction characteristics and density as well as porosity of the sintered products. Intragranular pores are found to be strongly influencing the magnetostriction characteristics. Similarly, correlation is found between the magnetostriction parameters and the Curie temperature, indicating the role of cation distribution which affects the magnetic anisotropy. Sintering the compacts made from nanocrystalline powders at 1450 degrees C for a very short duration is found to give high values of magnetostriction coefficient. However, higher values of magnetostriction at low magnetic fields are obtained for samples sintered at lower temperatures for longer duration and having relatively lower density. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Cobalt ferrite, Magnetostriction, Microstructure, Nanocrystalline, Sintering}, issn = {0955-2219}, doi = {10.1016/j.jeurceramsoc.2013.09.018}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article {46089, title = {Size-controlled cobalt ferrite nanocrystals: magnetically separable reusable nanocatalysts for selective oxidation of styrene}, journal = {ChemistrySelect}, volume = {4}, year = {2019}, month = {JUN }, pages = {6524-6531}, type = {Article}, abstract = {

Superparamagnetic cobalt ferrite (CFO) nanocrystals (NCs) with sizes similar to 6 nm and similar to 4 nm were synthesized using a facile solvothermal method using fatty acids, lauric acid and stearic acid, as the capping agents. The synthesized nanocrystals were well characterized by XRD, FT-IR, XPS, SEM and TEM. The formation mechanism was explored and it was shown that the fatty acid was actually chemisorbed as a carboxylate onto the surface of CFO NCs. The experimental results specify that the size and size distribution of the CFO NCs were highly dependent on the length of fatty acid hydrophobic chain. Corresponding changes of the magnetic properties were investigated by measuring magnetization as a function of field and temperature, which suggest that the CFO NCs were superparamagnetic in nature. The catalytic properties for the oxidation of styrene in organic medium were examined by using the synthesized CFO NCs with sizes similar to 6 nm and similar to 4 nm. The synthesized CFO NCs, well dispersible in organic media, were demonstrated to be highly catalytically active, reached 100\% conversion of styrene in 12 h with similar to 77\% and similar to 82\% selectivity for styrene oxide respectively. The magnetic CFO nanocatalysts were easily separated and recovered from the reaction medium by an external magnet, and reused for several cycles without losing catalytic selectivity for styrene oxide.

}, keywords = {Cobalt ferrite, epoxidation, Fatty acids, magnetic properties, nanocrystals}, issn = {2365-6549}, doi = {10.1002/slct.201900714}, author = {Jeyavani, Vijayakrishnan and Pawar, Sayali and Dadwal, Arun and Joy, Pattayil Alias and Mukherjee, Shatabdi Porel} }