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Alternative Routes to Highly Dispersed Cobalt Ferrite Nanocomposites
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , 95 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:19
Keyword [en]
aqueous precipitation, cobalt ferrite, nanoparticles, synthesis, size distribution, silane/silsesquioxane, epoxy, nanocomposites, magnetic cellulose
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4328ISBN: 978-91-7178-627-2 (print)OAI: oai:DiVA.org:kth-4328DiVA: diva2:11821
Public defence
2007-04-20, Sal K2, KTH, Teknikringen 28, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100811Available from: 2007-04-12 Created: 2007-04-12 Last updated: 2010-08-11Bibliographically approved
List of papers
1. Synthesis and characterization of cubic cobalt ferrite nanoparticles
Open this publication in new window or tab >>Synthesis and characterization of cubic cobalt ferrite nanoparticles
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2005 (English)In: Ninth International Conference on Ferrites (ICF-9) / [ed] Soohoo, RF, 2005, 835-840 p.Conference paper, Published paper (Refereed)
Abstract [en]

The preparation of approximately 20 g cubic cobalt ferrite nanoparticles (edge length 30-60 nm) with composition CoxFe3-xO4 (0.85 center dot x center dot 1.00 +/- 0.02) using the co-precipitation method in a batch type reactor has been investigated. The morphology, composition, size and size distribution of the synthesized particles were characterized by transmission electron microscopy, X-ray diffraction and the BET method. The majority of the particles were cubic although spherical particles were also observed. Aging of the suspensions resulted in a narrowing of the initial size distribution with no effect on the morphology and composition of the particles.

Keyword
particles, powders, precipitation
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-24041 (URN)000227460600129 ()1-57498-218-4 (ISBN)
Conference
9th International Conference on Ferrites (ICF-9), San Francisco, CA, AUG 22-27, 2004
Note

QC 20100811

Available from: 2010-08-11 Created: 2010-08-11 Last updated: 2016-12-21Bibliographically approved
2. Controlled synthesis of near-stoichiometric cobalt ferrite nanoparticles
Open this publication in new window or tab >>Controlled synthesis of near-stoichiometric cobalt ferrite nanoparticles
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2005 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, no 20, 5109-5118 p.Article in journal (Refereed) Published
Abstract [en]

Large batches of more than 18 g of cobalt ferrite nanoparticles (CoxFe3-xO4, x being close to 1) have been prepared by the chemie douce approach using aqueous solutions of metal salts at 90 degrees C mixed with solutions of hydroxide ions under air atmosphere. By suitable choice of the metal ion to hydroxide ion ratio, it was possible to prepare nanoparticles with the stoichiometric composition (CoFe2O4). The composition and the density of the nanoparticles could be controlled by varying the metal ion to hydroxide ion molar ratio in the reactor. Adjusting the initial concentration ratios of the reactants prior to the mixing allowed the variation of the average size of the nanoparticles. The repeatability of the average particle diameter of the synthesis was typically 5 nm and average particle sizes could be controlled between 50 and 80 nm determined by nitrogen adsorption measurements (consistent with the number size average 35-60 mn obtained by transmission electron microscopy studies). Aging of the suspensions resulted in a narrowing of the initial broad unimodal distribution. The narrowing of the size distribution was associated with the phase transformation of delta-FeOOH platelets to spinel phase. The spinel nanoparticles had different morphologies: cubic, spherical, and occasionally irregular. Nanoparticles with the stoichiometric composition were a mixture of cubical and spherical shapes. Nanoparticles with less than the stoichiometric cobalt content had an irregular morphology, whereas nanoparticles with greater than the stoichiometric concentration of cobalt were predominantly spherical.

Keyword
magnetic-properties, particles, manganese, hematite, powders, precipitation, hydrolysis, oxidation, goethite
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-15078 (URN)10.1021/cm0501665 (DOI)000232326700029 ()2-s2.0-26944488702 (Scopus ID)
Note
QC 20100811Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
3. Enhanced coercivity in Co-rich near-stoichiometric CoFe3-xO4+delta nanoparticles prepared in large batches
Open this publication in new window or tab >>Enhanced coercivity in Co-rich near-stoichiometric CoFe3-xO4+delta nanoparticles prepared in large batches
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2007 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 20, 4957-4963 p.Article in journal (Refereed) Published
Abstract [en]

The relationship between the structure and composition with the magnetic properties of near stoichiometric cobalt ferrite nanoparticles CoxFe3-xO4+delta (0.85 < x < 1.1) prepared in large batches with average sizes in the range 60-210 nm has been investigated. Chemical analysis and Rietveld refinement of the X-ray diffraction data in conjunction with Mossbauer spectroscopy allowed us to identify an interplay between particle size, microstructure (concentration of interstitial ions, microstrain, cation arrangement in octahedral and tetrahedral sites), and composition, which sensitively controls the magnetic properties such as coercivity and saturation magnetization. In all cases, cobalt-rich compositions resulted in a higher coercivity, whereas lower degrees of inversion and higher iron contents led to slightly higher saturation magnetization values.

Keyword
cobalt ferrite nanoparticles, magnetic nanoparticles, spinel, nanocrystals, mossbauer, cofe2o4, nanostructures, crystalline, biomedicine, anisotropy
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-17000 (URN)10.1021/cm070827t (DOI)000249871500016 ()2-s2.0-35348816145 (Scopus ID)
Note
QC 20100811Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
4. Core-shell nanostructured cobalt ferrite-sisesquioxane-epoxy composites: nanofiller surface treatment, particle dispersion, mechanical and magnetic properties
Open this publication in new window or tab >>Core-shell nanostructured cobalt ferrite-sisesquioxane-epoxy composites: nanofiller surface treatment, particle dispersion, mechanical and magnetic properties
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(English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, 1-44 p.Article in journal (Refereed) Submitted
Abstract [en]

Magnetic core-shell cobalt ferrite-silsesquioxane-epoxy nanocomposites have been prepared with uniform nanoparticle distribution. The nanoparticles were surface-treated with methyl- (MTMS), aminopropyl- (APTMS), glycidoxypropyl- (GPTMS) trimethoxy-silane. The optimum coating process was performed in a water/merthanol solution on the particles directly after their synthesis without prior drying. The GPTMS-coatings were 30 nm thick and the nanoparticles dispersed well in epoxy without sedimentation. The MTMS-coated nanoparticles (3 nm coating) formed weak agglomerates in epoxy but showed no sedimentation. The APTMS-coated particles formed stronger agglomerates, which led to sedimentation of the aorticles during molding. The GPTMS-based composites showed higher fracture toughness than the MTMS-based composites. This was attributed to the presence of large agglomerates in the latter systems and to the stronger interface between coating and epoxy in the former systems. Ultrasonic alkaline etching allowed precis determination of the ferrite content of the core-shell nanoparticles. Magnetometry showe a markedly lower coercivity for nanoparticles with thin coatings (MTMS) than for the nanoparticles with thicker coatings (GPTMS) suggesting the occurrence of magnetic exchange interaction in the former systems. The nanocomposites showed no influence of surface coating on coercivity or saturation magnetization suggesting that the inter-particle distances were greater than 0.5 nm.

Keyword
nanocomposites, cobalt ferrite, epoxy, core-shell nanoparticles
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-24042 (URN)
Note
QC 20100811Available from: 2010-08-11 Created: 2010-08-11 Last updated: 2017-12-12Bibliographically approved
5. Nanoparticle decoration of bacterial cellulose fibres: a method to obtain porous high-surface area ultra-flexible ferromagnertic materials
Open this publication in new window or tab >>Nanoparticle decoration of bacterial cellulose fibres: a method to obtain porous high-surface area ultra-flexible ferromagnertic materials
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(English)Manuscript (preprint) (Other academic)
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-24044 (URN)
Note
QC 20100811Available from: 2010-08-11 Created: 2010-08-11 Last updated: 2010-12-09Bibliographically approved

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