References of "Koutzarova, T"
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See detailOptical and structural characterization of TiO2 films doped with silver nanoparticles obtained by sol-gel method
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Optical Materials (2013), 36

Nanostructured titanium oxide films with incorporated Ag nanoparticles were deposited by sol-gel spin coating method. The films were annealed at 300 °C, 400 °C, 500 °C and 600 °C in oxygen and nitrogen ... [more ▼]

Nanostructured titanium oxide films with incorporated Ag nanoparticles were deposited by sol-gel spin coating method. The films were annealed at 300 °C, 400 °C, 500 °C and 600 °C in oxygen and nitrogen ambient. X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and UV-VIS spectroscopy had been applied for studying the influence of the thermal treatments and the gas ambient on the structural and optical properties of TiO2 and TiO2:Ag films. The XRD analysis revealed the presence of metallic Ag phase without traces of silver oxides and these results were confirmed by FTIR spectra. It has been revealed that the annealing temperatures and the ambient, where the annealing is carried out is crucial for TiO2 crystallization, when there is Ag incorporation and especially for appearance of anatase and rutile phase. The nitrogen and oxygen ambient influences quite different the crystallization of TiO2:Ag films. Transmission and absorption spectra have been analyzed. Optical band gap values were evaluated for pure titania and Ag incorporated TiO2 films. © 2013 Elsevier B.V. All rights reserved. [less ▲]

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See detailDifferences in the structural and magnetic properties of nanosized barium hexaferrite powders prepared by single and double microemulsion techniques
Koutzarova, T.; Kolev, S.; Ghelev, Ch et al

in Journal of Alloys & Compounds (2013), 579

Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microemulsion technique, namely, single microemulsion and double microemulsion, were studied. The influence was ... [more ▼]

Barium hexaferrite powders of nanometer particle size synthesized via two variants of the microemulsion technique, namely, single microemulsion and double microemulsion, were studied. The influence was explored of the type of microemulsion technique on the microstructure and on the magnetic properties of the barium hexaferrite powders. The average particle size of the barium hexaferrite powders was in the range from 110 nm to 442 nm depending on the method and conditions of synthesis. The particles with size below 150 nm had irregular shapes between spherical and platehexagonal; the bigger ones had an almost perfect hexagonal shape. The powders obtained by single microemulsion had better magnetic characteristics (saturation magnetization of 65.12 emu/g and coercivity field of 3.6 × 105 A/m) than those obtained by double microemulsion. © 2013 Elsevier B.V. All rights reserved. [less ▲]

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See detailMagnetic properties of nanosized MgFe2O4 powders prepared by auto-combustion
Ghelev, Ch; Koutzarova, T.; Kolev, S. et al

in Journal of Physics: Conference Series (2012), 356(1), 012048

Targets were prepared to be used for magnetron sputtering and laser ablation and their microstructural and magnetic properties were investigated. The base material was nanosized MgFe2O4 powder produced by ... [more ▼]

Targets were prepared to be used for magnetron sputtering and laser ablation and their microstructural and magnetic properties were investigated. The base material was nanosized MgFe2O4 powder produced by citrate auto-combustion synthesis. The auto-combusted powders were annealed at temperatures in the range 600 - 1000°C in air to study the effect of temperature on thofe formation MgFe2O4. The saturation magnetization Ms was 24.30 emu/g at room temperature. © Published under licence by IOP Publishing Ltd. [less ▲]

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See detailPreparation and characterisation of Ag incorporated Al2O3 nanocomposite films obtained by sol-gel method
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Crystal Research and Technology (2012), 47(5), 579-584

Sol-gel route has been applied for a deposition of the thin films of aluminum oxide and Ag embedded in Al2O3 films. The films are spin-coated on Si and quartz substrates with the film thickness of 120 nm ... [more ▼]

Sol-gel route has been applied for a deposition of the thin films of aluminum oxide and Ag embedded in Al2O3 films. The films are spin-coated on Si and quartz substrates with the film thickness of 120 nm. XRD analysis has been used for the determination of the film structure. FTIR spectroscopy is applied for studying vibrational properties of the obtained coatings. Optical characterization is done by UV-VIS spectroscopy. The formation of Ag nanoparticles has been confirmed by XRD and optical data. The sol-gel process is found to be useful technology for incorporation of Ag nanoparticles in the metal oxide matrices. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. [less ▲]

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See detailPreparation and characterization of ZnO-TiO(2) films obtained by sol-gel method
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Journal Of Non-Crystalline Solids (2011), 357(15), 2840-2845

The sol-gel route has been applied to obtain ZnO-TiO(2) thin films. For comparison, pure TiO(2) and ZnO films are also prepared from the corresponding solutions. The films are deposited by a spin-coated ... [more ▼]

The sol-gel route has been applied to obtain ZnO-TiO(2) thin films. For comparison, pure TiO(2) and ZnO films are also prepared from the corresponding solutions. The films are deposited by a spin-coated method on silicon and glass substrates. Their structural and vibrational properties have been studied as a function of the annealing temperatures (400-750 degrees C). Pure ZnO films crystallize in a wurtzite modification at a relatively low temperature of 400 degrees C, whereas the mixed oxide films show predominantly amorphous structure at this temperature. XRD analysis shows that by increasing the annealing temperatures, the sol-gel Zn/Ti oxide films reveal a certain degree of crystallization and their structures are found to be mixtures of wurtzite ZnO, Zn(2)TiO(4), anatase TiO(2) and amorphous fraction. The XRD analysis presumes that Zn(2)TiO(4) becomes a favored phase at the highest annealing temperature of 750 degrees C. The obtained thin films are uniform with no visual defects. The optical properties of ZnO-TiO(2) films have been compared with those of single component films (ZnO and TiO(2)). The mixed oxide films present a high transparency with a slight decrease by increasing the annealing temperature. (C) 2011 Elsevier B.V. All rights reserved. [less ▲]

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See detailStudy of ZnO sol-gel films: Effect of annealing
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Materials Letters (2010), 64(10), 1147-1149

Thin films of zinc oxide were deposited by spin coating method on different substrates. The obtained samples were thermally treated at temperatures from 400 degrees C up to 850 degrees C. The structural ... [more ▼]

Thin films of zinc oxide were deposited by spin coating method on different substrates. The obtained samples were thermally treated at temperatures from 400 degrees C up to 850 degrees C. The structural study was performed by XRD and FTIR techniques in order to observe the effect of the annealing temperatures. The sol-gel ZnO films showed polycrystalline hexagonal structure. The optical transmittance reached 91% and it diminished with increasing annealing temperatures. (C) 2010 Elsevier B.V. All rights reserved. [less ▲]

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See detailEffect of annealing temperatures on properties of sol-gel grown ZnO-ZrO2 films
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Crystal Research And Technology (2010), 45(11), 1154-1160

Mixed ZnO-ZrO2 films have been obtained by sol-gel technology. By using spin coating method, the films were deposited on Si and glass substrates. The influence of thermal annealings (the temperatures vary ... [more ▼]

Mixed ZnO-ZrO2 films have been obtained by sol-gel technology. By using spin coating method, the films were deposited on Si and glass substrates. The influence of thermal annealings (the temperatures vary from 400 degrees C to 750 degrees C) on their structural properties has been studied. The structural behavior has been investigated by the means of XRD and FTIR techniques. The results revealed no presence of mixed oxide phases, the detected crystal phases were related to the hexagonal ZnO and to crystalline ZrO2. The sol-gel ZnO-ZrO2 films showed polycrystalline structure with a certain degree of an amorphous fraction. The optical transmittance reached 91% and it diminished with increasing the annealing temperatures. The optical properties of the sol-gel ZnO-ZrO2 films, deposited on glass substrates are excellent with high transparency and better then those of pure ZrO2 films, obtained at similar technological conditions. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [less ▲]

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See detailElectrochromic TiO2, ZrO2 and TiO2-ZrO2 thin films by dip-coating method
Ivanova, T.; Harizanova, A.; Koutzarova, T. et al

in Materials Science & Engineering : B (2009), 165(3), 212-216

Sol-gel processing of TiO2, ZrO2 and mixed Ti/Zr oxide thin films has been studied as application of these coatings in electrochromic devices. Their structural transformations as a function of annealing ... [more ▼]

Sol-gel processing of TiO2, ZrO2 and mixed Ti/Zr oxide thin films has been studied as application of these coatings in electrochromic devices. Their structural transformations as a function of annealing temperatures were analyzed by XRD and FTIR techniques. Electrochromic behavior of the three kind materials was investigated by cyclic voltammetry and the basic electrochromic characteristics were determined. (c) 2009 Elsevier B.V. All rights reserved. [less ▲]

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See detailFrom RE-211 to RE-123. How to control the final microstructure of superconducting single-domains
Cloots, Rudi ULg; Koutzarova, T.; Mathieu, J.-P. et al

in Superconductor Science and Technology (2005), 18(3), 9-23

This paper reviews the usual techniques for producing YBCO-type single-domains and the microstructure of the as-obtained samples. The problems of seed dissolution and parasite nucleations are discussed in ... [more ▼]

This paper reviews the usual techniques for producing YBCO-type single-domains and the microstructure of the as-obtained samples. The problems of seed dissolution and parasite nucleations are discussed in detail. The formation of microstructural defects, such as pores and cracks, is examined. An important part of this review is devoted to the study of the influence of RE-211 particles (RE2BaCuO5 where RE denotes Y, Yb, Nd, Sm, Dy, Gd, Eu or a mixture of them. Generally Nd4Ba2Cu 2O10 is preferred to Nd2BaCuO5) for the microstructure and properties of RE-Ba-Cu-O single-domains. Pushing/trapping theory is described in order to explain the spatial distribution of RE-211 particles in the RE-123 ((RE)Ba2Cu3O7-δ) monoliths. The formation of RE-211-free regions is discussed. Different ways to limit the RE-211 coarsening are reviewed. Microstructural defects in the RE-123 matrix caused by the RE-211 particles are presented. It is also shown that RE-211 particles play a significant role in the mechanical properties of single-domain samples. We finish this review by discussing the infiltration and growth process as a good technique to control the microstructure. © 2005 IOP Publishing Ltd. [less ▲]

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See detailInvestigation of DyBa2CU3O7-d superconducting domains grown by the infiltration technique starting with small size Dy-211 particles
Mathieu, Jean-Philippe; Koutzarova, T.; Rulmont, André ULg et al

in Superconductor Science and Technology (2005), 18(2 Sp. Iss. SI), 136-141

An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy ... [more ▼]

An infiltration and growth process is here used as an alternative to the classical top-seeded melt-textured growth process for the production of Dy-123 single-domains with finely dispersed small size Dy-211 particles. The starting materials are the 211-particles and a barium and copper rich liquid phase precursor. The infiltration and growth process allows for controlling both the spatial and size distribution of the 211-particles in the final superconducting 123-single-domain. The main parameters (set-ups, maximum processing temperature with respect to the peritectic temperature, nature of reactant, porosity of the 211-preform) of the infiltration and growth process are discussed. Moreover, different processes of chimie douce are shown in order to produce Dy-211 particles with controlled shape and size, particles that can be used as precursors for the infiltration and growth process. [less ▲]

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See detailThe contribution of 211 particles to the mechanical reinforcement mechanism of 123 superconducting single domains
Mathieu, Jean-Philippe; Cano, I. G.; Koutzarova, T. et al

in Superconductor Science and Technology (2004), 17(1), 169-174

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values ... [more ▼]

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values when performed in (001) planes rather than in planes parallel to the c-axis. Moreover, the cracks pattern around the indentation follows preferential orientation in planes parallel to the c-axis whereas a classical 'four-cracks' pattern is observed in the (001) planes. It has been possible to show the crucial role played by the 211 particles in the deviating mechanism of cracks and the relevance of the high homogeneity of 211-particle distribution in the material. [less ▲]

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