On the permittivity of titanium dioxide

Bonkerud, Julie; Zimmermann, Christian; Weiser, Philip; Vines, Lasse; Monakhov, E. V.

doi:10.1038/s41598-021-92021-5

Cited by 42 publications

(31 citation statements)

References 16 publications

(24 reference statements)

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“…Direct assessment of Equation (3) yielded the value of the coating permittivity ε in the range 200–250. This is consistent by the order of magnitude with the estimates for rutile in [ 56 ] and for anatase in [ 57 ]; however, it was 5-fold higher than the estimate of anodic titania film permittivity ε = 45 [ 58 ].…”

Section: Discussionsupporting

confidence: 88%

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

et al. 2021

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The problem of the optimization of properties for biocompatible coatings as functional materials requires in-depth understanding of the coating formation processes; this allows for precise manufacturing of new generation implantable devices. Plasma electrolytic oxidation (PEO) opens the possibility for the design of biomimetic surfaces for better biocompatibility of titanium materials. The pulsed bipolar PEO process of cp-Ti under voltage control was investigated using joint analysis of the surface characterization and by in situ methods of impedance spectroscopy and optical emission spectroscopy. Scanning electron microscopy, X-ray diffractometry, coating thickness, and roughness measurements were used to characterize the surface morphology evolution during the treatment for 5 min. In situ impedance spectroscopy facilitated the evaluation of the PEO process frequency response and proposed the underlying equivalent circuit where parameters were correlated with the coating layer properties. In situ optical emission spectroscopy helped to analyze the spectral line evolutions for the substrate material and electrolyte species and to justify a method to estimate the coating thickness via the relation of the spectral line intensities. As a result, the optimal treatment time was established as 2 min; this provides a 9–11 µm thick PEO coating with Ra 1 µm, 3–5% porosity, and containing 75% of anatase. The methods for in-situ spectral diagnostics of the coating thickness and roughness were justified so that the treatment time can be corrected online when the coating achieves the required properties.

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Section: Discussionsupporting

confidence: 88%

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

et al. 2021

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“…The intensity of this satellite peak at 5.9 eV from the center of gravity of the main peaks (another indication for Fe 2+ [ 88 ]) is sensitive to the polarizability of the environment of the Fe atoms via the extra-atomic relaxation, one of the relaxation processes related to the photoemission event [ 89 , 90 ]. In contrast to FeO, Fe atoms in the Fe-TiO 2 sample were surrounded by TiO 2 , which has about 40-times higher permittivity than FeO [ 91 , 92 ]. This justifies the different relative intensity of the satellite peak compared to FeO [ 87 ] and identifies the iron oxidation state as pure Fe 2+ .…”

Section: Resultsmentioning

confidence: 99%

Enhanced Fe-TiO2 Solar Photocatalysts on Porous Platforms for Water Purification

et al. 2022

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In this study, polyethylene glycol-modified titanium dioxide (PEG-modified TiO2) nanopowders were prepared using a fast solvothermal method under microwave irradiation, and without any further calcination processes. These nanopowders were further impregnated on porous polymeric platforms by drop-casting. The effect of adding iron with different molar ratios (1, 2, and 5%) of iron precursor was investigated. The characterization of the produced materials was carried out by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Optical characterization of all the materials was also carried out. SEM showed that pure TiO2 and Fe-TiO2 nanostructures presented similar nanosized and spherical particles, which uniformly covered the substrates. From XRD, pure TiO2 anatase was obtained for all nanopowders produced, which was further confirmed by Raman spectroscopy on the impregnated substrates. XPS and UV–VIS absorption spectroscopy emission spectra revealed that the presence of Fe ions on the Fe-TiO2 nanostructures led to the introduction of new intermediate energy levels, as well as defects that contributed to an enhancement in the photocatalytic performance. The photocatalytic results under solar radiation demonstrated increased photocatalytic activity in the presence of the 5% Fe-TiO2 nanostructures (Rhodamine B degradation of 85% after 3.5 h, compared to 74% with pure TiO2 for the same exposure time). The photodegradation rate of RhB dye with the Fe-TiO2 substrate was 1.5-times faster than pure TiO2. Reusability tests were also performed. The approach developed in this work originated novel functionalized photocatalytic platforms, which were revealed to be promising for the removal of organic dyes from wastewater.

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“…Complex electric permittivity ε * can be expressed as ε ′ + iε ″, and the loss factor tanδ can be described as the ratio of ε ″/ ε ′. ε * was measured by the dielectric spectroscopy indirectly by measuring complex capacitance C * and calculated by Equation (1) [ 32 , 33 ]: C * = ε * ε 0 A / h , where ε 0 is the vacuum permittivity (8.85 × 10 −12 As/(V·m)), A is the surface area, and h is the height of the measured sample.…”

Section: Resultsmentioning

confidence: 99%

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism

et al. 2021

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The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe3O4 nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10−4 S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.

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On the permittivity of titanium dioxide

Cited by 42 publications

References 16 publications

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

Investigation of Biocompatible PEO Coating Growth on cp-Ti with In Situ Spectroscopic Methods

Enhanced Fe-TiO2 Solar Photocatalysts on Porous Platforms for Water Purification

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism

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