Anisotropic electrical conduction from heterogeneous oxidation states in plasma sprayed TiO2 coatings

Sharma, Anjali; Gouldstone, Andrew; Sampath, Sanjay; Gambino, R. J.

doi:10.1063/1.2382456

Cited by 27 publications

(10 citation statements)

References 56 publications

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“…The difference in the Seebeck coefficient is attributed to the presence of oxygen defects which is inversely proportional to the carrier density whereas electrical conductivity depends upon combination of oxygen vacancy, microstructure and crystallinity23. Increase in hydrogen content of the plasma can lead to greater oxygen loss and thus further phase reduction (Ti 4 O 7 ) with associated increase in electrical conductivity and reduction in Seebeck coefficient as well.…”

Section: Resultsmentioning

confidence: 99%

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Thermoelectric properties of in-situ plasma spray synthesized sub-stoichiometry TiO2−x

Lee

Han

Seshadri

et al. 2016

Sci Rep

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The thermoelectric properties of sub-stoichiometric TiO2−x deposits produced by cascaded-plasma spray process are investigated from room-temperature to 750 K. Sub-stoichiometric TiO2−x deposits are formed through in-situ reaction of the TiO1.9 within the high temperature plasma flame and manipulated through introduction of varying amounts of hydrogen in the plasma. Although the TiO2−x particles experience reduction within plasma, it can also re-oxidize through interaction with the surrounding ambient atmosphere, resulting in a complex interplay between process conditions and stoichiometry. The deposits predominantly contain rutile phase with presence of Magneli phases especially under significantly reducing plasma conditions. The resultant deposits show sensitivity to thermoelectric properties and under certain optimal conditions repeatedly show Seebeck coefficients reaching values of −230 μV K−1 at temperatures of 750 K while providing an electrical conductivity of 5.48 × 103 S m−1, relatively low thermal conductivity in the range of 1.5 to 2 W m−1 K−1 resulting in power factor of 2.9 μW cm−1 K−2. The resultant maximum thermoelectric figure of merit value reached 0.132 under these optimal conditions. The results point to a potential pathway for a large-scale fabrication of low-cost oxide based thermoelectric with potential applicability at moderate to high temperatures.

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Section: Resultsmentioning

confidence: 99%

“…Sharma et al 23. observed that plasma-sprayed TiO 2 deposits behave as n -type semiconductor with reasonable conductivities (1.76 × 10 3 S cm −1 ) up to about 823 K, after which rapid re-oxidation occurs with concomitant increases in resistance.…”

mentioning

confidence: 99%

Thermoelectric properties of in-situ plasma spray synthesized sub-stoichiometry TiO2−x

Lee

Han

Seshadri

et al. 2016

Sci Rep

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“…Concerning the influence of powder thermal oxidation, we could adopt discussion opened with Sharma et al [30]. The authors of this reference oxidatively annealed the as-sprayed coatings, which were oxygen-deficient, and showed that the splat boundaries are more electrically conductive in the as-sprayed material but become more insulating than the splat core after annealing.…”

Section: Chemistry Photochemistry and Electrochemistrymentioning

confidence: 99%

Photocatalytic and electrochemical properties of single- and multi-layer sub-stoichiometric titanium oxide coatings prepared by atmospheric plasma spraying

et al. 2016

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We studied the photocatalytic and electrochemical impedance properties of two different sub-stoichiometric titania powders deposited using plasma spraying. Two different commercial powders with markedly diverse mean size as well as size distribution were chosen. Thermal oxidation of these as-received powders was carried out to restore the O/Ti ratio to be 2.0. By this way, another two kinds of feedstock powders were obtained. Total of four kinds of feedstock powders were used in the experiments. All powders were sprayed using identical plasma spraying parameters. For some spraying runs, carbon steel served as the substrate, and for others, the previously sprayed titania coating from a different kind of feedstock. Combinations of single-and double-layer coatings were studied. Porosity, microstructure, phase composition, chemical composition, band gap based on reflectance measurement, and photocatalytic activity were examined. Electrochemical impedance spectroscopy demonstrated substantial differences between samples sprayed from the fine and coarse powders. Coatings from oxidized powders were slightly more photocatalytic. High spraying distance used for several of them was good for obtaining low band gap, whereas surface roughness and phase composition were not substantially different compared to standard spraying distance coatings.

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“…object oriented finite element analysis-OOF) resulting in establishment of microstructure-property relationships [48,49]. 4) New techniques have been developed for mechanical, thermal and functional characterization of these anisotropic layered coatings including the ability to extract design relevant properties [50][51][52][53][54][55][56]. Of particular importance is the knowledge of stress evolution and residual stresses associated with coating formation and cooling.…”

Section: Enhancements In Scientific Understandingmentioning

confidence: 99%

Partnership for accelerated insertion of new technology: case study for thermal spray technology

Sampath

Dwivedi

Valarezo

et al. 2013

Integr Mater Manuf Innov

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Introduction: Materials and manufacturing innovation in complex engineering systems such as those in aerospace, energy, heavy machinery is extremely challenging as they typically involve lengthy and costly development cycles and generally follow stringent guidelines and defined road maps. Incorporating academic science and disruptive advances into this product development cycle is challenging. Effective partnerships via integrated academic-industry study groups and joint value proposition of scientific advances and models, can accelerate insertion of new knowledge/technologies in this class of materials and manufacturing ecosystems. Case Description: This paper describes such a partnership and integration framework through exemplary case studies in thermal spray materials processing. Thermal spray is a platform materials manufacturing technology enabling deposition of advanced coatings for wide range of materials applications in aerospace, energy, heavy machinery, electronics and biomedical devices. It is a complex process involving many facets of engineering sciences including thermo-fluids, heat transfer, materials science and mechanics, incorporating non-equilibrium phenomena and multi-scale structure/behavior. The required breadth and depth of process and materials knowledge for advancing the technology is very significant, resulting in lengthy, trial and error based developments. Specific case studies illustrate knowledge advancement through science and models, development of measurement tools and simulations, along with industrial demonstration studies, addressing the utility in the manufacturing enterprise. Together, they represent a framework for establishing integrated computational and experimental materials engineering concepts and serve as a model ecosystem for accelerating innovation in complex industrial manufacturing processes.

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Anisotropic electrical conduction from heterogeneous oxidation states in plasma sprayed TiO2 coatings

Cited by 27 publications

References 56 publications

Thermoelectric properties of in-situ plasma spray synthesized sub-stoichiometry TiO2−x

Thermoelectric properties of in-situ plasma spray synthesized sub-stoichiometry TiO2−x

Photocatalytic and electrochemical properties of single- and multi-layer sub-stoichiometric titanium oxide coatings prepared by atmospheric plasma spraying

Partnership for accelerated insertion of new technology: case study for thermal spray technology

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