Effect of Different Types of Pores on Thermal Conductivity of YSZ Thermal Barrier Coatings

Huang, Yiling; Hu, Ningning; Zeng, Yi; Song, Xuemei; Lin, Chucheng; Liu, Ziwei; Zhang, Jimei

doi:10.3390/coatings9020138

Cited by 20 publications

(16 citation statements)

References 23 publications

(31 reference statements)

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“…The measurements above for porosity fractions (considering medium-and coarse-powder coatings) are well in agreement with the recorded literature data [25,26]. Deshpande et al [25] prepared APS alumina and YSZ coatings by powders of different size distributions and morphologies.…”

Section: Image Processing Analysissupporting

confidence: 88%

“…Huang et al [26] prepared different YSZ coatings using different spray parameters and measured the total porosity and number of pores in a prespecified scanning area. They also classified pores in terms of aspect ratio (big & small pores) and orientation (horizontal & vertical) to investigate their influence on thermal conductivity of the coatings.…”

Section: Image Processing Analysismentioning

confidence: 99%

“…has been reported that the number of pores plays a significant role in reducing the thermal conductivity of ceramic coatings [26]. They measured the thermal conductivity of plasma sprayed YSZ coatings and found that thermal conductivity is reduced from 1.4 to 0.8 W/(m.K), for coatings of higher pore number, although all coatings were having almost the same total porosity.…”

Section: Thermal Insulationmentioning

confidence: 99%

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Porosity Characterization and Its Effect on Thermal Properties of APS-Sprayed Alumina Coatings

2019

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In the thermal spraying process, the porosity of ceramic coatings contributes directly to the efficiency of the thermal insulation. The size, shape, and distribution of the pores determine the level of both thermal and sintering resistance. In this work, three different atmospheric plasma sprayed (APS) alumina coatings were fabricated with the same spraying parameters using alumina powders with fine, medium, and coarse particle size. The microstructure of the obtained coatings was analyzed regarding the obtained total porosity, pore size, and pore shape. It was found that it is expedient to divide the pore size range into fine, medium, and large sizes. The shape was characterized with regard to the circularity aspect. In this way, all types of cracks can be considered as oblate pores and were included in the calculation of the total porosity. In the case of using fine feedstock powder, the densest coatings were produced among all coatings, and the fraction of fine pores and cracks are thereby substantially higher. However, the total porosity increases with increasing feedstock powder size. A connection was also made between thermal insulation and porosity fraction which includes fine pores and cracks.

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Section: Image Processing Analysissupporting

confidence: 88%

Section: Image Processing Analysismentioning

confidence: 99%

Section: Thermal Insulationmentioning

confidence: 99%

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Porosity Characterization and Its Effect on Thermal Properties of APS-Sprayed Alumina Coatings

2019

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“…Additionally, CT data is used to analyze the three dimensional dis tribution of spherical like pores within coatings in comparison with their thermal diffusivity at the very same positions. In contrast to other publications [5,26], the porosity distribution as well as the average pore size follows the thermal diffusivity along the crankcase positions such that positions with high thermal diffusivity also show high por osity values as well as high pore sizes and vice versa (Fig. 5 and 6).…”

Section: Discussioncontrasting

confidence: 63%

“…5 and 6). In general, higher porosity within the thermally sprayed material should lower the thermal conductivity and hence the thermal diffusivity [5,26]. Therefore, the percentage of spherical pores may not be the dominant effect influencing the thermal diffusivity, but the shape shows a significant influence.…”

Section: Discussionmentioning

confidence: 99%

Thermal wave interferometry measurements and microstructural analysis of twin wire arc spray cylinder coatings for passenger car engines

Arbogast

Schaller

Lindemann

et al. 2020

Infrared Physics & Technology

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With intent to increase the efficiency of combustion engines in passenger cars, thermally sprayed cylinder bore coatings replaced cast iron liners as cylinder running surfaces over the past years. Since the functionality of an engine depends on the life-long integrity of these coatings only a few μ 100 m thick, monitoring their physical properties in series production is most important. This contribution focuses on the non-destructive testing of thermally sprayed coatings by thermal wave interferometry (TWI), investigating the relationship between thermal and microstructural properties. Microstructural characteristics such as laterally expanded splat interfaces or spherical pores correlate with macroscopic quality criteria such as adhesion, cohesion, or corrosion resistance. Further on, especially splat interfaces act as thermal barriers within the coatings. Hence, TWI thermal diffusivity measurements were compared to optical microscopy images of polished cross sections and threedimensional X-ray computed tomography data at multiple positions in a crankcase. Both, microscopy images as well as computed tomography data were analyzed quantitatively by image processing algorithms. Due to this, local variations in thermal diffusivity were found, which revealed a significant correlation with microstructural characteristics. Further on, a significant influence of the amount, size, and shape of microstructural volume defects on the local thermal diffusivity of thermally sprayed coatings is carried out in this contribution.

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A Promising Radiation Thermal Protection Coating Based on Lamellar Porous Ca‐Cr co‐Doped Y₃NbO₇ Ceramic

Chen

Zou

et al. 2023

Adv Funct Materials

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Dissipation of heat efficiently from a hot object via radiation while minimizing the inward heat conduction is the key requirement of radiation thermal protection. In this study, a Ca‐Cr co‐doped Y3NbO7 coating with lamellar porous structure is fabricated, which shows an ultra‐low thermal conductivity (<0.7 W m−1 K−1) and near‐unity emissivity (>0.9) across a broad wavelength range of ≈1–24 µm. This record high emissivity to thermal conductivity ratio (≈1.3) is experimentally and theoretically revealed from a multi‐scale perspective. The diffusoin‐mediated thermal conduction feature of niobates combined with lamellar porous structure of the coating reduces its thermal conductivity to an impressive 0.5 W m−1 K−1 at 25 °C, surpassing the theoretical amorphous limitation of 0.72 W m−1 K−1. Experiments and FDTD calculation results demonstrate that the intrinsic emissivity dips at shallow extinction wavelengths (1 and 8 µm) and strong phonon‐polariton resonances wavelengths (>13 µm) can be effectively compensated by the multiple scattering/absorption and gradual modulation of conical shape/effective refractive index induced by surface micro‐protrusion structures, respectively. Furthermore, the coating exhibits robust mechanical and thermal stability with a high bonding strength (18.3 MPa) and thermal expansion coefficient (≈11 × 10−6 K−1 at 1200 °C) comparable to YSZ, showing great potential in the radiation thermal protection field.

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Effect of Different Types of Pores on Thermal Conductivity of YSZ Thermal Barrier Coatings

Cited by 20 publications

References 23 publications

Porosity Characterization and Its Effect on Thermal Properties of APS-Sprayed Alumina Coatings

Porosity Characterization and Its Effect on Thermal Properties of APS-Sprayed Alumina Coatings

Thermal wave interferometry measurements and microstructural analysis of twin wire arc spray cylinder coatings for passenger car engines

A Promising Radiation Thermal Protection Coating Based on Lamellar Porous Ca‐Cr co‐Doped Y₃NbO₇ Ceramic

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Effect of Different Types of Pores on Thermal Conductivity of YSZ Thermal Barrier Coatings

Cited by 20 publications

References 23 publications

Porosity Characterization and Its Effect on Thermal Properties of APS-Sprayed Alumina Coatings

Porosity Characterization and Its Effect on Thermal Properties of APS-Sprayed Alumina Coatings

Thermal wave interferometry measurements and microstructural analysis of twin wire arc spray cylinder coatings for passenger car engines

A Promising Radiation Thermal Protection Coating Based on Lamellar Porous Ca‐Cr co‐Doped Y3NbO7 Ceramic

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Product

Resources

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A Promising Radiation Thermal Protection Coating Based on Lamellar Porous Ca‐Cr co‐Doped Y₃NbO₇ Ceramic