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Hameed, P., Gopal, V., Björklund, S., Ganvir, A., Sen, D., Markocsan, N. & Manivasagam, G. (2019). Axial Suspension Plasma Spraying: An ultimate technique to tailor Ti6Al4V surface with HAp for orthopaedic applications. Colloids and Surfaces B: Biointerfaces, 173, 806-815
Open this publication in new window or tab >>Axial Suspension Plasma Spraying: An ultimate technique to tailor Ti6Al4V surface with HAp for orthopaedic applications
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2019 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 173, p. 806-815Article in journal (Refereed) Published
Abstract [en]

Dissolution of atmospheric plasma sprayed (APS) hydroxyapatite (HAp) coatings on Ti-6Al-4 V medical implants have always been a challenge to overcome in the field of biomedical industry. In the present work, an attempt has been made to develop a HAp coating using a novel thermal spray process called axial suspension plasma spraying (SPS), which leads to thin adherent coatings. Two HAp coatings fabricated by APS (P1 and P2) and four SPS HAp coatings (S1, S2, S3 and S4) produced with varying spraying parameters were characterized in terms of (1) microstructure, porosity, hardness, adhesion strength, contact angle and phase purity; (2) corrosion resistance in 10% Fetal bovine serum (FBS); (3) in-vitro cell adherence and cell viability using human umbilical cord blood-derived mesenchymal stem cells (hMSCs). Amongst different APS and SPS coatings, P1 and S3 exhibited superior properties. S3 coating developed using SPS exhibited 1.3 times higher adhesion strength when compared to APS coating (P1) and 9.5 times higher corrosion resistance than P1. In addition, both S3 and P1 exhibited comparatively higher biocompatibility as evidenced by the presence of more than 92% viable hMSCs. © 2018 Elsevier B.V.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Adhesion; Aluminum alloys; Aluminum coatings; Aluminum corrosion; Atmospheric corrosion; Biocompatibility; Bond strength (materials); Cell adhesion; Cell culture; Contact angle; Corrosion resistance; Corrosion resistant coatings; Corrosive effects; Hydroxyapatite; Mammals; Phase shifters; Plasma jets; Sprayed coatings; Stem cells; Ternary alloys; Thermal spraying; Titanium alloys; Vanadium alloys, Atmospheric plasma spraying; Corrosion studies; hMSCs; Suspension plasma spraying; Ti-6 Al-4 V, Plasma spraying
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13115 (URN)10.1016/j.colsurfb.2018.10.071 (DOI)000454377300095 ()30551296 (PubMedID)2-s2.0-85055725408 (Scopus ID)
Note

Available online 26 October 2018.

Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2019-01-18Bibliographically approved
Zhang, X., Li, C., Withers, P. J., Markocsan, N. & Xiao, P. (2019). Determination of local residual stress in an air plasma spray thermal barrier coating (APS-TBC) by microscale ring coring using a picosecond laser. Scripta Materialia, 167, 126-130
Open this publication in new window or tab >>Determination of local residual stress in an air plasma spray thermal barrier coating (APS-TBC) by microscale ring coring using a picosecond laser
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2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 167, p. 126-130Article in journal (Refereed) Published
Abstract [en]

A picosecond laser for incremental annular trench cutting is combined with digital image correlation (DIC) to extend the incremental ring-core method to the profiling of residual stress in thick (>100 μm) coatings. In this case the local residual stress in a TBC is depth profiled after exposure to 1150 °C for 190 h. The topcoat was found to be in compression with an average compressive stress of −94 ± 8 MPa which is representative of the stresses that would be generated elastically on cooling from a stress-free temperature of ~970 °C. The stress profile measurements have been validated by high-energy synchrotron X-ray diffraction measurements. © 2019

Keywords
Computerized tomography; Picosecond lasers; Plasma spraying; Residual stresses; Stress analysis; Thermal barrier coatings; Yttria stabilized zirconia; Yttrium oxide; Zirconia, Air plasma spray; D. digital image correlation (DIC); High-energy synchrotron X-rays; Hole drilling; Non destructive; Stress-free temperature; X ray micro-computed tomography; Yttria partially stabilized zirconia, Compressive stress
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-13850 (URN)10.1016/j.scriptamat.2019.03.036 (DOI)000468720000026 ()2-s2.0-85064181710 (Scopus ID)
Funder
EU, European Research Council, No. 695638 CORREL-CT.
Note

Funders: Engineering and Physical Science Research Council, (EPSRC), EP/P025021/1, EP/F007906/1 , EP/F001452/1 , EP/I02249X , EP/M010619/1 , EP/F028431/1 , and EP/M022498/1

Available from: 2019-05-24 Created: 2019-05-24 Last updated: 2019-07-25Bibliographically approved
Gupta, M. K., Markocsan, N., Li, X.-H. & Kjellman, B. (2019). Development of bondcoats for high lifetime suspension plasma sprayed thermal barrier coatings. Surface & Coatings Technology, 371(SI), 366-377
Open this publication in new window or tab >>Development of bondcoats for high lifetime suspension plasma sprayed thermal barrier coatings
2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 371, no SI, p. 366-377Article in journal (Refereed) Published
Abstract [en]

Fabrication of thermal barrier coatings (TBCs) by suspension plasma spraying (SPS) seems to be a promising alternative for the industry as SPS TBCs have the potential to provide lower thermal conductivity and longer lifetime than state-of-the-art allowing higher engine efficiency. Further improvements in lifetime of SPS TBCs and fundamental understanding of failure mechanisms in SPS TBCs are necessary for their widespread commercialisation. In this study, the influence of varying topcoat-bondcoat interface topography and bondcoat microstructure on lifetime was investigated. The objective of this work was to gain fundamental understanding of relationships between topcoat-bondcoat interface topography, bondcoat microstructure, and failure mechanisms in SPS TBCs. Seven sets of samples were produced in this study by keeping same bondcoat chemistry but varying feedstock particle size distributions and bondcoat spray processes. The topcoat chemistry and spray parameters were kept identical in all samples. Three-dimensional surface measurements along with scanning electron microscopy images were used to characterise bondcoat surface topography. The effect of varying interface topography and bondcoat microstructure on thermally grown oxide formation, stresses and lifetime was discussed. The results showed that varying bondcoat powder size distribution and spray process can have a significant effect on lifetime of SPS TBCs. Smoother bondcoats seemed to enhance the lifetime in case of SPS TBCs in case of same bondcoat chemistry and similar bondcoat microstructures. When considering the samples investigated in this study, samples with high velocity air-fuel (HVAF) bondcoats resulted in higher lifetime than other samples indicating that HVAF could be a suitable process for bondcoat deposition in SPS TBCs. © 2018 Elsevier B.V.

Keywords
Air, Failure (mechanical), Microstructure, Particle size, Plasma jets, Plasma spraying, Scanning electron microscopy, Size distribution, Sprayed coatings, Surface measurement, Surface topography, Thermal conductivity, Thermal spraying, Topography, Bond coats, Interface topography, Lifetime, Suspension plasma spraying, Thermal barrier coating (TBCs), Thermally grown oxide, Thermal barrier coatings
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13178 (URN)10.1016/j.surfcoat.2018.11.013 (DOI)000472694300037 ()2-s2.0-85056458705 (Scopus ID)
Funder
Knowledge Foundation, 20160022
Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-10-16Bibliographically approved
Mahade, S., Curry, N., Björklund, S., Markocsan, N. & Joshi, S. V. (2019). Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions. Materials, 12(14), Article ID E2238.
Open this publication in new window or tab >>Durability of Gadolinium Zirconate/YSZ Double-Layered Thermal Barrier Coatings under Different Thermal Cyclic Test Conditions
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2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 14, article id E2238Article in journal (Refereed) Published
Abstract [en]

Higher durability in thermal barrier coatings (TBCs) is constantly sought to enhance the service life of gas turbine engine components such as blades and vanes. In this study, three double layered gadolinium zirconate (GZ)-on-yttria stabilized zirconia (YSZ) TBC variants with varying individual layer thickness but identical total thickness produced by suspension plasma spray (SPS) process were evaluated. The objective was to investigate the role of YSZ layer thickness on the durability of GZ/YSZ double-layered TBCs under different thermal cyclic test conditions i.e., thermal cyclic fatigue (TCF) at 1100 °C and a burner rig test (BRT) at a surface temperature of 1400 °C, respectively. Microstructural characterization was performed using SEM (Scanning Electron Microscopy) and porosity content was measured using image analysis technique. Results reveal that the durability of double-layered TBCs decreased with YSZ thickness under both TCF and BRT test conditions. The TBCs were analyzed by SEM to investigate microstructural evolution as well as failure modes during TCF and BRT test conditions. It was observed that the failure modes varied with test conditions, with all the three double-layered TBC variants showing failure in the TGO (thermally grown oxide) during the TCF test and in the ceramic GZ top coat close to the GZ/YSZ interface during BRT. Furthermore, porosity analysis of the as-sprayed and TCF failed TBCs revealed differences in sintering behavior for GZ and YSZ. The findings from this work provide new insights into the mechanisms responsible for failure of SPS processed double-layered TBCs under different thermal cyclic test conditions.

Keywords
burner rig test, double-layered TBC, gadolinium zirconate, suspension plasma spray, thermal cyclic fatigue, yttria stabilized zirconia
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:hv:diva-14438 (URN)10.3390/ma12142238 (DOI)000480454300026 ()31336713 (PubMedID)2-s2.0-85070469165 (Scopus ID)
Funder
Knowledge Foundation, Dnr-20140130
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-15
Zhang, P., Sadeghi, E., Chen, S., Li, X.-H., Markocsan, N., Joshi, S. V., . . . Peng, R. L. n. (2019). Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings. Surface & Coatings Technology, 364, 43-56
Open this publication in new window or tab >>Effects of surface finish on the initial oxidation of HVAF-sprayed NiCoCrAlY coatings
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2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 364, p. 43-56Article in journal (Refereed) Published
Abstract [en]

Oxide scale formed on HVAF-sprayed NiCoCrAlY coatings and the effect of surface treatment were investigated by a multi-approach study combining photo-stimulated luminescence, microstructural observation and mass gain. The initial oxidationbehaviour of as-sprayed, polished and shot-peened coatings at 1000 °C is studied. Both polished and shot-peened coatings exhibited superior performance due to rapid formation of α-Al2O3 fully covering the coating and suppressing the growth of transient alumina, assisted by a high density of α-Al2O3 nuclei on surface treatment induced defects. Moreover, the fast development of a two-layer alumina scale consisting of an inward-grown inner α-Al2O3 layer and an outer layer transformed from outward-grown transient alumina resulted in a higher oxide growth rate of the as-sprayed coating.

Keywords
Oxidation, Transient to alpha transformation, Surface treatment, Polishing, Shot-peening, Photo-stimulated luminescence spectroscopy
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13736 (URN)10.1016/j.surfcoat.2019.02.068 (DOI)000463302800006 ()2-s2.0-85062231529 (Scopus ID)
Funder
Swedish Energy Agency, KME-703
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-07-01Bibliographically approved
Ganvir, A., Calinas, R. F., Markocsan, N., Curry, N. & Joshi, S. V. (2019). Experimental visualization of microstructure evolution during suspension plasma spraying of thermal barrier coatings. Journal of the European Ceramic Society, 39(2-3), 470-481
Open this publication in new window or tab >>Experimental visualization of microstructure evolution during suspension plasma spraying of thermal barrier coatings
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2019 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, no 2-3, p. 470-481Article in journal (Refereed) Published
Abstract [en]

This paper investigates the evolution of microstructure of thermal barrier coatings (TBCs) produced by suspension plasma spraying (SPS) through a careful experimental study. Understanding the influence of different suspension characteristics such as type of solvent, solid load content and median particle size on the ensuing TBC microstructure, as well as visualizing the early stages of coating build-up leading to formation of a columnar microstructure or otherwise, was of specific interest. Several SPS TBCs with different suspensions were deposited under identical conditions (same substrate, bond coat and plasma spray parameters). The experimental study clearly revealed the important role of suspension characteristics, namely surface tension, density and viscosity, on the final microstructure, with study of its progressive evolution providing invaluable insights. Variations in suspension properties manifest in the form of differences in droplet momentum and trajectory, which are found to be key determinants governing the resulting microstructure (e.g., lamellar/vertically cracked or columnar).

Keywords
Suspension plasma spraying, Thermal barrier coatings, Droplet momentum, Columnar microstructure, Microstructure evolution
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12948 (URN)10.1016/j.jeurceramsoc.2018.09.023 (DOI)000450379400042 ()2-s2.0-85053889817 (Scopus ID)
Funder
Region Västra Götaland, RUN 612-0974-13
Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2018-12-20Bibliographically approved
Mahade, S., Curry, N., Jonnalagadda, K. P., Peng, R. L., Markocsan, N. & Nylén, P. (2019). Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray. Surface & Coatings Technology, 357, 456-465
Open this publication in new window or tab >>Influence of YSZ layer thickness on the durability of gadolinium zirconate/YSZ double-layered thermal barrier coatings produced by suspension plasma spray
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2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 357, p. 456-465Article in journal (Refereed) Published
Abstract [en]

In this work, three double layered thermal barrier coating (TBC) variations with different gadolinium zirconate (GZ) and YSZ thickness (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400YSZ respectively, where the prefixed numbers before GZ and YSZ represent the layer thickness in μm), were produced by suspension plasma spray (SPS) process. The objective was to investigate the influence of YSZ thickness on the thermal conductivity and thermal shock lifetime of the GZ/YSZ double layered TBCs. The as sprayed TBCs were characterized using SEM, XRD and porosity measurements. Thermal diffusivity measurements were made using laser flash analysis and the thermal conductivity of the TBCs was calculated. The double layered TBC with the lowest YSZ (400GZ/100YSZ) thickness showed lower thermal diffusivity and thermal conductivity. The double layered TBCs were subjected to thermal shock test at a TBC surface temperature of 1350 °C. Results indicate that the TBC with a higher YSZ thickness (100GZ/400YSZ) showed inferior thermal shock lifetime whereas the TBCs with low YSZ thickness showed comparatively higher thermal shock lifetimes. Failure of the TBCs after thermal shock test was analyzed using SEM and XRD to gain further insights.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Gadolinium; Plasma jets; Plasma spraying; Thermal conductivity; Thermal shock; X ray diffraction; Yttria stabilized zirconia; Yttrium oxide; Zirconia, Diffusivity measurements; Double layered; Gadolinium zirconate; Layer thickness; Porosity measurement; Surface temperatures; Suspension plasma sprays; Thermal barrier coating (TBC), Thermal barrier coatings
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13106 (URN)10.1016/j.surfcoat.2018.10.046 (DOI)000455691100067 ()2-s2.0-85055204877 (Scopus ID)
Funder
Knowledge Foundation, 20140130
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2019-02-04Bibliographically approved
Chen, Y., Zhang, X., Zhao, X., Markocsan, N., Nylén, P. & Xiao, P. (2019). Measurements of elastic modulus and fracture toughness of an air plasma sprayed thermal barrier coating using micro-cantilever bending. Surface & Coatings Technology, 374, 12-20
Open this publication in new window or tab >>Measurements of elastic modulus and fracture toughness of an air plasma sprayed thermal barrier coating using micro-cantilever bending
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2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 374, p. 12-20Article in journal (Refereed) Published
Abstract [en]

The elastic modulus and fracture toughness of an air plasma sprayed thermal barrier coating (APS TBC) were measured using the micro-cantilever bending technique. The micro-cantilevers were machined by a focused ion beam with their central arms either parallel or normal to the bond coat/topcoat interface. Such orientations allowed direct measurements of both the in-plane and out-of-plane elastic moduli as well as mode I fracture toughness by bending. The calculated elastic modulus along the in-plane and out-of-plane direction is 144 GPa and 110 GPa, respectively, suggesting that the APS TBC is elastically anisotropic at microscale. The derived mode I fracture toughness along the plane parallel to the interface is 0.40 MPam. This relatively low toughness reflects the weak fracture resistance of the highly-flawed APS for short cracks at microscale. The measurements in this study can be incorporated into micromechanical life time prediction models of the APS TBCs. © 2019 Elsevier B.V.

Keywords
Elastic moduli; Ion beams; Microstructure; Nanocantilevers; Plasma jets; Plasma spraying; Thermal barrier coatings, Air plasma sprayed thermal barrier coatings; Direct measurement; Lifetime prediction; Measurements of; Micro-cantilevers; Micro-mechanical; Mode-i fracture toughness; Out-of-plane direction, Fracture toughness
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14455 (URN)10.1016/j.surfcoat.2019.05.031 (DOI)000486360000002 ()2-s2.0-85066829982 (Scopus ID)
Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2019-10-16
Aranke, O., Gupta, M. K., Markocsan, N., Li, X.-H. & Kjellman, B. (2019). Microstructural Evolution and Sintering of Suspension Plasma-Sprayed Columnar Thermal Barrier Coatings. Journal of thermal spray technology (Print) (1-2), 198-211
Open this publication in new window or tab >>Microstructural Evolution and Sintering of Suspension Plasma-Sprayed Columnar Thermal Barrier Coatings
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2019 (English)In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, no 1-2, p. 198-211Article in journal (Refereed) Published
Abstract [en]

Suspension plasma spray (SPS) is capable of producing coatings with porous columnar structure, and it is also a much cheaper process compared to the conventionally used electron beam physical vapor deposition (EB-PVD). Although TBCs with a columnar microstructure that are fabricated using SPS have typically lower thermal conductivity than EB-PVD, they are used sparingly in the aerospace industry due to their lower fracture toughness and limited lifetime expectancy. Lifetime of TBCs is highly influenced by the topcoat microstructure. The objective of this work was to study the TBCs produced using axial SPS with different process parameters. Influence of the microstructure on lifetime of the coatings was of particular interest, and it was determined by thermal cyclic fatigue testing. The effect of sintering on microstructure of the coatings exposed to high temperatures was also investigated. Porosity measurements were taken using image analysis technique, and thermal conductivity of the coatings was determined by laser flash analysis. The results show that axial SPS is a promising method of producing TBCs having various microstructures with good lifetime. Changes in microstructure of topcoat due to sintering were seen evidently in porous coatings, whereas dense topcoats showed good resistance against sintering.

Place, publisher, year, edition, pages
ASM International, 2019
Keywords
columnar microstructure, sintering, suspension plasma spray, thermal barrier coating, thermal conductivity, thermal cyclic test
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13077 (URN)10.1007/s11666-018-0778-z (DOI)000456599500018 ()2-s2.0-85055871819 (Scopus ID)
Funder
Knowledge Foundation
Note

First Online: 25 October 2018

This article is an invited paper selected from presentations at the 2018 International Thermal Spray Conference, held May 7-10, 2018, in Orlando, Florida, USA, and has been expanded from the original presentation.

Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2019-03-21Bibliographically approved
Vijay, S., Wang, L., Lyphout, C., Nylén, P. & Markocsan, N. (2019). Surface characteristics investigation of HVAF sprayed cermet coatings. Applied Surface Science, 493, 956-962
Open this publication in new window or tab >>Surface characteristics investigation of HVAF sprayed cermet coatings
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2019 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 493, p. 956-962Article in journal (Refereed) Published
Abstract [en]

Superhydrophobic surfaces that are durable and can be easily manufactured are of high interest for many industrial applications. Measuring and understanding roughness in the context of superhydrophobicity is the first step in creation of a surface that does not require activation to be hydrophobic. In this study, the as sprayed surface of different cermet (WC-10Co4Cr and Cr3C2-25Ni20Cr) coatings produced by High Velocity Air Fuel (HVAF) spraying – have been investigated to assess their wetting ability. In order to address the challenges raised by the specific roughness profile of thermal spray surfaces, two routes have been adapted and used for surface characteristics analysis i.e. statistical and fractal. Results show that both methods have a strong correlation to wettability. Roughness parameters Sdq and Sdr show good correlation with advancing contact angle. Hausdorff Dimension of a sub-micrometer profile shows good relation with the contact angle and provides information for state of the droplet. To determine how to increase the contact angle of the coating surface, coating parameters such as CGS Density have been correlated with Hausdorff Dimension. Both methods provide good understanding in terms of wettability of rough cermet surfaces. © 2019 Elsevier B.V.

Keywords
Air; Cermets; Contact angle; Fractals; Hydrophobicity; Sprayed coatings; Statistical methods; Surface roughness, Advancing contact angle; Cermet coatings; Fractal analysis; High velocity air fuels; Hydrophobic surfaces; Roughness parameters; Super-hydrophobic surfaces; Surface characteristics, Wetting
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14483 (URN)10.1016/j.apsusc.2019.07.079 (DOI)2-s2.0-85069570632 (Scopus ID)
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-02
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9578-4076

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