Sliding Wear Behavior of Al2O3-TiO2 Coatings Fabricated by the Suspension Plasma Spraying Technique

[EN] The friction and dry sliding wear behavior of alumina and alumina-titania near-nanometric coatings were examined. Coatings were obtained by the suspension plasma spraying technique. Dry sliding wear tests were performed on a ball-on-disk tribometer, with an Al2O3 ball as counterpart material, a normal load of 2 N, a sliding distance of 1200 m and a sliding speed of 0.1 m/s. The effect of including TiO2 in the fabricated coatings on friction coefficient behavior, wear rates and wear damage patterns was determined. The addition of TiO2 to the coatings was found to greatly increase wear resistance by, for example, 2.6-fold for 40 wt% of TiO2. The analysis of the wear surface was correlated with microstructural parameters, mechanical properties and wear rates.The authors wish to thank for the Spanish Ministry of Economy and Competitiveness (MAT2012-38364-C03) and the Autonomous Government of Valencia for funding for the stay in SPCTS-UMR CNRS (France), and the French FCENANOSURF consortium funded by the French Ministry and Industry and local governments of Region Centre and Region Limousin.Klyatskina, E.; Espinosa Fernández, L.; Darut, G.; Segovia López, EF.; Salvador Moya, MD.; Montavon, G.; Agorges, H. (2015). Sliding Wear Behavior of Al2O3-TiO2 Coatings Fabricated by the Suspension Plasma Spraying Technique. Tribology Letters. 59(1):1-9. https://doi.org/10.1007/s11249-015-0530-5S19591Pawlowski, L.: The Science and Engineering of Thermal Spray Coatings. Wiley: Hoboken (2008)Lampe, Th, Eisenberg, S., Cabeo, E.R.: Plasma surface engineering in the automotive industry—trends and future prospective. Surf. Coat. Technol. 174–175, 1–7 (2003)Wang, Y., Jiang, S., Wang, M., Wang, S., Xiao, T.D., Strutt, P.R.: Abrasive wear characteristics of plasma sprayed nanostructured alumina/titania coatings. Wear 237, 176–185 (2000)Kabacoff, L.T.: Nanoceramic coatings exhibit much higher toughness and wear resistance than conventional coatings. AMPITAC Newslett. 6(1), 37–42 (2002)Wang, M., Shaw, L.L.: Effects of the powder manufacturing method on microstructure and wear performance of plasma sprayed alumina–titania coatings. Surf. Coat. Technol. 202, 34–44 (2007)Shaw, L.L., Goberman, D., Ren, R., Gell, M., Jing, S., Wang, Y., Xiao, T.D., Strutt, P.R.: The dependency of microstructure and properties of nanostructured coatings on plasma spray conditions. Surf. Coat. Technol. 130, 1–8 (2000)Dahotre, N.B., Nayak, S.: Nanocoatings for engine application. Surf. Coat. Technol. 194(1), 58–67 (2005)Sathish, S., Geetha, M., Aruna, S.T., Balaji, N., Rajam, K.S., Asokamani, R.: Sliding wear behavior of plasma sprayed nanoceramic coatings for biomedical applications. Wear 271, 934–941 (2011)Pawlowski, L.: Finely grained nanometric and submicrometric coatings by thermal sparing: a review. Surf. Coat. Technol. 202, 4318–4328 (2008)Xiao, D., Wang, Y., Strutt, P.: Fabrication and evaluation of plasma sprayed nanostructured alumina–titania coatings with superior properties. Mater. Sci. Eng. 301, 80–89 (2001)Tjong, S.C., Chen, H.: Nanocrystalline materials and coatings. Mater. Sci. Eng. 45, 1–88 (2004)Fauchais, P., Montavon, G., Bertrand, G.: From powders to thermally sprayed coatings. J. Therm. Spray Technol. 19, 56–80 (2010)Lima, R.S., Marple, B.R.: Thermal spray coatings engineered from nanostructured ceramic agglomerated powders for structural, thermal barrier and biomedical applications: a review. J. Therm. Spray Technol. 16, 40–63 (2007)Fauchais, P., Etchart-Salas, R., Delbos, C., Tognonvi, M., Rat, V., Coudert, J.F., Chartier, T.: Suspension and solution plasma spraying of finely structured layers: potential application to SOFCs. J. Phys. D Appl. Phys. 40, 2394–2406 (2007)Ramachandran, K., Selvajaran, V., Ananthapadmanabhan, P.V., Sreekumar, K.P.: Microstructure, adhesion, micro hardness, abrasive wear resistance and electrical resistivity of the plasma sprayed alumina and alumina–titania coatings. Thin Solid Films 315, 144–152 (1998)Lee, S.W., Morillo, C., Lira-Olivares, J., Kim, S.H., Sekino, T., Niihara, K., Hockey, B.J.: Tribological and microstructural analysis of Al2O3/13TiO2 nanocomposites to use in femoral head of hip replacement. Wear 225, 1040–1044 (2003)Dejang, N., Watcharapasorn, A., Wirojupatump, S., Niranatlumpong, P., Jiansirisomboon, S.: Fabrication and properties of plasma-sprayed Al2O3/TiO2 composite coatings: a role of nano-sized TiO2 addition. Surf. Coat. Technol. 204, 1651–1657 (2010)Yimaz, S.: An evaluation of plasma sprayed coatings based on Al2O3 and Al2O3–13wt% TiO2 with bond coat on pure titanium substrate. Ceram. Int. 35, 2017–2022 (2009)Fervel, V., Normand, B., Coddet, C.: Tribological behavior of plasma sprayed Al2O3-based cermet coatings. Wear 230(1), 70–77 (1999)Vargas, F., Ageorges, H., Fauchais, P., López, M.E.: Mechanical and a tribological performance of Al2O3 coatings elaborated by flame and plasma spraying. Surf. Coat. Technol. 205, 1132–1136 (2010)Bacciochini, A., Ilavsky, J., Montavon, G., Denoirjean, A., Ben-ettouil, F., Valette, S., Fauchais, P., Wittmann-teneze, K.: Quantification of void network architectures of suspension plasma-sprayed (SPS) yttria-stabilized zirconia (YSZ) coatings using ultra-small-angle X-ray scattering (USAXS). Mater. Sci. Eng. 528, 91–102 (2010)ASTM International: ASTM G99-03: Standard test method for wear testing with a pin-on-disc apparatus. ASTM annual book of standards. ASTM International: West Conshohocken (2003)Lancaster, K.: The influence of substrate hardness on the formation and endurance of molybdenum disulphide films. Wear 10, 103–107 (1967)Fauchais, P., Rat, V., Delbos, C., Fazilleau, J., Coudert, J.F., Chartier, T., Bianchi, L.: Understanding of suspension plasma spraying of finely structured coatings for SOFC. IEEE Plasma Sci. 33(2), 920–930 (2005)Bannier, E., Vicent, M., Rayón, E., Benavente, R., Salvador, M.D., Sánchez, E.: Effect of TiO2 addition on the microstructure and nanomechanical properties of Al2O3 suspension plasma sprayed coatings. Appl. Surf. Sci. 316, 141–146 (2014)Darut, G., Klyatskina, E., Valette, S., Carles, P., Denoirjean, A., Montavon, G., Ageorges, H., Segovia, F., Salvador, M.D.: Architecture and phases composition of suspension plasma sprayed alumina–titania sub-micrometer-sized coatings. Mater. Lett. 67, 241–244 (2012)Fauchais, P., Montavon, G.: Latest developments in suspension and liquid precursor thermal spraying. J. Therm. Spray Technol. 19(1–2), 226–239 (2010)Darut, G., Ben-Ettouli, F., Denoirjean, A., Montavon, G., Ageourges, H., Fauchais, P.: Dry sliding behavior of sub-micrometer-sized suspension plasma sprayed ceramic oxide coatings. J. Therm. Spray Technol. 19, 275–285 (2010)Tingaud, O., Bacciochini, A., Montavon, G., Denoirjean, A., Fauchais, P.: Suspension DC plasma spraying of thick finely-structured ceramic coatings: process manufacturing mechanisms. Surf. Coat. Technol. 203, 2157–2161 (2009)Guesama, S., Bounazef, M., Nardin, P., Sahraoui, T.: Wear behavior of alumina–titania coatings: analysis of process and parameters. Ceram. Int. 32, 13–19 (2006)Espinosa-Fernández, L., Borrell, A., Salvador, M.D., Gutierrez-Gonzalez, C.F.: Sliding wear behavior of WC–Co–Cr3C2–VC composites fabricated by conventional and non-conventional techniques. Wear 307, 60–67 (2013)Zhang, J., Moslehy, F.A., Rice, S.L.: A model for friction in quasi-steady-state. Part I. Derivation. Wear 149, 1–12 (1991)Zhang, J., Moslehy, F.A., Rice, S.L.: A model for friction in quasi-steady-state sliding Part II. Numerical results and discussion. Wear 149, 13–25 (1991)Bolelli, G., Cannilo, V., Lusvarghi, L., Manfredini, T.: Wear behaviour of thermally sprayed ceramic oxide coatings. Wear 261, 1298–1315 (2006)Normand, B., Fervel, V., Coddet, C., Nikitine, V.: Tribological properties of plasma sprayed alumina–titania coatings: next term role and control of the microstructure. Surf. Coat. Technol. 123, 278–287 (2000)Hutchings, I.: Tribology: friction and wear of engineering materials. Mater. Des. 13, 187 (1992)Ahn, J., Hwang, B., Song, E.P., Lee, S., Kim, N.J.: Correlation of microstructure and wear resistance of Al2O3–TiO2 coatings plasma sprayed with nanopowders. Metall. Mater. Trans. A 37, 1851–1860 (2006)Erickson, L.C., Hawthorne, H.M., Troczynski, T.: Correlations between microstructural parameters, micromechanical properties and wear resistance of plasma sprayed ceramic coatings. Wear 250, 569–575 (2001)Song, E.P., Ahn, J., Lee, S., Kim, N.J.: Microstructure and wear resistance of nanostructured Al2O3–8 wt%TiO2 coatings plasma-sprayed with nanopowders. Surf. Coat. Technol. 201, 1309–1315 (2006)Tucker Jr., R.C.: ASM Handbook Volume 5A: Thermal Spray Technology. ASM International, Materials Park (2013)Stachowiack, G.W., Batchelor, A.: Engineering Tribology Handbook. Elsevier-Butterworth-Heineman: Oxford (2005)Fischer, T.E., Zhu, Z., Kim, H., Shin, D.S.: Genesis and role of wear debris in sliding wear of ceramics. Wear 245, 53–60 (2000)Lima, R.S., Moureau, C., Marple, B.R.: HVOF-sprayed coatings engineered from mixtures of nanostructured and submicron Al2O3–TiO2 powders: an enhanced wear performance. J. Therm. Spray Technol. 16, 866 (2007

Suspension High Velocity Oxy-Fuel (SHVOF)-sprayed alumina coatings: microstructure, nanoindentation and wear

Suspension High Velocity Oxy Fuel Spraying (SHVOF) can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from sub-micron sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt% amorphous phase and 26 wt% crystalline phase (95 wt% gamma and 3 wt% alpha alumina) while the 72 kW coating contained lower 58 wt% amorphous phase and 42 wt% crystalline phases (73 wt% was alpha and 26 wt % gamma). The 101 kW coating had a dry sliding specific wear rate between 4-4.5 x 10-5 mm3/Nm, 2 orders of magnitude higher than the 72 kW coating wear rate of 2-4.2 x 10-7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pull out of the coating was responsible for the wear of the 101 kW coating, explained by mean fracture toughness three times lower than the 72 kW coating, owing to the almost complete absence of alpha alumina

Identification of distinct subgroups of Sj\uf6gren\u27s disease by cluster analysis based on clinical and biological manifestations: data from the cross-sectional Paris-Saclay and the prospective ASSESS cohorts

\ua9 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: Sj\uf6gren\u27s disease is a heterogenous autoimmune disease with a wide range of symptoms—including dryness, fatigue, and pain—in addition to systemic manifestations and an increased risk of lymphoma. We aimed to identify distinct subgroups of the disease, using cluster analysis based on subjective symptoms and clinical and biological manifestations, and to compare the prognoses of patients in these subgroups. Methods: This study included patients with Sj\uf6gren\u27s disease from two independent cohorts in France: the cross-sectional Paris-Saclay cohort and the prospective Assessment of Systemic Signs and Evolution of Sj\uf6gren\u27s Syndrome (ASSESS) cohort. We first used an unsupervised multiple correspondence analysis to identify clusters within the Paris-Saclay cohort using 26 variables comprising patient-reported symptoms and clinical and biological manifestations. Next, we validated these clusters using patients from the ASSESS cohort. Changes in disease activity (measured by the European Alliance of Associations for Rheumatology [EULAR] Sj\uf6gren\u27s Syndrome Disease Activity Index [ESSDAI]), patient-acceptable symptom state (measured by the EULAR Sj\uf6gren\u27s Syndrome Patient Reported Index [ESSPRI]), and lymphoma incidence during follow-up were compared between clusters. Finally, we compared our clusters with the symptom-based subgroups previously described by Tarn and colleagues. Findings: 534 patients from the Paris-Saclay cohort (502 [94%] women, 32 [6%] men, median age 54 years [IQR 43–64]), recruited between 1999 and 2022, and 395 patients from the ASSESS cohort (370 [94%] women, 25 [6%] men, median age 53 years [43–63]), recruited between 2006 and 2009, were included in this study. In both cohorts, hierarchical cluster analysis revealed three distinct subgroups of patients: those with B-cell active disease and low symptom burden (BALS), those with high systemic disease activity (HSA), and those with low systemic disease activity and high symptom burden (LSAHS). During follow-up in the ASSESS cohort, disease activity and symptom states worsened for patients in the BALS cluster (67 [36%] of 186 patients with ESSPRI score <5 at month 60 vs 92 [49%] of 186 at inclusion; p<0\ub70001). Lymphomas occurred in patients in the BALS cluster (five [3%] of 186 patients; diagnosed a median of 70 months [IQR 42–104] after inclusion) and the HSA cluster (six [4%] of 158 patients; diagnosed 23 months [13–83] after inclusion). All patients from the Paris-Saclay cohort with a history of lymphoma were in the BALS and HSA clusters. This unsupervised clustering classification based on symptoms and clinical and biological manifestations did not correlate with a previous classification based on symptoms only. Interpretation: On the basis of symptoms and clinical and biological manifestations, we identified three distinct subgroups of patients with Sj\uf6gren\u27s disease with different prognoses. Our results suggest that these subgroups represent different heterogeneous pathophysiological disease mechanisms, stages of disease, or both. These findings could be of interest when stratifying patients in future therapeutic trials. Funding: Fondation pour la Recherche M\ue9dicale, French Ministry of Health, French Society of Rheumatology, Innovative Medicines Initiative 2 Joint Undertaking, Medical Research Council UK, and Foundation for Research in Rheumatology

Microstructure and indentation mechanical properties of YSZ nanostructured coatings obtained by suspension plasma spraying

[EN] A commercial nanosuspension of yttria-stabilised zirconia (YSZ) was successfully deposited on austenitic stainless steel substrate by suspension plasma spraying technique (SPS). A SG-100 torch with internal radial injection was used for the spraying. The pneumatic system transported the feed suspension from the containers to the plasma torch. In order to study the effect of the spraying parameters, a factorial model was used to design the experiments, changing both spraying translation speed and suspension flow rate. The coating microstructure was characterised by FEG-SEM. All coatings displayed a two-zone microstructure formed by nanometre-sized particles surrounded by fully molten areas. Moreover, crystalline phases were determined by XRD and Raman spectroscopy. Mechanical properties were also determined using nanoindentation technique. Nanoindentation tests showed a bimodal distribution of the mechanical properties (hardness and Young's modulus) which is related to the two zones (molten and partially molten) present in the coatings. (C) 2012 Elsevier B.V. All rights reserved.This work has been supported by the Spanish Ministry of Science and Innovation (project MAT2009-14144-C03) and the Research Promotion Plan of the Universitat Jaume I, action 2.1 (ref. E-2011-05) and action 3.1 (ref. PREDOC/2009/10). The authors are grateful to Leszek Łatka for his help in plasma spray experiments.Carpio, P.; Rayón Encinas, E.; Pawlowski, L.; Cattini, A.; Benavente Martínez, R.; Bannier, E.; Salvador Moya, MD.... (2013). Microstructure and indentation mechanical properties of YSZ nanostructured coatings obtained by suspension plasma spraying. Surface and Coatings Technology. 220:237-243. https://doi.org/10.1016/j.surfcoat.2012.09.047S23724322

Mechanical properties of double-layer and graded composite coatings of YSZ obtained by atmospheric plasma spraying

Double-layer and graded composite coatings of yttria-stabilized zirconia were sprayed on metallic substrates by atmospheric plasma spray. The coating architecture was built up by combining two different feedstocks: one micro- and one nanostructured. Microstructural features and mechanical properties (hardness and elastic modulus) of the coatings were determined by FE-SEM microscopy and nanoindentation technique, respectively. Additional adherence and scratch tests were carried out in order to assess the failure mechanisms occurring between the layers comprising the composites. Microstructural inspection of the coatings confirms the two-zone microstructure. This bimodal microstructure which is exclusive of the layer obtained from the nanostructured feedstock negatively affects the mechanical properties of the whole composite. Nanoindentation tests suitably reproduce the evolution of mechanical properties through coatings thickness on the basis of the position and/or amount of nanostructured feedstock used in the depositing layer. Adhesion and scratch tests show the negative effect on the coating adhesion of layer obtained from the nanostructured feedstock when this layer is deposited on the bond coat. Thus, the poor integrity of this layer results in lower normal stresses required to delaminate the coating in the adhesion test as well as minor critical load registered by using the scratch test.This work has been supported by the Spanish Ministry of Science and Innovation (Project MAT2012-38364-C03) and co-funded by ERDF (European Regional Development Funds).Carpio-Cobo, P.; Rayón Encinas, E.; Salvador Moya, MD.; Lusvarghi, L.; Sanchez, E. (2016). Mechanical properties of double-layer and graded composite coatings of YSZ obtained by atmospheric plasma spraying. Journal of Thermal Spray Technology. 25(4):778-787. https://doi.org/10.1007/s11666-016-0390-zS778787254Y.S. Tian, C.Z. Chen, D.Y. Wang, and J.I. Quianmao, Recent Developments in Zirconia Thermal Barrier Coatings, Surf. Rev. Lett., 2005, 12, p 369-378S. Sampath, U. Schulz, M.O. Jarligo, and S. Kuroda, Processing Science of Advanced Thermal-Barrier Systems, MRS Bull., 2012, 37(10), p 903-910D.R. Clarke, M. Oeschsner, and N.P. Padture, Thermal-Barrier Coatings for More Efficient Gas-Turbine Engines, MRS Bull., 2012, 37(10), p 891-898A. Feuersein, J. Knapp, T. Taylor, A. Ashary, A. Bolcavage, and N. Hitchman, Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review, J. Therm. Spray Technol., 2008, 17(2), p 199-213R.S. Lima and B.R. Marple, Thermal Spray Coatings Engineered from Nanostructured Ceramic Agglomerated Powders for Structural, Thermal Barrier and Biomedical Applications: A Review, J. Therm. Spray Technol., 2007, 16(1), p 40-63P. Fauchais, G. Montavon, R.S. Lima, and B.R. Marple, Engineering a New Class of Thermal Spray Nano-based Microstructures from Agglomerated Nanostructured Particles, Suspensions and Solutions: An Invited Review, J. Phys. D Appl. Phys., 2011, 44(9), p 093001P. Carpio, Q. Blochet, B. Pateyron, L. Pawlowski, M.D. Salvador, A. Borrell, and E. Sánchez, Correlation of Thermal Conductivity of Suspension Plasma Sprayed Yttira Stabilized Zirconia Coatings with some Microstructural Effects, Mater. Lett., 2013, 107, p 370-373R. Vassen, A. Stuke, and D. Stöver, Recent Developments in the Field of Thermal Barrier Coatings, J. Therm. Spray Technol., 2009, 18(2), p 181-186H. Dai, X. Zhong, J. Li, Y. Zhang, J. Meng, and X. Cao, Thermal Stability of Double-Ceramic-Layer Thermal Barrier Coatings with Various Coating Thickness, Mater. Sci. Eng. A—Struct., 2006, 433(1), p 1–7V. Viswanathan, G. Dwivedi, and S. Sampath, Multimaterial Thermal Barrier Coating Systems: Design, Synthesis, and Performance Assessment, J. Am. Ceram. Soc., 2015, 98(6), p 1769-1777M. Saremi and Z. Valefi, Thermal and Mechanical Properties of Nano-YSZ-Alumina Functionally Graded Coatings Deposited by Nano-agglomerated Powder Plasma Spraying, Ceram. Int., 2014, 40(8), p 13453-13459A. Portinham, V. Teixeira, J. Carneiro, J. Martins, M.F. Costa, R. Vassen, and D. Stoever, Characterization of Thermal Barrier Coatings with a Gradient Porosity, Surf. Coat. Technol., 2005, 195(2), p 245-251P. Carpio, E. Bannier, M.D. Salvador, R. Benavente, and E. Sánchez, Multilayer and Particle Size-Graded YSZ Coatings Obtained by Plasma Spraying of Micro- and Nanostructured Feedstocks, J. Therm. Spray Technol., 2014, 23(8), p 1362-1372S. Nath, I. Manna, and J.D. Majumdar, Nanomechanical Behavior of Yttria Stabilized Zirconia (YSZ) Based Thermal Barrier Coating, Ceram. Int., 2015, 41(4), p 5247-5256P. Carpio, E. Rayón, L. Pawlowski, A. Cattini, R. Benavente, E. Bannier, M.D. Salvador, and E. Sánchez, Microstructure and Indentation Mechanical Properties of YSZ Nanostructured Coatings Obtained by Suspension Plasma Spraying, Surf. Coat. Technol., 2013, 220, p 237-243H.B. Guo, H. Murakami, and S. Kuroda, Effect of Hollow Spherical Powder Size Distribution on Porosity and Segmentation Cracks in Thermal Barrier Coatings, J. Am. Ceram. Soc., 2006, 89(12), p 3797-3804R.S. Lima, A. Kucuk, and C.C. Berndt, Integrity of Nanostructured Partially Stabilized Zirconia After Plasma Spray Processing, Mater. Sci. Eng. A, 2001, 313(1), p 75-82E. Rayón, V. Bonache, M.D. Salvador, and E. Sánchez, Hardness and Young’s Modulus Distributions in Atmospheric Plasma Sprayed WC-Co Coatings Using Nanoindentation, Surf. Coat. Technol., 2011, 205(17), p 4192-4197J.A. Wollmershauser, B.N. Feigelson, E.P. Gorzkowski, C.T. Ellis, R. Goswami, S.B. Qadri, J.G. Tischler, F.J. Kub, and R.K. Everett, An Extend Hardness Limit in Bulk Nanoceramics, Acta Mater., 2014, 69, p 9-16L. Wang, Y. Wang, X.G. Sun, J.Q. He, Z.Y. Pan, and C.H. Wang, Microstructure and Indentation Mechanical Properties of Plasma Sprayed Nano-Bimodal and Conventional ZrO2-8 wt% Y2O3 Thermal Barrier Coatings, Vacuum, 2012, 86(8), p 1174-1185G.S. Barroso, W. Krenkel, and G. Motz, Low Thermal Conductivity Coating System for Application up to 1000 °C by Simple PDC Processing with Active and Passive Fillers, J. Eur. Ceram. Soc., 2015, 35(12), p 3339-3348R. Ghasemi, R. Shoja-Razavi, R. Mozafarinia, H. Jamali, M. Hajizadh-Oghaz, and R. Ahmadi-Pidani, The Influence of Laser Treatment on Hot Corrosion Behavior of Plasma-Sprayed Nanostructured Yttria Stabilized Zirconia Thermal Barrier Coatings, J. Eur. Ceram. Soc., 2014, 34(8), p 2013-2021E. Rayón, V. Bonache, M.D. Salvador, E. Bannier, E. Sánchez, A. Denoirjean, and H. Ageorges, Nanoindentation Study of the Mechanical and Damage Behaviour of Suspension Plasma Sprayed TiO2 Coatings, Surf. Coat. Technol., 2012, 206(10), p 2655-2660J.J. Roa, E. Jiménez-Piqué, R. Martínez, G. Ramírez, J.M. Tarragó, R. Rodríguez, and L. Llanes, Contact Damage and Fracture Micromechanisms of Multilayered TiN/CrN Coatings at Micro- and Nano-length Scales, Thin Solid Films, 2014, 571(2), p 308-31

Structure property relationship of suspension thermally sprayed WC-Co nanocomposite coatings.

Tribomechanical properties of nanostructured coatings deposited by suspension high velocity oxy-fuel (S-HVOF) and conventional HVOF (Jet Kote) spraying were evaluated. Nanostructured S-HVOF coatings were obtained via ball milling of the agglomerated and sintered WC-12Co feedstock powder, which were deposited via an aqueous-based suspension using modified HVOF (TopGun) process. Microstructural evaluations of these hardmetal coatings included transmission electron microscopy, x-ray diffraction, and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The nanohardness and modulus of the coated specimens were investigated using a diamond Berkovich nanoindenter. Sliding wear tests were conducted using a ball-on-flat test rig. Results indicated that low porosity coatings with nanostructured features were obtained. High carbon loss was observed, but coatings showed a high hardness up to 1000 HV2.9N. S-HVOF coatings also showed improved sliding wear and friction behavior, which were attributed to nanosized particles reducing ball wear in three-body abrasion and support of metal matrix due to uniform distribution of nanoparticles in the coating microstructure

Serum Neurotrophin Profile in Systemic Sclerosis

International audienceBACKGROUND: Neurotrophins (NTs) are able to activate lymphocytes and fibroblasts; they can modulate angiogenesis and sympathic vascular function. Thus, they can be implicated in the three pathogenic processes of systemic sclerosis (SSc). The aims of this study are to determine blood levels of Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF) and Neurotrophin-3 (NT-3) in SSc and to correlate them with clinical and biological data.METHODS: Serum samples were obtained from 55 SSc patients and 32 control subjects to measure NTs levels by ELISA and to determine their relationships with SSc profiles. FINDINGS: Serum NGF levels were higher in SSc patients (288.26 ± 170.34 pg/mL) than in control subjects (170.34 ± 50.8 pg/mL, p<0.001) and correlated with gammaglobulins levels and the presence of both anti-cardiolipin and anti-Scl-70 antibodies (p<0.05). In contrast, BDNF levels were lower in SSc patients than in controls (1121.9 ± 158.1 vs 1372.9 ± 190.9 pg/mL, p<0.0001), especially in pulmonary arterial hypertension and diffuse SSc as compared to limited forms (all p<0.05). NT-3 levels were similar in SSc and in the control group (2657.2 ± 2296 vs 2959.3 ± 2555 pg/mL, NS). BDNF levels correlated negatively with increased NGF levels in the SSc group (and not in controls). CONCLUSION: Low BDNF serum levels were not previously documented in SSc, particularly in the diffuse SSc subset and in patients with pulmonary hypertension or anti-Scl-70 antibodies. The negative correlation between NGF and BDNF levels observed in SSc and not in healthy controls could be implicated in sympathic vascular dysfunction in SSc