| 1. |
- Alemon, B., et al.
(författare)
-
Ion beam analysis, corrosion resistance and nanomechanical properties of TiAlCN/CNx multilayer grown by reactive magnetron sputtering
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 331, s. 134-139
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Tidskriftsartikel (refereegranskat)abstract
- A novel TiAlCN/CNx, multilayer coating, consisting of nine TiAlCN/CNx periods with a top layer 0.5 mu m of CNx, was designed to enhance the corrosion resistance of CoCrMo biomedical alloy. The multilayers were deposited by dc and RF reactive magnetron sputtering from Ti0.5Al0.5 and C targets respectively in a N-2/Ar plasma. The corrosion resistance and mechanical properties of the multilayer coatings were analyzed and compared to CoCrMo bulk alloy. Ion beam analysis (IBA) and X-ray diffraction tests were used to measure the element composition profiles and crystalline structure of the films. Corrosion resistance was evaluated by means of potentiodynamic polarization measurements using simulated body fluid (SBF) at typical body temperature and the nanomechanical properties of the multilayer evaluated by nanoindentation tests were analyzed and compared to CoCrMo bulk alloy. It was found that the multilayer hardness and the elastic recovery are higher than the substrate of CoCrMo. Furthermore the coated substrate shows a better general corrosion resistance than that of the CoCrMo alloy alone with no observation of pitting corrosion.
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| 2. |
- Alemon, B., et al.
(författare)
-
Tribocorrosion behavior and ions release of CoCrMo alloy coated with a TiAlVCN/CNx multilayer in simulated body fluid plus bovine serum albumin
- 2015
-
Ingår i: Tribology International. - : Elsevier. - 0301-679X .- 1879-2464. ; 81, s. 159-168
-
Tidskriftsartikel (refereegranskat)abstract
- While the CoCrMo biomaterial is currently employed in artificial joints, there are medical concerns regarding its metal ion release and material loss caused by tribocorrosion. In this work, a TiAlVCN/CNx multilayer coating has been employed to improve the tribocorrosion-resistance of the CoCrMo substrate. During the tribocorrosion test, with the sample immersed in a simulated body fluid containing bovine serum albumin, open-circuit potential measurements showed more noble potential as well as a reduction of both the friction coefficient and wear-rate during the sliding phase. Inductive coupled plasma results demonstrate that the multilayer coating effectively blocked the emigration of metallic ions.
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| 3. |
- Ali, Sharafat, et al.
(författare)
-
Novel transparent Mg-Si-O-N thin films with high hardness and refractive index
- 2016
-
Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 131, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for glass materials with better mechanical and optical properties for display and electronic applications. This paper describes the deposition of novel thin films of Mg-Si-O-N onto float glass substrates. Amorphous thin films in the Mg-Si-O-N system with high nitrogen and magnesium contents were deposited by reactive RF magnetron co-sputtering from Mg and Si targets in Ar/N2/O2 gas mixtures. The thin films studied span an unprecedented range of compositions up to 45 at% Mg and 80 at% N out of cations and anions respectively. Thin films in the Mg-Si-O-N system were found to be homogeneous and transparent in the visible region. Mechanical properties like hardness (H) and reduced elastic modulus (Er) show high values, up to 21 GPa and 166 GPa respectively. The refractive index (1.87-2.00) increases with increasing magnesium and nitrogen contents.
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| 4. |
- Ali, Sharafat, 1976-, et al.
(författare)
-
Synthesis and characterization of the mechanical and optical properties of Ca-Si-O-N thin films deposited by RF magnetron sputtering
- 2017
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 315, s. 88-94
-
Tidskriftsartikel (refereegranskat)abstract
- Ca-Si-O-N thin films were deposited on commercial soda-lime silicate float glass, silica wafers and sapphire substrates by RF magnetron co-sputtering from Ca and Si targets in an Ar/N-2/O-2 gas mixture. Chemical composition, surface morphology, hardness, reduced elastic modulus and optical properties of the films were investigated using X-ray photoelectron spectroscopy, scanning electron microscopy, nanoindentation, and spectroscopic ellipsometry. It was found that the composition of the films can be controlled by the Ca target power, predominantly, and by the reactive gas flow. Thin films in the Ca-Si-O-N system are composed of N and Ca contents up to 31 eq. % and 60 eq. %, respectively. The films thickness ranges from 600 to 3000 nm and increases with increasing Ca target power. The films surface roughness varied between 2 and 12 nm, and approximately decreases with increasing power of Ca target. The hardness (4-12 GPa) and reduced elastic modulus (65-145 GPa) of the films increase and decrease with the N and Ca contents respectively. The refractive index (1.56-1.82) is primarily dictated by the N content. The properties are compared with findings for bulk glasses in the Ca-Si-(Al)-O-N systems, and it is concluded that Ca-Si-O-N thin films have higher values of hardness, elastic modulus and refractive index than bulk glasses of similar composition. (C) 2017 Elsevier B.V. All rights reserved.
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| 5. |
- Ali, Sharafat, 1976-, et al.
(författare)
-
Thin films in M-Si-O-N thin systems
- 2017
-
Ingår i: 44th International Conference on Metallurgical Coating and Thin Films (ICMCTF), San Diego, CA, USA, 24-28 Apr 2017.
-
Konferensbidrag (refereegranskat)
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| 6. |
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| 7. |
- Aouadi, S, et al.
(författare)
-
ICMCTF 2014 : Preface
- 2014
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 572, s. 1-1
-
Tidskriftsartikel (refereegranskat)abstract
- The 41st International Conference on Metallurgical Coatings andThin Films (ICMCTF), sponsored by the Advanced Surface EngineeringDivision (ASED) of the American Vacuum Society (AVS), was heldfrom April 28 to May 2, 2014 in San Diego, California, USA.The week's technical program consisted of 37 technical sessions,which were organized into 13 symposia. The conference opened witha Plenary Lecture by Prof. Sybrand van der Zwaag, Materials Scienceand Engineering at the faculty of Aerospace Engineering at the TUDelft, The Netherlands, on “Self-healing Materials: an Alternative Approachto Create More Durable/Reliable Materials and Products”. TheExhibition Keynote Lecture was presented by Prof. Timothy P. Weihs,Department of Materials Science and Engineering at the Johns HopkinsUniversity, Baltimore, MD, USA, on “Driving Commercial Applicationsand Exploring Scientific Questions with Reactive Multilayer Foils”.During the conference week, a well subscribed poster session wasattended by a large and appreciative attendee audience. An expansivelarge two-day interactive industrial exhibition, with more than 50booths,was held inwhich companies displayed theirmost recent developmentsin vacuumscience and plasma-based deposition technologies.In addition to the technical symposia sessions, there were threefocused topical sessions, and six specialized short courses offered.Professor Jindrich Musil from the faculty of Applied Sciences atthe University of Bohemia, Plzeň, Czech Republic, was the recipientof the 2014 ASED R.F. Bunshah Annual Award; he presented the HonoraryLecture, “Advanced Hard Nanocomposite Coatings with UniqueProperties”. The award recognizes and honors Prof. Musil's seminalcontributions to the development of advanced nanocomposite coatingswith enhanced hardness, oxidation resistance, toughness, and crackresistance.The ASED Annual ICMCTF Graduate Student Awards werepresented to Shiyu Liu (Gold Medal), University of Cambridge, UK;Samantha K. Lawrence (Silver Medal), Purdue University, WestLafayette, IN, USA; and Trevor Hardcastle (Bronze Medal), Universityof Leeds, UK.The electronic submission and handling of manuscripts via theElsevier Editorial System (EES), including the selection of reviewersand evaluation ofmanuscripts,were identical to the procedures appliedto manuscripts submitted as regular contributions for publication ininternational scientific journals. Following the tradition practiced since1987, the accepted manuscripts are published in the archival journalsSurface and Coatings Technology and Thin Solid Films. ICMCTF 2014proceedings are open-access to the participants for one year via theElsevier journals' web sites.The organization of this conference and the preparation of proceedingsvolumes would have been impossible without the tremendouseffort and dedication of many individuals, including the General Chair,Yip-Wah Chung, Northwestern University, USA, and the ProgramChair, Claus Rebholz, the University of Cyprus, the team of symposiaand session chairs that made possible the realization of an exciting technicalprogram. We especially thank all the authors and presenters fortheir contributions; we also thank the hundreds of reviewers for theirtimely submission of high quality reports. To our sponsors,we acknowledge,appreciate, and thank these companies for their most generousand continuing support.The 42nd International Conference on Metallurgical Coatings andThin Films (ICMCTF 2015) will be held in San Diego, California, April20–24, 2015, with Claus Rebholz, University of Cyprus, as the GeneralChair and Suneel Kodambaka, the University of California at Los Angeles, as the Program Chair.
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| 8. |
- Aouadi, Samir, et al.
(författare)
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ICMCTF 2017-Preface
- 2017
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Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 644
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
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| 9. |
- Aouadi, Samir, et al.
(författare)
-
ICMCTF 2018-Preface
- 2019
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Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 357, s. 1014-1014
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
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| 10. |
- Bakoglidis, Konstantinos, et al.
(författare)
-
Comparative study of macro- and microtribological properties of carbon nitride thin films deposited by HiPIMS
- 2017
-
Ingår i: Wear. - : ELSEVIER SCIENCE SA. - 0043-1648 .- 1873-2577. ; 370
-
Tidskriftsartikel (refereegranskat)abstract
- The macro- and microtribological properties of carbon nitride thin films deposited by high power impulse magnetron sputtering at different substrate bias voltages (V-b) were investigated. V-b of -100, -150, -200, and-300 V were used. A Hysitron Triboindenter TI950 and a reciprocating Tribotechnic tribometer with diamond counterparts were used in order to assess the tribological performance of the films at the micro- and macroscale, respectively. Initial Hertzian contact pressures of 2.5 GPa, 3.3 GPa and 3.9 GPa were chosen for the comparative measurements at both scales. At the macroscale, films with higher initial roughness present an increased wear. Debris creation and asperity deformation takes place causing abrasive wear. At the microscale, compression of the surface material occurs. The run-in friction shows similar trends at both scales; an initial decrease and an increase thereafter. Steady-state friction is not reached at the microscale, attributed to the absence of a graphitic tribolayer in the contact. At the macroscale, all films show abrasive wear and debris creation. Here, the changes in friction coefficients are attributed to the debris loss from the contact during the tribotests. The CN film tested at 2.5 GPa shows a continuous increase of friction, due to the continuous loss of debris from the contact. The other films reach a steady-state friction coefficient, since most of the debris is lost before the end of the tribotests. (C) 2016 Elsevier B.V. All rights reserved.
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| 11. |
- Bakoglidis, Konstantinos D., 1985-
(författare)
-
Low Friction and Wear Resistant Carbon Nitride Thin Films for Rolling Components Grown by Magnetron Sputtering
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The scope of this licentiate thesis is the investigation of carbon based thin films suitable for rolling components, especially roller bearings. Carbon and carbon nitride are materials with advantageous tribological properties and high resiliency. Such materials are required in order to withstand the demanding conditions of bearing operation, such as high loads and corrosive environments. A fundamental condition for coated bearings is that the deposition temperature must be striktly limited. Thus, carbon nitride (CNx) thin films were synthesized here at low temperature of 150 oC by different reactive magnetron sputtering techniques, which are mid-frequency magnetron sputtering (MFMS), direct current magnetron sputtering (DCMS), and high power impulse magnetron sputtering (HiPIMS). While DCMS is a very well studied technique for carbon based films, MFMS and HiPIMS are relatively new sputtering techniques for carbon, and especially CNx depositions. Using different magnetron sputtering techniques, different ionization conditions prevail in the chamber during each process and influence the obtained film properties at a great extent. It was found that bias duty cycles and the amount of working gas ions are key parameters and affect the morphology and microstructure as well as the mechanical response of the films. Moreover, different bias voltages, from 20 V up to 120 V were applied during the processes in order to investigate the changes that the different ion energies induce in the film structure.The structural, mechanical and tribological properties of CNx films are also presented in this licentiate thesis. The morphology of CNx films strongly depends on both the deposition technique and ion energy. The special configuration of MFMS mode produces highly homogeneous and dense films even from low applied bias voltages, while in HiPIMS mode high bias voltages above 100 V must be applied in order to produce films with similar structural characteristics. DCMS is also proven as a good technique for homogeneous and dense films. Low bias voltages do not favor homogeneous structures, thus at 20 V all techniques produced films with columnar structures with intercolumnar voids. High bias voltages influence the N incorporation in the films, with the appearance of re-sputtering of N-containing species and a promotion of sp2 bonding configurations with increasing ion energy. Nevertheless, the different deposition mode influences the sp2 content in different ways, with only MFMS showing a clear increase of sp2 content with increasing bias voltage and HiPIMS showing relatively constant sp2 content. The morphology and microstructure of the CNx films affects their mechanical response, with higher ion energies producing harder films. A dependency of hardness and elastic modulus with increasing ion energy was obtained, where for all deposition modes, hardness and elastic modulus increase linearly with increasing bias voltage. Films with hardness as high as 25 GPa were synthesized by MFMS at 120 V , while the softer film yielded a hardness of 7 GPa and was deposited by HiPIMS at 20 V . The elastic recovery of the films differs with increasing ion energies, presenting a correlation with the C sp2 bond content. The highest elastic recovery of 90% was extracted for the film deposited by MFMS at 120 V and is a value similar to the elastic recovery obtained for FL-CNx films. All films developed compressive residual stresses, depending also on the ion energies and the deposition mode used. It is demonstrated that the induced stresses in the films increase when denser and more homogeneous film morphologies are obtained and with higher Ar intercalcation. Low friction coefficients were obtained for all films between 0.05 and 0.07, although the deposition conditions are not detrimental for the development of friction coefficient. The wear resistance of the films was found to be dependent on the morphology and to some extent on the microstructure of the films. Harder, denser, and more homogeneous films have higher wear resistance. Especially, CNx films deposited by MFMS at 120 V present no wear.The tribological characteristics of the surface of the films were also investigated at nanoscale by a new reciprocal wear test. In this wear test, the recording of the track profile is performed in between consecutive test cycles, eliminating also thermal drift. The very low wear of the films deposited by MFMS at 100 V and 120 V revealed that during the wear test a phase transformation on the surface may take place, possibly graphitization. It is also demonstrated the way that the surface characteristics, such as asperities and roughness affects the tribological measurements. Attention is also turned to the presence of large asperities on the film surface and the way they affect the obtained average friction coefficient and tribological measured data.
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| 12. |
- Bakoglidis, Konstantinos D., et al.
(författare)
-
Nanotribological properties of wear resistant a-CNx thin films deposited by mid-frequency magnetron sputtering
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The nanotribological properties of amorphous carbon nitride (a-CNx) thin films deposited with mid-frequency magnetron sputtering (MFMS) were investigated at the nanoscale using an in-situ technique in a Hysitron Triboindenter TI 950. The friction coefficient, wear rate, track roughness, and the track profiles were recorded as a function of the number of linear reciprocal cycles, revealing the manner that the nanotribological and surface properties change during the wear test. The surface composition of the films was evaluated by x-ray photoelectron spectroscopy (XPS). The friction coefficient ranges between 0.05 – 0.07, while the wear coefficient ranges from 9.4 x 10-8 up to 1.5 x 10-4 mm3/Nm. Debris particles and surface modifications characterize the friction and lubrication behavior in the track. The friction and main lubrication mechanism on the modified surface changes after the removal of debris particles, while this change appears at different cycle for each CNx film depending on the substrate bias voltage. Films grown at higher bias are modified earlier than films grown at lower bias. The wear behavior can be divided into two, track roughnessdependent, regimes; (1) films with track roughness > 1 nm showed wear with obvious tracks and (2) the films with roughness < 1 nm showed negative wear at the nanometer scale with a volume of material projected in the area of the wear track. This material volume is believed to be result of a surface modification, where the molar volume of the modified surface is larger than the molar volume of the surface before the wear test.
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| 13. |
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| 14. |
- Broitman, Esteban, 1958-
(författare)
-
A new method for in-situ measurement of nano-friction and nano-wear of thin films by using the Triboindenter TI-950
- 2014
-
Ingår i: Nanobrucken 2014. - Saarbrucken, Germany : INM - Leibniz Institute for New Materials. ; , s. 24-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Triboindenter present many advantages for the measurement of friction and wear at the nanoscale. A reciprocating multi-cycle linear test can be programmed, from where it is possible to obtain simultaneously the friction force and wear rate from the lateral force and vertical displacement sensors, respectively. The friction values have high precision but the wear data is usually wrong in long duration tests because the drift rate is only measured just before the test start. Alternatively, one can program the SPM scanning mode of the instrument with a high load in order to produce the wear of the surface. At the end of the experiment, a squared hole is produced which can be measured using the SPM facility of the system. However, this wear experiment does not allow the simultaneous measurement of the friction coefficient.In this talk I will present a new methodology to measure in-situ the friction and wear of thin films using a Triboindenter TI-950 from Hysitron. I will show how the possible changes of drift rate during long-time tests can be overcome, obtaining simultaneous precise values of friction and wear rate as a function of time. I will discuss how the Triboimage® software can be adapted to this methodology in order to get realistic values of friction and wear. Finally I will show some results for soft (H < 1GPa) Pb films and very hard (H ~ 35 GPa) nitride coatings
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| 15. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
A Novel Oxide Characterization Method of Nickel Base Alloy 600 Used in Nuclear Plant Reactors
- 2013
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Konferensbidrag (refereegranskat)abstract
- The Alloy 600 is a polycrystalline nickel base alloy used in pressurized water reactors (PWR) of nuclear power plants. Long term exposure of the alloy to primary water of PWR generates an oxide film that strongly influences the stress corrosion cracking behavior of the alloy. Recently, it has been shown that the oxide film structure, composition and thickness depend on the dissolved hydrogen content in the primary water. In this work we have explored a novel approach which enables a high spatial resolution oxide thickness measurement by nanomechanical testing. Oxide films have been grown on Alloy 600 specimens exposed between 5000 and 35000 hours at 320-330°C with hydrogen levels in the range 5 to 25 mL H2/kg H2O. A Triboindenter TI-950 from Hysitron was used to measure the change of nanomechanical properties in polished cross-sections. The increase of hardness has been correlated to the presence of oxides.
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| 16. |
- Broitman, Esteban, et al.
(författare)
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Adhesion improvement of carbon-based coatings through a high ionization deposition technique
- 2012
-
Ingår i: Journal of Physics, Conference Series. - : Institute of Physics. - 1742-6588 .- 1742-6596. ; 370:012009
-
Tidskriftsartikel (refereegranskat)abstract
- The deposition of highly adherent carbon nitride (CNx) films using a pretreatment with two high power impulse magnetron sputtering (HIPIMS) power supplies in a master-slave configuration is reviewed. SKF3 (AISI 52100) steel substrates were pretreated in the environment of a high ionized Cr+Ar plasma in order to sputter clean the surface and implant Cr metal ions. CNx films were subsequently deposited at room temperature by DC magnetron sputtering from a high purity C target in a N-2/Ar plasma discharge. All processing was done in an industrial-scale CemeCon CC800 coating system. A series of depositions were obtained with samples pretreated at different bias voltages (DC and pulsed). The adhesion of CNx films, evaluated by the Daimler-Benz Rockwell-C test, reaches strength quality HF1. Adhesion results are correlated to high resolution transmission electron microscopy observations confirming the formation of an optimal interfacial mixing layer of Cr and steel. The throwing power increase for HIPIMS coatings is associated to the higher ionization in the plasma discharge.
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| 17. |
- Broitman, Esteban, 1958-, et al.
(författare)
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Advanced Carbon-Based Coatings
- 2014. - 4
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Ingår i: Comprehensive Materials Processing. - : Elsevier. - 9780080966007 ; , s. 389-412
-
Bokkapitel (refereegranskat)abstract
- This chapter focuses on the development of alloyed diamondlike coatings, in particular a new class of fullerene-like (FL) materials. We describe unique resilient FL compounds by self-organization of nano-curved sp2-hybridized carbon features, with tuned mechanical and surface energy properties. These unique resilient materials consist of bent and intersecting hexagonal basal planes, fabricated by the incorporation of odd-member rings. Cross-linking enables the material to extend the strength of the covalently 2D hexagonal graphene network into 3D. The microstructural properties of three types of coatings, which have the possibility to be applied on a large scale, are described: carbon nitride, phosphorous carbide, and carbon fluoride.
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| 18. |
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| 19. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Beschichtungsverfahren und Vorrichtung zum Beschichten
- 2007
-
Patent (populärvet., debatt m.m.)abstract
- described are a method and an apparatus for coating bodies by means of Magnetron sputtering. The magnetron is the power over both a Pulsed power supply supplied, the peaks with very high Power density of the magnetron outputs, as well as a Power supply that has a constant power or a pulsed Power with comparatively low power densities to the magnetron emits.
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| 20. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Comparative study on the properties of ZnO nanowires and nanocrystalline thin films
- 2012
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 213, s. 59-64
-
Tidskriftsartikel (refereegranskat)abstract
- The microstructural, morphological, optical and water-adsorption properties of nanocrystalline ZnO thin films and ZnO nanowires were studied and compared. The ZnO thin films were obtained by a sol–gel process, while the ZnO nanowires were electrochemically grown onto a ZnO sol–gel spin-coated seed layer. Thin films and nanowire samples were deposited onto crystalline quartz substrates covered by an Au electrode, able to be used in a quartz crystal microbalance. X-ray diffraction measurements reveal in both cases a typical diffraction pattern of ZnO wurtzite structure. Scanning electron microscopic images of nanowire samples show the presence of nanowires with hexagonal sections, with diameters ranging from 30 to 90 nm. Optical characterization reveals a bandgap energy of 3.29 eV for the nanowires and 3.35 eV for the thin films. A quartz crystal microbalance placed in a vacuum chamber was used to quantify the amount and kinetics of water adsorption onto the samples. Nanowire samples, which have higher surface areas than the thin films, adsorb significantly more water.
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| 21. |
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| 22. |
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| 23. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Fullerene-like Carbon Nitride : A New Carbon-based Tribological Coating
- 2008. - 1
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Ingår i: Tribology of Diamond-Like Carbon Films. - Boston, MA : Springer. - 9780387302645 ; , s. 620-653
-
Bokkapitel (refereegranskat)abstract
- In 1994, researchers at Linköping University discovered the fullerene-like allotrope of carbon nitride (FL-CNx) by using reactive magnetron sputtering in a nitrogen-containing atmosphere at rather low ion energy assistance. FL-CNx is a predominantly sp2-hybridized material with nitrogen structurally incorporated either substitutionally in a graphite sheet or in a pyridine-like manner, which initiates bending by formation of pentagons and cross-linking, respectively. The assumed nitrogen-induced cross-linkage between the sheets contributes considerably to the strength of FL-CNx by preventing interplanar slip. This results in an extremely fracture tough, elastic, and compliant material, which deforms by reversible bond rotation and bond angle deflection rather than slip and bond breaking.
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| 24. |
- Broitman, Esteban, et al.
(författare)
-
Fullerene-like carbon nitride - A new form of DLC solid lubricant coatings
- 2008
-
Ingår i: Tribology of diamondlike carbon films: fundamentals and applications. - Berlin : Springer. - 9780387302645 - 9780387498911 ; , s. -664
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This book highlights some of the most important structural, chemical, mechanical and tribological characteristics of DLC films. It is particularly dedicated to the fundamental tribological issues that impact the performance and durability of these coatings. The book provides reliable and up-to-date information on available industrial DLC coatings and includes clear definitions and descriptions of various DLC films and their properties.
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| 25. |
- Broitman, Esteban, et al.
(författare)
-
High-temperature nanoindentation of epitaxial ZrB2 thin films
- 2016
-
Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 124, s. 117-120
-
Tidskriftsartikel (refereegranskat)abstract
- We use in-situ heated nanoindentation to investigate the high-temperature nanomechanical properties of epitaxial and textured ZrB2 films deposited by magnetron sputtering. Epitaxial films deposited on 4H-SiC(0001) show a hardness decrease from 47 GPa at room temperature to 33 GPa at 600 °C, while the reduced elastic modulus does not change significantly. High resolution electron microscopy (HRTEM) with selected area electron diffraction of the indented area in a 0001-textured film reveals a retained continuous ZrB2 film and no sign of crystalline phase transformation, despite massive deformation of the Si substrate. HRTEM analysis supports the high elastic recovery of 96% in the films.
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| 26. |
- Broitman, Esteban
(författare)
-
Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale: A Critical Overview
- 2017
-
Ingår i: Tribology letters. - : SPRINGER/PLENUM PUBLISHERS. - 1023-8883 .- 1573-2711. ; 65:1
-
Forskningsöversikt (refereegranskat)abstract
- The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods used to measure the indentation hardness of materials at different scales are compared, and main issues and misconceptions in the understanding of these methods are comprehensively reviewed and discussed. Basic equations and parameters employed to calculate hardness are clearly explained, and the different international standards for each method are summarized. The limits for each scale are explored, and the different forms to calculate hardness in each method are compared and established. The influence of elasticity and plasticity of the material in each measurement method is reviewed, and the impact of the surface deformation around the indenter on hardness values is examined. The difficulties for practical conversions of hardness values measured by different methods are explained. Finally, main issues in the hardness interpretation at different scales are carefully discussed, like the influence of grain size in polycrystalline materials, indentation size effects at micro-and nanoscale, and the effect of the substrate when calculating thin films hardness. The paper improves the understanding of what hardness means and what hardness measurements imply at different scales.
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| 27. |
- Broitman, Esteban, et al.
(författare)
-
Industrial-scale deposition of highly adherent CNx films on steel substrates
- 2010
-
Ingår i: Surface & Coatings Technology. - : Elsevier Science B.V., Amsterdam.. - 0257-8972 .- 1879-3347. ; 204:21-22, s. 3349-3357
-
Tidskriftsartikel (refereegranskat)abstract
- Highly adherent carbon nitride (CNx) films were deposited using a novel pretreatment with two high power impulse magnetron sputtering (HIPIMS) power supplies in a master-slave configuration: one to establish the discharge and one to produce a pulsed substrate bias. During the pretreatment, SKF3 (AISI 52100) steel substrates were pulse-biased in the environment of a HIPIMS Cr plasma in order to sputter clean the surface and to implant Cr metal ions. Subsequently. CNx films were prepared at room temperature by DC unbalanced magnetron sputtering from a high purity graphite target in a N-2/Ar discharge at 3 mTorr. All processing was done in an industrial CemeCon CC800 system. A series of depositions were obtained with samples at different bias voltages (DC and pulsed) in the range of 0-800 V. Scanning transmission microscopy (STEM) and high resolution transmission electron microscopy (HRTEM) show the formation of an interface comprising a polycrystalline Cr layer of 100 nm and an amorphous transition layer of 5 nm. The adhesion of CNx films evaluated by the Daimler-Benz Rockwell-C reach strength quality HF1, and the scratch tests gives critical loads of 84 N. Adhesion results are correlated to the formation of an optimal interfacial mixing layer of Cr and steel.
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| 28. |
- Broitman, Esteban, 1958-, et al.
(författare)
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Influence of deposition parameters on the microstructure of ion-plated films
- 1996
-
Ingår i: AIP Conference Proceedings. - : American Institute of Physics (AIP). - 0094-243X .- 1551-7616. ; 378, s. 356-359
-
Tidskriftsartikel (refereegranskat)abstract
- Ion plating is essentially vapor deposition onto a substrate which is the cathode of a glow discharge. The most important characteristic of the technique is that the growing film is subjected to a flux of high energy particles (neutrals and ions). In this study we report information about the effect of ion plating parameters on grain diameter and crystallite size distribution. At a constant potential grain size remains constant with the increase of ion density. On the other hand, at a constant ion density the grain size decreases with the substrate potential increment. Ion bombardment also has an effect on the crystallite size distribution. The ion plated films show a higher degree of uniformity in grain size than vacuum evaporated films. In contrast with vacuum evaporated films, where the grain size is proportional to the thickness, no variation of grain size with film thickness has been observed for the ion‐plated films. Electron diffraction patterns have shown that the orientation remains near random over the entire J and V range studied.
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| 29. |
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| 30. |
- Broitman, Esteban, et al.
(författare)
-
Microstructural, nanomechanical, and microtribological properties of Pb thin films prepared by pulsed laser deposition and thermal evaporation techniques
- 2016
-
Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 34:2, s. 021505-
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, the authors compare the morphological, structural, nanomechanical, and microtribological properties of Pb films deposited by thermal evaporation (TE) and pulsed laser deposition (PLD) techniques onto Si (111) substrates. Films were investigated by scanning electron microscopy, surface probe microscopy, and x-ray diffraction in theta-2 theta geometry to determine their morphology, root-mean-square (RMS) roughness, and microstructure, respectively. TE films showed a percolated morphology with densely packed fibrous grains while PLD films had a granular morphology with a columnar and tightly packed structure in accordance with the zone growth model of Thornton. Moreover, PLD films presented a more polycrystalline structure with respect to TE films, with RMS roughness of 14 and 10 nm, respectively. Hardness and elastic modulus vary from 2.1 to 0.8 GPa and from 14 to 10 GPa for PLD and TE films, respectively. A reciprocal friction test has shown that PLD films have lower friction coefficient and wear rate than TE films. Our study has demonstrated for first time that, at the microscale, Pb films do not show the same simple lubricious properties measured at the macroscale. (C) 2015 American Vacuum Society.
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| 31. |
- Broitman, Esteban, et al.
(författare)
-
Nanomechanical and microtribological properties of yttrium thin films for photocathode engineering
- 2019
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 37:3
-
Tidskriftsartikel (refereegranskat)abstract
- The authors study the nanomechanical and microtribological properties of yttrium (Y) thin films deposited by pulsed laser deposition on Cu polycrystalline substrates. Nanoindentation tests reveal that such films have a high hardness of H = 2.3 GPa and a reduced elastic modulus of 71.7 GPa with respect to the Cu substrates. The friction coefficient between a diamond tip and the Y film reaches a steady state value of mu similar to 0.34, lower than that for the Cu (mu similar to 0.38). Moreover, nano-scratch experiments show that Y films are more scratch-resistant than the Cu substrates, probably due to their greater hardness, higher elastic recovery, and lower friction coefficient. Their results confirm that the mechanical and tribological properties of the Y films are suitable for designing and fabricating scratch-resistant hybrid photocathodes and can reduce instabilities and unwanted discharges in the cavity of the radio-frequency gun. Furthermore, the low surface roughness and the low work function of the material are important characteristics for a photocathode based on the Y thin film for the production of high-brightness electron beams. Published by the AVS.
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| 32. |
- Broitman, Esteban, et al.
(författare)
-
Nanoscale piezoelectric response of ZnO nanowires measured using a nanoindentation technique
- 2013
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 15:26, s. 11113-11118
-
Tidskriftsartikel (refereegranskat)abstract
- We report the piezoelectric properties of ZnO nanowires (NWs) obtained by using a nanoindenter with a conductive boron-doped diamond tip. The direct piezoelectric effect was measured by performing nanoindentations under load control, and the generated piezoelectric voltage was characterized as a function of the applied loads in the range 0.2-6 mN. The converse piezoelectric effect was measured by applying a DC voltage to the sample while there was a low applied force to allow the tip being always in physical contact with the NWs. Vertically aligned ZnO NWs were grown on inexpensive, flexible, and disposable paper substrates using a template-free low temperature aqueous chemical growth method. When using the nanoindenter to measure the direct piezoelectric effect, piezopotential values of up to 26 mV were generated. Corresponding measurement of the converse piezoelectric effect gave an effective piezoelectric coefficient d(33)(eff) of similar to 9.2 pm V-1. The ZnO NWs were also characterized using scanning electron microscopy, X-ray diffraction, and high-resolution transmission electron microscopy. The new nanoindentation approach provides a straightforward method to characterize piezoelectric material deposited on flexible and disposable substrates for the next generation of nanodevices.
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| 33. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Novel method for in-situ and simultaneous nanofriction and nanowear characterization of materials
- 2015
-
Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : America Vacuum Society. - 0734-2101 .- 1520-8559. ; 34
-
Tidskriftsartikel (refereegranskat)abstract
- Nowadays, there is an increased need to know the nanotribological properties of protectivecoatings used in part devices operating under nano- and microcontact situations, e.g., hard diskdrives, magnetic heads, microelectromechanical systems and microsensors, etc. Therefore, there isa demand for instruments and methods testing friction and wear at the nano- and microscales. Inthis work, the authors present a new methodology to measure simultaneously the friction, and wearof a surface. The authors have designed an experiment, where a probe is permanently scanning a10 lm track in a reciprocal movement. Different loads are applied in order to obtain thetopographic information which is used to calculate the wear rate and roughness evolution. Forcelateral sensors register simultaneously the friction force variations. The experimental input data areinformation vectors that contain: load (lN), friction force (lN), vertical Z displacement (nm),lateral X displacement (nm), and time (s). The data are processed using a simple program runningin MathLabVR which eliminates the thermal drift. The software output gives the resulting frictioncoefficient, track roughness, and wear rate as a function of the running cycles of the probe. Thenew method builds a novel bridge to relate tribological mechanisms at different scales
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| 34. |
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| 35. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Resistividad Eléctrica de Películas Delgadas de Oro Obtenidas por Ion-Plating [Electrical Resistivity of Au Thin Films Deposited by Ion-Plating]
- 1992
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Ingår i: Anales AFA. - Buenos Aires, Argentina : Asociacion Fisica Argentina. ; 3:1, s. 357-360
-
Tidskriftsartikel (refereegranskat)abstract
- Es sabido que la resistividad eléctrica de las películas delgadas es mayor que la del material en volumen aún para espesores para los cuales el efecto Fuchs-Sondheimer es despreciable. En este caso, la mayor contribución a la resistividad se debe a impurezas y defectos cristalinos. Por eso es interesante hacer mediciones eléctricas en películas en que se pueda establecer la variación de la resistividad con la concentración de defectos, en especial bordes de grano. Esto puede lograrse comparando películas depositadas en vacío y por ion-plating porque esta última produce películas con tamaño de grano significativamente menor que las evaporadas en vacío. En este trabajo se presentan mediciones de la resistividad de películas continuas de oro obtenidas por ambas técnicas, antes y después de tratamientos técnicos. El tamaño de grano de las películas fue observado por microscopía electrónica. Se discuten los resultados en función de la contribución a la resistividad del scattering en los bordes de grano.
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| 36. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Resistividad Eléctrica Residual en Péliculas Delgadas [Residual Electrical Resistivity in Thin Metal Films]
- 1994
-
Ingår i: Anales AFA. - Buenos Aires, Argentina : Asociacion Fisica Argentina. ; 5:1, s. 280-282
-
Tidskriftsartikel (refereegranskat)abstract
- Ha sido bien establecido que la resistividad de las películas, delgadas depende fuertemente de su estructura. Para entender mejor dicha influencia se comparó la resistividad residual (0°K) de películas obtenidas por evaporación en vacío y por ion-plating. Las películas obtenidas por esta última técnica se caracterizan por tener un diámetro de grano menor y mayor uniformidad en tamaño y forma de los granos. La resistividad residual fue determinada midiendo la resistividad a distintas temperaturas para muestras de distintos espesores. El tamaño de grano se obtuvo por microscopía electrónica de transmisión.
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| 37. |
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| 38. |
- Broitman, Esteban, et al.
(författare)
-
Structural and Mechanical Properties of CNx and CPx Thin Solid Films
- 2012
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Ingår i: Key Engineering Materials. - : Trans Tech Publications. - 1013-9826 .- 1662-9795. ; 488-489, s. 581-584
-
Tidskriftsartikel (refereegranskat)abstract
- The inherent resiliency, hardness and relatively low friction coefficient of the fullerene-like (FL) allotrope of carbon nitride (CNx) thin solid films give them potential in numerous tribological applications. In this work, we study the substitution of N with P to grow FL-CPx to achieve better cross- and inter-linking of the graphene planes, improving thus the materials mechanical and tribological properties. The CNx and CPx films have been synthesized by DC magnetron sputtering. HRTEM have shown the CPx films exhibit a short range ordered structure with FL characteristics for substrate temperature of 300 degrees C and for a phosphorus content of 10-15 at.%. These films show better mechanical properties in terms of hardness and resiliency compared to those of the FL-CNx films. The low water adsorption of the films is correlated to the theoretical prediction for low density of dangling bonds in both, CNx and CPx. First-principles calculations based on Density Functional Theory (DFT) were performed to provide additional insight on the structure and bonding in CNx, CPx and a-C compounds.
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| 39. |
- Broitman, Esteban
(författare)
-
The nature of the frictional force at the macro-, micro-, and nano-scales
- 2014
-
Ingår i: Friction. - : Springer Berlin/Heidelberg. - 2223-7690 .- 2223-7704. ; 2:1, s. 40-46
-
Tidskriftsartikel (refereegranskat)abstract
- Nowadays it is accepted that the friction force is a combined effect arising from various phenomena: adhesive forces, capillary forces, contact elasticity, topography, surface chemistry, and generation of a third body, etc. Any of them can dominate depending on the experimental force and length scales of the study. Typical forces in macro-tribology are in the Newtons, while are reduced to milli-/micro-Newtons, and nano-Newtons in micro- and nano-tribology, respectively. In this paper, experimental friction results from fullerene like CN x films and single-crystal Si at the three scales will be discussed. The complex and broad variety of processes and phenomena connected with the dry friction coefficient at the macro-, micro-, and nano-scale point of view will be highlighted.
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| 40. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Thin Film Humidity Sensors (Sensores de Humedad de Película Delgada)
- 1991
-
Ingår i: Anales AFA. - Buenos Aires, Argentina : Asociacion Fisica Argentina. ; 2:1, s. 277-279
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper the construction and characterization of a humidity sensor with an alumina thin film responsive element is described. The capacitive sensor, made by thin film technology, consists of a dielectric layer of Al2O3 film deposited between metal electrodes.
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| 41. |
- Broitman, Esteban, 1958-, et al.
(författare)
-
Thin Film Temperature Sensors (Sensores de Temperatura de Película Delgada)
- 1990
-
Ingår i: Anales AFA. - Buenos Aires, Argentina : Asociacion Fisica Argentina. ; 1:1, s. 336-338
-
Tidskriftsartikel (refereegranskat)abstract
- Ni thin films of 1800 Å thick were deposited by ion-plating and designed by photolithography to be used as temperature sensors. The resistive paths were finished with contact Cu welding terminals. After being coated with a protective layer of SiOx, they were subjected to heat stabilization treatments. Small, stable and accurate sensors were obtained.
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| 42. |
- Broitman, Esteban, et al.
(författare)
-
Tribological and Nanomechanical Behavior of Liquid Wood
- 2019
-
Ingår i: Journal of tribology. - : ASME. - 0742-4787 .- 1528-8897. ; 141:2
-
Tidskriftsartikel (refereegranskat)abstract
- During the last decades, there has been an increased interest in the use of lignin-based composites following the ideas of developing green materials for fossil-based raw materials substitution. The biopolymer Arboform is a mixture of lignin, plant fibers, and additives, which is nowadays successfully used in many applications. As a thermoplastic, it can be molded and is therefore also called "liquid wood." In this paper, we report a study comparing the nanomechanical and tribological properties of Arboform (AR), and Aramid-reinforced Arboform (AR-AF) composite biopolymers. The samples were produced in an industrial-scale injection molding machine. Nanoindentation experiments have revealed that, in both series of biopolymer samples, an increase in temperature or a change in the injection direction from 0 deg to 90 deg produces an increase in hardness. On the other hand, Youngs modulus is slightly affected by the increase in temperature, and not affected by the injection angle. Tribological characterization has shown that all samples, except the AR-AF injected at 175 degrees C, present noticeable wear and have a similar friction coefficients mu similar to 0.44-0.49 at Hertzian contact pressures p(0) between 90 and 130 MPa. Interestingly, the reinforced polymer produced at 175 degrees C shows no wear and low friction of mu similar to 0.19 at p(0)=90 MPa. Our results show that the reinforced Arboform biopolymers are a good candidate to replace other polymers in many mechanical and tribological applications.
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| 43. |
- Broitman, Esteban, et al.
(författare)
-
Tribology of Carbon-Based Coatings : Past, Present, and Future
- 2013
-
Ingår i: Proceeding of the 2<sup>nd</sup> International Workshop of Tribology Tribaries 2013. - 9789872932909 ; , s. 7-10
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this talk, the development of carbon-based coatings will be reviewed. The most recent findings in the synthesis, characterization and application of carbon-based coatings will be highlighted. Future perspectives of new fullerene-like carbon-based tribological coatings will be discussed. Novel applications of fullerene-like CNx, CPx, and CFx will be envisioned.
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| 44. |
- De Bona, J., et al.
(författare)
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Differences in the Sliding Wear Track Patterns Between UHMWPE/Steel and UHMWPE/CNx Pairs
- 2012
-
Ingår i: Procedia Materials Science. - : Elsevier. - 2211-8128. ; 1, s. 329-336
-
Tidskriftsartikel (refereegranskat)abstract
- This work explores the effect of surface modification of stainless steel with a carbon nitride (CNx) film, under sliding wear of the UHMWPE/steel. Wettatibility of CNx coatings is assessed by means of the sessile drop method using two different liquid media. Microhardness and stiffness of CNx coatings are estimated by depth-sensing indentation. The sliding performance of UHMWPE against stainless steel and CNx was evaluated using a pin on disk tribometer. It is demonstrated that CNx surface properties are quite different from those of stainless steel, with a concomitant substantial reduction of the coefficient of friction of UHMWPE/CNx in comparison with the one of UHMWPE/steel under sliding conditions. Even tough imposed sliding conditions do not conduct to wear mass loss in UHMWPE, wear track patterns against steel and CNx are quite different.
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| 45. |
- De Feudis, M., et al.
(författare)
-
Diamond graphitization by laser-writing for all-carbon detector applications
- 2017
-
Ingår i: Diamond and related materials. - : ELSEVIER SCIENCE SA. - 0925-9635 .- 1879-0062. ; 75, s. 25-33
-
Tidskriftsartikel (refereegranskat)abstract
- The surface of a detector grade CVD polycrystalline diamond sample (5 x 5 x 0.05 mm(3)) was irradiated by an ArF excimer laser (lambda = 193 nm, T = 20 ns) to produce graphitic conductive layers. In particular, two sets of four parallel graphitic strip-like contacts, with 1 mm pitch, were created along the whole sample on the top and on the rear surfaces of the sample respectively. The two series of stripes lie normally to each other. Such a grid allows to obtain a segmented all-carbon device capable of giving bi-dimensional information on particle detection processes in nuclear applications. Afterwards, an extensive characterization of the samples was performed: SEM and micro-Raman investigations to study the morphological and structural evolution of the irradiated areas, EDS measurements to individuate any absorption phenomena from environment associated to laser treatment, and nanoindentation mapping to understand how the hard-soft transformation occurred depending on the locally transferred energy. Finally, current-voltage analyses were carried out checking the ohmic behavior of the diamond-graphite contact. By comparing the results of the different characterization analyses, a strong periodidty of the modified surface properties was found, confirming the reliability and reproducibility of the laser-induced graphitization process. The results demonstrate that the laser-writing technique is a good and fast solution to produce graphitic contacts on diamond surface and therefore represents a promising way to fabricate segmented all-carbon devices. (C) 2016 Elsevier B.V. All rights reserved.
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| 46. |
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| 47. |
- Diliegros-Godines, C. J., et al.
(författare)
-
Mechanical and tribological properties of CdO + SnO2 thin films prepared by sol–gel
- 2015
-
Ingår i: Journal of Sol-Gel Science and Technology. - : Springer. - 0928-0707 .- 1573-4846. ; 74:1, s. 114-120
-
Tidskriftsartikel (refereegranskat)abstract
- We report the mechanical and tribological properties of transparent conductive oxide CdO + SnO2 coatings. The films were deposited on glass substrates by the sol–gel technique using, as precursor solution, a mixture of CdO and SnO2 solutions obtained at room temperature. Depending on the Sn atomic concentration percentage values the X-ray diffraction patterns show three types of films constituted of (1) CdO + Cd2SnO4, (2) Cd2SnO4 and (3) Cd2SnO4 + CdSnO3 crystals. Reciprocal microfriction tests revealed that films with Cd2SnO4 phase have friction values in the range 0.48–0.51 and a low wear rate of ~5 × 10−5 mm3 N−1 m−1. Nanoindentation tests have shown an increment of the elastic modulus from 50 GPa for CdO + Cd2SnO4 films to 90 GPa for Cd2SnO4 films, while the hardest coating was the one constituted by Cd2SnO4 crystals with H = 5.7 GPa, comparable to the hardness and elastic modulus reported for ITO films.
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| 48. |
- Eriksson, Robert, et al.
(författare)
-
Influence of substrate material on the life of atmospheric plasmas prayed thermal barrier coatings
- 2013
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 232:15, s. 795-803
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal barrier coatings (TBCs) are used in gas turbines to prolong the life of the underlying substrates and to increase the efficiency of the turbines by enabling higher combustion temperatures. TBCs may fail during service due to thermal fatigue or through the formation of non-protective thermally grown oxides (TGOs). This study compares two atmospheric plasma sprayed (APS) TBC systems comprising of two identical TBCs deposited on two different substrates (Haynes 230 and Hastelloy X). The thermal fatigue life was found to differ between the two TBC systems. The interdiffusion of substrate elements into the coating was more pronounced in the TBC system with shorter life, however, very few of the substrate elements (only Mn and to some extent Fe) formed oxides in the bond coat/top coat interface. Fractography revealed no differences in the fracture behaviour of the TBCs; the fracture occurred, in both cases, to about 60% in the top coat close to the interface and the remainder in the interface. Nanoindentation revealed only small differences in mechanical properties between the TBC systems and a finite element crack growth analysis showed that such small differences did not cause any significant change in the crack driving force. The oxidation kinetics was found to be similar for both TBC systems for the formation of Al2O3 but differed for the kinetics of non-Al2O3 TGOs where the TBC system with shortest life had a faster formation of non-Al2O3 TGOs caused by a faster Al depletion. The difference in non-Al2O3 TGO growth kinetics was considered to be the main reason for the difference in life.
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| 49. |
- Eriksson, Robert, et al.
(författare)
-
Stresses and Cracking During Chromia-Spinel-NiO Cluster Formation in TBC Systems
- 2015
-
Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 24:6, s. 1002-1014
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal barrier coatings (TBC) are used in gas turbines to reduce the temperatures in the underlying substrate. There are several mechanisms that may cause the TBC to fail; one of them is cracking in the coating interface due to extensive oxidation. In the present study, the role of so called chromia-spinel-NiO (CSN) clusters in TBC failure was studied. Such clusters have previously been found to be prone to cracking. Finite element modeling was performed on a CSN cluster to find out at which stage of its formation it cracks and what the driving mechanisms of cracking are. The geometry of a cluster was obtained from micrographs and modeled as close as possible. Nanoindentation was performed on the cluster to get the correct Young’s moduli. The volumetric expansion associated with the formation of NiO was also included. It was found that the cracking of the CSN clusters is likely to occur during its last stage of formation as the last Ni-rich core oxidizes. Furthermore, it was shown that the volumetric expansion associated with the oxidation only plays a minor role and that the main reason for cracking is the high coefficient of thermal expansion of NiO. © 2015 ASM International
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| 50. |
- Flores-Ruiz, F. J., et al.
(författare)
-
Micro-tribological performance of fullerene-like carbon and carbon-nitride surfaces
- 2018
-
Ingår i: Tribology International. - : Pergamon Press. - 0301-679X .- 1879-2464. ; 128, s. 104-112
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the microtribological behavior of amorphous and fullerene-like (FL) carbon and carbon-nitride coatings deposited by filtered-cathodic-arc. All films show similar friction coefficients but different wear mechanisms. The FL films exhibit a surface swelling with the formation of a layer that thickens during the test, limiting wear and maintaining a low friction. X-ray photoelectron spectroscopy on worn FL film surfaces show an increase in the sp(2)-content, indicating that the lubricious layer generated by the wear process is probably the result of re-hybridization due to plasticity induced by localized shear. In contrast, the wear results of the amorphous films, involving tribomechanical and tribochemical surface phenomena, show that the surface layer formed during sliding is a precursor to the onset of wear.
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