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  • 1.
    Aghasibeig, Maniya
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Laser cladding of a featureless iron-based alloy2012In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 209, p. 32-37Article in journal (Refereed)
    Abstract [en]

    Laser cladding experiments with powder injection technique were carried out to create coatings of Fe-8.1Cr6.4Mn-5.3Si-6.9Mo-3.6C alloy on AISI 1018 steel substrates using a diode laser. Analysis of the clad layers showed that an almost featureless structure was formed at different dilutions between 1% and 4%. The featureless phase with a high hardness of 1155 HV was characterized as a metastable solid solution of e phase. However, the featureless structure appeared to be very brittle with numerous cracks. After heat-treatment, it decomposed into a bainitic structure with a high hardness of 884 HV.

  • 2. Bexell, U.
    et al.
    Olsson, M.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Samuelsson, J.
    Sundell, P. E.
    A tribological study of a novel pre-treatment with linseed oil bonded to mercaptosilane treated aluminium2003In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 166, no 03-feb, p. 141-152Article in journal (Refereed)
    Abstract [en]

    In sheet metal forming processes, lubricants are necessary in order to prevent galling, i.e. material transfer from the sheet metal to the tool surface and to control friction. Today, dry lubricants are increasingly being used for solving this problem. Among these, multifunctional coatings, often referred to as permanent coatings, normally based on organic resins, are lubricants which have the potential to increase the formability without additional lubrication, give corrosion protection, fingerprint and scratch resistance during handling and transport and finally, serve as a pre-treatment before painting. With increasing concern about the environment and human health it is important to develop new environmentally friendly pre-treatments in the surface engineering of metal substrates. This is mainly due to the toxic and carcinogenic properties of the chromium based surface pre-treatments frequently used in the industry. During the last decade, simple solution-dip silane based pre-treatments have emerged as promising candidates for the replacement of currently used pre-treatments of metals. A silane film can give good corrosion protection properties but is often too thin to prevent galling under a forming operation. A renewed interest for using vegetable oils in surface engineering has appeared lately due to several factors. Vegetable oils are renewable resources, modem technology can produce more well defined and pure oils, and the fatty acid content can be altered with modern crops development techniques. With the proper choice of silane pre-treatment of a metal surface, a vegetable oil can be coupled to the surface and give the desired lubrication properties. In this paper, aluminium sheets have been pre-treated with a mercapto silane after which a vegetable oil has been attached. The coupling between the silane and the oil was obtained through a photoinduced thiol-ene reaction using UV-radiation. The influence of different process parameters on the friction and wear behaviour was evaluated using modified scratch testing. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and contact angle measurements were used to characterise the as-deposited surface films and their tribological behaviour, i.e. failure mechanisms. The results obtained show that the unsaturated vegetable oil has reacted with the thiol groups via the thiol-ene reaction forming a surface film. Also, the results show that the thickness of the films is of importance for the tribological characteristics, i.e. a too thin layer (less than 25 A in the present work) results in high friction and severe adhesive wear. However, a thicker layer with enhanced load carrying capacity can be produced with a proper heat treatment of the deposited vegetable oil. Finally, the results show that thick (more than 200 Angstrom in the present work) silane films are sensitive to brittle fracture when exposed to a sliding contact.

  • 3. Beyhaghi, Maryam
    et al.
    Kashefi, Mehrdad
    Kiani-Rashid, Alireza
    Khaki, Jalil Vandati
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    In-situ synthesis of nanostructured NiAl-Al2O3 composite coatings on cast iron substrates by spark plasma sintering of mechanically activated powders2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 272, p. 254-267Article in journal (Refereed)
    Abstract [en]

    Bulk pellets and coatings of NiAl-Al2O3 composites on gray cast-iron substrates are fabricated by spark plasma sintering (SPS) at 700 and 1050 degrees C using a highly reactive powder-mixture of "13Al + 8Ni + 3NiO" activated by 1 hour ball milling. The reactions are complete in all cases, except for the coating produced at the lower temperature. At both temperatures, the pellets experienced internal explosions, due to the intense reactivity of the powder, producing inhomogeneous microstructures. At 1050 degrees C, the heat absorption from the substrates resulted in damped reactions producing homogenous, dense, fully reacted NiAl-Al2O3 composite coatings with crystallite sizes of 73 nm and 65 nm, respectively. A bond layer forms by growing into the substrate and diffusion of Fe, Ni, Al and Si is found in the coating, the bond layer and the substrate. In all cases, the adherence of coatings to substrates is good with no signs of pores or cracks. The products are examined by LOM, SEM, EDS, XRD, Vickers hardness indentation and scratch testing. The SPS process is analyzed by FEM-simulations using a homogeneous reaction model where the properties are given by linear combinations of reactants and products. Melting enthalpies of all compounds are taken into consideration when calculating the maximum reaction temperatures for various combustion times and gap conductivities between powder and graphite parts of the SPS apparatus. The maximum reaction temperatures are calculated for pellets and for coatings on cast iron substrates and also for mixtures of activated and already reacted powder. The results are shown as isotherms. Comparison to experiments suggests a reaction time exceeding 1 s and a gap conductivity of less than 10 kW.m(-2).K-1. For ignition at 500 degrees C, the adiabatic temperature is estimated to 2056 degrees C.

  • 4. Blomqvist, A.
    et al.
    Århammar, Cecilia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Pedersen, H.
    Silvearv, F.
    Norgren, S.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Understanding the catalytic effects of H(2)S on CVD-growth of alpha-alumina: Thermodynamic gas-phase simulations and density functional theory2011In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 7, p. 1771-1779Article in journal (Refereed)
    Abstract [en]

    The catalytic effect of H(2)S on the AlCl(3)/H(2)/CO(2)/HCl chemical vapor deposition (CVD) process has been investigated on an atomistic scale. We apply a combined approach with thermodynamic modeling and density functional theory and show that H(2)S acts as mediator for the oxygenation of the AI-surface which will in turn increase the growth rate of Al(2)O(3). Furthermore we suggest surface terminations for the three investigated surfaces. The oxygen surface is found to be hydrogenated, in agreement with a number of previous works. The aluminum surfaces are Cl-terminated in the studied CVD-process. Furthermore, we find that the AlClO molecule is a reactive transition state molecule which interacts strongly with the aluminum and oxygen surfaces.

  • 5. Brodin, H
    et al.
    Eskner, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    The influence of oxidation on mechanical and fracture behaviour of an air plasma-sprayed NiCoCrAlY bondcoat2004In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 187, no 1, p. 113-121Article in journal (Refereed)
    Abstract [en]

    The influence of isothermal oxidation on room-temperature mechanical and fracture behaviour of an air plasma-sprayed Ni-23Co-17Cr12Al-0.5Y bondcoat was investigated by the miniaturised disc bending test (MDBT) technique. Disc specimens were extracted from the bondcoat region of both as-received and oxidised thermal barrier coating (1000 degreesC, 1000 h). Microstructure analysis revealed that the nonoxidised bondcoat consisted mainly of gamma-phase (Ni-structure) and beta-NiAl. After 500 h of oxidation no NiAl remained in the bondcoat, an effect due to internal as well as external oxidation of Al. The former resulted in the formation of an extensive oxide network and the latter in the formation of an oxide scale between the topcoat and the bondcoat. The crack propagation behaviour of the bondcoat, both in non-oxidised and oxidised condition can be characterised as intergranular with stable growth. The crack propagation resistance is substantial due to the lamellar gain (splat) orientation and the extensive intergranular oxide network, acting as crack deflection and crack branching mechanisms. As an effect of oxidation, crack propagation resistance of the bondcoat increases but the strain to crack initiation decreases.

  • 6.
    Ekström, Madeleine
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Thibblin, A.
    Tjernberg, A.
    Blomqvist, C.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Evaluation of internal thermal barrier coatings for exhaust manifolds2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 272, p. 198-212Article in journal (Refereed)
    Abstract [en]

    Seven different thermal barrier coatings (TBC) intended for coating the inside of an exhaust manifold to reduce its material temperature were studied. They comprised five plasma-sprayed (mullite, forsterite, La2Zr2O7, 8YSZ, and nanostructured 8YSZ) and two sol-gel composite (one sprayed and one dipped) coatings, which were examined for their thermal insulation properties and oxidation and spallation resistance. Thermal cyclic tests in air and in exhaust gas in a diesel test engine showed that thermal expansion mismatch between substrate and TBC was most crucial for TBC lifetime. Moreover, thermal modeling indicated that it is possible to reduce the material temperature by 50 °C, which is important for improving the fatigue life of exhaust manifolds. This reduction can be obtained with a 0.2 mm thick TBC with thermal conductivity close to 0.1 W/m K, or a 3–6 mm thick TBC with thermal conductivity 1.5–3 W/m K. 

  • 7. Eskner, M.
    et al.
    Sandström, Rolf
    KTH, Superseded Departments, Materials Science and Engineering.
    Measurement of the ductile-to-brittle transition temperature in a nickel aluminide coating by a miniaturised disc bending test technique2003In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 165, no 1, p. 71-80Article in journal (Refereed)
    Abstract [en]

    Nickel aluminide coatings are often employed to enhance the corrosion and oxidation resistance of nickel base gas turbine blades and vanes, as the high near-surface content of Al increases the ability to form an Al2O3 protective scale. The ductility of the coating depends on the type of aluminisation process and Ni-base material. In order to prevent coating degradation during service it is important to assess the ductile-to-brittle transition temperature (DBTT) in ductility of the coating. To determine the DBTT a miniaturised disc bending test (MDBT) technique is used, where a biaxial tensile stress is applied to a disc specimen. The DBTT of a NiAl coating, applied by a high-activity aluminium pack cementation process to a polycrystalline Ni-base superalloy (IN738 LC), was evaluated using the MDBT technique between room temperature (RT) and 860 degreesC. Test results gave a DBTT in biaxial ductility of the coating of approximately 760 degreesC. Above 760 degreesC, a significant increase in ductility was noted. Fractographic examination showed that the coating fractures in a mainly transgranular mode at RT but in a predominately intergranular mode at elevated temperatures, even at temperatures above DBTT.

  • 8. Eskner, M.
    et al.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Mechanical properties and temperature dependence of an air plasma-sprayed NiCoCrAlY bondcoat2006In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 200, no 8, p. 2695-2703Article in journal (Refereed)
    Abstract [en]

    The elastic and inelastic properties were investigated for an air plasma-sprayed bondcoat (Ni-23Co-17Cr-12Al-0.5Y) at temperatures up to 800 degrees C. The yield strength was evaluated by using a miniaturised disc-bending test while the stress-strain behaviour and elastic modulus were determined through spherical indentation. The material was tested in both as-coated and heat-treated conditions (1500 h, 1000 degrees C). From the disc-bending tests it was observed that both conditions were macroscopically brittle both at low and high temperatures, with slow and stable crack propagation in the inter-splat region. Between room temperature and 500 degrees C the yield strength is constant and yield occurs by inter-splat shearing, but above this temperature the yield strength decreases due to yielding of the splats. This behaviour was confirmed by the fractographical examination that showed an inter-splat fracture surface at room temperature with small amount of plastic features, but at 800 degrees C a more dimpled and ruptured fracture appeared. Small difference in yield strength was found between the two conditions, and they had similar temperature dependence. However, their indentation stress-strain response was different, where the heat-treated condition had the largest resistance against inelastic deformation. The value of the elastic modulus was for the as-coated condition 137 GPa at 25 degrees C and 127 GPa at 800 degrees C, and for the heat-treated condition 226 GPa at 25 degrees C and 192 GPa at 800 degrees C, the difference between the two conditions being a result of internal oxidation.

  • 9.
    Eskner, Mats
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sandström, Rolf
    KTH, Superseded Departments, Materials Science and Engineering.
    Measurement of the elastic modulus of a plasma-sprayed thermal barrier coating using spherical indentation2004In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 177, p. 165-171Article in journal (Refereed)
    Abstract [en]

    Failure in plasma-sprayed thermal barrier coatings systems mostly takes place in the ceramic topcoat or at the interface between the topcoat and the bondcoat. The failure normally occurs by spallation of the topcoat at shutdown operations from high temperatures where compressive thermal-mismatch stresses are induced in the topcoat. In order to analyse the residual stresses, knowledge about the elastic modulus for the different components in the coating system is required. In this work, a spherical indentation method has been used for room-temperature measurement of the elastic modulus of both the topcoat (300-mum-thick air-plasma sprayed ZrO2-8wt,%Y2O3) and the bondcoat (150-mum-thick air-plasma sprayed Ni-23Co-17Cr-12Al-0.5Y). This method gives the compressive modulus, which for the top-coat may be more adequate as it has different modulus in tensile and compressive stress states due to its microstructure. Measurements were made on specimens in as-coated condition and after heat treatment (1500 h at 1000 degreesC). A significant increase in the elastic modulus of the bondcoat was observed as a result from the heat treatment, from 137 to 226 GPa, which is explained by the internal oxidation at the initial weak inter-splat regions. A sintering effect and a change in the elastic modulus were also observed for the topcoat as a result of the beat-treatment, where the elastic modulus increased from 38 to 60 GPa.

  • 10.
    Gavrilov, Nemanja
    et al.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Momcilovic, Milan
    Univ Belgrade, Inst Nucl Sci Vinca, POB 522, Belgrade 11000, Serbia..
    Dobrota, Ana S.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Stankovic, Dalibor M.
    Univ Belgrade, Inst Nucl Sci Vinca, POB 522, Belgrade 11000, Serbia.;Univ Belgrade, Innovat Ctr, Fac Chem, Studentski Trg 12, Belgrade 11158, Serbia..
    Jokic, Bojan
    Univ Belgrade, Fac Technol & Met, Karnegijeva 4, Belgrade 11000, Serbia.;Univ Arts Belgrade, Fac Appl Arts, Kralja Petra 4, Belgrade 11000, Serbia..
    Babic, Biljana
    Univ Belgrade, Inst Phys, Pregrev 118, Belgrade 11080, Serbia..
    Skorodumova, Natalia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Mentus, Slavko V.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia.;Serbian Acad Arts & Sci, Knez Mihajlova 35, Belgrade 11000, Serbia..
    Pašti, Igor
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    A study of ordered mesoporous carbon doped with Co and Ni as a catalyst of oxygen reduction reaction in both alkaline and acidic media2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 349, p. 511-521Article in journal (Refereed)
    Abstract [en]

    The incorporation of trace amounts (< 0.2%) of Co and Ni noticeably enhanced the catalytic activity of nitrogen free ordered mesoporous carbon (OMC) towards oxygen reduction reaction (ORR). (Co,Ni)-doped OMCs were characterized by N-2-adsorption measurements, X-ray powder diffraction, field emission scanning electron microscopy and Raman spectroscopy methods, and their ORR activity was estimated by voltammetry on rotating disk electrode in acidic and alkaline media. (Co,Ni)-doped OMCs show modest activities in acidic media, while the catalytic activity in alkaline media is rather high. The measured activities are compared to the Pt-based and Pt-free ORR catalysts reported in the literature. The number of electrons consumed per O-2 in metal-doped OMCs was found to vary between 2 and 4, which is advantageous in comparison to metal-free OMC. Also, the mass activities of metal-doped OMCs were found to be up to 2.5 times higher compared to that of metal-free OMC. We suggest that the ORR activity is governed by a balance between (i) textural properties, which determine the electrochemically accessible surface of the catalyst and which are influenced by the addition of a metal precursor, and (ii) novel active sites formed upon the introduction of metals into the carbon structure. In particular, our Density Functional Theory calculations suggest that Co and Ni atoms embedded into the single vacancies of graphene can activate the O-2 molecule and contribute to the decomposition of peroxide.

  • 11. Gu, H.
    et al.
    Wang, C.
    Gong, S.
    Mei, Y.
    Li, H.
    Ma, Weimin
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
    Investigation on contact angle measurement methods and wettability transition of porous surfaces2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 292, p. 72-77Article in journal (Refereed)
    Abstract [en]

    Various solid surfaces (e.g., smooth titanium surface, smooth aluminum surface, polished copper surfaces, polished silver surfaces and porous copper surfaces) were prepared to quantify the reliability of half-angle algorithm and axisymmetric drop shape analysis (ADSA) algorithm for calculating contact angles. Besides, the effects of surface conditions on contact angle values were also investigated. The experimental results of 10 repeated tests for each surface show that both algorithms have good accuracy for an acute contact angle, while the ADSA algorithm is better than the half-angle algorithm for an obtuse contact angle. Furthermore, with the decrease of surface roughness, the contact angle increases but the standard deviation of contact angles by 10 repeated tests decreases. In addition, the porous layer on copper surface by electrochemical deposition shows a super hydrophilic property, but it could change to be super hydrophobic after exposed in ambient air for 24 h. Interestingly, the surface wettability reverses to be super hydrophilic again after it is immersed in water, and the inorganic contamination is the reason of formal change from the super hydrophilic status to the super hydrophobic status.

  • 12.
    Gudmundsson, Jon Tomas
    et al.
    University of Iceland.
    Alami, J
    Linköping University.
    Helmersson, Ulf
    Linköping University.
    Spatial and Temporal Behavior of the Plasma Parameters in a Pulsed Magnetron Discharge2002In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 161, no 2-3, p. 249-256Article in journal (Refereed)
  • 13.
    Hallén, Anders
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Linnarsson, Margareta K.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Ion implantation technology for silicon carbide2016In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 306, p. 190-193Article in journal (Refereed)
    Abstract [en]

    Ion implantation is a key process technique for semiconductor materials, in particular silicon, for local tailoring of the semiconductor properties. The wide bandgap semiconductor silicon carbide (SiC) features outstanding material properties for high power and high temperature electronic devices, but the properties of SiC also make it difficult to manufacture and process the material. The development of implantation technology for SiC has therefore necessitated several changes, from mainstream silicon implantation technology. This paper will discuss the difficulties with implantation of SiC for manufacturing of electronic devices and also describe how the problems have been overcome, for instance by implantation at elevated temperatures and using high temperature post-implant annealing. (C) 2016 Elsevier B.V. All rights reserved.

  • 14.
    Hedenqvist, Mikael S.
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Johansson, K. S.
    Barrier properties of SiOx-coated polymers: multi-layer modelling and effects of mechanical folding2003In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 172, no 1, p. 7-12Article in journal (Refereed)
    Abstract [en]

    The oxygen permeability properties of poly(ethylene terephthalate), low- and high-density polyethylenes and polypropylene coated with SiOx using cold plasma were studied. A previously developed computer model for the calculation of transport properties in laminates containing very different layer thickness was fitted to experimental permeability data to obtain the oxygen transport properties of the SiOx coating. For the first time, to the best of our knowledge, it was possible to obtain the oxygen diffusivity and solubility of a SiOx coating on a polymer substrate. The effects of folding the laminates through 90degrees on the permeability properties of the SiOx coating were also investigated. The surface roughness of the substrates was obtained by atomic force microscopy and the morphology of the laminate surfaces was analysed by scanning electron microscopy. The oxygen diffusivity and solubility of a 45-nm-thick SiOx coating deposited on a 4000-fold thicker polypropylene substrate were 5 x 10(-12) cm(2) s(-1) and 0.72 cm(2) (STP) cm(-3) atm(-1), respectively. The diffusivity was approximately four orders of magnitude lower than that of the polymer substrate and, surprisingly, the solubility was higher than that of the polypropylene film. A hypothesis to explain these results is that the coating contained voids and, according to the permeability time lag, these were not continuous through the coating. The oxygen permeability of the coating increased with increasing substrate surface roughness, and was consequently lowest for poly(ethylene terephthalate). The folding operation initiated cracks in the coating, and the resulting increase in oxygen permeability was greater in the rougher substrates.

  • 15.
    Jamshidi, Asghar
    et al.
    KTH.
    Noroozi, Mohammad
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Moeen, M.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hamawandi, Bejan
    KTH.
    Lu, J.
    Hultman, L.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Radamson, Henry
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Growth of GeSnSiC layers for photonic applications2013In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 230, p. 106-110Article in journal (Refereed)
    Abstract [en]

    This work presents epitaxial growth of intrinsic and doped GeSnSiC layers using Ge2H6, SnCl4, CH3SiH3, B2H6, PH3 and Si2H6 deposited at 290-380 degrees C on strain relaxed Ge buffer layer or Si substrate by using reduced pressure chemical vapor deposition (RPCVD) technique. The GeSnSi layers were compressively strained on Ge buffer layer and strain relaxed on Si substrate. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters and that the Sn content in epi-layers could be tailored by growth temperature. The Sn segregation caused surface roughness which was decreased by introducing Si and Si-C into Ge layer. The Sn content in GeSn was carefully determined from the mismatch, both parallel and perpendicular, to the growth direction when the Poisson ratio was calculated for a certain Ge-Sn composition. The X-ray results were excellently consistent with Rutherford Backscattered Spectroscopy (RBS). Strain relaxed GeSn layers were also used as virtual substrate to grow tensile-strained Ge layers. The Ge cap layer had low defect density and smooth surface which makes it a viable candidate material for future photonic applications.

  • 16.
    Keraudy, Julien
    et al.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden.;Oerlikon Surface Solut AG, Oerlikon Balzers, Iramali 18, LI-9496 Balzers, Liechtenstein..
    Viloan, Rommel Paulo B.
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Raadu, Michael A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Brenning, Nils
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Lundin, Daniel
    Univ Paris Saclay, Univ Paris Sud, CNRS, LPGP,UMR 8578, F-91405 Orsay, France..
    Helmersson, Ulf
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden..
    Bipolar HiPIMS for tailoring ion energies in thin film deposition2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 359, p. 433-437Article in journal (Refereed)
    Abstract [en]

    The effects of a positive pulse following a high-power impulse magnetron sputtering (HiPIMS) pulse are studied using energy-resolved mass spectrometry. This includes exploring the influence of a 200 mu s long positive voltage pulse (U-rev = 10-150 V) following a typical HiPIMS pulse on the ion-energy distribution function (IEDF) of the various ions. We find that a portion of the Ti+ flux is affected and gains an energy which corresponds to the acceleration over the full potential U-rev. The Ar+ IEDF on the other hand illustrates that a large fraction of the accelerated Ar+, gain energies corresponding to only a portion of U-rev. The Ti+ IEDFs are consistent with the assumption that practically all the TO-, that are accelerated during the reverse pulse, originates from a region adjacent to the target, in which the potential is uniformly increased with the applied potential U-rev while much of the Ar+ originates from a region further away from the target over which the potential drops from U-rev to a lower potential consistent with the plasma potential achieved without the application of U-rev. The deposition rate is only slightly affected and decreases with U-rev, reaching 90% at U-rev = 150 V. Both the Ti IEDF and the small deposition rate change indicate that the potential increase in the region close to the target is uniform and essentially free of electric fields, with the consequence that the motion of ions inside the region is not much influenced by the application of U-rev. In this situation, Ti will flow towards the outer boundary of the target adjacent region, with the momentum gained during the HiPIMS discharge pulse, independently of whether the positive pulse is applied or not. The metal ions that cross the boundary in the direction towards the substrate, and do this during the positive pulse, all gain an energy corresponding to the full positive applied potential U-rev.

  • 17. Kocabaş, M.
    et al.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Curioni, M.
    Cansever, N.
    Nickel fluoride as a surface activation agent for electroless nickel coating of anodized AA1050 aluminum alloy2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 364, p. 231-238Article in journal (Refereed)
    Abstract [en]

    In this study, the use of nickel fluoride tetrahydrate (NiF 2 ·4H 2 O) as a surface activator and sealant at the same time for the coating of electroless nickel-phosphorus (Ni-P) on anodized aluminum alloy AA1050 is proposed. The usage of the activator resulted in more efficient deposition of Ni-P, improved adhesion properties, and increased wear and friction behavior as opposed to non-activated conditions. Scanning electron microscopy (SEM) and confocal laser microscopy (CLM) analyses of ultramicrotome-cut cross sections of Ni-P coated specimens, surface-activated by NiF 2 ·4H 2 O, revealed a more well-structured metal-coating interface as opposed to non-activated conditions.

  • 18.
    Lundvall, Oscar
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Gulppi, M.
    Paez, M. A.
    Gonzalez, E.
    Zagal, J. H.
    Pavez, J.
    Thompson, G. E.
    Copper modified chitosan for protection of AA-20242007In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 201, no 12, p. 5973-5978Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to examine chitosan, which is a good film former, as a corrosion protective coating for AA-2024-T3 aluminium alloy. The aluminium samples were first anodized to increase adhesion of the subsequently dip coated film from a chitosan-acetic acid solution. To further increase the protective ability of the chitosan coating, the coated samples were immersed in a copper ion solution for 24 h. The copper salts used were sulphate and acetate. The chitosan membranes exposed to copper ion solutions revealed a reduced permeability in comparison with the unexposed samples, and an increase in stability in aqueous solutions, as revealed by a steady state and a high open circuit potential in borax solution. From UV-Vis spectroscopic measurement of the film on ITO glasses, the reduction in permeability of the chitosan film modified by copper ions appears to be associated with copper cross linking within the chitosan structure.

  • 19. Minea, T. M.
    et al.
    Costin, C.
    Revel, A.
    Lundin, Daniel
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Caillault, L.
    Kinetics of plasma species and their ionization in short-HiPIMS by particle modeling2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 255, p. 52-61Article in journal (Refereed)
    Abstract [en]

    The ionization efficiency of High Power Impulse Magnetron Sputtering (HiPIMS) discharges is the key parameter leading to (i) gas ion production and consequently controlling the sputtering effectiveness and (ii) sputtered vapor ionization, self-consistently linked to self-sputtering and thin film properties. To study the HiPIMS discharge time dependent two dimensional Particle in Cell (2D PIC) modelling coupled with Monte Carlo treatment of the plasma kinetics is discussed in terms of numerical scheme and stability criteria. The first microscopic results are presented for very short pulses (similar to 5 mu s) using superimposed DC pre-ionization. During this modeled HiPIMS short-pulse the plasma density increases at least two orders of magnitude driven by the pulse voltage, which also continues for a short time in the afterglow. During the pulse voltage plateau, the plasma potential shows a linear dependency going away from the target with two slopes over two space regions. First region is very narrow (<0.5 mm), corresponding to the cathode sheath in front of the race-track, while the second region, much larger, corresponds to the pre-sheath or Ionization Region (IR). Modeling results show an increasing electric field in the sheath with the voltage rise of the pulse, while it stays almost constant in the IR, corresponding to about 150 Vcm(-1), in agreement with reported probe measurements. The local electron energy distribution functions in the IR and further out in the Diffusion Region (DR) are very different. IR electrons are much more energetic compared to the ones found in the DR, which have an important low energy population as a result of the ionization processes. The transport of sputtered metal vapor from the target is simulated by 3D Monte Carlo (MC) modeling, in the intermediary pressure range - between ballistic and diffusive. Using the self-consistent output of plasma density maps from PLC with MC transport of sputtered vapor including their possible ionization when they cross the HiPIMS dense plasma, it is possible to estimate the metal ionization fraction, found here slightly lower than in previous reported works.

  • 20.
    Peng, Hao
    et al.
    Shanghai Univ, State Key Lab Adv Special Steels, Shanghai 200072, Peoples R China.;Shanghai Univ, Shanghai Key Lab Adv Ferromet, Shanghai 200072, Peoples R China.;Shanghai Univ, Dept Mat Sci & Engn, Shanghai 200072, Peoples R China..
    Wu, Guangxin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Shanghai Univ, State Key Lab Adv Special Steels, Shanghai 200072, Peoples R China.;Shanghai Univ, Shanghai Key Lab Adv Ferromet, Shanghai 200072, Peoples R China.;Shanghai Univ, Dept Mat Sci & Engn, Shanghai 200072, Peoples R China..
    Peng, Wangjun
    Shanghai Univ, State Key Lab Adv Special Steels, Shanghai 200072, Peoples R China.;Shanghai Univ, Shanghai Key Lab Adv Ferromet, Shanghai 200072, Peoples R China.;Shanghai Univ, Dept Mat Sci & Engn, Shanghai 200072, Peoples R China..
    Cao, Borui
    Meishan Iron & Steel Co, Nanjing 210039, Jiangsu, Peoples R China..
    Zhang, Jieyu
    Shanghai Univ, State Key Lab Adv Special Steels, Shanghai 200072, Peoples R China.;Shanghai Univ, Shanghai Key Lab Adv Ferromet, Shanghai 200072, Peoples R China.;Shanghai Univ, Dept Mat Sci & Engn, Shanghai 200072, Peoples R China..
    The effect of silicon on spangle size in hot-dipped 55 wt%Al-Zn coatings2017In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 327, p. 110-117Article in journal (Refereed)
    Abstract [en]

    The effect of various silicon levels on spangle size in hot-dipped 55 wt%Al-Zn-xSi (x = 0.5, 1.0, 1.6, 2.0, 4.0, all in wt%) coatings was studied. The results showed that as silicon content was increased from 0.5 to 4.0 wt%, spangle size increased gradually from the minimized range to the normal range. Spangle range transition occurred in silicon content between 1.0 and 1.6 wt%. Correlation between intermetallic species and spangle sizes under various silicon contents was investigated. It was found that in the process of spangle size from the minimized to the normal, intermetallic species of the alloy layer were also subject to a regular change of phase transformation from FeAl3 to T-5 (also refers to alpha-AlFeSi), especially remarkable in the range of silicon content where spangle range transited. Phase evolution of the intermetallic layer in various silicon levels was quantitatively analyzed by thermodynamic modelling using Pandat software package, which provided a deep understanding of how the silicon content affect the formation of intermetallic species and controlled the change of intermetallic layer underneath the overlay. First-principles calculations were performed to evaluate the lattice mismatch between intermetallic species and primary alpha-Al, which gave an interpretation of how the intermetallic species influenced the nucleation behavior of primary alpha-Al during solidification and then controlled the spangle size.

  • 21. Samuelsson, Mattias
    et al.
    Lundin, Daniel
    Jensen, Jens
    Raadu, Michael A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Gudmundsson, Jon Tomas
    KTH, School of Electrical Engineering (EES).
    Helmersson, Ulf
    On the film density using high power impulse magnetron sputtering2010In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 205, no 2, p. 591-596Article in journal (Refereed)
    Abstract [en]

    The influence on thin film density using high power impulse magnetron sputtering (HIPIMS) has been investigated for eight different target materials (Al, Ti, Cr. Cu, Zr, Ag, Ta, and Pt). The density values as well as deposition rates have been compared to results obtained from thin films grown by direct current magnetron sputtering (DCMS) under the same experimental conditions. Overall, it was found that the HIPIMS deposited coatings were approximately 5-15% denser compared to the DCMS deposited coatings This could be attributed to the increased metal ion bombardment commonly seen in HIPIMS discharges, which also was verified using a global plasma model to assess the degree of ionization of sputtered metal One key feature is that the momentum transfer between the growing film and the incoming metal ions is very efficient due to the equal mass of film and bombarding species, leading to a less pronounced columnar microstructure As expected the deposition rates were found to be lower for HiPIMS compared to DCMS For several materials this decrease is not as pronounced as previously reported in the literature, which is shown in the case of Ta. Pt, and Ag with rate(HIPIMS)/rate(DCMS)-70-85%. while still achieving denser coatings.

  • 22. Selvadurai, APS
    et al.
    Kringos, Nicole
    TU Delft, The Netherlands.
    Scarpas, A.
    Bond Stress Development at a Surface Coating Substrate Interface due to the Action of a Nucleus of Thermo-Elastic Strain2008In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 9, p. 1704-1711Article in journal (Refereed)
    Abstract [en]

    The class of problems dealing with surface reinforced elastic media is encountered in many areas of materials engineering, notably in connection with surface layers that are used to provide protection to an otherwise softer substrate. These problems are of particular importance to the assessment of the mechanical behaviour of thin films and other forms of industrial coatings. This paper examines the problem related to the flexure of a plate-like surface layer that is bonded to an elastic halfspace region, and where the flexure of the coating is induced by a nucleus of thermo-elastic strain acting within the halfspace region.

  • 23.
    Thibblin, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB, SE-15187 Sodertalje, Sweden..
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Influence of microstructure on thermal cycling lifetime and thermal insulation properties of yttria-stabilized zirconia thermal barrier coatings for diesel engine applications2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 350, p. 1-11Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) may improve the fuel efficiency of heavy-duty diesel engines by reducing heat losses. A combination of durability, low thermal conductivity, and high directional hemispherical reflectance is required for a TBC in the combustion chamber. These properties are evaluated for yttria-stabilized zirconia coatings, produced using atmospheric plasma spraying (APS) and plasma spray-physical vapour deposition (PS-PVD). The influences of different types of microstructure and metallic coatings on the surface are studied. APS coatings with segmentation cracks and PS-PVD coatings with columnar microstructure have the best thermal cycling lifetime, while nanostructured and conventional APS coatings have the lowest thermal conductivities. The nanostructured APS coating has the highest reflectance at low temperatures, while the columnar PS-PVD coating has the highest reflectance at elevated temperatures. It is further demonstrated that a thin silver layer improves the reflectance of a dense, segmented APS YSZ coating.

  • 24.
    Thibblin, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Scania CV AB.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Influence of microstructure on thermal cycling lifetime, thermal insulation, and mechanical properties of yttria-stabilized zirconia thermal barrier coatingsIn: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) may improve the fuel efficiency of heavy-duty diesel engines by reducing heat losses. A combination of durability, low thermal conductivity, and high reflectance is required for a TBC in the combustion chamber. These properties are evaluated for yttria-stabilized zirconia coatings, produced using atmospheric plasma spraying (APS) and plasma spray–physical vapour deposition (PS-PVD). The influences of different types of microstructure and reflective metallic coatings on the surface are studied. APS coatings with segmentation cracks and PS-PVD coatings with columnar microstructure have the best thermal cycling lifetime, while nanostructured and conventional APS coatings have the lowest thermal conductivities. The nanostructured APS coating has the highest reflectance at low temperatures, while the columnar PS-PVD coating has the highest reflectance at elevated temperatures. It is further demonstrated that a thin silver layer improves the reflectance of a dense, segmented APS YSZ coating.

  • 25.
    Thibblin, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Scania CV AB.
    Kianzad, Siamak
    Scania CV AB.
    Jonsson, Stefan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Mechanical Metallurgy.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Running-in Behaviour of Thermal Barrier Coatings in the Combustion Chamber of a Diesel EngineIn: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coatings (TBCs) have the potential to improve the fuel efficiency of heavy-duty diesel engines by reducing heat losses. A method for in-situ measurement of heat flux from the combustion chamber of a heavy-duty diesel engine has been developed and was used to study the running-in behaviour of different TBC materials and types of microstructures. The in situ measurements show that the initial heat flux was reduced by up to 4.7 % for all investigated TBCs compared to a steel reference, except for an yttria-stabilized zirconia (YSZ) coating with sealed pores that had an increase of 12.0 % in heat flux. Gd2Zr2O7 had the lowest initial value for heat flux. However, running-in shows the lowest values for YSZ after 2–3 h. Potential spallation problems were observed for Gd2Zr2O7 and La2Zr2O7.

  • 26. Århammar, C.
    et al.
    Endrino, J. L.
    Ramzan, M.
    Horwat, D.
    Blomqvist, Andreas
    Rubensson, J. -E
    Andersson, J.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Probing temperature-induced ordering in supersaturated Ti-1 (-) xAlxN coatings by electronic structure2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 242, p. 207-213Article in journal (Refereed)
    Abstract [en]

    The ordering of supersaturated cubic titanium aluminum nitride (c-Ti0.35Al0.65N) coatings is probed from room temperature up to and above the point of spinodal decomposition, using Near Edge X-ray Absorption Fine-structure (NEXAFS) and first principles calculations. The measured and calculated nitrogen (N) K spectra suggest that unoccupied N p states hybridize with Ti d states. When temperature is raised the N p-Ti d overlap decreases, whereas hybridization between N p and Al p tends to increase. The observed spectral changes with temperature together with calculations of defect heat of formation suggest a depletion of N in the surroundings of Ti in c-Ai(1) (-) xAlxN and/or in the formed c-TiN.

1 - 26 of 26
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