ICMCTF2014 Session B5-3: Hard and Multifunctional Nano-Structured Coatings
Tuesday, April 29, 2014 8:00 AM in Room Sunset
Time Period TuM Sessions | Abstract Timeline | Topic B Sessions | Time Periods | Topics | ICMCTF2014 Schedule
B5-3-1 Struture of CrN/NbN Nano-scale Multilayer Coating Deposited by Cathodic Arc Technique
Juliano Araujo, Roberto Souza (University of São Paulo, Brazil); Nelson Lima (Energetic and Nuclear Research Institute, Brazil); André Tschiptschin (University of São Paulo, Brazil)
Nano-scaled multilayer CrN/NbN coatings were produced in an industrial-size cathodic arc physical vapor deposition (PVD) chamber, with an alternate three cathodes (Cr/Nb/Cr) configuration. Microstructural and compositional characterization of the CrN and NbN nanolayers was obtained. Sharp interfaces between the nanolayers were obtained. Four multilayer NbN/CrN coatings were produced with different periodicities (20 nm, 10 nm, 7.5 nm and 5 nm) with total thickness of 30µm in all cases. The coatings were characterized by X-Ray diffraction (XRD) and Transmission Electron Microscopy (TEM), which provided the lattice parameter in each of the constituent layers and structural description of the multilayers, respectively. Coatings were also analyzed in terms of hardness, using an instrumented micro-hardness tester. The multilayer coating system was composed of CrN and NbN with similar structures, but with a lattice mismatch, which varies the fraction of the region with lattice strain depending on periodicity. For the thicker individual layers, the adjustment of lattice parameter at the interfaces does not represent a predominant fraction of the entire structure, i.e. the separate peaks of NbN and CrN can be distinguished in the XRD analysis. In the presence of low periodicity (lower than 10nm), the lattice of each constituent may be coherently strained to each other and just one intermediate lattice (d-spacing) is detected for NbN/CrN multilayer. TEM observations showed that the interfaces were sharp with no apparent interdiffusion. The formation of columnar polycrystalline grain structure in the multilayers of several micrometers in size appear, indicating that despite of stratified structure, grain growth is not always interrupted by the different interfaces. From high to low periodicity, the multilayer NbN/CrN coatings show promising enhancements on hardness. Hence, the interfacial effects can dominate multilayer structure and properties, leading to unusually large strain and a trend for stabilization of metastable structure.
B5-3-2 The Role of a Superelastic Interlayer on the Tribological Behaviour of Hard Coatings
Mauro Callisti (National Centre for Advanced Tribology Southampton, UK); Brian Mellor, Tomas Polcar (University of Southampton, UK)
Hard protective coatings have been undergoing development for decades and further improvement to their mechanical and tribological properties is more and more challenging. Nowadays most research is aimed at improving the tribological behaviour of hard and functional coatings through the optimisation of their microstructure. The combination of different layers is another possible way of improving the tribological behaviour of protective coatings. The use of bonding layers mitigates the differences in mechanical and thermal properties between coating and substrate. As a consequence, the nature of this bonding interlayer plays an important role on the response of the coatings to the complex stress conditions occurring in a tribological scenario.
Among the possible interlayer candidates a layer with the capability of accommodating large deformation, thus protecting the substrate from plastic deformation as well as improving the adhesion of the top layer to substrate, was chosen. One of the potential classes of materials satisfying the above mentioned requirements is the Ni-Ti-based alloys which are known to exhibit superelastic properties also when sputter deposited.
In this study two different superelastic layers were fabricated by magnetron sputtering, namely a Ni-rich Ni-Ti and a (Ni, Cu)-rich Ni-Ti-Cu film, 2 µm thick, were deposited on steel substrates. In order to obtain superelastic properties, the films [#] were isothermally annealed for 1 hour at 500°C in a high vacuum environment. Subsequently the superelastic layers as well as bare steel substrates were coated with a 2 µm thick protective layer (hard and self-lubricant coatings) by magnetron sputtering.
The chemical composition of every single layer was measured by Energy-dispersive X-ray spectroscopy (EDS), while the structure was evaluated by grazing-incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). The mechanical properties of the single layers as well as those of the bilayers were measured by nanoindentation. Finally, the tribological behaviour of the bilayers and of the single layers were characterised by pin-on-disc testing.
The microstructural and mechanical properties of the different designs were correlated and discussed in relation to the measured tribological properties. A first comparison was performed in order to evaluate whether the use of a superelastic interlayer was beneficial to the tribological behaviour of a functional top layer. In addition the use of different superelastic interlayers, i.e. Ni-Ti and Ni-Ti-Cu, in the bilayers was investigated, the Ni-Ti-Cu being characterised by a different microstructure compared to the Ni-Ti composition.
B5-3-3 Contemporary Thin Film Ceramics Behaviour in the Extreme Environments
Vladimir Vishnyakov (Manchester Metropolitan University, UK)
All manmade relies on materials. New technologies require temperatures and working environments well beyond ability of traditional alloys and thin films. Thin films provide economy of scale, deliver exclusive properties to the point of exploitation and in many cases exist in the state which is impossible to achieve in the bulk form. The choice of thin film for the application needs to rely on understanding of the application condition and film/substrate behaviour in the application environment. The hardness and good oxidation resistance are not enough to satisfy diversity of application and environments. Slowly the pattern of thin film properties satisfying particular extreme environments is developing and this will help to predict film behaviour at the punishing conditions of multiple damage events, critical loads and high temperatures. New ternary and quaternary ceramic films such as naturally nano-laminated MAX phases and amorphous carbonitrides have excellent potential and are the candidate materials to be used in most demanding applications. Understanding the deposition conditions and further material characterisation are vital for the insight of the link between chemistry, atomic structure, bonding and engineering properties of such films. The paper will review our contemporary understanding of the chain from basic principles to the applications.
B5-3-5 The Microstructure and Mechanical Properties Evaluation of Cr-Si-B-N/Ti-Si-B-N Multilayered Thin Films
Li-Chi Hsu, Jyh-Wei Lee (Ming Chi University of Technology, Taiwan)
Recently, the boron contained transition metal nitride thin films have been studied extensively due to their excellent mechanical and thermal properties. The addition of Si element into such nitride coating also provided amorphous phase to strengthen the coating effectively by the formation of a nanocomposite microstructure. In this study, the Cr-Si-B-N/Ti-Si-B-N multilayered thin films with different Si contents were deposited by a reactive pulsed DC magnetron sputtering system using CrB2, TiB2 and Si targets. The phase structure of coatings was studied by means of the X-ray diffractometer (XRD). The microstructures of thin films were examined by the field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The nanoindentation, scratch tests, Daimler-Benz Rockwell-C (HRC-DB) adhesion tests, pin-on-disk wear tests were used to evaluate the hardness, adhesion, and tribological properties of thin films, respectively. It was observed that the nanocomposite microstructure of Cr-Si-B-N/Ti-Si-B-N multilayered thin films was obtained when the proper silicon content was controlled. Effects of silicon contents on the microstructure, hardness and tribological properties of coatings were discussed in this work.
Keywords: Cr-Si-B-N/Ti-Si-B-N multilayered thin film, nanocomposite, nanoindenter, scratch test, Daimler-Benz Rockwell-C adhesion test
B5-3-6 Study of Sensing Properties of Zinc Oxide and Cu-doped Zinc Oxide Nanowires
YuWen Yeh, Chuan-Pu Liu (National Cheng Kung University, Taiwan); RueyChi Wang (National Kaohsiung University, Taiwan); Jow-Lay Huang (National Cheng Kung University, Taiwan)
In this study, a single ZnO nanowire detector is described. ZnO and Copper doped ZnO nanowires have been prepared by low-temperature chemical vapor deposition method at 575°C. The morphology and microstructure of the nanowires were characterized by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM), respectively. Low temperature photoluminescence spectroscopy is employed to analyze optical emissions of nanowires. With X-ray diffraction (XRD), we can investigate that Cu-doped ZnO nanowires are hexagonal phase with c-axis orientation. The X-ray photoelectron spectroscopy (XPS) data indicated that doping concentration of copper was high to 3.0 at%. The sensor device was fabricated by the e-beam lithography technology.
Keywords: ZnO nanowires, Cu-doping, chemical vapor deposition, gas sensor
B5-3-7 Fabrication of n-type ZnO and p-type Cu2O Nanostructures and its Photoelectrochemical Properties
Yen-Hsing Chen, Yu-Min Shen (National Cheng Kung University, Taiwan); Sheng-Chang Wang (Southern Taiwan University, Taiwan); Jow-Lay Huang (National Cheng Kung University, Taiwan)
In this work, n-type ZnO and p-type Cu2O nanostructures e lectrodeposited via high aspect ratio anodic alumina oxide (AAO) template assistance, using ZnSO4 and CuSO4 electrolyte, respectively. The ZnO and Cu2O nanostructures of morphology and crystallinity were characterized by using X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The thickness and channel diameter of AAO template were about 150 μm and 110~160 nm, respectively. ZnO nanostructures fabricated under various electrolyte concentrations of 0.1M and 0.5M ZnSO4 were nanotubes and nanowires, respectively. The Cu2O contained in Cu/Cu2O complex nanowires will increase with decreasing deposition current density. Both ZnO and Cu/Cu2O nanostructure were uniformly corresponded to AAO’s pore size, the diameter was about 140 nm. The carrier concentrations of the films were calculated by Mott–Schottky equation from Electrochemical Impedance Spectroscopy (EIS). The films were examined by one-step and two-step systems for hydrogen evolution from water splitting under visible light illumination, hydrogen generation efficiency were calculate by photocurrent from photoelectrochemical analysis (PEC) in Na2SO4 solution.