Syposium E Poster Session

Thursday, May 2, 2013 5:00 PM in Room Grand Hall

EP1 Controlled Vacuum Annealing of TiZrN Thin Film on Si (001) and AISI 304 Stainless Steel Deposited by Unbalanced Magnetron Sputtering
Po-Hsien Wu, Jia-Hong Huang, Ge-Ping Yu (National Tsing Hua University, Taiwan, Republic of China)
The purpose of this study is to investigate the effect of controlled vacuum annealing of TiZrN thin film at different temperature. After heat treatment, TiZrN thin film was expected to have no apparent changes in the mechanical properties and no oxide on the surface of thin film. A series of TiZrN coatings were deposited on Si (001) and AISI 304 stainless steel substrates using unbalanced magnetron sputtering. Specimens were later annealed respectively at different temperature ranging from 700°C to 1000°C for 1 hour to 4 hours in vacuum(4.5X10-6torr). X-ray diffraction (XRD) was used to characterize the microstructure of the TiZrN films. The texture coefficient and grain size were both calculated according to the result of θ/2θ scans. Coating thickness was obtained from field-emission gun scanning electron microscope (FE-SEM). X-ray photoelectron spectroscopy (XPS) was used to characterize the bonding state and compositions of the coatings. The hardness of the TiZrN films was measured using nanoindenter. Secondary Ion Mass Spectrometer (SIMS) was used to characterize the compositional depth profiles. The residual stress was determined by laser curvature methods. The electrical resistivity of the TiZrN films was measured using a four-point probe. The corrosion resistance of the TiZrN thin films was obtained from potentiodynamic scanning conducted from -600 to 800 mV in 1M H2SO4 +0.05M KSCN solutions respectively. After heat treatment, there is no oxide observed on the surface of TiZrN thin films. The residual stress was relaxed after heat treatment. The grain size increased slightly after heat treatment. T he texture coefficient was still (111). The hardness and the electrical resistivity of TiZrN thin film both were lower.
EP2 Fracture Toughness Measurement of ZrN Hard Coatings
Yu-Hsiang Chen, Ge-Ping Yu, Jia-Hong Huang (National Tsing Hua University, Taiwan, Republic of China)
Hardness is one of the important mechanical properties of hard coatings, but toughness is even more crucial in the engineering applications. Many techniques have been developed for assessing fracture toughness of hard coatings; nevertheless, there is still no standard testing method. Although several methods such indentation, buckling, bending, and tension tests can be used to quantitatively measure the fracture toughness of bulk materials, these stress-based methods cannot be directly applied on hard coatings. Owing to the thickness limitation of thin films, specific substrate shape and micro-precracks are difficult to be routinely produced. On the other hand, for thin-film coatings, the energy-based methods may be better than stress-based methods in the measurement of fracture toughness. However, external stress is commonly needed to apply on the specimens in both techniques, which also complicate the experimental setup. Recently, we developed an energy-based technique by controlling the residual stress and film thickness, without applying external stress, to measure the fracture toughness of TiN hard coatings, in which the substrate and size effects were greatly reduced. The results showed that the fracture toughness of random-textured TiN hard coating was 16.7 J/m2 which is close to previous literature values. Since ZrN coatings have better corrosion resistance, lower resistivity, and higher mechanical properties than TiN coatings, while fewer toughness data of ZrN are available. The purpose of this study was to measure the fracture toughness of ZrN hard coatings. Following our previous testing technique, residual stress was used as the stress source for the toughness measurement, which could be measured by the laser curvature method. By controlling the deposition parameters and film thickness the residual stress of ZrN films could be adjusted. From fracture mechanics, the average storage energy (Gs) can be evaluated by the stress difference before and after crack initiated, and then the toughness of the ZrN coatings can be obtained from Gs, and the critical thickness can also be assessed.
EP3 Producing Thick TiN Films by Controlling Deposition Parameters in Magnetron Sputtering
MingLun Cai, Ge-Ping Yu, Jia-Hong Huang (National Tsing Hua University, Taiwan, Republic of China)

Due to its superior mechanical properties, titanium nitride (TiN) has been widely applied in industry, especially in hard and protective coatings. For the deposition of TiN coatings, people usually focused on adjusting the deposition parameters, such as bias voltage, nitrogen flow rate and substrate temperature, to produce harder and thicker coatings. However, as the film thickness increases to a few μm, the residual stress may increase concomitantly and thereby causing film spallation. The purpose of this study was to develop a deposition method to produce TiN coatings with a thickness larger than 3 μm and above without using Ti interlayer, in other words, to produce a thick TiN coating with low residual stress.

TiN was deposited on p-type (100) Si by unbalanced magnetron sputtering (UBMS). The controlling deposition parameter was either the opening of gate valve between turbomolecular pump (TP) and deposition chamber or the pumping speed of TP. The flux of argon and nitrogen was adjusted at a fixed ratio to maintain the same pressure in the chamber. The film thickness was measured by scanning electron microscopy (SEM). The Hardness of the film was measured using nanoindentation (NIP). X-ray photoelectron spectroscopy (XPS) was used to characterize the bonding state and compositions of the coatings. The preferred orientation of TiN coating was determined using X-ray diffraction (XRD). Laser curvature method was used to measure the residual stress of the TiN film. Using the proposed method, we could successfully produce TiN films with a thickness more than 4 μm and the residual stress was less than -2 GPa. By lowering pumping speed, the lifetime of TP can be effectively prolonged, which would be beneficial to the hard coating industry.

EP4 Wear Behavior and Failure Mechanism of a Solid Lubricant Coating on One Side or Both Sides of Counterbodies
Jiao Yang, Vincent Fridrici, Philippe Kapsa (Ecole Centrale de lyon, France)

Wear is the progressive damage, which occurs on the surface of a component as a result of its motion relative to the adjacent working parts. To prevent from wear damage, solid lubricants have been introduced to protect the surface of materials and to prolong the service life of element. In the past 40 years, many studies have been done on them, especially for the MoS2 coating. The experimental studies described in the previous works are all based on the observed trend using the coated flat substrate. Experiments on the comparison of MoS2 based coating lifetime under one side coated or two side coated counterbodies is, however, lacking, which is popular problems in the linear guidance system and ball screw drives.

Therefore, it is interesting to do some research to explore the effect of coating position on the coating lifetime and friction coefficient. In this study, the coating was sprayed on the ball or cylinder and flat substrate. The FE model was chosen to model the stress distribution for different conditions, to get a better understanding of the wear mechanism of the coating.

In this study, an aerosol sprayed MoS2 based varnish was deposited on a cleaned and polished 304 stainless steel flat surface and AISI52100 ball or cylinder surface at room temperature. The thickness of the coating is about 10 µm (flat) and 12 µm (ball and cylinder). The normal force is varied from 100 N to 1000 N and displacement amplitude is from ± 10 µm to ± 40 µm.

Some results could be drawn from this study. Firstly, the coating sprayed on substrate will lower contact pressure and enlarge the contact area. The coating on the flat has the similar maximum contact pressure as coating on the cylinder or ball, but they have different contact areas. Secondly, under lower contact pressure of cylinder-on-flat, there is a significant stress gradient between substrate and coating, especially at the interface of coating and substrate. Hence, coating failure occurs easier at the interface, which leads to a lower coating lifetime. In this low contact stress situation, patches of debris appears to be extruded back and forth in steady-state sliding, while in the high contact stress, this debris movement is delayed. The plastic shearing of the junctions forms plucks off the tips of the softer asperities leaving them adhering to the harder surface in the high contact stress, thereby forming the tribo-film and bringing a longer lifetime. Thirdly, the coating on the ball/cylinder has always higher coating lifetime than coating on flat, because the debris generated between two contact bodies could form more easily the transfer film or stay on the wear track.

EP5 Investigation of Internal Stress Levels and Characteristics during Electrocodeposition of Ni-MoS2 Composite Coatings
Ebru Saraloglu Guler, İshak Karakaya (Middle East Technical University, Turkey); Erkan Konca (Atilim University, Turkey); Metehan Erdoğan (Middle East Technical University, Turkey)

Internal stress in plated deposits has been a common problem that may affect the functionality of coatings. Coatings may develop cracks, blisters, distortions and peel away from the substrate material when the stress levels are high. Electrodeposition parameters, such as; current density, coating thickness, pH and temperature of the bath affect the levels and the characteristics of internal stress of coatings. Furthermore, insoluble particles in electrocodeposition are also expected to make contributions. The influence of the electrocodeposition parameters and their interaction effects on the internal stress during the electrodeposition of Ni and Ni-MoS2 composite coatings were studied by fractional factorial design. The parameters studied and their ranges were; MoS2 particle concentration (0-5 g/l), temperature (30-50ºC), pH (2-4), current density (1.2-4.8 A/dm2), and coating thickness (25-50µm). MoS2 addition into Watts bath resulted in the decrease of the tensile internal stress values of the composite coatings or even changed the stress character from tensile to compressive. Moreover; low stress values were obtained when pH was low and coating thickness was high. The temperature of the Watts bath did not show a significant effect. However, the effect of current density was seen to depend on other electroplating parameters.

EP6 Impact Wear Resistance of CrN, CrAlN and TiAlN PVD Coatings on Cemented Carbide and M2 Steel Substrates
Jiliang Mo, Minhao Zhu (Southwest Jiaotong University, China); Sarah Banfield (University of Sheffield, UK); Jonathan Housden (Tecvac Ltd, UK); Adrian Leyland, Allan Matthews (University of Sheffield, UK)
The impact wear resistance of CrN, CrAlN and TiAlN coatings deposited on cemented carbide and M2 steel substrates by an electron-beam (EB) plasma-assisted (PA) Physical Vapour Deposition (PVD) technique were evaluated by dynamic ball-on-plate impact wear testing. The test is used to assess the resistance of coatings to dynamic, high-cycle loading caused by the repeated impact of a 6 mm diameter tungsten carbide ball at a impact frequency (f) of 9 Hz. After the wear tests, the wear craters were studied by stylus profilometry, SEM and EDX, to investigate wear behaviour. It is shown that all the three coatings on cemented carbide substrates exhibited good impact wear resistance. The impact wear mechanisms were mainly adhesive wear. No interface failure was found and the impact wear process of the coatings can be described as a gradual process of reduction in coating thickness by repeated impact loading. The maximum depths of the wear craters of the three coatings on M2 steel substrates were much higher than the coating thickness as soon as the coatings were subjected to 103 impact cycles; however, the coatings still remained on the surface in good condition until a certain much higher impact cycles when the coatings were damaged by main impact wear mechanisms of micro-cracking and micro-spallation.
EP7 Examples for the Time Dependent Effective Indenter Concept
Nick Bierwisch (Saxonian Institute of Surface Mechanics, Germany); Norbert Schwarzer (Saxonian Institute of Surface Mechancis, Germany); Arif El Seweifi (Forum Zehlendorf, Germany); Michael Griepentrog, Philipp Reinstädt (BAM Berlin, Germany)

The effective indenter concept was introduced by Bolshakov et al in 1995 [1]. It's well known that this concept is the theoretical basis of the standard analysis method for nanoindentation measurements, the Oliver & Pharr method [2]. With some extensions this concept is also applicable to more complex mechanical contact experiments on layered or viscose materials for normal and multi-axial loading conditions. This was shown in many papers in the last 15 years [e.g. 3,4].

This work will focus on presenting examples for these extensions, mainly the extension for time dependent material behaviour. So analysis results for viscose materials (like polymers or soft metals) for different test methods (indentation, scratch and tribotests) will be presented.

[1] A. Bolshakov, W. C. Oliver, G. M. Pharr, MRS Symp. Proc 356, p 675 (1995)

[2] W. C. Oliver, G. M. Pharr, J. Mat. Res. 7 (1992) 1564-1583.

[3] N. Schwarzer, J. Mater. Res., Vol. 24, No. 3, March 2009, 1032 – 1036

[4] N. Schwarzer, Phil. Mag. 86 (33-35) 21 Nov – 11 Dec 2006, 5153 – 5767

EP8 Effect of Implant Diameter and Length on Stress Distribution for Titanium and Zirconia İmplants with 15° Angled Abutment by using Finite Element Analysis (FEA)
Filiz Karabudak, Ruhi Yesildal, Funda Bayindir (Atatürk University, Turkey)
The purpose of this study was to analyze stress distribution patterns in implant restorations created in different length and diameter made of titanium and zirconia with 15° angled abutment by using three dimensional finite element analysis. For Titanium models; Ti-6Al-4V for implant fixture, connection element and abutment, yttrium tetragonal zirconium polycrystal (Y-TZP) for zirconium framework, feldsphatic porcelain for superstructure material and for zirconia models; Y-TZP for implant fixture, connection element, abutment and zirconium framework, feldsphatic porcelain for superstructure material were used. A comparison of the areas between titanium and zirconium implants with maximum stress for implants of the same length but different diameters and same diameters with different lengths showed different variances.Key Words: Zirconia, Titanium, MIMICS, feldsphatic porcelain, Stress analaysis, implant lenth, implant diameter
EP9 Coated Polymers for Low Friction and Wear of Roller Bearing Cages in Lightweight Design
Thomas Sander, Bernd Vierneusel, Stephan Tremmel, Sandro Wartzack (Friedrich-Alexander-University Erlangen-Nuremberg, Germany)
Solid cages made of polymer materials are often used in high-speed rotary bearings to keep the inertial forces small. The freedom in geometric design due to the injection molding process allows the realization of sustainable cage shapes. The material polyamide PA 66 is already being used in mass-produced bearings, often glass fiber reinforced to increase strength, modulus of elasticity and maximum operating temperatures. To improve the tribological properties of PA 66, particles of the solid lubricant MoS2 can be added to the plastic granulate. However, the mechanical properties are deteriorated by these particles since they are usually the starting point of cracks and fractures. As an alternative to these composite materials, the friction between cage and rolling elements can be reduced by the use of PTFE, having a substantially higher density, lower strength and a lower modulus of elasticity, in comparison with PA 66. The wear on the cage has a significant influence on the cage pocket clearance or rib guidance clearance. Dynamic bearing analyses show that this in turns has influence on the hydrodynamic pressure buildup in the gaps. Consequently, a suitable cage material must provide a variety of positive characteristics in a balanced relationship with each other. The PVD thin film technology allows the combination of a suitable substrate material with low density, high strength and stiffness with the excellent tribological sliding properties of the coating material, without affecting the tolerances uncontrollably. This poster gives an overview of conventional cage materials and layer combinations on fiber reinforced polyamide substrates regarding friction and wear on the basis of model tests. The possibility of variation of the sputtered solid lubricant molybdenum disulfide by modification of the microstructure and by doping elements is in the focus of the investigations. The tribological and mechanical properties are compared with sputtered a-C (amorphous carbon film) and conventional materials for roller bearing cages. The coating adhesion is determined by a modified scratch test for polymer substrates.
EP10 Tribological Properties of Hard a-C:H:F Coatings
Cedric Jaoul (Université de Limoges - CNRS, France); Olivier Jarry (Sulzer Sorevi); Pascal Tristant (Université de Limoges - CNRS, France); Etienne Laborde (Université de Limoges - CNRS); Maggy Colas, Jean-Pierre Lavoute (Université de Limoges - CNRS, France); Laureline Kilman (Sulzer Sorevi); Hélène Ageorges, Christelle Dublanche-Tixier (Université de Limoges - CNRS, France)

Hydrogenated amorphous carbon (a-C:H) thin films are among the best coating solutions for the reduction of automotive fuel consumption because of its very good tribological properties. Quite high values for hardness are required to withstand high contact pressure occurring for example in the cam-tappet contact in automotive motorsport engine. Commercial coatings exist with adapted sub-layers to obtain a good adhesion of highly stressed DLC (Diamond-Like Carbon) on the steel substrate. Since wear can occur, the development of wear-resistant coating is still necessary.

Each deposition process lead to a DLC film with specific properties correlated with hydrogen content and sp3/sp2 bonded carbon ratio. Many elements have been introduced in the a-C:H matrix to modify and improve some properties of this material. For fluorine containing DLC, friction and wear properties improvement can be observed [1] but hardness is strongly decreasing with fluorine introduction [2]. Objective is thus to obtain hard a-C:H:F with enhanced tribological properties compared to standard a-C:H without changing deposition parameters.

DLC films are produced by radio-frequency PECVD with different combinations of precursors in order to explore various F/H ratios. ERDA-RBS measurements are performed to determine the chemical composition of the films. Chemical bonding is observed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Then, Young modulus and hardness are measured by nanoindentation. To conclude, tribological tests are performed with a ball-on-disc tribometer to measure wear resistance and friction coefficient in dry conditions. Fluorine introduction led to a decrease of hydrogen content and hardness. Coatings with less than 6 at.% of F kept a hardness superior to 28 GPa and wear resistance was improved.

[1] Donnet C., Recent progress on the tribology of doped diamond-like and carbon alloy coatings: a review, Surface and Coatings Technology, 1998, vol. 100-101, p. 180-186

[2] Bottani C.E., Lamperti A., Nobili L., Ossi P.M., Structure and mechanical properties of PACVD fluorinated amorphous carbon film, Thin Solid Films, 2003, vol. 433, p. 149-154

EP11 Microtribological Properties of Extremely Thin Diamond-like Carbon Films Deposited using Bend-type Filtered Cathodic Vacuum Arc and Electron Cyclotron Resonance Chemical Vapor Deposition Techniques
Shohei Yamazaki, Shojiro Miyake (Nippon Institute of Technology, Japan)
In magnetic storage devices, nanometer scale wear and minute fluctuations in friction degrade equipment performance. Therefore, an improvement in the nanotribology of the magnetic head medium is important for the advancement of the fast growing magnetic recording industry. Thus, extremely thin protective films play an important role in realizing higher reliability magnetic storage devices. In this study, m icrotribological properties such as nanoscratching, nanowear, and low load reciprocating friction of extremely thin diamond-like carbon (DLC) films deposited using bend-type filtered cathodic vacuum arc (FCVA) and electron cyclotron resonance chemical vapor deposition (ECR-CVD) techniques were evaluated. The structure and composition of these DLC films were evaluated using Raman spectroscopy, transmission electron microscopy, and auger electron spectroscopy (AES). These analyses showed that the FCVA-DLC films have tetrahedral structures, while the ECR-CVD-DLC films have a-CH structures. The AES measurements showed that the actual thickness after deposition matched the target thickness. The nanoindentation hardness and nanowear resistance were evaluated by atomic force microscopy. The nanoindentation hardness of the 100-nm-thick DLC films deposited by FCVA and ECR-CVD were 57 and 25 GPa, respectively, at a 40 mN load. However, it was difficult to evaluate the hardness of DLC films with a thickness of a few nanometers by this nanoindentation test. In contrast, nanometer scale wear tests could be used to evaluate the extremely thin DLC films. The wear depths of 1.0- and 2.0-nm-thick FCVA-DLC films were extremely low at less than 1.0 nm, even after 20 sliding cycles. The wear depths of 0.8-, 1.0-, and 2.0-nm-thick ECR-CVD-DLC films were nearly 1.0 nm after only one sliding cycle and exceeded the film thicknesses after a few sliding cycles. These results reveal the differences in the nano wear resistance between these extremely thin DLC films and the superior nano wear resistance of FCVA-DLC thin films. In a 10 mN load reciprocating friction test, the friction coefficients of nanometer-thick ECR-CVD-DLC films fluctuated, and the damage caused to these films was greater than that caused to the FCVA-DLC films. On the basis of the dependence of the friction properties on the film thickness, we can conclude that the friction coefficients of FCVA-DLC films are low and stable. In contrast, the friction coefficients of ECR-CVD-DLC films that are thinner than 1.0 nm are as high as those of Si (100) substrates. Therefore, these results reveal the excellent wear resistance of extremely thin films deposited by FCVA.
EP12 Deposition and Tribological Properties of Multilayer and Mixed Films Composed of Gold and Diamond-like Carbon
Shindo Takanori, Miyake Shojiro (Nippon Institute of Technology, Japan)

To improve the tribological properties of materials for use in various fields, the application of solid lubricant films that lower the friction coefficient is desirable. Among solid lubricant materials, although soft metals have a higher friction coefficient and poorer durability than other solid lubricants such as graphite and MoS2, these metals are currently used in electrical and mechanical parts such as electrical contacts owing to their high electrical conductivity. Therefore, low-friction, wear-resistant electroconductive solid lubricant films are desired. In contrast, diamond-like carbon (DLC) films have low friction and high wear resistance. Coating with hydrogen-free DLC films is highly advantageous. Lubricants such as polyalphaolefin (PAO) with and without glycerol monooleate (GMO) are capable of significantly reducing the friction of hydrogen-free DLC films under boundary lubrication conditions. Research on the development of nanometer period multilayer films for improving film hardness has thus been carried out. To apply these multilayer films as solid lubricants, we proposed a nanoperiod multilayer solid lubricant film with friction lower than that of conventional solid lubricants. This study aims to realize lower friction and electroconductive solid lubricant films on the basis of a nanoperiod multilayer solid lubricant model. To develop electroconductive solid lubricant films, multilayer and mixed films composed of gold and DLC layers were deposited using bias radio frequency sputtering. Then, the electroresistivity and tribological properties of the deposited films were evaluated. The electroresistivities of 80 at% gold-DLC multilayer and mixed films were low at values less than 0.03 Ω cm, while the electroresistivities of 50 at% gold content multilayer and mixed films were low at 15–18 Ω cm. The 50 at% gold content multilayer films had a higher Young’s modulus and hardness than the gold monolayer films and values similar to those of DLC films.

The friction coefficient of the nanoperiod multilayer film was the lowest of all the tested samples. In addition, the wear depths of the multilayer films were smaller than those of the gold and DLC mixed and monolayer films in air. The friction coefficient and wear durability were considerably improved for the multilayer films among the samples tested under water boundary lubrication conditions. Under PAO boundary lubrication conditions with and without GMO, the wear durability of the multilayer films was superior, and the damage to the multilayer films was less than that for the gold monolayer film and similar to that for the DLC film.

EP14 Deposition and Characterization of Bismuth Containing Hard Coatings
Roberto Mirabal, Sandra Rodil, Phaedra Silva-Bermudez, Stephen Muhl, Giovanni Ramirez (Universidad Nacional Autónoma de México - Instituto de Investigaciones en Materiales, Mexico); Joao Oliveira, Albano Cavaleiro (Faculdade Ciencias E Tecnologia Da Universidade De Coimbra, Portugal)

Bismuth is a soft semimetal with a rhombohedral graphite-like quasi-layered structure and a low melting point of 271oC. These characteristics point to the use of Bi or Bi-compounds for self lubrication applications where low friction and low wear rates are required. However, pure Bi and its compounds are very soft. Therefore our proposal is the inclusion of Bismuth into a hard coating using the methodologies developed for nanocomposite thin films; either as nano-sized particles into a hard matrix or as a lamellar structure, alternating a bismuth layer with a hard-coating layer. Then, the excellent frictional properties of Bismuth could be exploited in combination with materials that provide mechanical resistance. Bismuth sputtered films for mechano-tribological applications and its addition into metal nitride coatings have been poorly studied, therefore there is a strong need to define the deposition conditions adequate to achieve a stable and adhered coating. In this work, we report the deposition of Bismuth containing niobium nitride coatings using a confocal dual sputtering system. Both targets (2”) were ignited simultaneously, but using different powers; 400 W direct current for the Nb target (99.95 %) and 6,10 and 20 W radio frequency for the Bi target (99.999%). The coatings were deposited on Silicon at 200 oC using a mixture a fixed Ar/N2 (14/6) flow ratio. The deposition pressure was 3 mTorr starting from a backing pressure below 5x10-6 Torr. The composition of the coatings was obtained by both X-ray photoelectron, to clearly detect the presence of oxidized phases, and energy dispersive spectroscopy, in order to detect the presence of segregated bismuth. The Bi segregation and NbN structure were also studied by X-ray diffraction. The coefficient of friction of the coatings was measured by pin-on-disk tests using a load of 5 N and a sliding distance of 500 m.

Acknowledgement: The research leading to these results has received funding from the European Community Seven Framework Program (FP7-NMP-2010-EU-MEXICO) and CONACYT under grant agreements Nº 263878 and 125141, respectively.

EP15 A Laboratory-scale Pin-sliding Instrument for Triboluminescence Measurement
Sirichai Leelachao, Shinji Muraishi (Tokyo Institute of Technology, Japan)

A report on the design and construction of an inexpensive, compact triboluminescence measuring setup is presented. The system simply composes of a rotating stage and a stainless steel sliding pin. The counter pin is interchangable. An optical fiber, being connected to spectrophotometer, is used for detecting the generated light signal from the luminescent materials. A visible emission is measured from the bottom of the contact area. Any experimental parameters, such as an external load or rotation speed, are able to be adjusted. ZnS-based phosphor powders are selected as a reference sample. A characteristic emission from substitutional Mn+2 ions at wavelength of 580 nm is able to be recorded even the load is 0.5N. Further information of the equipment with the results on triboluminescence of the phosphors are also included and discussed.

EP16 An Overview of Interfacial Fracture Energy Predictions for Stacked Thin Films Using Four-Point Bending Framework
Chang-Chun Lee, Yi-Jing Lai (Chung Yuan Christian University, Taiwan, Republic of China); Chien-Chao Huang (National Nano Device Laboratories, Taiwan, Republic of China)
Adhesion of stacked thin films in advanced devices becomes significantly important as the concerned characteristic dimensions continue scaling down to the regime of several nanometers. The occurrence of interfacial fracture is easily examined during the manufactured process with thermal cycles and the inherent poor adhesions of stacked films. Therefore, developing a robust predicting methodology regarding interfacial fracture energy of dissimilar materials is necessary and urgent to meet the mechanical requirements of investigating novel material and subsequent device structures. For this reason, in according with interfacial fracture mechanics, this research overviews several useful approaches, such as J-integral method, modified virtual crack closure technique (VCCT), and analytical solutions derived from the relation between stress field of delaminated tip and crack tip opening displacements (CTOD). Through the testing vehicles of four-point bending framework, the validations of foregoing predicted approaches by using finite element analysis (FEA) are acquired as comparing the simulated results with related experimental data. The critical energies of 18J/m2, 78.53J/m2, 52.01J/m2, and 71.02J/m2 for the bonded interfaces of SiO2/SiLK, Ta/SiLK, TaN/SiLK, and Si3N4/SiLK stacked thin films are precisely judged, respectively. Predicted results of J-integral method match well with the estimation of modified VCCT. As the interfacial crack length increases, the results reveal that opening fractured mode is dominant at the beginning of crack advances along bonded interface of Ta/SiLK, TaN/SiLK, and Si3N4/SiLK stacked film. All the results shown in this research could be regards as a design guideline of interfacial fractured behavior for stacked films utilized in the developments of advanced device technologies.
EP17 Thermo-mechanical Failure Behavior of Copper TSV Induced by Transient Selective Annealing Technology
Chang-Chun Lee, Yin-Hao Lin (Chung Yuan Christian University, Taiwan, Republic of China); Chien-Chao Huang (National Nano Device Laboratories, Taiwan, Republic of China)
For the purpose of providing multi-functions in a complicated microsystem, the use of three-dimensional (3D) integrated circuit (IC) technology with through silicon via (TSV) interposers is regarded as a promising framework to meet the foregoing requirements. However, managing the related process stability of 3D-IC manufactured integration is still a thorny issue, especially for the thermo-mechanical behavior of copper filled TSV interposer during the annealing operation. In this work, a transient annealing process is successfully applied on the filled copper only, that is, one selective heating technology. To address this concerned problem, a transient thermal-structural coupling analysis by using a nonlinear finite element simulation is proposed. As compared with the experimental data, the present simulated methodology is validated to be highly reliable. The analytic results show that high temperature deteriorates from the top surface of copper TSV to other regions within a silicon-based TSV interposer. Via a transformation of the above-mentioned thermal load in a mechanical analysis, the maximum thermal stress is examined to occur on the exposed top surface of silicon interposer close to interface between copper TSV and Ta thin barrier film when the power keeps supply for the annealing of copper metal. In other words, the phenomenon of stress-induced fracture among bonded films is prone to be observed so as to worsen subsequent mechanical reliability of 3D-IC devices. In accordance with the results presented in this investigation, the improvement could be suggested and acquired by optimizing the fabricated parameters in annealing processes. The technology provides a high throughput and reliable process on TSV manufacturing.
EP18 Global Elastic Anisotropy of Polycrystalline Metallic Thin Films and Multilayers
Damien Faurie, Philippe Djemia (LSPM-CNRS, Université Paris 13, Sorbonne Paris-Cité, France); Eric Le Bourhis, PierreOlivier Renault (Institut P' - Universite de Poitiers, France); Olivier Castelnau (PIMM, ENSAM Paris, France); Renald Brenner (UMPC, Paris, France); Philippe Goudeau (Institut P’ - Université de Poitiers, France)

Elastic properties of anisotropic metallic thin films were investigated experimentally by several complementary techniques, namely in-situ tensile testing under X-ray diffraction (XRD), nanoindentation, and Brillouin light scattering (BLS). Specimens were probed along different directions to reveal the strong effects of elastic anisotropy at the (local) grain and (global) film scales. XRD allows the investigation of both local and global anisotropies, while BLS and nanoindentation are limited to global analyses. A micro-mechanical model, based on the Self-Consistent scheme, and accounting for the actual microstructure of the films, is applied to interpret experimental data. Although different kind of elastic constants can be determined with the used experimental techniques (static/dynamic, local/global), a good agreement is obtained, showing that comparison of these techniques is feasible when carried out carefully.

In the case of nanometric multilayers, a three-scale transition model is proposed for estimating the effective elastic constants from the intrinsic properties of elementary constituents (grains), taking into account the thickness ratio of each sublayer (in the case of multilayers) and the grains orientation distribution in each kind of layers. We show that the elastic anisotropy at the sample scale can be greater in the case of multilayers than in the case of single-layers, as confirmed experimentally by Brillouin light scattering.

EP19 On the Meaning and Requirements of the Concept of an Effective Indenter
Marcus Fuchs (Chemnitz University of Technology, Germany)

The Oliver & Pharr method [1] is probably the most widely used methodology for the analysis of nanoindentation measurements in order to mechanically characterize thin films and coatings. It is based on the implicit assumption of the concept of an effectively shaped indenter which was introduced later by Bolshakov [2]. This concept implies certain model assumptions (e.g. a flat surface and a monolithic half space) which may not be met by sophisticated coating structures. Nevertheless, the Oliver & Pharr method is frequently used in literature to analyze such sophisticated coating structures (e.g. multi-layer coatings, thin films, gradient coatings), even though extensions to this method allowing a proper analysis of such sophisticated surface structures have already been developed by Schwarzer [3]. This work will explain the model assumptions in order to help understanding them by means of adapted schemata of the “effective indenter” concept and examples which illustrate the significant differences in the analysis results (e.g. elastic modulus E, hardness H, yield strength Y, stress profiles, etc.) between the original Oliver & Pharr method and the extended one by Schwarzer.

[1] W. C. Oliver, G. M. Pharr, J. Mat. Res. 7 (1992) 1564-1583.

[2] A. Bolshakov, W. C. Oliver, G. M. Pharr, MRS Symp. Proc 356, p 675 (1995).

[3] N. Schwarzer, J. Phys. D: Appl. Phys., 37 (2004) 2761-2772.

EP21 Friction Characteristics Degradation of Cup Anemometer used for Wind Energy Potential Measurements
Miodrag Zlatanovic (School of Electrical Engineering, Serbia); Djordje Romanic (Republic Hydrometeorogical Service, Serbia)
The first step in order to minimize the error in predicting a wind farm production is to improve the wind measuring technique and long term wind climate prediction methods. Wind speed sensors based on different measuring principles are used but cup anemometers invented nearly 170 years ago still serves as a reference instrument. The angular velocity of this anemometer is directly proportional to the wind speed. Since the instrument contains moving parts some degradation of performance may occur during long term operation at open field conditions. Several material pairs for manufacturing the shaft and bearing as a tribological pair used for cup anemometer construction were selected. Special lubricants were applied to lower the friction coefficient in case of metal contact surface, but in some cases self lubricated tribological pairs were used. Long term field operation of NRG #40 cup anemometer with the shaft made of fully hardened beryllium copper and self-lubricating modified teflon bearings was analyzed. Sensor performance degradation due to dry friction whip was found and analyzed in details in several papers. In this paper the degradation of anemometer performance detected after three years of continuous operation was investigated and recalibration was carried out in an aerodynamic tunnel. A significant change of calibration curve was found with increased offset value. The origin of calibration offset is mostly due to the aerodynamic torque, but in considered case the friction torque influence not clearly related to dry friction whip was found. A method to recognize the friction torque change during sensor field operation was suggested which allows for friction characteristics prediction and correction of wind speed data.
EP23 Enhanced Wear Resistance and Mechanical Properties of the WC-12%Co HVOF Thermally Sprayed Coatings Doped with MWCNTs
Maria Rodriguez (Universidad Central de Venezuela (UCV), Venezuela (Bolivarian Republic of)); Jaume Caro (Fundació CTM Centre Tecnològic, Spain); Eric Anglaret, Nicole Fréty (Université Montpellier II, France); Linda Gil (Universidad Nacional Experimental Politécnica (UNEXPO), Vicerrectorado Puerto Ordaz, Venezuela (Bolivarian Republic of))
WC-Co is widely used as a tribological coating material requiring a combination of high toughness, high hardness, and good strength. Herein, an attempt has been made to further enhance the mechanical and wear properties of tungsten carbide cobalt coatings by reinforcing multi wallet carbon nanotubes (MWCNTs) using thermal spraying. In this work 0.35% w of MWCNTs were mixed by jar-milling in ethanol solution with WC-12%Co microcrystalline powders at different blended times. The mix was thermally spayed using HVOF process onto a plain steel substrate. Also, coatings deposited with both WC-12%Co microcrystalline and nanostructured powders, using the same thermal spray process, were evaluated and compared with samples doped with MWCNTs. The microstructures of the coatings were characterized using scanning electron microscopy, energy dispersive spectroscopy (EDS), Raman test and X-ray diffraction (XRD). The mechanical properties were assessed using micro-Vickers hardness, nanoindentation and wear measurements by two different tests. Effects of doping times of MWCNTs on the phases, microstructure, wear and mechanical properties of the coatings were investigated. The results showed that the best results were obtained when using a blending time of 36 hours. MWCNTs reinforcement improved the hardness of the coating by almost 18 % and decreased the abrasion wear rate of the coating by almost 70%. WC-Co reinforced with 0.35 wt.% CNT blended during 36 hours had an elastic modulus 260 ± 8 GPa, hardness of 16.6 GPa ± 0.64 and a coefficient of friction of 0.24. It was concluded that the CNT reinforcement increased the wear resistance by forming intersplat bridges while the improvement in the hardness was attributed to the deformation resistance of CNTs under indentation.
EP24 Evaluations of the Residual Stress in the Plasma Sprayed Multi-layer Electrodes of the Solid Oxide Fuel Cell
Yung-Chin Yang, Yen-Ching Wang (National Taipei University of Technology, Taiwan, Republic of China); Chang-Sing Hwang, Chun-Huang Tsai (Institute of Nuclear Energy Research)
The advantage of porous metallic supported solid oxide fuel cell (MSC) produced by APS process is to have a SOFC cell applied in the harsh environment with large cell area and effective production cost. However, through the spraying process, residual stresses are unavoidably developed in coatings due to the differences in thermal expansion coefficients, and different cooling conditions between the coating and the substrate. In this study, we investigated the residual stress of each membrane electrodes, which under the cyclic redox treatments. The results show that all of the components of MSC (LSCM buffer, NiO/LDC anode, LDC buffer, LSGM electrolyte, LSCF cathode) reveal compressive residual stress after plasma spraying. However, the stress states of these components become complicated and irregular after the redox treatments. The strain state of both LSCM buffer layer and anode were changed from compressive to tensile. We also found that the original stress state was changed when the upper component was deposited. For example, the original stress state was 0.78% in compressive; after the NiO/LDC anode deposited on the LSCM buffer, the anode side of LSCM revealed the compressive strain with 3.34% and the matrix side of LSCM revealed the tensile strain with 10.65%. Two strain states coexisted in a layer resulted in the coating failure occurred in the interface between the opposite stress states. Therefore, the redox treatments indeed affect the strain state of the MSC components and the influences on the cell durability should not be ignored. The more research results will be described in detail.
EP25 Microstructure and Properties of WC-Co Carbides Coatings Obtained by Different Methods of High Velocity Thermal Spray Process
Krzysztof Szymański, Grzegorz Moskal, Hanna Myalska (Silesian University of Technology, Poland)

Microstructural characterization of WC - based coatings obtained by standard and modified HVOF method was showed in this article. Two different standard feedstock powders of WC-Co 88-12 and 83-17 (by Amperit) type was used to deposition of coating o steel substrate. The aim of investigation was related to comparison of microstructure and basic mechanical properties of coatings depending of applied method of deposition. The range of investigations included characterization of feedstock powders by SEM, EDS, XRD and EBSD method and their technological properties as well. In second step the characterization of deposited coatings were made, especially evaluation of theirs overall quality, porosity, micro-hardness distribution, adhesion of coatings to substrate alloys and theirs tendency to cracks. To characterization of coatings microstructure the same methods were used. Adhesion to substrate alloy and tendency to crack of coatings were characterized by bend test and Brinell hardness measurement on polished top surface of carbide coatings.

Financial support of Structural Funds in the Operational Program - Innovative Economy (IE OP ) financed from the European Regional Development Fund - Project No POIG.0101.02-00-015/09 is gratefully acknowledged.

EP27 Characteristics of Structure and Selected Properties of High Velocity Oxy-fuel Thermal Sprayed WC-Co Type Coatings with the use of Ultra-fine Powders
Aleksander Iwaniak (Silesian University of Technology, Poland); Grzegorz Wieclaw, Krzysztof Rosner (Certech Sp. z o.o., Poland)
The use of the of high velocity oxy-fuel method and classic powders of graining 45µm in the process of thermal spraying allows to obtain coatings resistant to abrasiveness and having porosity of 1%. Devices having the minimum burner power of 45 kV are needed. In the study, the structure of thermally sprayed WC-Co coatings was analyzed. The coatings were sprayed with the use of ultra-fine powders of graining ranging from 1 to 10µm and nanostructure. For spraying ultra-fine powder, the burner with power 20÷40 kW was used. The structure of coatings obtained from classic powders (45µm) and ultra-fine ones of graining 1÷10µm were compared. Structural tests were done with the use of light microscopy (LM), High Resolution Scanning Electron Microscope (EDS), phase composition (XRD) and electron probe micro-analyzer (EPMA) together with chemicals mapping. The coatings spayed with the use of ultra-fine powders were characterized by porosity smaller than 0.1% and high hardness of 1200 HV0.3. The tests for erosive wear showed better resistance of the coatings obtained with the use of smaller graining powders.

This research was conducted as a part of Innotech program founded by The National Centre for Research and Development in Warsaw (Poland).

EP28 Deformation and Failure Mechanisms of Magnetron Sputtered Cu/TiN Multilayers
Rejin Raghavan, Daniel Esqué-de los Ojos, Alex Montagne (Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland); Eluxka Almandoz, Gonzalo Fuentes (AIN-Centre of Advanced Surface Engineering, Spain); Johann Michler (Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland)
Multilayered films of Cu and TiN were deposited by magnetron sputtering on Si (100) with a thickness ratio of 1:2 and individual layer thicknesses varying across two orders of magnitude from 500 to 5 nm. The mechanical behavior of all the Cu/TiN multilayers was studied by compression of micro-pillars FIB machined within the multilayered film with the Si (100) substrates forming the base of micro-pillars, whose heights were chosen equal to the film thickness. The stress-strain curves obtained from the micro-pillar compression experiments reveal that at the length scales close to 500 and 50 nm, corresponding to the individual layer thicknesses of Cu, the yielding of the overall multilayer is governed by the size dependent yield stress of Cu. On the other hand, the failure of the multilayer is governed by the inter-columnar shear strength of the TiN columns formed within the individual TiN layers. An interesting change in flow and failure response is observed at the smallest individual layer thicknesses of Cu (5 nm) and TiN (10nm). While the yield stress of this multilayer is higher than the 500 nm Cu and 1000 nm TiN multilayer and lower than the 50 nm Cu and 100 nm TiN multilayer, the failure stress is highest among all the multilayers. Thus, while a transition in the yield stresses occurs when the interlayer thicknesses are smaller than 50 nm, a continuous increase in failure stresses and a change in failure mechanism is observed. The transition in yield stress of the multilayers is discussed in terms of potential inverse Hall-Petch behavior, change in strain hardening of the Cu and potential plasticity of TiN. The increase in failure stress is explained in terms of the increase in inter-columnar shear strength of the TiN columns. These observations and arguments are reinforced with FEM simulations. A 2D axisymmetric model is used during simulations where length and mesh sensitivity are avoided by properly defining the model. A piecewise elastic-power law plastic relation is used to capture the uniaxial behavior of Cu, while TiN is considered as a perfectly elastic material. Size dependence of yield stress and residual stresses obtained from present experimental results and literature are used during simulations to obtain the experimental trends. In summary, the findings and analysis suggest that a multilayer with optimal individual interlayer thicknesses could be designed to obtain the desirable merger of strength and toughness.