AVS2013 Session SE-ThP: Poster Session

Thursday, October 31, 2013 6:00 PM in Hall B

Thursday Evening

Time Period ThP Sessions | Topic SE Sessions | Time Periods | Topics | AVS2013 Schedule

SE-ThP-1 Gas Barrier Properties of Hydrogenated Amorphous Carbon Films Synthesized by Atmospheric Pressure Plasma on Nitrogen-Plasma-Treated Polyethylene Terephthalate Substrates
Yuya Futagami, Tomoaki Hirako, Mayui Noborisaka, Akira Shirakura, Tetsuya Suzuki (Keio University, Japan)
Gas barrier properties of hydrogenated amorphous carbon (a-C:H) films synthesized at atmospheric pressure have been investigated for applications to packaging materials. In this study, a-C:H films were synthesized on N2-plasma-treated polyethylene terephthalate (PET) substrates by atmospheric pressure plasma enhanced chemical vapor deposition method. PET substrates were treated with various plasma treatment time at atmospheric pressure prior to synthesis of 500-nm-thick a-C:H films. The effects of N2 plasma treatment on the properties of PET surface and a-C:H/PET were investigated in terms of chemical binding structure, surface free energy, roughness, adhesion and oxygen transmission rate (OTR). Formation of new C-N bonds were observed on the PET surfaces by N2 plasma treatment from X-ray photoelectron spectroscopy analysis, and the adhesion strength between a-C:H films and PET substrates was improved in tape tests. As the plasma treatment time increased from 0 to 5 s, OTR of the a-C:H films on N2-plasma-treated PET substrates decreased from 5.6 to 3.1 cc/(m2∙24h∙atm), which is five times less OTR than those of uncoated PET substrates. However by increasing the plasma treatment time from 5 to 40 s, the surface roughness of PET substrate and OTR of a-C:H/PET were increased to 10.5 nm and 4.2 cc/(m2∙24h∙atm). This result indicates that the proper time of N2 plasma treatment on PET substrates is effective for improving adhesion and gas barrier properties of a-C:H films.
SE-ThP-2 Recycling and Diffusion of Ions in High Power Impulse Magnetron Sputtering Plasmas
Liang Meng, Priya Raman, He Yu, David Ruzic (University of Illinois at Urbana Champaign)
***PLEASE NOTE THAT D. RUZIC CANNOT BE THE PRESENTER. HE IS ALREADY AN INVITED SPEAKER AND YOU MAY PRESENT ONE PAPER (ORAL OR POSTER) IN THE SYMPOSIUM*** In high power impulse magnetron sputtering (HiPIMS), ions either diffuse towards the substrate for the deposition or are recycled to sputter or self-sputter the target. Both processes were studied here to further understand the underlying mechanisms. For the diffusion, plasma across the entire chamber was characterized using a 3D scanning triple Langmuir probe. An obvious plasma expansion originated from the “race track” region was observed. The expansion speed and orientation varied with both pulsing parameters and magnetic field strength. These parameters were also found to affect the metal ionization fraction on the substrate. A lower magnetic field strength gave a higher ion fraction (e.g. up to 60% for Cu in a 200 Gauss field while about 30% in an 800 Gauss field) despite a lower plasma density. The corresponding lower plasma potential drop across the bulk plasma was accounted for the effect. Then, the fluxes of plasma species towards the cathode were directly measured through an orifice on the target. Quartz crystal microbalance and current collecting plate behind grid filters were used to determine the fluxes of argon ions, metal ions, and metal atoms. The self-sputtering effect during HiPIMS was supported by a higher fraction of metal ions obtained at a higher pulse peak current. A delayed detection of ion flux for 10 to 40 µs from the onset of pulse likely supported the theory of localization of ionization zone during the HiPIMS ignition.
SE-ThP-3 Mechanical Properties and Impact Resistance of CrAlSiN and TiAlSiN Coatings
Yin-Yu Chang, Yu-Chen Yang, Yu-Kai Chou, Jia-Xu Liu (National Formosa University, Taiwan, Republic of China)
The extension of the tool life is a considerable goal for high speed precision forming tools. Therefore, it is interested to reduce the friction and wear for such tools. The employment of hard coatings, in form of metal and ceramic, increases the production and maintenance costs. In this study, CrAlSiN and TiAlSiN coatings have been deposited on cemented carbide tools by using cathodic-arc evaporation with plasma enhanced duct equipment. Titanium, TiAl, TiSi and CrAlSialloy cathodes were used for the deposition. The alloy content of the deposited coating was correlated with the evaporation rate of cathode materials. The microstructure of the deposited coatings was characterized by using a field emission gun high resolution transmission electron microscope (FEG-HRTEM, FEI Tecnai G2 20 S-Twin), equipped with an energy-dispersive x-ray analysis spectrometer (EDS), operated at 200 keV for high-resolution imaging. Glancing angle X-ray diffraction was used to investigate the microstructure and phase identification of the films. The composition and depth profile were assessed by wavelength-dispersive x-ray spectroscopy (WDS). Mechanical properties, such as the hardness and elastic modulus, were measured by means of nanoindention. To evaluate the correlation between impact fracture resistance and hardness/elastic modulus ratio of the deposited coatings, an impact test was performed using a cyclic loading device with a tungsten carbide indenter as an impact probe. The design of CrAlSiN and TiAlSiN coatings is anticipated to inhibit the grain growth, and leads to grain refinement effect, which expected to increase the hardness and impact resistance of coatings.
SE-ThP-4 Preferential Growth of Oxide Nanorods on Multicomponent TiAlSiN Coated Stainless Steels after Thermal Oxidation
Yin-Yu Chang, Yu-Chen Yang (National Formosa University, Taiwan, Republic of China)
Transition metal nitrides, such as TiN and CrN, have been used as protective hard coatings due to their excellent tribological properties. Recently, multicomponent TiAlSiN coatings have been developed in order to possess high hardness and good thermal stability at temperature exceeding 800 oC. In this study, a series of TiAlSiN coatings with different alloy contents (Ti0.67Al0.32Si0.01N, Ti Al Si N, and Ti0.85Al0.03Si0.12N) were deposited onto an SS304 substrate by using cathodic arc evaporation. Cathodes of Ti, TiAl (50 at.% of Al and 50 at.% of Si) and Ti0.8Si0.2 (80 at.% of Al and 20 at.% of Si) alloy targets were used. The as-deposited films were annealed at 800 oC for different time from 20 minutes to 100 minutes in air to analyze the different preferential oxidation behaviors of TiAlSiN coatings. The surface morphology and microstructure of the deposited and oxidized coatings was investigated by field emission scanning electron microscopy (FESEM) equipped with an energy-dispersive x-ray analysis spectrometer (EDS). X-ray diffractometry was performed using PANalytical X’pert Pro diffractometer with a high resolution ψ goniometer and Cu radiation in both glancing angle and high-angle configurations for phase identification. The correlation between the preferential growth of oxide nanorods and the deposited multicomponent TiAlSiN coatings was discussed. During the oxidation process, Ti, Al, and Si would diffuse outward to form oxidative layers of Al2O3, TiO2, and SiO2 at high temperature. The Ti0.67Al0.32Si0.01N with higher Al content ratio showed that needle-like α-Al2O3 oxides preferentially grow from the macroparticle defect sites. Oxide nanorods were uniformly found on the oxidized Ti0.8Al0.17Si0.03N with smaller content of Al. The Ti0.85Al0.03Si0.12N with the highest Si and the lowest Al contents showed only short TiO2 nanorods uniformly grow on the surface. Therefore, the kinetic oxidation behavior of TiAlSiN coatings varied with the alloy content and phase segregation via high temperature oxidation.
SE-ThP-5 Oxidation Resistance and Hardness of CrAlN based Films Deposited by the Arc Ion Plating Method
Takanori Mori, Tetsuya Suzuki (Keio University, Japan)
In the field of hard coatings, oxidation resistance and high hardness of the coatings are among the main concerns. In this study, CrAlSiYN films with various silicon content were synthesized and investigated their oxidation resistance and hardness. The films were deposited on cemented carbide, silicon and SUS304 substrates by the arc ion plating method. X-Ray Diffraction results showed that the CrAlSiYN films had NaCl-type structure. With increasing the silicon content, the lattice paramete rs for cubic CrAlSiYN films decreased from 0.416 nm to 0.413 nm. The solid solubility limit of silicon into CrAlYN film was about 3 at. %. Hardness of CrAlSiYN films was measured using conventional micro-Vickers hardness tester and the result showed that CrAlSiYN films with high Si content exhibited high hardness (about 30 GPa). Using the flow discharge optical emission spectrometry depth profiling method, an oxygen peak was only observed around surface of films after annealed at 1000°C for 1 hour in air. The cross-sectional transmission electron microscopy observation of oxide layer of CrAlSiYN films showed that yttrium stimulated the formation of amorphous oxide, and its silicon or yttrium oxide prevented diffusion of oxygen and metal such as chromium. Incorporation of silicon and yttrium maintained the stable oxidation layer of Cr2O3 or Al2O3 produced at the surface under high temperature and improved oxidation resistance of CrAlN films.
SE-ThP-6 Tribological Properties and Thermal Stability of TiAlCN Coatings Deposited by ICP-assisted Sputtering
HanJoo Choe, Soon-Ho Kwon, Jung-Joong Lee (Seoul National University, Republic of Korea)

In this study, the tribological and thermal properties of TiAlCN coatings were investigated to evaluate their feasibility in automobile applications. TiAlCN coatings with carbon compositions between 25 and 65 at.% were prepared by inductively coupled plasma (ICP) assisted sputtering and were annealed at 400, 500, and 600°C in air. The structures and compositions of the coatings were studied by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and Auger electron spectroscopy. The hardness and tribological performance were evaluated by micro-indentation and ball-on disk tests. The wear rates were calculated using a non-contact 3D surface profiler. At a carbon composition > 50 at.%, the coatings featured a mixture of amorphous and crystalline phases and exhibited superior tribological performance compared to that of commercialized carbon or nitride coatings. Raman spectroscopy revealed that even when the amorphous carbon phase has a relatively high sp2 to sp3 ratio, there are sufficient amounts of TiAlN grains to support the hardness in the coatings. The coating hardness decreased slightly after high-temperature annealing due to graphitization in the amorphous carbon phase, however, the friction coefficients and wear rates were reduced with the annealing temperature.

SE-ThP-7 Structure and Mechanical Properties of Tungsten-Yttrium Based Coatings
Gustavo Martinez, Chintalapalle Ramana (University of Texas at El Paso)

The challenging environment associated with a fusion reactor will require the utilization of advanced materials in order to enable successful development of fusion energy for the future. Tungsten(W)-based materials have been considered for nuclear reactor applications for its outstanding properties such as high melting point, low vapor pressure, high thermal conductivity, and low thermal expansion coefficient. However, pure W exhibits low fracture toughness at all temperatures and a high ductile to brittle transition, which depends on the chemical and microstructure. The present work was focused on the W-Y based alloy coatings grown by sputter-deposition. The sputtering was performed using a W-Y target to fabricate coatings on to MgO(100) substrates. W-Y coatings were made at various growth temperatures (Ts) ranging from room temperature to 500 oC. The structural and mechanical properties of the coatings were evaluated as a function of Ts. While the ultimate goal is to investigate the performance of W-Y coatings as a structural material in the next generation nuclear reactors, preliminary results obtained on the crystal structure, composition, stress evolution and mechanical properties of the coatings are presented and discussed.

SE-ThP-8 A New Testing Method for Surfaces Subjected to Combined Impact and Sliding Loads
Panos Epaminonda, Claus Rebholz (University of Cyprus)

There are a large number of factors involved in wear processes (e.g. mechanical, physical and chemical properties, surface topography, loading), making the precise theoretical and quantitative approach of wear a challenge even for “simple” tribo-systems. Many of these factors are hard to measure, may vary with time and space, and there is not yet a general theory available of how to link the basic properties with the tribological response. Several well established testing methods (e.g. pin-on-disk, fretting and impact tests) have been widely used to study treated surfaces and coatings on various substrates. However, many of these existing techniques have limitations in their ability to characterize materials, since they mainly focus on a single mode of loading and wear (e.g. only impact or sliding).

In this study, a new Dynamic Impact and Sliding Test (DIST) for the tribo-mechanical evaluation of surfaces under complex loading conditions is presented, where the surfaces are simultaneously subjected to sliding and impact loading. Such modes exist in many critical applications, from biomedical (e.g. hip/knee implants) to automotive applications (e.g. diesel injectors, engine valves, cam shafts), in cutting tools, general machine parts and systems, etc. Instruments and techniques for combined loading situations (such as the proposed DIST) are a feasible way for fast, economical and reliable evaluation of complex tribo-systems with high practical and industrial interest. Expected benefits include the time and cost effective evaluation of various surfaces and the better understanding of their peculiarities under such multi mode loading conditions. Some of the unique characteristics of the DIST (e.g. combined impact and sliding testing; wear area in a single point; pre-setting of desired maximum wear depth possible; evaluation of materials’ properties and behavior in a single run) are presented.

SE-ThP-9 Exploring Crater Roughness for Durable Sol-Gel Derived Superhydrophobic Coatings
Brendan Dyett, Alex Wu, Robert Lamb (The University of Melbourne, Australia)

Characterized as exhibiting water droplet contact angles > 150° and sliding angles < 5 °, superhydrophobic films have attracted considerable research attention as a result of their remarkable non-wetting properties and potential applications in self-cleaning, anti-fouling and anti-icing. The combination of hydrophobic chemistry and surface roughness necessary for imparting such non-wetting characteristics presents a challenge towards industrial applicability due to the intrinsic frail nature of highly rough surfaces.[1] Sol-gel synthesis offers a versatile and scalable means for producing superhydrophobic films. However, traditional sol-gel approaches are often reliant on ‘needle-like’ aggregations of nanoparticles to impart surface roughness. This surface structure, whilst ideal for minimizing solid-water interactions is inherently fragile.[2, 3] Upon contact, high aspect-ratio asperities experience excessive pressures usually exceeding the mechanical properties of the material[4], consequently such superhydrophobic films are very easy to abrade and damage. To overcome this challenge a templating method was used to engineer more robust structures. Discrete polymer spheres were embedded within an alkoxysilane sol-gel to form a continuous, robust, thin film. Roughness was then engineered into the film by thermally degrading the polymer spheres within the gel network, leaving behind crater-like structures with durability far exceeding its predecessor’s. The resultant crater-like films exhibited pencil hardness exceeding 4H, eclipsing traditional films’ pencil hardness, typically of the order 8B – HB. This avenue may provide a scalable approach for controlling roughness features in durable superhydrophobic films and allow for large scale application in areas of self-cleaning and anti-fouling.

References

1. Verho, T., et al., Advanced Materials, 2011. (5): p. 673-678.

2. Nakajima, A., K. Hashimoto, and T. Watanabe, Monatshefte für Chemie/Chemical Monthly, 2001. (1): p. 31-41.

3. Nakajima, A., et al., Thin Solid Films, 2000. (1–2): p. 140-143.

4. Bhushan, B. and M. Nosonovsky, Acta materialia, 2003. (14): p. 4331-4345.

SE-ThP-10 Abrasion Resistance and Adhesion Promotion for SiOC(-H) / Polycarbonate System using Nanosilica Contained Acrylic Intermediate Layers
Taiki Masuko, Mayui Noborisaka, Takanori Mori, Akira Shirakura, Tetsuya Suzuki (Keio University, Japan)

SiOC(-H) films were synthesized on polycarbonate substrates from mixture of trimethylsilane (TrMS) and O2 gases by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) method to improve the abrasion resistance of polycarbonate substrates.

In order to improve the adhesion to polycarbonate substrates, we applied the acrylic intermediate layer prepared by ultraviolet curing method between SiOC(-H) films and polycarbonate substrates. The nanosilica particles were mixed with pentaerythritol triacrylate and pentaerythritol tettraacrylate at various concentrations to control the hardness of the intermediate layer.

The scratch resistance of SiOC(-H) films deposited on polycarbonate substrates with the intermediate layer was improved as the pencil hardness of the intermediate layer increased. After the taber abrasion tests of the SiOC(-H) films deposited on polycarbonate substrates with the intermediate layer, the occurrence of delamination was inspected by digital microscope. The delamination was confirmed to be markedly suppressed as the hardness of the intermediate layer increased.

The haze difference (ΔHaze) between before and after the abrasion tests exhibited sufficient abrasion resistance of 3.5% after 1000 revolutions when the 500 nm thick-SiOC(-H) film was deposited on polycarbonate substrates with the intermediate layer contained 25 wt.% nanosilica particles.

SE-ThP-11 Highly Conformal and Size-Controlled Nanofabrication of Macro-scale Three-Dimensional Biotemplated Inorganic Nanonetworks
Hakan Ceylan, Cagla Ozgit-Akgun, Turan Erkal, Inci Donmez, Ruslan Garifullin, Fatih Genisel, Ayse Tekinay, Ali Okyay, Mustafa Guler, Necmi Biyikli (Bilkent University, Turkey)

By combining organic and inorganic nanomaterials using two different material growth techniques (self assembly and atomic layer deposition), we demonstrate a facile and reliable fabrication method for TiO2 and ZnO semiconductor nanonetworks. Self-assembled peptide-amphiphile nanofibers are used as three-dimensional organic nano-templates, whereas subsequently atomic layer deposited metal-oxide films formed the conformal inorganic functional nano-coatings. Apart from the traditional organic templates, we used a fully dried, three-dimensional (cm-scale), highly interconnected peptide nanofibrous network template, which enabled atomic layer deposition (ALD) precursors to be homogenously deposited with exceptional conformity. The wall thickness of the inorganic nanotubes can be precisely controlled by simply altering the number of ALD cycles. TiO2 and ZnO nanonetworks demonstrated superior performance compared to the unstructured TiO2 and ZnO substrates in photocatalytic activity because of the enhanced specific surface area of the photocatalysts with nanostructured morphology. Importantly, immobilization of the photocatalysts on a solid support enabled recycling of the material, which can dramatically reduce the treatment cost and prevent secondary contamination of the water sources with inorganic materials. Furthermore, we discovered that there is an optimal wall thickness for gaining photocatalytic advantage through nanostructuring for both TiO2 and ZnO. This optimum nanotube wall thickness was found to be around ~8 nm for both TiO2 and ZnO. These results demonstrate significant potential of using peptide-based organic templates to fabricate high-quality TiO2 and ZnO nanostructures not only for photocatalysis, but for several applications where increased surface area plays a crucial role: chemical/gas sensing, dye synthesized solar-cells , etc. Further studies can be extended to other transition-metals and their compounds, such as oxides, nitrides, and sulfides. As a result of the rapid and convenient scaling of the peptide nanofibers into macro-size networks, new opportunities could be available for fabrication of a wider range of inorganic materials.

SE-ThP-12 Ion Beam Profile Etching for X-ray Focusing Mirrors
Chian Liu, Jun Qian, Assufid Lahsen (Argonne National Laboratory)

For microfocusing x-ray mirrors, an elliptical shape is essential for aberration-free optics. However, it is difficult to polish elliptical mirrors to x-ray quality smoothness. Previously we have invented and succeeded a profile coating technique to make elliptical Kirkpatrick-Baez (KB) mirrors using flat Si substrate [1]. We found that it is advantageous to pre-figure the flat surface so that less coating is needed [2]. In this presentation we describe our attempt to pre-figure the flat Si substrates using a profile etching technique with a commercial broad beam ion source.

In profile etching, a contoured graphite mask placed above the ion source and right below a moving substrate determines the desired surface profile along a direction perpendicular to the substrate moving direction after etching. The shape of the contour is calculated point by point on the profiling direction from the ion beam distribution and the desired profile. When the substrate is moving across the mask during ion etching, the etching depth is proportional to the length of the opening of the mask along the moving direction and the weight of the ion beam distribution along the path. By equating the summation of relative weighting to the required etching depth at the same point, the length of the opening at that position can be determined. Repeating this process for the whole length of the profile, a contour can be determined. The substrate can be moved at a constant speed and multiple moving passes are used until the desired etching depth is reached.

Initial design of the profile-etching setup and primary results are presented. Major challenges and obstacles will be discussed.

[1]. “From flat substrate to elliptical KB mirror by profile coating”, C. Liu, R. Conley, L. Assoufid, Z. Cai, J. Qian, and A. T. Macrander, AIP Conf. Proc. 705, 704, 2004.

[2]. “Plastic Deformation in Profile-Coated Elliptical KB Mirrors,” C. Liu, R. Conley, J. Qian, C. M. Kewish, W. Liu, L. Assoufid, A. T. Macrander, G. E. Ice, and J. Z. Tischler, ISRN Optics, vol. 2012, Article ID 151092, doi:10.5402/2012/151092, (2012).

* This work is supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Time Period ThP Sessions | Topic SE Sessions | Time Periods | Topics | AVS2013 Schedule