ICMCTF2009 Session TSP: TSP Poster Session

Thursday, April 30, 2009 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic TS4 Sessions | Time Periods | Topics | ICMCTF2009 Schedule

TSP-1 Thermal Conductivity of Polymer-Ceramic-Metallic Nanolaminates
A.R. Waite (Air Force Research Lab/UTC, Inc./University of Dayton); J.G. Jones (Air Force Research Lab); A.A. Voevodin (Air Force Research Lab/University of Dayton); C. Muratore (Air Force Research Lab/UTC, Inc.); A.M. Urbas (Air Force Research Lab); J.O. Enlow (Air Force Research Lab/UES); T.J. Bunning (Air Force Research Lab)
A novel multilayer polymer-metal-ceramic nanolaminate coating was synthesized by room temperature Plasma Enhanced Chemical Vapor Deposition (PECVD) and Magnetron Sputtering (MS) processes. The nanolaminate was deposited in a custom built, two-chamber CVD-PVD system. The polymer deposited was a low refractive index, highly cross-linked fluoropolymer deposited by PECVD from an octafluorocyclobutane gas precursor. The high refractive index ceramic layers were deposited by MS of a TiO2 target. High and low thermal conductivity metal layers were also deposited by MS. This nanolaminate structure realizes the idea of creating an optical coating from a stack of high and low refractive index dielectrics with the additional functionality of an enhanced thermal conductivity in the coating plane. Thermal conductivity of the optical coating was tuned by inserting very thin metallic layers of varying composition (Ti and Cu) and thicknesses into the nanolaminate structure. The fluoropolymer and TiO2 layers were approximately 100 nm and 60 nm, while the metal layers varied from 1 to 10 nm. The refractive indices of the fluoropolymer and TiO2 were 1.38 and 2.31, respectively, at a wavelength of 532 nm. The nanolaminate thermal conductivities were measured by Time Domain Thermoreflectance (TDTR) using a laser pump probe technique.
TSP-2 Surfaces Incorporating Phase Change Materials for Controlled Storage and Release of Thermal Energy
C. Muratore (Air Force Research Laboratory); S. Aouadi (Southern Illinois University Carbondale); A.A. Voevodin (Air Force Research Lab/University of Dayton)
Applications on multiple size scales require maintenance of a constant temperature for optimal performance. The utility of phase change materials (PCMs) where thermal energy can be stored and released without changes in temperature through the PCM latent heat of fusion and/or vaporization, has been demonstrated in macroscale applications such as plasterboard for building interiors or textiles for winter clothing which both employ embedded volumes of encapsulated wax tuned to melt at a temperature slightly above the desired operating temperature. Energy is stored through the melting process. If the temperature drops below the melting point, energy is released as the wax solidifies. Phase change materials would also be useful for temperature maintenance at the micro- and nanoscale. For example, optical links between microprocessors and other chips where changes in temperature-dependent characteristics of optical sources and receivers (i.e., wavelength and current) can ren der the device inoperable unless the intended temperature of operation is maintained. One means of passive temperature maintenance on this size scale is through composite surfaces incorporating phase change materials. Laser patterning and reactive ion etching of oxidized silicon substrates with 20 micron wide by 10 micron deep holes were investigated initially. The holes were filled with materials known to undergo phase changes at target operating temperatures. The initial reservoir geometry was 20 microns wide by 10 microns deep. Surfaces with 40 percent coverage of reservoirs with these dimensions were expected to store up to 1 joule of thermal energy when filled with bismuth. This energy could be stored and released as the ambient temperature deviated from the PCM melting point to modulate the surface temperature as the ambient temperature fluctuated. Metallized samples of silicon containing PCM-filled reservoirs were studied with an infrared microscope to identify the te m perature profile on the surface as the material was heated and cooled from behind to observe temperature discontinuities induced by phase changes. Equivalent total reservoir volumes with different dimensions and fractional surface coverage were produced using both techniques to investigate the dependence surface temperature and phase change temperature on reservoir geometry.
TSP-3 Anti-Bacterial TiNx-Ag Coatings on Titanium Dental Implants
Y.-Y. Chang, C.-C. Hsuer, P.-J. Lin, H.-T. Hsu, D.-Y. Wang (Mingdao University, Taiwan)
Titanium-based materials have been used for dental implants due to their excellent biological compatibility, superior mechanical strength and high corrosion resistance. The osseointegration rate of titanium dental implants is related to their composition and surface treatment. A better anti-bacterial performance of the abutment seated in the prosthetic crown is beneficial for the osseointegration rate. In this study, Ti2N-Ag coatings with different titanium and Ag content were deposited on bio-grade pure Titanium dental implant materials. A twin-gun magnetron sputtering system was used for the deposition of the Ti2N-Ag coating. The Ag content in the deposited coatings was controlled by the magnetron power ratio of Ag/Ti targets. WDS was used to characterize the composition of the deposited Ti2N-Ag coatings. The crystalline structure and bonding states of the coatings were analyzed by XRD and XPS. The bacterial adhesion and bactericidal effects of the Ti2N-Ag coated Titanium was assessed using E-coli cell tests. Growth and killing kinetics on Ti2N-Ag coatings were determined by an optical density (OD) analysis at 600 nm. It is proposed that the nanostructure and Ag content of the Ti2N-Ag coatings were correlated with the biocidal property.
TSP-4 A Study of the Anti-Microbial Properties of TiN/Ag Nanocomposite Coatings
P.J. Kelly, H. Li, K.A. Whitehead, J. Verran (Manchester Metropolitan University, United Kingdom); R.D. Arnell (University of Central Lancashire, United Kingdom)
Titanium nitride (TiN) is a hard, wear resistant coating material, which is widely applied to components operating in an abrasive wear environment. When co-deposited with silver, the coatings form a nanocomposite structure consisting of nanoparticles of silver embedded in a TiN matrix. Silver is lubricious, and the ‘self-lubricating’ nature of these coatings, combined with their high hardness and scratch resistance makes them attractive for tribological applications. However, combining these properties with the inherent anti-microbial nature of silver also opens up novel applications for TiN/Ag nanocomposite films in, for example, the bio-medical or food processing industries, where surfaces that are durable, safe, readily cleanable and resistant to microbial contamination are required. In this study, TiN/Ag coatings have been deposited by co-sputtering onto tool steel and stainless steel substrates. By control of the target powers, the silver content of the films w as varied in the range 0-25 atomic percent and the films have been characterised using SEM, XRD, EDX and AFM to determine the size, shape and distribution of the silver nanoparticles. The initial interaction, i.e., attachment and retention, of specific microorganisms on the coated substrates has also been assessed. The microorganisms tested included Escherichia coli and Staphylococcus aureus. The antimicrobial activity of diffusible components of the surfaces was tested using zones of inhibition assays, whilst antimicrobial activity by contact was assessed using live/dead staining (and microscopic analysis) and agar overlay methods. The strength of attachment of retained cells was assessed using AFM.
TSP-5 Carbon Nanotube - MoS2 Nanocomposites as Self-Lubricating Coatings
B. Sirota, X. Zhang, B. Luster, A. Church (Southern Illinois University Carbondale); C. Muratore (Air Force Research Lab/UTC, Inc.); A.A. Voevodin (Air Force Research Lab/University of Dayton); P. Kohli, S. Talapatra, S. Aouadi (Southern Illinois University Carbondale)
Solid Lubricants (SLs) characterized by low friction coefficient and wear rates drastically improve the life span of instruments which undergo extreme frictional wear. However, the performance of SLs such as sputtered or nanoparticulate molybdenum disulfide (MoS2), tungsten disulphide (WS2), or graphite deteriorates heavily under extreme operational conditions (for example elevated temperatures3). Here, we show that composites of carbon nanotubes (CNT)-MoS2, produced by electrodeposition of MoS2 on vertically aligned CNT films have low coefficients of friction (~0.03) and wear rates (~ 10-13 mm3/N.mm) even at 300°C (two orders of magnitude better than nanoparticulate MoS2). The high load bearing capacity of CNTs provides a strong enduring support to MoS2 nanoclusters and is responsible for their ultra low wear rates. The technique described here to produce SLs with extremely appealing frictional properties will provide valuable solutions for a variety of tribological ap plications.
TSP-7 Molecular Dynamics Atom-by-Atom Simulations of Chemical Vapor Deposition of SiNH
J. Houska, J.E. Klemberg-Sapieha, L. Martinu (Ecole Polytechnique de Montreal, Canada)

In this contribution, we report molecular dynamics (MD) simulations of the atom-by-atom chemical vapor deposition of SiNH materials from N2-SiH4 plasma. The interatomic interactions are described by empirical potentials of Tersoff type. Each step of the deposition process consists of impacts of SiHx and N radicals (both energetic ions and slow neutrals) onto material surface, a constant-energy MD run, a thermalization run, and removal of desorbed (resputtered) particles.

We calculate sticking coefficient of individual elements at various ion energies (20-300 eV) and SiHx radicals compositions (x=1-3), and show formation of (a) interface (mixing) layers due to damaging of the Si substrate and (b) hydrogenated SiN networks. We investigate how the particle flux composition, ions-to-neutral ratio, energy of ions and deposition temperature affect the material’s characteristics such as density or hydrogen content. We find that a higher SiHx-to-N ratio leads to low-density, voids-containing networks, and calculate size of the voids. Using both classical MD simulations and ab-initio liquid-quench simulations, we investigate bonding preferences in SiNH networks, including formation of unbonded H2 molecules.

The calculated results, compared with an experiment, allow one to predict relationships between particle fluxes, compositions and structures of SiNH materials for optical or electronic devices.

TSP-8 Corrosion Resistance of Stainless Steel Bipolar Plates for Fuel Cell by High Temperature Nitrogen Implantation
D.H. Kwon, K.K. Kim, J.S. Kim (Pusan National University, Korea); S.M. Moon (Korea Institute of Machinery & Materials, Korea); J.S. Lee (Korea Atomic Energy Research Institute, Korea); M.C. Kang (Pusan National University)

Ion implantation is a novel surface modification to enhance the mechanical, chemical and electrical properties of substrate surface using high energy ions. Metallic bipolar plates for the proton exchange membrane fuel cell offer many advantages over conventional graphitic materials. These include relative low cost, high strength, and ease of manufacture. As a metallic bipolar plate can be easily shaped from thin sheet with complex shape, significant improvement in the fuel cell power/volume ratio can be achieved.

However, corrosion of the metallic bipolar plates is a severe problem. Corrosion affects the performance and lifetime of a fuel cell. The research on surface modification has been advanced to improve the properties of engineering materials. This experiment was performed in the high temperature in order to increase the implanted depth. The samples are implanted with 50~120 keV N-ion at substrate temperature ranging from 50~400℃. Nano-hardness and AES(Auger electrons spectroscopy) were measured from nitrogen ion implanted layer. The sliding wear and impact wear properties of ion implanted samples depend strongly on the ion doses and implantation temperature.

TSP-9 Antibacterial Properties and Tribology of a-C:Ag Coatings Deposited by Pulsed Cathodic Filter Arc
J. Endrino (Instituto de Ciencia de Materiales de Madrid, Spain); M. Allen (Ohio State University); J.C. Sanchez-Lopez (Instituto de Ciencia de Materiales de Sevilla, Spain); R. Escobar Galindo (Instituto de Ciencia de Materiales de Madrid, Spain); A. Anders (Lawrence Berkeley National Laboratory); J.H. Horton, T.M. Horton (SUNY Upstate Medical University); J.M. Albella (Instituto de Ciencia de Materiales de Madrid, Spain)
Amorphous carbon (a-C) is known to be a biocompatible material with good chemical inertness, this makes it a strong candidate to be used as a matrix that embeds metallic elements with an antimicrobial effect. We have deposited a set of a-C:Ag films using a dual-cathode pulsed filter cathodic arc source, the arc pulse frequency of the silver and graphite cathodes was controlled in order to obtain samples with various silver contents. In this study, we analyze the advantages of incorporating silver into a-C by studying the antimicrobial properties and tribology of the deposited films. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). The deposited films were characterized by X-ray diffraction (XRD) and Raman spectroscopy. The bactericidal efficacy against staphylococcus of samples deposited on 24­well tissue culture plates was evaluated.
TSP-11 Bactericidal Effect of TiO2 Particle with Magnetic Core on Fish Pathogens
T.C. Cheng, K.S. Yao (Mingdao University, Taiwan); C.I. Chang (Fisheries Research Institute, Taiwan); H.C. Hsu, C.J. Hwang, D.Y. Wang, C.Y. Chang (Mingdao University, Taiwan)
The UV irradiated TiO2 has been used to disinfect bacteria in water. It is usually used either in powder form or coating on supporting materials such as glass or active carbon. Although the efficiency of bactericidal effect of TiO2 powder is higher than those of coated TiO2 due to large reaction surface, the recovery of TiO2 powder from water to be reused is difficult. Therefore, we develop a simple method to coat TiO2 on magnetic particles, evaluate its bactericidal effect on fish pathogens, and recollect form water with magnet. Nano-iron-particles are synthesized and added to TiO2 sol-gel followed by 400 °C calcinations. Thereafter, TiO2 are grinded into powder. Particles containing iron are collected with magnet and then their photocatalytic activity is confirmed by the degradation of indigo carmine dye under UV-A irradiation. The particles size, crystal and surface structure are characterized using scanning electron microscope (SEM) and X-ray diffractometry (XRD) before and after evaluation of bactericidal effect on fish pathogens (Edwardsiella tarda and Streptococcus iniae). Highly bactericidal effects are found while no significant change on TiO2 particles properties after they were recollected easily from water using magnet. This result strongly suggests that TiO2 particle with iron core can be applied widely in other solution without the TiO2 recovery problems.
TSP-12 Simultaneous Oxidation and Hydroxyapatite Coating on Titanium and Enhancement of Bioactivity of Osteoblast-Like Cells
S.K. Moon (Yonsei University College of Dentistry, Korea); B.Y. Kim (Incheon National University, Korea); K.Y. Kim (MST Technology Company, Korea); K. Kim, D.H. Lee, M.H. Hong, Y.K. Lee (Yonsei University College of Dentistry, Korea)
Titanium alloys have been proved to be very suitable materials for load bearing bioimplant application and have successfully been used in biomedical and dental implants. Unfortunately, titanium exhibits poor osteoinductive properties like most metals. This drawback has recently been addressed by coating the metal with a layer of the hydroxyapatite(HA). Titanium oxide(TiO2) coatings on titanium alloys have demonstrated acting as a chemical barrier against release of metal ions from the implant. However, the chemical bond with the living bone in the body is not very strong, therefore a double layer of HA/TiO2 coatings on titanium alloys should possess a very good combination of biochemical stability and mechanical properties. Many techniques have been investigated for deposition of HA onto titanium alloys. Among theses techniques, plasma spraying is the most popular method, but it is difficult to apply uniform coating on implants with complex geometries. Micro-arc oxidati on represents a relatively new surface modification technique where thick, hard and anticorrosive oxide coatings can be easily and cost-effectively fabricated. In this study, a phosphate salt solution was used as the electrolyte for micro-arc oxidation. HA powder and ethylenediol were added to the distilled water for the preparation of the HA suspensions. pH value of the solution was adjusted in the range of 4-11 using ethylenediamine and malonic. For micro-arc oxidation, the specimens were immersed in a phosphate salt with containing various amount of hydroxyapatite. A d.c. of 400 V was applied, giving a current density of 20-40 mA/cm2 and raising the bath temperature around 75°C. After characterization of the coating film using XRD, SEM and EPMA, osteoblast-like MG 63 cells were cultured onto the hybrid coating film of titanium up to 4 weeks. Culture onto the hybrid coating film exhibited significant higher attachment as well as proliferation of osteoblast-like MC 63 cells than those of titanium alloys (p<0.05). This result indicates that a hybrid combination of micro-arc oxidation and electrophoretic deposition could be expected to be a promising coating technique onto titanium alloys.
TSP-13 Preparation and Properties of Branched Polymers as Postoperative Tissue Adhesion Barriers
S.-R. Hsieh (Taichung Veterans General Hospital, Taiwan); C.-J. Chang, T.-D. Way, T.-W. Hung (Feng Chia University, Taiwan)
Undesirable tissue-adhesions after surgical treatment often induce severe problems. Biocompatible polymers and oligomers with pendent polyethylene glycol-polycaprolactone (PEG/PC) diblock or polyethylene glycol-polylactide (PEG/PL) diblock side chains were synthesized as postoperative tissue adhesion barriers. The chemical structure of the side chain and the relative length of each block changed the flexibility of the films. The degradation properties of the polymer/oligomer composite films can be tuned by introducing oligomers with smaller molecular weight. The viability of the fibroblast NIH3T3 cells in the presence of the polymers were assessed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. It confirms the low toxicity of the polymers to fibroblast NIH3T3 cells. The animals received surgical defects to their pericardium and left parietal pleura of the chest wall. The polymeric films were applied to and cover the pleural defects o f chest wall. After 28 days, the pericardial and pleural space of the animal was examined by direct observation of adhesion and histological examination. The surgical surfaces covered with the films presented no tissues-adhesion. The histological examination of the tissues confirms that these films are very effective in preventing post-surgical tissue adhesion.
TSP-14 Coating of Electrically Conductive CNT/PTFE Composite Film on the Metal Bipolar Plate for PEMFC
Y. Show, K. Takahashi (Tokai University, Japan)
Metal bipolar plate for fuel cell (FC) has advantages of high manufacturability and mechanical strength. The fuel cell using metal bipolar plates generally shows lower output power than that of carbon bipolar plates, because its surface is corroded and increases contact resistance between bipolar plate and membrane electrode assembly (MEA) in fuel cell. In this study, electrically conductive film, consisting of carbon nanotube (CNT) and Polytetrafluoroethylene (PTFE), was coated on the metal bipolar plate for PEMFC. The composite film coating increased the output power of the Fuel Cell. The CNT/PTFE film was formed from dispersion fluids of the CNT and the PTFE. CNT dispersion was made from multi-wall type CNT. Cellulose derivatives were added into water to disperse the CNT. Water based commercial PTFE dispersion was used in this study. The dispersion fluids of the CNT and the PTFE were mixed and stirred by applying the ultrasonic wave. The CNT/PTFE dispersion was appli ed to stainless steel bipolar plate at the thickness 50mm. The bipolar plates were dried under the atmosphere of 40°C for 30 min, and then were heated at 350°C for 10min. The fuel cell using the bare stainless steel bipolar plates showed maximum output power of 1.7W. The bipolar plate coated with the composite film showed the maximum output power of 2.7W. Impedance analyzer measurement for these FCs indicated that the composite film coating decreased the contact resistance between the bipolar plate and the MEA. Therefore, the FC fabricated with the metal bipolar plate, which is coated with the CNT/PTFE composite film, shows high output power.
TSP-20 Modeling Film Growth in Reactive Sputtering Process
S. Faddeeva, J. Oseguera, S. Martínez, F. Castillo (ITESM-CEM, Mexico)
The film thickness and the rate of film growth in reactive sputtering processes are of great practical interest. Based on Berg’s model and associated with mass balance during deposition rate, we introduce film thickness and the rate thin layer growth. For these approach different temperatures for substrates, walls and target were considered; chemical reactions for compound formation were assumed. Predicted results are compared with experimental ones.
TSP-21 Influence of a Lateral Electric Field on Nucleation, Growth, and Conductivity of Gold Films on Sapphire
M.S. Byrne, R.J. Lad (University of Maine)
While electric fields directed normal to a substrate are routinely used to modify the energetics of arriving species during film growth, very few studies have investigated the influence of lateral electric fields on the surface transport and resulting morphology of thin films. We have used a Pt electrode structure on r-sapphire substrates to apply a large lateral electric field (up to 105 V/m) during the initial nucleation and growth of Au films. The current through a load resistor was measured during film deposition to monitor the film conductivity and to determine the onset of percolation conductivity between the Au nuclei as they begin to coalesce. In addition, atomic force microscopy and high resolution scanning electron microscopy observations were made of film morphology at various Au coverages. Because Au does not wet the sapphire substrate, three-dimensional Au islands form and measurable electrical conductivity does not occur until the equivalent Au film thickness is greater than approximately 8 nm. The film morphology was found to be influenced by the electric field, but the exact mechanism for morphological changes is unclear. The resulting film structures formed in the presence of the lateral electrical field may be attributable to a number of factors including enhanced surface adatom transport, local heating effects, and electromigration.
TSP-24 Growth Characteristics and Sintering Behavior of YSZ Thin Film Prepared by E-Beam Evaporation at Various Pressures
H.-H. Huang (Cheng Shiu University, Taiwan); M.-C. Huang, M.-H. Chen, C.-F. Yang (National Kaohsiung First University of Science and Technology, Taiwan); C.-Y. Hsu (Cheng Shiu University, Taiwan)
Deposited at working pressure ranging from 1*10-5 to 1*10-3 Torr, the yttria-stabilized zirconia, YSZ, thin film had been prepared by E-beam evaporation at substrate temperature of 200°C. The XRD, TEM, SEM and UV-Vis were respectively used to determine the structure, microstructure, morphology and transmittance of YSZ thin films. Results show that the YSZ thin film with fluorite phase was obtained and XRD reflection peaks of (111), (200), (220), (311), (222) and (400) were found. The preferred orientation of [200] was found when thin films prepared at low working pressure, however, the [111] was at high pressure. The grain size and internal strain of YSZ films both decrease with working pressure increasing. The transmittance of YSZ films deposited at various working pressures is similar which is in the range of 70-90%, meanwhile, the energy gaps of YSZ thin film were similar in the range of 3.73-3.78 eV. After 1200°C sintering, the nano-grain ed morphology was obtained.
Time Period ThP Sessions | Topic TS4 Sessions | Time Periods | Topics | ICMCTF2009 Schedule