MS&T'11 Poster Session: Nanotechnology
Program Organizers: Chris Wood, TMS
Tuesday 11:00 AM
October 18, 2011
Room: Exhibit Hall C
Location: Greater Columbus Convention Center
187 A Comparative Study of Electroless Deposition Route Involving Zn and Cu+ or Cu2+: Chuncai Kong1; Shaodong Sun1; Zhimao Yang1; 1School of Science, MOE Key Laboratory for Non-Equilibrium Synthesis and Modulation of Condensed Matter, Xi’an Jiaotong University
Metal Cu nanomaterials have been increasing studied because of unusual properties and potential applications in electrode modification, electrical conductivity and microdevices. In this work, Cu dendritic nanostructures are synthesized through an electroless deposition route between Zn foil and Cu+ or Cu2+ in aqueous solution. The difference of reduction potential between Cu2+/Cu pair and Cu+/Cu pair modifies the deposition of copper leading to the unlike of morphologies, structures and properties of obtained Cu dendritic nanostructures. Nanoparticle-aggregated copper mesocrystal is observed for the production obtained from the reaction with Cu+. In contrast, there is only single crystal in the reaction with Cu2+. Diffusion-limited and oriented attachment mechanisms are adopted to account for the formation mechanism of Cu dendritic nanostructures. Most importantly, these results reported in this work provide insights into the mechanism for dendritic nanostructures formation via electroless deposition as well as a general way to fabricate other nanomaterials.
188 A Simple Method for the Synthesis of Pt-Ag-Au Alloy Nanoparticles: Haidong Zhao1; Shengchun Yang1; Shengwu Guo1; 1Xi'an Jiaotong University
Noble metal alloy nanoparticles have received special attention owe to the possibility of tuning the optical, electronic and catalytic properties over a broad range by simply adjusting the alloy composition. In this paper, Ag-Au alloy nanoparticles with varying mole fractions were prepared by the co-reduction of chlorauric acid and silver nitrate with sodium borohydride at refluxed temperature. Then the Pt-Ag-Au alloy nanoparticles with tunable composition were prepared by a replacement reaction between Ag-Au alloy nanoparticles and chloroplatinic acid at room temperature. As the UV absorption spectrum results show only one plasmon absorption, which indicated that the Pt, Ag, Au leads to a homogeneous formation of alloy nanoparticles, and the maximum of the plasmon band red-shifts linearly with increasing platinum content. Furthermore, the size distribution of the alloy nanoparticles is examined using TEM.
189 Adsorption Thermodynamics of PAA on Ceria Nanoparticles and Its Biocompatibility: Shashank Saraf1; Amit Kumar1; Soumen Das1; Ajay Karakoti2; Sudipta Seal1; 1AMPAC, NSTC, MMAE, University of Central Florida; 2EMSL, PNNL
Ceria is found to be both SOD and Catalase mimetic, which is very essential for biological applications, but requires stable dispersion of ceria nanoparticles (NC). Here we calculated Gibbs free energy of adsorption by varying physiosorption parameters. Free energy of dispersion is computed as a function of chemical state of NC and molecular weight of polymer. NC prepared by thermal hydrolysis method was used to put adlayers of three different molecular weights of PAA. The physico-chemical properties of the colloidal dispersion of NC before and after attaching with PAA were characterized by DLS, TEM, UV-Vis and XRD. Coating thickness is characterized by TGA and BET. Langmuir Isotherm approximation is done to find out the Free energy. Biocompatibility is checked by toxicity analysis on Human osteosarcoma cell line using MTT assay shows that it is independent of MW of polymer. Further Biocompatibility is correlated to the nanoparticle dispersion in polymeric medium.
190 Analysis of the Key Factors Controlling Sintering of LSM/CGO Multilayer Laminates: Tesfaye Molla1; Tesfaye Molla1; Henrik Frandsen1; Rasmus Bjørk1; Søren Foghmoes1; Eugene Olevsky2; Nini Pryds1; 1Fuel cell and Solid State Chemistry division, Risoe DTU; 2San Diego State University
In this work, factors controlling co-sintering of ceramic layers are analyzed. Multi-layer planar ceramic system based on Ce0.9Gd0.1O1.95-d (CGO) and La0.85Sr0.15MnO3-d (LSM) conventional and ultrafine powders is fabricated by tape casting and sintering techniques starting from ceramic with different particle size, porosity and thickness for each layer. Key factors controlling the camber evolution during the de-binding sintering steps in different time-temperature conditions are followed by in-situ non-contact optical dilatometry measurements. The analysis of the densification for the multilayer system is implemented with an extensive characterization of the microstructural evolution of the processed materials. A constitutive sintering model for the multilayer system is also formulated to predict the camber evolution and densification resulting for selected sintering profiles. An optimal sintering procedure can be thus designed to enhance the planarity and microstructure of the multilayer system as well as to avoid mechanical failure of the powder-based materials during the co-firing process.
191 Carbon Nanotube-Assisted Formation of Aluminum Nanoparticles: Hye Yun Jeong1; Kang Pyo So1; Eun Sun Kim1; Young Hee Lee1; 1sungkyunkwan University
Facile fabrication of aluminum nanoparticles is difficult due to self aggregation effect during ball milling process. Here we report a new method to fabricate aluminum nanoparticles using carbon nanotubes (CNTs) as a breaking media and cold welding inhibitor. The ball milling process was used to transfer mechanical force to CNT for breaking aluminum powder into nanoparticles. The mechanism was analyzed in two step processes. Firstly, fracture dominant process was achieved by using CNTs as cold welding inhibitor during ball milling process. Secondly, the fractured aluminum particles were further broken by CNTs, which was confirmed by SEM and TEM observations. The particle size distribution was analyized by dynamic light scattering measurements. The degree of encapsulation of carbon nanotubes into aluminum particles was analyzed by thermogravimetric analyzer and Raman spectroscopy. Mechanical properties of encapculated aluminum nanoparticles were further investigated.
192 Catalyst-Assisted Low Temperature Synthesis of Zinc Oxide Nanostructures by Vapor Phase Transport: Michael Marshall1; Tarek Trad1; 1University of Texas at Brownsville
Zinc oxide nanostructures were grown on Si(100) substrates coated with a monolayer of cobalt ferrite nanoparticles. The synthesis was achieved at substrate temperatures as low as 300 °C. Nanostructures and catalyst particles' size distribution and morphology were characterized by scanning electron microscopy and atomic force microscopy. Crystal structure and quality of the ZnO product was determined by X-ray diffraction. The effects of catalyst addition, precursor temperature, carrier gas flow rate, substrate position relative to the precursor, and the deposition temperature range were studied. The relatively simple reaction process offers an opportunity to investigate the physical synthesis of ZnO nanostructures on flexible, low-melting point substrates and may prove useful for the development of hybrid polymer-ZnO nanostructured solar cells.
193 Deformation Mechanism of Nanocrystalline Copper Films during Uniaxial Relaxation Test at Room Temperature: Saethavuth Krasienapibal1; Shoichi Nambu1; Junya Inoue1; Toshihiko Koseki1; 1The University of Tokyo
Void formation and twinning mechanism in nanocrystalline Cu thin films having the grain size of 70-200nm were investigated. Cu thin films were deposited by DC-Magnetron Sputtering on polyimide substrates and uniaxial stress relaxation test was conducted at room temperature on each Cu thin film. Changes in void formation, grain size distribution and twin density were observed as a function of relaxation time. The results indicate that there is a transition of the accommodation process from twin mediated plasticity to void formation when the average grain size of Cu is around 100nm. Twinning mechanism dominates the relaxation in Cu film having larger average grain size, while void formation occurs preferentially in Cu film as average grain size decreases. In this research, the grain size, strain and strain rate dependences of twinning mechanism and the void formation process are discussed.
194 Effect of Equal Channel Angular Pressing on the Thermal Stability, Microstructure and Mechanical Properties of ETP Copper: OSCAR HIGUERA COBOS1; JAIRO MUÑOZ BOLAÑOS1; PABLO RODRIGUEZ CALVILLO2; JOSE CABRERA MARRERO1; 1UNIVERSIDAD POLITECNICA DE CATALUÑA; 2Fundación CTM
Samples of ETP copper were subjected to ECAP deformation using a Φ=90º and ψ= 37° die for up to 16 passes following route Bc. Differential scanning calorimetry was used to estimate the recrystallization temperature after each ECAP pass. The recrystallization temperature decreased until 7th ECAP passes, but slight increases in the 5th and the 8th passes were observed. Electron backscattering diffraction was used to evaluate microstructural behavior. Low angle misorientations were observed in the 1st pass, which indicate that a large quantity of subgrains is generated. In the 8th and 16th passes a large increase of misorientation θ≥20º was observed, which indicates formation of a more stable microstructure. Regarding the mechanical behavior, the main changes were introduced in the 1st pass but a gradual increment was observed in the consecutive ECAP passes.
195 Finite Element Modelling of Copper by Equal Channel Angular Extrusion: Arkanti Krishnaiah1; 1Osmania University
Equal channel angular extrusion (ECAE) is a severe plastic deformation SPD) method for obtaining bulk nanostructured materials. The ECAE die consists of two equal channels that intersect at an angle, usually between 90o and 135o. . In the present study, the plastic deformation behavior of copper during the ECAE process with 120o die was investigated. To analyze the deformation behavior and the related strain distributions in the specimen, the commercial FE code ABAQUS has been used. The properties of the materials are strongly dependent on the shear plastic deformation behavior during equal channel angular extrusion (ECAE), which is controlled mainly by die geometry, material properties, and the friction between billet and the die. The ECAE process for these conditions was explained using the two different friction conditions of 0.15 and 0.01 to all sliding surfaces. The effective strain by the theoretical equation is in good agreement with the FEM results.
196 Hydrothermal Synthesis of Ga4Tin-4O2n-2: Brittany Higgins1; Doreen Edwards1; 1Alfred University
Beta-gallia rutile (BGR) intergrowths, generally expressed as Ga4Tin-4O2n-2, where n is an odd integer ≥ 5, are under investigation for their potential in photocatalytic and photovoltaic applications. Solid state reactions are the traditional processing method for these materials, however this method generally produces greater-than-micron sized powders. Because high surface area is needed for the envisioned application, a method that produces a smaller particle sizes is desired. In these experiments, we explore the use of hydrothermal synthesis for preparing BGR powders from various titanium-containing precursors, including titanium dioxide (rutile and anatase), titanium isopropoxide, and dihydrobis (ammonium lactato) titanium IV. Temperature, pressure, pH, and concentration variables were also modified to observe the effects on synthesized powders. Powder morphology was observed using SEM imaging, while particle size was determined using dynamic light scattering and surface area measurements. In addition, X-ray diffraction was used to determine phase purity and crystallite size.
197 Improving the Wettability of Aluminum on Carbon Nanotubes: Kang Pyo So1; Il Ha Lee1; Dinh Loc Duong1; Tae Hyung Kim1; Eun Sun Kim1; Dong Hoon Keum1; Seong Chu Lim1; Kay Hyeok An2; Young Hee Lee1; 1Sungkyunkwan University; 2Chonju machinery research center
The wetting of a metal on carbon nanotubes is difficult due to the large difference of their surface tensions and is a bottleneck for making metal-carbon nanotube (CNT) composites. Here, we report a simple method to enhance the wettability of metal particles on the CNT surface by applying aluminum, which is the largest surface tension material. This method involves two steps: i) Al nanoparticles are decorated on multiwalled CNTs by electroplating and ii) Al powder is further spread on Al-electroplated CNTs, followed by high temperature annealing to accommodate complete wetting of the aluminum. The large surface tension difference is overcome by forming Al-C covalent bonds initiated by defects of the CNTs. The decrease of the D-band intensity, the G-band shift in the Raman, and the formation of Al-C covalent bonds, as confirmed by x-ray photoelectron spectroscopy, were in agreement with our structural model of CNT-vacancy-O-Al determined by density functional calculations.
198 Influence of Growth Condition on Ga and N Co-Doped Zinc Oxide Films and Its Effect on PEC Response for Solar Driven Hydrogen Production: Sudhakar Shet1; Yanfa Yan1; Nuggehalli Ravindra2; John Turner1; Mowafak Al-Jassim1; 1National Renewable Energy Laboratory; 2New Jersey Institute of Technology
The co-doped ZnO:(Ga:N) thin films were deposited by co-sputtering in different O2 gas flow ratio in mixed N2 and O2 ambient at room temperature followed by annealing. ZnO:(Ga:N) films exhibited enhanced crystallinity comparing to ZnO and ZnO:N film grown at the same conditions. We found that the O2 gas flow ratio in mixed N2 and O2 gas ambient is very sensitive factor for depositing co-doped ZnO:(Ga:N) without phase separation. The ZnO:Ga,N film without the phase separation exhibited much better crystallinity, the reduced bandgap, and proper depletion width, resulting in the significantly improved PEC property. On the contrary, the PEC responses of ZnO:(Ga:N) films with phase segregation of Zn3N2 were not too high, compared to the ZnO:(Ga:N) films without the phase separation, due to the photo-inactive Zn3N2 phase.
199 Influence of Pressing Temperature on Microstructure Evolution and Mechanical Behavior of Ultrafine-Grained Cu Processed by Equal-Channel Angular Pressing: Haiming Wen1; Yonghao Zhao1; Troy Topping1; Dustin Ashford1; Roberto Figueiredo2; Cheng Xu3; Terence Langdon4; Enrique Lavernia1; 1University of California, Davis; 2Universidade Federal de Minas Gerais; 3Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences; 4University of Southern California, University of Southampton
Copper was processed by ECAP at different temperatures from room temperature (RT) to 523 K. The influence of pressing temperature on microstructure evolution and tensile behavior was investigated. The results show that as ECAP temperature increased, grain size and ductility both increased, whereas dislocation density and yield strength decreased. From RT to 473 K the mechanism governing microstructural refinement is continuous dynamic recrystallization (CDRX), whereas at 523 K the mechanism changes to discontinuous dynamic recrystallization (DDRX). At higher ECAP temperatures, the kinetics of CDRX are retarded leading to a lower fraction of equiaxed grains/high-angle grain boundaries. At 523 K, DDRX induces a high fraction of equiaxed grains with a very low dislocation density which appears responsible for the observed high tensile ductility. The sample processed at 523 K possessed a good combination of strength and ductility, suggesting ECAP at elevated temperatures as an interesting engineering approach. (Advanced Engineering Materials 2011)
200 Investigation of the Formation and Extraordinary Thermal Stability of Mg Nano-Grains in Ti2AlC-Mg Composites: Babak Anasori1; Michel Barsoum1; 1Drexel University
Recently we reported on the formation of Mg nano-grains by spontaneously melt infiltrating Mg into Ti2AlC porous preforms. This procedure leads to composites with phenomenal strengths. The Mg nano-grains are also so stable that annealing at 500 °C for 8 h did not lead to their coarsening. Neither did heating the composites to 50°C higher than the melting point of Mg. It is believed that thin oxide layers at the Mg grain boundaries as well as Mg penetration into the Ti2AlC planes confine the Mg nanograins and prevent them from coarsening. Herein, the composite's microstructure is studied by scanning electron and transmission electron microscopy on bulk samples, fractured surfaces, as well as Mg/Ti2AlC diffusion couples. The results shed light on why the Mg forms as nano-grains and why they are as stable as they are.
201 MgO Tunnel Barrier for Room Temperature Spin Injection and Detection in Semiconductors: Nathan Gray1; Ashutosh Tiwari1; 1University of Utah
We have developed a novel all-electrical technique of spin injection and detection in semiconductors using NiFe/MgO tunnel-barrier-contacts at room temperature.1 In this talk, using the specific examples of Si and ZnO, we will show that by employing NiFe/MgO tunnel-barrier-contacts in a local three-point device structure, all three main operations required for a spintronic device i.e. spin injection, detection and manipulation can be accomplished at room temperature in a non-optical configuration. Carrier diffusion lengths as high as 328 nm in Si channels has been achieved using our method. These lengths are good enough to realize room-temperature spintronic devices.
202 Microstructure Exploration of High Strength High Ductility Iron-Based Glassy NanoMaterials
: Sheng Cheng1; Alla Sergueeva1; Brian Meacham1; Daniel Branagan1; 1The Nanosteel Co
Bulk metallic glasses (BMG) possess many attractive properties, but lack adequate tensile ductility for practical applications. Previous studies suggest that failure under unconstrained loading conditions results from runaway shear banding propagation. Here, we design and optimize a spinodal glass matrix microconstituent (SGMM) microstructure in an iron-based metallic glasses that can effectively suppress runaway shear bands. As a result, high-strength materials can be developed with significant tensile ductility as well as novel work hardening ability. High-resolution electron microscope studies suggest that the arresting events are inherently promoted by a spinodally decomposed crystalline architecture in a glass matrix. The resulting SGMM structure acts to elevate the energy barrier for shear band propagation, effectively blunting the shear band. Subsequent shear band interactions result in further arresting generating the unique deformation ability to exhibit plastic flow at room temperature.
203 Multiwalled Carbon Nanotubes Decorated with Va and Ni by Gamma Irradiation: Ahlam Abdulghani1; Jessika Rojas1; Vivek Rao1; Muthanna Al-Dahhan1; Stoyan Toshkov2; Carlos Castano1; 1Missouri University of Science and Technology; 2University of Illinois at Urbana-Champaign
While single and multi-walled carbon nanotubes (CNTs) have been investigated as good potential candidates to achieve high hydrogen storage, reproducibility and mechanism of storage remain issues to be reckoned with. High purity level and the addition of certain metallic nanoparticles seem to improve the hydrogen storage capacity of CNTs. Gamma irradiation is presented here as an innovative method to generate and attach vanadium and nickel nanoparticles to CNTs. Hydrogen storage capacity of the resulting nanostructure will be analyzed. Further cleaning of CNTs by acid treatment is also studied here, which is aimed at reducing the presence of metallic impurities and create functional groups at the surface of the CNT. FTIR, SEM, STEM and XPS were used for morphological chemical and structural characterization of the nanostructures.
204 Plasma Sprayed Titanium Oxide-Carbon Nanotube Composite Coating for Dye Sensitized Solar Cells: Cheng Zhang1; Anup Kumar Keshri1; Arvind Agarwal1; 1Florida International University
TiO2 is an attractive material for dye sensitized solar cells (DSSC) because it is inexpensive and non-toxic as compared to the Si-based solar cells. Plasma spraying is an ideal method to produce TiO2 based DSCC due to its high deposition rate and ease of scale-up. In the present study, TiO2-carbon nanotube (CNT) based composite is explored as DSCC material. It has been shown in the literature that carbon nanotubes improve the conversion efficiency of DSSC in many ways. This study investigates the role of CNT addition in terms of phase transformation from anatase to rutile, microstructural properties and photocatalytic properties. TiO2 and TiO2-CNT coatings are prepared by plasma spraying on the stainless steel and FTO glasses. These composite coatings are characterized by X-ray diffraction and scanning electron microscopy. Photocatalytic properties are also measured by MB solution method.
205 Reversible Ferromagnetic Switching in Undoped and Doped (Co and Mn) ZnO Thin Films: Siddhartha Mal1; Sudhakar Nori1; John Prater2; Jagdish Narayan1; 1North Carolina State University; 2Army Research Office
We have introduced defects in ZnO (undoped and doped with Co and Mn) epitaxial thin films using laser irradiation with the aid of nanosecond laser pulses and thermal annealing. In contrast to the as grown samples, the laser irradiated films show a significant decrease in resistivity, enhancement in UV emission, while maintaining the same wurtzite crystal structure. Room-temperature ferromagnetism (RTFM) is observed in laser-irradiated samples, which increased with the number of laser pulses up to a certain value where it saturates and decreases upon subsequent increase in the number of pulses. The induced ferromagnetism as well as the enhanced electrical conductivity can be eliminated with thermal annealing. Reversible ferromagnetism was also demonstrated in both Co and Mn doped ZnO thin films using laser irradiation and thermal treatments and that the magnetization in Co and Mn doped films were found to be strong function of growth conditions.
206 Siloxane Polymer Microspheres Compositing with Nano Silver-Copper Alloy Colliod: Qunyan Wei1; Depeng Zhao1; Shixiong Wang1; Xiangjun Yang1; 1Yunnan university,School of Chemstry Science and Technology
A new method was developed for compositing silver-copper alloy on siloxane polymer microspheres. The method does not make use of an external electron source, but of a catalyst polymer reaction. The process is mainly performed in two steps: a first step in which Silver-copper nanoparticles alloy were synthesized by a modified solvent based polyol reduction using PVP (Mw = 7000–10000) as a structure-directing agent and poly ethylene glycol (PEG) as a reducing agent without exotic seeds and a second step comprised nanoparticles catalyzing alkylsilane. When the alkylsilane is attached to the PVP-capped silver-copper nano-particles surface, it loses hydrogen, forming weak metals–Si bonds then forming siloxane polymer microspheres.
207 Site-Specific Texture Analysis of High Pressure Torsion Processed BCC Metals Using Synchrotron Radiation: Jonathan Ligda1; Brian Schuster2; Ruslan Valiev3; Zenji Horita4; Qiuming Wei1; 1UNC Charlotte; 2Army Research Laboratory; 3Institute of Physics of Advanced Materials; 4Kyushu University
Through high pressure torsion (HPT), metal grain size can reach into the nanocrystalline regime, below 100 nm, resulting in very high strengths. However, this method creates a grain size gradient due to the variation in the induced strain with radial position. Grains are smaller further from the disk center. Recent results also suggest changes in the deformation mode. Site-specific microcompression of nanocrystalline Ta shows switching from homogenous deformation to localized plastic flow at the disk edge. To understand why this switch occurs, synchrotron x-rays are utilized for site-specific texture analysis at multiple locations on the HPT disk to map out any texture changes with position. Tests are performed at Argonne National Lab’s Advanced Photon Source on six different bcc metals in two different orientations. Preliminary results show evidence of torsion fibres for bcc metals, {110}<uvw> and {hkl}<111>, also the (110) pole figures show very different textures between the orientations.
208 Structure of Carbon Nanotubes Grown by Arc-Discharge Technique under Argon, N2 and O2 Atmosphere at Different Conditions: Ghazala Hermiz1; Izzat Al-Essa1; Ghuson Mohammed1; 1baghdad university-college of science
Carbon nanotubes powder and thin films were prepared by arc-discharge technique at room temperature on glass substrate and silicon wafer under different pressure (10-3, 10-4, and 10-5) mbar of Ar, N2 and O2 gases from graphite rode. Thickness of the film is 350nm .The nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and energy dispersion X-ray analysis (EDXA).X-ray diffraction studies under different annealing times (10, 20 and 30) minute at fixed temperatures is measured. Also effect of gas pressure on the structural of the films was examined. The XRD analysis showed that CNT powder was nearly amorphous and peaks appear which indexed on the basis of the hexagonal graphite nature of the CNT when treated in acid treatment. The XRD of CNT thin films grown in Ar and N2 atmosphere show the same results under annealing time, with contrast with O2 atmosphere.
209 Synthesis and Characterization of Cobalt Aluminate and Fe2O3 Nanocomposite Electrode for Solar Driven Water Splitting to Produce Hydrogen: Sudhakar Shet1; Kwang-Soon Ahn2; Yanfa Yan1; Heli Wang1; Nuggehalli Ravindra3; John Turner1; Mowafak Al-Jassim1; 1National Renewable Energy Laboratory; 2Yeungnam University; 3New Jersey Institute of Technology
Cobalt aluminate-Fe2O3 p-n nanocomposite electrodes were deposited on the silver coated stainless steels and annealed at 800 C. Their photoresponses were investigated and compared with that of p-type Cobalt aluminate. We found that nanocomposite electrodes exhibited much improved photoresponses as compared to p-type Cobalt aluminate. We attribute the improvement to the band offset at the formed three-dimensional p-n junction, which promote photo-generated carrier separation and reduce carrier recombination.
210 Synthesis and Polymorph Stability of TiO2-SnO2 Nanoparticles Prepared by Pechini Method: Douglas Gouvêa1; Joice Miagava1; Annick Rubbens2; Pascal Roussel2; 1Universidade de São Paulo; 2Ecole Nationale Supérieure de Chimie de Lille
One of the main challenges in the development of nanomaterials is the particle size control. The modification of the surface composition of nanomaterials may be an approach to control the size by decreasing the surface energy. In this work, the TiO2-SnO2 system was studied regarding the effects of surface modification in the particle size stabilization and rutile or anatase polymorphic stability. Powders of Ti(1-x)O2 – SnxO2 (with 0 ≤ x ≤ 1) were prepared by Pechini method at 500 ° C by 15 h . The great similarity between cation valences and structure for the two oxide materials indicates that only modifications on chemical composition of surface are responsible by particle size stability and rutile phase stabilization.
211 Synthesis and Size Distribution Narrowing of Naked Noble Metals Nanoparticles Made in Imidazolium Ionic Liquid: Miao Shi1; Yong Wang1; Whitney Shook1; Hong Yang1; 1University of Rochester
Ionic liquids (ILs) have attracted much research interest because their unique physical and chemical properties, including negligible vapor pressure, thermal and air stability, low flammability. In this work, we show the synthesis of noble metals, such as gold and platinum, using1-butyl-3-methylimidazolium bis(triflylmethyl-sulfonyl)imide ([BMIM][Tf2N]) ionic liquid without the conventional capping agents. The resultant nanoparticles can be stabilized in the IL phase. Noticeably, these nanoparticles can be stabilized in either organic or aqueous phase using different ligand chemistry, providing great flexibility for surface modifications and resulting in dramatic narrowing in size distribution. The catalytic activity of Pt in hydrogenation of cyclohexene was studied.
212 Tailoring the Relative Si3N4 and SiC Contents in Si3N4/SiC Nanopowders through Carbothermic Reduction and Nitridation of Silica Fume: Jyothi Suri1; Leon Shaw1; 1University of Connecticut
The present study demonstrates the synthesis of nano-Si3N4/SiC composite powders from silica fume, for the first time. The processing approach to convert the waste silica fume to advanced nanocomposites is based on the integrated mechanical and thermal activation (IMTA) process. The nano-Si3N4/SiC powders synthesized have particle sizes as small as 15-30 nm. It has been shown that the carbothermic reduction and nitridation temperature as well as the graphite concentration in the starting SiO2+C mixture are the important parameters to obtain Si3N4 and SiC nanopowders and control their crystal sizes. The synthesis conditions to tailor the relative contents of Si3N4 and SiC (changing from as high as 37 wt.% to as low as 3.1 wt.% SiC) in the final powder mixture have been investigated, and the mechanisms responsible for the observed relationship between processing conditions and the characteristics of the final powder have been identified.
213 Thiol-Dependent Cytotoxicity of Zn-Based Quantum Dots: Sonia Bailon1; Oscar Perales-Perez1; 1UPRM
The extremely small size of quantum dots (QDs) empowers them with properties that can be very useful in cancer treatment by photodynamic therapy (PDT) and bioimaging. The present work is focused on the evaluation of the cytotoxicity of water-soluble ZnS@ZnSe QDs, synthesized in presence of two different thiols (thioglycolic acid, TGA, and 3-mercaptopropionic acid, MPA), in human-pancreatic cells (PANC-1). The toxicity of Zn-based QDs was dependent of the type of thiol. The cell viability percentage decreased from 77.7% ± 7.1% down to 46.7% ± 0.9 % using 200 ppm and 300 ppm, respectively, of QDs synthesized with MPA. The viability of PANC-1 in presence of QDs synthesized with TGA decrease from 49.5% ± 8.8% to 46.8% ± 7.8% using 200 and 300 ppm, respectively. Our results suggested the feasibility of using Zn-based QDs at doses lesser than 200 pm as non-toxic fluorophores and as a potential material in nanomedicine.
214 Transport Mechanism of Olfactory Information Using Terpene Sensing Properties of Nanostructured MIP: Sung Pil Lee1; Jaehun Jung1; 1Kyungnam University
Resistive type terpene sensors were fabricated for detection of the terpene gases, and for studies on the transport mechanism of olfactory information. Lift-off technique was applied for interdigitated Au electrodes on the alumina substrate. Self-assembly monolayer was spin-coated first for the improvement between substrate and polymer, and MIP solution with conductive polymer and cross-linker was casted and polymerized. After extracting process of target terpene molecules, nanostructured MIP layer was obtained for the terpene detection. The five terpene sensors which extracted each molecule responded to each gas and the resistance changes were linear to gas concentrations. If sensitivity is defined as S= ΔI/Io, the sensitivity of the α-pinene sensor was 0.47 ppm-1, which was the highest value among the target gases. The parameters of proposed model for the transport mechanism of olfactory information were type of gas, concentrations, diffusion coefficient and selectivity. The simulated result was compared with empirical one.
215 Uniform Elongation of Ultra-Fine Grained Steels Evaluated by Micro-Compression Tests: Takashi Nagoshi1; Akinobu Shibata2; Masato Sone1; Yoshikazu Todaka3; 1Tokyo institute of technology; 2Kyoto university; 3Toyohashi university of technology
Micro-sized compression tests were conducted to investigate work hardening behavior of ultra-fine grained steels. Compression tests was needed to achieve uniform deformation condition. Micro-compression pillar with uniform dimensions (non-tapered, non-filleted) were carefully fabricated by FIB milling. EBSD analysis of high pressure torsion processed steels was performed to observe deformation microstructure. Grains were elongated to shear direction and grain size was decreased down to 300 nm in diameter with increasing strain amount. 0.5% offset stress was around 1.5 GPa and did not dependent on the grain boundary character distributions. Uniform elongations which were determined using considere criterion were decreased with decreasing grain size. It is not conformed in traditional tensile test due to early failure without uniform deformation.
216 Using Nanoindentation to Study Residual Stress State and Constitutive Properties in A/B Metallic Multilayer Thin Films: Michael Gram1; Nikolas Antolin1; Peter Anderson1; 1Ohio State University
Experiments show that magnetron-sputtered Cu/Ni multilayer thin films can have large, alternating tensile/compressive stress states that serve to confine plasticity to individual layers. A hypothesis is that this imparts large plastic strength, as evidenced by experimental micro-pillar compression and nanoindentation testing. Accordingly, we employ a finite element analysis of indentation to test this hypothesis and to study, in general, the effects of coherency stress, substrate confinement, constituent stress-strain behavior, and bilayer period on nanoindentation traces. The results do not support the hypothesis, in that predicted plateau hardness values are independent of the magnitude of local tension/compression between A/B layers. Rather, they are dependent only on average film stress and average yield properties. To address this deficiency in plateau hardness data, we propose use of early stage indentation traces to determine properties of individual layers. This is applied to Cu/Ni multilayer thin films over a range of layer thicknesses.
217 ZnO:GaN Thin Films for Photoelectrochemical Water Splittting Application: Sudhakar Shet1; Yanfa Yan1; Heli Wang1; Nuggehalli Ravindra2; John Turner1; Mowafak Al-Jassim1; 1National Renewable Energy Laboratory; 2New Jersey Institute of Technology
ZnO and mixed ZnO:GaN thin films were synthesized on FTO substrates by reactive rf magnetron sputtering in mixed N2 and O2 ambient. Mixed ZnO:GaN films exhibited better crystallinity compared to ZnO film and bandgap narrowing was observed for mixed ZnO:GaN thin films. The n-type conductivity is revealed for the both ZnO and ZnO:GaN thin films by Mott-Schottky plots as well as photocurrent polarity in I-V analysis. ZnO:GaN thin films exhibited improved photocurrents than ZnO film. Our results suggest a potential method for synthesizing heterogeneous photocatalyst with both high crystallinity and bandgap reduction, which should help to improve their PEC performance.