Nanostructured Surfaces for Improved Functional Properties : Session II
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Surface Engineering Committee
Program Organizers: Rajeev Gupta, The University of Akron; Homnero Casaneda, Texas A&M University; Sandip Harimkar, Oklahoma State University; Arvind Agarwal, Florida International University; Bobby Mathan, James Cook University

Wednesday 2:00 PM
March 1, 2017
Room: Pacific 23
Location: Marriott Marquis Hotel

Session Chair: Debrupa Lahiri, Indian Institute of Technology Roorkee; Rajeev Gupta, The University of Akron

2:00 PM  
Fabrication of Mesoporous Gold-coated Polystyrene Particles for Enzyme Immobilization: Seongcheol Choi1; Rafael Vazquez-Duhalt2; Olivia Graeve1; 1University of California, San Diego; 2Universidad Nacional Autonoma de Mexico
    In this study, we introduce the fabrication of mesoporous gold-coated polystyrene particles, characterized by their controllable pore size and shell thickness, and investigated their use as supports for the immobilization of chloroperoxidase enzymes. The purpose is to maximize the enzymatic activity and stability. First, sub-micron polystyrene particles, surrounded by sulfate groups with sodium cations, were prepared using a soap-free emulsion polymerization. Second, the polystyrene particles were functionalized by coating their surface with poly-L-histidine (PLH) for uniform and ultra-thin growth of the gold layer. Third, mono-sized silica nanoparticles were fabricated by using an L-lysine-catalyzed sol-gel method. Next, the mono-sized silica nanoparticles were deposited in isolation on the PLH-coated polystyrene particles by electrostatic attraction. Finally, ultra-thin gold shells were grown on the PLH-polystyrene particles, followed by etching of the silica with sodium hydroxide solution at 80C. The morphology and the properties of the mesoporous particles as promising enzyme substrates will be described.

2:20 PM  Cancelled
Directional Wetting at the Nano Scale: Mohammad Khalkhali1; Hao Zhang1; Qingxia (Chad) Liu1; 1University of Alberta
    Wettability is a fundamental interaction between water and substrate, which governs many applications around us. This phenomenon is primary quantified the contact angle at the solid-liquid interface which can be well described by the famous Young’s equation. Despite the simplicity of the wettability in question, the uncertainty in the experimentally and theoretically measured contact angles is still unresolved. Molecular dynamics (MD) simulation is a suitable tool that can complement experiment to provide a deeper understanding at the atomic scale. Recently, we developed a method to accurately calculate the contact angle from MD simulations. Using this method, we studied the wetting properties of different crystallographic surfaces of ZnS. We showed that by custom designing surfaces at the atomic scale, wetting properties can deviate from the Young’s equation. Directional wetting properties were also observed in some cases suggesting that the surface is hydrophobic along one direction and hydrophilic along the other.

2:40 PM  
Fabrication of Au-coated Ag Nanowires for OLED Applications: Sunho Kim1; Hoo-Jeong Lee1; 1Sungkyunkwan University
    Transparent conductive electrodes (TCE) are one of the integral elements in OLED. The commercialized material for TCE is ITO and, however, its lack of flexibility is a shortcoming for next-generation flexible devices. Among several candidates, Ag NWs-networked film is a very promising material due to its excellent electrical performance and high flexibility. However, the low work function of Ag is a problem when they are used for the anode of OLED by introducing a high hole injection barrier between the anode and hole injection layer. In this work, we propose gold coating on the surface of Ag NWs. The work function of gold (~5.0eV), which is higher than that of silver (~4.7eV), could decrease the hold injection barrier. The morphology and work function enhancement of Au-coated Ag NWs were investigated and the OLED device based on of Au-coated Ag NWs shows a significant improvement in performance.

3:00 PM  
Thermally Reduced Graphene Oxide Film on Soda Lime Glass and Its Temperature-time Dependence of de-bonding Energy: Raj Kumar1; R. Manoj Kumar1; Debrupa Lahiri1; Indranil Lahiri1; 1Indian Institute of Technology Roorkee
    Transparent conducting electrodes, such as ITO and FTO coated glass, have received much attention in the field of solar cells, light emitting diodes, flat panel displays and field emission device. But being highly brittle, toxic and expensive, ITO and FTO coated glass need to be replaced with a suitable material with high conductivity, transmittance, flexibility and low processing cost. Graphene is one of the materials, which meets all these criteria successfully. In the present research, graphene oxide (GO) was deposited on soda lime glass through a simple and cost-effective thin film deposition technique (dip coating), followed by reduction of GO to rGO through thermal annealing process. The film shows uniform transparency and conductivity throughout the substrate. Since device life depends on adhesion of film with the substrate, the de-bonding energy of GO and temperature-time dependence of the de-bonding energy of rGO with soda lime glass was quantified through nano-scratch technique.

3:20 PM Break

3:35 PM  
Effect of Slurry Flow Rate on Planarization of c-plane (0001) GaN Surface by Chemical Mechanical Planarization (CMP) Method: P Parthiban1; Dibakar Das1; 1University of Hyderabad
    GaN is an important material for opto- and microelectronic devices. But, the availability of large size device grade epi-ready wafer surfaces is difficult. Due to the extreme mechanical hardness and chemical resistance material removal (MR) leading to planarization of the surfaces is a challenging task. Chemical mechanical planarization (CMP) is an effective technology in creating epi-ready surfaces from the bulk materials. The efficiency and output of the CMP process (material removal rate (MRR) and surface roughness/planarity) are largely dependent on the appropriate selection and combination of the CMP processing parameters. This study involves the effect of slurry flow rate on planarization of C-plane (0001) GaN surface. An improved MRR with decreasing surface roughness has been observed with increasing slurry flow rate from 10-40ml/ min. The MRR and nanostructured surface roughness (rms) data will be presented as a function of slurry flow rate for fixed other CMP process variables.

3:55 PM  
Development of Nano-sized Intra-precipitates in Nanostructured Materials Using the Pre-existing Embryo and Desired Texture: Hongyun Luo1; Pingwei Xu1; 1Beihang University
    In the nanostructured (NS) materials produced by severe plastic deformation, precipitates tend to nucleate at grain boundaries, which would worsen the properties. In this paper, the nano-sized precipitates in the grain interior are tailored in the NS Aluminum alloy by the design of the embryo and desired texture. The embryo is the solute-rich structures (solute clusters) segregated to dislocations within grains due to strain-induced dissolution of initial precipitates into the matrix. Meanwhile, the preferred orientation of desired plane parallel to the habit plane of the precipitates is realized by the deformation with a controlled strain and strain rate. During deformation, the partial dislocations were found in NS aluminum alloy with intra-precipitates (which is high stacking-fault energy alloy), that means the extrinsic toughening mechanism during loading. The precipitate- or/and texture-governed properties are expected to be improved in the NS materials.

4:15 PM  
Effect of Surface Nanostructuring on the Liquid Aluminizing Behavior of Ti6Al4V: Qingsong Mei1; Ye Ma1; Juying Li2; Feng Chen1; 1Wuhan University; 2Wuhan Polytechnic University
    A nanostructured layer was fabricated on the surface of Ti6Al4V alloy by high pressure surface rolling (HPSR). The effect of surface nanocrystallization on the liquid aluminizing behavior of Ti6Al4V was investigated. Results showed that aluminizing of the HPSR sample led to formation of a graded Al-TiAl3 surface layer containing TiAl3 particles dispersed in Al, while a continuous layer of TiAl3 was formed between Al and the matrix in the coarse-grained sample. Meanwhile, the thickness of the surface diffusion layer of the aluminized HPSR sample was much larger than that of the aluminized coarse-grained sample. The enhanced aluminizing kinetics and graded distribution of TiAl3 phase in the surface diffusion layer of the HPSR sample was related to the enhanced grain boundary diffusion and reaction and matrix migration resulted from the surface nanostructure.