Innovation in Materials Science II

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Authors: G.S. Reddy, Mallikarjuna N. Nadagouda, Jainagesh A. Sekhar
Abstract: Provided in this article are the quantitative and qualitative morphological results describing the action of several nanostructured surfaces for bactericidal and bacteriostatic action. Results are also provided to illustrate microbial corrosion and its impact. Biofilm formation is correlated to colony formation. Nanostructured surfaces, i.e. surfaces with welded nanoparticles are noted to display biocidal activity with varying efficacies. Porous nanostructures, on stainless steel and copper substrates, made of high purity Ag, Ti, Al, Cu, MoSi2, and carbon nanotubes, are tested for their efficacy against bacterial colony formation for both gram-negative, and gram-positive bacteria. Silver and Molybdenum disilicide (MoSi2) nanostructures are found to be the most effective bactericidal agents with MoSi2 being particularly effective in both low and high humidity conditions. Bacteriostatic activity is also noted. The nanostructured surfaces are tested by controlled exposures to several microbial species including (Gram+ve) bacteria such as Bacillus Cereus and (Gram-ve) bacteria such as Enterobacter Aerogenes. The resistance to simultaneous exposure from diverse bacterial species including Arthrobacter Globiformis, Bacillus Megaterium, and Cupriavidus Necator is also studied. The nanostructured surfaces were found to eliminates or delay bacterial colony formation, even with short exposure times, and even after simulated surface abrasion. The virgin 316 stainless steel and copper substrates, i.e. without the nanostructure, always displayed rapid bacterial colony evolution indicating the lack of antimicrobial action. The efficacy of the nanostructured surface against colony formation (bacterial recovery) for E-Coli (two strains) and virus Phi 6 Bacteriophage with a host Pseudomonas Syringae was also studied. Preliminary results are presented that also show possible anti-fungal properties by the nanostructured MoSi2. When comparing antimicrobial efficacy of flat polished surfaces (no curvature or nanostructure) with nanostructure containing surfaces (high curvature) of the same chemistry, shows that bacterial action results from both the nanostructure size and chemistry.
Authors: Masanori Suzuki, Toshihiro Tanaka
Abstract: Hydrothermal treatment has been conducted to create porous glass or ceramics as value-added materials for the recycling of slag and glass. Under hydrothermal conditions, slag and glass react with a high pressurized H2O and hydrate glass phase containing plenty of H2O is formed to connect raw materials particles to make ceramic materials. The hydrothermal process takes advantages of energy costs, because it can be operated at a low temperature compared to conventional sintering processes. Since the hydrothermal process uses H2O to fabricate ceramic materials, it can be regarded as energy-saving, eco-friendly, and spontaneous materials processing. In the present study, we introduce some applications of hydrothermal treatments to slag / glass to produce functional porous ceramic materials.
Authors: Fei Yu, M. Bahner, Vikram K. Kuppa
Abstract: As a new material, graphene is considered to have great potential in photovoltaic applications, due to its superior physical and electronic properties. In this manuscript, the behavior of graphene nanosheets prepared by different processing methods were investigated in order to probe their applicability in polymer-based bulk heterojunction optoelectronic devices. Raman spectroscopy was employed to study the formation of interfaces between the conjugated polymer and graphene, while photoluminescence quenching was used to investigate charge transfer from P3HT to graphene. The current-voltage characteristics of fabricated cells were investigated to elucidate the role of graphene in their performance. We demonstrate that the addition of small quantities of graphene promotes exciton dissociation and charge transport in P3HT:PCBM BHJ devices, leading to a novel paradigm for organic solar cells.
Authors: V.Y. Filimonov
Abstract: A new approach to the consideration of the thermal explosion macrokinetic features for monomolecular reactions in homogeneous systems based on a strict accounting of burnout during the reaction process is proposed. It is established, that the qualitative changes of the phase trajectory structure (phase portrait) on the plane: heating rate-temperature determine the characteristic modes of reaction. This approach makes it possible to go beyond the Semenov theory and allows us to consider the variety of the reaction modes. From this point of view, the theory of Semenov is a special case which is valid only for reactions of zero order. The phase trajectories analyze on the parametrical plane Semenov criterion – Todes criterion gives an opportunity to define the regions of the thermal explosion degeneration, the transition regions and the region of the thermal explosion realization. With the use of such consideration, the necessary and sufficient conditions of the thermal explosion are found.
Authors: Y.D. Bensah, H.P. Li, Jainagesh A. Sekhar
Abstract: The principle of maximum entropy generation rate principle is reviewed for its applicability in Materials Science. The principle of MEPR states that, if there are sufficient degrees of freedom within a system, it will adopt a stable state at which the entropy generation (production) rate is maximized. Where feasible, the system will also try and adopt a steady state. MEPR determines the most probable state. MEPR thus allows for pathway selections that can occur in an open thermodynamic system. Recent work also shows that isolated systems and closed thermodynamic systems also display this principle. The Belousov-Zhabitonsky reaction is also described in the Sgen context. Both solidification morphologies and micropyretic process generated morphologies are studied as examples of the Sgen and MEPR.
Authors: Seval Genc, Bora Derin
Abstract: Magnetorheological (MR), Electrorheological (ER), and Ferrofluids are considered as a class of smart materials due to their novel behavior under an external stimulus such as a magnetic and electrical field. The behavior of these synthetic fluids offer techniques for achieving efficient heat and mass transfer, damping, drag reduction, wetting, fluidization, sealing, and more. Magnetorheological fluids are suspensions of non-colloidal, multi-domain and magnetically soft particles organic and aqueous liquids. Electrorheological fluids are suspensions of electrically polarizable particles dispersed in electrically insulating oil. Ferrofluids are known as magnetic liquids that are colloidal suspensions of ultrafine, single domain magnetic particles in either aqueous or non-aqueous liquids. In this review article a history of these fluids is given, together with a description of their synthesis in terms of stability and redisperibility and how it is understood in various parts of the science and technology. Then the structural changes and rheological properties of these smart fluids under an external stimulus together with a series of applications are presented.
Authors: Shyan Lung Chung, Chun Hung Lai
Abstract: Aluminum nitride has been acknowledged as an important industrial material because of its unique combination of high thermal conductivity and high electrical resistivity. Although there have been several excellent reviews on the synthesis of aluminum nitride, little has been mentioned on the combustion synthesis of AlN. In this work, the combustion synthesis methods for synthesis of AlN are reviewed and classified according to the phases involved in the reaction, the types of reactants (and additives) used and the design principles for the synthesis processes. Problems critical to combustion synthesis of AlN to obtain products with high product yields and low impurity contents are summarized and discussed.
Authors: Woo Hyoung Lee, Woo Hyuck Choi, Xue Fei Guo, William R. Heineman, Paul L. Bishop
Abstract: Microelectrodes, needle-shaped biochemical microsensors fabricated from pulled glass micropipettes, are one of the most prominent, novel methods for studying biofilms. The pulled glass tip can have a diameter of 3–20 μm, allowing for the measurement of the concentrations of specific biological and chemical compounds in microbial communities. Net specific consumption and production rates (i.e., biological activity) at a certain depth can be estimated from the measured concentration profiles. This article is focused on solid-state, needle-type, electrochemical microsensors for detecting important water quality parameters (e.g., oxygen, pH, nitrite, chlorine species, redox, and phosphate). Sensing materials include gold (including a gold-electroplated sensing surface), platinum, carbon-fiber, carbon nanotube, iridium, and cobalt. Emphasis is placed on the material science chemistry behind how electrochemical microelectrode sensors operate. Innovative applications of microsensors, including microelectromechanical systems (MEMS) microelectrode array sensor microfabrication, and three-dimensional microprofile measurement and interpretation will also be demonstrated. Carbon nanotubes (CNTs) are a relatively new member in the carbon family and are being used in biofilm research. Distinctive properties of CNTs and the relationship between structure and their electrochemistry performance are discussed. The electrochemical application of CNTs is focused on nitrite detection.
Authors: Stephen J. Pearton, Wan Tae Lim, Erica Douglas, Hyun Cho, F. Ren
Abstract: There is increasing interest in use of conducting oxide materials in new forms of transparent, flexible or wearable electronics on cheap substrates, including paper. While Si-based thin film transistors (TFTs) are widely used in displays, there are some drawbacks such as light sensitivity and light degradation and low field effect mobility (<1 cm2/Vs). For example, virtually all liquid crystal displays (LCDs) use TFTs imbedded in the panel itself. One of the promising alternatives to use of Si TFTs involves amorphous or nanocrystalline n-type oxide semiconductors. There have been promising results with zinc oxide, indium gallium oxide and zinc tin oxide channels. In this paper, recent progress in these new materials for TFTs on substrates such as paper is reviewed. In addition, InGaZnO transistor arrays show promise for driving laminar electroluminescent, organic light-emitting diode (OLED) and LCD displays. These transistors may potentially operate at up to an order of magnitude faster than Si TFTs. We have fabricated bottomgate amorphous (α-) indium-gallium-zinc-oxide (InGaZnO4) thin film transistors (TFTs) on both paper and glass substrates at low processing temperature (≤100°C). As a water and solvent barrier layer, cyclotene (BCB 3022-35 from Dow Chemical) was spin-coated on the entire paper substrate. TFTs on the paper substrates exhibited saturation mobility (μsat) of 1.2 cm2.V-1.s-1, threshold voltage (VTH) of 1.9V, subthreshold gate-voltage swing (S) of 0.65V.decade-1, and drain current onto- off ratio (ION/IOFFSubscript text) of ~104. These values were only slightly inferior to those obtained from devices on glass substrates (μsat~2.1 cm2.V-1.s-1, VTH ~0 V, S~0.74 V.decade-1, and ION/IOFF=105- 106). The uneven surface of the paper sheet led to relatively poor contact resistance between source-drain electrodes and channel layer. Future areas for development are identified.

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