Preparation of ultra‐low‐density microcellular materials

Microcellular polymeric materials can be obtained by the polymerization of a high‐internal‐phase emulsion. These materials are good candidates as targets toward inertial confinement fusion. This application requires severe specifications, including a very low density and a small cell size. In this study, we examined the influence of parameters such as emulsification conditions, surfactant nature, and the presence of a porogen on the obtainment of those requirements. It was possible to obtain microcellular polymeric foams with apparent densities as low as 0.0126 g/cm³. However, it was difficult to obtain very low material density and still maintain a small average pore size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2053–2063, 2005     

Rapid Discrimination of Neuromyelitis Optica Spectrum Disorder and Multiple Sclerosis Using Machine Learning on Infrared Spectra of Sera

Neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) are both autoimmune inflammatory and demyelinating diseases of the central nervous system. NMOSD is a highly disabling disease and rapid introduction of the appropriate treatment at the acute phase is crucial to prevent sequelae. Specific criteria were established in 2015 and provide keys to distinguish NMOSD and MS. One of the most reliable criteria for NMOSD diagnosis is detection in patient’s serum of an antibody that attacks the water channel aquaporin-4 (AQP-4). Another target in NMOSD is myelin oligodendrocyte glycoprotein (MOG), delineating a new spectrum of diseases called MOG-associated diseases. Lastly, patients with NMOSD can be negative for both AQP-4 and MOG antibodies. At disease onset, NMOSD symptoms are very similar to MS symptoms from a clinical and radiological perspective. Thus, at first episode, given the urgency of starting the anti-inflammatory treatment, there is an unmet need to differentiate NMOSD subtypes from MS. Here, we used Fourier transform infrared spectroscopy in combination with a machine learning algorithm with the aim of distinguishing the infrared signatures of sera of a first episode of NMOSD from those of a first episode of relapsing-remitting MS, as well as from those of healthy subjects and patients with chronic inflammatory demyelinating polyneuropathy. Our results showed that NMOSD patients were distinguished from MS patients and healthy subjects with a sensitivity of 100% and a specificity of 100%. We also discuss the distinction between the different NMOSD serostatuses. The coupling of infrared spectroscopy of sera to machine learning is a promising cost-effective, rapid and reliable differential diagnosis tool capable of helping to gain valuable time in patients’ treatment.     

The effect of oxygen and the reduction temperature of the Pt/Al2O3 catalyst in enantioselective hydrogenation of 1-phenyl-1,2-propanedione

The effect of oxygen and catalyst reduction temperature in enantioselective hydrogenation of 1-phenyl-1,2-propanedione over commercial Pt/Al₂O₃ catalyst was investigated. Dichloromethane was used as solvent. The catalyst was modified in situ with (−)-cinchonidine. Relatively high enantiomeric excesses (65%) of (R)-1-hydroxy-1-phenyl-2-propanone were obtained with the solvent used as received, i.e. containing traces of dissolved oxygen and other impurities. Dichloromethane dissociated partially on the Pt/Al₂O₃ surface causing desorption of methane, ethene and HCl from the catalyst during TPD according to mass spectrometric analysis. Under anaerobic conditions the reaction rate was low giving only about 40% enantiomeric excesses of (R)-1-hydroxy-1-phenyl-2-propanone. When injecting 5 mm³ of oxygen into the reactor a beneficial effect was observed (i.e. higher reaction rate and enantiomeric excess) in comparison with anaerobic conditions. Poisoning effect of oxygen was observed when injecting 500 mm³ of oxygen into the reactor. Effect of catalyst reduction temperature was studied at three different temperatures (170, 400 and 455°C). Highest reaction rates and enantiomeric excesses were obtained with the catalyst reduced at 400°C. Methane was desorbed from the catalyst at temperatures between 263 and 383°C which could be the explanation for the lower activity of the catalyst reduced at 170°C. It was demonstrated that small amounts of oxygen can have a beneficial effect in enantioselective hydrogenation of 1-phenyl-1,2-propanedione and also that catalyst reduction temperature plays an important role in obtaining high enantiomeric excesses.     

Infrared and ultraviolet–visible spectroscopic studies of silica, [(Cp)2ZrCl2] and trimethylaluminum interactions

Infrared and UV–vis studies of metallocene immobilization on silica are reported here. The results have indicated changes in the Zr coordination sphere of metallocene depending on the immobilization route used. The reaction of [(Cp)₂ZrCl₂] with silica formed [(Cp)₂ZrCl]⁺[SiO]⁻ species. The same metallocene, reacting with TMA modified silica, formed monomethylated and dimethylated species by the substitution of chloro for methyl ligands, stabilized on the surface by interaction with “MAO-like” species (methylaluminoxane, MAO). These monomethylated and dimethylated cationic zirconium species are the active centers for the polymerization reaction. Different order of TMA addition in the silica modification step generated surface species of a similar nature, differing in their relative quantities. The highest amount of these active species was obtained when the support was added to the TMA solution rather than adding the TMA solution to the silica support. This was the most significant parameter affecting catalytic activity in ethylene polymerization.     

Deposition and Characteristics of Submicrometer-Structured Thermal Barrier Coatings by Suspension Plasma Spraying

In the field of thermal barrier coatings (TBCs) for gas turbines, suspension plasma sprayed (SPS) submicrometer-structured coatings often show unique mechanical, thermal, and optical properties compared to conventional atmospheric plasma sprayed ones. They have thus the potential of providing increased TBC performances under severe thermo-mechanical loading. Experimental results showed the capability of SPS to obtain yttria stabilized zirconia coatings with very fine porosity and high density of vertical segmentation cracks, yielding high strain tolerance, and low Young??s modulus. The evolution of the coating microstructure and properties during thermal cycling test at very high surface temperature (1400?°C) in our burner rigs and under isothermal annealing was investigated. Results showed that, while segmentation cracks survive, sintering occurs quickly during the first hours of exposure, leading to pore coarsening and stiffening of the coating. In-situ measurements at 1400?°C of the elastic modulus were performed to investigate in more detail the sintering-related stiffening.     

Laser monitoring of non‐Newtonian liquids during dip coating

Dip coated films, widely used in the coating industry, are usually measured by capacitive methods with micrometric precision. In this work, interferometric determination of thickness evolution in real time, for the first time to our best knowledge, is applied to volatile non‐Newtonian liquids with several viscosities and distinct dip withdrawing speeds. Thickness evolution during the process depends on time as predicted by a power law model. Comparison with measured results (uncertainty of ± 0.007 μm) showed very good agreement after initial steps of the process. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Synthesis and properties of water soluble single‐walled carbon nanotube graft ionic polyacetylene nanocomposites

Water‐soluble single‐walled carbon nanotube‐polyacetylene [SWNT‐PA, SWNT‐P(2EPy‐MeTf)] nanocomposites have been synthesized by using the surface initiated “grafting‐from” method. The FT‐IR spectra confirmed the formation of an amide bond between the functionalized SWNTs and the initiator, 4‐(2‐Aminoethyl) pyridine, to polymerize N‐Methyl‐2‐ethynlypyridinium triflate (2EPy‐MeTf). UV‐vis spectroscopy indicated that the degree of polymerization of P(2EPy‐MeTf) in the SWNT‐polyacetylene composites is 15, based on the Lewis‐Calvin equation. The SWNT‐polyacetylene composites have been characterized by TGA, AFM, and TEM. From TGA analysis, the loading of SWNTs in the SWNT grafted ionic polyacetylenes is estimated to be 22%. AFM and TEM images clearly showed that the nanotube is wrapped with the PA. The SWNT‐polyacetylene composites displayed high water solubility (8 mg/ml). The room temperature electrical conductivity of the doped SWNT‐polyacetylene composites was found to be in the range of 10⁻³ to 10⁻⁴ S/cm, an order of magnitude of increase over neat P(2EPy‐MeTf) and a two order of magnitude increase over Dendrimer‐polyacetylen composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

A new generation of sensors based on extraordinary optical transmission

[Reaction: see text]. Plasmonic-based chemical sensing technologies play a key role in chemical, biochemical, and biomedical research, but basic research in this area is still attracting interest. Researchers would like to develop new types of plasmonic nanostructures that can improve the analytical figures of merit, such as detection limits, sensitivity, selectivity, and dynamic range, relative to the commercial systems. They are also tackling issues such as cost, reproducibility, and multiplexing with the goal of providing the best plasmonic-based platform for chemical analysis. In this Account, we will describe recent advances in the optical and spectroscopic properties of nanohole arrays in thin gold films and their applications for chemical sensing. These nanostructures support the unusual phenomenon of "extraordinary optical transmission" (EOT), that is, they are more transparent at certain wavelengths than expected by the classical aperture theory. The EOT is a consequence of surface plasmon (SP) excitations; hence, the resonance should respond to the adsorption of organic molecules. We explored this effect and implemented the integration of the arrays of nanoholes as sensing elements in a microfluidic architecture. We then demonstrated how these devices could be applied in biochemical affinity tests. Arrays of nanoholes offer a small sensing footprint and operate at normal transmission mode, which make them more suitable for miniaturization. This new approach for SPR sensing is more compatible with the lab-on-chip concept and offers the possibility of high-throughput analysis from a single sensing chip. We explored the field localization properties of EOT for surface-enhanced spectroscopy. We could control the enhancement factors for SERS and SEFS by adjusting the geometry of the arrays. The shape of the individual nanoholes offers another handle to tune the enhancement factor for surface-enhanced spectroscopy and SPR sensitivity. Apexes in shaped nanostructures function as optical antennas, focusing the light at extremely small regions at the tips. We observed additional surface enhancement by tuning the apexes' properties. The extra enhancement in these cases originated only from the small number of molecules in the apex regions. The arrays of nanoholes are an exciting new substrate for chemical sensing and enhanced spectroscopy. This class of nanomaterials has the potential to provide a viable alternative to the commercial SPR-based sensors. Further research could exploit this platform to develop nanostructures that support high field localization for single-molecule spectroscopy.     

Catalytic behavior of hybrid Co/SiO2-(medium-pore) zeolite catalysts during the one-stage conversion of syngas to gasoline

The catalytic properties of 10-MR (membered ring) zeolites (ZSM-5, MCM-22, IM-5, ITQ-2, all with a similar Si/Al ratio of ca. 15) in hybrid Co/SiO₂-zeolite catalysts for the direct conversion of syngas to mainly high-octane gasoline-range hydrocarbons has been studied under typical Fischer-Tropsch (FT) conditions: 250 °C, 2.0 MPa, and H₂/CO = 2. Special emphasis has been given to the deactivation behavior and the characterization of the amount and nature of the carbonaceous deposits formed by a combination of techniques (elemental analysis, TGA (thermogravimetric analyses), GC–MS, and DR (diffuse reflectance) UV–vis spectroscopy). The presence of the medium-pore zeolite increases the gasoline yield by about 20–50%, depending on the particular zeolite, and enhances the formation of branched products with respect to the base Co/SiO₂ catalyst, which is explained by the promotion of isomerization and cracking of long-chain (C₁₃₊) n-paraffins formed on the FT component. The initial zeolite activity is mostly determined by the surface acidity rather than by the total amount of Brønsted acid sites, pointing out to the existence of limitations for the diffusion of the long-chain n-paraffins through the 10-MR channels under FT conditions. Thus, ITQ-2 bearing the largest surface area presents the highest initial yield of branched gasoline-range products, followed by ZSM-5, IM-5, and MCM-22. All zeolites experience a loss of activity with TOS, particularly during the initial reaction stages. This deactivation is governed by the morphological and structural properties of the zeolite, which finally determine the amount and location of the coke species, and not by the acidity.     

Evaluation of the effect of heat input in superduplex stainless steel deposition by the plasma powder process*

Plasma powder surfacing is one of the latest processes for application of coatings, with control of dilution as its main feature. Surfacing with superduplex stainless steels is an interesting option for the construction and repair of equipment for applications in a highly corrosive environment, allowing the desired characteristics to be achieved: corrosion resistance and good mechanical properties. The aim of this work is to assess the ferrite content in the weld metal and the mechanical characteristics via microhardness profiles in surfacing of C-Mn steel pipes with deposition of UNS S32760 by plasma powder surfacing. Welding operations were carried out on pipes with deposition of SDSS, employing three welding heat input levels, varying the welding speed or the welding current. Then the geometry was analysed, the ferrite content in the weld metal was quantified and the microhardness profile was recorded. Variation in welding heat input caused changes in weld bead geometry, with variation in the welding current producing the most significant changes. Increase in heat input caused decrease in ferrite content of the weld metal. Regarding microhardness, only the condition with a higher level of welding current gave sufficiently high levels of microhardness in the weld metal.