Characterization and preparation of new multiwall carbon nanotube/conducting polymer composites by in situ polymerization

Composites based on poly(diphenyl amine) (PDPA) and multiwall carbon nanotubes (MWNTs) were prepared by chemical oxidative polymerization through two different approaches: in situ polymerization and intimate mixing. In in situ polymerization, DPA was polymerized in the presence of dispersed MWNTs in sulfuric acid medium for different molar composition ratios of MWNT and DPA. Intimate mixing of synthesized PDPA with MWNT was also used for the preparation of PDPA/MWNT composites. Transmission electron microscopy revealed that the diameter of the tubular structure for the composite was 10–20 nm higher than the diameter of pure MWNT. Scanning electron microscopy provided evidence for the differences in the morphology between the MWNTs and the composites. Raman and Fourier transform IR (FTIR) spectroscopy, thermogravimetric analysis, X‐ray diffraction, and UV–visible spectroscopy were used to characterize the composites and reveal the differences in the molecular level interactions between the components in the composites. The Raman and FTIR spectral results revealed doping‐type molecular interactions and coordinate covalent‐type interactions between MWNT and PDPA in the composite prepared by in situ polymerization and intimate mixing, respectively. The backbone structure of PDPA in the composite decomposed at a higher temperature (>340°C) than the pristine PDPA (～300°C). This behavior also favored the molecular level interactions between MWNT and PDPA in the composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3721–3729, 2006     

The determination of polymer interfacial tension by drop image processing: Comparison of theory and experiment for the pair,poly(dimethyl siloxane)/polybutndiene

The interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co-workers. Qualitative agreement is obtained with both types of theory when the Flory-Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperature.     

Immobilizing chromium in stainless steel slags with MnO addition

This work investigates the stabilizing impact of MnO on the leaching behavior of hazardous Cr-containing CaO-SiO₂-Al₂O₃-Cr₂O₃-MnO stainless steel slags after equilibrating at various elevated temperatures and evaluates the potential immobilization of Cr into a MnCr₂O₄ spinel phase from the existing Cr₂O₃ phase. The MnCr₂O₄ spinel phase was found to be an excellent Cr-stabilizer in stainless steel slags, where the leaching tendency of potentially hazardous Cr-related ions decreased with higher MnO content and lower equilibration temperatures within the range of 0 to 15 mass pct. and 1500 to 1300°C, respectively. Thermodynamic calculations by conducting the phase stability diagram also showed that the MnCr₂O₄ spinel phase was relatively stable and the Ca₃Si₂O₇ (Ca_3-xMn_xSi₂O₇) phase was relatively unstable compared with other crystal phases in acid extractant with pH value of 3.2. Combined with the scanning electron microscopy and X-ray powder diffraction results along with the thermodynamic calculations, the leached Cr-related ions was predominantly originating from the unstable amorphous glass phase.     

Changes in electrochemical impedance with microstructural development in TBCs

Thermal barrier coatings (TBCs) are improving the performance and efficiency of advanced gas turbine engines by allowing higher inlet temperature and insulation of critical hot-section components. Monitoring the integrity of TBCs prior to failure is critical to the overall performance of gas turbine en gines and requires a robust nondestructive evaluation (NDE) technique. In this paper, changes in electrochemical impedance with microstructural degradation of critical constituents in TBCs are summarized for the development of electrochemical impedance spectroscopy as an NDE technique for TBCs.     

Isothermal oxidation of physical vapor deposited partially stabilized zirconia thermal barrier coatings

Thermal barrier coatings (TBCs), consisting of physical vapor deposited (PVD) partially stabilized zirconia (PSZ, 8 wt.%Y₂O₃) and a diffusion aluminide bond coat, were characterized as a function of time after oxidative isothermal heat treatment at 1373 K in air. The experimental characterizations was conducted by X-ray diffraction analysis and scanning electron microscopy (SEM) with energy-dispersive spectroscopy. During cooling to room temperature, spallation of the PSZ ceramic coatings occurred after 200 and 350 h of isothermal heat treatment. This failure was always sudden and violent, with the TBC popping from the substrate. The monoclinic phase of zirconia was first observed on the bottom surface of the PVD PSZ after 200 h of isothermal heat treatment. The failure of TBCs occurred either in the bond coat oxidation products of αAl₂O₃ and rutile TiO₂ or at the interface between the oxidation products and the diffusion aluminide bond coat or the PSZ coating.     

Design and Implementation of a Ubiquitous Robotic Space

This paper describes a concerted effort to design and implement a robotic service framework. The proposed framework is comprised of three conceptual spaces: physical, semantic, and virtual spaces, collectively referred to as a ubiquitous robotic space. We implemented a prototype robotic security application in an office environment, which confirmed that the proposed framework is an efficient tool for developing a robotic service employing IT infrastructure, particularly for integrating heterogeneous technologies and robotic platforms.     

Implementation of mmWave long-range backhaul for UAV-BS

Uncrewed aerial vehicles (UAVs) have become a vital element in nonterrestrial networks, especially with respect to 5G communication systems and beyond. The use of UAVs in support of 4G/5G base station (uncrewed aerial vehicle base station [UAV-BS]) has proven to be a practical solution for extending cellular network services to areas where conventional infrastructures are unavailable. In this study, we introduce a UAV-BS system that utilizes a high-capacity wireless backhaul operating in millimeter-wave frequency bands. This system can achieve a maximum throughput of 1.3 Gbps while delivering data at a rate of 300 Mbps, even at distances of 10 km. We also present the details of our testbed implementation alongside the performance results obtained from field tests.     

Dominance of Plasmonic Resonant Energy Transfer over Direct Electron Transfer in Substantially Enhanced Water Oxidation Activity of BiVO4 by Shape‐Controlled Au Nanoparticles

The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape‐controlled Au NPs on bismuth vanadate (BiVO₄) are studied, and a largely enhanced photoactivity of BiVO₄ is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO₄ achieves 2.4 mA cm^?2 at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO₄. It is the highest value among the previously reported plasmonic Au NPs/BiVO₄. Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape‐controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells.     

Facile synthesis of CsPbBr3/PbSe composite clusters

In this work, CsPbBr₃ and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr₃ quantum dots modified the electronic structure of CsPbBr₃, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr₃ perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr₃ quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr₃/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr₃/PbSe sample with a 1:1 Cs:Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr₃ reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr₃ quantum dots.