Morphology-dependent activity of Pt nanocatalysts for ethanol oxidation in acidic media: Nanowires versus nanoparticles

The morphology of nanostructured Pt catalysts is known to affect significantly the kinetics of various reactions. Herein, we report on a pronounced morphology effect in the electrooxidation of ethanol and carbon monoxide (CO) on Pt nanowires and nanoparticles in an acidic solution. The high resolution transmission electron microscopy analysis showed the inherent morphology difference between these two nanostructured catalysts. Voltammetric and chronoamperometric studies of the ethanol electrooxidation revealed that these nanowires had a higher catalytic activity by a factor of two relative to these nanoparticles. The rate for CO monolayer oxidation exhibits similar morphology-dependent behavior with a markedly enhanced rate on the Pt nanowires. In situ infrared reflection–absorption spectroscopy measurements revealed a different trend for chemisorbed CO formation and CO₂-to-acetic acid reaction product ratios on these two nanostructures. The morphology-induced change in catalytic activity and selectivity in ethanol electrocatalysis is discussed in detail.     

Enhanced Oxygen Reduction Activity of IrCu Core Platinum Monolayer Shell Nano-electrocatalysts

Designing novel cathode materials for a proton exchange membrane fuel cell with high activity for the oxygen reduction reaction, low Pt loading, and enhanced long-term stability is imperative for its sustainability. To date, Pt monolayer based electrocatalysts deposited on a metallic core substrate have shown promising possibilities. In this study, we synthesized bimetallic IrCu nanoparticles and used them as a core for Pt monolayer electrocatalysts. It was found that the de-alloyed IrCu nanoparticle surfaces increased both the mass and specific activities of the resulting Pt monolayer catalyst. In addition, we demonstrated that Pt monolayer electrocatalysts with a de-alloyed IrCu core have a better stability than those using a non-dealloyed core based on a 5,000 potential cycling test. These data describe a new simple synthesis of a high-performance catalyst suitable for practical applications.     

Evaluation of the phytomass source for composite preparation

The properties of lignocellulose materials from the trunk and bark of trees, and from agricultural sources were investigated by thermogravimetry (TG) and pyrolysis–gas chromatography/mass spectrometry (Py‐GC/MS). The goal was to learn which of the phytomass sources is the most accessible to dehydration and aldol reactions, and in this way could be considered suitable for composite preparation by the thermal pressing treatment. The bagasse second differential thermal analysis peak in air is at the highest temperature acceptable for intermolecular dehydration/crosslinking, and therefore we consider bagasse to be the most suitable candidate for composite preparation. From the TG results in air at 250°C, it follows that willow wood and bagasse are the most thermally resistant sources. The data obtained by Py‐GC/MS analysis showed glycolaldehyde and acetic acid as dominant markers related to adhesion properties via aldol condensation. The detected sum amount of glyceraldehyde and acetic acid decreases in the order: beech wood > bagasse > acacia wood > sugar beet pulp, whereas the remaining species produced much less of it. By comparing results run at above conditions with composite preparation using the pressing thermal treatment at a temperature of 150°C and pressures up to 800 kPa, the suggested evaluation was examined for application on sugar beet residue. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The influence of lubricating greases on rolling bearing failure

Significant savings can be made by the correct use of lubricants in terms of energy consumption, replacement parts, maintenance costs and the reduction of machinery downtime, because the service life of machines is one of the most important aspects of engineering. Planned preventive maintenance means the minimisation of failures and of maintenance costs; the technology should allow identification of the tribomechanical systems in all operating conditions and of the tribological regime and duration of operation. Despite the enormous advances that have been made over the last thirty years in the theory of rolling bearing lubrication, the successful operation of rolling bearings remains highly dependent on empirical knowledge. The aim of the present study is to investigate the influence of lubricating grease on rolling bearing failure; the experimental work was carried out at a metalworking factory.     

Reliability characterization of a soot particle sensor in terms of stress- and electromigration in thin-film platinum

In this work we present a systematic investigation of various failure mechanisms for thin-film platinum heater structures and interdigitated electrodes as components of a resistive type soot particle sensor. We study the role of stress-migration and electromigration and their interaction for the reliability of these sensors. The influence of a titanium adhesion layer and gases from the ambient atmosphere are also studied. Lifetime determination and optical and scanning electron microscopy are applied for samples which have experienced different load conditions to understand qualitatively and quantitatively the phenomena. The aim of this work is to enable time-to-failure prediction and thus provide guidelines for limiting temperature and current density in the actual sensor to ensure its stability over lifetime. We use dedicated, application-related test structures to ensure that the results are applicable to sensor lifetime estimations.     

Software-Defined Fog Network Architecture for IoT

Rapid increase in number and diversity of Internet-connected devices raises many challenges for the traditional network architecture, which is not designed to support a high level of scalability, real-time data delivery and mobility. To address these issues, in this paper we present a new model of Internet of Things architecture which combines benefits of two emerging technologies: software-defined networking and Fog computing. Software-defined networking implies a logically centralized network control plane, which allows implementation of sophisticated mechanisms for traffic control and resource management. On the other hand, Fog computing enables some data to be analysed and managed at the network edge, thus providing support for applications that require very low and predictable latency. In the paper, we give detailed insight into the system structure and functionality of its main components. We also discuss the benefits of the proposed architecture and its potential services.     

“A Music Lesson”

The author is a two time recipient of Senior Fulbright Teaching and Research grants and has spent considerable time in Latin American architectural programs. The article provides a number of critical observations with respect to exisiting pedagogical approaches prevalent in South and Latin America and reflects on how these affect current architectural practice. Among the principal ideas discussed are the formation of design ideology, teacher-student interaction and the development of social and ethical responsibilities of professionals vis-a-vis existing conditions in the emerging nations.     

Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis

Using a combination of density functional theory (DFT) calculations and an array of experimental techniques including in situ X-ray absorption spectroscopy, we identified, synthesized, and tested successfully a new class of electrocatalysts for the oxygen reduction reaction (ORR) that were based on monolayers of Pt deposited on different late transition metals (Au, Pd, Ir, Rh, or Ru), of which the Pd-supported Pt monolayer had the highest ORR activity. The amount of Pt used was further decreased by replacing part of the Pt monolayer with a third late transition metal (Au, Pd, Ir, Rh, Ru, Re, or Os). Several of these mixed Pt monolayers deposited on Pd single crystal or on carbon-supported Pd nanoparticles exhibited up to a 20-fold increase in ORR activity on a Pt-mass basis when compared with conventional all-Pt electrocatalysts. DFT calculations showed that their superior activity originated from the interaction between the Pt monolayer and the Pd substrate and from a reduced OH coverage on Pt sites, the result of enhanced destabilization of Pt–OH induced by the oxygenated third metal. This new class of electrocatalysts promises to alleviate the major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.     

Transparent PMMA/silica nanocomposites containing silica nanoparticles coating under supercritical conditions

This work reports the preparation of PMMA/silica nanocomposites with high optical transparency and enhanced mechanical properties using a melt compounding method. The surface of SiO₂ particles was modified with a γ-methacryloxypropyltrimethoxy silane coupling agent in a supercritical carbon dioxide-ethanol mixture and by conventional procedure. Dispersion of silica nanoparticles in ethanol at low temperatures plays an important role in deagglomeration and dispersion of nanosilica, which leads to the optimal particle-matrix bonding in composites. The optimal mechanical and optical properties were found for composites loaded with 5 wt% silica nanoparticles treated under supercritical coating method.