Suppression of Catastrophic Failure in Metallic Glass–Polyisoprene Nanolaminate Containing Nanopillars

One considerable concern in metallic glass is enhancing ductility by suppressing catastrophic failure by the instantaneous propagation of shear bands. Compressed nanopillars with alternating CuZr metallic glass and polyisoprene nanolaminates exhibit >30% enhancement in plastic flow, as compared with monolithic glass, without sacrifice of strength. A suppression of stochastic strain burst signature in these metallic glass‐polymer composites is reported, which is an undesirable characteristic ubiquitously present in monolithic metallic glass and in metallic glass‐metal composites. The intermittent stochastic signature is quantified in each metallic glass‐containing nanolaminate system by constructing histograms of burst size distributions and provide theoretical foundation for each behavior. The exceptional mechanical properties emergent in these MG‐polymer nanolaminate composites are attributed to the combination of nanometer size‐induced shear band suppression in metallic glasses and the damping capability of the polyisoprene layers.     

NERC's Reliability Assurance Initiative: What Registered Entities Can Do

In the summer of 2003, a handful of power lines in Ohio tripped after making contact with overgrown trees. Over the next 13 minutes, the electric grid experienced cascading failures that left an estimated 50 million people in the United States and Canada without power. Two years later, Congress added Section 215 to the Federal Power Act, giving the Federal Energy Regulatory Commission (FERC) jurisdiction over the reliability of the bulk power system (BPS). Section 215 also directed FERC to designate an Electric Reliability Organization (ERO) to establish and enforce reliability standards with penalties up to a million dollars per day per violation.     

The influence of hydrogen pressure on the heterogeneous hydrogenation of β-myrcene in a CO2-expanded liquid

This paper presents the second part of work on the effect of hydrogen partial pressure on the hydrogenation of a terpene in a CO₂-expanded liquid. The effect of hydrogen partial pressure on the hydrogenation of β-myrcene possessing three CC bonds catalysed by alumina-supported ruthenium and rhodium was studied. Experiments were performed at various hydrogen pressures in the range from 2.0 up to 4.5 MPa at a fixed total pressure of 12.5 MPa. In all the conditions the reaction proceeded in two phases (liquid + gas), that is, the total pressure was below the critical pressure of the CO₂ + β-myrcene + H₂ system. The liquid phase volume is expanded in relation to the initial volume of β-myrcene in a fashion that is strongly dependent on the hydrogen and carbon dioxide pressures. An increase of H₂ pressure concomitantly diminishes carbon dioxide pressure, which leads to the enhancement of the liquid phase in hydrogen and a terpene. It does not direct to straightforward higher reaction rate, but surprisingly the effect of higher concentrations either hydrogen or β-myrcene is opposite. It is attributed to the fact that the hydrogenation of β-myrcene rate-controlling factor turns out to be the hydrogen to β-myrcene ratio which decreases as the hydrogen pressure increases. These unexpected appealing results present that lower pressures of hydrogen guide to higher hydrogen/β-myrcene ratios in the liquid phase, but on the other hand they also amplify the initial reaction rate constant. The obtained results are opposite to the results achieved for effect of hydrogen pressure on the Pd-catalysed hydrogenation of limonene consisting of two CC double bonds.     

Chemical characterization of crude petroleum using nanospray desorption electrospray ionization coupled with high-resolution mass spectrometry

Nanospray desorption electrospray ionization (nano-DESI) combined with high-resolution mass spectrometry was used for the first time for the analysis of the polar constituents of liquid petroleum crude oil samples. The analysis was performed in both positive and negative ionization modes using three solvents, one of which (acetonitrile/toluene mixture) is commonly used in petroleomics studies while two other polar solvents (acetonitrile/water and methanol/water mixtures) are generally not compatible with petroleum characterization using mass spectrometry. The results demonstrate that nano-DESI analysis efficiently ionizes petroleum constituents soluble in a particular solvent. When acetonitrile/toluene is used as a solvent, nano-DESI generates electrospray-like spectra. In contrast, strikingly different spectra were obtained using acetonitrile/water and methanol/water. Comparison with the literature data indicates that these solvents selectively extract water-soluble constituents of the crude oil. Water-soluble compounds are predominantly observed as sodium adducts in nano-DESI spectra indicating that addition of sodium to the solvent may be a viable approach for efficient ionization of water-soluble crude oil constituents. Nano-DESI enables rapid screening of different classes of compounds in crude oil samples based on their solubility in solvents that are rarely used for petroleum characterization providing better coverage of the crude oil composition as compared to electrospray ionization (ESI). It also enables rapid characterization of water-soluble components of petroleum samples that is difficult to perform using traditional approaches.     

Chemical analysis of complex organic mixtures using reactive nanospray desorption electrospray ionization mass spectrometry

Reactive nanospray desorption electrospray ionization (nano-DESI) combined with high-resolution mass spectrometry was utilized for the analysis of secondary organic aerosol produced through ozonolysis of limonene (LSOA). Previous studies have shown that LSOA constituents are multifunctional compounds containing at least one aldehyde or ketone groups. In this study, we used the selectivity of the Girard's reagent T (GT) toward carbonyl compounds to examine the utility of reactive nano-DESI for the analysis of complex organic mixtures. In these experiments, 1-100 μM GT solutions were used as the working solvents for reactive nano-DESI analysis. Abundant products from the single addition of GT to LSOA constituents were observed at GT concentrations in excess of 10 μM. We found that LSOA dimeric and trimeric compounds react with GT through a simple addition reaction resulting in formation of the carbinolamine derivative. In contrast, reactions of GT with monomeric species result in the formation of both the carbinolamine and the hydrazone derivatives. In addition, several monomers did not react with GT on the time scale of our experiment. These molecules were characterized by relatively high values of the double bond equivalent and low oxygen content. Furthermore, because addition of a charged GT tag to a neutral molecule eliminates the discrimination against the low proton affinity compounds in the ionization process, reactive nano-DESI analysis enables quantification of individual compounds in the complex mixture. For example, we were able to estimate for the first time the amounts of dimers and trimers in the LSOA mixture. Specifically, we found that the most abundant LSOA dimer was detected at the ～0.5 pg level and the total amount of dimers and trimers in the analyzed sample was ～11 pg. Our results indicate that reactive nano-DESI is a valuable approach for examining the presence of specific functional groups and for the quantification of compounds possessing these groups in complex mixtures.     

Growth of heavily doped monocrystalline and polycrystalline SiGe-based quantum dot superlattices

Various SiGe-based Quantum Dot Superlattices (QDSLs) were grown using an industrial Chemical Vapor Deposition tool with the intent to develop efficient thermoelectric thin films at a large scale. We report first on the growth of monocrystalline SiGe-based QDSLs. We were able to control the SiGe spacer width and the sizes and densities of Ge dots. A vertical ordering behavior was observed for large dot structures, but not for those with the smallest dots (30-70 nm wide, 3 nm high). In situ B doping operated during growth led to hole densities of 5 × 10¹⁹ to 1 × 10²⁰ cm^− 3. We also report on the growth of polycrystalline SiGe-based QDSLs with the same equipment. We show in particular that vertically aligned Ge dots were formed in a similar way as in monocrystalline structures despite the presence of stacking faults and grain boundaries. A heavy p doping was also obtained on some of these structures.     

In situ nanomechanical measurements of interfacial strength in membrane-embedded chemically functionalized Si microwires for flexible solar cells

Arrays of vertically aligned Si microwires embedded in polydimethylsiloxane (PDMS) have emerged as a promising candidate for use in solar energy conversion devices. Such structures are lightweight and concurrently demonstrate competitive efficiency and mechanical flexibility. To ensure reliable functioning under bending and flexing, strong interfacial adhesion between the nanowire and the matrix is needed. In situ uniaxial tensile tests of individual, chemically functionalized, Si microwires embedded in a compliant PDMS matrix reveal that chemical functionality on Si microwire surfaces is directly correlated with interfacial adhesion strength. Chemical functionalization can therefore serve as an effective methodology for accessing a wide range of interfacial adhesion between the rigid constituents and the soft polymer matrix; the adhesion can be quantified by measuring the mechanical strength of such systems.     

Ultrahigh strength of dislocation-free Ni3Al nanocubes

Individual Ni(3) Al nanocubes under pressure are investigated by comparing the compressive strength of both dislocation-free and irradiated Ni(3) Al nanocubes. The results are dicussed in light of the size-dependent and size-independent strength of face-centered cubic (fcc) nanocrystals in the framework of dislocation nucleation at free surfaces. This study sheds more light on the understanding of fundamental deformation mechanisms and size-affected strength in dislocation-free metallic nanocrystals.