A new approach for synthesis of well-crystallized Y zeolite from bentonite and rice husk ash used in Ni-Mo/Al2O3-Y hybrid nanocatalyst for hydrocracking of heavy oil

A series of Ni-Mo/Al₂O₃-Y hybrid nanocatalysts were synthesized for hydrocracking of heavy oil. The well crystallized Y zeolite was synthesized from mineral bentonite and rice husk ash by a two-step synthesis method. The solution combustion method was applied to develop a fast and simple technique for preparing of alumina-supported NiMo catalyst with high hydrodesulfurization activity. Such activity may be due to the morphological and textural modification as a consequence of the release of a high amount of exhaust gases during the combustion process. The XRD analysis revealed that the P zeolite was a competitive phase presented in the obtained product that could be eliminated using a two-step synthesis method. Compared to a one-step method, the pore volume and external surface area of the synthesized zeolite by the two-step method increased by 74 and 62%, respectively. The hydrocracking results illustrated that the synthesized zeolite was able to convert 66% of heavy oil to lighter products and reduce the viscosity up to 60%. Furthermore, the amount of sulfur removal was found to be 58%. The spent catalyst characterization suggested that the type of deposited coke was hard coke with the unsaturated aromatic ring which could be responsible for the pores blockage after the cracking reaction.     

Photonic crystal-based permutation switch for optical networks

We present, for the first time, the design of a low-cross talk scalable permutation switch employing photonic crystal ring resonators in an optical network. Through this novel approach, the transition between different states of the \(2 \times 2\) optical switch, as the basic element, is achieved by applying different operating wavelengths. Subsequently, the shuffling mechanisms in \(3 \times 3\) and \(4 \times 4\) optical networks are realized by controlling the position of photonics crystal ring resonators. Lowest cross talk levels of 6 and 5% are obtained for “bar” and “cross” switching states, respectively.     

Contribution of first- versus second-generation products to secondary organic aerosols formed in the oxidation of biogenic hydrocarbons

Biogenic hydrocarbons emitted by vegetation are important contributors to secondary organic aerosol (SOA), but the aerosol formation mechanisms are incompletely understood. In this study, the formation of aerosols and gas-phase products from the ozonolysis and photooxidation of a series of biogenic hydrocarbons (isoprene, 8 monoterpenes, 4 sesquiterpenes, and 3 oxygenated terpenes) are examined. By comparing aerosol growth (measured by Differential Mobility Analyzers, DMAs) and gas-phase concentrations (monitored by a Proton Transfer Reaction Mass Spectrometer, PTR-MS), we study the general mechanisms of SOA formation. Aerosol growth data are presented in terms of a "growth curve", a plot of aerosol mass formed versus the amount of hydrocarbon reacted. From the shapes of the growth curves, it is found that all the hydrocarbons studied can be classified into two groups based entirely on the number of double bonds of the hydrocarbon, regardless of the reaction systems (ozonolysis or photooxidation) and the types of hydrocarbons studied: compounds with only one double bond and compounds with more than one double bond. For compounds with only one double bond, the first oxidation step is rate-limiting, and aerosols are formed mainly from low volatility first-generation oxidation products; whereas for compounds with more than one double bond, the second oxidation step may also be rate-limiting and second-generation products contribute substantially to SOA growth. This behavior is characterized by a vertical section in the growth curve, in which continued aerosol growth is observed even after all the parent hydrocarbon is consumed.     

GaN nanorod Schottky and p-n junction diodes

Conductive atomic force microscopy has been used to characterize single GaN nanorod Schottky and p-n junction diodes. The ideality factor, reverse breakdown voltage, and the Schottky barrier height of individual nanorod diodes were compared to those from conventional thin-film diodes. Large-area contacts, enabling diodes with arrays of GaN nanorods in parallel, were also fabricated and their electrical characteristics investigated. The defect-free nature of the GaN nanorods and enhanced tunneling effects due to nanoscale contacts have been invoked to explain the electrical behavior of the nanorod diodes.     

Novel approach to the synthesis of core-shell particles by sacrificial polymer shell method

In this work a new approach has been developed for the synthesis of SiO₂@Y₂O₃ particles with core-shell structure. The method is based on the synthesis of a covalently bonded sacrificial polymer shell grown onto silica particles. It is suitable to promote and stabilize the adsorption of different ions, namely Yttrium from its nitrate solution. After calcination and consequent elimination of the sacrificial polymer shell, the SiO₂@Y₂O₃ core-shell particles are obtained. Results reveal that the shell thickness of these core-shell particles is higher and more uniform than that of particles prepared without sacrificial polymer shell.     

Graphene decoration with metal nanoparticles: towards easy integration for sensing applications

A simple and versatile method for the decoration of CVD grown graphene with metal nanoparticles is presented. The mechanism of nanoparticle formation is galvanic displacement resulting in physically adsorbed clusters. The single layer graphene obtained by this method can be easily transferred. Integration onto a gas sensing transducer is presented as proof of concept.     

Developing economic order quantity model for non-instantaneous deteriorating items in vendor-managed inventory (VMI) system

This paper develops an economic order quantity model for non-instantaneous deteriorating items with and without shortages to investigate the performance of the vendor-managed inventory (VMI) system. This model is developed for a two-level supply chain consisting of a single supplier and single retailer with a single non-instantaneous deteriorating item. A numerical example and sensitivity analysis are provided to illustrate how increasing or reducing the related parameters change the optimal values of the decision variables of the two proposed models. The results show that VMI works better and charges lower cost in all conditions.     

Functionalization of Scanning Force Microscopy Cantilevers via Galvanic Displacement Technique

A galvanic displacement technique is used to coat silicon scanning force microscopy cantilevers with copper. The copper coating is characterized using X-ray photoelectron spectroscopy, scanning force microscopy, contact angle measurements, scanning electron microscopy and energy-dispersive X-ray spectroscopy. This coating technique results in uniform, reflective and conformal films and hence, no stress-induced bending of the cantilever is observed. To demonstrate the effectiveness of this approach for tribological studies, the coated cantilevers are chemically modified with alkanethiol monolayers in order to functionalize the cantilevers. The effect of changed surface energy are detected with adhesion measurements in water and ethanol.     

Nonenzymatic glucose sensing based on deposited palladium nanoparticles on epoxy-silver electrodes

A new approach for nonenzymatic glucose sensing, based on a simple modification of epoxy-silver surfaces deposited on the tip of commercial copper electric wires, is presented. Palladium was galvanically displaced on the surface of the epoxy-silver surface in order to obtain metal nanoparticles that act as catalyst for the direct oxidation of glucose. Scanning electron microscopy revealed the formation of the metal nanoparticles. X-ray photoelectron spectroscopy confirmed the metallic nature of the formed nanostructures on the surface. Electrochemical characterization and calibration of the palladium-modified epoxy-silver electrode is reported, obtaining a linear range of 1–20 mM for the detection of glucose with low interference of ascorbic acid and uric acid. A simple 3-step coulometry was used as the detection technique. The developed sensing material is believed to be a great candidate for integration in small devices for clinical essays, due to the simplicity and cost effectiveness of the presented approach, compared to the state-of-the-art devices reported recently in the literature. Simplicity in the coulometry determinations makes these Pd-modified epoxy-silver sensors a good candidate for easy glucose determinations.