High Surface Area MoS2/Graphene Hybrid Aerogel for Ultrasensitive NO2 Detection

A MoS₂/graphene hybrid aerogel synthesized with two‐dimensional MoS₂ sheets coating a high surface area graphene aerogel scaffold is characterized and used for ultrasensitive NO₂ detection. The combination of graphene and MoS₂ leads to improved sensing properties with the graphene scaffold providing high specific surface area and high electrical and thermal conductivity and the single to few‐layer MoS₂ sheets providing high sensitivity and selectivity to NO₂. The hybrid aerogel is integrated onto a low‐power microheater platform to probe the gas sensing performance. At room temperature, the sensor exhibits an ultralow detection limit of 50 ppb NO₂. By heating the material to 200 °C, the response and recovery times to reach 90% of the final signal decrease to <1 min, while retaining the low detection limit. The MoS₂/graphene hybrid also shows good selectivity for NO₂ against H₂ and CO, especially when compared to bare graphene aerogel. The unique structure of the hybrid aerogel is responsible for the ultrasensitive, selective, and fast NO₂ sensing. The improved sensing performance of this hybrid aerogel also suggests the possibility of other 2D material combinations for further sensing applications.     

Platinum Nanoparticle Loading of Boron Nitride Aerogel and Its Use as a Novel Material for Low‐Power Catalytic Gas Sensing

A high‐surface‐area, highly crystalline boron nitride aerogel synthesized with nonhazardous reactants has been loaded with crystalline platinum nanoparticles to form a novel nanomaterial that exhibits many advantages for use in a catalytic gas sensing application. The platinum nanoparticle‐loaded boron nitride aerogel integrated onto a microheater platform allows for calorimetric propane detection. The boron nitride aerogel exhibits thermal stability up to 900 °C and supports disperse platinum nanoparticles, with no sintering observed after 24 h of high‐temperature testing. The high thermal conductivity and low density of the boron nitride aerogel result in an order of magnitude faster response and recovery times (<2 s) than reported on alumina support and allow for 10% duty cycling of the microheater with no loss in sensitivity. The resulting 1.5 mW sensor power consumption is two orders of magnitude less than commercially available catalytic gas sensors and unlocks the potential for wireless, battery‐powered catalytic gas sensing.     

Enhanced compressive strength of carbon aerogels with low density and high specific surface areas

Journal of Porous Materials - Glycidol was firstly used as catalyst to synthesize resorcinol (R) and formaldehyde (F) aerogels and carbon aerogels (CAs). The density, morphology, specific surface...     

Controlled Synthesis of a Thin LTL Zeolitic Membrane Using Nano‐Sized Seeds: Characterization and Permeation Performance

Industrial zeolitic membranes which offer a remarkable selectivity compared to polymeric membranes, suffer of the lower flux due of their larger thickness (e.g., 10–30 μm). This problem can be addressed by controlled synthesis of nanolayers, resulting in thinner membrane layers (e.g., 0.5–5 μm). An aluminosilicate gel with a molar composition of 20SiO₂:Al₂O₃:10K₂O:400H₂O was used to prepare several membranes of zeolite L by means of a controlled hydrothermal synthesis on the surface of a porous alumina disc seeded with nanozeolite LTL crystals. Nanocrystallites of LTL zeolite with an average particle size of 80–100 nm were successfully synthesized and characterized. Using these nanoparticles as seeds, a zeolite L layer with an average thickness of 2 μm was synthesized on the alumina support at 150 °C.     

Solid‐state Materials and Methods for Hydrogen Storage: A Critical Review

Hydrogen is important as a new source of energy for automotive applications. It is clear that the key challenge in developing this technology is hydrogen storage. Current methods for hydrogen storage have yet to meet all the demands for on‐board applications. High‐pressure gas storage or liquefaction cannot fulfill the storage criteria required for on‐board storage. Solid‐state materials have shown potential advantages for hydrogen storage in comparison to other storage methods. In this article, the most popular solid‐state storage materials and methods including carbon based materials, metal hydrides, metal organic frameworks, hollow glass microspheres, capillary arrays, clathrate hydrates, metal nitrides and imides, doped polymer and zeolites, are critically reviewed. The survey shows that most of the materials available with high storage capacity have disadvantages associated with slow kinetics and those materials with fast kinetics have issues with low storage capacity. Most of the chemisorption‐based materials are very expensive and in some cases, the hydrogen absorption/desorption phenomena is irreversible. Furthermore, a very high temperature is required to release the adsorbed hydrogen. On the other hand, the main drawback in the case of physisorption‐based materials and methods is their lower capacity for hydrogen storage, especially under mild operating conditions. To accomplish the requisite goals, extensive research studies are still required to optimize the critical parameters of such systems, including the safety (to be improved), security (to be available for all), cost (to be lowered), storage capacity (to be increased), and the sorption‐desorption kinetics (to be improved).     

Finnish architectural competitions: structure,criteria and judgement process

The structure of the Finnish architectural competition system is examined to understand how a peer-review process works for the judgement and selection of the best architectural design. The evaluation of criteria in the competition process is clarified to determine how architectural issues are conceived and examined by the professional jury members. The thought processes of the architect-dominated jurors are elucidated; particularly design criteria connected with practitioners' tacit knowledge and experienced eyes. Open and direct interviews were conducted with seven architects who have direct involvement in the Finnish competition processes. They represent a wide array of practitioners' role at the board of jury, from the Finnish Architects Association (SAFA) which is officially responsible for arranging major architectural competitions to invited architect and design competitors.

La structure du système finlandais des concours d'architecture est examinée de manière à comprendre comment fonctionne un processus de contrôle par les pairs qui vise à juger et sélectionner les meilleures conceptions architecturales. L'évaluation des critères intervenant dans le processus des concours est clarifiée, afin de déterminer comment les membres de jury de professionnels conçoivent et envisagent les questions d'architecture. Les processus de réflexion des jurés, qui sont en majorité des architectes, sont expliqués; tout particulièrement les critères de conception liés aux connaissances implicites et à l'?il exercé des praticiens. Des entretiens directs et ouverts ont été menés avec sept architectes qui participent directement aux processus des concours finlandais. Ils sont largement représentatifs du rôle exercé par les praticiens au sein de la commission de jury de l'Association des Architectes Finlandais (SAFA) qui a officiellement la responsabilité d'organiser les principaux concours d'architecture auprès des architectes et concepteurs invités à concourir.

Mots clés: concours d'architecture, évaluation de la conception, qualité de la conception, évaluation par les pairs, Finlande     

Synthesis of BZSM‐5 Membranes Using Nano‐Zeolitic Seeds: Characterization and Separation Performance

Nanoseeds of BZSM‐5 zeolite with a narrow particle size distribution of 100–200 nm were successfully prepared under mild hydrothermal conditions. Thin and oriented BZSM‐5 membranes of 3–4 μm, prepared at low temperature, were manufactured and examined for the separation of 5 wt‐% ethanol/water mixtures. Separation factor and flux were 13.93 and 1.11 kg m^–2h^–1, respectively. The temperature of synthesis showed a remarkable influence on the morphology, crystal orientation and separation performance of the membranes. The thinner a,b‐oriented membrane showed a higher separation performance than the thicker h0h‐oriented one.     

Disabling of Nanoparticle Effects at Increased Temperature in Nanocomposite Solders

The use of nanoparticles to control grain size and mechanical properties of solder alloys at high homologous temperature is explored. It is found that silica nanoparticles in the 100?nm range coated with 2?nm to 3?nm of gold can be dispersed within solders during the normal reflow soldering process, and that these particles are effective in hardening the solder and restricting dynamic grain growth during compression testing at low homologous temperature. As the homologous temperature increases towards 0.75, the effects of the nanoparticles on both mechanical properties and dynamical grain growth reduce, and by homologous temperatures of 0.86 the effects have completely disappeared. This behavior is explained by introducing the concept of an effective volume fraction of pinning nanoparticles, and the practical implications for using nanoparticles to control solder properties via Zener pinning at high homologous temperatures are discussed.     

Thermally assisted semiconductor-like to insulator transition in gold-poly(methyl methacrylate) nanocomposites

Gold-polymethylmethacrylate (PMMA) nanocomposites were fabricated by mixing gold nanoparticles capped with oleylamine in polymethylmethacrylate. The samples were analysed using UV-vis absorption spectroscopy, transmission electron microscopy, small angle x-ray scattering, Fourier transform infrared spectrometry (FTIR) and x-ray photoelectron spectroscopy (XPS). Electrical resistivity of nanocomposite samples was measured by a four-probe technique in the 70-300?K range. The nanocomposites showed a transition with an onset at ～160-165?K. They exhibited a semiconductor-like conductivity at higher temperatures and nearly temperature independent conductivity at lower temperatures. The interfacial interaction of Au nanoparticles and PMMA polymer is investigated using FTIR and XPS. A ligand-exchange process occurs when capped gold nanoparticles are incorporated in PMMA polymer.     

Gold-Nano Particles Supported on Na-Y and H-Y Types Zeolites: Activity and Thermal Stability for CO Oxidation Reaction

Gold nano particles (GNP) were deposited on Na-Y and H-Y zeolite substrates using chloroauric acid (HAuCl₄) solution. The synthesized catalysts were then characterized and the catalytic activity toward CO oxidation reaction was investigated using a tubular fix bed micro reactor under atmospheric pressure. It was found that CO conversion of 100% and 5% can be achieved at 20 °C on Au/Na-Y and Au/H-Y fresh catalysts, respectively. Thermal stability of catalysts was also investigated by treating the catalysts at 400 °C for 4 h. After thermal stability test, activity tests of the catalysts at 20 °C were shown that CO conversion of Au/Na-Y catalyst was decreased to 65% whereas the activity of the Au/H-Y at 20 °C was increased up to 15%. Characterization tests were revealed that the structures of the zeolitic supports were remained unchanged after thermal pretreatment.