Oxidation Study of an EB-PVD MCrAlY Thermal Barrier Coating System

In this paper the oxidation kinetics data on a TBC system where the NiCoCrAlY bond coat and the YSZ topcoat are both applied by the EB-PVD process are presented. The oxidation testing was performed at 950, 1050 and 1150 °C with times up to 1000 h. SEM analysis and modelling of the TGO growth rate show that the TGO is formed in two stages and that the initial oxide formed during the manufacture of the topcoat is non-protective. A global expression is derived for the oxidation kinetics at the three temperatures.     

Deposition and characteristics of chromium nitride thin film coatings on precision balls for tribological applications

Thin film hard coatings on rolling element surfaces can enhance the overall wear resistance of rolling element bearings, as demonstrated previously for coated tapered, cylindrical, and spherical roller bearings. Hard coatings in ball bearings are less common because of the difficulty in achieving uniform film thickness on a ball surface. This limitation is overcome by a new process for depositing chromium nitride coatings with uniform thickness on precision balls using ion beam assisted deposition (IBAD) e-beam evaporation. Scanning electron microscopy indicated that the deposited films were smooth and conformal on the ball surfaces with no areas of localized delamination. Auger electron spectroscopy confirmed that Cr₂N and CrN bulk film stoichiometry was achievable by modulating the argon to nitrogen process gas ratio during deposition. Transmission electron microscopy revealed dense, polycrystalline film structure. Film hardness and elastic modulus as measured using nanoindentation on the coated balls met expectations for chromium nitride, and tribological testing of the coated balls in angular contact ball bearings under moderate contact stress levels demonstrated adequate film adhesion for practical use of these coatings in bearing applications.     

Water�CGas Shift and CO Methanation Reactions over Ni�CCeO2(111) Catalysts

X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO₂(111) surfaces. Upon adsorption on CeO₂(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500?C800 K) leads to partial reduction of the ceria substrate with the formation of Ni²⁺ species that exists as NiO and/or Ce_1?xNi_xO_2?y. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO₂(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce⁺³ cations, CO dissociates on the surface at 300 K forming NiC_x compounds that may be involved in the formation of CH₄ at higher temperatures. At medium and large Ni coverages (>0.3 ML), the Ni/CeO₂(111) surfaces are able to catalyze the production of methane from CO and H₂, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (<0.3 ML), the Ni/CeO₂(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water?Cgas shift reaction.     

Hierarchical NiMn Layered Double Hydroxide/Carbon Nanotubes Architecture with Superb Energy Density for Flexible Supercapacitors

A hierarchical nanostructure composed of NiMn‐layered double hydroxide (NiMn‐LDH) microcrystals grafted on carbon nanotube (CNT) backbone is constructed by an in situ growth route, which exhibits superior supercapacitive performance. The resulting composite material (NiMn‐LDH/CNT) displays a three‐dimensional architecture with tunable Ni/Mn ratio, well‐defined core‐shell configuration, and enlarged surface area. An electrochemical investigation shows that the Ni₃Mn₁‐LDH/CNT electrode is rather active, which delivers a maximum specific capacitance of 2960 F g^–1 (at 1.5 A g^–1), excellent rate capability (79.5% retention at 30 A g^–1), and cyclic stability. Moreover, an all‐solid‐state asymmetric supercapacitor (SC) with good flexibility is fabricated by using the NiMn‐LDH/CNT film and reduced graphene oxide (RGO)/CNT film as the positive and negative electrode, respectively, exhibiting a wide cell voltage of 1.7 V and largely enhanced energy density up to 88.3 Wh kg^–1 (based on the total weight of the device). By virtue of the high‐capacity of pseudocapacitive hydroxides and desirable conductivity of carbon‐based materials, the monolithic design demonstrated in this work provides a promising approach for the development of flexible energy storage systems.     

A Supermolecular Photosensitizer with Excellent Anticancer Performance in Photodynamic Therapy

A supermolecular photosensitizer with excellent anticancer behavior when used for photodynamic therapy (PDT) is fabricated by the incorporation of zinc phthalocyanines (ZnPc) into the gallery of a layered double hydroxide (LDH). The composite material possesses uniform particle size (hydrodynamic diameter ～120 nm), and the host–guest and guest–guest interactions result in a high dispersion of ZnPc in a monomeric state in the interlayer region of the LDH matrix, with high singlet oxygen production efficiency. In vitro tests performed with HepG2 cells reveal a satisfactory PDT effectiveness of the ZnPc(1.5%)/LDH composite photosensitizer: a cellular damage as high as 85.7% is achieved with a rather low dosage of ZnPc (10 μg/mL). An extraordinarily high specific efficacy is demonstrated (31.59 μg^?1 (J/cm²)^?1), which is over 185.5% enhancement compared with the previously reported photosensitizers under similar test conditions. Furthermore, an in vivo study of the ZnPc(1.5%)/LDH demonstrates excellent PDT performance with an ultra‐low dose (0.3 mg/kg) and a low optical fluence rate (54 J/cm²). In addition, the ZnPc/LDH photosensitizer displays high stability, good biocompatibility, and low cytotoxicity, which would guarantee its practical application. Therefore, this work provides a facile approach for design and fabrication of inorganic–organic supermolecular materials with greatly enhanced anticancer behavior.     

Hierarchical Nanowire Arrays Based on ZnO Core−Layered Double Hydroxide Shell for Largely Enhanced Photoelectrochemical Water Splitting

Well‐aligned hierarchical nanoarrays containing ZnO core and layered double hydroxide (LDH) nanoplatelets shell have been synthesized via a facile electrosynthesis method. The resulting ZnO@CoNi–LDH core?shell nanoarray exhibits promising behavior in photoelectrochemical water splitting, giving rise to a largely enhanced photocurrent density as well as stability; much superior to those of ZnO‐based photoelectrodes. This is attributed to the successful integration of photogenerated electron–hole separation originating from the ZnO core and the excellent electrocatalytic activity of LDH shell. This work provides a facile and cost‐effective strategy for the fabrication of multifunctional nanoarrays with a hierarchical structure, which can be potentially used in energy storage and conversion devices.     

The Hinterland Urbanised?

What defines the urban? And can the non-urban necessarily always be classified as rural? Neil Brenner , Director of the Urban Theory Lab at Harvard University Graduate School of Design, reflects on the lack of an overarching theory to describe these realms, and argues that what we call the countryside or the hinterland has become key to the process of capitalist urbanisation.     

Effect of ionic strength on the reactivity ratios of acrylamide/acrylic acid (sodium acrylate) copolymerization

The ionic strength (IS) of polyelectrolyte solutions plays an important role in influencing reaction kinetics. The largely unstudied effect of IS on monomer reactivity ratios and copolymerization rates of acrylamide (AAm) and acrylic acid (AAc), in the form of sodium acrylate (NaAc), is investigated. Salt addition affects the nature of overall charges of the polyelectrolyte solution and diminishes the electrostatic repulsions between reacting chains. Therefore, changing the IS of the solution by incorporating salts affect not only the point estimates of the monomer reactivity ratios but also the overall behavior of the copolymerization (with a transition to azeotropic behavior). Experimental results on copolymerization rates confirm the observed trends in reactivity ratio behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40949.