Preparation of CoSe nanoparticles by microwave-assisted polyol method: effect of Se/Co ratio, support type and synthesis conditions on oxygen reduction activity

Highly methanol-tolerant CoSe nanoparticles supported on different carbon substrates were synthesized by microwave heating of glycerol solutions of cobalt(II) acetate and sodium selenite at different Se/Co mole ratios in the presence of different concentrations of acetic acid and ammonia. The resulting CoSe catalysts were used for the electrochemical oxygen reduction reaction (ORR) in acidic solution in the presence of methanol. The ORR activity of the catalyst was increased by increasing its Se content up to 50?mol%. The presence of acetic acid or ammonia in the synthesis solution significantly affects the electrocatalytic performance of the CoSe catalyst; highest activity was observed when the catalyst was synthesized at NH₃/Co(II) mole ratio of 6. Among the catalysts prepared on different supports including carbon black (Vulcan XC-72R), and nanoporous carbons synthesized from resorcinol-formaldehyde and phloroglucinol-formaldehyde resins, the one supported on the carbon prepared from the last resin exhibited highest electrocatalytic activity for ORR.     

Green and Efficient Procedure for the Trimethylsilylation of Hydroxy Groups and Their Regeneration Using Sulfamic Acid as Recyclable Catalyst

Structurally diverse alcohols and phenols were efficiently transformed into their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of sulfamic acid (SA) at room temperature under both acetonitrile and solvent-free conditions. Deprotection of these trimethylsilyl ethers to their parent alcohols and phenols was also achieved using this catalyst in water at room temperature.     

Piezoelectric Performance of Microcellular Polypropylene Foams Fabricated Using Foam Injection Molding as a Potential Scaffold for Bone Tissue Engineering

Abstract

Piezoelectric properties and adequate porosity play important roles in bone tissue engineering. In this paper we describe the fabrication of piezoelectric polypropylene (PP) foam using injection molding to be utilized as a potential cost-effective scaffold for bone tissue engineering. One-side mechanical skin removal from the foam was used to investigate the effect of the solid skin on the piezoelectric performance. The microcellular structure, relative density, crystalline structure, mechanical properties, piezoelectric properties under repeated impact pressure and biocompatibility of the scaffolds were investigated using scanning electron microscopy (SEM), water displacement method, differential scanning calorimetry (DSC), uniaxial tension tests, piezoelectric tests and MTT assays, respectively. Uniform spherical cells, with an average size of 75?µm and a density of 1.23?×?10⁶ cells/cm^?3, suitable for bone regeneration, were imaged by SEM. The DSC results showed β crystals formation in the PP foam during the foaming process which would be valuable for mechanical properties. The foaming process did not reduce the mechanical properties significantly. The foaming process promoted the piezoelectric responses by 134, 922, and 87%, respectively, for the PP samples with 3, 2 and 1?mm thickness. The biocompatibility test suggested improved cellular biocompatibility by foaming. Overall, the results demonstrated the development of a cost-effective scaffold for tissue engineering.     

Vibro-acoustic response of an elliptical plate-cavity coupled system to external shock loads

A general fully coupled three-dimensional vibro-acoustic model is developed to investigate the forced non-stationary acousto-structural response of a thin elastic plate of elliptical planform which is backed by a reverberant, rigid, and finite (closed) elliptic cylindrical acoustic enclosure, while under the action of general external transverse loads of arbitrary temporal and spatial variations. The Laplace transform with respect to the time coordinate is invoked, and the classical method of separation of variables in elliptic coordinates is used to obtain the transformed solutions as a linear combination of even and odd modes in terms of products of radial and angular Mathieu functions. A linear system of coupled algebraic equations is ultimately obtained, which is truncated and then solved numerically by implementing Durbin’s numerical Laplace transform inversion scheme. Detailed numerical simulations are conducted for the temporal histories of plate center-point displacement and on-axis cavity acoustic pressure for air-coupled elliptic aluminum plates of selected aspect ratios when subjected to external loadings of practical interest (i.e., an impulsive point load, a uniformly distributed pulse load, and a blast load). Also, acoustic radiation into the backing enclosure is examined by using appropriate 2D images of the internal sound field for selected cavity depths and plate eccentricities. The presented results confirm that the acousto-elastic characteristics of the coupled plate-cavity system are significantly influenced by the plate aspect ratio, cavity depth and the transverse loading configuration. Validity of the work is established through the computations made by using a commercial finite element package.     

Improved photoelectrocatalytic activity of anodic TiO2 nanotubes by boron in situ doping coupled with geometrical optimization: Application of a potent photoanode in the purification of dye wastewater

Journal of Solid State Electrochemistry - A comparative study on the photoelectrocatalytic activity of anodic TiO2 nanotubes (TNTs) and boron-doped TiO2 nanotubes (BTNTs) was performed through...     

An experimental and numerical study on an innovative metastructure for 3D printed thermoplastic polyurethane with auxetic performance

Metamaterials are specifically designed materials that possess unique properties that cannot be found in naturally occurring substances. These remarkable materials have the capability to bring about a significant transformation across a wide range of industries. Auxetic structures are a recent area of research possess a distinctive characteristic known as a negative Poisson's ratio. Unlike conventional materials that contract when stretched, auxetic structures actually expand in two dimensions. In this study, a new auxetic structure was introduced, and thermoplastic polyurethane samples were 3D printed using a fused filament fabrication method. The samples are then subjected to strains ranging from 5% to 50% and Poisson's ratios are measured both experimentally and numerically using finite element method in Ansys software. By comparing the results of the experimental research and simulation, it is evident that applying strains within this range causes the Poisson's ratio of the samples to change from −0.81 to −0.14 and it showed that the newly introduced structure is auxetic. According to the analysis of root mean square error, the hexagonal mesh with a size of 0.7 mm consistently produced the most accurate results, aligning closely with the experimental sample. Given that this is an entirely novel auxetic structure within the category of arrow-head auxetic structures, there is potential for future research to be conducted in order to further develop and enhance this model.