Macroscale Size Research Articles

In situ synthesis of flexible Bi7O9I3/carbon paper with enhanced photocatalytic activity

Although Bi7O9I3 is an oxygen-rich bismuth oxyiodide with higher photocatalytic activity than BiOI, its applicability for photocatalytic oxidation is limited by the rapid recombination of photogenerated carriers and poor reusability. Depositing Bi7O9I3 on flexible macro-sized carbonaceous materials is a promising approach for promoting photogenerated electron migration and improving reusability. In this study, a composite consisting of Bi7O9I3 supported on graphitic carbon paper (Bi7O9I3-CP) was synthesized via the in situ transformation of a BiOI-deposited carbon paper precursor (BiOI-CP). The as-prepared Bi7O9I3-CP exhibited higher visible-light-driven photocatalytic activity than both Bi7O9I3 and BiOI-CP precursor for phenol removal. The improved photocatalytic activity of Bi7O9I3-CP was attributed to its hierarchical structure and promoted carrier separation, as revealed by photoluminescence, pore structure, and reactive radical analyses. Moreover, owing to its macroscale size and flexibility, the Bi7O9I3-CP composite could be easily operated and reused, which are favorable for practical applications.

CROSS-SCALE MODELING OF LIQUID FLOWS IN HUMAN BODIES

Multiple modeling approaches to liquid flows in human bodies are reviewed. They span from the macroscale size > 1 mm to the nanoscale size only on the 1 nm scale. They can respectively model the flows of the blood in large arteries, small arteries, arterioles, and capillaries; and the flows of water through the nanopores of the capillary wall, the cellular membrane, and the cellular connexon. They are respectively the macroscale continuum flow modeling, the mesoscale one-dimensional continuum flow modeling, the microscale dissipative particle dynamics method, the macro-nano multiscale flow modeling, and the nanoscale flow modeling. Integrating these approaches together can give comprehensive simulations of liquid flows in human bodies.

Visualisation of sulphur on single fibre level for pulping industry

In the pulp and paper industry, about 5 Mt/y chemithermomechanical pulp (CTMP) are produced globally from softwood chips for production of carton board grades. For tailor making CTMP for this purpose, wood chips are impregnated with aqueous sodium sulphite for sulphonation of the wood lignin. When lignin is sulphonated, the defibration of wood into pulp becomes more selective, resulting in enhanced pulp properties. On a microscopic fibre scale, however, one could strongly assume that the sulphonation of the wood structure is very uneven due to its macroscale size of wood chips. If this is the case and the sulphonation could be done significantly more evenly, the CTMP process could be more efficient and produce pulp even better suited for carton boards. Therefore, the present study aimed to develop a technique based on X-ray fluorescence microscopy imaging (µXRF) for quantifying the sulphur distribution on CTMP wood fibres. Firstly, the feasibility of µXRF imaging for sulphur homogeneity measurements in wood fibres needs investigation. Therefore, clarification of which spatial and spectral resolution that allows visualization of sulphur impregnation into single wood fibres is needed. Measurements of single fibre imaging were carried out at the Argonne National Laboratory’s Advanced Photon Source (APS) synchrotron facility. With a synchrotron beam using one micrometre scanning step, images of elemental mapping are acquired from CTMP samples diluted with non-sulphonated pulp under specified conditions. Since the measurements show significant differences between sulphonated and non-sulphonated fibres, and a significant peak concentration in the shell of the sulphonated fibres, the proposed technique is found to be feasible. The required spatial resolution of the µXRF imaging for an on-site CTMP sulphur homogeneity measurement setup is about 15 µm, and the homogeneity measured along the fibre shells is suggested to be used as the CTMP sulphonation measurement parameter.

Supraparticles on beads for supported catalytically active liquid metal solutions - the SCALMS suprabead concept.

A novel GaPt-based supported catalytically active liquid metal solution (SCALMS) material is developed by exploiting the suprabead concept: Supraparticles, i.e. micrometer-sized particles composed of nanoparticles assembled by spray-drying, are bonded to millimeter-sized beads. The suprabeads combine macroscale size with catalytic properties of nanoscale GaPt particles entrapped in their silica framework.

Developing dual nano/macroporous starch bioaerogels via emulsion templating and supercritical carbon dioxide drying

In this study, emulsified oil droplets were employed as a temporary porogen to obtain dual nano/macroporous starch aerogels by supercritical carbon dioxide (SC-CO2) drying. This method took advantage of the solubility of the oil droplet porogens in acetone, and the insolubility of corn starch in this solvent, so this process could be integrated into the typical aerogel processing method. The effect of porogen content and starch concentration on physical and mechanical properties and the internal morphology of the obtained aerogels were studied. While the neat starch aerogel showed a compact structure in macroscale size with interconnected nanopores, the sacrificing oil droplet porogens induced macropores in the emulsion-templated aerogels. Furthermore, the nanoporous structures of starch aerogels were also well-preserved in which the macropores were surrounded by fine and interconnected nanofibrous networks. It resulted in aerogels that exhibited internal morphology in two scales (macropores and nanopores) with a high surface area (156–190 m2/g).

Co@C nanorods as both magnetic stirring nanobars and magnetic recyclable nanocatalysts for microcatalytic reactions

The rapid and effective mixing of reactants and catalysts is essential in liquid-phase catalytic reaction to boost mass transport. However, the routinely used magnetic stirring method is impractical for ultra-small systems such as lab-on-chip and flow cell due to the macroscale size of the magnetic bars. Herein, we developed a facile strategy to synthesize catalytically active magnetic Co@C nanorods, which could serve as both high-performance catalysts and magnetic stirring nanobars for micro-catalytic reactions. The Co@C core-shell structure endows the materials with high catalytic activity and excellent durability, while the strong magnetism of Co nanoparticles renders the nanorod catalyst unique stirring capability under an external rotating magnetic field, which significantly promotes the mass transport and also the catalytic efficiency in micro-catalytic reactions. Inspired by the unique structure and properties, the mixing ability and catalytic activity of Co@C nanorods were evaluated in several systems.

Size Effects and Beyond-Fourier Heat Conduction in Room-Temperature Experiments

Abstract It is a long-lasting task to understand heat conduction phenomena beyond Fourier. Besides the low-temperature experiments on extremely pure crystals, it has turned out recently that heterogeneous materials with macro-scale size can also show thermal effects that cannot be modeled by the Fourier equation. This is called over-diffusive propagation, different from low-temperature observations, and is found in numerous samples made from metal foam, rocks, and composites. The measured temperature history is indeed similar to what Fourier’s law predicts but the usual evaluation cannot provide reliable thermal parameters. This paper is a report on our experiments on several rock types, each type having multiple samples with different thicknesses. We show that size-dependent thermal behavior can occur for both Fourier and non-Fourier situations. Moreover, based on the present experimental data, we find an empirical relation between the Fourier and non-Fourier parameters, which may be helpful in later experiments to develop a more robust and reliable evaluation procedure.

Tunable macroscale structural superlubricity in two-layer graphene via strain engineering

Achieving structural superlubricity in graphitic samples of macroscale size is particularly challenging due to difficulties in sliding large contact areas of commensurate stacking domains. Here, we show the presence of macroscale structural superlubricity between two randomly stacked graphene layers produced by both mechanical exfoliation and chemical vapour deposition. By measuring the shifts of Raman peaks under strain we estimate the values of frictional interlayer shear stress (ILSS) in the superlubricity regime (mm scale) under ambient conditions. The random incommensurate stacking, the presence of wrinkles and the mismatch in the lattice constant between two graphene layers induced by the tensile strain differential are considered responsible for the facile shearing at the macroscale. Furthermore, molecular dynamic simulations show that the stick-slip behaviour does not hold for incommensurate chiral shearing directions for which the ILSS decreases substantially, supporting the experimental observations. Our results pave the way for overcoming several limitations in achieving macroscale superlubricity using graphene.

In-situ fabricated anisotropic halide perovskite nanocrystals in polyvinylalcohol nanofibers: Shape tuning and polarized emission

We report an in-situ fabrication of halide perovskite (CH3NH3PbX3, CH3NH3 = methylammonium, MA, X= Cl, Br, I) nanocrystals in polyvinylalcohol (PVA) nanofibers (MAPbX3@PVA nanofibers) through electrospinning a perovskite precursor solution. With the content of the precursors increased, the resulting MAPbBr3 nanocrystals in PVA matrix changed the shape from ellipsoidal to pearl-like, and finely into rods-like. Optimized MAPbBr3@PVA nanofibers show strong polarized emission with the photoluminescence quantum yield of up to 72%. We reveal correlations between the shape of in-situ fabricated perovskite nanocrystals and the polarization degree of their emission by comparing experimental data from the single nanofiber measurements with theoretical calculations. Polarized emission of MAPbBr3@PVA nanofibers can be attributed to the dielectric confinement and quantum confinement effects. Moreover, nanofibers can be efficiently aligned by using parallel positioned conductor strips with an air gap as collector. A polarization ratio of 0.42 was achieved for the films of well-aligned MAPbBr3@PVA nanofibers with a macroscale size of 0.5 cm × 2 cm, which allows potential applications in displays, lasers, waveguides, etc.

Whisker-Like Formations in Sn-3.0Ag-Pb Alloys

AbstractIn this study, different types of whisker-like formations of Sn-3.0Ag based alloy were presented. In the experimental process the amount of Pb element was changed between 1000 and 2000 ppm, and the furnace atmosphere and cooling rate were also modified. The novelty of this work was that whisker-like formations in macro scale size were experienced after an exothermic reaction. The whiskers of larger sizes than general provided opportunities to investigate the microstructure and the concentration nearby the whiskers. In addition, the whisker-like formations from Sn-Ag based bulk material did not only consist of pure tin but tin and silver phases. The whisker-like growth appeared in several forms including hillock, spire and nodule shaped formations in accordance with parameters. It was observed that the compound phases were clustered in many cases mainly at hillocks.

Sticky surface: sphere–sphere adhesion dynamics

We present a multi-scale model to study the attachment of spherical particles with a rigid core, coated with binding ligands and suspended in the surrounding, quiescent fluid medium. This class of fluid-immersed adhesion is widespread in many natural and engineering settings, particularly in microbial surface adhesion. Our theory highlights how the micro-scale binding kinetics of these ligands, as well as the attractive/repulsive surface potential in an ionic medium affects the eventual macro-scale size distribution of the particle aggregates (flocs). The bridge between the micro–macro model is made via an aggregation kernel. Results suggest that the presence of elastic ligands on the particle surface lead to the formation of larger floc aggregates via efficient inter-floc collisions (i.e. non-zero sticking probability, g). Strong electrolytic composition of the surrounding fluid favours large floc formation as well. The kernel for the Brownian diffusion for hard spheres is recovered in the limit of perfect binding effectiveness (g→1) and in a neutral solution with no dissolved salts.

Phenomena of Multicale Fracture of Brittle Materials and its Application to Teaching in Strength Theory

Multi-scale science is the challenge and opportunity of science in the 21th century, and turbulence of liquid and fracture of solid will be the classical problems of multi-scale mechanics. The failure process of brittle materials displayed a multi-scale mechanics feature that amounts of micro damages grow large trans-scale and nonlinear and evolve to a macro catastrophic transition in the end. So, the concepts of scale and hierarchy of material are inescapable in strength theory to be used explaining solid fracture, it is the main puzzle of the strength theory at present. In the paper, in order to show the phenomena of multi-scale fracture, numeric method is used to simulate the failure process of brittle material, during which micro cracks initiate, grow large, aggregate and in the end form a run-through fracture band in the sample. The result of the numeric simulation shows that the micro cracks of a meso-scale size initiate due to tensile strain and the sample of a macro-scale size breaks down due to tensile-shearing strain under uniaxial tensile or due to compression-shearing strain under uniaxial compression. It powerfully disabused the puzzles in teaching strength theory of brittle material. The further discussion concluded that for a brittle material grain of meso-scale size, the theory of Maximum Tensile Strain is reasonable in explaining the strength, as for a brittle material sample of a macro-scale size, the mohr-columb theory is reasonable for its strength owing to the two important factors of cohesive strength and friction factorwere introduced.

Effect of surface morphology of macro-scale perlite particles on adsorption process of Malachite Green dye

Perlite is a mineral compound. It is a mixture of SiO2, Al2O3, Na2O, K2O, Fe2O3 and so on. Its high porosity and low density cause that it is being used as an adsorbent to remove organic and inorganic pollutants from wastewater in many researches. But its capacity depends on its structure as an adsorbent. In this research, the effect of macro-scale size of perlite particles has been investigated on adsorption capacity and procedure. The results show that the difference is in perlite macro-scale size of surface morphology and there is no significant difference in micro-scale size.

Design of micro-scale highly expandable networks of polymer-based substrates formacro-scale applications

An investigation was performed to design a network of nodes interconnected by conductivemicrowires in polymer-based substrates, which can be expanded to cover an area which isseveral orders of magnitude larger for macro-scale integration. The substrates can bepotentially designed to host nano/micro-sensors/actuators and electronics to create afunctional network for various applications. The major focus of the research is to develop aprocess to ensure that the network transition from a micro-scale fabrication to amacro-scale deployment is controllable, reliable and stable without failure. Thekey concept of the proposed design is to remove microscopically unnecessarymaterials from the substrate to create a network of infrastructures that can bestretched and expanded to a macro-scale size of several orders of magnitude.Material reduction is achieved by engineering a network of thousands of micronodesinterconnected by extendable microwires, which are the key element to perform uniformexpansions of the network in all directions, to allow precise location of the nodes, tomaximize the polymer expansion per unit area and to allow translation onlyof the nodes. The number of nodes, the bidimensional stretching ratio of thenetwork and the material reduction are linked to the processable substrate size,to the final area coverage upon full expansion and to the in-plane area of thenodes and wires. In this paper we demonstrate that an expandable network with200 µm diameternodes and 4 µm wide wires is characterized by a 99.7% material reduction and a 25 600% bidimensional stretching ratio.A 5041 micronode network was built on a 100 mm diameter wafer and was expanded to a final areaof 1 m2 at low strain levels. The expanded node network is integrated into materials of differentrigidities and is proven to resist under bending and twisting of the hosting material. Theproposed flexible, expandable polymer design is a cost-effective approach that has thepotential to build a bridge between the engineering of the nano/microscopic devices andtheir exploitation on the macroscopic scale. In particular, this approach can be used forwired or wireless sensor network applications as well as for the realization of innovativematerials.