Ni-Al laminates have shown promise as reactive materials due to their high energy release through intermetallic reaction. In addition to the traditional ignition methods, the reaction may be initiated in hot spots tha...
Ni-Al laminates have shown promise as reactive materials due to their high energy release through intermetallic reaction. In addition to the traditional ignition methods, the reaction may be initiated in hot spots that can be created during mechanical loading. The explosively driven thick walled cylinder (TWC) technique was performed on two Ni-Al laminates composed of thin foil layers with different mesostructues: concentric and corrugated. These experiments were conducted to examine how these materials accommodate large plastic strain under high strain rates. Finite element simulations of these specimens with mesostuctures digitized from the experimental samples were conducted to provide insight into the mesoscale mechanisms of plastic flow. The dependence of dynamic behaviour on mesostructure may be used to tailor the hot spot formation and therefore the reactivity of the material system.
A butterfly‐like phosphorescent platinum(II) binuclear complex can undergo a molecular structure change in which the Pt–Pt distance shortens upon photoexcitation, which leads to the formation of two distinct excited...
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A butterfly‐like phosphorescent platinum(II) binuclear complex can undergo a molecular structure change in which the Pt–Pt distance shortens upon photoexcitation, which leads to the formation of two distinct excited states and dual emission in the steady state, that is, greenish‐blue emission from the high‐energy excited state at the long Pt–Pt distance and red emission from the low‐energy excited state at the short Pt–Pt distance. This photoinduced molecular structure change has a strong dependence on the molecule’s surrounding environment, allowing its application as self‐referenced luminescent sensor for solid–liquid phase change, viscosity, and temperature, with greenish‐blue emission in solid matrix and rising red emission in molten liquid phase. With proper control of the surrounding media to manipulate the structural change and photophysical properties, a broad white emission can be achieved from this molecular butterfly.
This work reports the preparation of flower-like ZnO for applications in the catalytic oxidation of methyl orange (MO) in aqueous solution. The wurtzite ZnO samples with flower-like morphologies were obtained via a d-...
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The development of new antimicrobials effective against drug-resistant bacterial infections is a significant scientific challenge, requiring new molecular targets and antimicrobial strategies. Amphiphilic synthetic po...
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In recent years, platinum-based single crystalline nanoalloys as nanoscale catalysts, such as Pt-M (M = Ni, Co, Fe..etc.), have exhibited improved catalytic performance due to the increase in the surface-to-volume rat...
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In recent years, platinum-based single crystalline nanoalloys as nanoscale catalysts, such as Pt-M (M = Ni, Co, Fe..etc.), have exhibited improved catalytic performance due to the increase in the surface-to-volume ratio. Some Pt-M nanopolyhedra such as nanocubes and nano-octahedra have been reported with enhanced activity when being used as electrocatalysts. In order to further establish a correlation between the exposed nanocrystal facets (shapes) and their corresponding activities, a pursuit of shape-controlled nanocatalyst synthesis is essential. Although PtPb nanoalloys have been prepared using solution-based methods, few studies have highlighted their catalytic activity as a function of the nanocrystal shape. This work focuses on a modified polyol synthesis technique and an adjustment of the Pb-metal precursor, which serves as a “buffer” in the nucleation stage of the shape-controlled nanoalloy development. Using this developed synthetic strategy, shape-controlled hexagonally close-packed PtPb nanoalloys can be prepared in a one-pot synthesis without additional post-treatment. The as-prepared PtPb nanocrystals demonstrate an improved anode electrocatalytic performance.
A series of laser pump, x-ray probe experiments show that above band gap photoexcitation can generate a large out-of-plane strain in multiferroic BiFeO3 thin films. The strain decays in a time scale that is the same a...
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A series of laser pump, x-ray probe experiments show that above band gap photoexcitation can generate a large out-of-plane strain in multiferroic BiFeO3 thin films. The strain decays in a time scale that is the same as the photo-induced carriers measured in an optical transient absorption spectroscopy experiment. We attribute the strain to the piezoelectric effect due to screening of the depolarization field by laser induced carriers. A strong film thickness dependence of strain and carrier relaxation is also observed, revealing the role of the carrier transport in determining the structural and carrier dynamics in complex oxide thin films.
Colloidal crystals belong to a new class of materials with unusual properties in which the big challenge is to grow large-scale structures of a given symmetry in a well-controlled and inexpensive way. Recently, templa...
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Colloidal crystals belong to a new class of materials with unusual properties in which the big challenge is to grow large-scale structures of a given symmetry in a well-controlled and inexpensive way. Recently, template-assisted crystallization was successfully exploited experimentally in the case of colloidal particles dispersed in isotropic fluids. In liquid crystal (LC) colloids, particles are subjected to long-range anisotropic elastic forces originating from the anisotropic deformation of the underlying order parameter. These effective interactions are easily tunable by external electric or magnetic fields, light, temperature, or confinement and, thus, provide additional handles for better control of colloidal assembly. Here we use the coupling between microsculptured bounding surfaces and LC elasticity in order to guide the self-assembly of large-scale colloidal structures. We present explicit numerical calculations of the free energy landscape of colloidal particles in the presence of convex protrusions modeled as squared pyramids comparable to the size of the particles. We show the existence of strong trapping potentials that are able to efficiently localize the colloidal particles and withstand thermal fluctuations. Three-dimensional optical imaging experiments support the theoretical predictions.
True triaxial tests have been carried out on two porous sandstones,Coconino（n = 17.5%） and Bentheim（n = 24%） to investigate the effect of the intermediate principal stress（σ） on compressive strength, failure-pl...
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ISBN:
(纸本)9781138000575
True triaxial tests have been carried out on two porous sandstones,Coconino（n = 17.5%） and Bentheim（n = 24%） to investigate the effect of the intermediate principal stress（σ） on compressive strength, failure-plane angle and failure *** rocks were selected because they are similar to sandstones forming hydrocarbon reservoirs,as well as to those being considered for CO *** both rocks the increase in strength asσ rose above a givenσ was found to be similar to that established in crystalline rocks,but the maximum rise in strength was considerably *** mode in Coconino sandstone was in the form of a steeply inclined shear band,or fault,at lowerσ,with the slope becoming gentler asσ increased,culminating in multiple parallel and conjugate bands at the highestσ attempted（=150 MPa）.Bentheim sandstone failure mode experienced a similar evolution in a narrower range（σ between 0 to 80 MPa）,but as loading continued,failure was in the form of shear-enhanced compaction bands with angle dropping to～45°and lower,and reaching 0°atσ = 150 MPa（creating pure compaction bands）.Failure-plane angle in both rocks increased by up to 15°asσ was raised above a givenσ.
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