Narrow Results

We prove the existence Gibbs states describing rigid interfaces in a disordered solid-on-solid (SOS) for low temperatures and for weak disorder in dimension D ≥ 4. This extends earlier results for hierarchical models to the more realistic models and proves a long-standing conjecture. The proof is based on the renormalization group method of Bricmont and Kupiainen originally developed for the analysis of low-temperature phases of the random field Ising model. In a broader context, we generalize this method to a class of systems with non-compact single-site state space.

The tension of the interface between the high and low temperature phases of finite temperature Quantum Chromodynamics is an important characteristic of the quarkhadron phase transition. We discuss its cosmological effects and its determination, for planar and spherical interfaces, with lattice Monte Carlo techniques for the case of pure glue, N_t=2 SU(3) gauge theory.

To investigate order-order interfaces, we perform multimagnetical Monte Carlo simulations of the 2D and 3D Ising model. Stringent tests of the numerical methods are performed by reproducing with high precision exact 2D results. In the physically more interesting 3D case we estimate the amplitude of the critical interfacial tension.

Molecular dynamics and Monte Carlo methods are applied to study the liquid free surfaces in model liquid crystals. The simulation results suggest that the attractive interactions promote parallel alignment of the molecules at the nematic free surface in the Gay–Berne model, in agreement with theoretical predictions. A change in the orientation from planar to homeotropic is observed and explained in terms of a competing effect between attractive and repulsive interactions. Finally, the simulation results give clear evidence that the hard-core repulsions favor homeotropic orientation at the nematic free surface, in agreement with most theories.

A general procedure is presented for the multiscale analysis of atomistic models of fluctuating interfaces driven by the deposition of new material. Beginning with a lattice Langevin formulation of kinetic Monte Carlo simulations, we derive stochastic partial differential equations by regularizing the atomistic transition rules. Subsequent coarse-graining is accomplished by calculating renormalization-group trajectories from initial conditions determined by the regularized equations. We apply this methodology to the Wolf–Villain model of relaxation upon deposition and to a model for the self-organization of heteroepitaxial nanostructures.

Using first-principle calculation in combination with the Chen–Möbius inversion method, we get the interfacial potentials of the Fe[110]/TMC[100] (TM = Ti, Zr and Hf) interface system. Based on the interfacial potentials, we investigate the interfacial stability, misfit dislocations and tensile fracture of the semi-coherent interfaces of Fe[110]/TMC[100] (TM = Ti, Zr and Hf). The different sizes of the misfit dislocation models are employed to compare the interfacial energy. Results indicate that Fe[110]/HfC[100] interface is more stable than Fe[110]/TMC[100] (TM = Ti and Zr). The analysis of different tensile fracture processes shows that the misfit dislocations play an important role in the fractures of interfaces between iron and transitional metal carbides.

We have carried out the calculations of vibrational dynamics in the low-dimensional structure with dimensions on the nanometer scale by using the matching formalism. The nanostructure model consists in the surface step produced at a perpendicular interface between two truncated thin films with different thickness. The theoretical approach determines the vibrational field in the direction where the translation symmetry is broken. The calculation concerns in particular the phonon dispersion curves localized on the interface and step edge, and employs the matching procedure in the harmonic approximation. The nearest and next nearest neighbors elastic force constants between the mass sites in the model, as well as a modification of the elastic strain field induced by the presence of the step, are considered. Analytic expressions are obtained for the phonon dispersion relations of the localized surface and edge elastic waves and the bulk phonons near a step. The breakdown of translational symmetry perpendicular to the step edge gives rise to several Raleigh-like branches localized in the neighborhood of step and interface. The effects of varying the elastic force constants at an interface and the strain field parameter near the step are studied. These factors influence the number of localized modes as well as their frequency, intensity and attenuation.

In this study, Al–Ti–Co was used to improve the surface performance of pure Ti. Laser cladding is an important surface modification technique, which can be used to improve the surface performance of pure Ti. Laser cladding of the Al–Ti–Co + TiB₂ pre-placed powders on pure Ti can form ceramics reinforced the composite coating, which improved the wear resistance of the substrate. Characteristics of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness and wear tests. And the laser-cladded coating can also have major dilution from the substrate. Due to the action of the fine grain strengthening and the phase constituent, the wear resistance and microhardness of pure Ti surface were greatly improved.

Nanocrystals of maghemite (γ-Fe₂O₃) have been prepared at the interface of organic-aqueous layer by the reaction of ferric acetylacetonate in toluene with sodium hydroxide in aqueous solution. The nanocrystals of γ-Fe₂O₃ formed at the interface of the organic-aqueous layer have been confirmed by X-ray diffraction (XRD) pattern. The sample has been characterized morphologically by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques. Magnetic hysteresis loop and zero-field cooling measurements exhibited superparamagnetism behavior for γ-Fe₂O₃ nanocrystals.

The interfacial adsorption of surfactants at planar nematic liquid crystal (NLC)–water interface induces an ordering transition from a tilted to perpendicular anchoring with the increase in surfactant concentration at $C_N=C∕C_{\mathrm{\text{cmc}}}\ll 1$, where $C_{\mathrm{\text{cmc}}}$ is the Critical Micelle Concentration of surfactants in water. In this study, we show that depending upon the surfactant structure a tilted to perpendicular NLC anchoring transition is observed at $C∕C_{\mathrm{\text{cmc}}}\ge 1$ in 5CB droplets of size 50–70$\mu$m. Micrometer sized 5CB droplets are deposited on glass surfaces using flow coating of 5CB-in-ethanol solutions. When placed on 5CB drop decorated glass surfaces, the aqueous surfactant solutions of aliphatic chain surfactants (SDS, CTAB and CPBr) at $C_N<1$, result in an optical transition to a bright-cross texture attributed to the tilted anchoring of 5CB molecules at 5CB–water interface. At $C∕C_{\mathrm{\text{cmc}}}\ge 1$, perpendicular anchoring of 5CB molecules at 5CB–water interface results in a droplet texture with a hedgehog defect. In contrast, aqueous solutions of SDBS lead to 5CB droplets with a bright-cross texture regardless of the surfactant concentration in the aqueous phase. These results indicate that the orientation of 5CB molecules is independent of the nature of the surfactant headgroup. In addition, 5CB droplet decorated OTS treated glass substrates show a hedgehog texture which disappears completely on exposure to organic vapors with the response time-dependent on the polarity of the vapor molecules.

This paper studies the effect of anisotropic surface tension on the morphological stability of deep cellular crystal in directional solidification by using the matched asymptotic expansion method and multiple variable expansion method. We find that the morphological stability of deep cellular crystal growth with anisotropic surface tension shows the same mechanism as that with isotropic surface tension. The deep cellular crystal growth contains two types of global instability mechanisms: the global oscillatory instability, whose neutral modes yield strong oscillatory dendritic structures, and the low-frequency instability, whose neutral modes yield weakly oscillatory cellular structures. Anisotropic surface tension has the significant effect on the two global instability mechanisms. As the anisotropic surface tension increases, the unstable domain of global oscillatory instability decreases, whereas the unstable domain of the global low-frequency instability increases.

Numerical prediction of mixed-mode failure along interfaces between polymeric foams and metals in foam-filled composite structures can be facilitated if interfacial cohesive laws are known. In this paper, we characterize the cohesive behavior of the interface between a polyurethane (PU) closed-cell foam and galvanized mild steel by extending an experimental approach suggested by [Lundsgaard–Larsen et al. [2008] Engineering Fracture Mechanics 75(8), 2514–2530]. A simplified approach for calculating the fracture energy and for extracting cohesive relations from the fracture energy-total crack opening displacement data is presented. We find that there is a substantial amount of normal separation in tests that are designed to be purely mode II, and a small amount of tangential motion in tests designed to be purely mode I. The interfacial cohesive laws extracted from our experiments suggest that the normal traction depends not only the normal and tangential displacements but also the tangential traction.

Different properties and phenomena that polymer nanocomposites exhibit compared to the base polymers or conventional polymers (polymers with micron scale particles) are attributed to interfaces features. As a consequence, theories and models (such as Lewis' model, Tsagaropoulos' model and the multicore model proposed by Tanaka) have been proposed, primarily to interpret the physical, chemical and electrical structure of interfaces. Moreover, these models try to explain several different phenomena and properties that polymer nanocomposites exhibit based on the interfaces features. According to these models, the interface with thickness comparable to the diameter of the nanoparticle consists of multilayers. In this paper, a detailed review and analysis of these models and theories is presented. Differences and similarities of the models are also discussed.

A new photocatalyst structure, dendritic hierarchical AgCl assembled by numerous nanoscaled particles, was obtained via simple and effective one-step gas–solid interfacial method for the first time. The macromorphology of the prepared AgCl also displays a dendritic shape as the microperspective. The Ag–AgCl made from the dendritic hierarchical AgCl exhibits a stable photocatalytic performance.

Lanthanum hydroxycarbonate (LaCO₃OH), a kind of fluorescence materials, was less studied in application for photocatalysis. In this paper, LaCO₃OH/In(OH)₃/In₂S₃ (LCO/IO/IS) heterostructures were firstly synthesized by a mild two-step hydrothermal method and investigated by various technologies. The activity of as-prepared samples was evaluated by the degradation of Rhodamine B (RhB) under visible light ($\lambda \ge 420$nm). When the content of LaCO₃OH is 15mol.% (La/In), the obtained sample exhibits the highest performance, beyond two times as high as that of In(OH)₃/In₂S₃. The improved photodegradation activity might be ascribed to higher adsorption capability and photosensitization of RhB due to proper energy structures of the heterostructures, which prompts the effective separation of electrons and holes. This work extends the application of rear earth salts (lanthanum hydroxycarbonate) for purification of dye waste water.

Implementing bottom-up approaches to control the columnar architecture of thin films at the nanoscale is a powerful tool for developing surface properties. While inclined columns, zigzags or helices made of a single material are now commonly produced by oblique angle deposition processes, the creation of more complex and original structures associating at least two different materials still remains a challenging task, even more on silicon substrate. Herein, we show how to prepare tungsten/molybdenum columns exhibiting a checkerboard-like structure with motifs of a few tens of nanometers. Although understanding the growth phenomena becomes more problematic when two components are simultaneously provided during the film fabrication, this original combination of controlled mosaics in columnar thin films enables new opportunities to produce some unusual nanostructures for functional materials.

Several biochar frame electromagnetic interference shielding composites have been developed; however, integrating high shielding effectiveness (SE) and low reflection coefficient ($R$) into biochar frames with excellent electrical conductivity have proven to be a great challenge. Herein, because of the abundant groups on the surface of the intricate fibers of the loofah sponge, it absorbed many iron ions, which can form a Fe₃O₄ coating when they react with hydroxyl groups. After carbonization, the Fe₃O₄ coating still tightly held the carbonized fibers in a porous structure, forming a biochar frame with consecutive magnetic/conductive interfaces. Furthermore, the incorporation of a Fe₃O₄ coating did not negatively affect the electrical conductivity of the composites obtained ($\sim$21 S/m) but instead endowed the composites with good magnetic properties. The resultant composites had an SE, specific SE, $R$ and green index ($g_s$) of 47.2 dB, 363 dB/cm, 0.089, and 10.2, respectively, which were better than those of previously reported biochar-based shielding materials. The synergistic effect of the three-dimensional carbon frame, magnetic coating, and porous structure is responsible for excellent green shielding abilities.

Whole brain emulation aims to re-implement functions of a mind in another computational substrate by carefully emulating the function of fundamental components, and by copying the connectivity between those components. The precision with which this is done must enable prediction of the natural development of active states. To accomplish this, in vivo measurements at large scale and high resolution are critically important. We propose a set of requirements for these empirical measurements. We then outline general methods leading to acquisition of a structural and functional connectome, and to the characterization of responses at large scale and high resolution. Finally, we describe two new project developments that tackle the problem of functional recording in vivo, namely the "molecular ticker-tape" and the integrated-circuit "Cyborcell".

Electrocatalytic hydrogen evolution reaction (HER) is a promising approach for clean and sustainable hydrogen production. Its large-scale application relies on the availability of low cost and efficient electrocatalysts. Earth-abundant transition-metal carbides (TMCs) are regarded as potential candidates to replace state-of-the-art but expensive platinum-group electrocatalysts. Recently, heterostructured catalysts have attracted attention, which are composed of electrochemically active materials and various functional additives. Herein, we summarize the recent research progress on TMC-based heterosturcutured HER catalysts. We begin with the fundamentals of HER and the strength of TMCs. Subsequently, classified and summarized different TMC-based catalysts heterostructured with phosphides, dichalogenides, oxides, carbides, and carbon materials are presented. Finally, future opportunities and challenges are discussed for the progress of heterostructed TMCs.

Philosophically, embedded-cooling strategies seek to remove as many barriers as possible between the primary thermal management solution and the component(s) of interest. However, in many cases, such as three-dimensional chip stacks and flexible electronics, conduction processes can still limit primary or secondary heat transfer pathways. Thus, materials development and an enhanced understanding of conduction physics represent opportunities for improving the cooling performance of the overall solution. Here, recent advances in bulk cubic crystals, two-dimensional layered materials, and advances in understanding conduction physics are briefly discussed, with a critical outlook on their potential for improving embedded cooling of electronic devices.