Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application

This book is a collection of the research articles and review article, published in special issue "Structural, Magnetic, Dielectric, Electrical, Optical and Thermal Properties of Nanocrystalline Materials: Synthesis, Characterization and Application"

Geometric theory of topological defects: methodological developments and new trends

Liquid crystals generally support orientational singularities of the director field known as topological defects. These latter modifiy transport properties in their vicinity as if the geometry was non-Euclidean. We present a state of the art of the differential geometry of nematic liquid crystals, with a special emphasis on linear defects. We then discuss unexpected but deep connections with cosmology and high-energy-physics, and conclude with a review on defect engineering for transport phenomena

Towards a solution of the closure problem for convective atmospheric boundary-layer turbulence

We consider the closure problem for turbulence in the dry convective atmospheric boundary layer (CBL). Transport in the CBL is carried by small scale eddies near the surface and large plumes in the well mixed middle part up to the inversion that separates the CBL from the stably stratified air above. An analytically tractable model based on a multivariate Delta-PDF approach is developed. It is an extension of the model of Gryanik and Hartmann [1] (GH02) that additionally includes a term for background turbulence. Thus an exact solution is derived and all higher order moments (HOMs) are explained by second order moments, correlation coefficients and the skewness. The solution provides a proof of the extended universality hypothesis of GH02 which is the refinement of the Millionshchikov hypothesis (quasi- normality of FOM). This refined hypothesis states that CBL turbulence can be considered as result of a linear interpolation between the Gaussian and the very skewed turbulence regimes. Although the extended universality hypothesis was confirmed by results of field measurements, LES and DNS simulations (see e.g. [2-4]), several questions remained unexplained. These are now answered by the new model including the reasons of the universality of the functional form of the HOMs, the significant scatter of the values of the coefficients and the source of the magic of the linear interpolation. Finally, the closures 61 predicted by the model are tested against measurements and LES data. Some of the other issues of CBL turbulence, e.g. familiar kurtosis-skewness relationships and relation of area coverage parameters of plumes (so called filling factors) with HOM will be discussed also

SYNTHESIS, CHARACTERIZATION AND APPLICATION OF BLOCK COPOLYMER AND NANOPARTICLE COMPOSITES

The “bottom-up” fabrication of functional hybrid material can be achieved by using directed self-assembly of functional nanoparticles (NP) and block copolymers (BCP) as templates. The versatile nanostructures of BCP provide possibilities to precisely control NPs spatial distribution and the resulting hybrid materials exhibit enhanced electrical, mechanical and optical functionalities. Three main topics related to BCP/NP composites are discussed in this dissertation: I) the spatial distribution of large NP in linear BCP; II) the morphology control of BCP templates with new architectures; and III) the magneto-optical properties of hybrid material using magnetic NPs. For well-ordered BCP/NP composite, the ratio of NP core diameter (dcore) and BCP domain width (L) has been generally limited with dcore/L \u3c 0.3 when BCP/NP interactions are relatively neutral or weak. By modifying the Au NPs with hydrogen bonding (H-bonding) donor group, the selective spatial distribution of Au NPs ranges in size up to 0.8 times that of the target domain width in symmetric polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP). In addition, H-bonding meditated 15 nm NPs can be directed by linear BCP of dcore/L up to 0.4 at 20wt % loading. The H-bonding interactions between NP and BCP provide favorable enthalpic interaction to overcome the inherent entropy penalties mainly arising from polymer chain stretching upon the sequestration of large particles. On the other hand, the extensive chain entanglements of linear BCP still remain a challenge for hybrid materials with the consequence of long processing duration, many defects and lack of orientation. Bottlebrush BCPs (BBCPs) exhibit much lower degree of chain entanglement due to the highly extended confirmation. A systematic study was conducted to investigate the morphology transitions that occur in polystyrene-block-poly (ethylene oxide) (PS-b-PEO) BBCPs upon varying PEO volume fraction (fPEO) from 22 % to 81 %. Either symmetric or asymmetric lamellar morphologies were observed in the BBCPs over an exceptionally wide range of fPEO from 28 % to 72 %. A microphase transition temperature TMST was observed over a temperature range of 150-180 ℃. Finally, enhanced magneto-optical (MO) composites with excellent Faraday rotation (FR) response were fabricated using iron platinum (FePt) NPs and PS-b-P2VP linear BCP. Gallic acid (GA) functionalized FePt NPs with average dcore from 1.9 to 9.3 nm were selectively incorporated into a P2VP domain through H-bonding interactions. The use of copolymer template to selectively arrange the magnetic NPs enabled high MO performance with limited trade-off of scattering loss, providing a simple strategy to prepare functional materials for MO applications. Verdet constants of a 10 wt % loaded 4.9 nm FePt NP composite reached absolute magnitudes as high as ~ -6×104 °/T⋅m at 845 nm, as determined by FR measurements at room temperature, which is comparable to today’s benchmark materials

Quantum Engineering in Open Quantum Systems

The huge technological advancement achieved in the last years has allowed for the emergence of a new field of physics dubbed \u201cquantum engineering\u201d: with this term people refer to a wide range of topics, from planning and building physical systems for specific tasks to developing algorithms to control those systems, from ways to create specific quantum states to new theoretical tools to describe and plan new physical systems. As the field of quantum engineering covers many topics in physics, this is reflected in the community interested in it, ranging from quantum optics theorists to solid state experimentalists. This also includes the possibility, and sometimes the necessity, for a scientist willing to enter the field to study very different problems, as it happened for the material in this thesis, where at least two main topics are covered. One of them is the study of open quantum systems, more specifically in the context of collisional model and cascade networks. The latter are networks of quantum systems interacting through the interaction with a common environment with unidirectional, i.e. chiral, propagation of the signal. Thanks to the chirality of the environment it is possible to obtain non symmetrical couplings between the quantum systems composing the network, opening the way to engineer the steady state of the system. The tool used to derive master equation describing dynamics and properties of such systems is the one of collisional models: these models are nowadays extensively used in a wide range of topics concerning open quantum systems, from the description of both Markovian and non Markovian dynamics, to quantum optics and quantum thermodynamics. In collisional models the environment is depicted as a collection of smaller systems, dubbed ancillas, which interact in a collisional fashion with the quantum system under examination. This way of describing open systems dynamics leads to a discrete master equation on which it is then possible to enforce a continuous time limit. Among the advantages provided by such an approach there is the simplicity with which is possible to switch from a Markovian to a non-Markovian dynamics and the possibility of keeping track of the environmental degrees of freedom. The last feature cited is the one exploited in this thesis when studying a quantum system thermalizing through the interaction with a thermal bath: having at disposal the environmental state at each discrete step of the thermalization process, it is possible to compute the thermodynamic functionals relative to the environment. Specifically, by computing the quantum mutual information between the system and the environment, it is possible to show that the final joint state reached by the system and the environment is a factorized state. The other part of this thesis focuses instead on quantum state engineering by potential engineering. By appropriately engineering a potential profile, it is possible to obtain a class of quantum states, dubbed stretchable, which have the property of having a flat wave function in some regions, somehow analogously to what happens in photonic metamaterials: in this materials, where either the permittivity or the permeability is zero, the temporal and spatial variation of the electric field are decoupled, leading to the possibility of having a stretched wave with both large frequency and large wavelength. Finally, in this thesis it is shown how, by properly engineering a spatially varying potential landscape, it is possible to attach a geometric phase to the quantum state of a traveling wave. More specifically, as the confining potential of a traveling wave varies along a closed loop in parameters space, it is possible to implement an operation, usually called holonomy, which attaches a geometric phase to the state, analogously to what happens in the Berry phase phenomenon for a time dependent Hamiltonian

Active Materials

What is an active material? This book aims to redefine perceptions of the materials that respond to their environment. Through the theory of the structure and functionality of materials found in nature a scientific approach to active materials is first identified. Further interviews with experts from the natural sciences and humanities then seeks to question and redefine this view of materials to create a new definition of active materials

Active Materials

What is an active material? This book aims to redefine perceptions of the materials that respond to their environment. Through the theory of the structure and functionality of materials found in nature a scientific approach to active materials is first identified. Further interviews with experts from the natural sciences and humanities then seeks to question and redefine this view of materials to create a new definition of active materials