Journal of Applied physics,Vol.33 : 1962年に発表されたレオロジー関連の論文

Chirality in nanoscience may offer new opportunities for applications beyond the traditional fields of chirality, such as the asymmetric catalysts in the molecular world and the chiral propellers in the macroscopic world. In the last two decades, there has been an amazing array of chiral nanostructures reported in the literature. This review aims to explore and categorize the common mechanisms underlying these systems. We start by analyzing the origin of chirality in simple systems such as the helical spring and hair vortex. Then, the chiral nanostructures in the literature were categorized according to their material composition and underlying mechanism. Special attention is paid to highlight systems with original discoveries, exceptional structural characteristics, or unique mechanisms.

Emerging chirality in nanoscience

Low-dimensional SiC nanostructures: Fabrication, luminescence, and electrical properties

Synthesis forms a vital aspect of the science of nanomaterials. In this context, chemical methods have proved to be more effective and versatile than physical methods and have therefore, been employed widely to synthesize a variety of nanomaterials, including zero-dimensional nanocrystals, one-dimensional nanowires and nanotubes as well as two-dimensional nanofilms and nanowalls. Chemical synthesis of inorganic nanomaterials has been pursued vigorously in the last few years and in this article we provide a perspective on the present status of the subject. The article includes a discussion of nanocrystals and nanowires of metals, oxides, chalcogenides and pnictides. In addition, inorganic nanotubes and nanowalls have been reviewed. Some aspects of core–shell particles, oriented attachment and the use of liquid–liquid interfaces are also presented.

https://www.bibalex.org/CSSP/papers/Attachments/Dalton_review.pdf

Synthesis of inorganic nanomaterials

Widespread approaches to fabricate surfaces with robust micro- and nanostructured topographies have been stimulated by opportunities to enhance interface performance by combining physical and chemical effects. In particular, arrays of asymmetric surface features, such as arrays of grooves, inclined pillars, and helical protrusions, have been shown to impart unique anisotropy in properties including wetting, adhesion, thermal and/or electrical conductivity, optical activity, and capability to direct cell growth. These properties are of wide interest for applications including energy conversion, microelectronics, chemical and biological sensing, and bioengineering. However, fabrication of asymmetric surface features often pushes the limits of traditional etching and deposition techniques, making it challenging to produce the desired surfaces in a scalable and cost-effective manner. We review and classify approaches to fabricate arrays of asymmetric 2D and 3D surface features, in polymers, metals, and ceramics. Analytical and empirical relationships among geometries, materials, and surface properties are discussed, especially in the context of the applications mentioned above. Further, opportunities for new fabrication methods that combine lithography with principles of self-assembly are identified, aiming to establish design principles for fabrication of arbitrary 3D surface textures over large areas.

Engineering of Micro‐ and Nanostructured Surfaces with Anisotropic Geometries and Properties

Amorphous silicon carbide nanosprings, as well as biphase (crystalline core/amorphous sheath) helical nanowires, have been synthesized by plasma enhanced chemical vapor deposition Both variants grow via the vapor−liquid−solid mechanism The formation of the amorphous silicon carbide nanosprings is explained in terms of the contact angle anisotropy model initially proposed to explain the formation of amorphous boron carbide nanosprings A modified contact angle anisotropy model, where the presence of temperature gradients within the catalyst are imposed, has been proposed to explain the formation of the biphase helical nanowires The basis for this model is that the crystalline core acts to pin the catalyst, thereby prohibiting nanospring formation The model is supported by the experimental observation of a transition to nanospring growth at the point of extinction of the crystalline core of a linear biphase nanowire at a position where the catalyst is off-center with respect to the axis of the growth di

Silicon Carbide Nanosprings

Fe2O3 magnetic nanoparticles (MNPs) have been coated with silica, followed by covalent attachment of the actinide specific chelators to separate nuclear waste in acidic conditions. A general model is developed to relate the surface coating to the particle’s magnetization change, providing an alternative way to characterize the size-distribution/aggregation of MNPs. The optimized silica coating protects the Fe2O3 MNPs from iron leaching under highly acidic conditions, facilitates the dispersion of MNPs, and dramatically increases the loading capacity of chelator onto the MNPs. Compared with the uncoated counterparts, the silica coated MNPs show enhanced actinide separation efficiency.

Silica coated magnetic nanoparticles for separation of nuclear acidic waste

Micromagnetic modeling analysis and magnetic force microscopy studies were performed in order to characterize the magnetization configuration and magnetic switching behavior in two types, PM I and PM II, of submicron Pac-man-shaped Ni80Fe20 magnetic elements. It was found that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution. In particular, the vortex-formation driven switching is replaced by quasicoherent reversal by removing the central core part at the center of element. The sensitive dependence of remanent magnetic configuration and switching behavior on sample geometry is discussed in terms of the competition between the exchange and demagnetizing energy terms.

Micromagnetic configurations and switching mechanism in Pac-man-shaped submicron Ni80Fe20 magnets

Experimental and numerical micromagnetic studies of the magnetization configuration and switching process in Pac-man (PM) shaped Ni/sub 80/Fe/sub 20/ samples with different geometries defined by the variation of the slot angle were presented. Scanning electron microscope images of patterned PM-I and PM-II magnetic elements were shown. These permalloy films were sputter deposited and their magnetic configurations were measured. The results concluded that vortex core formation and vortex-driven complex magnetization reversal can be effectively suppressed by modifying the slot angles. The hysteresis loops and domain configurations during the reversal implied that PM-II elements with large slot angles were more suitable for magnetic random access memory (MRAM) applications.

Micromagnetic domain structures and magnetization switching mechanism in submicrometer thin-film elements

The creation of multifunctional nanoma- terials by combining organic and inorganic compo- nents is a growing trend in nanoscience. The unique size-dependent properties of magnetic nanoparticles (MNPs) make them amenable to numerous applica- tions such as carriers of expensive biological catalysts, in magnetically assisted chemical separation of heavy metals and radionuclides from contaminated water sources. The separation of minor actinides from high- level radionuclide waste requires a sorbent stable in acidic pH, with ease of surface functionalization, and a high capacity for binding the molecules of interest. For the described experiments, the MNPs with 50 nm average size were used (size distribution from 20 to 100 nm and an iron content of 80-90 w/w%). The MNPs that have been double coated with an initial silica coating for protection against iron solubilization and oxidation in nitric acid solution (pH 1) and a second silica/polymer composite coating incorporat- ing partially imbedded poly(allylamine) (PA). The final product is magnetic, highly swelling, containing (95% water, with (0.5 mmol amines g -1 available for functionalization. The amine groups of the mag- netic resin were functionalized with the chelating molecules diethylenetriaminepentaacetic acid (DTPA) and N,N-dimethyl-3-oxa-glutaramic acid (DMOGA) for separation of minor actinides from used nuclear fuel.

H. Han

Papers

Silicon Carbide Nanosprings

Silica coated magnetic nanoparticles for separation of nuclear acidic waste

Micromagnetic configurations and switching mechanism in Pac-man-shaped submicron Ni80Fe20 magnets

Micromagnetic domain structures and magnetization switching mechanism in submicrometer thin-film elements

Highly hydrated poly(allylamine)/silica magnetic resin