Hexagonal Microstructures Research Articles

Automatic hammering of nano-patterns on special polymer film by using a vibrating AFM tip

Complicated nano-patterns with linewidth less than 18 nm can be automatically hammered by using atomic force microscopy (AFM) tip in tapping mode with high speed. In this study, the special sample was thin poly(styrene-ethylene/butylenes-styrene) (SEBS) block copolymer film with hexagonal spherical microstructures. An ordinary silicon tip was used as a nano-hammer, and the entire hammering process is controlled by a computer program. Experimental results demonstrate that such structure-tailored thin films enable AFM tip hammering to be performed on their surfaces. Both imprinted and embossed nano-patterns can be generated by using a vibrating tip with a larger tapping load and by using a predefined program to control the route of tip movement as it passes over the sample’s surface. Specific details for the fabrication of structure-tailored SEBS film and the theory for auto-hammering patterns were presented in detail.

Particle and breath figure formation of triblock copolymers having self‐complementary hydrogen‐bonding units

AbstractNovel triblock copolymers having self‐complementary hydrogen‐bonding units were synthesized by using reversible addition–fragmentation transfer polymerization. As characterized by dynamic light scattering and atomic force microscopy, these polymers formed noncovalently crosslinked polymer particles and showed an aggregation behavior by intermolecular and intramolecular interactions. At low concentration, polymers formed nanoparticles, and the particle diameter increased with increasing polymer concentration. Well‐ordered hexagonal microstructures were prepared by “Breath Figure” technique with the triblock copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Ultraviolet-assisted synthesis of hourglass-like ZnO microstructure through an ultrasonic and microwave combined technology

Well-defined hexagonal hourglass-like ZnO microstructures have been synthesized by using simultaneous ultrasound and microwave irradiation methods with the assistance of ultraviolet as well as double sonication (at 25 and 40kHz). The structure and morphology of as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectrum. The results show the synergistic effect of ultrasound and microwave on the formation of ZnO microstructures. Meanwhile, the possible growth mechanism was proposed to elucidate the formation of hexagonal hourglass-like ZnO microstructures.

Study on Hexagonal Mesoporous Silica Film for Antireflective Coating

In this paper, ordered mesoporous silica film as a novel antireflective coating was directly synthesized via evaporation induced self-assembly (EISA) process with cetyltrimethylammonium bromide (CTAB) as template surfactant. The mesoporous silica film exhibits ordered 2D hexagonal microstructure as demonstrated by transmission electron microscopy (TEM) and small angle X-ray diffraction (SAXRD). The average transmittance of the coated glass is about 98%, which indicates an increasing transmitted light of 7.5% in the wavelength between 400nm and 800nm. The mechanical performance and hydrophobicity tests prove that the films have excellent scratch resistance and long-time stability. The results of the characterizations and tests show that the film prepared by this convenient method would be very useful and promising for lots of commercial applications.

Controllable Synthesis of Hexagonal, Bullet-Like ZnO Microstructures and Nanorod Arrays and Their Photocatalytic Property

Hexagonal, bullet-like ZnO microstructures and nanorod arrays have been prepared successfully by a simple hydrothermal method without surfactants. The structure and composition of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), infrared spectrum (IR), and UV–vis diffusive reflectance spectrum (UV–vis). The as-synthesized bullet-like ZnO has hexagonal microstructures with an average diameter of about 10 μm and a length of 30 μm. The obtained ZnO nanorod arrays are highly oriented. Their average diameter is around 50–100 nm, and their length is about 1 μm. In the present work, the effect of concentration, heating temperature, and time on the morphology of ZnO structures was studied experimentally, and their formation was discussed in detail. The photocatalytic degradation of methylene blue (MB) was also investigated.

Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Cyclochlamydidae n. fam., Entoliidae and Pectinidae) from the Vanuatu Archipelago

This paper documents the species of Pectinoidea Rafinesque, 1815 collected in Vanuatu during the SANTO 2006 expedition. A total of 49 species (13 Propeamussiidae Abbott, 1954, 4 Cyclochlamydidae n. fam., 1 Entoliidae Teppner, 1922, and 31 Pectinidae Rafinesque, 1815) are represented, of which 70% are new records for Vanuatu. A new family, Cyclochlamydidae n. fam., is established for the genera Cyclochlamys Finlay, 1926, Chlamydella Iredale, 1929 and Micropecten n. gen., formerly placed in Propeamussiidae, but differing by their sculptured prodissoconch (smooth in Propeamussiidae), an occasionally antimarginally sculptured right valve (smooth or weak commarginally sculptured in Propeamussiidae), a (common) simple outer prismatic layer of longitudinally hexagonal microstructure on the right valve (an outer layer of columnar calcite in Propeamussiidae). The family Cyclochlamydidae n. fam. includes about 30 species, all with adult size in the 1.2-6 mm range, and living mainly in the Southern Hemisphere and Indo-West Pacific; the family is not known from the Arctic, the Atlantic, or the northern and eastern Pacific. One new genus, Micropecten n. gen., and two new species, Cyclochlamys aperta n. sp. and Micropecten excuratus n. gen., n. sp., are described.

Microstructural morphology in early dermal denticles of hammerhead sharks (Elasmobranchii: Sphyrnidae) and related taxa

AbstractMello, W.C., de Carvalho, J.J., Brito, P.M.M. 2011. Microstructural morphology in early dermal denticles of hammerhead sharks (Elasmobranchii: Sphyrnidae) and related taxa. —Acta Zoologica (Stockholm) 00: 1–7.This study uses scanning electron microscopies to investigate and describe the microstructural diversity of dermal denticles in the family Sphyrnidae, which comprises all living hammerhead shark species, comparing them to other related taxa (i.e. Carcharhinus dussumieri, Carcharhinus plumbeus, Carcharhinus acronotus, Rhizoprionodon acutus, Negaprion brevirostris and Hemigaleus microstoma). The results reveal that sphyrnids present noticeable microstructures in the dermal denticles, distinguishing them from the other related species investigated. Additionally, scale patterns are the same in three distinct body regions (i.e. cephalic, branchial and dorsal fin). Species of Sphyrnidae that reach bigger total lengths and that are widely distributed (i.e. Sphyrna lewini and Sphyrna mokarran) presented more, smaller and nearly hexagonal microstructures that do not cover the entire scale surface, unlike species reaching smaller sizes and restricted to coastal habits (i.e. Sphyrna tiburo, Sphyrna tudes, Sphyrna media and Eusphyra blochii). The sphyrnid scales are similar to R. acutus and C. dussumieri rather than to the other species, but it is not possible to identify the sphyrnid species only by scale features. It is clear that a similar morphology of scales is not necessarily related to similar life habits, and that they are candidates to provide new characters in phylogenetical studies among sphyrnids.

A simple method for fabricating two- and three-dimensional photorefractive photonic lattices microstructures

We demonstrate an approach for easy fabrication of two- and three-dimensional optically induced nonlinear photonic lattices microstructures in photorefractive crystal by applying spatial filter and amplitude mask. The experimental setup of this method is very simple and flexible without complicated optical adjustment system. It can be applied in almost any optical laboratories. Two-dimensional hexagonal, square and three-dimensional hexagonal nonlinear photonic lattices microstructures have been produced in an iron-doped lithium niobate photorefractive crystal. The period of the induced photonic lattices microstructures can be dominated easily. This method is easily extended to generate more complex photonic lattices microstructures in photorefractive crystals, such as quasicrystal lattice.

Synthesis and characterization of ZnO with hexagonal dumbbell-like bipods microstructures

High crystalline ZnO with hexagonal dumbbell-like bipods morphology was successfully synthesized via N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB)-assisted hydrothermal microemulsion route. X-ray diffraction, scanning electron microscopy, photoluminescence spectrum and Ultraviolet and Visible absorption spectroscopy were used to characterize the structure, morphologies and properties of the as-prepared samples. The results demonstrated that the hydrothermal reaction time had obvious influence on the shape and size of the ZnO products. The Ultraviolet and Visible absorption spectra indicated that the as-prepared ZnO had a strong and broad absorption band from ultraviolet to visible region. The photoluminescence spectra of the synthesized ZnO exhibited a very strong UV emission at ∼380 nm, indicative of their high crystal quality. Meanwhile, the possible growth mechanism for the formation of hexagonal dumbbell-like ZnO microstructures was proposed.

Hydrothermal Synthesis, Microstructure and Photoluminescence of Eu-Doped Mixed Rare Earth Nano-Orthophosphates.

Eu3+-doped mixed rare earth orthophosphates (rare earth = La, Y, Gd) have been prepared by hydrothermal technology, whose crystal phase and microstructure both vary with the molar ratio of the mixed rare earth ions. For LaxY1–xPO4: Eu3+, the ion radius distinction between the La3+ and Y3+ is so large that only La0.9Y0.1PO4: Eu3+ shows the pure monoclinic phase. For LaxGd1–xPO4: Eu3+ system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires. Similarly, YxGd1–xPO4: Eu3+, Y0.1Gd0.9PO4: Eu3+ and Y0.5Gd0.5PO4: Eu3+ samples present the pure hexagonal phase and nanorods microstructure, while Y0.9Gd0.1PO4: Eu3+ exhibits the tetragonal phase and nanocubic micromorphology. The photoluminescence behaviors of Eu3+ in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure).

Facile synthesis and assembly of CuS nano-flakes to novel hexagonal prism structures

Highly ordered hexagonal prism microstructures of copper sulfide (CuS) by assembling nano-flakes have been synthesized with high yield via a facile one-step route. We synthesized CuS microstructures using low cost beginning materials CuSO 4·5H 2O and Na 2S 2O 3·5H 2O under lower reaction temperature (60 °C). Hexamethylinetetramin (C 6H 12N 4, HMT) was introduced into the reaction system as a capped agent. The influence of reaction time and capping agent (HMT) on the final structure of products was studied systematically. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopes (EDS), and transmission electron microscopy (TEM). The possible mechanism for the formation of the interesting highly ordered hexagonal prism microstructures CuS was also proposed.

A Markov Chain Fracture Model for Intergranular Crack Propagation in Polycrystalline Materials

A model for intergranular damage propagation in polycrystalline materials is proposed, based on Markov Chain theory, Monte Carlo simulation and percolation concept. The model takes into account crack branching and coalescence, multiple crack nucleation sites, crack-turning etc., as well as the effect of grain boundary plane orientations with respect to the external stress direction. Both honeycomb and voronoi microstructures were utilized as the input microstructures. The effect of multiple crack nucleation sites has been found to have great influence on the crack propagation length. It has been observed that percolation threshold reported in the literature based on hexagonal microstructure is not applicable when the effect of external stress direction on the susceptibilities of grain boundaries is considered. The successful integration of voronoi algorithm with the Markov Chain and Monte Carlo simulations has opened up the possibilities of evaluating the intergranular crack propagation behaviour in a realistic manner.

Surface Wettability in Terms of the Height and Depression of Diverse Microstructures and Their Sizes

Surface wettability in terms of the height, depression, and sizes of diverse microstructures was examined. We considered three different types of microstructures: square pillars, square pores, and hexagonal pores. An increase in pore fraction causes a decrease in the contact area between a water drop and the microstructures, resulting in an increase in contact angle. It was verified that the contact angle of the square pillar microstructure is higher than those of the square pore and hexagonal pore microstructures for the same pore fraction. Of the pore-based microstructures, the square-pore microstructure has a higher contact angle than the hexagonal pore microstructure. However, it was observed that water drops were more stable with respect to pore fraction on the hexagonal pore microstructures. In addition, compared with the pillar microstructure, the pore-based microstructures exhibited more stable contact angles for different structure heights.

Is Pd2(DBA)3 a Feasible Precursor for the Synthesis of Pd Nanoparticles?

The organometallic reagent tris(dibenzylideneacetone) dipalladium(0) [Pd2(DBA)3] has been used as a reagent for synthesis of hexagonal microstructures ranging from 0.5−10 μm. We have shown elsewhere that Pd2(DBA)3 spontaneously forms hexagonal and cubic microstructures. The results obtained herein confirm that microstructures formed by spontaneous aggregation of Pd2(DBA)3 produce the same morphology and carbonaceous chemical composition as those produced with a process that has been called RNA-mediation by pyridyl-modified RNA (pmRNA). Synthesis products from both methods of preparation were analyzed using a combination of scanning transmission electron microscopy (STEM), electron energy loss spectroscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Indexing of electron diffraction patterns from hexagonal molecular crystals and metallic Pd nanoparticles combined with STEM Z-contrast imaging and X-ray dot maps were used to positively differentiate the two materials. On the...

Phase change and electrical characteristics of Ge–Se–Te alloys

Effects of Se contents in Ge–Se–Te ternary systems are investigated using edge contact type phase change random access memory cell structures. Increasing the Se content from 6 to 35 at% crystallization temperature and Ovonic switching threshold voltage are increased due to the large grain growth of hexagonal microstructure in the Ge–Se–Te alloys.

Homogenisation of periodic Cosserat media

The present work deals with the development of homogenisation procedures for Cosserat materials with periodic micro-structure. The procedure developed by Forest et al. (2001) for continuum heterogeneous linear elastic Cosserat media is recalled and extended to discrete Cosserat media. The nature of the homogeneous equivalent medium depends on the hierarchy of three characteristic lengths: the size l of the heterogeneities, the Cosserat intrinsic length lc and the typical size L of the considered structure. When l and lc are comparable and much smaller than L, the effective medium is a Cauchy one, whereas the case lc ∼ L leads to a Cosserat effective medium. Applications to square, hexagonal, cubic and tetrakaidecahedral cell micro-structures are provided. We critically address the other existing homogenisation procedures.

Poroelastic properties of anisotropic cylindrical composite materials

The present work is devoted to the determination of the effective poroelastic properties of anisotropic materials, such as porous nanocomposites and microbiotissues. The poroelastic field of composite materials in a transversely isotropic medium is determined by using the general self-consistent method (GSCM), and the dependence of material properties of the composites on porosity is considered. A hexagonal transversely isotropic model is used and treatment processes are proposed for application to microstructures or macrostructures. Several numerical examples are presented to validate the proposed model, and the results obtained from the model are compared with those obtained from a random-array model, a hexagonal-array model using the strain energy approach (SEA), the dilute suspension of the GSCM, the self-consistent method (SCM) and the effective self-consistent method (ESCM). An explicit solution of poroelasticity is provided, and the effects of the solid matrix anisotropy and pore space on the effective poromechanical properties considered. The numerical results for the hexagonal microstructure using the GSCM agree much better with those obtained from experimental investigation in both wet and dry situations than those obtained from other methods. Finally, the influences of fatigue on micromechanical properties for wet and dry conditions are also described.

The effect of the surface wettability of nanoprotrusions formed on network-type microstructures

Hexagonal network-type silicon microstructures with nanoprotrusions were designed, fabricated, and their surface wettability was characterized. The nanoprotrusions were fabricated by reactive ion etching (RIE). The microstructures were fabricated by deep reactive ion etching (DRIE). For hydrophobicity, plasma polymerized fluorocarbon (PPFC) of a hydrophobic nature was coated onto the surface of the microstructures with nanoprotrusions. Through a comparison of the contact angles between hexagonal network-type microstructures with nanoprotrusions and those without nanoprotrusions, the effect of the nanoprotrusions on the surface wettability was evaluated. The average value of the contact angles measured from microstructures with nanoprotrusions was 18° higher than that measured from microstructures without nanoprotrusions. Nanoprotrusions decrease the contact area between a water droplet and the surface, causing the contact angles to increase considerably. The wetting mode of the nano- and micro-multiscale structured surface changed with the pore ratio of the microstructures. While the water was fully supported by the nanoprotrusions at a low pore ratio, the water fully wetted the nanoprotrusions at a high pore ratio.

Analytical relations between effective material properties and microporosity: Application to bone mechanics

This work deals with the problem of reconstruction of microstructural parameters of viscoelastic composite material from measurements of its effective properties. The Stieltjes representation of the effective shear complex modulus of two-component composite material is exploited to recover information about structural parameters. This representation is derived from problem of torsion of a heterogeneous cylinder using asymptotic expansions method. The microstructural information is contained in the spectral measure in this analytical representation. The spectral function can be recovered from the measurements over a range of frequencies. The problem of reconstruction of the spectral measure is very ill-posed. Regularized algorithm is derived to ensure stability of the results. We apply the proposed method to recovery of porosity of cancellous bone from measurements of its effective shear modulus. Bone is modeled as a medium with a microstructure composed of two viscoelastic isotropic or/and transversely isotropic materials, with the components representing trabeculae (elastic component) and bone marrow (viscoelastic component). Porosity is understood as volume fraction of bone marrow. To verify the approach we apply it to analytically and numerically simulated response of a cylinder filled with a composite material with hexagonal microstructure. The proposed method does not use any specific assumptions about the microgeometry of the composite and is applicable to any two-phase composite medium.

Electrochemical Controllable Synthesis of Bismuth Hexacyanoferrate(II) Nanoplates and Its Application in Electrocatalysis

A facile electrochemical approach was developed for the controllable synthesis of bismuth hexacyanoferrate(II) (BiHCF(II)) nanoplates. The composition, morphology, and structure of the as-prepared BiHCF(II) nanoplates were characterized by the techniques such as infrared spectrum, thermogravimetry, inductively coupled plasma mass spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectrum, powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The formula of the prepared BiHCF(II) nanoplates could be assigned to KBi[Fe(CN)6]·xH2O. It was observed that the nanoplates and their flowerlike aggregations could be obtained in the electrolytes containing different concentration of HNO3. The nanoplates were prepared at the potential for 0.2 V (versus SCE) and could be further grown to a good single-crystalline hexagonal microstructure at 0.6 V. To the best of our knowledge, the structures have not been reported before. The modified Au electrode by the BiHCF(II) nanoplates showed good electrochemical properties, especially with a stable anodic response over the pH range from 2.0 to 11.0. Also, the electrode possesses prominent electrocatalytic activity toward the reduction of hydrogen peroxide.