Hexagonal Rods Research Articles

Hexagonal-Rod Growth Mechanism and Kinetics of the Primary Cu6Sn5 Phase in Liquid Sn-Based Solder

A hexagonal-rod growth mechanism is proposed to describe the growth behavior of the primary Cu6Sn5 phase in liquid Sn-based solder. After Sn-6.5 at.%Cu solder had been maintained at 250°C for 10 h, a large number of hexagonal-rod-type Cu6Sn5 grains were found to have separated within it. Our observations show that these hexagonal rods had side facets in the \(\{ 10\overline{1} 0\}_{\mathrm{\eta} }\) family and round ends close to the {0002}η family. Moreover, the nucleation of the hexagonal rods was studied, and the corresponding growth kinetics found to be governed by a Cu-supply-controlled mechanism rather than an interfacial-reaction-controlled or Cu-diffusion-limited mechanism. More importantly, the anisotropic growth of the Cu6Sn5 phase was confirmed to be the dominant reason for production of these primary hexagonal rods with high aspect ratio. This may represent an avenue for synthesis of nanosized Cu6Sn5 single crystals for use as anode materials in lithium-ion batteries. Additionally, our Cu6Sn5 hexagonal-rod growth mechanism may provide insight into morphological and kinetic studies on interfacial Cu6Sn5 grains and similar intermetallics.

Synthesis of h-MoO<sub>3</sub> and (NH<sub>4</sub>)<sub>2</sub>Mo<sub>4</sub>O<sub>13</sub> Using Precipitation Method at Various pH Values and their Photochromic Properties

(NH4)2Mo4O13 and h–MoO3 nanocrystalline powders were synthesized by precipitation method at a varied pH range from 5.0 to 1.0. The crystal structure, morphology and optical property of samples were determined by X–ray diffractometer (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectrophotometer (UV-vis DRS). At pH 2.0, 3.0 and 5.0, homogenous plate–like (NH4)2Mo4O13 was seen, whereas the heterogeneous hexagonal rod–shaped MoO3 was found at very low pH of 1.0 and 1.5. Band gap energy of the synthesized (NH4)2Mo4O13 and h–MoO3 were 3.38 and 3.18 eV, respectively. Photochromic properties of the products were illustrated by color difference before and after UV irradiation using CIE Lab color system. The synthesized h–MoO3 provided a strong photochromic performance, while the (NH4)2Mo4O13 showed non–photochromic properties. Intercalation of H+ in h-MoO3 were studied using electrochemical characterization by cyclic voltammetry (CV). The diffusion coefficient of the samples increases with decreasing pH of the solution.

Experimental study of heavy-liquid metal (LBE) flow and heat transfer along a hexagonal 19-rod bundle with wire spacers

An experimental campaign considering a 19-pin hexagonal rod bundle with wire spacers, cooled by forced-convective LBE was completed at the Karlsruhe Liquid Metal Laboratory (KALLA). In the frame of the European research project SEARCH (Safe Exploitation Related Chemistry for HLM Reactors, 2011–2015) the geometry and operating conditions of temperature, flow velocity and power density are representative of the fuel assemblies envisaged for the MYRRHA reactor. An extensive test matrix is evaluated, with 33 experimental runs covering a wide range of Reynolds (ca. 14000–48000) and Péclet (ca. 400–1500) numbers, as well as thermal powers (up to 295kW) at 200°C inlet temperature, indicating a good degree of reproducibility within the relatively small experimental uncertainties.Both the pressure drop and heat transfer performances are studied. When possible, a comparison with correlations available in the reviewed literature (namely, friction and heat transfer coefficients) is given. Furthermore, the detailed cross-sectional temperature distribution at three selected axial positions is obtained in the experiments and represents the main validation data for CFD. In non-dimensional terms, these profiles could be repeated at different operating conditions, for example hot and cold spots are consistently found at given locations.

Synthesis and Characterization of ZnO/CuO Nanocomposites on Porous 3D Ni Substrate and Its Photoelectric Behavior

ZnO/CuO semiconducting nanocomposites have been prepared by stepwise hydrothermal method on porous 3D nickel substrate. The flower shaped p-typed CuO nanoflakes were successfully grown on the tips of n-type ZnO hexagonal rods. The material was characterized by scanning electron microscope, energy-dispersive X-ray spectroscopy, and X-ray diffraction. UV-vis diffuse reflectance spectroscopy was employed to determine the band gape and overlapping band region of the composite material. The as grown ZnO/CuO semiconducting nanocomposite was further analyzed for I-V behavior under UV light, which has shown the production of 0.016 A current at around 0.8 V potential difference.

On the early stages of precipitation in dilute Mg–Nd alloys

We report on a first-principles and experimental study of precipitation in supersaturated solid solutions of Mg-rich Mg–Nd alloys. A cluster expansion Hamiltonian combined with Monte Carlo simulations was used to calculate a metastable HCP temperature-composition phase diagram. Aging studies were performed on dilute Mg–Nd alloys that were then characterized with HAADF-STEM. The early stage decomposition of these alloys is dominated by the thermodynamic stability of different Nd orderings on the HCP crystal structure. The observed progression of Guinier-Preston zones can be rationalized by a successive reduction of the Nd chemical potential. HAADF-STEM studies confirm the appearance of β' -like precipitates, however, the observed Nd ordering does not exclusively consist of zig-zag Nd rows but also contains linear strips of Nd-hexagons at non-periodic intervals. First-principles calculations predict that these orderings are stable compounds that belong to a family of hybrid phases formed by combining the β' ordering with the hexagons of β″ (D019) along the [010]β' direction. We label this hierarchy of orderings as β′′′. A high degree of degeneracy among the different β′′′ phases is predicted. This along with a strong composition dependence of the misfit strain is likely responsible for the observed disorder of Nd-hexagon strips. Our experimental and first-principles evidence does not support the formation of Mg3 Nd having D019 ordering. Rather, the features reported as D019 are isolated hexagonal GP rods that show no long-range periodicity. Our study suggests the following precipitation sequence for binary Mg–Nd alloys: SSSS→GP Zones(N,V,hexagons)→β′′′→β1(Mg3Nd)→β(Mg12Nd)→βe(Mg41Nd5).

Study on the similarity of photonic crystal ring resonator cavity modes and whispering-gallery-like modes in order to design more efficient optical power dividers

In this study, we discuss the wave pattern characteristics of confined cavity modes inside photonic crystal ring resonators (PCRRs). Despite different physical origins, these cavity modes are analogous to the whispering-gallery (WG-like) modes. Because of the absence of perfectly circular symmetry in our PC cavity, the WG-like modes are not degenerate, but they form a close doublet in which the field pattern of each of these doublets repeats itself by $$180^{\circ }/m$$180?/m where "m" is the azimuthal index number of WG-like modes. The cavity modes are named according to their symmetric field pattern, and WG-like ones are named by their azimuthal mode numbers "m." Based on the study of these similarities, we propose a $$1\times 2$$1×2 and a $$1\times 4$$1×4 T-junction- like power dividers. Through study of the similar properties of these cavity modes with WG-like modes, we have enhanced the output power of both dividers to 49.6 and 24.5 %, respectively. The permittivity of the hexagonal photonic crystal rod is $$\varepsilon _{h}= 12.04$$?h=12.04 surrounded by air as the background medium. For our PCRR, the dominant resonating mode is the cavity mode with hexapole field pattern or equivalently WG-like mode with azimuthal mode number of $$m\,=\,6$$m=6. The normalized frequencies for this mode and its doublet are $$a/\lambda = 0.348066$$a/?=0.348066 and 0.348301, respectively. The photonic band structure, PC waveguide guided mode and electric field patterns of the confined cavity modes inside the PCRR are calculated using the PWE method, and the transmission spectra are calculated by means of 2D-FDTD simulation method.

Synthesis of hybrid metal-organic frameworks of {FexMyM'1-x-y}-MIL-88B and the use of anions to control their structural features.

The controlled formation of metal-organic frameworks (MOFs) or coordination polymers (CPs) with suitable components and structural features is one of the most important themes in MOF research. In particular, the reliable preparation of hybrid MOFs containing more than two different kinds of metal ions or organic linkers and a comprehensive understanding of the structural flexibility of MOFs are the central issues for the production of MOFs with the desired properties. We report the synthesis of micro-sized hybrid MOF particles [also known as coordination polymer particles (CPPs)] containing two or three kinds of metal ions in each particle: {FexMyM'1-x-y}-MIL-88B (MIL stands for Materials of Institut Lavoisier, M and M' = Ga, Co, or Mn). Scanning electron microscopy images revealed the formation of well-defined uniform micro-sized hexagonal rods, and energy-dispersive X-ray spectroscopy and elemental mapping images verified the simultaneous incorporation of two or three kinds of metal ions within the CPPs. Interestingly, the structural features of CPPs made from MIL-88B were controlled by altering the anions involved in the structure. Incorporating large acetylacetonate anions within the structure resulted in the closed MIL-88B structure with a small cell volume. However, the open MIL-88B structure with a large cell volume was obtained when small chloride anions were incorporated. The intermediate semi-open MIL-88B structure was also prepared using nitrate anions. Three different structural forms of MIL-88B were verified by powder X-ray diffraction, whole pattern fitting, and thermogravimetric analysis.

Novel multiform morphologies of hydroxyapatite: Synthesis and growth mechanism

Morphological evolution of materials becomes a prodigious challenge due to their key role in defining their functional properties and desired applications. Herein, we report the synthesis of hydroxyapatite (HAp) microstructures with multiform morphologies, such as spheres, cubes, hexagonal rods and nested bundles constructed from their respective nanoscale building blocks via a simple cost effective hydro/solvothermal method. A possible formation mechanism of diverse morphologies of HAp has been presented. Structural analysis based on X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirms the purity of the HAp microstructures. The multiform morphologies of HAp were corroborated by using Field emission scanning electron microscope (FESEM).

Hydrothermal synthesis of hexagonal ZnO microstructures in HPMC polymer matrix and their catalytic activities

ZnO microcrystals with hexagonal morphologies are synthesized via a fast and facile hydrothermal route using hexamethylene tetramine (HMTA) as reducing agent and hydroxylpropyl methyl cellulose (HPMC) as morphology directing agent. In the absence of HPMC, hexagonal rod shaped ZnO microcrystals are formed whereas hexagonal bar and both end open hexagonal bar shaped structures are obtained in the presence of different amounts of HPMC. Synthesized ZnO microstructures are characterized using XRD, SEM and fluorescence spectroscopic study. The strong asymmetric blue emission band from ZnO microrod has been explained due to the presence of extended Zni states within the microcrystals. Photocatalytic activities of the microcrystals are investigated by monitoring the photochemical degradation of Methylene Blue. It has been observed that the catalytic efficiency of hexagonal both end open bar shaped ZnO microcrystals is higher than the other ZnO structures.

Ba3Pt4Al4-Structure, Properties, and Theoretical and NMR Spectroscopic Investigations of a Complex Platinide Featuring Heterocubane [Pt4Al4] Units.

Ba3Pt4Al4 was prepared from the elements in niobium ampules and crystallizes in an orthorhombic structure, space group Cmcm (oP44, a = 1073.07(3), b = 812.30(3), c = 1182.69(3) pm) isopointal to the Zintl phase A2Zn5As4 (A = K, Rb). The structure features strands of distorted [Pt4Al4] heterocubane-like units connected by condensation over Pt/Al edges. These are arranged in a hexagonal rod packing by further condensation over Pt and Al atoms with the barium atoms located inside cavities of the [Pt4Al4](δ-) framework. Structural relaxation confirmed the electronic stability of the new phase, while band structure calculations indicate metallic behavior. Crystal orbital Hamilton bonding analysis coupled with Bader effective charge analysis suggest a polar intermetallic phase in which strong Al-Pt covalent bonds are present, while a significant electron transfer from Ba to the [Pt4Al4](δ-) network is found. By X-ray photoelectron spectroscopy measurements the Pt 4f5/2 and 4f7/2 energies for Ba3Pt4Al4 were found in the range of those of elemental Pt due to the electron transfer of Ba, while PtAl and PtAl2 show a pronounced shift toward a more cationic platinum state. (27)Al magic-angle spinning NMR investigations verified the two independent crystallographic Al sites with differently distorted tetrahedrally coordinated [AlPt4] units. Peak assignments could be made based on both geometrical considerations and in relation to electric field gradient calculations.

Synthesis and structural studies of a new complex of catena-poly[p-anisidinium [[diiodidobismu-thate(III)]-di-μ-iodido] dihydrate

A new organic-inorganic hybrid material, {(C7H10NO)[BiI4]·2H2O} n , has been synthesized by slow evaporation of an aqueous solution at room temperature. The anionic sublattice of the crystal is built up by [BiI6] octa-hedra sharing edges. The resulting zigzag chains extend along the a-axis direction and are arranged in a distorted hexagonal rod packing. The p-anisidinium cations and the water mol-ecules are located in the voids of the anionic sublattice. The cations are linked to each other through N-H⋯O hydrogen bonds with the water mol-ecules, and also through weaker N-H⋯I inter-actions to the anionic inorganic layers.

Effects of 8-mer acidic peptide concentration on the morphology and photoluminescence of synthesized ZnO nanomaterials

An 8-mer ZnO-binding peptide, VPGAAEHT, was identified using a M13 pVIII phage display library and employed as an additive during aqueous-based ZnO synthesis at 65 °C. Unlike most other well-studied ZnO-binding sequences which are strongly basic (pI > pH 7), the 8-mer peptide was overall acidic (pI < pH 7) in character, including only a single basic residue. The selected peptide strongly influenced ZnO nanostructure formation. Morphology and optical emission properties were found to be dependent on the concentration of peptide additive. Using lower peptide concentrations (<0.1 mM), single crystal hexagonal rods and platelets were produced, and using higher peptide concentrations (≥0.1 mM), polycrystalline layered platelets, yarn-like structures, and microspheres were assembled. Photoluminescence analysis revealed a characteristic ZnO band-edge peak, as well as sub-bandgap emission peaks. Defect-related green emission, typically associated with surface-related oxygen and zinc vacancies, was significantly reduced by the peptide additive, while blue emission, attributable to oxygen and zinc interstitials, emerged with increased peptide concentrations. Peptide-directed synthesis of ZnO materials may be useful for gas sensing and photocatalytic applications in which properly engineered morphology and defect levels have demonstrated enhanced performance.

3D-Shaping of Ceramic Tapes to Manufacture a High-Temperature Miniaturized Furnace

This contribution shows results of 3D-shaping experiments of ceramic tapes. The structures were made by wrapping structured tapes around a hexagonal alumina rod. After lamination, the rod was removed and the structure was finally fired, similarly as reported in [1]. One out of many possible applications of such structures is a miniaturized furnace for sintering of critical materials, which could contaminate expensive chamber furnaces, for tempering of single gas sensors, or for fast heating at controlled rate. While LTCC technology can be applied only up to 600–700 °C, application of HTCC tapes can extend temperature range to above 1000 °C. Therefore, 99.99% alumina tape (ESL 44007) was used. The here-shown miniaturized furnace has a hexagonal form. For a proper temperature distribution in the furnace chamber, the furnace was equipped with six platinum heaters that can be controlled independently. Finite Elements Analysis (FEM) supported the design process. The paper discusses manufacturing route, beginning with a design process supported by FEM through 3D-shaping by wrapping structured tapes around an alumina rod and finally firing and functionality tests.

Evolution of ZnO Nanoflower-Like Structure Formation and Growth during Synthesis and Paste Preparation

ZnO nanoflowers were synthesized by co-precipitation method at low temperature (80°C) for dye-sensitized solar cell applications. ZnO nanostructures were grown at various pH values from Zinc nitrate tetrahydrate [Zn (NO3)2.4H2O], HMTA (Hexamethylenetetramine) and Potassium Hydroxide (KOH). The results indicate that by increasing pH from 6 to 12, the ZnO morphology evolves from aggregrated particles, prism-like and eventually flower-like structures. According the Scherrer equation the particle size of (100), (002), and (101) peaks tends to drop as the pH increased. HMTA is known as an effective reductant to produce hexagonal ZnO rods of various lengths and cross-sections. Low HMTA led to smaller petal and further addition caused the petal became wider. Annealing temperature should not be higher than 200°C.

Synthesis of magnetic hydroxyapatite by hydrothermal–microwave technique: Dielectric, protein adsorption, blood compatibility and drug release studies

The hydroxyapatite (HAp) nanoparticles with some magnetic ions (cobalt (Co), iron (Fe), nickel (Ni) etc) exhibit strong ferromagnetic properties, which play an important role in the targeted drug delivery and magnetic hyperthermia treatment of the tumours. Cobalt (Co2+) doped HAp (Co–HAp) was synthesized using a combinatorial methods of hydrothermal and microwave irradiation. The crystallinity was found to reduce with an increase in Co2+ incorporation. Pristine samples consisting of monodispersed spheres of size 121nm were diamagnetic. The incorporation of Co2+ (44ppm) leads to a significant reduction in size (55%) and change in morphology (spherical to hexagonal rods). The presence of 139ppm of Co2+, lead to the formation of a super paramagnetic porous structure consisting of hexagonal nanorods and nanospheres. There was a drastic increase in the magnetization (1.2×10−2 to 6.1×10−2emug−1) and dielectric constant (1–2476) on incorporation of cobalt. The Co–HAp exhibited better protein adsorption due to the increase in positive surface potential on addition of Co2+, as confimed by the zeta potential analysis. Further, Co2+ ions incorporated HAp exhibited enhanced haemocompatibility and sustained release of an anticancer drug (5-fluorouracil). This cobalt ion doped HAp could be a promising material for magnetic imaging, drug delivery and hyperthermia treatment.

Morphological and Structural Evolutions of Metal-Organic Framework Particles from Amorphous Spheres to Crystalline Hexagonal Rods.

Compositions as well as morphologies and structures of particles are vital factors that define their properties and applications. However, the morphology and structure changes associated with the composition change of metal-organic frameworks (MOFs) are barely studied. Herein, we report the morphology and structure changes of MOF particles associated with the ratio of two organic linkers incorporated within MOF particles, when they are constructed from the reactions of In(NO3)3 in the presence of isophthalic acid (H2IPA) and/or 1,4-benzenedicarboxylic acid (H2BDC). Two tendencies—the tendency of BDC and In(3+) to form porous crystalline hexagonal rods, and the tendency of IPA and In(3+) to form non-porous amorphous spherical particles—compete during the formation of MOF particles. Eventually, the incorporated ratio of BDC and IPA within the MOF particles, and thus their morphology and porosity, are controlled by altering the relative amounts of H2BDC and H2IPA used during the reactions.

Preparation of highly oriented Al:ZnO and Cu/Al:ZnO thin films by sol-gel method and their characterization

Highly oriented thin films of Al doped ZnO (Al:ZnO) and Cu co-doped Al:ZnO (Cu/Al:ZnO) thin films were successfully deposited by sol–gel spin coating on glass substrates. The deposited films were characterized using X-ray diffraction analysis and found to exhibit hexagonal wurtzite structure with c-axis orientation. SEM images revealed that hexagonal rod shaped morphologies were grown perpendicular to the substrate surface due to repeated deposition process. High transmittance values were observed for pure ZnO compared to Al:ZnO and Cu/Al:ZnO thin films. The band gap widening is caused by the increase of carrier concentration, which is believed to be due to Burstein-Moss effect due to Al and Cu doping. PL spectra of Cu/Al:ZnO thin films indicate that the UV emission peaks slightly shifted towards lower energy side. XPS study was carried out for Zn0.80Al0.10Cu0.10O thin films to analyze the binding energy of Al, Cu, Zn and O. Magnetic measurement studies exhibited ferromagnetic behavior at room temperature, which may be due to the increase in copper concentration in the doped films. The ferromagnetic behavior can be understood from the exchange coupling between localized ‘d’ spin of Cu ion mediated by free delocalized carriers.

Morphological and Structural Evolutions of Metal–Organic Framework Particles from Amorphous Spheres to Crystalline Hexagonal Rods

AbstractCompositions as well as morphologies and structures of particles are vital factors that define their properties and applications. However, the morphology and structure changes associated with the composition change of metal–organic frameworks (MOFs) are barely studied. Herein, we report the morphology and structure changes of MOF particles associated with the ratio of two organic linkers incorporated within MOF particles, when they are constructed from the reactions of In(NO3)3 in the presence of isophthalic acid (H2IPA) and/or 1,4‐benzenedicarboxylic acid (H2BDC). Two tendencies—the tendency of BDC and In3+ to form porous crystalline hexagonal rods, and the tendency of IPA and In3+ to form non‐porous amorphous spherical particles—compete during the formation of MOF particles. Eventually, the incorporated ratio of BDC and IPA within the MOF particles, and thus their morphology and porosity, are controlled by altering the relative amounts of H2BDC and H2IPA used during the reactions.

Lasing from an individual ZnO hexagonal microrod on the Au surface coated by a nanometer-scaled SiO2 layer

We demonstrate that an individual ZnO hexagonal microrod on the surface of Au substrates coated by a nanometer-scaled SiO2 layer can become a source for manufacture miniature ZnO plasmon lasers by surface plasmon polariton coupling with whispering-gallery modes (WGMs), and the SiO2 layer can tune the modes and intensity of ZnO emission. We achieve an abnormally low-threshold plasmonic WGM lasing from a ZnO hexagonal rod, and the threshold is 0.36 KW/cm2. These investigations show that this coupling mode holds a potential of ZnO hexagonal micro- and nanorods for data storage, bio-sensing, optical communications, as well as all-optic integrated circuits.

Openable electromagnetic actuator as a non-contact, agile tool for crimping operations

This work focuses on using electromagnetic forming (EMF) for creating a conformal interference fit between an aluminum outer tube and a coaxially aligned inner part using a novel tool known as an openable actuator, or simply O-actuator. The utility of the O-actuator is in applications where it is impractical or impossible to remove a crimped assembly from a traditional helical actuating coil. In this work, a fully conformal joint between aluminum alloy type 6061 tube of circular starting geometry and AISI 1018 steel hexagonal rod was created with an input electrical energy of 8kJ.