Crystal Sheet Research Articles

Self-Similar Nested Flux Closure Structures in a Tetragonal Ferroelectric

In specific solid-state materials, under the right conditions, collections of magnetic dipoles are known to spontaneously form into a variety of rather complex geometrical patterns, exemplified by vortex and skyrmion structures. While theoretically, similar patterns should be expected to form from electrical dipoles, they have not been clearly observed to date: the need for continued experimental exploration is therefore clear. In this Letter we report the discovery of a rather complex domain arrangement that has spontaneously formed along the edges of a thin single crystal ferroelectric sheet, due to surface-related depolarizing fields. Polarization patterns are such that nanoscale "flux-closure" loops are nested within a larger mesoscale flux closure object. Despite the orders of magnitude differences in size, the geometric forms of the dual-scale flux closure entities are rather similar.

Graphene: an emerging material for biological tissue engineering

Graphene, a carbon crystal sheet of molecular thickness, shows diverse and exceptional properties ranging from electrical and thermal conductivities, to optical and mechanical qualities. Thus, its potential applications include not only physicochemical materials but also extends to biological uses. Here, we review recent experimental studies about graphene for such bioapplications. As a prerequisite to the search to determine the potential of graphene for bioapplications, the essential qualities of graphene that support biocompatibility, were briefly summarized. Then, direct examples of tissue regeneration and tissue engineering utilizing graphenes, were discussed, including uses for cell scaffolds, cell modulating interfaces, drug delivery, and neural interfaces.

Synthesis of TiOF<sub>2</sub> Ball-Flowers and the Phase Transitions to TiO<sub>2</sub>

In the present work, TiOF2 ball-flowers were successfully synthesized through a simple low temperature hydrothermal route using titanium butoxide and hydrofluoric acid as precursors. The effect of synthesis temperature on the morphology of TiOF2 ball-flowers was also studied by scanning electron microscopy (SEM). The crystal characteristics of TiOF2 were analyzed based on X-ray powder diffraction (XRD) and transmission electron microscopy (TEM), which revealed that the TiOF2 ball-flowers were consist of hexagonal and cubic single crystal TiOF2 sheets. After an annealing treatment of 500°C for 2h, the single crystal TiOF2 sheets were converted to single crystal anatase TiO2 sheets exposed with {116} and {001} facets exposed respectively.

2-Oxo-2H-chromen-4-yl 4-methoxybenzoate

In the title mol­ecule, C17H12O5, the chromen-2-one ring and the 4-meth­oxy­benzoate side chain are inclined to one another at a dihedral angle of 69.82 (9)°. The crystal structure features parallel sheets of centrosymmetric R 2 2(6) dimers joined by a C(7) chain, resulting in centrosymetric tetra­mers of hydrogen-bonded mol­ecules with graph-set motif R 4 4(40). These centrosymetric tetra­mers are connected by a pair of hydrogen bonds described by an R 2 2(8) ring motif and a C(7) chain via C—H⋯O inter­actions. In the structure, there are also π–π stacking inter­actions between chromene benzene and the six-membered heterocyclic rings [centroid–centroid distance = 3.691 (2) Å] and weak C=O⋯π inter­actions [O⋯(ring centroid) distance = 3.357 (3) Å].

Local heat transfer characteristics of array impinging jets from elongated orifices

The aim of this research is to enhance the heat transfer on an impinged surface under an impinging jet array by minimizing a cross-flow effect. Conventional round orifices (aspect ratio, AR=1) are substituted by the elongated orifices with aspect ratio AR=4 and 8 with the same jet exit area. Two types of orifice arrangements; in-line and staggered arrays are compared. The experimental investigation was carried out at constant distance from orifice plate to impinged surface H=2DE (DE is equivalent diameter of orifice). The heat transfer characteristic was visualized using thermochromic liquid crystal sheet (TLCs) and the Nusselt number distribution was evaluated by an image processing technique. The flow characteristic on the impinged surface was also visualized by oil film technique. The results show that the cross-flow in a case of the jets issued from the orifices with AR=4 is considerably less significant than that in cases of the ones delivered from the orifices with AR=1 and 8. At Reynolds number of 13,400, the Nusselt numbers for the jet arrays issued from the elongated orifices with AR=4 with in-line and staggered arrangements are respectively 6.04% and 12.52% higher than those for the case of AR=1.

Estimation of temperature dependent heat transfer coefficient in a vertical rectangular fin using liquid crystal thermography

This paper presents a methodology for the estimation of temperature dependent heat transfer coefficient for a vertical rectangular fin by using the inverse heat transfer method with Liquid crystal thermography (LCT) data. Steady state, laminar natural convection experiments have been done on a vertical rectangular fin of size 150×250×4, (L×w×t, all dimensions are in mm). The variation of heat transfer coefficient is considered as a power law function of temperature excess (h=aoθb) and is derived from the basic Nusselt number equation used for laminar natural convection, Nu=aRab. With this functional form, the one dimensional fin equation in finite difference form is repeatedly solved using the Gauss–Seidel iterative method. Treating this as a one parameter estimation in ‘a’ the sum of the squares of the difference between the simulated and Thermochromic Liquid Crystal (TLC) measured temperatures is minimized with the Golden section search algorithm to retrieve ‘a’. Estimate of ‘a’ and the accompanying uncertainties are first reported for synthetically generated temperature distribution for assumed values of ‘a’. The effect of noise on the estimate of ‘a’ is discussed. This is followed by retrievals with experimentally obtained TLC temperature distribution for a range of heat inputs to the fin base. The required temperature distributions for accomplishing the retrievals over the surface are obtained using calibrated R40C5W Thermochromic Liquid Crystal (TLC) sheets. As an additional proof of the accuracy of the method, the retrieved value of ‘a’ is used to simulate the temperature distribution in the fin which is then compared with the actual TLC measured temperature distribution.

Thermal visualization on surface with transverse perforated ribs

This paper presents the heat transfer and flow characteristics in a channel with different types of transverse perforated ribs. The effects of perforation/hole inclination angle (θ=0°, 15° and 30°) and a location of hole on the rib (h=0.2H, 0.5H and 0.8H), have been examined. The investigation was performed at constant Reynolds number (Re) of 60,000. The experimental heat transfer results via Thermochromic liquid crystal sheet are reported along with the numerical flow characteristics. The results reveal that due to jet-like flows impinging on the surface, the inclined perforated rib considerably improve the heat transfer immediately downstream from the ribs, compared to straight perforated and solid ones, resulting in superior overall heat transfer performance.

Visualization of flow and heat transfer characteristics for swirling impinging jet

Flow and heat transfer characteristics of swirling impinging jet (SIJ) were studied experimentally at constant nozzle-to-plate distance of L=4D. The swirling jet is generated by inserting twisted tapes within a pipe nozzle. Effects of swirl on the impinged surface are investigated at twist ratios (y/W) of ∞ (straight tape), 3.64, 2.27, 1.82, and 1.52. The flow patterns of the free swirling jet and the swirling impinging jet were visualized by mixing dye with the jet flow. Distributions of temperature and convective heat transfer coefficient on the impinged surface were measured with thermochromic liquid crystal (TLC) sheet and image processing technique. Additionally, an oil film technique was performed as a complementary technique for flow visualization on the impinged surface. The experimental results reveal that there appear to be two peaks of heat transfer in the jet impingement region. The heat transfer enhancements in jet impingement region can be achieved at a low twist ratio of 3.64 which corresponds to the swirl number of 0.4.

119 不足膨張衝突噴流における平板の圧力と温度について(G01-8流体抵抗とその応用,G01 熱流体部門)

The underexpanded jet is broadly used in industries such as a cooling jet of heat-tempered glass and an assist gas of laser cutting In this study, a cooling effect was examined of the underexpanded jet impinging on a flat plate. The temperature distribution is visualized using a liquid crystal sheet, and additionally the static and total pressures are measured on the plate. As a result, two cooling rings appear on the plate and these locations are fixed regardless of nozzle-plate spacing.Furthermore, the raynolds number distribution was found to be independent of the nozzle-plate spacing Finally, the relation between the temperature and pressure distributions is discussed.

Large organic single crystal sheets grown from the gas–liquid and gas–liquid–solid interface

The growth of high-quality organic single crystals with controlled size is crucial to both the study of the fundamental physical properties of the materials, and to their practical utilization. Here, a novel gas–liquid interface technique is presented for the growth of anthracene (AN) and its doped single crystals. The AN single crystals showed sheet shape, large size of up to centimeter range, and neat surface morphology. The results of X-ray diffraction and optical measurements indicated that such laminated films exhibited higher crystalline quality and photoluminescence (PL) efficiency than those obtained by physical vapor transport (PVT) method or original solution growth (SG) method. The crystal formation process is explored by quoting the principle of Langmuir–Blodgett film and the terrace–ledge–kink crystal growth model. Such a crystal growth technique can be expanded to the gas–liquid–solid interface to directly grow AN single crystals on electrodes (such as silicon wafer and golden substrate), which may be valuable for the preparation of organic single crystal based devices including light-emitting diodes and field effect transistors.

Heat transfer enhancement by multiple swirling impinging jets with twisted-tape swirl generators

The flow and heat transfer characteristics of multiple swirling impinging jets ( M- SIJs) with 3 × 3 in-line arrangement, on impinged surfaces are reported. The experiments were conducted with four different jet-to-jet distances ( S/ D = 2, 4, 6 and 8) at the constant nozzle-to-plate distance of L/ D = 4. The swirling jets with the swirl numbers of 0.4 were associated with twisted tapes. The multiple conventional impinging jets ( M- CIJs) were also tested, for comparison. The flow patterns on an impinged surface were visualized using oil film technique while the distributions of temperature field and Nusselt number on impinged surface were evaluated via a thermochromic liquid crystal ( TLC) sheet coupled with image processing technique. The experimental results showed that the M- SIJs offered higher heat transfer rate on impinged surfaces than the M- CIJs of all jet-to-jet distances ( S/ D).

Generation of a twin beam at the cesium line and telecom wavelength by cavity phase matching

Cavity phase matching has been recently demonstrated as a phase-matching method for efficient nonlinear frequency conversion in a microcavity. Here we extend it to the Type I configuration using a sub-coherent-length optical parametric oscillator consisting of an MgO-doped lithium niobate crystal sheet. It generates a tunable single-longitudinal-mode twin beam, which covers the cesium D2 line of 852.1 nm and the extended band of optical communication. This microcavity is capable of peak output power of 58 kW with a maximum conversion efficiency of 18.5%. Broad applications in the areas of light-atom interaction, spectroscopy, optical telecommunication, and quantum optics can be expected.

Correlation between Microstructure and Toughness of Crab Carapace

Crab carapace is a kind of biomaterial in nature. It behaves favorable strength, stiffness and fracture toughness, which are closely related to its fine microstructure. The observation of scanning electron microscope (SEM) on the carapace of a Cyclodorippoidea crab shows that the carapace is a kind of natural bioceramic composite consisting of calcite crystal layers and collagen protein matrix. The observation also shows that the calcite crystal layers consist further of long and thin calcite crystal sheets and that all the calcite crystal sheets are arranged in a kind of parallel distribution. The maximum pullout energy of the calcite crystal sheets, which is closely related to the fracture toughness of the carapace, is investigated based on the representative model of the parallel distribution. It shows that the long and thin shape as well as the parallel distribution of the calcite crystal sheets enhance the maximum pullout energy and ensure the high fracture toughness of the carapace.

Cavity Phase Matching via an Optical Parametric Oscillator Consisting of a Dielectric Nonlinear Crystal Sheet

We experimentally demonstrate cavity phase matching for the first time using a sheet optical parametric oscillator which is made of an x-cut KTiOPO(4) crystal sheet. This microcavity presents 220 kW peak power capability for near-frequency-degenerate parametric outputs with up to 23.8% slope efficiency. It also features unique spectral characteristics such as single-longitudinal-mode and narrow linewidth. These attractive properties predict broad applications of such a mini-device, such as terahertz generation, photonic integration, spectroscopy, and quantum information, etc.

Numerical formability assessment in single crystals of magnesium

In this paper a rate-sensitive elastic–viscoplastic crystal plasticity constitutive model (CPCM) together with the Marciniak–Kuczynski (M–K) approach have been used to assess the formability of a magnesium single crystal sheet by simulating the forming limit diagrams (FLDs). Sheet necking is initiated from an initial imperfection in terms of a narrow band. A homogeneous deformation field is assumed inside and outside the band, and conditions of compatibility and equilibrium are enforced across the band interfaces. Thus, the CPCM only needs to be applied to two regions, one inside and one outside the band. The FLDs have been simulated under two conditions: (a) the plastic deformation mechanisms are basal, pyramidal 〈 c + a〉, and prismatic slip systems, and (b) the plastic deformation mechanisms are basal, pyramidal 〈 c + a〉, and prismatic slip systems, as well as extension and contraction twinning systems. The FLDs have been generated for two grain orientations. In the first orientation pyramidal 〈 c + a〉 and extension twinning systems, and in the second orientation basal and pyramidal 〈 c + a〉 slip systems, as well as contraction twinning systems have favourable orientation for activation. The effects of shear strains outside the necking band, strain rate sensitivity, and c/ a ratio on the simulated FLDs in the two grain orientations have been individually explored.

K3Gd(PO4)2

The title compound, tripotassium gadolinium(III) bis­[ortho­phosphate(V)], was synthesized by a high-temperature solution reaction. Of the 12 atoms of the asymmetric unit (1 × Gd, 2 × P, 3 × K, 6 × O), all but two O atoms (which are in general positions) lie on mirror planes. The crystal structure features sheets of composition [Gd(PO4)2]3− which extend parallel to (100) and are built up from isolated PO4 tetra­hedra and GdO7 monocapped prisms through corner- and edge-sharing. The K+ ions, which have coordination numbers of 10, 9 and 11, help to stack the anionic sheets along [100] into a three-dimensional structure.

Sulfur doped anatase TiO 2 single crystals with a high percentage of {0 0 1} facets

Extending the response range of wide-bandgap (3.2 eV) anatase TiO 2 photocatalysts into the visible light range can play an important role in promoting the practical applications of photocatalysts. Here, we report a route to prepare sulfur doped anatase TiO 2 single crystal sheets with a high percentage of {0 0 1} facets. The resultant TiO 2 sheets were investigated by a combination of experimental characterizations and electronic structure calculations. The synthesized sulfur doped anatase samples show an additional visible light absorption band from 400 nm to ca. 550 nm and some visible-light photocatalytic activity in OH radical generation and photodecomposition of organic dyes. The Ti–S bond structure causes not only visible light absorption but also changes to an extent the surface structures of doped anatase TiO 2 sheets. Theoretically, localized 3p states of S formed in the bandgap are implicated for the visible light absorption of the sulfur doped anatase TiO 2.

Inhomogenous Dislocation Nucleation Based on Atom Potential in Hexagonal Noncentrosymmetric Crystal Sheet

By introducing internal degree, the deformation of hexagonal noncentrosymmetric crystal sheet can be described by the revised Cauchy–Born rule based on atomic potential. The instability criterion is deduced to investigate the inhomogeneous dislocation nucleation behavior of the crystal sheet under simple loading. The anisotropic characters of dislocation nucleation under uniaxial tension are studied by using the continuum method associated with the instability criterion. The results show a strong relationship between yield stress and crystal sheet chirality. The results also indicate that the instability criterion has sufficient ability to capture the dislocation nucleation site and expansion. To observe the internal dislocation phenomenon, the prediction of the dislocation nucleation site and expansion domain is illustrated by MD simulations. The developed method is another way to explain the dislocation nucleation phenomenon.

Synthesis, Solution, and Structural Characterization of Tetrahydrofuranyl‐2,2‐Bisphosphonic Acid Disodium Salt

Bisphosphonates are biologically relevant therapeutics for bone disorders and cancer. Reaction of γ-chlorobutyric acid, phosphorus acid, and phosphorus trichloride without the use of solvent gave the tetrahydrofuranyl-2,2-bisphosphonate sodium salt (Na2H2L). The Na2H2L was isolated, characterized in solution by 1H, 13C, and 31P NMR spectroscopy and in solid state by single X-Ray crystallography. The crystal structure showed that the Na2H2L forms in the crystal infinite two-dimensional sheets stacked one parallel to the other. A comparison of the chelating properties of H2L2− with similar hydroxyl bisphosphonate ligands shows that the strength of the Na–O(furanyl/hydroxyl) bond is directly related to the total charge of the ligand anion.

Micro-bubble enhanced HIFU

High intensity focused ultrasound (HIFU) treatment that employs microbubbles to provide enhanced heating has been investigated in order to develop a less invasive and more rapid tumor ablation therapy. It has been demonstrated that microbubbles have significant effects on heating enhancement in vitro and in vivo experiments, however ultrasound propagation could be disturbed when there are too many microbubbles between the transducer and the focus. In this study, we develop a method to make a clear pass way for obtaining enhanced heating by using microbubbles just at the focus, thus avoiding heating on the pass way from the transducer to the target region. In this method, microbubbles are destroyed in front of the HIFU focus (on the transducer side) by irradiating a intense burst wave of microsecond order, before irradiating the ultrasound waves for heating the target region. The experiment is conducted in a medium of a polyacrylamide gel containing microbubbles, and a temperature-sensing liquid crystal sheet is set in the focus to observe the temperature distribution. The ultrasound frequency was 2.2 MHz and the intensity was 5000 W/cm2, and 20 burst waves were irradiated at pulse repetition frequency of 1 kHz. The number of wave pulses was varied. The continuous-wave frequency, intensity and irradiation time are 2.2 MHz, 1000 W/cm2 and 60 sec, respectively. As the number of pulses increased, the heating region moves from the transducer side to the focus. This is because microbubbles in front of the focus are destroyed and the ultrasound propagates around the target position effectively. These results suggest that the microbubble distribution and the heating position in the developed HIFU system can be controlled.