Sides Of Hexagon Research Articles

Hexagonal sheet Ag and Ag nanoparticle inside 3D-TiO2 NTAs decorated Ti gauze by electrodeposition

Noble metal nanoparticles have attracted extensive attention by many researchers because of their optical, electrical and magnetic advantages. Half hexagon sheet Ag and Ag nanoparticles inside 3D-TiO2 nanotube arrays (NTAs) on Ti gauze was firstly synthesized by electrodeposition. The addition has a great influence on the morphology of Ag. When Ag hexagonal side length reached a maximum of 2 μm for 20 pluses, hexagonal Ag would transform oval Sphere with depositional pulses continuing increases, Ag nanoparticle inside 3D-TiO2 NTAs also were found, and the Ag modified NTAs for 20 pulses with the best photo-catalytic activity degraded methyl orange (MO) under solar light irradiation. Due to 3D-TiO2 NTAs supporting Ag catalyst, which is a benefit for recycling after the catalyst. This work is expected to provide a fundamental guide for the design of novel morphology catalysts on Ti gauze, which is conducive to recycling.

Enhanced heat transfer characteristics of the mini hexagonal tube heat sink using hybrid nanofluids

The thermal performance of different hybrid nanofluids on the mini hexagonal tube heat sink has been investigated experimentally. Al2O3/SiO2-DIW, Al2O3/CuO-DIW, and CuO/SiO2-DIW nanofluids have been used as the working fluids. The aggregate of 0.01 volume fraction of Al2O3, CuO, and SiO2 nanoparticles for hybridizing ratios (80:20) has been considered to prepare deionized water-based hybrid nanofluids. The thermal performance of three different hybrid nanofluids inside the mini hexagonal tube heat sink has been assessed. The varying volumetric flow rates of 15–50 lph have been maintained on the hexagonal tube side and 50 lph on the mini passage side. Herein, the proposed hexagonal-shaped heat sink provides a larger heat contact surface to exchange the heat between the hybrid nanofluids and hot DIW. It is divulged that the increase in the volume flow rate of nanofluids promotes the higher Brownian motion, leading to an increase in convective heat transfer. Amongst three hybrid nanofluids, CuO/SiO2-DIW nanofluids have revealed a slight increase in pumping power while increasing the volume flow rate. From the experimental results, it is shown that the heat transfer coefficient, effectiveness, and Nusselt number have been improved by 54.5%, 42%, and 28.4%, respectively, for Al2O3/CuO-DIW nanofluids. Thus, Al2O3/CuO-DIW nanofluid can be deemed to be an efficient working fluid for the miniature heat sinks to accelerate the heat transfer rates.

Construction of soft polyurethane cushioning composites based on integral fabric air layer: Reaching new levels in compression and cushioning behaviors

AbstractIn order to prepare a cushioning composite with good resilience and compressibility, the 3D fabric was perforated into a hexagonal honeycomb, high elasticity porous polyurethane foam was used as substrate, and the air layer structure was encapsulated with the packaging film. By changing the hexagonal side length and wall thickness of the honeycomb structure, the integral fabric air layer polyurethane buffer composite was prepared. The properties of the structure were studied, and its compressive capacity under different compressive strains was analyzed. The results show that the mechanical properties of polyurethane foam were improved after adding the integral fabric air layer structure. When the composite HPU‐R1L2 (polyurethane cushioning composites with 1 cm side length and 2 cm wall thickness of hexagonal honeycomb) was compressed to 75%, its compressive capacity was 8.24 times that of PU (Polyurethane foam with 2.5% bentonite). The prepared composite HPU‐R1L1 (Polyurethane cushioning composites with 1 cm side length and 1 cm wall thickness of hexagonal honeycomb) absorbed 96.7% of the energy in the dynamic impact test, indicating that the composite cushioning performance was stronger than that of polyurethane foam. The HPU composites based on the synergistic reinforcement strategy of polyurethane foam and monolithic fabric air‐layer structures are an excellent candidate in the field of commodity packaging and personal protection.

Performance improvement of the mini hexagonal tube heat sink using nanofluids

The experimental investigation is accomplished to determine the improved performance of the mini hexagonal tube heat sink (MHTHS) using nanofluids (NFs). The three different NFs are prepared via a two-step method in which, Al2O3, MgO, and CuO nanoparticles with 0.1 vol fraction (VF) are dispersed into deionized water (DIW), individually. The experiment is conducted in the MHTHS under the following conditions. The volume flow rate (VFR) of DIW in the mini passage side (MPS) is maintained at 30 L per hour (lph), and the VFR of NFs in the hexagonal tube side (HTS) is varied from 10 lph to 50 lph. MgO-DIW NFs show the highest performance at 0.1 VF for 50 lph of HTS flow. Similarly, for 0.1 VF of Al2O3-DIW and CuO-DIW NFs, higher performance was achieved at 45lph of HTS flow. From the experimental data, the enhancement of the convective heat transfer coefficient (CHTC) of MgO-DIW, Al2O3-DIW, and CuO-DIW NFs are reported as 40%, 28%, and 22%, respectively. However, the augmentation of the overall heat transfer coefficient of MgO-DIW, Al2O3-DIW, and CuO-DIW NFs are 32 %, 24%, and 16%, respectively. Furthermore, the overall Effectiveness of MHTHS is enhanced by about 42% using MgO-DIW nanofluid. Hence, MgO-DIW NF could be used efficiently to cool the hexagonal-shaped miniature devices.

Characterization of two-dimensional cellular elastic topological insulators based on regular-hexagon carriers

An elastic topological insulator with pseudo-spin characteristics is designed based on honeycomb lattice phononic crystals with positive hexagonal carriers, which can realize path defect immunity and backscattering suppression transmission characteristics. By introducing a positive hexagon carrier with a certain size at the narrow diameter junction of the two-dimensional honeycomb structure to achieve symmetry breaking, a four-fold accidental degeneracy point can be obtained by adjusting the cell parameters. The main variable of the primitive cell is the hexagonal carrier side length [Formula: see text]. It is found that the four-fold Dirac point can be opened and a band gap can be formed by contracting the positive hexagonal carrier. Inversion of the energy band occurred in the separated two-fold degenerate state, for which the transformation of mediocre state and nonmediocre state had been realized so that the structure with acoustic pseudo-spin and topological edge state could be obtained. Based on the principle of body-edge state correspondence, the topologically protected edge acoustic transmission is simulated by the construction of the edge states combined with the connection of different structural systems. Further, different elastic phonon crystal structures are constructed, and the characteristics of path defect immunity and back-scattering suppression of elastic wave propagation by topological edge states are verified. The designed elastic topological insulators have great application prospects in the regulation of elastic waves.

Flow and heat transfer in a plain fin-and-hexagonal tube heat exchanger with different side ratios

Improving the thermo-hydraulic performance of heat exchangers (HEs) can considerably manage the energy requirements in various engineering processes. The fin-and-tube heat exchangers (FTHEs) are extensively utilized in recent decades, and they provide substantial benefits over the typical HEs such as high heat transfer surface. The shape and geometry of the tubes remarkably affect the thermal efficiency and pressure drop of these devices. There are many experimental and numerical investigations relating to improving the thermo-hydraulic performance of FTHEs with circular and elliptical tubes in the literature. In the current research, five various hexagonal tubes with different side ratios were utilized to enhance the performance of an FTHE. The impact of various hexagon side ratios on heat transfer capacity and fluid flow characteristic of the FTHE at different Reynolds numbers has studied numerically. According to the obtained results, the plain-fin-and hexagonal tube HE with the side ratio of 0.25 had the best performance. Although the lowest values of the Colburn factor and the weakest heat transfer belong to the FTHE with the side ratio of 0.25, it is preferred to circular tube HEs due to the lower pressure drop they cause.

Shape evolution and optical response of ZnO nanostructures grown on thermally evaporated ZnO and Au thin films

ZnO thin films of 100–400 nm thickness and 100 nm thickness Au thin films were deposited on glass substrates by thermal evaporation. Shape control of ZnO nanostructures on these films is achieved by microwave assisted hydrothermal synthesis at 90 °C for 30 min using zinc nitrate and zinc acetate as the precursors. There is a hierarchy of shapes comprising star shaped tetrapods and ball-shapes at the microscale made up of rice grains at the nanoscale on the ZnO and Au thin films respectively, when the precursor is zinc nitrate. The typical dimensions of the nano rice grains are 1 μm length, 100 nm width and tips of the order of 10 nm. In contrast, when the precursor is zinc acetate the nanostructures grow as hexagonal rods on the ZnO films and hexagonal tetrapods on the Au films with dimensions of 1–3 μm length and hexagon side of the order of 100–150 nm. Raman spectroscopy studies indicate the presence of defect related peaks in the nanostructures that are suppressed with increase in thickness of the ZnO films. The intensity of the defect peaks is much higher in the nanostructures grown on the Au films and is dependent on the precursor used to produce the nanostructures. Photoluminescence studies indicate that the ultraviolet-near band edge emission is the strongest on ZnO while defect related emission is prominent on the Au films. Shape control by microwave assisted hydrothermal synthesis is, thus, a facile low temperature method to produce nanostructures with different properties by simply changing the precursor and substrate on which they are grown.

Persistent Water Repellency of Syndiotactic Polymethylene with Perfluoroethyl Hexyloxycarbonyl Side Chains.

Polyacrylates bearing long fluoroalkyl (Rf) side chains are known to have ultralow surface energies that are appropriate for functional coating and fabric finishing. However, these long Rf chains cause health concerns because of the risk of toxic and bioaccumulative perfluoroalcanoic acid emission via oxidative degradation. This work demonstrates that incorporating a short Rf chain of perfluoroethylene at the end of the side chains of syndiotactic poly(substituted methylene) (PM) produces hydrophobicity. A contact angle of 105° of PM remains constant for more than 50 s, whereas that of the polyacrylate (PA) with the same side chain rapidly decreases from 85° to 44° over the same period. Such persistent water repellency of the PM is ascribed to a liquid crystal structure comprised the main chains arranged in a 2D hexagonal lattice and side chains that extend perpendicularly from these main chains.

Characterization of energy absorption for side hierarchical structures under axial and oblique loading conditions

This paper develops triangular, quadrangular and hexagonal side hierarchical structures to promote the energy absorption of thin-walled protective devices. The axial crush testing exhibits that side hierarchical structures can form stable folding deformation. The energy absorption of side hierarchical structures under oblique loads is further investigated by the numerical simulation, and the energy absorption of 7th order triangular hierarchical structure is 112% higher than that of the non-hierarchical triangular column under axial impact. The hierarchical factor and loading angle have great influence on the crushing response of side hierarchical structures, and the critical hierarchical order is observed for different side hierarchical structures. Furthermore, 4th order side hierarchical structures are believed with excellent comprehensive crashworthiness based on the technique for order preference by similarity to ideal solution (TOPSIS). Lastly, the wall thickness parameter of 4th order side hierarchical structures is further investigated to reveal the influence of material distribution on the crashworthiness, and results show that the energy absorption of 4th order hexagonal side hierarchical structure can much easier suffer the influence of wall thickness than that of the other two side hierarchical structures.

Regular hexagonal-prism microvoids in CeF3 single crystals

Microvoids are well-known crystal defects, usually exhibiting a rounded and/or irregular shape, which act as undesired scattering centers in optical applications. Here, for the first time, residual microvoids in the shape of perfect regular hexagonal-prisms are observed in apparently scattering-free CeF3 bulk single crystals. These microvoids reflect exactly the natural crystal habit in “negative” form: the prisms stand along the c-axis and the hexagonal sides are parallel to the six equivalent planes perpendicular to the a-axis. They distribute randomly with sizes up to 13 µm and heights in the submicron order with a maximum around 500 nm. The microvoids are formed by the embedding of bubbles during the crystallization process. The bubbles’ gas is possibly caused by the high vapor pressure of CeF3 itself at the high melting point.

Laser Shock Induced Deformation of Copper Foil on Diverse Molds and the Cross-Sectional Microstructure Changes

The microscale structures prepared on copper foil by laser shock deformation was introduced in the paper. The various sizes of hexagonal structures were successfully fabricated on copper foil with different molds. The influence of laser energy on the deformation depth of a hexagonal structure was studied using experiments. The morphology of the hexagonal structures on copper foil was observed by a three-dimensional profilometer, and mechanical property were characterized by a nanoindenter. A finite element model was established in order to describe the copper foil forming mechanism on mold and calculate the residual stress distribution. The microstructures and cross-section deformation of copper foil on different molds were also observed. The results indicated that the depth of hexagonal structures on 50# mold was higher than that of the structures on 100# mold and 230# mold, and the depth of hexagonal structures increased with the increasing of pulse laser energy. The copper foil above the mold hexagon side was bent and thinned after laser shock, and the grains of copper foil were also refining. The mechanical properties of copper foil were improved after laser shock was performed on the mold.

Experimental investigation on the effectiveness of MHTHS using different metal oxide-based nanofluids

In recent times, the mini heat sink is suggested for cooling the miniature components employed in several engineering applications. In the present work, the thermal performance of the mini hexagonal tube heat sink (MHTHS) was investigated experimentally. Nanofluids and deionized water (DIW) were made to flow through the hexagonal tube side and mini-passage side, respectively. For the preparation of different nanofluids of 0.01 volume fraction, DIW was considered to be a base fluid; Al2O3, CuO, and SiO2 nanoparticles were reckoned to be the supporting materials. Experiments were run under two different conditions in order to ascertain the enhanced thermal performance of the MHTHS. They are as follows: (1) keeping the flow rate of hot DIW constant at 30 L h−1 in the mini-passage side, the flow rates of nanofluids in the hexagonal tube were varied such as 15, 20, 25, 30, 35, 40, 45, and 50 L h−1; (2) keeping the flow rate of nanofluids constant at 30 L h−1 in the hexagonal tube side, the flow rates of hot DIW in the mini-passage side were varied such as 15, 20, 25, 30, 35, 40, 45, and 50 L h−1. From the experimental results, it divulges that the heat transfer coefficient and effectiveness were found to be higher for Al2O3–DIW nanofluid, while comparing other nanofluids. A further improvement in the thermal performance of MHTHS could be achieved at higher volume flow rates of nanofluids in the hexagonal tube side and constant volume flow rate of hot DIW in the mini-passage side.

Experimental investigation on the heat transfer performance of MHTHS using ethylene glycol-based nanofluids

Experimental investigation on the heat transfer characteristics of the nanofluids passing through mini hexagonal tube heat sink (MHTHS) was accomplished. Al2O3–EG, CuO–EG, and SiO2–EG nanofluids with volume fraction ranging from 0.01 to 0.04% were chosen in the present study. The dispersion of nanoparticles in ethylene glycol (EG) was used as the working fluids. The volume flow rate of nanofluids flow through the hexagonal tube side was varied from 15 to 50 L h−1, and the hot deionized water in mini passage side was kept constant at a volume flow rate of 30 L h−1. The heat transfer characteristics of nanofluids were studied with the concentration of nanoparticles in base fluid and effect of Reynolds number. The heat transfer coefficient of MHTHS was measured under fully developed laminar and turbulent flow conditions. Based on the experimental data, it was observed that thermal conductivity, heat transfer coefficient, and Nusselt number of CuO–EG nanofluid were found to be higher when compared to other two nanofluids. The thermal conductivity of nanofluids was enhanced with an increase in concentration of nanoparticles in EG. The enhancement in heat transfer coefficient of nanofluid was achieved at higher turbulence in turbulent flow. It was due to stable dispersion of nanoparticles in EG. Therefore, the enhancement in heat transfer coefficient was found to be 36%, 32%, and 22% for CuO–EG, Al2O3–EG, and SiO2–EG nanofluid, respectively, at the concentration of 0.04 vol%. At higher Reynolds number, the agglomeration of nanoparticles decreases. Hence, it caused a decrease in boundary layer thickness which leads to an increase in the heat transfer-enhanced Nusselt number. The friction factor of SiO2–EG nanofluid was found to be lower in turbulent flow regime, and furthermore, it had no substantial effect in laminar flow regime.

On impacting mechanical behaviors of side fractal structures

Abstract To enhance the impacting mechanical performance of the thin-walled structure, this paper proposes three new side fractal structures and investigates their crashworthiness by the experimental testing, simulation analysis and theoretical prediction. The energy absorption characteristics of the side fractal structure are characterized by quasistatic axial crushing experiment to verify the accuracy of the corresponding simulation models. Theoretical models of the side fractal structures are developed to predict the mean crushing force and the energy absorption. The accuracy of the theoretical model is verified by the simulation analysis, and the maximum error is 10.4%. Moreover, crashworthiness comparative studies are performed to investigate the mechanical behaviors of the side fractal structures by simulation analysis. The research results show that the maximum increment of the specific energy absorption of the hexagonal side fractal structure are higher 48.8% and 58.8% than those of the triangular and square side fractal structures with the same mass, respectively. The parameter study of the hexagonal side fractal structure is also conducted based on the theoretical model. Both the wall thickness t and the fractal factor N have important effects on the crashworthiness of the hexagonal side fractal structures. The research findings provide a good guidance for the design of an energy absorber of the protective system.

Surface-ordered phase of nonadeca-1,18-diene: Observed by molecular dynamics study

Phase properties of nonadeca-1,18-diene were investigated by the molecular dynamics simulation study, it is found that it has a new phase, surface-ordered phase, at temperature higher than the bulk-melting-point. • Nonadeca-1,18-diene has a new surface-ordered phase at temperature higher than bulk-melting-point. • Inner part of normal chain plays major role in forming surface-ordered phase. • End group of chain affects temperature of surface-ordered phase. • Center-of-mass of chain of crystalline monolayer shows fluctuation. It is newly found that normal alkane has a surface-ordered phase (SOP) at the temperature higher than its bulk-melting-point; is the SOP a property common to all the materials made of normal chain molecules? There is no answer yet. In order to solve the valuable subject, we first investigated the free surface behavior of nonadeca-1,18-diene, C 19 H 36 , by the molecular dynamics simulation. Initial state of the system for the simulation is a crystalline film consists of three lamellate layers, by long time heating with very low heating rate, it is found that, in temperature range from 352 K to 364 K, the middle layer is always in melt state while the two surface layers remain crystalline. According to the verification of state stability, this coexistence of melt and crystalline-monolayer at same temperature is identified as the SOP of nonadeca-1,18-diene; its significance is to show that there exists an intermediate state between the solid state and the liquid state. We found that the aggregation form of molecules of the two crystalline surface monolayer is hexagonal chain side packing, direction of chain axis is approximately parallel to the surface normal. By analyzing the SOP of nonadeca-1,18-diene and that of the normal nonadecane, it is found that the function of inner part of the chain is more important than the function of the end-group in forming the SOP. The properties of the surface-ordered phase can be very useful in manufacturing mechanical sensors, optical sensors and other aspects because of the remarkable changes in surface tension and light transmittance of the material.

Effect of structural parameters on low-velocity impact behavior of aluminum honeycomb sandwich structures with CFRP face sheets

This paper systematically investigates the low-velocity impact response and resulting damage behavior of aluminum honeycomb sandwich structures with carbon fiber reinforced plastic (CFRP) face sheets by combining the experimental and numerical methods. Low-velocity impact tests are conducted to determine and quantify the effects of structural parameters, such as face sheet thickness, cell wall thickness, honeycomb core height and hexagon side length, on the impact load, energy absorption, and failure mode. To further elucidate the impact behavior, a user VUMAT subroutine is developed to predict the progressive failure behavior of composite face sheets. Numerical simulation is performed to characterize the impact response and explore the deformation/failure mechanisms. The predicted impact load, energy absorption, contact time and failure mode agree well with measured counterparts. These studies reveal the face sheet thickness has particularly significant influence on the impact resistance performance of honeycomb structures. Cell wall thickness and side length of honeycomb core have notable effect on the impact load and structural stiffness of such structures, while which do not play a great role in energy absorption. Increase in core height has comparatively little effect on initial stiffness and energy absorption but makes the second peak loads decreasing for the perforation cases.

Effects of 6H-SiC substrate polarity on the morphology and microstructure of AlN films by HVPE with varied V/III ratio

AlN films grown by high temperature hydride vapor phase epitaxy (HVPE) on Si-face and C-face 6H-SiC substrates were investigated. The influences of the substrate polarity with varied V/III ratio on growth mode, structural characteristics and crystalline quality of hetero-epitaxial AlN films have been studied. With the increasing of V/III ratio, AlN grown on Si-face 6H-SiC substrates changed the growth mode from step-flow to 3D island growth, and correspondingly, its surface morphology got rougher. On the contrast, AlN on C-face substrates were consistently in 3D growth mode and maintained a relatively rough surface, with a high density of nanotubes generated, each of which consisting of hexagonal sides defined by {011¯0} facets and locating at the bottom of a V-shaped pit on the surface. Based on XRD, Raman and TEM analyses, it was found that the best AlN layer quality was obtained on the Si-face 6H-SiC at V/III ratio of 10.

Controlled generation and analysis of higher order quasi-non diffracting optical vortex lattices

The interference method is considered to be one of the most important methods to create higher order optical vortex lattices. This paper reintroduces this method in a newer way to generate various high order quasi non diffracting optical vortex lattices. The definite numbers of plane waves are used to generate higher order topological charge at the center of optical vortex lattices. The tips of the wave vectors of these plane waves lie on the projected equivalent hexagonal ring in transverse Fourier plane along propagation direction. Initially six plane waves are used to form higher order optical vortex. As the numbers of plane waves increases, the wave vector at each side of hexagon also increases and the combination would be a multiple of six plane waves such as twelve, eighteen and twenty-four etc. Further, the initial phase relation among these waves contributes more to get various higher order topological charges at the center of optical vortex lattices. Using this controllable initial phase, the different types of lattices are generated.

Identification of polar and nonpolar faces in ZnO nanostructures using conductive atomic force microscopy

ABSTRACTHere we present the local electrical characterization of individual ZnO nanorods (NRs) synthesized by spin coating method using precursor sol. Conductive atomic force microscopy (CAFM) was employed for investigating the local conductivity of these ZnO NRs. I-V curves studies on hexagonal top planes and rectangular side planes have shown nano-Schottky contact between ZnO NRs and tip. The Schottky barrier heights (SBHs) have been calculated to ∼0.63 eV, and ∼0.55 eV for these planes which are attributed to the polar and nonpolar faces respectively. This work provides a path way for constructing highly integrated nanoscale electronic devices with precise control.

Mechanical Analysis of a Hexagonal Joint

A hexagonal joint is mechanically analysed. A cross section of the receding contact between the male and female components is modelled as a plane strain problem. Particular attention is paid to the effect of the presence of fillets in the hexagonal male. Finite Element (FE) results show that, for each side of the hexagonal contact, the contact zone constitutes a small portion of the length of the hexagonal side, and separation occurs elsewhere. The normalized peak contact pressure and the contact length along the male sides are numerically evaluated.