Three-dimensional Periodic Structure Research Articles

Double-inverse-opal structured films of a hydrogel framework and mobile inorganic particles

Double-inverse-opal (DIO) structured assemblies are three-dimensionally ordered porous materials containing core particles inside. In this work, DIO structured films composed of mobile inorganic colloidal particles within an organic polymer gel framework were developed. As the organic backbone, a poly(N-isopropylacrylamide) gel (PNIPAM gel) was employed to enhance the flexibility and processability of the films. A three-dimensional periodic structure of fluorescent-labelled silica core particles in the film was observed with confocal microscopy. Thermally induced volume transitions of the PNIPAM gels were observed, which showed the potential for stimuli-responsive optical materials. By selective etching of the sacrificial shell layers surrounding the core particles, cavities formed around the cores, and they exhibited random Brownian motion inside these pockets in the film. As a new type of organic-inorganic composite material, the proposed DIO structured films possessed unique characteristics originating from the combination of a flexible backbone and mobile cores, applicable to stimuli-responsive photonic devices, reusable catalytic particle assemblies, etc.

Gradient polarization volume grating with wide angular bandwidth for augmented reality.

Angular bandwidth, which is critical to field-of-view, plays important role in diffractive optical waveguide augmented reality display. However, design and fabrication of large angular bandwidth is still a challenge. Herein, we demonstrate a liquid crystal reflective gradient polarization volume grating with three-dimensional gradient periodic structure for waveguide near-eye display. Two-beam polarization interference with special designed periodic gradient photomask are applied to chiral-dopant reactive mesogens doped with ultraviolet dye for generating gradient three-dimensional configuration of liquid crystals, resulting in gradient polarization volume grating with extended angle bandwidth of 61° while keeping 80% diffraction efficiency, with peak efficiency near 100%. The proposed gradient polarization volume grating provides an effective method to broaden the angular bandwidth in waveguide for wide field-of-view augmented reality display.

Effect of the metasurface on the electromagnetic wave absorption performance of cementitious materials

• Metasurface can significantly improve the EWAP of cementitious materials. • Integrated electromagnetic absorbing structures and materials method is designed. • MAPC-M exhibits a peak RL of −25.1 dB with a bandwidth of 11.64 GHz below −10 dB. • The effects of metasurface on the EWAP of MAPC are verified by CST simulation. Electromagnetic metasurface can effectively control the electromagnetic wave absorption performance (EWAP) of materials. This study presents an integrated structures and materials design method to improve the EWAP of cementitious materials. Based on a three-dimensional periodic array surface structure, nano-Fe 3 O 4 magnetic fluid is used as an absorber to develop metasurface cementitious electromagnetic absorbing materials. The experimental results show that the metasurface can effectively improve the EWAP of cementitious materials, achieving an excellent EWAP with a maximum reflection loss of −25.1 dB and a bandwidth of 11.64 GHz below −10 dB at 2–18 GHz. In addition, the CST simulation of the EWAP coincides with that obtained experimentally. In addition, the simulated electric and magnetic field distributions and magnetic loss density in the metasurface further demonstrate the synergistic effects of λ/4 resonance, edge diffraction, multiple reflection, and scattering on the dissipation of electromagnetic waves. Overall, these results indicate that electromagnetic metasurface can advance and promote the integrated design of materials and structures and the application of cementitious electromagnetic absorbing materials.

The Unconditionally Stable Associated Hermite FDTD Method for 3-D Periodic Structure Analysis

In this letter, the unconditionally stable associated hermite (AH) finite-difference time-domain (FDTD) method is extended to analyze three-dimensional (3-D) periodic structure. By combining the 3-D AH FDTD method and split-field technique, a 13-points coefficient matrix equation to eliminate phase shift is obtained with the corrected nonzero elements. To deal with the overflow at the periodic boundaries, the coefficient matrix is updated by the Floquet theory as long as the treatment of the angular points at the periodic boundary. The updating equation of the source term is derived by the total-field/scattered-field formula. The proposed method is verified by calculating the reflection coefficients of the infinite dielectric slab and the Jerusalem Cross FSS structure, respectively. The former shows a higher accuracy compared with the analytical solution with the average relative difference below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 60 dB, and reflects less sensitive to the angle of incidence. And the later represents 7 times efficiency than that of the split-field FDTD method while keeping a sound accuracy.

Cover Feature: SnBrP‐A SnIP‐type representative in the Sn−Br−P system (Z. Anorg. Allg. Chem. 10/2022)

The cover picture show double-helical SnBrP crystals grown in a vapor transport process and an illustration of the double helical structure with an outer [SnBr] and an inner [P]-helix. The inset above the structure denotes the results of an HR-TEM experiment where the rotating lattice character of SnBrP becomes obvious. As a result of very weak van der Waals interactions between SnBrP double helix strands, the material does not show a three-dimensional periodic structure, and the lattice rotates slightly on a 10 nm scale (DOI: 10.1002/zaac.202100347).

Ion Substitution Effect on Defect Formation in Two-Dimensional Transition Metal Nitride Semiconductors, AETiN2 (AE = Ca, Sr, and Ba).

A layered semiconductor, SrTiN2, has an interesting crystal structure as a two-dimensional (2D) electron system embedded in a three-dimensional bulk periodic structure because it has alternate stacking of a SrN blocking layer and a TiN conduction layer, in which the Ti 3dxy orbital forms the conduction band minimum (CBM) similar to the SrTiO3-based thin-film heterostructure. However, SrTiN2 has been reported to exhibit nearly degenerate conduction, but we reported that it would be due to the easy formation of nitrogen vacancies and oxygen impurities from air. In this paper, we extend the materials to family compounds, alkaline earth (AE) ion-substituted, AETiN2 (AE = Ca, Sr, and Ba), and investigated how we can suppress the defect formation by (hybrid) density functional theory calculations. All AETiN2 compounds possess thermodynamic stability in the wide nitrogen (N) chemical potential window. Especially, CaTiN2 is the most stable even against N-poor conditions. Unintentional carrier generation occurs due to the nitrogen vacancies (VN), oxygen substitution (ON), and hydrogen anion substitution (HN) at the nitrogen sites. The VN and HN impurities can be suppressed under N-moderate and N-rich conditions. The ON defect is easily formed in SrTiN2 and also in BaTiN2 under N-rich conditions, but its formation can be suppressed in CaTiN2. Present results suggest that high-purity CaTiN2 can be obtained under wider N chemical conditions, which would lead to the realization of the novel functional properties originating from Ti 3dxy 2D bands embedded in the bulk crystal structure.

A scheme to excite transverse electric graphene plasmon polariton with positive value of imaginary part of conductivity

We proposed a scheme to generate a transverse electric graphene plasmon polariton in which the imaginary part of conductivity need not be negative. In a three-dimensional periodic structure with graphene ribbons embedded in a medium, at a suitable frequency and wavelength, the periodic modification factor is not a real number but a purely imaginary one, which makes dispersion relations possibly satisfied, that is, a transverse electric graphene plasmon polariton can be excited in this case. The spectrum of the plasmon polariton is broadband. Furthermore, the coupling between the plasmon polariton and electromagnetic wave was enhanced and the enhancement is beneficial to design high efficiency optoelectronic devices.

Surface Field Distribution and Composite Scattering Characteristics of Three-dimensional Micro-nano Hemispherical Periodic Structure Optical Surface

Surface Field Distribution and Composite Scattering Characteristics of Three-dimensional Micro-nano Hemispherical Periodic Structure Optical Surface

Plasmon modulation in three-dimensional periodic structure of graphene ribbons

In the article the spectra of plasmon-polariton in a three-dimensional periodic structure of graphene ribbons embedded in a medium were studied at the first time and for a fixed carrier concentration, influences on the spectra from ribbon width, interface distance and period of ribbon were shown. Compared to those in monolayer periodic structure of graphene ribbons, sharp differences occur. Furthermore, there always exist a match point where frequencies of the plasmon-polarition and the electromagnetic radiation are the same. The study improved our basic knowledge on plasmon dynamics in graphene and was important in the design of high efficiency optoelectronic devices.

Research on bitumen molecule aggregation based on coarse-grained molecular dynamics

The design and application of bitumen rheological property is an essential part of road engineering, which is strongly associated with colloidal structure form by millions of molecules. Our work aims at developing a transferable CGMD model for the bitumen molecular system to explore the microstructure in the Mesoscopic scale. In the present study, we focus on the mapping site construction and the validation of the modified MARTINI forcefield based on Flory-Huggins theory. On this basis, the CGMD model owned 126,692 molecules were built to research the influencing factors of bitumen aggregation, the dynamic evolution process of a three-dimensional periodic layer structure was observed. The result shows that the diffusion coefficient order of asphaltene, resin, oil, and model average is resin > model average > oil > asphaltene, and the order does not vary with temperature. At different character temperatures, the diffusion coefficients value has changed in orders of magnitude, which is correspond to viscoelasticity studies. Meanwhile, the molecular relative concentration at different temperatures has revealed the aggregation behavior of asphaltene in the bitumen, when the temperature is high enough, all the asphaltene molecules are separate to a certain distance and keep stable. With the temperature decreasing, some asphaltene molecules tend to move closer and form smaller aggregate.

Design optimization of a novel bio-inspired 3D porous structure for crashworthiness

Porous structure is widely used in automobile, aerospace and other industrial fields due to its lightweight and high energy absorption capacity. In this study, a novel porous structure, i.e. hierarchical three-dimensional porous (H3DP) structure inspired by the bone in nature is created based on the primitive triply periodic minimal surface sheet structure, which is a basic three-dimensional periodic porous structure consist of triply periodic minimal surfaces. The numerical simulation for the axial crushing of the H3DP structures is carried out using the nonlinear finite element code through LS-DYNA. For accuracy of the numerical results, the finite element model is validated by the experiment performed for H3DP structures which are manufactured by selective laser melting technology using a EOS M290 machine. The numerical results showed that this novel bio-inspired H3DP structure had excellent energy absorption capacity. However, the crashworthiness of the H3DP structure is affected by design parameters such as wall thickness, ribs thickness, number of inner ribs and distance between the inner and outer walls. In order to obtain the optimal design of the H3DP structure with the best crashworthiness, a multi-objective optimization is implemented employing the Kriging (KRG) surrogate modeling method and Non-Dominated Sorting Genetic Algorithm II (NSGA-II). According to the crashworthiness comparison of the H3DP structure and the traditional energy absorbed structures, it is found that the H3DP structure had relatively higher energy absorption capacity than the primitive sheet structure as well as lots of previous traditional materials or structures in nature and engineering. Thus, the H3DP structure can be used as a good energy absorbing structure and had good application prospect in the field of impact engineering.

Fabrication and characterization of inverse opal tin dioxide as a novel and high-performance photocatalyst for degradation of Rhodamine B dye

Three-dimensional Inverse opal periodic structure and high specific surface area have been widely applied in many fields. Herein, inverse opal tin dioxide (SnO2) was fabricated successfully via a sol-gel method by the cooperative opal template. The crystal phase, surface morphology, surface area and optic absorption of inverse opal SnO2 were studied using an X-ray diffractometer (XRD), scanning electron microscope (SEM), BET-BJH, and ultraviolet-visible (UV-vis) spectroscopy. The photocatalytic performance of newly fabricated inverse opal SnO2 photocatalyst was tested for the removal of an organic dye pollutant Rhodamine B (RhB) under the visible light irradiation. Results revealed that inverse opal SnO2 showed high photocatalytic performance for RhB dye degradation, which was 1.4-times greater than that of conventional SnO2. Resultantly, 97.5% RhB dye was degraded by IOS-610 after 1 h treatment under the visible light irradiation. The photocatalytic activity enhancement was mainly due to a synergistic effect of the periodic structure of inverse opal SnO2 and the enlarged surface area. In conclusion, the findings suggest that the inverse opal photocatalyst is a promising choice for the degradation of RhB. The experimental results may help fabricate more universal opal-based inverse photocatalysts for the efficient degradation of environmental dyes and pollutants.

Prediction of radiation spectra of composite with periodic micron porous structure

In this work, one three-dimensional periodic composite structure consisting of alumina frame and inscribed nickel spheres is proposed for designing the micron composite porous structure. The finite-difference time domain method is applied for predicting the radiation spectra of proposed composite structure and distribution of absorbed radiative power. The spectral characteristics of composite structure are compared with the hollow ceramic frame structure and stacked metal spheres for analysis of radiative properties of discussed micron composite porous structure, then the effects by changing the number of layers and inner structure are summarized. Strong spectral selectivity is observed, while radiative properties of composite structure are harmonic results of hollow ceramic frame structure and stacked metal spheres. The absorptivity changes with increasing layers hardly, while the reflectivity and transmissivity are affected by number of layers obviously until the number of layers reaches three. When the number of layers exceeds three, the effects of increasing layers are ignorable. Besides, effects on the distribution of absorbed power inside composite porous structure are produced by upper two layers mainly. Furthermore, the radiation spectra are changed by placing hollow ceramic frame layers on the composite structure layer. The proposed composite structure and prediction of radiative properties can be helpful for designing the structure of micron porous materials and regulating the radiative transfer.

Extraction of effective constitutive parameters of artificial media using Bloch modes

The effective constitutive parameters of a three-dimensional periodic structure are calculated using its Bloch modes. These modes and their propagation constants are obtained from eigenvectors and eigenvalues of the generalized transfer matrix of a unit layer of the structure. Effective bulk permittivity and permeability tensors of the medium are obtained when two of the Bloch modes are dominant, i.e., propagate without significant decay inside the medium. The effect of the strongly decaying Bloch modes, which are excited at the interface with a conventional medium, are included by means of surface impedance matrices. The results are in excellent agreement with full-wave electromagnetic simulations.

Brilliant Coloured Monochromatic Photonic Crystals Films Generation from Poly (Styrene-Butyl Acrylate-Acrylic Acid) Latex

A one-pot synthetic procedure was successfully used to synthesize monodispersed poly (styrene-butyl acrylate-acrylic acid) (P (St-BA-AA)) colloidal spheres via emulsion polymerization. A glass transition temperature (Tg) of 108 o C was obtained by DSC analysis. Core-shell morphology was revealed by TEM micrograph. Evaporative induced self-assembly process was used to fabricate photonic crystals from the as-synthesized P (St-BA-AA) latexes. Microscopic analyses of the fabricated photonic crystal films revealed the assembling of colloidal particles which rearranged into a fascinating compact three-dimensional periodic hexagonal structure with manifold layer arrangement. The photonic crystal films displayed mesmerizing monochromatic yellow, blue and green colours which were obtained by controlling the size of the microspheres. The prospect of deliberately obtaining photonic crystals with monochromatic colours would be very useful in the generation of photonic crystals for sensing application. Keywords : poly (styrene-butyl-acrylate-acrylic acid); photonic crystals; ter-polymer; monochromatic

Preparation of inverse opal titanium dioxide for photocatalytic performance research

Inverse opal structure materials, with three-dimensional periodic structure and excellent optical properties, have been widely studied in many fields. In this study, visible light-driven inverse opal titanium dioxide photocatalysts were successfully fabricated via sol-gel method cooperating opal template. The surface morphology, chemical composition, crystal phase, optical absorption, optical reflectance and separation of charge carries of samples were symmetrically investigated by SEM, EDS, XRD, UV–vis DRS, UV-Raman and PL. It was found that such the structure existed electronic band gap and photonic band gap. Meanwhile, slow photon effect and larger specific surface area, reduced combination rate of photo-generated electron-hole pairs were certified. All of these properties contributed to promoting the photocatalytic redox activity of RhB degradation. Among the inverse opal TiO2 samples, IOT-610 fabricated by polystyrene microsphere opal template with the diameter of 610 nm had the best photocatalytic performance, showing 3.2 times higher than that of conventional TiO2. The results indicated that inverse opal structure photocatalyst is a preferential option for photocatalytic degradation of various environmental contaminants.

Direct observation of beta″ precipitate with a three-dimensional periodic structure in binary Mg–La alloy

It is a long-debated issue whether or not β′′ forms in magnesium-rare earth alloys. In this study, after solid solution and aging treatment, the binary Mg-3.0 wt% La alloys were characterized using atomic-resolution scanning transmission electron microscopy. A large number of β′′ metastable precipitate was captured successfully along [0001]α and 112¯0α directions. The [0001]α observation reveals that the inchoate β′′ is composed of single row of linked hexagonal rings. Under further aging, the expansion direction of the hexagonal ring is not limited to 112¯0α direction and the β′′ can reach a thickness of 5cβ′′ along [0001]α, demonstrating that the β′′ forms a three-dimensional periodic structure and the β′′ phase can form in binary MgLa alloy. Meanwhile, a planar defect with an ABCBA stacking fault can be formed usually in the interface between β′′ phase and α-Mg matrix, which contributes to alleviate the distortion of adjacent α-Mg matrix.

Solving the disordered structure of β-Cu2-xSe using the three-dimensional difference pair distribution function.

High-performing thermoelectric materials such as Zn4Sb3 and clathrates have atomic disorder as the root to their favorable properties. This makes it extremely difficult to understand and model their properties at a quantitative level, and thus effective structure-property relations are challenging to obtain. Cu2-xSe is an intensely studied, cheap and non-toxic high performance thermoelectric, which exhibits highly peculiar transport properties, especially near the β-to-α phase transition around 400 K, which must be related to the detailed nature of the crystal structure. Attempts to solve the crystal structure of the low-temperature phase, β-Cu2-xSe, have been unsuccessful since 1936. So far, all studies have assumed that β-Cu2-xSe has a three-dimensional periodic structure, but here we show that the structure is ordered only in two dimensions while it is disordered in the third dimension. Using the three-dimensional difference pair distribution function (3D-ΔPDF) analysis method for diffuse single-crystal X-ray scattering, the structure of the ordered layer is solved and it is shown that there are two modes of stacking disorder present which give rise to an average structure with higher symmetry. The present approach allows for a direct solution of structures with disorder in some dimensions and order in others, and can be thought of as a generalization of the crystallographic Patterson method. The local and extended structure of a solid determines its properties and Cu2-xSe represents an example of a high-performing thermoelectric material where the local atomic structure differs significantly from the average periodic structure observed from Bragg crystallography.

Tunable dichroic polarization beam splitter created by one-step holographic photoalignment using four-beam polarization interferometry

A tunable dichroic polarization beam splitter (tunable DPBS) simultaneously performs the follow functions: 1. Separation of a polarized incident beam into multiple pairs of orthogonally polarized beams; 2. Separation of the propagation direction of two wavelength incident beams after passing through the tunable DPBS; and 3. Control of both advanced polarization and wavelength separation capabilities by varying the temperature of the tunable DPBS. This novel complex optical property is realized by diffraction phenomena using a designed three-dimensional periodic structure of aligned liquid crystals in the tunable DPBS, which was fabricated quickly with precision in a one-step photoalignment using four-beam polarization interferometry. In experiments, we demonstrated that these diffraction properties are obtained by entering polarized beams of wavelengths 532 nm and 633 nm onto the tunable DPBS. These diffraction properties are described using the Jones calculus in a polarization propagation analysis. Of significance is that the aligned liquid crystal structure needed to obtain these diffraction properties was proposed based on a theoretical analysis, and these properties were then demonstrated experimentally. The tunable DPBS can perform several functions of a number of optical elements such as wave plates, polarization beam splitter, dichroic beam splitter, and tunable wavelength filter. Therefore, the tunable DPBS can contribute to greater miniaturization, sophistication, and cost reduction of optical systems used widely in applications, such as optical measurements, communications, and information processing.

Research on 3D periodic structure velvet fabric and its frequency response characteristics

Frequency selective surfaces (FSSs) based on textile or textile composite materials are increasingly becoming popular due to their textile nature of high flexibility, softness, low-cost, easy fabrication, and other textile characteristics compared to the traditional metal FSS, especially the two-dimensional FSS fabrics. In this study, a three-dimensional (3D) fabric periodic structure with conductive textile fabricated vertically on the common textile substrate, forming a U-shaped array, is proposed. An experimental validation has been conducted to verify whether the 3D frequency selective structure fabric has good frequency response characteristics and great design ability. The model samples of 3D periodic structure based on velvet fabric with different structure or material parameters were fabricated by hand. Through testing and analysis of transmission and reflection coefficients at 2–18 GHz using the shielding chamber method, the results show that the velvet height of the fabric model periodic structure has an obvious effect on the resonant frequency. With an increase in velvet height, the resonant peak will move towards lower frequency. With an increase of vertical velvet spacing, the resonant frequency will also move towards lower frequency. Velvet material has a slight influence on the frequency response characteristics. The frequency response characteristics of this structure are stable under different incident angles. The 3D periodic structure offers more design freedom and possibilities. Significant effects of wave absorption or selective filtering by the periodic structure can be achieved by regulating the structural parameters and material parameters together.