Alternating Layer Structure Research Articles

A strong, ductility maintained, and high-temperature resistant Ti-based composite with TiC@(TiCr2+α-Ti) reinforced particles

While material with light, strong, and high-temperature environment resistant is highly attractive to aeroengines, achieving the combination of all these properties in composite remains a challenge. As these properties typically require the combination of various materials, especially incorporating the extremely brittle intermetallic compound at room temperature into a particle-reinforced composite inherently troubled by the "strength-ductility" contradiction, which can easily exacerbate the inherent brittleness of the material. Herein, we present a composite based on Cr2AlC-Ti system, which generates reinforcements with TiC@(TiCr2+α-Ti) shell-core architecture in the Ti matrix through a straightforward eutectoid reaction. The reinforcements are continuously distributed on a macroscopic level, establishing a co-continuous structure with β-Ti in 3D space. Microscopically, the shell-core structure has a multi-level TiCr2/α-Ti alternating layer structure as in natural nacre. This multi-scale and multi-level structural design overcomes the brittleness of TiCr2 at room temperature by controlling its morphology and distribution, and achieves high content of ceramic particles in composite. The resulting composite has a compressive strength of about 2GPa at room temperature, and even at 600 °C when Ti matrix is completely softened, the composite has a commendable strength of about 800MPa.

Breathable graphene oxide/polyurethane layered membrane for chemical protective clothing

Chemical protective clothing is crucial for shielding operators from toxic and hazardous substances. However, the limited moisture permeability of these garments significantly affects worker comfort and functionality over long periods. In this study, we introduce a novel graphene oxide/polyurethane composite membrane with an innovative alternating layer structure and improved interlayer bonding, produced through a simple, scalable layer-by-layer assembly method. The outstanding L-GO/PU membrane offers robust chemical protection for up to 24 h against harmful agents like mustard gas and dichloromethane, while also showing excellent resistance to both acidic and alkaline solutions. With a moisture permeability of 3116 g m−2 d-1, this membrane ensures optimal comfort during extended use. Additionally, it demonstrates remarkable resistance to swelling, maintaining its structural integrity for 27 days during prolonged immersion in water. The L-GO/PU composite stands out as an excellent choice for chemical protective gear, combining high toxicity resistance with superior moisture management capabilities.

Significant conductivity enhancement in Al-rich n-AlGaN by modulation doping

Enhancing the conductivity in Al-rich n-AlGaN is a key issue for realizing AlGaN-based ultraviolet light-emitting diodes (UV-LEDs) with low operating voltage and high wall-plug efficiency, especially in a planar geometry of flip–chip configuration. An approach of modulation doping is herein proposed, where an alternating-layer structure consisting of Si-doped and unintentionally doped AlGaN is assembled to achieve the spatial separation of electron activation and transport. As massive electrons diffuse from the AlGaN:Si layer into the neighboring i-AlGaN ones and then drift, the ionized-donor scattering is effectively weakened, leading to a significant enhancement of mobility as well as conductivity. An impressive electrical property of n-Al0.6Ga0.4N with a lateral conductivity of 201.7 S/cm is realized as a consequence, being 2.1 times of that in the continuously doped one. Furthermore, the operating voltage of 280 nm UV-LEDs is correspondingly reduced by 0.1–0.2 V at 100 mA by adopting modulation-doped n-AlGaN in the n-cladding layer.

Investigation of guided wave propagation in nanoscale layered periodic piezoelectric plates based on Eringen's nonlocal and strain gradient theory

This paper investigates the dynamic propagation behavior of guided waves in nanoscale media composed of alternating layers of piezoelectric phases. The study employs Eringen's nonlocal and strain gradient theories to derive equations for symmetric wave propagation and the scattering relations of guided waves perpendicular to these structures. Dispersion curves are calculated and plotted to compare these theories, considering the influence of nanoscale size-effect, volume ratio of constituent layers, and material length scale. Using the strain gradient theory, the paper explores the impact of length scale parameters on the propagation behavior of horizontally polarized guided waves in an alternating layer structure of nanoscale piezoelectric material, specifically nanoscale piezoelectric laminates. The analysis involves calculating localization factors and dispersion curves to analyze the effects of size-effect and length scale parameters on wave propagation and band structures. Additionally, the study plots and analyzes changes in mechanical displacement and electrical potential, followed by an investigation and discussion of nanoscale size effects and the effects of the material's length scale parameter on dispersion curves and conversion modes within specific regions. The results highlight that the length scale effect parameter significantly impacts the mode conversion zones and band gap structures, more so than the NLPE continuum theory suggests. As the strain gradient parameter increases, these zones shift towards higher wavenumbers and to the right . Furthermore, introducing the length scale factor results in a substantial decrease in both the formation of conversion zones and the density of dispersion curves.

Cellulose Iβ behaviors in non-solvent liquid media: Molecular dynamic simulations

The structural changes of cellulose in non-solvent liquid media can provide insights into the high-value utilization of cellulose. This study includes molecular dynamics simulations of 36-chain cellulose Iβ microfibril model (Iβ-MF) behavior in 16 non-solvent liquids with different polarities at room temperature using two carbohydrate force fields (CHARMM36, GLYCAM06). Iβ-MF in CHARMM36 retains more than 70% of the tg conformation in 16 liquids, and the retention of the tg conformation increased with decreasing liquid polarity. Liquid polarity can affect the hydroxymethyl conformation of cellulose, which is only an appearance, and the real driving force behind is the electrostatic interaction between liquid molecules and cellulose. Furthermore, changing the 1,4 electrostatic scaling factor of GLYCAM06 can effectively affect the structural convergence of Iβ-MF. The Iβ-MF forms an alternating layer structure in the gg/gt conformation in a medium to high polarity non-solvent liquid, while the model undergoes untwisting. Model untwisting is inextricably linked to the degree of alternate layer structure formation. This paper provides a theoretical basis for the molecular study of nanocellulose structures from an energy-structure-property perspective.

Preparation and Properties of Epoxy/Multiwalled Carbon Nanotube Nanocomposite Foams with an Alternating Layer Structure.

Multilayered epoxy/multiwalled carbon nanotube (EP/MWCNT) composite foams with a density of 0.713 g/cm3 were prepared through the chemical foaming of laminated epoxy sheets in a mold with a fixed cavity. The difference in cell morphology and properties between adjacent layers in the multilayer foams (two- and four-layer) was tuned by MWCNT or chemical foaming agent (CFA) concentration. It was found that the storage modulus and microwave-absorbing ability of the multilayered EP/MWCNT foams were strongly associated with the loading direction, the thermal diffusivity was slightly direction-dependent, and the electromagnetic interference (EMI) shielding effectiveness (SE) was direction-independent. In addition, as the layer number increased, the mechanical, thermal, and electrical conductivity properties and EMI shielding performances of the multilayered composite foams showed different change tendencies. These results indicated that the effect of the multilayer structure on the properties of composite foams was different when they underwent force, heat, or electromagnetic microwave, and the underlying reasons were investigated in detail.

Chemical Vapour Deposition Graphene-PMMA Nanolaminates for Flexible Gas Barrier.

Successful ways of fully exploiting the excellent structural and multifunctional performance of graphene and related materials are of great scientific and technological interest. New opportunities are provided by the fabrication of a novel class of nanocomposites with a nanolaminate architecture. In this work, by using the iterative lift-off/float-on process combined with wet depositions, we incorporated cm-size graphene monolayers produced via Chemical Vapour Deposition into a poly (methyl methacrylate) (PMMA) matrix with a controlled, alternate-layered structure. The produced nanolaminate shows a significant improvement in mechanical properties, with enhanced stiffness, strength and toughness, with the addition of only 0.06 vol% of graphene. Furthermore, oxygen and carbon dioxide permeability measurements performed at different relative humidity levels, reveal that the addition of graphene leads to significant reduction of permeability, compared to neat PMMA. Overall, we demonstrate that the produced graphene–PMMA nanolaminate surpasses, in terms of gas barrier properties, the traditional discontinuous graphene–particle composites with a similar filler content. Moreover, we found that the gas permeability through the nanocomposites departs from a monotonic decrease as a function of relative humidity, which is instead evident in the case of the pure PMMA nanolaminate. This work suggests the possible use of Chemical Vapour Deposition graphene–polymer nanolaminates as a flexible gas barrier, thus enlarging the spectrum of applications for this novel material.

Self-Assembled 1T-MoS2/Functionalized Graphene Composite Electrodes for Supercapacitor Devices

Two-dimensional (2D) materials such as graphene and molybdenum disulfide (MoS2) have been investigated widely for applications in energy storage, including supercapacitors, due to their high specific surface area, potential redox activity, and mechanical flexibility. However, electrodes comprising either pure graphene and MoS2 have failed to reach their potential due to restacking of the layered structure and poor electrical conductivity. It has been shown previously that composite electrodes made from a mixture of graphene and MoS2 partially counteract these issues; however, performance is still limited by poor mixing at the nanoscale. Herein, we form a true composite electrode by chemically functionalizing the graphene so that the negatively charged surface can self-assemble with the positively charged 1T-MoS2 to give an alternating layer structure. These alternately restacked 2D materials were then used to produce supercapacitor electrodes, and their energy storage properties were characterized. This stacked structure has increased the interlayer spacing of 1T-MoS2 which was indicated by the increase in the intensity of the (001) peak in the X-ray diffraction spectra. Furthermore, the typically metastable 1T-MoS2 was stabilized by the interaction with the functionalized graphene, preventing it reverting back to the 2H phase, which was observed when pristine graphene was used. The graphene was functionalized using either 4-bromobenzenediazonium or 4-nitrobenzenediazonium, with the latter giving optimal capacitance when mixed with the MoS2. The alternative layer graphene–MoS2 structure was confirmed by Raman spectroscopy and electron microscopy, leading to a high specific capacitance (290 F cm–3 at 0.5 A g–1) and 90% retention of capacitance after 10 000 cycles.

Boosting current output of triboelectric nanogenerator by two orders of magnitude via hindering interfacial charge recombination

The performance of triboelectric nanogenerator is limited by interfacial charge losses due to alternate charge transfer. This is usually suppressed by addition of electron blocking, electron transporting layers or through external excitation. However, these approaches screen only electrons from the interface while the unstable positive charges remain. Herein, we report a stable tribopositive layer with an overall positive surface and embedded magnetic active negative centers for stabilizing positive charges to prevent cation recombination with anion of counterpart. Besides, a counterpart with high electron delocalization density is used for screening interfacial negative charges, leading to enhanced charge accumulation of 11 nC with short circuit current of 0.8 µA, increasing to 54 nC and 17.4 µA by staking 4 units of 2.25 cm2 device in alternate layered structure, with an enhancement rate of 15.1 nC and 5.6 µA per unit. Further, the embedded negative centers in response to magnetic field form skewed charge transporting channels, causing homogeneous distribution of potential on the tribopositive layer, effectively transporting charges to electrode via hindering bulk losses. The single unit shows 15,900% enhancement reaching 4.8 µA, 208 µC m−2 and 1.66 W m−2 and demonstrating the highest enhancement capacity compared to previously reported strategies and thus a promising potential for wearable electronics with high power demand.

Effect of the core-shell structure powders on the microstructure and thermal conduction property of YSZ/Cu composite coatings

The microstructure of thermal spray powders plays a significant role in the application performance of thermal protection coatings deposited by air plasma spraying. Based on the design of the spray powder structure, the [email protected] core-shell structure powders have the potential to be a thermal conduction anisotropy material for thermal protection coating, owing to the special alternate-layered structure formed during plasma spraying. To study the mechanism of the thermal conduction anisotropy of YSZ/Cu composite coatings, the YSZ coatings, [email protected] coatings and YSZ-Cu coatings were fabricated by YSZ powders, [email protected] core-shell structure powders and YSZ-Cu mechanical mixture powders, respectively. There were YSZ vertical thermal insulation layer and Cu horizontal thermal condition layer in the [email protected] coatings, which provides a structural basis for the realization of thermal conduction anisotropy. Compared with the YSZ-Cu coatings, the temperature difference between the back-surface center area and the edge area of the [email protected] coatings is significantly reduced by approximately 37%, which is attributed to the synergistic effect of alternate-layered comprising the YSZ layer and the high thermal conductivity Cu layer. [email protected] coatings can effectively prevent the rapid rise in local temperature by the analysis of finite-element simulation, which is beneficial for prolonging the service life of the thermal protection coating in a non-uniform temperature field.

About the Role of Interfaces on the Fatigue Crack Propagation in Laminated Metallic Composites.

The influence of gradients in hardness and elastic properties at interfaces of dissimilar materials in laminated metallic composites (LMCs) on fatigue crack propagation is investigated experimentally for three different LMC systems: Al/Al-LMCs with dissimilar yield stress and Al/Steel-LMCs as well as Al/Ti/Steel-LMCs with dissimilar yield stress and Young’s modulus, respectively. The damage tolerant fatigue behavior in Al/Al-LMCs with an alternating layer structure is enhanced significantly compared to constituent monolithic materials. The prevalent toughening mechanisms at the interfaces are identified by microscopical methods and synchrotron X-ray computed tomography. For the soft/hard transition, crack deflection mechanisms at the vicinity of the interface are observed, whereas crack bifurcation mechanisms can be seen for the hard/soft transition. The crack propagation in Al/Steel-LMCs was studied conducting in-situ scanning electron microscope (SEM) experiments in the respective low cycle fatigue (LCF) and high cycle fatigue (HCF) regimes of the laminate. The enhanced resistance against crack propagation in the LCF regime is attributed to the prevalent stress redistribution, crack deflection, and crack bridging mechanisms. The fatigue properties of different Al/Ti/Steel-LMC systems show the potential of LMCs in terms of an appropriate selection of constituents in combination with an optimized architecture. The results are also discussed under the aspect of tailored lightweight applications subjected to cyclic loading.

Current penetration depth and effective conductivity of a nano-scale p-GaN/u-GaN alternating-layer p-type structure

By combining the high mobility of a nm-scale u-GaN layer with the high hole concentration of the neighboring p-GaN layers for hole diffusing into the u-GaN layer, an extremely high effective conductivity in the lateral dimension can be obtained in a p-GaN/u-GaN alternating-layer structure. To better understand the current flow distribution and more accurately estimate the effective lateral conductivity and the current penetration depth, which is related to the vertical conductivity, in such a layered structure, we prepare a series of sample with different thickness combinations of the upper portion of a layered p-type structure to be characterized and the lower p-type portion of significantly higher conductivity. The measured sheet conductance results of the series of sample are fitted with a model, in which an exponential decay of conductance contribution with depth in the upper portion and a uniform distribution in the lower portion are assumed, to obtain the current penetration depth and effective conductivity of the upper portion. The relative size of the current penetration depth with respect to the total p-type layer thickness can be used as a criterion for high enough vertical conductivity in device application.

Construction of Highly Hierarchical Layered Structure Consisting of Titanate Nanosheets, Tungstate Nanosheets, Ru(bpy)32+, and Pt(terpy) for Vectorial Photoinduced Z-Scheme Electron Transfer.

To imitate the precisely ordered structure of the photoantennas and electron mediators in the natural photosynthesis system, we have constructed the Ru(bpy)32+-intercalated alternate-layered structure of titanate nanosheets and tungstate nanosheets via thiol-ene click reaction. Before nanosheet stacking, Pt(terpy) was immobilized at the edge of the titanate nanosheets. The visible-light-induced vectorial Z-scheme electron transfer reaction from the valence band of tungstate to the conduction band of titanate via the photoexcited Ru(bpy)32+ was demonstrated by the following two evidences: (1) From the results of the fluorescence decay of Ru(bpy)32+, the rate of the forward electron transfer from the photoexcited Ru(bpy)32+ to the conduction band of titanate was estimated as 1.16 × 108 s-1, which was 10 times faster than the backward electron transfer from the photoexcited Ru(bpy)3 to the conduction band of tungstate (1.02 × 107 s-1) due to a localization of Ru(bpy)32+ on the titanate nanosheets. (2) We observed the decrease of the electrons accumulated in the conduction band of the tungstate induced by photoexcitation of Ru(bpy)32+, demonstrating the forward electron transfer from the conduction band of tugnstate to the vacant highest occupied molecular orbital level of the photoexcitation Ru(bpy)32+. Finally, H2 gas was produced from the water dispersion of the alternate-layered structure under visible light irradiation, suggesting that the electrons getting to the conduction band of the titanate were transferred to the Pt(terpy) placed at the edge of the nanosheets, and reduced water to dihydrogen. Herein, n-octylamine species at the interlayer space played a role as hole scavenger; in other words, these molecules were oxidized by the hole in the conduction band of the tungstate nanosheets.

Two M(II)-diphosphonate coordination polymers: structural, fluorescent and magnetic studies (M = Cu,Ca)

Two examples of CuII/CaII-diphosphonate coordination polymers, [Cu2(L)(H2O)2]n 1 and {[Ca(L-H2)]2·2H2O}n 2 (H4L = H2O3PCH2N(C4H8)NCH2PO3H2), L-H2 = O3PCH2HN(C4H8)NHCH2PO3), N,N′-piperazinebis(methylenephosphonic acid)), have been hydrothermally synthesized and characterized by elemental analysis, FT-IR, PXRD, TGA and single-crystal X-ray diffractions. Compound 1 possesses a 2-D inorganic-organic alternate arrangement layer structure, in which ligand H4L shows a never reported multi-dentate coordination mode. Compound 2 possesses a 3-D open-framework structure with 1-D channel built from 44-atom rings. Results of fluorescent measurements indicate the maximum emission band centered at 435 nm of 1 should be due to the coordination effect with metal(II) ions, and the high energy emission peaks (383, 298 nm for 1 and 378, 300 nm for 2) could be derived from the intraligand π*→n transition station of H4L (382, 310 nm, λex = 235 nm). Magnetism analysis of 1 indicated antiferromagnetic interactions being from the 1-D magnetic chain with the binuclear unit [Cu2O2].

Ion Doping Effects on the Lattice Distortion and Interlayer Mismatch of Aurivillius-Type Bismuth Titanate Compounds.

Taking Bismuth Titanate (Bi4Ti3O12) as a Aurivillius-type compound with m = 3 for example, the ion (W6+/Cr3+) doping effect on the lattice distortion and interlayer mismatch of Bi4Ti3O12 structure were investigated by stress analysis, based on an elastic model. Since oxygen-octahedron rotates in the ab-plane, and inclines away from the c-axis, a lattice model for describing the status change of oxygen-octahedron was built according to the substituting mechanism of W6+/Cr3+ for Ti4+, which was used to investigate the variation of orthorhombic distortion degree (a/b) of Bi4Ti3O12 with the doping content. The analysis shows that the incorporation of W6+/Cr3+ into Bi4Ti3O12 tends to relieve the distortion of pseudo-perovskite layer, which also helps it to become more stiff. Since the bismuth-oxide layer expands while the pseudo-perovskite layer tightens, an analytic model for the plane stress distribution in the crystal lattice of Bi4Ti3O12 was developed from the constitutive relationship of alternating layer structure. The calculations reveal that the structural mismatch of Bi4Ti3O12 is constrained in the ab-plane of a unit cell, since both the interlayer mismatch degree and the total strain energy vary with the doping content in a similar trend to the lattice parameters of ab-plane.

Reducing Architecture Limitations for Efficient Blue Perovskite Light-Emitting Diodes.

Light-emitting diodes utilizing perovskite nanocrystals have generated strong interest in the past several years, with green and red devices showing high efficiencies. Blue devices, however, have lagged significantly behind. Here, it is shown that the device architecture plays a key role in this lag and that NiOx , a transport layer in one of the highest efficiency devices to date, causes a significant reduction in perovskite luminescence lifetime. An alternate transport layer structure which maintains robust nanocrystal emission is proposed. Devices with this architecture show external quantum efficiencies of 0.50% at 469 nm, seven times higher than state-of-the-art devices at that wavelength. Finally, it is demonstrated that this architecture enables efficient devices across the entire blue-green portion of the spectrum. The improvements demonstrated here open the door to efficient blue perovskite light-emitting diodes.

One-Step Electrodeposition of Layer by Layer Architectural Si-Graphene Nanocomposite Anode of Lithium Ion Battery with Enhanced Cycle Performance

One step electrodeposition is applied to prepare Si-Graphene (SiG) composites from Graphene(G)-SiCl4 -[BMP]tf2N ionic liquid. The SiG composites have shown an alternate layer-structure of Si and graphene caused by alternate processes of Si reduction and graphene adsorption on the electrode, which is confirmed by the regular current pulsation in the chronoamperometric curves during the whole electrodeposition process. The SEM and TEM morphologies indicate that each layer is about 120 nm thickness for the SiG3 composites electrodeposited from the 0.1852 mol · l− 1 Graphene(G)-SiCl4 -[BMP]tf2N ionic liquid, in which Si particle size is about 80–110 nm closely stick on 4–5 layers of graphene with a molar ratio of Si and C of 4.57:1. SiG3 anode displays a specific capacity of 1378 mAh · g−1 at the initial cycle, and 1083 mAh · g−1 at the end of 400 cycle (retention of 78%) at 4 A · g−1, as well as 988 mAh · g−1 at 8A · g−1, showing a good cycle life and rate performance. The layer-structured SiG anode significantly improve the conductivity and electrochemical performances of Si anode. The research provides a feasibility for electrodeposition preparation of layer-structured materials, especially for semiconductor-based alloys, graphene-based alloys in large-scale.

Flexible β-Ni(OH)2/graphene electrode with high areal capacitance enhanced by conductive interconnection

Free-standing and binder-free flexible electrodes have shown great promise for next-generation energy storage devices. However, improving effective charge collection and transportation of the electrodes is still a great challenge. Here, we design and fabricate a novel hierarchical conductive structure for supercapacitor electrode. The flexible and conductive β-Ni(OH)2/graphene film electrode with alternate layered structure is fabricated by facile filtration, and the novel flexible current collector is applied to these electrodes by screen printing. The integrated electrode exhibits outstanding flexibility and thinness. Based on the hierarchical conductive structure, the graphene as micro current collector in the composite electrode provides conductive pathways for β-Ni(OH)2, and the screen printed current collector enhances the charge collection and transportation for the electrode. As a consequence, the specific capacitance of the all-solid-state symmetric supercapacitor employing these electrodes is significantly improved by conductive interconnection. It manifests a high areal capacitance of 61.7 mF cm−2 at 5 mA cm−2, which is 3.7 times higher than that of the device with common assembly. This work provides a simple and effective strategy for developing high-performance supercapacitors.

The Smart Blending for Multilayer Structure of PLA/EVOH

The concept of smart blender to form a multilayer structure of PLA/EVOH has been developed. Unlike conventional mixing, smart blending provides a formation of multilayer structure by dictating the motion of stir rod to agitate melts. The PLA and EVOH are supplied separately by a single-screw extruder. An experimental rig is assembled at the end of a co-extruder, and melt from an extruder entered an experimental rig via a cylindrical port. The molten EVOH is recursively stretched and folded in an experimental rig of PLA major phase to give an alternating layer structure. The rod is rotated by variable speed motor that is independently controllable. The rod rotational speed and volumetric flow rates of EVOH and PLA are of our interest. Careful design of stir rod in smart blending is necessary for effective performance. The computational model provided the visualization of flow profile inside an experimental rig. The simulation determined the geometry of the stir rod required to achieve the spiral flow developed of the melt. The experimental results suggest that the injected streams of EVOH are stretched and folded to multiple and distributed layers ranging thickness from 10 to 200 um. The characteristic folding of EVOH melt depends on the volumetric flow rate of the screw extruder and rod rotational speed. However, the coalescence of EVOH layers is observed for high rod rotational speed.

A charge-transfer salt composed of methyl viologen and hexacyanidoferrate(II).

The methyl viologen dication, used under the name Paraquat as an agricultural reagent, is a well-known electron-acceptor species that can participate in charge-transfer (CT) interactions. The determination of the crystal structure of this species is important for accessing the CT interaction and CT-based properties. The title hydrated salt, bis(1,1'-dimethyl-4,4'-bipyridine-1,1'-diium) hexacyanidoferrate(II) octahydrate, (C12H14N2)2[Fe(CN)6]·8H2O or (MV)2[Fe(CN)6]·8H2O [MV2+ is the 1,1'-dimethyl-4,4'-bipyridine-1,1'-diium (methyl viologen) dication], crystallizes in the space group P21/c with one MV2+ cation, half of an [Fe(CN)6]4- anion and four water molecules in the asymmetric unit. The FeII atom of the [Fe(CN)6]4- anion lies on an inversion centre and has an octahedral coordination sphere defined by six cyanide ligands. The MV2+ cation is located on a general position and adopts a noncoplanar structure, with a dihedral angle of 40.32 (7)° between the planes of the pyridine rings. In the crystal, layers of electron-donor [Fe(CN)6]4- anions and layers of electron-acceptor MV2+ cations are formed and are stacked in an alternating manner parallel to the direction of the -2a + c axis, resulting in an alternate layered structure.