Multilayer Structure Research Articles

Realizing multi-level phase-change storage by monatomic antimony

With the growing need for extensive data storage, enhancing the storage density of nonvolatile memory technologies presents a significant challenge for commercial applications. This study explores the use of monatomic antimony (Sb) in multi-level phase-change storage, leveraging its thickness-dependent crystallization behavior. We optimized nanoscale Sb films capped with a 4-nm SiO2 layer, which exhibit excellent amorphous thermal stability. The crystallization temperature ranges from 165 to 245 °C as the film thickness decreases from 5 to 3 nm. These optimized films were then assembled into a multilayer structure to achieve multi-level phase-change storage. A typical multilayer film consisting of three Sb layers was fabricated as phase-change random access memory (PCRAM), demonstrating four distinct resistance states with a large on/off ratio (∼102) and significant variation in operation voltage (∼0.5 V). This rapid, reversible, and low-energy multi-level storage was achieved using an electrical pulse as short as 20 ns at low voltages of 1.0, 2.1, 3.0, and 3.6 V for the first, second, and third SET operation, and RESET operation, respectively. The multi-level storage capability, enabled by segregation-free Sb with enhanced thermal stability through nano-confinement effects, offers a promising pathway toward high-density PCRAM suitable for large-scale neuromorphic computing.

Effects of Alkyl Spacer Length in Carbazole-Based Self-Assembled Monolayer Materials on Molecular Conformation and Organic Solar Cell Performance.

Carbazole-based self-assembled monolayer (SAM) materials as hole transport layers (HTL) have led organic solar cells (OSCs) to state-of-the-art photovoltaic performance. Nonetheless, the impact of the alkyl spacer length of SAMs remains inadequately understood. To improve the knowledge, four dichloride-substituted carbazole-based SAMs (from 2Cl-2PACz to 2Cl-5PACz) with spacer lengths of 2-5 carbon atoms is developed. Single crystal analyses reveal that SAMs with shorter spacers exhibit stronger intermolecular interactions and denser packing. The molecular conformation of SAMs significantly impacts their molecular footprint and coverage on ITO. These factors result in the highest coverage of 2Cl-2PACz and the lowest coverage for 2Cl-3PACz on ITO. OSCs based on PM6:L8-BO with 2Cl-2PACz as HTL achieved high efficiencies of 18.95% and 18.62% with and without methanol rinsing of the ITO/SAMs anodes, corresponding to monolayer and multilayer structures, respectively. In contrast, OSCs utilizing the other SAMs showed decreased efficiencies as spacer length increased. The superior performance of 2Cl-2PACz can be attributed to its shorter spacer, which reduces series resistance, hole tunneling distance, and barrier. This work provides valuable insights into the design of SAMs for high-performance OSCs.

The mechanical behavior and deformation mode of multilayer composite structures based on triply periodic minimal surface elements

In this paper, the mechanical behavior and compression deformation mode of three types of composite multilayer structures based on triply periodic minimal surfaces (TPMS) were conducted through experiments and finite element analysis. The results indicate that the load-displacement curves under varying stain rates manifest a double-platform characteristic for all three structure types. The P-G four-layer structure and P-G six-layer structure have no discernible extrusion of the structural layers during compression, and the entirety of the structure displays an almost regular cubic configuration after compression. Nevertheless, local separation was observed in the extruded portion of the P-H six-layer structure after the structural deformation at higher strain rates. For the other conditions, the structure exhibited a bulge but did not display any local detachment or separation phenomena. During the deformation of the P-H six-layer structure, a dome-shaped region emerges in the first and fifth layers. The “crown” layer displays an inverted bell-shaped failure mode for the first layer structure, exhibiting downward extrusion. In contrast, the fifth layer structure displays an upward extrusion and exhibits a bell-shaped failure mode. The P-H 6-layer structure has the best energy absorption performance under quasistatic compression conditions for the P-G 4-layer, P-G 6-layer and P-H 6-layer structure. However, the energy absorption performance of the identical structure remains largely consistent across varying strain rate conditions.

Formation and snake-eating like solubilization mechanisms of rhamnolipid vesicles for oil components and amino acids

Rhamnolipid vesicles hold significant potential across a wide range of applications, yet their formation mechanisms and selective solubilization of organic molecules remain elusive. Employing dissipative particle dynamics (DPD) simulations, this study delves deeply into these aspects, uncovering a stepwise formation pathway from dispersed monomers to complex multi-layer vesicle structures. The fusion and growth of three-layer structures were identified as crucial steps in the development of stacked vesicles. Notably, double-chain rhamnolipids (Rh-C10-C10) exhibited enhanced stability in self-assembled structures compared to their single-chain counterparts (Rh-C10). Through a detailed analysis of parameters such as relative concentration distribution, radial distribution function, and density fields, the solubilization process of rhamnolipid vesicles was found to resemble a “snake-eating” mechanism. We also analyzed the solubilization sites, amounts, and vesicle sizes, elucidating the selective solubilization mechanisms of rhamnolipids for representative polar and non-polar compounds in crude oil, anisole and 1-hexene. The selectivity of rhamnolipid vesicles in solubilizing organic molecules was primarily influenced by polar attraction and steric hindrance, which together determined their solubilization sites within the vesicles. Additionally, the solubilization behavior and properties of five types of amino acids within rhamnolipid vesicles were explored, demonstrating analogous solubilization patterns that correlated with amino acid polarity. These results provide a foundation for optimizing the application of rhamnolipid vesicles, paving the way for potential advancements in drug delivery, environmental remediation, and oil recovery processes.

Preparation and characterization of functionally antibacterial multi-layer lignin core-shell structure material with adsorption and high efficiency of photocatalysis for Cr(Ⅵ)

Wastewater with chromium is a common heavy metal pollution in industrial pollution, affecting health of human seriously, while adsorption and photocatalysis are efficient for Cr(Ⅵ) removal. The multi-layer lignin core-shell structure materials were prepared with kraft lignin/polydopamine core-shell structure material, using non-covalent bonding to induce the in-situ induction of TiO2. The hydroxyl group of kraft lignin and the amino group of polydopamine provided abundant adsorption active sites with adsorption capacity being 299mg/g at pH of 2. The adsorption process conformed to the Freundlich isotherm model and the pseudo-second-order kinetic model. The removal rate of Cr(Ⅵ) reached more than 99.9% within 10min under simulated solar light with influence of adsorption and photocatalysis. The multi-layer lignin core-shell structure materials presented excellent antibacterial activity, with the inhibition rate against S.aureus and E.coli being 40% under dark conditions and 99% under simulated solar light because h+ or ·OH producing by TiO2. The antibacterial multi-layer lignin core-shell structure materials showed good universality in water pollution treatment.

Enhanced corrosion resistance of a novel periodic multilayered Si/(Si, N)-DLC coating against simulated coal mine water

In this study, a novel periodic multilayered DLC coating, which was composed of a Si interlayer and a Si/N co-incorporated DLC layer (Si/(Si, N)-DLC) per period, was deposited; the corrosion behavior under the neutral, acidic, or alkaline coal mine water environment and its periodic number dependence, especially the fundamental corrosion mechanism, were systemically explored. Results suggest that compare to the substrate, the introduction of multilayered Si/(Si, N)-DLC coating presents a dramatic enhancement in the corrosion resistance under coal mine water environment. However, with increasing the periodic number, the corrosion resistance of the multilayered coating strongly depends on the working environment, which exhibits an enhancement in neutral and alkaline environments while a degeneration in acidic environment. This is attributed to not only the prolongation of the corrosion path caused by the multilayered structure but also the formation of an insulating silicon oxide layer in neutral and alkaline environments. However, in acidic environments, the strong permeability of H+ with the smallest ionic radius easily infiltrates the inherent defects of the coating. This not only weakens the protective properties of the multilayer structure but also leads to hydrogen-induced cracking, ultimately diminishing corrosion resistance. These findings theoretically guide the development of the DLC coatings with excellent corrosion resistance for coal mine applications.

Structural design and enhanced energy density of Ba0.6Sr0.4TiO3/PVDF nanocomposites with multilayer gradient structure

With the development of science and technology, the application of electronic products is extensive, and it is developing in the direction of miniaturization, integration, and high performance. However, the development of electronic products is limited due to capacitors low energy storage density. This study selects inorganic nanoparticles with high dielectric constant as fillers and polyvinylidene fluoride as the matrix of composite materials. It adopts a layer-by-layer casting method to prepare multilayer Ba0.6Sr0.4TiO3/PVDF composites. It is found that the dielectric and energy storage performances of the multilayer composites doped with Ba0.6Sr0.4TiO3 are improved compared with the pure PVDF polymer films after the electrical properties test. A multi-layer composite material with a gradient distribution of fillers was designed and prepared to improve the energy storage density. The energy storage density of multilayer composites with a favorable gradient structure can reach up to 9.3 J/cm3 at 300 kV/mm. By analyzing the improved storage density mechanism, the results show that the design of the multilayer gradient structure can significantly reduce the electric field's local concentration, inhibit the formation of conductive paths, and significantly improve the composites' energy storage density.

Influence of expansion ratio and multilayered gradient structure on the electromagnetic interference shielding performance of lightweight poly (lactic acid)/carbon nanostructures composite foams

Influence of expansion ratio and multilayered gradient structure on the electromagnetic interference shielding performance of lightweight poly (lactic acid)/carbon nanostructures composite foams

Vacuum assisted desorption of sodium zirconate sorbent for enhancing cyclic stability in pre-combustion CO2 capture

Sodium zirconate (Na2ZrO3) is a promising material for pre-combustion CO2 capture due to its fast sorption kinetics and excellent cyclic stability at high temperatures under ideal condition (desorption in 100% N2). Still, there is a lack of study on the performance of Na2ZrO3 cyclic capture under harsh condition (desorption in high concentration CO2). In this study, Na2ZrO3 was prepared by wet-mixing and heated-drying, and the difference in the cyclic CO2 capture performance of the sample was compared between desorption under harsh condition and vacuum condition. The crystal structure of Na2ZrO3 was identified during the sorption-desorption cycles. The crystal structure was also modeled and simulated to analyze the reason for the superior capture performance from the monoclinic Na2ZrO3. It was found that the special interlocked and multilayered stacked structure of the monoclinic Na2ZrO3 allowed for high reactivity with CO2. It was found that high temperature solely had little help in the desorption of Na2ZrO3 under harsh condition, but vacuum condition promoted desorption of Na2ZrO3 in high fraction CO2, and vacuum desorption at 1000 °C-1050 °C resulted in Na2ZrO3 with both good capture performance and cycling stability. Vacuum desorption led to more complete reversion of Na2ZrO3 to the monoclinic state, benefiting for CO2 capture. This study attempted to simulate the harsh capture environments of real industrial applications and to explore the possibility of Na2ZrO3 as a carbon capture material for pre-combustion capture.

Preparation and Characterization of Waste Cotton Fabric Reinforced Polylactic Acid Green Composites with Multifunctional Properties in a Low-Carbon Process

The development and design of eco-friendly materials prove crucial for promoting the recycling of waste cotton textiles and reducing environmental pollution. In this study, waste cotton fabric (WCF) and polylactic acid (PLA) serve to produce cotton fabric-reinforced PLA composite material (CF/P). The CF/P is then integrated with traditional porous sound-absorbing materials to create a novel composite plate. This research highlights the potential of WCF reinforced plates for sound absorption and thermal insulation applications in the construction field of construction and reports the effects of variables such as hot pressing temperature, WCF mass fraction, and WCF layer alignment angle on the material properties. The optimum tensile strength, water absorption, and thermal conductivity of the prepared CF/P are 64.2 ± 1.8MPa, 1.98% ± 0.04%, and 0.03W/(m·K), respectively. By combining with porous sound-absorbing materials and modifying the layering structure of composite plates, its acoustic performance can be adjusted. The highest Sound Absorption Average (SAA) of plates with a multilayer composite structure is 0.67. Direct shaping through hot pressing diminishes the use of adhesives, thereby reducing costs and health hazards. This approach offers a practical and efficient solution for the recycling and repurposing of natural fibers.

High temperature oxidation resistance behavior of Ti3SiC2/Cu composites under migration of Ti and Cu atomic

The oxidation behavior and oxidation mechanism of Ti3SiC2/Cu composites were investigated using constant temperature oxidation method. The Ti3SiC2/Cu composites were prepared at different sintering temperatures. Results showed that the relationship between the oxidation reaction rate of Ti3SiC2/Cu composites in air at 700°C∼900°C and the oxidation temperature was in accordance with the parabolic law of oxidation kinetics. The oxidation weight gain and oxide layer thickness of Ti3SiC2/Cu composites at 700 °C and 800 °C were insignificant, with oxidation reaction rates of 3.0692×10-9 kg2m-4h-1 and 6.9856×10-9 kg2m-4h-1, respectively, and the oxidation rate of Ti3SiC2/Cu composites at 900 °C was enhanced to 1.00907×10-8 kg2m-4h-1. Ti3SiC2/Cu composites oxidized at 900°C formed a protective oxide layer, which was mainly a multilayer structure composed of different kinds of oxides: the outer layer was mainly composed of TiO2; the intermediate layer mainly consisted of CuO; the inner layer mainly made up of TiO2 and SiO2.

Polyethylene glycol modified polysiloxane and silver decorated expanded graphite composites with high thermal conductivity, EMI shielding, and leakage-free performance

Phase change thermal interface materials (PCTIMs) have attracted significant attention due to their dual capability in temperature control and thermal buffering. However, the widespread application of PCTIMs in electronic devices is hindered by critical drawbacks such as low thermal conductivity (к), absence of electromagnetic interference shielding effectiveness (EMI SE), poor flexibility, and susceptibility to leakage. In this study, leakage-free PCTIMs were successfully fabricated with ultra-high thermal conductivity (к∥ = 23.4 W m−1 K−1, к⊥ = 8.1 W m−1 K−1), outstanding phase change functionality, exceptional EMI SE (73.2 dB), and excellent flexibility. A polyethylene glycol-modified polydimethylsiloxane (pPDMS) was synthesized through chemical grafting, demonstrating its significant potential as substrates for PCTIMs. Moreover, a designed material called silver nanoparticles-decorated expanded graphite (Ag-EG), was prepared to facilitate multidimensional material collaboration and incorporated into the pPDMS matrix to obtain Ag-EG@pPDMS composites. This integration resulted in a three-dimensional (3D) multi-layer orientation structure that enabled superior thermal conductivity in both in-plane and through-plane directions. To investigate the influence of 3D multi-layer orientation structure on Ag-EG@pPDMS, theoretical analysis was conducted using Effective Medium Theory (EMT) and Foygel thermal conduction models, which were further simulated by finite element analysis confirming substantial enhancement in material properties attributed to the 3D multi-layer orientation structure. Thermal management and electromagnetic interference (EMI) shielding applications were conducted using computers, wireless bluetooth earphones, and other electronic devices, indicating the superior thermal conductivity and EMI shielding of Ag-EG@pPDMS composites.

High velocity impact performance of double ceramic stacking on multilayer sandwich armor structures

High velocity impact performance of double ceramic stacking on multilayer sandwich armor structures

Scalable production of flexible and multifunctional graphene-based polymer composite film for high-performance electromagnetic interference shielding

Graphene have gained significant interest for potential in lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials due to their high electrical conductivity, low density, and ability to dissipate electromagnetic waves, but its poor dispersibility and processability hinders its applications. Besides, there is an urgent need for EMI shielding materials with multifunctional features. Herein, we proposed a flexible graphene/carbon nanotubes/polyurethane (GC/PU) composite film with a dense three-dimensional multilayer structure. This resultant GC/PU film shows high tensile strength of 42.9 MPa, ultra-high conductivity of 2087.2 S/m, and X-band EMI shielding efficiency of 37.7 dB at a thickness of 130 μm and even higher value of 72.1 dB at 520 μm. Moreover, this GC/PU film demonstrates an excellent electric heating performance (surface temperature of 127.5 °C at 5.0 V, thermal response <20 s) and flame-retardant capability, which endows it with the capability of anti-icing/de-icing. Therefore, this work may provide a promising approach for developing high-performance EMI shielding composites that may be used in the areas of wearables, defense, and aerospace.

Crashworthiness of multi-layer gradient corrugated sandwich circular tube structures

A novel multi-layer gradient sandwich tube design, which combines corrugated and circular structures, was developed in this study. The results of quasi-static compression tests and ABAQUS numerical simulations demonstrate that the energy absorption of the multi-layer corrugated sandwich (A333N666) is 147% greater than that of a traditional corrugated sandwich (A3N6). The crushing force efficiency (CFE) increased by 29.3%, and the specific energy absorption (SEA) improved by 36%. For single-layer corrugated sandwich structures, the crashworthiness index increases with the wave number. However, this rate of increase diminishes over time. The crashworthiness index also increases with the wave number for multi-layer sandwich structures, and the magnitude of this increase becomes increasingly pronounced. Notably, experiments and numerical simulations show that the effect of the amplitude gradient arrangement on the crashworthiness index is more significant than that of the wave number gradient. The amplitude gradient arrangement (A432N666) demonstrates the best performance, exhibiting a 42.4% increase in SEA and a 33% increase in CFE compared to the single-layer corrugated sandwich structure (A3N6). Overall, the multi-layer amplitude gradient design exhibits exceptional crashworthiness. The findings of this study may provide valuable insights for the design of thin-walled structures.

Potentiometric enzymatic aptasensing of paralytic shellfish toxins using graphene-wrapped magnetic nanospheres and an all-solid-state cadmium-selective microelectrode

A highly sensitive potentiometric enzymatic aptasensing system for the detection of paralytic shellfish toxins (PSTs) is developed by integrating graphene-wrapped magnetic nanospheres (Fe3O4@SiO2@rGO) with an all-solid-state ion-selective microelectrode. The multilayered core-shell structure of Fe3O4@SiO2@rGO enhances the efficient adsorption of aptamer molecules tagged with cadmium sulfide (CdS) nanoparticles. These CdS-aptamer conjugates, when bound with PST molecules, can be desorbed from the Fe3O4@SiO2@rGO surface into the sample solution and subsequently digested by deoxyribonuclease I (DNase I). This digestion process releases the PST molecules for recirculation, significantly reducing the retention of CdS on the surface of Fe3O4@SiO2@rGO. After magnetic separation and acid dissolution, the released Cd2+ from the magnetic nanospheres are measured using an all-solid-state Cd2+-selective microelectrode, enabling sensitive potentiometric detection of PSTs. Using gonyautoxin 1/4 (GTX 1/4) as a model, the sensing system exhibits a linear concentration range from 5 to 150 pM and a low detection limit of 1.7 pM for GTX 1/4, and has been successfully applied in the analysis of seawater samples.

Tunning the omnidirectional bandgap of nanoporous silicon using a semi-sinusoidal refractive index profile

We report the theoretical comparison of the omnidirectional bandgap in a 1-D photonic crystal using sinusoidal and semi-sinusoidal refractive index profiles. It is found that the corresponding omnidirectional bandgap of the semi-sinusoidal widens and shifts to a higher wavelength range as a function of the asymmetric ratio of semi-sinusoidal profile. The asymmetric ratio plays an essential role in tunning the width of the omnidirectional bandgap due to the changed average refractive index and optical thickness. The semi-sinusoidal refractive index is experimentally achieved by changing the current waveform. Novel omnidirectional nanoporous silicon mirrors with an omnidirectional bandgap covering optical communication wavelength (1550 nm) were fabricated using a semi-sinusoidal current waveform. The experimental analogy was carried out by building up the multilayered dielectric structures of omnidirectional mirrors by anodic etching using a semi-sinusoidal current waveform. The experimental results were compared with the theoretical results investigated by the Transfer matrix method. It was shown that the distorted current profile impacts the quality of the omnidirectional bandgap although it does not affect the porous size range.

Enhancing Greenhouse Efficiency: A Quantum Genetic Algorithm Approach to Optimal Glass Thickness

Greenhouses are pivotal in extending the growing season for various crops by creating conducive environments that enhance plant growth. A critical factor in maximizing the efficiency of greenhouses is the optimization of light transmittance through multi-layer glass structures. This not only supports plant health but also conserves energy by maintaining a warmer internal climate. The application of quantum genetic algorithms (QGAs) to this context represents a significant advancement, as these algorithms excel in handling multi-objective optimization challenges. By targeting the precise calibration of glass thickness, QGAs can substantially influence the amount of solar energy harnessed within the greenhouse, especially when the sun is directly overhead at noon. This paper presents an in-depth study on the use of quantum genetic algorithms to optimize the thickness of three distinct layers of glass in greenhouse settings. Our findings reveal that QGAs are capable of generating various combinations of glass thickness that not only maximize the total energy transmitted but also ensure stability in the energy output across different scenarios. The robustness of QGAs in consistently deriving optimal solutions underscores their potential as a superior technique in architectural design for agricultural applications. Comparative analysis with classical genetic algorithms and random number optimization techniques further demonstrates the superiority of quantum genetic algorithms.

Visual Indicator for Intradialytic Hypotension Prediction Using Variation and Compensation of Heart Rate

Background: To date, most intradialytic hypotension (IDH) studies have proposed technologies to comprehensively predict the occurrence of IDH using the patient’s baseline information and ultrafiltration (UF) information, but it is difficult to apply the technologies while identifying the patient’s condition in real time. Methods: In this study, we propose an IDH indicator that uses heart rate (HR) change information to identify the patient’s condition in real time and visually shows whether IDH has occurred. The data used were collected from 40 dialysis patients in a clinical trial conducted in the Artificial Kidney Unit at Yeungnam University Medical Center, Korea, from 18 July to 29 November 2023. Results: The IDH indicator infers changes in the patient’s blood pressure during dialysis by analyzing the upper and lower maximum HRs based on the real-time average HR. Medical staff can respond to IDH in real time by looking at the IDH indicator, which visually expresses changes in the patient’s HR. In addition, we propose a multilayer perceptron structure that inputs upper and lower maximum HR information based on the average HR for the time interval accumulated in real time. In learning using 40 min of data up to 5 min before IDH occurred, models using two and five layers showed excellent performance, with accuracy of 88.6% and 85.2%, respectively. Conclusions: By combining IDH visual indicators and the multi-layer perceptron method, medical staff can effectively respond to IDH in real time.

2D Ti3C2Tx-MXene and its superstructures as dual-function electrodes for triboelectric nanogenerators for self-powered electronics

Selecting distinct materials to design a tribopositive and tribonegative electrode pair for a triboelectric nanogenerator (TENG) device is a challenging task, as the interfacial electric field causes surface charges to diffuse into the air or within the material itself, leads to charge deterioration. To address these challenges, there is a strong demand for engineered materials and electrode designs that enable effective charge accumulation and trapping to regulate their performance optimally. Herein, we introduce a unique electrode design for a contact-separation (CS) mode triboelectric nanogenerator TENG featuring multilayered Ti3C2Tx MXene/Kapton as tribonegative electrodes. For the tribopositive electrode, we developed an innovative synthesis strategy to create MXene-seeded layered TiO2 superstructures/PVA-based tribopositive electrodes. After optimization of both triboelectric layers, the optimized TENG showed an open-circuit voltage (Voc) ∼ 120 V, short-circuit current (Isc) ∼ 25 μA, and power density of 5.66 W·m−2. The surface terminations groups in highly conductive black MXene nanosheets and the oxygen vacancies in TiO2-layered superstructures provide abundant charge accumulation and trapping sites due to organized multilayered structures at both ends. Moreover, the induced polarization in the tribopositive layer due to the hybrid film could further hinder the free electrons’ drift to the bottom electrode, preventing charge recombination. The optimized TENG was tested as a pressure sensor to monitor different sensitive physiological movements of the human body. Further application of the designed TENG has been revealed by humidity sensing characteristics, powering LEDs, stopwatches, pedometers, and swiftly charging micro-capacitors by utilizing direct output power. By employing a controlled synthesis strategy, our approach leverages the unique properties of MXenes to function as both tribo-positive and tribonegative electrodes within the same device. This dual-function capability simplifies material selection and enhances overall device performance, presenting a transformative solution for next-generation TENG applications.