Bottom Layer Research Articles

Design and fabrication of a sandwich detector for material discrimination and contrast cancellation in dual-energy based x-ray imaging

Dual-energy imaging represents a versatile and evolving technology with wide-ranging applications in medicine and beyond. Recent technological developments increased the potential for improved diagnostic accuracy and expanded imaging capabilities across various fields. The purpose of this work is to design and develop an energy-integrating multilayer detector, known as a sandwich detector, aimed at single-shot dual-energy imaging tasks such as material discrimination and contrast cancellation. The sandwich detector uses two complementary metal oxide semiconductor advanced pixel sensors of 50 μm pixel size. The top and bottom sensors detect low-energy (LE) and high-energy (HE) photons, with sensors coupled with 250 and 600 μm scintillators, respectively. For better spectral separation between layers without excessively affecting the detected statistic in the bottom layer, the insertion of a 0.25-mm Cu filter between the layers was found to be the optimal choice, from among the tested 0-, 0.25-, and 0.5-mm filter options. The thickness selection for scintillator and intermediate Cu filter was carried out through a dual-energy simulation model. The experiments confirmed the model's reliability in selecting the optimal thicknesses of the intermediate Cu filter, thereby providing reassurance also on the choice of the top scintillator.

Resemblance of the global depth distribution of internal-tide generation and cold-water coral occurrences

Abstract. Internal tides are known to be an important source of mixing in the oceans, especially in the bottom boundary layer. The depth of internal-tide generation therefore seems important for benthic life and the formation of cold-water coral mounds, but internal-tide conversion is generally investigated in a depth-integrated sense. Using both idealized and realistic simulations on continental slopes, we found that the depth of internal-tide generation increases with increasing slope steepness and decreases with intensified shallow stratification. The depth of internal-tide generation also shows a typical latitudinal dependency related to Coriolis effects. Using a global database of cold-water corals, we found that, especially in Northern Hemisphere autumn and winter, the global depth pattern of internal-tide generation correlates (rautumn = 0.70, rwinter = 0.65, p < 0.01) with that of cold-water corals: shallowest near the poles and deepest around the Equator, with a decrease in depth around 25° S and N, and shallower north of the Equator than south. We further found that cold-water corals are situated significantly more often on topography that is steeper than the internal-tide beam (i.e. where supercritical reflection of internal tides occurs) than would be expected from a random distribution: in our study, in 66.9 % of all cases, cold-water corals occurred on a topography that is supercritical to the M2 tide whereas globally only 9.4 % of all topography is supercritical. Our findings underline internal-tide generation and the occurrence of supercritical reflection of internal tides as globally important for cold-water coral growth. The energetic dynamics associated with internal-tide generation and the supercritical reflection of internal tides likely increase the food supply towards the reefs in food-limited winter months. With climate change, stratification is expected to increase. Based on our results, this would decrease the depth of internal-tide generation, possibly creating new suitable habitat for cold-water corals shallower on continental slopes.

Wafer-scale development, characterization, and high temperature stabilization of epitaxial Cr2O3 films grown on Ru(0001).

This work outlines conditions suitable for the heteroepitaxial growth of Cr2O3(0001) films (1.5-20nm thick) on a Ru(0001)-terminated substrate. Optimized growth is achieved by sputter deposition of Cr within a 4mTorr Ar/O2 20% ambient at Ru temperatures ranging from 450 to 600 °C. The Cr2O3 film adopts a 30° rotated honeycomb configuration with respect to the underlying Ru(0001) substrate and exhibits a hexagonal lattice parameter consistent with that for bulk Cr2O3(0001). Heating to 700 °C within the same environment during film preparation leads to Ru oxidation. Exposure to temperatures at or above 400 °C in a vacuum, Ar, or Ar/H2 3% leads to chromia film degradation characterized by increased Ru 3d XPS intensity coupled with concomitant Cr 2p and O 1s peak attenuations when compared to data collected from unannealed films. An ill-defined but hexagonally well-ordered RuxCryOz surface structure is noted after heating the film in this manner. Heating within a wet Ar/H2 3% environment preserves the Cr2O3(0001)/Ru(0001) heterolayer structure to temperatures of at least 950 °C. Heating an Ru-Cr2O3-Ru heterostacked film to 950 °C within this environment is shown by cross-sectional scanning/transmission electron microscopy (S/TEM) to provide clear evidence of retained epitaxial bicrystalline oxide interlayer structure, interlayer immiscibility, and epitaxial registry between the top and bottom Ru layers. Subtle effects marked by O enrichment and O 1s and Cr 2p shifts to increased binding energies are noted by XPS in the near-Ru regions of Cr2O3(0001)/Ru(0001) and Ru(0001)/Cr2O3(0001)/Ru(0001) films after annealing to different temperatures in different sets of environmental conditions.

Influence of Time Gap on the Buildability of Cement Mixtures Designed for 3D Printing

This study provides novel insights into the nuanced impact of time gaps on the buildability of cement mixtures within the 3D printing process. In contrast to studies predominantly focused on rheological properties, this research addresses essential factors such as printed structure size, which inevitably affect the temporal intervals between layer depositions and consequently shape the buildability outcome. The investigation encompasses cement mixtures with diverse water-to-cement ratios (ranging from 0.26 to 0.36), varied setting accelerator concentrations (1.0 to 2.0 wt.%), and superplasticizer contents (0.25 and 0.5 wt.%), all explored across different time gaps (ranging from 5 to 25 min). The evaluation of buildability involves a meticulous assessment of the deformation of the bottom layer induced by adjacent layers. The findings underscore the substantial role played by chemical admixtures in fine-tuning rheological properties specific to each time gap, thereby influencing the size of the printed structure. The impact of the accelerator admixture is evident in its ability to reduce the minimum time gap required for optimal buildability while the superplasticizer emerges as a key player in enhancing fluidity without compromising the load-bearing capacity of the printed structures. To predict buildability for a given time gap, the study leverages the results of spreading diameter from the flow table test and the setting time from the Vicat test. Lastly, this study extends its scope to unveil insights into the intricate interplay between time gap and printing speed for 3D printed real-scale constructions by examining the relationship among these parameters across constructions with diverse built areas.

An Innovative Passive Noise Control Technique for Environmental Protection: An Experimental Study in Explosion Noise Attenuation

Passive noise control techniques are an effective way of mitigating environmental noise pollution caused by industrial activities, assisting with long-term sustainability in workplace health and safety. Excessive noise from various sources such as mining, construction, manufacturing, air blasting and large-scale gas and dust explosion investigations is challenging as it produces a high level of noise. Excessive explosion noise can have a significant impact on the surrounding environment and people. To suppress the noise to satisfactory levels for nearby occupants, several layers of acoustic barriers are employed. The effectiveness of each level of acoustic barrier is presented. A bottom ash granule base layer with a 300 mm thickness reduced the peak noise levels (136 dBA) by approximately 33 dBA. In the next stage, an autoclaved aerated concrete (AAC)-based 200 mm acoustic barrier was introduced, which suppressed 24 dBA of noise. The inside of the AAC acoustic barrier was finally covered with a 50 mm thick noise attenuation composite material layer constituted of a sound barrier and a sound absorber, and this composite material attenuated the noise level by 6 dBA. The entire noise suppression mechanism was found to be an effective way to suppress gas and dust explosion noise and satisfy the requirement of the occupant and sound level.

Shear strength of soil by using rice husk ash waste for sustainable ground improvement

AbstractIn the global construction industry, areas characterized by weak and expansive soils are on the rise, necessitating effective solutions for strength enhancement. Addressing this concern, sustainable soil amendments have gained attention, with rice husk ash (RHA) from rice milling industries being a notable focus. Our experimental study aimed to assess the shear strength of this innovative construction material, introducing a unique approach that considers subgrade layers with minimal cement dosage, including upper, bottom, and double layers a novel contribution yet unexplored in existing literature. In addition to conventional mechanical testing, we employed SEM (Scanning Electron Microscopy) and EDS (Energy-Dispersive X-ray Spectroscopy) analyses to comprehensively explore the treated soils' microstructural and elemental composition aspects. Examining sixteen specimen combinations of weak expansive soil-RHA-cement, varying proportions of RHA (2%, 4%, 6%) and cement (2%, 4%, 6%) were mixed to understand their effects on shear strength parameters. Our findings revealed significant shear strength improvement in each subgrade layer, with specimen 6%RHA6%C in the lower subgrade layer exhibiting the highest cohesive strength at 143 kN/m2. Notably, the double layer configuration, specimen 2%RHA6%C, achieved maximum deviatoric stresses of 383 kN/m2. This novel construction material contributes to effective waste management and presents an innovative engineering solution for sustainable ground improvement, offering promising prospects for future geotechnical advancements.

In-situ Atomic-Scale Observation of Brownmillerite to Ruddlesden-Popper Phase Transition Tuned by Epitaxial Strain in Cobaltites

Abstract Phase transitions involving oxygen ion extraction within the framework of the crystallographic relevance have been widely exploited for sake of superconductivity, ferromagnetism, and ion conductivity in perovskite-related oxides. However, atomic-scale pathways of phase transitions and ion extraction threshold are inadequately understood. Here we investigate the atomic structure evolution of LaCoO3 films upon oxygen extraction and subsequent Co migration, focusing on the key role of epitaxial strain. The brownmillerite to Ruddlesden-Popper phase transitions are discovered to stabilize at distinct crystal orientations in compressive- and tensile-strained cobaltites, which could be attributed to in-plane and out-of-plane Ruddlesden-Popper stacking faults, respectively. A two-stage process from exterior to interior phase transition is evidenced in compressive-strained LaCoO2.5, while a single-step nucleation process leaving bottom layer unchanged in tensile-strained situation. Strain analyses reveal that the former process is initiated by an expansion in Co layer at boundary, whereas the latter one is associated with an edge dislocation combined with antiphase boundary. These findings provide a chemo-mechanical perspective on the structure regulation of perovskite oxides and enrich insights into strain-dependent phase diagram in epitaxial oxides films.

Enhancing thermal conductivity and electromagnetic shielding performance of Ni-CNT/Al2O3/PVDF composite film with a multi-layered structure

To develop thermal interface materials with both high thermal conductivity and electromagnetic interference shielding, the polyvinylidene fluoride (PVDF) composite film was prepared by electrospinning and hot-pressing, using strategies of multi-layered structure and two fillers synergy of nickel modified carbon nanotube (Ni-CNT) and Al2O3 microspheres. The composite film consisted of a Ni-CNT filled PVDF electrospun fiber film as the top and bottom surface layers, and a PVDF electrospun fiber film electrostatically adsorbing Al2O3 microspheres and surface-sprayed with Ni-CNT as the middle layer. At a 20 wt% Ni-CNT in the surface layers and a 16.7 wt% Al2O3 and 5 wt% Ni-CNT in the middle layer, the composite film with a thickness of 0.1 mm exhibited optimal performances with electromagnetic wave shielding efficiency of 65 dB in the frequency range of 8.2–12.4 GHz, with 86% of the electromagnetic waves being absorbed. At the same time, the composite film had a high in-plane thermal conductivity of 4.02 W m−1 K−1, while maintaining a tensile strength of 25 MPa and flexibility.

Phytoplankton Communities’ Response to Thermal Stratification and Changing Environmental Conditions in a Deep-Water Reservoir: Stochastic and Deterministic Processes

Thermal stratification has become more extensive and prolonged because of global warming, and this change has had a significant impact on the distribution patterns of the phytoplankton communities. However, the response of phytoplankton community structures and assembly processes to thermal stratification is not fully understood. We predicted that the structure and assembly processes of phytoplankton communities would be affected by thermal stratification among water layers associated with environmental condition changes, reflecting certain patterns in temporal and spatial scales. Phytoplankton from Danjiangkou Reservoir were collected from October 2021 to July 2022 to verify this prediction. During the sampling period, Danjiangkou Reservoir remained thermally stratified with stability. The composition of the phytoplankton community in the surface layer significantly differed from that in both the thermocline and bottom layer. The phenomenon of thermal stratification affected the pattern of nitrogen and phosphorus distribution and, thus, the processes of the phytoplankton community structures. Deterministic processes had a greater influence on the assembly of the phytoplankton communities in the surface and bottom layers. In contrast, stochastic processes were more prevalent in the assembly of the thermocline phytoplankton community. The phytoplankton community within the thermocline layer exhibited a broader niche range than that in the surface and bottom layers, showing notable dissimilarity from that of the bottom layer. Canonical correspondence analysis (CCA) revealed that the vertical distributions of the phytoplankton communities were significantly correlated with NH4+-N, pH, and water temperature (WT). In summary, this study explained the distribution patterns of phytoplankton community structures and assembly processes in deep-water reservoirs during the stratification period. Additionally, the study explored the potential of using the distribution patterns of phytoplankton in stratified-state deep-water reservoirs under a subtropical–warm temperate climate as climate indicators in the context of global warming.

A single-layer multimode high gain circularly polarized metasurface antenna using CMA for C-band applications

Abstract This article presents an innovative design for a low-profile, high-gain circularly polarized (CP) antenna using a single-layer metasurface (MTS). The proposed design incorporates an MTS layer, comprising a 4 × 4 array of hexagonal-shaped patches, printed on the top layer of the substrate. The bottom layer features a coplanar waveguide-fed slotted ground. Circular polarization and broadside radiation are achieved through the application of characteristic mode analysis (CMA). CMA is employed to simultaneously excite desired modes, aiming for wideband circular polarization and gain enhancement. Experimental results validate the effectiveness of the design, with compact dimensions of 0.67λ0 × 0.67λ0 × 0.04λ0. The measurements demonstrate an impressive impedance bandwidth of 84.3% within the 3.7–9.1 GHz. Additionally, a 3-dB axial ratio bandwidth of 18.6% is observed between 4.96 and 5.98 GHz and 3.74% between 8.38 and 8.7 GHz. The antenna exhibits excellent radiation pattern characteristics, featuring a maximum gain of 10.08 dBi at 7.1 GHz. The radiation pattern is symmetrical with broadside directionality, making the antenna well-suited for sensing applications.

A miniaturized multicellular platform to mimic the 3D structure of the alveolar-capillary barrier

Several diseases affect the alveoli, and the efficacy of medical treatments and pharmaceutical therapies is hampered by the lack of pre-clinical models able to recreate in vitro the diseases. Microfluidic devices, mimicking the key structural and compositional features of the alveoli, offer several advantages to medium and high-throughput analysis of new candidate therapies. Here, we developed an alveolus-on-a-chip recapitulating the microanatomy of the physiological tissue by including the epithelium, the fibrous interstitial layer and the capillary endothelium. A PDMS device was obtained assembling a top layer and a bottom layer obtained by replica molding. A polycaprolactone/gelatin (PCL-Gel) electrospun membrane was included within the two layers supporting the seeding of 3 cell phenotypes. Epithelial cells were grown on a fibroblast-laden collagen hydrogel located on the top side of the PCL-Gel mats while endothelial cells were seeded on the basolateral side of the membrane. The innovative design of the microfluidic device allows to replicate both cell-cell and cell-extracellular matrix interactions according to the in vivo cell arrangement along with the establishment of physiologically relevant air-liquid interface conditions. Indeed, high cell viability was confirmed for up to 10 days and the formation of a tight endothelial and epithelial barrier was assessed by immunofluorescence assays.

Design of Efficient Inverted NiOX‐Based Three‐Terminal Back‐Contact All Perovskite Tandem Solar Cells

AbstractThe development of efficient all perovskite tandem solar cells has faced challenges related to current matching and optical losses. In this work, a design of a non‐coplanar three‐terminal (3T) all perovskite tandem solar cell is presented, which consists of a p‐i‐n inverted NiOX‐based CsPbI2Br perovskite top cell, and a FA0.6MA0.4Sn0.5Pb0.5I3 perovskite bottom cell with back‐contact (BC) device structure. It effectively mitigated the optical losses introduced in non‐absorbing layers and resulted in a 2.9% absolute efficiency improvement compared to that of planar sandwich‐type 3T tandems. Both optical and electrical characteristics of the multi‐terminal tandem cells are investigated. Then, it is focused on understanding the impact of top cell thickness on overall non‐coplanar BC 3T‐tandem performance, considering low‐energy photon optical reflection and carrier transport distance. Following optimizations of energy level and device structure, an efficiency of 32.16% is achieved, with non‐coplanar BC 3T device architecture: top cell consisting of hole extraction layer (ITO/NiOx), CsPbI2Br absorber layer, and electron extraction layer (ZnO/FA0.6MA0.4Sn0.5Pb0.5I3/SnO2/Ag); and bottom cell (Ni/NiOx/FA0.6MA0.4Sn0.5Pb0.5I3/SnO2/Ag); bottom perovskite layer has two functions, one is electron transport layer for top cell, and the other is low‐energy photon absorption layer in bottom cell. It provides insight and a promising pathway for manufacturing high‐efficient all perovskite tandem solar cells.

Mean-field study of magnetic properties and hysteresis behavior in a bilayer graphene Ising system

Using the mean-field approximation based on the Gibbs-Bogoliubov inequality for the free energy, we conducted an investigation into the magnetic properties and hysteresis behavior of a graphene Ising bilayer, where the top and bottom layers are occupied by spins σ = 3/2 and S = 5/2, respectively. The effects of exchange interactions, crystal fields, external magnetic field and temperature on the total magnetization, partial magnetizations of each layer, total magnetic susceptibility, blocking temperature and hysteresis loops of the system were thoroughly analyzed. The variations of the blocking temperature as a function of various parameters in the system’s Hamiltonian were presented. Furthermore, we demonstrated the existence of multiple hysteresis loop behaviors under specific physical conditions.

A Periosteum-Bioinspired Electrospun Janus Membrane with Antibacterial and Osteogenic Dual Function.

For a guided bone regeneration membrane, it is critical to possess osteogenic capability while inhibiting infection caused by bacteria. Inspired by the bilayer structure of the native periosteum, an electrospun Janus membrane with osteogenic and antibacterial dual-function is fabricated for guided bone regeneration. Hydrophilic moxifloxacin (MXF) and hydrophobic icariin (ICA) are loaded in the nanofibers made of a mixture of polycaprolactone and gelatin at the top and bottom layers, respectively, leading to the opposing hydrophilic/hydrophobic properties of the bilayer Janus membranes. The as-obtained Janus membrane exhibits excellent physical properties (tensile strength > 6.0MPa) and robust biocompatibility, indicating the immense potential as a suitable replacement for the native periosteum. The membrane has a superior surface morphology and outstanding degradation performance in vitro. Besides, the rapid release of MXF and the slow release of ICA can meet the different needs of drug release rates. Only ≈30% ICA is released from the as-obtained Janus membrane after 21 d while almost 80% MXF is released. Mimicking the bilayer structure of the native periosteum, the electrospun Janus membrane containing ICA and MXF exhibits excellent comprehensive properties, which provides a promising strategy for preparing multifunctional scaffolds for tissue engineering.

Numerical simulation of gas diffusion and explosion limit of VOCs in containment integrated leak rate test

CILRT is an important work in the overhaul of nuclear power plants. VOCs from paints and cleaners used in the containment during the overhaul will migrate inside the containment, and the numerous rooms and compartments inside the containment make the air flow impeded, and the VOCs may be enriched to bring combustion risk. The complete fire risk analysis method includes volatilization kinetics of chemicals, mixture explosion limits, and numerical simulation of VOCs diffusion and migration. The volatilization rate at the lowest room temperature of 20°C is used as a conservative input, the complement of CAITA realistic model is used as the flow domain, and the geometry is appropriately simplified, and the steady ventilation process, the internal flow and the laws of diffusion and agglomeration of 12 kinds of VOCs gases in the 9-h pressure-holding process are investigated by Computational Fluid Dynamics. The simulation results of steady ventilation show that the VOCs gases are almost uniformly carried by the air to all spaces inside the containment, and the explosion risk is low. The concentration field of the steady ventilation process was taken as the initial boundary condition and unsteady state simulation of the 9-h holding pressure process was performed. The results show that the gas flow inside the containment basically stops after 3456 s of pressure holding. With the extension of time, the VOCs gases accumulate at the bottoms of the three lower layers of the containment under the effect of laminar diffusion and gravitational settling, where the total concentration of the mixed gases reaches the highest at the bottom of the lowest layer. The total concentration of the VOCs gas mixture was below the lower explosion limit throughout the 9-h pressure-holding process, and the explosion risk was low.

A Dual Mode MoTe2/WS2/WSe2 Double Van der Waals Heterojunctions Phototransistor for Optical Imaging and Communication

AbstractVan der Waals (vdW) heterostructures, formed by stacking different two‐dimensional (2D) materials, have emerged as a promising platform for next‐generation optoelectronic devices through band engineering. While various all‐2D and mixed‐dimensional heterojunction phototransistors based on p–n junctions or Schottky junctions have been developed, their performance, often constrained by the trade‐off between responsivity (R) and response speed, limits their widespread application. Here, a dual‐mode phototransistor based on a MoTe2/WS2/WSe2 double vdW heterostructure is designed. The bottom WSe2 layer effectively modulates the entire MoTe2/WS2 heterojunction channel, enabling both photoconductive and photovoltaic modes with exceptional optoelectronic properties in a single device. Specifically, the proposed device exhibits a maximum R of 2540 A W−1 and an impressive specific detectivity of 8 × 1012 Jones under the photoconductive mode. Under the photovoltaic mode, it achieves a fast response speed of 35.3/49.1 µs and a high light on/off ratio of 2 × 105. Additionally, the device exhibits latent potential for high‐resolution imaging across various wavelengths and fast optical communication. This work offers a rational alternative for achieving dual‐mode photodetection and highlights its promising application prospects in imaging and optical communication.

Evolution of Graphene Dirac Fermions in Electric Double‐Layer Transistors with a Soft Barrier

AbstractThe interface and dielectric environment of graphene transistors are of great importance to commercial circuit integrations. The tangling bond in oxide‐based dielectric severely lagged the carrier mobility while the 2D dielectric layer (for instance, hexagonal boron nitride) unavoidably hastened complicated condensed physics even at room temperature. Herein, multilayer black phosphorus (BP) a versatile and widely‐tunable dielectric candidate for manifesting graphene fermions is demonstrated. Because of hetero‐interfacial charge redistributions, a vertical electric double‐layer between the bottom BP layer and top graphene spontaneously forms with the central BP layer as a soft barrier. Under dual‐gate modulation, abnormal step‐like evolution of Dirac fermions and charge‐transfer quantum Hall effect arises while the intrinsic Dirac behavior of graphene is preserved, ascribing to the gate‐tunable charge redistributions of dielectric BP layer. Moreover, the electric double‐layer transistors apply equally well to bilayer graphene with similar Dirac behavior but an enhanced interfacial charge interference. The findings not only create a new avenue to manipulate the fermions by assembling graphene with narrow‐gapped 2D layered materials but also promote electric double‐layer transistors as a new build block to design multifunctional devices.

Comparison of the Properties and Structure of Montmorillonites Modified with Polyvinylpyrrolidone

The modification method of aluminosilicate clays and the modifier content have a decisive influence on the structure and properties of the obtained nanocomposites. Therefore, the development and research of new techniques of nanoclays modification are of great importance for polymer nano-chemistry. The work studied the modification of montmorillonite (MMT) using polyvinylpyrrolidone (PVP) in an aqueous colloidal solution with the subsequent separation of three separate fractions of the solution according to the previously developed method. The influence of the initial mass ratio of components (MMT/PVP) on the structure and thermal properties of the modified MMT in each solution layer was determined. Scanning electron microscopy (SEM), X-ray diffraction (XRD), thermal gravimetry (TG), differential scanning calorimetry (DSC), and Fourier-transform infrared (FTIR) spectroscopy were used for research. It was established that the mass ratio of components in the initial solution has almost no effect on the structure of MMT in the top and middle solution layers, but significantly affects the yield of final products. Different structures can be obtained in the bottom layer of the solution. Still, intercalated MMT was obtained exclusively at the mass ratio of MMT/PVP = 1:2. In addition, the work investigated the structure and thermal properties of modified montmorillonites with the same PVP content, and it has been proven that such composites have dissimilar structures and properties when obtained by different methods.

EXPLORING EPITAXIAL GRAIN GROWTH AND MARANGONI-INDUCED CONVERSION IN COLUMNAR DENDRITES: A STUDY OF INCONEL 718 ADDITIVE MANUFACTURING VIA DIRECT LASER ENERGY DEPOSITION

This study characterizes the microstructure changes of Inconel 718 (IN718) by laser cladding (LC). Well-bonded pore-free, crack-free, single-layer, and multi-layer (overlapped) LC was done on IN718 with the same powder. The basic microstructure illustrates the presence of [Formula: see text], [Formula: see text], and [Formula: see text] -phases. The precipitation of an irregularly shaped laves phase was observed with dendritic grains in the top and bottom regions of the single-track LC. Further, the epitaxial grain growth of columnar dendrites was observed in the interdendritic region along the laves phase. High leveraging of quick-dissolving behaviors of the laves phase in multi-track LC enhances the high-temperature mechanical performance. Modified grain morphology of the multi-track LC in terms of size, shape, and orientation is reported. Columnar dendrites (short and long) are the most common grains, with varied sizes and orientations reported in line with the Marangoni effect. The microhardness at the top layer of single and multi-track exhibited a higher value of 490.6[Formula: see text]HV and 500.7[Formula: see text]HV, respectively, which is comparatively lower than the bottom layer of single and multi-track samples. The influencing process parameter over clad width is scan speed, and over clad height is powder feed. The nonlinear mathematical model is proposed with a reliability of 99.22% and 99.52% for clad width and height, respectively.

High-performance, large-area flexible SERS substrates prepared by reactive ion etching for molecular detection

In the realm of molecular detection, the surface-enhanced Raman scattering (SERS) technique has garnered increasing attention due to its rapid detection, high sensitivity, and non-destructive characteristics. However, conventional rigid SERS substrates are either costly to fabricate and challenging to prepare over a large area, or they exhibit poor uniformity and repeatability, making them unsuitable for inspecting curved object surfaces. In this work, we present a flexible SERS substrate with high sensitivity as well as good uniformity and repeatability. First, the flexible polydimethylsiloxane (PDMS) substrate is manually formulated and cured. SiO2/Ag layer on the substrate can be obtained in a single process by using ion beam sputtering. Then, reactive ion etching is used to etch the upper SiO2 layer of the film, which directly leads to the desired densely packed nanostructure. Finally, a layer of precious metal is deposited on the densely packed nanostructure by thermal evaporation. In our proposed system, the densely packed nanostructure obtained by etching the SiO2 layer directly determines the SERS ability of the substrate. The bottom layer of silver mirror can reflect the penetrative incident light, the spacer layer of SiO2 and the top layer of silver thin film can further localize the light in the system, which can realize the excellent absorption of Raman laser light, thus enhancing SERS ability. In the tests, the prepared substrates show excellent SERS performance in detecting crystalline violet with a detection limit of 10−11 M. The development of this SERS substrate is anticipated to offer a highly effective and convenient method for molecular substance detection.