Applied Research最新文献

The present study focuses on the archaeometric investigation of 10 brown tesserae belonging to Early Christian/Byzantine wall mosaics of three monuments of Thessaloniki, inscribed on the World Heritage List of UNESCO: Rotunda, St. Sophia, and St. Demetrios. The tesserae were analyzed via optical microscopy (OM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and UV-Vis reflectance spectroscopy to define their composition and technological characteristics. Nine of the tesserae are made of silica glass while one tessera is made of a siliceous rock. The majority of the glass tesserae, despite the chronological distance of the monuments they were collected from, present similar technological features, base glass composition, colorants, and opacifiers. Metallic copper is the main element responsible for the brown color in relation to iron which serves as a reducing agent. Opacification is attributed to tin compounds.

The pressure response of crystalline trans-cinnamic acid is studied by means of Raman spectroscopy up to 6 GPa. Pressure application causes the reversible shift of all the observed Raman peaks to higher frequencies and changes in their relative intensities, with the intermolecular vibrational modes being by far more sensitive to pressurization compared to the intramolecular ones. The present high-pressure Raman data indicate the structural stability of the trans-cinnamic acid crystal and molecular conformation up to the highest pressure attained in the experiments, the importance of the hydrogen bonding, as well as the considerable strengthening of the intermolecular interactions at elevated pressures.

A rapid headspace gas chromatography method has been developed for the determination of residual organic solvents in photoinitiators. Using water-glyceryl triacetate as the solvent, the method was used to determine the residual levels of 11 volatile organic compounds (VOCs), namely, benzene, toluene, xylene, methanol, ethanol, acetonitrile, acetone, n-hexane, dichloromethane, tetrahydrofuran, and ethyl acetate, in photoinitiators. Under the selected instrument operating conditions, all the residual solvents were completely separated. A detailed analysis was conducted on these 11 organic solvents. The mass concentrations of these solvents were linearly correlated with the chromatographic peak area, with a linear R² is called determination coefficient R² ≥ 0.99, and the relative standard deviation (n = 5) was less than 5.8%. The recovery rates of n-hexane and toluene were 90.3% and 102.9%, respectively. The method exhibits good precision and accuracy, making it suitable for the rapid detection and inspection of 11 residual VOC components in photoinitiators. The practical applicability of the method was evaluated by blue applicability grade index and the score was 75.0 demonstrating its good practicality and applicability.

Selective laser melting (SLM) is a contemporary manufacturing method that offers numerous advantages for producing various components. This research focuses on the examination of a dental implant sample fabricated using the SLM method. The investigation encompasses multiple aspects, including hardness, dimensional accuracy, strength, and surface properties. The results demonstrate that the hardness of the SLM sample is comparable to that of machined samples, establishing it as a viable alternative to traditional production methods. Dimensional tests reveal that the SLM sample adheres to the required acceptance limits for critical dimensions. The strength of the sample, with a value of 700 MPa, proves to be acceptable for medical applications. The presence of surface porosity and holes in the SLM sample highlights its potential for enhanced bone ossification. However, challenges associated with thread construction in the SLM process require further attention. Overall, this research showcases the promising aspects of the SLM method for dental implant production, while also identifying areas for future investigation and improvement.

Effective manipulation and control of fluids in microfluidic channels requires robust bonding between the different components. Polydimethylsiloxane (PDMS) is widely employed in microchannel fabrication due to its affordability, biocompatibility, and straightforward fabrication process. However, PDMS's low surface energy poses challenges in bonding with many organic and inorganic substrates, hindering the development of hybrid microfluidic devices. In this study, a simple and versatile three step process is presented for bonding PDMS microchannels with organic (cyclic olefin copolymer (COC)) and inorganic substrates (lithium niobate (LiNbO₃)) using plasma activation and a silane coupling agent. Initially, the PDMS surface undergoes oxygen/argon plasma activation, followed by functionalization with (3-aminopropyl) triethoxysilane (APTES). Subsequently, the COC or LiNbO₃ is plasma activated and brought into contact with PDMS under a load at a specific temperature. Characterization by Fourier transform infrared, scanning electron microscopy, atomic force microscopy, and contact angle measurements confirmed the successful treatment of the substrates. In addition, bonding strength of the fabricated hybrid devices was assessed through leakage and tensile tests. Under optimized conditions (100°C and 4% v/v APTES), PDMS-COC hybrid microchannels achieved a flow rate of 600 mL/h without leakage and a tensile strength of 562 kPa. Conversely, the PDMS- LiNbO₃ assembly demonstrated a flow rate of 216 mL/h before leakage, with a tensile strength of 334 kPa. This bonding method exhibits significant potential and versatility for various materials in microfluidic applications, ranging from biomedical research to enhanced oil recovery.

The absorption spectra of various sizes of nanoparticles of copper (Cu), silver (Ag), and gold (Au) are theoretically investigated. The density functional theory (DFT), time-dependent DFT (TDDFT), and real-time TDDFT are used to demonstrate how size and shape affect their optical properties and how these are evolved as the number of atoms increases. For this reason, the focus was turned on almost spherical nanoparticles cut out from the corresponding crystal structure (called 0D), elongated ones (1D), and flattened ones (2D). The nature of the observed absorption peaks is further analyzed with the help of transition contribution maps and induced density plots which help us identify the emergence of probable plasmonic resonances as the size of the nanoparticles increases.

In this paper, molecular dynamics (MD) simulations and machine learning (ML) methods are combined to obtain the transport properties, such as viscosity and thermal conductivity, of five basic elements, which are computationally hard to obtain at the nanoscale and extremely demanding to estimate accurately through an experimental procedure. Starting from an experimental database from literature sources, we extend the (P-T) space on which the transport properties are calculated by employing MD simulations and ML predictions, in a synergistic mode. Results refer to all fluid states (gas, liquid, supercritical), under ambient and supercritical conditions, suggesting an alternative path that can be accurately followed to bypass expensive experiments and costly numerical simulations. Nine different ML algorithms are exploited and assessed on their prediction ability, with tree-based architectures achieving increased accuracy on the implied data set. The proposed computational platform runs fast in a common python Jupyter environment, both for MD and ML, and can be adjusted and extended for the calculation of material properties both in interpolation and extrapolation applications.

Over the past several years, atomically thin two-dimensional carbides, nitrides, and carbonitrides, otherwise known as MXenes, have been expanded into over fifty material candidates that are experimentally produced, and over one hundred fifty more candidates that have been theoretically predicted. They have demonstrated transformative properties such as metallic-type electrical conductivities, optical properties such as plasmonics and optical nonlinearity, and key surface properties such as hydrophilicity, and unique surface chemistry. In terms of their applications, they are poised to transform technological areas such as energy storage, electromagnetic shielding, electronics, photonics, optoelectronics, sensing, and bioelectronics. One of the most promising aspects of MXene's future application in all the above areas of interest, we believe, is reliably developing their flexible and bendable electronics and optoelectronics by printing methods (henceforth, termed as printed flexible MXetronics). Designing and manipulating MXene conductive inks according to the application requirements will therefore be a transformative goal for future printed flexible MXetronics. MXene's combined property of high electrical conductivity and water-friendly nature to easily disperse its micro/nano-flakes in an aqueous medium without any binder paves the way for designing additive-free highly conductive MXene ink. However, the chemical and/or structural and hence functional stability of water based MXene inks over time is not reliable, opening research avenues for further development of stable and conductive MXene inks. Such priorities will enable applications requiring high-resolution and highly reliable printed MXene electronics using state-of-the art printing methods. Engineering MXene structural and surface functional properties while tuning MXene ink rheology in benign solvents of choice will be a key for ink developments. This review article summarizes the present status and prospects of MXene inks and their use in inkjet-printed (IJP) technology for future flexible and bendable MXetronics.

Recently, rhenium (Re) based ohmic contacts to GaN have been studied for their low resistivity, smooth surface morphology, and sharp edge acuity at low annealing temperatures. In this work, we discuss the evolution of surface microstructures for Re-Al-Ni-Au ohmic contacts on n-GaN as a function of Re layer thickness and annealing temperature. For all Re thicknesses, the Al and Ni segregate into agglomerates that increase in size with increasing annealing temperature. These agglomerates are surrounded by Al-Au films. Along with the underlying Re layer, they form different crystallographic phases of Re-Al-Ni, Al₆Re, AlAu₂, and Al₂Au₅. This, along with the formation of Re-N phases at the metal-semiconductor interface leads to low resistivity ohmic contacts on n-GaN. Investigating the evolution of the contact microstructure is an important step in understanding the behavior of the Re-based ohmic contact system.

The development of metal matrix composites is important for industrial applications that require lightweight materials with high strength, stiffness, and wear resistance. In this investigation, Al2024 alloy was reinforced with fly ash and silicon (SiC) carbide hybrid composites using the stir-squeeze cast technique. Two sets of composites were fabricated: one with 3 wt% fly ash and 3 wt% SiC, and the other with 3 wt% fly ash, 5 wt% SiC, and 3 wt% fly ash, 7 wt% SiC The composites were prepared using 25 and 75 mm diameter dies. Microstructural characterization of the specimens was performed using scanning electron microscope, X-ray powder diffraction, and energy dispersive X-ray spectroscopy analysis. Mechanical properties, such as yield strength, ultimate tensile strength, and hardness, were determined according to American Society for Testing and Materials standards. The hybrid composites fabricated in the 25 mm diameter cast iron molds exhibited superior mechanical properties compared to those prepared in the 75 mm diameter molds. The addition of fly ash and SiC particulates enhanced the mechanical properties of the Al2024 alloy. These composites showed improved strength, toughness, and ductility.