Use of Neural Networks for Lifetime Analysis of Teeming Ladles

When describing the behaviour and modelling of real systems, which are characterized by considerable complexity, great difficulty, and often the impossibility of their formal mathematical description, and whose operational monitoring and measurement are difficult, conventional analytical-statistical models run into the limits of their use. The application of these models leads to necessary simplifications, which cause insufficient adequacy of the resulting mathematical description. In such cases, it is appropriate for modelling to use the methods brought by a new scientific discipline-artificial intelligence. Artificial intelligence provides very promising tools for describing and controlling complex systems. The method of neural networks was chosen for the analysis of the lifetime of the teeming ladle. Artificial neural networks are mathematical models that approximate non-linear functions of an arbitrary waveform. The advantage of neural networks is their ability to generalize the dependencies between individual quantities by learning the presented patterns. This property of a neural network is referred to as generalization. Their use is suitable for processing complex problems where the dependencies between individual quantities are not exactly known.

Manufacturing of Ti-Nb-Cr-V-Ni-Al Refractory High-Entropy Alloys Using Direct Energy Deposition

High-entropy alloys (HEAs) are composed of 5-35 at% of five or more elements, have high configurational entropy, do not form intermetallic compounds, and have a single-phase face-centered cubic structure or body-centered cubic structure. In particular, refractory HEAs (RHEAs), based on refractory materials with excellent mechanical properties at high temperatures, have high strength and hardness at room temperature and excellent mechanical properties at low and high temperatures. In this study, the Ti-Nb-Cr-V-Ni-Al RHEAs were deposited using direct energy deposition (DED). In the microstructure of Ti-Nb-Cr-V-Ni-Al, the sigma, BCC A2, and Ti2Ni phases appeared to be different from the BCC A2, BCC B2, and Laves phases predicted in the phase diagram. This microstructure was similar to that of the casted Ti-Nb-Cr-V-Ni-Al and had a constructed fine grain size. It was found that the growth of these microstructures was due to the DED process, which has a fast solidification rate. The fine grain size caused high hardness, and the microhardness of the Ti-Nb-Cr-V-Ni-Al was measured to be about 900 HV. In addition, in order to analyze the thermal properties of Ti-Nb-Cr-V-Ni-Al composed of the refractory material, the heat-affected zone (HAZ) was analyzed through a preheating test. The HAZ was decreased, owing to the high thermal diffusivity of Ti-Nb-Cr-V-Ni-Al.

Ultrathin TiN Epitaxial Films as Transparent Conductive Electrodes

Titanium nitride (TiN), a transition-metal compound with tight covalent Ti-N bonding, has a high melting temperature and superior mechanical and chemical stabilities compared to noble metals. With a reduction in thickness, the optical transmittance of TiN films can be drastically increased, and in combination with its excellent electrical conductivity, the ultrathin and continuous TiN film can be considered as an ideal alternative of the metal oxide electrodes. However, the deposition of ultrathin and continuous metallic layer with a smooth surface morphology is a major challenge for typical deposition methods such as thermal evaporation or reactive sputtering. In particular, defects mainly related with oxygen contents and surface scattering can significantly limit the performance of ultrathin TiN films. In this work, ultrathin TiN films with 2-10 nm in thickness are grown by using the nitrogen plasma-assisted molecular-beam epitaxy (MBE) method in an ultrahigh vacuum environment. Excellent surface morphology with a root-mean-square roughness of ≤0.12 nm and a high optical transparency of 75% over the whole visible regime are achieved for ultrathin TiN epitaxial films. The dielectric properties determined by the spectroscopic ellipsometry and the electrical properties measured by the terahertz spectroscopy and the Hall effect method reveal that the percolation thickness of the TiN epitaxial film is less than 2.4 nm and its electrical conductivity is higher than 1.1 × 10⁴ Ω^-1 cm^-1. These features make MBE-grown ultrathin TiN epitaxial films a good candidate for robust, low cost, and large-area transparent conductive electrodes.

Broadband Absorption Based on Thin Refractory Titanium Nitride Patterned Film Metasurface

In this paper, a thin metasurface perfect absorber based on refractory titanium nitride (TiN) is proposed. The size parameter of the metasurface is investigated based on the finite difference time domain method and transfer matrix method. With only a 15-nm-thick TiN layer inside the silica/TiN/silica stacks standing on the TiN substrate, the near-perfect absorption throughout the visible regime is realized. The cross-talk between the upper and lower dielectric layers enables the broadening of the absorption peak. After patterning the thin film into a nanodisk array, the resonances from the nanodisk array emerge to broaden the high absorption bandwidth. As a result, the proposed metasurface achieves perfect absorption in the waveband from 400 to 2000 nm with an average absorption of 95% and polarization-insensitivity under the normal incidence. The proposed metasurface maintains average absorbance of 90% up to 50-degree oblique incidence for unpolarized light. Our work shows promising potential in the application of solar energy harvesting and other applications requiring refractory metasurfaces.

Refractory materials and plasmonics based perfect absorbers

In the past decades, metamaterial light absorbers have attracted tremendous attention due to their impressive absorption efficiency and significant potential for multiple kinds of applications. However, the conventional noble metals based metamaterial and nanomaterial absorbers always suffer from the structural damage by the local high temperature resulting from the strong plasmonic photo-thermal effects. To address this challenge, intensive research has been conducted to develop the absorbers which can realize efficient light absorption and simultaneously keep the structural stability under high temperatures. In this review, we present detail discussion on the refractory materials which can provide robust thermal stability and high performance for light absorption. Moreover, promising theoretical designs and experimental demonstrations that possess excellent features are also reviewed, including broadband strong light absorption, high temperature durability, and even the easy-to-fabricate configuration. Some applications challenges and prospects of refractory materials based plasmonic perfect absorbers are also introduced and discussed.

Quadratic Meta-Reflectors Made of HfO2 Nanopillars with a Large Field of View at Infrared Wavelengths

Metasurfaces, being composed of subwavelength nanostructures, can achieve peculiar optical manipulations of phase, amplitude, etc. A large field of view (FOV) is always one of the most desirable characteristics of optical systems. In this study, metasurface-based quadratic reflectors (i.e., meta-reflectors) made of HfO₂ nanopillars are investigated to realize a large FOV at infrared wavelengths. First, the geometrical dependence of HfO₂ nanopillars' phase difference is analyzed to show the general principles of designing infrared HfO₂ metasurfaces. Then, two meta-reflectors with a quadratic phase profile are investigated to show their large FOV, subwavelength resolution, and long focal depth. Furthermore, the two quadratic reflectors also show a large FOV when deflecting a laser beam with a deflecting-angle range of approximately ±80°. This study presents a flat optical metamaterial with a large FOV for imaging and deflecting, which can greatly simplify the optical-mechanical complexity of infrared systems, particularly with potential applications in high-power optical systems.

Analysis and Prediction of Corrosion of Refractory Materials by Potassium during Biomass Combustion-Thermodynamic Study

As a kind of renewable resource, biomass has been used more and more widely, but the potassium contained in biomass can cause corrosion of the refractory. For a better understanding of corrosion thermodynamic mechanisms, the five components of common refractory materials (magnesium chrome spinel MgO·Cr₂O₃, magnesium aluminum spinel MgO·Al₂O₃, Al₂O₃, MgO, and Cr₂O₃) with potassium salts (K₂CO₃, K₂SO₄, and KCl) under high-temperature were studied by using the FactSage^TM 7.0 software. Thermodynamic calculation results indicate that MgO is the best corrosion resistance of the five components of refractory materials. Based on the obtained results, the corrosion experiments in the laboratory were carried out (muffle furnace or high-temperature tube furnace) for corrosion reaction of KCl and MgO. The chemical compositions of the corroded samples were analyzed by X-ray diffraction (XRD). Under laboratory conditions (600–1200 °C), no corrosion products have been observed in the high-temperature corrosion experiments. The result indicates that to prevent the corrosion processes, refractories should contain as much MgO as possible.