Optical properties of refractory TiN, AlN and (Ti,Al)N coatings

© 2015 SPIE. Titanium nitride is a golden-colored semiconductor with metallic optical properties. It is already widely used in room temperature spectrally-selective coatings. In contrast, aluminum nitride is a relatively wide-band gap, non-metallic material. Both nitrides have exceptional thermal stability, to over 1000 °C, but are susceptible to oxidation. We will show here that composite coatings consisting of these materials and their complex oxides have considerable potential for spectrally-selective applications, including at elevated temperatures. In particular, we examine the metastable materials produced by magnetron sputtering. The effective dielectric functions of these materials can be tuned over a wide range by manipulation of their microstructure. This provides a strategy to assemble materials with tunable dielectric functions using a 'bottom-up' approach. The results are compared to those achievable by conventional, 'top-down', planar optical stacks comprised of alternating layers of TiNx and AlN

Spectrally Selective Solar Absorbers based on Ta:SiO 2 Cermets for Next‐Generation Concentrated Solar–Thermal Applications

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim An iterative algorithm is used to design a spectrally selective thin-film stack to provide maximum solar-to-thermal conversion efficiency at the very high operating temperatures associated with high solar concentrations. The resulting stack is then fabricated by magnetron sputtering and characterized. It is composed of two Ta:SiO2 layers with differing Ta nanoparticle contents on a refractory metal substrate. A SiO2 antireflecting overlayer completes the stack. Optical and microstructural characterizations indicate that the stack achieves 97.6% solar absorptance up to 900 °C. Spectral selectivity and thermal stability improve on annealing in two ways, first, due to recrystallization of Pt or Ta back reflectors which lowers room temperature thermal emittance to 0.15 from 0.18, and to 0.14 from 0.21, respectively; and second, due to alloying of substrate atoms with the Ta nanoparticles of the cermet

High temperature optically stable spectrally-selective Ti<inf>1-x</inf>Al<inf>x</inf>N-based multilayer coating for concentrated solar thermal applications

© 2019 Elsevier B.V. Spectrally-selective solar absorbing coatings based on the Ti1-xAlxN system were deposited using DC magnetron sputtering. Due to their refractory nature and very suitable optical properties, these were considered for high temperature solar thermal energy conversion. The composition of Ti1-xAlxN, (effectively, the Ti/Al ratio) was optimized to achieve a maximized solar absorptance. The optimum composition was then tested in a tandem absorber which included anti-reflective layers. A stainless steel substrate was used in order to simulate service in parabolic trough-based power plants that use stainless steel pipe to carry the heat-transfer fluid. High temperature annealing of the stack caused structural modifications but the solar absorptance of 92% was retained even after annealing at 900 °C

Electrical excitation and charge-state conversion of silicon vacancy color centers in single-crystal diamond membranes

© 2020 Author(s). The silicon-vacancy (SiV) color center in diamond has recently emerged as a promising qubit for quantum photonics. However, the electrical control and excitation of the SiV centers are challenging due to the low density of free carriers in doped diamond. Here, we realize electrical excitation of SiV centers in a single-crystal diamond membrane, which is promising for scalable photonic architectures. We further demonstrate electrical switching of the charge states of the SiV centers by applying a forward bias voltage to the fabricated diamond-membrane devices and identify the position of the SiV-/SiV0 charge transition level. Our findings provide a perspective toward electrical triggering of color centers in diamond and accelerate the development of scalable quantum nanophotonic technologies

Choice of Weapon Sample Based on Fuzzy Logic in Defense Management Measures

The possibility of improving the capability-based planning process is being investigated in order to minimize the need for weapons and military equipment and to maximize the acquisition of capabilities during their life cycle. Using the theory of fuzzy sets, the assessment of alternative samples of weapons and military equipment is carried out. A fuzzy inference model for determining the usefulness of weapons and military equipment in acquiring opportunities has been developed, based on fuzzy logic. The modeling of alternative models of weapons and military equipment was carried out in terms of costs at the stages of the life cycle “Use” and “Support” using the modern software environment MATLAB. The simulation results provided an opportunity at the planning stage to improve the efficiency of defense resource management using the value of the usefulness of weapons and military equipment. The introduction of the developed model into defense management makes it possible to automatically determine weapons and military equipment without the participation of experts, taking into account the cost of their life cycle and to bring the planning process closer to Euro-Atlantic approaches