Optical properties of dense zirconium and tantalum diborides for solar thermal absorbers

Abstract

Ultra-high temperature ceramics (UHTCs) are interesting materials for a large variety of applications under extreme conditions. This paper reports on the production and extensive characterization of highly dense, pure zirconium and tantalum diborides, with particular interest to their potential utilization in the thermal solar energy field. Monolithic bulk samples are produced by Spark Plasma Sintering starting from elemental reactants or using metal diboride powders previously synthesized by Self-propagating High-temperature Synthesis (SHS). Microstructural and optical properties of products obtained by the two processing methods have been comparatively evaluated. We found that pure diborides show a good spectral selectivity, which is an appealing characteristic for solar absorber applications. No, or very small, differences in the optical properties have been evidenced when the two investigated processes adopted for the fabrication of dense TaB2 and ZrB2, respectively, are compared

Elastic properties, thermal stability, and thermodynamic parameters of MoAlB

“…1(b). The density of 6.45 g/cm 3 determined by the Archimedes method suggests that all samples were fully dense.…”

“…where D is the experimentally measured thermal diffusivity value and ρ is the sample density (6.45 g/cm 3 ). Based on these results, κ tot is 25.6 W m −1 K −1 at 373 K and decreases gradually to 22.3 W m −1 K −1 at 1073 K. In other words, its temperature dependence is relatively weak.…”

“…These properties, among others, make them useful for applications ranging from wear-resistant coatings [1], refractory crucibles, high-temperature (HT) electrodes [2], solar absorbers [3], permanent magnets [4], and primary battery electrodes [5][6][7]. Despite renewed interest in the binary TMBs for structural aerospace components related to hypersonic flight and atmospheric reentry of space vehicles, these compounds in their nominally pure form suffer from poor oxidation resistance in air above 1200…”

Titanium diboride ceramics for solar thermal absorbers

“…The surface of obtained samples has-been characterized from the microstructural and topological points of view. The hemispherical reflectance spectrum has been measured from 0.3 to 15 µm wavelength, to evaluate the potential of this material as solar absorber for future concentrating solar plants.selectivity which makes them appealing for sunlight absorption up to very high temperatures with reduced thermal losses [3][4][5][6][7][8][9][10][11]. Moreover, these materials also have well known characteristics such as ultra-refractoriness, good chemical stability at high temperature, good thermal conductivity, hardness and superior mechanical properties [12][13][14][15], which have implied their successful use for aerospace, military and, in general, for all applications where high temperatures conjugate extremely demanding performances [12][13][14][15][16][17][18].…”

“…Indeed, the only literature source is limited to the spectral range from 0.4 to 1.0μm and is referred to thin films [52].The present investigation is first aimed to the optimization of the SPS conditions for the full densification of additive free TiB2 powders synthesized by SHS. In this regard, it should be noted that the combination of the SHS and the SPS techniques was recently exploited for the fabrication of other UHTC systems, both in monolithic [11,53,54] and composite forms [55][56][57][58][59].Subsequently, in the present work we report on microstructure, topological characterization, and hemispherical reflectance spectra in the wavelength range 0.3-15 μm of TiB2 produced by the twosteps SHS-SPS technique, with the aim to evaluate the material potential for solar absorber applications.…”