Titanium diboride ceramics for solar thermal absorbers

Abstract

Titanium diboride (TiB2) is a low-density refractory material belonging to the family of ultra-high temperature ceramics (UHTCs). This paper reports on the production and microstructural and optical characterization of nearly fully dense TiB2, with particular interest to its potential utilization as novel thermal solar absorber. Monolithic bulk samples are produced starting from elemental reactants by a two-step method consisting of the Self-propagating High-temperature Synthesis (SHS) followed by the Spark Plasma Sintering (SPS) of the resulting powders. 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

SiC-TiC nanocomposite for bulk solar absorbers applications: Effect of density and surface roughness on the optical properties

“…However, SiC is not spectrally selective as it has a high spectral emittance [8,9]. Transition metal carbides, nitrides and borides of column IV have been subject of many investigations due to their inherent spectral selectivity [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Among these materials, titanium carbide could be a good candidate because it is spectrally selective and it has good mechanical properties.…”

An overview of ultra-refractory ceramics for thermodynamic solar energy generation at high temperature

“…The base properties outlined in this and previous studies [13,14,16,17,28] can be the starting point for future development of ground-breaking materials with specific properties tunable according to the needs imposed by the application.…”

“…The increasing interest in these materials is due to their unique combination of properties, including the highest melting points of any group of materials, >3000°C, elevate strength at extreme temperature, like 600-800 MPa at 1500-2100°C [11], high thermal conductivity, 80-110 W/mK up to 2000°C [12] and chemical stability. Recently, it has been found that most of these compounds also have the characteristic of being intrinsic solar selective materials [13][14][15][16][17][18][19], but the understanding of the optical properties of these materials is still very scanty, especially at high temperature. UHTCs have thus the potential to be suited for application in high temperature solar receivers, once their basic properties have been properly investigated and correlated to the bulk and surface characteristics.…”

“…Particular emphasis was devoted to identify their correlation with relevant material characteristics, such as compositions, porosity, surface finishing. Several ultra-refractory boride and carbides have been studied in the framework of the project [13][14][15][16][17], allowing to identify the most promising materials for solar absorber applications. This work describes, as a case study, an extensive work on ZrB 2based ceramics, consolidated through different processes, with or without MoSi 2 as secondary phase, textured or with controlled porosity.…”

“…A clearer picture of the complex relationships amongst process-microstructure-optical properties of UHTCs can be defined taking advantage of our experience gained in recent years on this subject [13,14,16,17,28]. In particular, the research activity revealed interesting findings, but also pointed out some critical issues in the use of UHTCs as solar absorbers.…”