Thermal stability and high-temperature behavior of the natural borate colemanite: An aggregate in radiation-shielding concretes

Abstract

Colemanite is a natural borate that can be used as an aggregate in neutron-radiation shielding concretes. In this study, we report its thermal behavior, up to 500°C, by describing: 1) its dehydration mechanisms and 2) its thermo-elastic parameters. The thermal expansion of colemanite is significantly anisotropic. The refined volume thermal expansion coefficient at ambient conditions is: V0 = 4.50(10)10-5 K-1. The loss of structural H2O occurs at least from ~ 240 °C and at T > 325 °C, an irreversible amorphization occurs, followed by a complete dehydration. The potential implications on the use of colemanite as concrete-aggregate are discussed.

Estimation of gamma-rays, and fast and the thermal neutrons attenuation characteristics for bismuth tellurite and bismuth boro-tellurite glass systems

“…The challenge depends prevailingly upon the type and energy of the radiation. Any material, in principle, can be employed for X-rays, c-rays, and neutron attenuation if it has an appropriate thickness to absorb and/or diffuse incident photons or neutrons to a safer level [2][3][4]. Also, the type of shielding material depends upon the application areas.…”

“…Further, for gamma radiation good shielding ability, and fast and thermal neutron beam absorption, glasses must possess high density, large atomic number, high absorption cross-section, and light elements in composition (e.g., B, Li) for an efficient elastic scattering. In this regard, heavy metal oxides (HMOs) such as Bi 2 O 3 (density = 8.9 g/cm 3 ) and BaO (density = 5.72 g/cm 3 )-based glasses are highly desirable due to their large effective atomic number (Z eff ), high density, and non-toxicity. Here, Bi 2 O 3 closely matches PbO in density and c-ray attenuation (strong absorption of gamma-rays), and due to weak field strength, Bi 3? ion cannot be viewed as a glass former.…”

“…Conversely, B 2 O 3 is a traditional oxide glass former, which exhibits low cationic size (* 41 pm) and high bond strength (* 809 kJ/mol), could be prepared at low melting temperatures, and possesses low viscosity, excellent glass-forming ability, high optical transparency, and heat resistance including moderate RE ion solubility. However, B 2 O 3 glasses show hygroscopic nature, low density (* 2.5 g/cm 3 ), and high phonon energy (* 1300-1500 cm -1 ) [18]. Thus, boro-tellurite glasses demonstrate a combination of borate and tellurite qualities such as the ease of fabrication, enhanced UV transparency, moderate phonon energy, high chemical durability and thermal stability, and contains tetrahedral BO 4 , trigonal BO 3 , trigonal bipyramidal TeO 4 , TeO 3?1 polyhedra, and TeO 3 pyramidal structural units in their network [19,20].…”

“…S5 and P1 ? P6 samples refer to the substitution of lower-density TeO 2 (5.67 g/cm 3 ) and B 2 O 3 (2.46 g/cm 3 ) chemicals with higher-density Bi 2 O 3 (8.9 g/cm 3 ) compound (Tables 1 and 2).…”

Physical-radiation shielding properties of concrete contains colemanite and ulexite

“…Besides those recent works, there has been several studies done using this kind of materials in order to shield radiation including gamma and also neutron. [24][25][26][27][28] In this paper, concrete mixes with different aggregate replacement ratios of colemanite or ulexite ranging from 0% to 50% were produced with increments of 10%. Mechanical properties including compressive strength, flexural strength and elastic modulus were determined.…”