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Group VIA of 2D Xenes materials
Published in Zongyu Huang, Xiang Qi, Jianxin Zhong, 2D Monoelemental Materials (Xenes) and Related Technologies, 2022
Chemical vapor deposition (CVD) has also been reported to synthesis 2D Te nanoflakes. Zhang et al. developed a hydrogen-assisted CVD method and successfully synthesized ultrathin Te nanoflakes on mica substrate.8 As illustrated in Figure 5.2(g), during the reaction proceeds, tellurium dioxide (TeO2) was employed as Te precursor and H2 was used as the reducing atmosphere. The as-synthesized Te nanoflakes exhibited the triangular shape, and the thickness of thinnest sample could be down to 5 nm (Figure 5.2(h)). The DFT calculations and experiments confirmed the growth mechanism origins from the formation of volatile intermediates, which increased the vapor pressure of the source and promoted the reaction.
Tellurium Behavior in the Containment Sump: Dissolution, Redox, and Radiolysis Effects
Published in Nuclear Technology, 2021
Anna-Elina Pasi, Henrik Glänneskog, Mark R. St.-J Foreman, Christian Ekberg
In aqueous solution, tellurium speciation is highly dependent on redox and pH conditions.21 Tellurium can exist in oxidation states −2, +2, +4, and +6, of which +4 and +6 are the most abundant in natural waters.39 Solid elemental tellurium is stable in water or aqueous solution but not in extremely alkaline solution (pH > 10) or in the presence of an oxidizing agent. If elemental tellurium is brought to an aerated solution, it is covered by tellurium dioxide, TeO2 (Ref. 40), which is an amphoteric compound and thus can act as an acid or a base depending on the prevailing conditions. The dominant Te(IV) species in neutral aqueous solution is tellurous(IV) acid H2TeO3, which can undergo either protonation to form a cationic product or deprotonation to form anionic products, depending on the pH. The solubility of TeO2 is relatively low with a minimum at around 2.1 × 10−10 mol/dm3 at pH 5.5 (Ref. 41). However, the solubility increases in both extremes of the pH scale when TeO2 dissolves as an ionic species. This is a result of the amphoteric nature of TeO2. In a hydrated form, TeO2•H2O, the solubility increases significantly and reaches a maximum at 1.6 × 10−2 mol/dm3 in alkaline solution.41 Chemical equilibrium and thermodynamic data for Te(IV) species are presented in Table II (Refs. 14 and 21).