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Atomic layer deposition
Published in Michel Houssa, κ Gate Dielectrics, 2003
Precursors should not etch the material formed during the deposition process, but in a few cases this has been found to occur. An example related to the high-κ gate oxides is etching of niobium oxide by niobium chloride through formation of niobium oxychloride: Nb2O5(s)+3NbCl5(g)→5NbOCl3(g)
Introduction
Published in Kwang Leong Choy, Chemical Vapour Deposition (CVD), 2019
CVD performed at atmospheric pressure is called atmospheric pressure CVD. The CVD process was initially performed at atmospheric pressure in the 1880s for the preparation of carbon fibre [145], whereby a filament (e.g., pencil carbon) was heated in an organic solution (e.g., naphtha, turpentine, beeswax, balsam). Another example is the metal (e.g., Nb, Ta) deposited onto the carbon filament from the chemical reduction reaction of metal chloride (e.g., Niobium Chloride) gaseous precursor in hydrogen with a heating source such as a Bunsen burner, according to the equation
Introduction
Published in Kwang Leong Choy, Chemical Vapour Deposition (CVD), 2019
CVD performed at atmospheric pressure is called atmospheric pressure CVD. The CVD process was initially performed at atmospheric pressure in the 1880s for the preparation of carbon fibre [145], whereby a filament (e.g., pencil carbon) was heated in an organic solution (e.g., naphtha, turpentine, beeswax, balsam). Another example is the metal (e.g., Nb, Ta) deposited onto the carbon filament from the chemical reduction reaction of metal chloride (e.g., Niobium Chloride) gaseous precursor in hydrogen with a heating source such as a Bunsen burner, according to the equation
The Tantalum Metals (1801–1866): Nineteenth-Century Analytical Chemistry and the Identification of Chemical Elements
Published in Ambix, 2022
Although niobium is generally named as Rose’s most important discovery, he did not develop any fundamentally new methods in order to identify it. Rather, he relied on various chemical tests which had been added as additional steps in the classical “wet” and “dry” methods during the preceding decades. Rose followed Berzelius’ approach both for the analysis of tantalite minerals and the production of (what he thought was) metallic niobium.42 Among his tests for detecting niobium was also a blue colouration that had initially been identified by Friedrich Wöhler (1800–1882) as a property of tantalic acid.43 Furthermore, he had adopted his predecessors’ habit of characterising the chlorides in addition to the oxides. Thus, for example, Rose claimed the discovery of the metal pelopium on the basis of his production of a distinct metallic acid from a white chloride which, contrary to tantalum and niobium chloride, turned yellow when heated.44
Visible-light Bi-Fe-Nb-O photoanodes for solar-light driven hydrogen production
Published in Environmental Technology, 2021
Allan Ramone de Araujo Scharnberg, Felipe Amorim Berutti, Annelise Kopp Alves
To produce the photoanodes, four syntheses were performed, varying the iron amount (Bi2FeXNbO7, x = 0, 0.8, 1, 1.2). The films were synthetized by sol gel method in three stages: (a) dissolution of the stoichiometric amounts of metal precursor, iron nitrate, (Fe(NO3)3.9H2O/Synth) in 5 ml of Acetylacetone (Sigma-Aldrich) under magnetic stirring for 15 min. Parallel to this process, stoichiometric quantities of bismuth nitrate (Bi(NO3)3.5H2O/Vetec) were solubilized in 5 ml of Acetylacetone under magnetic stirring for 15 minutes. Niobium chloride (NbCl5) was solubilized in 4 ml of hydrochloric acid under magnetic stirring for 5 min. (b) After total mix of both, the solution containing bismuth was homogenized with the solution containing iron. (c) Then, the niobium containing solution was titrated to the above, kept under constant stirring until complete homogenization, forming a uniform orange-yellow coloration sol. The synthesis occurred at ambient temperature (25°C), and in an acid medium (pH ∼ 5). Figure 1 illustrates the synthesis process and photoanodes fabrication. More details of this synthesis were published elsewhere [31].
Recovery of Zirconium from Zircaloys Using a Hydrochlorination Process
Published in Nuclear Technology, 2021
Rosendo Borjas Nevarez, Bruce McNamara, Frederic Poineau
The Zr + Nb TGA plot, Fig. 9a, shows two mass loss curves. The first curve corresponds to the evaporation of NbCl5 and represents a 50% sample loss. The second curve corresponds to the sublimation of ZrCl4 and represents an additional 35% mass loss. The 14% mass residue suggests the presence of oxides or oxychlorides in this sample as well. The Zr + Nb DSC plot, Fig. 9b, also shows a positive slope for the first part of the run. There are three main endothermic peaks. The first peak at 195°C matches the niobium chloride evaporation curve. The second peak at 256°C matches ZrCl4 sublimation. The loop-shaped peak near 325°C is caused by a phase transition of the nonvolatile material.