The reaction of nitrogen with dilute solutions of barium in liquid lithium: electrical resistivity, X-ray phase analysis, kinetic and thermal analysis studies

Abstract

The reaction of nitrogen with liquid lithium containing dissolved barium which follows a solutionprecipitation mechanism has been studied. Initially, nitrogen dissolves in the liquid metal to form an homogeneous solution; t h e reaction is first order with respect to nitrogen with an activation energy of 33.6 k J mol-l. Subsequently, it reacts to form a precipitate of Li,N; the Li,N crystallisation face is dependent on the barium content of the solution, nitrogen solubility rising with increasing barium content. The ternary nitride, LiBaN, is only formed on cooling the solution; there is no evidence for Ba,N or Ba,N, formation. This behaviour contrasts with that in the corresponding Na-M-N (M = Sr or Ba) systems where the solubility is directly proportional to the alkaline-earth metal content of the solution and the precipitating phase is the alkaline-earth metal subnitride, M,N ( M = Sr or Ba). Analysis of the crystallisation fields of Li, Li,Ba, LiBaN and Li,N indicated they are separated by monovariant curves which fall from the binary eutectics (Li-Ba, x,, = 0.1 05 and 416 K; Li-N, degenerate at 453.5 K, Li,N-LiBaN, unknown) through a quasi-peritectic equilibrium involving liquid, lithium, Li,Ba and LiBaN (372 K) to a ternary eutectic point based on liquid, lithium, Li,N and LiBaN (368 K).

Nitridosilicates and Oxonitridosilicates: From Ceramic Materials to Structural and Functional Diversity

“…[158] AlN in particular has received considerable attention, [159,160] but the nitridosilicate materials MgSiN 2 (which can be derived from AlN by replacing 2 Al 3+ by Mg 2+ /Si 4+ ) [161] and more recently b-Si 3 N 4 [162] have also been considered to be potentially effective and rather stable thermal conductors. The thermal conductivities estimated by a modified Slack equation for MgSiN 2 , AlN, and b-Si 3 N 4 ceramics at 300 K equal 28, 200, and 105 W m À1 K À1 , respectively, in agreement with the highest experimental values of [25][26][27]266, and 105-120 W m À1 K À1 . [161,163,164] Further nitridosilicates have been investigated regarding their thermal conductivity.…”

“…The reactions were conducted in closed tantalum crucibles at temperatures of about 900 8C. The ability of liquid lithium to dissolve a variety of metals, [26] inorganic salts, and even complex anions (for example [CN 2 ] 2À ) [27] opened the door to a number of new nitridosilicates. [28,29] Crucial for syntheses of nitrides in liquid alkali metals seems to be a significant solubility of nitrogen, which is even enhanced when alkaline earth metals are added.…”

Nitridosilicate und Oxonitridosilicate: von keramischen Materialien zu struktureller und funktioneller Diversität

“…Die Reaktionen wurden in geschlossenen Tantalampullen bei Temperaturen von ungefähr 900 8C durchgeführt. Die Fähigkeit von flüssigem Lithium, eine Vielzahl von Metallen, [26] anorganischen Salzen und sogar komplexen Anionen wie [CN 2 ] 2À [27] zu lçsen, çffnete den Zugang zu einer Reihe neuartiger Nitridosilicate. [28,29] Bei der Synthese von Nitriden in flüssigen Alkalimetallen scheint die beträchtliche Lçslichkeit von Stickstoff, die sich durch Zusätze von Erdalkalimetallen sogar noch steigern lässt, entscheidend zu sein.…”

Chain‐Type Lithium Rare‐Earth Nitridosilicates – Li5Ln5Si4N12 with Ln = La, Ce

“…Due to the broad spectrum of applications of lithium in radiochemistry the reactivity of liquid lithium with other elements has been well examined. [20][21][22] It has been shown that both nitrogen and silicon are soluble to a comparable extend in liquid lithium, and moreover, a variety of metals can be solved at moderate temperatures in lithium-rich systems as well. [21] Consequently, the use of lithium melts seemed to be a promising approach for the synthesis of novel nitridosilicates.…”