Ein Strontium‐ und Chlor‐freies rotes pyrotechnisches Leuchtsignal mit hoher spektraler Reinheit

Abstract

Durchd ie drohende Reglementierung der in roten pyrotechnischen Leuchtsätzen enthaltenen Strontium-und Organochlorverbindungen durchd ie US-Umweltschutzbehçrder ichtet sich der Fokus zunehmend auf die Entwicklung alternativer chlorfreier Leuchtsätze.A us diesem Grund berichten wir über die Entwicklung Lithium-basierter roter Leuchtsätze mit hoher Farbqualitätu nd Lichtreinheit. Diese Formulierungen verzichten vollkommen auf Strontium und Organochlorverbindungen. Stattdessen fungiert ein neu synthetisiertes,n ichth ygroskopisches,s tickstoffreiches Dilithiumsalz gleichzeitig als Oxidationsmittel und Farbgeber.D ie Lithium-basierten Mischungen kçnnen sowohli mm ilitärischen als auch im zivilen Bereicha ls Ausgangspunkt fürd ie Entwicklung von umwelt-und gesundheitsverträglicheren Leuchtsätzen dienen.

Comparison of Functionalized Lithium Dihydrobis(azolyl)borates with Their Corresponding Azolates as Environmentally Friendly Red Pyrotechnic Coloring Agents

“…In contrast to all other elements mentioned above, in the case of lithium it is the metastable atomic species, which provokes two emission lines of high intensity at 671 and 610 nm . Regarding that chlorine donors have fallen into disrepute due to their combustion to highly carcinogenic polychlorinated aromatics, this is a further advantage of lithium. The presence of chlorine is even considered to have an adverse effect on the light output of a lithium‐containing pyrotechnic formulation .…”

“…Furthermore, the probability of higher energetic electron transitions leading to a blue shift of the dominant wavelength should be low, if cool flame temperatures are adjusted . Despite all this theoretical knowledge on lithium flame chemistry the selection of chlorine‐free lithium‐based pyrotechnic compositions is very narrow . Additionally, a significant percentage of these show a burning behavior rather comparable to a strobe than to a flare, which might be due to the strong tendency of lithium to attract water in some form.…”

The Lithium Salts of Bis(azolyl)borates as Strontium‐ and Chlorine‐free Red Pyrotechnic Colorants

“…[4] Lithium is the only other element capable of producing a color close to the desired purplish red of strontium in a pyrotechnic composition as shown by Klapötke et al with the example of dilithium 3,3Ј-diamino-4,4Ј-dinitramino-5,5Ј-bi-1,2,4-triazolate trihydrate (Li 2 ANAT). [5] The low health hazard posed by lithium is expressed by its application in the treatment of mental disorders. [6] As in the case of a lithium-containing pyrotechnic composition gaseous atomic lithium is the metastable red light-emitter to be formed during burn-down, [7] requirements of a low combustion temperature and a reducing flame atmosphere for a lithium-based red-burning composition.…”

“…Lithium is the only other element capable of producing a color close to the desired purplish red of strontium in a pyrotechnic composition as shown by Klapötke et al with the example of dilithium 3,3'‐diamino‐4,4'‐dinitramino‐5,5'‐bi‐1,2,4‐triazolate trihydrate (Li 2 ANAT) . The low health hazard posed by lithium is expressed by its application in the treatment of mental disorders .…”

“…As in the case of a lithium‐containing pyrotechnic composition gaseous atomic lithium is the metastable red light‐emitter to be formed during burn‐down, special precautions have to be taken in order to achieve a satisfying color performance. In contrast to molecular strontium(I) chloride elemental lithium produces two distinct emission lines at 671 and 610 nm, which are covered by any kind of continuum. When lithium reacts with water vapor in the flame to give gaseous lithium hydroxide or when magnesium combusts to solid magnesium oxide, such a broad emission band occurs and a rather pinkish flame color is observed , .…”