Templated Non-Oxide Sol-Gel Preparation of Well-Ordered Macroporous (inverse opal) Ta₃N₅ Films

Abstract

Reactions of Ta(NMe2)5 and n-propylamine are shown to be an effective system for sol-gel processing of Ta3N5. Ordered macroporous films of Ta3N5 on silica substrates have been prepared by infiltration of such a sol into close-packed sacrificial templates of cross-linked 500 nm polystyrene spheres followed by pyrolysis under ammonia to remove the template and crystallize the Ta3N5. Templates with long-range order were produced by controlled humidity evaporation. Pyrolysis of a sol-infiltrated template at 600 °C removes the polystyrene but does not crystallize Ta3N5, and X-ray diffraction shows nanocrystalline TaN plus amorphous material. Heating at 700 °C crystallizes Ta3N5 while retaining a high degree of pore ordering, whereas at 800 °C porous films with a complete loss of order are obtained.

Precursor chemistry of metal nitride nanocrystals

“…Firing at 600 °C leads to TaN while heating to 800 °C yields Ta 3 N 5 . 88 It is thus clear from the above that nanocrystals of the group 5 nitrides have not been convincingly obtained in colloidal form. While this is the first challenge for the future, the second challenge is to control the oxidation state and the polymorphism of these materials.…”

“…In 2013, a sol–gel pathway was demonstrated with Ta(NMe 2 ) 5 and n -propylamine. 88 Transamination occurs readily but the condensation appears to be slower than for titanium (see section on titanium nitride for details on transamination and condensation). Upon solvent evaporation a gel was formed.…”

Synthesis and processing of silicon nitride and related materials using preceramic polymer and non-oxide sol-gel approaches

“…Reactions of transition metal amides with ammonia are usually poorly controlled, and a less reactive cross-linker such as a primary amine is necessary to achieve controlled sol-gel processing [28,224,225]. Löffelholz et al mixed boron, titanium, zirconium and tantalum dimethylamides with Si(NHMe)4 and achieved gelation by cross-linking with ammonia without a requirement for a catalyst [226,227].…”

Effects of ammonolysis and of sol–gel titanium oxide nitride coating on carbon fibres for use in flexible supercapacitors

“…58 Non-oxide sol-gel methods can be used to produce a range of morphologies including metal nitride powders, lms and porous structures. [59][60][61][62][63] We recently showed that sols based on Ti(NMe 2 ) 4 and n PrNH 2 could be used to coat nanocrystalline LiFePO 4 powders providing an effective conductive surface when the powders were incorporated into lithium battery cathodes. 64 Herein we use an adaptation of that process to coat carbon bres with the aim of exploiting a redox functionality in the coatings to provide increased capacitance.…”