Catalytic ammonolytic sol–gel preparation of a mesoporous silicon aluminium nitride from a single-source precursor

Sol–gel preparation of low oxygen content, high surface area silicon nitride and imidonitride materials

“…Fitting the PDF data up to 10 Å to the Rietveld-derived structure ( Fig. 6 and Table S2 †) resulted in lattice parameters of a = 7.760 (14) and c = 5.614(18) Å, a good match to both the Rietveld fit and the literature values for…”

“…13 Sol-gel processing from [Si(µ-NH)(NMe 2 ) 2 ] 3 has used trifluoromethanesulfonic (triflic) acid as a gelation catalyst and Cheng et al suggested that the triflate rather than the protons was responsible for the increase in the ammonolysis and condensation rates, operating by displacement of NMe 2 groups prior to nucleophilic attack on the silicon by ammonia. 14 Our work on silicon nitride sol-gel processing has used Si(NHMe) 4 with ammonia as previously described by Jansen, but introduced the triflic acid catalyst to control reaction rates as described by Bradley. 9,11,15 This is an effective route to monolithic aerogels and coatings, and combines useful features from both previous approaches as the precursor system is straightforward but control over the gelation process is effective.…”

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

“…This procedure has been used to provide controlled gelation to yield monolithic gels [210] and in dip-coating to provide continuous films by evaporationcondensation [211]. Cheng et al suggested that the triflate anions, rather than the protons introduced from the acid, were important in the catalysis of the condensation process, probably by attacking silicon centres first then providing a good leaving group when they are attacked by amide groups on other silicon centres [212]. Use of ammonium triflate as the catalyst resulted in slower gelation (suggesting the acid may have some role), but allowed the process to be simplified by addition of the catalyst from the start of the reaction [207]:…”

Preparation, Structural Characterization, and Thermal Ammonolysis of Two Novel Dimeric Transition Silylamide Complexes

“…The exclusively MN n environment of the ceramogenic metal centers renders them attractive as single‐source precursors to multinary silicon‐based nitride ceramics. The presence of peripheral Si(NMe 2 ) 3 groups leads to multinary imidosilicate gels with high atomic‐level homogeneity as precursors to micro‐ and mesoporous homogenous ternary nitride‐based materials 41–48 . In this paper, we report attempts to prepare two novel dimeric transition silylamide complexes, {Zr[NHSi(NMe 2 ) 3 ] 2 [μ‐NSi(NMe 2 ) 3 ]} 2 and {Hf[NHSi(NMe 2 ) 3 ] 2 [μ‐NSi(NMe 2 ) 3 ]} 2 , their structural characterization using single‐crystal X‐ray crystallography, and their thermal ammonolysis to give a mesoporous silicon zirconium imide powder Si 3 Zr(N)(NH) x (NH 2 ) y (NMe 2 ) z and a microporous silicon hafnium imide powder.…”