“…The sol-gel technique is an attractive approach for preparing micro/ mesoporous oxide materials as powders, membranes and filters with high purity and homogeneity due to its flexibility and low temperature preparation of sols and gels [3]. A number of sol-gel processes to prepare highly porous nonoxide ceramics have also been reported, e.g., boron nitride [4][5][6][7][8], metal (carbo)nitrides [9][10][11][12][13][14], silicon carbonitride [15][16][17][18][19][20][21] and boron carbonitride [22,23]. A sol-gel process in an ammono-system has been used to prepare polymeric boron-, titano-and tantalo-silazanes by controlled co-ammonolysis of the elemental alkylamides [24].…”
“…The sol-gel technique is an attractive approach for preparing micro/ mesoporous oxide materials as powders, membranes and filters with high purity and homogeneity due to its flexibility and low temperature preparation of sols and gels [3]. A number of sol-gel processes to prepare highly porous nonoxide ceramics have also been reported, e.g., boron nitride [4][5][6][7][8], metal (carbo)nitrides [9][10][11][12][13][14], silicon carbonitride [15][16][17][18][19][20][21] and boron carbonitride [22,23]. A sol-gel process in an ammono-system has been used to prepare polymeric boron-, titano-and tantalo-silazanes by controlled co-ammonolysis of the elemental alkylamides [24].…”
“…21 Ceramic Si/C/N membranes were fabricated and tested for their gas separation properties. 22 In a recently published communication we reported on a novel sol-gel route to B 4 C. 23 B-trichloroborazene (B 3 N 3 H 3 Cl 3 ) reacts with BTSC in THF or toluene or even without any solvent to form non-oxide gels.…”
B-trichloroborazene B3N3H3Cl3 reacts with bis(trimethylsilyl)carbodiimide Me3Si−NCN−SiMe3 in THF or toluene, or without any solvent, to form non-oxide gels. The xerogels,
amorphous B/C/N materials, and (semi)crystalline pyrolysis products were characterized
using infrared (FTIR) and Raman spectroscopy, 11B- and 15N-nuclear magnetic resonance
spectroscopy (NMR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM),
transmission electron microscopy (TEM), and elemental analysis. In addition, the pyrolysis
process was investigated through thermal gravimetry coupled with mass spectrometry
(TG−MS). The xerogels consist of a three-dimensional polymeric network of borazene rings
linked by carbodiimide groups. Interestingly, the sol−gel transition is phenomenologically
analogous to oxide systems and the polymers are almost free of chlorine and trimethylsilyl
endgroups. Pyrolysis at 1200 °C provides an amorphous ceramic with the composition
BC0.23N1.1Si0.05H0.09 ≈ B4CN4. This material starts to crystallize around 1600 °C under
evolution of nitrogen, forming nearly pure B4C at 2000 °C. Very small amounts of amorphous
carbon as well as carbon nanotubes were also present.
“…Pyrolysis of these gels at 1000 °C under a NH 3 flow led to the formation of mesoporous silicon boron nitride and silicon aluminum nitride composites. ,, Preliminary results of investigation of the use of the silicon boron nitride and silicon nitride ceramics derived from the mesoporous gels prepared from B[NHSi(NMe 2 ) 3 ] 3 and tris (dimethylamino)silylamine, respectively, indicate that they can be formed into stable mesporous membranes and used as efficient selective gas filters in solid-state gas sensor applications. − This synthetic flexibility, simplicity and control over the ceramic morphology suggested that our nonaqueous sol−gel approach to synthesising mesoporous silicon nitride with a large surface area and narrow pore size distribution could be applicable to the preparation of effective M/Si 3 N 4 catalysts incorporating transition metal nanoparticles, such as palladium, for gas-phase reactions and reactions in solution requiring heterogeneous catalysts . Several other important sol−gel routes to nitrides have been reported, which may also be used to prepare highly porous materials, e.g., boron nitride, − metal (carbo)nitrides, − silicon carbonitride, − and boron carbonitride. , 1 . Three General Methods Used to Prepare Mesoporous Silicon Nitride Doped with Palladium Nanoparticles…”
Section: Introductionmentioning
confidence: 99%
“…22 Several other important sol-gel routes to nitrides have been reported, which may also be used to prepare highly porous materials, e.g., boron nitride, [23][24][25][26][27] (carbo)nitrides, [28][29][30][31][32][33] silicon carbonitride, [34][35][36][37][38][39][40] and boron carbonitride. 41,42 In this paper, we now report three practical and efficient chemical approaches using nonaqueous sol-gel chemistry for the preparation of mesoporous silicon nitride nanocomposites incorporating palladium nanoparticles as potential heterogeneous catalysts, see Scheme 1. The three different routes facilitate chemical control of the nanocomposite components crystal morphology (amorphous/crystalline) and macroscopic structural morphology (size, density, and dispersity of the pores).…”
Mesoporous palladium/silicon nitride nanocomposites were prepared via three different chemical routes to generate simultaneous control of the solid-state morphology of the palladium nanoparticles and that of the silicon nitride support at the same time as controlling the pore size and size distribution. Pyrolysis of the reaction product of silicon diimide gel with PdCl 2 under a NH 3 flow at 1000 °C gave a composite with highly crystalline Pd nanoparticles dispersed in an R-Si 3 N 4 matrix. A composite with partially crystallized Pd nanoparticles dispersed in an amorphous Si 3 N 4 matrix was obtained by the hydrogen reduction of the reaction product of silicon nitride with PdCl 2 , whereas hydrogen reduction of an impregnated mixture of Si 3 N 4 with bis(dibenzylideneacetone)palladium (DBA) led to the formation of a composite with amorphous Pd nanoparticles dispersed in an amorphous Si 3 N 4 matrix. Most of these new mesoporous nanocomposites exhibit a high surface area >400 m 2 g -1 and a narrow pore size distribution of 5-12 nm with a loading of up to 2% Pd nanoparticles 2-20 nm in diameter. Preliminary investigations show that these nanocomposites are potentially useful heterogeneous catalysts for a range of liquidphase chemical reactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
