Supplementary Figures from Preparation and structure of SiOCN fibres derived from cyclic silazane/poly-acrylic acid hybrid precursor

Ceramic matrix composite (CMC) materials have been considered a desired solution for lightweight and high-temperature applications. Simultaneously, among all different CMC reinforcements, polymer-derived ceramic (PDC) fibres have gained attention for the intrinsic thermal stability and mechanical strength with simple and cost-effective synthesis techniques. Here, carbon-rich silicon oxycarbide (SiOC) fibres were synthesized via hand-drawing and polymer pyrolysis of a hybrid precursor of 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasilazane (TTCSZ) and poly-acrylic acid (PAA). The type of silazane reported in this work is considered as a major precursor for SiCN; however, it is unspinnable, due to its unfavourable physical properties (low viscosity) and chemical structure (cyclic rather than linear structure). The introduction of PAA to TTCSZ to create a hybrid precursor remarkably improved the spinnability of the silazane and should be widely applicable to other unspinnable PDC pre-ceramic polymers. Investigations on the structural and compositional development of the fibres were mainly conducted via Raman spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance and thermo-gravimetric analysis to determine spinnability, free carbon content, cross-linking and pyrolysis behaviour of the fibres, respectively

SEM

SEM images used in the manuscrip

Supplementary Figures from Preparation and structure of SiOCN fibres derived from cyclic silazane/poly-acrylic acid hybrid precursor

Ceramic matrix composite (CMC) materials have been considered a desired solution for lightweight and high-temperature applications. Simultaneously, among all different CMC reinforcements, polymer-derived ceramic (PDC) fibres have gained attention for the intrinsic thermal stability and mechanical strength with simple and cost-effective synthesis techniques. Here, carbon-rich silicon oxycarbide (SiOC) fibres were synthesized via hand-drawing and polymer pyrolysis of a hybrid precursor of 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl-cyclotetrasilazane (TTCSZ) and poly-acrylic acid (PAA). The type of silazane reported in this work is considered as a major precursor for SiCN; however, it is unspinnable, due to its unfavourable physical properties (low viscosity) and chemical structure (cyclic rather than linear structure). The introduction of PAA to TTCSZ to create a hybrid precursor remarkably improved the spinnability of the silazane and should be widely applicable to other unspinnable PDC pre-ceramic polymers. Investigations on the structural and compositional development of the fibres were mainly conducted via Raman spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance and thermo-gravimetric analysis to determine spinnability, free carbon content, cross-linking and pyrolysis behaviour of the fibres, respectively

Viscosity

Viscosity information used in the manuscrip

Facile Synthesis and High Rate Capability of Silicon Carbonitride/Boron Nitride Composite with a Sheet-Like Morphology

We report synthesis of a sheet-like composite composed of hexagonal boron nitride (or BN) chemically integrated with silicon carbonitride (SiCN) matrix via a simple pyrolysis route. The composite offers several unique features such as improved electrical conductivity, high-temperature oxidation resistance (at 1000 °C), and high electrochemical activity toward Li-ions generally not observed in SiCN or boron-doped SiCN. Tested as electrode in Li-ion half-cell, SiCN/BN show charge capacity of ∼517 mAh g^–1 at 100 mA g^–1 and 283 mAh g^–1 at 2400 mA g^–1 with respect to total weight of electrode. Additionally, a stable charge capacity of ∼401 mAh g^–1 at 100 mA g^–1 is retained even after continuous operation for 1000 cycles at 1600 mA g^–1. Chemical characterization of the composite suggests that addition of BN to polysilazane in moderate amounts (∼10 wt %) and subsequent pyrolysis resulted in an increased free-carbon content in the amorphous SiCN phase, which exceeded the percolation limit, leading to the improved electrical conductivity and Li-reversible capacity

Ab Initio Study of the Hydroxylated Surface of Amorphous Silica: A Representative Model

A new complete, representative model for the hydroxylated surface of amorphous silica is presented and characterized by means of periodic DFT calculations. This model accounts for the experimentally encountered ring size distribution, Si−O−Si and O−Si−O angles, silanols density, and distribution (isolated, associated, geminals). Properties such as NMR shifts, dehydrogenation energies, OH vibrational frequencies, and the interaction with water are investigated. The results are compared with former experimental and theoretical results. This new representative model for this complex surface would probably help the investigation of its reactivity toward amino acids or other organic molecules, opening new perspectives in the understanding of the chemistry of amorphous materials

From <i>Operando</i> Raman Mechanochemistry to “NMR Crystallography”: Understanding the Structures and Interconversion of Zn-Terephthalate Networks Using Selective ¹⁷O‑Labeling

The description of the formation, structure, and reactivity of coordination networks and metal–organic frameworks (MOFs) remains a real challenge in a number of cases. This is notably true for compounds composed of Zn2+ ions and terephthalate ligands (benzene-1,4-dicarboxylate, BDC) because of the difficulties in isolating them as pure phases and/or because of the presence of structural defects. Here, using mechanochemistry in combination with operando Raman spectroscopy, the observation of the formation of various zinc terephthalate compounds was rendered possible, allowing the distinction and isolation of three intermediates during the ball-milling synthesis of Zn3(OH)4(BDC). An “NMR crystallography” approach was then used, combining solid-state NMR (1H, 13C, and 17O) and density functional theory (DFT) calculations to refine the poorly described crystallographic structures of these phases. Particularly noteworthy are the high-resolution 17O NMR analyses, which were made possible in a highly efficient and cost-effective way, thanks to the selective 17O-enrichment of either hydroxyl or terephthalate groups by ball-milling. This allowed the presence of defect sites to be identified for the first time in one of the phases, and the nature of the H-bonding network of the hydroxyls to be established in another. Lastly, the possibility of using deuterated precursors (e.g., D2O and d4-BDC) during ball-milling is also introduced as a means for observing specific transformations during operando Raman spectroscopy studies, which would not have been possible with hydrogenated equivalents. Overall, the synthetic and spectroscopic approaches developed herein are expected to push forward the understanding of the structure and reactivity of other complex coordination networks and MOFs

Synthesis and Characterization of Transparent PDMS−Metal-Oxo Based Organic−Inorganic Nanocomposites

Poly(dimethylsiloxane)(PDMS)−metal-oxo nanocomposites have been prepared as transparent monoliths from dimethyldiethoxysilane (DMDES) and metal alkoxides, M(OR)n, where M = Al(III), Ge(IV), Sn(IV), Ti(IV), Zr(IV), Nb(V), and Ta(V). An accurate structural analysis of these hybrid materials has been performed by FTIR, Raman, and multinuclear NMR (1H, 13C, and 29Si) spectroscopies, SAXS, and DSC measurements. These techniques show that all the hybrid systems present a structure based on amorphous metal-oxo nanodomains embedded within the siloxane network. However, a strong influence of the cross-linking metal nature on the size of the metal-oxo nanoparticles and on the extent of the interface between inorganic domains and the siloxane component has been found. Spectroscopic measurements reveal a more important nanophase separation for the PDMS systems incorporating Al(III), Ti(IV), or Zr(IV) species as cross-linking agent than for the ones cross-linked with Nb(V), Ta(V), or Ge(IV) (in which 45% of the silicon atoms are spatially near a metal species)

Leucine on Silica: A Combined Experimental and Modeling Study of a System Relevant for Origins of Life, and the Role of Water Coadsorption

Leucine on silica constitutes an interesting system from the point of view of origins of life studies since leucine coadsorbed on SiO2 together with glutamic acid can give rise to rather long linear polypeptides upon activation. It is also an ideal system to test methods of molecular characterization of biomolecules deposited on mineral surfaces since it combines a small-scale model of peptides and proteins, which are among the most important components of biodevices, with one of the most widely used inorganic materials. We have deposited l-leucine on a high surface fumed silica in the submonolayer range and characterized it by a multipronged approach including macroscopic information (thermogravimetry, X-ray diffraction), in situ spectroscopic methods (IR, multinuclear solid-state NMR including single-pulse and CP-MAS, 2-D HETCOR), and molecular modeling by density functional theory (DFT), including calculation of NMR parameters. Specific information can be obtained on the adsorption and interaction mechanism. Leucine is rather strongly adsorbed without any covalent bonds, through the formation of a specific lattice of H-bonds that often involve coadsorbed water molecules. Its state is indeed strongly dependent on the drying procedure: insufficient drying results in liquid-like surroundings for the leucine functional groups, while vacuum drying only retains a limited number of waters (of the order of 5 per leucine molecule). The most stable models have zwitterionic leucine interacting directly with surface silanols through their ammonium group, while the carboxylate interacts through bridging waters. Experimental NMR chemical shifts are satisfactorily predicted for these models, and leucine can be viewed as a probe for specific groups of surface sites known as silanol nests

Design of a Series of Preceramic <i>B</i>-Tri(methylamino)borazine-Based Polymers as Fiber Precursors: Architecture, Thermal Behavior, and Melt-Spinnability^†

A series of poly[B-(methylamino)borazine] were synthesized by thermolysis of a monomeric B-tri(methylamino)borazine at various temperatures between 150 and 200 °C and then characterized for suitability as a fiber precursor. Polymerization mechanisms and polymer architectures are discussed. It was shown that poly[B-(methylamino)borazine] represents a network combining a majority of −N(CH3)− bridges with a small proportion of B−N bonds, both connecting borazine rings, and −N(H)CH3 groups. Both the ratio between flexible −N(CH3)− bridges and rigid B−N bonds and the relative amounts of plasticizing −N(H)CH3 groups cause different responses to thermal properties and spinnability (glass transition, spinning temperatures, melt throughput, and fiber drawing). Based on fiber shape visualization using CCD camera during extrusion, appreciable melt-spinnable compounds are prepared between 160 and 185 °C. Such polymers display a chemical formula of [B3.0N4.4±0.1C2.0±0.1H9.3±0.2]n (n ∼ 7.5), a glass transition between 64 and 83 °C, tailored flexibility, and sufficient plasticity to successfully produce fine-diameter green fibers