Catalyst-assisted Pyrolysis Of Polymeric Precursor Research Articles

Synthesis of self-helix structure Si3N4 nanobelts and its reinforcement effect on HA coating

ABSTRACT A self-helix structure Si3N4 nanobelts reinforced hydroxyapatite (HSN/HA) coating has been synthesised on carbon/carbon composites by a combination method of catalyst-assisted pyrolysis of polymeric precursors and electrochemical deposition. The morphology, microstructure, and bonding strength of the coating were analysed. An individual Si3N4 nanobelt showed a self-helical shape. The bonding strength between HSN/HA coating and carbon/carbon composites reached 12.5 ± 0.72 MPa, higher than that of pure HA coating (6.38 ± 0.32 MPa). HSN/HA coating has the potential to apply to hard tissue substitution surgery in the future.

In-situ synthesis and growth mechanism of silicon nitride nanowires on carbon fiber fabrics

Silicon nitride (Si3N4) nanowires were in-situ fabricated on carbon fiber fabrics up to 5cm×11cm in area via catalyst-assisted pyrolysis of polymeric precursors. The obtained products were randomly oriented around the carbon fibers with the diameter of 30–150nm and the length of several hundred micrometers. The effects of process parameters including the preparation temperature, flow rate of nitrogen, catalyst proportion, and volume fraction of acetone on the synthesis of Si3N4 nanowires were discussed. Accordingly, a set of optimized process parameters was determined. The microstructure of the nanowires indicated that their formation obeyed a solid–liquid–gas–solid (SLGS) growth mechanism.

Synthesis of n-type SiC nanowires with tailored doping levels

Doping of one-dimensional silicon carbide nanomaterials with tailored doping types and levels is highly required for their potential applications in functional nanodevices. In the present work, we have reported the synthesis of N-doped 3C–SiC nanowires via catalyst-assisted pyrolysis of polymeric precursors with Co(NO3)2 as the catalysts. The resultant products were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy spectrum (EDS). It was found that a relatively low partial pressure played a determined role on the introduction of N dopants into the SiC nanowires. The pyrolysis temperatures had a profound effect on the doping levels of N, enabling the tunable n-type doping of 3C–SiC nanowires. Current work suggests a facile technique for the synthesis of n-type SiC nanomaterials with a uniform spatial distribution of N dopants in a controlled manner, which could be useful for manufacturing optoelectric nanodevices.

Morphology-Controlled Synthesis of SiC Nanowires by Catalyst-Assisted Pyrolysis of Polymeric Precursor

Two different types of morphology are observed in synthesis of SiC nanowires by catalyst-assisted pyrolysis of polymeric precursor while Au acts as the catalyst. Both two types of SiC nanowires are well oriented and uniform in diameter. The results indicate that longer (~20 μm) and slimmer (~100 nm) nanowires are tends to be produced in high temperature (1450°C), while shorter (~10 μm) and thicker (200~300 nm) ones are tends to be produced in low temperature (1420°C). Then we make a discussion on the mechanism of the growth of SiC nanowires based on the VLS (Vapor-Liquid-Solid) process.

Facile conversion of silicon nitride nanobelts into sandwich-like nanosaws: towards functional nanostructured materials

A unique Si3N4 sandwich-like nanosaw has been successfully fabricated by the catalyst-assisted pyrolysis of polymeric precursors. The nanosaws are configured as nanoteeth “welded” to the sidewall of a conventional nanobelt and the “soldering region” between the nanobelt and nanoteeth. For each nanosaw, there are numerous defects in the central “soldering region”, but little defects in the zigzag or flat sidewalls. The teeth (zigzag sidewalls) are terminated by the \(\{11\bar{2}0\}\) family of planes with a lower surface energy. The sandwich-like nanosaw exhibits unique optical properties, which are different from previously reported Si3N4 nanostructures, demonstrating a likelihood of constructing sandwich-like nanosaw devices with functionalities applicable for working in high-temperature and harsh environments.

Controlled Al-Doped Single-Crystalline 6H-SiC Nanowires

We report for the first time the synthesis of Al-doped 6H-SiC nanowires with high yield and high quality. The nanowires were obtained by the catalyst-assisted pyrolysis of polymeric precursors with FeCl2 as the catalyst. The doping concentrations were controlled by tailoring the Al concentrations in the precursors. It was observed that the Al dopants caused red-shifts of the photoluminescence bands. The results suggest a simple technique to synthesize Al-doped SiC nanomaterials in a controlled manner. The obtained nanowires could be useful for making optical and electronic nanodevices.

Mass production of very thin single-crystal silicon nitride nanobelts

We report the large-scale synthesis of very thin single-crystalline Si 3N 4 nanobelts with high yield via catalyst-assisted pyrolysis of polymeric precursors. The obtained nanobelts, which show a perfect crystal structure and smooth surface, are up to several millimeters in length with typical width and thickness of ∼800 nm and tens of nanometers, respectively. It is believed that the nanobelts were grown via a vapor–solid process, in which Al catalyst played a key role. This result provides a possibility for mass producing high quality, very thin Si 3N 4 nanobelts.

Catalyst-Assisted Pyrolysis of Polymeric Precursors: A New Method to Synthesize Low-Dimensional Nanomaterials

Catalyst-Assisted Pyrolysis of Polymeric Precursors: A New Method to Synthesize Low-Dimensional Nanomaterials

Controlled Al-Doped Single-Crystalline Silicon Nitride Nanowires Synthesized via Pyrolysis of Polymer Precursors

Al-doped single-crystalline Si(3)N(4) nanowires were synthesized by catalyst-assisted pyrolysis of polymeric precursors. The doping levels can be controlled by tailoring the Al concentration in the precursors. It is found that the Al concentration has a significant effect on the shape, sizes, and phase compositions of the synthesized Si(3)N(4) low-dimensional nanomaterials. The photoluminescence measurements revealed that the Al dopants have a profound effect on the emission behavior. The current study provides a simple way to realize the controlled doping in Si(3)N(4) nanomaterials, which could be useful for applications in optoelectronic nanodevices.

Optical properties of single-crystalline α-Si3N4 nanobelts

The optical properties of single-crystalline α-Si3N4 nanobelts synthesized via catalyst-assisted pyrolysis of polymeric precursor were characterized by absorption, photoluminescence (PL) and photoluminescence excitation (PLE). The optical absorption spectrum showed that the nanobelts exhibited indirect absorption behavior with optical band gap of ∼5.0eV. Three broad peaks centered at 1.8, 2.3, and 3.0eV were observed from the room-temperature PL spectrum of the nanobelts. The PLE spectra suggested the existence of multifold energy levels within the gap. A qualitative model was proposed to explain the observed absorption, PL and PLE spectra.

Growth of platelike and branched single-crystalline Si 3N 4 whiskers

In this communication, we report for the first time the growth of platelike and branched Si 3N 4 whiskers via catalyst-assisted pyrolysis of polymeric precursors. The as-prepared whiskers are single crystalline with a uniform thickness and width. The thickness and width of the Si 3N 4 whiskers range from 200 to 300 nm and 800 to 1200 nm, respectively. The platelike α-Si 3N 4 whiskers grew along [010] direction, while the branches grew along [001] direction. A growth mechanism based on solid–liquid–gas–solid reaction/crystallization is proposed. The formation of platelike whiskers instead of cylindrical whiskers is attributed to an anisotropic growth at an early nucleation/growth stage.

Synthesis of silicon carbide nanorods by catalyst-assisted pyrolysis of polymeric precursor

In this Letter, we report the synthesis of β-SiC nanorods by the pyrolysis of a polysilazane polymeric precursor in the presence of 3 wt% FeCl 2 as a catalyst. The precursor is completely converted to the nanorods after heat-treated at 1700 °C for 2 h, accompanied by ∼50% weight loss. Electron microscopy study reveals that the nanorods preferentially grow along [1 1 1] direction; and the diameters of the nanorods range from 80 to 200 nm and lengths are ∼4 μm. A solid–liquid–solid growth mechanism is proposed.