The fate and role of in situ formed carbon in polymer-derived ceramics
TL;DR: In this paper, a review article highlights the recent progress in the polymer-derived ceramics (PDCs) field with the focus on the fate and role of the in situ formed carbon, and potential advanced structural and functional applications of the PDCs related to the carbon are evaluated.
About: This article is published in Progress in Materials Science.The article was published on 2020-04-01. It has received 203 citations till now. The article focuses on the topics: Ceramic matrix composite & Carbon.
Citations
More filters
TL;DR: In this paper, a single-source pre-precursor was synthesized by the reaction of an allylhydrido polycarbosilane (AHPCS) and divinyl benzene (DVB) to form carbon-rich SiC.
Abstract: In order to enhance dielectric properties of polymer-derived SiC ceramics, a novel single-source-precursor was synthesized by the reaction of an allylhydrido polycarbosilane (AHPCS) and divinyl benzene (DVB) to form carbon-rich SiC. As expected, the free carbon contents of resultant SiC ceramics annealed at 1600 °C are significantly enhanced from 6.62 wt% to 44.67 wt%. After annealing at 900–1600 °C, the obtained carbon-rich SiC ceramics undergo phase separation from amorphous to crystalline feature where superfine SiC nanocrystals and turbostratic carbon networks are dispersed in an amorphous SiC(O) matrix. The dielectric properties and electromagnetic (EM) absorption performance of as-synthesized carbon-rich SiC ceramics are significantly improved by increasing the structural order and content of free carbon. For the 1600 °C ceramics mixed with paraffin wax, the minimum reflection coefficient (RCmin) reaches –56.8 dB at 15.2 GHz with the thickness of 1.51 mm and a relatively broad effective bandwidth (the bandwidth of RC values lower than –10 dB) of 4.43 GHz, indicating the excellent EM absorption performance. The carbon-rich SiC ceramics have to be considered as harsh environmental EM absorbers with excellent chemical stability, high temperature, and oxidation and corrosion resistance.
85 citations
TL;DR: In this article, the most recent major and important advancements in some micro-nano multiscale strategies, including nanoparticles, nanowires, carbon nanotubes/fibers, whiskers, graphene, ceramic fibers and hybrid micro/nano structures, for C/C and/or the coatings, to achieve high-temperature oxidation/ablation-resistant C/Cs.
85 citations
TL;DR: In this paper , the most recent major and important advancements in some micro-nano multiscale strategies, including nanoparticles, nanowires, carbon nanotubes/fibers, whiskers, graphene, ceramic fibers and hybrid micro/nano structures, for C/C and/or the coatings, to achieve high-temperature oxidation/ablation-resistant C/Cs.
82 citations
TL;DR: Performance across all indicators was majorly improved in the graphene aerogel/SiOC nanocomposites, compared with unsupported SiOC, and was attributed to mechanisms across multiple length-scales.
Abstract: Amorphous polymer-derived silicon oxycarbide (SiOC) is an attractive candidate for Li-ion battery anodes, as an alternative to graphite, which is limited to a theoretical capacity of 372 mAh/g. However, SiOC tends to exhibit poor transport properties and cycling performance as a result of sparsely distributed carbon clusters and inefficient active sites. To overcome these limitations, we designed and fabricated a layered graphene/SiOC heterostructure by solvent-assisted infiltration of a polymeric precursor into a modified three-dimensional (3D) graphene aerogel skeleton. The use of a high-melting-point solvent facilitated the precursor’s freeze drying, which following pyrolysis yielded SiOC as a layer supported on the surface of nitrogen-doped reduced graphene oxide aerogels. The fabrication method employed here modifies the composition and microstructure of the SiOC phase. Among the studied materials, the highest levels of performance were obtained for a sample of moderate SiOC content, in which the graphene network constituted 19.8 wt % of the system. In these materials, a stable reversible charge capacity of 751 mAh/g was achieved at low charge rates. At high charge rates of 1480 mA/g, the capacity retention was ∼95% (352 mAh/g) after 1000 consecutive cycles. At all rates, Coulombic efficiencies >99% were maintained following the first cycle. Performance across all indicators was majorly improved in the graphene aerogel/SiOC nanocomposites, compared with unsupported SiOC. The performance was attributed to mechanisms across multiple length scales. The presence of oxygen-rich SiO₄–ₓCₓ tetrahedral units and a continuous free-carbon network within the SiOC provides sites for reversible lithiation, while high ionic and electronic transport is provided by the layered graphene/SiOC heterostructure.
57 citations
TL;DR: In this paper, a lightweight and flexible ZrC/SiC hybrid nanofiber mat was successfully fabricated by electrospinning and high temperature pyrolysis with polycarbosilane (PCS) and Zirconium acetylacetone ((Zr(acac)3) as precursors.
52 citations
References
More filters
TL;DR: In this paper, a model and theoretical understanding of the Raman spectra in disordered and amorphous carbon is given, and the nature of the G and D vibration modes in graphite is analyzed in terms of the resonant excitation of \ensuremath{\pi} states and the long-range polarizability of the long range bonding.
Abstract: The model and theoretical understanding of the Raman spectra in disordered and amorphous carbon are given. The nature of the G and D vibration modes in graphite is analyzed in terms of the resonant excitation of \ensuremath{\pi} states and the long-range polarizability of \ensuremath{\pi} bonding. Visible Raman data on disordered, amorphous, and diamondlike carbon are classified in a three-stage model to show the factors that control the position, intensity, and widths of the G and D peaks. It is shown that the visible Raman spectra depend formally on the configuration of the ${\mathrm{sp}}^{2}$ sites in ${\mathrm{sp}}^{2}$-bonded clusters. In cases where the ${\mathrm{sp}}^{2}$ clustering is controlled by the ${\mathrm{sp}}^{3}$ fraction, such as in as-deposited tetrahedral amorphous carbon (ta-C) or hydrogenated amorphous carbon (a-C:H) films, the visible Raman parameters can be used to derive the ${\mathrm{sp}}^{3}$ fraction.
12,593 citations
TL;DR: Raman spectra are reported from single crystals of graphite and other graphite materials as mentioned in this paper, and the Raman intensity of this band is inversely proportional to the crystallite size and is caused by a breakdown of the k-selection rule.
Abstract: Raman spectra are reported from single crystals of graphite and other graphite materials. Single crystals of graphite show one single line at 1575 cm−1. For the other materials like stress‐annealed pyrolitic graphite, commercial graphites, activated charcoal, lampblack, and vitreous carbon another line is detected at 1355 cm−1. The Raman intensity of this band is inversely proportional to the crystallite size and is caused by a breakdown of the k‐selection rule. The intensity of this band allows an estimate of the crystallite size in the surface layer of any carbon sample. Two in‐plane force constants are calculated from the frequencies.
9,373 citations
TL;DR: In this article, the authors focus on the origin of the D and G peaks and the second order of D peak and show that the G and 2 D Raman peaks change in shape, position and relative intensity with number of graphene layers.
6,496 citations
TL;DR: In this article, the authors compared the deduced dependence of the experimental observables on the load with the experimental evidence and concluded that the most realistic model is one in which increasing the load increases both the number and size of the contact areas.
Abstract: The interpretation of certain phenomena occuring at nominally flat surfaces in stationary or sliding contact is dependent on the assumed distribution of the real area of contact between the surfaces. Since there is little direct evidence on which to base an estimate of this distribution, the approach used is to set up a simple model and compare the deduced theory (e.g., the deduced dependence of the experimental observables on the load) with the experimental evidence. The main conclusions are as follows. (a) The electrical contact resistance depends on the model used to represent the surfaces; the most realistic model is one in which increasing the load increases both the number and size of the contact areas. (b) In general, mechanical wear should also depend on the model. However, in wear experiments showing the simplest behavior, the wear rate is proportional to the load, and these results can be explained by assuming removal of lumps at contact areas formed by plastic deformation; moreover, this particular deduction is independent of the assumed model. This suggests that a basic assumption of previous theories, that increasing the load increases the number of contacts without affecting their average size, is redundant.
5,771 citations
TL;DR: In this review, experimental results for the D, D' and G' bands obtained with different laser lines, and in samples with different crystallite sizes and different types of defects are presented and discussed.
Abstract: Raman spectroscopy has historically played an important role in the structural characterization of graphitic materials, in particular providing valuable information about defects, stacking of the graphene layers and the finite sizes of the crystallites parallel and perpendicular to the hexagonal axis Here we review the defect-induced Raman spectra of graphitic materials from both experimental and theoretical standpoints and we present recent Raman results on nanographites and graphenes The disorder-induced D and D′ Raman features, as well as the G′-band (the overtone of the D-band which is always observed in defect-free samples), are discussed in terms of the double-resonance (DR) Raman process, involving phonons within the interior of the 1st Brillouin zone of graphite and defects In this review, experimental results for the D, D′ and G′ bands obtained with different laser lines, and in samples with different crystallite sizes and different types of defects are presented and discussed We also present recent advances that made possible the development of Raman scattering as a tool for very accurate structural analysis of nano-graphite, with the establishment of an empirical formula for the in- and out-of-plane crystalline size and even fancier Raman-based information, such as for the atomic structure at graphite edges, and the identification of single versus multi-graphene layers Once established, this knowledge provides a powerful machinery to understand newer forms of sp2 carbon materials, such as the recently developed pitch-based graphitic foams Results for the calculated Raman intensity of the disorder-induced D-band in graphitic materials as a function of both the excitation laser energy (Elaser) and the in-plane size (La) of nano-graphites are presented and compared with experimental results The status of this research area is assessed, and opportunities for future work are identified
3,601 citations