Silicon Oxycarbide Research Articles

Electrochemical Performance of Polymer-Derived Silicon-Oxycarbide/Graphene Nanoplatelet Composites for High-Performance Li-Ion Batteries.

Amorphous polymer-derived silicon-oxycarbide (SiOC) ceramics have a high theoretical capacity and good structural stability, making them suitable anode materials for lithium-ion batteries. However, SiOC has low electronic conductivity, poor transport properties, low initial Couloumbic efficiency, and limited rate capability. Therefore, there is an urgent need to explore an efficient SiOC-based anode material that could mitigate the abovementioned limitations. In this study, we synthesized carbon-rich SiOC (SiOC-I) and silicon-rich SiOC (SiOC-II) and evaluated their elemental and structural characteristics using a broad spectrum of characterization techniques. Li-ion cells were fabricated for the first time by pairing a buckypaper composed of carbon nanotubes with SiOC-I or SiOC-II as the anode. When mixed with graphene nanoplatelets, the SiOC-II/GNP composites exhibited improved electrochemical performance. High specific capacity (average specific capacity of 744 mAh/g at a 0.1C rate) was achieved with the composite anode (25 wt % SiOC-II and 75% GNP), which was much better than that of monolithic SiOC-I, SiOC-II, or GNPs. This composite also exhibited excellent cycling stability, achieving 344 mAh/g after 260 cycles at a 0.5C rate and high reversibility. The enhanced electrochemical performance is attributed to better electronic conductivity, lower charge-transfer resistance, and short ion diffusion length. Due to their superior electrochemical performance, SiOC/GNP composites with CNT buckypaper as a current collector can be considered a promising anode material for LiBs.

A materials informatics approach for composition and property prediction of polymer-derived silicon oxycarbides

Polymer-derived silicon oxycarbide (SiOC) materials enable the formation of homogeneous microstructures and high temperature stable properties. However, the relationships between the processing parameters and microstructures/properties have not been clearly understood. In this study, a materials informatics approach was employed to the SiOC materials to analyze and estimate the relationships. Datasets were constructed from results of previously reported literature about SiOC. The correlation analysis provided processing parameter ranking regarding the corresponding influences on the properties and microstructures. Such an understanding can be utilized for desired material fabrication. Machine learning models with high accuracy were proposed using the ranked features obtained from the correlation analysis. In addition, important points on the data collection, correlation analysis, and machine learning as well as limitations of the current dataset were discussed. The proposed workflow for the SiOC materials can be extended to different types of polymer-derived ceramics by incorporating various features and targets involved in the processing variables, microstructures, and properties.

A superelastic SiOC@carbon ceramic spring for multifunctional pressure sensor in wide temperature range

With the flourishing development in space exploration and human motion detection, the wide-temperature flexible pressure sensors are urgently required in various complex application situations. One massive challenge of current available sensors is to enhance the oxidation resistance property, which is crucial for their applications in high-temperature environments. Herein, we fabricated a superelastic silicon oxycarbide @carbon (SiOC@C) ceramic spring, possessing a porous lamellar and spring-like structure. The spring-like structure tends to deform and absorb the energy under the external loads, and then the anisotropic lamellar structure can effectively and uniformly release the stress. The as-prepared SiOC@C spring exhibits excellent superelasticity, high compressibility (60%), and robustness (∼99.0% maximum stress retention after 1000 cycles at 50% compression). Meanwhile, the SiOC@C spring-derived sensor possesses a high sensitivity under low pressure (282.46 kPa−1 at < 1.3 kPa), a low detection limit (< 0.098 Pa) and a short response/recovery time (∼12 ms/4 ms). Moreover, benefiting from the high/low-temperature resistance of SiOC nanolayer coated on the carbon framework, the SiOC@C spring-based sensor can function properly at a wide temperature range from − 196 °C to 500 °C, showing the potential application in various fields of biomedical monitoring, space exploration, and automotive industries.

ReaxFF Simulation of Pyrolysis Behaviors of Polysiloxane Precursors with Different Carbon Content

Polymer-derived ceramics are a promising class of high-temperature materials. This work uses LAMMPS and reactive force field (ReaxFF) energy potential to first-time quantify the atomic evolution of the polymer-to-ceramic conversion. Three different polymer structures are selected based on initial carbon content and molecular structure differences. From these simulations, the ceramic composition, yield, atomic structure, bond change, and radial distribution function (RDF) are comprehensively analyzed and provided data that are not available otherwise. The ceramic compositions correlate with the polymer compositions. The C-rich precursor forms C–C bonds through Si–O, Si–C, and C–H bond losses while less C-rich polymers have no significant C–C bond formation during C–H bond loss. The end structures have vastly different Si–O-rich and C-rich domain sizes, which cannot be observed by any bulk analysis. For the first time, H presence and cluster separation are shown to be determined by the polymer molecular structure. The RDF results show that higher pyrolysis temperature leads to more C–C bond formation. Even at 2100 K, C–H bonds are still prevalent and there is no long-range ordering. Such fundamental understanding provides new knowledge about polymer atomic evolution to silicon oxycarbide (SiOC) ceramics.

Highly Microporous Nitrogen-Doped Carbon Derived from Silicon Oxycarbide Ceramics for Supercapacitor Application

Highly Microporous Nitrogen-Doped Carbon Derived from Silicon Oxycarbide Ceramics for Supercapacitor Application

SiCO Ceramics as Storage Materials for Alkali Metals/Ions: Insights on Structure Moieties from Solid-State NMR and DFT Calculations.

Polymer-derived silicon oxycarbide ceramics (SiCO) have been considered as potential anode materials for lithium- and sodium-ion batteries. To understand their electrochemical storage behavior, detailed insights into structural sites present in SiCO are required. In this work, the study of local structures in SiCO ceramics containing different amounts of carbon is presented. 13 C and 29 Si solid-state MAS NMR spectroscopy combined with DFT calculations, atomistic modeling, and EPR investigations, suggest significant changes in the local structures of SiCO ceramics even by small changes in the material composition. The provided findings on SiCO structures will contribute to the research field of polymer-derived ceramics, especially to understand electrochemical storage processes of alkali metal/ions such as Na/Na+ inside such networks in the future.

Silicon oxycarbide-encapsuled bismuth for superior lithium storage

Bi is a promising anode for Li-ion batteries (LIBs) because of its suitable working voltage and high volumetric capacity. Nonetheless, the inevitable volume expansion during Bi alloying reactions results in severe capacity loss and cell failure. Herein, to achieve reliable alloying with high reversibility, a polymer-derived ceramic silicon oxycarbide (SiOC) coating was formed on Bi nanoparticles (NPs) by the facile dispersion of bismuth hydroxide in silicone oil and subsequent calcination. The embedment of Bi NPs in the sturdy SiOC domain relieved the local mechanical strain developed by Bi alloying upon Li+-ion insertion/extraction, achieving a highly stable capacity (507 mAh g−1 after 150 cycles at 50 mA g−1), outstanding long-term cyclability (380 mAh g−1 at 0.5 A g−1 after 500 cycles), and good cell integrity. When this composite anode was coupled with a LiNi0.5Co0.2Mn0.3O2 cathode, the full cell exhibited high gravimetric and volumetric energy densities of 343 Wh kg−1 and 607 Wh L−1, respectively. Further, kinetic and postmortem analyses confirmed the superiority of amorphous SiOC as a protective layer that hinders undesirable solid electrolyte interface generation, active material conductivity loss, and particle isolation.

Spark plasma sintered Si(Hf)OC nanocomposites exhibiting thermally stable dielectric behavior processed through precursor route

This work uses hafnium n tetra butoxide precursor to modify silicon oxycarbide (SiOC) with an easy, novel, and economical procedure to synthesize Si(Hf)OC nanocomposites. FTIR analysis confirmed the formation of Si–O-Hf linkages during cross-linking. The as-pyrolyzed powders were sintered using the spark plasma sintering technique. X-ray diffractograms confirmed the in-situ crystallization of tetragonal HfO2 in an amorphous SiOC matrix. The morphological features were imaged using electron microscopy. The dielectric properties of sintered Si(Hf)OC nanocomposites were investigated at varied temperatures (25 °C–250 °C) and frequency ranges (10−1 Hz–106 Hz) for the first time. At room temperature, the ε՚ value at 1 kHz is found to be 14, which is almost double the value of pure sintered SiOC (ε՚∼5). The dielectric loss (tanδ) is less than 0.07 at 1 kHz at room temperature, which is significantly less than sintered SiOC (tanδ ∼0.5). An increase in permittivity is associated with high permittivity t-HfO2 nanocrystals and additional interfacial/space charge polarization at the interfaces between the t-HfO2 and SiOC matrix. At high-frequency regions (>1 kHz), the dielectric properties of nanocomposites were found to be thermally stable (up to 250 °C). At low-frequency regions (<70 Hz), the material exhibits a rise in dielectric permittivity with increasing temperature, most likely due to charge carrier accumulation at the interfaces of t-HfO2, SiO2, and carbon in the SiOC matrix through the migration of thermally activated charge carriers.

WS2 Nanotube-Embedded SiOC Fibermat Electrodes for Sodium-Ion Batteries.

Layered transition metal dichalcogenides (TMDs) such as tungsten disulfide (WS2) are promising materials for a wide range of applications, including charge storage in batteries and supercapacitors. Nevertheless, TMD-based electrodes suffer from bottlenecks such as capacity fading at high current densities, voltage hysteresis during the conversion reaction, and polysulfide dissolution. To tame such adverse phenomena, we fabricate composites with WS2 nanotubes. Herein, we report on the superior electrochemical performance of ceramic composite fibers comprising WS2 nanotubes (WS2NTs) embedded in a chemically robust molecular polymer-derived ceramic matrix of silicon-oxycarbide (SiOC). Such a heterogeneous fiber structure was obtained via electrospinning of WS2NT/preceramic polymer solution followed by pyrolysis at elevated temperatures. The electrode capacity fading in WS2NTs was curbed by the synergistic effect between WS2NT and SiOC. As a result, the composite electrode exhibits high initial capacity of 454 mAh g-1 and the capacity retention approximately 2-3 times higher than that of the neat WS2NT electrode.

Understanding SiOC atomic structures via synchrotron X-ray and reactive force field potential studies

Silicon oxycarbide (SiOC) is a unique system that can generate various compositions and microstructures via different polymeric precursors and pyrolysis conditions. However, understanding of the atomic structure evolution, such as cluster formation, phase evolution, and atomic coordination, is lacking. In this study, cluster evolution and atomic coordination for different SiOC ceramics pyrolyzed at 1200 °C and 1500 °C were investigated by high energy X-ray diffraction (HE-XRD) and radial distribution function (RDF) analysis. A new Reactive Force Field (ReaxFF) molecular dynamics modeling approach was developed to understand nanocluster separation and early-stage atomic radial coordination. For the first time, we demonstrate that orthorhombic SiO2 forms and converts to growth resistant amorphous SiO2. Cubic β-SiC also forms at lower temperatures than reported, along with a minor amount of hexagonal SiC that has never been reported. The RDF data support such phase evolution understanding. ReaxFF simulation provides direct data on atomic mixing, elemental separation, and effects of precursor molecular structures and compositions, especially in the early stage of the pyrolysis. The simulated RDF data complement the experimental data, revealing the significant presence of C–H bonds along with Si–O and C–C bonds.

Polymer-derived SiOC ceramics: A potential catalyst support controlled by the sintering temperature and carbon content

A series of silicon oxycarbide ceramics with varying carbon content from ca. 10 wt% to ca. 40 wt% were prepared by thermal pyrolysis of four commercially available polysiloxanes and subsequent spark plasma sintering (SPS) at 1200 °C, 1400 °C, and 1600 °C. The results showed that the high carbon content led to a porous microstructure, and for SiOC with ca. 40 wt% carbon content, its porosity and specific surface area at 1600 °C reached 34% and 262 m2/g, respectively. The electrochemical behavior of materials was evaluated. It was shown that SiOC has a certain degree of electrocatalytic activity, and the sample with 10 wt% carbon content obtained at 1200 °C exhibited an overpotential of 450 mV vs. RHE at 10 mA·cm−2 in acid medium. Finally, it was analyzed that the electrochemical behavior of SiOC is closely related to the phase composition and microstructure of the resulting ceramics.

The Role of Carbon Content: A Comparison of the Nickel Particle Size and Magnetic Property of Nickel/Polysiloxane‐Derived Silicon Oxycarbide

A facile and novel processable method to synthesize the Ni nanoparticles (Ni NPs) by tailoring their size in the matrix of the silicon oxycarbide (SiOC) ceramic system is reported. This method is based on polymer‐derived ceramics (PDCs), instead of the conventional powder route. The specific structural characteristics and magnetic properties of the various Ni NPs/SiOC composites as a function of carbon content are systematically investigated. The magnetic properties are experimentally investigated as a function of NP size and measurement temperature. It is demonstrated that the change in the size of Ni NPs (average from ≈4 to ≈ 19 nm) determines the magnetic nature of superparamagnetism. Zero‐field‐cooled (ZFC) and field‐cooled (FC) magnetization studies under magnetic fields of 100 Oe are performed. The saturated M versus H (M–H) loops (saturation magnetization) increase and the coercivity decreases with the size reduction of Ni NPs. It is an indicator of the presence of superparamagnetic behavior and single‐domain NP for ceramic materials.

Novel silicon oxycarbide/spodumene glass-ceramic composites with tailored thermal expansion coefficient

Highly densified silicon oxycarbide (SiOC)/spodumene composites with low coefficient of thermal expansion (CTE) were obtained just selecting the spark plasma sintering temperature employed. For the first time we proposed the use of spodumene a cheap and natural available lithium aluminium silicate mineral as meltable/active filler for SiOC-derived composites, due to its powerful fluxing properties and also its very low CTE. SiOC/spodumene composites sintered at 1200 ⁰C display a very low CTE (0.128±0.004–1.902±0.002 × 10−6 K−1) due to the α,β-transformation of spodumene. At higher sintering temperatures the CTE increases to 3.288±0.004 × 10−6 and 4.516±0.006 × 10−6 K−1 (1300 and 1400 ⁰C) due to the β-SiC formation. In this range of temperature, spodumene promotes the phase separation of SiOC and subsequent crystallization of cristobalite and β-SiC. The maximum values of hardness (11.5 ± 0.5 GPa) and elastic modulus (91±4 MPa) are reached at 1300 ⁰C, where the SiOC/composite displays a neat densification and the lowest roughness (1.61±0.01 nm).

Synthesis of Silicon Oxycarbide Beads from Alkoxysilane as Anode Materials for Lithium-Ion Batteries.

Silicon is an important anode material for lithium-ion batteries because of its high theoretical capacity. However, the large volume expansion of silicon anodes hinders its commercial utilization. As an alternative, silicon oxycarbides (SiOCs) mitigate the expansion of anodes during lithiation, and the synthesis of SiOC beads from silanes is rather simple and at a low cost. In this study, we compared three different reactor setups for making the SiOC beads from methyltrimethoxysilane (MTMS) and found that the control of residence time was crucial. Thereby, the batch reactor turned out to be the easiest one for making monodispersed beads. We also reduced the O/Si ratio of the SiOC beads by adding dimethyldimethoxysilane (DMDMS) for better battery performance. The first-cycle delithiation capacity of the most stable material was over 1796 mA h/g, with an initial Coulombic efficiency of 82%, while the capacity retention after 170 cycles was 67% (992 mA h/g) at a charging rate of 2 A/g in the potential range of 0.01-3 V. This was among the best of the reported data so far for the SiOC beads from MTMS.

Near zero-strain silicon oxycarbide interphases for stable Li-ion batteries.

We investigate silicon oxycarbide nanotubes that incorporate Si, SiC, and silicon oxycarbide phases, which exhibit near zero-strain volume expansion, leading to reduced electrolyte decomposition. The composite effectively accommodates the formation of c-Li15Si4, as validated by in situ TEM analyses and electrochemical tests, thereby proposing a promising solution for Li-ion battery anodes.

Influence of polymer synthesis route and organic fraction content on structure and porosity of silicon oxycarbide ceramics

This paper describes the structural and textural characteristics of silicon oxycarbide ceramics obtained from three different hybrid polymers by varying pyrolysis temperature. The first polymer was prepared by hydrosilylation between poly(hydromethylsiloxane) and divinylbenzene in stoichiometric proportions; the second was similarly obtained, but with excess of divinylbenzene (60 wt.%) and the third was also synthesized with 60 wt.% divinylbenzene, involving simultaneously hydrosilylation and radical reactions. Precursors were pyrolysed under argon at 1000, 1200 and 1500?C to produce silicon oxycarbide-based ceramics. Silicon carbide phase development and devitrification resistance were influenced by the disordered and ordered residual carbon fraction, which was directly related to the polymer structure. High specific surface area and pore volume values were obtained in C-richer ceramics at 1500?C derived from poly(divinylbenzene) network-containing precursor. Silicon oxycarbide matrices, derived from hybrid polymers containing graphitic carbon and silicon carbide phases together with different amount of porosity, revealed desirable features for electrochemical applications and adsorbent systems.

A review of silicon oxycarbide ceramics as next generation anode materials for lithium-ion batteries and other electrochemical applications

The present review outlines a comprehensive overview of the research on silicon oxycarbide (SiOC) materials, which are synthesized by various synthetic routes and are investigated as alternatives to crystalline silicon anodes.

Application of N-Doped Carbon–Silicon Oxycarbide Based on POSS Synthesis in Lithium-Ion Batteries

Si/C materials have attracted much attention as anode materials for lithium-ion batteries. Here, nitrogen-doped silica carbon composites with a carbon-coated structure were synthesized using poly(1-vinylimidazole) in the presence of octavinyl-silsesquioxane followed by annealing and magnesium thermal reduction processes of the polymer precursor (PPVIm). Benefiting from the moderate Si–O–C bonds, the prepared NSiOC possesses a high first discharge capacity of 1862.3 mAh·g–1 at 0.2 A·g–1 and an initial Coulombic efficiency of 70.0% at 30 °C. When the temperature rises to 60 °C, the first discharge and charge specific capacities of the synthesized anode material at 0.2 A·g–1 increase to 2103.0 and 1528.7 mAh·g–1 with an ultralong lifespan of more than 1000 cycles. Moreover, the results show that the degradation of performance during the initial phase of cycles can be ascribed to the formation of an SEI layer and insufficient electrolyte penetration. The battery maintains a steady state (nearly 600 consecutive cycles) for a long time afterward as the activation of the anode material increases, attributed to the low expansion coefficient originating from the porous structure of the carbon capping layer and silicon oxide. In addition, the electrochemical attenuation process of the electrode material with a unique inorganic silica skeleton and exceptional electrochemical performance was also investigated for the assistance of future design in high-performance electrode materials.

Simulation of Silicon Oxycarbide Waveguides for Shorter Band Photonics

In this research paper, we design and simulate Silicon Oxycarbide (SiOC) channel waveguides and photonic passive device such as directional coupler. SiOC channel waveguides are designed for different values of width and height at shorter wavelength band that is 1310 nm wavelength window with refractive index of SiOC (ncore) =2.2 μm and SiO2 (nclad) = 1.444 μm. TE and TM fundamental mode is achieved at width = 1.5 microns and height = 0.5 microns to understand the single mode operation of SiOC channel waveguides. The minimum bending radius of SiOC waveguide is found to be 30 microns that is large enough to integrate the large scale devices. Directional coupler is designed to measure the coupling power between waveguides with gap 0.6, 0.7 and 0.8 microns that gives the 3dB coupling at 20, 40 and 100 microns. In this research, silicon oxycarbide is presented as potential material platform for the highly efficient photonic devices.

Polymer-derived microporous SiOC ceramic coated gallium nitride sensor for selective H2/CO detection

In this work enhancement of H2/CO selectivity of GaN sensors coated with amorphous microporous silicon oxycarbide (SiOC) filter layer has been studied. Amorphous SiOC ceramic has been synthesized by pyrolysis of vinyl-functionalized polysiloxane at 700 °C under argon. N2-adsorption measurement confirms formation of microporous SiOC ceramic. SiOC layer with a thickness of about 6 µm was coated on GaN sensor substrate after two-fold coating/pyrolysis steps. Transient response characteristics and sensor signals of uncoated GaN and SiOC-coated GaN sensors were measured towards H2 (50, 500 and 1000 ppm) and CO (50, 70 and 100 ppm) in nitrogen at 400 °C. Uncoated GaN showed high sensor signal towards both H2 and CO whereas for SiOC-coated GaN almost no sensing towards CO was found.