Role of polysiloxanes in the synthesis of aligned porous silicon oxycarbide ceramics

Chauhan, Pawan Kumar; Sujith, R. I.; Parameshwaran, R.; Prasad, Abhay

doi:10.1016/j.ceramint.2019.01.116

Cited by 16 publications

(22 citation statements)

References 25 publications

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“…The first is a high-intensity absorption band at around 3500 cm -1 , assigned to the hydroxyl group which represents adsorbed water on the surface. In addition, the bands near 1050 cm -1 and 800 cm -1 are attributed to Si-O-Si and Si-C, respectively [14]. The presence of the absorption band for Si-O stretching vibration mode and the absence of Si-H absorption band around 2150 cm -1 is an indication of the completion of the pyrolysis process and the formation of the ceramics.…”

Section: Resultsmentioning

confidence: 94%

“…The synthesis of the GNP incorporated ceramic was carried out through the polymer precursor route which involves the curing of the polymeric mixture followed by pyrolysis till 1000˚C. The [14]. The R18 sample discussed in reference [14] was chosen for the studies since it has the highest specific surface area and pore volume, which are key to hydrogen adsorption.…”

Section: Methodsmentioning

confidence: 99%

“…The [14]. The R18 sample discussed in reference [14] was chosen for the studies since it has the highest specific surface area and pore volume, which are key to hydrogen adsorption. GNP was added in different weight fractions of 0.3 wt.%, 3wt.%, and 6 wt.%to the polymeric precursor mixture to establish its effect on the pore morphology and structure of the Si-O-C.…”

Section: Methodsmentioning

confidence: 99%

“…After Pt addition, again the mixture was stirred for 15 min at 600 rpm. This was followed by pouring these stirred precursors blends in a ceramic crucible for overnight curing at 220˚C [14]. The curing process was followed by pyrolysis till 1000˚C.…”

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Experimental Investigation and modeling of hydrogen storage in graphene nanoplatelets incorporated silicon oxycarbide ceramics

Chauhan¹,

Vidhukiran²,

Parameshwaran³

et al. 2021

Preprint

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The present work focuses on synthesizing graphene nanoplatelets (GNP) incorporated amorphous silicon oxycarbide ceramic (Si-O-C) for hydrogen adsorption. The changes in the structure of the ceramic upon addition of GNP has been studied using X-ray diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy and Fourier Transform Infrared (FT-IR) spectroscopy. A theoretical framework to quantify these changes is proposed in line with existing structural model. Hydrogen adsorption studies have been carried out at 100K and 2 bar using Sievert’s apparatus. Maximum gravimetric storage density (GD) of 0.16 wt.% was observed after adding 0.3 wt.% of GNP, in comparison to 0.35 wt.% for the non-GNP sample. Pores sized 2–5 nm were found to be critical for hydrogen adsorption. The study finds that GNP addition leads to an increase in the size of the silica nanodomains. This increase in nanodomain size results in increase in the pore sizes of the existing mesopores, thereby reducing the overall hydrogen uptake. Further, the addition of GNP beyond 3 wt.% is found to increase the coordination of mixed bonds (Si-O-C) in the interface which results in agglomeration and subsequent loss of porosity in the composite.

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Section: Resultsmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Experimental Investigation and modeling of hydrogen storage in graphene nanoplatelets incorporated silicon oxycarbide ceramics

Chauhan¹,

Vidhukiran²,

Parameshwaran³

et al. 2021

Preprint

Self Cite

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“…The two main routes are either atom-deposition-based [15][16][17] or organosilicon-polymeric-preceramic-precursor-based. In the latter, either commercially available polysiloxanes [18,19], networked organosilicon polymers [20,21], or polysilsesquioxane gels obtained using the sol-gel method [22,23] can be annealed at temperatures exceeding 700 • C [24]. The last route is especially interesting for scientists, as it allows the easy customization of the preceramic polymer atom content by mixing small alkoxysilanes with a variable number of Si-C bonds [25], as well as different organic side groups [26].…”

Section: Introductionmentioning

confidence: 99%

Macromonomers as a Novel Way to Investigate and Tailor Silicon-Oxycarbide-Based Materials Obtained from Polymeric Preceramic Precursors

et al. 2021

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It has been shown that bifunctional monomers (D units), which are used to increase the carbon content in silicon oxycarbide precursors, can form volatile oligomers, thus affecting the amount of carbon available during the transition into the final material in the annealing process. Additionally, an uneven distribution of carbon-rich mers may lead to the formation of a free-carbon phase, instead of the incorporation of carbon atoms into the silicon matrix. In this study, a novel two-step approach was utilized. Firstly, a macromonomer containing a number of structural units with precise structure was synthesized, which was later polycondensed into a ceramic precursor. Chlorodimethylsilane modified 2,4,6,8-tetramethylcyclotetrasiloxane was used as a silicon oxycarbide precursor monomer containing both T and D structural units (i.e., silicon atoms bonded to three and two oxygen atoms, respectively), with well-defined interconnections between structural units. Such a macromonomer prevents the formation of small siloxane rings, and has a very limited number of possible combinations of structural units neighboring each silicon atom. This, after investigation using IR, XRD, TG and elemental analysis, gave insight into the effect of “anchoring” silicon atoms bonded to two methyl groups, as well as the impact of their distribution in comparison to the materials obtained using simple monomers containing a single silicon atom (structural unit).

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Thermodynamic stabilization of crystalline silicon carbide polymer‐derived ceramic fibers

Leonel

Mujib

Singh

et al. 2022

Int J Ceramic Engine & Sci

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Three crystalline SiC fibers were studied: Tyranno, Hi-Nicalon, and Sylramic.Thermodynamic stability of the SiC fibers was determined by high temperature oxide melt solution calorimetry. Results shed light on the thermodynamic penalty or benefit associated with microstructural modification of the ceramic fibers, and how energetics correlate to mechanical properties. Enthalpies of formation from components (SiC, SiO 2 , Si 3 N 4 , and C, ∆H • f,comp ) for Tyranno, Hi-Nicalon, and Sylramic are −12.05 ± 8.71, −58.75 ± 6.93, and −71.10 ± 8.71 kJ/mol Si, respectively. The microstructure in Sylramic offers the greatest stabilizing effect, thus resulting in its much more exothermic enthalpy of formation relative to elements and crystalline components. In contrast, the microstructure in Tyranno offers the least stabilization. The thermodynamic stability of the fibers increases with increasing mixed bonding (Si bonded to both C and O). From mechanical testing, Young's moduli of Tyranno, Hi-Nicalon, and Sylramic are 112, 205, and 215 GPa, respectively. Greater thermodynamic stability is correlated with a higher Young's modulus.

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Role of polysiloxanes in the synthesis of aligned porous silicon oxycarbide ceramics

Cited by 16 publications

References 25 publications

Experimental Investigation and modeling of hydrogen storage in graphene nanoplatelets incorporated silicon oxycarbide ceramics

Experimental Investigation and modeling of hydrogen storage in graphene nanoplatelets incorporated silicon oxycarbide ceramics

Macromonomers as a Novel Way to Investigate and Tailor Silicon-Oxycarbide-Based Materials Obtained from Polymeric Preceramic Precursors

Thermodynamic stabilization of crystalline silicon carbide polymer‐derived ceramic fibers

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