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On the thermodynamically stable amorphous phase of polymer-derived silicon oxycarbide.

Yu L, Raj R - Sci Rep (2015)

Bottom Line: In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them.We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase.In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side.

View Article: PubMed Central - PubMed

Affiliation: University of Colorado at Boulder Boulder, Colorado 80309, USA.

ABSTRACT
A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown that the amorphous phase is thermodynamically stable. In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them. We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase. The approach highlights how density functional theory computations can be combined with the classical analysis of phase transformations to explain the behavior of a complex material. In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side.

No MeSH data available.


Related in: MedlinePlus

Plots of Eq. (6) showing the domain size where the amorphous state is stable.A deeper minimum and a shift of the minimum to the right implies greater stability of the amorphous state.
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f3: Plots of Eq. (6) showing the domain size where the amorphous state is stable.A deeper minimum and a shift of the minimum to the right implies greater stability of the amorphous state.

Mentions: Plots of Eq. (6) for different values of α = 0.25 to 2.0 are shown in Fig. 3. The minimums become deeper and move towards a large size of the nanodomains as α increases, reflecting the increasing role of the edge bonds. The values for α are derived from first principles calculations, as described in the next section.


On the thermodynamically stable amorphous phase of polymer-derived silicon oxycarbide.

Yu L, Raj R - Sci Rep (2015)

Plots of Eq. (6) showing the domain size where the amorphous state is stable.A deeper minimum and a shift of the minimum to the right implies greater stability of the amorphous state.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588588&req=5

f3: Plots of Eq. (6) showing the domain size where the amorphous state is stable.A deeper minimum and a shift of the minimum to the right implies greater stability of the amorphous state.
Mentions: Plots of Eq. (6) for different values of α = 0.25 to 2.0 are shown in Fig. 3. The minimums become deeper and move towards a large size of the nanodomains as α increases, reflecting the increasing role of the edge bonds. The values for α are derived from first principles calculations, as described in the next section.

Bottom Line: In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them.We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase.In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side.

View Article: PubMed Central - PubMed

Affiliation: University of Colorado at Boulder Boulder, Colorado 80309, USA.

ABSTRACT
A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown that the amorphous phase is thermodynamically stable. In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them. We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase. The approach highlights how density functional theory computations can be combined with the classical analysis of phase transformations to explain the behavior of a complex material. In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side.

No MeSH data available.


Related in: MedlinePlus