Phase evolution in Zr-doped preceramic polymer derived SiZrOC hybrids

Anand, Rahul; Sahoo, Sarmila; Nayak, Bibhuti B.; Behera, Shantanu K.

doi:10.1016/j.ceramint.2019.12.196

Cited by 20 publications

(8 citation statements)

References 31 publications

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“…The width between the D and G peaks becomes wider in the direction of the higher wavenumber. This phenomenon may be attributed to the broadening of the phonon spectrum of the Zr mixed bond at higher frequencies . Moreover, the observations align with the model proposed by Ferrari and Robertson, as follows: (1) When the G peak shifts from 1510 to 1600 cm –1 and I D / I G increases, the free carbon undergoes a transition state from amorphous carbon to nanocrystalline graphite.…”

Section: Resultssupporting

confidence: 87%

“…This phenomenon may be attributed to the broadening of the phonon spectrum of the Zr mixed bond at higher frequencies. 24 Moreover, the observations align with the model proposed by Ferrari and Robertson, 34 as follows: (1) When the G peak shifts from 1510 to 1600 cm −1 and I D /I G increases, the free carbon undergoes a transition state from amorphous carbon to nanocrystalline graphite. (2) When the G peak moves from 1600 to 1580 cm −1 and I D /I G decreases, the transition from nanocrystalline graphite to graphite at the free carbon occurs.…”

Section: Evolution Of Chemical Composition During Pyrolysis the Redis...supporting

confidence: 84%

“…Valuable insights can be gained by referring to experiences with SiOC ceramic materials. Previous studies have investigated the addition of metal elements such as Al, Ti, Zr, and Hf to the SiOC system, resulting in significant improvements in its nanostructures and performance. − Du et al fabricated SiOC/M (M = Fe, Al, and Zr) ceramics through thermal decomposition in the temperature range of 1200–1400 °C. Phase and microstructural analysis demonstrated that SiOC/Zr exhibited the best stability, mainly attributed to the formation of the ZrO 2 phase .…”

Section: Introductionmentioning

confidence: 99%

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Effect of Zr on the Microstructure and High-Temperature Phase Separation Evolution of SiOC Aerogels

Han,

Wu,

Huang

et al. 2023

Langmuir

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SiZrOC aerogels were synthesized through the pyrolysis of the zirconium source-doped SiOC system using zirconyl chloride octahydrate (ZrOCl2·8H2O) at temperatures ranging from 900 to 1300 °C. This study investigates the microstructure evolution and phase separation of SiOC and SiZrOC aerogels during the pyrolysis process. Upon pyrolysis, both aerogels exhibited a Si–O–C structure with a high thermal stability. The introduction of zirconium elements significantly enhanced the pore volume (3.20 cm3/g) and porosity (96.0%) and reduced the thermal conductivity (0.023 W·m–1·K–1) of the organic–inorganic precursor aerogel. Moreover, the three-dimensional pore structure was retained even under high-temperature pyrolysis conditions. SiZrOC-1100 displayed a high specific surface area of 273.52 m2/g, a high pore volume of 1.70 cm3/g, and a low thermal conductivity of 0.033 W·m–1·K–1. At high temperatures, the SiZrOC phase transformation produces tetragonal ZrO2, which inhibits the graphitization process of free carbon and the growth of SiC grains. Furthermore, the phase separation process of the SiO x C y matrix structure generated oxygen-rich SiO x C4–x units, while carbon-rich SiO x C4–x units were negligible below a pyrolysis temperature of 1200 °C. Between 900 and 1200 °C, SiZrOC is composed of amorphous SiOC, amorphous ZrO2, microcrystalline t-ZrO2, and free carbon phase. These findings provide valuable insights into the preparation of high-performance SiOC aerogels.

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Section: Resultssupporting

confidence: 87%

Section: Evolution Of Chemical Composition During Pyrolysis the Redis...supporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Zr on the Microstructure and High-Temperature Phase Separation Evolution of SiOC Aerogels

Han,

Wu,

Huang

et al. 2023

Langmuir

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“…The lower degree of phase separation observed in SiZrOC can be attributed to the substantial formation of t-ZrO 2 microcrystals during the pyrolysis process, which effectively inhibits the segregation of carbon and silicon dioxide within the SiO x C y matrix, 36 as well as the occurrence of carbon thermoreduction reactions. 37 As illustrated in Figure 8, the eV, corresponding to the bimodal structure of ZrO 2 (Figure 8c).…”

Section: Thermal Stability Mechanism Of Sizroc Aerogelsmentioning

confidence: 99%

SiZrOC Aerogels with Low Thermal Conductivity and Enhanced Thermal Stability for Applications in High-Temperature Nanoscale Thermal Insulators

Han,

Wu,

Huang

et al. 2023

ACS Appl. Nano Mater.

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The continuous, random three-dimensional nanostructure of aerogels is the key determinant of their exceptional thermal insulating performance. However, at elevated temperatures, sintering can lead to disruption of this nanostructure. SiOC and SiZrOC aerogels were prepared by pyrolyzing organic–inorganic precursor aerogels at 1000 °C under an Ar atmosphere. The pyrolysis treatment resulted in the formation of a Si–O–C structure with excellent thermal stability. Following calcination at 1000 °C for 0.5 h, SiZrOC demonstrated a specific surface area retention rate of 76.8% and a pore volume retention rate of 75.8%, surpassing the most advanced ZrO2–SiO2 aerogel. Additionally, SiZrOC consistently exhibited outstanding thermal insulation performance, with thermal conductivities of 0.0273 and 0.0332 W m–1 K–1 before and after calcination at 1000 °C, respectively. Notably, it was observed for the first time that the rearrangement of Si–C and Si–O bonds caused by pyrolysis induced a loosening effect on the SiO4 structure within the aerogel. Consequently, during subsequent aerobic calcination, SiOC and SiZrOC underwent another phase separation stage, resulting in a further increase in the number of Si–O–C structures, which offers an approach to improve thermal insulation properties in extreme environments. The superior thermal stability and thermal insulation performance make SiZrOC a promising candidate for applications in high-temperature nanoscale thermal insulation materials.

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“…[3,17,18] Therefore, initial precursors and high temperature processing conditions can have a profound in uence on the nal properties of polymerderived ceramic (PDC) nanocomposites. [19,20] Synthesis of such nanocomposites has been performed through the pyrolytic conversion of single source polymeric precursors. For instance, different metal precursors of Al [21,22], Y [23], Ti [24,25], Zr[26-28], and Hf [29] were used to transform the molecular structure of the preceramic precursors that exhibited altered microstructures of SiCN ceramics upon pyrolysis.…”

Section: Introductionmentioning

confidence: 99%

A novel TiO2-TiC-TiC0.3N0.7-C-SiCN multiphase ceramic nanocomposite from preceramic polymer pyrolysis

Anand¹,

Nayak²,

Behera

2022

Preprint

Self Cite

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The current investigation describes the synthesis of SiTiCNO ceramics derived from a mixture of a preceramic polymer (polyvinylsilazane) and tetrabutyl orthotitanate precursors by crosslinking at 300 oC and pyrolysis in the temperature range of 900 oC - 1400 oC in flowing nitrogen atmosphere. Crosslinked precursor was studied through DSC-TG to estimate ceramization temperature as well as ceramic yield. Further, the evolution of phase and nanostructure with temperature in the composite SiTiCNO ceramics was analyzed by the help of different characterization techniques, such as XRD, Raman, and electron microscopy. Ti-doped SiCN ceramic systems appeared as single-phase SiTiCNO amorphous ceramics up to 1100 oC. The phase separation of SiTiCNO ceramics started at 1200 oC and exhibited TiO2 nanocrystals in the SiCN matrix. Ti-doping was found to accelerate the separation of the free carbon phase from the SICN matrix, and the said carbon had better graphitic order in the Ti-doped samples as compared to the undoped SiCN of equivalent thermal history. At 1400 oC, high temperature stable phases such as TiC and TiC0.3N0.7 were formed along with predominant rutile-TiO2 phase within the Si-Ti-O-C-N matrix. A uniform distribution of these nanocrystals in the SiCN matrix at 1400 oC were observed through TEM/HRTEM analysis. The current work exhibits the formation of a unique multiphase composite with the co-existence of nanocrystalline phases uniformly distributed within a polymer derived ceramic matrix.

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Phase evolution in Zr-doped preceramic polymer derived SiZrOC hybrids

Cited by 20 publications

References 31 publications

Effect of Zr on the Microstructure and High-Temperature Phase Separation Evolution of SiOC Aerogels

Effect of Zr on the Microstructure and High-Temperature Phase Separation Evolution of SiOC Aerogels

SiZrOC Aerogels with Low Thermal Conductivity and Enhanced Thermal Stability for Applications in High-Temperature Nanoscale Thermal Insulators

A novel TiO2-TiC-TiC0.3N0.7-C-SiCN multiphase ceramic nanocomposite from preceramic polymer pyrolysis

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