Preparation of SiOC/HfO2 fibers from silicon alkoxides and tetrachloride hafnium by a sol–gel process

Yan, Xiao; Su, Dong; Duan, Haozhi; Zhang, Fengrui

doi:10.1016/j.matlet.2015.02.067

Cited by 16 publications

(6 citation statements)

References 19 publications

(33 reference statements)

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“…After modification with the metal alkoxides, it is reported that the formed Si-O-M absorption bands are found in the range between 900 cm −1 and 970 cm −1 , 19 which is highlighted by the dotted rectangle in Figure 3. As shown for the HfTi_PMS_Pr sample, the metal-alkoxide-modified precursor reveals the presence of the characteristic Si-O-Hf band located at ~960 cm −1 , which demonstrates that Hf has been incorporated into the Si-O network 24 through the reaction as deduced in Figure 2. The Si-O-Ti absorption band, which is expected to exist in the same range, 25 was not detected in the current work for all kinds of modified polymers due to the low concentration of 3 wt% addition of Ti(O n Bu) 4 to the PMS.…”

Section: Single-source Precursor Synthesis and Polymer-to-ceramic Tmentioning

confidence: 73%

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Sun

Wen

et al. 2019

J Am Ceram Soc

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SiOC/HfO2‐based ceramic nanocomposites with in situ formed HfO2 nanoparticles were prepared via a single‐source precursor (SSP) approach starting from a polymethylsilsesquioxane (PMS) modified by Hf‐ and Ti‐alkoxides. By varying the alkyl‐group of the employed Hf‐alkoxides, SiOC/HfO2‐based ceramic nanocomposites with different HfO2 polymorphs formed via thermal decomposition of the SSP under the same heat‐treatment conditions. Using PMS chemically modified by Hf(OnBu)4, tetragonal HfO2 phase was formed after the synthesis at 1100°C in Ar, whereas both, tetragonal and monoclinic HfO2 nanocrystals, were analyzed when replacing Hf(OnBu)4 by Hf(OiPr)4. After oxidation of the synthesized nanocomposites in air at 1500°C, a facile formation of oxidation‐resistant HfSiO4 (hafnon) phase occurred by the reaction of HfO2 nanocrystals with silica present in the SiOC nanocomposite matrix derived from Hf(OiPr)4‐modified SSPs. Moreover the amount of hafnon is dramatically increased by the additional modification of the polysiloxane with Ti‐alkoxides. In contrast, ceramic nanocomposites derived from Hf(OnBu)4‐modified SSPs, almost no HfSiO4 is detected after oxidation at 1500°C even though in the case of Ti‐alkoxide‐modified single‐source precursor.

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Section: Single-source Precursor Synthesis and Polymer-to-ceramic Tmentioning

confidence: 73%

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Sun

Wen

et al. 2019

J Am Ceram Soc

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“…SiOC PDCs have amorphous microstructures of mixed SiO 4−x C x that separate into SiO 2 , SiC and C at high temperatures and ultimately degrade into SiC and CO gas (>1300 • C). Incorporating other elements, such as B [8,[10][11][12], Al [13][14][15], Nb [16], Zr [4,17,18], Ti [19][20][21], or Hf [12,[22][23][24], in the Si-C-N or Si-O-C systems may greatly enhance the thermostability of ceramic products by preventing or impeding the crystallization and phase segregation of the ceramic phases in inert or oxidizing environments [7]. Initially, at the crosslinking stage, B atoms may improve the formation of the crosslinking network and increase the yield and structural density of SiBOC [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Further information on the processing/manufacturing [6,[26][27][28][29][30][31][32], physical and mechanical properties [26][27][28][29][30][31][33][34][35][36][37] and micro/nanostructures [5,26,27,29,31,32,34,35,[38][39][40] of PDCs can be found in the previously published review articles. Incorporating other elements, such as B [8,[10][11][12], Al [13][14][15], Nb [16], Zr [4,17,18], Ti [19][20][21], or Hf [12,[22][23][24], in the Si-C-N or Si-O-C systems may greatly enhance the thermostability of ceramic products by preventing or impeding the crystallization and phase segreg...…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Properties and Applications of Si-Based Polymer-Derived Ceramics: A Review

2021

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Ceramics derived from organic polymer precursors, which have exceptional mechanical and chemical properties that are stable up to temperatures slightly below 2000 °C, are referred to as polymer-derived ceramics (PDCs). These molecularly designed amorphous ceramics have the same high mechanical and chemical properties as conventional powder-based ceramics, but they also demonstrate improved oxidation resistance and creep resistance and low pyrolysis temperature. Since the early 1970s, PDCs have attracted widespread attention due to their unique microstructures, and the benefits of polymeric precursors for advanced manufacturing techniques. Depending on various doping elements, molecular configurations, and microstructures, PDCs may also be beneficial for electrochemical applications at elevated temperatures that exceed the applicability of other materials. However, the microstructural evolution, or the conversion, segregation, and decomposition of amorphous nanodomain structures, decreases the reliability of PDC products at temperatures above 1400 °C. This review investigates structure-related properties of PDC products at elevated temperatures close to or higher than 1000 °C, including manufacturing production, and challenges of high-temperature PDCs. Analysis and future outlook of high-temperature structural and electrical applications, such as fibers, ceramic matrix composites (CMCs), microelectromechanical systems (MEMSs), and sensors, within high-temperature regimes are also discussed.

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“…Such nanoscale dispersions can be achieved using the sol–gel method. Generally, this method is carried out using a polymer modified using silica alkoxide in the main chain or at the terminal and metal alkoxide [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Previously, we have investigated a polycarbonate/titania hybrid system composed of linear 1,6-hexanediol (PHMCD) and cyclic 1,4-cyclohexanedimethanol (PCHCD) as non-toxic alternatives to bisphenol A [ 35 ].…”

Section: Introductionmentioning

confidence: 99%

Polycarbonate/Titania Hybrid Films with Localized Photo-Induced Magnetic-Phase Transition

et al. 2020

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Materials that exhibit the photo-induced magnetic-phase transition of titania are receiving significant attention because they can be easily switched between diamagnetism and paramagnetism by UV irradiation. However, it is difficult to store photo-induced titanium (Ti3+) in air because of its easy oxidation upon oxygen exposure. In this study, titania/polycarbonate hybrid films were prepared using linear 1,6-hexanediol (PHMCD), cyclic 1,4-cyclohexanedimethanol (PCHCD), or their copolymerized carbonate oligomers using the sol–gel method. The oxygen permeability of the hybrid film decreased as the ratio of the ring structure increased by a factor of approximately 32 from PHMCD with only the chain structure to PCHCD with only the ring structure. These hybrid films can generate Ti3+ under a UV irradiation of 250 W for 2 h, and the difference in oxygen permeability significantly affected the lifetime of the Ti3+ by a factor of up to 120. In addition, the tensile tests and IR measurements demonstrated that UV irradiation had little effect on the mechanical intensity and matrix chemical structure. Moreover, the magnetic susceptibility of Ti3+ present in PCHCD was confirmed to be 6.2 (10−3 emu/g(titania)) under an external magnetic field of 5 T induced using a superconducting quantum interference device.

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Preparation of SiOC/HfO2 fibers from silicon alkoxides and tetrachloride hafnium by a sol–gel process

Cited by 16 publications

References 19 publications

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

Phase evolution of SiOC‐based ceramic nanocomposites derived from a polymethylsiloxane modified by Hf‐ and Ti‐alkoxides

High-Temperature Properties and Applications of Si-Based Polymer-Derived Ceramics: A Review

Polycarbonate/Titania Hybrid Films with Localized Photo-Induced Magnetic-Phase Transition

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