Synthesis and Characterization of Ceramic Precursor Aluminum-Containing Polycarbosilane and its Pyrolysis

Yu, Yuxi; Zhang, Ying; Yang, Jingming; Tang, Ming

doi:10.1007/s10904-007-9143-2

Cited by 25 publications

(11 citation statements)

References 18 publications

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“…In addition to the Si‐Al‐Si bonds, Si‐O‐Al bonds are also identified by analyzing the structures of PACS and the byproducts reported by Cao et al Other methods have also been developed for preparing PACS. In order to reduce the sublimation of Al (acac) 3 and favor heat transfer during the reaction process, PACS is prepared by the reaction of liquid polysilacarbosilane (PSCS) instead of solid PCS with Al (acac) 3 at atmospheric pressure . PSCS is a low‐molecular‐weight compound having Si‐Si and Si‐CH 2 ‐Si linkage in the backbone, which can be prepared by thermal decomposition of polydimethylsilane (PDMS).…”

Section: Introductionmentioning

confidence: 99%

“…This is important because aluminum plays a role as a sintering aid in densifying the structure and suppressing grain growth of the SiC fiber during pyrolysis and sintering process . It is essential to control the structure and molecular weight of the precursor to improve its good spinnability and high strength of the final product, particularly to PACS, because it has more ring and branching structures than PCS . The different preparation method of PACS probably leads to differences in its molecular structure, and the synthetic mechanism may not be identical.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of polyaluminocarbosilane with low branched molecular structure using liquid polysilacarbosilane and aluminum acetylacetonate by high‐pressure method

Duan

Chen

et al. 2018

Applied Organom Chemis

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The synthesis of polyaluminocarbosilane (PACS) using liquid polysilacarbosilane (PSCS) and aluminum acetylacetonate [Al (acac)3] by a high‐pressure method is reported for the first time. The effects of reaction time, temperature and feed ratio on the structure of PACS are investigated in detail by gel permeation chromatography, Fourier transform‐infrared, 1H‐NMR, 29Si‐NMR and 27Al‐NMR methods. It was found that the molecular weight and its polydispersity, as well as the branching degree of the molecular structure of PACS, increase with reaction time and temperature. Increasing the weight percentage of Al (acac)3 has a similar effect as temperature. Combined with the gas chromatography–mass spectroscopy results, the reaction mechanism is proposed, which contains three main reactions: (i) cleavage and rearrangement reaction of PSCS; (ii) silicon‐free radicals react with Al (acac)3, leading to cleavage of O=C and/or O‐C bonds and formation of AlOx ligands; and (iii) conversion reaction of Al ligands from AlO6 into AlO5 and AlO4. It is also found that PACS prepared by high‐pressure method has a lower branched molecular structure in comparison to its analog prepared under ambient pressure conditions, and it is achieved to increase the molecular weight and ceramic yield of PACS, which is beneficial for the processing and overall quality of the final product.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis of polyaluminocarbosilane with low branched molecular structure using liquid polysilacarbosilane and aluminum acetylacetonate by high‐pressure method

Duan

Chen

et al. 2018

Applied Organom Chemis

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“…In several publications, the structures of the polymorphs and their properties were reported, e.g., the synthesis and crystal structure [36], Density Functional Theory (DFT) calculations to probe the crystal structure of the polymorphs [37], crystal structure and luminescence [38], thermal cell-expansion (under light irradiation) [39], luminescence of Al(acac) 3 :Cr 3+ [40], thermodynamics of sublimation of Al(acac) 3 [41], just to name a few. The huge number of papers is due to possible applications, i.e., Al(acac) 3 is a common precursor for the preparation of alumina Al 2 O 3 , [36,[42][43][44] for thin films via CVD [45,46] or nanoparticles [42] and several polymers, e.g., polycarbosilanes (PACS) [47,48]. It is also used as charging additive for liquid electrostatic toners [49] and as additive for perowskite precursor solutions improving crystal quality and reducing strain in the films for perowskite solar cells [50].…”

Section: Introductionmentioning

confidence: 99%

In Situ Studies on Phase Transitions of Tris(acetylacetonato)-Aluminum(III) Al(acac)3

et al. 2016

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Abstract:In situ investigations on the nucleation and crystallization processes are essential for understanding of the formation of solids. Hence, the results of such experiments are prerequisites for the rational synthesis of solid materials. The in situ approach allows the detection of precursors, intermediates, and/or polymorphs, which are mainly missed in applying ex situ experiments. With a newly developed crystallization cell, simultaneous in situ experiments with X-ray diffraction (XRD) and luminescence analysis are possible, also monitoring several other reaction parameters. Here, the crystallization of the model system tris(acetylacetonato)-aluminum(III) Al(acac) 3 was investigated.In the time-resolved in situ XRD patterns, two polymorphs of Al(acac) 3 , the α-and the γ-phase, were detected at room temperature and the influence of the pH value onto the product formation was studied. Moreover, changes in the emission of Al(acac) 3 and the light transmission of the solution facilitated monitoring the reaction by in situ luminescence. The first results demonstrate the potential of the cell to be advantageous for controlling and monitoring several reaction parameters during the crystallization process.

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“…In order to promote the high-temperature performance of SiC fibers, many recent studies have focused on introducing heterogeneous elements, like Ti [14,15], Al [16][17][18] into SiC fibers. Boron element is also reported to promote the high-temperature performance of SiC fibers by holding back the growth of SiC crystallites [19,20].…”

Section: Introductionmentioning

confidence: 99%

Preparation and Properties of Pinacolborane Modified Polycarbosilane as SiC Fiber Precursor

Shang

Shao

Zhu

2015

J Inorg Organomet Polym

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Pinacolborane (PINB) was adopted as a novel boron resource to modify polycarbosilane (PCS) in order to produce a fusible boric precursor for SiC fibers. Several boric PCS (B-PCS) were obtained by varying the reaction temperature and PCS to PINB weight ratio in the reactants. The soft point and average molecular weight of the B-PCS increased after modification and the precursors showed well melt-spinning property validated by a filature experiment. The ceramic conversion process of the B-PCS was studied by thermogravimetric analysis and infrared spectrum method. Although \0.3 wt% of boron was involved, the ceramic yield of PCS was greatly enhanced. Moreover, the crystallization of the boric precursors was obviously blocked at 1400 and 1600°C compared to pure PCS, which make the B-PCS a promising precursor for heat-resisting SiC fiber suitable for massive manufacture.

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Synthesis and Characterization of Ceramic Precursor Aluminum-Containing Polycarbosilane and its Pyrolysis

Cited by 25 publications

References 18 publications

Synthesis of polyaluminocarbosilane with low branched molecular structure using liquid polysilacarbosilane and aluminum acetylacetonate by high‐pressure method

Synthesis of polyaluminocarbosilane with low branched molecular structure using liquid polysilacarbosilane and aluminum acetylacetonate by high‐pressure method

In Situ Studies on Phase Transitions of Tris(acetylacetonato)-Aluminum(III) Al(acac)3

Preparation and Properties of Pinacolborane Modified Polycarbosilane as SiC Fiber Precursor

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