A novel processing approach for free-standing porous non-oxide ceramic supports from polycarbosilane and polysilazane precursors

Konegger, Thomas; Patidar, Rajesh Kumar; Bordia, Rajendra K.

doi:10.1016/j.jeurceramsoc.2015.03.009

Cited by 41 publications

(36 citation statements)

References 19 publications

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“…Pore opening size distribution as a function of cross‐linking temperature, determined by mercury intrusion porosimetry on pyrolyzed samples (30 vol% UHMW ‐ PE , 10 μm; data for 105°C partially reproduced from Ref. ).…”

Section: Resultsmentioning

confidence: 99%

“…Our processing approach for the preparation of planar polymer‐derived ceramic supports was first described in a recent contribution . After degassing of the preceramic polymer under vacuum, a corresponding amount of sacrificial filler powders was added, yielding typical mixtures between 12 and 30 g. The mixture was magnetically stirred under vacuum for a minimum duration of 30 min.…”

Section: Methodsmentioning

confidence: 99%

“…In contrast to the majority of previous works employing this combination of materials, the preceramic polymer is used in its initial, liquid state, thus allowing a more versatile shaping through a casting process with subsequent curing. We reported on this processing approach recently, and showed its general feasibility for the preparation of porous, free‐standing structures in the Si–C and Si–C–N systems . A core objective of this present work is an in‐depth correlation between a number of processing parameters and the resulting materials' performance in terms of permeability and strength, as well as the evaluation of its long‐term stability in oxidizing, neutral, and reducing atmospheres at high temperatures, thus leading to the development of a material system well suited for potential membrane or catalysis applications.…”

Section: Introductionmentioning

confidence: 99%

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Planar, Polysilazane‐Derived Porous Ceramic Supports for Membrane and Catalysis Applications

2015

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Porous, silicon carbonitride-based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh-molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizing both the composition as well as cross-linking parameters, maximum characteristic biaxial flexural strengths of 65 MPa and porosities of 42% were achieved. The evolution of an interconnected, open-pore network during thermal porogen removal and conversion of the preceramic polymer led to air permeabilities in the order of 10−14 m2. The materials were further exposed to long-term heat treatments to demonstrate the stability of properties after 100 h at 800°C in oxidizing, inert, and reducing environments. The determined performance, in combination with the versatile preparation method, illustrates the feasibility of this processing approach for the generation of porous ceramic support structures for applications at elevated temperatures in a variety of fields, including membrane and catalysis science.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Planar, Polysilazane‐Derived Porous Ceramic Supports for Membrane and Catalysis Applications

2015

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“…[3,4] Separation processes employing porous ceramic materials, such as micro-and ultrafiltration or gas separation, have gained increasing attention in various industrial sectors, reaching from chemical and biochemical processing to energy-and environment-related fields, with the particular benefit of improved operability in harsh thermal and chemical environments compared to conventional polymer-based materials. [5] A wide variety of methods and approaches has been reported on the generation of porous Si 3 N 4 and related ceramics, including direct foaming, [6] the addition of pore-forming agents, [7][8][9] combustion synthesis, [10] freeze-casting, [11] or phase separation. [12] Another straightforward approach is partial sintering, where the sintering process is halted before full densification, thus retaining an open-porous pore network between partially connected Si 3 N 4 particles in the final material.…”

Section: Introductionmentioning

confidence: 99%

Open‐Porous Silicon Nitride‐Based Ceramics in Tubular Geometry Obtained by Slip‐Casting and Gelcasting

Brouczek

Konegger

2017

Adv Eng Mater

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Owing to its unique properties, silicon nitride is a frequently used materials choice in highly demanding applications in terms of thermal and mechanical load. In this work, porous silicon nitride-based support materials in hollowtube configuration are generated through colloidal forming, and their respective properties for potential applications in the fields of membranebased separation, filtration, or catalysis are evaluated. Shaping of the ceramics is achieved by two distinct casting techniques, slip-casting, and gelcasting, and the results of the respective methods are set in relation. Furthermore, a special focus is set on the correlation between sintering parameters and resulting porosity. Subsequently, air permeabilities of the generated structures are determined, illustrating a direct relation between processing parameters and resulting permeability. Darcian permeability values of up to 9 Á 10 À16 m 2 are observed for samples exhibiting total porosities between 32 and 41 %. The findings allow for a predictability of suitable permeation properties for the structures' anticipated application as complex-shaped non-oxide ceramic supports for membrane-based separation or catalysis, or as high-performance filter materials.

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“…The most effective method to solve this problem is to composite the oxide with non-oxides. The resulting composites typically have high hot strength, good thermal shock resistance, and excellent corrosion resistance to metallurgical slag [4][5][6][7]. In the 1970s, the Japanese introduced graphite into magnesia and prepared magnesia-carbon refractories, which prolonged the service life of refractories for electric furnaces and converters to ten times the service life of the original oxide refractories [8].…”

Section: Introductionmentioning

confidence: 99%

In situ reaction mechanism of MgAlON in Al–Al2O3–MgO composites at 1700°C under flowing N2

Tong

Yan

et al. 2017

Int J Miner Metall Mater

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Abstract:The Al-Al 2 O 3 -MgO composites with added aluminum contents of approximately 0wt%, 5wt%, and 10wt%, named as M 1 , M 2 , and M 3 , respectively, were prepared at 1700°C for 5 h under a flowing N 2 atmosphere using the reaction sintering method. After sintering, the Al-Al 2 O 3 -MgO composites were characterized and analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results show that specimen M 1 was composed of MgO and MgAl 2 O 4 . Compared with specimen M 1 , specimens M 2 and M 3 possessed MgAlON, and its production increased with increasing aluminum addition. Under an N 2 atmosphere, MgO, Al 2 O 3 , and Al in the matrix of specimens M 2 and M 3 reacted to form MgAlON and AlN-polytypoids, which combined the particles and the matrix together and imparted the Al-Al 2 O 3 -MgO composites with a dense structure. The mechanism of MgAlON synthesis is described as follows. Under an N 2 atmosphere, the partial pressure of oxygen is quite low; thus, when the Al-Al 2 O 3 -MgO composites were soaked at 580°C for an extended period, aluminum metal was transformed into AlN. With increasing temperature, Al 2 O 3 diffused into AlN crystal lattices and formed AlN-polytypoids; however, MgO reacted with Al 2 O 3 to form MgAl 2 O 4 . When the temperature was greater than (1640 ± 10)°C, AlN diffused into Al 2 O 3 and formed spinel-structured AlON. In situ MgAlON was acquired through a solid-solution reaction between AlON and MgAl 2 O 4 at high temperatures because of their similar spinel structures.

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A novel processing approach for free-standing porous non-oxide ceramic supports from polycarbosilane and polysilazane precursors

Cited by 41 publications

References 19 publications

Planar, Polysilazane‐Derived Porous Ceramic Supports for Membrane and Catalysis Applications

Planar, Polysilazane‐Derived Porous Ceramic Supports for Membrane and Catalysis Applications

Open‐Porous Silicon Nitride‐Based Ceramics in Tubular Geometry Obtained by Slip‐Casting and Gelcasting

In situ reaction mechanism of MgAlON in Al–Al2O3–MgO composites at 1700°C under flowing N2

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