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High-Temperature Thermomechanics of ...

Tank, Mehul.

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High-Temperature Thermomechanics of BNNT Nanocomposites.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	High-Temperature Thermomechanics of BNNT Nanocomposites./
作者:	Tank, Mehul.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
面頁冊數:	131 p.
附註:	Source: Dissertations Abstracts International, Volume: 85-03, Section: B.
Contained By:	Dissertations Abstracts International85-03B.
標題:	Industrial engineering. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30526598
ISBN:	9798380386746

High-Temperature Thermomechanics of BNNT Nanocomposites.
Tank, Mehul.

High-Temperature Thermomechanics of BNNT Nanocomposites. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 131 p.

Source: Dissertations Abstracts International, Volume: 85-03, Section: B.

Thesis (Ph.D.)--The Florida State University, 2023.

This item must not be sold to any third party vendors.

This report presents a Ph.D. dissertation for assessing and developing multifunctional BNNT composites and their fundamental mechanisms and manufacturing applicable for space or high-temperature composite structures. The report will cover the critical elements accomplished, focusing on the decomposition and high-temperature stability of BNNTs, high-precision polymer and ceramic SLA 3D-printed BNNT composites, hybrid composites, and nanotube composite modeling techniques.The research on the physical properties of BNNTs shows that they have a stable broad band gap, excellent mechanical strength, high thermal conductivity, and high oxidation resistance. A fundamental understanding of the thermal behavior of reinforcement materials is crucial to fully exploiting their properties in composites. The high-quality, high-purity BNNTs were tested to thermal failure in an inert atmosphere for the first time up to 2500°C. A significant fraction of the BNNTs survived to temperatures as high as 2200°, which was verified with transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and the BNNT samples were completely undamaged at temperatures as high as 1800°C. Observed color darkening, significant weight loss, an increased boron atomic level, significant weight gain upon oxidation, the presence of boron oxide compounds in an oxidized sample, and the observed boron clusters at the nanoscale indicate dissociation of BN in the sample at 2200°C. The stability of BNNT structures was observed up to 2000°C, with local/partial wall dissociation or unzipping, and complete survivability of highly crystalline BNNTs is demonstrated up to 1800°C.Furthermore, the unique approach of applying such BNNTs towards manufacturing of 3D printed ceramics and confidently exposing them to high temperature environments for sintering is demonstrated. 3D printed ceramic nanocomposite with 0.1 wt% of BNNT was prepared by fusing at high temperatures. The length effect of nanoscale reinforcements on the mechanical properties of the printed ceramic composites reported significant improvements up to 55% in bending strength and 72% in bending modulus with just 0.1 wt% BNNT addition. A 63% thermal diffusivity improvement of ceramic by adding BNNTs is observed using laser flash analysis.A high-quality BNNT inter-ply hybrid composite structure containing alternating CF and BNNT layers was manufactured, building upon the knowledge developed. BNNTs have excellent interfacial bonding with matrices; therefore, they can act as a pseudo-reinforcement in the z-direction, similar to stitching. Post-test fracture analysis and crack propagation reveal excellent BNNT adhesion. Thermal diffusivity performance showed consistent improvement across the temperature range up to 150°C.Examination of BNNTs as a thermal protective ablative layer under flame conditions resulted in a maximum of 31% backside temperature reduction and a 14% weight loss due to the ablation of the protective BNNT surface layer. Ultimately, the overall analysis shows that hybrid BNNT/CF composites are excellent candidates for thermal protection applications and innovates the manufacturing and modelling methods for improved performance. In contrast to ceramics and metal alloys, with high densities and poor oxidation resistance, lightweight nanocomposite hybrids could enhance the efficiency and multifunctionality of space vessels.

ISBN: 9798380386746Subjects--Topical Terms:

526216
Industrial engineering.
Subjects--Index Terms:

Boron nitride nanotubes

High-Temperature Thermomechanics of BNNT Nanocomposites.
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500 $a Source: Dissertations Abstracts International, Volume: 85-03, Section: B.
500 $a Advisor: Sweat, Rebekah.
502 $a Thesis (Ph.D.)--The Florida State University, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a This report presents a Ph.D. dissertation for assessing and developing multifunctional BNNT composites and their fundamental mechanisms and manufacturing applicable for space or high-temperature composite structures. The report will cover the critical elements accomplished, focusing on the decomposition and high-temperature stability of BNNTs, high-precision polymer and ceramic SLA 3D-printed BNNT composites, hybrid composites, and nanotube composite modeling techniques.The research on the physical properties of BNNTs shows that they have a stable broad band gap, excellent mechanical strength, high thermal conductivity, and high oxidation resistance. A fundamental understanding of the thermal behavior of reinforcement materials is crucial to fully exploiting their properties in composites. The high-quality, high-purity BNNTs were tested to thermal failure in an inert atmosphere for the first time up to 2500°C. A significant fraction of the BNNTs survived to temperatures as high as 2200°, which was verified with transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and the BNNT samples were completely undamaged at temperatures as high as 1800°C. Observed color darkening, significant weight loss, an increased boron atomic level, significant weight gain upon oxidation, the presence of boron oxide compounds in an oxidized sample, and the observed boron clusters at the nanoscale indicate dissociation of BN in the sample at 2200°C. The stability of BNNT structures was observed up to 2000°C, with local/partial wall dissociation or unzipping, and complete survivability of highly crystalline BNNTs is demonstrated up to 1800°C.Furthermore, the unique approach of applying such BNNTs towards manufacturing of 3D printed ceramics and confidently exposing them to high temperature environments for sintering is demonstrated. 3D printed ceramic nanocomposite with 0.1 wt% of BNNT was prepared by fusing at high temperatures. The length effect of nanoscale reinforcements on the mechanical properties of the printed ceramic composites reported significant improvements up to 55% in bending strength and 72% in bending modulus with just 0.1 wt% BNNT addition. A 63% thermal diffusivity improvement of ceramic by adding BNNTs is observed using laser flash analysis.A high-quality BNNT inter-ply hybrid composite structure containing alternating CF and BNNT layers was manufactured, building upon the knowledge developed. BNNTs have excellent interfacial bonding with matrices; therefore, they can act as a pseudo-reinforcement in the z-direction, similar to stitching. Post-test fracture analysis and crack propagation reveal excellent BNNT adhesion. Thermal diffusivity performance showed consistent improvement across the temperature range up to 150°C.Examination of BNNTs as a thermal protective ablative layer under flame conditions resulted in a maximum of 31% backside temperature reduction and a 14% weight loss due to the ablation of the protective BNNT surface layer. Ultimately, the overall analysis shows that hybrid BNNT/CF composites are excellent candidates for thermal protection applications and innovates the manufacturing and modelling methods for improved performance. In contrast to ceramics and metal alloys, with high densities and poor oxidation resistance, lightweight nanocomposite hybrids could enhance the efficiency and multifunctionality of space vessels.
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650 4 $a Materials science. $3 543314
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