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Physical Properties of Bulk Carbon N...

Boyd, Samuel J.,

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Physical Properties of Bulk Carbon Nanotube Conductors Impacting Radio Frequency Waveguide Measurements /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Physical Properties of Bulk Carbon Nanotube Conductors Impacting Radio Frequency Waveguide Measurements // Samuel J Boyd.
作者:	Boyd, Samuel J.,
面頁冊數:	1 electronic resource (197 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-02, Section: B.
Contained By:	Dissertations Abstracts International86-02B.
標題:	Electrical engineering. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31556487
ISBN:	9798383705667

Physical Properties of Bulk Carbon Nanotube Conductors Impacting Radio Frequency Waveguide Measurements /
Boyd, Samuel J.,

Physical Properties of Bulk Carbon Nanotube Conductors Impacting Radio Frequency Waveguide Measurements /Samuel J Boyd. - 1 electronic resource (197 pages)

Source: Dissertations Abstracts International, Volume: 86-02, Section: B.

Recent developments in radio frequency (RF) electronics motivate the interest in developing multi-functional materials which have effective electrical properties with increasing frequency that minimize the conventional skin effect. Carbon nanotubes (CNTs) are emerging as a candidate material due to high direct current (DC) electrical conductivity, flexure tolerance, corrosion resistance, and low density. The DC electrical conductivity of CNT networks is affected by the high resistance junctions between individual or bundled CNTs. Strategies to modify the properties of these junctions have included chemical doping, nano-metal deposition, and physical densification. Alternating current (AC) conductivity measurements of bulk CNT materials to date have shown constant or even increasing values up to 120 GHz. Thus, this dissertation focuses on applying doping and metallization strategies for improving DC electrical properties to altering the AC conductivity of bulk CNTs.AC conductivity measurements were performed using a rectangular waveguide-based technique up to 40 GHz. Initially, a comparison of purified and KAuBr4-doped commercial MWCNT sheet was made to the as-received material. The as-received MWCNT sheet showed a decrease with frequency, whereas the purified sample (with reduced iron impurities) provided a stable AC conductivity. Laser ablation-based thinning of the purified MWCNT sheet produced increased transmission, which was shown to improve measurement accuracy. The laser-thinned purified MWCNT sheet was subsequently doped with KAuBr4 and demonstrated a 3-4x AC conductivity enhancement. The purified MWCNT sheet was also deposited with varying weight loadings (% w/w) of platinum using a Joule heating-driven chemical vapor deposition (CVD) technique. Platinum overcoating of the MWCNT network was observed, consistent with previous studies, resulting in a 1.4x increase in AC conductivity.A high frequency modeling technique using the generalized Drude conduction theory was applied to the experimental measurements from purified, KAuBr4-doped, or platinum-deposited MWCNT sheet to better understand the high frequency effects of each process. The fit results showed that inclusion of KAuBr4 or platinum nano-metal to the MWCNT network increased the material's plasma frequency, which is attributed to higher carrier density in the material leading to enhanced AC conductivity. Finally, a demonstration of the enhanced RF properties for CNTs was performed using free-standing thin films to directly measure the EMI shielding effectiveness using the rectangular waveguide setup from 10 GHz to 15 GHz. Thus, the work exhibits a practical application of the CNT conductive materials that combines thin film optical transparency and surface conformability with favorable RF shielding properties.

English

ISBN: 9798383705667Subjects--Topical Terms:

649834
Electrical engineering.
Subjects--Index Terms:

AC conductivity

Physical Properties of Bulk Carbon Nanotube Conductors Impacting Radio Frequency Waveguide Measurements /
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520 $a Recent developments in radio frequency (RF) electronics motivate the interest in developing multi-functional materials which have effective electrical properties with increasing frequency that minimize the conventional skin effect. Carbon nanotubes (CNTs) are emerging as a candidate material due to high direct current (DC) electrical conductivity, flexure tolerance, corrosion resistance, and low density. The DC electrical conductivity of CNT networks is affected by the high resistance junctions between individual or bundled CNTs. Strategies to modify the properties of these junctions have included chemical doping, nano-metal deposition, and physical densification. Alternating current (AC) conductivity measurements of bulk CNT materials to date have shown constant or even increasing values up to 120 GHz. Thus, this dissertation focuses on applying doping and metallization strategies for improving DC electrical properties to altering the AC conductivity of bulk CNTs.AC conductivity measurements were performed using a rectangular waveguide-based technique up to 40 GHz. Initially, a comparison of purified and KAuBr4-doped commercial MWCNT sheet was made to the as-received material. The as-received MWCNT sheet showed a decrease with frequency, whereas the purified sample (with reduced iron impurities) provided a stable AC conductivity. Laser ablation-based thinning of the purified MWCNT sheet produced increased transmission, which was shown to improve measurement accuracy. The laser-thinned purified MWCNT sheet was subsequently doped with KAuBr4 and demonstrated a 3-4x AC conductivity enhancement. The purified MWCNT sheet was also deposited with varying weight loadings (% w/w) of platinum using a Joule heating-driven chemical vapor deposition (CVD) technique. Platinum overcoating of the MWCNT network was observed, consistent with previous studies, resulting in a 1.4x increase in AC conductivity.A high frequency modeling technique using the generalized Drude conduction theory was applied to the experimental measurements from purified, KAuBr4-doped, or platinum-deposited MWCNT sheet to better understand the high frequency effects of each process. The fit results showed that inclusion of KAuBr4 or platinum nano-metal to the MWCNT network increased the material's plasma frequency, which is attributed to higher carrier density in the material leading to enhanced AC conductivity. Finally, a demonstration of the enhanced RF properties for CNTs was performed using free-standing thin films to directly measure the EMI shielding effectiveness using the rectangular waveguide setup from 10 GHz to 15 GHz. Thus, the work exhibits a practical application of the CNT conductive materials that combines thin film optical transparency and surface conformability with favorable RF shielding properties.
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653 $a AC conductivity
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653 $a Chemical doping
653 $a Chemical vapor deposition
653 $a Electromagnetic interference shielding
653 $a Radio frequency
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