Thermal Transport Properties of Dry Spun Carbon Nanotube Sheets

The thermal properties of carbon nanotube- (CNT-) sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an IR Camera. The heat flux of CNT-sheet was compared to that of copper, and it was found that the CNT-sheet has significantly higher specific heat transfer properties compared to those of copper. CNT-sheet is a potential candidate to replace copper in thermal transport applications where weight is a primary concern such as in the automobile, aircraft, and space industries

Quantifying the Effects of Hyperthermal Atomic Oxygen and Thermal Fatigue Environments on Carbon Nanotube Sheets for Space-Based Applications

The effects of atomic oxygen and thermal fatigue on two different types of carbon nanotube sheets were studied. One set was treated with nitric acid, while the other set was left untreated. Monotonic tensile tests were performed before and after exposure to determine the effects of either exposure type on the sheets’ mechanical properties. Electrical conductivity and electromagnetic interference measurements were recorded to determine the effects of AO-exposure and thermal cycling on the sheets’ electrical properties. Neither exposure type affected the sheets’ specific strengths. Both exposure types increased the sheets’ specific stiffnesses and decreased the sheets’ strains at failure. The electrical conductivity of both sheets decreased due to the different exposure types, while the EMI shielding effectiveness was unaffected. Scanning electron microscopy was used to observe any changes in the sheets’ surface morphologies, while energy-dispersive X-ray spectroscopy was used to determine the effects of AO on the sheets’ chemical makeup

Functionalization of Carbon Nanotube Yarn by Acid Treatment

Carbon nanotube (CNT) yarn was functionalized using sulfuric and nitric acid solutions in 3:1 volumetric ratio. Successful functionalization of CNT yarn with carboxyl and hydroxyl groups (e.g., COOH, COO–, OH, etc.) was confirmed by attenuated total reflectance spectroscopy. X-ray diffraction revealed no significant change to the atomic in-plane alignment in the CNTs; however, the coherent length along the diameter was significantly reduced during functionalization. A morphology change of wavy extensions protruding from the surface was observed after the functionalization treatment. The force required to fracture the yarn remained the same after the functionalization process; however, the linear density was increased (310%). The increase in linear density after functionalization reduced the tenacity. However, the resistivity density product of the CNT yarn was reduced significantly (234%) after functionalization

Quantifying the electrical behavior of carbon nanotube sheet enhanced with acid functionalization and polymer intercalation

The electrical properties of carbon nanotube (CNT) sheet manufactured using different production (standard and enhanced) and post-processing (none, acid treatment, polymer intercalation) methods were analyzed. These properties included the electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE). The acid treatment significantly improved the electrical conductivity of the CNT sheet, while polymer intercalation did not affect the electrical conductivity. The enhanced production reduced the electrical conductivity by more than 40% for all specimen sets. With the exception of the acid-treated standard specimen, the EMI SE was consistent throughout all specimen sets. The electrical conductivity and EMI SE were presented as functions of the thickness, areal density, and density. There was no correlation between these material properties and the electrical conductivity of the untreated or polymer-intercalated specimens. The production method seems to influence how these properties affect the acid-treated specimens. The EMI SE was directly correlated to the thickness and inversely correlated to the density. The EMI SE was directly correlated to the areal density for almost all specimen types. Scanning electron microscopy revealed an increase in catalyst impurities in the enhanced production specimens and an increase in CNT agglomeration in both the acid-treated and polymer-intercalated specimens