Browsing by Author "Fang, Shaoli"
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Item Enhancing the Strength, Toughness, and Electrical Conductivity of Twist-Spun Carbon Nanotube Yarns by π Bridging(Elsevier Ltd, 2019-05-10) Liang, X.; Gao, Y.; Duan, J.; Liu, Z.; Fang, Shaoli; Baughman, Ray H.; Jiang, L.; Cheng, Q.; Fang, Shaoli; Baughman, Ray H.The weak interfacial interactions between carbon nanotube (CNT) always results in low stress load transfer efficiency in CNT yarns, herein we fabricated strong, highly conducting CNT yarns at room temperature using molecules having aromatic end groups, π bridging neighboring CNTs. The resulting CNT yarns have high tensile strength with 1697 ± 24 MPa, toughness with 18.6 ± 1.6 MJ/m³, and electrical conductivity with 656.2 S/cm, which are 3.9, 2.5, and 3.5 times, respectively, as high as that of the neat CNT yarn. The specific tensile strength of the resulting CNT yarn is higher than that for previously reported CNT yarns fabricated at room temperature, even that for some CNT yarns fabricated using corossive environments or extreme temperature. This π bridging strategy provides a promising avenue for fabricating high performance CNT yarns under ambient conditions. ©2019 Elsevier LtdItem Photothermal Bimorph Actuators with In-Built Cooler for Light Mills, Frequency Switches, and Soft Robots(Wiley-VCH Verlag) Li, J.; Zhang, Rui; Mou, L.; Jung de Andrade, Monica; Hu, X.; Yu, K.; Sun, J.; Jia, T.; Dou, Y.; Chen, H.; Fang, Shaoli; Qian, Dong; Liu, Z.; 295272933 (Qian, D); Zhang, Rui; Jung de Andrade, Monica; Fang, Shaoli; Qian, DongPhotothermal bimorph actuators are widely used for smart devices, which are generally operated in a room temperature environment, therefore a low temperature difference for actuation without deteriorating the performance is preferred. The strategy for the actuator is assembling a broadband-light absorption layer for volume expansion and an additional water evaporation layer for cooling and volume shrinkage on a passive layer. The response time and temperature-change-normalized bending speed under NIR, white, and blue light illumination are at the same level of high performance, fast photothermal actuators based on polymer or polymer composites. The classical beam theory and finite element simulations are also conducted to understand the actuation mechanism of the actuator. A new type of light mill is designed based on a wing-flapping mechanism and a light-modulated frequency switch. A fast-walking robot (with a speed of 26 mm s -1 ) and a fast-and-strong mechanical gripper with a large weight-lifting ratio (˜2142), respectively, are also demonstrated. ©2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimItem Sequentially Bridged Graphene Sheets with High Strength, Toughness, and Electrical Conductivity(National Academy of Sciences) Wan, S.; Li, Y.; Mu, Jiuke; Aliev, Ali E.; Fang, Shaoli; Kotov, N. A.; Jiang, L.; Cheng, Q.; Baughman, Ray H.; Mu, Jiuke; Aliev, Ali E.; Fang, Shaoli; Baughman, Ray H.We here show that infiltrated bridging agents can convert inexpensively fabricated graphene platelet sheets into high-performance materials, thereby avoiding the need for a polymer matrix. Two types of bridging agents were investigated for interconnecting graphene sheets, which attach to sheets by either π–π bonding or covalent bonding. When applied alone, the π–π bonding agent is most effective. However, successive application of the optimized ratio of π–π bonding and covalent bonding agents provides graphene sheets with the highest strength, toughness, fatigue resistance, electrical conductivity, electromagnetic interference shielding efficiency, and resistance to ultrasonic dissolution. Raman spectroscopy measurements of stress transfer to graphene platelets allow us to decipher the mechanisms of property improvement. In addition, the degree of orientation of graphene platelets increases with increasing effectiveness of the bonding agents, and the interlayer spacing increases. Compared with other materials that are strong in all directions within a sheet, the realized tensile strength (945 MPa) of the resin-free graphene platelet sheets was higher than for carbon nanotube or graphene platelet composites, and comparable to that of commercially available carbon fiber composites. The toughness of these composites, containing the combination of π–π bonding and covalent bonding, was much higher than for these other materials having high strengths for all in-plane directions, thereby opening the path to materials design of layered nanocomposites using multiple types of quantitatively engineered chemical bonds between nanoscale building blocks.Item Terahertz Surface Plasmon Polaritons on Freestanding Multi-Walled Carbon Nanotube Aerogel Sheets(2012-05-08) Nguyen, T. D.; Liu, S.; Lima, Marcio Dias; Fang, Shaoli; Baughman, Ray H.; Nahata, A.; Vardeny, Z. V.; 0000 0003 5232 4253 (Baughman, RH); Lima, Marcio Dias; Fang, Shaoli; Baughman, Ray H.We demonstrate that multi-walled carbon nanotubes (MWCNTs) are capable of supporting surface plasmon-polaritons (SPPs) at terahertz (THz) frequencies. To achieve this, we fabricated sub-100 μm-thick freestanding and highly oriented multi-walled carbon nanotube (MWCNT) aerogel sheets. Utilizing terahertz time-domain spectroscopy, we measured the complex index of refraction of the sheets for two orthogonal nanotube orientations. We found that the MWCNT sheets exhibit highly anisotropic THz polarization behavior. Based on the extracted dielectric properties of the medium, which show that it exhibits metallic behavior in the THz spectral range, we investigated the existence and propagation of SPPs by studying the resonantly enhanced transmission through periodic MWCNT hole arrays. We found that carbon nanotubes support SPP excitations that propagate along the tubes, but highly suppress these surface waves in the direction perpendicular to the nanotubes.