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Individual carbon nanotubes (CNTs) exhibit exceptional mechanical properties. However, difficulties remain in fully realizing these properties in CNT macro-assemblies, because the weak inter-tube forces result in the CNTs sliding past one another. Herein, a simple solid-state reaction is presented that enhances the mechanical properties of carbon nanotube fibers (CNTFs) through simultaneous covalent functionalization and crosslinking. This is the first chemical crosslinking proposed without the involvement of a catalyst or byproducts. The specific tensile strength of CNTFs obtained from the treatment employing a benzocyclobutene-based polymer is improved by 40%. Such improvement can be attributed to a reduced number of voids, impregnation of the polymer, and the formation of covalent crosslinks. This methodology is confirmed using both multiwalled nanotube (MWNT) powders and CNTFs. Thermogravimetric analysis, differential scanning calorimetry, x-ray photoelectron spectroscopy, and transmission electron microscopy of the treated MWNT powders confirm the covalent functionalization and formation of inter-tube crosslinks. This simple one-step reaction can be applied to industrial-scale production of high-strength CNTFs.

Um estudo comparativo envolvendo técnicas de análise por espectroscopia no infravermelho com transformada de Fourier (FTIR) de transmissão, reflexão e fotoacústica é apresentado com análise de poliamida-6. O potencial e as limitações destes métodos são investigados para analisar as alterações espectrométricas que ocorrem no interior e na superfície da poliamida-6, reciclada, e irradiada na presença de oxigênio, com feixe de elétrons de 1,5 MeV, na dose de 500 kGy. As técnicas mostram-se sensíveis para detectar pequenas mudanças de estruturas que ocorrem na poliamida-6 reciclada e irradiada. Os espectros sugerem formação de grupos --OH, HOC=O-, e -C=O, e mudanças estruturais relacionadas com grupos NH e -CN-C=O. Basicamente, as mesmas alterações espectrométricas são observadas com o uso das técnicas, sendo mais evidenciadas no interior das amostras pela espectroscopia-FTIR de transmissão, e na sua superfície, pela microscopia-FTIR.

Individual carbon nanotubes (CNTs) exhibit excellent mechanical, electrical and thermal properties, leading to development of a new generation of advanced lightweight materials and spacecraft electronics substituting the electronics based on silicon. The direct assembly of CNTs into macroscopic fibers or sheets has been a way to overcome their dispersion and processing challenges. Because of a wide range of applications of this material, we investigate effectively the defects on CNT yarns structures created by electron beam and gamma sources and their impact on the morphology and mechanical properties. The irradiated samples with electron beam at doses of 400, 600 and 800 kGy had a decrease in the strength from 219.60 ± 18.90 MPa for pristine yarn to 108. 86 ± 23.77, 153.15 ± 21.63, 170.50 ± 25.78 MPa, respectively. The sample irradiated with gamma in air at dose of 100 kGy had the strength increased slightly as compared with the pristine sample and an increase in the elasticity modulus from 8.79 ± 1.19 to 19.63 ± 2.02 GPa as compared to CNT pristine yarn. The quality of the CNT yarns that was gamma irradiated in air with absorbed dose of 100 kGy was not affected by the radiation process with improvement of 123% of the Young's modulus.

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