Production and Characterization of Activated Carbon Fiber from Textile PAN Fiber

This paper presents the preparation and characterization of carbon fiber felt and activated carbon fiber felt from textile polyacrylonitrile fiber. Carbon fibers are usually related to aircraft manufacturing or high mechanical purposes. Activated carbon fibers are known as excellent adsorbent materials. Despite all advantages, carbon fiber and activated carbon fiber are expensive materials because of their raw material cost. On the other hand, in this study, carbon fiber felt and activated carbon fiber felt were produced from textile polyacrylonitrile fiber, which is cheaper than their precursor, polyacrylonitrile fiber, and can be converted into carbon fiber felt and activated material with high micropore content and surface area. This research describes the transformation of textile polyacrylonitrile fiber in its oxidized form. After that, the oxidized material was transformed in felt and, in the sequence, converted into carbon fiber felt and activated carbon felt. The carbon fiber felt and activated carbon fiber felt were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscope. N-2 isotherms were performed to qualify the material obtained for further electrochemical applications. The main result was the conversion dynamics of textile polyacrilonitrile fiber into carbon fiber in felt form and activated carbon fiber in felt with high surface area and high micropores content.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Inst Nacl Pesquisas Espaciais, Coordenacao Labs Associados, Lab Associado Sensores & Mat, Ave Astronautas,1-758,Jardim de Granja, BR-12227010 Sao Jose Dos Campos, SP, BrazilUniv Fed Sao Paulo, Inst Ciencia & Tecnol, Curso Engn Mat, Sao Jose Dos Campos, SP, BrazilInst Aeronaut & Espaco, Dept Ciencia & Tecnol Aeroespacial, Div Mat, Sao Jose Dos Campos, SP, BrazilUniv Fed Sao Paulo, Inst Ciencia & Tecnol, Curso Engn Mat, Sao Jose Dos Campos, SP, BrazilWeb of Scienc

Microporus activated carbon fiber felt from Brazilian textile PAN fiber: preparation, characterization and application as super capacitor electrode

Activated carbon fibers (ACF) are known as excellent adsorbent materials due to their fast adsorption rate and easy handling characteristic. The ACF can be manufactured from the polyacrylonitrile fiber, based on an usual carbon fibers (CF) production process accomplished by an additional activation process. The aim of the present work is to describe the production, chemical/morphological characterization and application potentiality of activated carbon fiber felt (ACFF) produced from textile PAN fiber, using a set of homemade equipment. The 5.0 dtex PAN fiber tow with 200 thousand filaments was oxidized and used as raw material for felt production. The oxidized PAN fiber felt (OPFF) was displaced in a special sample holder, carbonized (900 °C) and then activated in CO2 atmosphere at 1000 °C in an electric tubular furnace. All steps of the process were performed as fast as possible, and characterization was done by 77 K N2 isotherms, adsorption isotherms in liquid phase, scanning electronic microscope, X-ray diffraction and surface chemistry by Bhoem methodology. The results confirmed the production of essentially microporous (pore < 3.2 nm, centered on 1.2 nm) and 1,300 m2 g-1 surface area. The ACFF produced have demonstrated a strong potential application as electrode supercapacitor

Formation of Composite Polyaniline and Graphene Oxide by Physical Mixture Method

The development of polyaniline and graphene oxide composites aims to join the unique properties of each material for aerospace applications. The present paper demonstrates an easy and quick method, compared to the ones found in the literature, to obtain a composite made with polyaniline doped with dodecylbenzenesulfonic acid, a combination commonly called polyaniline, and graphene oxide. Nowadays, the most common studied methods are electrochemistry and in situ chemical polymerization. Differently from these methods, the films were obtained by a physical mixture of equimolar suspension of graphene oxide (4 mg/mL) with 3 concentrations of polyaniline powder: 2550 and 75%, being compared to pure graphene oxide and polyaniline. The morphology and structure behavior of all the films were studied, besides the bonding nature between both materials. The films were analyzed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The apparent interaction between graphene oxide corrugated sheets and polyaniline grains was verified by scanning electron microscopy images. It can be noticed, as the concentration of polyaniline increases, that more polymer was entrapped. To prove the formation of polyaniline/graphene oxide composite, X-ray diffraction and Fourier transform infrared spectroscopy techniques demonstrated the changes on graphene oxide crystallographic plans and on the chemical bonding between polyaniline and graphene oxide, suggesting an interaction between polyaniline and graphene oxide, especially in the composite with 50% polyaniline/50% graphene oxide. Differential scanning calorimetry was used to highlight this effect through the increase in thermal stability. The method of physical mixture was efficient to obtain the polyaniline/graphene oxide composites.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Instituto Tecnológico de AeronáuticaDivisão de Química of the Instituto de Aeronáutica e EspaçoInst Tecnol Aeronaut, Dept Ciencia & Tecnol Aeroespacial, Sao Jose Dos Campos, BrazilInst Aeronaut Espaco, Dept Ciencia Tecnol Aeroespacial, Div Mat, Sao Jose Dos Campos, BrazilUniv Fed Sao Paulo, Inst Ciencia Tecnol, Campus Parque Tecnol, Sao Jose Dos Campos, BrazilInst Nacl Pesquisas Espaciais, Lab Associado Sensores, Sao Jose Dos Campos, BrazilInst Aeronaut Espaco, Dept Ciencia Tecnol Aeroespacial, Div Mat, 50 Vila Acacias, Sao Jose Dos Campos, BrazilUniversidade Federal de São Paulo – Instituto de Ciência e Tecnologia – Campus Parque Tecnológico – São José dos Campos/SP – BrazilWeb of Scienc

Study and characterization of carbon xerogels from tannin-formaldehyde system as catalyst support applications

This contribution reports the use of an organic gel, xerogel, as catalyst support for Cu. The xerogel was synthesized from the system tannin-formaldehyde at pH 3, using F-127 Pluronic as surfactant. The surface area values were higher than 900 m2/g even after the Cu (10%, wt) impregnation. The morphological analysis by SEM-FEG revealed the presence of spheres arranged in a tridimensional structure. XRD diffractograms showed the presence of CuO and Cu2O crystalline phases combined with the amorphous structure of the porous carbon. From XRD analysis it is possible to infer the Cu species are heterogeneously dispersed on the support with the co-existence of small and larger clusters, which is in agreement with Raman spectroscopy. Raman study also indicated a highly defect/disorder structure of the xerogel derivatives, ensuing the short-range structural order of the carbonic structure and oxygen groups decorating the carbon surface. XPS results corroborate with XRD and Raman results, detecting the presence of CuO and Cu2O. In addition to the mentioned Cu species, XPS also detected Cu0 which may be originated from the chemical interaction between the electron oxygen groups with the Cu precursor. The high surface area and the thermal stability (~ 300 oC) of Cu/XCTF envisages its feasibly for relevant catalytic applications.Keywords: Carbon xerogels, tannin, renewable process, catalyst support

Process of converting human hair into hollow carbon filament for electrochemical capacitor

Carbon material is the largest material used as electrode on advanced energy storage devices. The modern lifestyle requires more energy, consequently, more smart energy use and efficient devices are needed. The constant evolution of materials technologies looking for green material and renewable raw material, that have minimal impact on the environment, is one of the most important subjects studied in recent years.  The scientific and industry community are paying more attention to new forms of carbon such as nanotubes, graphene, and activated carbon fiber. The purpose of this work is to convert human hair into a hollow carbon filament to be used as a supercapacitor electrode. The human hair needs 3 stages to be converted into carbon filament: textile manufacture, oxidation, and carbonization. The electrochemical behavior was analyzed in a threeelectrode electrochemical cell system with 2 M of H2SO4 electrolyte medium. The behavior of the electrode was characterized electrochemically by galvanostatic charge/discharge curves, cyclic voltammetry, and electrochemical impedance spectroscopy, showing 163 F g-1 of a maximum value of specific capacitance.Keywords: Residue. Human hair. Felt. Carbon filament. Supercapacitor.

Obtenção de nanofios de carbono a partir de copolímero de PAN eletrofiados para aplicação como supercapacitores

Atualmente, existe uma demanda na busca por materiais com alta densidade de potência, longo ciclo de vida e baixo impacto ambiental que são em sua maioria utilizados para a produção de supercapacitores, sendo esses considerados fontes promissoras de energia para sistemas eletrônicos. Os tipos de materiais mais promissores para essa aplicação são os baseados em carbono, devido à sua flexibilidade, área superficial e boa estabilidade eletroquímica. Para a produção de materiais carbonosos, o principal precursor utilizado é a poliacrilonitrila (PAN) e suas variações a partir da adição de monômeros, como o acrilato de metila (MA). Geralmente, esses materiais são utilizados em formas de mantas, fios ou nanofibras produzidos a partir de processos de fiação e posteriormente carbonizados para gerar o material carbonáceo. Um dos processos de fiação que tem sido amplamente estudado para a obtenção de nanofibras de carbono é o processo de eletrofiação. Portanto, este trabalho apresenta os resultados obtidos do processo de carbonização de mantas eletrofiadas a partir de solução de PAN homopolímero (PANH) e PAN-co-acrilato de metila 6 % (PA6MA) com dimetilformamida (DMF) com o intuito de obter material para uso em supercapacitores. Os polímeros utilizados foram analisados por DSC para a obtenção dos valores relacionados a faixa de ciclização, sendo possível observar uma melhor estabilidade térmica relacionada as amostras de PAN6MA com faixa de temperatura de 240-312 °C e temperatura máxima do pico exotérmico de 292 °C. As mantas obtidas pelo processo de eletrofiação foram oxidadas a 235°C por 5min e carbonizadas a 900 °C por 5 min. As mantas obtidas, antes e após o processo de carbonização, foram analisadas por MEV apresentando fibras de superfície lisa, dispersas aleatoriamente e de dimensões nanométricas, sendo os valores de diâmetro aproximado de 219 nm para as nanofibras de carbono de PANH (NfcPANH) e 185 nm para as nanofibras de carbono de PAN6MA (NfcPAN6MA). As mantas carbonizadas foram analisadas pela técnica RAMAN e foi possível a obtenção de dados referentes a estrutura carbônica presente nas amostras, onde os valores obtidos demonstraram que as amostras de NfcPAN6MA apresentaram menor valor de grau de cristalinidade medida a partir da relação entre as bandas D e G conhecido como fator ID/IG, sendo o valor obtido igual a 1,06 para as NfcPNA6MA e 1,24 para as NfcPANH, isso demonstra uma maior presença de estruturas grafíticas cristalinas quando comparadas as amostras produzidas a partir da PANH. Para obtenção das características capacitivas foram realizados levantamento das curvas carga/ descarga por análise cronopotenciométrica, foi possível observar as melhores características relacionadas a capacitância específica e estabilidade de ciclagem em baixas correntes aplicadas para as amostras de PAN6MA com valores de capacitância específica de 270,9 F/g, densidade de energia de 30,0 Wh/kg e densidade de potência de 153,5 W/kg. Os resultados obtidos demonstraram que o material apresentou potencial para a aplicação proposta.Palavras-chave: Eletrofiação, Carbonização, Supercapacitor, Copolímero PAN

Deposição de recobrimentos de proteção térmica e ambiental por plasma spray utilizando precursor híbrido de SiO2+ZrO2/ Plasma spray deposition of thermal and environmental protection coatings using SiO2+ZrO2 hybrid precursor

Compósitos reforçados com fibra de carbono (C/C) são materiais amplamente utilizados em componentes estruturais, especialmente quando expostos as intensas cargas aerotermodinâmicas. Sua alta resistência e excepcional tenacidade à fratura, combinados com suas propriedades refratárias, resistência à erosão, corrosão e desgaste tornam este material ideal para aplicações em componentes estruturais, submetidos a altas temperaturas, tais como turbinas e veículos de reentrada atmosférica. Quando utilizados em atmosferas inertes ou em vácuo, os compósitos C/C mantêm suas propriedades a temperaturas superiores a 2000°C. Porém, nas condições de ambientes oxidantes e de elevadas temperaturas, os compósitos a base de fibras de carbono sofrem intensa degradação devido à elevada catalicidade de reações entre o carbono e o oxigênio, dificultando e, muitas vezes, impossibilitando seu uso em dispositivos aeroespaciais. Neste contexto, o objetivo deste trabalho é a deposição de recobrimentos de barreira ambiental (Environmental Barrier Coating, EBC), utilizando precursores híbridos de ZrO2+SiO2 visando proteção contra oxidação dos compósitos estruturais de C/C. Os recobrimentos serão depositados por meio do processo de spray a plasma de alta velocidade (High Velocity Plasma Spray, HVPS)

Reciclagem de fibras de carbono oriundas de compósitos estruturais de matriz epóxi por processo térmico de pirólise e aplicação como materiais de eletrodo em supercapacitores

Compósitos poliméricos reforçados com fibras de carbono são materiais cada vez mais utilizados em diferentes segmentos industriais, em especial, os segmentos aeronáuticos e automobilísticos devido a sua elevada resistência mecânica e baixa massa específica. Desta forma, existe grande preocupação com o descarte e a reciclagem dos componentes que representam produtos de alto valor econômico agregado, principalmente fibras de carbono. O processo de pirólise tem sido um dos métodos de reciclagem de compósitos para recuperar as fibras de carbono a partir da degradação da matriz polimérica. No setor de energia, fibras de carbono são traduzidas como bons materiais de armazenamento de energia, por apresentar desejáveis características condutoras e capacitivas que potencializam sua aplicação como material de eletrodo em supercapacitores. Neste sentido, a proposta deste trabalho consiste em viabilizar o uso de fibras de carbono recicladas por pirólise de compósitos epóxi reforçado com fibras de carbono como material de eletrodo de supercapacitores e avaliar a influência dos tratamentos termoquímico e químico sobre suas propriedades capacitivas. Imagens FEG-MEV mostraram que as fibras de carbono foram praticamente limpas permanecendo um mínimo de carbono residual sobre a superfície. A área BET e as análises FTIR, Raman e de voltametria cíclica mostraram que os tratamentos termoquímico e químico realizados na FCP não contribuíram para melhorar a capacidade de armazenamento de cargas na interface eletrodo/eletrólito, pelo contrário, o tratamento químico levou a uma grande redução da capacidade da FCP no armazenamento de energia devido a incorporação de grupos OH e COOH. As curvas de carga/descarga evidenciam boa ciclabilidade e os valores de capacitância específica para a fibra de carbono reciclada de 34 Fg-1, densidade de potência de 37,6 Wkg-1 e densidade de energia de 4,7 Whkg-1encontram-se dentro da faixa para aplicações como eletrodos de supercapacitores.Palavras-chave:Fibra de Carbono. Pirólise. Supercapacitores.

Investigation of sustainable porous carbon as radar absorbing material

Radar Absorbing Materials (RAMs) are composite materials able to attenuate an incident electromagnetic wave. Usually, RAMs are made of a polymeric matrix and an electromagnetic absorbent filler, such as silicon carbide or carbon black. Several materials have been investigated as potential fillers, aiming to improve the Reflection Loss (RL) and absorption bandwidth broadening. In this paper, a composite made with silicone rubber and biochar was investigated as a sustainable porous carbon made with biomass waste. Five different composites were characterized, composed of 1 - 5 wt.% of biochar in the silicone rubber. Although the RL of pure biochar composites is not significant, it was demonstrated here how a biochar composite can improve the RL of a RAM material when it is applied as a double-layer structure. While the RL of a ferrite-based RAM with 2.0 mm thickness reaches -28 dB, a combination of this RAM with biochar composite reaches ~ -60 dB with the same thickness. The double-layer structure with 2.3 mm thickness can have an absorption bandwidth of 2.95 GHz over the X-band frequency range, and a structure with 2.6 mm thickness can reach a RL of ~-76 dB. This demonstrates a sustainable, cheaper, and lighter material application (i.e., biochar), which is successfully used in the development of high-efficient electromagnetic shield or sensors.Keywords: Biochar, permittivity, RAM, sustainability, reflectivity.

Evolution of TiO2 nanotubular morphology obtained in ethylene glycol/glycerol mixture and its photoelectrochemical performance

The evolution of TiO2 nanotubular morphology, synthesized in a mixture of fluorinated ethylene glycol and glycerol electrolyte, was studied as a function of the anodization time. The samples were characterized by FEG-SEM, XRD, XPS, UV-Vis and EIS. The formation of single-or double-walled TiO2 nanotube structure can be efficiently controlled by the anodization time. For anodization times less than 30 minutes, a compact oxide layer is formed, followed by double-walled nanotube formation up to 120 minutes and single-walled nanotubes up to 240 minutes. XPS analyses show that the samples obtained with short anodization time have a high carbon content and oxygenated surface species compared to the longer-time anodized sample; however, binding energy peaks for Ti 2p remained invariant. The performances of TiO2 nanotubular photoelectrodes were evaluated in photoelectrochemical water splitting where TiO2 nanotubes anodized for 120 minutes presented the best performance that was related to their optimal morphology and charge transportation