Characterization of carbon thin films prepared by the thermal decomposition of spin coated polyacrylonitrile layers containing metal acetates

Darányi, Mária; Sarusi, István; Sápi, András; Kukovecz, Ákos; Erdöhelyi, András

doi:10.1016/j.tsf.2011.06.040

Cited by 11 publications

(12 citation statements)

References 40 publications

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“…The greatest weight loss was 52% happened in the temperature range of 280-450 8C, which corresponds to the precarbonization, and chain scissions reaction dominates in this temperature range with the emission of HCN, NH 3 , and oligomers. [19][20][21][22] Relatively, 10.7% of the weight lost in the temperature range of 800-1300 8C, which corresponds to the high temperature carbonization, and non-carbon atoms elimination reaction dominates in this temperature range with the emission of N 2 , etc. 22 However, only a little weight lost before 280 8C, which corresponds to stabilization.…”

Section: Resultsmentioning

confidence: 99%

The conjugated plane formed in polyacrylonitrile during thermal stabilization

Shuai

Cao

2016

J of Applied Polymer Sci

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The formation process and mechanism of the pseudo‐graphite sheets of polyacrylonitrile (PAN) during thermal treatment in inert atmosphere were investigated by thermo‐gravimetry (TG) and X‐ray diffraction (XRD). According to the results, the conjugated plane originally formed during stabilization was proposed as the basic planar structure of the pseudo‐graphite sheets, and it was connected and stacked to form pseudo‐graphite microcrystal through chain scission reaction and non‐carbon atoms elimination reaction in 280–450 °C and 800–1300 °C respectively. The in situ measurements for time dependence of ultraviolet‐visible (UV‐vis) and Fourier transform infrared spectra (FTIR) were applied to study the conjugated plane of PAN during isothermal stabilization. It was found that with the higher temperature the conjugated plane forms more rapidly, and it has higher conjugated extent with the extending of heating time. The FTIR data showed that both cyclization and dehydrogenation are beneficial to the evolution of conjugated plane in the first 3 h, but only cyclization continues after 3 h at 250 °C. Further investigation indicated that stabilized PAN with large quantity and high conjugated extent of the conjugated plane would contribute to get large size of pseudo‐graphite microcrystal after carbonization, which is consistent with the former assumption. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43890.

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Section: Resultsmentioning

confidence: 99%

The conjugated plane formed in polyacrylonitrile during thermal stabilization

Shuai

Cao

2016

J of Applied Polymer Sci

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“…36 The second step of weight loss of about 15 wt% happened after 800 C due to the emission of nitrogen. 37 As a result, a residue of 40.6%, 44.5%, and 41.8% was left at the end of this thermal program in at-homo-PAN, at-co-PAN, and iso-homo-PAN, respectively, suggesting that the stabilized at-co-PAN is the most stable one during carbonization, which could be ascribed to the cross-linking of the macromolecular chain by the comonomer. Similarly, the thermal degradation of PAN samples stabilized in air also starts at about 300 C and shows a gradual weight loss with a residue of 49.0%, 45.2%, and 52.8% in at-homo-PAN, atco-PAN, and iso-homo-PAN, respectively.…”

Section: Carbonization Processmentioning

confidence: 94%

The formation of conjugated structure and its transformation to pseudo-graphite structure during thermal treatment of polyacrylonitrile

Shuai

Gao

et al. 2016

High Performance Polymers

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Three types of polyacrylonitrile (PAN) were considered in order to investigate the effect of molecular composition and configuration on the formation of conjugated structures during stabilization and the conversion of that to pseudo-graphite sheets after carbonization. The stabilization process was performed in an inert or oxidative atmosphere with a temperature ramp from 180°Cto 280°C. The thermal behavior was studied by differential scanning calorimetry, and the change of chemical groups and conjugated structures was detected by in situ measurement of infrared (Fourier transform infrared) and ultraviolet–visible spectroscopy, respectively. The carbonization process of the stabilized samples was performed using a thermogravimetric analyzer under nitrogen atmosphere in the temperature range of 150°C–1200°C, and Raman spectra were applied to study the pseudo-graphite sheets of the residuals. It is suggested that the introduction of comonomer or the improvement of the isotactic regularity of the polymer chain are helpful to promote the stabilization reactions and accelerate the formation of conjugated structures rather than the extent of conjugation during stabilization in nitrogen. Moreover, they are also beneficial to obtain higher degree of graphitization and larger size of the pseudo-graphite sheets with less structural defects after carbonization. While stabilization is performed in air, atactic PAN copolymer has the highest extent of stabilization among these three PAN samples, but they are extremely close. PAN samples with comonomer or higher isotacticity still show a little advantage in the formation speed of the conjugated structures. After carbonization, PAN with higher isotacticity has the highest carbon yield and graphitization degree and the largest size of pseudo-graphite sheets with least structural defects. In addition, the presence of oxygen during stabilization is contributory to increase the extent of stabilization and generate some bigger conjugated structures, which leads to obtain higher graphitization degree and larger size of pseudo-graphite sheets, but it also brings more structural defects.

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“…19 Sputtering and spin coating of polymer precursor followed by pyrolysis techniques were widely used for fabricating carbon thin films. [21][22][23][24][25] Compared to non-photosensitive polymer based and sputtered based techniques, use of photoresist as a precursor allows us to fabricate three dimensional micro-patterned carbon electrodes. Micropatterning of electrode enhances the lithium ion intercalation by minimizing the lithium ion transport distance (diffusion length) and increased surface area.…”

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Effect of Current Collector and Pyrolysis Temperature on the Electrochemical Performance of Photoresist Derived Carbon Films

Kakunuri

Sharma

2016

ECS J. Solid State Sci. Technol.

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SU-8, an epoxy based negative photoresist has been demonstrated as a potential precursor to fabricate thin films and three-dimensional micropatterned arrays in glassy carbon. However, the use of silicon wafer as a substrate cum collector limits their use in real battery devices. In accordance with the commercial lithium ion battery architecture and also owing to enhanced conductivity, we have successfully demonstrated the use of stainless steel (SS) wafer as a current collector to prepare binder free SU-8 derived carbon thin films. Standard carbon microelectromechanical systems (C-MEMS) process parameters were tuned to obtain a uniform, crackfree carbon thin film on SS wafer upon pyrolysis. Further, we varied the final pyrolysis temperature to examine its effect on the microstructure and composition as characterized with X-ray diffraction, Small angle X-ray scattering, Raman spectroscopy and CHNS-O elemental analyzer respectively. The microstructural changes in the carbon films at different pyrolysis temperature were then correlated with their electrochemical performance as investigated using galvanostat charge/discharge experiments, impedance spectroscopy and cyclic voltammetry. Selection of an appropriate current collector and optimizing the pyrolysis temperature yielded excellent cyclic stability and coulombic efficiency with 400 mAh g −1 reversible capacity after 100 cycles, nearly double to as reported in the literature. Carbon is one of the most commonly used anode material used in commercial rechargeable lithium (Li) ion batteries. Based on microstructure and their behavior on heat-treatment, carbonaceous materials can be classified as graphite (highly crystalline), graphitizable soft carbons and non-graphitizable hard carbons.1 Among the various carbonaceous materials, graphite materials of different grade have been studied extensively with their reported Li-ion intercalation capacities in the range of 215-370 mAh g −1 which is closer to theoretical capacity of graphite (372 mAh g −1 ). [2][3][4][5] In literature, hard carbons have been prepared by pyrolyzing different precursor materials like cotton wool, rice husk, tea leaves, isotropic pitches, epoxy novolac resins, and various other polymers.6-11 These hard carbons show much higher reversible capacity (400-700 mAh g −1 ) than that of graphite (372 mAh g −1 ). However, large irreversible capacity, average cyclic stability and hysteresis during charging and discharging for hard carbons limit their use in commercial lithium-ion batteries to secondary choice after graphitic carbons.12 Adsorption of lithium ions on the surface of the nanopores formed by random arrangement of small graphene sheets with minimal lamellar stacking like "house of cards" (Figure S1), doping of lithium at the edges of small crystallites and binding of one lithium atom with one hydrogen atom on average is known to be accountable for this higher capacity. 9,13-15 Along with these reasons, hydroxyl, carboxyl functional groups and moisture content which is very reactive to Li metal ...

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Characterization of carbon thin films prepared by the thermal decomposition of spin coated polyacrylonitrile layers containing metal acetates

Cited by 11 publications

References 40 publications

The conjugated plane formed in polyacrylonitrile during thermal stabilization

The conjugated plane formed in polyacrylonitrile during thermal stabilization

The formation of conjugated structure and its transformation to pseudo-graphite structure during thermal treatment of polyacrylonitrile

Effect of Current Collector and Pyrolysis Temperature on the Electrochemical Performance of Photoresist Derived Carbon Films

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