Studies on changes in morphology during carbonization and activation of pretreated viscose rayon fabrics

Gurudatt, K.; Tripathi, Vishal

doi:10.1016/s0008-6223(98)00124-9

Cited by 27 publications

(15 citation statements)

References 3 publications

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“…As already shown by the thermal behavior of untreated viscose rayon, pyrolysis of cellulose is strongly associated with dehydration and depolymerization reactions. The depolymerization of untreated cellulose results in the formation of levoglucosan which can evaporate showing an endothermic reaction or undergo aromatization showing an exothermic reaction 30…”

Section: Resultsmentioning

confidence: 99%

Enhancement of oxidative stabilization of viscose rayon fibers impregnated with ammonium sulfate prior to carbonization and activation steps

Karacan

Soy

2012

J of Applied Polymer Sci

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The oxidative thermal stability of microcrystalline plant-based viscose rayon cellulose fiber was improved in the presence of an ammonium sulfate solution. The structural characterization of the oxidized samples was carried out using a combination of fiber thickness, linear density, burning test, X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared (IR) spectroscopy measurements. Oxidized viscose rayon fibers showed physical and chemical transformations with increasing oxidation temperature and were characterized by a reduction in fiber diameter and linear density values together with color changes with increasing oxidation temperature. The results obtained from XRD analysis showed the loss of crystallinity due to the amorphization processes. XRD analysis also showed increasing conversion to a highly crosslinked and cyclized structure with progressing temperature. The DSC and TGA measurements indicated that there was an improvement in thermal stability. The results obtained from IR spectra showed the progress of dehydrogenation and dehydration reactions. IR spectra in the 2000-800 cm À1 region showed a loss of crystalline structure confirming the results of XRD. The IR spectra of the oxidized samples also showed the conversion of primary hydroxyl (OH) groups to carbonyl (C¼ ¼O) groups and the presence of C¼ ¼C double bonds arising from the formation of a cyclized and crosslinked structure.

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Section: Resultsmentioning

confidence: 99%

Enhancement of oxidative stabilization of viscose rayon fibers impregnated with ammonium sulfate prior to carbonization and activation steps

Karacan

Soy

2012

J of Applied Polymer Sci

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“…It is known that a good precursor for carbon fiber always has the following characteristics: a round cross‐section, fine denier, high strength and modulus, few physical defects, etc 23, 27, 29–33. Figure 3 shows the SEM photographs of the precursors.…”

Section: Resultsmentioning

confidence: 99%

Lyocell fibers as the precursor of carbon fibers

Peng

Shao

2003

J of Applied Polymer Sci

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ABSTRACT:In this work, Lyocell fibers, used as carbon fiber precursors, were investigated. Lyocell fibers used for the carbon precursors and the carbon fibers themselves were produced in our laboratory. The mechanical properties morphology and structure of the precursors and the obtained carbon fibers were studied and compared to those of rayon. The results show that Lyocell fibers have higher tenacity and modulus, and better thermal stability than rayon fibers. Scanning electron microscopy (SEM) experiments show that Lyocell precursors have round cross-sections and fewer defects in the fibers, while rayon fiber has an oval cross-section and many defects. Wide angle X-ray diffraction (WAXD) results for the Lyocell precursors indicate that the degree of crystallinity of the Lyocell precursor is higher than that of a rayon precursor. They also show that Lyocell based carbon fibers have better mechanical properties than those that are rayon-based. WAXD data of the obtained carbon fibers show that the crystallinity of Lyocell-based carbon fiber is higher than that of rayon-based carbon fiber. It is concluded that the Lyocell fibers are better precursors for carbon fibers than rayon.

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“…1 However, the calculated Lc and La values are not exactly equal to the stacking height and lateral size of the crystallites because these equations are, in fact, actually derived for highly graphitized carbons and are not suitable for turbostratic (fully disordered) carbons. Therefore, these can be used as convenient relative estimates of actual stacking height and lateral size of the crystallites [29]. The actual crystallite sizes, therefore, are likely to be slightly greater than the calculated values.…”

Section: Xrd Patternsmentioning

confidence: 99%

X-ray Diffraction Patterns of Activated Carbons Prepared under Various Conditions

Girgis¹,

Temerk²,

Gadelrab³

et al. 2007

Carbon letters

146

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A series of activated carbons (ACs) were derived from sugarcane bagasse under two activation schemes: steam-pyrolysis at 600-800°C and chemical activation with H 3 PO 4 at 500°C. Some carbons were treated at 400, 600°C, or for 1-3 h, and/or in flowing air during pyrolysis of acid-impregnated mass. XRD profiles displayed two broad diffuse bands centered around 2θ = 23 and 43°, currently associated with diffraction from the 002 and 100/101 set of planes in graphite, respectively. These correspond to the interlayer spacing, Lc, and microcrystallite lateral dimensions, La, of the turbostratic (fully disordered) graphene layers. Steam pyrolysis-activated carbons exhibit only the two mentioned broad bands with enhancement in number of layers, with temperature, and small decrease in microcrystallite diameter, La. XRD patterns of H 3 PO 4 -ACs display more developed and separated peaks in the early region with maxima at 2θ = 23, 26 and 29°, possibly ascribed to fragmented microcrystallites (or partially organized structures). Diffraction within the 2θ = 43° is still broad although depressed and diffuse, suggesting that the intragraphitic layers are less developed. Varying the conditions of chemical activation inflicts insignificant structural alterations. Circulating air during pyrolysis leads to enhancement of the basic graphitic structure with destruction and degradation in the lateral dimensions.

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Studies on changes in morphology during carbonization and activation of pretreated viscose rayon fabrics

Cited by 27 publications

References 3 publications

Enhancement of oxidative stabilization of viscose rayon fibers impregnated with ammonium sulfate prior to carbonization and activation steps

Enhancement of oxidative stabilization of viscose rayon fibers impregnated with ammonium sulfate prior to carbonization and activation steps

Lyocell fibers as the precursor of carbon fibers

X-ray Diffraction Patterns of Activated Carbons Prepared under Various Conditions

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