Estimation of Cellulose Crystallinity of Lignocelluloses Using Near-IR FT-Raman Spectroscopy and Comparison of the Raman and Segal-WAXS Methods

Agarwal, Umesh P.; Reiner, Richard R.; Ralph, Sally A.

doi:10.1021/jf304465k

Cited by 113 publications

(94 citation statements)

References 28 publications

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“…Hemicelluloses do not show a peak at 380 cm À1 , whereas they can show broad peaks in the CH 2 bending vibration region. Thus, use of the 380 cm À1 Raman peak intensity is advantageous for CI calculation [48]. Figure 1c displays the IR spectra of the same samples.…”

Section: Correlation Of "Apparent" Crystallinity Estimated From Xrd mentioning

confidence: 99%

Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

Lee

Dazen

Kafle

et al. 2015

Advances in Polymer Science

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Although the cellulose crystallinity index (CI) is used widely, its limitations have not been adequately described. In this study, the CI values of a set of reference samples were determined from X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and infrared (IR), Raman, and vibrational sum frequency generation (SFG) spectroscopies. The intensities of certain crystalline peaks in IR, Raman, and SFG spectra positively correlated with the amount of crystalline cellulose in the sample, but the correlation with XRD was nonlinear as a result of fundamental differences in detection sensitivity to crystalline cellulose and improper baseline corrections for amorphous contributions. It is demonstrated that the intensity and shape of the XRD signal is affected by both the amount of crystalline cellulose and crystal size, which makes XRD analysis complicated. It is clear that the methods investigated show the same qualitative trends for samples, but the absolute CI values differ depending on the determination method. This clearly indicates that the CI, as estimated by different methods, is not an absolute value and that for a given set of samples the CI values can be compared only as a qualitative measure.

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Section: Correlation Of "Apparent" Crystallinity Estimated From Xrd mentioning

confidence: 99%

Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

Lee

Dazen

Kafle

et al. 2015

Advances in Polymer Science

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“…In addition to XRD, crystallinity in cellulose samples can be determined with many other methods, such as Raman spectroscopy (Schenzel et al 2005;Agarwal et al 2013;Kim et al 2013), infrared spectroscopy (Kljun et al 2011;Chen et al 2013;Kim et al 2013), differential scanning calorimetry (Gupta et al 2013;Kim and Kee 2014), sum frequency generation vibration spectroscopy (Barnette et al 2012;Kim et al 2013), and solid state nuclear magnetic resonance (NMR) (Davies et al 2002;Liitiä et al 2003;Park et al 2009;Kim et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Comparison of sample crystallinity determination methods by X-ray diffraction for challenging cellulose I materials

2016

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Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger (n ¼ 16) and more varied collection of samples than previous studies have presented is used. In particular, samples (n ¼ 6) with low crystallinity and small crystallite sizes are included. A good linear correlation (r 2 ! 0:90) between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity.

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“…Cellulose crystallinity of woods can be determined using a number of analytical techniques, such as X-ray diffraction (Andersson et al 2003;Leppänen et al 2009), NMR (Newman and Hemmingson 1990;Newman 1999), Raman (Agarwal et al 2013a), and sum frequency generation vibrational spectroscopy (Barnette et al 2012). It is clear from the literature that various methods provide values of crystallinity that are different (Park et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…Subsequently, using the univariate Raman method, the crystallinity of woods and other lignocelluloses was estimated (Agarwal et al 2013a) and it was reported that with proper corrections for the contributions of syringyl lignin and hemicelluloses, the method generated accurate values of wood crystallinity. In this context, it is important to note that compared to Segal-WAXS (Segal et al 1959), the Raman estimate is usually lower because it is correlated with the 21-Segal-WAXS, where 21 designates the 2h where amorphous contribution was measured (and subtracted) (Agarwal et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In the WAXS-based crystallinity determinations, wood has been sampled in various ways; for example, as a wood wafer (Andersson et al 2003;Howell et al 2011), wood chip (Barnette et al 2012), and ground wood (Wellwood et al 1974;Andersson et al 2003;Agarwal et al 2013a). Andersson et al (2003) reported that for the investigated annual ring samples, the observed crystallinity from the tangential face was significantly higher compared to the ground wood where the fiber orientation was random.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of fiber orientation and milling on observed crystallinity in jack pine

et al. 2014

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Influences of fiber orientation and milling on wood cellulose crystallinity were studied using jack pine wood. The fiber orientation effects were measured by sampling rectangular wood blocks in radial, tangential, and cross-sectional orientations. The influence of milling was studied by analyzing the unsieved and sieved milled wood fractions (all \1,000 lm). Fiber orientation effect was manifested in both X-ray and Raman measurements and was dependent upon the orientation of the sampled wood blocks. In Raman, the observed crystallinity was similar between the blocks sampled on the tangential and the radial faces. However, the estimated values were 5.5 % lower compared to that measured in a powdered sample pellet. Moreover, in these sampling modes, the orientation of the block with respect to the direction of the electric vector of the laser made a difference only for the tangential mode of sampling. When a wood block was sampled on the crosssectional face, the observed Raman crystallinity was 3.9 % higher from that of the pellet. The observed crystallinity did not significantly differ with change in sample orientation with respect to the electric vector direction. In contrast, the Segal-WAXS study of the blocks indicated that compared to the pellet, the estimated crystallinities in the radial, tangential, and cross-sectional sampling modes were 5, 2, and 11 % lower, respectively. This suggested that the radial and the tangential faces of the blocks can be used to estimate the crystallinity of wood. With regard to the effect of milling on Raman and Segal-WAXS estimates, the wood crystallinity did not depend upon the particle sizes of the fractionated samples and was similar to that of the original unfractionated ground wood.

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Estimation of Cellulose Crystallinity of Lignocelluloses Using Near-IR FT-Raman Spectroscopy and Comparison of the Raman and Segal-WAXS Methods

Cited by 113 publications

References 28 publications

Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

Comparison of sample crystallinity determination methods by X-ray diffraction for challenging cellulose I materials

Impacts of fiber orientation and milling on observed crystallinity in jack pine

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