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Cited by 19Terahertz technology and applicationsMicrowave and Dielectric Measurement TechniquesSpectroscopy and Laser Applications

Influence of Particle Size on Optical Constants From Pellets Measured With Terahertz Pulsed Spectroscopy

Open access
Bardon, Tiphaine, May, Robert K., Taday, Philip F., Strlic, Matija·2016·IEEE Transactions on Terahertz Science and Technology
DOI 10.1109/tthz.2016.2538641
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Abstract

Particle size is shown to influence both the overall value and the measurement precision of the refractive index and absorption coefficient of a sample diluted with high density polyethylene (HDPE) powder and compressed in a pellet. However, excessive grinding of a sample before it is mixed with HDPE powder can result in the formation of large particle clusters. These aggregates can induce internal scattering of the terahertz pulse within the pellet as well as lead to different mechanical properties of the pellet, which may change the distribution of air pores. These phenomena result in extracted optical constants with low accuracy and precision. The present work introduces a simple experimental procedure to improve the precision and accuracy of optical constants from spectroscopic pellets. This procedure consists of moderately grinding the sample powder in fine HDPE powder with a pestle and mortar. The standard deviation of the refractive index of Prussian blue has been observed to reduce from 0.14 to 0.02 following this procedure.

AI snapshot

Written from the paper’s full text.

TL;DR

Particle size and mixing procedure affect the accuracy and precision of terahertz optical constants extracted from HDPE pellets, with excessive grinding creating aggregates and internal scattering. Moderately grinding sample powder with HDPE in a pestle and mortar improved Prussian blue refractive-index standard deviation from 0.14 to 0.02.

Key findings

  • Sucrose particle size influenced both refractive index and absorption coefficient: refractive-index standard deviation increased with larger particles, reaching 0.10 for particles >250 µm, while the absorption-coefficient slope increased from 0.28 ± 0.12 (53–75 µm) to 6.76 ± 1.14 (>250 µm).
  • For Prussian blue, Procedure a (extra grinding before mixing) gave refractive index 1.87 ± 0.14 and absorption slope 1.39 ± 0.51; Procedure c (moderate grinding of the powder mixture) gave 1.48 ± 0.02 and 0.23 ± 0.03, reducing the refractive-index standard deviation from 0.14 to 0.02.
  • Pellets from Procedures a and b had average refractive indices offset by 0.3 to 0.4 compared with homogeneous pellets; Procedure c pellets were thicker but had decreased time delays, attributed to internal scattering in inhomogeneous pellets.
  • Sucrose spectral features at 48, 55, 60, 74, 85, and 94 cm⁻¹ were well observed for particles below 150 µm, but broadened and were not consistently observed for larger particles, with additional non-repeatable features for particles >250 µm.

Methods

  • Sucrose powders were prepared in five size categories (53–75, 75–106, 106–150, 150–250, and >250 µm) and mixed with HDPE at a 10% mass ratio; Prussian blue was mixed with HDPE at 10% using three procedures (a, b, c). Each mixture was pressed into triplicate 400-mg pellets of 13 mm diameter and 3.53–3.87 mm thickness.
  • Pellets were measured in transmission with a TPS Spectra 3000 terahertz time-domain spectrometer in a nitrogen-purged compartment; 1800 scans at 30 Hz were co-averaged, with working spectral ranges of 5–100 cm⁻¹ for sucrose and 5–70 cm⁻¹ for Prussian blue at 1.2 cm⁻¹ resolution. A pure polyethylene pellet was used as reference.
  • Constant and frequency-dependent refractive indices and absorption coefficients were calculated, and SEM/optical microscopy was used to observe particle sizes and pigment distribution.

Limitations

  • The paper states the procedure may not be used for materials prone to phase transformation during grinding or blending with a pestle and mortar.
  • The paper states that the absorption-coefficient calculation does not correct for scattering losses originating within the pellet, so it indicates total extinction including absorption and scattering from powder particles and air pores.
  • Evident from the text: some supporting data, including time-domain waveforms and results from Prussian blue from other suppliers, are not shown; findings are based on sucrose and Prussian blue with triplicate pellets, so broader generalizability is not fully demonstrated.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1109/tthz.2016.2538641

Cites

22 of 22 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 15 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § Influence of Particle Size on Optical Constants From Pellets Measured With Terahertz Pulsed Spectroscopy · p. 1

    Excessive grinding of a sample before it is mixed with HDPE powder can result in the formation of large particle clusters.

    “However, excessive grinding of a sample before it is mixed with HDPE powder can result in the formation of large particle clusters.”
    • Also stated in: § III. RESULTS AND DISCUSSION · p. 5 · plain
      “the fine Prussian blue powder was further ground prior to its mixing with HDPE and this resulted in the formation of aggregates which can be larger than 500 m.”
    Quote in the paperSubstantial claim
  • Findingown data
    § III. RESULTS AND DISCUSSION · p. 5

    The average refractive indices for pellets resulting from Procedure a and b have an offset of 0.3 to 0.4 compared to refractive indices from homogeneous pellets.

    “Finally, Fig. 4(b) and Table I indicate that the average refractive indices for pellets resulting from Procedure a and b have an offset of 0.3 to 0.4 compared to refractive indices from homogeneous pellets.”
    Quote in the paperSubstantial claim
  • Findingown data
    § III. RESULTS AND DISCUSSION · p. 5

    Further grinding fine Prussian blue powder prior to mixing with HDPE resulted in the formation of aggregates which can be larger than 500 μm.

    “Fig. 3(a) shows an example of such a cluster at the surface of a spectroscopic pellet: the fine Prussian blue powder was further ground prior to its mixing with HDPE and this resulted in the formation of aggregates which can be larger than 500 m.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The particle clusters observed on the surface of spectroscopic pellets by microscopy are representative of the particle distribution throughout the pellet.
  • Findingreasoning
    § III. RESULTS AND DISCUSSION · p. 5

    The standard deviation for both refractive index and absorption coefficient is larger for particle sizes comprised between 53-75 μm than for particle sizes between 75-106 μm.

    “It should be noted that the standard deviation for both refractive index and absorption coefficient is larger for particle sizes comprised between 53-75 m than for particle sizes between 75-106 m.”
    Quote in the paperSubstantial claim
  • Findingown data
    § III. RESULTS AND DISCUSSION · p. 5

    Optical constant values extracted from pellets produced with Procedure c are significantly more reproducible than values extracted from pellets produced with Procedure a.

    “Standard deviations reported in this figure clearly indicate that optical constant values extracted from pellets produced with Procedure c are significantly more reproducible than values extracted from pellets produced with Procedure a .”
    Quote in the paperSubstantial claim
  • May combine two claims. 26
  • Classified as probably not a substantial claim. 14
  • The quote only partly states this claim. 3

  • May combine two claims.

    Findingown data
    § Influence of Particle Size on Optical Constants From Pellets Measured With Terahertz Pulsed Spectroscopy · p. 1

    Particle size influences both the overall value and the measurement precision of the refractive index and absorption coefficient of a sample diluted with high density polyethylene (HDPE) powder and compressed in a pellet.

    “Particle size is shown to influence both the overall value and the measurement precision of the refractive index and absorption coefficient of a sample diluted with high density polyethylene (HDPE) powder and compressed in a pellet.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § III. RESULTS AND DISCUSSION · p. 5

    The signals from Procedures a and b are more attenuated and have a broader full-width at half-maximum (FWHM) with respect to their reference signals than the signals from Procedure c.

    “Analyzing the time-domain waveforms (data not shown here), the signals from Procedures a and b are more attenuated and have a broader full-width at half-maximum (FWHM) with respect to their reference signals than the signals from Procedure c .”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data
    § B. Terahertz Time-Domain Spectroscopy · p. 2

    The terahertz beam diameter at the focal plane is 6.5 mm at 1.2 THz and 3.5 mm at 3 THz.

    “The results indicate a beam diameter of 6.5 mm at 1.2 THz and 3.5 mm at 3 THz.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). The quote only partly states this claim.

    Findingnone given
    § D. Thickness Measurements · p. 3

    In this study, Δd varied between 164-553 μm.

    “In this study, was found to vary between 164-553 m.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § III. RESULTS AND DISCUSSION · p. 5

    Using Procedure c, homogeneous pellets of similar thickness difference and time delays than those shown for 'Prussian blue c' were obtained from Prussian blue from other suppliers; as a result, refractive index and absorption coefficient values were found to be comparable.

    “Prussian blue from other suppliers have also been analyzed (data not shown here). Using Procedure c , homogeneous pellets of similar thickness difference and time delays than those shown for 'Prussian blue c' in this study were obtained. As a result, refractive index and absorption coefficient values were found to be comparable.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § Influence of Particle Size on Optical Constants From Pellets Measured With Terahertz Pulsed Spectroscopy · p. 1

    A simple experimental procedure improves the precision and accuracy of optical constants from spectroscopic pellets.

    “The present work introduces a simple experimental procedure to improve the precision and accuracy of optical constants from spectroscopic pellets.”
    • Also stated in: § III. RESULTS AND DISCUSSION · p. 5 · plain
      “This work introduces a simple experimental procedure to minimize scattering from particles so as to improve the precision (i.e., reduce random errors) of the optical constants extracted from diluted spectroscopic pellets.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning
    § III. RESULTS AND DISCUSSION · p. 4

    For larger particles, these spectral features broaden and are not consistently observed.

    “However, for larger particles these spectral features broaden and are not consistently observed.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning
    § III. RESULTS AND DISCUSSION · p. 4

    The average time delays for sucrose pellets reported in Table I do not display a systematic decrease with smaller particle size, while their standard deviations do.

    “This is the reason why the average time delays for sucrose pellets reported in Table I do not display a systematic decrease with smaller particle size, while their standard deviation do.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § III. RESULTS AND DISCUSSION · p. 5

    This procedure produced a homogeneous powder, and the resulting spectroscopic pellet could be considered as a homogeneous medium with respect to the wavelength of the incident beam.

    “This procedure produced a homogeneous powder, and the resulting spectroscopic pellet could be considered as a homogeneous medium with respect to the wavelength of the incident beam, as observed in Fig. 3(c).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The particle clusters observed on the surface of spectroscopic pellets by microscopy are representative of the particle distribution throughout the pellet.

  • May combine two claims.

    Findingown data
    § III. RESULTS AND DISCUSSION · p. 4

    For particles larger than 75 μm, the increasing baseline of absorption coefficients is more pronounced and less reproducible with increasing particle size.

    “A similar phenomenon is observed for the absorption coefficients in Fig. 2: for particles larger than 75 m, the increasing baseline is more pronounced and less reproducible with increasing particle size.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingcitation
    § A. Spectroscopic Pellets · p. 2

    Individual Prussian blue particles could not be resolved with the optical microscope, but the average size of particle aggregates was found to be below 13 μm.

    “Prussian blue pigment (L. Cornelissen & Son, London, U.K.) was dispersed on a glass slide and examined under optical microscope: individual particles could not be resolved with the optical microscope, as observed by Eastaugh et al. [22], but the average size of particle aggregates was found to be below 13 m.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [22] [22] R. Siddall, T. Chaplin, V. Walsh, and N. Eastaugh , Pigment Compendium . Routledge, U.K.: Taylor & Francis, 2008. -

      Not checked in the free run.

  • May combine two claims.

    Findingown data
    § III. RESULTS AND DISCUSSION · p. 4

    The slope of the linear fit of the absorption coefficient between 5-25 cm^-1 increases with increasing particle size, together with its standard deviation.

    “the slope of the linear fit of the absorption coefficient between 5-25 cm increases with increasing particle size, together with its standard deviation, as reported in Table I.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data
    § III. RESULTS AND DISCUSSION · p. 4

    The average value and standard deviation of the refractive index is lower for particles with sizes between 75 and 106 μm, and both increase with larger particle sizes, until reaching a standard deviation of 0.1 for particles larger than 250 μm.

    “While the average value and standard deviation of the refractive index is lower for particles with sizes between 75 and 106 m, both are seen to increase with larger particle sizes, until reaching a standard deviation of 0.1 for particles larger than 250 m.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § III. RESULTS AND DISCUSSION · p. 4

    Such spectral artifacts and distortions, together with increasing baselines, were also observed by Shen et al. for sucrose particles >250 μm in a powder cell, and by Franz et al. for phenyllactic acid particles 400-600 μm diluted with PE and compressed into pellets.

    “Such spectral artifacts and distortions, together with increasing baselines, were also observed by Shen et al. [7] for sucrose particles with sizes more than 250 min a powder cell, and by Franz et al. [8] for phenyllactic acid particles with sizes between 400-600 m, diluted with PE and compressed into pellets.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [7] [7] Y. C. Shen, P. F. Taday, and M. Pepper, 'Elimination of scattering effects in spectral measurement of granulated materials using terahertz pulsed spectroscopy,' Appl. Phys. Lett. , vol. 92, no. 5, 2008, Art. no. 051103. - source

      Not checked in the free run.

    • cites [8] [8] M. Franz, B. M. Fischer, and M. Walther, 'The Christiansen effect in terahertz time-domain spectra of coarse-grained powders,' Appl. Phys. Lett. , vol. 92, no. 2, 2008, Art. no. 021107. - source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims. The quote only partly states this claim.

    Study design and conductreasoning
    § D. Thickness Measurements · p. 3

    To minimize uncertainties in refractive index due to thickness measurements, a caliper with an accuracy of 1 μm was selected, and calculations of Δd were made using the average of triplicate thickness measurements on each pellet.

    “To minimize uncertainties in due to thickness measurements, a caliper with an accuracy of 1 m was selected, and calculations of were made using the average of triplicate thickness measurements on each pellet.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning
    § III. RESULTS AND DISCUSSION · p. 4

    The change in the degree of overlap of the scattered signals would change the shape of the waveform, and therefore its spectral dependency in the frequency-domain; this is why additional spectral features may be observed for pellets containing particles with sizes similar to or larger than the wavelength of the incident pulse.

    “The change in the degree of overlap of the scattered signals would change the shape of the waveform, and therefore its spectral dependency in the frequency-domain: this is why additional spectral features may be observed for pellets containing particles with sizes similar to or larger than the wavelength of the incident pulse.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation
    § A. Spectroscopic Pellets · p. 1

    Prussian blue is regarded as the first modern synthetic pigment and was widely used in artworks and documents due to its availability and ease of use.

    “Prussian blue is regarded as the first modern synthetic pigment and was widely used in artworks and documents due to its availability and ease of use [21].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [21] [21] J. Kirby and D. Saunders, National Gallery Company Ltd., London, U.K., 'Fading and colour change of Prussian blue: Methods of manufacture and the influence of extenders,' National Gallery Tech. Bull. , vol. 25, pp. 73-99, 2004 [Online]. Available: http://www.nationalgallery.org.uk/technical-bulletin/kirby\_saunders2004 -

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § III. RESULTS AND DISCUSSION · p. 4

    Scattering can influence the time delay between terahertz pulses transmitted through the reference and sample pellets: a terahertz pulse experiencing an internal reflection on a large particle will escape the spectroscopic pellet at a later time than a pulse experiencing no internal reflection, and the measured Δt would be larger.

    “Such scattering can also influence the time delay between the terahertz pulses transmitted through the reference and sample pellets: a terahertz pulse experiencing an internal reflection on a large particle will escape the spectroscopic pellet at a later time than a pulse experiencing no internal reflection, and the measured would be larger.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation
    § I. INTRODUCTION · p. 1

    A granular form of the material is often diluted into a low absorbing material, such as polyethylene powder, and the powder mixture then compressed into a thick pellet.

    “To overcome these issues, a granular form of the material is often diluted into a low absorbing material, such as polyethylene powder, and the powder mixture then compressed into a thick pellet [5], [6].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [5] [5] K.-E. Peiponen, J. A. Zeitler, and M. Kuwata-Gonokami , Terahertz Spectroscopy and Imaging , K.-E. Peiponen and M. Kuwata-Gonokami, Eds. Berlin, Germany: Springer-Verlag, 2013, vol. 171. - source

      Not checked in the free run.

    • cites [6] [6] P. U. Jepsen, D. G. Cooke, and M. Koch, 'Terahertz spectroscopy and imaging-modern techniques and applications,' Laser Photon. Rev. , vol. 5, no. 1, pp. 124-166, Jan. 2011. - source

      Not checked in the free run.

    • Rests on an assumption: HDPE powder is low-absorbing and does not significantly contribute to the measured absorption or scattering.

  • May combine two claims.

    Premisereasoning
    § III. RESULTS AND DISCUSSION · p. 4

    For particles smaller than the incident wavelength, the media constituting the pellet can be considered homogeneous, and the terahertz beam is not scattered.

    “For particles smaller than the incident wavelength, the media constituting the pellet can be considered homogeneous, and the terahertz beam is not scattered.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § III. RESULTS AND DISCUSSION · p. 4

    Walther et al. reported that the refractive index of a solid spectroscopic pellet obtained from milled sucrose powder diluted with polyethylene is 1.8 on average over the frequency range 0.2-4 THz.

    “Walther et al. [20] reported that the refractive index of a solid spectroscopic pellet obtained from milled sucrose powder diluted with polyethylene is 1.8 on average over the frequency range 0.2-4 THz.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [20] [20] M. Walther, B. M. Fischer, and P. U. Jepsen, 'Noncovalent intermolecular forces in polycrystalline and amorphous saccharides in the far infrared,' Chem. Phys. , vol. 288, pp. 261-268, 2003. - source

      Not checked in the free run.

  • May combine two claims.

    Premisereasoning
    § III. RESULTS AND DISCUSSION · p. 5

    Unlike white sucrose particles, Prussian blue is intensely colored, which makes it possible to observe clusters of particles in the white HDPE matrix.

    “Prussian blue fine particles are known to form aggregates [22] and unlike white sucrose particles are intensely colored, which makes it possible to observe clusters of particles in the white HDPE matrix.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given
    § III. RESULTS AND DISCUSSION · p. 5

    Scattering may also occur due to the presence of air pores of sizes similar to the incident wavelength and embedded in a homogeneous matrix.

    “Yet scattering may also occur due to the presence of air pores of sizes similar to the incident wavelength and embedded in a homogeneous matrix.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Influence of Particle Size on Optical Constants From Pellets Measured With Terahertz Pulsed Spectroscopy · p. 1

    These aggregates can induce internal scattering of the terahertz pulse within the pellet and lead to different mechanical properties of the pellet, which may change the distribution of air pores.

    “These aggregates can induce internal scattering of the terahertz pulse within the pellet as well as lead to different mechanical properties of the pellet, which may change the distribution of air pores.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given
    § A. Spectroscopic Pellets · p. 1

    The strong contrast in color between the white polyethylene matrix and Prussian blue facilitates the observation of the effects of sample preparation on the homogeneity of the pellet.

    “The strong contrast in color between the white polyethylene matrix and Prussian blue facilitates the observation of the effects of sample preparation on the homogeneity of the pellet.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § III. RESULTS AND DISCUSSION · p. 5

    Different powders would present different mechanical properties once diluted with HDPE and pressed into a pellet, and the number and size of the pores within a pellet may differ depending on the mixing procedures and on the nature of the sample material (its compressive strength and expansion properties, its hygroscopicity, the nature of its surface forces).

    “Different powders would present different mechanical properties once diluted with HDPE and pressed into a pellet, and the number and size of the pores within a pellet may differ depending on the mixing procedures (as observed here for Prussian blue) and on the nature of the sample material (its compressive strength and expansion properties, its hygroscopicity, the nature of its surface forces).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductreasoning
    § C. Refractive Index Calculations · p. 2

    Equation (4) does not correct for scattering losses originating from within the pellet; therefore α is indicative of total extinction and encompasses absorption by the sample powder as well as scattering from powder particles and air pores.

    “Equation (4) does not correct for any scattering losses originating from within the pellet. Therefore, is indicative of the total extinction of the terahertz beam, and encompasses any absorption by the sample powder, as well as scattering from powder particles and air pores.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: HDPE powder is low-absorbing and does not significantly contribute to the measured absorption or scattering.

  • May combine two claims.

    Interpretationreasoning
    § III. RESULTS AND DISCUSSION · p. 4

    While pellets constituted of large particles of sucrose can be considered birefringent, that does not mean that sucrose itself is birefringent.

    “Therefore, while we can consider that pellets constituted of large particles of sucrose are birefringent, that does not mean that sucrose itself is birefringent.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § I. INTRODUCTION · p. 1

    Previous studies have investigated the influence of particle size of granular materials on the spectral signature in the terahertz region, observing changes in the monotonic increase of the baseline, anomalous spectral features and distortions of vibrational absorption bands.

    “Previous studies have investigated the influence of the particle size of granular materials on the spectral signature (absorbance, transmittance, absorption or attenuation coefficient spectra) of the material in the terahertz region, observing changes in the monotonic increase of the baseline, anomalous spectral features and distortions of vibrational absorption bands [7]-[12].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [7]-[12]

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationown data
    § III. RESULTS AND DISCUSSION · p. 5

    At a critical particle size, the active surface area of a particle is such that surface forces (e.g., electrostatic or van der Waals) start to be significant and sample particles may have a preferred affinity to bind with other sample particles, rather than with HDPE particles; this would create clusters of sample particles which can be assimilated to large sample particles and would lead to

    “This could be explained by the fact that at a critical particle size, the active surface area of a particle is such that surface forces (e.g., electrostatic or van der Waals) start to be significant and sample particles may have a preferred affinity to bind with other sample particles, rather than with HDPE particles. This would create clusters of sample particles which can be assimilated to large”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Study design and conductreasoning
    § D. Thickness Measurements · p. 3

    The error in refractive index caused by an error in the reading of the thickness of the pellets is a function of Δd.

    “Using (1), it can be observed that the error in refractive index caused by an error in the reading of the thickness of the pellets is a function of :”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation
    § I. INTRODUCTION · p. 1

    A study has recently suggested a curve-fitting equation to distinguish the absorption behavior of the material from scattering-induced effects in heterogeneous and scattering specimens.

    “A study has recently suggested a curve-fitting equation to distinguish the absorption behavior of the material from scattering-induced effects in heterogeneous and scattering specimens [12].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] [12] V. V. Kornienko, R. a. Akhmedzhanov, I. E. Ilyakov, A. D. Mishin, P. a. Prudkovskii, O. V. Samotokhin, B. V. Shishkin, and G. K. Kitaeva, 'Scattering effects in terahertz wave spectroscopy of granulated solids,' IEEE Trans. THz Sci. Technol. , vol. 5, no. 4, pp. 1-8, Jul. 2015. - source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given
    § III. RESULTS AND DISCUSSION · p. 5

    This procedure may not be used for materials prone to phase transformation during grinding or blending with a pestle and mortar.

    “Finally, it should be noted that this procedure may not be used for materials prone to phase transformation during grinding or blending with a pestle and mortar.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given
    § I. INTRODUCTION · p. 1

    Many substances commonly studied with terahertz TDS are white, therefore the distribution of their particles within the white polyethylene matrix is difficult to observe.

    “Many substances commonly studied with terahertz TDS are white, therefore the distribution of their particles within the white polyethylene matrix is difficult to observe.”
    Quote in the paperNot a substantial claim
34 of 34

  • The paper relies on this without support.

    HDPE powder is low-absorbing and does not significantly contribute to the measured absorption or scattering.

    “mixed with a low-absorbing HDPE powder”
    “The signal transmitted through a 360-mg pellet of pure polyethylene powder was used as a reference measurement.”

  • The paper relies on this without support.

    The particle clusters observed on the surface of spectroscopic pellets by microscopy are representative of the particle distribution throughout the pellet.

    “Fig. 3(a) shows an example of such a cluster at the surface of a spectroscopic pellet”
    “the resulting spectroscopic pellet could be considered as a homogeneous medium with respect to the wavelength of the incident beam, as observed in Fig. 3(c).”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • The size of microspheres (or pores) plays a crucial role in the presence of anomalous spectral features.

    “Importantly, it has been shown that the size of microspheres (or pores) plays a crucial role in the presence of anomalous spectral features [9], [11].”

    From Unveiling the Origin of Spurious Features in THz-TDS of Powder Compacts (2025) · cites this paper as [9]

  • For compacted granular samples, anomalous spectral features have been observed in polyethylene, ammonium nitrate powder, flour, salt, Prussian Blue dye, Dinitrotoluene, and common sugars.

    “For compacted granular samples, these features have been observed in polyethylene [7], ammonium nitrate powder, flour, and salt [8], Prussian Blue dye [9], Dinitrotoluene [11], and common sugars [11], [13].”

    From Unveiling the Origin of Spurious Features in THz-TDS of Powder Compacts (2025) · cites this paper as [9]

  • Anomalous spectral features have been observed in THz-TDS measurements of granular samples and samples with rough surfaces.

    “The presence of anomalous spectral features has been observed when performing THz-TDS on granular samples [7], [8], [9], [10], [11] and samples with rough surfaces [12], [13], [14], [15].”

    From Unveiling the Origin of Spurious Features in THz-TDS of Powder Compacts (2025) · cites this paper as [9]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Refractive index does not increase across all larger sucrose particle sizes

    Minor

    The stated increase in average refractive index with larger particle size does not hold for the largest category. Table I gives 1.84 for 150-250 μm particles but 1.77 for particles larger than 250 μm.

1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. siddall, 2008, The Pigment Compendium
  2. kirby, 2004, Fading and colour change of Prussian blue: Methods of manufacture and the influence of extenders, Nat Gallery Tech Bulletin, 25, 73

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Related

Authors
Bardon, T., May, R. K., Taday, P. F., & Strlic, M.
Affiliations
  • University College London (GB)
  • TeraView (United Kingdom) (GB)
ORCID
Taday, Philip F.
Venue
IEEE Transactions on Terahertz Science and Technology
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
Published
2016-05
Volume
6
Issue
3
Pages
408-413
ISSN
  • 2156-342X (ISSN-L)
  • 2156-3446
DOI
10.1109/tthz.2016.2538641
OpenAlex
W2337534119
Semantic Scholar
b8a4af12225fa59d4e360d9cf19aa53306bb21bb
Cited by
19
References
22
Citations by year
2026: 1 · 2025: 4 · 2024: 1 · 2022: 3 · 2021: 4 · 2020: 1 · 2019: 2 · 2018: 2 · 2017: 1
FWCI
0.77
Type
journal article
Language
en
Open access
Licence
Locations
  • IEEE Transactions on Terahertz Science and Technology (publishedVersion, cc-by)
  • UCL Discovery (University College London) (submittedVersion, cc-by)
Topics
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Terahertz technology and applications
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Microwave and Dielectric Measurement Techniques
  • Physical Sciences › Chemistry › Spectroscopy › Spectroscopy and Laser Applications
Keywords
particle size, optical constants, refractive index, absorption coefficient, terahertz spectroscopy, pellets, high-density polyethylene, sample grinding, particle aggregates, internal scattering, air pores, Prussian blue, measurement precision

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-08.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-08.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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