Raman spectroscopy of powders: Effects of light absorption and scattering

Waters, D. N.

doi:10.1016/0584-8539(94)80196-7

Cited by 38 publications

(39 citation statements)

References 11 publications

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“…[5] In addition to absorption in these samples, multiple scattering processes occur that affect the observed Raman intensities. Kubelka and Munk [6] were the first to develop a theory to describe the optical properties of diffuse reflectance measurements.…”

Section: Introductionmentioning

confidence: 99%

“…[7] The Raman intensity is related to the particle size of the powder and is generally accepted to decrease for a set of samples having a constant absorption coefficient with decreasing particle size. [5,8] This paper describes how Raman spectroscopy can be used to measure the surface morphology of sintered powder components. A number of components were manufactured using different processing conditions in the SLS process that would affect the degree of sintering between particles.…”

Section: Introductionmentioning

confidence: 99%

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Using Raman spectroscopy to monitor surface finish and roughness of components manufactured by selective laser sintering

Beard

Ghita

Evans

2010

J Raman Spectroscopy

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Selective laser sintering (SLS) is an additive manufacturing process used to realise fully functional component manufacture. Numerous parameters are used in the process to control variables such as laser power, scan speed, laser spot size and overlap of scan vectors. All of these parameters can dramatically alter the sintering process and therefore final component properties. This paper presents how Raman spectroscopy intensity effects, caused by the surface roughness of the components produced, can be used to monitor the degree of sintering between particles in the SLS process.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Using Raman spectroscopy to monitor surface finish and roughness of components manufactured by selective laser sintering

Beard

Ghita

Evans

2010

J Raman Spectroscopy

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“…This procedure requires the knowledge of a quantitative relation between reflectance R and Raman intensities, as shown by Schrader and Bergmann 11 and Waters. 12 In this paper, we describe time-dependent in situ Raman experiments on two different types of zirconiabased catalysts which are active for the isomerization of light alkanes. 13 -16 A fixed-bed flow reactor was used as an in situ Raman cell and the activity of the catalysts was determined simultaneously by on-line gas chromatography.…”

Section: Introductionmentioning

confidence: 99%

Time‐resolved in situ Raman spectroscopy of working catalysts: sulfated and tungstated zirconia

Kuba

Knözinger

2002

J Raman Spectroscopy

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The spectra of time-dependent in situ Raman experiments on sulfated and tungstated zirconia catalysts during the isomerization reaction of n-pentane are presented and discussed. A purpose-made in situ Raman cell which was used for this application is described. The choice of appropriate experimental parameters, namely laser power and laser wavelength, is discussed. During the experiments the activity and selectivity of the catalysts were determined simultaneously by on-line gas chromatography. The sulfated zirconia catalyst shows structural changes in the sulfate region during the reaction. One of two different types of initially present sulfate species is eroded during the reaction, presumably due to a reduction to H 2 S. The activity shows a typical induction period followed by a fast deactivation. No coke formation is observed. Since fast deactivation occurs, coke formation cannot be the only reason for the deactivation of the catalyst. The tungstated catalyst shows strong darkening after initiation of the reaction with increasing time-on-stream (TOS). This leads to the disappearance of the catalyst bands. However, coke formation indicated by a broad band at 1590 cm −1 can be observed. Since darkening has a strong effect on Raman intensities, the time evolution of the observed bands is not obtained correctly. We propose a new method to correct for the effect of the darkening. The change of the diffuse reflectance of the catalyst is determined by the variation of the intensity of laser plasma lines. Based on an approximate equation proposed by Waters which correlates the Raman intensities and the diffuse reflectance of a sample, a correction factor for the spectra is obtained. After the intensity correction the spectra indicate that most of the coke is formed in the first few minutes of the reaction followed by a constant formation rate with TOS.

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“…In general, these optical properties are wavelength dependent. [54][55][56][57][58] In fluorescence spectroscopy, however, diffuse reflectance correction of spectral distortions in biological media has been studied extensively. Analytical models based on photon migration theory 43 , diffusion theory 45,59,60 , as well as empirical models 61 , have been reported to obtain "intrinsic fluorescence."…”

Section: Optical Properties Biological Tissuementioning

confidence: 99%