Comment on the Raman study of the thermal transformation of calcium hydroxide

Seehra, M. S.

doi:10.1016/0022-4596(86)90187-8

Cited by 4 publications

(4 citation statements)

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“…MgO and NaCl; compare, for example, Refs . or the halite spectrum in the RRUFF database) does not possess any Raman active modes, except for second order effects involving the scattering of two phonons giving rise to two overlapping and relatively sharp bands at 530 cm −1 and 660 cm −1 as well as to a broad signal at about 1000 cm −1 . Bringing our results into play, we can confirm the spectrum observed by Galvan‐Ruiz et al ., but follow the other studies in the interpretation that CaO does not have a first‐order Raman spectrum.…”

Section: Resultsmentioning

confidence: 99%

“…More generally, the well‐known dependence of Raman intensity on the change in polarizability of a molecule or crystal during a vibration causes vibrations with covalent bonds involved to be on average by far more Raman active than vibrations along bonds with high ionic character. Therefore, no alkali (M 2 O) or earth alkali oxide (MO) gives rise to detectable Raman bands except for very weak second‐order contributions . These compounds strongly react with water and CO 2 leading to the formation of covalent OH and CO bonds.…”

Section: Discussionmentioning

confidence: 99%

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Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)₂ and CaCO₃

Schmid

Dariz

2014

J Raman Spectroscopy

119

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In microscopy studies of 19 th -century cement stone, we found free lime in the form of darkened spherical structures, as they were described in the literature already. When trying to determine their phase composition by Raman spectroscopy, we encountered contradictive assignments in literature spectra of the lime phases CaO, Ca(OH) 2 and CaCO 3 and observed strong spectral features that have been ignored or erroneously assigned so far. In this study we present Raman spectra of pure lime phases and of a naturally grown calcite crystal, burnt limestone (quick lime, mainly CaO), aged slaked lime putty (mainly Ca(OH) 2 ), and carbonated lime putty (mainly CaCO 3 ). Based on the results, we shed light mainly onto these two questions: (1) Does CaO have a Raman spectrum? (2) Which features in the spectra are luminescence bands that could be (and already have been) misinterpreted as Raman bands? We proof our assignment of luminescence bands in lime phases by using three different laser wavelengths for excitation, and give hypotheses on the origin of the luminescence as well as practical advices on how to identify these misleading features in Raman spectra. This article is mainly addressed to users of Raman spectroscopy in different fields of material analysis who might not be aware of the presence of interfering bands in their spectra.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)₂ and CaCO₃

Schmid

Dariz

2014

J Raman Spectroscopy

119

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“…However, it is possible to observe second order effects which give rise to sharp bands at 530 and 660 cm -1 , as well as a broad signal at about 1000 cm -1 [15] .…”

Section: Introductionmentioning

confidence: 99%

Influence of water vapour and carbon dioxide on free lime during storage at 80°C, studied by Raman spectroscopy

Dubina

Korat

Black

et al. 2013

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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10Micro-Raman spectroscopy has been used to follow the reaction of free lime (CaO) exposed 11 for 24 hours to moist air at 80 °C under conditions of different relative humidities (10 -80 % 12 RH). X-ray diffraction and SEM imaging were applied as complementary techniques. The 13 conversion of lime to calcium hydroxide and its subsequent carbonation to various calcium 14 carbonate polymorphs was found to strongly depend on the relative humidity. At low RH (10 15 -20 %), only Raman spectroscopy revealed the formation of early amorphous CaCO 3 which 16 in the XRD patterns was detected only at ≥ 40 % RH. However, XRD analysis could identify 17 the crystalline polymorphs formed at higher relative humidities. Thus, between 20 and 18 60 % RH, all three CaCO 3 polymorphs (calcite, aragonite and vaterite) were observed via 19 XRD whereas at high relative humidity (80 %), calcite was the predominant reaction product. 20The results demonstrate the usefulness of Raman spectroscopy in the study of minor cement 21 constituents and their reaction products on air, especially of amorphous character. 22 23

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“…The Raman bands for CaO are difficult to characterize, as it is usually present in the surface as the Ca(OH) 2 phase and CaCO 3 in the samples. Some authors [32][33][34] claim that CaO does not possess any Raman-active modes, except for second-order effects involving the scattering of two phonons giving rise to two overlapping bands at 530 cm −1 and 660 cm −1 , as well as a broad signal at about 1000 cm −1 [35]. For our CaO sample, we did not observe Raman bands at the above-mentioned positions with obvious intensity, confirming that CaO indeed does not have a first-Order Raman spectrum.…”

Section: Xps Analysismentioning

confidence: 99%

ZnO–Doped CaO Binary Core–Shell Catalysts for Biodiesel Production via Mexican Palm Oil Transesterification

Arenas-Quevedo,

Manríquez,

Wang

et al. 2024

Inorganics

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This work investigates biodiesel production via transesterification of Mexican palm oil with methanol catalyzed by binary solid base core–shell catalysts with improved catalytic stability. A series of CaO–ZnO mixed solids were prepared using an inexpensive co–precipitation method by varying ZnO content from 5 to 20 mol%. Several factors, such as surface basicity, ZnO content, phase compositions, and thermal treatment of the catalysts, were all proven to be crucial for the production of biodiesel with good quality. Thermal treatment could effectively remove the surface adsorbed water and impurities and improved the catalytic activity. The addition of ZnO to CaO significantly enhanced the catalysts’ stability; however, it led to lower surface basicity and slightly diminished catalytic activity. ZnO doping inhibited the formation of surface Ca(OH)2 and promoted the formation of Ca–Zn–O or CaZn2(OH)6 phase as the core and a surface CaCO3 shell, which effectively decreased Ca2+ leaching by approximately 74% in methanol and 65% in a methanol–glycerol (4:1) mixture. A combined method of separation and purification for obtaining clean biodiesel with high quality was proposed. The biodiesel obtained under the control conditions exhibited properties which satisfied the corresponding standards well.

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Comment on the Raman study of the thermal transformation of calcium hydroxide

Cited by 4 publications

References 5 publications

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)₂ and CaCO₃

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)₂ and CaCO₃

Influence of water vapour and carbon dioxide on free lime during storage at 80°C, studied by Raman spectroscopy

ZnO–Doped CaO Binary Core–Shell Catalysts for Biodiesel Production via Mexican Palm Oil Transesterification

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Comment on the Raman study of the thermal transformation of calcium hydroxide

Cited by 4 publications

References 5 publications

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)2 and CaCO3

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)2 and CaCO3

Influence of water vapour and carbon dioxide on free lime during storage at 80°C, studied by Raman spectroscopy

ZnO–Doped CaO Binary Core–Shell Catalysts for Biodiesel Production via Mexican Palm Oil Transesterification

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Product

Resources

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Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)₂ and CaCO₃

Shedding light onto the spectra of lime: Raman and luminescence bands of CaO, Ca(OH)₂ and CaCO₃