Raman Spectroscopy of Potassium Acetate-Intercalated Kaolinites Over the Temperature Range 25-300 Degrees C Plus
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Raman spectra of the hydroxyl-stretching region of potassium acetate-intercalated kaolinite were obtained under an atmosphere of both air and nitrogen using a thermal stage over the temperature range 25-300 °C. At 25 °C, an additional band at 3606 cm-1 attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion is observed with a concomitant loss of intensity in the bands attributed to the inner surface hydroxyls. Heating the intercalated complex to 50 °C results in two hydroxyl-stretching wavenumbers at 3594 and 3604 cm-1. At 100 °C, the bands shift to 3600 and 3613 cm-1. At temperatures from 100 to 300 °C, bands are observed in similar positions. Upon cooling in air to 25 °C, the acetate-bonded inner surface hydroxyl stretching wavenumber shifts back to 3606 cm-1. Upon heating the intercalated kaolinite to 300 °C under an atmosphere of nitrogen and upon cooling the acetate-bonded inner surface hydroxyl stretching wavenumber is observed at 3601 cm-1. Upon cooling to 150 °C and subsequently to 25 °C, two bands are observed at 3611 and 3600 cm-1. Upon rehydration, the hydroxyl stretching wavenumber returns to 3606 cm-1. The changes in the Raman spectra of the hydroxyl-stretching region during dehydration and rehydration are reversible. When the potassium acetate-intercalated kaolinite is heated to 300 °C and cooled to 25 °C, the inner-hydroxyl band is observed at 3630 cm-1. The shift in the wavenumber of the inner hydroxyl band is attributed to the insertion of the potassium ion in the ditrigonal cavity of the siloxane layer.Keywords:
Atmospheric temperature range
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Deuteration of expanded hydrazine-kaolinite complex at room temperature shifts the infrared stretching frequencies of the inner-surface hydroxyls from 3695, 3670, and 3650 cm(-1) to 2725, 2710, and 2698 cm(-1), respectively, and the inner hydroxyls absorbing at 3620 cm(-1) to 2675 cm(-1). The OH-OD exchange for the inner-surface hydroxyls varies from 60 to 67 percent, whereas it is only 22 percent for the inner hydroxyls.
Halloysite
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The infrared absorption, infrared emission, and Fourier transform (FT)-Raman spectra of a series of gibbsites well defined by X-ray diffraction have been obtained. Hydroxyl stretching frequencies were found ∼ at 3670, 3620, 3524, 3452, 3395, 3375, and ∼ 3300 cm −1 . Hydroxyl deformation vibrations were observed at 1059, 1023, 969, 938, and 915 cm −1 . Hydroxyl stretching bands were observed in the Raman spectra at 3524, 3436, and 3365 cm −1 and correspond well with the three infrared bands. These bands are both Raman and infrared active. The bands at ∼ 3670, 3620, and 3395 cm −1 are infrared active only. The hydroxyl stretching frequencies show a pronounced blue shift, while the hydroxyl deformation modes show a pronounced red shift. Infrared absorption bands were observed at 3413, 3283, and 3096 cm −1 for the hydroxyl stretching frequencies and at 1024, 969, and 914 cm −1 for the hydroxyl deformation frequencies. Low-frequency infrared absorption vibrations were found at ∼ 860, 838, 800, 747, 666, ∼ 625, 585, 560, 522, 452, and 423 cm −1 and infrared emission bands at 834, 778, 728, 652, 640, 609, 580, 512, and 489 cm −1 . The infrared emission low-frequency bands moved to higher frequencies upon thermal treatment. The dehydroxylation of gibbsite was followed by the combination of infrared emission spectroscopy and differential thermal analysis over the 200 to 750 °C temperature ranges. Dehydroxylation is followed by the loss of intensity of the hydroxyl stretching frequencies observed at 3620 and 3351 cm −1 and by the loss of intensity of the hydroxyl deformation modes at 1024 cm −1 . Dehydroxylation starts at 220 °C and is complete by 350 °C. Some variation in the gibbsite endotherms was found between the synthetic and natural gibbsite dehydroxylations. Spectral changes in the low-frequency bands confirm that dehydroxylation commenced at 220 °C.
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Pyrophyllite
Talc
Muscovite
Diamond anvil cell
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Raman spectra of the hydroxyl-stretching region of a low defect kaolinite were obtained at temperatures between ambient and the predehydroxylation temperatures of 500°C, using a Raman microprobe equipped with a thermal stage. At 25°C, Raman bands of the kaolinite hydroxyl stretching region were observed at 3691, 3683, 3670, 3652 and 3621 cm. Upon heating the kaolinite, the band at 3621 cm moved to higher wavenumbers and is observed at 3629 cm at 500 °C. The other four bands attributed to the inner surface hydroxyl groups of kaolinite shift to lower wavenumbers. The 3691 cm band ascribed to the longitudinal optic vibration shifts to 3674 cm at the predehydroxylation temperature of 500°C. The 3683 cm band ascribed to the transverse optic vibration is observed at 3667 cm at 500°C. Upon cooling the Raman spectrum of the kaolinite differed from the initial 25 °C spectrum, suggesting the thermal treatment caused some stacking disorder. The changes in the band position are determined by the strength of the hydrogen bonds formed between the inner surface hydroxyls and the oxygen of the next adjacent layer. Copyright (C) 2000 John Wiley and Sons, Ltd.
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The dehydroxylation of boehmite has been studied by the application of infrared emission spectroscopy over the 200 to 750 °C temperature range. The dehydroxylation is followed by the loss of intensity of the hydroxyl stretching frequencies observed at 3478, 3319, and 3129 cm −1 and by the loss of intensity of the hydroxyl deformation modes at 1140 and 1057 cm −1 . Dehydroxylation starts at 250 °C and is complete by 450 °C. No difference was found between the synthetic and natural boehmite dehydroxylation. The hydroxyl stretching frequencies show a pronounced blue shift, while the hydroxyl deformation modes show a pronounced red shift. Infrared absorption bands were observed at 3413, 3283, and 3096 cm −1 for the hydroxyl stretching frequencies and at 1161 and 1071 cm −1 for the hydroxyl deformation frequencies. Low-frequency infrared absorption bands are observed at 749, 635, and 542 cm −1 and infrared emission bands at 811, 716, 611, and 456 cm −1 . The infrared emission low-frequency bands moved to higher frequencies upon thermal treatment. Spectral changes in the low-frequency bands confirm that dehydroxylation commenced at 250°C. Infrared emission spectroscopy allows the phase changes of the Al 2 O 3 –H 2 O alumina system to be studied in situ at the elevated temperatures.
Boehmite
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Abstract Expansion of kaolinite with potassium acetate reduces the intensity of the 3695 cm −1 absorption band and causes the appearance of an additional one at 3600 cm −1 . Subsequent deuteration with D 2 O vapor shifts the 3695 cm −1 and 3600 cm −1 absorption bands to 2725 cm −1 and 2650 cm −1 respectively. The hydroxyls absorbing at 3620 cm −1 do not interact with the acetate anion and do not readily exchange with D 2 O vapor. Deuteration of expanded hydrazine-kaolinite complex at room temperature shifts the infrared stretching frequencies 3695, 3670, 3650 and 3620 cm −1 to 2725, 2710, 2698 and 2675 cm −1 respectively. The OH-OD exchanges for the hydroxyls absorbing at 3695, 3670 and 3650 cm −1 are 67, 60 and 62 per cent respectively, and for the 3620 cm −1 only 22 per cent. The 3695, 3670 and 3650 cm −1 absorption bands are correlated predominantly to inner-surface hydroxyls and the 3620 cm −1 to inner hydroxyls located below the holes in the silica tetrahedral layer. The ν (OH) absorption bands at 3695, 3670 and 3650 cm −1 , and the ν (OD) at 2725, 2698, and 2675 cm −1 are pleochroic, whereas the 3620 cm −1 absorption band is non-pleochroic. The direction of the dipole moment change of OH groups absorbing at 3695 cm −1 and 3670 cm −1 , and of OD groups absorbing at 2725 cm −1 and 2698 cm −1 , is nearly at right angles to the basal plane (001); for the 3650 cm −1 and 2675 cm −1 bands, the angle is large, but less than 90°. The inner hydroxyls absorbing at 3620 cm −1 have their dipole moment change inclined at about 15° to the “ab” cleavage plane. A comparison of the ν (OH) and ν (OD) absorption intensities for the film rotated 45° and normal to the infrared incident radiation shows that the pleochroism is more intense in the ν (OD) region than in the ν (OH) region. This indicates that partial deuteration perturbs the direction of dipole moment change of the “hydrogen bond” with respect to the initial orientation prior to deuteration; the net result is the formation of larger angles between the direction of the OD dipole moment changes and the basal plane (001) than existed for OH prior to deuteration.
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Abstract The Raman spectrum at 298 K of hydrazine‐intercalated kaolinite shows a single band at 3620 cm −1 . No other hydroxyl stretching bands are observed. Upon obtaining the spectrum at liquid nitrogen temperature the band is observed at 3616 cm −1 , the same position as for the inner hydroxyl of the non‐intercalated kaolinite. Hence this band is assigned to the inner hydroxyl of kaolinite. After exposure to the atmosphere for 10 min and upon obtaining spectra at 77 K, two additional bands are observed at 3607 and 3625 cm −1 . These additional bands are only observed after the onset of deintercalation. The band observed at 3625 cm −1 is assigned to the inner surface hydroxyls, hydrogen bonded to the hydrazine. The fact that the band is only observed after the onset of deintercalation suggests that the band is Raman inactive and infrared active. Raman spectroscopic analysis indicates that there are two types of hydrazine molecules as evidenced by two NH bands, (a) weakly hydrogen bonded as evidenced by two bands observed around 3300 and 3312 cm −1 and (b) a strongly hydrogen‐bonded hydrazine as evidenced by bands at 2890 and 2948 cm −1 . The two NH symmetric stretching bands at around 3300 and 3312 cm −1 combined with the two NH antisymmetric stretching bands at 3361 and 3367 cm −1 suggest that there are two slightly different NH 2 units in the hydrazine‐intercalated complex. Copyright © 2002 John Wiley & Sons, Ltd.
Hydrazine (antidepressant)
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Pyridine-N-oxide
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Raman spectroscopy of potassium acetate‐intercalated kaolinites over the temperature range 25–300,°C
Abstract Raman spectra of the hydroxyl‐stretching region of potassium acetate‐intercalated kaolinite were obtained under an atmosphere of both air and nitrogen using a thermal stage over the temperature range 25–300 °C. At 25 °C, an additional band at 3606 cm −1 attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion is observed with a concomitant loss of intensity in the bands attributed to the inner surface hydroxyls. Heating the intercalated complex to 50 °C results in two hydroxyl‐stretching wavenumbers at 3594 and 3604 cm −1 . At 100 °C, the bands shift to 3600 and 3613 cm −1 . At temperatures from 100 to 300 °C, bands are observed in similar positions. Upon cooling in air to 25 °C, the acetate‐bonded inner surface hydroxyl stretching wavenumber shifts back to 3606 cm −1 . Upon heating the intercalated kaolinite to 300 °C under an atmosphere of nitrogen and upon cooling the acetate‐bonded inner surface hydroxyl stretching wavenumber is observed at 3601 cm −1 . Upon cooling to 150 °C and subsequently to 25 °C, two bands are observed at 3611 and 3600 cm −1 . Upon rehydration, the hydroxyl stretching wavenumber returns to 3606 cm −1 . The changes in the Raman spectra of the hydroxyl‐stretching region during dehydration and rehydration are reversible. When the potassium acetate‐intercalated kaolinite is heated to 300 °C and cooled to 25 °C, the inner‐hydroxyl band is observed at 3630 cm −1 . The shift in the wavenumber of the inner hydroxyl band is attributed to the insertion of the potassium ion in the ditrigonal cavity of the siloxane layer. Copyright © 2001 John Wiley & Sons, Ltd.
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Atmospheric temperature range
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Expansion of kaolinite with potassium acetate and with hydrazine followed by deuteration, shifts the absorption frequency at 3695 cm -1 to lower values, but does not affect the intensity of the 3620-cm -1 absorption band. The band at 3695 cm -1 is correlated predominantly to inner-surface hydroxyls with the dipole at right angles to the basal plane and the band at 3620 cm -1 is related to inner hydroxyls with the dipole inclined toward empty octahedral sites.
Basal plane
Absorption band
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