Modification of kaolinite by controlled hydrothermal deuteration – a DRIFT spectroscopic study

Clay Minerals ◽  
2004 ◽  
Vol 39 (3) ◽  
pp. 349-362 ◽  
Author(s):  
Hui Ming
Keyword(s):  
Diffuse Reflectance ◽  
Near Infrared ◽  
Vibration Mode ◽  
Lattice Structure ◽  
Structural Defects ◽  
Hydroxyl Group ◽  
Isomorphous Substitution ◽  
Lattice Vibrations ◽  
Diffuse Reflectance Infrared ◽  
Hydroxyl Band

AbstractKaolinites were modified by controlled hydrothermal deuteration. Both infrared and near infrared vibration spectra of deuterated kaolinite were investigated by Diffuse Reflectance Infrared Fourier Transform spectroscopy. The stretching vibrations (v) of deuteroxyl groups of the kaolinite were observed at 2726, 2709, 2697 and 2667 cm-1, respectively. The overtone bands (2n) of the deuteroxyl groups were visible in NIR regions at 5454, 5419, 5388 and 5342 cm-1, respectively. The lattice vibrations of the kaolinite taking part in deuteration included 937, 915, 792, 751 and 690 cm-1 which are assigned to hydroxyl group-related deformation or translation-vibration mode. The hydroxyl band at 3435 cm-1 with its deuteroxyl band at 2542 cm-1 resulted from unevenly distributed structural defects, either due to the isomorphous substitution of foreign cations or the imperfections of the kaolinite lattice structure.

Optimization of Diffuse Reflectance Infrared Spectroscopy Accessories

1986 ◽  
Vol 40 (8) ◽  
pp. 1082-1085 ◽  
Author(s):  
T. Hirschfeld
Keyword(s):  
Diffuse Reflectance ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Sampling Procedure ◽  
Signal To Noise ◽  
Ellipsoidal Mirror ◽  
Diffuse Reflectance Infrared Spectroscopy ◽  
Central Opening ◽  
Low Efficiency ◽  
Diffuse Reflectance Infrared

The value of diffuse reflectance as an infrared or near-infrared spectroscopic sampling procedure has been limited by the low efficiency of accessories designed for it. In terms of signal-to-noise ratio, these average 2–6% for integrating spheres and 10–12% for various ellipsoidal mirror arrangements. Much better performances, up to 37% efficiency, can be obtained by optimizing a concentric confocal ellipsoidal mirror arrangement by using a very large central opening in the amular collector mirror, and adapting the throughput of the detector to the geometry of the collected beam.

Study of the interactions between caesium bromide and kaolinite by photoacoustic and diffuse reflectance infrared spectroscopy

1991 ◽  
Vol 69 (4) ◽  
pp. 749-754 ◽  
Author(s):  
Kirk H. Michaelian ◽  
Shmuel Yariv ◽  
Ahmed Nasser
Keyword(s):  
Infrared Spectroscopy ◽  
Diffuse Reflectance ◽  
Hydroxyl Group ◽  
Ambient Atmosphere ◽  
Intercalation Complex ◽  
Wet Grinding ◽  
Diffuse Reflectance Infrared Spectroscopy ◽  
Inner Surface ◽  
Diffuse Reflectance Infrared ◽  
Mechanochemical Reactions

The mechanochemical reactions between CsBr and kaolinite that occur during shaking, grinding at ambient atmosphere (air grinding), and grinding in the presence of a few drops of water (wet grinding), were investigated by photoacoustic and diffuse reflectance infrared spectroscopy and by thermal weight loss. An intercalation complex was formed by the wet grinding technique but not by mixing or air grinding. For comparison, the mechanochemical reactions of kaolinite with CsCl and CsI were also investigated. No complex of CsI was formed but CsCl gave an intercalation complex by air or wet grinding and, after an aging period of 3 months, also by mixing. A structure is suggested for the intercalation complex in which a water molecule coordinated to the large caesium cation donates one proton to an inner surface oxygen and another proton to the halide, while accepting a proton from an inner surface hydroxyl group. Key words: kaolinite, infrared spectroscopy, intercalation.

scholarly journals Changes of Pd Oxidation State in Pd/Al2O3 Catalysts Using Modulated Excitation DRIFTS

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 116
Author(s):  
Gian Luca Chiarello ◽  
Ye Lu ◽  
Miren Agote-Arán ◽  
Riccardo Pellegrini ◽  
Davide Ferri
Keyword(s):  
Particle Size ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Oxidation State ◽  
Diffuse Reflectance ◽  
X Ray ◽  
Spectral Changes ◽  
Diffuse Reflectance Infrared ◽  
X Ray Absorption ◽  
Reversible Reduction

Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions.

Towards 3D image-based nanocrystallography by means of transmission electron goniometry

2004 ◽  
Vol 839 ◽  
Author(s):  
Peter Moeck ◽  
Wentao Qin ◽  
Philip B. Fraundorf
Keyword(s):  
Lattice Structure ◽  
Three Dimensions ◽  
Structural Defects ◽  
Transmission Electron ◽  
Means Of Transmission ◽  
Z Contrast ◽  
Individual Nanoparticles ◽  
Nanocrystal Model ◽  
The Ideal

ABSTRACTIt is well known that the crystallographic phase and morphology of many materials changes with the crystal size in the tens of nanometer range and that many nanocrystals possess structural defects in excess of their equilibrium levels. A need to determine the ideal and real structure of individual nanoparticles, therefore, arises. High-resolution phase-contrast transmission electron microscopy (TEM) and atomic resolution Z-contrast scanning TEM (STEM) when combined with transmission electron goniometry offer the opportunity of develop dedicated methods for the crystallographic characterization of nanoparticles in three dimensions. This paper describes tilt strategies for taking data from individual nanocrystals “as found”, so as to provide information on their lattice structure and orientation, as well as on the structure and orientation of their surfaces and structural defects. Internet based java applets that facilitate the application of this technique for cubic crystals with calibrated tilt-rotation and double-tilt holders are mentioned briefly. The enhanced viability of image-based nanocrystallography in future aberration-corrected TEMs and STEMs is illustrated on a nanocrystal model system.

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