Requirements for Thermal Analysis by Variable-Temperature Diffuse Reflectance Infrared Spectroscopy

1992 ◽  
Vol 46 (10) ◽  
pp. 1508-1513 ◽  
Author(s):  
Robert L. White
Keyword(s):  
Infrared Spectroscopy ◽  
Calcium Oxalate ◽  
Diffuse Reflectance ◽  
Variable Temperature ◽  
Calcium Oxalate Monohydrate ◽  
Quantitative Information ◽  
Center Frequency ◽  
Effect Of Temperature ◽  
Diffuse Reflectance Infrared Spectroscopy ◽  
Diffuse Reflectance Infrared

The effect of temperature on diffuse reflectance infrared spectroscopy measurements is discussed. Instrumental parameters that determine the accuracy of variable-temperature diffuse reflectance Fourier transform infrared spectroscopy (VT-DRIFTS) measurements are identified, and methods for removing baseline artifacts resulting from fluctuations in these parameters are given. Procedures for extracting structure-specific quantitative information from DRIFTS spectra acquired at different temperatures are outlined. The use of VT-DRIFTS to generate vibration-specific absorbance band intensity and center frequency temperature profiles for calcium oxalate monohydrate is described, and correlations between these profiles and the known thermal behavior of calcium oxalate monohydrate are given.

VT-DRIFTS: A Two-Dimensional Infrared Thermal Analysis Method

1993 ◽  
Vol 47 (9) ◽  
pp. 1492-1496 ◽  
Author(s):  
Robert L. White
Keyword(s):  
Thermal Analysis ◽  
Diffuse Reflectance ◽  
Variable Temperature ◽  
Calcium Oxalate Monohydrate ◽  
Poly Vinyl Alcohol ◽  
Analysis Method ◽  
Temperature Dependent ◽  
Structure Changes ◽  
Diffuse Reflectance Infrared Spectroscopy ◽  
Diffuse Reflectance Infrared

Thermal analysis by using variable-temperature diffuse reflectance infrared spectroscopy (VT-DRIFTS) is described. Techniques for extracting spectral information from VT-DRIFTS data regarding temperature-dependent solid-state structure changes are discussed. The use of VT-DRIFTS for investigating the thermal degradation mechanisms of calcium oxalate monohydrate and poly(vinyl alcohol) and for profiling the Lewis and Brønsted acid strength distributions for an HZSM-5 zeolite by monitoring pyridine desorption as a function of temperature is described.

Determination of Kinetic Parameters for the Dehydration of Calcium Oxalate Monohydrate by Diffuse Reflectance FT-IR Spectroscopy

1994 ◽  
Vol 48 (5) ◽  
pp. 561-568 ◽  
Author(s):  
Alfred A. Christy ◽  
Egil Nodland ◽  
Alan K. Burnham ◽  
Olav M. Kvalheim ◽  
Birger Dahl
Keyword(s):  
Crystal Structure ◽  
Calcium Oxalate ◽  
Kinetic Parameters ◽  
Diffuse Reflectance ◽  
Variable Temperature ◽  
Calcium Oxalate Monohydrate ◽  
Water Molecules ◽  
Ft Ir ◽  
Bending Modes ◽  
Diffuse Reflectance Infrared

Variable-temperature diffuse reflectance infrared spectroscopy was used to study the reaction kinetics of the dehydration of calcium oxalate monohydrate. The kinetic analysis of the dehydration process indicates that there are two reactions taking place, as well as the presence of two different equimole water molecular environments in the crystal structure of calcium oxalate monohydrate. Partial least-squares calibration of the dehydration profiles was carried out to identify the evolution sequence of the two different types of water molecules in the crystal structure of calcium oxalate monohydrate. The results indicate that the water molecules in the crystal structure which are responsible for the stretching absorptions at 3428 and 3336 cm−1 are eliminated first at a higher rate, during the first part of the reaction, and the others responsible for the absorptions at 3486 and 3058 cm−1 are eliminated at a later stage. The unexpected and unidentified band arising from bending modes of one of the types of water molecules is shown to arise from the same water molecules that are responsible for the stretching absorptions at 3486 and 3058 cm−1. Kinetic parameters were determined for the dehydration step, and the overall activation energy calculated for the dehydration step is in agreement with values reported in the literature. However, the clear presence of two distinct reactions invalidates all previous determinations of reaction order.

Variable-Temperature Diffuse Reflectance Infrared Studies of Calcium Oxalate Monohydrate

1992 ◽  
Vol 46 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Robert L. White ◽  
Jiu Ai
Keyword(s):  
Mass Spectrometry ◽  
Fourier Transform ◽  
Calcium Oxalate ◽  
Diffuse Reflectance ◽  
Variable Temperature ◽  
Calcium Oxalate Monohydrate ◽  
Quadrupole Mass ◽  
Infrared Studies ◽  
Infrared Spectral ◽  
Diffuse Reflectance Infrared

The thermal degradation of calcium oxalate monohydrate is studied by using diffuse reflectance Fourier transform infrared spectroscopy combined with quadrupole mass spectrometry (DRIFTS/MS). DRIFTS/MS results are correlated with thermogravimetric analyses to verify the thermal properties of samples studied. Infrared spectral evidence for CaC2O4H2O dehydration and infrared spectra for three different CaC2O4 phases are given. In addition, the significance of a band at 1085 cm−1 assigned to CO22− which appears during the decomposition of CaC2O4 to CaCO3 is discussed.

Figures of Merit for a Diffuse Reflectance Accessory Using an On-Axis Ellipsoidal Collecting Mirror

1988 ◽  
Vol 42 (3) ◽  
pp. 428-433 ◽  
Author(s):  
E. H. Korte
Keyword(s):  
Infrared Spectroscopy ◽  
Noise Level ◽  
Diffuse Reflectance ◽  
Field Of View ◽  
Figures Of Merit ◽  
Size Dependent ◽  
Diffuse Reflectance Infrared Spectroscopy ◽  
Diffuse Reflectance Infrared

The attainable efficiency of an accessory for diffuse reflectance infrared spectroscopy where both the irradiation and detection optics are located on the same side of the sample is analyzed, the size-dependent noise level of the detector being taken into account. The resulting figures of merit are found to reach up to more than 0.3, when standard detectors of 60° field-of-view are considered.

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