Error Analysis and Correction for Quantitative Phase Analysis Based on Rietveld-Internal Standard Method: Whether the Minor Phases Can Be Ignored?

XRPD is a powerful tool for material characterization in general, and for in-situ studies of chemical processes in particular. The use of an intense X-ray source, .i.e. synchrotron X-rays, coupled with fast X-ray detection permits time-resolved diffraction experiments allowing in-situ quantitative phase analysis during the early ages of cement hydration. Calcium sulfoaluminate, CSA, cements may have variable compositions, but all of them contain high amounts of ye'elimite, Ca4Al6O12SO4. Commercial CSA cements have special applications such as high strength developments at early-ages. Ye'elimite is very reactive and most of its hydration heat is released during the first eight hours of hydration . The aim of this work is to better understand the early age hydration of stoichiometric (orthorhombic) and doped (pseudo-cubic) ye'elimite samples. The parameters studied by SXRPD, LXRPD and calorimetry have been: polymorphism; water/ye'elimite ratio; and sulfate (gypsum and anhydrite) contents. This work has allowed establishing mechanisms and kinetics for hydration of ye'elimite samples by in-situ SXRPD with internal standard methodology. Moreover, pastes were also studied by ex-situ LXRPD with the external standard method, G-factor, at 2 and 7 days. Both strategies were able to quantify the amorphous contents, including free water. It is important to highlight that the results obtained at early ages, by the internal standard method, are in agreement with those obtained at later ages, G-method, showing the consistence and complementarity of both methodologies. The hydration of stoichiometric ye'elimite in the presence of gypsum is strongly hastened, when compared to the hydration process without gypsum. However, the presence of gypsum has a little effect in the hydration of doped ye'elimite. Moreover, anhydrite has also accelerated the hydration of stoichiometric ye'elimite, although its lower solubility has provoked the formation of an intermediate phase in the first hours.

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Accuracy in quantitative phase analysis of mixtures with large amorphous contents. The case of stoneware ceramics and bricks

Journal of Applied Crystallography ◽

10.1107/s160057671400627x ◽

2014 ◽

Vol 47 (3) ◽

pp. 835-846 ◽

Cited By ~ 15

Author(s):

Alessandro F. Gualtieri ◽

Vincenzo Riva ◽

Andrea Bresciani ◽

Stefano Maretti ◽

Marco Tamburini ◽

...

Keyword(s):

Phase Analysis ◽

Internal Standard ◽

Quantitative Phase Analysis ◽

Experimental Conditions ◽

X Ray ◽

Quantitative Phase ◽

Factor Method ◽

Counting Statistics ◽

First Time ◽

X Ray Absorption

For the first time, this work inspects the accuracy of quantitative phase analysis of both crystalline and amorphous components of stoneware tiles and bricks. A number of variables were considered: the nature of the internal standard, experimental conditions and counting statistics. The so-calledG-factor method has also been applied. The results of the X-ray powder diffraction analysis have been compared with the results obtained with optical microscopy and image analysis. Only the mixtures spiked with corundum and silicon yielded accurate weight estimates of the amorphous fraction, whereas the use of highly X-ray absorbing internal standards (such as fluorite, rutile and zincite) resulted in gross underestimations. In fact, microabsorption effects are found to drastically reduce the accuracy of the results when standards with linear X-ray absorption coefficients higher than 100 cm−1are employed. It was found that very low counting statistics reduced the calculated amorphous fractions in both bricks and stoneware tiles owing to partial masking of the major peak of the internal standard, namely corundum. The application of theG-factor method to the systems investigated was also evaluated. The results are poorer than those obtained using the internal standard.

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Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19821973 ◽

1982 ◽

Vol 47 (7) ◽

pp. 1973-1978 ◽

Cited By ~ 2

Author(s):

Jiří Karhan ◽

Zbyněk Ksandr ◽

Jiřina Vlková ◽

Věra Špatná

Keyword(s):

Standard Deviation ◽

Nmr Spectroscopy ◽

Standard Method ◽

Internal Standard ◽

Internal Standard Method ◽

Concentration Region ◽

Experimental Conditions ◽

Curve Method ◽

Sample Preparation Procedure

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.

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