Quantitative phase composition

The methods that have proved effective for quantitative determination of phases in clinkers are based on light microscopy (Section 4.2.1), X-ray diffraction (Section 4.3.2) and calculation from the bulk chemical analysis. The last two of these are applicable also to cements. SEM with image analysis (Section 4.3.1) shows promise, but other methods that have been investigated, such as IR spectroscopy, appear to have little potential. Sections 4.4.2 to 4.4.5 describe a method of calculation from the bulk analysis and Section 4.4.6 compares the results of the various methods. 

---

TG/DTA, TPR, and complementary techniques for characterizing catalysts in the working state (e.g., XRD Raman, IR, and UV-vis spectroscopies) can provide structural and metal valence information under reaction conditions. However, the capability of TR-XAFS spectroscopy to reveal quantitative phase composition and average metal valence together with the evolution of the local structure of a catalyst under varying (reaction) conditions, combined with a time resolution of 100 ms will continue to be a very powerful tool for kinetics investigations in solid-state chemistry and heterogeneous catalysis. 

Fig. 3.1 shows these changes for a typical clinker. No attempt has been made to show a detailed sequence of phases below 1300°C, as sufficient data do not exist, and minor phases, including sulphates, are omitted. Quantitative phase compositions at various stages vary considerably with starting materials and other factors. 

In another approach, widely used in the USA and elsewhere, the quantitative phase composition is estimated using a procedure due to Bogue (B24). It is necessary also to know the content of free lime, which may be determined by a chemical extraction method (Section 4.3.3). The calculation is as follows ... 

Calculation of quantitative phase composition from bulk analysis... 

For a calculation of the quantitative phase composition of a clinker from the bulk chemical analysis to give correct results, the following conditions are necessary and sufficient ... 

The experimental considerations applying to calcium silicate pastes (Sections 5.1 and 5.2) are equally relevant to cement pastes. Of the methods so far used in attempts to determine the degrees of reaction of the individual clinker phases as a function of time, QXDA (C39,D12,T34,P28) has proved much the most satisfactory. Procedures are essentially as for the analysis of a clinker or unreacted cement (Section 4.3.2), but it is necessary to take account of overlaps with peaks from the hydration products, and especially, with the C-S-H band at 0.27-0.31 nm. The water content of the sample must be known, so that the results can be referred to the weight of anhydrous material. If a sample of the unhydrated cement is available, and its quantitative phase composition has been determined, it may be used as the reference standard for the individual clinker phases in the paste. 

There are probably no effective direct methods at present for determining either C-S-H or AFm phases in cement pastes in both cases, this is probably attributable to the low degree of crystallinity. Odler and Abdul-Maula (015) found that determination of AFm phase by QXDA was only semiquantitative. Postulated quantitative phase compositions of cement pastes may, however, be tested by comparing observed and calculated TG curves (Section 7.3.3). 

The essential input data are (a) the bulk chemical composition of the cement, (b) the quantitative phase composition of the cement and the chemical compositions of its individual phases, (c) the fraction of each phase that has reacted, (d) the w/c ratio, (e) the COj content of the paste and an estimate of how it is distributed among phases, and (0 the composition of each hydrated phase for the specified drying condition. If (b) is unknown, it may be estimated as described in Section 4.4, and if (c) is unknown, it may be estimated from the age as described by Parrott and Killoh (P30), or, more simply though less precisely, by using empirical equations (D12,T37). If the phase composition by volume and porosities are to be calculated, densities of phases are also required. 

In principle, it should be possible to calculate the heat of hydration from the quantitative phase compositions of the unreacted mix and of the paste, using standard enthalpies of formation. The sensitivity of such calculations to small errors in the latter data probably renders this approach unsatisfactory with existing data. 

In Section 7.3.3, a method was described for calculating the quantitative phase composition of a cement paste by weight and by volume for various drying conditions. Fig. 8.5 includes porosities thus calculated for 18-month-... 

Although (quantitative phase compositions, temperatures, and pressures for such a highly non-ideal mixture cannot be expected from this e(quation of state, a reasonably accurate description of global phase behavior can be obtained. 

A notable exception is a study by Hesse et al. (2008) who investigated the effect of powder grain size and grain size distribution on the spatial distribution of calcium phosphate phases in atmospheric plasma-sprayed hydroxyapatite coatings incubated in r-SBF (SBF-H, Table 7.8). Coatings were mechanically abraded under dry conditions in steps of 40 pm by abrasive SiC paper, and the newly created surfaces analysed by XRD with Rietveld refinement for their quantitative phase composition. The results of this depth profiling are shown in Figure 6.8. 

In catalysis, the Rietveld method is extensively used to determine the quantitative phase composition of a sample and to calculate its average size of crystallites with the aid of the Scherrer equation. Also, it can give information on the lattice parameter changes and microstmctural and size effects that may occur in the sample synthesis or after its catalytic use. 

Quantitative Phase Analysis. Once the identity of the components in a sample are known, it is possible to determine the quantitative composition of the sample. There are several different methods for doing a quantitative analysis, but the most rehable method is to use mixtures of known composition as standards. The computer can determine quantitatively the relative amounts of each component in the unknown sample. For accurate calculations of relative amounts in the unknown sample, it is necessary that the sample and standards have uniform distributions of crystaUites. Often the sample and standards are rotated during data collection to provide a more even distribution of crystaUites which diffract. 

The use of Equation (22) is very general, but it is also possible, with accurate measurements and data treatment, to perform the quantitative phase analysis in semi-crystalline materials without using any internal standard. This procedure is possible only if the chemical compositions of all the phases, including the amorphous one, are known. If the composition of the amorphous phase is unknown, the quantitative analysis without using any internal standard can still be used provided that the chemical composition of the whole sample is available [51]. This approach, until now, has been developed only for the XRD with Bragg-Brentano geometry that is one of the most diffused techniques in powder diffraction laboratories. 

This procedure allows quantitative phase analysis without using any internal standard, but it requires the knowledge of the composition of the sample and a careful treatment of the experimental data, which have to be corrected for the air scattering. 

Applications The general applications of XRD comprise routine phase identification, quantitative analysis, compositional studies of crystalline solid compounds, texture and residual stress analysis, high-and low-temperature studies, low-angle analysis, films, etc. Single-crystal X-ray diffraction has been used for detailed structural analysis of many pure polymer additives (antioxidants, flame retardants, plasticisers, fillers, pigments and dyes, etc.) and for conformational analysis. A variety of analytical techniques are used to identify and classify different crystal polymorphs, notably XRD, microscopy, DSC, FTIR and NIRS. A comprehensive review of the analytical techniques employed for the analysis of polymorphs has been compiled [324]. The Rietveld method has been used to model a mineral-filled PPS compound [325]. 

The phase composition of glycine crystal forms during the drying step of a wet granulation process has been studied, and a model developed for the phase conversion reactions [88], X-ray powder diffraction was used for qualitative analysis, and near-infrared spectroscopy for quantitative analysis. It was shown that when glycine was wet granulated with microcrystalline cellulose, the more rapidly the granulation... 

Qualitative and quantitative analyses with HPLC are very similar to those with GC (Sections 12.7 and 12.8). In the absence of diode array, mass spectrometric, and FTIR detectors that give additional identification information, qualitative analysis depends solely on retention time data, tR and C (Remember that tR is the time from when the solvent front is evident to the peak) Under a given set of HPLC conditions, namely, the mobile and stationary phase compositions, mobile phase flow rate, column length, temperature (when the optional column oven is used), and instrument dead volume, the retention time is a particular value for each component. It changes only when one of the above parameters changes. Refer to Section 12.7 for further discussion of qualitative analysis. 

With regard to quantitative measurements of APG surfactants in, e.g. environmental samples, the authors stressed that it was of crucial importance to promote the formation of the desired molecular (or adduct) ion in order to obtain reproducible mass spectra. If tuning of the ESI interface parameters did not suffice to yield abundant ions of the selected species, acquisitions of the mass spectrometric detector after negative ionisation in conjunction with appropriate selection of the mobile phase composition were used as an alternative despite the lower sensitivity in this mode [1,2],... 

In this study, it has been possible to devise a procedure which can be used to generate reliable phase compositions for both the hydrocarbon - rich phase and the aqueous phase over a wide range of temperature and pressure. Moreover, the calculation procedure has been successfully applied to non-hydrocarbon -water systems with quantitative results. 

QUANTITATIVE CAROTENOID COMPOSITION (PG/CELL), OBTAINED BY HPLC ANALYSIS, OF H. PLUVIALIS CELLS IN THE STATIONARY PHASE IN CULTURES WITH DIFFERENT CONCENTRATIONS OF NITRATE (G/L), ACETATE AND MALONATE (% W/V)... 

A new HP-TLC method has been applied for the quantitative analysis of flavonoids in Passiflora coerulea L. The objective of the experiments was the separation and identification of the compound(s) responsible for the anxiolytic effect of the plant. Samples were extracted with 60 per cent ethanol or refluxed three times with aqueous methanol, and the supernatants were employed for HPTLC analysis. Separation was performed on a silica layer prewashed with methanol and pretreated with 0.1 M K2HP04, the optimal mobile phase composition being ethyl acetate-formic acid-water (9 1 l,v/v). It was established that the best extraction efficacy can be achieved with 60 - 80 per cent aqueous methanol. The HPTLC technique separates 10 different flavonoids, which can be used for the authenticity test of this medicinal plant [121],... 

For determining the robustness of a method a number of parameters, such as extraction time, mobile-phase pH, mobile-phase composition, injection volume, source of column lots and/or suppliers, temperature, detection wavelength, and the flow rate, are varied within a realistic range and tlie quantitative influence of the variables is determined. If the influence of a parameter is within a previously specified tolerance, this parameter is said to be witliin the robustness range of the method. These method parameters may be evaluated one factor at a time or simultaneously as part of a factorial experiment. 

Crystallization was followed by analyzing the solid product quantitatively by x-ray powder diffraction. Prepared mixtures of a standard sample of mordenite and the amorphous substrate of mordenite composition were used to establish a calibration curve for the quantity of mordenite based on the summation of x-ray peak intensities. For zeolites A and X, the unreacted aluminosilicate gel was used to prepare mixtures with standard samples of zeolites A and X for quantitative phase identification. 

Our previous studies [22] showed that the uncalcined MCM-41 and lamellar phases prepared using the same surfactant as a template exhibit dramatically different thermogravimetric behavior, which manifests itself in distinctly different temperatures of the weight change events. This provided a clear opportunity for detection of lamellar constituents in MCM-41 and for quantitative determination of the composition of MCM-41/lamellar mixed samples. Indeed, the percentages of the lamellar phases in these samples assessed from the TGA data were remarkably close to those obtained using quantitative X-ray diffraction and gas adsorption analysis [22]. This demonstrated that in favorable cases, TGA can be used for semi-quantitative determination of the phase composition of MMSs. 

---