The invention relates to physical methods of analysis of the chemical composition of a substance, in particular to x-ray method, and can be used in various industries, in the study of minerals, rocks and soils, when determining concentrations of mineral components of an analyte. This method is particularly interesting in connection with the extensive experimental research on the modeling of the processes of mineral formation, where the data is quantitative phase analysis allows to judge about the change of depositional environments help to evaluate the potential of sediment accumulation and preservation of oil and gas.

Known methods of determining the concentration at x-ray phase analysis.

The method of internal standard [1]. The essence of the method consists in determining the concentration of the desired phase x_irelative intensities of analytical lines of this phase and add in the analyzed sample at a constant concentration of the internal phase reference (x_e=const).

The intensity of the reflection phase x₁mixed with internal standard according to the equation:

For the internal standard

For the relationship of the intensities will receive

Equation (3) Osnach the em adding to the sample internal standard in the continuous concentration of the contents of the desired phase x₁in proportion to the ratio of the intensities of J₁/J_e. Revealed here the linear dependency is set on three artificial mixtures of different concentrations.

The method of external standard [2]. Attempts to avoid the need to add to each sample a certain amount of internal standard and the exception process weighing and mixing of sample and standard have led to the development of methods, partially or fully exclude this procedure. The method employs a special sample holder, representing a circular hole in the plexiglass to fill with powder samples, the center of which is pressed a metal rod. Its end surface coincides with the plane of the sample. Upon irradiation of the sample x-ray beam, this rod gives several strong lines and thus is the standard that is external to the sample. Pre-calibrated and receiving graphical dependencies are the same as in the method of internal standard. By eliminating the procedure of weighing and mixing of the substances of the sample and the reference time is reduced to the analysis of each sample.

The disadvantages of the method include the limited choice of materials-standards, necessity is eredeti standard sample holder, the ability to change the reflectivity of the front-end part of the benchmark during the oxidation, dezentrale or mechanical damage. The approximate ratio of the exposed surfaces of the standard and the sample is 1:10. The absolute error in the determination of the concentrations of the individual phases of this method 2-3%.

The basis of the invention is the creation of high-precision and vysokodispersnogo method of determining the concentration of phase-in substances of complex chemical composition.

This task is solved in that in the method of determining the concentration of phase in the substance of complex chemical composition that includes irradiation of the sample analyte monochromatic gamma or x-rays, recording the intensity of the coherently scattered determined by the phase of the primary radiation according to the invention simultaneously or sequentially with the registration of the specified intensity log intensity decoherence scattered the same breakdown of the primary radiation, and then the ratio of these intensities establish concentration-defined phase.

First, a method based on x-ray phase and x-ray fluorescence analysis methods.

Determination of the content of crystalline phases (minerals)that are included in the composition of the studied what brazza, can be carried out by comparative evaluation of the intensities of diffraction peaks in the powder diffraction pattern. The possibility of solving this problem is based on the existence of a dependence of the intensity of the diffraction maximum concentration of each crystalline phase, which is part of the sample. In General, this dependence is not linear, because in addition to the concentration of this phase on the intensity of the diffraction maximum impact absorption coefficient of the sample, depending on the concentration of all phases, i.e. the matrix effect.

In the proposed method, the elimination of matrix effect is achieved by simultaneously or sequentially with the registration of the intensity of the coherently scattered determined by the phase of the primary radiation record the intensity decoherence scattered the same breakdown of the primary radiation and the concentration determined phase set in relation to the above intensities.

Theoretical foundations of the method.

The loss of energy of the primary beam due to absorption in the sample is given by the expression

where J₀- the intensity of the primary beam; J is the intensity of the primary beam after passing through a layer of matter of thickness d; μ - the linear absorption coefficient, cm^-1.

The expression (1) is true for straw is about monochromatic radiation [as μ =ƒ(λ), where λ - wavelength radiation] and homogeneous substance samples.

The basis of all methods for quantitative phase analysis is the following fundamental equation [3]

where J_ithe intensity of some of the selected reflex phase i;

K_iexperimental constant that depends on the energy of the primary beam from the structure of the analyzed phase indices (hkl) and shooting conditions; μ_i ^*mass absorption coefficient phase i.

x_ithe content of phase i in the sample, %; ρ_iis the density of phase i.

The mass absorption coefficient does not depend on the aggregate state of matter.

At the conclusion of the formula (2), it was assumed that diffraction occurs from the surface of a flat sample (shooting on reflection), composed of a homogeneous mixture of n components, and the thickness of the sample is infinite.

In the proposed method shows the possibility of applying new, at first glance, somewhat surprising for quantitative x-ray phase analysis method, similar to the way standard - background, widely used in x-ray fluorescence analysis [4].

The diffraction pattern represents the peaks of the diffraction maxima of the coherently scattered primary radiation of different phases of the substance of the sample placed on CPF is strong line background representing including decoherence scattered by the substance of the sample of the primary radiation.

The essence of this method lies in the fact that the analytical parameter is the ratio of J_i- the intensity of the measured reflection phase i to the intensity of the J_sdecoherence scattered analyzed substance samples of the primary x-ray radiation.

It is easy to see the similarity of expressions (2) to determine the J_ithe intensity of the measured reflection phase i and the expression for determining the intensity i of the line fluorescence spectrum of the analyzed element, for a monochromatic primary beam and an infinitely thick sample:

where k_i- proportionality constant that does not depend on the chemical composition of the samples;

With_andand C_m- contents-defined component and filler elements in the sample (C_a+C_m=1);

m_OAand M_iamass absorption coefficients of the primary and characteristic radiation in the designated component;

m_omand m_eimass absorption coefficients of the primary and characteristic radiation in the filler samples;

ϕ and ψ - angles to the surface of the primary sample and selection of characteristic radiation.

Because when removing the pattern is allow the fall and selection equal, and in the role of the characteristic radiation is coherently scattered primary monochromatic radiation, that is, m_OA=m_iaand m_om=m_ei(3) can be represented as

where K_i=K_i/sinϕ is the coefficient of proportionality that depends on the geometry of the shooting, but do not depend on the chemical composition of the sample.

The obtained expression correlates with the expression (2).

The intensity decoherence scattered analyzed the breakdown of radiation is described by the following expression

where K_s- proportionality constant that does not depend on the chemical composition of the samples;

m_2Aand m_2mmass absorption coefficients of the scattered radiation respectively defined phase and the filler samples.

In this case, (5) can be represented as:

As follows from expressions (3), (4) and (2), the intensity of the defined phases, as well as the intensity of the fluorescence decreases with increasing absorptive capacity of the sample. Moreover, a significant increase of the mass ratio of filler samples the intensity may decrease by several times, which can lead to a relative error of determining the content of each component in the bore is only hundred percent! Similarly behaves the dependence of the intensity decoherence scattered radiation from the absorbing ability of the sample, what follows from expressions (5) and (6). Thus, the ratio of these intensities is significantly less dependent on the absorptive capacity of the sample, therefore, should be used as an analytical parameter.

The invention is illustrated by the figures, where figure 1 shows the dependence of the intensities of the analyzed phase components J_iand decoherence scattered breakdown of the primary radiation J_sfrom the mass absorption coefficient of the filler samples when measuring samples with the same content of ZrO₂(1%), but different fillers, the mass absorption coefficient for the different samples varied in the range from 0.5 to 60 cm²/g (the intensities are normalized relative to the I₀).

As can be seen from the figure, at a constant concentration of the analyzed element, the dependence of the intensity of the analyzed phase components J_ifrom the values of the mass absorption coefficient of the filler samples persists, which leads to a considerable increase in the error analysis when a significant change of the material composition of the samples.

But the figure also shows that the intensity of the reflex phase and analyzed decoherence scattered radiation differ slightly throughout the given interval changes of absorption the overall ability of the filler. This confirms that the analytical parameter η=J_i/J_sslightly depends on the matrix of the sample and can be used as an analytical parameter.

Figure 2 shows the dependence of the analytical parameter η from the mass absorption coefficient of the filler samples at fixed other parameters. As can be seen from the figure, the dependence of the analytical parameter η from the mass absorption coefficient of filling of the sample is substantially less than the dependencies of the intensities of J_iand J_s.

Figure 3 presents the measurement scheme of the proposed method: 1 - source of study; 2 - sample; 3 - radiation detector; 4 - radiation detector.

Technical implementation of the method due to its simplicity, easy to implement on a national commercial diffractometers type DRONE. When a parallel dimension simultaneously recorded intensity of the measured phase and using an additional detector of the scattered radiation. Sequential measurement registers the intensity of the measured phase, then the detector is moved at a small angle (close to the measured phase), and the angular position of the sample remains unchanged and is logged intensity decoherence scattered radiation. And the concentration of the measured phase is determined by the relative intensities above what about the calibration curve, built on standards with guaranteed concentrations determined phase.

The proposed method can significantly reduce the influence of the chemical composition of the samples for measurement error, to reduce the systematic component of the error on the order and below the random component. Based on this method of analysis techniques tungsten and molybdenum products Asctrm on metrological characteristics meet the requirements of state Standards and have a high expressnet, accuracy and ease of implementation.

Sources of information taken into account:

1. Gerasimov NR. and other Guidance on the x-ray study of minerals. Leningrad: Nedra, 1975, p.100.

2. Gerasimov NR. and other Guidance on the x-ray study of minerals. Leningrad: Nedra, 1975. p.101.

3. Gerasimov NR. and other Guidance on the x-ray study of minerals. Leningrad: Nedra, 1975, p.100.

4. Mamikonyan SV Apparatus and methods fluorescent x-ray radiometric analysis. M: Atomizdat, 1976, p.29.

The method of determining the concentration of phase in the substance of complex chemical composition that includes irradiation of the sample analyte monochromatic gamma or x-rays, recording the intensity of coherently scattered determined by the phase of the primary radiation, otlichuy is the, simultaneously or sequentially with the registration of the specified intensity log intensity decoherence scattered the same breakdown of the primary radiation, and then the ratio of these intensities establish concentration-defined phase.