GB/T 14849.5-2014 English PDF (GBT14849.5-2014)

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GB/T 14849.5-2014: Chemical analysis of silicon metal -- Part 5: Determination of impurity elements content -- Analysis using an X-ray fluorescence method
GB/T 14849.5-2014
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.120.10
H 12
Replacing GB/T 14849.5-2010
Methods for chemical analysis of silicon metal - Part 5:
Determination of impurity contents - X-ray fluorescence
method
ISSUED ON: DECEMBER 05, 2014
IMPLEMENTED ON: MAY 01, 2015
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC；
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Method summary ... 5
4 Instruments and materials ... 6
5 Specimens ... 6
6 Steps ... 7
7 Precision ... 8
8 Quality assurance and control ... 9
9 Test report ... 10
Appendix A (Informative) Measurement condition parameters of two kinds of X-ray
fluorescence spectrometers ... 11
Appendix B (Informative) Possible elemental interference spectral lines ... 12
Methods for chemical analysis of silicon metal - Part 5:
Determination of impurity contents - X-ray fluorescence
method
1 Scope
This Part of GB/T 14849 stipulates the determination method of iron, aluminum,
calcium, manganese, nickel, titanium, copper, phosphorus, magnesium, chromium,
vanadium, cobalt content in industrial silicon.
This Part is applicable to the determination of iron, aluminum, calcium, manganese,
nickel, titanium, copper, phosphorus, magnesium, chromium, vanadium, cobalt in
industrial silicon. The determination range is as shown in Table 1.
2 Normative references
The following documents are essential to the application of this document. For the dated
documents, only the versions with the dates indicated are applicable to this document;
for the undated documents, only the latest version (including all the amendments) is
applicable to this standard.
GB/T 8170 Rules of rounding off for numerical values and expression and judgement
of limiting values
3 Method summary
X-ray fluorescence spectrometry is a qualitative and quantitative analysis, by measuring
the wavelength and intensity of the X-ray spectral lines, which are emitted by the
secondary excitation of chemical elements. The primary X-ray beam, which is
generated by the light pipe, is irradiated on the specimen. Each chemical element in the
specimen is excited, to emit its own secondary characteristic radiation. This secondary
ray reaches the spectroscopic crystal, through the collimator. Only the radiation of a
specific wavelength, that satisfies the diffraction conditions, is strengthened when it
exits the crystal, the radiation of other wavelengths is weakened.
This method is based on Bragg's theorem, namely formula (1):
Where:
n - Diffraction order;
λ - The wavelength of the incident beam (characteristic radiation), in nanometers
(nm);
d - Spacing between crystal planes, in centimeters (cm);
θ - The angle between the incident light and the crystal plane, in degrees (°).
In quantitative analysis, first measure the analytical line intensity of a series of standard
samples; draw a standard curve of intensity versus concentration; perform the necessary
mathematical correction for matrix effects; then calculate the element content,
according to the intensity of the element spectral lines in the analytical specimen.
4 Instruments and materials
4.1 Wavelength dispersive X-ray fluorescence spectrometer, Rh target light tube (refer
to Appendix A, for instrument parameter settings).
4.2 Vibration mill (including tungsten carbide grinding disc).
4.3 Tablet press (including press ring), which can provide 40 t pressure.
4.4 Balance: Sensitivity is 0.1 g.
4.5 Binder: Boric acid or starch (analytical pure).
4.6 Lining agent: Boric acid (industrial pure).
4.7 Triethanolamine (Analytical pure).
5 Specimens
The specimen shall be able to pass through a 0.149 mm standard sieve.
6 Steps
6.1 Sample
Weigh 15.0 g of specimen (5). Add 3.0 g of binder (4.5) and 3 drops of triethanolamine
(4.7). Vibrate and grind on the vibrating mill (4.2), until the specimen can pass through
a 0.074 mm standard sieve. Place a pad lining agent (4.6) under the bottom or wrap the
edge or place it in the pressure ring, which is then put into the tablet press (4.3). The
pressure is 30 t. The holding time is 30 s. After the pressure is released, take out the
sample. Blow off the surface impurities to prepare for testing. The sample thickness
shall not be less than 4 mm.
6.2 Number of measurements
Carry out two measurements independently. Take the average value.
6.3 Instrument calibration
6.3.1 Background correction
One or two backgrounds can optionally be measured, for constant elements.
6.3.2 Instrument drift correction
Correct the instrument drift, by measuring monitored samples.
6.4 Drawing of calibration curve
Select industrial silicon standard samples, to draw a standard curve. Each element shall
have a standard series, which have a sufficient content range and a certain gradient. The
curve is drawn according to the requirements of the instrument. When drawing, it shall
consider the spectral lines of other elements, which may interfere with the spectral lines
of each analyzed element. See Appendix B for common interfering element spectral
lines. Standard sample is prepared, according to step 6.1; the measurement is carried
out, according to 6.5.3.
6.5 Measurement
6.5.1 Preparation
Preheat the X-ray fluorescence spectrometer (4.1), until it is stable. Select working
parameters, according to the model of X-ray fluorescence spectrometer.
6.5.2 Measurement of monitored samples
Set the monitored sample name. Measure the X-ray intensity of the analyzed elements
in the monitored sample.