5:15 PM - 6:45 PM
[SCG45-P12] A study of the simplified quantitative analysis of smectite using X-ray diffraction and decreasing orientation by improvement of specimen holder.
Keywords:X-ray diffraction, smectite, quantitative analysis, orientation
1. Introduction
Smectite is the most common swelling clay. The content of smectite is often discussed because its swellability causes collapsing of mountain body in civil engineering works. There are some standards of possibility of collapsing in several laboratory test. In X-ray diffraction analysis (XRD), the reference value in smectite content is about 20 to 30% (ex. Yoshikawa et al., 1988).
2. Purpose
In this presentation, the high degree of orientation and the mass absorption coefficient (MAC) are focused. The high degree of orientation causes the problem of strengthen of the specific diffraction lines.
MAC affects the relationship between content of test component and intensity of diffraction line, and it becomes non-linear except the case of the MAC of test component and matrix are equal (Alexander and Klug, 1948).
To solve these problems, the specimen holder is improved uniquely for decreasing orientation, and the simplified quantitative analysis are devised which approximates linear between smectite content and intensity of diffraction line assuming that include some error.
3. Method
3.1. Improvement of specimen holder
Small bumps were made by epoxy resin on the bottom of Rigaku 0.5 mm glass holder for make the crystal orientation random forcibly. The effect of this improved holder was evaluated comparing with measurement of the same specimens using the Rigaku aluminum holder.
3.2. Simplified quantitative analysis
Evaluation target of smectite content is below 30 wt%. Specimens were weighed by electronic balance becoming for smectite (JCSS-3101) 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% in the standard materials of rhyolite(JR-1), basalt (JB-3) and gabbro (JGb-1) each, and those were stirred 20 minutes by agate mortar. The integrated intensity of obtained 001 diffraction lines of smectite were normalized by that of standard quartz which was measured in same condition. The simplified quantitative coefficient (SQC) was obtained from the slope of approximate straight line which the relationship between the normalized intensity and content of smectite.
3.3. Measuring conditions
The specimens were measured by Rigaku MiniFlex600. The measuring conditions are as follows; voltage: 40 kV, tube current: 15 mA, divergence slit: 1.25°, scan speed: 2°/min, scan range (2θ): standard quartz 26.0° to 27.0°, smectite 3.5°to 10.0°, fluorite 46.0° to 47.0°.
4. Results
4.1. Evaluation of improvement of specimen holder
JR-1 which was mixed smectite and the specimen using for making calibration curve of IRM were measured by using the improved glass holder and the normal aluminum holder. In the measurement using aluminum holder, as smectite content increased, the results moved away from linear relation and made nearly quadaric curve in both specimens. However, in the case of the improved holder, the relationship of normalized intensity and smectite content was almost linear (Fig. 1).
4.2. Calculation of SQC and evaluation of quantitative value
Compared with weighing value of smectite and normalized intensity in three standards which were mixed smectite in each amount, as MAC increases from rhyolite to gabbro, intensities of smectite decreased. For covering larger area of MAC, data of rhyolite and gabbro were used for make approximation line, and obtained the value of 6.57 x 10-3 as SQC from slope of the line (Fig. 2). In recalculation of smectite content using obtained SQC, quantitative values in almost all of specimens were in ±3 wt% from weighing value.
To verify the validity of quantitative values, three natural specimen and the glass powder specimens which were mixed smectite becoming 10 wt% and 30wt% were measured respectively. About natural specimens, IRM was conducted and were compared the values. In all specimens, the quantitative values were in ±3 wt% from weighing values or quantitative values by IRM. However, SQC is needed to obtain for the diffractometer each by each, and regular check of SQC is also needed even same diffractometer.
Smectite is the most common swelling clay. The content of smectite is often discussed because its swellability causes collapsing of mountain body in civil engineering works. There are some standards of possibility of collapsing in several laboratory test. In X-ray diffraction analysis (XRD), the reference value in smectite content is about 20 to 30% (ex. Yoshikawa et al., 1988).
2. Purpose
In this presentation, the high degree of orientation and the mass absorption coefficient (MAC) are focused. The high degree of orientation causes the problem of strengthen of the specific diffraction lines.
MAC affects the relationship between content of test component and intensity of diffraction line, and it becomes non-linear except the case of the MAC of test component and matrix are equal (Alexander and Klug, 1948).
To solve these problems, the specimen holder is improved uniquely for decreasing orientation, and the simplified quantitative analysis are devised which approximates linear between smectite content and intensity of diffraction line assuming that include some error.
3. Method
3.1. Improvement of specimen holder
Small bumps were made by epoxy resin on the bottom of Rigaku 0.5 mm glass holder for make the crystal orientation random forcibly. The effect of this improved holder was evaluated comparing with measurement of the same specimens using the Rigaku aluminum holder.
3.2. Simplified quantitative analysis
Evaluation target of smectite content is below 30 wt%. Specimens were weighed by electronic balance becoming for smectite (JCSS-3101) 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% in the standard materials of rhyolite(JR-1), basalt (JB-3) and gabbro (JGb-1) each, and those were stirred 20 minutes by agate mortar. The integrated intensity of obtained 001 diffraction lines of smectite were normalized by that of standard quartz which was measured in same condition. The simplified quantitative coefficient (SQC) was obtained from the slope of approximate straight line which the relationship between the normalized intensity and content of smectite.
3.3. Measuring conditions
The specimens were measured by Rigaku MiniFlex600. The measuring conditions are as follows; voltage: 40 kV, tube current: 15 mA, divergence slit: 1.25°, scan speed: 2°/min, scan range (2θ): standard quartz 26.0° to 27.0°, smectite 3.5°to 10.0°, fluorite 46.0° to 47.0°.
4. Results
4.1. Evaluation of improvement of specimen holder
JR-1 which was mixed smectite and the specimen using for making calibration curve of IRM were measured by using the improved glass holder and the normal aluminum holder. In the measurement using aluminum holder, as smectite content increased, the results moved away from linear relation and made nearly quadaric curve in both specimens. However, in the case of the improved holder, the relationship of normalized intensity and smectite content was almost linear (Fig. 1).
4.2. Calculation of SQC and evaluation of quantitative value
Compared with weighing value of smectite and normalized intensity in three standards which were mixed smectite in each amount, as MAC increases from rhyolite to gabbro, intensities of smectite decreased. For covering larger area of MAC, data of rhyolite and gabbro were used for make approximation line, and obtained the value of 6.57 x 10-3 as SQC from slope of the line (Fig. 2). In recalculation of smectite content using obtained SQC, quantitative values in almost all of specimens were in ±3 wt% from weighing value.
To verify the validity of quantitative values, three natural specimen and the glass powder specimens which were mixed smectite becoming 10 wt% and 30wt% were measured respectively. About natural specimens, IRM was conducted and were compared the values. In all specimens, the quantitative values were in ±3 wt% from weighing values or quantitative values by IRM. However, SQC is needed to obtain for the diffractometer each by each, and regular check of SQC is also needed even same diffractometer.