JP2004226231A - Method of manufacturing glass bead for fluorescent x-ray analysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the uniformity of glass beads to conduct precise fluorescent X-ray analysis. <P>SOLUTION: This method includes a temperature elevation process 1 for rising a temperature of glass bead composition powder containing sample powder to a prescribed set temperature in a crucible, a dissolving process 2 for dissolving the glass bead composition powder in the set temperature, a stirring process 3 for stirring the dissolved material of the glass bead composition powder by oscillating the crucible, a temperature lowering stirring process 4 for conducting the stirring while lowering the temperature of the dissolved material, and a cooling process 5 for cooling the dissolved material after the temperature lowering stirring process 4 to solidify it. A temperature-down target value is preferably set to a melting point of a glass fusing agent that is a main component of the glass bead, or a temperature near thereto, in the temperature lowering stirring process 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a glass bead which is a sample for X-ray fluorescence analysis.
[0002]
[Prior art]
X-ray fluorescence analysis is utilized in a wide range of fields, such as ceramics and metals, because nondestructive, simple and quick qualitative and quantitative analysis of elements in a sample can be performed. When performing this fluorescent X-ray analysis, there are various methods of pretreatment of the sample. In the field of ceramics, a method of producing a glass bead containing a sample powder is generally used. This glass bead eliminates non-uniformity, grain size effects, etc., which are problems specific to ceramics, and is useful for improving the accuracy of analysis.
[0003]
The above-mentioned glass bead is manufactured by a process as shown in FIG. FIG. 5A is a block diagram of the process, and FIG. 5B is a diagram showing a temperature change of the glass bead material in each process. In manufacturing a glass bead, first, a weighed sample powder and a glass flux are put into a deep-dish platinum-made crucible, and a slight release agent is added thereto. Thereafter, the crucible is set in the heating furnace, and the temperature is raised to a predetermined set temperature (1200 ° C. in the illustrated example) (heating step 11). Then, the glass bead composition powder including the sample powder is dissolved while maintaining the set temperature (dissolution step 12).
[0004]
In the next step, the melting material of the glass bead composition powder is stirred by rocking such as tilting and rotating the crucible (stirring step 13). Thereafter, the crucible is taken out of the heating furnace and cooled to solidify the molten material (cooling step 13). Thus, a glass bead containing the sample powder is obtained. Normally, the bottom surface of the glass bead (the surface that was in contact with the inner bottom surface of the crucible) serves as an analysis surface during X-ray fluorescence analysis.
[0005]
In a conventional method of manufacturing a glass bead, in a cooling step, the surface of the glass bead is subjected to pressure molding with a pressure surface such as a noble metal alloy (see Patent Document 1). According to this method, the surface undulation and swelling of the analysis surface of the glass bead are eliminated, and the flatness is improved, so that the dispersion of the analysis value is reduced.
[0006]
[Patent Document 1]
JP-A-10-170414 [0007]
[Problems to be solved by the invention]
By the way, in the field of ceramics, for example, fluorescent X-ray analysis using a glass bead is frequently used for analyzing the molar ratio of barium titanate. In the molar ratio analysis of barium titanate, conventionally, a molar ratio accuracy of about 1 to 2/1000 has been accepted, but recently, an order of magnitude higher than 1/10000 is required. I have.
[0008]
In order to achieve such a high required accuracy, it is not sufficient to simply increase the flatness of the analysis surface of the glass bead as in the invention described in Patent Document 1, and the concentration distribution of the sample inside the glass bead is insufficient. It is necessary to increase the homogeneity by making the temperature uniform.
[0009]
Therefore, an object of the present invention is to improve the homogeneity of a glass bead so that X-ray fluorescence analysis using a glass bead can be performed with higher accuracy.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the inventor of the present invention has conducted various experiments and studies and found that the solidification process of the glass bead is important for improving the homogeneity of the glass bead. The findings obtained by the inventors are as follows.
[0011]
Usually, when the heating and the stirring are completed, the crucible containing the melted material is placed on a cooling stand provided with an air-cooling fan and cooled to room temperature. At this time, it takes about 1 minute until the melted glass flux solidifies. Because the specific heats of the crucible and the glass flux are greatly different, a temperature gradient is created between the crucible and the glass flux within the time until the material solidifies, and accordingly, inside the glass bead, In addition to the concentration gradient, a phenomenon occurs in which the chemical composition changes due to the Soret effect. In particular, in the surface portion of the glass bead, which is in contact with the inner bottom surface of the crucible and becomes an analysis surface later, concentration segregation becomes remarkable. In the fluorescent X-ray analysis using a glass bead, since the analysis depth is several μm to several hundred μm, the X-ray intensity greatly fluctuates due to the concentration segregation described above.
[0012]
The present invention has been made based on the above findings, and includes a heating step of heating a glass bead composition powder containing a sample powder, which has been put into a crucible, to a predetermined set temperature, and a glass bead at the set temperature. A dissolving step of dissolving the composition powder, a stirring step of stirring the melting material of the glass bead composition powder by shaking the crucible, and a temperature lowering stirring step of performing the stirring while lowering the temperature of the melting material, A cooling step of cooling and solidifying the melted material after the temperature lowering and stirring step comprises a method of manufacturing a glass bead for X-ray fluorescence analysis.
[0013]
The rocking in the above configuration means a movement applied to the crucible from the outside to agitate the molten material in the crucible, such as tilting of the crucible, rotation around the vertical axis, shaking, turning, or a combination thereof. . Further, the cooling in the cooling and stirring step may be a cooling by natural heat radiation, a cooling by controlling the ambient temperature, or a continuous cooling or a stepwise cooling. The temperature may be lowered specifically, and the specific method of the temperature drop is not particularly limited.
[0014]
In the manufacturing method having the above configuration, the melted material stirred in the stirring step is stirred while the temperature is lowered in the next temperature lowering stirring step. Therefore, the molten material is agitated until it reaches a solidification temperature or a temperature close thereto. By this stirring, the temperature gradient inside the melted material is largely eliminated, and accordingly, the concentration gradient is also largely eliminated. Since the cooling step is continued in the temperature lowering and stirring step, the molten material in which the concentration gradient has been largely eliminated solidifies as it is, and becomes a homogeneous glass bead with almost no concentration segregation.
[0015]
The temperature lowering and stirring step may be appropriately performed within a period during which stirring is possible, that is, within a period of time until the viscosity of the dissolved material increases and stirring becomes impossible. The target value is set, and during the cooling process until reaching the cooling target value, if the stirring by rocking the crucible is performed following the stirring process, the stirring is performed without interruption. In addition, the effect of the stirring becomes more remarkable, and a treatment suitable for the dissolution and solidification of the molten material is performed, so that a glass bead that is more uniform and has no variation in quality among products can be obtained.
[0016]
The target temperature for cooling in the temperature lowering and stirring step is desirably set within a temperature range including a temperature above and below the melting point of the glass flux, which is a main component of the glass bead composition powder. The temperature is desirably set within a temperature range from 150 ° C. higher than the melting point of the flux to 30 ° C. lower than the melting point of the glass flux.
[0017]
If the target temperature is set to a value exceeding 150 ° C. higher than the melting point of the glass flux, the temperature of the molten material drops to the target temperature, and after the temperature lowering and stirring process is completed, the molten material solidifies. Since it takes time to complete the process, concentration segregation occurs within that time, which may reduce the homogeneity of the glass bead. On the other hand, if the target temperature is set to a value lower than the temperature 30 ° C. lower than the melting point of the glass flux, solidification of the molten material starts before the temperature of the molten material decreases to the target temperature, and stirring Becomes impossible.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a view showing the steps of a method for manufacturing a glass bead for X-ray fluorescence analysis according to one embodiment of the present invention. FIG. 1A is a block diagram of the steps, and FIG. FIG. 3 is a diagram illustrating a temperature change of a glass bead material. In this diagram, the horizontal axis represents time (seconds), and the vertical axis represents temperature (° C.). As shown in FIG. 1A, the production method of the present invention includes a temperature raising step 1, a melting step 2, a stirring step 3, a temperature lowering stirring step 4, and a cooling step 5.
[0019]
In the method for producing a glass bead of the present invention, first, a deep dish-shaped crucible made of platinum is prepared, and a sample powder, a glass flux such as lithium tetraborate or sodium tetraborate, and a halogenated halide are prepared. A release agent such as an alkali compound is charged, and these are mixed. In this case, the glass flux is precisely weighed with respect to the sample powder so as to have a certain dilution ratio. Thus, the crucible into which the glass bead composition powder including the sample powder is charged is set inside an electric furnace type or high frequency type heating furnace.
[0020]
Temperature raising step 1: In this step 1, the crucible and the glass bead composition powder inside the crucible are heated by heating in a heating furnace, and the temperature is raised to a set temperature. The set temperature is set in a high temperature range from 1000 ° C. to 1300 ° C., which is considerably higher than the melting point of the glass. In the embodiment shown in FIG. 1, the set temperature is 1200 ° C.
[0021]
Melting Step 2: When the temperature of the glass bead composition powder reaches the set temperature, the melting step 2 is started. In the melting step 2, the heating is continued to melt the glass bead composition powder so that the temperature of the glass bead composition powder is kept substantially at the set temperature. Since the set temperature is much higher than the melting point of the glass, the glass bead composition powder dissolves in a liquid state.
[0022]
Stirring step 3: In this step 3, the crucible is shaken to stir the glass bead composition powder dissolved in the liquid (hereinafter, referred to as dissolved material). Here, the rocking motion of the crucible means a motion applied to the crucible from outside to stir the molten material in the crucible, such as a tilt of the crucible, a rotation around a vertical axis, or a motion of a combination thereof. Therefore, the above-mentioned swing may include swinging left and right, front and rear, and turning. During the stirring step 3, the heating is continued so that the temperature of the melted material is kept substantially at the set temperature.
[0023]
Temperature lowering agitation step 4: This is a step characteristic of the production method of the present invention, and is a step of performing agitation by rocking the crucible while lowering the temperature of the molten material. The rocking motion of the crucible for stirring in this step 4 may be the same as the rocking motion of the crucible in the stirring step 3 described above, but the type of motion and the cycle of the motion may be changed. Further, the temperature decrease in this step 4 may be a temperature decrease by controlling the ambient temperature, a temperature decrease by natural heat radiation inside the heating furnace in which heating is stopped or outside the heating furnace, or a continuous temperature decrease. Gradual cooling may be used. In short, in step 4, the temperature may be lowered over time, and a specific method of the temperature reduction is not particularly limited.
[0024]
In the temperature lowering / agitating step 4, a temperature lowering target value is set as shown in FIG. This temperature drop target value may be set to a temperature higher than the temperature at which the viscosity of the molten material becomes high and stirring becomes impossible, but in fact, the glass flux which is the main component of the glass bead composition powder is used. Is set within the temperature range including the temperature above and below the melting point of In the case shown in the figure, 950 ° C., which is higher than the melting point of 875 ° C., is set as the temperature lowering target value in response to the glass flux of lithium tetraborate having a melting point of 875 ° C. Then, the cooling is continued until the temperature of the molten material reaches the cooling target value. Further, the stirring by the rocking of the crucible is performed continuously to the stirring step 3 described above. Stirring is continued while cooling is continued.
[0025]
In addition, it is desirable that the target temperature is specifically set within a temperature range from 150 ° C. higher than the melting point of the glass flux to 30 ° C. lower than the melting point of the glass flux. This means that if the target temperature is set to a value exceeding a temperature 150 ° C. higher than the melting point of the glass flux, it takes a considerable time for the molten material to solidify after the completion of the temperature lowering and stirring step, This is because concentration segregation occurs within time. On the other hand, if the target temperature is set to a value lower than the temperature 30 ° C. lower than the melting point of the glass flux, solidification of the molten material starts before the temperature of the molten material decreases to the target temperature, and stirring Becomes impossible.
[0026]
Cooling step 5: In this step 5, the crucible containing the molten material is taken out of the heating furnace, placed on a cooling stand equipped with an air-cooling fan, and cooled to room temperature. This causes the molten material to solidify into a glass bead.
[0027]
In the manufacturing method of the present invention including each of the above steps, in the temperature lowering and stirring step following the stirring step, the dissolved material is stirred while the temperature is lowered. Therefore, the molten material is agitated until it reaches a solidification temperature or a temperature close thereto. By this stirring, the temperature gradient inside the melted material is largely eliminated even though the temperature of the melted material is lowered, and accordingly, the concentration gradient is also largely eliminated. Then, the molten material in which the concentration gradient has been largely eliminated is solidified as it is in the next cooling step, so that a homogeneous glass bead having almost no concentration segregation can be obtained.
[0028]
【Example】
As an example of the present invention, a glass bead containing barium titanate was manufactured as a sample for Ba / Ti molar ratio analysis of barium titanate according to the manufacturing method shown in FIG. Lithium tetraborate was used as the glass flux. The set temperature in the temperature raising step, the melting step, and the like is 1200 ° C. The time required for each step is as shown in FIG.
[0029]
FIG. 2 shows the conditions of the embodiment and the conventional example, and the results (molar ratio of Ba / Ti of barium titanate). As shown in FIG. 2A, in the embodiment of the present invention, the temperature lowering target value in the temperature lowering and stirring step is set to four values, high and low. In Example a of the present invention, the target temperature is 1000 ° C., in Example b, the target temperature is 950 ° C., in Example c, the target temperature is 900 ° C., and in Example d, the target temperature is 900 ° C. 850 ° C.
[0030]
In each of Examples a to d, there are a case where the cooling in the cooling step is a rapid cooling and a case where the cooling is a slow cooling. The rapid cooling here is forced cooling by an air cooling fan. Slow cooling is forced cooling by an air cooling fan after keeping the temperature for 30 seconds. In each of Examples a to d, samples of glass beads obtained by performing rapid cooling are a1, b1, c1, and d1, and samples obtained by performing slow cooling are a2, b2, c2, and d2. .
[0031]
In the conventional example, a glass bead containing barium titanate was manufactured by the manufacturing method shown in FIG. The glass flux and the set temperatures in the temperature raising step and the like are the same as in the embodiment of the present invention. Also in this conventional example, there are a case where the cooling in the cooling step is a rapid cooling and a case where the cooling is a slow cooling. In the conventional example, a glass bead sample obtained by performing rapid cooling is x1, and a sample obtained by performing slow cooling is x2.
[0032]
In addition, six glass beads were produced for each of these samples, and the average of the measured values obtained for the six glass beads was defined as the measured value of the sample.
[0033]
Of the 10 types of glass beads obtained as described above, the measured values of the glass beads x1, a1, b1, c1, and d1 obtained by quenching were set to “1”, and the temperature was gradually cooled. FIG. 2B shows the rate of change of the measured values of the glass beads x2, a2, b2, c2, and d2 obtained by performing the above.
[0034]
Referring to FIG. 2B, the rate of change of the measured value between the case where the cooling is performed rapidly and the case where the cooling is performed gradually is smaller in the examples a to d of the present invention than in the conventional examples x1 and x2. I understand. In addition, it can be seen that, between Examples a to d of the present invention, the change rate of rapid cooling / slow cooling is smaller as the target temperature drop is closer to the melting point of the glass flux. In short, in the embodiment of the present invention, if the target temperature is set to a value close to the melting point of the glass flux, it can be understood that cooling in the cooling step may be rapid cooling or slow cooling.
[0035]
FIG. 3 shows the calculated coefficient of variation of the measured value for each of the ten types of glass beads obtained as described above. From FIG. 3, it can be seen that the coefficient of variation is smaller in the example in which the target temperature decrease value is closer to the melting point of the glass flux. In short, in the example of the present invention, it can be seen that a measured value having a smaller coefficient of variation is obtained for a glass bead having a lower temperature target value closer to the melting point of the glass flux. The coefficient of variation CV is calculated by the following equation (1):
CV (%) = (σ _n-1 / average value) × 100 (1)
Was calculated by In the equation (1), σ _n-1 is a standard deviation.
[0036]
FIG. 4 mainly shows the results of an experiment performed to show the homogeneity of the glass beads obtained by the production method of the present invention. As shown in FIG. 4A, in Example c of the present invention, a glass bead was manufactured in accordance with the process shown in FIG. In the conventional example, a glass bead was manufactured according to the process shown in FIG.
[0037]
In each of the embodiment c and the conventional example, there are a case where the cooling in the cooling step is rapid cooling and a case where the cooling is slow cooling. The conditions for the rapid cooling and the slow cooling here are the same as those described with reference to FIG. Further, for each of the rapid cooling and the slow cooling, there are a case where a new crucible is used and a case where an old crucible is used. The surface undulation of the new crucible is about 40 μm, and the surface undulation of the old crucible is about 400 μm.
[0038]
In the conventional example, a glass bead sample obtained by slow cooling using a new crucible was xn1, a glass bead sample obtained by rapid cooling was xn2, and a glass bead was obtained by slow cooling using an old crucible. The glass bead is xo1, and the one obtained by quenching is xo2. In Example c of the present invention, a sample of a glass bead obtained by performing slow cooling using a new crucible was cn1, and a sample obtained by performing rapid cooling was cn2, and an old crucible was used. The glass bead obtained by cooling is co1, and the one obtained by quenching is co2.
[0039]
The analysis surface was polished for each of the eight types of glass beads obtained as described above (conventional four types xn1, xn2, xo1, and xo2, and fourth example of the present invention, cn1, cn2, co1, and co2). The analysis was performed without performing the above, and after that, the analysis surface was subjected to a predetermined polishing, and then the analysis was performed. The polishing was performed over several stages while changing the size of the abrasive particles, and then ultrasonic cleaning was performed with ethanol.
[0040]
The measured values of the above eight types of glass beads, in which the measured value obtained before polishing was “1”, and the rate of change of the measured value obtained from the glass bead after polishing was expressed. This is FIG. 4B.
[0041]
FIG. 4B shows that the rate of change of the measured value after polishing is smaller in Example c of the present invention than in the conventional example. Further, between the embodiments of the present invention, the rate of change of the measured value after polishing is uniformly smaller than in the conventional example, regardless of the cooling method during the cooling step or the old or new crucible used, It can be seen that the surface undulation of the crucible has little effect. From this, it can be seen that in the glass bead obtained by the manufacturing method of the present invention, there is no large difference between the measured values before and after polishing, and the concentration is accordingly uniform.
[0042]
【The invention's effect】
As described above, according to the present invention, the molten material to be a glass bead is stirred until the solidification temperature or a temperature close to the solidification temperature is reached, and this stirring significantly eliminates the concentration gradient inside the molten material. . And since it solidifies in that state, a homogeneous glass bead with almost no concentration segregation can be obtained.
[Brief description of the drawings]
FIG. 1 is a view showing steps of a method for manufacturing a glass bead for X-ray fluorescence analysis according to one embodiment of the present invention, wherein (A) is a block diagram of the steps, and (B) is a glass bead material in each step. FIG. 4 is a diagram showing a temperature change of the radiator.
FIGS. 2A and 2B are diagrams showing the results of the implementation of the embodiment of the present invention and the conventional example. FIG. 2A is a table showing the conditions of the embodiment, and FIG. FIG. 4 is a diagram showing the rate of change of the measured value of the glass bead obtained in the case of rapid cooling and the case of slow cooling.
FIG. 3 is a diagram showing a coefficient of variation of measured values of glass beads obtained in an example of the present invention and a conventional example.
4A and 4B are diagrams showing the results of the implementation of the embodiment of the present invention and the conventional example. FIG. 4A is a table showing the conditions of implementation, and FIG. 4B is a diagram showing the embodiment of the present invention and the conventional example. FIG. 4 is a graph showing the rate of change of measured values of the glass bead obtained before and after polishing.
5A and 5B are diagrams showing steps of a conventional method of manufacturing a glass bead for X-ray fluorescence analysis, in which FIG. 5A is a block diagram of the steps, and FIG. 5B is a line showing a temperature change of the glass bead material in each step. FIG.
[Explanation of symbols]
Reference Signs List 1 temperature rising step 2 melting step 3 stirring step 4 temperature lowering stirring step 5 cooling step 5

Claims (4)

Heating the glass bead composition powder containing the sample powder into the crucible to a predetermined set temperature, a melting step of dissolving the glass bead composition powder at the set temperature, and shaking the crucible. A stirring step of stirring the melted material of the glass bead composition powder, a cooling stir step of performing the stirring while lowering the temperature of the melted material, and a cooling step of cooling and solidifying the melted material after the cooling stir step. A method for producing a glass bead for X-ray fluorescence analysis, comprising: 2. The temperature lowering and stirring step, wherein a temperature lowering target value is set, and during the temperature lowering process until the temperature lowering target value is reached, stirring by rocking a crucible is performed subsequent to the stirring step. 3. Of producing a glass bead for X-ray fluorescence analysis. The manufacturing of the glass bead for X-ray fluorescence analysis according to claim 2, wherein the target temperature is set within a temperature range including a temperature above and below a melting point of a glass flux as a main component of the glass bead composition powder. Method. The X-ray fluorescence analysis according to claim 3, wherein the temperature range in which the target temperature is set is a temperature range from 150 ° C higher than the melting point of the glass flux to 30 ° C lower than the melting point of the glass flux. Production method of glass beads for automobiles.

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