JP2891524B2 - Graphite crucible for oxygen determination - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a graphite crucible for oxygen determination. More specifically, the present invention relates to a graphite crucible for oxygen quantification that can improve the accuracy and precision of quantitative analysis of oxygen elements contained in a sample.

(Prior Art) Conventionally, when quantifying an oxygen element contained in steel, non-ferrous metal, ceramics, superconducting material, etc., generally, these analytical samples are used, for example, as shown in FIG. It is measured in a graphite crucible (a), heated to a high temperature in a stream of an inert gas such as helium, and oxygen contained in the sample is reacted with carbon in the graphite crucible (a) to convert oxygen into carbon monoxide (CO). ), And the method of detecting this CO and quantifying the oxygen content of the sample has been widely adopted.

(Problems to be Solved by the Invention) However, in this analysis method, there is a problem that the structure of the graphite crucible and its catalytic activity greatly affect the accuracy and accuracy of the oxygen analysis value.

That is, since the conventional graphite crucible (a) shown in FIG. 3 has a cylindrical shape, the surface area of the inner wall portion (a) of the crucible is small, and therefore, the contact area between the molten sample and the graphite is small. That is, it causes a decrease in reproducibility of the reaction for converting oxygen in the sample into CO. In addition, when this graphite crucible (A) is used, the molten sample often creepes on the inner wall (A) of the crucible (A) during the analysis, and there is a problem that the surrounding area is contaminated. there were.

On the other hand, since the coexisting elements contained in the sample are various, the form of oxygen element bonded to these elements is also complicated and diverse, and it is considered that the surface area inside the graphite crucible (a) is constant. If so, the accuracy and accuracy of the quantitative analysis of the oxygen element depends on the quality of the reducing activity of the graphite crucible (a) for the oxygen element.

The present invention has been made in view of the above circumstances, can eliminate the disadvantages of the conventional graphite crucible, can improve the accuracy and precision of the quantitative analysis of the oxygen element contained in the sample, It is an object of the present invention to provide an improved graphite crucible for oxygen determination.

(Means for Solving the Problems) The present invention solves the above-mentioned problems by providing a bottom portion with a plurality of step portions together with a creep preventing groove at the center of the inner wall, and impregnating with a metal element. Provided is a graphite crucible for oxygen quantification, characterized in that:

For example, as shown in FIGS. 1 and 2, in the graphite crucible for oxygen determination (1) of the present invention, for example, two step portions (2) are provided at the bottom corresponding to the sample melting portion.
Forming (3), reducing the volume thereof, increasing the contact area between the sample and the graphite of the crucible (1), improving the recovery rate of oxygen in the sample, and obtaining a stable recovery rate. I do. There is no particular limitation on the shape, number and the like of the step portions, and they can be appropriately determined according to the strength, electric conductivity and the like of the crucible.

In addition, a rise preventing groove (4) is provided at the center of the inner wall to prevent the molten sample from rising.

Further, the crucible inner wall is impregnated with a metal element such as iron, cobalt, nickel, palladium, and platinum. When such a metal element is heated to a high temperature of, for example, 900 ° C. or more, the crucible (1) cuts the carbon bond of the graphite constituting the graphite crucible (1) to generate a carbon element, thereby reducing the oxygen element in the sample. Reducing activity is remarkably improved. Thereby, the generation rate of CO can be increased. There is no particular limitation on the method of impregnating the metal element, and an appropriate method such as a chemical or electrochemical method can be adopted.

(Operation) The graphite crucible for oxygen quantification of the present invention has a plurality of steps at the bottom together with a groove for preventing swelling at the center of the inner wall, and comprises iron, cobalt, nickel, palladium,
Since metal elements such as platinum are impregnated, oxygen quantitative errors due to the amount, type, etc. of the sample can be significantly reduced. The precision and accuracy of the quantitative analysis of the oxygen element contained in the sample can be improved.

(Example) Hereinafter, an example is shown and the graphite crucible for oxygen determination of this invention is demonstrated in more detail.

Example 1 A high-purity graphite material was subjected to lathe processing to form a graphite crucible having a structure and a shape as shown in FIGS. These graphite crucibles were impregnated with nickel by an electrochemical method as shown below.

First, 30 to 50 graphite crucibles processed as described above were placed in a 500 ml polyethylene resin beaker, and washed three times with 300 ml of deionized water (0.3 μs / cm).

Then, after filling with deionized water and leaving for 12 hours,
The deionized water was removed by decantation and air dried. Thereafter, the nickel electrode was used as an anode and the graphite crucible was used as a cathode in a dilute hydrochloric acid electrolyte at 0.5 to 0.6 V for several minutes to impregnate the graphite crucible with nickel. The graphite crucible impregnated with nickel was put into a reduction tube, and reduced in a mixed gas stream of helium + hydrogen (10%). The nickel content of the graphite crucible thus prepared was 4.5-6.5%.

Next, test values were measured eight times from the graphite crucible. The average value of the eight measurements was 0.00071%, so the test value was small and extremely stable.

Example 2 Using the nickel-impregnated graphite crucible produced in Example 1,
Elemental oxygen was quantified in iron standard samples for oxygen quantitative analysis.

 Table 1 shows the results.

As is clear from Table 1, the analysis accuracy was improved and the analysis result was also good.

Of course, the present invention is not limited by the following examples. It goes without saying that various aspects are possible for details of the material of the graphite crucible, the number and shape of the steps of the crucible, the type of the metal element to be impregnated in the crucible, the method of impregnation thereof, and the like.

(Effects of the Invention) As described in detail above, the present invention provides a graphite crucible for oxygen quantification that can improve the precision and accuracy of quantitative analysis of an oxygen element contained in a sample.

[Brief description of the drawings]

1 and 2 are a cross-sectional view and a plan view, respectively, illustrating a graphite crucible for oxygen determination according to the present invention. FIG. 3 is a sectional view showing a conventional graphite crucible. 1 ... graphite crucible, 2, 3 ... stepped portion 4 ... groove for preventing creeping up

Claims (2)

(57) [Claims] 1. A crawling prevention groove at the center of an inner wall,
A graphite crucible for oxygen determination characterized by having a plurality of steps at the bottom and being impregnated with a metal element. 2. The graphite crucible for oxygen determination according to claim 1, wherein the graphite crucible is impregnated with iron, cobalt, nickel, palladium and / or platinum.