The method of testing of ultra-high purity graphite trace impurity
Technical field
The present invention relates to carbon element industry technology field, the method of testing that more specifically relates to the trace impurity content in a kind of ultra-high purity graphite, can be widely used in diamond synthesis and be higher than 4 9(99.99% with purifying dag and purity) mensuration of the impurity content of above graphite, especially in the sample analysis of impurity content, provide test result accurately less than 20ppm.
Background technology
The goods of carbon and graphite and the ash content of material thereof are called the analytical test of impurity content again, in general, all are to carry out according to the analytical test method of standard GB/T8133.17-1999 regulation.But, test for the trace impurity content in the ultra-high purity graphite, diamond synthesis purifying dag for example, the graphite for reactor of nuclear power station, the monocrystalline silicon thermal field is with graphite etc., according to said method analyze, will feel that the test findings error is too big, the layman often is difficult to according to said method provide analytical test result accurately. draw the test findings that numerical value is negative sometimes even.
It is unexpected that principal element have 2 points, and the one, the impurity content in the sample is small especially, diamond synthesis purifying dag for example, domestic standard requirement≤30ppm; American-European standard-required≤20ppm; West standard-required≤the 10ppm of Cree Inc.; The graphite for reactor of nuclear power station, its technical standard requirement≤5ppm; The monocrystalline silicon thermal field technical standard requirement≤50ppm of graphite; Second it be that the test error of analytical test method of GB/T8133.17-1999 regulation is bigger.
The ceramic crucible of the splendid attire sample that is adopted in this analytical test method,, before high temperature sintering, the weight differential after the calcination is bigger.And each weight behind high temperature sintering, all can change irregular seeking because of residing environment temperature in the cooling procedure is different with humidity.In order to lower its rate of change before and after the high temperature sintering as far as possible, professional scientific research institution can adopt that expensive rare metal---platinum is made the crucible of splendid attire sample, but as the common engineering manufacturing industry, it is obviously too high that it detects cost.
Summary of the invention
The objective of the invention is to be to provide a kind of method of testing of ultra-high purity graphite trace impurity content, method is easy, and is fast, accurately with low cost, solved the too big problem of test findings error of the analytical test method of GB/T8133.17-1999 regulation.
To achieve the above object, the present invention adopts following technical measures:
The maternal quantity of sample is strengthened, the ceramic crucible of test splendid attire sample before high temperature sintering with calcination after rate of change k, in the computing formula of test findings, add the rate of change factor, thus greatly the raising of degree measuring accuracy.
A kind of method of testing of ultra-high purity graphite trace impurity comprises the following steps:
A, the maternal quantity of sample is increased to 4~5 times of maternal quantity of the sample of GB/T8133.17-1999 regulation;
The ceramic crucible of B, test splendid attire sample before high temperature sintering with calcination after rate of change k, its value by the sample cup test it, temperature is controlled at 800~850 ℃;
C adds the rate of change factor in the computing formula of test findings, specific as follows:
A = (G1-G2*k)?/?G?X?100%
In the formula: A---ash content or impurity content;
The maternal weight of G---sample;
G1---the ceramic crucible after the calcination and the weight of sample residue;
G2---the weight of the ceramic crucible of splendid attire sample;
The rate of change of the ceramic crucible sample cup before and after K---the calcination.
The maternal quantity that adds bulk specimen, the ceramic crucible of test splendid attire sample before high temperature sintering with calcination after the rate of change; Thereby in the computing formula of test findings, add the rate of change factor. greatly the raising of degree measuring accuracy.Test error by original ± 25% narrow down to ± 5% in.
The present invention compares with the analytical test method of existing GB/T8133.17-1999 regulation, has the following advantages and effect:
The inventive method is easily gone, and equipment is simple, and is easy to operate, is applicable to that diamond synthesis is higher than 4 9(99.99% with purifying dag and purity) more than the mensuration of impurity content of graphite.No matter be that professional or other staff can both very fast association, especially for the test findings error rate, will drop to ± 5% in.Greatly the raising of degree measuring accuracy.
Embodiment
Embodiment 1:
The maternal quantity of sample is increased to 4~5 times of maternal quantity of the sample of GB/T8133.17-1999 regulation; The ceramic crucible of test splendid attire sample before high temperature sintering with calcination after rate of change k, its value by the sample cup test it; In the computing formula of test findings, add the rate of change factor.
A kind of method of testing of ultra-high purity graphite trace impurity comprises the following steps:
A, the maternal quantity of sample is increased to 4~5 times of maternal quantity of the sample of GB/T8133.17-1999 regulation;
The ceramic crucible of B, test splendid attire sample before high temperature sintering with calcination after rate of change k, its value by the sample cup test it; Temperature is controlled at 800 or 810 or 815 or 822 or 829 or 834 or 838 or 842 or 847 or 850 ℃;
C, in the computing formula of test findings, add the rate of change factor, specific as follows:
A=?(G1-G2*k)?/?G?X?100%
In the formula: A---ash content or impurity content;
The maternal weight of G---sample;
G1---the ceramic crucible after the calcination and the weight of sample residue;
G2---the weight of the ceramic crucible of splendid attire sample;
The rate of change of the ceramic crucible sample cup before and after K---the calcination.Thereby greatly the raising of degree measuring accuracy.Test error by original ± 25% narrow down to ± 5% in.