Hello everyone
I'm wondering what possible test methods are available for measuring carbon content in carbon brushes used in electrical motor.
The sample is a solid piece with carbon and copper content in range of 50-50%.
Does anybody has any idea?
I don't know specifically about C brushes, but the approach for highly pure substances is to measure the contaminants not the major constituent
An infrared absorption method after combustion might be usable.
The sample is combusted and the gas is analyzed via infrared absorption method to determine the total content of carbon in the sample.
However, as your sample contains quite a lot of carbon, only a small sample mass might be usable, but this might depend on the calibration of the equipment used.
Dear Mohammadehsan Salarpour, if you are sure that the sample is only constituted of copper and carbon, I suggest you weigh 1 g of your sample, then transfer it to a beaker or a round bottom flask with a condenser on top, then add about 50 -100 mL of concentrated nitric acid to your sample. Put a stir bar in the flask and stir the mixture under boiling condition for 2-3 hours so that copper is dissolved completely. Afterward, let the mixture coll down to room temperature, sieve it through a filter paper weighted in advance, wash it 2-3 times with distilled water and dry it in the oven. Now you can obtain the weight of pure carbon by subtracting the weight of filter paper and that of filter paper+carbon. Please note, the digestion procedure must be carried out under the fume hood or outdoors since it releases toxic nitrogen oxide gases.
Best,
Mahdi Ghamsari Thank you for detailed solution. Unfortunately aside from copper and carbon, there are other elements too, but I guess this method for determining Carbon content would be quite practical.
Marcus Sommerfeld Thank you for answering, I found an instrument which is specialized for determining Carbon and Sulfur content of sample, and its mechanism is based on what you described.
Dear Paul Milham , the problem is that I have no idea what other element might be present in the sample, but I know two main component are carbon and copper.
Thank you for response.
Is the C/Cu ratio all that's important? Might such materials be made with a limited range of proportions? Could you take a look using EDAX?
Paul Milham Yes they are made into brushes with different combinations of C/Cu ratio with the help of powder metallurgy method.
EDAX is a semi-quantitative method which cannot be applied to measure amount of light elements such as Carbon. The result cannot be trusted.
As a way forward might not an EDAX observation tell you what to look for?
Paul Milham No definitely not because EDAX analysis is semi-qualitative.
- Badges
- Science topic