10 mg/kg
A total residue target
10 ppm by mass equals 10 milligrams per kilogram. It describes a bulk ash result, not a separate limit for every element.
Graphite purity decision guide
Screen your requirement, then compare ash and element-specific evidence before choosing a graphite grade.
10 mg/kg
10 ppm by mass equals 10 milligrams per kilogram. It describes a bulk ash result, not a separate limit for every element.
Method matters
ASTM C561-23 describes an ash test for comparing commercial graphite grades and says it is not intended for purified graphite.
Lot specific
Confirm which elements matter, the analytical method and detection limits, and the exact material lot being qualified.
01 · Define
Identify the component location, operating temperature and atmosphere, process stage, and contamination limits that matter.
02 · Measure
Request total ash and any element-specific results as distinct measurements, with the method and reporting limit for each.
03 · Qualify
Confirm sample identity, graphite grade, machining or purification history, and acceptance criteria before approving production.
A single ash number is not a complete impurity specification. Ask the supplier to make the sample, method, and acceptance scope explicit.
| Question | Ask for | Why it matters |
|---|---|---|
| What does “10 ppm ash” mean? | Test method, sample preparation, units, and the report’s stated scope. | Methods can have different applicability and do not identify every element by themselves. |
| Which contaminants are controlled? | A process-defined element list with result, method, and detection or quantitation limit. | A total ash value cannot show whether a specific impurity is below its own limit. |
| Does the report cover this order? | Lot or batch identifier and a traceable link to the quoted grade and part. | A typical or historical result may not describe the material being delivered. |
| What does the result not prove? | Sampling limits, measurement uncertainty, and any elements or process conditions not covered. | Material screening does not replace qualification in the buyer’s furnace and process. |
Published SiC growth research measures impurities at multiple stages, including source material and grown crystals. This supports tracing contamination through the process; it does not establish a universal graphite ash cutoff or prove that graphite is the only source.
Halogen treatment is one established graphite-purification route, but an advertised process or nominal grade is not a substitute for a report that meets the buyer’s agreed test and acceptance criteria.
Evidence checked 2026-09-28. Standard summaries and published studies do not specify your acceptance limits; verify the current method revision and qualification scope with your lab and supplier.
No. It is a total residue target. Request separate limits and results for elements that matter to your process.
For a mass fraction, yes. Confirm whether the report uses a mass basis and whether results are reported on a dry or other agreed sample basis.
Ask for the test method and its reporting or quantitation limit. The limit must be low enough to determine whether the agreed acceptance criterion is met; “below” does not mean zero.
Do not assume the numbers are interchangeable. Confirm the methods’ scope, sample preparation, reporting basis, and whether the lab has validated a comparison.
ASTM’s public C561-23 scope says the method is not intended for purified graphites. Agree with your lab and supplier on a suitable validated method for the material and target.
No universal cutoff is established by the evidence cited here. Define the limit from the component, process, and buyer qualification data.
Not automatically. Ask which sample and processing stage the report represents, and agree how it relates to the delivered part and lot.
A process description does not establish a lot result. Verify the delivered material against the agreed method, sample scope, and acceptance criteria.
Do not assume so. A coating may address a defined pathway, but substrate purity, coating integrity, and furnace qualification remain separate checks.
Not reliably from ash level alone. Compare quotes with the same geometry, grade, purification route, batch quantity, test scope, and delivery terms.
Send the component drawing, process conditions, ash target, element limits, and report expectations. Engineering can review the requested grade and inspection scope against the part and process.
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Attach DWG, STEP, or PDF drawings and include purity, tolerance, quantity forecast, and delivery country.
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