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
10ppm Ash Graphite
Screen your requirement, then compare ash and element-specific evidence before choosing a graphite grade.
Published September 28, 2026 · Evidence reviewed October 8, 2026
Choose all three process inputs, then review the requirement. Your selections are needed before a screening result can be shown.
What a 10 ppm ash target tells you
Method matters
Check the test scope
ASTM C561-23 describes an ash test for comparing commercial graphite grades and says it is not intended for purified graphite.
Lot specific
Set limits from the process
Confirm which elements matter, the analytical method and detection limits, and the exact material lot being qualified.
Turn a purity target into a supplier specification
01 · Define
Name the component and process
Identify the component location, operating temperature and atmosphere, process stage, and contamination limits that matter.
02 · Measure
Separate ash from elements
Request total ash and any element-specific results as distinct measurements, with the method and reporting limit for each.
03 · Qualify
Tie the report to the supplied lot
Confirm sample identity, graphite grade, machining or purification history, and acceptance criteria before approving production.
Evidence to request before buying
A single ash number is not a complete impurity specification. Ask the supplier to make the sample, method, and acceptance scope explicit.
Swipe horizontally to compare all columns.
| 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. |
Need to align a lot report with your part and process limits?
Request an engineering reviewWhat the evidence can support
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. Published work on natural graphite for nuclear applications does not establish the delivered component’s purity; an advertised process or nominal grade is not a substitute for a report that meets the buyer’s agreed test and acceptance criteria.
Limits, alternatives, and trade-offs
- Measurement risk: a method outside its validated range can make a low result hard to interpret; agree on method and reporting limits.
- Cost risk: price depends on grade, part geometry, batch size, purification, machining, and inspection scope. Request a like-for-like quote instead of relying on a generic premium.
- Qualification risk: coatings and furnace bake-outs may affect a specific contamination pathway, but they do not automatically qualify the substrate or replace process validation.
Sources and method notes
- ASTM C561-23, Standard Test Method for Ash in a Graphite Sample — its public scope says the method estimates nonburnable residues for comparing commercial graphite grades and is not intended for purified graphites.
- Schulz et al., “Impurity incorporation during sublimation growth of 6H bulk SiC,” Journal of Crystal Growth (1999) — a primary study using SIMS and ICP methods across materials and growth stages; its sample and process conditions limit how broadly its findings can be applied.
- Shen et al., “Thermal and gas purification of natural graphite for nuclear applications,” Carbon 173 (2021) — reports thermal and halogen gas purification experiments on natural graphite. Its feedstock and nuclear-use context do not establish results for a specific machined component or lot.
Evidence checked 2026-10-08. Standard summaries and published studies do not specify your acceptance limits; verify the current method revision and qualification scope with your lab and supplier.
Frequently asked questions
Measurement and test reports
Does 10 ppm ash mean every impurity is below 10 ppm?
No. It is a total residue target. Request separate limits and results for elements that matter to your process.
Is 10 ppm the same as 10 mg/kg?
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.
What should a result reported as “below 10 ppm” include?
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.
Can I compare ash results from different test methods?
Do not assume the numbers are interchangeable. Confirm the methods’ scope, sample preparation, reporting basis, and whether the lab has validated a comparison.
Should I use ASTM C561 for purified graphite?
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.
Grade selection and purchasing
Is 10 ppm a universal semiconductor-grade threshold?
No universal cutoff is established by the evidence cited here. Define the limit from the component, process, and buyer qualification data.
Does a block test report automatically cover the machined part?
Not automatically. Ask which sample and processing stage the report represents, and agree how it relates to the delivered part and lot.
Does purification guarantee that a lot meets 10 ppm?
A process description does not establish a lot result. Verify the delivered material against the agreed method, sample scope, and acceptance criteria.
Alternatives and cost
Can a coating replace a low-ash substrate?
Do not assume so. A coating may address a defined pathway, but substrate purity, coating integrity, and furnace qualification remain separate checks.
Can you estimate the price premium from the ash target?
Not reliably from ash level alone. Compare quotes with the same geometry, grade, purification route, batch quantity, test scope, and delivery terms.
Review your ash and element limits
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.
Inquiry Email
Attach DWG, STEP, or PDF drawings and include purity, tolerance, quantity forecast, and delivery country.
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