High-purity molybdenum disilicide powder

01

Set the impurity and silicon limits

MoSi2 has a molecular weight of 152.12 g/mol. [4] Höganäs' data sheet PD-5146 (issue 3, 2007) describes MoSi2 as a greyish powder in three grades: Grade A allows at most 0.5% oxygen, Grade B 1.5% and Grade C 2.0%. Silicon is 36.3–36.9% for Grade A, 36.1–36.9% for B and 35.9–36.9% for C; carbon is at most 0.2% for A and B and 0.3% for C; nitrogen at most 0.1% for A and B and 0.2% for C. [1]

SAM's thermal-spray MoSi2 grades list purity above 99.0% for 0.5–1.0 µm and above 99.9% for coarser sizes, oxygen from at most 1.0% for the finest grade to at most 0.3% for −325 mesh, nitrogen at most 0.05–0.10%, carbon at most 0.1% and silicon 33.2–36.9%; SAM notes these figures are based on theoretical data. [2]

Höganäs supplies an inspection document in accordance with EN 10204 with every shipment. [1] Ask for the oxygen, carbon, nitrogen, silicon and particle size results on that certificate.

Give the supplier the end use (heating elements, sintered parts, thermal spray, coating), the oxygen, carbon, nitrogen and silicon limits, particle size distribution or mesh, surface area, apparent density or flow needs, lot size, packaging and the certificate type required.

02

Set the particle size, surface area and form

Höganäs measures particle size by laser diffraction (Microtrac) per ASTM C 1070. Its D50 is 5.5–7.5 µm for Grade A, 3.5–5.0 µm for Grade B and 2.0–3.0 µm for Grade C, with D90 of 10.5–13.5 µm, 7.0–10.5 µm and 3.5–5.0 µm. BET surface area per DIN ISO 9277 is at most 1.0 m²/g for Grade A and at least 0.9 m²/g and 1.5 m²/g for B and C. Apparent density by Scott volumeter per ASTM B 329 is 18.0–28.0 g/inch³ for A and 15.0–25.0 g/inch³ for B; Grade C is not free-flowing. [1]

SAM offers spherical MoSi2 for thermal spraying in average particle sizes of 0.5–1.0 µm, 1.0–3.0 µm, 10.0–60.0 µm and −325 mesh, and says it forms a silica passivation layer at high temperature that prevents further oxidation; it lists uses in heating elements, oxidation-resistant coatings and high-temperature structural parts. [2] Kanthal's Super MoSi2 heating elements are rated up to 1,850 °C (3,360 °F) in oxidizing, inert, carburizing, nitriding and reducing atmospheres. [3]

Höganäs packs Grades A and B as 50 kg in 30 l steel drums and Grade C as 50 kg in 60 l drums, each with a polyethylene inlet, nine drums (450 kg) to a 1,140 × 1,140 mm pallet. [1]

Editorial calculation: with 1 in³ = 16.387 cm³, 18.0–28.0 g/inch³ is about 1.10–1.71 g/cm³ and 15.0–25.0 g/inch³ is about 0.92–1.53 g/cm³; 0.5%, 1.5% and 2.0% oxygen are 5,000, 15,000 and 20,000 ppm. [1]

03

What to ask a MoSi2 powder supplier to show on the lot certificate

Ask any supplier for a data sheet and a lot certificate showing oxygen, carbon, nitrogen and silicon, D10/D50/D90 and the method used, BET surface area, apparent density or flow, particle shape, packaging, lead time and minimum order.

04

Oxygen, silicon, carbon and nitrogen, size distribution, BET and apparent density

Höganäs' grades A, B and C carry at most 0.5%, 1.5% and 2.0% oxygen alongside their particle sizes, so fix oxygen and size together for the end use. [1]

05

D50, purity, oxygen, BET, apparent density and flow for a MoSi2 powder order

Höganäs states apparent density in g/inch³ by Scott volumeter, which converts to about 0.92–1.71 g/cm³ across its grades (editorial calculation); six rows here, including melting point and resistivity, have no published value. [1]

06

Send the use, chemistry and size data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Use: [heating elements; sintered parts; thermal spray; coating]
Chemistry: [O max; C max; N max; Si range]
Size: [D10; D50; D90; mesh]
Surface: [BET m²/g]
Flow: [apparent density; free-flowing]
Certificate: [EN 10204 type]
Quantity: [kg; packaging]

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