High-Temperature Induction Heating of Rock Powder

Application: Materials Research and Testing

Industry: Academic & Research

Application Objectives:

A leading research university needed to heat a mineral powder mixture (SiO₂–TiO₂–Al₂O₃ system) to 1500 °C inside a 92‑bar pressurized chamber. The goal was to evaluate feasibility without carbon liners and compare platinum vs. tungsten crucibles for clean, high‑temperature operation.

The Challenge:

Heating fine powder samples in a high-pressure (92 bar) 500 °C environment while preventing contamination and achieving uniform 1500 °C temperature within 10 minutes.

Equipment:

• Power Supply: SOLO-12 (12 kW, 230 V 3 ph, 150–400 kHz)
• Heat Station: HS-24W
• Coil: Custom helical copper coil (3/16″ OD × 0.024″ wall)
• Accessories: Zircar ceramic insulation, IR pyrometers (IGAR 6), pressurized chamber feedthrough

Materials:

• Rock powder (SiO₂, TiO₂, Al₂O₃, FeO, Fe₂O₃, MgO, CaO, Na₂O, K₂O, Cr₂O₃, MnO)
• Crucibles tested: platinum and tungsten

Key Parameters:

• Target Temperature: 1500 °C
• Frequency: ~200 kHz
• Power: 4–6 kW regulated
• Time, quick ramp and holding for: 90 min (Platinum) / 2–10 min (Tungsten)
• Pressure Environment: 92 bar (planned), tests performed in open air

Process:

Initial tests were conducted in open atmosphere using the 12 kW SOLO system. A platinum cup containing rock powder was heated with a custom helical coil until the sample reached 1500 °C. The cup partially melted, proving susceptor heating feasibility but revealing the need for a more temperature-resistant crucible. Subsequent trials used a tungsten crucible under similar conditions. The sample reached high temperature rapidly (~2 min) before visible oxidation and smoke limited the test duration. Post-cooling analysis confirmed the tungsten crucible remained intact with powder sintered inside.

Results and Conclusions:

Susceptor induction heating of fine rock powder to 1500 °C is feasible. The platinum crucible allowed stable heating but failed structurally at 1500 °C. Tungsten crucible proved significantly more resistant and retained structural integrity. SOLO-12 system provided sufficient power and control, confirming suitability for R&D material studies in high-temperature environments. For operation under 92 bar, additional validation of coil tubing is advised, though the copper coil wall thickness (0.024″) appears sufficient for initial trials.

Reference Info: AR 3463-9223