High-Temperature Alumina Ceramic Sleeves and Cylinders Metallized Ceramic Thermal Protection Tubes

Alumina ceramic sleeves are hollow cylindrical components made from high-purity alumina (Al₂O₃) ceramic material. They are produced by dry-pressing, isostatically pressing, or slip-casting fine alumina powder, followed by sintering at temperatures exceeding 1600°C.

Their core functions are to isolate, insulate, protect, guide, and support objects (such as shafts, rods, wires, sensors, etc.) passing through them. They utilize the exceptional properties of ceramic to address demanding operating conditions that metal or plastic sleeves cannot handle.

The value of alumina ceramic sleeves stems entirely from their material properties:

1. Extremely hard and wear-resistant: With a Vickers hardness of 1500-1650 HV, they withstand high-speed erosion and wear, ensuring an extremely long service life.
2. Excellent electrical insulation: As an excellent insulator, they offer stable performance under high frequencies and high voltages, effectively preventing current leakage and short circuits. 3. Excellent High-Temperature Resistance: Long-term operating temperatures can reach 1600°C, with excellent thermal stability, resisting oxidation, deformation, and melting at high temperatures.
4. Excellent Chemical Stability: Resistant to strong acids, alkalis, and various organic solvents, it remains rust-free and suitable for corrosive environments.
5. Low Friction Coefficient and Smooth Surface: Can be polished to a mirror-like finish, achieving a low friction coefficient and reducing wear and tear on passing objects.
6. High Mechanical Strength: High compressive strength allows it to withstand significant pressure, but it is also brittle and requires protection from impact and stress concentration.

Alumina ceramic sleeves have a wide range of applications and are categorized below based on their core functions:
1. As Insulators and Protective Sleeves

• Thermocouple/RTD Protective Sleeves: Attached to the outside of a temperature sensor and inserted into molten metal, high-temperature furnaces, or corrosive media, they protect the metal sensor inside from damage due to heat, corrosion, and physical impact. Their insulating properties also prevent interference with temperature measurement signals.
• High-Temperature Furnace Observation Hole Sleeves: Installed on the furnace wall, they serve as a support and insulator for the observation window, withstanding the high temperatures within the furnace and maintaining insulation from the furnace wall.

2. As Wear-Resistant Guide Sleeves

• Wire Guide Sleeves: Used in wire drawing machines, stranding machines, and fiber optic braiding machines, they guide metal wires and optical fibers. Their extremely wear-resistant, smooth surface minimizes scratches on the wire and ensures product quality.
• Mechanical Guide Sleeves: Serving as linear guide sleeves for precision shafts and rods in automated equipment and measuring instruments, their high hardness ensures consistent accuracy over time, while their low friction ensures smoother movement.

3. As Fixing and Insulating Bushings

• Insulating bushings for electronic components: In circuit boards, power modules, and high-voltage equipment, they provide mechanical fixation and electrical isolation for bolts, pins, and terminal blocks, preventing short circuits between conductors at different potentials.
• Semiconductor Equipment Retaining Rings: In wafer processing equipment (such as CVD and etching machines), they are used to secure and insulate various components, withstand plasma environments, and prevent the release of metallic contaminants.

4. As Special Function Sleeves

• Laser Sleeves: In CO₂ laser tubes, they serve as positioning sleeves for the discharge tube and electrodes. Their excellent insulation prevents high-voltage breakdown, while their high-temperature resistance withstands the heat generated by the laser.
• Deep Well Pump Insulating Sleeves: In multi-stage deep well pumps, they isolate the impeller shaft and prevent electrochemical corrosion.