Can an experimental multi zone rotary furnace be evacuated?

The experimental multi temperature zone rotary furnace can be evacuated, and the vacuum function is one of its core designs, which can meet complex requirements such as high-temperature anaerobic environment, low-pressure experiments, and atmosphere purification. The following is an explanation from four aspects: technical principles, functional functions, typical application scenarios, and operational points:

1. Technical principle: Implementation method of vacuum system
The experimental multi temperature zone rotary furnace achieves vacuum pumping inside the furnace through an external vacuum pump, and its key technologies include:
Sealing structure design
The furnace body adopts a double-layer water-cooled jacket or all metal sealing structure, combined with high-temperature resistant sealing rings (such as fluororubber and perfluoroether rubber), to ensure that the vacuum degree can still be maintained at high temperatures (≤ 1600 ℃).
The furnace door, air inlet, exhaust outlet and other parts are designed for quick disassembly and assembly, which is convenient for maintenance and sealing inspection.
Vacuum pump selection
Usually equipped with a mechanical pump (such as a rotary vane pump) as the front stage pump to achieve coarse vacuum (≤ 10 Pa); If a higher vacuum degree (≤ 10 ⁻ ³ Pa) is required, molecular pumps or diffusion pumps can be connected in series.
The vacuum pump is connected to the furnace body through stainless steel pipes, and the inner wall of the pipes is polished to reduce gas adsorption.
Vacuum degree control
Real time monitoring of furnace pressure through vacuum gauges (such as resistance gauges and ionization gauges), combined with electric valves to automatically adjust the pumping rate and maintain the target vacuum degree.
Some high-end models support program temperature rise and vacuum degree linkage control, such as automatically switching to high vacuum mode when the temperature rises to 500 ℃.

2. The core role of vacuum function
Create an anaerobic environment
Isolate oxygen at high temperatures to prevent material oxidation or decomposition. For example:
Sintering of positive electrode materials for lithium batteries: Under vacuum or inert atmosphere, to avoid the increase in porosity caused by CO ₂ generated by the decomposition of Li ₂ CO ∝, and to improve material density (≥ 5.0 g/cm ³).
Metal powder metallurgy: Vacuum sintering can eliminate oxide films on the surface of powders, promote densification, and make titanium alloys have a density of ≥ 99.5%.
Reduce reaction temperature
At low pressure, the boiling point of a substance decreases and the activation energy of the reaction decreases. For example:
Nanomaterial synthesis: Carbon nanotubes are prepared by chemical vapor deposition (CVD) under vacuum, and the growth temperature can be reduced to 600-700 ℃, saving 30% energy consumption compared to atmospheric pressure conditions.
Metal purification: When zone refining is carried out under vacuum, the impurity segregation coefficient increases, and the silicon purity can reach 9N (99.99999999%).
Remove volatile impurities
Vacuum environment can accelerate the volatilization of low boiling point impurities (such as water and organic matter) in materials. For example:
Ceramic material gluing: Under vacuum at 400-600 ℃, the binder (such as polyvinyl alcohol) in the ceramic body can be completely decomposed and expelled, avoiding the generation of bubbles during subsequent sintering.
Purification of semiconductor materials: Annealing silicon single crystals under vacuum can reduce oxygen content (≤ 10 ¹⁷ atoms/cm ³) and improve minority carrier lifetime (≥ 1000 μ s).

3. Typical application scenarios
Preparation of new energy materials
Solid state electrolyte synthesis: Sulfide solid electrolytes (such as Li ∝ PS ₄) are deposited by sputtering under vacuum to avoid reaction with moisture in the air and improve ion conductivity (≥ 10 ⁻ ³ S/cm).
Silicon based negative electrode material processing: The vacuum rotary furnace can achieve simultaneous carbon coating and densification of silicon particles, alleviate volume expansion (≤ 120%), and improve initial efficiency (≥ 90%).
Metallurgical Industry
High purity metal purification: Electron beam melting of metals such as titanium and zirconium under vacuum can remove gas impurities (such as H, O, N), with a purity of ≥ 99.995%.
Difficult to melt metal processing: When vacuum sintering tungsten (W) or molybdenum (Mo) alloys, oxidation can be avoided to increase brittleness and improve fracture toughness (≥ 15 MPa · m ¹/²).
environmental science
Hazardous waste treatment: Pyrolysis of mercury containing waste under vacuum can reduce the boiling point of mercury (from 356.6 ℃ to ≤ 200 ℃) and improve the recovery rate (≥ 95%).
Fly ash melting and solidification: Vacuum environment can reduce the volatilization loss of heavy metals, making the solidification rate of Pb and Cd in fly ash ≥ 99%, and the leaching toxicity ≤ 0.01 mg/L.

4. Operation points and safety regulations
Vacuum pumping and heating sequence
It is necessary to first evacuate to the target pressure (such as ≤ 10 Pa) before starting to heat up, to avoid air entering the furnace at high temperatures and causing oxidation or explosion (such as lithium metal reacting with oxygen).
During the cooling process, if it is necessary to break the vacuum, inert gas (such as N ₂) should be filled to atmospheric pressure first, and then the furnace door should be opened to prevent air backflow.
Vacuum monitoring and maintenance
Regularly check the accuracy of the vacuum gauge, with a calibration error of ≤ 5%, to ensure data reliability.
After replacing the sealing ring, a leakage rate test (≤ 10 ⁻⁹ Pa · m ³/s) should be conducted to avoid a decrease in vacuum degree affecting the experiment.
Safety protection measures
Install a cold trap at the exhaust port of the vacuum pump to prevent volatile impurities from entering the pump body and damaging the equipment.
Equipped with hydrogen alarm device and emergency shut-off valve, if the experiment involves flammable gases (such as H ₂), it needs to be operated under vacuum to reduce the risk of explosion.