What gases can be passed through a tube furnace with gas flow?

The tubular furnace with gas flow can be filled with a variety of gases, which can be divided into the following categories according to process requirements:

1. Protective gas
Nitrogen (N ₂)
Function: As an inert gas, it prevents materials from oxidizing at high temperatures.
Applications: metal annealing, ceramic sintering, semiconductor manufacturing, etc.
Mixed use: often mixed with hydrogen gas (N ₂+H ₂) or hydrocarbons (N ₂+CH ₄) for protection during heating or carburizing treatment.
Argon gas (Ar)
Function: More inert than nitrogen, suitable for materials that are more sensitive to oxidation.
Application: Preparation of high-purity metals, synthesis of nanomaterials (such as CVD method for growing carbon nanotubes).
Advantages: It can reduce oxygen partial pressure, simulate an approximate vacuum environment, and reduce impurity pollution.

2. Reducing gas
Hydrogen (H ₂)
Function: Accelerate the heating process and reduce metal oxides (such as reducing copper oxide to copper).
Application: Reduction reactions in metallurgy and chemical industry, reduction of silicon oxide in semiconductor manufacturing.
Safety precautions: Combustible gases should be mixed in proportion to avoid the risk of explosion.
Carbon monoxide (CO)
Function: Similar to hydrogen, it participates in reduction reactions.
Application: carburizing treatment, metal heat treatment.

3. Oxidizing gas
Oxygen (O ₂)
Function: Provide oxygen source, promote combustion or oxidation reaction.
Application: Material oxidation treatment, synthesis reactions (such as testing methane combustion activity in catalyst evaluation).
Key control points: It is necessary to accurately control the flow rate to avoid excessive oxidation.
air
Function: Contains approximately 21% oxygen, suitable for processes with less stringent oxidation requirements.
Application: Oxidation treatment or heat treatment of certain materials.

4. Mixed gas
Nitrogen based mixed gas
N ₂+H ₂: Used to protect heating or reduction reactions.
N ₂+hydrocarbons (such as CH ₄): used for protecting heating or carburizing treatment.
N ₂+CH ∝ OH: It can protect heating and also serve as a carrier gas during carburizing.
Ammonia decomposition mixed gas
Composition: After evaporation and gasification of anhydrous liquid ammonia, a mixture containing 25% N ₂ and 75% H ₂ is obtained through catalytic reaction.
Application: brazing, sintering and other processes.
Special mixed gas
N ₂+hydrocarbons+oxidizing media (such as CO ₂, H ₂ O, air): used for carburizing treatment.
Ammonia combustion mixed gas: mainly composed of N ₂, used for sintering stainless steel powder.

5. Special gas
Ammonia gas (NH3)
Function: Provide a nitrogen source for depositing silicon nitride films or participating in nitriding reactions.
Application: Semiconductor manufacturing, catalyst preparation.
Methane (CH ₄)
Function: As a carbon source, it is used to deposit carbon based films (such as diamond-like carbon films) or participate in carbonization reactions.
Application: Synthesis and surface modification of nanomaterials.
Silane (SiH ₄)
Function: Used for depositing silicon-based thin films (such as amorphous silicon and silicon nitride).
Applications: Semiconductor manufacturing, solar cell production.
Doping gas
Phosphine (PH ∝): used for n-type doping to prepare n-type semiconductor thin films.
Borane (B ₂ H ₆): used for p-type doping and preparation of p-type semiconductor thin films.

6. Other gases
Helium (He)
Function: As a carrier gas, it has high thermal conductivity and helps control the reaction temperature.
Application: Processes that require precise temperature control.
Sulfur hexafluoride (SF ₆)
Function: Used for etching or surface treatment in certain special processes.
Application: Specific steps in semiconductor manufacturing.