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.