Can small tube furnaces in laboratories be ventilated with gas?

The small tube furnace used in the laboratory can pass gas, and its gas inlet function is one of the important characteristics of the equipment, which can meet the requirements of various experimental scenarios for atmospheric environment. The following is a detailed explanation about the gas flow in small tube furnaces:

1. Types of gases that can be introduced
Small tube furnaces support the introduction of multiple gases, including but not limited to:
Inert gases, such as nitrogen (N ₂) and argon (Ar), are used to prevent material oxidation at high temperatures. For example, in the process of metal sintering or ceramic preparation, introducing inert gas can protect the sample from the influence of air.
Reductive gases, such as hydrogen (H ₂) and carbon monoxide (CO), are used for reduction reactions or removal of oxides from materials. For example, in metal reduction experiments, hydrogen can reduce metal oxides to pure metals.
Reactive gases, such as oxygen (O ₂) and ammonia (NH3), are used in oxidation reactions or chemical vapor deposition (CVD) processes. For example, in the preparation of semiconductor materials, the introduction of ammonia gas can participate in the synthesis of nitrides.
Mixed gases: Specific ratios of mixed gases (such as H ₂/Ar, NH ∝/N ₂) can be configured according to experimental requirements to achieve more complex reaction conditions.

2. Core components of ventilation system
The ventilation system of a small tube furnace typically includes the following key components:
Gas inlet: There are gas interfaces at both ends or sides of the furnace body, supporting single or multiple gas inlets. Some high-end models are equipped with quick switching valves, which can achieve instant replacement of gas types.
Mass Flow Meter (MFC): Precisely controls gas flow rate with an accuracy of ± 1% F.S. (full range). For example, in CVD experiments, the flow rate of the reaction gas needs to be controlled within a range of a few sccm (standard cubic centimeters per minute).
Gas mixing device: used to mix multiple gases to ensure precise proportions. For example, when synthesizing nitride thin films, SiH ₄ and NH3 need to be mixed in a ratio of 1:3.
Exhaust gas treatment system: including condenser, gas washing cylinder or catalytic combustion device, used to treat harmful gases (such as CO, NOx) generated in experiments, in compliance with environmental requirements.

3. Application scenarios of ventilation experiment
Chemical Vapor Deposition (CVD):
Example: By introducing SiH ₄ and NH3 at 1000 ℃, a silicon nitride (Si3N4) film can be deposited on a silicon wafer with better thickness uniformity.
Advantage: By precisely controlling gas flow rate and temperature, uniform growth and composition control of thin films can be achieved.
Catalyst preparation and activation:
Example: Calcination of γ – Al ₂ O3 at 800 ℃ under N ₂ atmosphere to prepare a catalyst support with a large specific surface area for automobile exhaust purification.
Advantage: Inert atmosphere can prevent catalyst from sintering or deactivation at high temperatures.
Metal reduction and purification:
Example: High purity iron powder is prepared by reducing iron oxide (Fe ₂ O3) at 1200 ℃ in an H ₂ atmosphere.
Advantages: Reductive gases can efficiently remove oxygen from metal oxides and obtain pure metals.
Biomass pyrolysis and gasification:
Example: Pyrolysis of biomass (such as rice husks and sawdust) at 800 ℃ under N ₂ atmosphere, studying its gasification characteristics and product distribution.
Advantages: Inert atmosphere can prevent biomass from burning at high temperatures and focus on pyrolysis reactions.

4. Safety precautions for ventilation operation
Gas leakage detection:
Before the experiment, it is necessary to check whether the air circuit connection is tight, and use soap water or leak detector to detect leaks.
Regularly replace sealing rings and joints to prevent leakage caused by aging.
Explosion proof measures:
The furnace is equipped with a pressure relief valve, which automatically releases pressure when the pressure inside the furnace exceeds the set value (such as 0.02MPa).
Flammable gases such as hydrogen should be kept away from sources of ignition, and explosion-proof electrical appliances should be installed in the experimental area.
Ventilation requirements:
The experiment should be conducted in a fume hood to ensure timely exhaust of exhaust gases.
The exhaust treatment system needs regular maintenance to prevent blockage or failure.
Personal protection:
Operators are required to wear protective goggles, gloves, and lab coats to prevent burns caused by gas or high temperatures.
The hydrogen experiment requires two or more people to be present and supervise each other.