What should be noted when customizing an experimental muffle furnace for experimentation?

Customized experimental muffle furnaces must strictly follow operating procedures during the experiment to ensure experimental safety, accurate data, and extend equipment lifespan. The following is a detailed explanation of key precautions:

1. Preparation before the experiment
Sample pretreatment
Drying treatment: Water containing samples should be dried in advance (such as drying at 105 ℃ for 2 hours) to avoid splashing or furnace rupture caused by severe vaporization of water at high temperatures.
Crushing and mixing: Samples with uneven particles (such as ore and soil) need to be crushed to a uniform particle size (usually ≤ 200 mesh) and thoroughly mixed to ensure uniformity in heat treatment.
Packaging and support: Volatile or molten samples (such as metals and salts) should be stored in high-temperature resistant crucibles (such as alumina and platinum) and placed in the center of the furnace to reduce the influence of thermal gradients.
Equipment inspection
Electrical safety: Check whether the power cord is damaged, whether the grounding is good, and avoid the risk of leakage.
Furnace state: Confirm that there are no residual samples or impurities in the furnace to prevent chemical reactions or contamination of new samples at high temperatures.
Temperature control system: Calibrate temperature sensors with standard substances (such as nickel chromium nickel silicon thermocouples) to ensure temperature control accuracy (usually within ± 1 ℃).
environmental condition
Ventilation requirements: The muffle furnace should be placed in a well ventilated laboratory to avoid the risk of poisoning or explosion caused by the accumulation of high-temperature gases (such as CO, SO ₂).
Space layout: At least 30cm of heat dissipation space should be reserved around the furnace body, away from flammable materials such as organic solvents and paper.

2. Operation specifications in the experiment
temperature control
Heating rate: Set a reasonable heating curve based on the properties of the sample. For example:
Ceramic sintering: Initial heating rate ≤ 5 ℃/min to avoid cracking caused by thermal stress;
Metal oxidation: Quickly raise the temperature to the target temperature (such as 10 ℃/min) to reduce side reactions.
Constant temperature stage: After reaching the target temperature, it is necessary to maintain sufficient time to ensure complete reaction (such as ash content determination requiring constant temperature for 1 hour).
Cooling control: It is prohibited to directly open the furnace door for rapid cooling. Instead, programmed cooling or natural cooling should be used to reach room temperature before sampling to prevent cracking of the furnace due to thermal stress.
Atmosphere protection
Inert gas introduction: For oxygen sensitive samples (such as lithium metal and carbon materials), high-purity argon gas (99.999%) or nitrogen gas should be introduced, with a flow rate controlled at 50-100mL/min, to ensure that the oxygen content in the furnace is ≤ 0.1%.
Reductive atmosphere: When preparing metal powders, hydrogen gas can be introduced (with explosion-proof devices), but the hydrogen concentration must be strictly controlled (usually ≤ 4%) to avoid the risk of explosion.
Vacuum environment: When processing high-purity materials (such as semiconductor silicon wafers), it is necessary to evacuate to below 10 ⁻ Pa to prevent impurity contamination.
Real time monitoring
Temperature recording: Use a data acquisition system (such as LabVIEW) to record temperature curves in real time for subsequent analysis of reaction kinetics.
Video surveillance: For volatile or molten samples, the sample status can be monitored through observation windows or endoscopes to adjust experimental parameters in a timely manner.

3. Post experimental processing
Sample extraction
Protective measures: Wear high-temperature gloves (temperature resistance ≥ 1000 ℃) and goggles, use long handled crucible pliers to remove samples, and avoid burns.
Cooling method: Transfer the sample to a dryer or insulation board for natural cooling, and do not place it directly on a metal table (which may cause thermal stress cracking).
Equipment maintenance
Furnace cleaning: After the furnace has cooled to room temperature, use a soft bristled brush to remove any residue and avoid scratching with hard objects (which may damage the inner wall of the furnace).
Heating element inspection: Regularly check whether the resistance wire, silicon carbon rod or silicon molybdenum rod is broken or oxidized, and replace aging components in a timely manner.
Furnace door sealing: Clean the furnace door sealing ring to ensure no impurities remain and prevent high-temperature gas leakage.
data sorting
Experimental report: Record key parameters such as temperature curve, atmosphere conditions, and sample state to provide reference for subsequent experiments.
Abnormal analysis: If the experimental results deviate from expectations (such as abnormal ash content), factors such as temperature control, sample uniformity, or atmosphere purity need to be checked.

4. Safety protection measures
Personal Protection
Protective equipment: Laboratory personnel are required to wear lab coats, heat-resistant gloves, goggles, and gas masks (when handling toxic gases).
Emergency training: Regularly conduct emergency drills for fires, burns, gas leaks, etc., and master the use of fire extinguishers (such as CO ₂ fire extinguishers) and first aid kits.
Equipment safety
Overtemperature protection: Set the overtemperature alarm threshold (usually 20-50 ℃ higher than the target temperature) and enable the automatic power-off function.
Leakage protection: Install a residual current circuit breaker (RCD) to ensure that the power is automatically cut off when the leakage current is ≤ 30mA.
Explosion proof design: For flammable and explosive experiments (such as hydrogen reduction), an explosion-proof muffle furnace should be selected and equipped with a hydrogen concentration monitor.
Waste Disposal
Toxic gas emissions: Neutralize acidic gases (such as SO ₂, Cl ₂) through exhaust gas treatment devices (such as alkali absorption towers) before discharging.
Solid waste: Sort and collect the residue (such as metal oxides) after high-temperature treatment, and hand it over to professional institutions for treatment to avoid environmental pollution.

5. Common Problems and Solutions
Large temperature fluctuations
Reason: Improper setting of temperature controller parameters, aging of thermocouples, or poor contact of heating elements.
Solution: Re calibrate the temperature controller, replace the thermocouple or tighten the heating element connection wire.
Furnace cracking
Reason: Rapid heating/cooling rate, sample splashing impact, or furnace material defects.
Solution: Strictly control the temperature change rate, use crucibles to hold samples, and contact suppliers to replace the furnace.
Insufficient purity of atmosphere
Reason: Gas leakage, insufficient gas purity, or vacuum pump malfunction.
Solution: Check the sealing of the gas circuit, replace high-purity gas or repair the vacuum pump.