1、 Sample preparation: Details determine data accuracy
Particle control
The sample particles should be uniform (recommended particle size ≤ 0.5mm) to avoid thermal gradient interference with peak shape. Block shaped samples can be sliced instead of crushed to prevent electrostatic agglomeration.
Fiber samples need to be cut to a length of 1-2mm, while powder samples need to be compacted to reduce voids.
Usage and distribution
Solid samples are recommended to be 5-20mg (metal/chemical melting point testing requires 1-5mg), and liquids should not exceed 2/3 of the crucible capacity.
A small amount of sample should be laid flat at the bottom of the crucible, with particles placed in the center to avoid accumulation on one side.
Pressing and sealing
Inorganic samples need to be ground and sieved, while polymer samples need to be evenly dispersed. Liquid samples need to be sealed for testing, and if they contain volatile substances, a perforated crucible cover is required.
2、 DSC differential scanning calorimeter setting: precise control of key parameters
Temperature and rate
The heating rate is usually selected as 10-20 ℃/min, sensitivity testing (such as purity analysis) requires<10 ℃/min, and weak phase transitions (such as Tg) can be increased to 1 ℃/min.
The termination temperature requires a 2-minute baseline stabilization time to avoid sample decomposition and contamination of the furnace body.
Crucible selection
Aluminum crucibles (≤ 600 ℃) are used for routine testing, while ceramic crucibles (≤ 1000 ℃) are used for high-temperature experiments. Sealed discs are used for liquid or volatile samples.
Gas control
Nitrogen gas (50mL/min) is commonly used for purging, helium gas (25mL/min) is used below -100 ℃, and oxygen gas is used for oxidation experiments. Traffic adjustment needs to be completed before data collection.
3、 Data collection: avoid interference and errors
Environment and Operation
The laboratory temperature should be constant (20-30 ℃), avoiding vibration or opening the furnace cover, as slight touch can cause peaks and valleys in the curve.
During data collection, it is prohibited to adjust the gas flow rate to avoid baseline drift.
Secondary heating and calibration
Complex samples (such as those containing impurities) require secondary heating: melting and cooling before measurement to ensure uniform crystallization.
Monthly calibration of baseline and temperature, annual professional maintenance to ensure long-term stability.
4、 Maintenance and Safety of DSC Differential Scanning Calorimeter: Extending Instrument Life
Cleaning and maintenance
Do not use hard objects to clean the sample holder, use ear wash balls to clean dust in the experimental area, and burn at high temperatures (500 ℃/20 ℃/min) in case of severe pollution.
The furnace cover should be gently removed with tweezers to avoid burns or damage.
Safe operation
Confirm that the sample has no risk of decomposition/explosion before testing, and replace the ceramic crucible for high-temperature experiments (>550 ℃).
Shutdown sequence: Cool down to room temperature → Close software → Disconnect air source → Power off the host.