High Temperature Differential Thermal Analyzer

I. Basic Principle

High Temperature Differential Thermal Analyzer (HT-DTA) analyzes the physical or chemical changes of materials at high temperature by measuring the temperature difference between the sample and the reference. When the sample undergoes a heat-absorbing or exothermic reaction (e.g., phase change, decomposition, oxidation), its temperature deviates from the reference, and the instrument records the temperature difference (ΔT) versus temperature/time curve to identify the characteristic points of the reaction (e.g., melting point, decomposition temperature).

II. Instrument Composition

1. 

High temperature furnace body

Heating element: silicon carbon rod (1600℃), molybdenum wire (1800℃) or platinum-rhodium alloy (1500℃).

Furnace chamber material: alumina ceramic or graphite, high temperature resistant and low thermal inertia.

2. 

Sample holder

Material: platinum crucible (oxidation resistant), alumina crucible (inert).

Dual thermocouples: monitor sample and reference temperatures separately (type S or type B thermocouples).

3. 

Control system

Temperature control accuracy: ±1°C (PID algorithm).

◦ 

Temperature rise rate: 0.1~50℃/min, support program temperature rise.

4. 

Atmosphere system

Inert gas (N₂, Ar), oxidizing (O₂), reducing (H₂/CO) environment control.

Vacuum option: up to 10-³ Pa to avoid gas interference.

5. 

Data acquisition and analysis software

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Real-time display of ΔT curve, automatic labeling of peak temperature and integral enthalpy change.

Core parameters and selection points

Parameter

Description

Temperature range

Conventional type: RT~1500℃; Ultra-high-temperature type: RT~2400℃ (special furnace body is required).

Sensitivity

Minimum detection of thermal effects (e.g. 0.1μV), determines the ability to recognize tiny reactions.

Warming rate

Rapid warming (50°C/min) is suitable for screening experiments; slow (1°C/min) is used for high-resolution analysis.

Atmosphere control

Multiplexed gas mixing system supporting dynamic atmosphere switching (e.g. oxidizing → inerting).

Sample capacity

Standard crucible size (e.g. 5mm diameter), large capacity optional (research batch reaction).

IV. Typical Application Areas

1. 

Ceramics and refractories

Optimization of the sintering process: determination of the optimal sintering temperature (identification of crystalline phase transitions by exothermic peaks).

Decomposition reactions: analyze kaolin (Al₂O₃-2SiO₂-2H₂O) dehydration and mullite generation.

2. 

Metals and alloys

Melting behavior: determination of the melting point of alloys (e.g., initial melting temperature of nickel-based high-temperature alloys).

Oxidation kinetics: assessment of the oxidation resistance of metals at high temperatures (e.g. oxidative weight gain of titanium alloys at 800°C).

3. Catalyst studies

Activation temperature range: Determine the activation temperature of the catalyst by heat absorption peaks. 

Carbon accumulation analysis: detect exothermic reactions during catalyst deactivation.

4. Nuclear Materials

High-temperature stability testing of uranium/plutonium compounds (inert atmosphere to prevent oxidation).

V. Example of operation flow

Example: Phase transition analysis of zirconium oxide (ZrO₂)

1. Sample preparation:

Powdered samples are pressed and loaded into a platinum crucible with α-Al₂O₃ (reference material) separately.

2. 

Parameter setting:

Temperature increase range: RT~1500°C, rate 10°C/min, air atmosphere.

3. 

Data acquisition:

Monitoring of ΔT curve with heat absorption peak at ~1170°C (tetragonal phase → cubic phase transition).

4. Result analysis:

The peak temperature corresponds to the phase transition temperature and the peak area is integrated to calculate the enthalpy of the phase transition.