Definition
A thermogravimetric analyzer is a thermal analytical instrument used to measure the relationship between the mass of a substance with temperature or time. It provides quantitative data for the study of thermal stability, compositional decomposition and reaction kinetics of materials by recording the mass change curve of samples under programmed temperature control conditions.
Principle
Thermogravimetric analyzers are based on the principle of mechanical equilibrium and usually employ highly sensitive microbalances. The sample is placed in a specific atmosphere and heated according to a preset program, and its mass changes are converted into electrical signals by the balance and recorded in real time. The functional relationship of mass change with temperature or time can be expressed as:
Δm = f(T) or Δm = f(t)
Δm represents mass change, T represents temperature, and t represents time.
Measurement method
Common measurement modes include dynamic heating and isothermal methods. The dynamic heating method changes the temperature at a constant rate and records the continuous mass change. The isothermal law monitors the change of mass over time at a constant temperature. The measurement process needs to control parameters such as sample quality, heating rate, atmosphere flow, etc., and use reference materials for instrument calibration.
Influencing factors
Measurement results are influenced by a variety of factors. In terms of sample characteristics, particle size, bulk density, and initial mass affect heat conduction and gas diffusion. In the instrument parameters, the heating rate is too fast may lead to thermal hysteresis, and the atmosphere type and flow rate may change the reaction mechanism. In addition, the heat capacity and catalysis, balance sensitivity and temperature calibration accuracy of the crucible material all have an impact on the data reliability.
Application
In the field of materials science, this instrument is used to determine the decomposition temperature of polymer materials, the crystallization water content of inorganic substances, and the thermal stability of composite materials. It can be used in the chemical industry for catalyst inactivation research and reaction kinetics analysis. In terms of environmental monitoring, it is suitable for the analysis of coal combustion characteristics and the study of waste pyrolysis behavior. In the pharmaceutical industry, it is used in the determination of drug crystalline water and the evaluation of thermal decomposition characteristics.
Selection
When selecting an instrument, consider the temperature range, balance sensitivity, atmosphere control system, and data acquisition capabilities. The temperature range should cover the reaction interval of the material to be tested, and the balance resolution should meet the required requirements for the detection of expected mass changes. Multi-atmosphere switching ability is necessary for the study of redox reactions. Additionally, sample holder compatibility, temperature calibration methods, and software analysis capabilities should be considered to ensure that the instrument configuration matches the research objectives.