1、 Technical principle: Quality changes reveal the thermal behavior of matter
Thermogravimetric AnalyzerThermogravimetric Analyzer (TGA) uses programmed temperature control technology to accurately measure the dynamic changes in the mass of a sample with temperature (or time) during heating, cooling, or constant temperature processes. The core principle is based on the physical or chemical changes that occur when a substance is heated (such as evaporation, decomposition, oxidation, reduction, etc.), which directly lead to a decrease or increase in sample quality. For example:
Plastic loses weight due to the decomposition of organic matter between 200-400 ℃;
Inorganic materials (such as calcium carbonate) decompose into calcium oxide and carbon dioxide at 600-700 ℃, releasing gases that lead to a decrease in quality;
Metal materials may undergo oxidation to form oxides at high temperatures, resulting in an increase in mass.
TGA generates a thermogravimetric curve (TG curve) by continuously recording changes in mass, with temperature or time on the x-axis and mass or mass percentage on the y-axis. Each point on the curve corresponds to the mass state at a specific temperature. By analyzing the characteristics of the curve, such as weight loss steps and slope changes, key information such as the thermal stability, decomposition temperature, and reaction kinetics of the material can be obtained. For example, the TG curve of polymer materials usually shows multiple weight loss steps, corresponding to processes such as volatile matter (water, solvent), polymer decomposition, and carbon combustion.
2、 Core structure: Precision system ensures measurement accuracy
TGA consists of five core modules, which work together to achieve high-precision measurement:
High precision balance system
Function: Continuously monitor changes in sample quality, with a sensitivity of 0.1 μ g (microgram level), capable of capturing small fluctuations in quality.
Design: Adopting the principle of electromagnetic force balance or quartz spring structure to ensure stable operation in high temperature environments.
Application: For example, in drug analysis, the balance can accurately measure the moisture content in the sample (such as 0.1% humidity changes).
Program-controlled heating furnace
Temperature range: from room temperature to 1500 ℃ (some models can reach 1600 ℃), covering the majority of material testing requirements.
Temperature control accuracy: ± 0.25 ℃, ensuring linearity and repeatability of temperature changes.
Heating rate: adjustable from 0.1-200 ℃/min, suitable for different experimental scenarios (such as rapid thermal decomposition or slow heating to simulate actual working conditions).
Structure: The furnace body adopts platinum rhodium alloy heating elements, combined with a water cooling system to prevent overheating, and the crucible support design reduces thermal conduction errors.
Gas management system
Function: Control the atmosphere around the sample (such as inert gas N ₂, Ar or reactive gas O ₂ Air)， Simulate different environmental conditions.
Design: Multi channel gas switching valve, mass flow meter (MFC) for precise control of gas flow rate (such as 10-200mL/min), to avoid gas flow fluctuations affecting measurement.
Application: For example, in metal material testing, Ar gas is used to prevent high-temperature oxidation; In catalyst research, the oxidation-reduction reaction is observed by switching the O ₂/N ₂ atmosphere.
Data Collection and Processing System
Hardware: 24 bit high-precision AD converter with a sampling frequency of 100Hz, ensuring no data loss.
Software: Supports multi curve overlay analysis (such as TG-DTG combination), dynamic model fitting (such as Flynn Wall Ozawa method), and automatic report generation function.
Output: Generate TG curve and micro commercial thermogravimetric curve (DTG curve, derivative of mass change rate with temperature), revealing details such as reaction rate peak temperature.
Sample crucible and sensor protection device
Crucible material: Select according to the characteristics of the sample (such as alumina crucible for high temperature testing, platinum crucible for corrosive samples).
Protection design: When the testing temperature exceeds 1300 ℃, a sapphire plate is placed between the crucible and the sensor to prevent the sample from reacting with the platinum sensor; For explosive samples, micro testing (<5mg) is used and an explosion-proof cover is provided.
3、 Technical advantages and application scenarios
TGA, with its non-destructive nature, high sensitivity, and wide temperature range, has become a key tool for material research and development, quality control, and process optimization
Materials Science: Evaluating the thermal stability of polymers (such as the temperature resistance level of plastics and rubber), analyzing the composition of composite materials (such as glass fiber content).
Chemical Engineering: Study catalyst activity (such as calculating catalyst sintering temperature through weight loss curves), optimize pyrolysis processes (such as biomass gasification conditions).
In the field of medicine: determining the moisture content of drugs (such as alternative Karl Fischer method that meets pharmacopoeia requirements), evaluating the impact of excipients on stability (such as comparing TG curves of different formulations).
Environmental Science: Analyzing the thermal decomposition characteristics of pollutants (such as the behavior of plastic waste in incinerators), evaluating the weather resistance of materials (such as simulating mass changes in high temperature and high humidity environments).
4Thermogravimetric AnalyzerTechnological development trends
Modern TGA is developing towards higher precision, wider temperature range, and multifunctional applications:
Ultra microbalance: sensitivity increased to 0.01 μ g, suitable for testing nanomaterials.
High pressure TGA: The pressure range is extended to 100 bar, simulating deep-sea or chemical high-pressure environments.
Combined technology: Used in conjunction with mass spectrometry (MS), infrared spectroscopy (FTIR), or differential scanning calorimetry (DSC) to achieve synchronous analysis of mass changes and gas products or thermal effects (such as TGA-MS combined identification of decomposition product types).