Thermogravimetry-Differential Thermal Analysis and Mass Spectrometry (TG-DTA-MS)

Figure 1. TG-DTA-MS equipment.

Features

• Thermal (decomposition) reaction process of a sample

• Identification of gases generated at each reaction temperature.

Application Examples

• Heat-induced structural changes (TG-DTA) of rubber, organic films, adhesives, biopolymers, metals (melting), ceramics, and lithium-ion rechargeable battery materials

• Analysis of volatile compounds, their pyrolysates, and temperature dependence of amount of pyrolysate (TG-DTA-MS)

Principle

It is then possible to measure the weight change due to redox, thermal decomposition, adsorption/desorption, evaporation, volatilization, and other thermal changes.

Figure 2. Schematic figure of a horizontal TG-DTA device.

MS is available when (gas) molecules generated by heating are ionized by thermal electrons (electron impact method, EI) or light (photoionization method, PI). As a result, molecular ions, fragment ions, and/or neutral fragments are then generated (see Figure 3). These ions then enter a mass separator (Figure 4) which has two pairs of diagonally located electrodes, one for creating a DC electric field and one for creating a radio frequency (about 1.2 MHz) electric field. The ions then oscillate in the compound electric field and advance in the direction of the green arrow shown in Figure 4. By adjusting the DC voltage, only ions of a specific mass/charge ratio are allowed to reach the detector, and the corresponding ion current is measured.

Mass spectrometry can identify the gases and molecular species generated at the TG-DTA stages. This enables continuous monitoring of microscopic information that can reveal macroscopic data and structural information.

Figure 3. Principle of ionization by impact of either electrons (EI) or photons (PI)
Figure 4. Principle of mass separation (quadrupole mass spectrometer).

Data examples

Figure 5. TG-DTA-MS charts (calcium oxalate monohydrate).

Figure 6. Mass spectrum of calcium oxalate monohydrate at $507\ {^\circ}\text{C}$ (see Figure 5). $mz^{- 1}$ ratios 12, 16, 28, and 44 correspond to C, O, CO, and $\text{C}\text{O}_{\text{2}}$, respectively.

Data delivery formats

• TG-DTA-MS charts, MS at specific temperatures (PDF file)

• Corresponding numerical data (comma-separated .csv text files)

Measurement specifications

Property	Value	Unit	Notes
Maximum sample diameter	4	mm	Al, Pt, or AlO container
Temperature range	25-1400	$${^\circ}\text{C}$$
Temperature rise rate	2-20	$${^\circ}\text{C mi}\text{n}^{\text{-1}}$$
Measurement atmosphere	He, pseudo air		Pseudo air: 20% $\text{O}_{\text{2}}$, 80% He
Mass/charge range	10-200	$$mz^{- 1}$$	MS analysis, electron impact (EI)
	10-410

Items for enquiries

• Purpose and scope of the analysis

• Sample information:

  1. Quantity, availability of pre-analysis samples

  2. Structure, composition, shape, and possibility of breaking, cleaving, pulverization of sample

  3. Handling instructions

• Delivery date:

  1. Desired delivery dates of preliminary and final results

  2. Handling instructions

• Other relevant information

Caution

• Measurements may be discontinued for materials that generate corrosive and/or contaminating gases that could damage the equipment.

• This measurement is carried out by MST’s subcontractor.