Accelerated Rate Calorimetry
Instrument Modes
- Heat-search mode: Initially, the heating elements in the adiabatic chamber heats the sample a little, stops, and let the sensors search for self-heatup. If the self-heatup is above a prespecified value, the cycle stops, and we go in to adiabatic mode.
- Adiabatic mode: The self-heatup is measured.
- Events: Self-heatup initializing temp, Venting temp (for cells), accelerated heat output and uncontrolled heat output (thermal runway)
- Separator meltdown: Endotherm reaction displayed by small lowering of heat generation.
- Events: Self-heatup initializing temp, Venting temp (for cells), accelerated heat output and uncontrolled heat output (thermal runway)
- Usual specifics:
- Instrument: EV+ARC from Thermal Hazard Technologies.
- Videocamera, Window, two cable connections, pressure sensor, and gas release.
- Chamber: 40cm diameter, 44cm depth. Sealed by Si-gasket and 40kg lid with magnet lock released at 1bar overpressure.
- Program: ARC-ES v6.3.2
- Heat rate:
- Heated to \(60^\circ\)C, thereafter \(5^\circ\)C steps in the searching phase.
- Wait time was 50 minutes, and search time is determined by software.
- With self-heat rate above\(0.2^\circ\)C/min, it eneters adiabatic mode.
- Measured until \(250^\circ\)C or until heat rate is below \(0.2^\circ\)C/min
- Instrument: EV+ARC from Thermal Hazard Technologies.
Source: M.Sc. degree of Torleif Lian (FFI)
Sample holder
- Should be described in detail.
- Will absorb heat from the experiment: Lower temp rise than expected
- Heat lost by sample container can be explaied by the \(\varphi\)-factor:
- \(\varphi = 1 + \frac{m_b c_b}{m_s c_s}\)
- m = mass, c = heat cap, b = bomb, s = sample
- Ideally: It should be close to that of a full lithium cell
Analytics
- Lowered heat-rate may not be because of a break between two exotherms, but rather an endoterm. This can be indicated by pressure increase at the temperature where the endotherm is: Why would there be a pressure increase if there is no reaction?
