Performance Characterization of CO₂ Phase Change Excitation Agent under the Synergistic Effect of Titanium Powder Content and Zero Oxygen Balance

To improve the performance of the CO₂ phase change excitation agent, titanium powder with mass fractions of 2%, 4%, 6%, 8%, and 10% was added to the excitation agent. The contents of ammonium oxalate and salicylic acid were controlled to adjust the zero oxygen balance, respectively. The ignition reliability, pressure performance, thermal decomposition characteristics, safety performance and temperature resistance property were investigated by on-site ignition tests, thermogravimetric analysis, temperature resistance performance tests and theoretical calculations. The results show that: all the excitation agents are successfully ignited inside the tube after adding titanium powder with mass fractions of 2%, 4%, 6%, and 8%. The peak pressure is directly associated with the heat release amount of the excitation agent. Within the addition range of this test, the excitation agent with 8% titanium powder has the best pressure performance inside the tube. After adding titanium powder with a mass fraction of 8%, the peak pressures of excitation agent without adjusting the oxygen balance, with adjusting the zero oxygen balance through ammonium oxalate, and with adjusting the zero oxygen balance through salicylic acid increase by 11.81%, 14.27%, and 17.85%, respectively. The apparent activation energies of the three samples decrease by 5.96 kJ/mol, increase by 33.47 and 6.80 kJ/mol, respectively, indicating that adjusting the zero oxygen balance can optimize the thermal stability of the excitation agent. After adding titanium powder with a mass fraction of 8%, the safety of the excitation agent is good, and the temperature index T_s is above 90 ℃.