Study on the Mechanism of Hygrothermal Aging of B/KNO₃ Igniter Compositions

ABSTRACT The aging of igniter compositions is considered one of the primary factors affecting the reliability of the ignition devices, particularly influenced by external factors such as humidity. To study the mechanism of hygrothermal aging in boron/potassium nitrate (BPN) (B/KNO 3 ), we designed the experiments to characterize their properties and investigate their aging mechanism. By constructing the two‐phase interface of BPN, aging experiments were conducted under controlled humidity conditions. Subsequently, the B/KNO 3 samples underwent comprehensive characterization using thermal analysis, a super‐depth microscope, an x‐ray diffractometer, an x‐ray photoelectron spectrometer, and an inductively coupled plasma spectrometer. The results revealed that under high humidity conditions, potassium nitrate exhibits significant hygroscopic dissolution and diffusion behavior. Notably, as the relative humidity increases, the diffusion phenomenon becomes more pronounced. When the relative humidity rises to 80% RH, after 10 days of aging at 60°C, the diffused potassium nitrate accounts for nearly one‐tenth of its original mass. A thorough analysis of the hygroscopic diffusion behavior of potassium nitrate and its implications for the aging characteristics of the BPN igniter boron interface was conducted. X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy with energy‐dispersive spectrometer (TEM–EDS) analysis showed that the humidity‐induced diffusion of potassium nitrate acts as the primary catalyst for accelerating the oxidation of boron. Laser ignition experiments confirmed that the oxidation of B caused by hygrothermal aging significantly reduces the combustion performance of the BPN. This critical finding underscores the pivotal role played by KNO 3 in facilitating boron oxidation, thus providing a scientific foundation for a deeper understanding of the hygrothermal aging mechanisms in BPN igniter.