Study on field electron emission characteristics and microstructure corrosion of titanium dominated by crystal orientation

The traditional “micro-protrusion” model of field electron emission (FEE) assumes electron emission primarily occurs at surface protrusions. However, as surface smoothness improves, this classical model inadequately explains FEE behavior. This study investigates titanium with different preferential orientations, systematically analyzing its FEE characteristics to establish a novel “grain orientation-phase transformation” FEE model. This model elucidates the mechanisms of electron emission and the microstructural evolution during the FEE process, providing theoretical guidance for the design and optimization of high-performance FEE materials. 1. Traditional micro-protrusions model: • There are many protrusions on the surface of metallic materials. • When an electric field is applied, the strength of the microscopic electric field at the protrusions is higher and electrons are emitted from the protrusions. 2. Crystal orientation-phase transition model: • With improved polishing techniques, visible protrusions on the surface of the material no longer exist. • The grains on the surface of the metal exhibit different orientations, each with a different work function. • When a voltage is applied, electrons are emitted from the crystal with the lower work function instead of the protrusions. • As electrons continue to be emitted, currents within the metal cause dislocations to drift and accumulate near the surface of the material. • Accumulated dislocations increase the local resistance, which increases the local temperature as the current continues to pass through, causing phase transitions or eruptions to occur in tiny regions. The process comprehensively illustrates the complex microstructural evolution during FEE, highlighting crystal orientation’s decisive influence on electron emission behavior. • Crystal orientation, rather than surface protrusions, plays a decisive role in titanium’s field electron emission performance. • First-principles calculations and multiscale characterization demonstrate that electrons preferentially emit from low work function crystal planes rather than grain boundaries or defect sites. • A novel “crystal orientation–phase transformation” model elucidates the mechanisms of field electron emission and microscale corrosion. • The proposed mechanism offers valuable guidance for the design and development of other field electron emission materials. Field electron emission (FEE) has significant applications in high-gradient accelerators, cold cathode electron sources, and high-power electronic devices. However, its microscopic mechanisms and the evolution of material microstructure remain unclear. This research focuses on pure titanium (TA2) with different preferred orientations, combining FEE experimental tests, multi-scale Microstructural characterization, and first-principles calculations to systematically investigate the influence of grain orientation on field emission performance and microstructural evolution. FEE tests show that radial samples with preferential growth along the (0002) plane exhibit higher emission thresholds (240 kV/cm) and maximum sustainable voltages (460 kV/cm). Multi-scale characterization and first-principles calculations reveal that electrons preferentially emit from low work function crystal planes rather than grain boundaries or defects. Based on these findings, a “crystal orientation − phase transformation” model for FEE is proposed, elucidating the corrosion mechanism of titanium microstructure under FEE current, explaining processes such as dislocation generation and migration, phase transformation, and surface craters evolution. This crystal orientation dominated mechanism can be extended to other metallic materials, providing new insights for designing high-performance FEE materials.