【摘要】 在 77—295 K温区和氢浓度 0—0. 35范围采用正电子湮没寿命测量方法研究了Pd0. 75Ag0. 25Hx氢化物合金. 充氢后正电子湮没寿命谱可以用两个寿命成分表征. 短寿命成分τ1不随温度和氢浓度变化, 是自由正电子湮没寿命; 长寿命成分τ2及其相对强度I2不随温度变化, 但随氢浓度的增加分别增大和减小, τ2是氢气泡捕获的正电子湮没寿命, τ2增大和I2减小说明随氢浓度增大氢聚集成的气泡的尺度增大, 而浓度减小. 实验结果表明, 氢脆的微观机理是氢气泡致脆.更多还原

【Abstract】 The metal hydride PdAgH_x with a hydrogen concentration x ranging from 0 to 0.35 has been investigated by positron annihilation lifetime method in the temperature region between 77 K and 295 K. The measured lifetime spectra in metal hydride PdAgH_x are characterized by two lifetimes τ₁ and τ₂. The short lifetime τ₁ is independent of both hydrogen concentration and temperature, which is ascribed to the annihilation lifetime of free positrons. The long lifetime τ₂ and its intensity I₂ do not change with temperature, while τ₂ increases and I₂ decreases with increasing of hydrogen concentration. τ₂ is attributed to the lifetime of positrons trapped at the hydrogen bubble. The increase of τ₂ indicates the growth of the hydrogen bubble, and the decrease of I₂ shows the reduction of the hydrogen bubble concentration. The experimental result shows a microscopic mechanism that the hydrogen bubble produced causes hydrogen embrittlement.更多还原