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应用二次离子质谱法对Pyrex玻璃表层中离子交换和扩散现象进行研究的过程中,我们发现当玻璃表层中的钠几乎全部被钾取代时,银的扩散显著减少。在温度为335℃,银的原子百分数为2%时,Ag-Na和Ag-K的相互扩散系数分别为1.4×10~(-11)和5.2×10~(-14)厘米~2秒~(-1)。这一迹象可以成功地用于阻止由于银扩散至玻璃中而产生的痕量损失。文中举二例:如掺有痕量银的可可粉,在400℃下灰化2小时,再用硝酸+高氨酸(1+1)加热,使氧化分解(见表1)。又如稀硝酸银(1M硝酸溶液含0.5ppmAg)溶液蒸发至干(见表2)。从银的损失量来看,使用Pyrex烧杯(以熔融硝酸钾于500℃处理2小时)的效果近似于石英烧
In a study of ion exchange and diffusion phenomena in the Pyrex glass surface using secondary ion mass spectrometry, we found that silver diffusion was significantly reduced when almost all of the sodium in the glass surface was replaced by potassium. The interdiffusion coefficients of Ag-Na and Ag-K are respectively 1.4 × 10 ~ (-11) and 5.2 × 10 ~ (-14) cm ~ 2sec at the temperature of 335 ℃ and the atomic percentage of silver is 2% (-1). This indication can be successfully used to prevent trace losses due to the diffusion of silver into the glass. Two examples are given in this paper: cocoa powder mixed with traces of silver, ashed at 400 ° C for 2 hours, and then oxidized by heating with nitric acid + hydrogen (1 + 1) (see Table 1). Another example is dilute silver nitrate (1M nitric acid solution containing 0.5ppmAg) solution was evaporated to dryness (see Table 2). In terms of the loss of silver, the effect of using a Pyrex beaker (treated with molten potassium nitrate at 500 ° C for 2 hours) is similar to that of quartz burned