Phase transition and pitting corrosion behaviour for Mo—implanted aluminium

Molybdenum ions are implanted into aluminium with high ion flux and high dose at elevated temperatures of 200℃, 400℃ and 500℃. Due to the high temperature and high flux of vacancies and interstitial atoms, the atom diffusion and chemical effects are enhanced during the ion implantation. The effects increase with increasing ion flux and dose, so that new phase formation and phase transition emerge noticeably. X-ray diffraction analysis shows that when the aluminium is implanted with Mo ions at a low ion flux (25μA/cm²), the Al₅Mo alloy is formed. The atomic ratio of Mo/Al of the Al₅Mo phase is close to 20%. When the aluminium is implanted with Mo ions at a high ion flux (50μA/cm²), the phase transition from Al₅Mo to Al₁₂Mo appears, and the latter is dominant, which is determined to be the final phase. The ratio of Mo/Al in Al₁₂Mo is 7.7%. Rutherford backscattering spectroscopy indicates also that the Mo/Al atom ratio is ～7% to ～8% in Mo-implanted aluminium. The atomic ratios of the constituents in Al₅Mo and Al₁₂Mo are of stoichiometric composition for these alloys. The thicknesses of the Al₁₂Mo alloy layers for Mo-implanted Al with ion doses of 3×10¹⁷/cm² and 1×10¹⁸/cm² are 550nm and 2000nm, respectively. The pitting corrosion potential V_p increases obviously. It is clear that due to the formation of Al₁₂Mo alloy layer, the pitting corrosion resistance is enhanced.     

Y升温注入Al形成Y-Al合金研究

利用金属蒸汽真空弧（MEVVA）源所产生的强束流离子注入铝研究了相变、增强扩散和钇铝合金的形成条件，X射线衍射分析表明注入层有Al3Y和Al2O3出现，从背散射分析可以发现，Y原子有着明显的增强扩散和外扩散效应，Y离子的深度分布已达620nm，远大于LSS理论的预计值，注入层钇铝原子比可达到17%-24%，连续铝合金层已经形成。     

泰勒定理的一个证明方法

证明拉格朗日型余项的泰勒定理有很多方法。本文介绍一种借助拉格郎日中值定理和积分中值定理用积分法来证明的方法,所得的定理条件与结论都较强。但条件是极易满足的,结论强则便于用以研究问题,具有很大的实用性。     

论图书馆学学风建设

简单归纳了目前图书馆学研究中存在的主要问题，分析了学术风气对学术研究的影响，重点探讨了搞好图书馆学学风建设的有关问题。