高校学生欠费治理路径探究

受诸多因素的影响,国内许多高校财政拨款压减幅度较大,面临着突出的收支矛盾。建立健全学费和宿费拖欠治理机制,强化教育事业收入资金时效,切实做好学费和宿费清缴工作,将成为缓解高校收支矛盾和实现精细化管理的有效途径。文章通过梳理高校学生欠费治理的发展历史,分析了高校学生欠费的原因,提出高校学生欠费治理的对策建议,为切实解决高校学生欠费问题、缓解高校收支矛盾提供参考。

氮气流量对CrCN镀层摩擦学性能的影响

目的研究氮含量对Cr CN镀层结构和摩擦学性能的影响。方法采用微弧离子镀技术制备Cr CN镀层,通过改变氮气的流量来改变镀层中氮元素含量。利用扫描电子显微镜(SEM)和原子力显微镜(AFM)观察镀层的截面和表面形貌,采用划痕法对镀层与基体的结合强度进行评价,采用维氏硬度计测试镀层的显微硬度,利用针盘式摩擦磨损试验机测定镀层的摩擦系数。结果当通入的氮气流量逐渐增大时,镀层由致密细小的颗粒逐步演变为含微孔的柱状组织。当氮气流量为3 m L/min时,镀层中生成的弥散分布的硬质相具有显著的强韧化作用,镀层的膜基结合力和硬度分别达到最大值41 N和1476HV,摩擦系数略微增大。继续增大氮气流量后,镀层性能有所下降。结论通过控制氮气流量来控制镀层中氮元素的含量,可以显著优化镀层结构和性能,达到结合强度、硬度和摩擦系数的最优化配置。

表面处理技术对钛合金疲劳性能影响的研究进展

针对钛合金表面硬度较低、耐磨性较差、易高温氧化等缺陷,选择适当的表面处理技术能够使其得以改善。由于钛合金对疲劳性能十分敏感,在表面处理过后,对其疲劳性能有较大影响。因而本文归纳了钛合金表面处理的多种方法,如电镀、化学镀、热喷涂、激光处理、阳极氧化、微弧氧化、物理气相沉积技术等。根据钛合金疲劳断裂现状及表面改性技术的特点,讨论了表面技术的应用、材料的选择和结构的设计对钛合金基体疲劳性能的影响。分析并总结了涂层在疲劳断裂过程起到的作用及影响疲劳性能的的主要原因,展望了未来钛合金表面改性方法、涂层材料及结构的研究趋势。以期为制备高强度、耐摩擦磨损和提升钛合金基体疲劳性能的表面改性涂层提供参考。

Corrosion resistance of composite coating on magnesium alloy using combined microarc oxidation and inorganic sealing

The combined microarc oxidation (MAO) and inorganic sealing process was used to deposit a composite coating to improve the corrosion resistance of AZ31 magnesium alloy.The surface morphologies of the resulting duplex coatings were studied by SEM.Furthermore,the corrosion resistance of the coated Mg alloy substrates was investigated using electrochemical workstation and dropping corrosion test.The results show that the composite coating surface consists of Mg,Si,O and Na.It is difficult to deposit inorganic coating on a thick MAO coating surface.As the composite coating was solidified by CO2 under 175 °C,it exhibits a better corrosion resistance than the MAO monolayer,owing to the thick and compact inorganic coating.

Influence of aging modes on microstructure and mechanical properties of AZ80 magnesium alloy

The microstructure and mechanical properties of AZ80 magnesium alloy after solid solution and aging treatments were studied by using optical microscope （OM）, X-ray diffraction （XRD）, scanning electron microscopy （SEM） as well as tensile testing. The results indicated that β-Mg17Al12 phase was getting to distribute discontinuously along the grain boundary after treated at 395℃ ageing for 12 h followed by water-cooling, but it did not dissolve into α-Mg completely. The residualβ-Mg17Al12 phase distributed along the grain boundary and had block-like or island shapes. The size of α-Mg was getting to be coarsening but not significantly. The β-Mg17Al12 precipitates appeared in discontinuous and continuous pattems from supersaturated α-Mg solid solution after aged at 200℃. The precipitation patterns were associated with the aging time essentially. The tensile strength and elongation of the alloy increased significantly but the hardness and yield strength decreased after solid solution treatment. However, with the prolonging of aging time, the hardness and strength of alloy increased while the ductility decreased.

偏压对电弧离子镀CrAlN涂层微观结构及耐侵蚀性能的影响

通过在TC11钛合金上利用电弧离子镀技术制备了铬铝氮(CrAlN)涂层。采用X射线衍射(XRD),扫描电子显微镜(SEM),能量色散X射线光谱(EDS),纳米压痕仪等对CrAlN涂层微观结构和力学性能(如硬度和弹性模量)进行了分析。为了研究偏压对CrAlN涂层固体颗粒耐侵蚀性的影响,还进行了一系列固体颗粒侵蚀实验。结果发现,随着偏压从0 V增加至200 V,CrA1N涂层的择优生长取向逐渐从(200)转变为(111)晶面。硬度从15.1 GPa增加至接近20 GPa。同时,表面逐渐平整,大颗粒和针孔的数量减少,对CrAlN涂层的耐侵蚀性能均有一定影响。偏压150 V时,CrAlN涂层获得最小侵蚀速率,其在30°时为0.032μm/g,90°时为1.869μm/g。这些结果表明,选择适当的偏压,CrAlN涂层能够获得更优异的固体颗粒耐侵蚀性。