Effect of intermetallic phases on the anodic oxidation and corrosion of 5A06 aluminum alloy

Intermetallic phases were found to influence the anodic oxidation and corrosion behavior of 5A06 aluminum alloy. Scattered intermetallic particles were examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) after pretreatment. The anodic film was investigated by transmission electron microscopy (TEM), and its corrosion resistance was analyzed by electrochemical impedance spectroscopy (EIS) and Tafel polarization in NaCl solution. The results show that the size of Al-Fe-Mg-Mn particles gradually decreases with the iron content. During anodizing, these intermetallic particles are gradually dissolved, leading to the complex porosity in the anodic film beneath the particles. After anodizing, the residual particles are mainly silicon-containing phases, which are embedded in the anodic film. Electrochemical measurements indicate that the porous anodic film layer is easily penetrated, and the barrier plays a dominant role in the overall protection. Meanwhile, self-healing behavior is observed during the long immersion time.     

液体超声驻波声场实验研究

研究了以蒸馏水为介质的驻波声场对微小颗粒群的作用,观察了颗粒群的运动规律,并应用声流和声辐射压力理论对其进行分析.运用谱分析方法,探讨了驻波声场中的空化现象.结果表明,大部分颗粒在声压波腹处聚集,而在声压波节处明显出现了高次谐波,说明空化效应发生在声压波节处.     

浓雾天气气溶胶颗粒物的输运和转化特性

近年来,随着城市建设和经济的发展,气溶胶颗粒物污染问题日益严重,尤其是城市浓雾天气,颗粒物成为首要污染物.因此,消除雾污染,净化空气,引起人们的关注.介绍了气溶胶颗粒物和雾的基本特征,以及雾层内气溶胶颗粒物的湍流扩散、化学转化特性及动力学特性,阐述了有关气溶胶颗粒物输运问题的国内外研究概况,展望了未来研究的方向.     

复合吸水颗粒深部液流转向剂注入性研究

由于吸水网络与控制网络的互穿结构,复合吸水材料颗粒具有吸水膨胀速度可控、吸水后强度高的特点。通过填砂管模型、变径管模型研究了复合吸水颗粒深部液流转向剂的注入特性、吸水后在孔喉中的运移情况。实验结果表明：在粒径小于孔喉尺寸的前提下,未吸水膨胀前颗粒可以顺利注入;吸水后即使颗粒直径大于孔喉直径也可以通过拉伸变形顺利通过,通过后立即恢复原状。注入过程中填砂管渗透率降低,颗粒膨胀后渗透率进一步降低,颗粒膨胀后在驱替压力足够大的情况下依然可以在填砂管微孔中运移。     

冻融循环作用下橡胶颗粒沥青混合料耐久性试验研究

以AC—13连续型密级配为基础,以橡胶颗粒代替部分集料的形式加入到沥青混合料中,制备橡胶颗粒量掺量为1%~3%的橡胶颗粒沥青混合料。在冻融循环条件下测定混合料的空隙率,并进行冻融劈裂试验,研究冻融循环作用下橡胶颗粒沥青混合料的耐久性。试验结果表明:随着冻融循环次数的增加,沥青混合料的劈裂抗拉强度逐步降低,空隙率逐步变大,两者相关性较大;同等条件下,随着橡胶颗粒掺量的增加,沥青混合料的劈裂抗拉强度逐渐降低,空隙率逐渐增大。橡胶颗粒的掺加在一定程度上降低了沥青混合料的劈裂抗拉强度,2%掺量下的橡胶颗粒沥青混合料劈裂抗拉强度比最优。     

钼酸镧超细微粒催化剂的合成及表征

以柠檬酸为络合剂,采用溶胶-凝胶法合成了La2(MoO4)3超细微粒催化剂,使用DTA-TG、IR、XRD以及BET比表面测试等表征手段,考察了制备条件与热处理条件对复合氧化物超细微粒形成、结构和表面积的影响。结果表明：本文法制备的La2(MoO4)3复合氧化物的比表面积远远大于共沉淀法制得的类似样品的比表面积,在氮气气氛中分解La2(MoO4)3凝胶中的柠檬酸,可有效地避免柠檬酸分解发生氧化燃烧而引起微粒烧结。     

Annealing crystallization and catalytic activity of ultrafine NiB amorphous alloy

Annealing crystallization of ultrafine NiB amorphous alloy prepared by the chemical reduction method was studied by DTA, XRD and XAFS techniques. The XRD and XAFS results have revealed that the crystallization process of ultrafine NiB amorphous alloy proceeds in two steps. First, ultrafine NiB amorphous alloy is crystallized to form metastable nanocrystalline Ni₃B at an annealing temperature of 325℃. Second, the nanocrystalline Ni₃B is further decomposed into crystalline Ni at 380℃ or higher tempera ture, the local structure around Ni atoms in resultant product is similar to that in Ni foil. It was found that the catalytic activity of nanocrystalline Ni₃B for benzene hydrogenation is much higher than that of ultrafine NiB amorphous alloy or crystalline Ni. The result indicates that the active sites of nanocrystalline Ni₃B for benzene hydrogenation are composed of both Ni and B with proper geometry configuration.     

Anti-aggregation dispersion of ultra fine particles by electrostatic technique

The dispersion of ultrafine particles in the air can be achieved by mechanical method or surface modification. In this work, the electrostatic technique was first employed for anti-aggregation of ultrafine particles. When the relative humidity of the air is within the region of 70%-75%, effective storage time of ultrafine particles can reach 72 h after treatment by the electrostatic technique. The experimental results showed that this technique imparted ultrafine particles much more pronounced anti-aggregation property. In the dry air, the critical diameter of ultrafine particles anti-aggregated by the electrostatic technique is the function of particle property and charging field intensity. The critical diameter is inversely proportional to the square of the charging field intensity.     

超重力法合成纳米碳酸钙的研究(Ⅰ)最佳反应时间的确定

采用红外光谱法动态跟踪研究在超重力法下合成纳米碳酸钙的整个碳化过程。实验表明,该方法得到的结果符合常规pH计与电导仪记录的转化点,并与电镜形貌分析观察到晶形完全转化为立方型的反应时间相吻合。     

橡胶颗粒沥青混合料低温性能影响因素研究

通过对橡胶颗粒沥青混合料进行低温弯曲试验,并运用统计学检验和灰熵法对试验结果进行分析。结果表明:对于不同掺量橡胶颗粒的沥青混合料,掺加3%橡胶颗粒能显著提高沥青混合料的低温性能,其灰熵关联度顺序为:沥青用量>流值>毛体积密度>空隙率。