聚酯/聚醚型聚氨酯互换膜材的制备与应用

为了优化聚氨酯(PUR)包膜尿素控释性能,采用多亚甲基多苯基异氰酸酯分别与聚酯和聚醚多元醇按不同配比混合,依照不同次序先后喷涂在尿素颗粒表面制备聚酯型和聚醚型PUR互换层包膜尿素并利用分光光度法研究其控释性能。通过接触角、热重分析和扫描电子显微镜对膜材的润湿性、热稳定性和形貌进行了表征,并采用傅立叶变换红外光谱分析了尿素释放过程中膜层的结构变化。结果表明,聚酯型PUR的疏水性弱于聚醚型PUR,但热稳定性高于后者;两者的包覆次序影响PUR包膜尿素的控释效果,聚酯型PUR为外层、聚醚型PUR为内层时控释性能优良,当两者包覆比例(质量比)为1.5∶1.5时,释放期最长可达84 d。     

A review of the operating limits in slot die coating processes

Slot die coating is a pre‐metered process commonly used for producing thin and uniform films. It is an important film fabrication method for applications where precise coating is required. A major concern in slot die coating processes is how to determine the operating limits to set the appropriate range of operating parameters, including coating speed, flow rate, vacuum pressure, coating gap, liquid viscosity and surface tension, etc. Operating limits directly determine the effectiveness and efficiency of the process. In this article, the current state of academic research on operating limits in slot die coating processes is reviewed. Specifically, the theories, mechanisms, and empirical conclusions related to the limits on vacuum pressure, the low‐flow limit, the limit of wet thickness for zero‐vacuum‐pressure cases, the limit of dynamic wetting failure, and the limits of coating speed for a specific flow rate are reviewed. The article concludes with some recommendations for future work. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2508–2524, 2016     

Preparation and Characterization of Silver‐Doped Cu(In,Ga)Se2 Films via Nonvacuum Solution Process

Cu(In,Ga)Se₂ films doped with different contents of silver ions (Ag⁺) were successfully prepared using nonvacuum spin coating followed by selenization at elevated temperatures. Increasing the Ag⁺ ion content increased the lattice parameters of the chalcopyrite structure, and shifted the A1 mode in the Raman signals to low frequencies. The band gaps of the prepared (Ag,Cu)(In,Ga)Se₂ (ACIGS) films were considerably increased, thereby increasing the open‐circuit voltage (V_oc) of the solar cells. As Ag⁺ ion content increased, the microstructures of ACIGS films became densified because the formed (Cu,Ag)₂In alloy phase with a low melting point facilitated liquid‐phase sintering. The evaporation of selenium species was correspondingly suppressed in the films during selenization, thereby reducing the selenium vacancies. The improvement in the microstructures and the defects of ACIGS films increased short‐circuit current (J_sc) and fill factor of the solar cells. The spectral response of the solar cells was also enhanced remarkably. This study demonstrated that incorporation of Ag⁺ ions into Cu(In,Ga)Se₂ films substantially improved the efficiency of the solar cells.     

Fracture Characteristics and Damage Evolution of Coating Systems Under Four‐Point Bending

The fracture and damage behaviors of ceramic coating/alloy substrate systems under four‐point bending were investigated using a scanning electron microscope to observe in situ tests. Both the thin and thick coatings fractured by tensile instability at the pure bending sections, and multiple transverse cracks that were vertical to the interface occurred in the coatings. The average crack spacing was greater for the thick coatings than for the thin ones. A catastrophic failure model was developed to explain the damage evolution behavior of the coatings. The damage was found to increase sharply near the failure point.     

占空比对Fe-Ni-Cr合金镀层成分及耐蚀性的影响

采用脉冲电沉积方法在黄铜基体上制备出纳米晶Fe-Ni-Cr合金镀层,并研究了占空比对其成分及耐蚀性的影响。结果表明:当占空比为50%时,制备的Fe-Ni-Cr合金镀层成分稳定,其中Cr的质量分数达到37.4%;晶粒尺寸约为12.6nm;在3.5%的NaCl溶液中的自腐蚀电位约为-200mV,自腐蚀电流密度约为0.27μA/cm2,电荷转移电阻约为12 000Ω/cm2,耐蚀性最好。     

湿法超声机械镀锌-铝层耐蚀性的研究

采用湿法超声机械镀设备制备了Zn-5%Al复合镀层。用多功能扫描电子显微镜及其配备的能谱分析仪观察并分析了复合镀层的形貌及成分,用划格法测试了复合镀层与基体间的结合强度,并用中性盐雾腐蚀试验法测试了复合镀层的耐蚀性。结果表明:湿法超声机械镀Zn-5%Al复合镀层表面平整、结合强度高、耐蚀性好,是一种综合性能优良的防护镀层。     

AZ31B镁合金复合镀镍层的制备及其耐蚀性研究

在AZ31B镁合金表面以化学镀镍/电镀镍两步法制备了复合镀镍层。采用SEM、XRD、划痕仪、电化学方法对复合镀镍层的微观形貌、成分、晶体结构、结合力、耐蚀性等进行了表征。结果表明:复合镀镍层结构致密、表面光亮、没有明显缺陷,与基体之间具有良好的结合力,且比单一化学镀镍层具有更好的耐蚀性。     

稀土离子对化学镀镍的影响

以镀液稳定性、镀速、镀层光泽度和镀层中磷的质量分数为评价指标,考察La3+、Nd3+和Y3+对柠檬酸体系化学镀镍的影响。结果表明:加入适量的稀土离子,可明显提高镀液的稳定性;当稀土离子的质量浓度为2~4mg/L时,可适当地提高镀速和镀层光泽度;当Y3+的质量浓度为4mg/L时,综合性能最佳。向镀液中添加稀土离子,可起到细化镀层晶粒和改善镀层性能的作用,但镀层中不含稀土元素。     

电镀层状锡工艺的研究

采用电沉积方法在酸性体系下制得具有层状结构的镀锡层。研究了主盐、明胶、HIT-905添加剂及电流密度对镀锡层外观的影响,确定了较优的镀液组成及工艺条件。在优化工艺下得到了具有明显层状结构的镀锡层。