Ag^(+)改性沸石-聚氨酯涂料用于混凝土下水道微生物诱导混凝土腐蚀行为

微生物诱导混凝土腐蚀(MICC)是指硬化混凝土浆体中生物产生的硫酸与水化产物之间的化学反应,它将导致早期强度降低、劣化,甚至结构破坏。本文探讨了表面涂覆改性沸石聚氨酯胶凝材料的杀菌性能。研究了银改性沸石-聚氨酯涂层在硫氧杆菌接种的环境中8周的抗菌性能。通过分析pH值、光密度(OD)、硫酸盐产量和细菌数量来评估沸石-聚氨酯涂层在硫氧杆菌接种产生硫酸环境中的抗菌性能。对缺乏细菌附着和样品表面变形的微菌落、pH降低滞后、OD值增加和硫酸盐产量进行分析,结果表明,与未改性的聚氨酯涂层相比,加入银改性沸石的样品(不论沸石类型)均表现出抗菌性能。银改性沸石的抑菌性能是由于在水溶液中释放的银离子抑制了细菌的细胞功能,导致细胞损伤从而起到抑菌作用。

银对多孔Ti-30 at%Ta形状记忆合金的微观结构、力学性能、腐蚀行为和生物相容性的影响

本文采用粉末冶金技术和微波烧结工艺制备了xAg/Ti-Ta。采用光学和扫描电子显微镜(SEM)、X射线衍射仪(XRD)、压缩试验和形状记忆试验研究了xAg/Ti-30Ta(x=0,0.41 at%,0.82 at%和2.48 at%)形状记忆合金(SMAs)的热力学、力学和生物性能。结果表明,Ag的加入对颗粒的孔径和形状有显著影响,在Ag加入量为0.41 at%时,颗粒的最小孔径为11μm,相对密度为72%。断裂应力和应变随着Ag的增加而增加,Ag加入量为0.41 at%的合金断裂应力应变达到最大。0.82 at%Ag/Ti-Ta表现出更好的耐蚀性和生物相容性,具有与纯Ti和Ti6Al4V合金类似的性能,具备作为生物材料的应用前景。

自由锻Ti-Ni形状记忆合金的显微组织和超弹性（英文）

采用放电等离子烧结(SPS)法将元素钛粉和镍粉制备成Ti-51%Ni形状记忆合金(SMAs)。研究目的是采用自由锻二次加工以提高SPS合金的性能。对自由锻前后合金的显微组织、相变温度和超弹性进行比较。结果表明,自由锻可以显著提高Ti-Ni形状记忆合金的拉伸强度和形状记忆性能,自由锻后合金的韧性从6.8%提高到了9.2%,超弹性的应变范围从5%增加到7.5%,应变恢复速率从72%提高到92%。Ti-51%Ni合金显微组织中含有立方奥氏体相(B2)基体、单斜马氏体相(B19′)、第二相(Ti_3Ni_4,Ti_2Ni和TiNi_3)和氧化物相(Ti_4Ni_2O,Ti_3O_5)。自由锻后再经500°C时效处理的最终样品的马氏体相变温度向高温方向偏移,这是由于Ti_3Ni_4相(透射电镜下可以观察到)的析出而导致基体中Ni含量的减少。总之,自由锻可以提高Ti-51%Ni形状记忆合金的超弹性和力学性能。

Investigation of three steps of hot corrosion process in Y_2O_3 stabilized ZrO_2 coatings including nano zones

Phase transformation of tetragonal ZrO2 to monoclinic phase and also increment of bond coat oxidation kinetic（TGO thickening） can substantially restrict the life time of thermal barrier coating systems（TBCs）. So, nanostructured and conventional Y2O3 stabilized ZrO2 coatings were evaluated in fused V2O5-Na2SO4 salts during thermal exposure in air. Microstructural characterization showed lower hot corrosion products（monoclinic zirconia, YVO4 crystals） formation and reduction of TGO thickness in thermal barrier coating system consisting of nanostructured Y2O3 stabilized ZrO2（YSZ） top coat. It was found that inhomogeneities, pores and micro-cracks played a principal role in the molten salts infiltration into the YSZ coating during three steps of hot corrosion process. In the nanostructured YSZ coating with tri-model structure, nano zones which surrounded by fully molten parts could fill the aforementioned defects and could act as barrier for the oxygen and corrosive molten salts penetration into the TBC.

Effect of Y_2O_3 stabilized ZrO_2 coating with tri-model structure on bi-layered thermally grown oxide evolution in nano thermal barrier coating systems at elevated temperatures

Bi-layered thermally grown oxide （TGO） layer plays a major role in the spallation of Y2O3 stabilized ZrO2 （YSZ） layer form the bond coat in the thermal barrier coating （TBC） systems during oxidation. On the other hand, bi-layered TGO formation and growth in the TBC systems with nanostructured YSZ have not been deeply investigated during cyclic oxidation. Hence, Inconel 738/NiCrAlY/normal YSZ and Inconel 738/NiCrAlY/nano YSZ systems were pre-oxidized at 1000 °C and then subjected to cyclic oxidation at 1150 °C. According to microstructural observations, nanostructured YSZ layer over the bond coat should have less mi-cro-cracks and pinholes, due to the compactness of the nanostructure and the presence of nano zones that resulted in lower O infiltration into the nanothermal barrier coating system, formation of thinner and nearly continuous mono-layered thermally grown oxide on the bond coat during pre-oxidation, lower spinels formation at the Al2O3/YSZ interface and finally, reduction of bi-layered thermally grown oxide thickness during cyclic oxidation. It was found that pre-heat treatment and particularly coating microstructure could influence microstructural evolution （bi-layered TGO thickness） and durability of thermal barrier coating systems during cyclic oxidation.