Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： Polyaniline/TiO2 nano composites with different weight ratios of polyaniline to TiO2 were synthesized using chemical oxidative polymerization through polymerizing polyaniline (PANI) onto the nano TiO2 surface. The prepared PANI/TiO2 composites were characterized by FTIR, XRD and SEM. Then PANI/TiO2/epoxy resin coating was prepared by blending epoxy resin with polyaniline/TiO2 nano powders, while coating formulation with excellent mechanical performance was acquired through orthogonal experiments and trial corrosion tests. The corrosion performance of X70 steel coated with the optimal coating was examined in S2- and Cl- containing solutions at different temperatures. The results show that there exists strong interaction between the nano TiO2 particle and PANI within the PANI/TiO2 composites. Many factors could affect the mechanical property of the coatings, according to their impact degree, which may be ranked as the following sequence: PANI＞TiO2＞curing temperature＞solvent content＞solvent ratio. The optimal PANI/TiO2/epoxy resin coating with excellent mechanical properties and corrosion performance could be acquired by an optimal process with the following parameters: the mass ratio of PANI to epoxy resin is 1 to 100; TiO2 to epoxy resin is 1 to 100; curing at 60 ℃. The content of solvent to epoxy resin is 5 to 10 and NMP/n-butanol=2/1(solvent molar ratio). Furthermore, at 72 h after immersion of the optimal coating in 3.5%NaCl solution at 65 ℃, a maximum appeared on its impedance vs time curve, whilst the coating keeps an excellent corrosion resistance even after immersion in 3%Na2S solution for 120 h at 80 ℃.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： TiAl-Nb alloys have been determined as the advanced direction for the development of the high temperature TiAl alloys, so being one of the advanced materials for turbines of aircraft engines and gas-burning power-generation plants. However, highly-Nb addition can lead to the complex solidification behavior of TiAl-Nb alloy and multi- phase microstructure, which is important for the mechanical properties during the alloy design. Bridgman type directional solidification experiments were conducted for Ti-46Al-(8, 9, 10)Nb alloy. The effect of the growth rate and Nb content on the microstructure, phase transition and microsegregation was investigated, and finally the selection diagram of the phase transition and the microstructure of the directional solidified TiAl-Nb alloy were obtained. The results show that the planar-cellular-dendritic evolution of solid-liquid interface can be observed with the increase of the growth rate. Meanwhile the fully b phase solidification changes to the peritectic solidification with the increase of the growth rate, and correspondingly the final microstructure is composed of the a2/g lamellar structure and a multiphase microstructure (B2 phase, a2/g lamellar structure) respectively. The increase of the b-stabilizer Nb content can promote the fully b phase solidification and the formation of the multiphase microstructure (B2 phase, a2/g lamellar structure). The contribution of the growth rate and the Nb content to the phase transition and the microstructure is connected with the solute segregation (S- segregation, b- segregation) closely. The increase of the S-segregation amplitude can easily promote the peritectic reaction, which always leads to the highly solute segregation and the concentrated distribution of plenty of B2 phase in the core of the dendrite. b-segregation is the mainly origin of the B2 phase formation, in which the Nb enrichment in the retained b phase directly determines the morphology and the dimension of the B2 phase. Finally according to the selection diagram of the solidification process and the microstructure of the Ti-46Al alloy with the growth rate and the Nb content, the high Nb content and the low growth rate during fully b solidification should be selected for the prefer microstructure with the homogeneous distribution and the low solute segregation.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-04 Cooperative journals: 《金属学报》
Abstract：通过Bridgman定向凝固技术对Al-12%Ni（质量分数）过共晶合金在1~100μm/s的生长速率范围内进行恒速定向凝固以及不同初始生长条件和变速比下的跃迁加速定向凝固实验，获得耦合共晶组织的条件。研究发现，生长速率为1μm/s时，经过一定距离生长后，组织中无单独生长的初生相，获得耦合共晶组织；而当生长速率为2～100μm/s时，初生Al3Ni相领先生长且呈现典型小平面生长特性。跃迁加速实验表明，跃迁加速前的初始组织对最终组织有决定性影响，只有当跃迁前的组织中无单独生长的初生相时，跃迁后才可在较高生长速率下获得耦合共晶组织。同时定向凝固可以有效提高Al-12%Ni合金的强度和塑性，跃迁加速获得的耦合共晶组织延伸率也得到进一步提高。
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