面向海水冷却塔结构的纳米水泥基热电超材料及其智能阴极保护与劣化自监测机制

Under humid but hot, condensation salt, acid pollution condition, seawater cooling tower structure and the corresponding protection mortar frequently seriously corrode and crackly deteriorate, their serve lives are urgent to improve. Here, Basis on effectively relieving shrinkage cracking and anti-permeability durability of protection mortar, Carbon nanotube (CNT) with superior mechanical/electrical properties, conductive polyaniline (PANI), nanoscale MnO2 with high thermoelectric efficiency are employed to compatibly co-modify cement mortar, to fabricate nano cement-based thermal-electric meta-materials (CMCTM) with high potential and low resisitivity; “Three-in-One” multifunctions coupling mechanisms on intrinsic toughening, thermoelectric generating, mechanical-electric sensing of CMCTM while its inner and outer layer existing temperature difference are revealed combined with fiber bridging and electron transportation effect of CNT, conjugated conducting effect of PANI, Seebeck and quantum confinement effect of MnO2; CMCTMs are assembled into thermal-electric module, serving as cathodic protection (CP) power, an electrochemistry circuit are established to evaluate the CP effect on steel bar in concrete corrosion solution, the mechanism of the corrosion self-immunity of reinforcement is clarified; Combined with distributed monitoring node and microstrip antenna, self-monitoring integrating structure system for seawater cooling tower structure is constructed based on CMCTM thermo-electric module (mechano-electric sensor), and its durability assessment and serve life model is setup according to long-term responses on intelligent CP and damage self-monitoring.

处于高湿热、高盐污、酸结露环境下海水冷却塔结构及相应防护砂浆层常腐蚀剥落、劣化开裂，服役寿命亟待提升。本项目拟在有效缓解防护层收缩开裂及抗渗耐久的基础上，将力/电性能俱佳的碳纳米管（CNT）、导电聚苯胺（PANI）及高热电效率的纳米MnO2科学配伍来协同改性砂浆，制成具有高电动势、低电阻率的纳米水泥基热电超材料（CMCTM）；结合CNT纤维桥联与电子输运、PANI共轭导电以及MnO2塞贝克与量子约束效应揭示两侧存在温差时CMCTM拥有本征增韧、温差发电及力电传感 “三位一体”多元耦合功能的内在机理；将CMCTM集成热电模块充当阴极保护（CP）电源，搭建电化学回路评价对含混凝土腐蚀液钢筋CP效果，阐明钢筋腐蚀自免疫机制；结合分布式监测节点及微带天线，集成基于CMCTM热电模块（力电传感器）海水冷却塔自监测一体化结构体系，依据智能CP与损伤自监测长效响应机制建立其耐久性评估与寿命预测模型。

海工结构常会因钢筋腐蚀而过早失效。传统防腐法难以解决其结构钢筋腐蚀及防护层结垢、剥落开裂的问题，需要发展自带电源的阴极防护（CP）技术，并将防护层发展成感知一体化智能层等，提升海工结构服役寿命。可利用水泥基热电材料热电效应实现外加电流式CP的电流自供给。然而，传统水泥基热电材料的热电转换效率较低，且不具备结构服役中的劣化自监测特性。如若能将高性能热电组分掺入水泥基体中，利用其产生高量级的驱动电压，同时复合优异的电导组分，降低内阻提高热电转换效率的同时兼顾力电传感性能，则有望综合实现热电性能与力电传感性能，达到海工结构热电防护层CP与劣化监测的同步效果。.关键数据：1）当反应温度为180℃，反应时间为24h时，通过硫酸锰和过硫酸铵的水热反应获得直径70-80nm、直径500nm-1μm、晶型β-MnO2为主的nMnO2纳米颗粒。2）NTEC的热电性能随nMnO2掺量的增加而显著加强，0.2 wt% CNTs/5.0 wt% nMnO2的NTEC电导率、Seebeck系数、热电功率因数可分别达到0.231 S/cm、3612 μV/℃、301.4 μWm-1℃-2。3）NTEC的氯离子扩散系数（λc）仅为2.65×10-11m2/s，相较空白组下降了63.7%。4）结合相应塔菲尔极化曲线，经阴极保护后的NTEC腐蚀电流密度Icorr仅为7.58×10-2 μA/cm2，远比未保护的小很多，两者差值接近40%，腐蚀极化电压降低了60%，腐蚀概率大大降低。5）在各个腐蚀龄期下，含NTEC的阴极防护（UP）容抗弧直径更大，相位角更加稳定、低频区的|Z|值更大，表明其CP的作用已经产生并且有效。从EIS曲线发现，不含NTEC（NP）钢筋经过21d腐蚀后的Rct值仅为29.26 kΩ•cm2，而UP在同期却高达3232.93 kΩ•cm2，能够抑制腐蚀电荷转移。6）当CNTs的掺量为0.1 wt.%时，NTEC在循环荷载下的电阻率变化幅度最大，应力灵敏度、稳定度及线性度分别为1.28 %/MPa、3.90%、4.65%，能发展其用作感知一体化智能层。.科学意义：一方面，将可将NTEC集成热电发电模块，并结合电化学方法综合评价基于温差发电的NTEC热电模块直接用作海工混凝土钢筋阴极防护系统电流供给源。另一方面，将NTEC用作感知一体化智能层，进行海工结构劣化监测。