SiC-Al2O3-SiO2复合陶瓷涂层组织结构及抗烧蚀性能研究

目的提高C/C复合材料的抗氧化性能。方法采用大气等离子喷涂在C/C复合材料表面制备SiC-Al_2O_3-SiO_2(SAS)复合陶瓷涂层,并选用氧-乙炔在1500℃对涂层进行抗氧化烧蚀性能考核。利用XRD、SEM、EDS等检测分析手段,对团聚粉末和球化粉体以及烧蚀前后涂层的成分及组织进行检测。结果经过等离子球化处理后,三种粉体流动性为90 s/50 g左右,粉末松装密度为1 g/cm~3左右。与团聚的SiC-Al_2O_3-SiO_2粉体相比,粉末流动性提升了20%左右,松装密度提高了20%,更加适宜等离子喷涂工艺。采用球化处理SiC-Al_2O_3-SiO_2粉体制备得到的涂层组织明显优于采用团聚粉体制备的涂层,涂层致密区域明显增大,内部缺陷数量和尺寸减少。在1500℃烧蚀600s后,SiC-36%Al_2O_3-4%SiO_2涂层具有最佳的抗烧蚀效果,涂层整体完整,质量烧蚀率为1.62×10~(-4) g/s。结论 SiC-Al_2O_3-SiO_2体系解决了等离子喷涂制备SiC涂层过程中沉积率低、SiC分解的问题。SiC-Al_2O_3_-SiO_2涂层具有良好的抗氧化烧蚀效果,烧蚀过程中SiO_2和Al_2O_3形成的莫来石相具有良好的高温稳定性、抗热震性以及较低的热膨胀率和氧扩散率,可以进一步提高涂层的抗氧化烧蚀效果。     

液相等离子喷涂制备Au-WO3复合涂层及其气敏机理

目的提高WO_3基涂层的气敏性能。方法以WCl_6为前驱体原料,加入一定量的纳米Au颗粒制成稳定的喷涂浆料,采用液相等离子体喷涂技术制备出Au掺杂的WO_3基复合涂层。通过扫描电子显微镜(SEM)及其附带的能谱仪、X射线衍射仪(XRD)等对Au-WO_3复合涂层的微观结构进行表征。通过自主搭建的气敏性能测试系统对所制备Au-WO_3复合涂层的气敏性能进行测试,并探讨了涂层的气敏机理。结果前驱体液滴在等离子体热源作用下发生溶剂蒸发、WO_3形核、结晶和长大等一系列反应,随后形成的WO_3固体粒子发生熔化或半熔化,并加速撞击到基体表面形成涂层。在同等条件下,喷涂距离对WO_3气敏涂层的结晶度和形貌有很大影响,适宜的喷涂距离(170 mm)下获得的涂层结晶完整且晶粒细小(20～50 nm),有利于涂层气敏性能的发挥。Au-WO_3复合涂层的气敏性能均显著优于纯WO_3涂层。结论复合涂层气敏性能的改善归因于涂层中Au和WO_3界面处所形成的肖特基结使复合涂层的导电性降低,接触势垒高度增加,初始电阻值变大。     

La2O3改性Ti/MoS2镍基复合涂层微观组织和 摩擦学性能研究

目的 为提升Ni60A+Ti/MoS2复合涂层的力学性能和摩擦学性能。方法 利用激光熔覆技术在HT270灰铸铁表面制备了La2O3改性镍基自润滑复合涂层,通过硬度测试、摩擦磨损实验、XRD测试分析和扫描电镜分析,对比分析了La2O3添加量对复合涂层的微观组织、相组成、显微硬度和室温及200 ℃条件下摩擦学性能的影响。结果 La2O3改性后的涂层主要由CrNiFeC、NiTi、(Fe,Cr)7C3、Cr7C3、TiC、Ti2CS、MoS2相和La2O3组成。添加La2O3后可以明显细化晶粒,使组织更加均匀致密,提高了熔覆层显微硬度及耐磨性。当La2O3的添加量为1.0%时,涂层的硬度值最高达776HV0.2。La2O3改性后,涂层的摩擦学性能也得到了优化。室温时,1.0%La2O3涂层的磨损失重仅为1.8 mg,摩擦系数为0.48,与未添加La2O3的涂层相比,磨损失重降低了47.1%,摩擦系数也明显降低;200 ℃高温磨损时,1.0%La2O3涂层的磨损失重降低了41.3%,摩擦系数降低到0.50。结论 La2O3的加入可以有效提高涂层的减摩性和耐磨性等摩擦学性能,同时还能优化涂层的组织结构和硬度等力学性能。采用激光熔覆技术制备的La2O3改性镍基涂层,力学性能和摩擦学性能得到有效提高。     

等离子喷涂Cr2O3/TiO2高温氧化物陶瓷 复合涂层的微观组织及电化学性能

目的 通过等离子喷涂工艺,在油气管道X70管线钢表面制备出Cr2O3/TiO2高温氧化物陶瓷复合涂层,研究该涂层的微观组织与电化学性能。方法 采用9MC Plasma Control Unit等离子喷涂系统,基于线切割尺寸为40 mm×24 mm×6 mm的X70管线钢基体表面,沉积Cr2O3/TiO2高温氧化物陶瓷复合涂层。利用金相显微镜和扫描电子显微镜观察该复合涂层的微观组织与形貌,利用X射线衍射仪分析该复合涂层的物相组成,利用电化学工作站测定该复合涂层的电化学腐蚀性能。结果 Cr2O3/TiO2高温氧化物陶瓷复合涂层由完全熔化区和半熔化区双态组成,呈典型的等离子喷涂层状结构,层与层之间结合较紧密,分布着富Cr2O3沉积区与富TiO2沉积区,无相变产生,完全熔融的TiO2液相可嵌入到未完全熔融的Cr2O3结构间隙中形成固溶结构。经电化学腐蚀性能测试,其自腐蚀电位介于-0.4 ~ -0.3 V之间,高于X70管线钢基体的自腐蚀电位-0.6 ~ -0.5 V,腐蚀倾向滞后,表现出好的抗腐蚀性能。结论 研究选取的等离子喷涂参数较合适,并成功制备出了能明显提高油气管道X70管线钢抗电化学腐蚀性且组织分布均匀的Cr2O3/TiO2高温氧化物陶瓷复合涂层。     

DCOIT复合Zn-Ni合金抗菌镀层的制备及其耐SRB腐蚀性能研究

目的 提高Zn-Ni合金镀层的耐微生物腐蚀性能。方法 在硫酸盐电镀液中添加梯度浓度的4,5-二氯-N-辛基-4-异噻唑啉-3-酮（DCOIT）,利用恒电流沉积方法,在碳钢表面阴极电沉积获得DCOIT复合Zn-Ni合金镀层。通过电沉积电位监测与电流效率计算评价DCOIT对电沉积过程的影响,利用扫描电子显微镜、电子能谱、X射线晶体衍射等研究DCOIT对Zn-Ni复合镀层形貌、结构与Ni含量的影响,使用傅里叶红外吸收光谱和荧光显微观察法验证DCOIT的成功复合及复合镀层的抗菌性能,最后将DCOIT复合Zn-Ni合金镀层暴露于硫酸盐还原菌（SRB）中,监测菌液的pH与菌体浓度,同时计算镀层的腐蚀速率,并观察镀层的腐蚀形貌,评价复合镀层的耐SRB腐蚀性能。结果 DCOIT在电沉积过程中会吸附在沉积表面,造成沉积电位负移,并略微降低了电流效率。DCOIT的添加显著改变了复合镀层的形貌、结构与Ni含量,其Ni含量与DCOIT的添加量呈线性增长关系,导致其晶体结构转变。DCOIT以有效形式存在于复合Zn-Ni合金镀层中,并显示出抗菌性能,DCOIT添加量为2 mmol/L时,镀层中的复合量最高,抗菌性能最好。最后,DCOIT复合Zn-Ni合金镀层能有效抑制环境中SRB的生长与代谢,自身腐蚀速率减慢,耐蚀性能明显增强。结论 DCOIT能够以有效形式复合于Zn-Ni合金镀层内部,并有效提高了镀层的抗菌性能,使其获得增强的耐SRB腐蚀性能。     

电镀Ni-P-Ti3C2Tx合金镀层的制备以及性能研究

目的提高Ni-P合金镀层的硬度及腐蚀防护性能。方法块体Ti3AlC2颗粒经过氢氟酸的刻蚀作用得到二维层状结构的Ti_3C_2T_x材料,并通过电沉积技术将其掺杂到Ni-P合金镀层中,从而制备出Ni-P-Ti_3C_2T_x复合合金镀层,研究复合合金镀层的成分、表面形貌、表面接触角和硬度,并结合动电位极化曲线以及尼奎斯特阻抗图,分析Ti_3C_2T_x颗粒掺杂对Ni-P合金镀层性能的影响。结果通过深入研究复合合金镀层的性能,发现随着Ti_3C_2T_x颗粒掺杂量的增加,Ni-P-Ti_3C_2T_x合金镀层的表面粗糙程度不断增加,这可能是由于导电的Ti_3C_2T_x颗粒使得合金镀层的树枝状结晶增加,而且合金镀层的表面接触角增大,对于提高合金镀层的腐蚀防护性能有很大的促进作用。由于Ti_3C_2T_x颗粒的掺杂,合金镀层的显微硬度得到了提高,这主要是依靠于弥散增韧的作用以及有限的晶界。Ni-P-Ti_3C_2T_x合金镀层的腐蚀防护性能随着Ti_3C_2T_x颗粒掺杂量的增加,出现了先增加后减小的趋势。结论 Ti_3C_2T_x颗粒的掺杂对提高Ni-P合金镀层的硬度以及腐蚀防护性能有一定的作用。     

无人机技术在工程建设领域的应用研究

建设领域的应用现状,在梳理无人机技术基本原理、“无人机性能研究?技术初步交叉融合?技术广泛交叉融合”3 个发展阶段的基础上,分析无人机技术在工程项目不同阶段的应用现状及未来应用前景,无人机是很好的自动化采集工具,与三维点云技术密不可分,通过三维影像技术在厦门地铁三号线车站大型施工场地的应用实践,对无人机辅助工程项目施工阶段的场地布置和进度管控中的技术可行性进行探讨,并提出有效利用无人机开展三维建模工作的建议。     

Fuzzy‐sliding mode control of nonlinear smart base‐isolated building under earthquake excitation

In this paper, the effectiveness of the fuzzy sliding mode control strategy on three‐dimensional benchmark building with smart base isolation under seismic excitation has been examined. One of the appropriate control theories for such this nonlinear system is the sliding mode control theory; discontinuous sliding mode theory has weakness such as chattering phenomena. In this paper, we used a combination of fuzzy logic and sliding mode theory for the deletion of this defect. The proposed control theory has been scrutinized by applying on lately developed nonlinear three‐dimensional base‐isolated benchmark building. This building because of the three‐dimensional nature, coalescing of lateral and torsional responses, continuity of responses of the superstructure, and base is modeled with three degrees of freedom on every floor. In this building eight actuators assigned only at the base level and in the two directions (x, y). In other words, 16 actuators are located underneath the structure. Furthermore, the base isolation system has been modeled by considering lateral coupled equations for a better examination of the performance of the system. The results indicate that reduction of control performance is remarkable. Also, utilizing proposed control theory can decrease the responses of building in two main directions and, particularly, in the rotational degree of freedom.     

3D reconstruction of existing concrete bridges using optical methods

Routine bridge inspections usually consist of visual observations. These inspections are time-consuming and subjective. There is a need to identify new inspection techniques for infrastructure that reduce traffic disturbance, and improve the efficiency and reliability of the acquired data. This study compared the performance of three different imaging technologies for the three-dimensional (3D) geometric modeling of existing structures: terrestrial laser scanning, close-range photogrammetry, and infrared scanning. Each technology was used to assess six existing concrete railway bridges. The technologies were compared in terms of geometric deviations, visualization capabilities, the level of the inspector’s experience, and degree of automation. The results suggest that all methods investigated can be used to create 3D models, however, with different level of completeness. Measurements such as span length, deck widths, etc. can be extracted with good accuracy. Although promising, a full off-site inspection is currently not feasible as some areas of the bridges were difficult to capture mainly due to restricted access and narrow spaces. Measurements based on terrestrial laser scanning were closer to the reality compared to photogrammetry and infrared scanning. The study indicates the no special training is needed for photogrammetry and infrared scanning to generate a 3D geometric model.     

A simplified method for instability and second‐order load effects of framed structures: Story‐based approach

Several building codes such as ANSI/AISC 360‐16 and EC3 EN 1993‐1‐1 require the use of a proper design method to consider instability and second‐order load effect problems for individual system elements and the entire structural system. Various methods are available to assess stability. All of these methods should consider P‐Δ and P‐δ effects (second‐order effects). The following calculation procedures are presented in this study: (a) a simplified method is developed for P‐Δ and P‐δ analysis in regular frames under the effect of constant axial loads to obtain story drifts and end moments; (b) this method can be applied to an entire building or any individual story, that is, story‐based design is possible; and (c) column effective length factors are obtained for individual columns. In addition, design tables are presented.