喷雾干燥YPSZ纳米结构热喷涂粉末材料制备及表征

YPSZ纳米结构粉末材料的研究是热喷涂制备YPSZ纳米结构涂层必须首先进行研究的问题。本文采用喷雾干燥方法制备适合于热等离子体喷涂的YPSZ纳米结构粉末原料,同时采用等离子体喷涂制备涂层。利用扫描电子显微镜分析晶粒大小、颗粒形貌,X射线衍射分析相组成,对喷雾干燥后粉末进行热重-差热分析,测定粉末的松装密度、振实密度及流动性。结果表明制备的YPSZ粉末材料具有实心、流动性好、松装密度高、振实密度高、球形度高、单斜相少等优点,采用热等离子体喷涂沉积制备YPSZ纳米结构涂层。     

热处理对喷雾干燥制备的Al2O3纳米团聚体粉末的影响

对喷雾干燥和经不同温度热处理后的Al2O3纳米团聚体粉末的松装密度及振实密度进行了测试,通过扫描电镜观察分析了团聚体粉末颗粒的大小和形貌以及纳米晶颗粒的大小,采用X射线衍射分析了热处理后粉末的相组成.实验结果表明,在1050～1250℃热处理后的Al2O3纳米团聚体粉末颗粒仍近似球形,粒径在10～90μm之间.随着热处理温度升高,纳米团聚体大颗粒表面发生塌陷,大颗粒之间发生连接,大颗粒内部纳米颗粒明显长大.低于1250℃热处理后的粉末流动性好,振实密度高,适于等离子体喷涂制备纳米结构涂层.     

热喷涂用纳米结构Al_2O_3/TiO_2/SiO_2团聚体粉末的研究

对喷雾干燥和不同温度热处理后Al2O3/TiO2/SiO2纳米团聚体粉末的流动性、松装密度及振实密度进行了测试,对喷雾干燥后的粉末进行了热重-差热分析,通过扫描电镜观察了粉末颗粒形貌和大小,采用X射线衍射分析了不同温度热处理后粉末的相组成,并对粉末的综合性能进行了比较。实验结果表明:在1000～1450℃热处理后的Al2O3/TiO2/SiO2纳米团聚体粉末颗粒仍近似球形,粒径在10～100μm之间。随着热处理温度升高,纳米团聚体大颗粒表面发生塌陷,大颗粒之间发生连接,大颗粒内部纳米颗粒明显长大。低于1250℃热处理后的粉末流动性好,振实密度高,适于等离子体喷涂制备纳米结构涂层。     

以蔗糖为前驱体制备TiC/Fe复合涂层

以TiFe粉和蔗糖为原料,通过蔗糖的热分解碳化制备Ti-Fe-C系反应热喷涂复合粉末,利用普通氧乙炔火焰喷涂成功制备出TiC/Fe复合涂层.采用XRD、SEM和TEM等对喷涂粉末和涂层的组织结构、涂层中的TiC颗粒进行了分析.研究结果表明:TiC/Fe复合涂层主要由TiC颗粒均匀分布于Fe基体中的复合强化片层构成,片层中TiC颗粒呈球形或近球形,粒径约为50nm;纳米级TiC颗粒增强的复合强化片层占涂层体积的60%以上.     

HVOF喷涂纳米WC-17Co涂层组织结构及力学行为研究

利用超音速火焰喷涂(HVOF)技术制备了普通、超细纳米WC-17Co涂层.研究了喷涂粉末、涂层的微观组织结构和物相成分,测试了涂层的显微硬度、弹性模量、断裂韧性.研究表明,纳米WC-17Co涂层中形成了纳米尺度的胞状结构和长条状结构,并有网状的非晶结构生成.WC-17Co涂层表面均匀致密,3种涂层均是由熔化再结晶区、半熔化区和未熔化区等构成.涂层中条带结构不明显,明显区别于等离子涂层.纳米涂层组织结构更致密,碳化物颗粒分布更均匀.3种涂层中,WC都是主相,W2C、Co6W6C的含量很少.纳米涂层的显微硬度、弹性模量、断裂韧性最高.     

钼基体上真空等离子体喷涂钨涂层的研究

采用真空等离子体喷涂(VPS)技术制备出厚度超过0.8 mm的金属钨涂层,并对涂层进行了高温热处理.结果显示:金属钨涂层主要呈层状结构,其密度可达到理论密度的98%以上;工艺参数对喷涂涂层性能有较大影响,特别是对涂层密度、结合强度有影响;高温热处理引起界面结构变化,形成钨钼混合层,且再结晶形成细小的晶粒;和CVD方法以及常压等离子体喷涂方法制备的钨涂层相比,低压等离子体喷涂具有明显的优势.     

等离子喷涂溶胶制备纳米ZrO2涂层工艺及涂层结构表征

采用等离子喷涂溶胶工艺制备了氧化锆纳米涂层.并用x射线衍射仪、扫描电镜观察了溶胶干燥粉末和涂层的物相组成及显微结构.结果表明,溶胶自然干燥后为非晶态,通过加热可以得到晶体结构,等离子喷涂形成的涂层为单斜相与立方相的混合晶体结构.制备的涂层由熔化较好的颗粒形成的致密块体和微裂纹组成.本方法能够得到晶粒很细的纳米结构涂层.     

热障涂层用La2O3、Y2O3共掺杂ZrO2陶瓷粉末的制备及其相稳定性

采用反向化学共沉淀法制备了热障涂层用La₂O₃-Y₂O₃-ZrO₂（LaYSZ）原始复合粉末, 将原始粉末团聚造粒和热处理后得到适于等离子喷涂的团聚粉末. 采用电感耦合等离子体原子发射光谱（ICP-AES）、扫描电子显微镜（SEM）、霍尔流速计、X射线衍射（XRD）等方法分别对LaYSZ的化学组成、微观形貌、流动性和松装密度、高温相稳定性进行了研究. 结果表明: LaYSZ团聚粉末室温呈四方ZrO₂结构, 在1150℃热处理2h后为致密的球形或近球形颗粒, 粉末流动性较好, 适于等离子喷涂. LaYSZ团聚粉末在1300℃热处理100h后仍保持单一的四方ZrO₂晶型, 而8YSZ中有12mol%的四方相转变为单斜相; LaYSZ在1400℃热处理100h后, 单斜相含量为2mol%, 而8YSZ中单斜相含量达到47mol%, 表明La₂O₃、 Y₂O₃共掺杂稳定ZrO₂较单一Y₂O₃ 稳定ZrO₂具有更好的高温相稳定性.     

SPPS纳米结构涂层的研究进展

对溶盐前驱体注入等离子体液相喷涂制备纳米结构涂层的研究进展进行了综述.介绍了液体原料注入等离子体喷涂的过程及机理,对采用液相喷涂方法制备纳米结构涂层的优异性能以及存在的问题进行了分析,并对其应用及进一步的发展进行了展望.     

大气和低压等离子喷涂氧化铝涂层

根据大气(APS)和低压等离子喷涂(LPPS)的特点,采用两种不同的高纯氧化铝粉末制备了高纯氧化铝涂层.分别采用XRD和SEM对两种涂层的相和结构进行了研究,对涂层的显微硬度和断裂韧性进行了评价,并对涂层制备工艺和性能的关系进行了分析.结果表明:低压等离子喷涂制备的高纯氧化铝涂层韧性和致密性明显优于常压喷涂氧化铝涂层.     

热喷涂纳米结构涂层技术的研究进展

与传统材料的热喷涂涂层相比,纳米结构涂层在力学和摩擦学等方面的性能有了一定的提高.作者综述了国内外在应用热喷涂技术制备纳米结构涂层方面的研究进展.介绍了纳米结构喂料的制备、热喷涂纳米结构涂层的构筑方法、涂层的特殊性能以及应用情况.从目前国内外的情况来看,热喷涂纳米结构涂层技术的研究取得了较大的进展.随着技术、工艺的不断完善,其必将在很多领域取代传统的涂层.     

Application Study on Ceria Based Thermal Barrier Coatings

The industrial application of APS sprayed YPSZ coatings for thermal insulation is established in several branches. As the main potential to increase the efficiency of combustion processes is thermal efficiency and the state‐of‐the‐art systems are limited to surface temperatures below 1200°C for long term applications, there is interest in concepts, that allow an increase of the process temperature. Ceria and ceria based ceramics show an outstanding potential for use at temperatures exceeding 1200°C. A triple‐layer thermal barrier system in consideration of the established system – MCrAlY bond coat and YPSZ – and an additional ceria based top coating are investigated. TBC systems with two different ceria powders are produced by APS and HVOF spraying and evaluated with concern to the microstructure, bond strength, thermal shock behaviour and long term compatibility of the constituents. HVOF sprayed coatings contain more oxygen, are more dense than APS sprayed coatings and do not show segmentation due to cracks perpendicular to the surface. APS sprayed pure ceria coatings show a columnar morphology inside single splats forming the coating. The bond between YPSZ and ceria and the total bond strength of the thermal barrier system exceeds the cohesion inside the ceria coating. The thermal shock resistance of ceria coatings with high silica and sulphur content is low. Long term sintering investigations prove the compatibility of ceria and YPSZ at 1150°C.     

热喷涂纳米结构涂层的研究现状

介绍了国内外喷涂用纳米结构喂料的制备方法以及在应用热喷涂技术制备纳米结构涂层方面的研究进展.与传统材料的热喷涂涂层相比,纳米结构涂层在力学、摩擦学以及耐磨防腐蚀性能方面有了较大的提高.     

材料表面摩擦学设计新方法——纳米结构耐磨涂层的组装

总结了组装纳米耐磨结构涂层的产生背景、材料学基础、意义及国内外研究现状，介绍了间接法组装纳米结构耐磨涂层所需纳米结构喂料的组成、构筑方法和加工步骤，综述了直接法和间接法组装纳米结构耐磨涂层的技术路线及工艺条件，并首次提出了将纳米低维材料的制备与纳米喂料的构筑有机的结合在一起的研究思想，进而设计了固相反应构筑法、液相反应原位喷雾干燥法等加工纳米结构喂料的新方法。     

梯度热障涂层热冲击性能研究

采用等离子喷涂的方法,分别获得了２ｍｍ ＺｒＯ２－ＮｉＣｒＡｌ和ＺｒＯ２－Ｎｉ／Ａｌ系梯度热障涂层。热冲击实验结果表明,两种涂层具有不同的失效机理。ＺｒＯ２－ＮｉＣｒＡｌ系的失效是由于基于基体氧化引起的涂层整体脱落;而ＺｒＯ２－Ｎｉ／Ａｌ系的失效是支径向裂纹扩展到Ｎｉ／Ａｌ底层氧化共同作用的结果。     

Microstructure and indentation mechanical properties of plasma sprayed nano-bimodal and conventional ZrO2–8wt%Y2O3 thermal barrier coatings

The nanostructured agglomerated feedstock used for plasma spraying was obtained by the nanoparticle reconstituting technique. Nanostructured and conventional ZrO₂–8wt%Y₂O₃ (8YSZ) thermal barrier coatings (TBCs) have been prepared by atmospheric plasma spraying (APS) on 45# steel substrates with the NiCrAlY as the bond-layer. The microstructure and phase composition of feedstocks and corresponding coatings were characterized. The top layer of nanostructured 8YSZ TBCs is denser and has fewer defects than that of conventional TBCs. The elastic modulus, micro-hardness and Vickers hardness of nanostructured 8YSZ TBCs exhibit bimodal distribution while the conventional 8YSZ exhibit mono-modal distribution. The elastic modulus and elastic recoverability were also obtained by the nanoindentation test. The results indicate that the elastic modulus of nanostructured 8YSZ coating is lower than that of conventional 8YSZ coating, but the nanostructured 8YSZ coating has higher elastic recoverability than that of the conventional 8YSZ coating. The prediction of the average elastic modulus was established by the mixture law and weibull distribution according to the fraction of phases with different molten characteristic.     

Thermal barrier coatings produced by laser cladding

A 2kW C0₂ laser has been used to clad a mild steel substrate with two different ceramic coatings, namely yttria partially stabilized zirconia (8 wt% YPSZ) or a mixture of YPSZ and pure alumina powder. A range of laser processing parameters has been investigated. Results have been obtained showing the possibility of using the laser beam for producing a clad layer of thermal barrier coating with different topography depending on the processing conditions.On leave from Scientific Research Council, Baghdad, Iraq.     

碳化钨/钴热喷涂粉末和涂层的研究进展

热喷涂传统碳化钨/钴金属陶瓷作为耐磨涂层已得到广泛的应用。近几年来,纳米结构涂层的热喷涂研究成为新的发展趋势。本文总结了传统和纳米结构 WC/Co热喷涂粉末的制备方法及其性质对涂层性能的影响因素,分析了涂层的微观结构和脱碳机理,简述了热喷涂纳米结构及纳米结构 微米结构 WC/Co涂层的研究进展,并指出了其发展方向。     

Influence of high velocity oxy-fuel parameters on properties of nanostructured TiO<Subscript>2</Subscript> coatings

A liquid fuel high velocity oxy-fuel (HVOF) thermal spray process has been used to deposit TiO₂ nanostructured coatings utilizing a commercially available nanopowder as the feedstock. The coatings were characterized by means of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. Photocatalytic activity was evaluated as a rate constant of decomposition reaction of methylene blue (MB) determined from the changes of relative concentration of MB with UV irradiation time. The results indicate that the sprayed TiO₂ coatings were composed of both TiO₂ phases viz. anatase and rutile, with different phase contents and crystallite sizes. A high anatase content of 80% by volume was achieved at 0·00015, fuel-to-oxygen ratio with nanostructure coating by grain size smaller than feedstock powder. Photocatalytic activity evaluation results indicated that all the TiO₂ coatings are effective to degradation MB under UV radiation and their activities differ in different spray conditions. It is found that fuel flow rate strongly influenced on phase transformation of anatase to rutile and by optimizing the rate which can promote structural transformation and grain coarsening in coating and improving photocatalytic activity.