等离子喷涂氧化锆涂层的显微结构分析

利用透射电镜(TEM)、扫描电镜(SEM)和X射线衍射仪(XRD)等分析技术,表征了等离子喷涂氧化锆涂层的显微结构.结果表明:等离子喷涂氧化锆涂层是由典型的柱状晶粒组成的层状结构;柱状晶粒晶型发育完整,晶粒之间具有清楚晶界;涂层表面存在明显的完全熔融区和未熔融区;涂层中分布有一定的大气孔.涂层的主晶相是四方氧化锆,没有单斜氧化锆相存在;涂层中裂纹的扩展是穿晶断裂和沿晶断裂共存.     

氧化锆涂层(薄膜)的应用与研究

重点归纳了氧化锆(Zr02)作为热障涂层材料的应用和研究内容，并对Zr02功能薄膜材料和生物涂层材料的研究进行了简单总结。对纳米氧化锆涂层的研究现状进行初步介绍。     

新型窑具砖涂层

在过去的 10年里 ,许多陶瓷窑中的传统重质氧化锆窑具已被轻质的含氧化锆涂层的氧化铝制品取代 ,这改变了只有高级碳化硅制品才能做窑具的现状。氧化铝片状制品上可以涂上 0 .6 35～ 1.5 2 4ｍｍ厚的氧化锆涂层 ,从而得到一种耐用、高性能、截面积小的制品 ,它的截面积不足传统窑具砖截面积的 1/ 4。小的截面积使窑的可用空间增大 ,允许每窑煅烧更多的产品。同时 ,这种含氧化锆涂层的材料还具有重量轻、表面洁净的优点新型窑具砖涂层@李光辉     

等离子喷涂纳米二氧化锆涂层性能的研究

采用大气等离子喷涂技术,在镍基高温合金基体上制备了纳米氧化锆涂层.运用扫描电镜对涂层显微结构进行观察和分析,同时测试了涂层的显微硬度、结合强度扣热震性能.结果表明:纳米氧化锆涂层由完全融化区和部分融化区组成,孔隙率约为7%,显微硬度为655.81 HV,结合强度为54.37 MPa,在1 000℃下,可承受40次热循环,涂层无明显脱落现象.     

纳米颗粒粒径对等离子喷涂法制备氧化锆纳米涂层的影响

利用扫描电镜(SEM)、场发射扫描电镜(FESEM)、透射电镜(TEM)、比表面积吸附法(BET)等分析测试技术,研究了3种不同纳米尺寸氧化锫粉粒的造粒性能、沉积效率以及对等离子喷涂涂层晶粒大小、涂层熔融性能、结合强度的影响.结果表明:纳米氧化锆粉体一次颗粒粒径大小显著影响纳米粉体的喷雾造粒性能、沉积效率、涂层表面粗糙度、涂层晶粒粒径和结合强度大小.本试验中,利用颗粒一次粒径范围为50～70 nm的纳米氧化锆粉体,等离子喷涂制备了晶粒粒径范围为80～120 nm,沉积效率为43%,涂层表面粗糙度为5.92 μm,结合强度为27 MPa的纳米结构氧化锆涂层.     

金属表面电泳法制备陶瓷涂层的研究进展

陶瓷涂层具有耐磨、耐蚀、耐高温和抗微生物侵蚀等性能。介绍了国内外用电泳沉积法制备生物陶瓷涂层、碳化硅陶瓷涂层、氧化钛陶瓷涂层、氧化铝陶瓷涂层、氧化硅陶瓷涂层及氧化锆陶瓷涂层的研究进展,揭示了防腐领域中陶瓷涂层存在的问题,提出了解决方法并展望了未来的研究方向。     

水性金属防腐隔热涂料的研制

采用空心玻璃微珠作为隔热填料制备隔热中间层,并用纳米氧化锆和金红石型二氧化钛作为反射型填料制备了反射面漆。研究了空心玻璃微珠粒径和用量、反射面漆中填料种类、纳米氧化锆及中间层与面漆层厚度变化对配套涂层隔热性能的影响,并测试了配套涂层的防腐性能。结果表明:当选择65μm直径的空心玻璃微珠且用量为配方总量的7%,中间层和面漆层厚度分别为150μm和70μm,面漆中采用绢云母和纳米氧化锆时,配套涂层的隔热性能最好;箱体内部中心点温差为10.3℃,反射面漆太阳反射比为0.83,配套涂层的耐中性盐雾性能达55 d以上。     

铝合金表面氧化锆转化膜的结构与性能

采用氟锆酸工艺在AA6061铝合金表面制备出氧化锆转化膜,用扫描电镜和能谱仪分析了氧化锆转化膜的组织形貌和结构,采用电化学方法和中性盐雾试验研究了氧化锆转化膜的耐蚀性能。结果表明,制备出的氧化锆转化膜为无色膜,主要由Zr和Al的氧化物组成。氧化锆转化膜的耐腐蚀性能优异。涂覆环氧树脂漆或聚氨酯漆后的涂层可以通过1500h的中性盐雾试验,氧化锆转化膜可以用作铝合金的涂漆前预处理膜。     

水性金属防腐隔热涂料的研制

采用空心玻璃微珠作为隔热填料制备了隔热中涂,采用纳米氧化锆和金红石(R)型二氧化钛作为反射型填料制备了反射面漆。研究了空心玻璃微珠的粒径和用量、反射面漆中填料种类、纳米氧化锆及中间层与面漆层厚度的变化对配套涂层隔热性能的影响,并测试了配套涂层的防腐性能。结果表明:当选择65μm直径的空心玻璃微珠且用量为配方总量的7%、中涂和面漆厚度分别为150μm和70μm、面漆中采用绢云母和纳米氧化锆时,配套涂层的隔热性能最好;箱体内部中心点温差为10.3℃,反射面漆太阳反射比为0.83,配套涂层的耐中性盐雾性能达55 d以上。     

氧化锆陶瓷粘接前表面处理方法的研究进展

对机械打磨与空气喷砂、摩擦化学硅涂层、高温化学硅涂层、蚀刻、激光照射、等离子喷涂及其他涂层技术对氧化锆陶瓷粘接前表面处理的优缺点进行了综述,展望了在临床应用前景。     

Porosity measurements in suspension plasma sprayed YSZ coatings using NMR cryoporometry and X-ray microscopy

A large variety of coatings are used to protect structural engineering materials from corrosion, wear, and erosion, and to provide thermal insulation. In this work, yttria-stabilized zirconia coatings produced by suspension plasma spraying were investigated with respect to their microstructure and especially their porosity, as the porosity affects the thermal insulation of the underlying component. To determine porosity, pore size distribution, and pore shape, the coatings were investigated using novel advanced characterization techniques like NMR cryoporometry and X-ray microscopy. In general, the porosity is inhomogeneously distributed and the coatings showed a large variety of pore sizes ranging from a few nanometers to micrometers.     

Microstructure, mechanical properties and thermal shock resistance of plasma sprayed nanostructured zirconia coatings

Nanostructured yttria stabilized zirconia (YSZ) coatings were deposited by Atmospheric Plasma Spraying (APS). X-ray diffraction (XRD) was used to investigate their phase composition, while scanning electron microscopy (SEM) was employed to examine their microstructure. The coatings showed a unique and complex microstructure composed of well-melted splats with columnar crystal structure, partially melted areas, which resembled the morphology of the powder feedstock, and equiaxed grains. Vickers microhardness of nanostructured zirconia coatings was similar to that of the conventional ones and strongly depended on the indentation load. Otherwise, a higher thermal shock resistance was found. This effect was addressed to the retention of nanostructured areas in coating microstructure and to the corresponding high porosity.     

Microstructure and Properties of Sprayed Ceramic Coating

The potential benefits of a thermal barrier coating on the heated side of diesel or turbine components are well documented, and this as well as other applications of ceramics in heat engines are being actively pursued. The ceramic coatings used in heat engines must be able to withstand severe thermal stress. The microstructure and properties of several sprayed coatings are described, including flame-sprayed alumina coatings, plasma-sprayed alumina coatings, and plasma-sprayed zirconia coatings. The results show that the modulus ( E ) of the coatings depends mainly on porosity and phase composition, and nonlinear stress-strain behavior is caused by the laminar grain structure of the coatings. The fracture strain of a coating is a major factor in the thermal shock resistance of that coating.     

Effect of carbon nanotubes and aluminum oxide on the properties of a plasma sprayed thermal barrier coating

To protect the structural components of a power generating unit from the corrosive environment, thermal spray coatings are applied to the components. In the present work, four different types of thermal barrier coating (TBC) viz. partially stabilised zirconia (8YSZ), zirconia-20% alumina (ZA) composite coating without carbon nanotube (CNT) reinforcement, and ZA with 1% and 3% CNT reinforcement. The coating was deposited on NiCrAlY coated P91 steel using a plasma spraying process. The coating microstructure and phases were characterised using field emission scanning electron microscope (FE-SEM) with energy dispersive spectroscopy (EDS). The phases of the coating were analyzed using X-ray diffraction technique. The effect of CNT reinforcement on the thermal conductivity, porosity, and hardness of the composite coatings was investigated. The protective behavior of the coatings was characterised by potentiodynamic polarization testing and electrochemical impedance measurements. The thermal conductivity of the composite coating was found to be increased with increasing CNT content. Hardness was found to be highest for 3% CNT reinforcement and the thermal conductivity was found to increase with decreasing porosity. The electrochemical measurements indicate that reinforcement of CNT in zirconia alumina composite coating improved its corrosion resistance.     

Improvement of 3Y-TZP aging behavior by means of zirconia-based protective layers

In this work 3 mol.% yttria-stabilized zirconia (Y-TZP) disks were pressed and subsequently coated, aiming at producing reliable protective coatings to avoid Low Temperature Degradation (LTD) of Y-TZP. Suspensions of 12Ce-TZP or 5Y-PSZ (5 mol.% yttria stabilized zirconia) powders with different solid contents were used as coatings. Accelerated aging was conducted for times of 2, 6 and 18 hours at 134 °C. Specimens were analyzed using XRD, SEM and Colorimetry. Suspensions with solid content of 23 wt% prepared with 12 mol% ceria stabilized zirconia showed coarsening porosity, while all other suspensions achieved acceptable results for this property. Suspensions with 28 wt% Ce-TZP and 23 wt% Y-PSZ were the selected conditions for the LTD studies. They were selected among the remaining conditions, based on their enhanced color properties and surface density, displaying layers with ∼7 μm and 5-10 μm, respectively. Coatings enhanced resistance to LTD.     

Plasma-sprayed nanostructured scandia-yttria and ceria-yttria codoped zirconia coatings: Microstructure,bonding strength and thermal insulation properties

Microstructure, thermal insulation behavior and bonding strength of nanostructured 5%scandia, 0.5%yttria codoped zirconia (5.5 ScYSZ) and 25%ceria, 2.5%yttria co stabilized zirconia (27.5%CYSZ) coatings were investigated. ScYSZ and CYSZ nanostructured granules (as a top coat) and commercial NiCrAlY powder (as a bond coat) were thermal sprayed on an Inconel 738 substrate. The results revealed ScYSZ coating to have higher bonding strength. Nevertheless, due to higher porosity and the presence of local strains, the thermal insulation of nanostructured CYSZ coating was higher than for ScYSZ coating.     

Dense yttria-stabilized zirconia coatings fabricated by plasma spray-physical vapor deposition

Plasma spray-physical vapor deposition (PS-PVD) is a novel technique which can offer new opportunities to obtain advanced microstructures. In this study, dense yttria-stabilized zirconia (YSZ) coatings were deposited using PS-PVD with proper parameters. The dependencies of the microstructure of the as-sprayed coatings on axial spray distance and radial position were discussed. Four typical coatings were selected for the current work. The corresponding microstructures, phase compositions and mechanical properties were studied in detail. These as-sprayed coatings had dense lamellar or lamellar/columnar hybrid microstructures, the lowest porosity was 0.44%. Both monoclinic and tetragonal zirconia were detected in the as-sprayed coatings. The distribution of yttrium was not homogeneous, especially in the coatings deposited at shorter spray distance. Furthermore, oxygen got lost partly during the spraying process with decreasing spray distance. The hardness (H) and Young's modulus (E) of the coatings changed simultaneously with the different microstructures. The maximum values of H and E were 16.6±0.6 and 234.3±10.1 GPa respectively, which were found in the densest coatings. The dense PS-PVD ceramic coatings might be applicable in anti-corrosion fields (such as alkali corrosion, marine corrosion and hot corrosion).     

Fractal Perimeters of Polishing-Induced Pull-Outs Present on Polished Cross Sections of Plasma-Sprayed Yttria-Stabilized Zirconia Coatings

Polished cross sections of plasma-sprayed yttria-stabilized zirconia coatings deposited using different process parameters were prepared with both hot- and vacuum-mounting techniques and investigated by image analysis. It was found that polishing-induced pull-outs were evidently present on the hot-mounted cross sections, and that the perimeter of these pull-outs could be described statistically by means of fractal analysis. In this work, values of the corresponding fractal dimension range from 1.45–1.54; they increase linearly while increasing fracture toughness, and decrease with the increase in porosity of the coatings. Thus, this fractal dimension may be regarded as a measure of the fracture toughness of the coatings, but only for hot-mounted samples.     

Plasma spray coatings for producing next-generation supported membranes

Ceramic systems as membranes play a critical role in synthesis gas production as well as gas separation technologies. This paper presents, the potential for thermal spray technology in natural gas-related programs, with a special emphasis on the production of ceramic membranes for oxygen gas separation processes. Yttria-stabilized zirconia (YSZ) coatings were deposited under different environments (air and vacuum) resulting in altered pore and crack distributions introduced during the spray process. We report on the characterization of these coatings using small-angle neutron scattering (SANS) and ultrasmall-angle X-ray scattering (USAXS) to explain the different pore structures observed for the two coating conditions. A quantitative representation of the microstructural features in these coatings is presented in terms of porosity, anisotropic void surface area and pore size distribution. Also, thermal and mechanical properties, complemented with impedance spectroscopy measurements, help understand coating behavior. Such comprehensive characterization, coupled with property measurements of the coatings, successfully demonstrates the potential of thermal spray technology in membrane production.*To whom correspondence should be addressed. E-mail: hherman@ms.cc.sunysb.edu     

Microstructural characterization of plasma-sprayed nanostructured zirconia powders and coatings

The objective of this paper was to study the melting state of nanoscale zirconia powders in plasma jet, examine the crystalline phase and microstructural characterization of the plasma sprayed nanostructured zirconia powders and coatings. The cross-section morphology of water-quenched powders revealed that most of the starting powders were molten in the plasma jet. Phase analysis using XRD spectra proved that the monoclinic phase zirconia of the starting powders transferred into tetragonal phase zirconia after the plasma spraying. SEM analysis indicated that the as-sprayed coatings exhibited lamellar structure, about 0.5–5 μm in thickness of a single lamella, which was found to be a characteristic feature of the plasma-sprayed nanostructured zirconia coating. Inside of the lamellae, columnar grains were observed. The mean grain size of the as-sprayed zirconia coating is about 80 nm.