共查询到20条相似文献,搜索用时 15 毫秒
1.
Guan-Jun Yang Kai-Xing Liao Chang-Jiu Li Sheng-Qiang Fan Cheng-Xin Li Shan Li 《Journal of Thermal Spray Technology》2012,21(3-4):505-513
The pore structure in nano-porous TiO2 coatings influences the ion diffusion property and the photovoltaic performance of dye-sensitized solar cells. In this paper, TiO2 coatings were deposited by vacuum cold spray (VCS) using a strengthened nanostructured powder. The pore structure, ion diffusion, and dye infiltration properties were examined to understand the coating deposition mechanism. Results showed that the pores in the VCS TiO2 coatings presented a bimodal size distribution with two peaks at ~15 and ~50?nm. Based on the impact behavior of spray powder particles, a deposition model was proposed to explain the formation mechanism of the pores in the VCS coating using strengthened nanostructured powder. It was found that, compared to the conventional unimodal-sized nano-pores in TiO2 coatings, the bimodal-sized nano-pores contributed to a higher ion diffusion coefficient of the coatings and thereby a higher photovoltage of the solar cells. 相似文献
2.
Porous Architecture of SPS Thick YSZ Coatings Structured at the Nanometer Scale (~50 nm) 总被引:1,自引:0,他引:1
Antoine Bacciochini Ghislain Montavon Jan Ilavsky Alain Denoirjean Pierre Fauchais 《Journal of Thermal Spray Technology》2010,19(1-2):198-206
Suspension plasma spraying (SPS) is a fairly recent technology that is able to process sub-micrometer-sized or nanometer-sized feedstock particles and permits the deposition of coatings thinner (from 20 to 100 μm) than those resulting from conventional atmospheric plasma spraying (APS). SPS consists of mechanically injecting within the plasma flow a liquid suspension of particles of average diameter varying between 0.02 and 1 μm. Due to the large volume fraction of the internal interfaces and reduced size of stacking defects, thick nanometer- or sub-micrometer-sized coatings exhibit better properties than conventional micrometer-sized ones (e.g., higher coefficients of thermal expansion, lower thermal diffusivity, higher hardness and toughness, better wear resistance, among other coating characteristics and functional properties). They could hence offer pertinent solutions to numerous emerging applications, particularly for energy production, energy saving, etc. Coatings structured at the nanometer scale exhibit nanometer-sized voids. Depending upon the selection of operating parameters, among which plasma power parameters (operating mode, enthalpy, spray distance, etc.), suspension properties (particle size distribution, powder mass percentage, viscosity, etc.), and substrate characteristics (topology, temperature, etc.), different coating architectures can be manufactured, from dense to porous layers, from connected to non-connected network. Nevertheless, the discrimination of porosity in different classes of criteria such as size, shape, orientation, specific surface area, etc., is essential to describe the coating architecture. Moreover, the primary steps of the coating manufacturing process affect significantly the coating porous architecture. These steps need to be further understood. Different types of imaging experiments were performed to understand, describe and quantify the pore level of thick finely structured ceramics coatings. 相似文献
3.
Guan-Jun Yang Chang-Jiu LiSheng-Qiang Fan Jin-Cheng Gao 《Surface & coatings technology》2011,205(10):3205-3210
The ion diffusion in porous TiO2 coating determines the limiting current density and the photovoltaic performance of a dye-sensitized solar cell. Nano-TiO2 coatings with unimodal nano-size distribution and bimodal size distribution were deposited by vacuum cold spray to examine the effects of the pore structure on the ion diffusion property and cell performance. Results show that the I3− ion diffusion coefficient increased with the increase in the mean pore size. The bimodal size distribution of nanometer-sized and submicrometer-sized pores in the coating was found to have a synergistic enhancement effect on the ion diffusion. Better ion diffusion performance contributed to a higher open circuit voltage. The optimal coating thickness (~ 30 μm) was nearly doubled in the cells with bimodal pore size distribution, compared with the previously reported optimal coating thickness (~ 15 μm) in the cell with unimodal pore size distribution. The reason is attributed to the high ion diffusion coefficient which allows a high limiting current density. 相似文献
4.
Suspension plasma spraying (SPS) is a new, innovative plasma spray technique using a feedstock consisting of fine powder particles suspended in a liquid. Using SPS, ceramic coatings with columnar microstructures have been produced which are used as topcoats in thermal barrier coatings. The microstructure contains a wide pore size range consisting of inter-columnar spacings, micro-pores and nano-pores. Hence, determination of total porosity and pore size distribution is a challenge. Here, x-ray microscopy (XRM) has been applied for describing the complex pore space of the coatings because of its capability to image the (local) porosity within the coating in 3D at a resolution down to 50 nm. The possibility to quantitatively segment the analyzed volume allows analysis of both open and closed porosity. For an yttria-stabilized zirconia coating with feathery microstructure, both open and closed porosity were determined and it could be revealed that 11% of the pore volumes (1.4% of the total volume) are closed pores. The analyzed volume was reconstructed to illustrate the distribution of open and closed pores in 3D. Moreover, pore widths and pore volumes were determined. The results on the complex pore space obtained by XRM are discussed in connection with other porosimetry techniques. 相似文献
5.
Effects of plasma spraying conditions on wear resistance of nanostructured Al2O3-8 wt.%TiO2 coatings plasma-sprayed with nanopowders were investigated in this study. Five kinds of nanostructured coatings were plasma-sprayed on a low-carbon steel substrate by varying critical plasma spray parameter (CPSP) and spray distance. The coatings consisted of fully melted region of γ-Al2O3 and partially melted region, and the fraction of the partially melted regions and pores decreased with increasing CPSP or decreasing spray distance. The hardness and wear test results revealed that the hardness of the coatings increased with increasing CPSP or decreasing spray distance, and that the hardness increase generally led to the increase in wear resistance, although the hardness and wear resistance were not correlated in the coating fabricated with the low CPSP. The main wear mechanism was a delamination one in the coatings, but an abrasive wear mode also appeared in the coating fabricated with the low CPSP. According to these wear mechanisms, the improvement of wear resistance in the coating fabricated with the low CPSP could be explained because the improved resistance to fracture due to the presence of partially melted regions might compensate a deleterious effect of the hardness decrease. 相似文献
6.
热喷涂热障涂层孔隙与涂层性能关系研究进展 总被引:3,自引:3,他引:0
孔隙在热障涂层中较为常见,孔隙对热障涂层的性能有利有弊。对热障涂层陶瓷层中孔隙的形成机理进行了综合分析,总结了热障涂层孔隙结构的调控方法,讨论了孔隙结构特征对热障涂层隔热性能和力学性能的影响。孔隙结构的引入将引起力学性能的下降,同时降低热障涂层的热导率,提高隔热效果。孔隙结构特征参数包括孔隙形状、孔隙间距、孔隙倾斜角、孔隙高宽比等,其中孔隙的倾斜角和高宽比对涂层导热性能的影响尤为重要,是孔隙结构的关键特征参数。通过原始粉末孔隙结构的保留、造孔剂(有机造孔剂、无机造孔剂)的搭配造孔、制备工艺(临界等离子喷涂参数、粒子扁平率等)的调节以及后续的孔隙处理,可实现热障涂层孔隙结构的调控。在实际应用过程中应同时兼顾力学性能和隔热性能,最重要的是保证热障涂层的有效寿命,需要综合考虑力学性能与导热性能的匹配。通过热障涂层孔隙结构特征的设计及分布控制,可实现孔隙结构高性能、高可靠性热障涂层的制备。 相似文献
7.
B. Robinson A. Tabecki S. Paul G. Shi A. Mills I. P. Parkin J. A. Darr H. L. de Villiers Lovelock 《Journal of Thermal Spray Technology》2017,26(1-2):161-172
The photocatalytic capabilities of titanium dioxide are widely published. Reported applications of titania coatings include air purification, water purification and self-cleaning. Suspension spray has been highlighted as a possible route for the deposition of highly active nanostructured TiO2 coatings. Published work has demonstrated the capabilities of suspension plasma spray and high-velocity suspension flame spray; however, little work exists for suspension flame spray (SFS). Herein, these three suspension spray processes are compared as regards their capability to produce photocatalytic TiO2 coatings and their potential for industrial scale-up. A range of coatings were produced using each process, manipulating coating parameters in order to vary phase composition and other coating characteristics to modify the activity. The coatings produced varied significantly between the processes with SFS being the most effective technique as regards future scale-up and coating photoactivity. SFS coatings were found to be up to nine times more active than analogous coating produced by CVD. 相似文献
8.
Nanostructured titania (TiO2) coatings were produced by high-velocity oxyfuel (HVOF) spraying. They were engineered as a possible candidate to replace
hydroxyapatite (HA) coatings produced by thermal spray on implants. The HVOF sprayed nanostructured titania coatings exhibited
mechanical properties, such as hardness and bond strength, much superior to those of HA thermal spray coatings. In addition
to these characteristics, the surface of the nanostructured coatings exhibited regions with nanotextured features originating
from the semimolten nanostructured feedstock particles. It is hypothesized that these regions may enhance osteoblast adhesion
on the coating by creating a better interaction with adhesion proteins, such as fibronectin, which exhibit dimensions in the
order of nanometers. Preliminary osteoblast cell culture demonstrated that this type of HVOF sprayed nanostructured titania
coating supported osteoblast cell growth and did not negatively affect cell viability.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
9.
Zhengping Mao Jun Wang Baode Sun Chengwu Yao 《Journal of Thermal Spray Technology》2009,18(4):563-571
Thick TiB2-TiC0.3N0.7 based composite coatings were deposited by reactive plasma spraying (RPS) successfully in air. The influence to the coating
properties (morphology, Vickers microhardness and corrosion resistant property) with Cr addition in the thermal spray powder
and TiB2-TiC0.3N0.7 based coatings treated by laser were investigated. The phase composition, structure and properties of composite coatings
were studied using XRD, SEM, EDS, Vickers microhardness and electrochemical testers. The results show that the Vickers microhardness
values and the density of laser surface treated coatings are improved significantly. The Cr addition in the thermal spray
powder can increase the density, improve the wettability of ceramic phases, uniform the phase distribution and enhance the
corrosion-resistant property of coatings. However, due to lower microhardness of metal Cr than ceramic phases in coatings,
the Vickers microhardness values of plasma sprayed coatings and plasma sprayed coatings with laser surface treatment are a
little lower than that of each coating without Cr addition in the thermal spray powder. 相似文献
10.
C. V. Cojocaru J.-M. Lamarre J.-G. Legoux B. R. Marple 《Journal of Thermal Spray Technology》2013,22(2-3):145-151
Evaluating and understanding the relationship between processing, microstructure and performance of a dielectric coating is essential for its practical usage and reliable application. In this study, the role of the powder feedstock on the properties of atmospheric plasma sprayed forsterite (Mg2SiO4) dielectric coatings was investigated by using different forsterite powder granulometries. The microstructural and porosity characteristics of the coatings associated with the spray conditions employed were assessed via scanning electron microscopy (SEM) and image analysis. The phase composition of the coatings was studied via x-ray diffraction and their crystallinity index determined. The electrical insulating characteristics were investigated using the dielectric breakdown test and impedance spectroscopy measurements. The electrical properties obtained were correlated with the microstructural characteristics and a performance comparison between forsterite and other dielectric coatings is presented. 相似文献
11.
B. G. Ravi S. Sampath R. Gambino J. B. Parise P. S. Devi 《Journal of Thermal Spray Technology》2006,15(4):701-707
Precursor plasma spray synthesis is an innovative and rapid method for making functional oxide ceramic coatings by starting
from solution precursors and directly producing inorganic films. This emerging method utilizes molecularly mixed precursor
liquids, which essentially avoids the handling and selection of powders, opening up new avenues for developing compositionally
complex functional oxide coatings. Precursor plasma spray also offers excellent opportunities for exploring the nonequilibrium
phase evolution during plasma spraying of multicomponent oxides from inorganic precursors. Although there have been efforts
in this area since the 1980s and early 1990s with the goal of synthesizing nanoparticles, only recently has the work progressed
in the area of functional systems. At the Center for Thermal Spray Research an integrated investigative strategy has been
used to explore the benefits and limits of this synthesis strategy. Water- and alcohol-based sol/solution precursors derived
from various chemical synthesis methods were used as feedstocks to deposit thin/thick films of spherical and nanostructured
coatings of yttrium aluminum garnet (YAG), yttrium iron garnet, lanthanum strontium manganate and Zr-substituted yttrium titanates,
and compositions of Y2O3-Al2O3 and their microstructural space centered around stoichiometric YAG. A detailed discussion of the salient features of the
radiofrequency induction plasma spraying approach, the results obtained in the investigations to develop various functional
oxide coatings, and process issues and challenges are presented.
This article was originally published inBuilding on 100 Years of Success: Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
12.
A figure of merit (FOM) has been developed to define the quality of ceramic (e.g., ZrO2) coatings on metal and alloy [Type 304SS and Alloy 600] surfaces. Zirconia (ZrO2) coatings were developed as a means of protecting the metal/alloy surfaces from stress corrosion cracking (SCC) in boiling water reactor (BWR) primary heat transport circuits, by inhibiting the cathodic reaction (reduction of oxygen and hydrogen peroxide) on the surface external to the crack. The distribution of pores in the coating plays an important role in corrosion prevention, such that the lower the porosity of the coating, the better the protection afforded to the system against SCC. Since the reactors operate at high temperature (e.g., at 288 °C under full power conditions), the temperature dependence of the FOM was investigated. The figure of merit (FOM) was developed by measuring impedance data over a wide range of frequency (10 mHz-5 kHz) at temperatures of 25, 100, 200, and 288 °C in hydrogenated, buffered solutions, with the hydrogen electrode reaction (HER) being used as a “fast” redox couple. An “equivalent circuit” analog was first developed from the bare surface impedance data and this analog was then employed in a second step to model the pore bottom in defining the pore distribution on the coated surface. A lognormal distribution (LND) of the pores was assumed and the parameters of the LND were determined using a constrained optimization technique to fit the model to the experimental data for the coated surface at different temperatures. The results suggest that, as temperature increases, the coating becomes more porous, making the substrate more susceptible to corrosion cracking. At 288 °C, 87% of the SS and 85% of the Ni-alloy surfaces become porous with the pore radius varying from 0.0001 cm to 0.01 cm. 相似文献
13.
Study of plasma- and detonation gun-sprayed alumina coatings using taguchi experimental design 总被引:1,自引:0,他引:1
P. Saravanan V. Selvarajan M. P. Srivastava D. S. Rao S. V. Joshi G. Sundararajan 《Journal of Thermal Spray Technology》2000,9(4):505-512
Atmospheric plasma spraying (APS) is a most versatile thermal spray method for depositing alumina (Al2O3) coatings, and detonation gun (D-gun) spraying is an alternative thermal spray technology for depositing such coatings with
extremely good wear characteristics. The present study is aimed at comparing the characteristics of Al2O3 coatings deposited using the above techniques by using Taguchi experimental design.
Alumina coating experiments were conducted using a Taguchi fractional-factorial (L8) design parametric study to optimize the spray process parameters for both APS and D-gun. The Taguchi design evaluated the
effect of four APS and D-gun spray variables on the measured coating attributes. The coating qualities evaluated were surface
roughness, porosity, microhardness, abrasion, and sliding wear. The results show that the coating quality is directly related
to the corresponding coating microstructure, which is significantly influenced by the spray parameters employed. Though it
is evident that the D-gun-sprayed coatings consistently exhibit dense and uniform microstructure, higher hardness, and superior
tribological performance, the attainment of suitable plasma-sprayed coatings can be improved by employing the Taguchi analysis. 相似文献
14.
A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes 总被引:3,自引:0,他引:3
Sundararajan G. Prasad K. U. M. Rao D. S. Joshi S. V. 《Journal of Materials Engineering and Performance》1998,7(3):343-351
In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications.
A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is
the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until
recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings
deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant
applications, namely, WC-12% Co, A12O3, and Cr3C2-MCr.
To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited
coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis
for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their
tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk
sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently
exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also
found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all
wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under
different modes of wear, whereas plasma sprayed Al2O3 shows least wear resistance to every wear mode. 相似文献
15.
One kind of conventional and two kinds of nanostructured Al2O3‐13%TiO2 coatings were prepared by plasma spray process. The phase composition and microstructure of coatings were examined by means of scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to investigate the corrosion behavior of coatings in aqueous hydrochloric acid solution. The results showed that nanostructured coatings had superior corrosion resistance compared to conventional Metco 130 coating. The corrosion resistance of coatings was mainly related to their microstructure and defects density. The EIS measurement for long time immersion in hydrochloric acid solution revealed that the corrosion resistance of coatings decreased with the increasing of immersion time. During the immersion period, electrochemical corrosion mainly occurred on the carbon steel substrate under NiCrAl coatings. In addition, the Al2O3‐13%TiO2 coatings were also failed during corrosion in aqueous hydrochloric acid solution. 相似文献
16.
V. S. Rudnev I. V. Malyshev I. V. Lukiyanchuk V. G. Kuryavyi 《Protection of Metals and Physical Chemistry of Surfaces》2012,48(4):455-461
Specific surface structures of ZrO2 + TiO2 (I) and ZrO2 +CeOx + TiO2 (II) coatings on titanium before and after annealing at 850°C for 24 h in air are studied. Whiskers are found on the surface of type-I coatings before annealing, and perfectly edged crystals composed of TiO2 and ZrO2 oxides are found upon annealing. Pores in both coatings have a multilevel structure. In the case of type-I coatings, orifices of pores are covered with titanium. In type-II coatings, pore orifices contain titanium, zirconium, and oxygen. Oxygen deficiency implies that titanium and zirconium are present in pore orifices in metallic state. In type-II coatings, the surface distribution of cerium is heterogeneous. Mechanical treatment of the annealed coatings causes their exfoliation from the substrate metal. In the case of both coatings, the exfoliating surfaces are composed of TiO2 blocks containing excess oxygen. 相似文献
17.
Al2O3-ZrO2 coatings were deposited by the suspension plasma spray (SPS) molecularly mixed amorphous powder and the conventional air
plasma spray (APS) Al2O3-ZrO2 crystalline powder. The amorphous powder was produced by heat treatment of molecularly mixed chemical solution precursors
below their crystallization temperatures. Phase composition and microstructure of the as-synthesized and heat-treated SPS
and APS coatings were characterized by XRD and SEM. XRD analysis shows that the as-sprayed SPS coating is composed of α-Al2O3 and tetragonal ZrO2 phases, while the as-sprayed APS coating consists of tetragonal ZrO2, α-Al2O3, and γ-Al2O3 phases. Microstructure characterization revealed that the Al2O3 and ZrO2 phase distribution in SPS coatings is much more homogeneous than that of APS coatings. 相似文献
18.
L. C. Erickson T. Troczynski H. M. Hawthorne H. Tai D. Ross 《Journal of Thermal Spray Technology》1999,8(3):421-426
A series of plasma sprayed coatings of controlled microstructure was obtained by spraying three monosize sapphire powders
using an axial injection torch in which the plasma gas composition and nozzle diameter were the only processing parameters
varied. The effects of changes in these parameters on the coating splat morphology, porosity, angular crack distribution,
and hardness are reported. The uniform, dense microstructure and the high hardness of 14 GPa (a level usually only associated
with chromia thermal spray coatings) of the best alumina coatings resulted from using tightly controlled processing conditions
and monodispersed precursor powders. The microstructural quality of plasma sprayed coatings and, hence, the coating properties
can be improved significantly by minimizing variations in processing and raw material parameters.
This paper originally appeared in Thermal Spray: Meeting the Challenges of the 21st Century; Proceedings of the 15th International Thermal Spray Conference, C. Coddet, Ed., ASM International, Materials Park, OH, 1998. This proceedings paper has been extensively reviewed according
to the editorial policy of the Journal of Thermal Spray Technology. 相似文献
19.
Electrochemical impedance spectroscopy (EIS) was employed to investigate the corrosion performance of nanoparticulate SiO2 modified epoxy coatings on carbon steel in 3.5 wt% NaCl solution, coupled with salt spray test. Capacitance‐gravimetric methods and delamination tests were performed to analyze the water uptake behavior and interface stability against delamination of modified coatings, respectively. Four systems were studied, including a clear coating and three pigmented coatings (with 1, 2, and 3 wt% nanoparticulate SiO2). The experimental results showed that nanoparticulate SiO2 particles can improve the anti‐corrosion performance of the coatings and the optimal addition content is 2 wt%. The results obtained with capacitance‐gravimetric measurements showed that the diffusion process of water through epoxy coatings with different pigment volume concentration (PVC) obeyed the second Fick's diffusion law in the initial period. Adding nanoparticulate SiO2 into epoxy coatings can act effectively. The positive influence is attributed to the reaction between nanoparticles and epoxy resin which is confirmed by FTIR, improving the barrier and dispersion effectiveness of coatings. The negative one is increasing the number of pores in the coatings when the adding amount is beyond the critical PVC. 相似文献
20.
In previous studies, it has been demonstrated that nanostructured Al2O3-13 wt.%TiO2 coatings deposited via air plasma spray (APS) exhibit higher wear resistance when compared to that of conventional coatings.
This study aimed to verify if high-velocity oxy-fuel (HVOF)-sprayed Al2O3-13 wt.%TiO2 coatings produced using hybrid (nano + submicron) powders could improve even further the already recognized good wear properties
of the APS nanostructured coatings. According to the abrasion test results (ASTM G 64), there was an improvement in wear performance
by a factor of 8 for the HVOF-sprayed hybrid coating as compared to the best performing APS conventional coating. When comparing
both hybrid and conventional HVOF-sprayed coatings, there was an improvement in wear performance by a factor of 4 when using
the hybrid material. The results show a significant antiwear improvement provided by the hybrid material. Scanning electron
microscopy (SEM) at low/high magnifications showed the distinctive microstructure of the HVOF-sprayed hybrid coating, which
helps to explain its excellent wear performance.
This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been
expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain
Montavon, Ed., ASM International, Materials Park, OH, 2007. 相似文献