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Behavior of yttria-stabilized zirconia (YSZ) during Laser Direct Energy Deposition of an Inconel 625-YSZ Cermet
摘要： Thermal barrier coatings (TBC) are regularly used today to protect and extend the service life of several superalloys which are extensively used in high temperature applications. The existing TBCs are typically between 0.1 to 0.5 mm in thickness, are deposited on metal substrates using plasma spray or electron beam vapor deposition, and can reduce temperatures at the substrate surface by up to 300 °C. For greater temperature reductions there is a need for thicker TBCs. The building of thick TBCs has to date been stymied by poor adhesion, and cracking during deposition. It has been suggested that a functionally graded approach may reduce the residual stresses which result in these defects. To date there have been few reports on the deposition of ceramic or cermet coatings using laser AM and none have reported on the phase stability of ceramic particles post-deposition. This paper is a first report on the phase stability of ceramic particles following the compositional segregation of elements during deposition using a powder feed additive manufacturing process. Functionally graded (FG), thick TBCs (>3 mm) consisting of Inconel 625 (IN625) and yttria-partially stabilized zirconia (8YSZ) were deposited on an A516 steel substrate via laser direct energy deposition (LDED). Good interfaces were observed between the bond coat (BC) and first cermet layer and between the graded cermet layers. In cermet layers that did exhibit good interfaces, fine, re-solidified, YSZ particles were homogeneously distributed within the Inconel 625 matrix. The YSZ particles exhibited a tetragonal lattice structure and were depleted of yttrium. In contrast, the thin YSZ layer formed on a cermet surface showed no yttrium depletion.
关键词： compositional stability,thick thermal barrier coatings,Multi-material additive manufacturing,functionally graded materials,ceramic additive manufacturing,phase stability of YSZ
更新于2025-09-12 10:27:22
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TiO <sub/>2</sub> ‐PDVB Janus particles enhanced compatibility of titanium dioxide and recycled waste styrofoam
摘要： People are always puzzled by “white pollution” in recent decade. Recycling of waste styrofoam as a coating is a good sustainable solution to resolve this problem. However, the poor compatibility between inorganic additives and polymer hinders the application of recycled polystyrene. In this article, anisotropic Janus particles were used to increase the compatibility of titanium dioxide/waste styrofoam coatings. SEM results show that Janus particles can be anchored at the interface between styrofoam and titanium dioxide, increasing the dispersion of titanium dioxide, and improving the compatibility of inorganic particles and organic polymer. The glass-transition temperature of styrofoam coating increases from 77 (cid:1)C to 89 (cid:1)C in titanium dioxide/styrofoam contained 1 wt % of Janus particles, which certi?ed that Janus particles have compatibilization on titanium dioxide/styrofoam coating. Attributing to this compatibilization, the tensile strength of titanium dioxide/styrofoam with 1 wt % of Janus particles rises about 45% compared with titanium dioxide/styrofoam. The yield stress, storage modulus, and viscosity of titanium dioxide/styrofoam contained 1 wt % of Janus particles are the smallest and the closest to Newtonian ?uid. Janus particles used in the recycled styrofoam coating is bene?t to expand the application of waste styrofoam and the new anisotropic Janus compatibilizer. ? 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48691.
关键词： Titanium dioxide,compabilization,composite coatings,waste styrofoam,Janus particles
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Ge/YbF <sub/>3</sub> and ZnS/YbF <sub/>3</sub> Thin-Film Combinations Open New Perspectives in Production of Broadband Optics for Mid-Infrared Laser Applications
摘要： Recently, the mid-infrared (MIR) spectral region has become more and more interesting for bio-medical laser applications since large organic molecules exhibit their fundamental vibrational and rotational modes in this range[1]. In this rapidly developing research area, high-quality optical interference coatings are highly demanded. In many laser systems (see, for instance [2]), it is required to separate initial high-power near-infrared beams originated from a driving laser from lower power MIR components emerged in a nonlinear crystal through a nonlinear process (for example, frequency difference generation). The corresponding multilayer dichroic filters reflecting the radiation in the near-infrared range and transmitting the MIR radiation are required. The coatings exhibit desired reflectance and phase in a near-infrared range and high transmittance in a required MIR region. The acceptable levels of reflectance and transmittance, width of the high-reflectance and high-transmittance ranges, polarization states as well as the angle of incidence are dependent on the laser setup. Along with the specified spectral performance, non-optical properties such as good adhesion, low mechanical stress, thermal stability, are of outmost importance. Low stress is crucial in order not to deform the laser beam wave front of the entire laser system and to avoid thermal lensing. Therefore, the choice of the appropriate evaporation materials and optimization of the high-vacuum deposition processes on the one hand and selection of optimal design solutions on the other hand are key elements in development of advanced multilayer optics for laser systems.
关键词： laser applications,dichroic filters,Ge/YbF3,ZnS/YbF3,optical interference coatings,mid-infrared
更新于2025-09-11 14:15:04
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Efficient Interfacial Solar Steam Generator with Controlled Macromorphology Derived from Flour via “Dough Figurine” Technology
摘要： Poor corrosion and wear resistance of magnesium (Mg) alloys restrict their applications. Herein, corrosion and wear-resistant films are formed upon Mg alloy AZ31 through a micro-arc oxidation (MAO) process in silicate electrolyte in the presence of carbon spheres (CS). Surface morphology, chemical composition, corrosion resistance, hardness, and coefficient of friction (CoF) of the MAO coatings are investigated using field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrometry (FTIR), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical and hydrogen evolution measurements, automatic micro-hardness testing, and reciprocating tribometer, respectively. Results demonstrate that the surface morphology and hardness of MAO coatings vary with the concentration of CS. The presence of CS results in an increased coating thickness from 8.0 (cid:1) 1.8 to 12.2 (cid:1) 1.8 μm, mean pore size from 0.7 (cid:1) 0.1 to 1.9 (cid:1) 0.1 μm, open porosity of MAO coating from 4.2 (cid:1) 0.4 to 5.6% (cid:1) 1.1%, and coating hardness from 347.0 (cid:1) 59.0 to 853.0 (cid:1) 67.3 Vickers-hardness (HV). Furthermore, CS-modified MAO coatings lead to improved corrosion resistance in comparison with that of the neat MAO counterparts. Moreover, the high hardness and formation of SiC of CS-modified coatings lead to a low and stabilized CoF, which implies an enhanced wear resistance.
关键词： micro-arc oxidation,coatings,corrosion resistance,carbon spheres,magnesium alloys
更新于2025-09-11 14:15:04
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The visible reflectance spectrum stability and water content resistivity of natural dye coating paint film consisting chlorophyll
摘要： The purpose of this paper is to study the colour stability and water content resistivity of the green colour coating paint film (consisting of chlorophyll) during exposure to ultraviolet A (UV-A). The natural green dye was prepared by immersing Cassia alata L. leaves in absolute ethanol. The extract was prepared in two batches of dye samples where one of it was a pure dye and the other was added with 3 Wt. % Cu(NO3)2 as an additive. Polymer blend as a binder was prepared by mixing poly(methyl methacrylate) (PMMA) and commercial acrylic polyol. The blended polymer was mixed with the natural dye in a specific ratio and applied as coating paint film on glass panel surfaces. The visible spectrum stability (colour stability) and water content resistivity of the coating paint films during exposure to UV-A were monitored. Addition of Cu(NO3)2 had improved the colour stability of the coating paint film. Fourier transform infrared spectroscopy analysis showed that both coating paint films do not absorb water and are resistive to water content. The ability of Cu(NO3)2 as an colour stability additive to the natural green dye applied in the coating paint film. The coating paint film developed in this work is suitable to be applied on glass substrates. The colour stability of the coating paint film was analysed by using the reflectance spectrum.
关键词： Chlorophyll,Colour stability,Natural dye,Paints,Organic coatings
更新于2025-09-11 14:15:04
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Correlation between defect absorption and nano-second laser-induced damage of HfO2/SiO2 based high reflective coatings at 1064?nm
摘要： The distribution of defect weak absorption and nanosecond pulse laser induced damage characteristics of HfO2/SiO2 multilayers were investigated. A combination of in-situ measurements of defect weak absorption distribution and laser induced damage threshold (LIDT) map was proposed, whereby the evolution of defect weak absorption and the laser induced damage morphology under laser irradiation was studied. During the laser irradiation, some nodular and scalded defects can be removed or passivated by the low flux laser, and the absorption of these defect types was reduced accordingly. Besides, catastrophic destruction defects with enhanced absorption after laser irradiation would develop into catastrophic damage. Further, two-dimensional scanning of the sample surface was used to study the relationship between defects weak absorption and the LIDT. The results indicated that the correlation of defects weak absorption intensity distribution and LIDT map depended on defect evaluation properties during the laser irradiation.
关键词： Nanosecond pulse laser,HfO2/SiO2 multilayers,High reflective coatings,Laser-induced damage,Defect absorption
更新于2025-09-11 14:15:04
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A study on microhardness and microstructural evolution of titanium/zirconium diboride cermet coatings with varying scan speeds during laser cladding on Ti6Al4V substrate
摘要： Titanium/zirconium diboride cermet coatings were deposited at different laser scan speeds on Ti–6Al–4V alloy using laser cladding technique. Microhardness of the coatings was compared with the microhardness of the substrate, while the microstructural morphologies of coatings were evaluated via scanning electron microscope with energy dispersive spectroscopy. In addition, resultant grain sizes of the coatings were observed and phases formed within the coatings were also examined. The microhardness of the coatings was seen to be four times harder than the substrate. Scanning electron microscopic images exhibited a refinement in grain size and the development of distinct microstructural features. X-ray diffraction patterns showed significant hard phases such as Al2Zr and Ti3B4 which may be responsible for the sky-rocketed microhardness values of the coatings. This study proffers profound insight on the influence of laser scan speed, during deposition, on the microhardness and microstructural morphology of titanium/zirconium diboride cermet coatings.
关键词： titanium/zirconium diboride cermet coatings,laser cladding technique,Ti6Al4V substrate,laser scan speed
更新于2025-09-11 14:15:04
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Fabrication of Luminescent Antireflective Coatings with CaMoO4:Eu3+/Ag Composite Structure
摘要： Highly transparent and luminescent CaMoO4:Eu3+/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an aluminum source in coating solutions, the sol–gel-derived films underwent a remarkable microstructural change during the hot water treatment due to the reaction between an amorphous alumina phase and water. This change brought both an antireflective effect (suppression of Fresnel reflection) and luminescence enhancement (suppression of total internal reflection) to the films. The introduction of Ag nanoparticles into the films further increased luminescence intensity without losing the antireflective effect.
关键词： calcium molybdate,silver nanoparticles,antireflective coatings,europium,nanocomposite,sol–gel method,photoluminescence
更新于2025-09-11 14:12:44
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Optical optimization of a multi-layer wideband anti-reflection coating using porous MgF2 for sub-micron-thick CIGS solar cells
摘要： The optical losses associated with sub-micron absorbers in CIGS solar cells can be reduced by light management techniques. 3-D optical modelling was used to optimize light in-coupling and internal rear reflectance in a 750-nm thick CIGS reference solar cell. At the front side, an effective medium approximation (EMA) approach for describing optical properties of a MgF2-based anti-reflection coating (ARC) was applied. Taking reflectance as the cost function and sequential nonlinear programming as the optimization algorithm, an optimal porous-on-compact double-layer ARC was determined. This led to a wideband light in-coupling with a 6.8% improvement in the photo-current density (Jph) with respect to the reference solar cell without ARC. Considering the variation of the sunlight direction due to day and seasonal changes, different light incidence angles were investigated. The results indicate that in this case, our designed double-layer ARC outperforms the standard compact MgF2 single-layer ARC. By using the EMA approach, the amount of computational memory can be reduced by a factor of 30, shortening the simulation time from four days to one hour. At the rear side of the cell, a point-contacted MgF2/Al2O3 reflector, in combination with our proposed front ARC, enhances the Jph by 11.3% considering the same reference solar cell. Compared to a much thicker cell (1600-nm thick absorber) with no light management applied, our front-and-rear optical approaches more-than-compensate optical losses resulting from using thinner absorbers. This design is suitable for industrial uptake and practical to realize. Additionally, the approach of using EMA for double-layer ARC optimization is innovative with respect to other ARC approaches applicable to not only chalcopyrite photovoltaic technologies.
关键词： Thin films,Antireflection coatings,Light management,Photovoltaic
更新于2025-09-10 09:29:36
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Improving the Accuracy of Broad-Band Monitoring of Optical Coating Deposition
摘要： A method for improving the accuracy of the broad-band monitoring of the process of depositing optical coatings is proposed. The method is based on determining the actual set of thicknesses of deposited layers in the deposition process. The effectiveness of the proposed approach is demonstrated in a series of model numerical experiments using a simulator of deposition process.
关键词： spectral characteristics,broad-band optical monitoring,multilayer optical coatings
更新于2025-09-10 09:29:36