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The influence of positive pulses on HiPIMS deposition of hard DLC coatings
摘要： Diamond-like carbon (DLC) coatings were deposited by a novel HiPIMS method that incorporates positive voltage pulses at the end of the conventional HiPIMS discharge. Different positive voltage amplitudes (100, 200, 300, 400 and 500 V) were used to evaluate the effect of this operation mode on the discharge process and the mechanical properties of the deposited DLC coatings. The application of positive pulses was observed to enhance the ionization of both the sputtered carbon and argon species. Mass spectroscopy measurements showed that a larger amount of high-energy C+ ions are generated, with ion energies proportional to the amplitude of the overshoot voltage. The ion bombardment induced by the positive pulses led to higher compressive residual stresses and densification of deposited DLC coatings. Moreover, their Raman spectra exhibited lower D-band and G-band intensity ratios (ID/IG) as the pulses voltage was increased which is indicative of higher sp3 content. Mechanical properties were evaluated by nanoindentation testing and the hardness of the deposited DLC films was observed to increase from 9.6 GPa (for no voltage pulse applied) to 22.5 GPa (for an applied positive pulse voltage of 500 V).
关键词： HiPIMS,Hard coatings,Diamond-like Carbon (DLC),Tribology
更新于2025-09-23 15:21:01
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Increasing Fracture Toughness and Transmittance of Transparent Ceramics using Functional Low-Thermal Expansion Coatings
摘要： Transparent polycrystalline ceramics have the potential to enable applications no other materials can, but to do so their strength and toughness must be improved. However, surface strengthening treatments like those used for glasses have so far remained elusive. Here for the first time, we report on engineering unprecedented surface compression, of the magnitude achieved for ion-exchange strengthened glasses (~750 MPa) in transparent ceramics. This was achieved by applying functional, low thermal-expansion yttria coatings onto yttria-stabilized zirconia substrates and thermally treating. In some instances, the treatment more than doubled the fracture toughness while simultaneously increasing light transmittance.
关键词： surface compression,transparent ceramics,fracture toughness,thermal-expansion mismatch,yttria coatings
更新于2025-09-23 15:21:01
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Strongly Enhancing Photocatalytic Activity of TiO2 Thin Films by Multi-Heterojunction Technique
摘要： The photocatalysts of immobilized TiO2 ?lm suffer from high carrier recombination loss when compared to its powder form. Although the TiO2 with rutile-anatase mixed phases has higher carrier separation ef?ciency than those with pure anatase or rutile phase, the single junction of anatase/rutile cannot avoid the recombination of separated carriers at the interface. In this study, we propose a TiO2/SnO2/Ni multi-heterojunction structure which incorporates both Schottky contact and staggered band alignment to reduce the carrier recombination loss. The low carrier recombination rate of TiO2 ?lm in TiO2/SnO2/Ni multi-heterojunction structure was veri?ed by its low photoluminescence intensity. The faster degradation of methylene blue for TiO2/SnO2/Ni multi-junctions than for the other fabricated structures, which means that the TiO2 ?lms grown on the SnO2/Ni/Ti coated glass have a much higher photocatalytic activity than those grown on the blank glass, SnO2-coated and Ni/Ti-coated glasses, demonstrated its higher performance of photogenerated carrier separation.
关键词： titanium dioxide,multijunction,thin ?lm,photocatalysis,functional coatings
更新于2025-09-23 15:21:01
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Development of Thick Superhydrophilic TiO <sub/>2</sub> –ZrO <sub/>2</sub> Transparent Coatings Realized through the Inclusion of Poly(methyl methacrylate) and Pluronic-F127
摘要： A thick coating of hierarchically porous double-templated TiO2?ZrO2?PMMA?PF127 with excellent self-cleaning properties and high transmittance has been developed for the first time on glass substrates using a simple dip-coating technique. Comparative studies of this sample with a thick and transparent coating of single-templated TiO2?ZrO2?PMMA have been performed to probe the origin of its exceptional properties. The formation of the composites, successful incorporation of the polymer into the matrix, and the porous nature of the films have been studied. The presence of Ti2+ in the double-templated samples has been confirmed, which suggest the chemisorption of water on the surface of the film. The variation in the self-cleaning properties of the samples on UV-illumination has also been studied. The double-templated film is found to possess the capability of good hydrophilic retention even 2 days after UV-irradiation.
关键词： PF127,self-cleaning,PMMA,transparent coatings,dip-coating,UV-irradiation,TiO2?ZrO2,superhydrophilic
更新于2025-09-23 15:21:01
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Poly (Vinyl Alcohol) Decorated Lithium Doped Stannous Oxide Nanocomposites as Highly Flexible UVA Shieldants
摘要： Herein, we report the successful fabrication of a series of mechanically flexible poly (vinyl alcohol) (PVA) nanocomposite films with varying amounts of lithium doped stannous oxide (Li0.4Sn0.8O) nanofillers (i.e., 0.0, 0.5, 1.0, 2.0 and 4.0 wt %) by mechanical shearing followed by film casting. The structural characterizations (FTIR) ascertain the success of lithium doped stannous oxide integrations with PVA matrix. While, electronic spectral studies sheds light on the changes in electronic band structure leading to a gradual decrease in optical band gaps associated electronic transition from valence band to conduction band. The UV-visible transmittance study substantiates the ability of nano fabricated polymeric films to efficiently shield UV radiations, in particular UVA radiations and thereby act as highly flexible and visible transparent UVA protective coatings.
关键词： Lithium doped stannous oxide,UVA protective coatings,Nano composite
更新于2025-09-23 15:21:01
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The restoration of the friction surfaces by laser cladding
摘要： The paper deals with laser cladding of wear-resistant coatings for restoring friction surfaces. It describes the modes of cladding technological process, and presents the results of wear tests. Wear-resistant coating based on the Ni-Cr-B-Si and alumina system, which exceeds 30HGSA steel by 11.5 times by wear resistance.
关键词： wear-resistant coatings,alumina,friction surfaces,Ni-Cr-B-Si,laser cladding
更新于2025-09-23 15:19:57
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Wettability, Photoactivity, and Antimicrobial Activity of Glazed Ceramic Tiles Coated with Titania Films Containing Tungsten
摘要： Self-cleaning coatings are advanced materials for the removal of pollutants and microorganisms by combining wettability, photocatalytic degradation, and antimicrobial activity. In this work, we propose a rational design of self-cleaning films based on TiO2 synthesized by sol?gel on commercial glazed ceramic tiles for building’s indoor applications. The synthesis strategy is based on hydrolysis and condensation of Ti-isopropoxide in the presence of W(VI) precursors to tune defects and crystallinity of the resulting W?TiO2 thin film. From the microstructure and surface composition analysis for different tungsten contents and annealing temperatures, we conclude that the film is composed by sintered TiO2 particles with adsorbed polytungstates (WOx) that inhibit anatase/rutile transformation. Polytungstates on TiO2 also induce surface defects that enhance water contact angle and inactivation of Escherichia coli under visible light. The presence of W(VI) has a negligible effect toward crystal violet degradation either under visible or under UV light. These results provide evidence on the existence of at least two different types of defects: (i) intrinsic defect from a sol?gel route and (ii) induced defect by tungsten species on the surface. Understanding the correlation between composition, structure, and self-cleaning properties provides a base for an efficient design of low-cost self-cleaning ceramic tiles that can be fully manufactured in an industrial plant.
关键词： photocatalytic degradation,sol?gel,W?TiO2,TiO2,antimicrobial activity,self-cleaning coatings
更新于2025-09-23 15:19:57
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Study on the Main Influencing Factors in the Removal Process of Non-Stick Fluoropolymer Coatings Using Nd:YAG Laser
摘要： The coatings with fluoropolymer resins rich in fluorinated ethylene propylene (FEP) and polytetrafluoroethylene (PTFE) are applied as anti-adherent coatings on aluminum–magnesium substrates for use in food containers. In many cases, due to wear, they must be stripped for the application of a new coating on the same substrate. There are several processes for this: blasting, plasma, pyrolysis, chemical processes, laser, high pressure water, and combinations of these. This work focuses on the characterization of the main factors that condition the FEP coating removal process by a continuous wave (CW) Nd:YAG laser, and on the determination of the efficiency of this type of technology used for this purpose. Stripping surface per unit of time and energy consumption per unit area has been determined among other efficiency indicators. Regarding the characterization of the coating object of study, its thickness, surface roughness, contact angle, microhardness and absorbance-reflectance responses have been determined, and the results have been compared with those obtained in the case of PTFE. In addition, to evaluate the mechanical damage caused in the substrate after coating removal by (CW) Nd:YAG laser, the tensile strength, Vickers hardness, Ra and Rz roughness, and the substrate thickness have been measured and analyzed.
关键词： laser coating removal,PTFE coatings,FPE coatings,Nd:YAG laser,laser stripping
更新于2025-09-19 17:15:36
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Silicon nitride and silica quarter-wave stacks for low-thermal-noise mirror coatings
摘要： This study investigates a multilayer high reflector with new coating materials for next-generation laser interferometer gravitational wave detectors operated at cryogenic temperatures. We use the plasma-enhanced chemical vapor deposition method to deposit amorphous silicon nitride and silica quarter-wave high-reflector stacks and studied the properties pertinent to the coating thermal noise. Room- and cryogenic-temperature mechanical loss angles of the silicon nitride and silica quarter-wave bilayers are measured using the cantilever ring-down method. We show, for the first time, that the bulk and shear loss angles of the coatings can be obtained from the cantilever ring-down measurement, and we use the bulk and shear losses to calculate the coating thermal noise of silicon nitride and silica high-reflector coatings. The mechanical loss angle of the silicon nitride and silica bilayer is dispersive with a linear weakly positive frequency dependence, and, hence, the coating thermal noise of the high reflectors show a weakly positive frequency dependence in addition to the normal 1/sqrt(f) dependence. The coating thermal noise of the silicon nitride and silica high-reflector stack is compared to the lower limit of the coating thermal noise of the end test mirrors of ET-LF, KAGRA, LIGO Voyager, and the directly measured coating thermal noise of the current coatings of Advanced LIGO. The optical absorption of the silicon nitride and silica high reflector at 1550 nm is 45.9 ppm. Using a multimaterial system composed of seven pairs of ion-beam-sputter deposited Ti:Ta2O5 and silica and nine pairs of silicon nitride and silica on a silicon substrate, the optical absorption can be reduced to 2 ppm, which meets the specification of LIGO Voyager.
关键词： quarter-wave stacks,silica,silicon nitride,gravitational wave detectors,thermal noise,mechanical loss,cryogenic temperatures,optical absorption,mirror coatings
更新于2025-09-19 17:15:36
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Accelerated aging of absorber coatings for CSP receivers under real high solar flux – Evolution of their optical properties
摘要： The use of durable high solar absorptance receivers is a key element in a CSP plant project. In this article, different receiver materials are studied: four alloy substrates (T91, T22, VM12, Inconel 617) combined with four new absorber coatings, operable in solar towers with molten salts or steam as heat transfer fluids, and a classic Pyromark? paint considered as a reference. In order to test the durability of the coatings, 200 solar accelerated aging cycles were applied on the samples, using a concentrated solar facility (named SAAF). The cycles were defined so as to apply realistic high solar flux and temperature on the front side of the samples, and with high cooling and heating rates reproducing the fast variation of solar irradiation due to cloudy weather and subsequent thermal shocks. The optical characteristics of the coatings were measured at the beginning and at regular intervals during the aging procedure. Different behaviors of the coatings were observed depending on the substrate, before any aging cycle. After this first aging campaign, some evolutions were observed on the solar absorptance or thermal emittance, depending on the substrate and the coating. Nevertheless, the degradations noticed are not significant enough to conclude about the durability of the coatings.
关键词： Optical characterization,CSP receiver absorber coatings,Solar furnace,Accelerated aging
更新于2025-09-19 17:15:36