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Effectively utilizing deep red to near-infrared (DR-NIR) phosphors to achieve the optimal performance of NIR phosphor-converted white LEDs (DR-NIR pc-wLEDs) is currently a research hotspot. In this study, an optical model of DR-NIR pc-wLEDs with virtual multilayer fluorescent films was established based on the Monte Carlo ray-tracing method. Different gradient distributions of the particles were assigned within the fluorescent film to explore their impact on the optical performance of pc-LEDs. The results show that, for the case with single-type particles, distributing more DR-NIR particles far from the blue LED chip increased the overall radiant power. The distribution of more DR-NIR particles near the chip increased the conversion ratio from blue to DR-NIR light. The ratio of the 707 nm fluorescence emission intensity to the 450 nm excitation light intensity increased from 1:0.51 to 1:0.28. For multiple-type particles, changes in the gradient distribution resulted in dual-nature changes, leading to a deterioration in the color rendering index and an increase in the correlated color temperature, while also improving the DR-NIR band ratio. The reabsorption caused by the partial overlap between the excitation band of the DR-NIR particles and the emission band of the other particles enhanced the radiant power at 707 nm. Distributing DR-NIR phosphor particles closer to the chip effectively amplified this effect. The proposed model and its results provide a solution for the forward design of particle distributions in fluorescent films to improve the luminous performance of DR-NIR pc-wLEDs. [ABSTRACT FROM AUTHOR]

Extreme wettability materials, which can enable high-efficiency oil/water separation, has become a widely discussed topic due to increasingly severe oil pollutions including frequent offshore oil-spills accidents and industrial oily wastewater emission. However, most of existing methods to prepare these materials involved complicated machining processes or dangerous operations, especially the use of corrosive or toxic chemicals. Herein, a novel and environment friendly method including mark electrochemical machining (MECM) and subsequent chemical immersion, was proposed to acquire micropore arrays on Al foil for efficient oil collection from oil/water mixtures. Micro-dimple arrays were generally fabricated by MECM process followed by CuCl2 immersion to make it through. Both simulation and experimental verification were conducted to elucidate how dimple structures varied with machining parameters. The micro-scale rectangular-shaped step-like structures on micropore arrays endowed as-prepared samples with excellent superhydrophibic and underwater superoleophobic properties. Moreover, oils with kinematic viscosities ranging from 0.41 to 74.4 cSt could be separated from water with separation efficiencies above 95%. The superhydrophilic Al foil still showed good durability through repeated oil/water separation tests, and retained its superhydrophilicity even after the storage in water for 120 hours. Therefore, this novel and green method gives researchers new insights into functional materials preparation for practical oil/water separation. [ABSTRACT FROM AUTHOR]

A morphology investigation of sectional stripes and adhering slag based on the vapor-to-melt ratio is carried out to reveal the effect of material removal proportion on the Nd:YAG laser cutting process. The influences of vapor-to-melt ratio on the morphology of sectional stripes and adhering slag (roughness, stripe width, and slag height) are investigated by the experimental observation and analysis. It is shown that the maximum particle diameter demonstrates the size of the hanging slag nodules, and the average particle diameter reflects the section stripe spacing. At a suitable vapor-to-melt ratio, the stripes with regular morphology and uniform width allow the molten layer to produce spherical particles with smaller diameter and uniform size. The molten pool is superimposed and the material is evenly paved, resulting in a good roughness of the section. Because of the good removal effect, the proportion of the membranous part hanging on the bottom surface is higher than that of the nodular part. Although the slag height is relatively obvious, the microcracks connected inside make the whole adhering slag easier to remove. The control of vapor-to-melt ratio is helpful for reducing the height of adhering slag and the proportion of nodular solidified materials, which has guiding significance for improving the cutting quality of the bottom surface of the plate. [ABSTRACT FROM AUTHOR]