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A double-layer white light converter with high efficiency heat transfer structure for high-power NUV LEDs/LDs
摘要： As a next-generation lighting technology, high-power light-emitting diodes (LEDs) and lasing diodes (LDs) lighting have attracted great attention to high-brightness applications. However, producing an efficient illumination-grade color converter with a conspicuous color rendering index (CRI) and a suitable correlated color temperature (CCT) remains an outstanding challenge in the field of high-power LEDs/LDs lighting. In this work, a double-layer white light converter with high efficiency heat transfer structure was designed and prepared by precisely coating a blue/green emitting phosphor-in-silicone (PIS) film on red emitting transparent ceramic substrate. The well-designed double-layer converter exhibits excellent optical properties that the optical-optical conversion efficiency can achieve 156 lm/W with conspicuous CRI (92.6), CIE chromaticity coordinate (0.332, 0.335) and suitable CCT (5511K), respectively. Furthermore, the heat transfer efficiency of the double-layer converter was analyzed and simulated by using infrared thermal imaging and steady state thermal simulation, which reduce the temperature efficiently than single-layer converter under high-power NUV LEDs/LDs excitation. These comprehensive performance show that the double-layer converters are promising as NUV LEDs/LDs-driven phosphors in high-power solid-state lighting devices.
关键词： high-power LED/LD,transparent ceramic,white light converter,thermal performance,double-layer structure
更新于2025-09-12 10:27:22
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Facile preparation and properties of polyvinylidene fluoride dielectric nanocomposites <i>via</i> phase morphology control and incorporation of multiwalled carbon nanotubes conductive fillers
摘要： A novel PVDF dielectric nanocomposite was achieved by controlling phase morphology and incorporating conductive ?llers simultaneously, and the mechanical, thermal, dielectric properties of the resultant dielectric nanocomposites were investigated. Mechanical analysis showed that incorporation of modi?ed MWCNTs (MWCNTs-COOH) in the PVDF nanocomposites resulted in signi?cant improvements on the tensile strength (Ts) and elasticity modulus (Em). When the ?ller content was 12 wt%, the Ts of MWCNTs-COOH/PVDF could reach 64.6 MPa. XRD test showed that the addition of MWCNTs-COOH and MWCNTs promoted the formation of β-phase of PVDF. DMA analysis showed that the glass-transition temperature of the PVDF nanocomposites slightly increases on loading of original MWCNTs and this effect was more pronounced on loading MWCNTs-COOH. The dielectric property analysis showed that the original MWCNTs were more likely to form local conductive networks in the PVDF matrix, promoting the electron displacement polarization, and improving the dielectric constant. When the contents of MWCNTs was 12 wt%, the percolation threshold was obtained and the dielectric constant (ε0) reached 286, which was 36 times of pure PVDF. Our work provides a simple way to fabricate polymer blends with excellent dielectric performances, good mechanical properties as well as good processing capability but low cost.
关键词： polyvinylidene ?uoride (PVDF),thermal performance,dielectric properties,multi-walled carbon nanotubes (MWCNTs),mechanical properties
更新于2025-09-11 14:15:04