热烈欢迎下一代照明技术可调白光LED的到来

单一的白光LED难以满足色彩与照明的应用需求．可调LED将是更好的选择 随着固态照明技术的性能与效率不断超越传统照明技术,该新技术得到了广泛应用。不过,如果我们只是用静态白光LED来取代传统技术的话,就难以真正发挥固态照明技术的全部潜力,不能充分实现产品的特色化。在智能驱动器支持下,LED照明灯具不仅能取代白光照明,而且还能实现新的功能,而这些功能用传统的照明技术是很难实现的。     

An optimization study for preventing silica gelation and improving filtration effectiveness during pH reduction of high concentration silica solutions

The steam generation processes at the steam-assisted gravity drainage facilities result in huge quantities of wastewater streams, which are characterized by high pH and high silica levels. These concentrated streams need to be neutralized before their disposal via down-hole injection. The neutralization of these high-pH brines results in the formation of a gel-like substance, which makes it difficult to filter the amorphous silica gel. The wastewater used in this study was synthetically prepared using sodium metasilicate to mimic high-concentration silica solutions. Our experiments did not show any advantage of a two-step pH-neutralization process over the single-step process for suppressing silica gelation. A systematic experimental campaign was undertaken to investigate the effects of SiO₂ concentration, NaCl:SiO₂ ratio, and pH on the residual silica concentration, percent silica removal, filtration rate, and filtration effectiveness. For NaCl:SiO₂ ratios higher than 4.5, silica precipitation during pH reduction did not lead to the formation of gel or sol. The response surface methodology (RSM), based on the Doehlert design of experiments, was implemented to optimize the responses and provide high efficacy with fewer experiments. The results from the analysis of variance (ANOVA) analyses of the experimental data were used to evaluate the significance of each term in the quadratic model. 3D response surfaces and 2D contour plots were generated for determining the optimal ranges of independent factors for achieving the maximum silica removal, the highest filtration rate, the best filtration effectiveness, and the minimum residual silica concentration. An optimum operating region was established from the RSM analysis and overlay plot.     

Enhanced piezoelectric strain response in 〈100〉 grain-oriented lead-free bismuth ferrite–based piezoelectric ceramics

The 〈100〉 grain-oriented 0.11(Bi_0.5K_0.5)TiO₃–0.23BaTiO₃–0.02Bi(Mg_0.5Ti_0.5)O₃–0.64BiFeO₃ piezoelectric ceramics were prepared by a reactive templated grain growth method using a platelike H_1.08Ti_1.73O₄·nH₂O (HTO) template and Bi₂O₃–KHCO₃–MgO–Fe₂O₃–BaCO₃ matrix particles. The high degree of texturing (a Lotgering orientation factor of 80%) and high density (95%) were achieved by employing weight-pressing treatment during the binder-removal and sintering treatment along with optimizing the sintering temperature. The water-quenching treatment has a significant impact on the enhancement of dielectric, ferroelectric, and piezoelectric properties with the increase of dielectric constant, remanent polarization, and piezoelectric strain constant from 764, 13.6 μC/cm², and 384 pm/V for the as-sintered ceramics to 812, 29.9 μC/cm², and 526 pm/V after the water-quenching treatment at 850°C, respectively. The obtained piezoelectric strain constant with a 1.8 times enhancement compared to that of the ceramics with randomly oriented grains is significantly higher than those reported for other lead-free piezoelectric ceramics with Curie temperature >300°C. This study suggested the strong potentiality of this material system for high-temperature actuator application.     

Light-Powered Self-Adaptive Mesostructured Microrobots for Simultaneous Microplastics Trapping and Fragmentation via in situ Surface Morphing

Microplastics, which comprise one of the omnipresent threats to human health, are diverse in shape and composition. Their negative impacts on human and ecosystem health provide ample incentive to design and execute strategies to trap and degrade diversely structured microplastics, especially from water. This work demonstrates the fabrication of single-component TiO₂ superstructured microrobots to photo-trap and photo-fragment microplastics. In a single reaction, rod-like microrobots diverse in shape and with multiple trapping sites, are fabricated to exploit the asymmetry of the microrobotic system advantageous for propulsion. The microrobots work synergistically to photo-catalytically trap and fragment microplastics in water in a coordinated fashion. Hence, a microrobotic model of “unity in diversity” is demonstrated here for the phototrapping and photofragmentation of microplastics. During light irradiation and subsequent photocatalysis, the surface morphology of microrobots transformed into porous flower-like networks that trap microplastics for subsequent degradation. This reconfigurable microrobotic technology represents a significant step forward in the efforts to degrade microplastics.     

Flexural behavior of stepped graphite/epoxy laminates

Cross-ply tapered/stepped laminates with taper angles of 1 and 2° between the top and bottom surfaces were fabricated using T300/943 graphite/epoxy by compression molding. Ply terminations were done internally within the laminate and externally on the surface of the laminate at various cross-sections in order to obtain the taper. Equivalent cross-ply specimens with internal and external ply terminations, respectively, were tested in three point bending. The bending stiffness of the equivalent corss-ply are nearly equal, while the failure modes are significantly different. The tapered laminates with internal ply terminations failed due to a series of delaminations originating at the step corners of the 0° plies. Macroscopically, the specimens with internal ply term nations failed by tensile fracture of the outer plies at relatively higher loads.     

Photocatalytic Activity of Pure and Zinc Doped Tin Oxide Nanoparticles Synthesized by One Step Direct Injection Flame Synthesis

A very simple and rapid Direct Injection Flame Synthesis (DIFS) method is effectively used to synthesize pure tin oxide (SnO₂) and zinc doped tin oxide (Zn:SnO₂) nanoparticles from the metallic tin (Sn) and zinc (Zn) powders for the photocatalytic degradation of methylene blue (MB) dye. The DIFS nanoparticles were characterized using XRD, Raman, UV–Vis, FESEM, PL and EDX studies. The X-ray diffraction analysis indicated that the synthesized SnO₂ and Zn:SnO₂ nanoparticles have pure tetragonal phases and their average crystallite size decreases when Zn was doped with SnO₂. Raman study confirmed the various mode of vibrations and the crystal structure of the synthesized nanoparticles. Purity, atomic percentage and chemical composition were analysed using Energy dispersive X-ray analysis and found to be free from impurities. The band gap energy increases from 3.5 to 3.6 eV upon doping which was revealed from the UV–Visible spectroscopic analysis. Photoluminescence analysis confirms the red shifted emission for Zn:SnO₂ due to the oxygen deficiency. The CIE chromaticity (x,y) for SnO₂ and Zn:SnO₂ was calculated from the emission spectra and the co-ordinates represents blue and violet region respectively. Field Emission Scanning Electron Microscopy analysis showed that the pure SnO₂ nanoparticles have irregular, agglomerated, nanoflowered and nanoclustered formation whereas Zn:SnO₂ nanoparticles has more crystalline, cubical and nanoflake structure. The photocatalytic activity was enhanced due to the presence of Zn in SnO₂ under UV light irradiation. The efficiency of MB degradation by SnO₂ was found to be 82% and enhanced to 88% upon doping. Thus the Zn doped SnO₂ nanoparticles synthesized by DIFS was found to be an effective photocatalyst than the pure SnO₂.