•Incoherent UV light treatment significantly enhances CFRP bonding strength.•UV treatment yields 10% higher bonding strength than laser-texturing.•The adhesion of UV treated samples exceeded the CFRP ...interlaminar strength.•UV treatment reduces CFRP surface WCA from 90° to 20°.•Combined IR laser & UV treatment has small gain over single laser treatment.
The preparation of Carbon Fibre Reinforced Polymers (CFRP) surfaces for adhesive bonding has been widely reported. Such reports include laser texturing using both near-infrared (IR) lasers and ultraviolet (UV) lasers. In this report, we present, for the first time, findings showing that surface treatment of CFRP using incoherent UV light, at 254 nm wavelength, can increase the adhesive bonding strength of CFRP by 75 % compared to non-treated samples. It is also around 10 % stronger than NIR laser-textured samples. However, combination treatments, where the UV irradiation is conducted either before or after laser texturing did not give a significant benefit over the laser-textured samples. A germicidal 46 W 254 nm UV lamp was used for the UV light treatment, while an IR nanosecond pulsed fibre laser operating at 1064 nm was used for the laser texturing treatment. The material tested was an autoclave-cured T700 CFRP composite.
The wettability of the treated CFRP surfaces and the adhesive bonding were quantitatively assessed. This study concludes that low-cost incoherent UV treatment effectively reduces the water contact angle of the CFRP surface and activates CFRP surfaces. All treatments led to bonding strengths at least 50% greater than for the untreated surfaces.
The predominant failure mode for UV-treated samples was Cohesive Substrate Failure (CSF), indicating that the adhesion strength exceeded the interlaminar shear strength of the CFRP material. All samples treated with the laser (including combined treatment with UV) exhibited Light Fibre Tear Failure.
Silicon carbide (SiC) nanopowders were synthesized under Ar atmosphere via the carbonization reaction method using silicon powders and expanded graphite as initial materials, and ferric nitrate as ...catalyst precursor. The effects of heat treatment temperature and the C/Si molar ratio on SiC products were studied. The microstructure, phase composition and chemical state of the products were analyzed by XRD, SEM, XPS, TEM and Raman. The photoluminescence (PL) properties of SiC nanopowders were tested. The results showed that the content of the 3C–SiC product is higher after heat treatment at 1400 °C for 3 h with a molar ratio of C/Si of 1:1. 3C–SiC exists in the form of particles and wires. The formation process of 3C–SiC can be explained by a two-step method, nucleation under catalysis and growth under Vapor-Solid (VS) mechanism. Two ultraviolet light emission peaks are observed at about 318 and 380 nm. The main PL spectra of 3C–SiC nanopowders exhibit larger blueshifts. The blueshift is attributed to the stacking fault, oxygen defects, morphology and quantum confinement effect. It has potential application prospects in ultraviolet detectors, optoelectronic devices and light emitters.
Light-emitting diode (LED) technologies are economical and efficient devices that could be considered in poultry processing as disinfection strategies. This study evaluated the efficacy of a ...LED-based device to reduce the microbial load on chicken meat and investigated it's impact on selected quality parameters. Quality parameters including pH, texture and color after LED-UV exposure and during subsequent storage for 7 days at 4 ̊C were investigated. Diced chicken breast fillets were exposed to UV light wavelengths of 255, 280, 300 and 365 nm for 2, 4, 6, 8 and 10 min. A microbiological analysis was conducted on chicken samples to enumerate bacterial counts. Reductions between 1.17 and 1.67 log CFU/g for total viable counts of mesophilic, psychrophilic bacteria and total Enterobacteriaceae counts were observed, whereas, up to 2 log CFU/g was obtained for Pseudomonas and lactic acid bacteria groups after treatment with wavelengths of 280, 300 and 365 nm. Furthermore, color, texture and pH were not affected by exposure to UV light at 280 nm even following 7 days storage. Thus, LED-based technologies could be applied on poultry meat to reduce the levels of spoilage bacteria while maintaining quality attributes.
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•Wavelengths of 280, 300 and 365 nm obtained the best inactivation results.•The most affected bacteria were the Pseudomonas genus and lactic acid bacteria.•Application of UV light at 280 min and storage did not alter pH, color and texture.•LED-UV based technology is a potential disinfection strategy of chicken fillets.
Organic ultraviolet filters (OUVFs) are used in a wide range of manufactured products including personal care (e.g. sunscreens) and plastic items. This review summarizes the available data regarding ...the toxic effects of OUVFs on marine and freshwater organisms and generates the predicted no-effect concentration (PNEC) values necessary for assessing ecological risk. Through a systematic search of the literature, 89 studies were identified and ecotoxicological data extracted. Collectively, these studies described toxicity testing with 39 OUVF from 10 structural classes, with derivatives of benzophenones (49%) and camphors (16%) most studied. There was a bias towards selecting freshwater species (61%), and evaluating single OUVF effects (87%) rather than OUVF mixtures. Short-term (acute) experimentation (58%) was marginally more common than long-term (chronic) testing (42%). Reproductive, developmental, genetic, and neurological toxicity were the most commonly identified effects in aquatic organism, and were associated with molecular interactions with steroid receptors, DNA, or the production of reactive oxygen species. Species sensitivity distribution and/or assessment factors were used to calculate PNECs for 22 OUVFs and the risk quotients for 12 OUVFs. When using maximum concentrations, high risk was observed for six OUVFs in marine environments (4-methylbenzylidene-camphor, octocrylene, padimate-O, benzophenone-1, and oxybenzone, ethylhexyl-4-methoxycinnamate), and for four OUVFs in freshwater environments (ethylhexyl-4-methoxycinnamate, octocrylene, avobenzone and oxybenzone). When using median concentrations, a risk to marine environments was observed for oxybenzone. The results of this review underline that there is limited knowledge of the pathological effects of OUVFs and their metabolites in aquatic environments, and this inhibits the development of informed water-quality guidelines.
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•Studies on effects of organic UV filters (OUVFs) in aquatic organisms were reviewed.•Evidence shows several OUVFs pose a risk to marine and freshwater environments.•Research has focused on effects of oxybenzone, and studies with freshwater biota.•Effects on endocrine system, growth, and stress response were most studied.•Mixture interactions are a key environmental issue but poorly understood.
OUVF research has focused on effects in freshwater more than marine organisms, yet evidence indicates OUVFs pose a risk to both; but current knowledge gaps inhibit the development of informed water-quality guidelines.
•Cr(VI) in soil could be reduced through combined UV and EKR technologies.•Soil organic matter and iron sources were electron donors and catalysts.•Organic acids enhanced total Cr(VI) removal through ...desorption and photoreduction.•This study firstly investigated more suitable organic acids for UV/EKR systems.
Reducing highly toxic and mobile Cr(VI) to environmentally less hazardous Cr(III) is vital research for remediating Cr-contaminated soil. In this study, a UV/EKR system, which combined electrokinetic remediation (EKR) technology with ultraviolet (UV) photoreduction, was employed to investigate the enhanced reduction of Cr(VI) in actual contaminated soil by oxalic, malic, and tartaric acids. The results demonstrated that the introduction of UV radiation resulted in the removal of 99.49% of Cr(VI) from the anolyte and further enhanced the removal efficiency of high-concentration Cr(VI) in the near-anode soil layer by 14.83% compared to traditional EKR. Among the three acids, malic acid exhibited superior performance, as it alleviated the clogging caused by precipitates, provided more photocatalyst Fe(III), and reduced the retention of the reduction product Cr(III) in the soil. This resulted in the removal rates of 90.38%, 83.82%, and 27.14% of water-soluble, weakly bound, and strongly bound Cr(VI), respectively in the near-anode soil layer. Therefore, the combination of organic acids and the UV/EKR technique shows high compatibility, offering a promising solution to the poor reduction efficiency of Cr(VI) in actual soil in the field of EKR. This approach provides new insights for the in-situ remediation of Cr-contaminated soil.
High‐quality epitaxy consisting of Al1−xGaxN/Al1−yGayN multiple quantum wells (MQWs) with sharp interfaces and emitting at ≈280 nm is successfully grown on sapphire with a misorientation angle as ...large as 4°. Wavy MQWs are observed due to step bunching formed at the step edges. A thicker QW width accompanied by a greater accumulation of gallium near the macrostep edge than that on the flat‐terrace is observed on 4° misoriented sapphire, leading to the generation of potential minima with respect to their neighboring QWs. Consequently, a significantly enhanced photoluminescence intensity (at least ten times higher), improved internal quantum efficiency (six times higher at low excitation laser power), and a much longer carrier lifetime are achieved. Importantly, the wafer‐level output‐power of the ultraviolet light emitting diodes on 4° misoriented substrate is nearly increased by 2–3 times. This gain is attributed to the introduction of compositional inhomogeneities in AlGaN alloys induced by gallium accumulation at the step‐bunched region thus forming a lateral potential well for carrier localization. The experimental results are further confirmed by a numerical modeling in which a 3D carrier confinement mechanism is proposed. Herein, the compositional modulation in active region arising from the substrate misorientation provides a promising approach in the pursuit of high‐efficient ultraviolet emitters.
Enhanced ultraviolet luminescence of AlGaN wavy‐quantum‐wells grown on large misoriented sapphires is demonstrated, enabled by the successful introduction of compositional inhomogeneities in AlGaN alloys induced by gallium accumulation and thus forming a 3D carrier confinement for radiative recombination. Herein, the compositional modulation in active region arising from large misoriented‐substrate offers a promising approach in the pursuit of high‐efficient ultraviolet emitters.
A semi-interpenetrating solid state polymer networks electrolytes (SISPEs) for rechargeable lithium metal batteries is proposed.
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•Semi-interpenetrating polymer solid electrolytes ...(SISPEs) with are synthesized via ultraviolet light curing.•The PVEC segment of the SISPEs can ensure high ionic conductivity.•The semi-interpenetrating polymer networks enhance the mechanical properties.•The LFP||SISPEs||Li cells exhibit a long-term stability and excellent cycling performance.
Electric vehicles and portable electronics pose an insatiable demand for safe and high-energy batteries. Herein, we report semi-interpenetrating solid state polymer networks electrolytes (SISPEs) for rechargeable lithium metal batteries. The synthesized SISPEs combine the poly(vinylethylene carbonate) (PVEC) segment containing carbonate moieties and the high molecular weight poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) with good mechanical properties. The carbonate moieties in the PVEC segment enable high ionic conductivity of 1.03 mS cm−1 at 25 0C. The incorporation of PVDF-HFP into the semi-interpenetrating polymer networks endows SISPEs with considerable mechanical properties and long-term stability of the symmetric Li cell at a current density of 0.2 mA cm−2 for over 2000 h. As a result, the assembled LiFePO4||SISPEs||Li batteries exhibit excellent cycling performance with high coulombic efficiency over 600 cycles at 0.5C. This study sheds light on rational design of high-performance composite polymeric electrolytes for rechargeable solid lithium metal batteries.
AlGaN based deep‐ultraviolet light‐emitting diodes (DUV‐LEDs) have a wide range of applications and a large market is expected. However, the efficiency of DUV‐LEDs is still much lower than that of ...blue LEDs due to a quite low light‐extraction efficiency (LEE). We improved the LEE of DUV‐LEDs by using a superlattice (SL) hole spreading p‐AlGaN contact layer, a dot matrix Ni/Au electrode and an Al reflector. DUV‐LED samples in which the SL p‐AlGaN contact layer has various period lengths, and forms two different p‐type electrodes, a conventional Ni/Au electrode and a dot matrix Ni/Au electrode with an Al reflector are fabricated. By comparing these LED samples, it is confirmed that contact layers with relatively longer periods are suitable both for vertical hole injection and lateral spreading of the holes. By increasing the Al content and recovering the transparency of the SL p‐AlGaN contact layer, the LEE is increased by up to a factor of 1.6.
Currently, an increase in the efficiency of deep‐ultraviolet light‐emitting diodes (DUV‐LEDs) is one of the major subjects toward the expected large market in sterilization. In this article, the increase of external quantum efficiency (EQE) of 280 nm‐band DUV‐LEDs by enhancing the light‐extraction efficiency (LEE) through introducing a superlattice (SL) hole spreading transparent p‐AlGaN contact layer, a dot matrix p‐type electrode and an Al reflector is demonstrated.
In this article, a novel graded superlattice (SL) p-AlGaN structure for deep ultraviolet light-emitting diode (DUV LED) capable of emitting 273 nm has been studied. It is observed that the output ...power in the case of graded SL p-AlGaN LED structure (GSLED) is significantly high (7.68-fold higher, at the current density of 200 A/cm²) compared with a conventional structure. Moreover, noticeable improvements in the maximum value of external quantum efficiency, as well as the efficiency droop, are achieved with the modified structures. The abrupt potential barrier height in conventional DUV LED (CLED) obstructs the hole injection inside the quantum well region. On the contrary, smoother band variation in GSLED prevents potential barrier height of hole and causes ease in the flow of hole into the quantum well (QW) region. Also, the electron concentration in the multiple-quantum-well (MQW) region for GSLED is increased by around 100% due to the reduced leakage of electrons toward the p-region.
Technologies for controlling gaseous emissions of livestock is of interest to producers, the public, and regulatory agencies. In our previous lab-scale study, the use of a photocatalytic coating on ...surfaces subjected to black ultraviolet light reduced emissions of key odorant compounds relevant to the livestock industry. Thus, an on-farm pilot-scale experiment was conducted at a commercial swine barn to evaluate a photocatalytic coating on surfaces subjected to ultraviolet light under field conditions. A flow-through reactor was constructed with a TiO2-based photocatalytic coating on the interior surfaces and black ultraviolet light fixtures. The reactor was deployed in a room downstream of the entire swine barn exhaust. Gas samples were collected from three sampling ports in the reactor, one at the inlet (control), the midpoint (half treatment) and the outlet (treatment). Compared to the control, significant reductions in emissions were observed for p-cresol (22%), odor (16%) and nitrous oxide (9%). A significant increase in carbon dioxide (3%) was also measured. Results show that the TiO2-based photocatalytic coating and black UV light are effective in mitigating odor, a key VOC responsible for downwind swine odor, and one important greenhouse effect gas when subjected to swine barn exhaust.
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•UV light and photocatalyst tested on farm to mitigate gaseous emissions.•Treatment reduced p-cresol emissions 22%.•Treatment reduced odor emissions 16%.•Treatment reduced N2O emissions 9%.•No significant change to CH4 emissions was observed.
