结构用工程竹抗紫外线老化性能的试验研究

紫外线是导致材料老化的主要因素之一,通过人工加速老化试验,模拟太阳光中的紫外线辐射,加上温湿度循环变化的影响,测试未经防护处理的工程竹的物理力学性能,并与花旗松木材在紫外线辐射下的物理力学性能变化进行对比,评价胶合竹、重组竹、花旗松木材试样的抗紫外线老化性能。结果表明,花旗松木材颜色对紫外线辐射比较敏感,受辐射面有明显的颜色变深,在紫外线辐射下胶合竹也发生颜色变黄但没有花旗松木材严重,重组竹的颜色变化不明显;除顺纹抗压强度胶合竹降幅最大外,顺纹抗压弹性模量、顺纹抗拉强度、抗弯强度、抗弯弹性模量均为花旗松木材降幅最大。总体来说,重组竹的抗紫外线老化性能最优,但胶合竹、重组竹、花旗松木材这三种材料在紫外线辐射作用下均有不同程度的力学性能退化,用于室外环境时需要进行防护处理。     

In situ synthesis and hydrothermal crystallization of nanoanatase TiO2–SiO2 coating on aramid fabric (HTiSiAF) for UV protection

TiO₂–SiO₂ thin film was prepared by sol‐gel method and coated on the aramid fabric to prepare functional textiles. The aramid fabric was dipped and withdrawn in TiO₂–SiO₂ gel and hydrothermal crystallization at 80^°C, then its UV protection functionality was evaluated. The crystalline phase and the surface morphology of TiO₂–SiO₂ thin film were characterized using SEM, XRD, and AFM respectively. SEM showed hydrothermal crystallization led to a homogeneous dispersion of anatase nonocrystal in TiO₂–SiO₂ film, and XRD suggested the mean particle size of the formed anatase TiO₂ was less than 30 nm. AFM indicated that hydrothermal treatment enhanced the crystallization of TiO₂. UV protection analysis suggested that the hydrothermally treated coated textile had a better screening property in comparison with TiO₂–SiO₂ gel and native aramid fabric. Microsc. Res. Tech. 78:918–925, 2015. © 2015 Wiley Periodicals, Inc.     

水性UV聚氨酯丙烯酸酯/二氧化硅复合材料的制备及涂膜性能

目的 制备光固化水性聚氨酯改性丙烯酸酯/二氧化硅（WPUA/SiO2）复合材料,提高水性光固化聚合物材料的涂膜性能。方法 制备含双键官能化的二氧化硅纳米粒子,将其引入到制备的可光固化聚氨酯改性丙烯酸酯乳液体系中,制备水性UV固化WPUA/SiO2复合乳液,研究复合材料制备方法,分析体系中官能化二氧化硅纳米粒子的分散稳定性及其对涂膜形貌、透光性、硬度等性能的影响。结果 由于WPUA和官能化二氧化硅纳米粒子均含有C==C,所制备的WPUA/SiO2复合材料可以用UV光进行固化,官能化二氧化硅纳米颗粒由于表面存在有机分子链,与水性聚氨酯改性丙烯酸酯相容性提高,使得二氧化硅纳米颗粒掺杂量达到10％（质量分数）时可存储稳定性达30天以上。固化后涂层的透光性和力学性能明显提升,涂层铅笔硬度达到3H,粘附性为1级,抗冲击强度大于50 kg?cm。结论 制备的WPUA/SiO2复合体系具有良好的稳定性,改性纳米粒子的掺杂对水性UV固化聚氨酯改性丙烯酸酯的力学性能有明显改善,且可提高复合涂层的透光性。     

Effect of vinyl acetate content on the photovoltaic-encapsulation performance of ethylene vinyl acetate under accelerated ultra-violet aging

The vinyl acetate (VA) content in ethylene vinyl acetate (EVA) can significantly affect its performance as an encapsulant in photovoltaic modules under field conditions. EVA films of varying VA content (18, 24, 33, and 40%) have been prepared using twin screw extruder with the necessary additives and subsequently cured at 150 °C. All the EVA films have been subjected to UV radiation at a wavelength of 340 nm for 1000 and 2000 h to simulate accelerated field aging. The effects of accelerated aging on the gel content, mechanical properties, transmittance, Fourier transform infra-red (FTIR) spectra, thermal stability, degree of crystallinity, and yellowness have been studied. The observations made in this study of UV aging up to 2000 h suggests that the optimum range of VA content in EVA should be between 18 and 33% by weight. VA content beyond 40% degrades almost all properties needed for an encapsulate material after aging of only 2000 h. VA content of around 18% is the most stable under UV aging conditions but has a slightly lower value of transmittance for the unaged sample although the difference in transmittance between different specimens decreases with UV aging. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48268.     

Synthesis of hydrophobic W18O49 nanorods for constructing UV/NIR-shielding and self-cleaning film

Nanomaterials with ultraviolet/near-infrared (UV/NIR) shielding property have great potential for developing energy-saving windows. In this work, we report low-cost W₁₈O₄₉ nanorods as UV/NIR shielding material. W₁₈O₄₉ nanorods with the length of ~20 or ~60 nm were prepared by simple solvothermal method, and they exhibited strong size-dependent absorption in the UV/NIR region. By mixing W₁₈O₄₉ nanorods with polydimethylsiloxane (PDMS), W₁₈O₄₉@PDMS films were constructed and they could shield 55.58% of UV and 75.89% of NIR light while transmit 58.03% of visible light. A sealed box with W₁₈O₄₉@PDMS-coated glass as the window exhibited a minimal temperature elevation (△T = 9.2 °C) compared to those coated with pure glass (△T = 18.2 °C) or ITO glass (△T = 12.1 °C), under the irradiation of solar light (0.6 W cm⁻²). Additionally, the films had a contact angle of 122 ± 2°, showing self-cleaning ability. Therefore, W₁₈O₄₉@PDMS films can act as cost-efficient UV/NIR-shielding and self-cleaning film.     

Synthesis and structural,morphological, compositional,optical and electrical properties of DBSA-doped PPy–WO3 nanocomposites

Synthesis of DBSA-doped PPy–WO₃ (organic–inorganic) nanocomposites, using a novel approach, has been proposed, and further envisaged for their structural, compositional, morphological, optical and electrical properties. DBSA-doped PPy–WO₃ nanocomposites demonstrate superior above mentioned properties than their counterparts i.e. either PPy or WO₃. The XRD spectra of nanocomposites supported to conclude that both i.e. PPy and DBSA have no impact on the crystallinity of WO₃ nanoparticles. The chemical structure of DBSA-doped PPy–WO₃ nanocomposites have been elucidated using FTIR spectra. The morphologies and surface roughnesses of the DBSA-doped PPy–WO₃ nanocomposites were confirmed using scanning electron microscope and atomic force microscope images, respectively. Interconnected type morphology and 13 nm average surface roughness were confirmed for DBSA doped PPy–WO₃ hybrid nanocomposites. The EDX and XPS analyses evidence that, the formation of DBSA doped PPy–WO₃ hybrid nanocomposites without any elemental impurities. The absorption peak of DBSA-doped PPy–WO₃ nanocomposites shift towards the lower wavelength side as compared to the PPy–WO₃ (50%) hybrid nanocomposites. Anionically charged sulfonate group which is supposed to stabilize doped state of the DBSA-PPy–WO₃ nanocomposites, may be responsible for this shift. The dc electrical conductivity of DBSA-doped PPy–WO₃ nanocomposites increases as the content of DBSA is increased from 10 to 50% this could be accounted for by the generation of conduction path through the PPy–WO₃ nanocomposites as DBSA has anionic surfactant nature by preventing an agglomeration of functional material.     

Improved bias stress stability of In–Ga–Zn–O thin film transistors by UV–ozone treatments of channel/dielectric interfaces

Possibility of improving the bias stress stability of amorphous In–Ga–Zn–O thin film transistors (a-IGZO TFTs) was explored by irradiating the channel/dielectric interface with ultraviolet (UV) light during the device fabrication process. The UV treatment of the channel/dielectric interface did not cause significant changes in the device performance itself. However, when the TFTs were tested under prolonged gate bias stress, the device with longest UV treatment showed the smallest time dependence of threshold voltage shift. This accompanied the smallest changes in the field effect mobility and subthreshold swing with extended bias stress. Such improvements in bias stress stability are attributed to the modification of the channel/dielectric interface due to the UV-generated ozone that in turn decreased the interface trap density and structurally modified the interface region on the dielectric side to prevent the redistribution of the trapped charges.     

The application of photography in investigating fraud

The impact of fraud on the world economy is significant. As fraud has evolved it has become more organized and increasingly cyber-enabled and committed across borders of law enforcement jurisdictions. The technological demands facing fraud investigators are increasing. Yet, little attention has been given to how forensic photography can help tackle emerging crime types, like fraud. This study reviews literature surrounding forensic photography and provides an up to date and collective narrative. This article focuses on the advancements in photography and how imaging-science techniques can apply to a fraud investigation. Photographic practice plays a key role in many crime investigations but must embrace continual change to ensure that it remains relevant to modern policing. Fresh approaches are essential and practitioners must fully utilize new technologies and adapt to tackle the increasingly demanding scope of fraud types.