Preparation of Internally Plasticized Ester of Cellulose Irradiated by Microwave and Its Properties

This paper demonstrates esterification of cellulose with long-chain carboxylic acid in a homogeneous phase irradiated by microwave. The esterification reaction system was cellulose, fatty acid, and LiCl/dimethylacetamide (LiCl/DMAc) using p-toluenesulfonyl chloride (Ts-Cl) as activating reagents. It was found that the use of a microwave resulted in a dramatic drop in reaction time (90s), two orders of magnitude faster than conventional reaction under heating. The degrees of substitution (DS) and molar yields of fatty acid, Ts-Cl amounts and reaction time, as well as the property of final products, were studied. Partially derivative celluloses, which underwent a significant change in morphological structure during the modification, presented obvious glass transition compared to starting cellulose. In agreement with this, the crystallization property of the internally plasticized esters was different from cellulose. Together, these results indicated the reaction of acylation.     

Effect of Ni7+ Ion Irradiation on Structure and Ammonia Sensing Properties of Thermally Oxidized Zinc and Indium Films

ZnO and In2O3 films were prepared by thermal oxidation of vacuum deposited zinc and indium films, respectively onto the glass substrate at 30 C. The fabricated films have been irradiated with 100-MeV Ni7+ ions at different fluences ranging from 5×1011 to 5×1013 ions/cm2. The structural and gas sensing properties of pristine and irradiated films have been discussed. X-ray diffraction (XRD) pattern of pristine and irradiated films reveal that the films are polycrystalline in nature and crystallinity increases after irradiation. In this study, highly porous In2O3 nanorods evolved when being irradiated at a fluence of 5×1013 ions/cm2 while ZnO film shows decrease in number of nanowires. The ammonia sensing performance of the Ni7+ irradiated In2O3 films shows an improvement as compared to its pristine counterpart.     

PET包装材料中紫外吸收剂迁移研究进展

PET包装材料广泛应用于食品包装中,为了提高对应的抗光氧化能力,会添加一定量的紫外吸收剂于其中,而紫外吸收剂在长期贮存过程中存在迁移溶出隐患。对PET包装材料中紫外吸收剂的种类、迁移机制及国内外迁移研究进展进行综述,并进行展望。     

Near tip stress intensity factor for an edge-crack in a Pb(ZrxTi1−x)O3 thin film with 90° domain switching under a continuous laser irradiation

The near tip stress intensity factor K_Itip for an edge-crack in a Pb(Zr_xTi_1−x)O₃ thin film was investigated by superposition of the applied stress intensity factor K_Iapp under a continuous laser irradiation and the shielding stress intensity factor ΔK_I for 90° domain switching. Both K_Iapp and ΔK_I were solved by the weight function method, and switching toughening was analyzed based on the small scale domain switching theory. Results show that K_Itip of the edge-crack in the thin film is significantly affected by the initial poling angle, and the edge-crack tip is toughened by the domain switching area with the increase of the initial poling angle. The methodology can predict the fracture toughening of Pb(Zr_xTi_1−x)O₃ thin films quantitatively.     

UV nanoimprint using flexible polymer template and substrate

Nano to micro-sized patterns were formed on a flexible polymer substrate using a flexible UV imprint stamp. A 6 in. diameter flexible UV nanoimprint template was fabricated using PVC hot embossing and DLC coating. Using the UV nanoimprint process with the DLC coated PVC template, nano to micro-sized patterns were clearly formed on the flexible PET substrate without a residual layer, due to the antistiction properties and high mechanical hardness of the DLC coating. By depositing a Cr layer on the imprinted resist pattern and lifting it off, Cr metal patterns were fabricated on the PET substrate.     

A numerical model of light adjustable lens

We model numerically the mechanical effects of UV induced photo-polymerization in elastomeric artificial lens. The elastomer is originated upon cross-linking of a silicone matrix. UV irradiation of one side of the lens polymerizes selectively a photosensitive macromer, causing local variations of its concentration. The subsequent diffusion of macromers from high concentration to low concentration zones modifies the shape of the lens and thus its dioptric power. In vitro experiments on artificial lens showed that the power change is dependent on UV exposure time, irradiation intensity and light pattern. With the aim to define a numerical tool able to predict the dioptric power adjustment as a function of the UV irradiation parameters, we setup a purely mechanic finite element model of the lens, adopting a hyperelastic material model embedded with eigen-deformations. Numerical simulations of axis-symmetric irradiation closely reproduced the experimental results, in terms of both lens geometry and dioptric power, for positive, negative and lock-in corrections.     

Composite Repair in Wind Turbine Blades: An Overview

Renewable energy sources such as wind energy—together with energy-efficient technologies—are essential to meet global energy demands and address climate change. Fiber-reinforced polymer composites, with their superior structural properties (e.g., high stiffness-to-weight) that allow lightweight and robust designs, play a significant part in the design and manufacture of modern wind turbines, especially turbine blades, for demanding service conditions. However, with the current global growth in onshore/offshore wind farm installations (with total global capacity of ～282 GW by the end of 2012) and trend in wind turbine design (～7–8 MW turbine capacity with ～70–80 m blade length for offshore installations), one of the challenges that the wind energy industry faces with composite turbine blades is the aspect of structural maintenance and repair. Although wind turbines are typically designed for a service life of about 20 years, robust structural maintenance and repair procedures are essential to ensure the structural integrity of wind turbines and prevent catastrophic failures. Wind blades are damaged due to demanding mechanical loads (e.g., static and fatigue), environmental conditions (e.g., temperature and humidity) and also manufacturing defects. If material damage is not extensive, structural repair is the only viable option to restore strength since replacing the entire blade is not cost-effective, especially for larger blades. Composite repairs (e.g., external and scarf patches) can be used to restore damaged laminate/sandwich regions in wind blades. With composite materials in the spar (～30–80 mm thick glass/carbon fiber laminates) and aerodynamic shells (sandwich sections with thin glass fiber skins and thick foam/wood as core), it is important to have reliable and cost-effective structural repair procedures to restore damaged wind blades. However, compared to aerospace bonded repairs, structural repair procedures in wind blades are not as well developed and thus face several challenges. In this regard, the area of composite repair in wind blades is broadly reviewed to provide an overview as well as identify associated challenges.     

Lactoperoxidase-mediated degradation of single-walled carbon nanotubes in the presence of pulmonary surfactant

Carbon nanotubes (CNTs) may elicit inflammatory responses following pulmonary exposure. Conversely, enzymatic biodegradation of CNTs by inflammatory cells has also been reported. The aim of this study was to study the degradation of oxidized single-walled CNTs (ox-SWCNTs) by lactoperoxidase (LPO), a secreted peroxidase present in the airways, and whether pulmonary surfactant affects this biodegradation. To this end, ox-SWCNTs were incubated in vitro with recombinant bovine LPO + H₂O₂ + NaSCN in the presence and absence of porcine lung surfactant (Curosurf®) and biodegradation was monitored using UV–Vis–NIR spectroscopy, Raman spectroscopy, and scanning electron microscopy. The interaction of recombinant LPO with bundles of ox-SWCNTs was confirmed by atomic force microscopy. Cell-free biodegradation of ox-SWCNTs was also observed ex vivo in murine bronchoalveolar lavage fluid in the presence of H₂O₂ + NaSCN. Our study provides evidence for biodegradation of ox-SWCNTs with a lung surfactant ‘bio-corona’ and expands the repertoire of mammalian peroxidases capable of biodegradation of ox-SWCNTs. These findings are relevant to inhalation exposure to these materials, as LPO serves as an important component of the airway defense system.     

基于有限元的脉冲激光辐照材料温度场研究

在激光超声检测过程中,为了合理加载脉冲激光的能量,以便获得幅值较大的超声波信号,同时避免脉冲激光造成材料的损伤,需要对脉冲激光辐照材料的温升进行数值计算。依据有限元理论,建立脉冲激光辐照材料的有限元模型,结合导热微分方程,将脉冲激光以热流密度的形式加载于材料表面,分析材料表层受激光辐照时的温度场,讨论有限元热分析时网格尺寸的选取对分析结果的影响。给出了材料表层受脉冲激光辐照时温度场的计算方法和网格尺寸的选择依据,并利用温度场的理论解析结果和应力场分析结果分别验证了温度场有限元计算方法的正确性和有效性。