Investigation of damage threshold to TiO2 coatings at different laser wavelength and pulse duration

Laser-induced damages to TiO2 single layers and TiO2/SiO2 high reflectors at laser wavelength of 1064 nm, 800 run, 532 urn, and pulse width of 12 ns, 220 ps, 50 fs, 8 ns are investigated. All films are prepared by electron beam evaporation. The relations among microstructure, chemical composition, optical properties and laser-induced damage threshold (LIDT), have been researched. The dependence of damage mechanism on laser wavelength and pulse width is discussed. It is found that from 1064 nm to 532 nm, LIDT is mainly absorption related, which is determined by film's extinction coefficient and stoichiometric defects. The rapid decrease of LIDT at 800 nm is due to the pulse width factor. TiO2 coatings are mainly thermally by damaged at long pulse (tau >= 220 ps). The damage shows ablation feature at 50 fs. (C) 2007 Elsevier B.V. All rights reserved.

Laser-induced damage of Ti O2 Si O2 high reflector at 1064 nm

A high laser-induced damage threshold (LIDT) TiO2/SiO2 high reflector (HR) at 1064 nm is deposited by e-beam evaporation. The HR is characterized by optical properties, surface, and cross section structure. LIDT is tested at 1064 nm with a 12 ns laser pulse in the one-on-one mode. Raman technique and scanning electron Microscope are used to analyze the laser-induced modification of HR. The possible damage mechanism is discussed. It is found that the LIDT of HR is influenced by the nanometer precursor in the surface, the intrinsic absorption of film material, the compactness of the cross section and surface structure, and the homogeneity of TiO2 layer. Three typical damage morphologies such as flat-bottom pit, delamination, and plasma scald determine well the nanometer defect initiation mechanism. The laser-induced crystallization consists well with the thermal damage nature of HR. (C) 2008 American Institute of Physics.

Impact of organic contamination on laser-induced damage threshold of high reflectance coatings in vacuum

The influence of organic contamination in vacuum on the laser-induced damage threshold (LIDT) of coatings is studied. TiO2/SiO2 dielectric mirrors with high reflection at 1064 nm are deposited by the electron beam evaporation method. The LIDTs of mirrors are measured in vacuum and atmosphere, respectively. It is found that the contamination in vacuum is easily attracted to optical surfaces because of the low pressure and becomes the source of damage. LIDTs of mirrors have a little change in vacuum compared with in atmosphere when the organic contamination is wiped off. The results indicate that organic contamination is a significant reason to decrease the LIDT. N-2 molecules in vacuum can reduce the influence of the organic contaminations and prtectect high reflectance coatings. (C) 2008 Elsevier B.V. All rights reserved.

Hole-Phonon Relaxation and Photocatalytic Properties of Titanium Dioxide and Zinc Oxide: First-Principles Approach

First-principles calculations for the temporal characteristics of hole-phonon relaxation in the valence band of titanium dioxide and zinc oxide have been performed. A first-principles method for the calculations of the quasistationary distribution function of holes has been developed. The results show that the quasistationary distribution of the holes in TiO2 extends to an energy level approximately 1eV below the top of the valence band. This conclusion in turn helps to elucidate the origin of the spectral dependence of the photocatalytic activity of TiO2. Analysis of the analogous data for ZnO shows that in this material spectral dependence of photocatalytic activity in the oxidative reactions is unlikely.

Early response to nanoparticles in the Arabidopsis transcriptome compromises plant defence and root-hair development through salicylic acid signalling

Background: The impact of nano-scaled materials on photosynthetic organisms needs to be evaluated. Plants represent the largest interface between the environment and biosphere, so understanding how nanoparticles affect them is especially relevant for environmental assessments. Nanotoxicology studies in plants allude to quantum size effects and other properties specific of the nano-stage to explain increased toxicity respect to bulk compounds. However, gene expression profiles after exposure to nanoparticles and other sources of environmental stress have not been compared and the impact on plant defence has not been analysed. Results: Arabidopsis plants were exposed to TiO2-nanoparticles, Ag-nanoparticles, and multi-walled carbon nanotubes as well as different sources of biotic (microbial pathogens) or abiotic (saline, drought, or wounding) stresses. Changes in gene expression profiles and plant phenotypic responses were evaluated. Transcriptome analysis shows similarity of expression patterns for all plants exposed to nanoparticles and a low impact on gene expression compared to other stress inducers. Nanoparticle exposure repressed transcriptional responses to microbial pathogens, resulting in increased bacterial colonization during an experimental infection. Inhibition of root hair development and transcriptional patterns characteristic of phosphate starvation response were also observed. The exogenous addition of salicylic acid prevented some nano-specific transcriptional and phenotypic effects, including the reduction in root hair formation and the colonization of distal leaves by bacteria. Conclusions: This study integrates the effect of nanoparticles on gene expression with plant responses to major sources of environmental stress and paves the way to remediate the impact of these potentially damaging compounds through hormonal priming.

Cellular and molecular responses of zebrafish to legacy and emerging pollutants: the specific cases of PAHs and metal oxide nanoparticles

270 p.

Research on operating conditions at the catalytic reactor for the combined removal of NOx and PCDD/PCDFs from MWI plants

The management of municipal solid waste (MSW), particularly the role of incineration, is currently a subject of public debate. Incineration shows to be a good alternative of reducing the volume of waste and eliminating certain infectious components. Moreover, Municipal Waste Incinerators (MWI), are reported to be highly hygienic and apart from that MWIs are immediately effective in terms of transport (incinerators can be built close to the waste sources) and incineration's nature. Nevertheless, the emissions of many hazardous substances make the Municipal Waste Incineration (MWI) plants to be unpopular. Metals (especially lead, manganese, cadmium, chromium and mercury) are concentrated in fly and bottom ashes. Furthermore, incomplete combustion produces a wide variety of potentially hazardous organic compounds, such as aldehydes, polycyclic aromatic hydrocarbons (PAH), chlorinated hydrocarbons including polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF), and even acid gases, including NOx. Many of these hazardous substances are carcinogenic and some have direct systemic toxicity.

Sintesi hidrotermal bidezko titanio dioxidozko nanohodien lorpena

[EUS] Gaur egun nanozientzia zientzia eta teknologia arlo guztietara zabaldu da, gizarte garapenean eragin handia izan du. Ikerkuntza arlo guztietara zabaldu da ezinezkoak ziruditen erronkak argitu eta ezezagunak ditugun ezagutzak garatzeko asmoz. Lan honetan TiO2 nanohagatxoen sintesia burutu da metodo hidrotermala erabiliz. Sintesi baldintzek lortutako produktuaren egituran eta forman duten eragina kontuan harturik, sintesia gertatzeko ezinbestekoak diren pHa, tenperatura eta denbora aztertu dira. Ondoren, tratamendu kimiko eta termiko ezberdinen bidez konposizio eta egitura ezberdinak lor daitezkeela frogatu da. Bereziki, surfaktante eta pHaren arabera egitura ezberdinak lortzen direla ikusirik. Sintetizatutako laginen karakterizazioa burutzeko X izpien difrakzioa, transmisio bidezko mikroskopia elektronikoa, infragorri espektroskopia, eta termograbimetria teknikak erabili dira. Hauen bidez NaTi3O6·(OH)x·(H2O)y , (TiO2)x(H2O)y , anatasa eta rutilo faseak identifikatu dira, eta nanohagatxoen lodiera eta morfologia ezberdinak ikusi dira.

Analysis of multivariate stochastic signals sampled by on-line particle analyzers: Application to the quantitative assessment of occupational exposure to NOAA in multisource industrial scenarios (MSIS)

In multisource industrial scenarios (MSIS) coexist NOAA generating activities with other productive sources of airborne particles, such as parallel processes of manufacturing or electrical and diesel machinery. A distinctive characteristic of MSIS is the spatially complex distribution of aerosol sources, as well as their potential differences in dynamics, due to the feasibility of multi-task configuration at a given time. Thus, the background signal is expected to challenge the aerosol analyzers at a probably wide range of concentrations and size distributions, depending of the multisource configuration at a given time. Monitoring and prediction by using statistical analysis of time series captured by on-line particle analyzers in industrial scenarios, have been proven to be feasible in predicting PNC evolution provided a given quality of net signals (difference between signal at source and background). However the analysis and modelling of non-consistent time series, influenced by low levels of SNR (Signal-Noise Ratio) could build a misleading basis for decision making. In this context, this work explores the use of stochastic models based on ARIMA methodology to monitor and predict exposure values (PNC). The study was carried out in a MSIS where an case study focused on the manufacture of perforated tablets of nano-TiO2 by cold pressing was performed

水体中有机物的紫外光降解研究

当前，水资源污染越来越严重，人类的健康面临着巨大的威胁。高级氧化技术作为一 种经济、高效、无二次污染的水体处理方法，一直是水污染控制与治理领域研究的热点。 本文以环境中典型的有机污染物苯酚和水体中主要有机物腐殖酸为研究对象，利用自 制的紫外光（ultraviolet，UV）离线降解装置，采用紫外-可见光谱法和总有机碳（TOC） 分析法分别研究水相中苯酚、腐殖酸的紫外光降解情况，系统地考察不同初始pH值、初始 浓度、光照时间、光照强度、反应容器等因素对光降解效果的影响。为了模拟实际水体条 件和提高光降解效率，在体系中分别加入NaCl、Na2CO3、NaNO3、NaNO2和双氧水等化学 成分，探讨这些化学物质对苯酚、腐殖酸的紫外光降解效率和降解途径的影响。最后，首 次构建了石英螺旋管内壁负载TiO2膜的在线降解装置，结合UV/H2O2/TiO2联用体系，进行 海水中有机物的光降解研究。 紫外可见光谱分析表明：光降解速率随初始pH 值的降低而提高，相同条件下苯酚在 酸性溶液中降解速率高于碱性溶液，说明苯酚分子比酚氧离子容易光降解；硝酸钠和亚硝 酸钠有利于苯酚的光降解，说明它们在紫外光下容易分解生成自由基；在苯酚水溶液中加 入双氧水，光照15 min 后，光降解效率达到97%。各种介质中苯酚的降解速率大小依次为： 1.5 mmol/L 过氧化氢溶液 ＞ 1.0 mmol/L 硝酸钠的海水 ＞ 海水 ＞ 纯水 ＞ 0.5 mol/L 氯化钠溶液。然而，TOC 数据显示氯化钠的存在对苯酚的矿化有促进作用；同光谱的降解 速率相比，矿化速率要小。 腐殖酸的光降解效率随初始质量浓度的减小而提高，当质量浓度为10 mg/L时，光照 30 分钟后，降解效率高达到88%；初始pH值对腐殖酸的降解效率影响很大，腐殖酸在碱 性条件下比在中性和酸性条件更容易光降解；硝酸钠等盐分对中性和碱性溶液中腐殖酸的 光降解没有明显促进作用，但对酸性溶液中腐殖酸的光降解促进作用明显。采用UV/H2O2联 合降解时，腐殖酸降解效率得到显著提高。 相比离线降解方式，采用石英螺旋管在线降解苯酚和腐殖酸，降解效率均提高了15 倍 以上；海水经过在线降解后，紫外可见光光谱吸光度值缓慢下降；经过多次在线光降解后， 在290 nm波长处出现强烈吸收峰，再次光照后很快消失。这种现象表明海水中可能存在着 粒

淡水藻源异味化合物的光降解和光催化降解研究

为探讨利用太阳光降解水中异味化合物的可行性,对2-甲基异莰醇(MIB)、β-柠檬醛(β-Cyclocitral)和β-紫罗兰酮(β-Ionone)等3种异味化合物在紫外光和太阳光下的光降解及光催化降解效果进行了研究。结果表明,单波长紫外光——UVC(254 nm)和UVB(312 nm)及太阳光均能有效降解纯水中的β-Cyclocitral和β-Ionone,但不能降解MIB。加入纳米TiO2后,在UVC(254 nm)、UVB(312 nm)和太阳光照射下,MIB、β-Cyclocitral和β-Ion

Hydrogen sensor based on silicon carbide (SiC) MOS capacitor

Silicon carbide (SiC) based MOS capacitor devices are used for gas sensing in high temperature and chemically reactive environments. A SiC MOS capacitor structure used as hydrogen sensor is defined and simulated. The effects of hydrogen concentration, temperature and interface traps on C-V characteristics were analysed. A comparison between structures with different oxide layer types (SiO2, TiO2 and ZnO) and thicknesses (50..10nm) was conducted. The TiO2 based structure has better performance than the SiO2 and ZnO structures. Also, the performance of the SiC MOS capacitor increases at thinner oxide layers. © 2012 IEEE.

不同光源下TiO_2膜对MC-RR光催化降解的比较研究

通过溶胶-凝胶法制备了纳米级的锐钛矿型TiO2膜,利用纯化的MC-RR分别研究了该膜在太阳光、UVA和UVC三种光源下对MC-RR的催化降解行为。结果表明,太阳光下TiO2膜对MC-RR的催化降解反应符合一级反应动力学,而在UVA和UVC下符合二级反应。不同光源下TiO2膜的催化效果差别较大,在太阳光下催化效果最为明显,反应速率常数由5.12×10-5·min-1增加到5.49×10-3·min-1,增加了两个数量级;UVA次之,由6.0×10-4L·mg-1·min-1增加到1.55×10-3L·mg-

UV/TiO_2薄膜体系光降解酞酸酯研究

采用自制玻璃负载TiO2薄膜,研究了UV-V is/TiO2以及UV/TiO2/H2O2体系对2种酞酸酯DBP和DEHP的光催化降解情况。研究结果表明,TiO2在暗处对酞酸酯没有降解作用;UV/TiO2体系能有效光降解DBP和DEHP,TiO2具有明显的光催化作用,增强因子分别为fDBP=2.06,fDEHP=1.53;在一定浓度范围内DBP在UV/TiO2体系中的降解速率与其初始浓度成负一级动力学关系;UV/TiO2/H2O2体系对DBP的光降解能力远大于UV/TiO2和UV/H2O2体系,H2O2能显

太阳光/多孔TiO_2膜催化降解微囊藻毒素

　太阳光/多孔TiO2膜体系对水中微囊藻毒素(MC-RR)具有较好的去除效果,反应可用准一级反应动力学描述。TiO2膜的镀膜次数对催化效果有重要影响,溶液的pH值对反应也有一定的影响,偏酸性条件对MC-RR的降解有利。在该体系中MC-RR主要通过光催化氧化作用被去除。