LED失效分析手段研究

介绍LED产品常见的失效分析手段,主要包含外观检查、电性能测试、X-Ray透视检查、开封检查、金相切片分析、扫描电镜和能谱分析等手段,并结合实际案例对几种方法进行描述。     

Pyrolysis behaviors of oil sludge based on TG/FTIR and PY-GC/MS

Pyrolysis is an alternative technology for oil sludge treatment. Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy and Pyrolysis-Gas Chromatography/Mass Spectrometry were employed to investigate the pyrolysis process and products of oil sludge. The pyrolysis process was divided into five stages: drying and gas desorption, oil volatilization, main pyrolysis, semi-coke charring, and mineral decomposition. The main reaction temperatures ranged from 497.6 K to 753.2 K. The products were mainly composed of pairs of alkane and alkene (carbon number ranges from 1 to 27). The mechanisms consisted of random chain scission followed by end chain scission at high temperatures with volatilization occurring during the whole process. This study is useful not only for the proper design of a pyrolysis system, but also for improving the utilization of liquid oil products.     

超声提取-气相色谱质谱法测定大气PM2.5中正构烷烃

建立了超声提取-气相色谱质谱法测定大气PM2.5中32种正构烷烃方法,经离子温度优化、前处理比较、空白滤膜考察等获得了最佳的实验条件。研究发现,高、中、低3种浓度标准曲线的相关系数均在0.995以上,3种浓度的空白样品加标回收率分别为72.2%~117.8%、73.5%~104.4%、73.8%~109.5%,精密度均小于10%,实际样品加标回收率为75.7%~108.9%。当采样体积为24 m3时,各目标化合物的方法检出限为0.046~2.6 ng/m~3;经正构烷烃浓度范围为0.17~64.3 ng/m~3的1月及浓度范围为0.53~7.67 ng/m~3的6月的实际样品验证,该方法的检出限和测量范围也可较好的满足实际样品的测定。     

Zinc and lead sequestration in an impacted wetland system

The fate and bioavailability of pollutant metals is important to the long-term health of freshwater wetland systems, particularly in areas with elevated background levels of trace metals. Precipitation of some authigenic mineral phases in wetland sediments can potentially limit metal bioavailability through sequestration in low-solubility compounds, such as metal sulfides. Zinc and Pb concentrations were analyzed in water, plant and sediment samples taken from a metal-contaminated wetland in Chicago, IL, USA in order to assess metal fate and bioavailability, while X-ray absorption spectroscopy (XAS) studies were conducted to determine zinc speciation in the wetland sediments. The results showed sequestration of metal into the pond sediments, most likely in iron precipitate phases. In surface sediments, re-release of Zn and Pb into pore waters was correlated with microbial iron reduction, while the presence of sulfide in anoxic pore waters corresponded to decreased dissolved concentrations of both elements. Analysis of extended X-ray absorption fine structure (EXAFS) data confirmed that sulfide compounds dominated zinc speciation throughout the sediment. Uptake of trace metals in Phragmites plants was limited primarily to plant roots, while concentrations of both Pb and Zn in aquatic vegetation were significantly elevated, representing a potential bioaccumulation hazard.     

光导纤维氨气敏荧光传感器的研制和应用

以大环冠醚为铵离子中性载体，吖啶橙为荧光ＰＨ指示剂，二者结合于增塑的ＰＶＣ膜中，样品氨浓度变化直接引起膜的荧光强度变化。基于该原理研制成不需内电解质溶液的光导纤维氨气敏荧光传感器。用以测定生活污水的氨氮，精密度实验的平均变异系数为０．９－１．３％；回收率为９５．４％－１０５．６％。     

火焰原子吸收分光光度法检测矿区环境的常见重金属

在红河州某矿区周围的土壤、池塘、鱼塘采集若干土壤、水样品.用氢氟酸-高氯酸-浓硝酸消化土壤样品,用硝酸处理水样品.实验中,原子吸收分光光度法的平均相关系数≧0.99906;测定元素的相对标准差从0.27%～1.67%,其平均相对标准偏差为1.005%;样品的回收率在102,8%～111.5%之间,表明该法可用于环境中的土壤样品和水样品中重金属元素的准确测定.在仪器的最佳工作状态,使用FAAS法检测矿区环境中的铅(Pb)、铜(Cu)、铬(Cr)、汞(Hg)的含量;依此来发现矿区周围环境的重金属分布规律和周围环境的安全性.     

Relating dissolved organic matter fluorescence and functional properties

The fluorescence excitation–emission matrix properties of 25 dissolved organic matter samples from three rivers and one lake are analysed. All sites are sampled in duplicate, and the 25 samples include ten taken from the lake site, and nine from one of the rivers, to cover variations in dissolved organic matter composition due to season and river flow. Fluorescence properties are compared to the functional properties of the dissolved organic matter; the functional assays provide quantitative information on photochemical fading, buffering capacity, copper binding, benzo[a]pyrene binding, hydrophilicity and adsorption to alumina. Optical (absorbance and fluorescence) characterization of the dissolved organic matter samples demonstrates that (1) peak C (excitation 300–350 nm; emission 400–460 nm) fluorescence emission wavelength; (2) the ratio of peak T (excitation 220–235 nm; emission 330–370 nm) to peak C fluorescence intensity; and (3) the peak C fluorescence intensity: absorbance at 340 nm ratio have strong correlations with many of the functional assays. Strongest correlations are with benzo[a]pyrene binding, alumina adsorption, hydrophilicity and buffering capacity, and in many cases linear regression equations with a correlation coefficient >0.8 are obtained. These optical properties are independent of freshwater dissolved organic carbon concentration (for concentrations <10 mg L⁻¹) and therefore hold the potential for laboratory, field and on-line monitoring and prediction of organic matter functional properties.     

Fluorescence excitation-emission spectroscopy with regional integration analysis for assessment of compost maturity

Composting of animal manures is believed as an alternative way for directly recycling them in farms, and therefore assessment of compost maturity is crucial for achieving high quality compost. Fluorescence excitation-emission matrices (EEMs) combined with regional integration analysis is presented to assess compost maturity. The results showed that the EEM contours of water-extract organic matter (WEOM) from immature composts exhibited four peaks at excitation/emission (Ex/Em) of 220/340 nm, 280/340 nm, 220/410 nm, and 330/410 nm, whereas EEM contour of WEOM from mature composts had only two peaks at Ex/Em of 230/420 nm and 330/420 nm. Pearson correlation demonstrated that peaks intensity rather than their ratios had a significantly correlation with the common indices assessing compost maturity, whereas the normalized excitation-emission area volumes (Φ_i,ns) from regional integration analysis had a stronger correlation with the common indices assessing compost maturity than peaks intensity. It is concluded that the Φ_i,ns from regional integration analysis are more suitable to assess the maturity of compost than the intensities of peaks. Therefore, the fluorescence spectroscopy combined with regional integration analysis can be used as a valuable industrial and research tool for assessing compost maturity, given its high sensitivity and selectivity.     

荧光分光光度法测定天然水中的挥发酚

天然水经过蒸馏后，直接用荧光分光光度计进行测定。激发波长为２７５ｎｍ，最佳发射波长为２９８ｎｍ，可定量测定水中的挥发酚。该方法灵敏、准确、节省试剂、简便易行，方法最低检出限可达２μｇ／Ｌ     

Insight into fluorescence properties of 14 selected toxic single-ring aromatic compounds in water: Experimental and DFT study

• The fluorescence peak location of 14 compounds interpreted at protein-like region. • The p-electron system inside aromatic ring contributes to the fluorophore region. • Functional group variation effects the emission spectra. • Decrease in quantum yield and increase in DE is due to atomic weight F>Cl>Br>I. • Theoretically results are in line with experimental ones. Various single-ring aromatic compounds in water sources are of great concern due to its hazardous impact on the environment and human health. The fluorescence excitation-emission matrix (EEMs) spectrophotometry is a useful method to identify organic pollutants in water. This study provides a detailed insight into the fluorescence properties of the 14 selected toxic single-ring aromatic compounds by experimental and theoretical analysis. The theoretical analysis were done with Time-Dependent Density Functional Theory (TD-DFT) and B3LYP/6-31G (d,p) basis set, whereas, Polarizable Continuum Model (PCM) was used to consider water as solvent. The selected compounds displayed their own specific excitation-emission (Ex/Em) wavelengths region, at Ex<280 nm and Em<340 nm, respectively. Whereas the theoretical Ex/Em was observed as, Ex at 240 nm–260 nm and Em at 255 nm–300 nm. Aniline as a strong aromatic base has longer Em (340 nm) than alkyl, carbonyl, and halogens substituted benzenes. The lone pair of electrons at amide substituent serves as a p-electron contributor into the aromatic ring, hence increasing the stability and transition energy, which results in longer emission and low quantum yield for the aniline. The fluorescence of halogenated benzenes illustrates an increase in the HOMO-LUMO energy gap and a decrease in quantum yield associated with atomic size (F>Cl>Br>I). In this study the theoretical results are in line with experimental ones. The understanding of fluorescence and photophysical properties are of great importance in the identification of these compounds in the water.