纤维增强气凝胶复合材料高温结构转变及热稳定性研究

目的研究高温受热条件下纳米复合隔热材料的结构转变特征及热稳定性。方法采用扫描电镜、X射线衍射仪、红外光谱仪及热重仪等检测方法。结果纤维增强气凝胶材料从室温到650℃存在连续的质量损失,从室温到放热前,质量损失为1.66%;365℃开始出现放热,温度升至398℃时达到峰值,整个放热过程对应质量损失约为1.3%;从435℃放热结束开始到650℃的质量损失为1.46%。经过400℃热处理后,试样比表面积从268m~2/g增加到437m~2/g;当试样热处理温度达到600℃时,试样的比表面积明显随之降低至198m~2/g。结论 SiO_2气凝胶复合材料以无定形结构为主,存在少量的二氧化钛晶体。在400℃左右,SiO_2气凝胶结构中硅甲基Si—CH_3发生氧化,产生明显的放热峰,之后硅羟基Si—OH之间发生缩聚反应,使600℃热处理后气凝胶中Si—O—Si网络骨架强度有所提高。未处理的纤维增强气凝胶材料试样上气凝胶纳米颗粒构成的块体较为良好地包裹在玻璃纤维表面,而经过600℃的高温热处理1 h后,块体气凝胶脱离了光滑的纤维表面,气凝胶纳米粒子发生收缩,致使材料比表面积下降。     

基于静止卫星GOCI传感器的大气污染过程AOD监测

针对北京及周边地区2017年11月2~8日的一次污染过程,利用韩国静止卫星COMs1GOCI数据,对北京地区进行AOD监测.AOD反演采用时间序列迭代算法,根据地表反射率随时间慢变而大气气溶胶随时间快变的理论,采取最小值拟合的方式,获取气溶胶光学厚度数据.反演结果与地基AERONET监测结果具有很好的一致性,两者的相关系数R²大于0.89.AOD监测结果表明,GOCI传感器1次/h的监测频率,可以很好地展现北京地区大气污染过程的开始,发展及消散过程,可以展示出一天之内AOD的变化,为大气污染监测以及气候变化研究提供依据.     

牛粪-化肥配施对水稻田氮磷迁移转化的影响

在控制外源N输入量相同的前提下,通过田间小区实验,探讨有机肥与化肥不同施用量（牛粪施用量：5,10,20t/hm²）对稻田田间土-水界面氮磷迁移转化特征的影响.结果表明：控制稻田水中NH₄⁺-N、NO₃^--N、TN和TP输出的最佳时期分别为施肥后的第5,30,7,20d,且TN和TP浓度随时间变化符合单指数衰减方程（0.7444≤R²≤0.9724;1.1×10^-6≤F≤0.0055）.采用牛粪部分代替化肥的施肥方式,在一定范围内能降低稻田退水中TN、TP输出负荷（41.8%、36.0%、64.3%;20.3%、39.1%、48.9%）,还可以降低稻田水中N/P,降低水体富营养化风险.同时,牛粪的施用可提高土壤中脲酶和磷酸酶的含量,促进氮磷向植物可吸收形态转化.综合经济成本和生态效益核算,采用10t有机肥代替无机肥的处理是相对经济环保的施肥方法,该施肥方式下,氮磷年输出负荷分别为17.70,1.26kg/hm².     

Effects of Na+ on Cu/SAPO-34 for ammonia selective catalytic reduction

Copper-exchanged chabazite (Cu/CHA) catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na⁺ ions on Cu/SAPO-34 for ammonia selective catalytic reduction (NH₃-SCR) are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na⁺ ion-exchanges with H⁺ and Cu^2 + of Cu/SAPO-34. The exchange of H⁺ is easier than that of isolated Cu^2 +. The exchanged Cu^2 + ions aggregate and form “CuAl₂O₄-like” species. The NH₃-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu^2 + and acid sites is responsible for the activity loss.     

碳量子点掺杂氮化碳提高的光电化学阴极保护性能研究

目的研究g-C_3N_4/C-Dots-M复合材料的光电化学阴极保护性能。方法采用X射线衍射(XRD)、扫描电子显微镜(SEM)和紫外可见漫反射光谱技术对样品的晶体结构、微观形貌和光吸收性能进行表征。通过电化学测试可见光照射下g-C_3N_4/C-Dots-M复合材料光电极偶联316L不锈钢后的光电化学阴极保护电流密度和电位变化曲线,研究材料的光电化学阴极保护性能。结果可见光照射下,该偶联体系的光致混合电位下降至-0.43 V(vs. Ag/AgCl),光电化学阴极保护电流密度达到4.3μA/cm。结论得益于碳量子点优异的电子传导特性,g-C_3N_4/C-Dots-550复合材料的光电化学阴极保护性能比纯g-C_3N_4的明显增强。该复合材料在光电化学阴极保护方面展现了较大的应用潜力。     

包装箱用碳纤维增强复合材料贮存寿命研究

目的研究碳纤维增强复合材料贮存条件下的性能变化趋势和寿命评估。方法对碳纤维增强复合材料开展四个不同温度条件下的热氧老化试验,按试验周期定期取样开展冲击性能测试,对试验数据采用寿命预估方法进行处理,对材料性能进行预估。结果通过数据计算分别得到我国热带海洋、干热沙漠等典型气候条件下的碳纤维增强复合材料贮存寿命分别为17.21~35.89年。结论碳纤维增强复合材料具有较好的贮存性能,在较为严酷的热带海洋气候和给定的失效判据条件下,寿命预计为17.21年。试验和数据处理方法可以较好地预计材料的性能变化趋势和开展寿命评估。     

Plant Phenology in Western Canada: Trends and Links to the View From Space

One feature of climate change is the trends to earlier spring onset in many north temperate areas of the world. The timing of spring flowering and leafing of perennial plants is largely controlled by temperature accumulation; both temperature and phenological records illustrate changes in recent decades. Phenology studies date back over a century, with extensive databases existing for western Canada. Earlier spring flowering has been noted for many woody plants, with larger trends seen for species that develop at spring's start. Implications for ecosystems of trends to earlier spring arrival include changes in plant species composition, changes in timing and distribution of pests and disease, and potentially disrupted ecological interactions. While Alberta has extensive phenology databases (for species, years, and geographic coverage) for recent decades, these data cannot provide continuous ground coverage. There is great potential for phenological data to provide ground validation for satellite imagery interpretation, especially as new remote sensors are becoming available. Phenological networks are experiencing a resurgence of interest in Canada (www.plantwatch.ca) and globally, and linking these ground-based observations with the view from space will greatly enhance our capacity to track the biotic response to climate changes.     

Effect of Humic Acid on the Bioavailability of γ-Hexachlorocyclohexane in Marsilea Minuta (L.)

Effect of various concentrations of humic acid (0.2 to 1%) on thebioavailability of -HCH in vegetative clones of theaquatic fern Marsilea minuta was studied in a staticexperimental bioassay system on different photoperiods. Additionof humic acid showed the reduction in the bioavailability of-HCH in all the photoperiods (72 hr light to 144 hrlight) at the interval of 16 hr light (L) and 8 hr dark (D) inboth aerial and submerged portion as compared to controlindicating its protective role in toxicity.     

Distribution of airborne particles from multi-emission source

The purpose of this work was to study the distribution of airborne particles in the surroundings of an iron and steel factory in southern Finland. Several sources of particulate emissions are lying side by side, causing heavy dust loading to the environment. This complicated multi-pollutant situation was studied mainly by SEM/EDX methodology.Particles accumulated on Scots pine bark were identified andquantitatively measured according to their element content,size and shape. As a result, distribution maps of particulateelements were drawn and the amount of different particle typesalong the study lines was plotted. Particulate emissions fromthe industrial or energy production processes were not themain dust source. Most emissions were produced from theclinker crusher. Numerous stockpiles of the industrial wastesand raw materials also gave rise to particulate emissions as aresult of wind erosion. It was concluded that SEM/EDXmethodology is a useful tool for studying the distribution ofparticulate pollutants.     

Factors influencing Aerosol Characteristics over Urban Environment

Atmospheric aerosols are an important contributing factor to turbidity in urban areas besides having impact on health. Aerosol characteristics show a high degree of variability in space and time as anthropogenic share of total aerosol loading is quite substantial and is essential to monitor the aerosol features over long time scales. In the present study extensive observations of columnar aerosol optical depth (AOD), total columnar ozone (TCO) and precipitable water content (PWC) have been carried over a tropical urban city of Hyderabad, India. Significant variations of AOD have been observed during course of the day with low values of AOD during morning and evening hours and high values during afternoon hours. Spectral variation of AOD exhibits high AOD at smaller wavelengths and vice versa except a slight enhancement in AOD at 500 nm. Anomalies in AOD, particulate matter and black carbon concentrations have been observed during May, 2003. Back trajectory analysis of air mass during these episodes suggested variation in air mass trajectories. Analysis of the results suggests that air trajectories from land region north of study area cause high loading of atmospheric aerosols. The results are discussed in the paper.