Cf/SiC 复合材料表面 HfO2涂层的制备及其抗热冲击性能研究

目的研究等离子喷涂条件下Cf/SiC复合材料表面HfO_2涂层的物相、显微组织及其抗热冲击性能。方法通过水热合成和喷雾造粒制备出HfO_2粉体,并利用等离子喷涂在Cf/SiC复合材料表面制备HfO_2涂层,研究涂层的物相、显微组织和抗热冲击性能。结果水热合成的纳米HfO_2为单斜相结构,颗粒的平均粒径为10~15nm;等离子喷涂制备的HfO_2涂层组织中存在微裂纹和孔隙,涂层为单斜相结构,且经1350℃热处理后涂层的相结构未发生改变。等离子喷涂的HfO_2涂层与Cf/SiC复合材料基体结合良好,未观察到涂层、基体间界面分离的现象。经1350℃、50周次的空冷热冲击试验后,涂层未发生破坏失效;在1350℃水冷热冲击条件下,热循环20次时涂层表面出现剥落,27次时脱落面积50%。结论通过等离子喷涂制备的HfO_2涂层与Cf/SiC复合材料基体结合良好,涂层能够抵御1350℃空冷、50周次热冲击,且未发生破坏失效,涂层的1350℃水冷热循环寿命达27次。     

Bi2O3-TiO2复合光催化剂协同处理铬-邻苯二甲酸酯复合污染

以硝酸铋和钛酸丁酯为前驱体,采用水热法制备了Bi_2O_3-TiO_2复合半导体材料,并利用X射线衍射(XRD)、紫外-可见吸收光谱(UVVis)、能谱分析(EDS)、X射线光电子能谱(XPS)等手段对复合材料的结构进行了表征.同时,考察了Bi_2O_3-TiO_2复合材料对重金属Cr(Ⅵ)和难降解邻苯二甲酸二丁酯(DBP)复合污染的处理性能,并探讨了复合催化剂协同处理复合污染的作用机制.结果表明:该复合催化剂在可见光下能同时降低重金属Cr(Ⅵ)和有机物DBP的浓度,抑制电子和空穴复合,表现出比对单一Cr(Ⅵ)及DBP污染物更高的处理效率.当Bi_2O_3含量为4%时,复合催化剂表现出最佳的光催化活性.     

Pd/Al2O3粒子电极电催化还原BrO3-的研究

针对常规方法难以去除水中Br_3~-的问题,采用浸渍煅烧法制备了负载型纳米Pd/Al_2O_3粒子电极,研究了该电极电催化还原Br O-3的效果.催化剂的结构表征表明该反应实现了Pd纳米晶的均匀负载,纳米Pd/Al_2O_3具有较高的电催化活性和较低的能耗,其最佳反应条件为3%Pd负载量,0.9 m A·cm-2电流密度和1 g·L催化剂投量,酸性条件可促进Br O-3的直接或间接还原.ESR检测证实了Pd的负载增强了反应体系活性物种[H]的生成,进而促进了Br O-3的间接电催化还原.     

N,N-双(二硫代羧基)乙二胺对微量络合镍的深度脱除特性研究

以柠檬酸镍(CA-Ni)、酒石酸镍(TA-Ni)、焦磷酸镍(SP-Ni)3种低浓度模拟络合镍废水为研究对象,选用自制的重金属捕集剂N,N-双(二硫代羧基)乙二胺(EDTC),对废水中的Ni进行深度脱除.重点研究了EDTC投加量、初始p H、反应时间对Ni去除效果的影响及螯合沉淀物的沉淀性能和溶出特性,同时分析了EDTC去除络合Ni的机理.研究结果表明,处理初始浓度5 mg·L~(-1)的CA-Ni、TA-Ni、SP-Ni,p H为4~8,EDTC最佳投加量分别为60 mg·L~(-1)、55 mg·L~(-1)和70 mg·L~(-1),PAM(聚丙烯酰胺)为1 mg·L~(-1),反应时间2 min,Ni的出水浓度均低于0.05mg·L~(-1),去除率达99%以上.螯合沉淀物沉降性能好且在弱酸弱碱条件下能稳定存在.红外光谱图和元素分析结果表明:EDTC与Ni发生螯合反应,即EDTC直接脱除络合镍中的Ni2+,并与Ni2+生成更稳定的螯合产物EDTC-Ni,进而有效地去除废水中Ni.     

Layered sphere-shaped TiO2 capped with gold nanoparticles on structural defects and their catalysis of formaldehyde oxidation

We describe here a one-step method for the synthesis of Au/TiO₂ nanosphere materials, which were formed by layered deposition of multiple anatase TiO₂ nanosheets. The Au nanoparticles were stabilized by structural defects in each TiO₂ nanosheet, including crystal steps and edges, thereby fixing the Au–TiO₂ perimeter interface. Reactant transfer occurred along the gaps between these TiO₂ nanosheet layers and in contact with catalytically active sites at the Au–TiO₂ interface. The doped Au induced the formation of oxygen vacancies in the Au–TiO₂ interface. Such vacancies are essential for generating active oxygen species (*O⁻) on the TiO₂ surface and Ti^3 + ions in bulk TiO₂. These ions can then form Ti^3 +–O⁻–Ti^4 + species, which are known to enhance the catalytic activity of formaldehyde (HCHO) oxidation. These studies on structural and oxygen vacancy defects in Au/TiO₂ samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials.     

Numerical evaluation of the effectiveness of NO2 and N2O5 generation during the NO ozonation process

Wet scrubbing combined with ozone oxidation has become a promising technology for simultaneous removal of SO₂ and NO_x in exhaust gas. In this paper, a new 20-species, 76-step detailed kinetic mechanism was proposed between O₃ and NO_x. The concentration of N₂O₅ was measured using an in-situ IR spectrometer. The numerical evaluation results kept good pace with both the public experiment results and our experiment results. Key reaction parameters for the generation of NO₂ and N₂O₅ during the NO ozonation process were investigated by a numerical simulation method. The effect of temperature on producing NO₂ was found to be negligible. To produce NO₂, the optimal residence time was 1.25 sec and the molar ratio of O₃/NO about 1. For the generation of N₂O₅, the residence time should be about 8 sec while the temperature of the exhaust gas should be strictly controlled and the molar ratio of O₃/NO about 1.75. This study provided detailed investigations on the reaction parameters of ozonation of NO_x by a numerical simulation method, and the results obtained should be helpful for the design and optimization of ozone oxidation combined with the wet flue gas desulfurization methods (WFGD) method for the removal of NO_x.     

In vitro evaluation of inorganic and methyl mercury mediated cytotoxic effect on neural cells derived from different animal species

To extend the current understanding of the mercury-mediated cytotoxic effect,five neural cell lines established from different animal species were comparatively analyzed using three different endpoint bioassays:thiazolyl blue tetrazolium bromide,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay(MTT),neutral red uptake assay(NRU),and Coomassie blue assay(CB).Following a 24-hr exposure to selected concentrations of mercury chloride(HgCl_2) and methylmercury(Ⅱ) chloride(MeHgCl),the cytotoxic effect on test cells was characterized by comparing their 50%inhibition concentration(IC_(50)) values.Experimental results indicated that both these forms of mercury were toxic to all the neural cells,but at very different degrees.The IC_(50)values of MeHgCl among these cell lines ranged from 1.15±0.22 to 10.31 ± 0.70 μmol/L while the IC_(50) values for HgCl_2 were much higher,ranging from 6.44 ± 0.36 to 160.97±19.63 μmol/L,indicating the more toxic nature of MeHgCl.The IC_(50) ratio between HgCl_2and MeHgCl ranged from 1.75 to 96.0,which confirms that organic mercury is much more toxic to these neural cells than inorganic mercury.Among these cell lines,HGST-BR and TriG44 derived from marine sea turtles showed a significantly high tolerance to HgCl_2 as compared to the three mammalian neural cells.Among these neural cells,SK-N-SH represented the most sensitive cells to both chemical forms of mercury.     

Spatial variance and assessment of nitrogen dioxide pollution in major cities of Pakistan along N5-Highway

This paper discusses the findings of the first car MAX-DOAS (multi-axis differential optical absorption spectroscopy) field campaign (300 km long) along the National Highway-05 (N5-Highway) of Pakistan conducted on 13 and 14 November, 2012. The main objective of the field campaign was to assess the spatial distribution of tropospheric nitrogen dioxide (NO₂) columns and corresponding concentrations along the N5-Highway from Islamabad to Lahore. Source identification of NO₂ revealed that the concentrations were higher within major cities along the highway. The highest NO₂ vertical column densities (NO₂ VCDs) were found around two major cities of Rawalpindi and Lahore. This study also presents a comparison of NO₂ VCDs measured by the ozone monitoring instrument (OMI) and car MAX-DOAS observations. The comparison revealed similar spatial distribution of the NO₂ columns with both car MAX-DOAS and satellite observations, but the car MAX-DOAS observations show much more spatial details. Maximum NO₂ VCD retrieved from car MAX-DOAS observations was up to an order of magnitude larger than the OMI observations in urban areas.     

A~2/O-MBR工艺在农村生活污水处理中的示范

A2/O-MBR工艺因其稳定的出水水质和良好的脱氮除磷效果,在我国城镇早已得到规模化应用。但在农村由于受各种条件制约,使该工艺的应用受到限制。通过A2/O-MBR工艺在四川农村地区散户的小规模示范,分析了其在污染物去除、建设、运行维护等方面的特点以及需注意的问题,为该技术在农村地区的推广应用做出积极的探索。     

纳米二氧化锰/还原态氧化石墨烯复合材料催化臭氧降解苯酚的研究

制备以还原态氧化石墨烯为载体的纳米二氧化锰催化剂,并以苯酚为目标降解物,研究了其催化臭氧化性能,对影响催化臭氧化效果因素及降解机理进行了初步探讨。使用SEM、TEM和XPS对材料进行表征;纳米二氧化锰/还原态氧化石墨烯催化臭氧降解苯酚反应为准一级反应;催化剂的最佳使用量为0.2 g/L;当p H=3时,苯酚催化臭氧化去除率相对于单独臭氧提高了119.0%;催化剂连续使用4次性能良好。