Experimental and theoretical research on the inhibition performance of ethanol gasoline/air explosion by C6F12O

The safety issue of ethanol gasoline and the methods to control or weaken its explosion have attracted attention. To clarify the effect of C₆F₁₂O (perfluoro(2-methyl-3-pentanone)) on the explosion of ethanol gasoline-air mixtures and intrinsic mechanism, the explosion overpressure and flame propagation behavior under different equivalence ratios (φ = 0.6–0.8) and C₆F₁₂O concentrations (χ_inh = 0–4.0%) were experimentally obtained. The detailed inhibitor reaction process was also obtained by CHEMKIN based on a new assembly kinetic mechanism. The results show that the effects of C₆F₁₂O on the explosion characteristics of ethanol gasoline varied with χ_inh and φ. For rich flames, C₆F₁₂O is more effective than and heptafluoropropane (C₃HF₇) and nitrogen (N₂) in suppressing explosions; for lean and equivalence ratio flames, the addition of C₆F₁₂O may result in more severe explosions. The decrease in chemical reactivity is mainly because the mole fractions of OH and H radicals and the proportion of paths H radicals involved decrease after adding C₆F₁₂O, and R1500: CF₃COF + H = CF₃CO + HF, R965: CF₂:O + H = CF:O + HF, R863: CF₃ + H = CF₂ + HF are main suppressing reactions.     

Experimental investigation of the performance of modified expanded graphite powder doped with zinc borate in extinguishing sodium fires

Sodium is the main cooling medium in the circuit of fourth-generation nuclear reactors, and its leakage constitutes a severe fire hazard because of its high chemical activity. In this study, expandable graphite (EG), which is a traditional sodium fire-extinguishing agent, was modified with zinc borate (ZB) as an intercalator, and the modified EG_ZB was characterized. Moreover, the effectiveness of the modified EG_ZB in extinguishing sodium fires was tested using a self-developed fire-extinguishing experimental device. This study's results indicated that EG, EG_ZB had a smaller particle size, higher thermal stability, higher fire-extinguishing speed, and lower powder mass consumption than EG. During the fire-extinguishing process, ZnO decomposed by ZB captured free radicals and inhibited the combustion reaction. Furthermore, B₂O₃ was adsorbed on the surface of the EG layer, which strengthened covering and asphyxiation. The findings of this study provide crucial information for effectively controlling fires caused by active metals and metallo-organic compounds.     

气溶胶辐射效应对气象和环境影响的观测与模拟研究

选取2015年和2019年不同代表年份,结合外场观测和数值模拟,分析了天津地区不同季节不同天气(晴天、多云、霾)下,气溶胶辐射效应对整层大气透过率和地表入射太阳辐射的影响,以及这种影响在不同年份的差异.借助WRF-Chem模式模拟分析了重污染期间气溶胶辐射效应对垂直方向上气象要素廓线、边界层结构以及PM_2.5浓度的反馈机制.结果表明:霾污染可导致大气透过率明显下降,春、秋、冬不同季节,霾污染导致中午大气透过率分别下降0.09,0.11和0.09.全年平均霾污染可导致大气透过率降低约15.5%.云量的增多也可导致大气透过率明显下降,多云天气下大气透过率相比晴天减小约22.4%.霾和云对大气透过率的影响还与太阳高度角有关,当太阳高度角>60°时,霾污染导致大气透过率下降8.6%.随污染等级提高,气溶胶对太阳辐射的衰减作用也越强,天津地区空气质量分别为Ⅰ～Ⅰ级时,中午地表入射短波辐射呈稳定下降趋势,依次为484,446,439,342,328和253W/m².重污染期间,气溶胶辐射效应导致大气低层(250m以下)降温(0.8℃)增湿(3.8%...     

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.     

Ag3PO4/g-C3N4复合光催化剂的制备及其可见光催化性能

采用简单的原位沉淀法合成了可见光驱动型光催化剂Ag₃PO₄/g-C₃N₄.利用X-射线衍射（XRD）、傅里叶红外光谱（FT-IR）、扫描电子显微镜（SEM）、X-射线能谱（XPS）以及紫外可见漫反射光谱（UV-Vis DRS）等表征手段对合成的样品进行了表征.与单一的Ag₃PO₄和g-C₃N₄相比,Ag₃PO₄/g-C₃N₄复合材料对左氧氟沙星表现出了更高的催化效率.根据能带分析和自由基捕获试验,提出了Ag₃PO₄/g-C₃N₄复合材料Z型异质结构的作用机制.     

Photodegradation mechanism of two dyes: the influence of adsorption behavior on the novel TiO2 particles

The relationship between adsorption behavior and photocatalytic mechanism of the two dyes was investigated. Adsorption isotherms showed that the adsorption of cationic pink FG was Langmuir type behavior, while the reactive brilliant red k-2G was Freundlich type behavior. The increasing pH favored the adsorption of FG but have little effect on the photodegradation. The increasing pH favored the adsorption and the photodegradation of k-2G. The presence of scavenger of hvb^ and OH. radical potassium iodide inhibited the degradation of k-2G, free radicals scavenger tetranitromethane inhibited the photodegradation of FG. These results indicated that the photodegradation of FG mainly via free radicals in solution, and the photodegradation of k-2G was mainly on the catalysts surface or near the interface of solid and solution by react with hvb^ and surface-bound OH.. The different effect of SO4^2- , HCO3^- on the adsorption and photodegradation of two dyes confirmed these results.     

改性生物炭负载纳米零价铁活化过硫酸盐降解活性蓝19的机理及老化研究

采用磷酸改性的黍糠基生物炭作为纳米零价铁(Nanoscale zero-valent iron,nZVI)载体,成功制备出一种高效非均相活化材料一磷酸改性生物炭负载纳米零价铁(nZVI@PBC),用来活化过硫酸盐(Persulfate,PS)降解印染废水中的典型染料—活性蓝(Reactive Blue 19,RB19)...     

台风“安比”对河北东南部地区一次O3污染影响的特征分析

利用欧洲中心ERA-Interim数据以及河北省环境监测站、气象站观测资料,对2018年7月22—24日台风"安比"影响河北前后的一次O_3污染过程的生成、维持、清除进行动力分析,结果如下:台风外围的副热带高压天气型结构有利于河北南部地区污染物的积聚,其演变对预报大气光化学污染具有重要的意义;台风降水对O_3污染有非常好的清除作用,降水量越大,清除效果越好;高压带内部的高温有利于光化学反应,有利于O_3污染的形成;近地层的弱风辐合场与下沉气流的双重作用对O_3污染形成有很好的贡献;旋转形变效应(ds)负值区与河北中南部O_3污染区域对应;动力条件促使湍流运动加强,对O_3污染的清除有很好的作用.通过相关系数检验发现石家庄、邢台5 cm土壤温度和臭氧小时浓度相关性较高(相关系数0.75～0.85),由于土壤温度增加速度低于地表温度增加速度,臭氧浓度增加速度也低于地表温度增加速度,因此5 cm土壤温度比地表温度更及时反映了臭氧光化学反应强度.     

Antioxidant responses to benzo[a]pyrene, tributyltin and their mixture in the spleen of Sebasticus marmoratus

It has been reported that there is an interaction between Benzo[a]pyrene （BaP）, a widespread carcinogenic polycyclic aromatic hydrocarbon, and tributyltin （TBT）, an organometal used as an antifouling biocide. This study was therefore designed to examine the potential in vivo influence of BaP, TBT and their mixture on splenic antioxidant defense systems of Sebastiscus marmoratus. The fish were exposed to water containing environmentally relevant concentrations of BaP, TBT and their mixture. Spleens were collected for biochemical analysis after exposure for 7, 25, 50 d and after recovery for 7, 20 d. Cotreatment with BaP and TBT for 7 d potentiated the induction of glutathione peroxidase （GPx） activity by BaP or TBT alone. The cotreatment for 25 and 50 d resulted in inhibition of GPx activity, which was similar to the effect of TBT. Splenic glutathione S-transferase （GST） activities were significantly elevated in S. marmoratus exposed to BaP starting from 7 d and remained high up to 25 d. However, no further activity change was found with prolonged exposure. Cotreatment of BaP and TBT primarily inhibited the GST activity, which was similar to the effect of TBT. Cotreatment with BaP and TBT for 25 or 50 d potentiated the depletion of GSH （glutathione） by BaP or TBT alone. MDA （malondialdehyde） contents in spleen of S. marmoratus were not significantly altered compared with the control during the test period. Spleen, as an immune organ, is sensitive to exposure of BaP or TBT. It should have an effective mechanism to counteract oxidative damage. Antioxidative defense systems in spleen of S. marmoratus should be considered as potential biomarkers. Short-term exposure of BaP or TBT could result in induction of antioxidant defense system. A significant decrease of these indices, such as GSH, GST, GPx might indicate more severe contamination.     

飞机起落架材料防护技术现状及研究进展

介绍了飞机起落架高强度钢的防护工艺及其防护特点。传统的防护工艺主要是镀铬和镀镉工艺,目前出现了无氰镀镉-钛、高速火焰喷涂(HVOF)涂层、低氢脆刷镀镉等新型防护工艺。通过对各新型防护工艺与传统工艺的工艺性能及耐腐蚀性能进行对比发现,各新型防护工艺都能很好地取代传统的防护工艺应用于飞机起落架的保护。