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线团式纳米NaY分子筛复合材料的制备及形成机理 总被引:1,自引:0,他引:1
通过在偏高岭土水热合成NaY分子筛的晶化过程中加入乙醇的方法,制备了线团式纳米NaY分子筛复合材料,用XRD、SEM、ICP OES研究了晶化过程中固液相结构和组成的变化,初步探讨了其形成机理,提出了制备纳米NaY分子筛复合材料的条件. 相似文献
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超积累植物体内的小分子螯合物质及其生理作用 总被引:7,自引:0,他引:7
螯合效应是超积累植物忍耐重金属的重要机理之一,不同的超积累植物对不同的重金属胁迫其体内产生的螯合物质不同。目前在超积累植物中发现的螯合物质以其分子量大小可分为两大类,即:草酸、组氨酸、苹果硫、柠檬酸及谷胱甘肽等小分子物质和金属硫蛋白、植物络合素、金属结合体及金属结合蛋白等大分子物质。本文就超积累植物体内的小分子螯合物质及其生理作用作一概述。 相似文献
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超声陈化法制备纳米NaY分子筛及形成机理研究 总被引:1,自引:0,他引:1
Nano-sized NaY zeolite was synthesized from metakaolin in the hydrothermal synthesis system by using ultrasonic during aging time.The process of crystallizing NaY zeolite was studied by XRD、SEM、ICP OES ,and the formation mechanism of nano-sized NaY zeolite was researched,finally the conditions of synthesizing nano-sized zeolite NaY had been brought forward. 相似文献
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羟基功能化离子液体中Ag纳米材料的制备及结构表征 总被引:2,自引:0,他引:2
Ag nanoparticles were prepared using hydroxyl-functionalized ionic liquids as reductant and reaction medium. Nanoparticles with different particle sizes were obtained by using ionic liquids with different structures, while nanorods were harvested when the reaction temperature was increased. The materials obtained were investigated by XRD and TEM. The results indicate that the crystal is in face-centred cubic structure for both of Ag nanoparticles and nanorods, and the diameter of Ag nanoparticles prepared in 1-ethoxyl-3-methyl imidazolium tetrafluoroborate ([C2OHmim]BF4), 1-(4′-hydroxyl)butyl-3-methyl imidazolium tetrafluoroborate ([C4OHmim]BF4) and 1-(6′-hydroxyl)hexyl-3-methyl imidazolium tetrafluoroborate ([C6OHmim]BF4) ionic liquid is about 25, 15 and 10 nm, respectively. And the diameter of Ag nanorods is about 200 nm and 2 μm in length. Finally, the formation mechanism of Ag nanoparticles and nanorods is proposed. 相似文献
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铟掺杂氧化锌-氧化硅纳米电缆芯-壳异质结构的制备及表征 总被引:1,自引:0,他引:1
利用碳热还原反应气相沉积法制备了铟掺杂氧化锌-氧化硅纳米电缆芯-壳异质结构. X射线衍射(XRD)、透射电子显微镜(TEM)及X射线能谱(EDS)研究表明, 纳米电缆内芯为结晶完好的单晶纤锌矿结构, 外壳包覆一层氧化硅非晶层. 纳米电缆直径为30-60 nm, 长径比大于100. 掺杂纳米异质结构的生长机理与传统的金属晶种辅助气-液-固(VLS)机理有所不同. 这种掺杂纳米异质结构有望作为理想的结构单元应用于纳米器件领域. 相似文献
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系统地研究了电离学说的发生、发展过程,发现电离学说与电解质溶液理论相伴发生、发展;电离学说的发展历程可分为4个历史阶段:对溶液的早期认识、电化学重要概念的提出、电离理论的提出、电离学说的完善。 相似文献
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用化学方法首次成功地制备出了用于电极活性材料的纳米Ag2O微粒,并通过TEM,XRD和XPS等测试技术进行了分析表征.同时,对每种方法纳米Ag2O的生成机理进行了初步的探讨,表明这些方法具有一定的普适意义. 相似文献
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采用FESEM、XRD和EDS分析了纳米二氧化硅烧结片在900℃的CaCl2熔盐中浸泡后结构和组成的变化,结果表明,由于纳米尺寸效应和CaCl2熔盐对二氧化硅的熔融(软化)具有助熔作用,纳米二氧化硅烧结片在900℃的CaCl2熔盐中由固态转变为熔融或半熔融态。根据对900℃的CaCl2熔盐中-1.2V恒电位电解不同时间电极片上反应区的结构和组成分析结果,提出了纳米二氧化硅电极片的硅/熔融二氧化硅/熔盐三相界面沿极片径向方向均匀推进的电解还原过程。通过对900℃的CaCl2熔盐中-1.2V恒电位电解5和15min电解产物的形貌、结构和成份分析,提出了硅纳米线在熔盐中的电化学成核与生长机理。 相似文献
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液体表面张力是了解表面现象过程中的重要概念,然而物理化学教材对该概念的阐述却未能做到详实易懂。因此,通过较多立体图示,详细讨论了液体表面张力的产生原因、弯曲液面边缘所受表面张力的方向以及施力相界面等相关问题,以期对教材中未能阐述的内容作以适当补充,降低初学者在概念理解上的难度。 相似文献
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全氟和多氟化合物环境问题研究 总被引:1,自引:0,他引:1
全氟和多氟化合物(PFASs)是一类具有重要应用价值的含氟有机化合物,许多全氟和多氟化合物难以光解、水解和被生物降解,因此具有环境持久性,并可沿食物链累积放大。2009年5月9日,全氟辛烷磺酸(PFOS)及其盐和全氟辛烷磺酰氟被正式列入持久性有机污染物(POPs)名单,由此全氟和多氟化合物成为近年最受关注的新型污染物,其环境问题研究进入到了新的广度和深度。本文将就其分析方法、环境存在、生物累积放大效应、人体暴露和健康效应、新型全氟和多氟化合物等方面的研究,特别是2009年PFOS等被纳入POPs公约以来取得的研究新进展,进行较为全面的综述,并在此基础上对有关发展趋势进行展望。 相似文献
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Many properties of oxide superconductors depend on the oxygen concentration and its distribution in the samples. The microgravimetric
method is very useful to study of oxide superconductors, as it allows investigations in vacuum and controlled environments
in classical applications: thermogravimetric analysis for the study of solid-state reactions, determinations of oxygen contents
in redox reactions and the combined measurement of mass and additional parameters, e.g. evolved gas analysis etc. Single-phase
samples of high-temperature superconductors were synthesized from stoichiometric mixtures of high-purity oxides and carbonates.
Appropriate amounts of the precursor powders were homogenized manually or by a mechanical ball mill and subsequently calcined
at temperatures in the 800 to 950°C range with intermediate grinding to ensure homogenous reaction. The lattice parameters
of all preparations were controlled, in both initial and final experiments, by the X-ray powder method (CuKα radiation), using
a Stadi P (Stoe) diffractometer with a position-sensitive detector. It is well known that temperature and mass can be measured
with an accuracy higher by orders of magnitude than it is still possible for the thermoanalyst to determine the transformation
temperatures or the mass changes due to overlapping partial reactions. Applications of Cahn microbalance to study of high-temperature
superconductors are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Chuansheng Yang Zhikai Mai Can Liu Shuanghong Yin Yantao Cai Chenglai Xia 《Molecules (Basel, Switzerland)》2022,27(11)
Drug resistance is still an obstacle in cancer therapy, leading to the failure of tumor treatment. The emergence of tumor drug resistance has always been a main concern of oncologists. Therefore, overcoming tumor drug resistance and looking for new strategies for tumor treatment is a major focus in the field of tumor research. Natural products serve as effective substances against drug resistance because of their diverse chemical structures and pharmacological effects. We reviewed the signaling pathways involved in the development of tumor drug resistance, including Epidermal growth factor receptor (EGFR), Renin-angiotensin system (Ras), Phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), Wnt, Notch, Transforming growth factor-beta (TGF-β), and their specific signaling pathway inhibitors derived from natural products. This can provide new ideas for the prevention of drug resistance in cancer therapy. 相似文献