共查询到20条相似文献，搜索用时 828 毫秒
1.
当物质分散成胶体的微粒时,一方面胶体微粒倾向于聚结成较大的颗粒,发生凝聚作用而从分散剂里沉淀析出;另一方面胶体微粒的表面具有较强的吸附能力,能从溶液中吸附某种离子,使胶体微粒带正电荷或负电荷,由于同一种胶体微粒带有相同的电荷,微粒间相互排斥而不容易聚集,从而使胶体能稳定存在。胶体微粒的这两种倾向性是由其本身的结构决定的。利用X射线、电子显微镜对胶体进行微观结构的研究,发现胶体微粒内部是由许多分散质分子或原子构成的胶核。胶核具有较强的吸附能力,若溶液中有少量电解质,它就会吸附离子。至于吸附什么离子,这与胶 相似文献
2.
Hong-bo PENG Di ZHANG Hao LI Chi WANG Bo PAN 《浙江大学学报(A卷英文版)》2014,15(8):606-617
研究目的：碳纳米颗粒由于其独特的优良性能被广泛应用,从而不可避免地进入环境。进入环境的碳纳米颗粒与有机污染物有很强的相互作用,并且碳纳米颗粒对有机污染物的吸附可能会影响污染物的环境风险和迁移。因此,本研究总结了目前有机污染物在碳纳米颗粒上吸附的研究进展,为有机污染物及碳纳米颗粒的环境行为研究及风险评价提供重要信息。重要结论：有机污染物和碳纳米颗粒的主要相互作用有憎水性、静电、氢键和π-π作用,这些作用及它们的强度受碳纳米颗粒的表面性质、形态及有机污染物的分子大小、结构和官能团等影响。不同的吸附机理可能同时控制有机物在碳纳米颗粒上的吸附过程,而且在不同的环境条件下吸附控制机理不同。区分吸附控制机理和影响因素的研究对预测有机污染物和碳纳米颗粒的环境行为和风险非常重要。 相似文献
3.
《实验室研究与探索》2015,(6):34-37
为了探究表面活性剂影响下硫化锌纳米晶的微观结构,以醋酸锌和吡咯啶二硫代氨基甲酸铵为原料,在表面活性剂十二烷基苯磺酸钠辅助下水热反应合成了具有纤锌矿和闪锌矿混合结构的硫化锌纳米晶。运用XRD、TEM及选区电子衍射对多种形态和粒径的纳米颗粒进行了表征。结果显示,产物中纤锌矿成分的比例随表面活性剂用量的增多而增大,同时纳米颗粒趋于粒径减小,粒径尺寸分布变宽,形态出现多样化,包括球形、多面体形以及六方片状,另外,高分辨透射电镜解析显示,颗粒中存在大量的孪晶和位错,许多相邻颗粒出现了取向连接生长。对表面活性剂在硫化锌水热合成过程中所起的作用及纳米颗粒的生长机理做了推测。 相似文献
4.
食品防腐剂焦亚硫酸钠生物毒性研究 总被引：2，自引：0，他引：2
为了直接可视化观察焦亚硫酸钠(SM)与红细胞作用后形态上的变化以及对细胞膜分子形貌的影响,利用纳米分辨率水平的原子力显微镜对经不同SM浓度的红细胞表面进行扫描观察.结果表明:与正常红细胞相比,经SM作用后的红细胞的高度明显降低,凹陷部分更加明显;对红细胞上小范围扫描成像的结果显示,受损后的红细胞膜表面结构发生了变化,膜表面颗粒排列的特征依然存在,但颗粒之间开始产生连接并团聚;SM具有生物毒性,能损伤红细胞膜,改变细胞膜的微结构,引起红细胞的溶血作用. 相似文献
5.
颜建河 《中学生数理化(高中版)》2015,(3):36-37
作为有机结构中不可或缺的元素"H",在有机化学学习中起着桥梁和纽带的作用。熟悉和掌握有机物中"H"的相关知识,可迅速找到解决有机化学方面问题的切入口。一、多角度认识有机物中的"H"1.结构中氢的变化。(1)有机物结构中的等效氢("H")。大家知道,多数有机物分子或分子中某一部分结构往往具有对称性,具有对称关系的碳上的氢具有相同性质,称之为等效氢,它们的取代物的性质也是相同的。判断等效氢常用方法有:①同一碳原子 相似文献
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空气负离子与空气质量 总被引：1，自引：0，他引：1
1 空气负离子的形成 中性的空气分子在某种外力(电场、碰撞、辐射等)作用下,有些外层电子会脱离原子核的束缚,成为自由电子.自由电子很快就会附着在气体分子或原子上,而且特别容易附着在氧分子或水分子上,成为空气负离子(也叫阴离子). 相似文献
8.
蛋白质的重要性质1·胶体性质蛋白质是高分子化合物,分子量一般在10~1000kD。根据测定所知,如分子量为34·5kD的球状蛋白,其颗粒的直径为4·3nm。所以,蛋白质分子颗粒的直径一般在1~100nm,在水溶液中呈胶体溶液,具有丁达尔现象、布朗运动、不能透过半透膜、扩散速度减慢、粘度大等特征。在水溶液中,蛋白质的胶体颗粒之外包围一层水膜,形成亲水性胶体,水膜把各个颗粒相互隔开,所以不会凝集成块而下沉。分子不能透过生物膜的特点,在生物学上有重要意义,它能使各种蛋白质分别存在于细胞内外不同的部位,对维持细胞内外水和电解质分布的平衡、物质代谢的调节都起着非常重要的作用。利用这一特性,可对含有小分子杂质的蛋白质溶液用半透膜袋进行分离提纯。2·蛋白质的变性与凝固天然蛋白质受理化因素的作用,使蛋白质的构象发生改变,导致蛋白质的理化性质和生物学特性发生变化,但并不影响蛋白质的一级结构,这种现象叫变性作用。其变性往往是可逆的,如被盐酸变性的血红蛋白,再用碱处理可恢复其生理功能。变性的实质是次级键(氢键、离子键、疏水作用等)的断裂,而形成一级结构的主键(共价键)并不受影响。蛋白质变性后的蛋白质称变性蛋白质,引起蛋白质分子变性... 相似文献
9.
雷能菁 《语文世界(高中版)》2023,(3):62-64
<正>布尔迪厄的经典文化资本理论将文化资本划为元形态、客观的形态、体制的形态三种不同形态,社会结构的变化过程往往是通过后两种形态促成元形态的生成和转变这一过程来完成的。文化的泛在性和复杂性决定了文化资本的泛在和复杂性,文化资本在各个社会文化场所具有强大的势能。作为进行教育的主要场所,学校教育中的文化资本在教学中有不可忽视的作用。 相似文献
10.
《潍坊教育学院学报》2015,(3):89-91
利用晶种法,制备得到长径比为6的金纳米棒胶体,在532nm激光激发下,研究其对Rhodamine6G(Rh6G)分子的荧光增强特性。实验结果表明,所制备金纳米棒胶体具有强的荧光增强特性。根据局域场增强机理可知,在外光场作用下,金纳米棒形成的强局部电场分布,对居于其附近的探针分子光谱辐射过程有很强的增强特性,从而实现荧光增强效应。 相似文献
11.
刘娟 《湖北广播电视大学学报》2011,31(11):159-160
实验测试了氨基磺酸系高效减水剂AH溶液的表面张力、AH在水泥颗粒表面的吸附量及ξ电位,结果表明：AH能够减小溶液表面张力,使分散体系的自由能降低;它在水泥颗粒表面呈环圈及尾状吸附,产生较大的立体空间位阻;掺AH的水泥粒子表面ξ电位绝对值较大,水泥颗粒间存在着较强静电斥力。这些均使得AH具有良好分散作用。此外,AH分子结构中存在的极性基团与水分子间的氢键缔合,在水泥粒子表面形成的溶剂化水膜的润滑,也对AH分散起到一定的加强作用。 相似文献
12.
《天津大学学报(英文版)》2018,(6)
Graphene oxide(GO) contains numerous functional groups that facilitate the intercalation of polar solvents. The properties and applications of GO are closely related to its interlayer spacing. We report on the changes in the interlayer spacing of GO after the adsorption of water molecules and the polar organic solvents C_2H_6O_2(EG), C_3H_7NO(DMF), C_5H_9NO(NMP). Experiments were conducted to investigate the variations in the functional groups and structure of GO after solvent adsorption, and they play a vital role in modeling and verifying the results of molecular dynamics simulation. The most stable GO structures are obtained through molecular dynamics simulation. The expansion of the interlayer spacing of GO after the adsorption of monolayer solvent molecules corresponds to the minimum three-dimensional size of the solvent molecules. The spatial arrangement of solvent molecules also contributes to the changes in interlayer spacing. Most adsorbed molecules are oriented parallel to the carbon plane of GO. However, as additional molecules are adsorbed into the interlaminations of GO, the adsorbed molecules are oriented perpendicular to the carbon plane of GO, and a large space forms between two GO interlayers. In addition, the role of large molecules in increasing interlayer spacing becomes more crucial than that of water molecules in the adsorption of binary solvent systems by GO. 相似文献
13.
司民真 《楚雄师范学院学报》2000,(3)
通过观察亚甲基蓝分子吸附在两种不同电性胶态纳米银上时 ,表面增强拉曼谱特征拉曼峰的变化 ,分析分子在这两种不同电性胶态纳米银表面上吸附方式的变化 相似文献
14.
INTRODUCTIONPlanewakeflowisonetypeoffreeshearflowandexistswidelyinnatureandmanyengi neeringsystems.Tounderstandthekineticchar acterofthelarge scalecoherentvortexstructuresandparticledispersioninplanewakeflowishelpfulforimprovingmanyprocessesinenergyengineering,chemicalengineeringandmaterialengineering .LargeeddysimulationinvolvesbothdirectsimulationandReynolds averagedapproaches.MethodshavebeendevelopedinrecentyearstosolvetheproblemofinstantaneousgasflowfieldandtosimulatehighReynoldsnumb… 相似文献
15.
ZHANG Ji-gao 《浙江大学学报(A卷英文版)》2007,8(3):361-369
Particle pollution in air, also sometimes known as fine dust contamination, may cause electric contact failure. Recent research further proved that the fine particle is becoming a major disruption of the electronic connectors in signal transmission system. This paper specifies the connector contact in mobile phone application. To study the contact failure of mobile phone, a series of inspections and analytical research methods are introduced. Special features that cause the contact failure are summarized. Particle accumulation is the main problem; organic material such as lactates from sweat of the human body may act as adhesives to stick the separate particles together and make them adhere on the contact surface; chemical properties of dust cause serious local corrosion. The corrosion products may trap the particles and firmly attach on the contact surface; micro motion frequently occurs at the contact interface. Hard particle can be embedded into the surface, and soft particle could be squeezed and inserted into the contact; silicon compounds in dust play the most important role in forming high resistance regions that lead to failure; deposition of particles depends on the amount of materials, static electricity attracting force and gravity force applied on the particles. Current dust test can hardly reflect the serious contact failure. It is difficult to simulate the complexity of contact failure caused by particle contamination. Thus alternative ways of simulation experiment and improvement of contact reliability are proposed. 相似文献
16.
To find out the detailed characteristics of the coherent structures and associated particle dispersion in free shear flow, large eddy simulation method was adopted to investigate a two-dimensional particle-laden wake flow. The well-known Sub-grid Scale mode introduced by Smagorinsky was employed to simulate the gas flow field and Lagrangian approach was used to trace the particles. The results showed that the typical large-scale vortex structures exhibit a stable counter rotating arrangement of opposite sign, and alternately form from the near wall region, shed and move towards the downstream positions of the wake with the development of the flow. For particle dispersion, the Stokes number of particles is a key parameter. At the Stokes numbers of 1.4 and 3.8 the particles concentrate highly in the outer boundary regions. While the particles congregate densely in the vortex core regions at the Stokes number of 0.15, and the particles at Stokes number of 15 assemble in the vortex braid regions and the rib regions between the adjoining vortex structures. 相似文献
17.
吴茂江 《雁北师范学院学报》2011,27(3)
从水的密度、水分子结构、冰的结构、水分子间的氢键及水分子的缔合等入题,分析了对水的反常膨胀;从微冰结构、晶体结构、极性分子及分子缔合几种解释方法,认为用水分子间形成氢键缔合水分子理论解释水的反常膨胀最为科学,与实验事实及晶体理论相吻合。 相似文献
18.
以甲基丙烯酸（AA）、烯丙基聚乙二醇（APEG）和二烯丙基二甲基氯化铵（DMDAAC）为原料通过溶液共聚制备出了一种两性聚羧酸系减水剂（APCs）．研究了单体对APCs性能的影响,测定了Zeta电位和吸附特性．结果表明引人阳离子单体可以增加饱和吸附量和分散性能．Zeta电位测定表明吸附着聚合物的水泥粒子之间的空间位阻是主要的分散机理． 相似文献
19.
YANG Wei CHEN Jie LI Xing LIANG Heng HE Wen-jie LI Gui-bai 《浙江大学学报(A卷英文版)》2007,8(9):1475-1481
Considering that contaminated raw water mostly contains high Ammonia-N and a majority of water treatment plants use prechlorination process in China,efficiency of chloramines as a coagulant aid in enhancing coagulation was investigated by Jar stirring and pilot-scale tests,using Yellow River water containing high concentration of natural organic matters (NOM) and bromide in winter. The jar tests results showed that,compared with no preoxidation,preformed chloramine apparently decreased the turbidity of settled and filtered water with low dosage (2.0 mg/L),and the aid-coagulation efficiency was further enhanced with the increase of chlorine (Cl2) to Ammonia-N (N) ratio. Pilot-scale studies indicated that,in comparison to the case without pre-oxidation,the turbidity removal efficiency of flotation and filtration effluent water was significantly improved,the particle counts of filtered water were decreased 63.4%,the average rate of filter head loss was reduced 18.2%,and filter run time was prolonged 15.7%. Therefore,chloramine preoxidation may substantially enhance the particle separation efficiency. 相似文献