共查询到16条相似文献,搜索用时 78 毫秒
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《化学物理学报》2020,(3)
基于非线性泊松-玻尔兹曼方程,推导了混合电解质溶液中考虑介电饱和度的表面电位的解析表达式.近似解析解和精确数值解计算出的表面电位在很大范围的电荷密度和离子强度条件下均具有很好的一致性.当表面电荷密度大于0.30 C/m~2时,介电饱和度对表面电位的影响变得尤为重要;当表面电荷密度小于0.30 C/m~2时,可忽略介电饱和度的影响,即基于经典泊松-玻尔兹曼方程可获得有效的表面电位解析模型.因此,0.3 C/m~2可作为是否考虑介电饱和度的颗粒临界表面电荷密度值.在低表面电荷密度时,考虑介质饱和度的表面电位解析模型可自然回归到经典泊松-玻尔兹曼理论的结果,得到的表面电位可以正确地预测一价和二价反离子之间的吸附选择性. 相似文献
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作为21世纪备受瞩目的材料,石墨烯兼具优异的电、热、光与力学性质,具有十分广阔的研究价值与应用价值.目前主要通过在金属基底上生长获得石墨烯,并将其转移至目标介电层基底上以构筑电子器件.转移过程不可避免地引入了褶皱、裂纹、破损以及聚合物/金属残留,严重损害了石墨烯的性能.因而直接在介电基底上制备高质量的石墨烯薄膜具有重要意义.本文总结了近年来在介电衬底上直接生长石墨烯的研究进展:阐述了金属辅助法、等离子体增强法以及热力学或动力学调控法等多种生长手段;介绍了多种介电/绝缘基底包括SiO_2/Si,Al_2O_3,SrTiO_3,h-BN,SiC,Si_3N_4以及玻璃表面生长石墨烯的特点与性能,分析了其可能的生长机理.根据拉曼谱图、薄层电阻、透光率、载流子迁移率等评估指标,将多种方法得到的石墨烯质量进行了总结与比较,并提出了直接在介电衬底上生成石墨烯的研究难点与趋势. 相似文献
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采用基于密度泛函理论的第一性原理平面波超软赝势法,建立了未掺杂,Al,N单掺杂和Al-N共掺杂3C-SiC的4种超晶胞模型,并分别对模型进行了几何结构优化,对比研究了其能带结构,态密度分布和介电常数.计算结果表明:Al掺杂会增大SiC的晶格常数,而N对SiC的晶格影响很小.Al掺杂会导致费米能级进入价带,使3C-SiC成为p型半导体,且带隙宽度略为加宽.N掺杂后的SiC其导带和价带均向低能端发生移动,带隙稍有减小.本征3C-SiC几乎不具备微波介电损耗性能.但是可以通过进行Al掺杂或N掺杂加以改善,Al掺杂后的效果尤为突出.计算发现Al-N共掺杂后的3C-SiC材料在8.2—12.4 GHz范围内其微波介电损耗性能急剧下降,与实验结果相符合,并对这一结果进行了讨论分析. 相似文献
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用扭摆及静电音频内耗仪研究了CuO在100~160K的内耗行为,实验结果表明在该温区存在一激活能为0.2eV的弛豫峰,而CuO的介电行为研究也表明在此范围有一弛豫峰,激活能为0.21eV。实验还进一步说明高温超导材料在该温区的反常行为与CuO无关。 相似文献
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采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了本征ZnO和Al掺杂ZnO的能带结构和介电常数,又采用固相反应法在600 ℃保温1.5 h分解得到ZnO和Al掺杂ZnO粉体.X射线衍射(XRD)对所得粉体的结构进行表征,X射线光电子谱(XPS)对掺入的Al的形态进行分析,矢量网络分析仪在8.2—12.4 GHz测试样品的微波介电性能.结果表明,Al掺杂后ZnO的晶胞体积基本不变,费米能级进入导带.实验所得粉体均具有ZnO的纤锌矿结构,Al是以替位杂质的形式进入ZnO晶格.实验与计算结果相比,都表
关键词:
Al掺杂ZnO
介电性质
能带结构
第一性原理 相似文献
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PT-PEK-c电光聚合物薄膜的厚度和介电性质 总被引:2,自引:0,他引:2
研制了新的PT-PEK-c电光聚合物薄膜材料,用准波导耦合m线方法测量了PT-PEK-c电光聚合物薄膜的厚度,并测量了该聚合物薄膜在1×102Hz到1×107Hz频率范围内的室温介电常数.测量结果为:厚度d=2.328±0.315μm,在10KHz下,介电常数εr=4023±0.063,介电损耗tanδ=0.003. 相似文献
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Yan Levin 《Journal of statistical physics》2003,110(3-6):825-834
In this contribution to the special issue of the Journal of Statistical Physics dedicated to Michael Fisher on his 70th birthday, I shall review two thermodynamically distinct routes for obtaining the interfacial tension of liquid-vapor interfaces in mixtures. A specific application to the calculation of excess surface tension of aqueous electrolyte solutions will be presented. 相似文献
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在放电间隙较大的介质阻挡放电中,利用高速照相机,同时观察到了体放电(VD)和沿面放电(SD)。采用光谱法,研究了VD和SD的光谱线形随放电参数的变化。在氩气介质阻挡放电中,测量了VD和SD的Ar Ⅰ(2P2→1S5)谱线展宽和频移随气压及放电间隙的变化。结果发现:SD的展宽和频移均比VD的大,说明SD的电子密度高于VD的电子密度;随着压强从40 kPa增大到60 kPa,VD和SD的谱线展宽及频移均增加,表明它们的电子密度均随压强的增大而升高;随着d值从3.8 mm增大到4.4 mm,VD和SD的谱线展宽也增加,反映它们的电子密度均随d值的增大而增加。 相似文献
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Relaxation process of surface charge owing to dielectric barrier discharge (DBD) in “needle – air gap – polyethylene terephthalate film – plane” configuration is considered. Experimental data of the surface charge relaxation (SCR) are obtained by means of the rotating capacitive probe. Taking into account Gaussian radial distribution of accumulated charge density, effective surface and volume electrical conductivities of a barrier dielectric, phenomenological model of SCR for any dielectric thickness is proposed and exact solutions are obtained. The adequacy of the model is confirmed by the numerical computation. There is a good agreement between the experimental results and the model calculations. 相似文献
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Gabriel Téllez 《Journal of statistical physics》2006,122(4):787-798
We complement a recent exact study by L. Šamaj on the properties of a guest charge Q immersed in a two-dimensional electrolyte with charges +1/−1. In particular, we are interested in the behavior of the density
profiles and electric potential created by the charge and the electrolyte, and in the determination of the renormalized charge
which is obtained from the long-distance asymptotics of the electric potential. In Šamaj’s previous work, exact results for
arbitrary coulombic coupling β were obtained for a system where all the charges are points, provided β Q < 2 and β < 2. Here, we first focus on the mean field situation which we believe describes correctly the limit β→ 0 but β
Q large. In this limit we can study the case when the guest charge is a hard disk and its charge is above the collapse value
β Q > 2. We compare our results for the renormalized charge with the exact predictions and we test on a solid ground some conjectures
of the previous study. Our study shows that the exact formulas obtained by Šamaj for the renormalized charge are not valid
for β Q > 2, contrary to a hypothesis put forward by Šamaj. We also determine the short-distance asymptotics of the density profiles
of the coions and counterions near the guest charge, for arbitrary coulombic coupling. We show that the coion density profile
exhibit a change of behavior if the guest charge becomes large enough (β Q≥ 2−β). This is interpreted as a first step of the counterion condensation (for large coulombic coupling), the second step
taking place at the usual Manning–Oosawa threshold β Q = 2. 相似文献
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The rutile (1 1 0)-aqueous solution interface structure was measured in deionized water (DIW) and 1 molal (m) RbCl + RbOH solution (pH 12) at 25 °C with the X-ray crystal truncation rod method. The rutile surface in both solutions consists of a stoichiometric (1 × 1) surface unit mesh with the surface terminated by bridging oxygen (BO) and terminal oxygen (TO) sites, with a mixture of water molecules and hydroxyl groups (OH−) occupying the TO sites. An additional hydration layer is observed above the TO site, with three distinct water adsorption sites each having well-defined vertical and lateral locations. Rb+ specifically adsorbs at the tetradentate site between the TO and BO sites, replacing one of the adsorbed water molecules at the interface. There is no further ordered water structure observed above the hydration layer. Structural displacements of atoms at the oxide surface are sensitive to the solution composition. Ti atom displacements from their bulk lattice positions, as large as 0.05 Å at the rutile (1 1 0)-DIW interface, decay in magnitude into the crystal with significant relaxations that are observable down to the fourth Ti-layer below the surface. A systematic outward shift was observed for Ti atom locations below the BO rows, while a systematic inward displacement was found for Ti atoms below the TO rows. The Ti displacements were mostly reduced in contact with the RbCl solution at pH 12, with no statistically significant relaxations in the fourth layer Ti atoms. The distance between the surface 5-fold Ti atoms and the oxygen atoms of the TO site is 2.13 ± 0.03 Å in DIW and 2.05 ± 0.03 Å in the Rb+ solution, suggesting molecular adsorption of water at the TO site to the rutile (1 1 0) surface in DIW, while at pH 12, adsorption at the TO site is primarily in the form of an adsorbed hydroxyl group. 相似文献
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A. Hilger N. Cüppers M. Tenfelde U. Kreibig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):115-118
We present novel experimental results about influences of surrounding foreign materials on optical properties of small silver
clusters. First we show spectra of free cluster beams produced with different seeding gases Ar, Kr, Xe. Second, we estimate, from measured spectra, the cluster deformations
and contact areas after deposition on different substrates (Cr2O3 and MgF2) at room temperature and on SiO2 at 110 K and between 160 K and 300 K. Third, we present and compare the static and dynamic charge transfer after embedding the clusters in various fluorides and compare with previous results on oxides.
Received 2 September 1998 and Received in final form 3 January 1999 相似文献