Faraday Discussions of The Chemical Society最新文献_第6页

Electric-field-induced aggregation in dilute colloidal suspensions 稀胶体悬浮液中电场诱导的聚集

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9909000017

Paul M. Adriani, A. Gast

引用次数: 22

Electrochemical inclusion of copper and iron species in a conducting polymer observed in situ using time-resolved X-ray absorption spectroscopy 用时间分辨x射线吸收光谱原位观察导电聚合物中铜和铁的电化学包合

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9908900041

D. Guay, G. Tourillon, A. Fontaine

引用次数: 9

Interacting particles in contact 相互作用的接触粒子

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9909000143

G. Frens

{"title":"Interacting particles in contact","authors":"G. Frens","doi":"10.1039/DC9909000143","DOIUrl":"https://doi.org/10.1039/DC9909000143","url":null,"abstract":"The depth of the potential well for contacting particles determines the texture of a floc. This energy can be calculated from the interaction forces between the particles. In electrocratic colloids it depends on the counter-ion valency z, the (local) potential ϕδ near the contact point and the curvature of the surfaces in contact. However, it does not depend on the Debye length, 1/κ, which measures the range of the repulsive forces.At a critical value Zc for the parameter Z=zeϕδ the minimum disappears. For Z Zc flocs are unstable: they would repeptize or at least rearrange their texture.Because the rules of Schulze and Hardy and of Eilers and Korff apply simultaneously it can be derived that ϕδ is low (Z < Zc) and that Z has an equal value in sols when they coagulate at equal rates in electrolytes with different z. This theoretical observation has been verified experimentally. The double-layer potential, ϕδ, is indeed inversely proportional to z under such conditions. As a consequence, the parameter γ= tanh (zeϕδ/4kBT), which represents the influence of double-layer potentials in the DLVO theory, becomes a constant for conditions of equal rate. But, unlike the suggestion in the classical theory γ≠ 1, and its value is required to account for experimental observations.When sols coagulate at the same rate the depth of the potential well for aggregates increases with z. This effect is readily observed, since it is reflected in the texture of the flocs which are formed. Both Z(i.e. ϕδ) and z are variables in the coagulation conditions, and can be used to control the porosity of flocs, sediments and materials, which are prepared by sol–gel and related methods.","PeriodicalId":12210,"journal":{"name":"Faraday Discussions of The Chemical Society","volume":"54 1","pages":"143-151"},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80411310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Structural studies of high-area zeolitic adsorbents and catalysts by a combination of high-resolution X-ray powder diffraction and X-ray absorption spectroscopy 高分辨率x射线粉末衍射和x射线吸收光谱相结合的高面积沸石吸附剂和催化剂的结构研究

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9908900119

E. Dooryhee, G. Greaves, A. T. Steel, R. P. Townsend, S. Carr, John Meurig Thomas, C. Catlow

{"title":"Structural studies of high-area zeolitic adsorbents and catalysts by a combination of high-resolution X-ray powder diffraction and X-ray absorption spectroscopy","authors":"E. Dooryhee, G. Greaves, A. T. Steel, R. P. Townsend, S. Carr, John Meurig Thomas, C. Catlow","doi":"10.1039/DC9908900119","DOIUrl":"https://doi.org/10.1039/DC9908900119","url":null,"abstract":"We have characterized at high temperature a model uniform heterogeneous catalyst for the oligomerization of hydrocarbons (a nickel-exchanged zeolite of initial composition Na59Al59Si133O384·xH2O treated with an aqueous solution of NiCl2 so as to yield a homogeneous distribution of Ni, with Si/Ni = 7) by recording the extended X-ray absorption fine structure (EXAFS) above the Ni edge and also its high-resolution diffraction pattern (at λ= 1.5486 A). We have obtained unique insights into the microenvironment of the Ni2+ ions in the as-prepared and the dehydrated as well as the reduced state of the catalyst; in particular, values of atomic coordinates, site-occupancy and bond lengths, have been obtained. High-resolution X-ray diffraction, using a specially constructed environmental cell, has enabled the precise location of sorbed Xe atoms in a sodium-exchanged zeolite X adsorbent (1.5 atoms of Xe per unit cell) under a pressure of 1.75 bar at room temperature to be determined from a Rietveld refinement of the powder diffraction pattern. Direct proof of the role of the strongly polarizing Na+ ion located at the SΠ site in firmly binding the Xe to the inner wall of the supercage is obtained.X-ray absorption near-edge structures (XANES) as well as parallel EXAFS studies above the Al, Si and Ga edges on a variety of other zeolites are also reported. Combined (Ga edge) XANES and EXAFS studies show that gallosilicate networks akin to those present in crystalline (gallo) zeolite X and Y are already formed in the precursor gel and are also present in the aqueous solution in contact with the colloidal-amorphous material, which together constitute the gel. We also report one of the first applications of Al EXAFS for the semi-quantitative study of the dealumination of faujasitic zeolites.","PeriodicalId":12210,"journal":{"name":"Faraday Discussions of The Chemical Society","volume":"246 1","pages":"119-136"},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76945566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 47

Langmuir monolayers: structures and phase transitions 朗缪尔单层膜:结构与相变

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9908900211

Z. Cai, S. Rice

{"title":"Langmuir monolayers: structures and phase transitions","authors":"Z. Cai, S. Rice","doi":"10.1039/DC9908900211","DOIUrl":"https://doi.org/10.1039/DC9908900211","url":null,"abstract":"This paper briefly reviews information recently obtained from grazing incidence X-ray diffraction studies of the structures of the several phases in the high-surface-density region of an amphiphile monolayer on water. We also present a new theory, based on a density functional formalism, for the transition between untilted (hexagonal) and tilted (distorted hexagonal) phases in these monolayers. We find that in the region from 0 to ca. 0.5 rad tilt angle the tilted states are thermodynamically more stable (ca. 0.2–2.0 kBT per segment lower in free energy) than the untilted state, so that the monolayer, when expanded, always adopts the value of tilt angle determined by the area per molecule. Eventually, for large tilt, say e.g. > 0.6 rad, the chemical potential of the monolayer increases as the tilt increases. There is, then, a minimum of the free energy versus tilt angle for which the constraint derived from the area per molecule is effectively relieved. We find that an incompressible monolayer has a small change in average density and a large change in area per molecule across the transition. Conversely, a monolayer with large compressibility has a large density change and a small change in area per molecule across the transition. Our analysis correctly reproduces the principal features of the observed phase transitions. We speculate on the nature of ‘island phases’ and the relation of these to the close-packed phases of the monolayer.","PeriodicalId":12210,"journal":{"name":"Faraday Discussions of The Chemical Society","volume":"64 1","pages":"211-229"},"PeriodicalIF":0.0,"publicationDate":"1990-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79512750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 10

X-Ray Scattering from Surfaces and Interfaces 表面和界面的x射线散射

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9908900181

R. Cowley, C. Lucas

引用次数: 9

Photoelectron diffraction study of O, N and C adsorption structures on Ni(100) and Cu(110) Ni(100)和Cu(110)表面O、N、C吸附结构的光电子衍射研究

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9908900311

A. Kilcoyne, D. P. Woodruff, A. W. Robinson, T. Lindner, J. Somers, D. Ricken, A. Bradshaw

引用次数: 6

Structure and dynamics of suspensions of charged rod-like particles 带电棒状粒子悬浮液的结构和动力学

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9909000245

B. Weyerich, B. D’Aguanno, E. Canessa, R. Klein

引用次数: 29

Structure of the Ge(111)-c(2 × 8) surface as determined from scattered X-ray intensities along crystal truncation rods 沿晶体截断棒的散射x射线强度测定了Ge(111)-c(2 × 8)表面的结构

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9908900169

R. V. Silfhout, J. V. D. Veen, C. Norris, J. E. MacDonald

引用次数: 32

Interaction potential of a dispersion of colloidal particles with a non-homogeneous surface potential 具有非均匀表面电位的胶体粒子分散的相互作用势

Faraday Discussions of The Chemical Society Pub Date : 1990-01-01 DOI: 10.1039/DC9909000235

A. J. Kuin

引用次数: 20