Surfaces salt segregation

In fact, different techniques revealed cadmium segregation and decrease of the Pb/Se ratio near the InP/PbSe interface, indicating that during the first steps of deposition a CdSe layer is formed on InP prior to the PbSe growth. It was suggested that selective adsorption of Cd(0) on the InP surface gives rise to an epitaxial CdSe monolayer, which facilitates an ordered PbSe growth on account of the small lattice mismatch (0.7%) at the CdSe/(rock salt)PbSe interface. Importantly, it was found... 

Using this method, homogeneous alloys, segregated alloys, layered bi-metallics, and decorated particles are all readily accessible. An obvious advantage of the precursor concept over the conventional salt-impregnation method is that both the size and the composition of the colloidal metal precursors may be tailored independent of the support. Further, the metal particle surface may be modified by lipophilic or hydrophilic protective shells and coated by intermediate layers, e.g., of oxide. The modification of the precursor by dopants is also possible. 

Mineral segregation in industry relies heavily on the selective adsorption of macromolecules onto the surfaces of those minerals that have particular industrial applications. This selectivity is governed mainly by the surface chemistry of the mineral and the type of polymer used as a flocculant. " Effectiveness of flocculation depends upon the charge, concentration and molecular weight of the polymer, and also the pH and salt concentration of the clay suspension. The bonding between the anionic flocculant polyacrylamide (PAM) and clay mineral surfaces has been effectively reviewed recently by Hocking et al and the reader is referred to this should they require an in-depth literature review. For more information on general colloidal chemistry of clay suspensions the reader is referred to the review of Luckham and Rossi." ... 

Chlorine Chemistry in ODEs and Br-Cl Interactions MARINE BOUNDARY LAYER. 4.1 Sea Salt Aerosols Reactive Chlorine Reactive Bromine Reactive Iodine Surface Segregation Effects IMPACT OF HALOGEN CHEMISTRY ON SPECIES OTHER THAN OZONE. 5.1 Alkanes. 5.2 Mercury. 5.3 Sulfur SALT LAKES... 

Knipping et al. (2000) used a box model to simulate the experiment of Oum et al. (1998a) and concluded that conventional chemical and physical processes do not explain the experimental observations. Molecular dynamics simulations of NaCl solutions showed that CP anions are segregated to the surface, facilitating surface reactions involving chloride. They suggested that reactions on the particle surface would be responsible for the release of CI2. According to their box model, the contribution of the interfacial mechanism is 40% of the total chlorine release at a pH of 4 its relative importance increases for less acidic particles (see Section 4.02.4.1 for a discussion of sea salt pH). 

Experimentally, surface-segregation effects were shown by Ghosal et al. (2000) who studied the surfaces of bromine-doped NaCl solids (the Br/Cl ratio was 33 times higher than that of seawater) by X-ray photoelectron spectroscopy. They found that bromine was predominantly present at the surface. Zangmeister et al. (2001) confirmed this result by using a variety of experimental techniques and a range of Br/Cl ratios that covers that of seawater. However, both experiments were performed on solid salts. 

As shown by Knipping et al. (2000) and Knipping and Dabdub (2002) for chlorine, surface segregation has the potential of increasing the release of halogens from sea salt aerosol. This should be pursued further, especially for Br and I , where the surface enrichment effects are predicted to be highest. These effects also likely play a role in polar ODEs. 

SEGREGATION OF SALT IONS AT AMORPHOUS SOLID AND LIQUID SURFACES... 

The combination of Metastable Impact Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy, UPS(Hel) has been applied to the study of the interaction between halides (Csl, CsF, and Nal) with solid water and methanol around their respective Tg values [11,12]. Surface segregation of iodide, but not of fluoride or Cs ions, took place from ASW, exposed to Csl or CsF vapour, during annealing [11]. The same behaviour was also derived from molecular dynamics (MD) simulations of the corresponding aqueous salt solutions. In contrast, no appreciable surface segregation of ions was observed in methanol under similar conditions, neither in the experiment nor in the simulation of the corresponding liquid solution. It was pointed out that, as far as solvation phenomena are concerned, water and methanol ices, when heated above their respective Tg values, behave remarkably similar to the corresponding liquid solutions. The surface propensity of iodide is also seen when Cs is replaced by Na [12]. 

One approach for preparing carbon supported, non-noble metal core, Pt shell type particles is depicted in Fig. 9.11. First, a bulk alloy of Co(Ni)Au(Pd) is formed on the carbon support by reduction of the metal salt precursors. Surface segregation of the noble metal is achieved by hydrogen treatment at temperatures between 600 and 850°C. After this, a Cu monolayer is deposited at underpotential (Cu UPD) and displaced by Pt atoms. °... 

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