Chemisorption mechanism

Theoretically, these intermolecular interactions could provide adhesion energy in the order of mJ/m. This should be sufficient to provide adhesion between the adhesive and the substrate. However, the energy of adhesion required in many applications is in the order of kJ/m. Therefore, the intermolecular forces across the interface are not enough to sustain a high stress under severe environmental conditions. It is generally accepted that chemisorption plays a significant role and thus, physisorption and chemisorption mechanisms of adhesion both account for bond strength. 

Works [40, 91] surveyed y versus temperature for deactivation of 02( Aj ) on quartz at 350- 900 K. The obtained temperature dependencies were in the Arrhenius form with the activation energy of 18.5kJ/mole. A conclusion was drawn up about the chemisorption mechanism of singlet oxygen deactivation on quartz surface. A similar inference was arrived at by the authors of work [92] relative to 02( A ) deactivation (on a surface of oxygen-annealed gold). 

The above data allow us to infer that in case of a reduced V20s/Si02 surface, a chemisorption mechanism of C>2( )-molecule... 

The adsorption of collectors on sulfide mineral occurs by two separate mechanisms chemical and electrochemical. The former results in the presence of chemisorbed metal xanthate (or other thiol collector ion) onto the mineral surface. The latter yields an oxidation product (dixanthogen if collector added is xanthate) that is the hydrophobic species adsorbed onto the mineral surface. The chemisorption mechanism is reported to occur with galena, chalcocite and sphalerite minerals, whereas electrochemical oxidation is reportedly the primary mechanism for pyrite, arsenopyrite, and pyrrhotite minerals. The mineral, chalcopyrite, is an example where both the mechanisms are known to be operative. Besides these mechanisms, the adsorption of collectors can be explained from the point of interfacial energies involved between air, mineral, and solution. 

The chemisorption mechanism can be well explained with the mineral, galena. The collector ion used is xanthate ion (C ). The mechanism of its adsorption occurs in the following steps ... 

A Chemisorption Mechanism for the Release of Hydrogen from Anthracite. 

Toward Understanding of Hydrogen Storage in Single-Walled Carbon Nanotubes by Investigations of Chemisorption Mechanism... 

Due to the multiple desorption products, the etching of the surface with halogen appears to be quite complex. A multi-step reaction mechanism has been suggested to account for the SiCl2 desorption species. In the case of fluorine atom adsorption, F atom abstraction and dissociative chemisorption mechanisms have been suggested. In order to account for the complex surface reactions, more studies are needed. 

We have examined theoretically [25] and discuss in this chapter the possibility of acid dissociation of nitric acid at an aqueous surface (Eq. (2)), a proton transfer reaction of the acid with a water molecule to produce the hydronium ion H3O+ and the nitrate ion NO3. This acid ionization has been reasonably suggested by Abbatt [13] to be a chemisorptive mechanism involved in the significant HNO3 uptake in the UT [13-16]. It (or rather its lack of occurrence) has also been argued to be important in the uptake of HNO3 by sea-salf aerosols [54] and is significanf for the renoxification process, which involves molecular HNO3 rather than the acid ionization product NO3 [53]. 

Is there anything we can learn in regard to the R.-M. synthesis from the results of our matrix studies Surely, it is daring to compare the reactions of silicon atoms with those on the surface of the contact mass. There are obvious analogies. The physisorption state on the surface [9] corresponds to n-adduct T-5b, while the more stable chemisorption state [9] is comparable with radical pair 4b + 3. The dissociative chemisorption on the surface probably occurs by a nucleophilic attack of methyl chloride (6b) on a silicon atom positioned at the surface of the contact mass. It is also possible that the next step, the formation of the surface-bound silylene, follows a pathway similar to the sequence T-5b methyl radical 3 + 4b — S-lb. The rate-determining step should be the fragmentation of the surface-bound methyl chloride (6b) into a methyl radical (3) and surface-embedded SiCl. That means that the mechanism of the R.-M. synthesis has to be looked at as a combination of the radical mechanism in the sense of Rochow and the chemisorption mechanism . Last but not least, the addition of the second methyl chloride may be comparable to the reaction path S-lb 8b. 

The exponent key is called the exposure number of the ensemble Q. k is the number of potential poison sites within the passivation range, which may each deactivate one or more of the metal atoms of the ensemble (1. The weight factor, qi, is the probability that the S-ensemble has an exposion number, k. It was shown for ensembles containing three or more sites that this model predicted ensemble concentrations corresponding to those calculated by Monte-CarTo simulation of chemisorption via a mobile precursor. As this is the most common chemisorption mechanism, the model is expected to be of rather general applicahility. 

Adsorption can result either from electrostatic interactions between molybdates and boehmite surface or from chemical interactions, i.e. from the formation of a iono-covalent bond through a chemisorption mechanism. The interaction mode is governed by the boehmite hydroxyl surface groups as well as by the solution molybdate species. The determination of the nature and concentration of the molybdenum species involved in the experiments (before and after the adsorption equilibrium) has been carried out by computer simulations (cf 2.2). Concerning hydroxyl surface groups, we referred to MUSIC modeling [11,12] as well as to the work of Raybaud et al. [13], who performed DFT studies on boehmite and so determined boehmite morphological and structural surface properties. 

At intermediate molybdenum loading, molybdate monomers and Anderson-type entities coexist on boehmite surface supporting the idea of a competitive adsorption mechanism. A chemisorption mechanism for molybdate monomers could lead to a limited dissolution of boehmite, necessary for the removal of A1 atoms required in the Anderson-type structure formation. This would explain the plateau reached in molybdate adsorption. 

The interactions between carbon blacks (other than graphitized carbons) and hydrocarbon elastomers are not purely physical. The increased interfacial adhesion resulting from chemisorptive mechanisms contributes significantly to the reinforcing action. 

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