Surface area oxidation effect

The STEM Is Ideally suited for the characterization of these materials, because one Is normally measuring high atomic number elements In low atomic number metal oxide matrices, thus facilitating favorable contrast effects for observation of dispersed metal crystallites due to diffraction and elastic scattering of electrons as a function of Z number. The ability to observe and measure areas 2 nm In size In real time makes analysis of many metal particles relatively rapid and convenient. As with all techniques, limitations are encountered. Information such as metal surface areas, oxidation states of elements, chemical reactivity, etc., are often desired. Consequently, additional Input from other characterization techniques should be sought to complement the STEM data. 

In supercapacitors, apart from the electrostatic attraction of ions in the electrode/electrolyte interface, which is strongly affected by the electrochemically available surface area, pseudocapacitance effects connected with faradaic reactions take place. Pseudocapacitance may be realized through carbon modification by conducting polymers [4-7], transition metal oxides [8-10] and special doping via the presence of heteroatoms, e.g. oxygen and/or nitrogen [11, 12]. 

The analysis of smoke and soot formation from polymers during combustion has been extensively studied 50,51 however, less is understood on how hydrated fillers influence this mechanism. It is likely that smoke reduction results from the deposition of carbon onto the high surface area oxide surface, produced on the decomposition of the filler.38 The volatilization of carbonaceous residue as carbon oxides then occurs, reducing obscuration effects from the smoke. 

The susceptibility of metal oxides to reduction and dissolution depends on mineralogy, crystallinity, surface area, the effectiveness of reducing and chelating agents, and microbial activity. Early culture studies with Ee(Hl)-respiring bacteria demonstrated that Ee(lll) reduction rates vary with mineral form or crystallinity... 

Supported M0S2 and WS2 No Promoter. Supports include high surface area oxides especially 7-AI2O3 and Si02, and carbon. The role of the support is to disperse the active components so increasing their effective surface area and catalytic activity. Oxide supports may also participate in isomerization and cracking. Interaction of an active component with a support during... 

Bonding modifiers are employed to weaken or strengthen the chemisorption bonds of reactants and products. Strong electron donors (such as potassium) or electron acceptors (such as chlorine) that are coadsorbed on the catalyst surface are often used for this purpose. Alloying may create new active sites (mixed metal sites) that can greatly modify activity and selectivity. New catalytically active sites can also be created at the interface between the metal and the high-surface-area oxide support. In this circumstance the catalyst exhibits the so-called strong metal-support interaction (SMSI). Titanium oxide frequently shows this effect when used as a support for catalysis by transition metals. Often the sites created at the oxide-metal interface are much more active than the sites on the transition metal. 

Supported metal catalysts comprise 0.1-20% by weight of a metal of Groups 8-11 dispersed over the surface of a support, which is typically a high-surface-area oxide. They are widely used on an industrial scale and in research laboratories. These materials are effective as catalysts because the metallic phase is present as extremely small particles, having a degree of dispersion of 10 to 100%. They are firmly anchored to the surface and are widely separated from each other, and hence do not readily coalesce or sinter. 

Common metals often form mixed oxides with the support compounds. For that reason common metals are usually used as massive metal catalysts. In the case of massive metal catalysts, a few weight percent of a promoter is added. Some promoters make mixed oxides with the active element and influence the reduction process and the surface area (structural promoter). Others are deposited on the metal surface and have an electronic interaction with the surface (chemical effect). Ammonia activity on Fe is known to be enhanced by adding AI2O3 and K2O. It is believed that AI2O3 stabilizes the high surface area of Fe (structural effect) and K2O promotes the ammonia activity per Fe surface area (chemical effect). The structural effect is well studied on Fe single crystal surfaces, where Fe(lll) is the most active plane and Fe(llO) is the next and Fe(lOO) is the least active plane [93]. Such studies have been expanded to other catalysts such as Re, and will be reviewed in Section 3.2.4.2. 

As already mentioned, the choice of the supercooled liquid as reference state has been questioned by some workers who use the saturation vapour pressure of the solid, which is measured at the working temperature in the course of the isotherm determination. The effect of this alternative choice of p° on the value of a for argon adsorbed on a number of oxide samples, covering a wide range of surface areas, is clear from Table 2.11 the average value of is seen to be somewhat higher, i.e. 18 OA. ... 

A discussion of the adsorption of water on oxides would be incomplete without some reference to the irreversible effects which are often encountered when samples of oxide, hydroxide or oxide-hydroxide are exposed to the vapour. These effects ( low-temperature ageing ), which manifest themselves in changes in surface area, in pore structure and sometimes in the lattice structure itself, are complex and difficult to reproduce exactly. ... 

Copper Corrosion Inhibitors. The most effective corrosion inhibitors for copper and its alloys are the aromatic triazoles, such as benzotriazole (BZT) and tolyltriazole (TTA). These compounds bond direcdy with cuprous oxide (CU2O) at the metal surface, forming a "chemisorbed" film. The plane of the triazole Hes parallel to the metal surface, thus each molecule covers a relatively large surface area. The exact mechanism of inhibition is unknown. Various studies indicate anodic inhibition, cathodic inhibition, or a combination of the two. Other studies indicate the formation of an insulating layer between the water surface and the metal surface. A recent study supports the idea of an electronic stabilization mechanism. The protective cuprous oxide layer is prevented from oxidizing to the nonprotective cupric oxide. This is an anodic mechanism. However, the triazole film exhibits some cathodic properties as well. 

Antimony trioxide (SbaOj). It is produced from stibnite (antimony sulphide). Some typical properties are density 5.2-5.67 g/cm- pH of water suspension 2-6.5 particle size 0.2-3 p,m specific surface area 2-13 m-/g. Antimony trioxide has been the oxide universally employed as flame retardant, but recently antimony pentoxide (SbaOs) has also been used. Antimony oxides require the presence of a halogen compound to exert their fire-retardant effect. The flame-retarding action is produced in the vapour phase above the burning surface. The halogen and the antimony oxide in a vapour phase (above 315 C) react to form halides and oxyhalides which act as extinguishing moieties. Combination with zinc borate, zinc stannate and ammonium octamolybdate enhances the flame-retarding properties of antimony trioxide. 

Silica gel and aluminium oxide layers are highly active stationary phases with large surface areas which can, for example, — on heating — directly dehydrate, degrade and, in the presence of oxygen, oxidize substances in the layer This effect is brought about by acidic silanol groups [93] or is based on the adsorption forces (proton acceptor or donor effects, dipole interactions etc) The traces of iron in the adsorbent can also catalyze some reactions In the case of testosterone and other d -3-ketosteroids stable and quantifiable fluorescent products are formed on layers of basic aluminium oxide [176,195]... 

The method of application, whether splash, spray, jet or mist, will have an effect on the lubricant. If oil is atomized, its surface area is increased and it is much more easily oxidized. The frictional heat generated by the meshing teeth will increase the rate of oxidation. The dissipation of... 

Studies of the influence of irradiation on the kinetics of oxidation have been confined to post-irradiation work. In general, prior irradiation increases reactivity, although there are considerable inconsistencies in the enhancements obtained The effects can be derived from an increased surface area associated with the swelling voids produced in the metal by the irradiation, and can also probably arise to a lesser extent from chemical effects of the fission products. 

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