Porous aging effects

Razi, E, Iraji, Zad A. and Rahimi, F. Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/Porous Si , (2010) Sensor. Actuat. B. 146, 53-60. 

Mulloni V, Mazzoleni C, Pavesi L (1999) Elaboration, characterization and aging effects of porous silicon microcavities formed on lightly //-type doped substrates. Semicond Sci Technol 14 1052 Murzina TV, Fedor Yu Sychev, Kolmychek I A, Aktsipetrov OA (2007) Tunable ferroelectric photonic ciystals based on porous silicon templates infiltrated by sodium nitrite. Appl Phys Lett 90 161120... 

As a general rule, boiler section deposits initially are often soft and porous but are prone to become harder and more adherent as they age. Thus, the presence of hard, dense scales and deposits in a boiler indicates that deposition has been occurring for a considerable time. The deposition of scales often produces a layered effect similar to the rings of a tree, indicating periodic changes in the water chemistry and perhaps providing some clues as to the history of the deposits. 

In an automobile s catalytic converter, CO and hydrocarbons present in the exhaust gases are oxidized. Unfortunately the effectiveness of these units decreases with use. The phenomenon was studied by Summers and Hegedus in /. Catalysis, 51, 185 (1978) by means of an accelerated aging test on a palladium impregnated porous pellet packed bed converter. From the reported data on hydrocarbon conversion shown below, develop an expression to represent the deactivation rate of this catalyst. 

Fio. 24. Effect of aging on the OH band of porous glass (A) original porous glass, (B) after aging for two years. 

Electrocatalytic investigations (185) on the preparation, properties, and long-term cathode performance of spongy Raney Ni type materials show that secondary structure (fine pores) and tertiary structure (coarser pores and cracks) depend on the chosen preparation procedure, and these factors determine the effective catalytic activity for the HER in a material way. Long-term performance is remarkably improved by controlled leaching of the Raney Ni alloy and oxidative aging (181,182,184) of the developed porous Raney Ni matrix. 

Figure 1. Effect of magnetic field on the modification of chemical composition of porous silicon during its ageing in air.

In this work these two factors were studied with the aim of determining (1) the effects of the coke H/C ratio on combustion and kinetics and (2) the role of the porous stmcture of the HZSM-5 zeolite in limiting combustion. In this study, coke equilibration conditions for reproducible regeneration were sought and the kinetics of coke combustion were determined. Aging and combustion of coke were studied in a differential scanning calorimeter, where the gas-solid contact in a fixed-hed reproduces the operational conditions of the regeneration step in the industrial reactor. 

Total energy calculations have been performed to understand the role of oxidation on the structural, electronic and optical properties of Si nanoclusters. Our aim is to explain the peculiar properties of aged porous Si samples, heavily oxidized Si nanoparticles and embedded Si nanocrystals. We have studied two types of structures isolated H-covered clusters, replacing Si-H bonds with various Si-0 bonds and Si nanoclusters embedded in a SiOz matrix. Regarding the isolated clusters we find that the optoelectronic properties depend on the type and the number of Si-O bonds at the cluster surface. For the embedded systems our results show that a close interplay between chemical and structural effects plays a key role in the light emission processes. 

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