Inert ceramics

Addition of both ion-conducting and inert ceramics enhances the conductivity of a polymer electrolyte. This increase is attributed to an increase in volume fraction of the amorphous phase [133-136]. No... 

Titanium nitride is a truly inert ceramic barrier, which is effective to 550°C. It is deposited by MOCVD or sputtering (see Ch. 10). 

Hydrotreating also produces some residuals in the form of spent catalyst fines, usually consisting of aluminum silicate and some metals (e.g., cobalt, molybdenum, nickel, tungsten). Spent hydrotreating catalyst is now listed as a hazardous waste (K171) (except for most support material). Hazardous constituents of this waste include benzene and arsenia (arsenic oxide, AS2O3). The support material for these catalysts is usually an inert ceramic (e.g., alumina, AI2O3). 

Molten carbonate fuel cells (MCFCs) are currently being developed for natural gas and coal-based power plants for electrical utility, industrial, and military applications. MCFCs are high-temperature fuel cells that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic lithium aluminium oxide (LiAI02) matrix. Since they operate at extremely high temperatures of 650°C and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs. 

Reforming in the CRG process occurs adiabatically at 450-550 C at pressures up to about 600 psig (41 atmospheres). The reactor is a vertical cylindrical pressure vessel containing a bed of the special high-nickel catalyst which is supported on a grid or on inert ceramic halls. The gas flow is downwards through the bed and distributors are provided at inlet and outlet. A layer of ceramic balls on top of the bed prevents disturbance of the catalyst by the entering gas. 

The catalyst is often loaded on screens supported by a stainless steel grid near the bottom of the reactor. Often, large inert ceramic balls are loaded at the very bottom, with slightly smaller ceramic balls above the first layer, and then the catalyst. Smaller inert ceramic balls can also be loaded above the catalyst bed and topped off with the larger balls. The layer of inert balls can be 6 in to 2 ft in depth. The balls restrict the movement of the bed and distribute the liquid across the catalyst. 

In a separate experiment two pilot plant reactors were connected in series. Each reactor was half filled with catalyst and half filled with inert ceramic spheres. The tail gas from the first reactor was fed into the second reactor after condensable products (H20, liquid products) had been removed. Following reaction, the catalyst was unloaded in sections from both reactors under nitrogen as described for the study involving the single reactor. 

Industrial reactors for catalytic incineration of VOCs contain ceramic or another inert packing material on the boundaries of the catalyst bed [9, 26]. In such reactors, the temperature after the inert ceramic packing can be estimated by the almost linear expression... 

If a thinner membrane is required, then one must choose a supported membrane. The permselective metal layer may be palladium or, more commonly, palladium-silver alloy, palladium-copper alloy, or other alloy of palladium. The permselective layer ranges in thickness from about 2-25 /an thinner than 2/rm is very difficult to achieve without introducing pin holes and other adverse defects into the permselective layer. The support layer is porous and is composed of either metal (such as sintered stainless steel or tightly woven wire cloth) or an inert ceramic alumina is very common. Since all of the mechanical strength is derived from the support layer, consideration must be given to its shape and thickness. 

Another example of encoding that does not interfere with chemistry was suggested in 1997 by Xiao and co-workers [38],The coding structure is an inert ceramic plate with a two-dimensional, laser-etched bar code. The encoded plate, which is a 3 mm X 3 mm square, is placed in the center of a laser optical synthesis chip (LOSC). The chip is a 1 cm X 1 cm square made of polypropylene grafted with polystyrene. The smallest possible size of the encoding ceramic plate is 0.5 mm X 0.5 mm. Unfortunately, the bar code cannot be modified during the coursa of the synthesis. 

The inert ceramic matrix which holds the electrolyte in place between the cathode and the anode serves two purposes first, it holds the electrolyte by capillary action and prevents the molten salts from completely flooding the porous electrodes second, the membrane acts to prevent the bulk diffusion of gases between the cathode and the anode side of the cell. If the electrolyte was not in chemical equilibrium with the process gas, localized density changes in the electrolyte caused by reaction (20) would cause the membrane to crack and allow bulk mixing of the process and sweep gas streams. 

Selective Catalytic Reduction (SCR) using ammonia as the reductant provides NOx reduction levels of greater than 80%. Three types of catalyst systems have been deployed commercially noble metal, base metal and zeolites. Noble metals are typically washcoated on inert ceramic or metal monoliths and used for particulate-free, low sulfur exhausts. They function at the lower end of the SCR temperature range (460-520°F) and are susceptible to inhibition by SOx [14]. Base metal vanadia-titania catalysts may either be washcoated or extruded into honeycombs [11]. Typically washcoated catalysts are only used for treating particulate-free, clean gas exhausts. Extruded monoliths are used in particulate-laden coal and oil-fired applications. The temperature window for these catalysts is 600-750°F. Zeolites may also be washcoated or extruded into honeycombs. They function at relatively high temperatures of 650-940°F [15]. Zeolites may be loaded with metal cations (such as Fe, Cu) to broaden the temperature window [16]. 

The technique results in a minimisation of dust emissions from moulding and finishing, as compared to sand moulding. The emissions of VOC are eliminated as no gas is emitted for the inert ceramic mould. Additionally the amount of waste (dust, metal) is reduced. The reduction of feeder systems results in a higher 5deld of castings per melt. 

The geothermal temperature optrode is based on the temperature-dependent phosphorescence of the Eu(III) ion (S). Briefly, Eu(III) and Er(ni) are doped into lattice sites within an inert ceramic-like carrier matrix (CaZiTi O,). The two dopants phosphoresce when excited with the 488-nm line of an argon ion laser. 

Catalytic reactions in the surface external nanospace, at the surface of impermeable liquids. Example of this catalytic system is Viladsen s catalyst [6,7], with microspheres of molten indium inside the cages of a porous inert ceramics (Figure 1.18). Since reaction rates are proportional to the catalysts area, this arrangement ensures very high accessible specific surface areas. 

Relatively inert ceramics elicit minimal tissue response and lead to a thin layer of fibrous tissue immediately adjacent to the surface. Surface-active ceramics are partially soluble, resulting in ion-exchange and the potential to lead to a direct chemical bond with bone. Bulk bioactive ceramics are fiilly resorbable, have much greater solubility fiian surface-active ceramics, and may ultimately be replaced by an equivalent volume of regenerated tissue. The relative level of bioactivity mediates the thickness of Ae interfacial zone between the biomaterial surface and host tissue (Fig. 13.1). There are, however, no standardized measures of reactivity, but the most common are pH changes, ion solubility, tissue reaction, and any number of assays that assess some parameter of cell function. 

Ceramics are fully oxidized materials and are therefore chemically very stable. Thus ceramics are less likely to elicit an adverse biological response than metals, which only oxidize at their surface. Three types of inert ceramics are of interest in musculoskeletal applications carbon, alumina, and zirconia. 

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