Honeycombing

The modern Russian MIA flaw detectors use pulse version of the method [1-3], which peirnits to produce very portable (0.7 - 1.5 kg) and simple instruments, convenient especially for in-service testing. The objects to be tested are multilayer structures of reinforced plastics, metals and other materials honeycomb panels, antenna fairings, propellers, helicopter rotors and so on. In mentioned instruments amplitude-frequency analog signal processing is used. 

In testing materials with high sound damping, the burst transmitter increases the signal-to-noise ratio to, typically, 12 dB. Typical applications honeycomb and concrete components, and air-coupled testing. 

Macroscopic properties often influence tlie perfoniiance of solid catalysts, which are used in reactors tliat may simply be tubes packed witli catalyst in tlie fonii of particles—chosen because gases or liquids flow tlirough a bed of tliem (usually continuously) witli little resistance (little pressure drop). Catalysts in tlie fonii of honeycombs (monolitlis) are used in automobile exliaust systems so tliat a stream of reactant gases flows witli little resistance tlirough tlie channels and heat from tlie exotlieniiic reactions (e.g., CO oxidation to CO,) is rapidly removed. 

This process may also be referred to as destmctive distillation. It has been appHed to a whole range of organic materials, more particularly to natural products such as wood (qv), sugar (qv), and vegetable matter to produce charcoal (see Fuels frombiomass). However, in the present context, coal usually yields coke, which is physically dissimilar from charcoal and appears with the more familiar honeycomb-type stmcture (27). 

Inorganic membranes (29,36) are generaUy more stable than their polymeric counterparts. Mechanical property data have not been definitive for good comparisons. IndustriaUy, tube bundle and honeycomb constmctions predominate with surface areas 20 to 200 m. Cross-flow is generaUy the preferred mode of operation. Packing densities are greater than 1000 /m. Porous ceramics, sintered metal, and metal oxides on porous carbon support... 

Infrared patterns can lead to detection of lack of bonding between surface platings, between coatings and base metal, or within bra2ed honeycombs and other composite materials where bonding is vital. Mote recent developments involve infrared television or image tubes similar to the types used for night vision in military and other appHcations. 

Work in the area of simultaneous heat and mass transfer has centered on the solution of equations such as 1—18 for cases where the stmcture and properties of a soHd phase must also be considered, as in drying (qv) or adsorption (qv), or where a chemical reaction takes place. Drying simulation (45—47) and drying of foods (48,49) have been particularly active subjects. In the adsorption area the separation of multicomponent fluid mixtures is influenced by comparative rates of diffusion and by interface temperatures (50,51). In the area of reactor studies there has been much interest in monolithic and honeycomb catalytic reactions (52,53) (see Exhaust control, industrial). Eor these kinds of appHcations psychrometric charts for systems other than air—water would be useful. The constmction of such has been considered (54). 

Ni, Pd)-Si-B powder, tape, RS foil AISI 300 series honeycomb stmctures. 

Au—Ni, sohd solution BAu preforms, wine, rods. nickel-base honeycomb stmctures. 

Cordierite [12182-53-5] Mg Al Si O g, is a ceramic made from talc (25%), kaolin (65%), and Al O (10%). It has the lowest thermal expansion coefficient of any commercial ceramic and thus tremendous thermal shock resistance. It has traditionally been used for kiln furniture and mote recently for automotive exhaust catalyst substrates. In the latter, the cordierite taw materials ate mixed as a wet paste, extmded into the honeycomb shape, then dried and fired. The finished part is coated with transition-metal catalysts in a separate process. 

The honeycomb roof is made from a hexagonal cell pattern similar to a beehive in appearance. The honeycomb is glued to a top and bottom aluminum skin that seals it. This roof rests directly on the Hquid. 

For centuries, the honeycomb of bees, ie, beeswax, was the material commonly referred to as wax. Substances having typical wax characteristics have traditionally come from iasects, eg, beeswax from vegetables, eg, camauba and from animal, eg, spermaceti, origins (1). Waxes from mineral and synthetic sources have been developed both as substitutes for waxes from traditional sources and for new appHcations. Waxes from minerals and synthetic sources now surpass waxes from traditional sources ia toimage and commercial importance. 

Ideally, the temperature and relative humidity during drying should be controlled if wood dries too rapidly, it is likely to spHt, check, warp, or honeycomb because of stresses. If wood dries too slowly, it is subject to development of stain and mold growth. 

The most widely used exhaust control device consists of a ceramic monolith with a thin-waHed open honeycomb stmcture. The accessible surface of this monolith system is iacreased by applyiag a separate coatiag, a wash coat, of a high surface area material such as gamma-alumiaa with the catalyticaHy active species impregaated iato this washcoat. The catalyst aeeds to oxidize hydrocarboas, coavert CO to CO2, and reduce NO. The whole system forms a catalytic converter that, suitably encased, is placed between the engine and the muffler/silencer unit. 

The color development of photochromic compounds can also be utili2ed as a diagnostic tool. The temperature dependence of the fa ding of 6-nitroindolinospiropyran served as the basis for a nondestmctive inspection technique for honeycomb aerospace stmctures (43). One surface of the stmcture to be exarnined was covered with a paint containing the photochromic compound and activated to a violet color with ultraviolet light. The other side of the stmcture was then heated. The transfer of heat through the honeycomb stmcture caused bleaching of the temperature-dependent photochromic compound. Defects in the honeycomb where heat transfer was inhibited could be detected as darker areas. 

Automobile exhaust catalysts have been developed that maximize the catalyst surface area available to the flowing exhaust gas without incurring excessive pressure drop. Two types have been extensively studied the monolithic honeycomb type and the pellet type. 

Use of the peUetted converter, developed and used by General Motors starting in 1975, has declined since 1980. The advantage of the peUetted converter, which consists of a packed bed of small spherical beads about 3 mm in diameter, is that the pellets were less cosdy to manufacture than the monolithic honeycomb. Disadvantages were the peUetted converter had 2 to 3 times more weight and volume, took longer to heat up, and was more susceptible to attrition and loss of catalyst in use. The monolithic honeycomb can be mounted in any orientation, whereas the peUetted converter had to be downflow. AdditionaUy, the pressure drop of the monolithic honeycomb is one-half to one-quarter that of a similar function peUetted converter. 

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