Metal honeycomb structure

Experimental results concerning the development of a small-scale 1 kW autothermal reformer of propane were reported by Rampe et al. [76]. In the proposed reactor, two reactions occur on a metal honeycomb structure coated with platinum. Air and water are mixed before they are fed to the reactor in counterflow to the product gas outside the reactor wall, where the water is vaporized and the steam and air are heated up. Then, they are mixed with propane at the bottom of the reactor. It was verified that the preheating operation mode led to about a 4% higher efficiency, since the higher inlet air temperature causes a higher temperature level in the reaction zone, resulting in improved kinetics of the reforming reaction. 

Refractory metals, titanium alloys, ceramics, metallic honeycomb structural materials, acrylic, composites, glass, silicon and graphite. 

Quite often, NBR adhesives are used to bond various kinds of gasketing (cork, fibre, foam, rubber, metal) to rigid superstructures, such as aircraft. Films cast from solution are often used to fabricate honeycomb structures for aircraft. 

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

Repair. Repairs for damaged bonded structure can be either mechanical or adhesively bonded. Mechanical repairs are metallic doublers on one or both sides of a damaged component, held on by fasteners. The fasteners transfer the load through the doubler around the damaged site and restore part functionality. Although common for metal-to-metal bonded structure, mechanical repair of sandwich structure is rare because of the risk of further delamination. Unless the doubler and fasteners are perfectly sealed, water can travel into the honeycomb core eventually causing freeze-thaw damage and delamination. 

The small particles are reported to be very harmful for human health [98]. To remove particulate emissions from diesel engines, diesel particulate filters (DPF) are used. Filter systems can be metallic and ceramic with a large number of parallel channels. In applications to passenger cars, only ceramic filters are used. The channels in the filter are alternatively open and closed. Consequently, the exhaust gas is forced to flow through the porous walls of the honeycomb structure. The solid particles are deposited in the pores. Depending on the porosity of the filter material, these filters can attain filtration efficiencies up to 97%. The soot deposits in the particulate filter induce a steady rise in flow resistance. For this reason, the particulate filter must be regenerated at certain intervals, which can be achieved in the passive or active process [46]. 

The process has been commercially implemented in Japan since 1977 [1] and a decade later in the U.S., Germany and Austria. The catalysts are based on a support material (titanium oxide in the anatase form), the active components (oxides of vanadium, tungsten and, in some cases, of molybdenum) and modifiers, dopants and additives to improve the performance, especially stability. The catalyst is then deposited over a structured support based on a ceramic or metallic honeycomb and plate-type structure on which a washcoat is then deposited. The honeycomb form usually is an extruded ceramic with the catalyst either incorporated throughout the stmcture (homogeneous) or coated on the substrate. In the plate geometry, the support material is generally coated with the catalyst. 

In most materials selection processes, it is virtually impossible to make materials choices independent of the product shape. This includes not only the macroscopic, or bulk, shape of the object such as hammer or pressure relief valve, but also the internal or microscopic shape, such as a honeycomb structure or a continuous-fiber-reinforced composite. Shape is so important because in order to achieve it, the material must be subjected to a specific processing step. In Chapter 7, we saw how even simple objects made from a single-phase metal alloy could be formed by multiple processes such as casting or forging, and how these processing steps can affect the ultimate properties of the material. As illustrated in Figure 8.6, function dictates the choice of... 

To overcome this challenge, other filter designs and construction materials were tested, such as packed-bed filters [41], foam ceramic filters [39, 42—44], sintered ceramic filters [18, 45, 46], candle-type filters made from metal or ceramics [22, 47], or honeycomb structures made from steel [48]. Among the construction materials, the performance of high-temperature ceramics, such as SiC, Zr02, or SiC>2, was investigated [18, 45, 46, 49],... 

Tape and film adhesives are most often used to bond large areas, such as for applications in the aerospace industry. For example, the joining of aluminum honeycomb structure to flat metal skins is often accomplished with thermosetting epoxy film adhesives. These films (Fig. 13.1) can easily be applied without the need to mix, meter, or apply a liquid coating. 

H. Masuda and K. Fukuda, Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina, Science 268 1466-1468 (1995). 

Honeycomb structures offered to the market have a similar cell density as the ceramic ones. After welding inlet and outlet cones to the outer shell, the metallic monolithic converter can be inserted directly into the exhaust gas pipe, which means that the canning procedure used for the ceramic monoliths is not needed anymore. 

We mentioned earlier (see Section V,C,1) that for the two-dimensional compounds of formula (catliMnCrCoxlg], with cat+ standing for a monovalent cation, each metal site of a given chirality (A or A) is surrounded by three metal sites of the opposite chirality (A or A), so that within a layer all the Mn(II) sites have the same chirality and all the Cr(III) sites have the other chirality. If the Mn(II) and Cr(III) sites had the same chirality, the hexagons of the honeycomb structure could no longer be closed, and the structure would be three- instead of two-dimensional. This structure as a whole would obviously be chiral 86). 

Of particular interest are the block honeycomb-structure SHS catalysts. In these catalytic systems, the gas-dynamic resistance is much lower than in conventional ones, the catalytic layer is immobilized, and the active surface is used more efficiently. The data on the oxidation of carbon monoxide and propane in the block oxynitride SHS catalyst (1.5% CO, 1.5% CsHg, 10% O2 W=7010 h ) are presented in Fig. 4. Note, that at high flow rates, the conversion degree for carbon monoxide and propane attains 100% at 450-500 C. The temperature of complete oxidation can be lowered upon immobilization of the "id transition metals (Co, Ni, Cr, and Fe) oxides on the catalyst surface. Efficiency of the catalysts with immobilized Co and Ni oxides (0.2%) for the oxidation of carbon monoxide and propane is shown in Fig. 5. In this case, carbon monoxide is oxidized at 400-450"C while propane is oxidized at 125-175°C. 

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