Foamed ceramic

Concerning the hydrodynamics and the dimensioning of the test reactor, some rules of thumb are a valuable aid for the experimentalist. It is important that the reactor is operated under plug-flow conditions in order to avoid axial dispersion and diffusion limitation phenomena. Again, it has to be made clear that in many cases testing of monolithic bodies such as metal gauzes, foam ceramics, or monoliths used for environmental catalysis, often needs to be performed in the laminar flow regime. 

X-ray photograph of a hip joint, a rectangular piece of foam ceramics, a round glass reinforced with titanium fibers and a ring made of metal and ceramics (picture by J Bormans). 

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],... 

The ceramizing capacity of polyboroxosiloxane elastomer provides a new P-free intumescent mechanism [57], The combustion of PP-polyboroxosiloxane 3 1 blend filled with 1.25% organo-modified SEP (OSEP, Pangel B40 product of Tolsa Ltd.) and 1.25% melamine borate lead to the formation of white foamed ceramic structure shown in Figure 13.15. 

The use of supported platinum-based catalysts in hydrogen cyanide synthesis has been described, and some are in use in certain plants. For instance, Merrill and Perry recommended natural beryl coated with platinum or a platinum alloy [12], and a range of alternative supports were considered by Schmidt and his co-workers [13], including coated foamed ceramic and monolithic substrates. They are claimed to have some advantages in ammonia oxidation [14,15]. 

The information is limited to the most important materials, metals, plastics, (thermoplastics, thermoset materials, foams), ceramics, glass and their possible combinations. For papers, cardboards, wood, rubber polymers, usually physically setting systems (solvent-based, dispersion, hot-melt adhesives) are utilized. In these cases, the adhesive selection with regard to the manufacturing conditions and demands is of less problematic nature. 

The aim of the present study is the investigation of activity of the catalysts based on foam materials (foam metals and foam ceramics) in the processes of deep oxidation of volatile aromatic compounds and neutralization of gas emissions of enameled wire production. 

The catalysts were prepared by thermal or chemical deposition of active cover based on Pt and Pd (using chloride precursors) or complex oxides of transition metals (using nitrate precursors) on the foam-metal or foam-ceramics support from aqueous solutions of the metal salts. The foam metal (Nichrome or steel) was coated with the layer of y-Al203 intermediate support in order to increase the catalyst surface area. Content of Pt or Pd in the catalysts accounted for 1 wt.%, concentration of the transition metal oxides amounted to 10-12 wt.%. 

The initial material for the foam catalyst may be any metal or alloy capable of existing, under normal conditions, in the metallic state (Cu, Ag, Ni, W, steel, Nichrome, etc.), or ceramics of various composition. Corrosion-resisting Nichrome and stainless steel are preferable materials of the foam support for deep oxidation processes. Foam ceramics is the most stable to corrosion however, it is brittle and can be broken under hard operating conditions. 

Figure 2 Activity of the catalysts supported on foam ceramics in toluene oxidation...

Figure 3 Catalytic activity of the foam samples in xylene oxidation (foam ceramics contains y-AjOs layer).

Testing the catalysts with different supports and methods of the active phase deposition revealed the better properties of the samples based on foam ceramics (Fig. 3). This is caused by higher surface area of this support. Foam ceramics has maximal amount of the intermediate layer y-AlaOs (up to 35 wt.%), whereas Nichrome contains only 15-18 wt.%. The samples without the intermediate support have much less surface area (5-8 m /g). 

Foam Nichrome seems to be a better support for Pt and Pd catalysts, whereas foam ceramics may be recommended for oxide catalysts. Foam ceramics are much cheaper and easier to prepare as compared with foam metals however, it is brittle and can not operate under hard mechanical loads. For the studied process ceramics may be used as the operating conditions are not too hard. 

Fig. 19. Microstructure of a SiC foam ceramic for filters and other applications [283]...

ABSTRACT Based on the studying on barrier device of gas explosion, an optimized design scheme of gas explosion barrier door with foam ceramics as the main body is proposed. The author uses ANSYS software and finite element method to simulate and compare the main performances of four typical doors in thickness, such as uniform thickness, thick in the upper and thin in the lower, thin in the upper and thick in the lower, secant circular. Results of simulation reveal that the moistest stability and good withstand voltage in structure dose the secant circular door have, describe optimization in detail and provide a feasible optimization of barrier device of gas explosion. 

Keyword, barrier device of gas explosion, foam ceramics, secant circular door, optimization design... 

The barrier device consist of three layers—porous metal plate and foam ceramics and porous metal plate, which is similar to the sandwich, as the fig 1 shown. The holes in the two porous metal plate have different center and diameter, and each hole facing the polluted air is filled by a hollow metal spheres to avoid mixing of fresh air and polluted air. As fig 2(a) and fig 2(b) shown, the fig 2(a) is the closed barrier door and the other is open. 

After gas explosion, shock waves will break the hollow metal spheres outside the first layer of symmetric porous metal material 2 and arrive at internal material. The special structure of the foam ceramics would reduce the pressure from gas explosion and block it, at the same time, decrease temperature of flame and speed of propagation. If the door can not bear the impact, the more barrier doors we need to set. As a result, the shock resistance of the first barrier door should be regarded as the important parameters, and it will be seriously influenced by the shape of barrier door. To find out most stable door. More analyses and researches on different shapes of doors s necessary. 

The designed barrier door is 200 cm long and 200 cm high and 6 cm thick, and consists of three layers—porous metal plate and foam ceramics and porous metal plate. According to the natural and fixed attribute of material itself, elastic modulus is 72Gpa and Poisson Ratio is 0.226. The elastic modulus and Poisson Ratio of metal plate is 206Gpa and 0.3, which is close to steel. 

The pressure distribution of different foam ceramics on each axis is shown as fig. 7(a), the shock wave pressure spread regularly and change greatly on Z axis secant circular door can sustain the maximum pressure of 24Mpa, which is 2.5 time than others. 

Baisheng Nie. The roles of foam ceramics in suppression of gas explosion overpressure and quenching of flame propagation. Journal of Hazardous Materials, 2011, 192 (2) 741-747. 

NIE Baisheng, Effect of Foam Ceramics Upon Gas Explosion Flame Propagation. Transactions of Beijing Institute of Technology. 2008,28(7). 

NIE Bai-sheng. The experiments and mechanism of foam ceramics affecting gas explosion process. Journal of... 

Cheng J., Liu J., Shao H. and Qiu Y. Continuous secondary fermentation of beer by yeast immobilized on the foam ceramic. Research Journal of Biotechnology 2 (3) (2007) 40 2. 

Polymer pyrolysis is also very flexible regarding the type of component that can be obtained fibers, films, membranes, foams, ceramic/ceramic joints, ceramic matrix composites, and monolithic bodies can all be fabricated. The present study has been focused on the formation of monolithic component and thin ceramic films. 

A typical foamed ceramic building material can be made from... 

A similar conclusion of superior performance of structured reactors was drawn from the CPO of ethanol in a comparison of foams, ceramic monoliths and pellets [28, 29]. However, it was stated that the pellets showed good activity and selectivity but poor suitability for mobile applications. In further comparisons of the... 

---