Ceramic aluminium oxide

Catalysts can be metals, oxides, sulfides, carbides, nitrides, acids, salts, virtually any type of material. Solid catalysts also come in a multitude of forms and can be loose particles, or small particles on a support. The support can be a porous powder, such as aluminium oxide particles, or a large monolithic structure, such as the ceramics used in the exhaust systems of cars. Clays and zeolites can also be solid catalysts. 

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. 

The carbides and nitrides are well known for their hardness and strength, and this section will briefly compare a number of these properties with those of the pure metals. Concentration will be placed here on the first row compounds, since these constitute a complete series, and Mo and W, since these are the most commonly studied metals. As will be shown, the physical and mechanical properties of carbides and nitrides resemble those of ceramics not those of metals. Comparisons will be made with boron carbide (B4C), silicon carbide (SiC), aluminium nitride (AIN), silicon nitride (Si3N4), aluminium oxide (A1203), and diamond, as representative ceramic materials. 

An important oxide in ceramics is silicon dioxide Si02 in the form of the minerals quartz and quartz sand (with aluminium oxide as a... 

In 1993 Rock patented the use of aluminium oxide ceramics as implant materials Patent-erteiling liber Aluminiumoxidekeramik fur das Innere und AuBere des menschlichen und tierischen Korpers . 

Aluminium oxide is the oldest ceramic material used in medicine. Bauxite and corundum are the main natural sources of aluminium oxide. Bauxite is a mixture of diaspore, gibbsite, iron hydroxides, clay minerals and quartz. It is formed by the tropical weathering of silicate rocks during which quartz and the elements sodium, calcium, magnesium and potassium are largely washed away. This is the reason why the remaining material becomes richer in the resistant elements titanium, iron and aluminium. The latter is extracted from this mixture in the form of aluminium hydroxide. In its turn this compound is converted into aluminium oxide by heating the mixture to 1200-1300 °C, this is called calcination. The hydroxide is thus made anhydrous. 

Aluminium oxide ceramics contain elements with an atom mass which is virtually identical to the atom mass of the elements in bone. The crystal lattice contains Al3+ and O 2 ions. The aluminium oxide is not stable in the air as it wants to combine with components in the air. That is why the surface of a crystal only contains O2-ions. These attract substances with a large dipole from the environment, like for instance water molecules and protein-containing body substances. Since the aluminium oxide implant in the body is covered by a layer of protein molecules, the body does not recognize the implant as nonself, and consequently the defence mechanism is not activated. 

In the case of so-called active soldering an active solder is used a metallic solder containing interface active additives which make certain that the molten solder wets the ceramics. An example of such a solder is a silver / copper alloy with a titanium or titanium / indium additive which can be used when soldering zirconium (IV) oxide to certain steels, aluminium oxide to nickel / cobalt or iron / nickel alloys and aluminium oxide to a iron / nickel / cobalt alloy. 

And now another important question is Should these Venus sculptures be classed as ceramic materials Initial analyses proved that they were made of silicon-containing ash and mammoth bone and possibly also mammoth fat, but no aluminium oxide or potassium oxide - which are always present in clay - were found. A later analysis of the Venus of Vestonice led to the concusion that a mixture of mammoth fat and bone, mixed with bone ash and local loess had been used but still no traces of potassium nor of aluminium. In the eighties the Venus was examined using more sophisticated equipment and the result was no bone or other organic components and no stone fragments. In the period 1955-1965 some researchers concluded that the animal statues of Dolni Vestonice were made of clay, and they called this terra cotta which means burned soil . Present studies indicate that the loess of Dolni Vestonice was used as raw material for the animal figurines. 

Campbell, G.H., Rtihle, M., Dagleish, B.J. and Evans, A.G. Whiskers toughening a comparison between aluminium oxide and silicon nitride toughened with silicon carbide , J. Am. Ceram. Soc., 73[3] (1990) 521-530. 

The traditional or conventional ceramics are generally in monolithic form. These include bricks, pottery, tiles and a variety of art objects. The advanced or high-performance monolithic ceramic materials represent a new and improved class of ceramic materials where, frequently, some sophisticated chemical processing route is used to obtain them. Generally, their characteristics are based on the high quality and purity of the raw materials used. Examples of these high-performance ceramics include oxides, nitrides, carbides of silicon, aluminium, titanium and zirconium, alumina, etc. 

I high 600 = CTI Ceramics, glass Aluminium oxide Epoxy resins Polyamide Polyethylene Polypropylene Silicone rubber... 

Broekaert J. A. C., Brandt R., Leis F., PlLGER C., POLLMANN D., Tschopel P. and Tolg G. (1994) Analysis of aluminium oxide and silicon carbide ceramic materials by inductively coupled plasma mass spectrometry, J Anal At Spectrom 9 1063-1070. 

A quick check of extrusion properties of ceramic compounds can be made using a simplified capillary-rheometric method. A one-point or two-point determination can, for example, make it possible to quickly select promising compound compositions. The accelerated test method was used in the development of a compound from aluminium oxide for making catalyst supports. Two criteria were here taken into account ... 

The results of the characterization of extrusion behaviour are explained using ceramic catalyst carrier compounds based on y-aluminium oxide. The solid phase of all compounds was the same, consisting of y-aluminium oxide and pseudobohmite in a ratio of 2 1. 

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