Slibgieten van commerciële siliciumnitride poeders

De eigenschappen van waterige slibs van siliciumnitride werden bestudeeerd aan 2 soorten commercieel verkrijgbare poeders. Er worden resultaten gegeven van metingen van z-potentiaal, kritische coagulatie coefficient en viscositeit als functie van pH, concentratie vlokmiddel en vaste stof-vloeistof verhouding. De optimale slibgiet condities worden gegeve

Surface layers of crystalline and vitreous silicates in alkaline solution

Phenomena occurring at the surfaces of calcium silicates in alkaline solutions have been studied. This knowledge is very important in understanding the behavior of suspensions of glazes, felspars or clay minerals. This behavior has been found to depend partially on whether the surface of the materials in question has a high degree of order or not - in other words, whether the solid is crystalline or vitreous. It is also found that surfaces of crystalline materials which have been disturbed or destroyed, by grinding for instance, show a behavior between the extremes of the completely crystalline or completely vitreous systems. An analysis is given for the manner in which the net change of the surface layers of åkermanite (Ca2MgSi2O7), pseudowollastonite (CaSiO3) and anorthite (CaAl2Si2O8) are built up in alkaline CaCl2 solutions and which processes occur during their formation. Special attention is given to the mutual stimulation of adsorption of Ca2+ and OH- ions by pseudowollastonite

Reaction-rate-limiting steps in carbothermal reduction processes

The production of ß-sialon (Si3A1303N5) and nonoxidic powders by carbothermal reduction of oxides is discussed. Special attention is paid to the rate-determining steps in the conversion process performed in a packed-bed reactor. It is shown that powders with specific surface area >10 m2/g can be produced by the correct choice of pellet size, gas flow rate, temperature, and raw material

Sintering and microstructure of Si3Al3O3N5 produced from kaolin

The sintering of Si3Al3O3N5 powder is discussed as an alternative for the more usual reaction sintering of a mixture of Si3N4, Al2O3 and AlN powders. As the Si3Al3O3N5 powder is produced from kaolin, attention is paid to impurities which are present in the kaolin. Finally properties of the sintered material are given