A process for the preparation of an alumina in the form of beads with a sulphur content in the range 0.001% to 1% by weight and a sodium content in the range 0.001% to 1% by weight with respect to the total mass of said beads is described, said beads being prepared by shaping an alumina gel having a high dispersibility by drop coagulation. The alumina gel is itself prepared using a specific precipitation preparation process in order to obtain at least 40% by weight of alumina with respect to the total quantity of alumina formed at the end of the gel preparation process right from the first precipitation step, the quantity of alumina formed at the end of the first precipitation step possibly even reaching 100%. The invention also concerns the use of alumina beads as a catalyst support in a catalytic reforming process.

A process for the preparation of an alumina in the form of beads with a sulphur content in the range 0.001% to 1% by weight and a sodium content in the range 0.001% to 1% by weight with respect to the total mass of said beads is described, said beads being prepared by shaping an alumina gel having a high dispersibility by drop coagulation. The alumina gel is itself prepared using a specific precipitation preparation process in order to obtain at least 40% by weight of alumina with respect to the total quantity of alumina formed at the end of the gel preparation process right from the first precipitation step, the quantity of alumina formed at the end of the first precipitation step possibly even reaching 100%. The invention also concerns the use of alumina beads as a catalyst support in a catalytic reforming process.

Fumed alumina powder with reduced moisture content Surface unmodified fumed alumina powder comprising less than 5% by weight of alpha-Al.sub.2O.sub.3, as determined by XRD analysis, having a numerical average particle size d.sub.50 of less than 5 ?m, as determined by SLS, and a ratio R.sub.150=KF.sub.150/BET of the water content KF.sub.150, as determined by Karl Fischer titration method after drying of the fumed alumina powder at 150? C. for 2 hours, to its BET surface area of not more than 0.0122 wt %?g/m.sup.2, preparation method and the use thereof.

Fumed alumina powder with reduced moisture content Surface unmodified fumed alumina powder comprising less than 5% by weight of alpha-Al.sub.2O.sub.3, as determined by XRD analysis, having a numerical average particle size d.sub.50 of less than 5 ?m, as determined by SLS, and a ratio R.sub.150=KF.sub.150/BET of the water content KF.sub.150, as determined by Karl Fischer titration method after drying of the fumed alumina powder at 150? C. for 2 hours, to its BET surface area of not more than 0.0122 wt %?g/m.sup.2, preparation method and the use thereof.

A system, process and related sintered article are provided. The process includes supporting a piece of inorganic material with a pressurized gas and sintering the piece of inorganic material while supported by the pressurized gas by heating the piece of inorganic material to a temperature at or above a sintering temperature of the inorganic material such that the inorganic material is at least partially sintered forming the sintered article. The inorganic material is not in contact with a solid support during sintering. The sintered article, such as a ceramic article, is thin, has high surface quality, and/or has large surface areas.

A plate-like alumina powder production method of the present invention comprises placing a transition alumina and a fluoride in a container such that the transition alumina and the fluoride do not come into contact with each other and then performing heat treatment to obtain a plate-like -alumina powder. The transition alumina is preferably at least one selected from the group consisting of gibbsite, boehmite, and -alumina. It is preferable that the amount of the fluoride used is set such that the percentage ration of F in the fluoride to the transition alumina is 0.17% by mass or more. The container preferably has a volume such that a value obtained by dividing the mass of F in the fluoride by the volume of the container is 6.510.sup.5 g/cm.sup.3 or more. The heat treatment is preferably performed at the temperature of 750 to 1,650 C.

A method comprises reacting an aluminum feedstock with an acid in the presence of water to provide an aluminum salt solution comprising an aluminum salt in water, wherein the aluminum salt comprises a reaction product of the acid and aluminum, and spray roasting the aluminum salt solution at a temperature of at least about 450 C. to provide an aluminum oxide powder, wherein the spray roasting is performed in a furnace lined with a refractory comprising alumina that is at least about 99.2% purity alumina, and wherein the aluminum oxide powder is 99.2% pure aluminum oxide or greater.

A system, process and related sintered article are provided. The process includes supporting a piece of inorganic material with a pressurized gas and sintering the piece of inorganic material while supported by the pressurized gas by heating the piece of inorganic material to a temperature at or above a sintering temperature of the inorganic material such that the inorganic material is at least partially sintered forming the sintered article. The inorganic material is not in contact with a solid support during sintering. The sintered article, such as a ceramic article, is thin, has high surface quality, and/or has large surface areas.

A crystalline Boehmite product and a method of forming said product is provided in which the crystalline Boehmite exhibits an average particle size (d50) that is less than 7,000 nanometers. This method comprises preparing an aqueous slurry by mixing together water, large aluminum oxide precursors, a highly dispersible Boehmite grade, and optionally, an organic dispersing agent; adjusting the pH of the slurry; heating the slurry for a predetermined duration of time; collecting the slurry to form a wet cake; and drying the wet cake to obtain the crystalline Boehmite product. The crystalline Boehmite product may be mixed with a plastic resin to form a flame retardant plastic mixture, which can be subjected to a conventional plastic processing method to form a flame retardant composite.

An alumina sintered body according to the present invention has a degree of c-plane orientation of 90% or more as determined by Lotgering's method from an X-ray diffraction profile obtained by irradiating a plate surface with X-rays in a range of 2=20 to 70. The alumina sintered body has no pores when a cross-sectional surface formed in a direction perpendicular to the plate surface is polished using an Ar.sup.+ ion beam and a mask and is examined under a scanning electron microscope at a magnification of 5,000 times. The alumina sintered body has a total mass fraction of impurity elements other than Mg and C of 100 ppm or less. This alumina sintered body has a high degree of orientation, high density, and high purity and thus has a higher optical translucency than those known in the art.