摘要:
An aqueous dispersion, having a silicon dioxide powder having a silicon dioxide content of 10 to 60 wt.%, wherein the aqueous dispersion is stable in the pH range of 2 to 6, the aqueous dispersion additionally contains at least one compound, which is at least partially soluble in aqueous solution in the pH range 2 to 6 in the form of polyvalent cations, these being stable in a silicate-like environment as an anionic component of the particle surface of the silicon dioxide powder, the quantity of cation-providing compound in relation to the surface of the silicon dioxide is 0.001 to 0.1 mg cation-providing compound/m2 silicon dioxide surface, the cation-providing compound being calculated as the oxide, and the zeta potential of the aqueous dispersion has values of less than or equal to zero.
摘要翻译:一种水分散体,其二氧化硅粉末的二氧化硅含量为10至60重量%,其中水分散体在pH范围为2至6时是稳定的,水分散体还含有至少一种化合物,其在 在多价阳离子形式的pH范围2〜6的水溶液中最少部分溶解,这些在作为二氧化硅粉末的粒子表面的阴离子成分的硅酸盐样环境中稳定,提供阳离子的化合物的量 相对于二氧化硅的表面为0.001〜0.1mg的提供阳离子的化合物/ m 2二氧化硅表面,阳离子提供化合物以氧化物计算,并且水溶液的ζ电位 色散的值小于或等于零。
摘要:
Process for the production of an aqueous dispersion of pyrogenically produced metal oxide and metalloid oxide powders with a BET surface area of between 5 and 600 m2/g, with a metal oxide or metalloid oxide content in the dispersion of between 5 and 25 wt. %, comprising the following steps: water, which is optionally adjusted to pH values of between 2 and 4 by adding acids, is circulated from a receiving vessel via a rotor/stator machine, and metal oxide or metalloid oxide powder is introduced, using a feed device, into the shear zone between the slots in the rotor teeth and the stator slots, continuously or discontinuously and with the rotor/stator machine running, in a quantity such that a predispersion with a solids content of between 20 and 40 wt. % results, and, after all the metal oxide powder or metalloid oxide powder has been added, the feed device closes and shearing continues in such a way that the shear rate is in the range of between 10000 and 40000 s−1, and then, by dilution, the predispersion is adjusted to the desired solids content of the dispersion while maintaining the dispersing conditions.
摘要:
Process for the production of an aqueous dispersion of pyrogenically produced metal oxide and metalloid oxide powders with a BET surface area of between 5 and 600 m2/g, with a metal oxide or metalloid oxide content in the dispersion of between 5 and 25 wt. %, comprising the following steps:water, which is optionally adjusted to pH values of between 2 and 4 by adding acids, is circulated from a receiving vessel via a rotor/stator machine, andmetal oxide or metalloid oxide powder is introduced, using a feed device, into the shear zone between the slots in the rotor teeth and the stator slots, continuously or discontinuously and with the rotor/stator machine running, in a quantity such that a predispersion with a solids content of between 20 and 40 wt. % results, and, after all the metal oxide powder or metalloid oxide powder has been added,the feed device closes and shearing continues in such a way that the shear rate is in the range of between 10000 and 40000 s−1, andthen, by dilution, the predispersion is adjusted to the desired solids content of the dispersion while maintaining the dispersing conditions.
摘要:
Process for the production of an aqueous dispersion of pyrogenically produced metal oxide and metalloid oxide powders with a BET surface area of between 5 and 600 m2/g, with a metal oxide or metalloid oxide content in the dispersion of between 5 and 25 wt. %, comprising the following steps:—water, which is optionally adjusted to pH values of between 2 and 4 by adding acids, is circulated from a receiving vessel via a rotor/stator machine, and—metal oxide or metalloid oxide powder is introduced, using a feed device, into the shear zone between the slots in the rotor teeth and the stator slots, continuously or discontinuously and with the rotor/stator machine running, in a quantity such that a predispersion with a solids content of between 20 and 40 wt. % results, and, after all the metal oxide powder or metalloid oxide powder has been added,—the feed device closes and shearing continues in such a way that the shear rate is in the range of between 10000 and 40000 s−1, and—then, by dilution, the predispersion is adjusted to the desired solids content of the dispersion while maintaining the dispersing conditions.
摘要:
Glass is produced by depositing presintering composition on a preform set into move in front of a plasma torch which moves back and forth substantially parallel to a longitudinal direction of the preform, a first feed duct feeds the plasma with grains of the presintering composition while optionally a second feed duct feeds the plasma with a fluorine or chlorine compound, preferably a fluorine compound, mixed with a carrier gas.
摘要:
A dispersion containing a high-surface-area, pyrogenically-produced aluminium oxide with a surface area and BET of more than 115 m2/g and a Sears number of more than 8 ml/2 g, is produced by mixing a high-surface-area, pyrogenically-produced aluminium oxide having a BET specific surface area of more than 115 m2/g and a Sears number of more than 8 ml/2 g, with water, setting a pH value of 2 to 11 (preferably 3 to 8) and dispersing the mixture by the introduction of controlled shearing forces.It can be used for the production of Inkjet media, digital imaging products and other printing medium.
摘要:
A dispersion containing a high-surface-area, pyrogenically-produced aluminium oxide with a surface area and BET of more than 115 m2/g and a Sears number of more than 8 ml/2 g, is produced by mixing a high-surface-area, pyrogenically-produced aluminium oxide having a BET specific surface area of more than 115 m2/g and a Sears number of more than 8 ml/2 g, with water, setting a pH value of 2 to 11 (preferably 3 to 8) and dispersing the mixture by the introduction of controlled shearing forces.It can be used for the production of Inkjet media, digital imaging products and other printing medium.
摘要:
Aqueous dispersions of a pyrogenically-produced aluminum oxide are prepared form a mixture containing water, additives and a high-surface-area pyrogenically-produced aluminum oxide with a BET specific surface area of more than 115 m2/g and a Sears number of more than 8 ml/2 g using controlled high shearing conditions. Prior to subjecting the mixture to high shear conditions, the pH of the mixture is adjusted to a value between of 2 to 11 (preferably 3 to 8). The aqueous dispersion has a mean particle size distribution of d50
摘要:
Aqueous dispersion comprising silicon/titanium mixed oxide powder with a BET surface area of 5 to 500 m2/g which has been prepared by flame hydrolysis and has a titanium dioxide content of 0.5 to 20 wt. %, based on the powder, water and at least one pH-regulating substance which can be removed completely from the reaction mixture on heating, the aqueous dispersion having a solids content of between 40 and 80 wt. %. A green body produced therefrom with a green density of between 40 and 85%. A shaped glass article of optical quality with a coefficient of thermal expansion of not more than 0.5×10−6/K produced from the green body.
摘要:
Sintered materials, especially sintered glasses, produced from pyrogenically produced silicon dioxide which has been processed to silicon granulates in a compacting step, and the use of such granulates in the production of formed glass bodies.