Abstract: The invention concerns a process for preparing organically modified aerogels, in which a) a silicic acid sol with a pH .ltoreq.4.0 is produced from an aqueous potassium silicate solution using at least one organic and/or inorganic acid; b) the resultant silicic acid sol is polycondensed by the addition of a base to form SiO.sub.2 gel; c) the gel produced in step b) is washed with an organic solvent until the water content of the gel is .ltoreq.5 wt %; d) the gel obtained in step c) is surface-modified with at least one C.sub.1-6 alcohol; and e) the surface-modified which are difficult to dissolve in the silicic acid sol. Before step b), the resultant salts, which are difficult to dissolve, are precipitated to the greates possible extent and separated from the silicic acid sol.

Abstract: An inorganic material comprising an aerogel, a process for its preparation, and its use. The invention relates to a composite material comprising from 10 to 95% by volume of aerogel particles whose particle diameter is less than 0.5 mm and a phyllosilicate as inorganic matrix material.

Abstract: A composite material comprising aerogel, a process for its preparation, and its use. The invention relates to a composite material comprising from 10 to 95% by volume of aerogel particles and at least one inorganic binder, a process for its preparation, and its use.

Abstract: The invention relates to a composite foam comprising from 10 to 90% by volume of SiO.sub.2 aerogel particles and from 90 to 10% by volume of a foam, preferably a polyurethane and/or polyolefin foam, a process for its preparation and its use.

Abstract: The invention relates to a composition comprising between 30 and 95% by volume of aerogel particles and at least one aqueous binder, where the particle diameter of the aerogel particles is less than 0.5 mm and the aerogel particles preferably have hydrophobic surface groups, a process for the preparation thereof, and the use thereof.

Abstract: The invention relates to a process for the production of modified SiO.sub.2 aerogels in whicha) a silicatic lyogel is prepared,b) if desired, the lyogel prepared in step a) is subjected to a solvent exchange with another organic solvent,c) the gel obtained in step a) or b) is reacted with at least one chlorine-free silylating agent, andd) the gel obtained in step c) is dried subcritically,wherein the chlorine-free silylating agent is a compound of the formula I ##STR1## wherein each R.sup.1 is identical or different and is selected from a group consisting of linear C.sub.1 -C.sub.6 -alkyl radicals, branched C.sub.1 -C.sub.6 -alkyl radicals, cyclohexyl radicals and phenyl radicals,R.sup.2, R.sup.3 and R.sup.4 are identical or different and are selected from the group consisting of hydrogen atoms, linear C.sub.1 -C.sub.6 -alkyl radicals, branched C.sub.1 -C.sub.6 -alkyl radicals, cyclohexyl radicals and phenyl radicals;and n=1, 2 or 3.

Abstract: The invention relates to a process for producing modified, fiber-reinforced xerogels having porosities greater than 60% and xerogel matrix densities below 0.6 g/cm.sup.3 and to their use as thermal insulating material.

Abstract: Process for the preparation of aerogels by subcritical drying of inorganic and organic hydrogels and lyogels to give aerogels, dielectric drying methods being used.

Abstract: Xerogels and a process for their preparation involving acidifying an aqueous waterglass solution, polycondensing the resulting silica by addition of a base, removing most of the water from the gel by washing the gel with an organic solvent, reacting the resulting gel with a silylation agent and then drying the silylated gel under subcritical conditions.

Abstract: The present invention relates to mat-shaped composites having porosities above 60% and densities below 0.6 g/cm.sup.3, comprising an aerogel and fibers dispersed therein, the aerogel having cracks and the aerogel fragments enclosed by the cracks, whose average volume is 0.001 mm.sup.3 to 1 cm.sup.3, being held together by the fibers. The present invention further relates to processes for producing the composites of the invention and to their use.

Abstract: The disclosure is a composite material having at least one layer of fiber web and aerogel particles, wherein the fiber web comprises at least one bicomponent fiber material, the bicomponent fiber material having lower and higher melting regions and the fibers of the web being bonded not only to the aerogel particles but also to each other by the lower melting regions of the fiber material, a process for its production and its use.

Abstract: The invention relates to a process for preparing modified SiO.sub.2 gels, in which the gel is aged using a solution of a condensable alkyl and/or aryl orthosilicate, or using an aqueous silicic acid solution, in order to strengthen the structure of the gel.

Abstract: Process for the preparation of aerogels by subcritical drying of inorganic and organic hydrogels and lyogels to give aerogels, dielectric drying methods being used.

Abstract: A process for the subcritical drying of a lyogel to give an aerogel comprises treating the lyogel with a heat transfer liquid which has a temperature above the boiling point of the pore liquid of the lyogel under the pressure of the system and subsequently separating the dried aerogel from the heat transfer liquid.

Abstract: The invention relates to modified SiO.sub.2 gels (xerogels), the preparation thereof and the use thereof as thermal insulators. The xerogels are prepared by acidifying an aqueous waterglass solution, polycondensing the silicic acid produced thereby, by adding a base, to an SiO.sub.2 gel, removing the water from the resulting gel by extractive distillation with an organic solvent which forms with water an azeotrope which separates on cooling into two phases, reacting the gel with a silylating agent, and then drying at pressures and temperatures which are below the critical pressure and/or the critical temperature of the organic solvent used for removing the water.

Abstract: The invention relates to a switching device comprising at least one feeding circuit provided for DC power supply to at least one subscriber's terminal unit. The feeding circuit is especially provided for digital subscribers' terminal units. The invention furthermore relates to the feeding circuit used. There is proposed to provide a first and a second limiting circuit. The first limiting circuit comprises a first series combination of a first supply transistor arrangement and a first supply resistor arrangement to limit a supply current flowing through the first series combination. The second limiting circuit comprises a second series combination of a second supply transistor arrangement and a second supply resistor arrangement to limit a supply current (Is) flowing through the second series combination. A potential (V0) present on the control input of the second supply transistor arrangement depends on the voltage (Ur) present on the first series combination.

Abstract: A low loss power supply device for generating at least one output voltage (Ua) from an input voltage (Ue) having an absolute value which is higher than that of the output voltage. The power supply device has a low power loss and minimum space requirements. The power supply device includes a controller for generating the output voltage and a DC/DC converter having a primary circuit and a secondary circuit. The primary circuit voltage is a difference voltage (U.sub.c1) derived from the output voltage and the input voltage. The secondary circuit generates the output voltage. A further saving of components is achieved by forming the controller from the primary circuit of the DC/DC converter with the primary circuit connected in series with the secondary circuit.

Abstract: An electrophoretic display including a cell having two plates spaced apart and provided at least regionally with electrodes, where at least one plate and an associated electrode facing the observer are transparent. The cell contains a suspension consisting of an inert dielectric liquid phase and a dispersed solid phase which at least in part are optically discriminable electrophoretic particles. The individual electrophoretic particles each are of practically the same density as the liquid phase, and at least part of the electrophoretic particles are pigment particles provided with a coating of organic material which is solid at the cell operating temperature but which melts at higher temperatures. The coating material contains at least one charge control agent. The charge control agent, preferably a salt of a divalent metal or metal of higher valency and of an organic acid, imparts a well-defined, uniform surface charge and a well defined, uniform surface potential to the particles.

Abstract: A method and apparatus for operating an electrophoretic indicating element driven by a drive signal, wherein the drive signal is modulated by an alternating voltage signal superimposed on the drive signal and having a frequency sufficiently high to prevent observation thereof. The modulating signal can have either a sinusoidal, triangular, or rectangular wave shape, or can be a succession of individual wave trains wherein the duration of each wave train is selected in accordance with the composition of the electrophoretic switching element.