Abstract:
Es wird ein Verbundkörper aus mindesten zwei Keramikschichten (11, 12) angegeben, bei dem die Keramikschichten (11, 12) an definierten Verbindungsstellen (13, 14) durch eine Kontaktschicht (15) aus einem Verbindungsmaterial miteinander felt verbunden rind. Zur Erzielung einer dauerhaften, thermisch stabilen Verbindung von Keramikschichten (11, 12) mit unterschiedlichen thermischen Ausdehnungskoeffizienten weist das Verbindungsmaterial einen niedrigen Elastizitäts-Modul auf. Bei der Herstellung des Verbundkörpers werden die Verbindungsstellen der Keramikschichten (11, 12) zur Bdldung einer poröse Oberflächenstruktur vorbehandelt, auf these das Verbindungsmaterial aufgetragen und each Aufeinanderlegen der Keramikschichten (11, 12) mit einander zugekehrten Verbindungsstellen (13, 14) und dazwischenliegendem Verbindungsmaterial der so zusammengestellte Verbundkörper einer Wärmebehandlung unterzogen.
Abstract:
L'invention concerne un procédé de métallisation par un alliage de silicium fusible à une température T1 de certaines zones de la surface d'une pièce en céramique oxyde non mouillable par ledit alliage, comprenant successivement une étape de dépôt de carbone sur lesdites zones à métalliser de ladite pièce, une étape de dépôt de l'alliage de silicium sous forme solide sur au moins une partie de ladite pièce, de façon à ce que ledit alliage ait au moins un point de contact avec lesdites zones à métalliser suivie d'une étape de chauffage à une température supérieure ou égale à T1, ledit alliage se rassemblant à l'état fondu sur lesdites zones à métalliser. Ce procédé s'applique également au brasage de pièces, dont l'une au moins est une pièce en céramique oxyde non mouillable par ladite composition.Application desdits procédés au domaine de l'électronique, de l'électrotechnique, du génie thermique, du génie chimique.
Abstract:
In accordance with the invention, a reactive multilayer structure comprises alternating layers of materials that exothermically react by a self-propagating reduction/oxidation reaction or by a self-propagating reduction/formation reaction. This combination of a reduction reaction and either an oxidation of formation reaction can lead to ductile reaction products and is frequently accompanied by the generation of large amounts of heat. As compared with conventional multilayer foils, the new multilayer structures are easier to fabricate, easier to handle, and produce more reliable bonds.
Abstract:
The invention relates to a material composite (1) that is vacuum-tight and resistant to thermal shocks, to a method for the production thereof and to its use. A permanent connection between an aluminum oxide sapphire (2) and an aluminum oxide ceramic (5) is attained by a first connecting layer (3) comprised of a manganese-silicate glass, in which at least one of the metals molybdenum, tungsten, palladium or platinum is incorporated, and by a second connecting layer (4) comprised of a manganese-silicate glass. To this end, the individual materials are fused by sintering. The material composite (1) is used for inserting a window comprised of aluminum oxide sapphire (2) into a housing (16) for a light-ignitable thyristor (24).
Abstract:
Reactive foils and their uses are provided as localized heat sources useful, for example, in ignition, joining and propulsion. An improved reactive foil (14) is preferably a freestanding multilayered foil structure made up of alternating layers (16, 18) selected from materials that will react with one another in an exothermic and self-propagating reaction. Upon reacting, this foil supplies highly localized heat energy that may be applied, for example, to joining layers, or directly to bulk materials that are to be joined. This foil heat-source allows rapid bonding to occur at room temperature in virtually an environment (e.g., air, vacuum, water, etc.). If a joining material is used, the foil reaction will supply enough heat to melt the joining materials. If no joining material is used, the foil reaction supplies heat directly to at least two bulk materials, melting a portion of each bulk, which upon cooling, form a strong bond. Additionally, the foil (14) may be designed with openings that allow extrusion of the joining (or bulk) material through the foil to enhance bonding.
Abstract:
A method enabling controlled selective heating of workpiece components during microwave brazing. Two workpiece components are joined by melting an adhesion interlayer material between the two components. An indication of when the interlayer has melted is provided. The temperature difference across the braze assembly (110) is monitored (140) and adjusted via a feedback loop (150) to reduce stresses in the braze joint resulting in a stronger braze joint.
Abstract:
The invention process is comprised of the following steps: a) preparation of a homogeneous mixture of boron nitride BN, aluminum, and a binder in the form of a liquid or paste, which will solidify by means of a chemical reaction and/or the drying of a thinner, the boron nitride and the aluminum being in powder form; b) forming of said mixture by mold casting, followed by pressing and heating at a temperature not higher than approximately 70 DEG C, in order to harden the binder and obtain a sold raw mix which can be handled; c) elimination of the binder by heating at a temperature of about 300 DEG C; d) impregnation of the pores of the raw mix by immersion in a bath of aluminum or aluminum alloy in molten state, separation of the impregnated preform from the bath, and cooling; e) machining of the Al-BN composite preform to obtain the final dimensions of the desired part; f) sintering and reaction at a temperature of between 900 and 1000 DEG C in order to form an aluminum nitride-based ceramic object; g) thermal treatment at a temperature of between 1100 and 1250 DEG C to produce the migration of the residual aluminum from the pores of the part, and the mechanical elimination of the aluminum collected on the surface after possible cooling.
Abstract:
Carbon-carbon composite parts (1, 2) are joined with minimum surface preparation. A reactive-bonding joint interlayer (5) having thickness greater than 1 mil is formed of fine particles of carbide-forming metallic ingredients and carbon. The joint layer (5) is sandwiched between the two carbon-carbon parts (1, 2) to be joined and the assembly is heated under a compressive pressure to a temperature sufficient to complete the bonding reaction. No special surface preparation is required for the carbon-carbon parts due to the nature of the reactive-bonding. The mechanical properties of the joint are assured by selecting the metal-carbon ingredients so that thermal expansion mismatch is minimized. Shear strength exhibited by the resulting joints is greater than the interlaminar shear strength of the carbon-carbon composite material.
Abstract:
Ceramics are joined to themselves or to metals using a transient liquid phase method employing three layers, one of which (18) is a refractory metal, ceramic or alloy. The refractory layer (18) is placed between two metal layers (20 and 22), each of which has a lower melting point than the refractory layer. The three layers are pressed between the two articles to be bonded (14 and 16) to form an assembly (12). The assembly is heated to a bonding temperature at which the refractory layer remains solid, but the two metal layers melt to form a liquid. The refractory layer reacts with the surrounding liquid and a single solid bonding layer is eventually formed. The layers may be designed to react completely with each other and form refractory intermetallic bonding layers. Another method for joining ceramic articles employs a ceramic interlayer sandwiched between two metal layers.