Reakcije sinteze i termodinamika stvaranja spoja tijekom sinteriranja sloja MoMn

Chemical reactions and thermodynamics of high temperature alumina metallization have been investigated. During the firing of MoMn paste, reactions start with oxidation of manganese. The formed Mn3O4 reacts with alumina and SiO2 at a temperature lower than 1200 °C. The formation of the metallizing layer is a consequence of lowering of the free energy of the system. It is caused by redox and dissolution reactions, the formation of the glass phase and crystallization process from the liquid phase. With available thermodynamical data and according to the atmospheric conditions, some reactions were predicted and confirmed by X-ray diffraction.Istraživane su kemijske reakcije i termodinamika visokotemperaturne metalizacije korunda. Tijekom paljenja smjese MoMn, reakcije počnu oksidacijom mangana. Nastali Mn3O4 reagira s korundom i SiO2 na temperaturi ispod 1200 ◦C. Nastajanje metalnog sloja je posljedica smanjenja slobodne energije sustava. Smanjenje je posljedica redoks reakcije, odvajanja faza, nastajanja staklene faze i kristalizacije iz tekuće faze. Neke su reakcije predvidene i potvrđene rendgenskom difrakcijom

Dodaci Al2O3 za krupnozrnate keramike za metalizaciju

The metal to ceramics seals are widely used as permanent seals in high vacuum technology. For these seals a coarse grain alumina ceramics is needed since a high temperature MoMn metallization is often applied because of several advantages, such as high mechanical strength, low dielectric losses at high frequencies and others. The coarse grain ceramics are produced by sintering alumina with different additives which have to promote densification and grain growth with the liquid phase during sintering. The CaO-SiO2 and CaO-MgO-SiO2 systems were used as additives in the present work. Different characteristics of the formed liquid phases have caused similar densification but different grain growth rates.Spojevi metal–keramika mnogo se upotrebljavaju kao trajni vakuumski spojevi. MoMn metalizacija se često upotrebljava radi velike čvrstoće, malih dielektričnih gubitaka i sl. Za tu metalizaciju nužne su krupnozrnate keramike koje se proizvode sinteriranjem Al2O3 s raznim dodacima koji pospješuju rast zrna u tekućoj fazi tijekom sinteriranja. U ovom radu opisuju se keramike s dodacima CaO–SiO2 i CaO–MgO–SiO2