Additional information is available at the end of the chapter http://dx.doi.org/10.5772/53325 1. Direct nitridation of boron according to 2B + N 2 = 2BNreaction. This method is limited since pure boron is an expensive element and nitridation of the element is not homogeneous even at high temperatures [2].

Hexagonal boron nitride (h-BN) based ceramics have been fabricated by hot-pressing in a nitrogen atmosphere at 1900°C for 60 min. under a pressure of 50 MPa with B2O3 as sintering additive. The phase composition was confirmed by XRD. The microstructural properties of h-BN powders and hot-pressed surfaces were evaluated by SEM-EDS analysis. The formation of the secondary phase was also investigated with particular interest on grain boundaries. The sintered densities were also determined by Archimedes’ method. The maximum relative density was obtained to be about 92 %. The effect of the existence of boron oxide on the boron nitride grain growth behaviour was discussed on the basis of microstructural features.

No abstract

In this study, the characterization of metal-ceramic interface was investigated. For the characterization, original opaque porcelain powder was applied on metal crown at three different temperatures and in three different times. To examine the occurrence at the interface of the metal-ceramic diffusion couple and the effects of the firing temperature and vacuumless waiting time, 9 samples were prepared by 3 different firing temperatures (905 o C, 930 o C, 955 o C) and 3 different times (30 s, 60 s, 90 s) in a vacuumless condition. During the firing process, the samples were exposed to vacuum. When the furnace was heated to the sintering temperature, vacuum was turned off and the samples were kept in this condition for 30 s, 60 s and 90 s. The interfaces of metal-ceramic diffusion couples that were occurred after firing were prepared for the EPMA investigation. According to the concentration profiles, diffusion coefficients of Ni and Cr in porcelain and their activation energies were calculated. As a result it was seen that, when metal-ceramic composite was exposed to heat, an atomic diffusion occurs between them.

In the paper were reviewed mechanical and chemical properties of the modern refractories applied in the metallurgical industry and was provided their classification for the goal of optimal selection of refractories kind for specific technological conditions, reducing costs and solving the environmental issues. For various applications in the steel industry, in the furnace linings for iron and steel making, metal and slag transport, heat treatment furnaces and the flues for the hot gas conduction, refractories are widely used. The refractories can also be classified according to the raw materials, which are used in the preparation and to the predominant minerals after production. Nowadays, hardly any standard bricks are used and there is a trend towards using monolithic refractories. Due to the improvement in the service life and highly productive modern steel making processes, the consumption of refractories is reduced.