Till today several kinds of ceramics and ceramic matrix composites are developed for extreme environmental conditions. Most of these ceramics have microstructures with relatively "big" crystals, having high rigidness and strong inclination to nick, pitting and rigid fractures, so they are not usable for collision with metallic or other bodies under high speeds like 800 m/sec or more. On the basis of several years experiments in development and testing of ceramic materials and corundum matrix composites the authors successfully developed new alumina-matrix composite materials reinforced with Si 2 ON 2 , SiAlON, AlN and Si 3 N 4 . These new alumina based ceramic matrix composites were tested under collisions with different metallic bodies having high densities and speeds higher than 800 m/sec. During the collisions the kinetic energy of flying metallic objects distributing to fracture energies, heatings and recrystallizations both of ceramic and metallic bodies. In the centres of collisions, where oxygen was absent, the authors have found new, high density "diamond-like Si 3 N 4 " materials with cubic crystals, where nitrogen atoms distributed in the centres of the cubes. These new crystal structures of Si 3 N 4 in the alumina matrix have extreme dynamic strength and hardness, like diamond. Having surplus of oxygene in the centres of collisions this new "diamond-like Si 3 N 4 " was not observed, when a very strong oxydation of metallic bodies was taken place. Using the energy conception of collision, the authors mathematically described the energy engorgements of destruction of ceramic materials and heating of participating bodies as well as energy engorgement used for the phase transformations of ceramic and metallic particles during their collision.

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Abstract. The use of technologically byproduct agricultural wastes in various segments of the brick and tile industry is increasing continuously. The additives, mixed into the raw clay ignite during the firing process, adding extra thermal energy from inside the mixture decreasing the energy requirements of the manufacturing process. Added to this, through the combustion of the bio-wastes the porosity increases enhancing the thermal insulation properties of the final product. We have investigated some common, agricultural wastes to determine their effect on the thermal properties of bricks. In our experiments industry relevant amounts of additives (sawdust, rice-peel, seed-shell) were added to the basic clay composition. We have prepared mixtures with additive concentrations of 0, 4, 7 percentage by weight. The preparations of the samples were (milling, drying and firing) following industrial standard procedures. Precise thermal conductivity data were gathered from all samples using a RAPID-K type static thermal conductivity measuring instrument. Our measurements show that by increasing the amount of the organic byproducts in the clay mixture it is possible to significantly decrease their thermal conductivity, leading to an improved insulation capability of commercial brick products. On the other hand, there was only a minor reduction in the mechanical strength found during previous works. The investigated agricultural byproducts were also ranked based on their effect on the product's thermal properties. It was found that the largest decrease to the thermal conductivity was caused by the sunflower seed-shell additive. Mixing 7 % wt. seed shell to the clay, we can decrease the thermal conductivity of the fired product from 0,27 W/m·K to 0,17 W/m·K (36%). We have found that under the same conditions the sawdust caused the least improvement, only a decrease of 0,27 W/m·K to 0,23 W/m·K (16%) was measured. IntroductionUsing renewable agricultural byproducts and waste materials as performance enhancing additives in the brick industry is gaining more and more ground recently [1,2,3]. The additives, mixed in the brick clay are burning out during the firing process producing extra energy, and decreasing the total energy need of the industrial furnace. At the beginning, sawdust, wood chips and other wood based materials were used, but more recently polymers and also renewable agricultural waste materials, like rice-peel or seed-shell are also present as additions in the brick and tile industry. The ignition of the additives provides extra thermal energy from inside the brick product, and decreases the required energy by the furnace. Beside of saving energy, the combustion removes the additives, creating pores, further decreasing the thermal conductivity and unfortunately also decreases the mechanical strength of the final product. Since the project was tied to the industry it seemed necessary to describe the thermal conductivity and other parameters primarily as function of the additive concentration, since this is a tech...

Strontium‐modified barium titanate ceramics with the compositional formula Ba1−xSrxTiO3 (barium strontium titanate, BSrxT) with (x = 0, 0.05, 0.125, 0.15, 0.20, and 0.3) have been synthesized through sol‐gel method. X‐ray diffraction (XRD) patterns of the as‐prepared ceramics, calcined at a relatively low temperature (950 °C/3 h), reveal that BSrxT ceramics possess tetragonal structure in the range of x = 0–20% and shift into a cubic structure at high Sr composition (x = 30%). Based on XRD and Fourier‐transform infrared spectroscopy analysis, the occupation of the Ba and/or Ti sites by strontium in the BaTiO3 system and the behaviors of the crystalline parameters as functions of the Sr content have been discussed. The scanning electron microscopy shows that the grain size and densification sensitively depend on the Sr content. The study of the thermal conductivity measurements performed on the as‐prepared ceramics reveals the influence of Sr content on the thermal conductivity value. However, the microstructure of BSrxT impacts the compressive strength, therefore, the value of the latter is found to be decreased when the grain size increased.

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