It is well known [i] that a composite based on refractory oxides in which spherical granules are used as the filler is characterized by increased thermal-shock resistance and strength for a given porosity.We have studied batches consisting of a spherical filler and a finely milled component (binder) to ensure sintering.As the filler we used clayey microspheres and alumina spheres obtained in various ways (spheres A, B and K). The properties are given in Table I.The alumina microspheres are totally spherical particles.The strength of a single granule is 0. i N and the specific surface, 0.7 m2/g.According to the x-ray structural analysis, the microspheres are formed of y-AI203.The mass fraction of Al20s in them is 99.5%.The x-ray phase analysis with a DRON-I.5 diffractometer showed that the A, B, and K spheres were formed from a-Al2Os.It was established by electron microscopy studies* that the surface of the A spheres was smooth and consisted of individual fragments, and was penetrated by pores; the surface of the B spheres was not uniform and had a relief and the shell of the spheres made up of individual aggregates; the surface of the K spheres had a fairly well developed relief.As the finely milled component of the batch we used a mixture of corundum and y-Al2Os.The corundum for the binder was obtained by firing AI=O3, analytically pure grade, in an oil-fired furnace at 1750~ with a dwell of 5-6 h at the maximum temperature.The fired materSal was milled for I0 h in a rubber-lined vibromill with solid alloy spheres with a material:sphere ratio of 1:8. The specific surface of the material determined using the BET method was 2.1-2.3 m2/g. The x-ray phase analysis showed that the material was ~-A1203.The y-alumina, the reactive material obtained from the decomposition of hydroargillite, was characterized by a specific surface of 226 m~/g. Before the preparation of the batches, it was ground in a corundum mortar for 15-20 min.For the preparation of the specimens, we carefully mixed the filler and the finely ground component; the mixture obtained was wetted with polyvinyl alcohol to a moisture content of 8-10% and was then rubbed through a sieve.Specimens of diameter and height 15 mm were pressed from the mass obtained in this way at a pressure of 40-50 N/mm 2. The specimens were fired in an oil-fired furnace at 1750~ with a dwell of 6 h.The apparent density and open porosity of the refractories were determined in accordance with GOST 2409-80 by hydrostatic weighing of the specimens saturated with water.Five parallel specimens were used for the determination.The error evaluated from the magnitude of the dispersion of reproducibility was < 2%.Linear shrinkage relative to the diameter and height was calculated from measurements made using a micrometer to an accuracy of 0.01 mm.The compressive-strength tests were carried out on 15-mm-diameter specimens using an MR-5-1 breaking machine with an ultimate force of 500 N. The accuracy of the determination was 10%.