Abstract: Process for making particulate ceramics having an alumina rich region near their surface, comprising the following steps:(a) mixing and pelletizing, with the aid of water, raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite;(b) drying the wet pellets from step (a);(c) mixing the dried pellets with alumina parting agent; and(d) firing the mixture of pellets and parting agent at a sufficient temperature (less than 1450.degree. C.) and for sufficient time for vitrification to occur.

Abstract: Ceramic particulates useful as a proppant in hydraulic fracturing and in gravel packing operations is provided which comprises a ceramic (sometimes vitreous) core surrounded by an epoxy resin coating. Novolac epoxy resin compounds without any substantial acid soluble filler are used to coat ceramic particulates similar to those discloses in U.S. Pat. Nos. 4,680,230 and 4,632,876. The result is a product which combines the excellent solvent resistance of the ceramics with the acid resistance of the resin. The resin coating gives the added benefits of lower specific gravity and improved crush resistance.

Abstract: Ceramic particulate useful as a proppant in hydraulic fracturing and in gravel packing operations is provided which comprises a ceramic (sometimes vitreous) core surrounded by an epoxy resin coating. Novolac epoxy resin compounds without any substantial acid soluble filler are used to coat ceramic particulates similar to those disclosed in U.S. Pat. Nos. 4,680,230 and 4,632,876. The result is a product which combines the excellent solvent resistance of the ceramics with the acid resistance of the resin. The resin coating gives the added benefits of lower specific gravity and improved crush resistance.

Abstract: A two-phase ceramic particulate useful as a proppant in hydraulic fracturing operations is provided which comprises a vitreous matrix phase containing a crystalline alumina phase. The new ceramic particles are characterized by:(i) a concentration gradient of alumina which increases from very low in the center to relatively high near the surface of the particles;(ii) a fired density less than about 2.9 g/cc; and(iii) closed cell microporosity.Certain embodiments of the inventive ceramic particulate are also characterized by a Krumbein roundness of at least 0.8 and are chemically stable.The ceramic is made by a process comprising the steps of:a. mixing and pelletizing, with the aid of water, the dry raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite;b. drying the wet pelletizer product;c. mixing the dried pellets with a parting agent; andd.