Abstract: A composite material of aluminum or an aluminum alloy, reinforced with a fiber or whisker form of unmodified alumina. The material is produced by preheating a mould and a mat of unmodified alumina to a temperature in the range of 700.degree. C. to 1050.degree. C. Molten aluminum or its alloy free of elements which react with the alumina are introduced into the mould to cover the mat. A pressure of at least 75 Kg/cm.sup.2 is applied to the contents of the mould to overcome the surface tension between the alumina and the molten mass of metal and to cause the molten mass to fully penetrate the alumina mat. Upon solidification of the molten aluminum, the composite material is obtained.

Abstract: This invention relates to a piston ring having two ring elements and a spacer-expander the latter including a series of interconnected parts each comprising two pairs of inwardly directed limbs, the inner ends of which are in contact with and resiliently load the ring elements, and a spacer element which extends transversely to space apart the ring elements at the outer periphery.

Abstract: The invention relates to the production of alumina whiskers from alumina-bearing material by preparing an intimate mixture of such material and carbon and then passing a stream of gaseous aluminium trihalide and an inert carrier gas thereover in a first zone at an elevated temperature, usually 1400.degree.C to 1800.degree.C, at which reaction occurs to form aluminium monohalide and carbon monoxide. The gaseous stream comprising the two latter materials is then passed to a second zone maintained at a less elevated temperature than the first zone, usually 1400.degree.-1000.degree.C, at which temperature the reaction is reversed to produce a gaseous stream carrying alumina and carbon. Under conditions of low supersaturation the alumina deposits as single crystal alumina whiskers from which any carbon can be removed by an oxygen-containing gas at temperatures of 800.degree.-1000.degree.C.