Abstract: A light-impermeable, high purity silicon carbide material including polycrystals of silicon carbide as a main ingredient, wherein the silicon carbide material has a porosity of not more than 0.1%, the content of each of metal elements contained in the silicon carbide material is not more than 200 ppb, a weight ratio of silicon relative to the entire weight of the silicon carbide material is 69.00 to 69.90 wt %, and a light transmittance of the silicon carbide material in a wavelength range of 0.4 to 25 .mu.m is not more than 0.05% per a thickness of 0.5 mm.

Abstract: An apparatus for delivering abrasive suspensions includes a reservoir containing an abrasive suspension, a loop for delivering the abrasive suspension to a point of use, the loop being connected to the reservoir, a pumping arrangement for circulating the abrasive suspension in the loop and for ensuring its return into the reservoir, the loop and the reservoir being arranged for recovering the abrasive suspension after circulation in the loop at a recovery point of the reservoir, and a control system for controlling the pumping arrangement so as to maintain a continuous circulation of the suspension.