Abstract: A method for producing silica brick comprising firing a siliceous stone material containing silica as a main component is disclosed, in which 0.05 to 0.25% by weight of Na.sub.2 O--CaO--SiO.sub.2 fused and solidified material and 0.1 to 1.0% by weight, in terms of Fe.sub.2 O.sub.3, of iron oxide are added to the siliceous stone material, before firing. Transformation of silica into tridymite is effectively accelerated to provide silica bricks mainly comprising tridymite with reduced contents of residual silica and amorphous glass and exhibiting improved creep resistance.

Abstract: A laser beam-transmitting section of a laser measuring instrument of dimensional change is arranged at one side of a specimen heating furnace, a laser beam-receiving section is arranged at the opposide side of the furnace, a slit fixture for shielding within-the-furnace radiation heat and light is provided inside a measuring window, a heat insulating material having a slit for shielding within-the-furnace radiation heat and light is provided inside said slit fixture, and a within-the-furnace radiation light shielding slit plate and a within-the-furnace radiation light reducing optical filter are disposed at the end faces of said respective laser beam-transmitting section and said laser beam-receiving section whereby measuring errors caused by the light and heat generated within the furnace are prevented (the interior of a specimen heating furnace core pipe can be replaced by various kinds of atmospheres as necessary, and it is possible to measure the dimensional change of small-size specimens of ceramics or t

Abstract: An apparatus for automatic measuring thermal dimensional change from the room temperature to 2,000.degree. C., comprising, (a) means for supporting a specimen of the material to be tested and heating said specimen, (b) means for measuring the dimensional change of the specimen during heating said specimen, said measuring means having photo diode linear array and the telescopic lens for forming an image of the heated specimen, (c) means for illuminating the specimen from the opposite side of the photo diode linear array, said means having electric lamp and condensor lens, the radiation characteristic curve of said lamp being different from that of heated specimen, (d) means for separating the light forming image from the light radiated from said heated specimen, said means having light filter and neutral density filter between said specimen and said optical lens, (e) means for processing and calculating the video signal from the photo diode linear array indicating the results of measurements.