Abstract: A refractory protective block protects heat exchange means connecting tubes to fins. The refractory protective block has an inside complementary shape corresponding to the surface shape of the heat exchange means and the refractory protective block is provided with recesses into which projections formed on the tubes are fitted and received. A pair of projections formed on the two adjacent tubes in the heat exchange means are arranged so as to confront each other. The refractory protective block has a high durability which does not break even when heat exchange means expand more than the refractory block at the time of the repetition of heating and cooling and which enable the dispersion of strain at the time of the repetition of expansion and contraction.

Abstract: A process for producing a silicon carbide sintered product, particularly, large-shaped silicon carbide sintered product by reaction sintering. Siliciding reaction can be carried out completely in a short period of time by adding an organic silicon polymer whose skelton is composed of silicon and carbon to the starting sintering material and using the same for the control of the reaction rate.

Abstract: Flaky .beta.-SiC mainly composed of .beta.-SiC which is obtained from an organic silicon polymer containing the carbon and silicon atoms as the major skeletal component and the method for producing such flaky .beta.-SiC are disclosed. Such .beta.-SiC is especially utilized as the starting material for ceramics having a laminar structure as well as for the refractories. The ceramics and refractories provided with such .beta.-SiC have excellent resistance to thermal shock, to thermal fatigue as well as to oxidation.

Abstract: Flaky .beta.-SiC mainly composed of .beta.-SiC which is obtained from an organic silicon polymer containing the carbon and silicon atoms as the major skeletal component and the method for producing such flaky .beta.-SiC are disclosed. Such .beta.-SiC is especially utilized as the starting material for ceramics having a laminar structure as well as for the refractories. The ceramics and refractories provided with such .beta.-SiC have excellent resistance to thermal shock, to thermal fatigue as well as to oxidation.

Abstract: Refractory moldings or repairing deposits formed by flame projection, composed of a solidified phase formed from fused fine refractory particles and nonfused coarse refractory particles dispersed in the solidified phase.The moldings or deposits have high thermal shock resistance and erosion resistance.They are produced by flame-projecting fine refractory particles and coarse refractory particles together into a mold or onto a substrate, e.g. onto a portion of a furnace to be repaired.

Abstract: Flaky .beta.-SiC mainly composed of .beta.-SiC which is obtained from an organic silicon polymer containing the carbon and silicon atoms as the major skeletal component and the method for producing such flaky .beta.-SiC are disclosed. Such .beta.-SiC is especially utilized as the starting material for ceramics having a laminar structure as well as for the refractories. The ceramics and refractories provided with such .beta.-SiC have excellent resistance to thermal shock, to thermal fatigue as well as to oxidation.

Abstract: A SiC-Si.sub.3 N.sub.4 composite system for special heat-resisting ceramic materials which is fabricated by firing in a nitriding gas atmosphere a green compact prepared from and composed of, as starting materials, silicon powder and an organic silicon polymer containing carbon and silicon atoms as the major skeletal components, whereby said composite system, as a final fired compact has an interwoven texture of SiC and Si.sub.3 N.sub.4 with sufficient micro gaps to absorb thermal stresses, wherein the quantitative ratio by weight of SiC to Si.sub.3 N.sub.4 in said composite system being in the range of 5%-20%:95%-80%.

Abstract: Present invention provides silica bricks of improved thermal conductivity and low gas permeability and method for manufacturing such silica bricks. The manufacturing method is substantially characterized in that siliceous raw mixture includes 0.5 to 10 percent by weight of nitride or carbide of metallic silicon and that, in the firing process from 1200.degree. to 1400.degree. C., the temperature elevation speed and the oxygen concentration at the exhaust port of the firing furnace take specific rates respectively different from the corresponding rates of conventional firing. In the above firing process, the nitride or carbide of metallic silicon is oxidized to form SiO.sub.2 and this SiO.sub.2 fills in pores of the matrix whereby silica bricks produced by the method of this invention can have high thermal conductivity and low gas permeability.