Abstract: A powdery composition based on silica for ceramic welding, in particular by projection, comprising from 10 to 90% of a phase of siliceous particles comprise at least 80% by weight of cristobalite and at most 15% by weight of tridymite, based on the total weight of the composition, from 90 to 10% by weight of conventional additives forming a binding phase, based on the total weight of the composition, said siliceous particles having a d50 comprised between 350 and 800 ?m, preferably between 400 and 500 ?m.

Abstract: A powdery composition based on silica for ceramic welding, in particular by projection, comprising from 10 to 90% of a phase of siliceous particles comprise at least 80% by weight of cristobalite and at most 15% by weight of tridymite, based on the total weight of the composition, from 90 to 10% by weight of conventional additives forming a binding phase, based on the total weight of the composition, said siliceous particles having a d50 comprised between 350 and 800 ?m, preferably between 400 and 500 ?m.

Abstract: The invention relates to a ceramic particle mixture containing, as components, a predominant portion by weight of frittable particles made of a ceramic material and particles of at least one additive, at least one additive being a dispersed absorbent solid inorganic material which has, for a laser beam emitted at a predetermined wavelength, a specific absorptivity that is greater than the absorptivity of the other components of the ceramic mixture, and which drastically breaks down when gas is emitted in the presence of the laser beam, said additive being present in proportions of less than 5% of the dry weight. The invention also relates to ceramic parts produced from such a mixture.

Abstract: Dry mix for treating refractory substrates, comprising combustible particles of at least one oxidizable substance which, in the presence of oxygen, gives rise to an exothermic reaction, and particles of at least one other substance, wherein these particles form together, during said exothermic reaction, a coherent mass capable of adhering to and/or interacting with the treated substrate, characterized in that it comprises, as particles of at least one other substance, particles of at least one expanding substance, in that the dry mix without the particles of this at least one expanding substance has a first bulk density and in that the mix comprising said at least one expanding substance has a second bulk density lower than said first bulk density.

Abstract: Method of spraying a pulverulent material into a carrier gas, comprising the acceleration of the carrier gas under pressure up to a sonic velocity before an expansion enabling the pulverulent material to be entrained, with formation of a constant stream of carrier gas entraining an adjustable predetermined amount of pulverulent materials, and safety device for spraying pulverulent material into a carrier gas.