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 d.sub.50 comprised between 350 and 800 μm, preferably between 400 and 500 μm.

There is provided a refractory article for use in metal casting and a composition for manufacture thereof, comprising a particulate refractory material, an oxidisable fuel, an oxidant, a sensitizer; a binder, and from 0.5 to 5 wt % CaSO.sub.4.

The present invention discloses a novel flash sintering process for synthesis of MAX phases, namely, but not limited to Ti.sub.2SnC and Ti.sub.3SiC.sub.2 in an extremely short time. The process is a combustion synthesis where a relatively low voltage in a range of 20-60 V/cm is applied using a DC/AC power source across the compact precursor material prior to ignition. The flash event is observed with a quick rise in current flow in a range of 100-300 mA/mm.sup.2 followed by measured temperature range of 1200-1400? C. in a green compact body of different MAX phase compositions. The process of the present invention enables the synthesis of MAX phases in air by suppressing oxidation of the material because of the very short residence time of the flashing event. In addition, the present invention focuses on synthesis of MAX phase in bulk to serve as the starting material for the development of two-dimensional MXenes.

A method of additive manufacturing to form a component comprises successively depositing a plurality of layers to form the component. Depositing at least one of the plurality of layers includes depositing a layer of a first particulate precursor over a platen, depositing a second particulate precursor on portions of the platen over the layer of the first particulate precursor specified by a controller, and directing energy to the second particulate precursor deposited on the portion of the platen to cause an exothermic chemical reaction between the first particulate precursor and the second particulate precursor. The exothermic chemical reaction produces heat that sinters products of the chemical reaction to fabricate the layer of the component.

A method of additive manufacturing to form a component comprises successively depositing a plurality of layers to form the component. Depositing at least one of the plurality of layers includes depositing a layer of a first particulate precursor over a platen, depositing a second particulate precursor on portions of the platen over the layer of the first particulate precursor specified by a controller, and directing energy to the second particulate precursor deposited on the portion of the platen to cause an exothermic chemical reaction between the first particulate precursor and the second particulate precursor. The exothermic chemical reaction produces heat that sinters products of the chemical reaction to fabricate the layer of the component.

Dense ceramic-metal composites and components and methods of manufacturing. A method of manufacturing a ceramic-metal composite includes forming a metal containing component into preform having a desired shape and dimensions with pores therein, infiltrating the pores of the preform with a multi-element liquid reactant, and reacting the metal containing component with the multi-element liquid reactant in a displacement reaction at an elevated temperature to form a less porous ceramic-metal composite.