In a method of treating a gas stream (32) containing combustible and/or reactive particles (34) at least a part of the particles (34) contained in the gas stream (32) is separated from the gas stream (32) by means of a separation device (36). The particles (34) separated from the gas stream (32) by means of the separation device (36) are supplied to a collecting vessel (40). The supply of particles (34) to the collecting vessel (40) is interrupted. A flame retardant material (57) is supplied to the collecting vessel (40) so as to form a cover layer of flame retardant material (57) on the particles (34) contained in the collecting vessel (40).

In a method of treating a gas stream (32) containing combustible and/or reactive particles (34) at least a part of the particles (34) contained in the gas stream (32) is separated from the gas stream (32) by means of a separation device (36). The particles (34) separated from the gas stream (32) by means of the separation device (36) are supplied to a collecting vessel (40). The supply of particles (34) to the collecting vessel (40) is interrupted. A flame retardant material (57) is supplied to the collecting vessel (40) so as to form a cover layer of flame retardant material (57) on the particles (34) contained in the collecting vessel (40).

An additive processing method includes providing a cover gas in a chamber in connection with additive fabrication of an article in the chamber, the cover gas entraining impurities during the additive fabrication, circulating the cover gas with entrained impurities from the chamber into a gas recirculation loop, removing the entrained impurities from the cover gas in the gas recirculation loop to generate a clean cover gas, circulating the clean cover gas into the chamber during the additive fabrication, and metering an amount of new cover gas provided into the chamber from a cover gas source connected to the chamber, the amount being metered with respect to an amount of the clean cover gas circulated into the chamber from the gas recirculation loop.

An additive processing method includes providing a cover gas in a chamber in connection with additive fabrication of an article in the chamber, the cover gas entraining impurities during the additive fabrication, circulating the cover gas with entrained impurities from the chamber into a gas recirculation loop, removing the entrained impurities from the cover gas in the gas recirculation loop to generate a clean cover gas, circulating the clean cover gas into the chamber during the additive fabrication, and metering an amount of new cover gas provided into the chamber from a cover gas source connected to the chamber, the amount being metered with respect to an amount of the clean cover gas circulated into the chamber from the gas recirculation loop.

A method is provided for the heat treatment of an object comprising at least one rare-earth element with a high vapor pressure. One or more objects comprising at least one rare-earth element with a high vapor pressure are arranged in an interior of a package. An external source of the at least one rare-earth element is arranged so as to compensate for the evaporation of this same rare-earth element from the object and/or to increase the vapor pressure of the rare-earth element in the interior of the package, and the package is heat treated.

The present disclosure provides three-dimensional (3D) printing systems, apparatuses, software, and methods for safe production of at least one requested 3D object, and for passivation of material accumulated on a filter of the 3D printing system.

The present disclosure provides three-dimensional (3D) printing systems, apparatuses, software, and methods for safe production of at least one requested 3D object, and for passivation of material accumulated on a filter of the 3D printing system.

A method includes additively manufacturing an article in an inert environment, removing the article from the inert environment and placing the article in a non-inert environment, allowing at least a portion the article to oxidize in the non-inert environment to form an oxidized layer on a surface of the article, and removing the oxidized layer (e.g., to smooth the surface of the article). The method can further include relieving stress in the article (e.g., via heating the article after additive manufacturing).

A method includes additively manufacturing an article in an inert environment, removing the article from the inert environment and placing the article in a non-inert environment, allowing at least a portion the article to oxidize in the non-inert environment to form an oxidized layer on a surface of the article, and removing the oxidized layer (e.g., to smooth the surface of the article). The method can further include relieving stress in the article (e.g., via heating the article after additive manufacturing).

An alumina sintered body having a low dielectric loss tangent and a method for manufacturing the alumina sintered body are provided. An alumina sintered body contains Al.sub.2O.sub.3 99.50 mass % or more, and 99.95 mass % or less and sodium and silicon, wherein at a surface layer A in any given cross-section and a central portion B of the cross-section in a depth direction from the surface layer A, a concentration ratio of sodium to silicon in the surface layer A is smaller than the concentration ratio of sodium to silicon at the central portion B.