A coating system for coating inorganic substrates with a wide range of functional materials without having to use the usually necessary high temperatures includes an aqueous solution as component K1, which aqueous solution contains at least Al(H.sub.2PO.sub.4).sub.3 and Al(NaHPO.sub.4).sub.3 in the following fractions on an oxide basis and in mass percent with respect to the total mass of the solution: P.sub.2O.sub.5=25.0 to 37.0, Al.sub.2O.sub.3=5.8 to 9.0, Na.sub.2O=0.1 to 2.0, and H.sub.2O=54.0 to 66.0, and which includes an additional component K2 having the constituents magnesium oxide, silicate, and borate, which are contained in K2 in the following fractions on an oxide basis and in mass percent with respect to the total mass of component K2: MgO=70.0 to 95.0, SiO.sub.2=1.0 to 19.0, and B.sub.2O.sub.3=1.0 to 3.0, wherein there is a reactivity of the magnesium oxide of 40 to 400 seconds in the citric acid test and the loss on ignition of component K2 is 0 to 3.0.

A catalytic refractory heating appliance includes a body formed from a silicon carbide refractory material having a porosity that permits ionic oxygen to pass through the refractory material. The body defines a gas flow channel. A catalyst coating is on a surface of the refractory material of the body, whereby the refractory material becomes an active component with catalytic capability. For example, when the catalytic refractory heating appliance is a fire tube carbon dioxide and sulfur compounds can be directly absorbed, or carbon monoxide is reduced to methane.

An article includes a silicon-containing region; at least one outer layer overlying a surface of the silicon-containing region; and a constituent layer on the surface of the silicon-containing region and between and contacting the silicon-containing region and the at least one outer layer, the constituent layer being formed by constituents of the silicon-containing region and being susceptible to creep within an operating environment of the article, wherein the silicon-containing region defines a plurality of channels and a plurality of ridges that interlock within the plurality of channels are formed in the silicon-containing region to physically interlock the at least one outer layer with the silicon-containing region through the constituent layer.

An article includes a silicon-containing region; at least one outer layer overlying a surface of the silicon-containing region; and a constituent layer on the surface of the silicon-containing region and between and contacting the silicon-containing region and the at least one outer layer, the constituent layer being formed by constituents of the silicon-containing region and being susceptible to creep within an operating environment of the article, wherein the silicon-containing region defines a plurality of channels and a plurality of ridges that interlock within the plurality of channels are formed in the silicon-containing region to physically interlock the at least one outer layer with the silicon-containing region through the constituent layer.