Hexavalent chromium-free slurry formulations which are suitable in the production of ceramic overlay coating systems are described. The formulations provide superior hot corrosion and heat oxidation protection for superalloy substrates. A basecoat slurry and topcoat slurry are provided. The basecoat slurry includes an aluminum phosphate based aqueous solution having a molar ratio of Al:PO.sub.4 higher than about 1:3 with the incorporation of metal oxide particles. The topcoat slurry includes an aluminum phosphate based aqueous solution having a molar ratio of Al:PO.sub.4 higher than about 1:3. Both of the basecoat slurry and the topcoat slurry are hexavalent chromium-free.

A method includes masking at least one hole of an article with a paste, wherein the hole opens onto a surface of the article, applying a coating to the surface of the article, and removing the paste including contacting the paste with water, leaving at least one open hole in the surface of the coated article. The paste includes about 40-80 wt % of a filler material, about 0.5-20 wt % of an inorganic binder, about 0.5-15 wt % of a polyhydroxy compound and about 5-25 wt % of water. The filler material includes a first material which includes alkali metal doped alumina, zirconium oxide, titanium oxide, silicon dioxide, or a combination thereof and a second material which includes a silicate. A weight ratio between the first and second materials is in a range of about 1-10.

A system for forming a hollow modular candle filter includes: a first filter portion having at least one open end; a hollow second filter portion having at least one open end; a sleeve configured to fit within the open end of the first filter portion and the open end of the second filter portion; and an adhesive configured to bind the sleeve to each of the first filter portion and the second filter portion.

A system for forming a hollow modular candle filter includes: a first filter portion having at least one open end; a hollow second filter portion having at least one open end; a sleeve configured to fit within the open end of the first filter portion and the open end of the second filter portion; and an adhesive configured to bind the sleeve to each of the first filter portion and the second filter portion.

A system for forming a hollow modular candle filter includes: a first filter portion having at least one open end; a hollow second filter portion having at least one open end; a sleeve configured to fit within the open end of the first filter portion and the open end of the second filter portion; and an adhesive configured to bind the sleeve to each of the first filter portion and the second filter portion.

A system for forming a hollow modular candle filter includes: a first filter portion having at least one open end; a hollow second filter portion having at least one open end; a sleeve configured to fit within the open end of the first filter portion and the open end of the second filter portion; and an adhesive configured to bind the sleeve to each of the first filter portion and the second filter portion.

A method of manufacturing a concrete product includes providing a metal-based cementing agent including at least one of Fe.sub.2O.sub.3 and Fe.sub.3O.sub.4, an aqueous phosphoric acid cement reacting agent, an aggregate having at least one metallic oxide, a setting agent including at least one of Fe.sup.+2 and Mn.sup.+2, and an acid scavenging agent including at least one of K-feldspar and magnesium silicate. The method includes mixing the metal-based cementing agent, the cement reacting agent, the aggregate, the setting agent and the acid scavenging agent together to form a liquid concrete mixture, and placing the liquid concrete mixture in a form and allowing the liquid concrete mixture to set up and cure into the concrete product. The method can optionally include the additional step of placing the concrete product into an oven at a temperature of between 170 and 190 C.

A method of manufacturing a concrete product includes providing a metal-based cementing agent including at least one of Fe.sub.2O.sub.3 and Fe.sub.3O.sub.4, an aqueous phosphoric acid cement reacting agent, an aggregate having at least one metallic oxide, a setting agent including at least one of Fe.sup.+2 and Mn.sup.+2, and an acid scavenging agent including at least one of K-feldspar and magnesium silicate. The method includes mixing the metal-based cementing agent, the cement reacting agent, the aggregate, the setting agent and the acid scavenging agent together to form a liquid concrete mixture, and placing the liquid concrete mixture in a form and allowing the liquid concrete mixture to set up and cure into the concrete product. The method can optionally include the additional step of placing the concrete product into an oven at a temperature of between 170 and 190 C.

A composite material containing a matrix and a fibrous reinforcement, in particular a textile embedded in the matrix. The matrix includes a geopolymer of the poly(phospho-sialate) type having the following formula I: (1) (—P—O—Si—O—Al—O—).sub.n in which n is greater than 2. The matrix further includes zirconium covalently bonded to the matrix, especially in the —ZrO form and/or in the —O—Zr—O form. The matrix has a melting temperature greater than 700° C., especially equal to or greater than 1200° C.

The present invention relates to a thermal emissivity coating composition comprising: a) an emissivity agent in an amount from 30 to 65% by weight with respect to the total weight of the thermal emissivity coating composition; b) a filler selected from the group consisting of oxides of aluminum, silicon, magnesium, calcium, boron and mixtures of two or more thereof, in an amount from 10 to 35 wt % with respect to the total weight of the thermal emissivity coating composition; and c) a binder in an amount from 12 to 52 wt % with respect to the total weight of the thermal emissivity coating composition; wherein the emissivity agent comprises cobalt oxide in an amount from 10 to 25 wt %, preferably 12 to 25 wt % with respect to the total weight of the thermal emissivity coating composition and further comprises chromium oxide and titanium oxide.