A method of altering a surface of a ceramic matrix composite to aid in nodule removal is described. A fiber preform comprising a framework of ceramic fibers is heated to a temperature at or above a melting temperature of silicon. During the heating, the fiber preform is infiltrated with a molten material comprising silicon. After the infiltration, the fiber preform is cooled, and the infiltrated fiber preform is exposed to a gas comprising nitrogen during cooling. Silicon nitride may be formed by a reaction of free (unreacted) silicon at or near the surface of the infiltrated fiber preform with the nitrogen. Thus, a ceramic matrix composite having a surface configured for easy nodule removal is formed. Any silicon nodules formed on the surface during cooling may be removed without machining or heat treatment.

An optical element includes an optical surface including a ceramic material. The optical element further includes a coating that includes a bifunctional molecule arranged on the optical surface. The bifunctional molecule includes a first functional group and a second functional group. The first functional group forms a covalent bond to the ceramic material of the optical surface, and the second functional group includes an aromatic functional group. The optical element further includes a carbon-containing material non-covalently bonded to the second functional group of the bifunctional molecule of the coating.

A method of forming a B.sub.4C layer as a component of an oxidation protection system as component of oxidation protection system on a carbon-carbon composite material may include forming a liquid mixture comprising a boron-compound and a carbon-compound. The method may further include applying the liquid mixture on the carbon-carbon composite material. The boron compound may comprise boric acid (H.sub.3BO.sub.3). In various embodiments, the carbon-compound comprises phenolic resin. In various embodiments, the method further includes heating the carbon-carbon composite material after applying the liquid mixture on the carbon-carbon composite material to from a boron carbide (B.sub.4C) layer.

A method of forming a B.sub.4C layer as a component of an oxidation protection system as component of oxidation protection system on a carbon-carbon composite material may include forming a liquid mixture comprising a boron-compound and a carbon-compound. The method may further include applying the liquid mixture on the carbon-carbon composite material. The boron compound may comprise boric acid (H.sub.3BO.sub.3). In various embodiments, the carbon-compound comprises phenolic resin. In various embodiments, the method further includes heating the carbon-carbon composite material after applying the liquid mixture on the carbon-carbon composite material to from a boron carbide (B.sub.4C) layer.

The present invention provides a concrete protective agent and a preparation method thereof, and a concrete protective film and a preparation method thereof. The concrete protective agent provided in the present invention includes the following components: water, oxalic acid, a defoaming agent, and a film-forming agent. When the concrete protective agent provided in the present invention is used for concrete protection, oxalic acid in the protective agent can react with calcium ions in concrete for in situ generation of calcium oxalate monohydrate inside and on a surface of concrete to obtain a protective film with strong adhesion to concrete. The film-forming agent in the protective agent is used as a template to adjust and control growth of calcium oxalate crystals, so as to improve waterproof performance and corrosion resistance to sulfate and chloride ions of the protective film. Preparation methods provided in the present invention are simple and practical and are suitable for mass production.

The present invention provides a concrete protective agent and a preparation method thereof, and a concrete protective film and a preparation method thereof. The concrete protective agent provided in the present invention includes the following components: water, oxalic acid, a defoaming agent, and a film-forming agent. When the concrete protective agent provided in the present invention is used for concrete protection, oxalic acid in the protective agent can react with calcium ions in concrete for in situ generation of calcium oxalate monohydrate inside and on a surface of concrete to obtain a protective film with strong adhesion to concrete. The film-forming agent in the protective agent is used as a template to adjust and control growth of calcium oxalate crystals, so as to improve waterproof performance and corrosion resistance to sulfate and chloride ions of the protective film. Preparation methods provided in the present invention are simple and practical and are suitable for mass production.

Provided are an apatite body easily producible and having a stable apatite composition and a method for producing the apatite body. The apatite body is formed of a sintered calcium carbonate body transformed at least at a surface into apatite and the sintered calcium carbonate body may be a porous sintered body.

Provided are an apatite body easily producible and having a stable apatite composition and a method for producing the apatite body. The apatite body is formed of a sintered calcium carbonate body transformed at least at a surface into apatite and the sintered calcium carbonate body may be a porous sintered body.

Methods are provided for forming high temperature coating over ceramic components, such as ceramic turbomachine components. In various embodiments, the method includes the step or process of at least partially filling a reactor vessel with a reaction solution containing a solution-borne rare earth cation source. A silicon-containing surface region of a ceramic component is submerged in the reaction solution, and a solvothermal growth process is carried-out. During the solvothermal growth process, the reaction solution is subject to elevated temperature and pressure conditions within the reactor vessel in the presence of a silicate anion source, which reacts with the solution-borne rare earth cation source to grow a rare earth silicate layer over the silicon-containing surface region of the ceramic component.

Methods are provided for forming high temperature coating over ceramic components, such as ceramic turbomachine components. In various embodiments, the method includes the step or process of at least partially filling a reactor vessel with a reaction solution containing a solution-borne rare earth cation source. A silicon-containing surface region of a ceramic component is submerged in the reaction solution, and a solvothermal growth process is carried-out. During the solvothermal growth process, the reaction solution is subject to elevated temperature and pressure conditions within the reactor vessel in the presence of a silicate anion source, which reacts with the solution-borne rare earth cation source to grow a rare earth silicate layer over the silicon-containing surface region of the ceramic component.