257 results about "Pyrochlore" patented technology

The invention discloses high-entropy ceramic powder used for a thermal barrier coating. The ceramic powder is characterized by having a pyrochlore structure and a chemical formula of RE2Zr2O7, wherein RE is any 3-7 different metal elements selected from rare earth elements including Y, La, Pr, Nd, Sm, Eu and Gd, and the percentage of one mole number of each RE element to the total mole number of all RE elements is 5%-35%. The preparation method comprises the following steps: mixing RE2O3 powder and ZrO2 powder, and heating the mixed powder under the heating condition of 1000-1700 DEG C for 1-10 h in an air atmosphere to obtain the high-entropy ceramic powder. According to the method provided by the invention, the high-entropy ceramic powder prepared by the method enriches a system of a thermal barrier coating material, has the advantages of low costs, simple and easy operation, a wide application range and the like, and is expected to be used in the field of thermal barrier coatings.

A method of catalytically reforming a reactant gas mixture using a pyrochlore catalyst material comprised of one or more pyrochlores having the composition A_2-w-xA′_wA″_xB_2-y-zB′_yB″_zO_7-Δ. Distribution of catalytically active metals throughout the structure at the B site creates an active and well dispersed metal locked into place in the crystal structure. This greatly reduces the metal sintering that typically occurs on supported catalysts used in reforming reactions, and reduces deactivation by sulfur and carbon. Further, oxygen mobility may also be enhanced by elemental exchange of promoters at sites in the pyrochlore. The pyrochlore catalyst material may be utilized in catalytic reforming reactions for the conversion of hydrocarbon fuels into synthesis gas (H₂+CO) for fuel cells, among other uses.

The invention relates to an anti-carbon-deposition Ni-based catalyst for hydrogen production by methane steam reforming and a preparation method thereof. By taking lanthanum nitrate, praseodymium nitrate, samarium nitrate, yttrium nitrate, zirconium nitrate, zirconium carbonate, zirconium oxychloride, and the like as precursors and taking ammonia as a precipitant, a pyrochlore composite oxide is prepared through using a coprecipitation method; and then the pyrochlore composite oxide is mixed with alumina by using a mechanical mixing method so as to obtain a pyrochlore alumina composite carrier. Nickel nitrate, nickel chloride, nickel sulfate, nickel oxalate and the like serving as nickel sources are loaded on the pyrochlore alumina composite carrier through direct immersion. The loading capacity of nickel in the catalyst accounts for 5-30% of the weight of the catalyst, the pyrochlore content of the catalyst is 5-50%, and the alumina content of the catalyst is 20-90%. By taking the pyrochlore alumina composite oxide as a carrier, the reaction activity and anti-carbon-deposition performance of the catalyst can be greatly increased; the preparation method of the catalyst is simple; and the catalyst has excellent catalytic activity and stability to methane steam reforming in a stationary bed.

A thin film comprising a pyrochlore represented by the formula:wherein x is from about 0.45 to about 0.73 and an article comprising a substrate and, coated on the substrate, a thin film of the pyrochlore are provided. Also provided is a process for depositing on a substrate the above pyrochlore thin film. The process includes the steps of coating the substrate with a composition comprising bismuth carboxylate, zinc carboxylate, niobium alkoxide, an organic solvent, an organic acid and an organic base, heating to remove organic components and annealing at a temperature and for a length of time sufficient to produce the pyrochlore thin film on the substrate.

The invention provides a composite rear earth pyrochlore-type oxide catalyst for catalyzing burning for removing soot of a diesel vehicle and a preparation method thereof, belonging to the technical field of a tail gas cleaning catalyst of the diesel vehicle. The expression formula of the composite metal oxide is A2B2-xMxO7, wherein A is La, B is Sn, M is Mn, Fe, Co, Ni or Cu. The invention adopts a coprecipitation method to prepare the catalyst, the preparation process is simple, and the cost is low. The preparation method comprises the following steps: mixing metal nitrate and tin tetrachloride solution; adjusting the pH value by ammonia solution; drying the obtained deposit; and roasting the deposit at the high temperature to obtain the composite rear earth pyrochlore-type oxide catalyst. Under the effect of the catalyst, a simulation diesel vehicle exhausts, the burning temperature of the soot particles is lowered to the exhaust range of the diesel vehicle, and the speed of the soot oxidation rate is improved. The catalyst is a useful catalyst for removing the pollution of soot particles of the diesel vehicle.

The invention discloses a high-temperature and high-pressure rapid synthesis method of Gd2Zr2O7 pyrochlore ceramic, which comprises the five steps of: batching, grinding, drying, dry pressing and high-temperature and high-pressure synthesis. The high-temperature and high-pressure rapid synthesis method has the beneficial effects that within the wide pressure and temperature scope, a multi-component oxide mixture is taken as a raw material, the synthesis of a Gd2-xAxZr2-yByO7 (x is more than or equal to 0 but less than or equal to 2, and y is more than or equal to 0 but less than or equal to 2) compound with a pyrochlore structure and the dense sintering of the ceramic is realized at the same time, and the time required is only 15-30 minutes, so that the preparation time of the pyrochlore ceramic is greatly shortened; and compared with the prior art, the time used is shortened by 100 times at least, the efficiency is improved, and the practicability is strong.

A high dielectric constant insulator including a thin film of a metal oxide selected from the group consisting of tungsten-bronze-type oxides, pyrochlore-type oxides, and combinations of Bi2O3 with an oxide selected from the group consisting of perovskites and pyrochlore-type oxides. An embodiment contains metal oxides represented by the general stoichiometric formulae AB2O6, A2B2O7 and A2Bi2B2O10, wherein A represents A-site atoms selected from the group of metals consisting of Ba, Bi, Sr, Pb, Ca, K, Na and La; and B represents B-site atoms selected from the group of metals consisting of Ti, Zr, Ta, Hf, Mo, W and Nb. Preferably, the metal oxides are (BaxSr1-x)(TayNb1-y)2O6,where 0</=x</=1.0 and 0</=y</=1.0; (BaxSr1-x)2(TayNb1-y)2O7, where 0</=x</=1.0 and 0</=y</=1.0; and(BaxSr1-x)2Bi2(TayNb1-y)2O10, where 0</=x</=1.0 and 0</=y</=1.0. Thin films according to the invention have a relative dielectric constant >/=40, and preferably about 100. The value of Vcc in the metal oxides of the invention is close to zero. The value of Tcc is <1000ppm, preferably <100.

The invention relates to a preparation method of single-phase pyrochlore-type La2Zr2O7 nano-powder. The preparation method is characterized in that the La2Zr2O7 nano-powder is obtained by ageing, drying and high-temperature roasting by using Zr<4+> and La<3+> hydration inorganic salt as a precursor, citric acid as a complexing agent, an amide organic matter as a gel accelerant and polyethylene glycol as a dispersing agent. The single-phase pyrochlore-type La2Zr2O7 nano-powder has the advantages that the particle size of the obtained La2Zr2O7 nano-powder is 20-100nm, the molar ratio of Zr to La is approximate to 1:1, the crystal structure of the La2Zr2O7 nano-powder is single-phase pyrochlore-type, and the La2Zr2O7 nano-powder has high degree of crystallinity and excellent performances such as low heat conduction, sintering resistance, good high-temperature stability and the like and is applied to the field of thermal barrier coatings of aviation turbine engines and protective coatings in high-temperature wet-oxygen environments.

The invention discloses a pyrochlore structural rare-earth zirconate material system capable of being used for a heat barrier coating. The chemical composition of the material is (0.5-x)R'2O3-0.5Sm2O3-xR''2O3-2ZrO2, wherein x is more than 0 and less than or equal to 0.25; the R' is rare-earth elements or composition thereof, the ion radius of which is greater than that of Sm; and R'' is rare-earth elements or composition thereof, the ion radius of which is smaller than that of Sm. The material provided by the invention has low thermal conductivity, high thermal stability and high-temperature sintering resistance; the thermal expansion performance of the material is stable compared with a single pyrochlore structural material; and the material is favorable for reducing thermal stress generated by mismatching of thermal expansion coefficients in the thermal cycle process, and can prolong the thermal cycle life of the coating. Because of good high-temperature phase stability, the pyrochlore structural rare-earth zirconate material can be used for designing and preparing a novel high-temperature heat barrier coating material, the use temperature of which is below 1,550 DEG C.

The invention relates to cerium-doped lanthanum zirconate nano powder and a preparation method thereof. The cerium-doped lanthanum zirconate nano powder is characterized in that the cerium-doped lanthanum zirconate nano powder is of a single-phase pyrochlore structure, has the particle size of 30 to 250nm, is uniformly distributed, is of a sphere shape, is prepared by carrying out doping on the Zr position by Ce and has the chemical formula of La2Zr2-xCexO7, wherein x is less than or equal to 0.5 and more than or equal to 0.1. The cerium-doped lanthanum zirconate nano powder is of the single-phase pyrochlore structure, has excellent anti-sintering performance, has small particle size, is uniformly distributed, has regular morphology and has stable structure at high temperature; the thermal expansion coefficient of the powder from the room temperature to the temperature of 1,400 DEG C can reach 12*10<-6<K<-1>; and the cerium-doped lanthanum zirconate nano powder has the thermal conductivity of lower than 1.5W.m<-1>.K<-1>, is particularly suitable for preparation of various high temperature resistance thermal barrier coating or high temperature resistance abrasion-resistant anticorrosion coating materials, and is applied to the industries of aerospace, gas turbines, ships, vehicles, machinery, chemical industry and the like.

A translucent ceramic having a high linear transmittance and a high refractive index, substantially not causing double refraction, and exhibiting a high anomalous dispersion has a pyrochlore compound represented by the general formula A_xB_yO_w (wherein 1.00≦x/y≦1.10 and w represents a positive number maintaining electroneutrality) as a main component. The main component has a cubic crystal system. Preferably, the A site comprises a trivalent metallic element, and the B site comprises a tetravalent metallic element. More preferably, A is at least one of La, Y, Gd, Yb, and Lu, and B is of at least one of Ti, Sn, Zr, and Hf. The translucent ceramic is useful as a material of, for example, an objective lens used in an optical pickup.

Heating devices such as self-cleaning ovens include at least one surface comprising metal oxide crystalline catalytic material disposed thereon. The metal oxide crystalline material includes perovskite and perovskite-like materials, pyrochlores, rare earth metal oxides, spinels, and combinations of the foregoing. Also disclosed herein are processes for process for forming a pyrocatalytic coating on a substrate.

The invention provides a preparation method of a gadolinium zirconate-based material, gadolinium zirconate-based ceramic pelletizing powder for ionic spraying and a preparation method of the gadolinium zirconate-based ceramic pelletizing powder. According to the preparation method, oxides are mixed and grinded at a rotation speed which is increased gradually, then large micro-grade granules of rawmaterials are gradually crushed into nano-grade powder, the powder of which the particle size is relatively uniform is made, the powder has a relatively high specific surface area, solid-phase reactions in later sintering process are carried out smoothly, or the mixed material of the powder is further pressed into blocks, then distances among mass points of the powder granules are further reduced, the pore content is reduced, the density is improved, mixed oxide blocks are prepared, the solid-phase reactions in later sintering process are carried out smoothly, the solid-phase reactions can bestill ensured without high-pressure sintering, and a stable pyrochlore structure can be prepared.

A piezoelectric device, including the following on a substrate in the order listed below: a lower electrode, a piezoelectric film which contains a Pb containing perovskite oxide represented by a general expression (P) below, and an upper electrode, in which the piezoelectric film has a layer of pyrochlore oxide on the surface facing the lower electrode, and the average layer thickness of the pyrochlore oxide layer is not greater than 20 nm.

A_aB_bO₃  (P)

where, A: at least one type of A-site element containing Pb as a major component, B: at least one type of B-site element selected from the group consisting of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, and Ni, and O: an oxygen element.

The invention discloses a preparation method of a high-efficiency nickel-based catalyst for producing hydrogen in methanol-steam reforming. According to the preparation method, a pyrochlore compounding oxide is prepared through a glycine-nitrate combustion method; metal nitrate or perchlorate is adopted as an oxidizing agent; an organic matter is used as fuel; self-propagating combustion is generated through an oxidation-reduction reaction between reaction mixtures; a pyrochlore-type composite oxide carrier is synthesized by utilizing the heat generated during combustion. Nickel nitrate, nickel sulfate, nickel oxalate, and the like are used as nickel sources, and the nickel sources are loaded on the pyrochlore-type composite oxide carrier by a direct immersion method. The loading quantity of nickel in the catalyst is 5-20 wt% of the catalyst, and the content of pyrochlore is 80-95% of the catalyst. The composite oxide, namely pyrochlore alumina, is utilized as a carrier, so that the reaction activity and the carbon-deposition resisting performance of the catalyst can be greatly improved; besides, the preparation method of the catalyst is simple, and the catalyst has high catalytic activity and stability for methanol-steam reforming in a stationary bed.

The invention relates to a method for preparing KNbWO6.H2O, belonging to the technical field of inorganic material preparation technology. The provided method comprises the following steps of: firstly processing Nb2O5 and KOH under hydrothermal condition to get [Nb6O19]8- solution; then adding a certain amount of octanol and H2WO4 in the [Nb6O19]8- solution, regulating the pH value of the reaction liquid by diluted hydrochloric acid, and then obtaining KNbWO6.H2O with a pyrochlore structure under the solvothermal condition. The method is simple, convenient, easy to carry out and low in cost, and overcomes the tedious steps of the conventional high temperature solid phase method, such as repeated high temperature firing and grinding; and the obtained KNbWO6.H2O is a monodispersed octahedron in appearance.

The invention discloses a preparation method of pyrochlore-type A2B2O7 transparent ceramics, relating to A2B2O7-series nano powder preparation by a sol-gel process and belonging to the field of ceramic material preparation. The preparation method comprises the following steps: at room temperature, weighing RE2O3 and ZrOCl2.8H2O or TiCl4 according to the stoichiometric proportion, dissolving the rare earth oxide in nitric acid, adding the ZrOCl2.8H2O or TiCl4 to be dissolved, adding a mixed solution containing a dispersing agent (NH4)2SO4 and PAA (polyacrylic acid), slowly and dropwisely adding into an ammonium bicarbonate solution to obtain a precursor, and drying; adding a certain amount of sintering assistant ethyl orthosilicate or silicon dioxide sol into the precursor, carrying out ball milling, drying, screening and calcining to obtain nano powder; and carrying out compression molding, isostatic cool pressing, vacuum sintering, annealing and polishing treatment to finally obtain the transparent A2B2O7-series ceramics. By adopting the self-made high-activity nano powder to prepare the transparent A2B2O7-series ceramics at low temperature, the technique is simple and feasible.

The present invention provides a composite dielectric film including a polymer and a ceramic with pyrochlore structure and a method of fabricating the same. The composite dielectric film includes a polymer matrix and a ceramic of a pyrochlore structure filled in such polymer matrix.

The present invention relates to a glass matrix which includes 4-70 wt.% SiO2, 0.5-20 wt.% Al2O3, 0-20 wt.% R2O, 0-30 wt.% R'O, 8-85 wt.% Ta2O5, 0-40 wt.% Nb2O5, and 0.01-1.0 wt.% R''2O3, where R2O + R'O is between about 2-35 wt.%, Ta2O5 + Nb2O5 is between about 8-85 wt.%, R is selected from a group consisting of Li, Na, K, and combinations thereof, R' is selected from a group consisting of Ba, Sr, Ca, Mg, Zn, Pb, and combinations thereof, and R'' is a rare earth element. The present invention also relates to use of the glass matrix in forming optic waveguides such as optic amplifiers. The present invention further relates to a transparent glass ceramic that contains pyrochlore, perovskite, or a combination thereof as its major crystal phase, and includes 4-40 wt.% SiO2, 1-15 wt.% Al2O3, 0-20 wt.% K2O, 0-12 wt.% Na2O, 0-5 wt.% Li2O, 8-85 wt.% Ta2O5, and 0-45 wt.% Nb2O5, wherein Ta2O5 + Nb2O5 is at least about 20 wt.% and (K2O + Li2O + Na2O) is between about 5-20 wt.%. Also disclosed is a method of making the glass ceramic and use of the glass ceramic as a ferro-electric component in electro-optical devices or as a filtering core in an optical filtering device.