A polycrystalline cubic boron nitride, PCBN, material is provided. The material comprises between 30 and 90 weight percent cubic boron nitride (cBN) and a matrix material in which the cBN particles are dispersed. The matrix material comprises particles of an aluminium compound; the matrix material particles having a d50 when measured using a linear intercept technique of no more than 100 nm.

A method of preparing cerium boride powder, according to the present invention, includes a first step for generating mixed powder by mixing at least one selected from among cerium chloride (CeCl.sub.3) powder and cerium oxide (CeO.sub.2) powder, at least one selected from among magnesium hydride (MgH.sub.2) powder and magnesium (Mg) powder, and boron oxide (B.sub.2O.sub.3) powder, a second step for generating composite powder including cerium boride (Ce.sub.xB.sub.y) and at least one selected from among magnesium oxide (MgO) and magnesium chloride (MgCl.sub.2), by causing reaction in the mixed powder at room temperature based on a ball milling process, and a third step for selectively depositing cerium boride powder by dispersing the composite powder in a solution.

Provided is a production method that can easily produce a calcium carbonate porous sintered body. The production method includes the steps of: preparing a dispersion liquid containing calcium carbonate and a gelling agent; adding a foaming agent to the dispersion liquid, followed by stirring until foamy to make a foam; turning the foam into a gel; and sintering the gelled foam to produce a calcium carbonate porous sintered body.

A process for producing metastable nanocrystalline alpha-alumina (-Al.sub.2O.sub.3) having particle sizes smaller than 12 nm. Starting crystallites of -Al.sub.2O.sub.3 having a particle size larger than 12 nm, typically on the order of about 50 nm, are ball-milled at low temperatures to produce a nanocrystalline -Al.sub.2O.sub.3 powder having a particle size of less than 12 nm, i.e., below the theoretical room temperature thermodynamic size limit at which -Al.sub.2O.sub.3 changes phase to -Al.sub.2O.sub.3, wherein the powder remains in the -Al.sub.2O.sub.3 phase at all times.

A method for producing a composite of cubic boron nitride dispersed in a SiAlON ceramic. This method involves mixing silicon nitride nanoparticles, aluminum nitride nanoparticles, silica nanoparticles, calcium oxide nanoparticles, and cubic boron nitride microparticles to produce a mixture. The cubic boron nitride may be coated with nickel. The mixture is sintered to produce the composite, and this sintering may involve spark plasma sintering and/or sintering at a relatively low temperature. The composite may comprise a mixture of Ca--SiAlON and -SiAlON ceramic reinforced by boron nitride in either or both cubic and hexagonal phases.

A cubic boron nitride sintered body has between 50% and 75% cubic boron nitride by volume and between 25% and 50% binder phase by volume, and inevitable impurities. The binder phase contains an Al compound and a Zr compound. The Al compound contains Al and one or more of N, O and B; and the Zr compound contains Zr and one or more of C, N, O and B. At a polished surface of the cubic boron nitride sintered body, 40% or more of the Zr compounds satisfy the ratio 0.25n/N0.8, where: N represents the number of line segments drawn radially at equal intervals from a center of gravity of a given Zr compound to a boundary with a non-Zr compound; and n represents the number among those N line segments which intersect a boundary between the given Zr compound and cubic boron nitride.

A method for producing a composite of cubic boron nitride dispersed in a SiAlON ceramic. This method involves mixing silicon nitride nanoparticles, aluminum nitride nanoparticles, silica nanoparticles, calcium oxide nanoparticles, and cubic boron nitride microparticles to produce a mixture. The cubic boron nitride may be coated with nickel. The mixture is sintered to produce the composite, and this sintering may involve spark plasma sintering and/or sintering at a relatively low temperature. The composite may comprise a mixture of Ca--SiAlON and -SiAlON ceramic reinforced by boron nitride in either or both cubic and hexagonal phases.

A method of producing polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y (Y-358) whereby powders of yttrium (III) oxide, a barium (II) salt, and copper (II) oxide are pelletized, calcined at 850 to 950? C. for 8 to 16 hours, ball milled under controlled conditions, pelletized again and sintered in an oxygen atmosphere at 900 to 1000? C. for up to 72 hours. The polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y thus produced is in the form of elongated crystals having an average length of 2 to 10 ?m and an average width of 1 to 2 ?m, and embedded with spherical nanoparticles of yttrium deficient Y.sub.3Ba.sub.5Cu.sub.8O.sub.y having an average diameter of 5 to 20 nm. The spherical nanoparticles are present as agglomerates having flower-like morphology with an average particles size of 30 to 60 nm. The ball milled polycrystalline Y.sub.3Ba.sub.5Cu.sub.8O.sub.y prepared under controlled conditions shows significant enhancement of superconducting and flux pinning properties.

An ion conductor including: at least one oxide represented by Formulae 1 to 3
Li.sub.4xM.sub.1xM.sub.xO.sub.4 Formula 1
wherein in Formula 1, 0x1 and 0x1 , M is a Group 4 element, M is an element of Group 2, an element of Group 3, an element of Group 5, an element of Group 12, an element of Group 13, a vacancy, or a combination thereof, with the proviso that when M is Zr, then x0, x0 and M is Be, Ca, Sr, Ba, Ra, Cd, Hg, Cn, Ga, In, TI, an element of Group 3, an element of Group 5, or a combination thereof;
Li.sub.4yMO.sub.4yA.sub.y Formula 2
wherein in Formula 2, M is a Group 4 element, A includes at least one halogen, with the proviso that when M is Zr, y0,
Li.sub.4+4zM.sub.1zO.sub.4 Formula 3
wherein in Formula 3, 0<z<1, and M is a Group 4 element.

A lead-free piezoelectric ceramic sensor material and a preparation method thereof and relates to the technical field of piezoelectric ceramic processing. The main raw materials of the lead-free piezoelectric ceramic sensor material disclosed in the present disclosure are a barium carbonate, a calcium carbonate, a zirconia, a titanium dioxide, a strontium carbonate, an erbium oxide, and a bismuth oxide. The preparation method is prepared through the steps of preparing ingredients, ball milling, granulating and tableting, debinding, and sintering, and the lead-free piezoelectric ceramic sensor material can be made into a lead-free piezoelectric sensor through applying an electrode and electrode polarizing. The present disclosure has an excellent compactness and a good chemical stability. And the piezoelectric sensor made of the lead-free piezoelectric ceramic sensor material has a high sensitivity, a strong working stability, an excellent piezoelectric and has a high Curie temperature.