Abstract: The invention pertains to hardware such as cutting tools with improved performance, wear-resistance and durability made from sintered polycrystalline aluminum nitride based ceramic composites containing secondary or dispersed phases for enhanced toughness. The articles of this invention provide good hardness, toughness, chemical inertness, thermal stability, lubricity, wear-resistance, and the ability to operate in the presence of liquid coolants, yielding good surface finish and long lifetime. The cutting tools of this invention are applicable to a wide range of industrial, biomedical, commercial and other applications.

Abstract: The present disclosure relates to porous ceramic articles and a method of making the same. The porous ceramic articles have microstructure of sinter bonded or reaction bonded large pre-reacted particles and pore network structure exhibiting large pore necks. The method of making the porous ceramic articles involves using pre-reacted particles having one or more phases. A plastic ceramic precursor composition is also disclosed. The composition includes a mixture of at least one of dense, porous, or hollow spheroidal pre-reacted particles and a liquid vehicle.

Abstract: A method of making an object using mold casting, comprising the steps of applying a slip mixture into a mold fabricated by 3D printing or additive manufacturing technique, and firing the mold containing the slip mixture. A composition of a slip mixture for use with a mold fabricated by 3D printing or additive manufacturing technique, the composition comprising calcium aluminate, from 10% to 60% by weight, and a filler. Such method and composition can provide efficient and economically viable ways of fabricating objects having complex shapes and high density.

Abstract: The invention relates to novel transparent glasses, vitroceramics, and transparent or translucent ceramics containing, in relation to the total composition of the glass, vitroceramic, or ceramic, at least 60 wt% of a composition having the following formula (I): (M1O)x(M2O)y(M3)2O3)z(Al2O3)100?x?y?z (I), where M1 is an element selected from among Ba and/or Sr, M2 is an element selected from among Mg or Ca, x and y are numbers such that 30?x+y?80, y is between 0% and 10% of x, M3 is an element selected from among B, Ga, or In, and z is a number between 0% and 10% of (100?x?y). The invention also relates to the method for manufacturing said compositions and to the uses of said compositions in the field of optics.

Abstract: Mixer for ceramic feedstock pellets with a tank, a mixing means, and heat exchange means including cooling means for the cooling of the content of this tank. Control means control the heat exchange means which include heating means arranged to heat the content of this tank to a temperature comprised between a lower temperature (TINF) and a higher temperature (TSUP) stored in a memory for a specific mixture, and the heating means exchange energy with a heat exchange and mixing temperature maintenance circuit, external to this tank, and wherein the thermal inertia of this circuit is higher than that of this fully loaded tank. The invention also concerns a method for mixing raw material for powder metallurgy, implementing a specific injection moulding composition and a specific binder.

Abstract: Disclosed herein are emissive ceramic elements having low amounts of certain trace elements. Applicants have surprisingly found that a lower internal quantum efficiency (IQE) may be attributed to specific trace elements that, even at very low amounts (e.g., 50 ppm or less), can cause significant deleterious effects on IQE. In some embodiments, the emissive ceramic element includes a garnet host material and an amount of Ce dopant. The emissive ceramic element may, in some embodiments, have an amount of Na in the composition less than about 67 ppm, an amount of Mg in the composition less than about 23 ppm, or an amount of Fe in the composition less than about 21 ppm.

Abstract: The invention provides novel paving stones and construction block composite materials and methods for preparation thereof. The paving stones and construction block composite materials can be readily produced from widely available, low cost precursor materials by a production process that involves compacting in a mold that is suitable for large-scale production. The precursor materials include calcium silicate, for example, wollastonite, and particulate filler materials which can comprise silicon dioxide-rich materials. Additives can include calcium carbonate-rich and magnesium carbonate-rich materials. Various additives can be used to fine-tune the physical appearance and mechanical properties of the composite material, such as colorants such as particles of colored materials, such as, and pigments (e.g., black iron oxide, cobalt oxide and chromium oxide).

Abstract: A method for producing an ? alumina sintered body for the production of a sapphire single crystal characterized in that a relative density is 60% or more, a closed porosity is 10% or less, a purity is 99.99% by mass or more, each content of Si, Na, Ca, Fe, Cu and Mg is 10 ppm or less, and a volume is 1 cm3 or more, and the ? alumina sintered body can be obtained by mixing 100 parts by weight of an ? alumina with 1 part by weight or more and 20 parts by weight or less of an ? alumina precursor to obtain a mixture, forming a compact from the obtained mixture, and firing the obtained compact.

Abstract: Disclosed herein are emissive ceramic materials having a dopant concentration gradient along a thickness of a yttrium aluminum garnet (YAG) region. The dopant concentration gradient may include a maximum dopant concentration, a half-maximum dopant concentration, and a slope at or near the half-maximum dopant concentration. The emissive ceramics may, in some embodiments, exhibit high internal quantum efficiencies (IQE). The emissive ceramics may, in some embodiments, include porous regions. Also disclosed herein are methods of make the emissive ceramic by sintering an assembly having doped and non-doped layers.

Abstract: A silicon nitride material is disclosed which has properties beneficial for efficient operation of a corona discharge igniter system in an internal combustion gas engine.

Abstract: A member covered with a hard coating according to the present invention has a hard coating which has excellent erosion resistance, a hardness (H) of 20 GPa or more as measured using a nano indenter and a ratio of the hardness (H) to a Young's modulus (E) (i.e., H/E) of 0.06 or more, and comprises Ti and/or Cr, Al and N, wherein the total amount of Ti and Cr relative to the total amount of elements other than non-metal elements in the coating is 0.1 to 0.6 inclusive in terms of atomic ratio and the amount of Al relative to the total amount of the elements other than the non-metal elements in the coating is 0.4 to 0.7 inclusive in terms of atomic ratio.

Abstract: A method of treating a preceramic material includes providing a preceramic polycarbosilane or polycarbosiloxane material that includes a moiety Si—O—M, where Si is silicon, O is oxygen and M is at least one metal, and thermally converting the preceramic polycarbosilane or polycarbosiloxane that includes the moiety Si—O—M material into a ceramic material.

Abstract: A sintered compact contains cubic sialon, ?-sialon, and at least one of a first component and a second component. The first component is at least one element selected from the group consisting of iron, cobalt, nickel, and group 4 elements, group 5 elements, and group 6 elements of the periodic table. The second component is at least one compound containing at least one element selected from the group consisting of group 4 elements, group 5 elements, and group 6 elements and at least one element selected from the group consisting of carbon, nitrogen, and boron.

Abstract: The invention provides a modified perovskite type composite oxide in which the particle surface of a perovskite type composite oxide is coated with a first component of at least one selected from TiO2 and SiO2 and a second component of at least one selected from a group consisting of Al, Zr, Nd, La, Ce, Pr, and Sm, wherein the coating is formed by hydrolyzing at least one selected from a hydrolyzable TiO2 precursor and a hydrolyzable SiO2 precursor as a source of the first component and a salt of at least one selected from a group consisting of Al, Zr, Nd, La, Ce, Pr, and Sm as a source of the second component, and then calcining them.

Abstract: The invention relates to a ceramic particle mixture containing, as components, a predominant portion by weight of frittable particles made of a ceramic material and particles of at least one additive, at least one additive being a dispersed absorbent solid inorganic material which has, for a laser beam emitted at a predetermined wavelength, a specific absorptivity that is greater than the absorptivity of the other components of the ceramic mixture, and which drastically breaks down when gas is emitted in the presence of the laser beam, said additive being present in proportions of less than 5% of the dry weight. The invention also relates to ceramic parts produced from such a mixture.

Abstract: Feed material comprising uniform solution precursor droplets is processed in a uniform melt state using microwave generated plasma. The plasma torch employed is capable of generating laminar gas flows and providing a uniform temperature profile within the plasma. Plasma exhaust products are quenched at high rates to yield amorphous products. Products of this process include spherical, highly porous and amorphous oxide ceramic particles such as magnesia-yttria (MgO—Y2O3). The present invention can also be used to produce amorphous non oxide ceramic particles comprised of Boron, Carbon, and Nitrogen which can be subsequently consolidated into super hard materials.

Abstract: The present invention relates to a composition for forming a friable-resistant dielectric porcelain material. The present invention also relates to a friable-resistant dielectric porcelain material formed from the composition of the present invention, a method of making a friable-resistant dielectric porcelain material, a friable-resistant dielectric porcelain material formed by the method of the present invention, a dielectric porcelain material comprising a particular composition, and a system for producing ozone using the dielectric porcelain material of to the present invention.

Abstract: An oxide sintered body having zinc oxide as a main component and containing magnesium, and a transparent conductive substrate are provided, and an oxide sintered body having zinc oxide and magnesium, wherein content of magnesium is from 0.02 to 0.30 as atom number ratio of Mg/(Zn+Mg); an oxide sintered body having zinc oxide, magnesium, gallium and/or aluminum, wherein content of gallium and/or aluminum is over 0 and equal to or lower than 0.09 as atom number ratio of (Ga+Al)/(Zn+Ga+Al), and content of magnesium is from 0.02 to 0.30 as atom number ratio of Mg/(Zn+Ga+Al+Mg); a target obtained by processing these oxide sintered bodies; and a transparent conductive film formed on a substrate by a sputtering method or an ion plating method, by using this target.

Abstract: A thin-film spectrally selective coating for receiver tube of vacuumed type for use in thermodynamic solar installations and operating both at medium temperature (up to 400° C.) and at high temperature (up to 550° C.), coating where the optically absorbing layer is a multilayer of cermet material of type: WyN—AlNx or MoyN—AlNx, material prepared with reactive co-sputtering technique from an Al target and a W or Mo target, process conducted under a transition regimen, under PFM (Plasma Emission Monitoring) or CVM (Cathode Voltage Monitoring) monitoring for the sole Al target, with inletting near the Al target of a N2 amount adequate for obtainment of a high-transparency, high growth rate sub-stoichiometric ceramic AlN and with inletting near the W or Mo target of a N2 amount adequate for obtainment of the sole W2N or Mo2N phase, phase very stable at high temperature, such as to make the cermet material as close as possible to the formulation W2N—AlNx or Mo2N—AlNx (with x comprised between 0.90 and 1.

Abstract: Disclosed is a process for producing ceramic particles, such as proppants, that have at least 10 percent total porosity. The process includes forming a particle precursor that includes 5 percent to 30 percent of a first ceramic material and at least 40 percent of a second ceramic material. The sintering temperature of the first ceramic material may be lower than the sintering temperature of a second ceramic material. Heating the precursor to a maximum temperature above the sintering temperature of the first material and below the sintering temperature of the second material. Also disclosed is a ceramic article that has a particular combination of chemistry and alumina crystalline phase.

Abstract: This invention relates to partially ordered and ordered oxynitride perovskites of the general formula ABO2N that are polar insulators. A comprises one or more cations or set of cations that sit in sites derived from the A-site in the perovskite structure. B comprises one or more cations or set of cations that sit in sites derived from the B-site in the perovskite structure. C comprises oxygen, O, with optionally some nitrogen, N, and D comprises N, with optionally some O. The total valence of the cations A+B is equal to the total valence of the anions 2 C+D. Also disclosed are methods of producing such oxynitride perovskites and uses of such oxynitride perovskites.

Abstract: A ceramic precursor batch composition comprising inorganic ceramic-forming ingredients, a binder, an aqueous solvent and a heteroatom polyol agent. The heteroatom polyol agent can be represented by X(R) where X is at least one of S, N, and P, and R is at least two of CH3, CH2CH2OH, CH2CH2CH2OH, CH2(CHOH)CH3, C(CH2OH)1-3, CH2OH, CH(CH2OH)CHOH, C(O)(CHOH)1-4CH2OH, and CH2CH2CH2OCH3. The presence of the heteroatom polyol agent provides a composition with a lower viscosity and/or a greater batch stiffening temperature (Tonset) allowing for increased rates of extrusion. Methods for producing a ceramic honeycomb body using this ceramic precursor batch composition are also provided.

Abstract: A method for manufacturing enamel layer includes the steps of: a substrate is provided; a spray paint is provided, the spray paint includes liquid fuel and enamel powders; providing a spraying device for spraying the spray paint, the liquid fuel of the spray paint spayed by the spraying device fires to heat and sinter the enamel powder to deposit on the substrate and form the enamel layer. The article manufactured by the method is also provided.

Abstract: A dielectric layer for an electrostatic chuck is formed of a ceramic material having a first phase including aluminum oxide and a second phase including composite carbonitride (Ti, Me)(C, N) that contains titanium as fine grains. The Me represents a transition element and metals of Group 4 to Group 6 such as Mo and W. The ceramic material that includes the second phase by 0.05 vol % to 2.5 vol % has a volume resistivity value of about 108 to 1013 (?·cm) necessary for a Johnsen-Rahbek type electrostatic chuck.

Abstract: The present invention relates to a process of forming ceramic articles that contain a high percentage of recycled alumina silicate in their composition. The fabrication process includes a fusing of the base material forming a reticulated network that is in-filled with a melted additive composition. The base material gives the article dimensional stability and strength while the additive composition gives the article water resistance and toughness In this invention, an additive powder with an engineered melting temperature is added to the recycled base material. The mixture is heated until the recycled aluminosilicate reaches the optimal fusing temperature. Heating is continued until the additive begins to melt filling the voids between the fused aluminosilicates particles. The article is then rapidly cooled to quench the fusing without cracking.

Abstract: A porous ceramic (honeycomb) structure skin coating and a method of producing a porous ceramic structure skin coating which provides a hardshell, strong, acid- and alkali-resistant, chip-resistant ceramic honeycomb structure coating which resists pollution control catalyst from being absorbed into the skin coating.

Abstract: A transparent, polycrystalline ceramic is described. The ceramic comprises crystallites of the formula AxCuByDvEzFw, whereby A and C are selected from the group consisting of Li+, Na+, Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Al3+, Ga3+, In3+, C4+, Si4+, Ge4+, Sn2+/4+, Sc3+, Ti4+, Zn2+, Zr4+, Mo6+, Ru4+, Pd2+, Ag2+, Cd2+, Hf4+, W4+/6+, Re4+, Os4+, Ir4+, Pt2+/4+, Hg2+ and mixtures thereof, B and D are selected from the group consisting of Li+, Na+, K+, Mg2+, Al3+, Ga3+, In3+, Si4+, Ge4+, Sn4+, Sc3+, Ti4+, Zn2+, Y3+, Zr4+, Nb3+, Ru3+, Rh3+, La3+, Lu3+, Gd3+ and mixtures thereof, E and F are selected mainly from the group consisting of the divalent anions of S, Se and O and mixtures thereof, x, u, y, v, z and w satisfy the following formulae 0.125<(x+u)/(y+v)?0.55 z+w=4 and at least 95% by weight of the crystallites display symmetric, cubic crystal structures of the spinel type, with the proviso that when A=C=Mg2+ and B=D=Al3+, E and F cannot both be O.

Abstract: The binder for monolithic refractories according to the present invention includes SrAl2O4; SrAl2O4 and 5 mass % or less of the remainder; or a mixture of SrAl2O4 and Al2O3.

Abstract: A sintered body includes an indium oxide crystal, and an oxide solid-dissolved in the indium oxide crystal, the oxide being oxide of one or more metals selected from the group consisting of aluminum and scandium, the sintered body having an atomic ratio “(total of the one or more metals)/(total of the one or more metals and indium)×100)” of 0.001% or more and less than 45%.

Abstract: Provided is a mono- or multilayer ceramic substrate which exhibits a high flexural strength. The substrate contains a sintered ceramic which includes respective crystal phases of quartz, alumina, fresnoite, sanbornite, and celsian, in which the relationship between the diffraction peak intensity A in the (201) plane of the fresnoite and the diffraction peak intensity B in the (110) plane of the quartz, measured by a powder X-ray diffractometry in the range of the diffraction peak angle 2?=10 to 40°, is A/B?2.5. The fresnoite crystal phase preferably has an average crystal grain size of 5 ?m or less. In firing to obtain this ceramic sintered body, the maximum temperature falls within the range of 980 to 1000° C.

Abstract: A conductive sintered oxide including: a first crystal phase represented by RE14Al2O9 and a second crystal phase having a perovskite structure represented by (RE21-cSLc)(AlxM1y)O3. RE1 is a first element group consisting of Yb and/or Lu and at least one element selected from Group IIIA elements excluding Yb, Lu and La. RE2 is a second element group consisting of at least one element selected from Group IIIA elements excluding La and including at least one of the elements constituting the first element group RE1. SL is an element group consisting of at least one of Sr, Ca and Mg and which includes Sr as a main element, and M1 is an element group consisting of at least one element selected from Groups IVA, VA, VIA, VIIA and VIII excluding Cr. The coefficient c is in the range of 0.18<c<0.50, and the coefficients x and y are in the range of 0.95?x+y?1.1.

Abstract: A sintered electroconductive oxide forming a thermistor element has a first crystal phase having a composition represented by RE14Al2O9 and a second crystal phase having a perovskite structure represented by (RE21-aSLa)MO3. The factor a of the second crystal phase is: 0.18<a<0.50, wherein RE1 represents at least one of Yb and Lu and at least one species selected from among group 3A elements excluding Yb, Lu, and La; RE2 represents at least one species selected from among group 3A elements excluding La and which contains at least one species selected from the group RE1; M represents Al and at least one species selected from group 4A to 7A, and 8 elements; and SL represents Sr, Ca, and Mg, with at least Sr being included at a predominant proportion by mole.

Abstract: A sintered particle has the following chemical analysis, as percentages by weight: ZrO2 partially stabilized with CeO2 and Y2O3: complement to 100%; Al2 10%-60%; additive selected from CaO, a manganese oxide, La2O3, SrO, BaO, and mixtures thereof: 0.2%-6; the quantity of CaO being less than 2%; impurities: <2%; the zirconia being stabilized with CeO2 and Y2O3 present in quantities such that, as molar percentages based on the sum of ZrO2, CeO2 and Y2O3: CeO2: 6 mol %-11 mol %; and Y2O3: 0.5 mol %-2 mol %; the particle being obtained by sintering at a sintering temperature higher than 1300° C., the sintering temperature being higher than 1400° C. if the additive is CaO or if the molar CeO2 content is in the range 10% to 11%.

Abstract: New process for obtaining lithium aluminosilicate-based (LAS) ceramic materials having a near-zero and negative thermal expansion coefficient within a temperature range of (?150° C. to 450° C.). These materials are applicable to the manufacture of components that require a high level of dimensional stability.

Abstract: The present invention provides a proton conducting thin film having a dense nanometric ceramic material with a relative density of at least about 90% and a grain size of less than about 30 nm, wherein the proton conducting thin film is capable of operating at temperatures of less than about 100° C. in the presence of water vapor. The present invention also provides an electrochemical device using the proton conducting thin film, and a method of making the proton conducting thin film.

Abstract: A process for producing a porous ceramic body may include: a) mixing a coated porogen with a silicate or an oxide ceramic precursor, wherein the porogen is decomposable to gaseous decomposition products and optionally solid products upon heating, and is coated with a coated agent; b) forming a green body from the mixture obtained in step (a); and c) firing the green body obtained in step (b) to obtain the ceramic body, whereby the porogen decomposes to form pores within the ceramic body, and the coating agent is deposited at the inner surface of the pores. The porogen may be coated with a coating agent which, upon firing, is deposited at the inner surface of the ceramic pores, so that porous ceramics having decreased weight and improved porosity are obtained, while maintaining good mechanical strength. A green body and porous ceramic body obtainable with the above-mentioned process are also described.

Abstract: The oxide matrix composite material is obtained by subjecting a fiber composed of at least one oxide or complex oxide and a matrix composed of at least one oxide or complex oxide to composite formation. For the fiber and the matrix, a component composition is selected such that the fiber and the matrix keep thermodynamic equilibrium to each other in a temperature range not exceeding the melting temperature, and a fiber diameter of the fiber at the time of equilibrium keeps ½ or more of a fiber diameter of the fiber at the start of the composite formation.

Abstract: A cBN sintered body tool has a cBN sintered body which includes 40 to 85% by volume of cBN, the remainder being a binder phase including at least one selected from at least one metal selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, Ni and Al, and at least one of a carbide, a nitride, a carbonitride, a boride and an oxide of these metals and mutual solid solutions thereof, and inevitable impurities. An amount of a Mo element contained in the cBN sintered body is 0.2 to 3.0% by weight based on a whole amount of the cBN sintered body.

Abstract: An additive manufacturing process includes providing a powder mixture having a ceramic constituent and a reactive metal constituent, and reacting and fusing the powder mixture with a directed energy source to form a geometry.

Abstract: A fragrant ceramic ornament and accessory with surface sandblasted and carved, includes a body of ornament and accessory, formed by a ceramic body capable of diffusing fragrance, wherein the ceramic body has a surface as an glaze layer or an electroplated layer which has concave pattern by sandblasting carving, wherein the concave pattern is an exposed portion of the ceramic body which loses the glaze layer or the electroplated layer and is concave on the surface of the ceramic body, wherein essential oil is absorbed into an inside of the ceramic body via the exposed portion. The surface carving is by a sandblasting process, which has long fragrance diffusing time and ability to change fragrance according to circumstances, so as to achieve an object of repeatedly using which is economical and environment-friendly, and prevent the perfume from contacting with the skin or clothes directly.

Abstract: The present invention is drawn to a lithia alumina silica material that exhibits a low CTE over a broad temperature range and a method of making the same. The low CTE of the material allows for a decrease in microcracking within the material.

Abstract: A molten alumina/zirconia grain mixture having the following chemical composition, in wt %: ZrO2+HfO2: 35 to 45.5%; Al2O3: 43.7 to 65%; other oxides: <10%; SiO2: <0.8%, which simultaneously adheres to a granulometric condition and to a densimetric condition.

Abstract: Disclosed is a method for making a refractory material from aluminum residues of aluminum recycling. At first, the aluminum residues is mixed with adhesive solution so that the percentage by weight of the adhesive solution is 5 wt % to 10 wt %. The mixture is granulated into grains. The grains are filled in a mold, pressed and then removed from the mold so that the grains are turned into a green body. The green body is heated in a furnace at a range of temperature from 1100° C. to 1400° C. so that the grains are sintered and become a refractory material.

Abstract: Provided is a method of producing carbon nanoparticles, involving: applying a mechanical shearing force to a graphite material in a ball mill container combined with a disc, the ball mill container configured to be rotatable in a first direction, and the disc configured to be rotatable in a second direction opposite to the first direction; and separating produced carbon nanoparticles from the graphite material. A method of producing an aluminum-carbon composite material, and an aluminum-carbon composite material obtained by such a method are also provided.

Abstract: Disclosed are cordierite bodies having relatively low thermal mass with good mechanical strength. The porous cordierite bodies generally include a primary cordierite ceramic phase as defined herein. Also disclosed are methods for making and using the cordierite bodies.

Abstract: New process for obtaining lithium aluminosilicate-based (LAS) ceramic materials having a near-zero and negative thermal expansion coefficient within a temperature range of (?150° C. to 450° C.). These materials are applicable to the manufacture of components that require a high level of dimensional stability.

Abstract: A process for preparing aluminum oxide with a low calcium content, in which (1) crude alpha- and/or gamma-aluminum oxide with a total calcium content in the range from 50 to 2000 ppm, based on the crude alpha- and/or gamma-aluminum oxide, is mixed with an aqueous solution or suspension comprising the compounds selected from the group of inorganic acid, organic acid and complexing agent, (2) the mixture from step (1) is admixed with a flocculating aid, (3) in the mixture of step (2), the solids are separated from the liquid, (4) the solids separated are mixed with water in the presence or in the absence of a flocculating aid, (5) in the mixture of step (4), the solids are separated from the liquid, (6) optionally, steps (4) and (5) are repeated once or more than once, (7) optionally, the solids separated optionally after addition of further compounds, are dried.

Abstract: A process of preparing a doped aluminum oxide, includes providing a solution comprising 8-hydroxyquinoline; an aluminum precursor; a dopant precursor, and a reaction solvent; isolating a precipitate from the solution; and calcining the precipitate to form the doped aluminum oxide. Compositions may be prepared which include tris(8-hydroxyquinolinato) aluminum and (8-hydroxyquinolinato)zM, wherein M is a metal ion and the value of z is equivalent to the oxidation state of the metal ion.

Abstract: Microparticles having crystalline needle or rod-shaped structures of, for example, an ettringite mineral grown and attached radially from their surface. A method including nucleating and growing crystalline needles/rods from the surface of a particle in the presence of a solution of calcium, sulfur, and aluminum such as calcium sulfoaluminate, lime and calcium sulfate is described. One example is the radial growth of ettringite needles on the surface of fly ash particles in calcium sulfoaluminate-based cement paste and concrete.

Abstract: A ceramic foam filter for molten aluminum alloys comprising an alumina silicate rich core and a boron glass shell and a chemical composition comprising: 20-70 wt % Al2O3, 20-60 wt % SiO2, 0-10 wt % CaO, 0-10 wt %; MgO and 2-20 wt % B2O3.