초록 ▼

An internally nucleated, toughened cordierite glass-ceramic is disclosed. The cordierite glass-ceramic has good oxidation resistance and fracture toughness and coefficient of thermal expansion rivaling that of silicon nitride. The glass-ceramic may be cast as a liquid. Annealing produces a material

An internally nucleated, toughened cordierite glass-ceramic is disclosed. The cordierite glass-ceramic has good oxidation resistance and fracture toughness and coefficient of thermal expansion rivaling that of silicon nitride. The glass-ceramic may be cast as a liquid. Annealing produces a material of high crystallinity combining high hardness, high Young's modulus, good thermal stability, high strength, low density and good dielectric properties. The glass-ceramic comprises interlocking crystalline phases dominated by cordierite and a second phase having an elongated or acicular structure. A third phase may comprise a crystalline ceramic that promotes acicularity of the second phase. The third phase is preferably capable of twinning.

대표청구항 ▼

What is claimed: 1. A cordierite glass-ceramic comprising at least three phases including: a) 50-80 vol. % of a first phase consisting essentially of cordierite having an aspect ratio of at least 2:1; b) 8-20 vol. % of a second phase consisting essentially of titanate having an aspect ratio of at l

What is claimed: 1. A cordierite glass-ceramic comprising at least three phases including: a) 50-80 vol. % of a first phase consisting essentially of cordierite having an aspect ratio of at least 2:1; b) 8-20 vol. % of a second phase consisting essentially of titanate having an aspect ratio of at least 5:1; and c) up to 20 vol. % of a third phase selected from a group consisting of anorthite, enstatite, aluminous enstatite, forsterite, fluormica, fluoramphibole, norbergite, Sr-feldspar, Ba-feldspar, spinel, sapphirine, mullite and xonotlite. 2. The cordierite glass-ceramic of claim 1, wherein the first phase has an aspect ratio of at least 5:1. 3. The cordierite glass-ceramic of claim 1, wherein the glass-ceramic comprises from 10-20 vol. % of the third phase. 4. A glass-ceramic having a CTE from 20-50��10-7/�� C. in the temperature range 25-300�� C. and a fracture toughness from 2.5 to 6.0 MPa.m0.5, the glass-ceramic formed from a composition comprising, in weight percent: SiO2 35-50% Al2O3 10-35% MgO 10-25% TiO2 7-20% CaO up to 5% SrO up to 10% F up to 5% provided that the sum of CaO and SrO comprises at least 0.5%, and wherein the glass-ceramic includes a microstructure comprising interlocking and acicular first and second crystal phases; and wherein the glass-ceramic includes a third crystal phase selected from the group consisting of forsterite, fluormica, fluoramphibole, norberaite, spine, sapphirine, mullite and xonotlite. 5. The glass-ceramic of claim 4, wherein the second phase comprises a titanate selected from a group consisting of magnesium titanate, aluminum titanate and combinations thereof 6. The glass-ceramic of claim 4, wherein the glass-ceramic further includes a crystal phase comprising a twinning ceramic compound selected from a group consisting of anorthite, Sr-feldspar, Ba-feldspar, enstatite, and aluminous enstatite.