Glass-Ceramic Article with Crystalline Shell for Transparency and Crack Resistance
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Solution Overview
Problem
Existing glass-ceramic materials struggle to achieve a balance between transparency and durability, as higher crystallinity for durability leads to lower transparency and vice versa, and current methods for forming glass-ceramics often result in suboptimal transparency and crack resistance.
Innovation Solution
A glass-ceramic article is developed with a composition of 25 mol %≤silica≤60 mol %, 12.5 mol %≤alumina≤45 mol %, and 12.5 mol %≤strontium oxide≤45 mol %, featuring a mostly amorphous interior surrounded by a crystalline shell with crystals oriented within 15 degrees of orthogonal to the major surfaces, and a method of manufacturing involving heat treatment and surface nucleation to create a crystalline shell around an amorphous interior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crystalline phase content is increased to improve durability and crack resistance, then the transparency of the glass-ceramic article deteriorates
Solution Approach 1:
The glass-ceramic article is segmented into two distinct regions: a crystalline shell layer and an amorphous interior layer. This segmentation allows each region to fulfill its optimal function - the crystalline shell provides crack resistance and durability, while the amorphous interior maintains high transparency. The article is divided into these functional zones rather than using a uniform composition throughout.
Solution Approach 2:
Different regions of the glass-ceramic article have different local compositions and properties. The shell layer has a crystalline structure with specific composition (25-60 mol% silica, 12.5-45 mol% alumina, 12.5-45 mol% strontium oxide) optimized for mechanical strength, while the interior has an amorphous structure optimized for optical clarity. Each local region is tailored to its specific functional requirements.
2Illumination intensity
If the amorphous phase content is increased to improve transparency, then the durability and crack resistance of the glass-ceramic article deteriorates
Solution Approach 1:
The glass-ceramic article is segmented into two distinct regions: a crystalline shell layer and an amorphous interior layer. This segmentation allows each region to fulfill its optimal function - the crystalline shell provides crack resistance and durability, while the amorphous interior maintains high transparency. The article is divided into these functional zones rather than using a uniform composition throughout.
Solution Approach 2:
Different regions of the glass-ceramic article have different local compositions and properties. The shell layer has a crystalline structure with specific composition (25-60 mol% silica, 12.5-45 mol% alumina, 12.5-45 mol% strontium oxide) optimized for mechanical strength, while the interior has an amorphous structure optimized for optical clarity. Each local region is tailored to its specific functional requirements.
3Reliability
If homogeneous nucleation is used to form crystals throughout the glass-ceramic, then crack resistance is improved, but transparency is significantly reduced
Solution Approach 1:
The harmful effect of widespread crystallization is extracted and confined to only the shell region. Instead of homogeneous nucleation distributing crystals throughout the entire article, the crystallization process is taken out and localized to the shell layer through controlled heterogeneous nucleation. This extraction of crystallization to specific regions preserves transparency in the interior while still providing crack resistance where crystals are present.
Solution Approach 2:
Heterogeneous nucleation sites are introduced at the surface or in the shell region before the crystallization process begins. This preliminary placement of nucleation sites ensures that crystals form only in the desired shell region during subsequent heat treatment, preventing unwanted crystallization in the interior and maintaining the transparency-durability balance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The glass-ceramic article achieves high transparency, with at least 80% of light in the visible spectrum being transmitted axially, while also enhancing durability by preventing crack propagation through the tortuous path created by the crystalline shell, thus addressing the limitations of existing glass-ceramic materials.
Implementation Method 1
Glass-ceramics are partially crystalline materials that can be formed by crystallizing a portion of amorphous glass. Crystallization can occur through some form of nucleation, such as homogeneous nucleation and heterogeneous nucleation.
Implementation Method 2
Crystallization can occur through some form of nucleation, such as homogeneous nucleation and heterogeneous nucleation.
Implementation Method 3
at least 80% of light having a wavelength in a range from 400 nm to 800 nm that is incident upon one of the first major surface or the second major surface the glass-ceramic article is transmitted axially through the glass-ceramic article to the other of the first major surface or the second major surface
Implementation Method 4
a method of manufacturing involving heat treatment and surface nucleation to create a crystalline shell around an amorphous interior
Data Source
AI summary
Embodiments of the disclosure relate to glass-ceramic or crystalline article. The article includes 25 mol %≤silica≤60 mol %, 12.5 mol %≤alumina≤45 mol %, and 12.5 mol %≤strontium oxide≤45 mol %. According to certain embodiments, an interior of the article is mostly amorphous glass, and the interior is at least partially surrounded by a shell that is mostly crystalline. The shell defines a first major surface on a first side of the interior and a second major surface opposite to the first major surface on a second side of the interior. According to certain other embodiments, the article is a crystalline article in which columnar crystals grow inwardly from opposing surfaces and meet at about a midline of the article.