Composite Crucible Mullite Reinforcement for Sagging

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Solution Overview

Problem

Conventional vitreous silica crucibles used in silicon crystal manufacturing lack sufficient high-temperature strength and durability, leading to issues like inward sagging and potential cracking, and require costly and hazardous coatings or stabilization layers.

Innovation Solution

A composite crucible design featuring a vitreous silica body with a mullite reinforcement layer on the upper end portion, combined with an opaque and transparent vitreous silica layer configuration, which enhances high-temperature strength and durability while maintaining cost-effectiveness and ease of handling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a conventional vitreous silica crucible is used, then the crucible can be manufactured at low cost and handled easily, but the high-temperature strength is insufficient leading to inward sagging and cracking

Engineering Contradiction:

Improvehigh-temperature strengthVSAvoidmanufacturing cost and complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent applies composite materials by combining vitreous silica (providing chemical inertness and ease of manufacture) with mullite reinforcement layers (providing high-temperature strength and resistance to sagging). The mullite layer contains alumina and silica in specific proportions, creating a composite structure that achieves both mechanical strength and manufacturing feasibility at high temperatures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by placing mullite reinforcement layers specifically at the upper end portion of the crucible where sagging and cracking occur most frequently. This localized reinforcement provides high-temperature strength exactly where needed, rather than uniformly throughout the entire crucible, thus maintaining cost-effectiveness while solving the strength problem.

Inventive Principle:

Principle #3Local quality

2Strength

If stabilization layers or coatings are applied to improve high-temperature strength, then the strength increases, but the manufacturing cost increases and hazardous materials are required

Engineering Contradiction:

Improvehigh-temperature strengthVSAvoidhazardous coatings and manufacturing cost

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by carefully controlling the chemical composition parameters of the mullite layer, specifically the alumina-to-silica ratio and the presence of crystallization promoters. By optimizing these parameters, the mullite layer achieves high-temperature strength without requiring hazardous stabilization coatings, and the composition is designed to prevent cracking while maintaining structural integrity.

Inventive Principle:

Principle #35Parameter changes

3Strength

If the crucible structure is reinforced to prevent sagging, then the high-temperature strength improves, but the handling characteristics may deteriorate

Engineering Contradiction:

Improvehigh-temperature strengthVSAvoidhandling characteristics

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The patent applies local quality by restricting the mullite reinforcement layer to the upper end portion of the crucible rather than the entire structure. This localized approach provides the necessary high-temperature strength where sagging occurs most, while keeping the lower and middle portions as conventional vitreous silica that maintains good handling characteristics and thermal shock resistance.

Inventive Principle:

Principle #3Local quality

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 composite crucible exhibits improved high-temperature strength, prevents inward sagging, and allows for long-term use without cracking, while maintaining the handling characteristics of conventional vitreous silica crucibles, thus enabling efficient silicon crystal production at lower costs.

Implementation Method 1

the difference in the thermal expansion coefficient between mullite and vitreous silica can cause formation of cracks in the crucible during heating the crucible

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

a composite crucible comprising a vitreous silica crucible body having a sidewall portion and a bottom portion, and a reinforcement layer provided on an outer surface side of an upper end portion of the vitreous silica crucible body

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS9527763B2Method of manufacturing composite crucible

Publication Date: 2016.12.27 SUMCO CORP

AI summary

A method of manufacturing a composite crucible includes: supplying mullite material powder to an upper region of a mold, and supplying second silica powder to a lower region provided below the upper region while rotating the mold; supplying third silica powder on an inner surface side of a layer made of the mullite material powder and the second silica powder; heating and fusing the mullite material powder, the second silica powder, and the third silica powder to form an opaque vitreous silica layer provided on the outer surface of the crucible, a transparent vitreous silica layer provided on an inner surface side of the crucible, and a mullite reinforcement layer provided on the outer surface side of an upper end portion of the crucible.