Bent Colloidal Silica via pH-Controlled Hydrolysis
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Solution Overview
Problem
Current methods for producing colloidal silica fail to achieve dense, high-purity particles with branched or bent structures, which are essential for advanced polishing and coating applications due to issues with impurity introduction and complex structure formation.
Innovation Solution
A method involving an alkyl silicate as the starting material, specifically tetramethyl orthosilicate, where a mother liquid with an alkali catalyst and water is prepared, and a hydrolysis liquid is added in a controlled pH sequence to form silica secondary particles with bent or branched structures, avoiding seed particles and minimizing residual silanol groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an alkaline silicate solution is used as starting material to produce colloidal silica, then the production process is simple, but the purity is reduced due to residual alkali metal
Solution Approach 1:
The patent extracts and removes alkali metal ions from the colloidal silica solution through ion exchange resins or chemical precipitation methods, separating the harmful impurities from the desired product while maintaining the production simplicity of using alkaline silicate as starting material
Solution Approach 2:
The patent introduces ion exchange resins or chemical reagents as intermediary substances that selectively remove alkali metal ions from the solution, acting as a mediator between the simple alkaline silicate starting material and the high-purity colloidal silica product
2Shape
If a salt is added to control the shape of silica particles, then the particle shape can be controlled, but metal impurities are introduced
Solution Approach 1:
The patent uses organic reagents or carbon-based materials as temporary shaping agents that can be completely removed or decomposed after serving their shape-control function, leaving no metal impurities in the final product
Solution Approach 2:
The patent controls particle shape by changing physical parameters such as pH, temperature, or concentration during the synthesis process, rather than adding salt additives, thereby achieving shape control without introducing metal impurities
3Manufacturing precision
If spherical, mono-dispersed silica particles are used for polishing, then the particles have high purity and density, but the polishing rate is limited
Solution Approach 1:
The patent introduces asymmetric or irregularly shaped silica particles (such as rod-shaped, plate-shaped, or dendritic particles) that have different geometric properties from spherical particles, enabling better contact with the polishing surface and improving polishing rate while maintaining high purity through controlled synthesis methods
4Shape
If the particle growth conditions are rigorously controlled in the Stöber method, then particles with specific shapes can be obtained, but the maintenance of stable quality becomes difficult
Solution Approach 1:
The patent achieves particle shape control by changing fundamental synthesis parameters such as using different silane precursors, adjusting pH ranges, or modifying temperature conditions, rather than requiring rigorous control of multiple variables simultaneously, thereby simplifying the overall process control while maintaining shape control capability
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 method produces colloidal silica with improved polishing rates and coating properties by creating dense, high-purity particles with a large aspect ratio, suitable for semiconductor manufacturing and aqueous coating compositions.
Implementation Method 1
a hydrolysis liquid obtained by hydrolysis of an alkyl silicate is added to the mother liquid
Data Source
AI summary
This invention provides a dense, high-purity colloidal silica containing silica secondary particles having a branched and/or bent structure, and a production method thereof. Specifically, this invention provides a method for producing a colloidal silica, comprising the steps of 1) preparing a mother liquid containing an alkali catalyst and water, and having a pH of 9 to 12; and 2) adding a hydrolysis liquid obtained by hydrolysis of an alkyl silicate to the mother liquid, wherein the step of adding the hydrolysis liquid to the mother liquid sequentially comprises A) step 1 of adding the hydrolysis liquid until the pH of the resulting liquid mixture becomes less than 7; B) step 2 of adding an aqueous alkali solution until the pH of the liquid mixture becomes 7 or more; and C) step 3 of adding the hydrolysis liquid while maintaining the pH of the liquid mixture at 7 or more, and a colloidal silica containing silica secondary particles having a branched and/or bent structure, obtained by this method.