Alpha-Alumina Abrasive Particles Using Alkali Metal Oxides
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Solution Overview
Problem
The availability of rare earth oxides, commonly used in alpha-alumina abrasive particles, has become limited, driving up costs and posing a challenge in maintaining superior abrasive performance in abrasive applications such as grinding stainless steel.
Innovation Solution
The development of abrasive particles comprising specific weight percentages of alpha-Fe2O3 seed particles, MgO, Li2O or alkali metal oxides, and Al2O3, which are formed through a process involving an alpha-alumina precursor dispersion, peptizing agents, and sintering, allowing for equivalent or superior abrasive performance without relying on rare earth oxides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rare earth oxides are used as modifiers in alpha-alumina abrasive particles, then abrasive performance is improved, but cost increases and supply becomes limited
Solution Approach 1:
The patent replaces expensive rare earth oxides with cheaper, more abundant alkali metal oxides (Li2O, Na2O, K2O) and MgO as modifiers in alpha-alumina abrasive particles. This substitution maintains abrasive performance while eliminating dependence on scarce and costly rare earth materials, directly addressing the technical contradiction between performance and manufacturing ease.
Solution Approach 2:
The patent modifies the chemical composition parameters of the abrasive particles by incorporating specific weight percentages of alkali metal oxides (0.02-0.40 wt% Li2O or equivalent molar amounts of other alkali metal oxides) and MgO (0.50-5.00 wt%). These parameter changes enable the material to achieve superior abrasive performance without using rare earth oxides, resolving the contradiction between performance reliability and manufacturing accessibility.
2Reliability
If seed particles are added to the dispersion, then abrasive performance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates seed particles (alpha-Fe2O3 or alpha-Al2O3) into the dispersion before gelling and sintering processes. This preliminary action allows the seed particles to serve as nucleation sites during sintering, controlling crystal growth and enhancing abrasive performance. The seed particles are added in controlled amounts (0.50-5.00 wt%) to achieve desired performance without excessive manufacturing complexity.
Solution Approach 2:
The patent creates a composite structure by combining seed particles with alpha-alumina precursor and modifiers in the dispersion. This composite approach allows the seed particles to influence the microstructure and properties of the final abrasive particles, enhancing performance while maintaining a relatively simple manufacturing process through uniform mixing and conventional sintering.
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
These abrasive particles exhibit superior abrasive performance, comparable to or exceeding that of commercially available alpha-alumina abrasive particles containing rare earth oxides, while avoiding the cost and supply issues associated with them, with negligible effects on non-seeded alpha-alumina-based particles.
Implementation Method 1
They are made by preparing a dispersion (e.g., a sol) comprising water, an alpha-alumina precursor such as, e.g., alumina monohydrate (boehmite), and optionally peptizing agent (e.g., an acid such as nitric acid), then gelling the dispersion, drying the gelled dispersion
Implementation Method 2
gelling the dispersion, drying the gelled dispersion, crushing the dried dispersion into particles
Implementation Method 3
calcining the particles to remove volatiles, and sintering the calcined particles at a temperature below the melting point of alpha-alumina
Data Source
Figure 1~4
AI summary
Abrasive particles include: 0.50 to 5.00 weight percent of seed particles for alpha-alumina formation selected from the group consisting of alpha-Fe2O3 seed particles, alpha-Al2O3 seed particles, and combinations thereof; 0.50 to 5.00 weight percent of MgO; 0.02 to 0.40 weight percent of Li2O or a molar equivalent amount of at least one alkali metal oxide selected from the group consisting of: Na2O; K2O; combinations of Na2O and Li2O; combinations of K2O and Li2O; combinations of Na2O and K2O; and combinations of Li2O, Na2O, and K2O; and 91.08 to 99.48 weight percent of Al2O3. Methods of making the abrasive particles and abrasive articles incorporating them are also disclosed.