Tungsten Oxide Powder Morphology Control for Low-Defect Intercalation
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Solution Overview
Problem
Existing methods for producing tungsten oxide powders with small particle sizes and low aspect ratios face issues such as grain growth, fracturing, and the formation of crystal defects, which adversely affect intercalation properties and stability.
Innovation Solution
A liquid phase synthesis method involving the preparation of an aqueous solution of tungstic acid, adjustment of pH to specific ranges, precipitation of tungstate crystals, drying, and firing in an oxygen-containing atmosphere to produce tungsten oxide powders with controlled particle sizes and aspect ratios, along with optional heat treatment for oxygen deficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If sublimation process using plasma flame is used to produce fine powders, then particle size is reduced to 50 nm or less, but grain growth occurs during heat treatment and aspect ratio increases to 10 or more
Solution Approach 1:
The patent changes the production method from sublimation to liquid phase synthesis, fundamentally altering the formation parameters. This results in powders with aspect ratios of 5 or less while maintaining fine particle sizes, eliminating the grain growth issue that occurs during sublimation heat treatment
Solution Approach 2:
The patent replaces the thermal field-based sublimation process with a chemical field-based liquid phase synthesis method. This substitution allows for controlled crystallization in a liquid environment, producing equant particles with low aspect ratios without the high-temperature grain growth problems of sublimation
2Manufacturing precision
If heat treatment is repeated to remove defects, then powder purity is improved, but grain growth occurs and aspect ratio increases to 10 or more
Solution Approach 1:
The patent performs preliminary crystallization control during the liquid phase synthesis process itself, forming well-defined crystals with low aspect ratios before any heat treatment is applied. This preliminary structure formation eliminates the need for repeated heat treatments that would otherwise cause grain growth and increase aspect ratio
Solution Approach 2:
The patent changes the crystallization parameters by using liquid phase synthesis instead of vapor phase sublimation. This results in different crystal growth kinetics that produce equant particles with aspect ratios of 5 or less, maintaining shape integrity even after necessary heat treatments for defect removal
3Shape
If liquid phase synthesis method is used, then aspect ratio is reduced to 5 or less, but many crystal defects are formed
Solution Approach 1:
The patent optimizes the liquid phase synthesis parameters including pH adjustment to specific ranges and controlled cooling rates. These parameter changes enable controlled crystallization that produces particles with aspect ratios of 5 or less while minimizing crystal defects through proper formation conditions
Solution Approach 2:
The patent employs pH adjustment as a feedback mechanism to control the crystallization process. By monitoring and adjusting pH levels during synthesis, the process ensures formation of crystals with appropriate morphology and minimal defects, achieving both low aspect ratio and high crystalline quality
4Reliability
If high temperature heat treatment is applied to produce oxygen deficiency, then intercalation property is improved, but grain growth occurs and particle size increases
Solution Approach 1:
The patent changes the thermal treatment parameters by applying heat treatment at controlled temperatures for specific durations to achieve oxygen deficiency. This optimized thermal processing creates the desired intercalation properties while preventing excessive grain growth and maintaining fine particle sizes through controlled kinetic conditions
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 yields tungsten oxide powders with average particle sizes of 10 μm or less, aspect ratios of 10 or less, and controlled crystal defects, enhancing intercalation properties and reducing fracture risk, suitable for applications in batteries, photocatalysts, and electrochromic devices.
Implementation Method 1
preparation of an aqueous solution of tungstic acid, adjustment of pH to specific ranges, precipitation of tungstate crystals
Implementation Method 2
firing in an oxygen-containing atmosphere to produce tungsten oxide powders with controlled particle sizes and aspect ratios, along with optional heat treatment for oxygen deficiency
Data Source
AI summary
According to one embodiment, a tungsten oxide powder is provided. The tungsten oxide has an average particle size along a major axis of 10 μm or less, an average aspect ratio of 10 or less, and 0 to 4 crystal defects per unit area of 9 nm2 on a surface or sectional surface in a direction of a minor axis of a primary particle.