Hexagonal Tungsten Oxide Production via pH-Controlled Sol-Gel
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Solution Overview
Problem
Existing methods for producing tungsten oxide typically result in monoclinic phases, which lead to slow discoloration rates and poor stability in electrochromic devices due to low charge mobility of electrolytes, whereas hexagonal tungsten oxide offers faster discoloration and improved stability but requires high temperature and high pressure processes or unsafe reducing atmospheres.
Innovation Solution
A method for producing hexagonal tungsten oxide at atmospheric pressure using an alkaline solvent with a pH of 8 to 9, adding tungsten chloride and an additive such as an amine compound or aliphatic hydrocarbon derivative, followed by strong acid addition to form nanoparticles, which are then separated, washed, dried, and heat-treated, allowing for the formation of hexagonal tungsten oxide without high temperature and high pressure conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If monoclinic tungsten oxide is used, then the material is stable at room temperature, but the charge mobility of electrolytes is low resulting in slow discoloration rate
Solution Approach 1:
The patent changes the crystal phase parameter of tungsten oxide from monoclinic to hexagonal by controlling the pH of the reaction solution (pH 2-9) and using specific additives during the sol-gel process. This parameter change transforms the material structure to achieve both high stability and fast discoloration rate simultaneously.
2Productivity
If hexagonal tungsten oxide is produced using conventional methods, then fast discoloration rate is achieved, but high temperature and high pressure processes or reducing atmospheres are required
Solution Approach 1:
The patent introduces an intermediary alkaline environment (pH 2-9) during the sol-gel process that mediates the formation of hexagonal tungsten oxide nanoparticles. This intermediary condition allows the hexagonal phase to form at room temperature without requiring high temperature, high pressure, or reducing atmosphere conventional methods.
Solution Approach 2:
The patent replaces the mechanical/thermal system (high temperature and pressure equipment) with a chemical system (pH-controlled sol-gel process). By substituting the manufacturing mechanism from thermal processing to chemical precipitation, the process becomes simpler and safer while producing the desired hexagonal phase.
3Quantity of substance
If monoclinic tungsten oxide nanoparticles are deposited, then the thin film has high density, but the inter-particle distances are small reducing charge mobility
Solution Approach 1:
The patent applies local quality by creating a hexagonal crystal structure with specific local atomic arrangement that naturally provides wider inter-particle distances and channels for ion transport. The local crystal structure quality is optimized to balance film density with charge mobility requirements.
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
This method enables the production of hexagonal tungsten oxide with enhanced charge mobility and stability, facilitating faster discoloration and improved cycling stability in electrochromic devices without the need for hazardous conditions or high-pressure processes, enabling mass production with improved safety and efficiency.
Implementation Method 1
adding tungsten chloride to the alkaline solvent to form a first reaction solution
Implementation Method 2
adding strong acid to the second reaction solution to form nanoparticles
Implementation Method 3
adding an additive to the first reaction solution to form a second reaction solution
Implementation Method 4
separating the precipitated nanoparticles through a centrifugal separation method
Implementation Method 5
heat treating the dried nanoparticles to form dry powder
Data Source
AI summary
Provided is a method for producing hexagonal tungsten oxide, the method including preparing an alkaline solvent having a pH of 8 to 9, which contains at least one of water or alcohol, adding tungsten chloride to the alkaline solvent to form a first reaction solution, adding an additive to the first reaction solution to form a second reaction solution, and adding strong acid to the second reaction solution to form nanoparticles. The additive includes any one of an amine compound having 1 to 8 carbon atoms or an aliphatic hydrocarbon derivative having 10 or more carbon atoms.