Photocatalyst Coating Suppresses Substrate Corrosion
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Solution Overview
Problem
Existing photocatalyst-coated bodies face challenges in maintaining effective decomposition of harmful gases and durability while preventing substrate corrosion, especially for organic substrates, with previous compositions either compromising photocatalytic activity or substrate stability.
Innovation Solution
A photocatalyst-coated body with a photocatalyst layer comprising 3-5% titanium oxide particles, 85-97% silica particles, and up to 10% binder, applied using a photocatalytic coating liquid with similar composition, which suppresses direct contact between photocatalyst and substrate to prevent corrosion and maintains hydrophilicity and photocatalytic activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of photocatalyst in the photocatalyst layer is increased to enhance decomposition of harmful gases, then the photocatalytic activity is improved, but the substrate (especially organic substrate) may be decomposed or deteriorated by the photocatalytic action
Solution Approach 1:
The patent introduces an intermediate layer between the photocatalyst layer and the organic substrate. This intermediate layer acts as a mediator that prevents direct contact between the photocatalyst and the substrate, thereby blocking the harmful photocatalytic decomposition of the substrate while allowing the photocatalytic activity to function. The intermediate layer is specifically designed to be transparent to UV light so that the photocatalytic action can still occur without damaging the underlying organic material.
Solution Approach 2:
The patent divides the coating structure into multiple segments: a photocatalyst layer containing titanium oxide particles, an intermediate layer separating it from the substrate, and the organic substrate itself. This segmentation allows each layer to perform its specific function independently - the photocatalyst layer decomposes harmful gases, the intermediate layer protects the substrate, and the substrate provides structural support.
2Stability of the object's composition
If an intermediate layer is provided to protect the substrate from photocatalytic deterioration, then substrate stability is improved, but the complexity of the coating structure increases
Solution Approach 1:
The intermediate layer is designed to perform multiple functions simultaneously: it protects the organic substrate from photocatalytic decomposition, maintains the structural integrity of the coating system, and allows UV light transmission to enable photocatalytic activity. By consolidating these multiple functions into a single layer, the patent reduces overall system complexity compared to having separate protective and functional layers.
3Strength
If the amount of binder in the photocatalyst layer is increased to improve coating properties, then film strength and weatherability are improved, but the photocatalytic activity may be reduced due to lower photocatalyst content
Solution Approach 1:
The patent optimizes the parameters of the photocatalyst layer by carefully controlling the ratio of photocatalyst particles to binder. The specification defines a specific range where the binder content is limited to 5-50 parts by weight per 100 parts by weight of photocatalyst, which corresponds to 5-33 wt% binder in the total photocatalyst layer. This parameter optimization ensures sufficient film strength and weatherability while maintaining adequate photocatalytic activity.
Solution Approach 2:
The patent creates a composite photocatalyst layer combining titanium oxide photocatalyst particles with a binder material. This composite structure allows the binder to provide mechanical strength and adhesion properties while the dispersed photocatalyst particles maintain their photocatalytic functionality. The synergistic combination of these materials achieves both film integrity and photocatalytic performance.
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 solution effectively maintains long-term hydrophilicity and photocatalytic activity, enhancing weatherability and decomposition of harmful gases, even in tropical regions with high UV exposure, while reducing substrate corrosion and production costs by eliminating the need for intermediate layers.
Implementation Method 1
a photocatalyst such as titanium oxide has been used in many applications such as an exterior material of an architectural structure. By use of a photocatalyst, various kinds of harmful substances can be decomposed utilizing a photo-energy
Implementation Method 2
dirt attached onto the surface of a substrate can be easily washed out with water by hydrophilizing the surface thereof coated with a photocatalyst
Data Source
AI summary
Disclosed is a photocatalyst-coated body with various excellent properties, especially excellent decomposition property of harmful gases and durability of a self-cleaning property based on the long term hydrophilicty of the photocatalyst, while suppressing corrosion of a substrate, especially of an organic substrate. The photocatalyst-coated body comprises a substrate and a photocatalyst layer formed on the substrate, wherein the photocatalyst layer contains, as its main components, photocatalyst particles in the range between more than 3% by mass and less than 5% by mass and inorganic oxide particles in the range between more than 85% by mass and less than 97% by mass, relative to 100% by mass of totality of the photocatalyst layer.