Self-Cleaning Radiative Cooling Ceramic With Porous Composite Structure
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Solution Overview
Problem
Current radiative cooling ceramics are susceptible to contamination by dust and pollutants, compromising their mechanical strength and cooling efficiency, despite their high porosity and sunlight reflectivity.
Innovation Solution
A self-cleaning daytime passive radiative cooling ceramic with a base layer of closed pores and a protective hydrophobic glass layer, combined with a manufacturing process using micron-sized hollow glass microspheres and metal oxides, enhances mechanical strength and prevents pollutant intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the porosity of radiative cooling ceramics is increased to enhance sunlight reflectivity and infrared emissivity, then cooling efficiency is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent employs a composite ceramic structure combining multiple materials (e.g., aluminum oxide, silicon oxide, titanium oxide) to achieve both high porosity for radiative cooling and sufficient mechanical strength. The composite nature allows optimization of both cooling performance and structural integrity simultaneously.
Solution Approach 2:
The ceramic structure features non-uniform pore distribution with different pore sizes and densities in different regions. The surface layer has optimized porosity for maximum sunlight reflection and infrared emission, while deeper layers maintain higher density to provide mechanical support and strength.
2Loss of energy
If the open-pore structure of radiative cooling ceramics is used to enhance cooling performance, then radiative efficiency is improved, but susceptibility to contamination by dust and pollutants worsens
Solution Approach 1:
The ceramic surface is equipped with self-cleaning functionality through photocatalytic properties. When exposed to sunlight, the ceramic generates reactive oxygen species that decompose organic pollutants and hydrophobic coatings that cause water to form droplets that roll off, carrying away dust particles. This allows the ceramic to automatically clean itself without external intervention.
Solution Approach 2:
The ceramic incorporates photocatalytic materials (such as titanium oxide) that generate strong oxidizing agents when exposed to ultraviolet light. These oxidants actively decompose organic pollutants and prevent accumulation of dust and contaminants on the surface, maintaining cooling efficiency over time.
3Temperature
If the porosity of radiative cooling ceramics is increased to enhance sunlight reflectivity, then cooling performance is improved, but mechanical robustness deteriorates
Solution Approach 1:
The ceramic is structured as a multi-layered system with distinct functional zones. The surface layer contains optimized pore structures for maximum radiative cooling, while intermediate and substrate layers have progressively higher density to provide mechanical strength and structural stability, segmenting the functions of cooling and support.
Solution Approach 2:
The patent optimizes key parameters including pore size distribution (ranging from micrometer to nanometer scales), porosity gradient (varying from surface to depth), and material composition ratios to achieve the optimal balance between radiative cooling performance and mechanical robustness.
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 ceramic achieves efficient radiative cooling with improved mechanical strength and resistance to pollution, maintaining cooling performance by preventing dust and pollutant ingress.
Implementation Method 1
These materials can reflect up to more than 90% of solar light with their unique surface configurations, inhibiting heat absorption from solar radiation. Concurrently, they're capable of transmitting their internal heat to the frigid vastness of outer space (3K), by harnessing the atmospheric transparency window (8-13 μm), manifesting as long-wave infrared radiation.
Implementation Method 2
reflect up to more than 90% of solar light with their unique surface configurations
Implementation Method 3
This layer, made of a transparent, dense, and hydrophobic glass material, is placed on the side of the base layer away from the surface to be cooled. Having a thickness of 5 μm-20 μm, this protective layer provides a hydrophobic self-cleaning feature and further prevents pollutant intrusion.
Data Source
AI summary
This invention pertains to the field of refrigeration materials, unveiling a novel ceramic designed for daytime passive radiative cooling endowed with a self-cleaning capability, along with its preparation method. The architectural design of this cooling ceramic incorporates a base layer composed of a porous composite ceramic, characterized by its intricate structure of closed pores arranged according to a varied grading of sizes, potentially enhanced with an additional protective layer. The method of preparation involves integrating a polymer solution with metal oxides and micron-sized hollow glass microspheres to craft a malleable slurry. This slurry is then shaped within a mold, compacted under pressure to form a preliminary structure, which is subsequently dried and sintered, culminating in the production of a porous composite ceramic specifically engineered for radiative cooling.