Solution-processed selective solar absorption coatings and methods of preparation thereof

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Solution Overview

Problem

Conventional selective solar absorption coatings face challenges with poor spectral selectivity and thermal instability, particularly at high temperatures, and are costly to produce due to complex high-vacuum fabrication processes.

Innovation Solution

A solution-processed selective solar absorption coating comprising an infrared reflector, an absorptive coating of ceramic nanoparticles such as transition metal nitrides or borides, and an SiO2 antireflection coating, prepared using a low-cost, solution-based method, providing excellent spectral selectivity and thermal stability up to 1,000 K.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If high-vacuum fabrication techniques (physical vapor deposition, chemical vapor deposition, lithographic methods) are used to produce selective solar absorption coatings, then manufacturing precision and coating quality are improved, but device complexity and production cost increase

Engineering Contradiction:

Improvecoating qualityVSAvoidfabrication process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex high-vacuum mechanical deposition systems with a simple solution-based dip-coating process. Instead of using physical vapor deposition or chemical vapor deposition equipment requiring high vacuum environments, the invention uses liquid precursor solutions that can be applied by simple immersion and drying, dramatically simplifying the fabrication process while maintaining coating quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the physical state of the coating material from vapor phase (requiring vacuum) to liquid solution phase (allowing ambient processing). By formulating precursors as soluble compounds that decompose to form the desired coating, the process parameters shift from vacuum maintenance and controlled deposition to simple solution application and thermal treatment

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional solution-based methods with resin binders are used, then ease of manufacture is improved, but thermal stability deteriorates at high temperatures

Engineering Contradiction:

Improvefabrication simplicityVSAvoidthermal stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent removes the resin binder component entirely from the coating formulation. By using inorganic precursor solutions that decompose to form pure inorganic coatings, the invention eliminates the organic binder that would otherwise decompose at high temperatures, thereby maintaining both solution-based fabrication simplicity and high-temperature thermal stability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the chemical composition of the coating from organic-resin-based to inorganic-oxide-based. This parameter change allows the coating to withstand high temperatures without decomposition, while the solution-based application method remains simple and low-cost

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If spectrally selective coatings are designed to reflect infrared radiation, then thermal emittance is reduced, but solar absorptance may be compromised

Engineering Contradiction:

Improvethermal radiation lossVSAvoidsolar energy absorption

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The patent applies different optical properties to different wavelength ranges through the coating structure. The porous TiO2-SiO2 composite structure provides high solar absorptance in the visible and near-infrared spectrum while the SiO2 matrix and pore structure provide infrared reflection, achieving spectral selectivity with high solar gain and low thermal emission

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention uses a composite material system combining TiO2 nanoparticles with SiO2 matrix. This composite provides synergistic properties: TiO2 absorbs solar radiation effectively while SiO2 provides infrared reflection and structural stability, achieving both high solar absorptance and low thermal emittance simultaneously

Inventive Principle:

Principle #40Composite materials

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 coating achieves high solar absorptance (up to 95%) with low thermal emittance (3% at 300 K and 22% at 1,000 K), demonstrating improved thermal stability and potential for large-scale, cost-effective production.

Implementation Method 1

an infrared reflector... The coating achieves high solar absorptance (up to 95%) with low thermal emittance (3% at 300 K and 22% at 1,000 K)

Methodology Applied

Scientific EffectInfrared reflection: Reflection

Implementation Method 2

an absorptive coating comprising ceramic nanoparticles selected from the group consisting of transition metal nitrides, transition metal borides, transition metal carbides... perfectly absorb sunlight in the visible-NIR range

Methodology Applied

Scientific EffectSolar absorption: Absorption (EM radiation)