Titanium Surface Color Control via Anodizing and Spark Discharge
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Solution Overview
Problem
There is a need for a titanium material with lower lightness and chroma, specifically in the L*a*b* color space of L*: 30 to 40, a*: 2.0 to 9.0, and b*: −7.0 to 18.0, suitable for exterior materials requiring a subdued appearance, such as those used in Japanese-style buildings and temples.
Innovation Solution
A titanium material is manufactured by performing blast processing with alumina or SiC on the surface, followed by anodizing at a low voltage in an acid solution to form a thin titanium oxide layer, and then generating spark discharge in an electrolytic solution containing nitrate or nitrite ions to achieve the desired color characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional anodizing is performed to achieve color development, then various color tones can be manufactured, but the lightness and chroma are too high for subdued appearance requirements
Solution Approach 1:
The patent applies parameter changes by precisely controlling the anodizing voltage (10-30V), electrolyte composition (nitrate/nitrite concentration), and treatment time to achieve the desired balance between low lightness/chroma and maintained color variety. This systematic parameter optimization enables the titanium material to exhibit subdued appearance while preserving color development capability.
Solution Approach 2:
The patent employs preliminary action by performing blast processing with alumina or SiC before anodizing to create a controlled surface roughness (Ra: 2.0-4.0 μm). This pre-treatment prepares the surface to receive the anodized layer, enabling better control over the final appearance properties and facilitating the achievement of low lightness and chroma while maintaining color tones.
2Reliability
If the outermost layer is removed to decrease carbon concentration and suppress discoloration, then durability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent replaces mechanical removal methods (such as mechanical or chemical etching) with an electrochemical approach. By performing anodizing in nitrate or nitrite-containing electrolytes, the carbon concentration near the surface is controlled electrochemically, reducing the need for complex mechanical or chemical pre-treatment steps while achieving the same discoloration suppression effect.
Solution Approach 2:
The patent utilizes an inert environment by performing anodizing in controlled electrolyte solutions that prevent carbon intrusion during the electrochemical process. This creates a protected environment where the titanium surface is treated without exposure to carbon-containing atmospheres, thereby suppressing discoloration without requiring complex carbon removal procedures.
3Illumination intensity
If a thin titanium oxide layer is formed by low voltage anodizing, then lightness is reduced, but the layer thickness becomes difficult to control
Solution Approach 1:
The patent implements feedback control by establishing a voltage-time relationship where the anodizing voltage (10-30V) and treatment time are coordinated to achieve precise thickness control. The process monitors and adjusts these parameters to ensure the oxide layer reaches the desired thickness (60-300 nm by GDS measurement) while maintaining low lightness properties, thereby resolving the control difficulty.
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 resulting titanium material exhibits lower lightness and chroma, making it suitable for applications requiring a subdued appearance, with improved resistance to discoloration and a wide range of color tones, effectively addressing the need for materials like those used in Japanese-style exterior designs.
Implementation Method 1
performing anodizing at a low voltage in an acid solution to form a thin titanium oxide layer
Implementation Method 2
performing anodizing of generating spark discharge in an electrolytic solution containing either or both of nitrate ions and nitrite ions
Implementation Method 3
color development is caused by utilizing the interferential action of a titanium oxide layer of a titanium base material
Data Source
AI summary
The titanium material includes a titanium oxide layer formed on a surface of titanium being a base material, the titanium oxide layer having a thickness measured by a glow discharge spectrometry of 60 to 300 nm, wherein: the titanium oxide layer contains 0.5 to 7.0 at % of nitrogen, and an arithmetic mean roughness Ra of a surface thereof is 2.0 to 4.0 μm; and a power spectrum of a surface roughness of the titanium material has a peak of an amplitude height of 0.005 to 0.020 μm in a range of a wavelength of 1.1 to 2.5 μm and has a peak of an amplitude height of 0.0010 to 0.0030 μm in a range of a wavelength of 0.80 to 0.98 μm. An L*a*b* color space may be L*: 30 to 40, a*: 2.0 to 9.0, and b*: −7.0 to 18.0.