Binder-Free Diamond Polycrystal for Hardness and Crack Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional diamond polycrystals have high hardness but insufficient toughness and cracking resistance, while ultra-high hardness nano twin-crystal diamond bulk materials have very high hardness but inadequate toughness and cracking resistance.
Innovation Solution
A diamond polycrystal with a Vickers hardness ratio (d′/d) of less than or equal to 0.98, composed of diamond grains with an average size of less than 100 nm, and without a binder phase, achieving high hardness and fracture toughness through direct conversion of non-diamond carbon materials at high pressure and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sintering aid and binder are used to obtain diamond polycrystal by sintering at high pressure and temperature, then the diamond polycrystal can be formed, but the mechanical properties such as hardness and strength decrease
Solution Approach 1:
The patent removes the binder phase from the diamond polycrystal structure by using acid treatment to dissolve and eliminate the binder, thereby eliminating its detrimental effect on mechanical properties while preserving the diamond grains and their bonding
Solution Approach 2:
The patent changes the chemical environment by introducing acid treatment as a post-processing step, which chemically dissolves the binder phase without affecting the diamond grains, thereby transforming the material composition to improve mechanical properties
2Temperature
If acid treatment is used to remove sintering aid, then heat resistance is improved, but hardness and strength become low
Solution Approach 1:
The patent introduces a specific acid treatment process as an intermediary step between sintering and final product formation, which selectively removes the binder phase while preserving the diamond grain structure, thereby achieving both heat resistance and high strength
Solution Approach 2:
The patent creates a composite structure where diamond grains are densely packed and bonded without a binder phase, achieving a material that combines the heat resistance of diamond with high strength through the absence of weak binder phases
3Strength
If non-diamond carbon material is directly converted to diamond at very high pressure and temperature, then no sintering aid or binder is needed, but the toughness and cracking resistance remain insufficient
Solution Approach 1:
The patent divides the carbon material into ultra-fine particles (average diameter of 1 μm or less) before conversion, creating numerous small diamond grains that can pack densely and bond effectively, thereby improving toughness and cracking resistance while maintaining high hardness
Solution Approach 2:
The patent optimizes the pressure and temperature parameters within specific ranges (5-15 GPa and 1500-2500°C) to achieve complete conversion of carbon particles to diamond grains with optimal size and bonding characteristics, balancing hardness and toughness
4Reliability
If diamond grains with small average size are used, then fracture toughness is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary size reduction of carbon particles to ultra-fine dimensions (1 μm or less) before the high-pressure high-temperature conversion process, ensuring that the resulting diamond grains are uniformly small and densely packed, thereby achieving good fracture toughness without excessive manufacturing complexity
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 diamond polycrystal exhibits excellent cracking resistance and high fracture toughness, suitable for high-load and micro-processing tools, maintaining high hardness and wear resistance without the mechanical property deterioration caused by binders.
Implementation Method 1
a non-diamond carbon material, such as graphite, glassy carbon, amorphous carbon, or onion-like carbon, can be directly converted into diamond at very high pressure and temperature without using a sintering aid and the like
Implementation Method 2
A conventional diamond polycrystal is obtained by sintering a diamond powder, which is a raw material, together with a sintering aid and a binder at high pressure and high temperature
Data Source
AI summary
In a diamond polycrystal, a value of a ratio (d′/d) of d′ to d is less than or equal to 0.98 in a Vickers hardness test performed under a condition defined in JIS Z 2244:2009, where the d represents a length of a diagonal line of a first Vickers indentation formed in a surface of the diamond polycrystal when a Vickers indenter with a test load of 4.9 N is pressed onto the surface of the diamond polycrystal, and the d′ represents a length of a diagonal line of a second Vickers indentation remaining in the surface of the diamond polycrystal after releasing the test load.