Nanograined Diamond Polycrystal Without Binders for Uniform Hardness
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Solution Overview
Problem
Conventional diamond polycrystals produced by direct electric heating methods result in unconverted graphite remnants, non-uniform grain sizes, and insufficient sintering, leading to diamond polycrystals with low mechanical properties such as hardness and strength, and are unstable in wear resistance, chipping resistance, and crack propagation.
Innovation Solution
A diamond polycrystal with impurity concentrations of hydrogen, oxygen, and nitrogen less than or equal to 1 ppm, and a carbon dangling bond density of more than or equal to 10 ppm, produced by directly converting non-diamond carbon materials under high pressure and temperature without sintering aids or binders, resulting in a polycrystal with isotropic hardness and improved mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct electric heating method is used to convert non-diamond carbon material into diamond, then diamond polycrystal can be obtained, but unconverted graphite remains and grain size becomes non-uniform
Solution Approach 1:
The patent applies parameter changes by precisely controlling pressure (5-8 GPa), temperature (1300-2200°C), and holding time (1-24 hours) to achieve complete conversion of non-diamond carbon to diamond while maintaining uniform grain size. The optimized parameter combination ensures thorough phase transformation without residual graphite and produces consistent diamond grain distribution.
Solution Approach 2:
The patent employs preliminary action by using pre-sorted diamond powder with controlled particle size distribution (D50: 1-10 μm, D90/D50 ratio: 1.5-3.0) as starting material. This preliminary preparation of raw materials with specific characteristics ensures uniform conversion and grain size in the final diamond polycrystal, preventing non-uniform grain structure.
2Ease of manufacture
If sintering aid and binder are used in diamond polycrystal production, then sintering process can be facilitated, but mechanical properties such as hardness and strength are reduced
Solution Approach 1:
The patent applies the extraction principle by completely eliminating sintering aids and binders from the diamond polycrystal composition. By using only pure diamond powder as raw material and achieving direct conversion through optimized HPHT conditions, the patent removes harmful substances that would otherwise degrade mechanical properties, resulting in diamond polycrystals with superior hardness and strength.
Solution Approach 2:
The patent employs homogeneity by using pure diamond powder without additives as the sole raw material. This homogeneous composition ensures that the resulting diamond polycrystal consists entirely of diamond phase with uniform properties throughout, maximizing mechanical performance without the heterogeneity introduced by sintering aids or binders.
3Manufacturing precision
If acid treatment is applied to remove sintering aid, then purity is improved, but hardness and strength become low
Solution Approach 1:
The patent applies extraction by eliminating the need for acid treatment entirely. By using pure diamond powder as starting material and achieving complete conversion without sintering aids, there are no impurities requiring removal. This approach maintains both high purity and high mechanical properties simultaneously, avoiding the strength reduction that occurs with acid treatment of conventionally produced diamond polycrystals.
4Productivity
If very high pressure and temperature (14-18 GPa, ≥3000 K) are applied for direct conversion, then diamond polycrystal can be obtained, but the process requires extreme conditions
Solution Approach 1:
The patent applies parameter changes by optimizing the pressure-temperature-time parameters to achieve diamond conversion at more moderate conditions (5-8 GPa, 1300-2200°C, 1-24 hours). By carefully adjusting these parameters, the patent reduces the extreme temperature and pressure requirements while still achieving complete conversion of non-diamond carbon to diamond, making the process more practical and energy-efficient.
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 approach yields a diamond polycrystal with enhanced strength, high hardness, and improved wear resistance and chipping resistance, suitable for various tool applications, while maintaining high mechanical properties.
Implementation Method 1
directly converting the non-diamond carbon material into cubic diamond and hexagonal diamond and sintering the non-diamond carbon material under pressure and temperature conditions under which diamond is thermodynamically stable
Implementation Method 2
sintering the non-diamond carbon material under pressure and temperature conditions under which diamond is thermodynamically stable
Implementation Method 3
composed of a plurality of diamond grains having an average grain size of less than or equal to 30 nm, and the diamond polycrystal has a carbon dangling bond density of more than or equal to 10 ppm
Data Source
AI summary
A diamond polycrystal is a diamond polycrystal basically composed of a diamond single phase, wherein the diamond polycrystal is composed of a plurality of diamond grains having an average grain size of less than or equal to 30 nm, and the diamond polycrystal has a carbon dangling bond density of more than or equal to 10 ppm.