Biphasic Nanoporous Vitreous Carbon for Crack-Free Thick Sections
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Solution Overview
Problem
Vitreous carbon materials face limitations in thickness and exhibit cracks when attempting to form large-size articles with commercial utility, due to restrictive thickness constraints and poor structural integrity.
Innovation Solution
A biphasic nanoporous vitreous carbon material is produced by mixing particulate vitrified carbon with a precursor resin and firing under an inert atmosphere, incorporating optional additives for modifying properties, and using a build-up approach with a bonding medium to create larger, defect-free sections without reinforcement, utilizing solid lubricants like graphite or MoS2 to reduce cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pure vitreous carbon is used, then excellent tribological properties are achieved, but thickness is limited to maximum approximately 0.2 in.
Solution Approach 1:
The invention divides the vitreous carbon formation process into segments: first forming a green body with resin binder at room temperature or low temperature, then pyrolyzing to form vitreous carbon. This segmentation allows the resin to provide structural support during formation, enabling greater thickness without compromising tribological properties of the final carbon product.
Solution Approach 2:
The resin binder performs preliminary structural support and binding actions before the vitreous carbon is fully formed through pyrolysis. The resin matrix is applied in advance to hold particulate vitreous carbon together, enabling formation of thick sections that would otherwise be impossible, and this preliminary structure is later converted to carbon during pyrolysis.
2Length of stationary object
If copper fiber matrix is incorporated to overcome thickness limitation, then thickness constraint is overcome, but vitreous carbon exhibits cracks and poor structural integrity
Solution Approach 1:
The invention changes the key parameter from metal fiber reinforcement to organic resin binder, fundamentally altering the binding mechanism. The resin provides flexible, crack-resistant bonding that accommodates thermal and mechanical stresses during pyrolysis, eliminating the cracking issue inherent in rigid copper fiber reinforcements while maintaining thick-section capability.
Solution Approach 2:
The invention creates a composite material system combining particulate vitreous carbon with organic resin binder (such as phenolic resin). This composite approach allows the resin to provide structural integrity during formation and processing, while the vitreous carbon particles provide the desired tribological properties, achieving both thickness and structural integrity without cracks.
3Area of stationary object
If large-size vitreous carbon articles are formed, then commercial utility is achieved, but cracks and poor structural integrity occur
Solution Approach 1:
The formation process is segmented into green body fabrication followed by pyrolysis. The resin binder enables the green body to be formed at large sizes with good structural integrity at room temperature, and the subsequent pyrolysis converts this structure to vitreous carbon while maintaining the large size and integrity, avoiding cracks that would occur in direct high-temperature formation.
Solution Approach 2:
The resin binder acts as an intermediary material that enables large-size formation. It provides temporary structural support during green body fabrication and processing, allowing large dimensions to be achieved, and then transforms into part of the final carbon structure through pyrolysis, mediating between the need for large size and the requirement for crack-free integrity.
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
This method enables the production of crack-free vitreous carbon in unlimited thicknesses with enhanced tribological properties and reduced manufacturing time, achieving superior hardness and wear characteristics while minimizing porosity and shrinkage.
Implementation Method 1
firing under an inert atmosphere to produce a solid, glassy carbon body
Implementation Method 2
produce a solid, glassy carbon body
Implementation Method 3
utilizing solid lubricants like graphite or MoS2 to reduce cracking
Implementation Method 4
bonding the plurality of cured vitreous carbon precursor articles to one another with a bonding medium comprising the precursor resin
Data Source
AI summary
A biphasic nanoporous vitreous carbon material with a cementitious morphology characterized by presence of non-round porosity, having superior hardness and tribological properties, as useful for high wear-force applications. The biphasic nanoporous vitreous carbon material is produced by firing, under inert atmosphere, of particulate vitrified carbon in a composition containing (i) a precursor resin that is curable and pyrolyzable to form vitreous carbon and, optionally, (ii) addition of one or more of the following: solid lubricant, such as graphite, boron nitride, or molybdenum disulfide; a heat-resistant fiber reinforcement, such as copper, bronze, iron alloy, graphite, alumina, silica, or silicon carbide; or one or more substances to improve electrical conductivity, such as dendritic copper powder, copper “felt” or graphite flake, to produce a superior vitreous carbon that is useful alone or as a continuous phase in reinforced composites, in relation to conventional glassy carbon materials.