Silicon-Enhanced SWNT Synthesis via Composite Target Vaporization
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Solution Overview
Problem
The dual pulsed laser vaporization (DPLV) synthesis of single wall carbon nanotubes (SWNTs) faces challenges in maintaining high yield and purity due to the clogging of SWNT deposits in small diameter tube furnaces and the decrease in SWNT percentage when switching to larger diameters, indicating that the confinement and availability of silicon play crucial roles in SWNT production.
Innovation Solution
Incorporating silicon oxide particles into the metal catalyst loaded graphitic targets, which are then vaporized using pulsed lasers in a larger diameter tube furnace without a plume confinement tube, to enhance the yield and purity of SWNTs by maintaining a consistent silicon presence in the vaporization plume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a small diameter tube furnace is used for DPLV synthesis, then SWNT yield and purity are maintained high through plume confinement, but the furnace clogs with SWNT deposits limiting production duration
Solution Approach 1:
The invention removes the plume confinement tube from the synthesis system, extracting the constraint that limited production duration. By eliminating the tube that would clog with SWNT deposits, the system can operate for extended periods without maintenance while still achieving high purity through the silicon-containing catalyst composition.
Solution Approach 2:
The invention changes the chemical composition parameters of the catalyst from pure metal to silicon-containing metal catalyst (e.g., FeSi, CoSi, NiSi with 1-20 at% Si). This parameter change fundamentally alters the synthesis mechanism, enabling high SWNT purity without requiring physical confinement, thus resolving the contradiction between purity maintenance and production duration.
2Duration of action of stationary object
If a larger diameter tube furnace is used to avoid clogging, then production duration is extended, but SWNT percentage decreases due to loss of plume confinement
Solution Approach 1:
The invention changes the catalyst composition to include silicon (1-20 at% Si in metal catalyst), which fundamentally alters the vaporization and nucleation process. This chemical parameter change replaces the need for physical confinement (small diameter tube), allowing large diameter furnaces to maintain high SWNT purity while extending production duration.
Solution Approach 2:
Silicon acts as an intermediary element in the catalyst composition, mediating the vaporization process to produce silicon-containing metal clusters that selectively catalyze SWNT formation. This intermediary silicon component enables high purity SWNT synthesis in large diameter furnaces without plume confinement, resolving the contradiction between furnace size and SWNT purity.
3Manufacturing precision
If silicon oxide particles are incorporated into the metal catalyst loaded graphitic target, then silicon presence in the vaporization plume is maintained, but the target composition complexity increases
Solution Approach 1:
The invention uses composite target material comprising metal catalyst particles (Fe, Co, or Ni) combined with silicon oxide (SiO2) and graphite. This composite composition ensures controlled silicon release during laser vaporization, maintaining consistent silicon presence in the plume to achieve high SWNT purity, while the composite structure manages the complexity through well-defined material combinations.
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 approach significantly increases the percentage of SWNTs produced, with minimal degradation over extended production runs, as evidenced by higher Haddon purity indices and increased yield, suggesting that silicon plays a critical role in the nucleation and growth of SWNTs.
Implementation Method 1
vaporizing at least a portion of the metal catalyst loaded graphitic target with pulsed lasers directed at the metal catalyst loaded graphitic target
Implementation Method 2
The pulsed lasers can generate Nd:YAG laser of 532 nm and 1064 nm wavelengths
Implementation Method 3
The tube furnace can be heated to about 1200° C
Implementation Method 4
The silicon oxide particles can be silicon (IV) oxide particles
Data Source
AI summary
Various examples are provided related to synthesis of single wall carbon nanotubes (SWNTs). In one example, a method includes providing a vapor including a metal catalyst, silicon at a level of about 10 at % of the metal catalyst with balance carbon; synthesizing single wall carbon nanotubes (SWNTs) from the vapor; and collecting the synthesized SWNTs. The vapor including the metal catalyst, silicon and carbon can be provided in a variety of ways. Synthesis of the SWNTs can be an oxygen free synthesis.