Nebulizer RF Plasma Torch for Nanoparticle Size Control
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Solution Overview
Problem
Current RF plasma-based techniques struggle to produce a large volume fraction of nanoparticles with diameters below 100 nm, resulting in a significant portion of particles having larger diameters that need to be rejected in nanoparticle production, due to the high probability of droplet coalescence and the inability to control particle size distribution effectively.
Innovation Solution
A method involving the formation of nebulized droplets using a nebulizer and feeding them into a radio frequency plasma torch, where the central gas is gradually replaced by an aerosol stream, allowing for the production of nanoparticles with over 50% of the total volume contributed by particles less than 50 nm, utilizing a plasma reactor coupled with a nebulizer and a modified RF plasma torch to achieve precise control over nanoparticle sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pre-atomized solution/suspension droplets are fed into the plasma region via a thin cooled probe, then the plasma synthesis process can proceed, but the droplet coalescence probability increases significantly due to the constricted probe diameter
Solution Approach 1:
The system segments the droplet delivery process by separating the nebulization function from the plasma injection function. A nebulizer generates droplets that are then carried by a carrier gas through a relatively large diameter tube (e.g., 1/4 inch) to the plasma region, avoiding the constricted probe path that causes coalescence. This segmentation allows each component to optimize its function without the constraints of a unified narrow probe design.
Solution Approach 2:
A carrier gas acts as an intermediary medium to transport the nebulized droplets from the nebulizer to the plasma region. This intermediary approach replaces direct probe insertion with a gas-phase transport mechanism, allowing droplets to be delivered without physical contact with constricted probe walls that would promote coalescence.
2Ease of manufacture
If a high-pressure water-cooled two-fluid type probe atomizer is used, then the atomization process can be maintained, but the droplet size remains too large (20-120 μm) for nanoparticle production
Solution Approach 1:
The system changes the operating parameters of droplet generation by using a nebulizer designed for fine droplet production rather than a probe atomizer. The nebulizer operates with different pressure and flow parameters that produce droplets in the sub-100 nm range, fundamentally altering the droplet size distribution to suit nanoparticle synthesis requirements.
Solution Approach 2:
The patent replaces the mechanical probe atomization system with a nebulization system that uses ultrasonic vibration or gas shear forces to generate droplets. This substitution of the droplet generation mechanism enables production of much smaller droplets suitable for nanoparticle synthesis while eliminating the limitations of probe-based atomization.
3Device complexity
If the probe is inserted directly into the plasma torch, then the droplet delivery path is established, but no scavenging mechanism can be attached to remove large droplets
Solution Approach 1:
The system moves the droplet delivery problem from a one-dimensional probe insertion geometry to a three-dimensional gas flow field. By using a carrier gas to transport droplets through a larger diameter tube to the plasma region, the system creates spatial room for additional components such as scavenging mechanisms while maintaining effective droplet delivery.
4Manufacturing precision
If current RF plasma-based techniques are used, then particles in the sub-100 nm range can be produced, but the majority of particle volume is concentrated in particles larger than 100 nm
Solution Approach 1:
The system performs preliminary size selection by using a nebulizer to generate droplets with a narrow size distribution centered in the sub-100 nm range before these droplets enter the plasma region. This preliminary action ensures that the starting material is already optimized for nanoparticle production, preventing the formation of large particles that would otherwise dominate the volume distribution.
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 effectively reduces the formation of unwanted large particles, achieving a high percentage of nanoparticles with diameters under 50 nm, with more than 70% of the total volume contributed by particles less than 50 nm, significantly improving the control over nanoparticle production in the 5-50 nm size range.
Implementation Method 1
feeding said plurality of nebulized droplets into a radio frequency plasma torch to generate a plurality of nanoparticles
Implementation Method 2
forming a plurality of nebulized droplets... nebulizing a liquid precursor
Data Source
AI summary
Methods of generating nanoparticles are described that comprises feeding nebulized droplets into a radio frequency plasma torch to generate nanoparticles, wherein the majority of the nanoparticles generated have a diameter of less than about 50 nm. These methods are useful for synthesizing nanoparticles of metals, semiconductors, ceramics or any other material class where the precursors are either in liquid form or can be dissolved or suspended in a suitable liquid. Methods of feeding nebulized droplets and central gas into a radio frequency plasma torch and apparatus for generating nanoparticles are also described.