Low–power plasma torch method for the production of crystalline spherical ceramic particles

2001 ◽  
Vol 16 (5) ◽  
pp. 1256-1265 ◽  
Author(s):  
Chun-Ku Chen ◽  
Seth Gleiman ◽  
Jonathan Phillips
Keyword(s):  
Particle Size ◽  
Low Power ◽  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Particle Density ◽  
Particle Collision ◽  
Average Particle ◽  
The Impact

A low-power, atmospheric pressure, microwave plasma torch was used to make spherical alumina particles of controlled size from irregularly shaped precursor powders. Detailed studies of the impact of operating parameters, particularly gas identity (argon or air), gas flow rates, and applied power, showed that particle size changed in a predictable fashion. The most important factor in controlling particle size appears to be precursor particle density in the aerosol stream that enters the plasma hot zone. This and other facts suggest that particle collision rate is primarily responsible for determining ultimate particle size, although atomic addition also plays a role. Reproducible volume average particle sizes ranging from 97 to 1150 μm3 were formed from precursor particles of order 14 μm3. Moreover, for the first time we report the creation of an atmospheric pressure low-power air plasma (<1 kW).

Optical diagnostics of a low power—low gas flow rates atmospheric-pressure argon plasma created by a microwave plasma torch

2009 ◽  
Vol 18 (2) ◽  
pp. 025030 ◽  
Author(s):  
Chuji Wang ◽  
Nimisha Srivastava ◽  
Susan Scherrer ◽  
Ping-Rey Jang ◽  
Theodore S. Dibble ◽  
...  
Keyword(s):  
Low Power ◽  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Argon Plasma ◽  
Optical Diagnostics ◽  
Flow Rates ◽  
Microwave Plasma Torch

scholarly journals Influence of gas flow on argon microwave plasma jet at atmospheric pressure

2011 ◽  
Vol 206 (6) ◽  
pp. 1449-1453 ◽  
Author(s):  
Shouichiro Iio ◽  
Kosuke Yanagisawa ◽  
Chizuru Uchiyama ◽  
Katsuya Teshima ◽  
Naomichi Ezumi ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Gas Flow ◽  
Microwave Plasma ◽  
Plasma Jet

scholarly journals Water-Dispersible Phytosterol Nanoparticles: Preparation, Characterization, and in vitro Digestion

2022 ◽  
Vol 8 ◽  
Author(s):  
Ao Li ◽  
Aixia Zhu ◽  
Di Kong ◽  
Chunwei Wang ◽  
Shiping Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Soybean Lecithin ◽  
Average Particle Size ◽  
Soy Protein Isolate ◽  
In Vitro Digestion ◽  
Bimodal Distribution ◽  
Average Particle ◽  
Food Ingredients ◽  
The Impact

For improving solubility and bioaccessibility of phytosterols (PS), phytosterol nanoparticles (PNPs) were prepared by emulsification–evaporation combined high-pressure homogenization method. The organic phase was formed with the dissolved PS and soybean lecithin (SL) in anhydrous ethanol, then mixed with soy protein isolate (SPI) solution, and homogenized into nanoparticles, followed by the evaporation of ethanol. The optimum fabrication conditions were determined as PS (1%, w/v): SL of 1:4, SPI content of 0.75% (w/v), and ethanol volume of 16 ml. PNPs were characterized to have average particle size 93.35 nm, polydispersity index (PDI) 0.179, zeta potential −29.3 mV, and encapsulation efficiency (EE) 97.3%. The impact of temperature, pH, and ionic strength on the stability of fabricated PNPs was determined. After 3-h in vitro digestion, the bioaccessibility of PS in nanoparticles reached 70.8%, significantly higher than the 18.2% of raw PS. Upon freeze-drying, the particle size of PNPs increased to 199.1 nm, resulting in a bimodal distribution. The solubility of PS in water could reach up to 2.122 mg/ml, ~155 times higher than that of raw PS. Therefore, this study contributes to the development of functional PS-food ingredients.

Flow Structure and Heat Transfer in Stagnation Flow CVD Reactor

2010 ◽  
Author(s):  
Nasir Memon ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Atmospheric Pressure ◽  
Gas Flow ◽  
Flow Reactor ◽  
Chemical Vapor ◽  
Design Parameters ◽  
Stagnation Flow ◽  
Inlet Length ◽  
The Impact

An experimental study is undertaken to investigate the flow structure and heat transfer in a stagnation flow Chemical Vapor Deposition (CVD) reactor at atmospheric pressure. It is critical to develop models that predict flow patterns in such a reactor to achieve uniform deposition across the substrate. Free convection can negatively affect the gas flow as cold inlet gas impinges on the heated substrate, leading to vortices and disturbances in the normal flow path. This experimental research will be used to understand the buoyancy-induced and momentum-driven flow structure encountered in an impinging jet CVD reactor. Investigations are conducted for various operating and design parameters. A modified stagnation flow reactor is built where the height between the inlet and substrate is reduced when compared to a prototypical stagnation flow reactor. By operating such a reactor at certain Reynolds and Grashof numbers it is feasible to sustain smooth and vortex free flow at atmospheric pressure. The modified stagnation flow reactor is compared to other stagnation flow geometries with either a varied inlet length or varied heights between the inlet and substrate. Comparisons are made to understand the impact of such geometric changes on the flow structure and the thermal boundary layer. In addition, heat transfer correlations are obtained for the substrate temperature. Overall, the results obtained provide guidelines for curbing the effects of buoyancy and for improving the flow field to obtain greater film uniformity when operating a stagnation flow CVD reactor at atmospheric pressure.

Study of graphene layer growth on dielectric substrate in microwave plasma torch at atmospheric pressure

2020 ◽  
Vol 105 ◽  
pp. 107798 ◽  
Author(s):  
Ondřej Jašek ◽  
Jozef Toman ◽  
Jana Jurmanová ◽  
Miroslav Šnírer ◽  
Vít Kudrle ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Graphene Layer ◽  
Microwave Plasma ◽  
Dielectric Substrate ◽  
Layer Growth ◽  
Microwave Plasma Torch

scholarly journals Gliding arc triggered microwave plasma arc at atmospheric pressure for coal gasification application

2014 ◽  
Vol 32 ◽  
pp. 1460345
Author(s):  
Vishal Jain ◽  
A. Visani ◽  
C. Patil ◽  
B. K. Patel ◽  
P. K. Sharma ◽  
...  
Keyword(s):  
High Temperature ◽  
Microwave Power ◽  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Microwave Plasma ◽  
Arc Discharge ◽  
Effluent Treatment ◽  
Plasma Arc ◽  
Gliding Arc ◽  
Consumable Electrodes

Plasma torch is device that efficiently converts electrical energy in to thermal energy for various high temperature applications. The conventional plasma torch comprises of consumable electrodes namely anode and cathode electrodes. The replacement of these electrodes is a complex process owing to its cooling and process shut down requirements. However, microwave plasma arc is electrode-less plasma arc system that is an alternative method to conventional arc technology for generating plasma arc. In this technique, microwave power is efficiently coupled to generate plasma arc by using the property of polar molecule to absorb microwave power. The absorption of microwave power is in form of losses due to intermolecular friction and high collisions between the molecules. This is an efficient method because all microwave power can be absorbed by plasma arc. The main feature of microwave plasma arc is its large uniform high temperature column which is not possible with conventional arc discharge methods. Such type of plasma discharge is very useful in applications where sufficient residence time for treat materials is required. Microwave arc does not require any consumable electrodes and hence, it can be operated continuously that makes it very useful for hazardous effluent treatment applications. Further, microwave cannot ionize neutral particles at atmospheric pressure and hence, a gliding arc is initiated between two thin electrodes in the cavity by applying very low power high voltage (3kV) AC source. In this report, the method for generating microwave arc of 1kW power using commercial microwave oven is elaborated.

scholarly journals Modeling of Miniemulsion Polymerization of Styrene with Macro-RAFT Agents to Theoretically Compare Slow Fragmentation, Ideal Exchange and Cross-Termination Cases

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 320 ◽  
Author(s):  
Dries Devlaminck ◽  
Paul Van Steenberge ◽  
Marie-Françoise Reyniers ◽  
Dagmar D’hooge
Keyword(s):  
Particle Size ◽  
Average Particle Size ◽  
Miniemulsion Polymerization ◽  
Monomer Conversion ◽  
Water Soluble ◽  
Explicit Calculation ◽  
Average Particle ◽  
Intermediate Radical ◽  
Raft Agent ◽  
The Impact

A 5-dimensional Smith-Ewart based model is developed to understand differences for reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization with theoretical agents mimicking cases of slow fragmentation, cross-termination, and ideal exchange while accounting for chain length and monomer conversion dependencies due to diffusional limitations. The focus is on styrene as a monomer, a water soluble initiator, and a macro-RAFT agent to avoid exit/entry of the RAFT leaving group radical. It is shown that with a too low RAFT fragmentation rate coefficient it is generally not afforded to consider zero-one kinetics (for the related intermediate radical type) and that with significant RAFT cross-termination the dead polymer product is dominantly originating from the RAFT intermediate radical. To allow the identification of the nature of the RAFT retardation it is recommended to experimentally investigate in the future the impact of the average particle size (dp) on both the monomer conversion profile and the average polymer properties for a sufficiently broad dp range, ideally including the bulk limit. With decreasing particle size both a slow RAFT fragmentation and a fast RAFT cross-termination result in a stronger segregation and thus rate acceleration. The particle size dependency is different, allowing further differentiation based on the variation of the dispersity and end-group functionality. Significant RAFT cross-termination is specifically associated with a strong dispersity increase at higher average particle sizes. Only with an ideal exchange it is afforded in the modeling to avoid the explicit calculation of the RAFT intermediate concentration evolution.

Cuprous Oxide Films Prepared by Using a Microwave Atmospheric Pressure Plasma Torch

2008 ◽  
Vol 47-50 ◽  
pp. 1015-1018 ◽  
Author(s):  
Hong Ying Chen ◽  
Lien Teng Kuo ◽  
Wan Yu Chang ◽  
Cheng Hsien Tsai
Keyword(s):  
Plasma Treatment ◽  
Cuprous Oxide ◽  
Atmospheric Pressure ◽  
Plasma Torch ◽  
Microwave Plasma ◽  
Cupric Oxide ◽  
Oxide Films ◽  
Atmospheric Pressure Plasma ◽  
Oxide Phase ◽  
Nitrogen Plasma

A 2.45 GHz microwave atmospheric pressure torch is employed to prepare cuprous oxide films. The sputtered copper films are firstly deposited on slide glass. After that, the films are annealed in air at 500°C for 12 h, which would directly oxidize into cupric oxide. The annealed films are then treated by atmospheric nitrogen plasma at 800 W for 10 min. The color changed significantly from black to reddish brown after nitrogen plasma treatment. The X-ray diffraction patterns show that annealed films are cupric oxide which is vanished after plasma treatment. The cuprous oxide films appeared after nitrogen plasma treatment. The resistivity of annealed films is 16.7 --cm, which reduce to 2.08 --cm after plasma treatment. The optical band gap of annealed films, cupric oxide phase, is 2.1 eV but the value shifts toward 2.4 eV after plasma treatment. The novel microwave plasma torch posses a fast and easy way to fabricate cuprous oxide films.

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