scholarly journals The Influences of Oxygen Concentration and External Heating on Carbon Nanotube Growth in Diffusion Flame

CFD Letters ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 45-62
Author(s):  
Lei Li ◽  
Muhammad Thalhah Zainal ◽  
Mohd Fairus Mohd Yasin ◽  
Norikhwan Hamzah ◽  
Mohsin Mohd Sies ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Nanotube ◽  
Oxygen Concentration ◽  
Cfd Simulation ◽  
High Yield ◽  
Synthesis Process ◽  
Excess Oxygen ◽  
Rate Model ◽  
Growth Region ◽  
Furnace Power

Tight control of the carbon nanotube (CNT) synthesis process in flames remains a challenge due to the highly non-uniform gradient of flame thermochemical properties. The present study aims to establish a baseline model for flame-enhanced chemical vapor deposition (FECVD) synthesis of CNT and to analyze the CNT growth region at varying flame and furnace conditions. The numerical model comprises a computational fluid dynamics (CFD) simulation that is coupled with the CNT growth rate model to simulate the flow field within the furnace and the CNT growth respectively. Validation of the flame shape, flame length, and temperature profile are carried with a reasonable comparison to experimental measurements. A parametric study on the effects of furnace heating capacity and oxidizer concentration is conducted. The results of the CNT growth rate model reveal that there is a positive correlation between the heater power and CNT length. Supplying a higher concentration oxidizer at a fixed furnace power is predicted to result in further improvement in CNT length and high yield region. Flame structure analysis showed that with the heater turned on at 750 W (corresponding to heat flux of 21,713W/m2), the growth region expands twofold when oxygen concentration is increased from 19% to 24%. However, the growth region shrinks when the oxygen concentration is further increased to 27% which indicates depletion of carbon source for CNT growth due to excess oxygen. The finding of this research could guide and optimize the experiment of the flame-assisted CNT production in the future.

scholarly journals ZnO/RGO Heterojunction Based near Room Temperature Alcohol SENSOR with Improved Efficiency

2021 ◽  
Vol 6 (1) ◽  
pp. 25
Author(s):  
Sanghamitra Ghosal ◽  
Partha Bhattacharyya
Keyword(s):  
Active Sites ◽  
Room Temperature ◽  
Surface Engineering ◽  
Gas Sensing ◽  
Energy Band Diagram ◽  
Future Generation ◽  
High Yield ◽  
Synthesis Process ◽  
Ethanol Sensor ◽  
Vapor Sensing

The systematic optimization of surface engineering (dimensionality) indeed plays a crucial role in achieving efficient vapor-sensing performance. Among various semiconducting metal oxides, owing to some of its unique features and advantages, ZnO has attracted researchers on a global scale due to its application in various fields, including chemical sensors. The concomitant optimization of the surface attributes (varying different dimensions) of ZnO have become a sensation for the entire research community. Moreover, the small thickness and extremely large surface of exfoliated 2D nanosheets render the gas sensing material an ideal candidate for achieving strong coupling with different gas molecules. However, temperature is a crucial factor in the field of chemical sensing. Recently, graphene-based gas sensors have attracted attention due to their variety of structures, unique sensing performances and room temperature working conditions. In this work, a highly sensitive and fast responsive low temperature (60 °C)-based ethanol sensor, based on RGO/2D ZnO nanosheets hybrid structure, is reported. After detailed characterizations, the vapor sensing potentiality of this sensor was tested for the detection of ethanol. The ethanol sensor offered the response magnitude of 89% (100 ppm concentration) with response and recovery time of 12 s/29 s, respectively. Due to excessively high number of active sites for VOC interaction, with high yield synthesis process and appreciably high carrier mobility, this has paved the way for developing future generation, miniaturized and flexible (wearable) vapor sensor devices, meeting the multidimensional requirements for traditional and upcoming (health/medical sector) applications. The underlying mechanistic framework for vapor sensing, using this hybrid junction, is explained with the Energy Band Diagram.

High-yield synthesis of conductive carbon nanotube tips for multiprobe scanning tunneling microscope

2007 ◽  
Vol 78 (1) ◽  
pp. 013703 ◽  
Author(s):  
H. Konishi ◽  
Y. Murata ◽  
W. Wongwiriyapan ◽  
M. Kishida ◽  
K. Tomita ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Scanning Tunneling Microscope ◽  
High Yield ◽  
Scanning Tunneling ◽  
Tunneling Microscope

Kinetics of the cytochrome c oxidase and reductase reactions in energized and de-energized mitochondria

1977 ◽  
Vol 55 (7) ◽  
pp. 706-713 ◽  
Author(s):  
Lars Chr. Petersen ◽  
Hans Degn ◽  
Peter Nicholls
Keyword(s):  
Steady State ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Oxygen Concentration ◽  
Respiration Rate ◽  
Redox State ◽  
Rat Liver Mitochondria ◽  
Excess Oxygen ◽  
Succinate Oxidation ◽  
State Reduction

1. Coupled, cytochrome-c-depleted ('stripped') rat liver mitochondria reducing oxygen in the presence of exogenous cytochrome c, with succinate or ascorbate as substrates, show marked declines in the steady-state reduction of cytochrome c in excess oxygen on addition of uncouplers. Calculated ratios of maximal turnover in the uncoupled state and in the energized state for the cytochrome c oxidase (EC 1.9.3.1) reaction lie between 3 and 6, as obtained with reconstituted oxidase-containing vesicles. The succinate-cytochrome c reductase activity in such mitochondria shows a smaller response to uncoupler than that of the oxidase.2. The respiration rates of uncoupled mitochondria oxidizing ascorbate in the presence of added cytochrome c follow a Michaelis–Menten relationship with respect to oxygen concentration, in accordance with the pattern found previously with the solubilized oxidase. But succinate oxidation tends to give nonlinear concave-upward double-reciprocal plots of respiration rate against oxygen concentration, in accordance with the pattern found previously with intact uncoupled mitochondria.3. From simultaneous measurements of cytochrome c steady-state reduction, respiration rate, and oxygen concentration during succinate oxidation under uncoupled conditions it is found that at full reduction of cytochrome c, apparent Km for oxygen is 0.9 μM and the maximal oxidase (aa3) turnover is 400 s−1 (pH 7.4, 30 °C).4. The redox state of cytochrome c in uncoupled systems reflects a simple steady state; the redox state of cytochrome c in energized systems tends towards an equilibrium condition with the terminal cytochrome a3, whose apparent potential under these conditions is more negative than that of cytochrome c.

Modulation of carbon nanotube yield and type through the collective effects of initially deposited catalyst amount and MgO underlayer annealing temperature

MRS Advances ◽  
2018 ◽  
Vol 4 (3-4) ◽  
pp. 139-146
Author(s):  
Takashi Tsuji ◽  
Guohai Chen ◽  
Kenji Hata ◽  
Don N. Futaba ◽  
Shunsuke Sakurai
Keyword(s):  
Carbon Nanotube ◽  
Annealing Temperature ◽  
Catalyst Surface ◽  
Catalyst System ◽  
Forest Growth ◽  
Collective Effects ◽  
High Yield ◽  
Force Microscopy ◽  
Atomic Force ◽  
Fe Catalysts

ABSTRACTRecently, the millimetre-scale, highly efficient growth of single-wall carbon nanotube (SWCNT) forests from iron (Fe) catalysts has been reported through the annealing of the magnesia (MgO) underlayer. Here, we report the modulation of the CNT yield (height) and average number of CNT walls for a Fe/MgO catalyst system through the collective effects of initial Fe amount and MgO annealing temperature. Our results revealed the existence of a well-defined region for high yield SWCNT forest growth in the domain of deposited Fe thickness and MgO annealing temperature. Through topographic examinations of the catalyst surface using atomic force microscopy, we confirmed that our results stem from the collective effects of increased amounts of surface-bound Fe through the amount of deposition and suppression of Fe subsurface diffusion, together govern the amount of surface-bound catalyst. The combination of these mechanisms determined the final nanoparticle size, density, and stability and could explain the three distinctly defined regions: low yield SWCNT growth, high yield SWCNT growth, and high yield multiwall CNT growth. Furthermore, we explained the observed borders between these three regions.

scholarly journals The role of positively charge poly-L-lysine in the formation of high yield gold nanoplates on the surface for plasmonic sensing application

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0259730
Author(s):  
Marlia Morsin ◽  
Suratun Nafisah ◽  
Rahmat Sanudin ◽  
Nur Liyana Razali ◽  
Farhanahani Mahmud ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Surrounding Medium ◽  
Resonance Effect ◽  
Maximum Yield ◽  
Single Layer ◽  
Localized Surface Plasmon ◽  
High Yield ◽  
Synthesis Process ◽  
Wavelength Shift ◽  
Plasmonic Sensor

An anisotropic structure, gold (Au) nanoplates was synthesized using a two-step wet chemical seed mediated growth method (SMGM) directly on the substrate surface. Prior to the synthesis process, poly-l-lysine (PLL) as a cation polymer was used to enhance the yield of grown Au nanoplates. The electrostatic interaction of positive charged by PLL with negative charges from citrate-capped gold nanoseeds contributes to the yield increment. The percentage of PLL was varied from 0% to 10% to study the morphology of Au nanoplates in term of shape, size and surface density. 5% PLL with single layer treatment produce a variety of plate shapes such as hexagonal, flat rod and triangular obtained over the whole substrate surface with the estimated maximum yield up to ca. 48%. The high yield of Au nanoplates exhibit dual plasmonic peaks response that are associated with transverse and longitudinal localized surface plasmon resonance (TSPR and LSPR). Then, the PLL treatment process was repeated twice resulting the increment of Au nanoplates products to ca. 60%. The thin film Au nanoplates was further used as sensing materials in plasmonic sensor for detection of boric acid. The anisotropic Au nanoplates have four sensing parameters being monitored when the medium changes, which are peak position (wavelength shift), intensity of TSPR and LSPR, and the changes on sensing responses. The sensor responses are based on the interaction of light with dielectric properties from surrounding medium. The resonance effect produces by a collection of electron vibration on the Au nanoparticles surface after hit by light are captured as the responses. As a conclusion, it was found that the PLL treatment is capable to promote high yield of Au nanoplates. Moreover, the high yield of the Au nanoplates is an indication as excellent candidate for sensing material in plasmonic sensor.

scholarly journals Influence of Ni Catalyst Layer and TiN Diffusion Barrier on Carbon Nanotube Growth Rate

2010 ◽  
Vol 5 (3) ◽  
pp. 539-544 ◽  
Author(s):  
Jean-Baptiste A. Kpetsu ◽  
Pawel Jedrzejowski ◽  
Claude Côté ◽  
Andranik Sarkissian ◽  
Philippe Mérel ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Nanotube ◽  
Diffusion Barrier ◽  
Catalyst Layer ◽  
Ni Catalyst ◽  
Carbon Nanotube Growth ◽  
Nanotube Growth ◽  
Tin Diffusion Barrier

scholarly journals Carbon Nanotube Sheet-Synthesis and Applications

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 2023
Author(s):  
Megha Chitranshi ◽  
Anuptha Pujari ◽  
Vianessa Ng ◽  
Daniel Chen ◽  
Devika Chauhan ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Large Scale ◽  
Hydrogen Gas ◽  
Synthesis Process ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Metal Ceramic ◽  
Commercial Applications ◽  
Manufacturing Problems

Decades of extensive research have matured the development of carbon nanotubes (CNTs). Still, the properties of macroscale assemblages, such as sheets of carbon nanotubes, are not good enough to satisfy many applications. This paper gives an overview of different approaches to synthesize CNTs and then focuses on the floating catalyst method to form CNT sheets. A method is also described in this paper to modify the properties of macroscale carbon nanotube sheets produced by the floating catalyst method. The CNT sheet is modified to form a carbon nanotube hybrid (CNTH) sheet by incorporating metal, ceramic, or other types of nanoparticles into the high-temperature synthesis process to improve and customize the properties of the traditional nanotube sheet. This paper also discusses manufacturing obstacles and the possible commercial applications of the CNT sheet and CNTH sheet. Manufacturing problems include the difficulty of injecting dry nanoparticles uniformly, increasing the output of the process to reduce cost, and safely handling the hydrogen gas generated in the process. Applications for CNT sheet include air and water filtering, energy storage applications, and compositing CNTH sheets to produce apparel with anti-microbial properties to protect the population from infectious diseases. The paper also provides an outlook towards large scale commercialization of CNT material.

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