scholarly journals Explaining Bamboo-Like Carbon Fiber Growth Mechanism: Catalyst Shape Adjustments above Tammann Temperature

2020 ◽  
Vol 6 (2) ◽  
pp. 18 ◽  
Author(s):  
Luís Sousa Lobo ◽  
Sónia A.C. Carabineiro
Keyword(s):  
Melting Point ◽  
Metal Nanoparticles ◽  
Bulk Diffusion ◽  
Pyrolytic Carbon ◽  
Metal Nanoparticle ◽  
Carbon Formation ◽  
Graphene Layers ◽  
Nanoparticle Shape ◽  
C Fibers ◽  
Nano Catalyst

The mechanism of bamboo-like growth behavior of carbon fibers is discussed. We propose that there is a requirement to have this type of growth: operation above the Tammann temperature of the catalyst (defined as half of the melting point). The metal nanoparticle shape can then change during reaction (sintering-like behavior) facilitating carbon nanotube (CNT) growth, adjusting geometry. Using metal nanoparticles with a diameter below 20 nm, some reduction of the melting point (mp) and Tammann temperature (TTa) is observed. Fick’s laws still apply at nano scale. In that range, distances are short and so bulk diffusion of carbon (C) atoms through metal nanoparticles is quick. Growth occurs under catalytic and hybrid carbon formation routes. Better knowledge of the mechanism is an important basis to optimize growth rates and the shape of bamboo-like C fibers. Bamboo-like growth, occurring under pyrolytic carbon formation, is excluded: the nano-catalyst surface in contact with the gas gets quickly “poisoned”, covered by graphene layers. The bamboo-like growth of boron nitride (BN) nanotubes is also briefly discussed.

The effect of graphene on surface plasmon resonance of metal nanoparticles

2018 ◽  
Vol 20 (38) ◽  
pp. 25078-25084 ◽  
Author(s):  
Haiyan Nan ◽  
Zhirong Chen ◽  
Jie Jiang ◽  
JiaQi Li ◽  
Weiwei Zhao ◽  
...  
Keyword(s):  
Surface Plasmon Resonance ◽  
Metal Nanoparticles ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
Localized Surface Plasmon Resonance ◽  
Metal Nanoparticle ◽  
Localized Surface Plasmon ◽  
Au Nps ◽  
Hybrid Schemes ◽  
Graphene Layers

Two transparent graphene–metal nanoparticle (NP) hybrid schemes, namely Au NPs covered by graphene layers and Au NPs encapsulated by graphene layers, are presented and the effect of graphene on the localized surface plasmon resonance of metal NPs is systematically investigated.

scholarly journals Carbon Formation at High Temperatures (550–1400 °C): Kinetics, Alternative Mechanisms and Growth Modes

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 465 ◽  
Author(s):  
Luís Sousa Lobo ◽  
Sónia A. C. Carabineiro
Keyword(s):  
Catalyst Surface ◽  
Bulk Diffusion ◽  
Carbon Formation ◽  
Carbon Structure ◽  
Graphene Layers ◽  
Rate Determining Step ◽  
Growth Modes ◽  
Higher Temperature ◽  
Hybrid Carbon ◽  
Gas Pressures

This Note aims at clarifying the alternative mechanisms of carbon formation from gases at temperatures above 550 °C. Both the growth of carbon nanotubes (CNTs) by a hybrid route, and of graphene layers deposition by a pyrolytic route are analyzed: the transition had no influence in apparent kinetics, but the carbon structure was totally different. The transition temperature from hybrid to pyrolytic growth varies with the gas pressure: higher temperature transition was possible using lower active gas pressures. The rate-determining step concept is essential to understanding the behavior. In catalytic and hybrid carbon formation, the slower step controls and determines kinetics. In the pyrolytic region, the faster step dominates, and carbon bulk diffusion is blocked: layers of graphene cover the external catalyst surface. It is easier to optimize CNTs growth (rate, shape, properties) knowing the details of the alternative mechanisms operating.

scholarly journals Averaged optical characteristics of an ensemble of metal nanoparticles

2019 ◽  
Vol 33 (18) ◽  
pp. 1950188
Author(s):  
P. M. Tomchuk ◽  
V. N. Starkov
Keyword(s):  
Metal Nanoparticles ◽  
Optical Conductivity ◽  
Field Vector ◽  
Metal Nanoparticle ◽  
Optical Characteristics ◽  
Nanoparticle Size ◽  
Nanoparticle Shape ◽  
Combined Application ◽  
Different Shapes ◽  
The Magnetic Field

A theory for the averaged optical characteristics of an ensemble of metal nanoparticles with different shapes has been developed. The theory is applicable both for the nanoparticle size at which the optical conductivity of the particle is a scalar and for the nanoparticle size at which the optical conductivity should be considered as a tensor. The averaged characteristics were obtained taking into account the influence of nanoparticle shape on the depolarization coefficient and the components of the optical conductivity tensor. The dependences of magnetic absorption by a spheroidal metal nanoparticle on the ratio between its curvature radii and the angle between the spheroid symmetry axis and the magnetic field vector were derived and theoretically considered. An original variant of the distribution function for nanoparticle shapes, which is based on the combined application of the Gaussian and “hat” functions, was proposed and analyzed.

Experimental and theoretical study of the characteristics of LSPR peaks for metal NPs produced by controlling Ar ambient gas pressure to enhance the efficiency of solar cells

2021 ◽  
pp. 1-6
Author(s):  
Serap Yiğit Gezgin ◽  
Abdullah Kepceoğlu ◽  
Hamdi Şükür Kiliç
Keyword(s):  
Metal Nanoparticles ◽  
Ag Nanoparticles ◽  
Solar Spectrum ◽  
Wavelength Region ◽  
Gas Pressure ◽  
Metal Nanoparticle ◽  
Ag Nanoparticle ◽  
Extinction Cross Section ◽  
Ambient Gas ◽  
Ar Gas

In this study, silver (Ag) nanoparticle thin films were deposited on microscope slide glass and Si wafer substrates using the pulsed-laser deposition (PLD) technique in Ar ambient gas pressures of 1 × 10−3 and 7.5 × 10−1 mbar. AFM analysis has shown that the number of Ag nanoparticles reaching the substrate decreased with increasing Ar gas pressure. As a result of Ar ambient gas being allowed into the vacuum chamber, it was observed that the size and height of Ag nanoparticles decreased and the interparticle distances decreased. According to the absorption spectra taken by a UV–vis spectrometer, the wavelength where the localised surface plasmon resonance (LSPR) peak appeared was shifted towards the longer wavelength region in the solar spectrum as Ar background gas pressure was decreased. This experiment shows that LSPR wavelength can be tuned by adjusting the size of metal nanoparticles, which can be controlled by changing Ar gas pressure. The obtained extinction cross section spectra for Ag nanoparticle thin film was theoretically analysed and determined by using the metal nanoparticle–boundary element method (MNPBEM) toolbox simulation program. In this study, experimental spectrum and simulation data for metal nanoparticles were acquired, compared, and determined to be in agreement.

scholarly journals Optimization of transition metal nanoparticle-phosphonium ionic liquid composite catalytic systems for deep hydrogenation and hydrodeoxygenation reactions

2015 ◽  
Vol 17 (3) ◽  
pp. 1597-1604 ◽  
Author(s):  
Abhinandan Banerjee ◽  
Robert W. J. Scott
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Transition Metal ◽  
Metal Nanoparticles ◽  
Metal Nanoparticle ◽  
Catalytic Systems ◽  
Phosphonium Ionic Liquid

Stable metal nanoparticles in tetraalkylphosphonium ionic liquids can catalyze hydrogenations, as well as phenol hydrodeoxygenation, owing to presence of adventitious borates.

Localized Laser Sintering of Metal Nanoparticle Inks Printed with Aerosol Jet® Technology for Flexible Electronics

2017 ◽  
Vol 14 (4) ◽  
pp. 132-139 ◽  
Author(s):  
Michael J. Renn ◽  
Matthew Schrandt ◽  
Jaxon Renn ◽  
James Q. Feng
Keyword(s):  
Metal Nanoparticles ◽  
Flexible Electronics ◽  
Low Cost ◽  
Damage Threshold ◽  
Laser Sintering ◽  
Heating Time ◽  
Metal Nanoparticle ◽  
Polymer Materials ◽  
Nanoparticle Inks ◽  
Short Heating Time

Direct-write methods, such as the Aerosol Jet® technology, have enabled fabrication of flexible multifunctional 3-D devices by printing electronic circuits on thermoplastic and thermoset polymer materials. Conductive traces printed by additive manufacturing typically start in the form of liquid metal nanoparticle inks. To produce functional circuits, the printed metal nanoparticle ink material must be postprocessed to form conductive metal by sintering at elevated temperature. Metal nanoparticles are widely used in conductive inks because they can be sintered at relatively low temperatures compared with the melting temperature of bulk metal. This is desirable for fabricating circuits on low-cost plastic substrates. To minimize thermal damage to the plastics, while effectively sintering the metal nanoparticle inks, we describe a laser sintering process that generates a localized heat-affected zone (HAZ) when scanning over a printed feature. For sintering metal nanoparticles that are reactive to oxygen, an inert or reducing gas shroud is applied around the laser spot to shield the HAZ from ambient oxygen. With the shroud gas-shielded laser, oxygen-sensitive nanoparticles, such as those made of copper and nickel, can be successfully sintered in open air. With very short heating time and small HAZ, the localized peak sintering temperature can be substantially higher than that of damage threshold for the underlying substrate, for effective metallization of nanoparticle inks. Here, we demonstrate capabilities for producing conductive tracks of silver, copper, and copper–nickel alloys on flexible films as well as fabricating functional thermocouples and strain gauge sensors, with printed metal nanoparticle inks sintered by shroud-gas-shielded laser.

Enhanced Plasmonic Behavior of Metal Nanoparticles Surrounded With Dielectric Shell

2019 ◽  
Author(s):  
Anil Yuksel ◽  
Michael Cullinan ◽  
Edward T. Yu ◽  
Jayathi Murthy
Keyword(s):  
Metal Nanoparticles ◽  
Near Infrared ◽  
Energy Transport ◽  
Near Field ◽  
Metal Nanoparticle ◽  
Infrared Wavelength ◽  
Laser Illumination ◽  
Dielectric Media ◽  
Dielectric Shell ◽  
Laser Sources

Abstract Metal nanoparticles have attracted intense attention due to their unique optical and thermal properties in various next generation applications such as micro-nano electronics and photonics. The near-field confinement between closely packed metal nanoparticles, which is enhanced due to their plasmonic behavior, creates high thermal energy densities under visible to near-infrared wavelength laser irradiation. As metal nanoparticles tend to be oxidized or change shape under laser illumination, resulting in nonlinear optical and thermal behavior, surrounding each metal nanoparticle with a dielectric shell could be a potential way to prevent these effects as well as to engineer their plasmonic behavior. In this study, we investigate energy transport within dimer and 4 nanoparticle (chain) configurations of 50 nm radius Au nanoparticles surrounded by dielectric shells under illumination from various laser sources in different dielectric media.

In situ growth of metal nanoparticles on boron nitride nanosheets as highly efficient catalysts

2016 ◽  
Vol 4 (48) ◽  
pp. 19107-19115 ◽  
Author(s):  
Li Fu ◽  
Guoxin Chen ◽  
Nan Jiang ◽  
Jinhong Yu ◽  
Cheng-Te Lin ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Metal Nanoparticles ◽  
Room Temperature ◽  
Reducing Agent ◽  
Metal Nanoparticle ◽  
In Situ Growth ◽  
Boron Nitride Nanosheets ◽  
Highly Efficient ◽  
Boron Nitride Nanosheet

We report a facile and general approach for the synthesis of boron nitride nanosheet (BNNS)–metal nanoparticle (NP) composites at room temperature without adding any reducing agent.

Metal nanoparticle photocatalysts: emerging processes for green organic synthesis

2016 ◽  
Vol 6 (2) ◽  
pp. 320-338 ◽  
Author(s):  
Sunari Peiris ◽  
John McMurtrie ◽  
Huai-Yong Zhu
Keyword(s):  
Visible Light ◽  
Metal Nanoparticles ◽  
Organic Synthesis ◽  
Visible Light Irradiation ◽  
Metal Nanoparticle ◽  
Light Irradiation ◽  
Inert Support ◽  
Pd Alloy

Metal nanoparticles (Au, Ag, Cu, Pd, Pt, Ir, Rh, Au–Pd alloyetc.) supported on inert support (ZrO2, zeolite) can be direct photocatalysts to series of organic synthesis with visible light irradiation.

Bulk Diffusion of Homovalent Atomic Probes of Scandium, Lanthanum and Thorium in Single Crystals of Tungsten

2010 ◽  
Vol 305-306 ◽  
pp. 1-13 ◽  
Author(s):  
S.M. Klotsman ◽  
G.N. Tatarinova ◽  
Alexander N. Timofeev
Keyword(s):  
Mass Spectrometry ◽  
Melting Point ◽  
Single Crystals ◽  
Periodic Table ◽  
Secondary Ion Mass Spectrometry ◽  
Volume Diffusion ◽  
Bulk Diffusion ◽  
Relaxation Energy ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

The volume diffusion of nonmagnetic homovalent atomic probes (APs) from the IIIB group of the periodic table of the elements (PTE)Sc, La, and Th in Whas been studied by the method of secondary ion mass spectrometry. The Arrhenius dependences have the following parameters: the coefficients DSc - (D0)Sc = (1.4  0.3)10-4 m2s-1 and QSc = (546±4) kJ/mole; the coefficients D¬La - (D0)La = (1.6  0.8)×10-6 m2s-1 and QLa = (41010) kJ/mole; and the coefficients DTh - (D0)Th = 4.4×10-6 m2s-1 and QTh = 447 kJ/mole. It has been found that the coefficients D5dAP(Tm)W of the bulk diffusion of transition 5d APs in W coincide at its melting point (Tm)W. The enthalpies, QWSc,La,Th, of the volume diffusion of nonmagnetic homovalent APs from the IIIB group of PTE increase linearly with decreasing relaxation volumes, , of these APs, which interact with vacancies in W. The sums, (Q + E)WSc,La,Th, of the bulk diffusion enthalpies, QWSc,La,Th, and the relaxation energy, (E)WSc,La,Th, of the environments of homovalent APs diffusing to W are nearly constant.

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