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Numerical investigation of convective heat transfer of single wall carbon nanotube nanofluid laminar flow inside a circular tube

Saeed Farqad Rasheed, Jasim Marwah A., Mahmood Natheer B., Jaffar Zahraa M.

Archives of Thermodynamics

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2021

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Vol. 42, no 2

103--119

EN

This study presents the behavior of a single wall carbon nanotube (SWCNT)/water nanofluid for convective laminar flow inside a straight circular pipe heated by a constant heat flux. Five volume fractions of SWCNT were used to investigate their effect on the heat transfer coefficient, Nusselt number, temperature distribution and velocity field in comparison with pure water flow. One model for each property was tested to calculate the effective thermal conductivity, effective dynamic viscosity, and effective specific heat of the SWCNT/water mixture. The models were extracted from experimental data of a previous work. The outcomes indicate that the rheological behavior of SWCNT introduces a special effect on the SWCNT/water properties, which vary with SWCNT volume fraction. The results show an improvement in the heat transfer coefficient with increasing volume fraction of nanoparticles. The velocity of SWCNT/water nanofluid increased by adding SWCNT nanoparticles, and the maximum increase was registered at 0.05% SWCNT volume fraction. The mixture temperature is increased with the axial distance of the pipe but a reduction in temperature distribution is observed with the increasing SWCNT volume fraction, which reflects the effect of thermophysical properties of the mixture.

2

Analysis of selected aspects of a tank gassing-up process on board liquefied petroleum gas carrier. Part I

Wieczorek Agnieszka

Archives of Thermodynamics

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2021

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Vol. 42, no 2

43--58

EN

The paper is a thermodynamics analysis of the removal of any inert gas from the tank using the vapors of any liquefied petroleum gas cargo (called cargo tank gassing-up operation). For this purpose, a thermodynamic model was created which considers two boundary cases of this process. The first is a ‘piston pushing’ of inert gas using liquefied petroleum gas vapour. The second case is complete mixing of both gases and removal the mixture from the tank to the atmosphere until desired concentration or amount of liquefied petroleum gas cargo in the tank is reached. Calculations make it possible to determine the amount of a gas used to complete the operation and its loss incurred as a result of total mixing of both gases.

3

Morphology Control of One-Dimensional Gallium Nitride Nanostructures by Modulating the Crystallinity of Sacrificial Gallium Oxide Templates

Ko Yun Taek, Park Mijeong, Park Jingyeong, Moon Jaeyun, Choa Yong-Ho, Lee Young-In

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 3

709--712

EN

In this study, we demonstrated a method of controllably synthesizing one-dimensional nanostructures having a dense or a hollow structure using fibrous sacrificial templates with tunable crystallinity. The fibrous Ga2O3 templates were prepared by calcining the polymer/gallium precursor nanofiber synthesized by an electrospinning process, and their crystallinity was varied by controlling the calcination temperature from 500°C to 900°C. GaN nanostructures were transformed by nitriding the Ga2O3 nanofibers using NH3 gas. All of the transformed GaN nanostructures maintained a one-dimensional structure well and exhibited a diameter of about 50 nm, but their morphology was clearly distinguished according to the crystallinity of the templates. When the templates having a relatively low crystallinity were used, the transformed GaN showed a hollow nanostructure, and as the crystallinity increased, GaN was converted into a denser nanostructure. This morphological difference can be explained as being caused by the difference in the diffusion rate of Ga depending on the crystallinity of Ga2O3 during the conversion from Ga2O3 to GaN. It is expected that this technique will make possible the tubular nanostructure synthesis of nitride functional nanomaterials.

4

The analysis of the properties of ablative composites with carbon and MMT nanofiller reinforcement

Szczepaniak R., Czubak K., Przybyłek P., Stabryn S.

Journal of KONES

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2017

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Vol. 24, No. 4

305--312

EN

One of the most important parameters in the selection of composite materials used for the protection of avionics instruments exposed to high temperatures are ablative properties. They constitute the main criterion in determining the composition and thickness of the protective material. In this article, the authors determine the ablative properties of a polymer matrix with carbon reinforcement and check the effect of using the MMT additive (montmorillonite) on the change in the resistance to the impact of a high heat flux. The tested materials play an important role in the defence, aviation and space industry. Ablative materials are the only ones to protect the rear wall surface from an excessive temperature rise while using a thin insulation wall. For the sake of the research, we prepared a series of samples of the composite produced with epoxy resin LH 145, H 147 hardener, carbon fibre mats and the addition of MMT. The prepared samples were tested on a unique stand in laboratory conditions. The findings obtained from the experimental testing after a detailed analysis were tabulated and presented in the form of graphs. The authors determined the ablative loss of mass of the individual samples, compared their internal temperatures, which had been measured with thermocouples, as well as the temperature on the backside of the sample. In addition, in order to complement the experimental studies of determining the temperature rise on the rear surface, the authors used a thermal imaging camera. Besides, they took photos of different layers of the examined structure, which had been exposed, to a heat stream, by means of a scanning microscope.

5

Molecular order and dynamics of 5CB liquid crystals in confined space - computer simulation

Gwizdała W., Gburski Z.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2015

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Vol. 19, No 1

35--64

EN

We studied the dynamical and structural properties of an important nematic 4-n-pentyl-4’-cyanobiphenyl (5CB) mesogen placed near carbon allotropes (graphene, nanotube), using modeling and molecular dynamics simulations (MD). Every investigated nanosystem (a free cluster of 5CB, a 5CB cluster confined in a single-walled carbon nanotube, 5CB mesogens located between two graphene sheets, a 5CB thin layer on a single-walled carbon nanotube, a thin layer of a 5CB molecules near graphene plane) contains a liquid crystal cluster consisting of 5CB molecules (22–98 molecules). We also performed a computer experiment for a 5CB bulk sample (196 5CB mesogens) with periodic boundary conditions. The following observables were calculated for several temperatures: mean square displacement, radial distribution function and second rank order parameter of 5CB clusters. The obtained results from MD simulations were discussed and compared with the experimental data.

6

Fabrication and characterization of TiO2 nanotube arrays on Ti membrane enlarged by anodic oxidation

Kim J. O., Cho C. H., Choi W. Y.

Materials Science Poland

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2015

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Vol. 33, No. 3

588--592

EN

TiO2 nanotube arrays have attracted a great deal of attention as photocatalytic and photoelectrode materials due to their large surface area, low cost and easy fabrication. Highly ordered TiO2 nanotube arrays for the photoelectrodes in dye-sensitized solar cells have been fabricated from Ti foil. However, the TiO2 nanotube arrays from Ti foil were not effective for the photocatalytic materials, because it had only one plane for the photocatalytic reaction. We have fabricated the TiO2 nanotube arrays from macroporous Ti metal membrane by anodic oxidation and tried to scale it up. Various factors were controlled to obtain the optimal microstructure of the TiO2 nanotube arrays on the surface of macroporous Ti metallic membrane. Microstructure and phase were studied by SEM and XRD, respectively. Temperature was a very important factor in anodic oxidation of large surface area. 10 μm thick TiO2 nanotube arrays on Ti metallic membrane having a large surface area were fabricated and some factors for scaling-up were discussed.

7

Wykorzystanie metody elementu skończonego (MES) do analizy wyników emisji polowej

Rymarczyk J., Stępińska I.

Elektronika : konstrukcje, technologie, zastosowania

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2015

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Vol. 56, nr 1

12-17

PL

W artykule przedstawiono wyniki symulacji oraz badań emisji polowej elektronów z warstw węglowo-niklowych zawierających nanorurki węglowe (warstwy CNT-Ni). Warstwy CNT-Ni otrzymuje się w wyniku procesu fizycznego jednoczesnego osadzania z fazy gazowej (metoda PVD) fulerenu C₆₀ i octanu niklu. Takie warstwy są modyfikowane metodą chemicznego osadzania z fazy gazowej (metoda CVD) ksylenu w podwyższonej temperaturze. Tak otrzymane warstwy nanorurek węglowych z nanoziarnami Ni wykazują emisję polową. Na podstawie symulacji metodą elementu skończonego (MES) rozkładu pola elektrycznego w układzie emitera z katodą z warstwy CNT-Ni można wnioskować, o rozkładzie wartości natężenia pola elektrycznego. Symulacje przeprowadzono przy zastosowaniu programu ANSYS. Zostało pokazane, że właściwości emisyjne warstw CNT-Ni zależą od morfologii i gęstości upakowania nanorurek na powierzchni.

EN

In this paper we present results of comparison of numerical simulation and experimental data for field emission studies of carbon-nickel nanocomposite films with different carbon nanotubes on surface (CNT-Ni film). Films were obtained by PVD method and next CVD modification. Finite Element Method (FEM) and ANSYS program (Ansys, Inc) were used to simulation of electric field distribution. Studies have shown that the emission properties of the CNT-Ni films depend on their morphology and topography. The experimental results and the modeling show that the better emission property has a film of rare spaced nanotubes than film with many nanotubes on surface.

8

Otrzymywanie i charakterystyka struktury nanorurek TiO2

Nocuń M., Kwaśny S.

Materiały Ceramiczne

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2012

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T. 64, nr 2

209-213

PL

Nanorurki z ditlenku tytanu znajdują coraz szersze zastosowania praktyczne, głównie w procesach katalitycznych i fotokatalitycznych. Podstawową zaletą nanorurek w stosunku do TiO2 w formie proszku jest znacznie większe rozwinięcie powierzchni i wyższa aktywność. Nanorurki TiO2 są jednak ciągle materiałem mało zbadanym zwłaszcza pod kątem zastosowań fotokatalitycznych w cienkich warstwach. W pracy opisano procedurę syntezy nanorurek tytanowych metodą hydrotermalną w roztworze alkalicznym. Celem pracy było porównanie struktury otrzymanych materiałów w zależności od formy krystalicznej materiału wyjściowego. Charakterystykę struktury nanorurek przeprowadzono w oparciu o technikę FTIR oraz spektroskopię Ramana, skład fazowy wyznaczono w oparciu o dyfrakcję rentgenowską, natomiast morfologię włókien analizowano za pomocą mikroskopii skaningowej i transmisyjnej.

EN

Titania nanotubes have wide practical applications mainly in catalytic and photocatalytic processes. The main advantage of the nanotubes with respect to TiO2 in a powder form is much greater surface development and higher activity. However, TiO2 nanotube material is still little explored especially for photocatalytic applications as thin films. This paper describes a procedure for the synthesis of titanium nanotubes by the hydrothermal method in an alkaline solution. The aim of this study was to compare the structure of the materials depending on a crystalline form of starting material. The characteristics of the structure of nanotubes was based on FTIR and Raman spectroscopy, the phase composition was determined by using X-ray diffraction and the morphology of the fibers was analyzed by scanning and transmission microscopy.

9

The pecularities of structure and diffraction by mis fit mixed-layer nanotubes

Figovsky O., Pashin D., Khalitov Z., Valeeva D., Chkanov A.

International Letters of Chemistry, Physics and Astronomy

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2012

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Vol. 2

7-14

EN

The analysis of diffraction by separate mixed-layer goffered nanotube's lattice is offered. Two extreme cases of the large and small size of coherent scattering regions (CSR) in a radial direction are considered. The qualitative explanation of observed diffraction effects is given.

10

Emisja polowa w rodzinie lamp fluorescencyjnych z zimną katodą z nanokompozytowych warstw Ni-C

Krawczyk S., Wronka H., Waszuk S., Czerwosz E.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 8

35-37

PL

W pracy omówiono badania emisji polowej dla katod wykorzystanych w konstrukcji lamp fluorescencyjnych oraz dla lamp, w których zamontowano te katody. Badania pokazały, że najsilniejsza emisja obserwowana jest dla katod o strukturze litej matrycy z kompozytu węglowego z nanorurkami wystającymi z wyrw w tej matrycy. Nanorurki w takiej matrycy rozmieszczone są rzadko, tzn. ich długość jest znacznie mniejsza od odległości między nimi.

EN

Field emission studies were performed for cathodes used in a construction of a fluorescent lamp and for lamps in which these cathodes were mounted. investigations exhibited that a most intensive emission is observed for a cathode that was composed of film basing on carbonaceous matrix in which carbon nanotubes are placed in a holes. These nanotubes are rarely distributed in the matrix what means that their length is much smaller than distance between them.

11

Nanorurki węglowe i kompozyty guma silikonowa-CNT jako materiały elektrodowe dla techniki polimerów elektroaktywnych

Żyłka P.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 2

39-41

PL

Elastyczne, odporne mechanicznie elektrody o dużej przewodności elektrycznej są niezbędne do efektywnego pobudzania niejonowych polimerów elektroaktywnych EAP. W artykule omówiono trendy w zakresie materiałów elektrodowych stosowanych w aktuatorach EAP. Przedstawiono wyniki prac nad uzyskaniem elektroprzewodzących kompozytów elastomerowych z nanorurkami węglowymi CNT. Stwierdzono, iż kompozyty guma silikonowa-CNT posiadają niski próg perkolacji co umożliwia wytwarzanie cienkich, elastycznych warstw elektrodowych.

EN

Electronic electroactive polymers EAP require compliant and conducting electrodes for effective operation. Current progress in electroding materials for EAP actuators is presented and illustrated with results of works aimed at fabrication of electrically conductive composite elastomeric materials modified with carbon nanotubes CNT. Silicone rubber-CNT compositions exhibit low percolation threshold which makes possible fabrication of conductive and elastic films.

12

Stability of Finite-size Argon Thin Film Coating Single Wall Carbon Nanotube

Kośmider M., Dendzik Z., Żurek S., Górny K.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2009

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Vol. 13, No 3

187-197

EN

The structure and the dynamics of the argon thin film coating (15,4) and (12,12) carbon nanotubes have been studied in a series of molecular dynamic simulations. In the studied temperature regime, the argon atoms in the thin film were well localized. Structural changes and diffusion process inside the argon layers were not been observed. The influence of the chirality and the radius of the nanotube to the cluster properties is also reported.

13

Structural and dynamic properties of water confined inside a single-walled carbon nanotube - Molecular dynamics study

Kosmider M., Sokol M., Dendzik Z., Gburski Z.

Materials Science Poland

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2005

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Vol. 23, No. 2

475--481

EN

Atomically detailed molecular dynamics simulation has been performed to study structural and dynamical properties of the cluster of water molecules (H2O)(80) confined inside an open-ended single-walled (10,10) carbon nanotube (SWNT). The structural and dynamical properties of the confined cluster have been compared with the analogous results for an unconfined cluster of water molecules.