Carbon nanotubes are cylindrical nanostructures made of rolled up graphene sheets with extraordinary mechanical and electrical properties. They can be single-walled or multi-walled depending on the number of concentric cylinders. Carbon nanotubes have a wide range of potential applications due to their strength, conductivity, and other properties including use in electronics, sensors, energy storage, and more. However, their toxicity must still be addressed before many applications.
Nano Material
Introduction and Synthesis
Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 1000 nanometres (10−9 meter) but is usually 1—100 nm (the usual definition of nanoscale[1]).
Nanomaterials research takes a materials science-based approach to nanotechnology, leveraging advances in materials metrology and synthesis which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, or mechanical properties.
Nanomaterials are slowly becoming commercialized[2] and beginning to emerge as commodities.[3]
Carbon Nanotubes(CNTs) | Characterisation and Purification methodsNitesh Sharma
Carbon nanotubes are one of the emerging materials developed in recent two decades. This report summarises the information of carbon nanotubes with their various synthesis techniques to produce CNTs. Different structures have been discussed like single-shell tubes, multi-shell tubes, bundles and cones. Notable state of the art characterization techniques like SEM, TEM, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, EDS, EDX, HRTEM has been also briefly discussed to study their structure- property correlation in this candidate material. Properties such as low dimensability, high surface-to-volume ratio is observed in carbon nanotubes. Unique mechanical, optical, electrical and electrochemical properties for carbon nanotubes are elaborately discussed here. Carbon nanotubes are advanced materials having tubular structure with nanometre diameter and large length/diameter ratio. Other properties such as density, stability is important for CNTs. Finally, prospects for carbon nanotubes are considered for carbon nanotubes.
Novel effects can occur in materials when structures are formed with sizes comparable to any one of many possible length scales, such as the de Broglie wavelength of electrons, or the optical wavelengths of high energy photons. In these cases quantum mechanical effects can dominate material properties. One example is quantum confinement where the electronic properties of solids are altered with great reductions in particle size. The optical properties of nanoparticles, e.g. fluorescence, also become a function of the particle diameter. This effect does not come into play by going from macrosocopic to micrometer dimensions, but becomes pronounced when the nanometer scale is reached.
Nanoelectronics refer to the use of nanotechnology in electronic components. The term covers a diverse set of devices and materials, with the common characteristic that they are so small that inter-atomic interactions and quantum mechanical properties need to be studied extensively.
It's simple to understand the synthesis. Hydrothermal method is a chemical reaction in water in a sealed pressure vessel, which is in fact a type of reaction at both high temperature and pressure.
Non-covalent protein-ligand interactions? Easy as PiDavid Thompson
This is a presentation made at the Chemical Computing Group UGM in 2010. The work describes a collaboration with a talented summer intern, wherein we looked at the challenging problem of non-covalvent protein-ligand interactions
Nano Material
Introduction and Synthesis
Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 1000 nanometres (10−9 meter) but is usually 1—100 nm (the usual definition of nanoscale[1]).
Nanomaterials research takes a materials science-based approach to nanotechnology, leveraging advances in materials metrology and synthesis which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, or mechanical properties.
Nanomaterials are slowly becoming commercialized[2] and beginning to emerge as commodities.[3]
Carbon Nanotubes(CNTs) | Characterisation and Purification methodsNitesh Sharma
Carbon nanotubes are one of the emerging materials developed in recent two decades. This report summarises the information of carbon nanotubes with their various synthesis techniques to produce CNTs. Different structures have been discussed like single-shell tubes, multi-shell tubes, bundles and cones. Notable state of the art characterization techniques like SEM, TEM, Raman Spectroscopy, Fourier Transform Infrared Spectroscopy, EDS, EDX, HRTEM has been also briefly discussed to study their structure- property correlation in this candidate material. Properties such as low dimensability, high surface-to-volume ratio is observed in carbon nanotubes. Unique mechanical, optical, electrical and electrochemical properties for carbon nanotubes are elaborately discussed here. Carbon nanotubes are advanced materials having tubular structure with nanometre diameter and large length/diameter ratio. Other properties such as density, stability is important for CNTs. Finally, prospects for carbon nanotubes are considered for carbon nanotubes.
Novel effects can occur in materials when structures are formed with sizes comparable to any one of many possible length scales, such as the de Broglie wavelength of electrons, or the optical wavelengths of high energy photons. In these cases quantum mechanical effects can dominate material properties. One example is quantum confinement where the electronic properties of solids are altered with great reductions in particle size. The optical properties of nanoparticles, e.g. fluorescence, also become a function of the particle diameter. This effect does not come into play by going from macrosocopic to micrometer dimensions, but becomes pronounced when the nanometer scale is reached.
Nanoelectronics refer to the use of nanotechnology in electronic components. The term covers a diverse set of devices and materials, with the common characteristic that they are so small that inter-atomic interactions and quantum mechanical properties need to be studied extensively.
It's simple to understand the synthesis. Hydrothermal method is a chemical reaction in water in a sealed pressure vessel, which is in fact a type of reaction at both high temperature and pressure.
Non-covalent protein-ligand interactions? Easy as PiDavid Thompson
This is a presentation made at the Chemical Computing Group UGM in 2010. The work describes a collaboration with a talented summer intern, wherein we looked at the challenging problem of non-covalvent protein-ligand interactions
Dr. Adam Gilmore and Dr. Jeff Bodycomb from HORIBA Scientific discuss using particle size and photoluminescence measurements to characterize single-walled carbon nanotubes.
New technology Model for 1 nm Transistors better than FIN-FET Technology.This slide Tells you in general about the nanotubes, how they are formed and why they are better than MOSFETs
Carbon nanotube is an allotrope of carbon and it is widely used in many Research and Development companies. The presentation will help students to get some idea on this topic.
Carbon Nano tubes and its Applications in the Field of Electronics and Comput...ijsrd.com
With rapid advancement of technology and unlimited quest in the intricate fields of science led man to confront nano tubes. It consists of C60 Fullerenes with tube like structures capped at both ends delivering extraordinary mechanical and electrical properties. It is hard to stress as extremely low turn on for fields and has high current densities. It is also the best emission field emitter for future field emission displays. Can be extensively used for fuel cells and field emission display. We throw a light on the research on nano tubes and it's general applications. In this paper we are focusing and questioning the field of research to ponder for the betterment off life to nano tube.
EFFECT OF FLAME RETARDANT ADDITIVES IN FLAME RETARDANT GRADE OF ABSArjun K Gopi
In this study the effect of flame retardants in flame retardant grade of abs is compared with natural ABS grade. ABS is a flammable material. It is easily burn with high flammability value. ABS materials without flame retardant are easily burned with a luminous yellow flame, smoking strongly and continue to burn after removal of the ignition source. So for some particular applications we are incorporating flame retardants into ABS. But the addition of flame retardants may leads to variation in properties. For that I have done several physical, thermal, and rheological tests to investigate the properties of the respective ABS grades. The results obtained was very interesting
The Internet is amazing, but overwhelming. This list of sites covers a wide array of interests, and each site listed can give you the information that you need without having to spend your valuable time searching and searching. Here are some of the most useful websites on the internet that you may not know about. These web sites, well most of them, solve at least one problem really well and they all have simple web addresses (URLs) that you can memorize.
Original Post http://www.attittudeblogger.in/2016/12/list-of-100-very-useful-websites.html
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Cancer cell metabolism: special Reference to Lactate PathwayAADYARAJPANDEY1
Normal Cell Metabolism:
Cellular respiration describes the series of steps that cells use to break down sugar and other chemicals to get the energy we need to function.
Energy is stored in the bonds of glucose and when glucose is broken down, much of that energy is released.
Cell utilize energy in the form of ATP.
The first step of respiration is called glycolysis. In a series of steps, glycolysis breaks glucose into two smaller molecules - a chemical called pyruvate. A small amount of ATP is formed during this process.
Most healthy cells continue the breakdown in a second process, called the Kreb's cycle. The Kreb's cycle allows cells to “burn” the pyruvates made in glycolysis to get more ATP.
The last step in the breakdown of glucose is called oxidative phosphorylation (Ox-Phos).
It takes place in specialized cell structures called mitochondria. This process produces a large amount of ATP. Importantly, cells need oxygen to complete oxidative phosphorylation.
If a cell completes only glycolysis, only 2 molecules of ATP are made per glucose. However, if the cell completes the entire respiration process (glycolysis - Kreb's - oxidative phosphorylation), about 36 molecules of ATP are created, giving it much more energy to use.
IN CANCER CELL:
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
Unlike healthy cells that "burn" the entire molecule of sugar to capture a large amount of energy as ATP, cancer cells are wasteful.
Cancer cells only partially break down sugar molecules. They overuse the first step of respiration, glycolysis. They frequently do not complete the second step, oxidative phosphorylation.
This results in only 2 molecules of ATP per each glucose molecule instead of the 36 or so ATPs healthy cells gain. As a result, cancer cells need to use a lot more sugar molecules to get enough energy to survive.
introduction to WARBERG PHENOMENA:
WARBURG EFFECT Usually, cancer cells are highly glycolytic (glucose addiction) and take up more glucose than do normal cells from outside.
Otto Heinrich Warburg (; 8 October 1883 – 1 August 1970) In 1931 was awarded the Nobel Prize in Physiology for his "discovery of the nature and mode of action of the respiratory enzyme.
WARNBURG EFFECT : cancer cells under aerobic (well-oxygenated) conditions to metabolize glucose to lactate (aerobic glycolysis) is known as the Warburg effect. Warburg made the observation that tumor slices consume glucose and secrete lactate at a higher rate than normal tissues.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
2. • Carbon nanotubes-nanostructures with large application
potential
• Carbon nanotube is a sheet of graphite rolled into tube with
bonds at the end of sheet forming the bonds that close the tube
• Allotropes of carbon (graphite , diamond , Amorphous carbon
and Fullerene ) (cylindrical members of the fullerene structural
family)
• With a nanostructure. length-to-diameter ratio of up to
132,000,000:1,which is significantly larger than any other material.
• Extraordinary strength and unique electrical properties, efficient
thermal conductors. (limited by their potential toxicity)
• They are less than 100 nanometers in diameter and can be as thin as 1
INTRODUCTION
3. • Carbon nanotubes are fullerene-related structures
which consist of graphene cylinders closed at either
end with caps containing pentagonal rings.
• Discovered in 1991 by the Japanese electron
microscopist Sumio Iijima.
• These are large macromolecules that are unique for
their size, shape, and remarkable physical properties.
4. • Carbon nanotubes have been synthesized for a long time as products
from the action of a catalyst over the gaseous species originating from
the thermal decomposition of Hydrocarbons.
• The worldwide enthusiasm came unexpectedly in 1991, after the
catalyst-free formation of nearly perfect concentric multiwall carbon
nanotubes (c-MWNTs ) was reported as by-products of the
formation of fullerenes by the electric-arc technique
• Economical aspects are leading the game to a greater and greater
extent. According to experts, the world market is predicted to be more
than 430M$ in 2004 and estimated to grow to several b $ before 2009.
5. Nanotubes could be produced in bulk
quantities by varying the arc-evaporation
conditions.
Nanotube hemispheric
• Nanotubes have a very broad range of
electronic, thermal, and structural
properties that change depending on the
different kinds of nanotube (defined by
its diameter, length, and chirality, or
twist).
• Besides having a single cylindrical wall
(SWNTs), Nanotubes can have multiple
walls (MWNTs)--cylinders inside the
other cylinders.
6. NANOTUBE GEOMETRY
There are three unique geometries of carbon nanotubes. The
three different geometries are also referred to as flavors. The
three flavors are armchair, zig-zag, and chiral [e.g. zig-zag (n, 0);
armchair (n, n); and chiral (n, m)]. These flavors can be classified
by how the carbon sheet is wrapped into a tube
7. • The (n,m) nanotube naming
scheme can be thought of as a
vector (Ch) in an infinite
graphene sheet that describes
how to "roll up" the graphene
sheet to make the nanotube.
T denotes the tube axis, and a1
and a2 are the unit vectors of
graphene in real space
Structure of Carbon Nanotubes
Single-Wall Nanotubes SWNTs
8. Most single-walled nanotubes (SWNT) have a diameter of
close to 1 nanometer, with a tube length that can be many
millions of times longer. The structure of a SWNT can be
conceptualized by wrapping a one-atom-thick layer of
graphite called graphene into a seamless cylinder. The way
the graphene sheet is wrapped is represented by a pair of
indices (n,m) called the chiral vector. The integers n and m
denote the number of unit vectors along two directions in
the honeycomb crystal lattice of graphene. If m = 0, the
nanotubes are called "zigzag". If n = m, the nanotubes are
called "armchair". Otherwise, they are called "chiral".
9. Single-Wall Nanotubes SWNTs
Armchair (n,n)
The chiral vector is
bent, while the
translation vector
stays straight
Graphene
nanoribbon
The chiral vector is
bent, while the
translation vector
stays straight
Zigzag (n,0) Chiral (n,m) n and m can be
counted at the end
of the tube
Graphene
nanoribbon
10. Single-Wall Nanotubes SWNTs
Fig. 3.3 Image of two neighboring chiral SWNTs within a
SWNT bundle as seen by high resolution scanning
tunneling microscopy (by courtesy of Prof. Yazdani,
University of Illinois at Urbana, USA)
12. Multiwall Nanotubes MWNT
longitudinal view of a concentric multiwall carbon nanotube
(c-MWNT) prepared by electric arc.
•Multi-walled nanotubes (MWNT)
consist of multiple rolled layers
(concentric tubes) of graphite;
•In the Russian Doll , sheets of
graphite are arranged in
concentric cylinders;
•In the Parchment model, a single
sheet of graphite is rolled in
around itself, resembling a scroll
of parchment or a rolled
newspaper. (3.3 Å);
13. Nanobud
•carbon nanotubes + fullerenes.
•useful properties of both fullerenes and
carbon nanotubes.
•In particular, they have been found to be
exceptionally good field emitters.
• In composite materials, the attached
fullerene molecules may function as
molecular anchors preventing slipping of
the nanotubes, thus improving the
composite’s mechanical properties
14. Extreme carbon nanotubes
•The longest carbon nanotubes (18.5 cm long) was reported in 2009. These
nanotubes were grown on Si substrates using an improved chemical vapor
deposition (CVD) method and represent electrically uniform arrays of
single-walled carbon nanotubes
•The thinnest carbon nanotube is armchair (2,2) CNT with a diameter of 3 Å
•The thinnest free standing single-walled carbon nanotube is about 4.3 Å
in diameter. Researchers suggested that it can be either (5,1) or (4,2)
SWCNT, but exact type of carbon nanotube remains questionable.
15. Synthesis of Carbon Nanotube
1 Laser Ablation – Experimental Devices
- graphite pellet
containing the catalyst put
in an inert gas filled quartz
tube;
-oven maintained at a
temperature of 1,200 ◦
C;
-energy of the laser beam
focused on the pellet;
-vaporize and sublime the
graphiteSketch of an early laser vaporization apparatus
The carbon species are there after deposited as soot in different regions:
water-cooled copper collector, quartz tube walls.
16. 2 Synthesis with CO2 laser
Fig. 3.10 Sketch of a synthesis reactor with a
continuous CO2 laser device
Vaporization of a target at a
fixed temperature by a
continuous CO2 laser beam (λ =
10.6μm). The power can be varied
from 100Wto 1,600 W.
The synthesis yield is controlled
by three parameters: the
cooling rate of the medium
where the active, secondary
catalyst particles are formed,
the residence time, and the
temperature (in the 1,000–
2,100K range) at which SWNTs
nucleate and grow.
17. 3 Electric-Arc Method – Experimental Devices
Sketch of an electric arc reactor. It consists
of a cylinder of about 30 cm in diameter
and about 1m in height.
After the triggering of the arc
between two electrodes, a
plasma is formed consisting
of the mixture of carbon
vapor, the rare inert gas
(helium or argon), and the
vapors of catalysts.
The vaporization is the
consequence of the energy
transfer from the arc to the
anode made of graphite
doped with catalysts.
18. Properties of Carbon Nanotube
•The strongest and stiffest materials .
•1/50,000th the thickness of a human hair.
•In 2000, a MWCN was tested to have a tensile strength of 63 gigapascals (the
ability to endure tension of 6300 kg on a cable with cross-section of 1 mm2
.)
•low density for a solid of 1.3 to 1.4 g·cm−3
•Standard single walled carbon nanotubes can withstand a pressure up to 24GPa
without deformation (hardness)
•Extraordinary electrical conductivity, heat conductivity, and mechanical properties.
• They are probably the best electron field-emitter known, largely due to their high
length-to-diameter ratios
19. Kinetic properties
Multi-walled nanotubes, multiple concentric nanotubes precisely nested within one
another, exhibit a striking telescoping property whereby an inner nanotube core may
slide, almost without friction, within its outer nanotube shell thus creating an
atomically perfect linear or rotational bearing.
Electrical properties
Semiconductor
Thermal properties
The strength of the atomic bonds in carbon nanotubes allows them to withstand
high temperatures. Because of this, carbon nanotubes have been shown to be very
good thermal conductors.
20. Application: Efficient Field
Emitters
The electrons are taking out from
the tips and sent onto an electron
sensitive screen layer.
Replacing the glass support and
protection of the screen by some
polymer-based material will even
allow the develop of flexible screens.
Fig. 3.28 (a) Principle of a field-emitter-
based screen. (b) SEM image of a
nanotube-based emitter system (top
view). Round dots are MWNT tips
seen through the holes
corresponding to the extraction grid.
The first commercial
flat TV sets and computers using
nanotube-based screens are
about to be seen in stores.
(Motorola, NEC, NKK, Samsung,
Thales, Toshiba, etc.)
21. Fig. 3.29a,b Demonstration of the ability of SWNTs in detecting
molecule traces in inert gases.
(a) Increase in a single
SWNT conductance when 20 ppm
of NO2 are added to an
argon gas flow.
(b) Same with 1% NH3 added to the
argon
gas flow
Application: Chemical
Sensors
22. • AFM probe tips. Single-walled carbon nanotubes have been attached to
the tip of
an AFM probe to make the tip "sharper". . Also, the flexibility of the nanotube
prevents damage to the sample surface and the probe tip if the probe tip
happens to "crash" into the surface. They attached carbon nanotubes to AFM
probes for the purpose of increased resolution as well as decreased wear on
sample and probe tip.
• Flat panel display screens. When a nanotube is put into an electric field,
it will emit electrons from the end of the nanotube like a small cannon. If those
electrons are allowed to bombard a phosphor screen then an image can be
created. When scientists instead use millions of carbon nanotubes as tiny
electron guns, the required dimensions change and the creation of a flat panel
display becomes possible. Advertising billboards have already been made and
are being used.
OTHER APPLICATIONS
23. • Nanoscale electronics/nanocomputing Scientists have exploited the
mechanical and electrical properties of carbon nanotubes to produce
molecular electronic devices. When nanotubes are placed in a grid, the
intersections of the nanotubes become bits of information that can be stored
non-volatilely.
Semiconducting nanotubes also can be used as single molecule transistors.
• Nanothermometer. A carbon nanotube can be partially filled with gallium
metal.
When the temperature is changed, the gallium metal expands or contracts to fill
or empty the carbon nanotube. The gallium level in the carbon nanotube varies
almost linearly with temperature. This new device may find use in certain
microscopies.
• Flash photography and carbon nanotubes. Scientists have discovered
that as grown
single-walled carbon nanotubes can be ignited by holding a conventional
camera flash a few centimeters away and flashing the sample.
24. • Actuators/Artificial muscles. An actuator is a device that can induce
motion. In
the case of a carbon nanotube actuator, electrical energy is converted to
mechanical energy causing the nanotubes to move. Two small pieces of
"buckypaper," paper made from carbon nanotubes, are put on either side of a
piece of double-sided tape and attached to either a positive or a negative
electrode. When current is applied and electrons are pumped into one piece of
buckypaper and the nanotubes on that side expand causing the tape to curl in
one direction. This has been called an artificial muscle, and it can produce 50
to
100 times the force of a human muscle the same size. Applications include:
robotics, prosthetics.
25. • Microelectro mechanical devices.
Dr. Morinobu Endo at Shinshu University mixed nylon with carbon fibers (not
nanotubes) 100-200 nm in diameter creating a nanocomposite materials that
could be injected into the world’s smallest gear mold. The carbon fibers have
good thermal conductivity properties that cause the nanocomposite material to
cool more slowly and evenly allowing for better molding characteristics of the
nanocomposite. The "improved" properties of the nanocomposite allow it more
time to fill the tiny micron-sized mold than nylon would by itself. The tiny gears
currently are being made in collaboration with Seiko for use in watches.
• Hydrogen storage. When oxygen and hydrogen react in a fuel cell,
electricity is produced and water is formed as a byproduct. If industry wants to
make a hydrogen-oxygen fuel cell, scientists and engineers must find a safe
way to store hydrogen gas needed for the fuel cell. Carbon nanotubes may be
a viable option. Carbon nanotubes are able to store hydrogen and could
provide the safe,
Editor's Notes
Composites can provide infrastructure applications with many benefits as listed here.
Infrastructure can have all these benefits an more when the proper materials and manufacturing process is selected.
But I believe that in order to achieve these goals, the engineer must specifically know the performance of his product. This includes the physical, mechanical, installation, cost, and quality that identifies the minimum performance specifications.
Composites are composed of polymers, reinforcing fibers, fillers, and other additives. Each of these ingredients play an important role in the processing and final performance of the end product.
In general terms, you could say that:
The polymer is the “glue” that holds the composite and influence the physical properties of the composite end product.
The reinforcement provides the mechanical strength properties to the end product.
The fillers and additives are processing aids and also impart “special” properties to the end product.
Other materials that we will cover include core materials. Depending on you application, core materials provide stiffness while being lightweight.
Polymers are generally petrochemical or natural gas derivatives and can be either thermoplastic or thermosetting. Both types of polymers are used in composites and can benefit when combined with reinforcing fibers.
However, the major volume of thermoplastic polymers are not used in composite form.
In contrast to thermoplastics, thermosetting polymers generally require reinforcing fibers of high filler loading in order to be used.
Properties required are usually dominated by strength, stiffness, toughness, and durability. The end-user must take into account the type of application, service temperature, environment, method of fabrication, and the mechanical propeties needed.
Proper curing of the resin is essential for obtaining optimum mechanical properties, preventing heat softening, limiting creep, and reducing moisture impact.
A graphite pellet containing the catalyst is put in the middle of an inert gas-filled quartz tube placed in an oven maintained at a temperature of 1,200 ◦C. The energy of the laser beam focused on the pellet permits it to vaporize and sublime the graphite by uniformly bombarding its surface. The carbon species swept by a flowof neutral gas are thereafter deposited as soot in different regions: on the conical water-cooled copper collector, on the quartz tube walls, and on the backside of the pellet.
The power can be varied from 100Wto 1,600 W. The temperature of the target is measured with an optical pyrometer, and these measurements are used to regulate the laser power to maintain a constant vaporization temperature. The gas, heated by the contact with the target, acts as a local furnace and creates an extended hot zone, making an external furnace unnecessary. The gas is extracted through a silica pipe, and the solid products formed are carried away by the gas flow through the pipe and then collected on a filter.
The principle of this technique is to vaporize carbon in the presence of catalysts (iron, nickel, cobalt, yttrium, boron, gadolinium, and so forth) under reduced atmosphere of inert gas (argon or helium). After the triggering of the arc between two electrodes, a plasma is formed consisting of the mixture of carbon vapor, the rare gas (helium or argon), and the vapors of catalysts. The vaporization is the consequence of the energy transfer from the arc to the anode made of graphite doped with catalysts. The anode erosion rate is more or less important depending on the power of the arc and also on the other
experimental conditions. It is noteworthy that a high anode erosion does not necessarily lead to a high carbon nanotube production.
SWNTs are deposited (provided appropriate catalysts are used) in different regions of the reactor:
(1) the collaret, which forms around the cathode;
(2) the web-like deposits found above the cathode;
(3) the soot deposited all around the reactor walls and bottom.
As opposed to regular (metallic) electron emitting tips, the structural perfection of carbon nanotubes allows higher electron emission stability, higher mechanical resistance, and longer life time. First of all, it allows energy savings since it needs lower (or no) heating temperature of the tips and requires much lower threshold voltage. As an illustration for the latter, producing a current density of 1mA/cm2 is possible for a threshold voltage of 3V/µm with nanotubes, while it requires 20V/µm for graphite powder and 100V/µm for regular Mo or Si tips. The subsequent reductions in cost and energy consumption are estimated at 1/3 and 1/10 respectively. Generally speaking, the maximum current density obtainable ranges between 106 A/cm2 and 108 A/cm2 depending on the nanotubes involved (e.g., SWNT or MWNT, opened or capped, aligned or not) [3.219–221]. lthough nanotube side-walls seem to emit as well as nanotube tips, many works have dealt (and are still dealing) with growing nanotubes perpendicular to the substrate surface as regular arrays (Fig. 3.28b). Besides, using SWNTs instead of MWNTs