Find research datasets worth reusing

opencc-by-4.0Dec 2023View details →

The potential of nitric acid-functionalized carbon nanotubes to mitigate bacterial biofilms

Pristine multi-walled carbon nanotubes were functionalized with nitric acid, followed by thermal treatment at 600 °C, and incorporated into a poly(dimethylsiloxane) matrix. The composites were characterized and their antibiofilm activity and antibacterial mechanisms were assessed by biofilm cell culturability and flow cytometry, respectively.

opencc-by-4.0Dec 2023View details →

Analyzing marine biofilms developed on carbon nanotube-modified surfaces by 3D OCT approach

Glass, epoxy resin, and carbon nanotubes (CNT) composite were analyzed regarding wettability by water contact angle measurement, and roughness by atomic force microscopy. Cyanobacterial biofilms formed by Nodosilinea cf. nodulosa LEGE 10377 were developed on these surfaces for seven weeks and under controlled hydrodynamic conditions. Biofilm wet weight and structural parameters such as biofilm thickness, contour coefficient, biovolume, porosity, and average size of non-connected pores obtained from Optical Coherence Tomography (OCT) were assessed.

opencc-by-4.0Nov 2021View details →

Datasets for Supervised Learning Model Predicts Protein Adsorption to Carbon Nanotubes

All used Datasets to pair with "Supervised Learning Model Predicts Protein Adsorption to Carbon Nanotubes" by Nicholas Ouassil*, Rebecca L. Pinals*, Jackson Travis Del Bonis-O'Donnell, Jeffrey W. Wang, and Markita P. Landry *Co-authors

opencc-by-4.0Sep 2022View details →

TEM Data on Strontium-deficient SrxCoO2–CoO2 nanotubes

Raw data ((scanning) transmission electron microscopy images, diffraction patterns and EDX/EELS spectra) obtained for work on Strontium-deficient SrxCoO2–CoO2 nanotubes as a high ampacity and high conductivity material published in Materials Horizons

opencc-by-4.0Aug 2021View details →

Membrane-Interacting DNA Nanotubes Induce Cancer Cell Death

This dataset contains the raw data that were used for the publication entitled, "Membrane-Interacting DNA Nanotubes Induce Cancer Cell Death" published in Nanomaterials on 4 August 2021. Abstract: DNA nanotechnology offers to build nanoscale structures with defined chemistries to precisely position biomolecules or drugs for selective cell targeting and drug delivery. Owing to the negatively charged nature of DNA, for delivery purposes DNA is frequently conjugated with hydrophobic moieties, positively charged polymers/peptides, cell surface receptor recognizing molecules or antibodies. Here, we designed and assembled cholesterol-modified DNA nanotubes to interact with cancer cells and conjugated them with cytochrome c to induce cancer cell apoptosis. By flow cytometry and confocal microscopy, we observed that DNA nanotubes efficiently bound to the plasma membrane as a function of the number of conjugated cholesterol moieties. The complex was taken up by the cells and localized to the endosomal compartment. Cholesterol-modified DNA nanotubes, but not unmodified ones, induced increased membrane permeability, caspase activation and cell death. Irreversible inhibition of caspase activity, with Z-VAD-FMK, however, only partially prevented cell death. Cytochrome c conjugated DNA nanotubes were also efficiently taken up but did not increased the rate of cell death. These results demonstrate that cholesterol-modified DNA nanotubes induce cancer cell death associated with increased cell membrane permeability and only partially dependent on caspase activity, consistent with a combined form of apoptotic and necrotic cell death. DNA nanotubes may be further developed as primary cytotoxic agents, or drug delivery vehicles, through cholesterol mediated cellular membrane interactions and uptake.

opencc-by-4.0Aug 2020View details →

Data and statistical analysis for: Bacterial nanotubes are a manifestation of cell death

Contains all data and code to reproduce the statistical analysis in the Supplementary file 2 for the paper "Bacterial nanotubes are a manifestation of cell death" to be published in Nature Communications. Contents: <ul> <li>statistical_analysis.Rmd is the main document written in R Markdown</li> <li>statistical_analysis.html is a compiled version of statistical_analysis.Rmd showing all the computed results.</li> <li>The Source data.xls file contains raw data used for the analysis - the sheet names indiciate the figure they refer to. See the main file for code that can read the data.</li> </ul> The code can also be accessed at <a href="https://github.com/cas-bioinf/nanotubes-death">https://github.com/cas-bioinf/nanotubes-death</a>

opencc-by-4.0Aug 2017View details →

A Single Walled Carbon Nanotube of the (6,5) Type

The files show a rotating single walled carbon nanotube as a continuos gif file. The Pictures also show a commonly used Polymer (PFO-Bpy) as it adsorbes on the carbon nanotube surfaces. * CNT created with Avogadro's CNT building tool. * PFO-Bpy and Toluene created with ChemBioDraw as molecular files and imported to Avogadro * Export from Avogadro to xyz file * import to blender using [molecular blender](https://github.com/smparker/molecular-blender) * Gif creation using [Bligify](https://github.com/doakey3/Bligify)

opencc-by-4.0Oct 2023View details →

Dataset on the Laser-induced graphitization of polydopamine on titania nanotubes

The following dataset contains various research data that is the basis for the research article:  "Laser-induced graphitization of polydopamine on titania nanotubes".This dataset contains the following folders corresponding to the techniques and procedures used in the paper: - DFT (.hdf5 libraries containing quantum chemistry results described in the paper including atomic coordinates and density of states data) - Electropolymerization (.txt files containing cyclic voltammetry curves of electropolymerization) - IMPS_IMVS (a library of folders containing .raw and .dat files used in IMPS = Intensity Modulated Photocurrent Spectroscopy and IMVS = Intensity Modulated Photovoltage Spectroscopy measurements) - Nanoindentation (.xlsx files containing nanoindentation data) - Photocurrent_maps (.dat files used to build photocurrent maps) - Photoelectrochemical_sensing (.dat files of photoelectrochemical sensing experiments) - Photoelectrochemistry (.opju libraries containing massive amounts of electrochemical and photoelectrochemical results described in the paper including EIS = Electrochemical Impedance Spectroscopy, CV = Cyclic Voltammetry, CA = Chronoamperometry, Raman spectroscopy)  - ReaxFF (.hdf5 libraries containing reactive molecular dynamics results) - SEM (.tiff SEM images) - Supplementary_fsTNT_PDA (a library of folders containing various supplementary data on loosely-spaced nanotubes including Raman, SEM, electrochemistry, and photoelectrochemistry data) - UV-vis (.csv files from diffuse reflectance spectroscopy measurements) - XPS (.xlsx files from X-Ray Photoelectron spectroscopy measurements)

opencc-by-4.0Nov 2023View details →

Research data on IMVS / IMPS Higher harmonics of the Si Photodioed / TiO2 nanotubes

The following dataset contains research data that is the basis of research article:"Higher harmonics of the Intensity Modulated Photocurrent/Photovoltage Spectroscopy Response - a Tool for studying Photoelectrochemical Nonlinearities"Contensts of the package are the following:a) Experimental results of the IMVS for the photodiode (2-electrode system)<ol><li>OCP vs. power density relations [2 files]</li><li>Higher harmonic spectra for varying AC components 10,20,30,40 and 50 % (DC component fixed at 50% = 2 mW) [25 files]</li></ol>b) Experimental results of the IMPS for the TiO2 nanotubes (3-electrode system)<ol><li>Photocurrent vs. power density relation for polarization potentials 200mV, 400mV, 600mV, 800mV, 1000mV [2 files]</li><li>Higher harmonic spectra for varying AC components 10,20,30,40 and 50% at +1000 mV polarization (DC component fixed at 50% = 2 mW) [20 files]</li><li>Higher harmonic spectra for varying polarization potential 200mV, 400mV, 600mV, 800mV (AC and DC components fixed at 50% and 50%) [31 files]</li></ol>

opencc-by-4.0Mar 2024View details →

TEM images of Cu decorated carbon nanotubes

Atlas of TEM images for proprietary copper-decorated carbon nanotubes.

opencc-by-4.0Dec 2021View details →

Computational Data supporting "Porous covalent organic nanotubes and their assembly in loops and toroids"

Computational research data supporting the article: Kalipada Koner, Shayan Karak, Sharath Kandambeth, Suvendu Karak, Neethu Thomas, Luigi Leanza, Claudio Perego, Luca Pesce, Riccardo Capelli, Monika Moun, Monika Bhakar, Thalasseril G. Ajithkumar, Giovanni M. Pavan, and Rahul Banerjee,  "Porous Covalent Organic Nanotubes and Toroids: A Carbon Nanotube Analogue"

opencc-by-4.0Jun 2022View details →

Carbon Nanotube Uptake in Cyanobacteria for Near-infrared Imaging and Enhancing Bioelectricity Generation in Living Photovoltaics

Dataset of the work entitled "Carbon Nanotube Uptake in Cyanobacteria for Near-infrared Imaging and Enhancing Bioelectricity Generation in Living Photovoltaics".

opencc-by-4.0Jul 2022View details →

(DATASET) Functionalized boron–nitride nanotubes: First-principles calculations.

Boron nitride nanotubes (BNNTs), a type of nanomaterial that was first made in 1995, have gained attention in the last two and a half decades, having been characterized as promising inorganic nanoparticles for the application and development of devices in nanomedicine (such as drug delivery systems), and chemical sensors, among other applications. With the use of density functional theory (DFT) calculations, we study the effect of functionalizing the surface of a BNNT with hydroxyl (-OH) and carboxyl (-COOH) organic groups at the N and B sites. The results indicate that the -OH radical remains adsorbed in the B site whereas it is detached from the surface when added to the N site. Very differently, the -COOH remains attached for both adsorption sites. Both functionalizations induced a magnetic moment, produced spin-polarized electronic bands, created flat impurity-like bands, decreased the band gaps, and modified the electron density of the nanotubes. All these changes can be used to control and modify the interaction of BNNTs with other molecules of interest like drugs, heavy metals, and greenhouse gasses, among other substances.

Structure of single-walled carbon nanotubes

Structure of single-walled carbon nanotubes Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com   Carbon nanotubes take on many different forms but generally fall into two groups. The first group is multi-walled carbon nanotubes and the second group is single-walled carbon nanotubes. A multi-walled carbon nanotube is basically a nested formation of multi-axial layered carbon pipes with caps at either end of the cylinder structure and can be created with various chemical reactions but are commonly fabricated using a form of carbon arc discharge in the proper environment. A single-walled carbon nanotube is essentially a rolled-up graphite sheet that forms a very small thin cylinder with no seam. The fabrication of a single-walled carbon nanotube is similar to a multi-walled carbon nanotube with the addition of a metallic catalyst. The length and diameter of a single-walled carbon nanotube is dependent on the type of metallic catalyst used and the environmental conditions employed during fabrication. Single-walled carbon nanotubes are of interest as they could play the same role in circuits as silicon does today. The advantage of single-walled carbon nanotubes is that they form naturally much smaller than most silicon transistors. This drastic reduction is size could result in a dramatic increase in the processing speed of electronics due to the reduced distances signals would have to travel. Single-walled carbon nanotubes have been obtained in early fabrication techniques using a carbon arc chamber similar to that used for fullerene production. An anode consisting of a graphite carbon rod and a cathode consisting of a rod with a piece of iron placed in a small dimple therein are placed in the chamber that is filled with methane and argon. The single-walled carbon nanotubes were found in soot-like deposits formed during the carbon arc process. A slightly different single-walled carbon nanotube was obtained using cobalt instead of iron and helium instead of methane and argon. Known methods of fabrication of single-walled carbon nanotubes result in a combination of semiconductors and conductors. Additionally, known methods of fabrication of single-walled carbon nanotubes result in very impure carbon nanotubes in that a low percentage of the resulting material constitutes single-walled carbon nanotubes. The use of known fabrication methods requires extensive purification processes afterward to remove the non-single-walled carbon nanotube structure. As the impurities are often larger than or similar in size to the single-walled carbon nanotubes, the use of filtering in the purification process proves difficult. Furthermore, known fabrication methods are inefficient, in that only one or two grams of carbon nanotubes are likely to be produced. These early fabrication techniques produced impure carbon nanotubes and only in small numbers. The catalytic materials used in single-walled carbon nanotube fabrication prevent the large scale fairly pure production of these structures. To date, other fabrication techniques have indicated little if any promise of being scaled into mass production of single-walled carbon nanotubes in either pure or impure form. In addition, all known production methods are labor and chemical intensive, thus making them very costly. The cylindrical sidewalls can be produced from different rolling directions to make single-walled carbon nanotube with distinct structures and properties. Due to cylindrical symmetry, there are only a handful of methods that are effective in making seamless cylinders, and they are characterized by the chiral vectors with integer indices. To establish the chiral vector, two atoms in the graphene sheet are selected, with one serving as the origin of the vector pointing toward the other atom. The graphene sheet is then rolled in a way that allows the two atoms to coincide. These structural variations result in differences in electrical conductivity and mechanical strength.

Structure of single-walled carbon nanotube reinforced polymer matrix composites

Structure of single-walled carbon nanotube reinforced polymer matrix composites Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com   A composite material, also called a composite, is a solid material that results when two or more different substances, each with its own characteristics, are combined to create a new substance whose properties are superior to those of the original components in a specific application. The term composite more specifically refers to a structural material within which a fibrous material is embedded. The remarkable properties of composites are achieved by embedding fibers of one substance in a host matrix of another. In materials science, a polymer matrix composite is a composite material composed of a variety of short or continuous fibers bound together by a matrix of organic polymers. Polymer matrix composites are designed to transfer loads between fibers of a matrix. Some of the advantages with polymer matrix composites include their light weight, high resistance to abrasion and corrosion, and high stiffness and strength along the direction of their reinforcements. The function of the matrix in polymer matrix composites is to bond the fibers together and transfer loads between them. Polymer matrix composites matrices are typically either thermosets or thermoplastics. Thermosets are by far the predominant type in use today. Thermosets are subdivided into several resin systems including epoxies, phenolics, polyurethanes, and polyimides. Of these, epoxy systems currently dominate the advanced composite industry. Unlike fiber-reinforced polymer matrix composites, nanomaterials reinforced polymer matrix composites are able to achieve significant improvements in mechanical properties at much lower loadings. Carbon nanotubes in particular have been intensely studied due to their exceptional intrinsic mechanical properties and low densities. In particular carbon nanotubes have some of the highest measured tensile stiffnesses and strengths of any material due to the strong covalent bonds between carbon atoms. However, in order to take advantage of the exceptional mechanical properties of the nanotubes, the load transfer between the nanotubes and matrix must be very large. Like in fiber-reinforced composites, the size dispersion of the carbon nanotubes significantly affects the final properties of the composite. Long carbon nanotubes lead to an increase in tensile stiffness and strength due to the large-distance stress transfer and crack propagation prevention. On the other hand, short carbon nanotubes do not lead to any enhancement of properties without any interfacial adhesion. However once modified, short carbon nanotubes are able to further improve the stiffness of the composite, however there is still very little crack propagation countering. In general, long and high aspect ratio carbon nanotubes lead to greater enhancement of mechanical properties, but are more difficult to process. Aside from size, the interface between the carbon nanotubes and the polymer matrix is of exceptional importance. In order to achieve better load transfer, a number of different methods have been used to better bond the carbon nanotubes to the matrix by functionalizing the surface of the carbon nanotube with various polymers. These methods can be divided into non-covalent and covalent strategies. Non-covalent carbon nanotube modification involves the adsorption or wrapping of polymers to the carbon nanotube surface, usually via van der Waal's or π-stacking interactions. In contrast, covalent functionalization involves direct bonding onto the carbon nanotube. This can be achieved in a number of ways, such as oxidizing the surface of the carbon nanotube and reacting with the oxygenated site, or using a free radical to directly react with the carbon nanotube lattice. Covalent functionalization can be used to directly attach the polymer to the carbon nanotube, or to add an initiator molecule which can then be used for further reactions.

Structure of carbon nanotubes

Structure of carbon nanotubes Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com   Carbon nanotubes, also called buckytubes, are nanoscale hollow tubes composed of carbon atoms. Single-walled carbon nanotubes are one of the allotropes of carbon, intermediate between fullerene cages and flat graphene, with diameters in the range of one nanometer. Although not made this way, single-walled carbon nanotubes can be idealized as cutouts from a two-dimensional hexagonal lattice of carbon atoms rolled up along one of the Bravais lattice vectors of the hexagonal lattice to form a hollow cylinder. In this construction, periodic boundary conditions are imposed over the length of this roll-up vector to yield a helical lattice of seamlessly bonded carbon atoms on the cylinder surface. Multi-walled carbon nanotubes consisting of nested single-walled carbon nanotubes weakly bound together by van der Waals interactions in a tree ring-like structure. If not identical, these carbon nanotubes are very similar to Oberlin, Endo, and Koyama's long straight and parallel carbon layers cylindrically arranged around a hollow tube. Multi-walled carbon nanotubes are also sometimes used to refer to double-walled and triple-walled carbon nanotubes. Carbon nanotubes can exhibit remarkable electrical conductivity, while others are semiconductors. They also have exceptional tensile strength and thermal conductivity because of their nanostructure and strength of the bonds between carbon atoms. In addition, they can be chemically modified. These properties are expected to be valuable in many areas of technology, such as electronics, optics, composite materials, nanotechnology, and other applications of materials science. Rolling up a hexagonal lattice along different directions to form different infinitely long single-walled carbon nanotubes indicates that all of these carbon nanotubes not only have helical but also translational symmetry along the carbon nanotube axis and many also have nontrivial rotational symmetry about this axis. In addition, most are chiral, meaning the carbon nanotube and its mirror image cannot be superimposed. This construction also allows single-walled carbon nanotubes to be labeled by a pair of integers. The structure of an ideal single-walled carbon nanotube is that of a regular hexagonal lattice drawn on an infinite cylindrical surface, whose vertices are the positions of the carbon atoms. Since the length of the carbon-carbon bonds is fairly fixed, there are constraints on the diameter of the cylinder and the arrangement of the atoms on it. In the study of carbon nanotubes, one defines a zigzag path on a graphene-like lattice as a path that turns 60 degrees, alternating left and right, after stepping through each bond. It is also conventional to define an armchair path as one that makes two left turns of 60 degrees followed by two right turns every four steps. On some carbon nanotubes, there is a closed zigzag path that goes around the carbon nanotube. One says that the carbon nanotube is of the zigzag type or configuration, or simply is a zigzag carbon nanotube. If the carbon nanotube is instead encircled by a closed armchair path, it is said to be of the armchair type, or an armchair carbon nanotube. An infinite carbon nanotube that is of the zigzag or armchair type consists entirely of closed zigzag or armchair paths, connected to each other. Novel chemical, electrical, and mechanical properties absent in other materials have been discovered in carbon nanotubes. Pristine carbon nanotubes are inert to most chemicals and need to be grafted with surface functional groups to increase their chemical reactivity and add new properties. For single-walled carbon nanotubes, electrical conductivity is dependent on the chiral vector and independent of the length as determined by quantum mechanics. Along the longitude directions, carbon nanotubes show superior mechanical strength, with the highest known tensile strength and elastic modulus among known materials.

Fluid mechanics of carbon nanotube reinforced polymer composites

Fluid mechanics of carbon nanotube reinforced polymer composites Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com   Fluid mechanics is the science concerned with the response of fluids to forces exerted upon them. It is a branch of classical physics with applications of great importance in hydraulic and aeronautical engineering and chemical engineering. Fluid mechanics is a subject with almost endless ramifications, and the account that follows is necessarily incomplete. Some knowledge of the basic properties of fluids will be needed. Fluids are not strictly continuous media in the way that all the successors of Euler and Bernoulli have assumed, for they are composed of discrete molecules. The molecules, however, are so small and, except in gases at very low pressures, the number of molecules per milliliter is so enormous that they need not be viewed as individual entities. There are a few liquids, known as liquid crystals, in which the molecules are packed together in such a way as to make the properties of the medium locally anisotropic, but the vast majority of fluids are isotropic. In fluid mechanics, the state of an isotropic fluid may be completely described by defining its mean mass per unit volume, or density, its temperature, and its velocity at every point in space, and just what the connection is between these macroscopic properties and the positions and velocities of individual molecules is of no direct relevance. A number of phenomena of considerable physical interest can be discussed using little more than the law of conservation of energy. However, the argument has so far been restricted to cases of steady flow. To discuss cases in which the flow is not steady, an equation of motion for fluids is needed, and one cannot write down a realistic equation of motion without facing up to the problems presented by viscosity, which have so far been deliberately set aside. Thermodynamics is the science of the relationship between heat, work, temperature, and energy. In broad terms, thermodynamics deals with the transfer of energy from one place to another and from one form to another. The key concept is that heat is a form of energy corresponding to a definite amount of mechanical work. Although thermodynamics developed rapidly during the 19th century in response to the need to optimize the performance of steam engines, the sweeping generality of the laws of thermodynamics makes them applicable to all physical systems. In particular, the laws of thermodynamics give a complete description of all changes in the energy state of any system and its ability to perform useful work on its surroundings. Classical thermodynamics does not involve the consideration of individual atoms or molecules. Such concerns are the focus of the branch of thermodynamics known as statistical thermodynamics, or statistical mechanics, which expresses macroscopic thermodynamic properties in terms of the behavior of individual particles and their interactions. It has its roots in the latter part of the 19th century, when atomic and molecular theories of matter began to be generally accepted. The application of thermodynamic principles begins by defining a system that is in some sense distinct from its surroundings. In general, systems are free to exchange heat, work, and other forms of energy with their surroundings. A particularly important concept is thermodynamic equilibrium, in which there is no tendency for the state of a system to change spontaneously. For example, the gas in a cylinder with a movable piston will be at equilibrium if the temperature and pressure inside are uniform and if the restraining force on the piston is just sufficient to keep it from moving. The system can then be made to change to a new state only by an externally imposed change in one of the state functions, such as the temperature by adding heat or the volume by moving the piston. A sequence of one or more such steps connecting different states of the system is called a process.

Fundamental interactions between carbon nanotubes and polymers

Fundamental interactions between carbon nanotubes and polymers Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com   Carbon nanotubes, also called buckytubes, are nanoscale hollow tubes composed of carbon atoms. The cylindrical carbon molecules feature high aspect ratios typically above one thousand, with diameters from about one nanometer up to tens of nanometers and lengths up to millimeters. This unique one-dimensional structure and concomitant properties endow carbon nanotubes with special natures, rendering them with unlimited potential in nanotechnology-associated applications. Carbon nanotubes are members of the fullerene family. According to the number of graphic shells, they are mainly categorized as single-walled and multi-walled carbon nanotubes. Novel chemical, electrical, and mechanical properties absent in other materials have been discovered in carbon nanotubes. Pristine carbon nanotubes are inert to most chemicals and need to be grafted with surface functional groups to increase their chemical reactivity and add new properties. Along the longitude directions, carbon nanotubes show superior mechanical strength, with the highest known tensile strength and elastic modulus among known materials. As for thermal properties, carbon nanotubes outperform diamond as the best thermal conductor. Applications of carbon nanotubes are aimed to make use of their unique properties to solve problems at the nanoscale. Their high surface area, together with the unique ability to carry any chemical compounds after surface modification, offers carbon nanotubes the potential to be used as nanoscale catalyst supports with high catalytic reactivity and chemical sensors. A polymer, is any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, that are multiples of simpler chemical units called monomers. The word polymer designates an unspecified number of monomer units. When the number of monomers is very large, the compound is sometimes called a high polymer. Polymers are not restricted to monomers of the same chemical composition or molecular weight and structure. Some natural polymers are composed of one kind of monomer. Most natural and synthetic polymers, however, are made up of two or more different types of monomers; such polymers are known as copolymers. Synthetic polymers are produced in different types of reactions. Many simple hydrocarbons, such as ethylene and propylene, can be transformed into polymers by adding one monomer after another to the growing chain. Polyethylene, composed of repeating ethylene monomers, is an addition polymer. Polyethylene is crystalline, translucent, and thermoplastic. It is used for coatings, packaging, molded parts, and the manufacture of bottles and containers. Polypropylene is also crystalline and thermoplastic but is harder than polyethylene. Other addition polymers include polybutadiene, polyisoprene, and polychloroprene, which are all important in the manufacture of synthetic rubbers. Some polymers, such as polystyrene, are glassy and transparent at room temperature, as well as being thermoplastic. Polystyrene can be colored any shade and is used in the manufacture of toys and other plastic objects. Many important polymers have oxygen or nitrogen atoms, along with those of carbon, in the backbone chain. Among such macromolecular materials with oxygen atoms are polyacetals. The simplest polyacetal is polyformaldehyde. It has a high melting point and is crystalline and resistant to abrasion and the action of solvents. Acetal resins are more like metal than are any other plastics and are used in the manufacture of machine parts such as gears and bearings. A linear polymer characterized by a repetition of ester groups along the backbone chain is called a polyester. Open-chain polyesters are colorless, crystalline, thermoplastic materials.

Thermodynamics of single-walled carbon nanotubes

Thermodynamics of single-walled carbon nanotubes Junjie Chen Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com   A system's condition at any given time is called its thermodynamic state. For a gas in a cylinder with a movable piston, the state of the system is identified by the temperature, pressure, and volume of the gas. These properties are characteristic parameters that have definite values at each state and are independent of the way in which the system arrived at that state. In other words, any change in value of a property depends only on the initial and final states of the system, not on the path followed by the system from one state to another. Such properties are called state functions. In contrast, the work done as the piston moves and the gas expands and the heat the gas absorbs from its surroundings depend on the detailed way in which the expansion occurs. The behavior of a complex thermodynamic system can be understood by first applying the principles of states and properties to its component parts, in this case, water, water vapor, and the various gases making up the atmosphere. By isolating samples of material whose states and properties can be controlled and manipulated, properties and their interrelations can be studied as the system changes from state to state. The concept of temperature is fundamental to any discussion of thermodynamics, but its precise definition is not a simple matter. It is necessary to have an objective way of measuring temperature. In general, when two objects are brought into thermal contact, heat will flow between them until they come into equilibrium with each other. When the flow of heat stops, they are said to be at the same temperature. The zeroth law of thermodynamics formalizes this by asserting that if an object A is in simultaneous thermal equilibrium with two other objects B and C, then B and C will be in thermal equilibrium with each other if brought into thermal contact. Object A can then play the role of a thermometer through some change in its physical properties with temperature, such as its volume or its electrical resistance. Energy has a precise meaning in physics that does not always correspond to everyday language, and yet a precise definition is somewhat elusive. The word is derived from the Greek word ergon, meaning work, but the term work itself acquired a technical meaning with the advent of Newtonian mechanics. As the science of physics expanded to cover an ever-wider range of phenomena, it became necessary to include additional forms of energy in order to keep the total amount of energy constant for all closed systems or to account for changes in total energy for open systems. Thermodynamics encompasses all of these forms of energy, with the further addition of heat to the list of different kinds of energy. However, heat is fundamentally different from the others in that the conversion of work or other forms of energy into heat is not completely reversible, even in principle. Although classical thermodynamics deals exclusively with the macroscopic properties of materials, such as temperature, pressure, and volume, thermal energy from the addition of heat can be understood at the microscopic level as an increase in the kinetic energy of motion of the molecules making up a substance. For example, gas molecules have translational kinetic energy that is proportional to the temperature of the gas: the molecules can rotate about their center of mass, and the constituent atoms can vibrate with respect to each other. Additionally, chemical energy is stored in the bonds holding the molecules together, and weaker long-range interactions between the molecules involve yet more energy. The sum total of all these forms of energy constitutes the total internal energy of the substance in a given thermodynamic state. The total energy of a system includes its internal energy plus any other forms of energy, such as kinetic energy due to motion of the system as a whole and gravitational potential energy due to its elevation.