The Thermo-Oxidative Behavior of Cotton Coated with an Intumescent Flame Retardant Glycine-Derived Polyamidoamine: A Multi-Technique Study

Linear polyamidoamines (PAAs) derived from the polyaddition of natural α-amino acids and N,N′-methylene bis(acrylamide) are intumescent flame retardants for cotton. Among them, the glycine-derived M-GLY extinguished the flame in horizontal flame spread tests at 4% by weight add-on. This paper reports on an extensive study aimed at understanding the molecular-level transformations of M-GLY-treated cotton upon heating in air at 300 °C, 350 °C and 420 °C. Thermogravimetric analysis (TGA) identified different thermal-oxidative decomposition stages and, coupled to Fourier transform infrared spectroscopy, allowed the volatile species released upon heating to be determined, revealing differences in the decomposition pattern of treated and untreated cotton. XPS analysis of the char residues of M-GLY-treated cotton revealed the formation of aromatic nanographitic char at lower temperature with respect to untreated cotton. Raman spectroscopy of the char residues provided indications on the degree of graphitization of treated and untreated cotton at the three reference temperatures. Solid state 13C nuclear magnetic resonance spectroscopy (NMR) provided information on the char structure as a function of the treatment temperature, clearly indicating that M-GLY favors the carbonization of cotton with the formation of more highly condensed aromatic structures.

Thick Si-doped DLC coatings with high load bearing capacity on cold working tool steels by PECVD

For improving the wear resistance, thick silicon doped hydrogenated amorphous carbon (a-SiC:H) coatings were deposited on cold working tool steels by Plasma Enhanced Chemical Vapor Deposition (PECVD) technology. The increase of the acetylene (C2H2) flow rate distinctly tuned the microstructure of a-SiC:H coatings, including an increase in the coating thickness (>15 μm), a decrease in the silicon content, a greater sp2/sp3 ratio and higher degree of graphitization. The highest hardness of 19.61 GPa and the greatest critical load of 50.7 N were obtained. The coating showed low wear rates against different friction pairs and presented excellent abrasive wear resistance at high applied load and the wear rates decreased with increasing loads, which exhibited an outstanding application prospect in cold working tool steels.

Fluctuations in Graphitization of Coal Seam-Derived Natural Graphite upon Approaching the Qitianling Granite Intrusion, Hunan, China

The Lutang graphite deposit in Chenzhou, Hunan province, China, is a well-known coal seam-derived graphite (graphite formed from coal during its natural evolution) deposit with proven reserves of 9.5 million tons and prospective reserves of around 20 million tons (2015 data). The graphite occurs at an andalusite bearing sericite quartz chlorite metamorphic mudstone around a c. 530 km2 Qitianling granite intrusion. A set of coal seam-derived graphite samples from the Lutang graphite deposit in Hunan was examined by geochemical, crystallographic, and spectroscopic techniques to assess changes in the degree of graphitization approaching the intrusion. The carbon content, degree of graphitization, and Raman spectral parameters of series coal seam-derived natural graphite samples show a fluctuating increase with increasing proximity to the granite intrusion. The profile of geological structural features has a close spatial correlation with the variations in the degree of graphitization of series coal seam-derived natural graphite, and a strain-enhanced graphitization model is proposed. Moreover, the geographical distribution and the degree of graphitization are positively related to changes in the iron content of chlorite, suggesting a graphitization process promoted by mineral catalysis during metamorphism. A close spatial relationship exists between graphite mineral and chlorite occurrences when approaching the intrusive mass. The results of this research are important for understanding the role of tectonic stress and mineral catalysis on the genesis of coal-derived graphite.

SYNTHESIS OF CARBON NANOFIBERS BASED ON HUMIC ACID AND POLYACRYONITRILE BY ELECTROSPINNING METHOD

The article describes a method for obtaining carbon nanofibers (CNFs) based on humic acid from oxidized coal of the Maikuben basin and polycarlonitrile (PAN) by electrospinning in laboratory conditions. The value of the interelectrode voltage was 20-25 kV. The elemental composition was determined and the surface morphology of the studied sample was studied, the type of modification of the carbon fiber was revealed. As a result of energy dispersive X-ray spectroscopy and scanning electron microscopy (SEM), the chemical composition of the initial CNF (C-48.73%) and the diameter of carbon fibers, which ranged from 148.6 nm to 1.36 μm, were found. The processes of oxidation and carbonization of the obtained samples were also carried out. The elemental composition of carbon after oxidation and carbonization was 87.75 and 89.16%, respectively, the diameter of the fibers was 117.5 nm -1.03 microns. The results of Raman scattering of light (RS) of carbonized CNF showed the degree of graphitization - 23.97%, the ratio I (D) / I (G) = 0.7, I (G) / I (D) = 1.4. The resistance of this material was 27 ohms. On the basis of SEM patterns of CNFs based on humic acid and PAN, it was found that the structure of the sample after oxidation and carbonization retains the original fibrous structure. It was also found that the diameter of nanofibers decreases from 1 μm to 117.5 nm, which may be associated with the release of volatile and heterogeneous components of the original product and the formation of a more structural thin porous filament.

The effect of changing graphitization temperature toward bio-graphite from Palm Kernel Shell

This paper focuses on the relationship between heat treatment temperature toward structural transformation from amorphous carbon to highly graphitic carbon material during a production stage.The following report discusses a simple strategy to convert the palm kernel shell (PKS) into highly crystalline, high quality graphite via simple two-step process. The production involves impregnation of catalyst followed by thermal treatment. Both XRD and Raman spectroscopy allowed the observation of microstructural change of the prepared sample at temperature ranging from 1000°C to 1400°C using Ferum catalyst. From XRD pattern it can be observed that as graphitization temperature increased, the degree of graphitization also increased. Overall sample prepared at higher temperature 1400°C shows a higher degree of graphitization. PKS sample graphitized at 1400°C with the aid of Ferum catalyst shows a sharp intensified peak at 2θ = 26.5° reflecting formation of highly crystalline graphite structure. Raman spectrum also suggests similar results to XRD in which PKS-1400 shows the presence of large amount of graphitic structure as the value of (Id/Ig) ratio is lower than in other samples. HRTEM analysis visibly shows define lattice fringe, which further confirms the structural transformation from amorphous to highly ordered graphitic carbon structure. Overall, good quality graphitic carbon structure from Palm Kernel shell was succesfully synthesised via utilization of PKS, Ferum catalsyt and heat treatment method.

Variable Temperature Synthesis of Tunable Flame-Generated Carbon Nanoparticles

In this study, flame-formed carbon nanoparticles of different nanostructures have been produced by changing the flame temperature. Raman spectroscopy has been used for the characterization of the carbon nanoparticles, while the particle size has been obtained by online measurements made by electrical mobility analysis. The results show that, in agreement with recent literature data, a large variety of carbon nanoparticles, with a different degree of graphitization, can be produced by changing the flame temperature. This methodology allows for the synthesis of very small carbon nanoparticles with a size of about 3-4 nm and with different graphitic orders. Under the perspective of the material synthesis process, the variable-temperature flame-synthesis of carbon nanoparticles appears as an attractive procedure for a cost-effective and easily scalable production of highly tunable carbon nanoparticles.

PRODUCTION OF CARBON NANOFIBERS BASED ON COAL TAR AND POLYACRYONITRILE BY ELECTROSPINNING METHOD

The article presents experiments on obtaining composite fibers based on Shubarkol coal tar (CT) and polycarlonitrile (PAN) by electrospinning in a laboratory setup. As a result of energy dispersive X-ray spectroscopy and SEM microscopy, the elemental composition (C-85.83%) and the diameter of the carbon fiber were determined, which ranged from 89.0 nm to 449.8 nm. The resulting CNF was subjected to oxidation in air at 300 °C, the holding time was 1 hour, after which the carbonization process was carried out at 800 °C, followed by cooling to room temperature. Raman spectra were recorded to study the degree of graphitization. The results of Raman scattering of light (RS) showed the degree of graphitization - 15.98%. Ratio I (D) / I (G) = 0.99, I (G) / I (D) = 1. The broad bands D (disordered part) and G (ordered graphite structure) suggest that CNFs contain partially graphitized carbon along with amorphous carbon. The ID / IG ratio represents the conversion of disordered carbon to graphite carbon during carbonization. The resistance of this material is 70-200 ohms. The results obtained confirm the semiconductor nature of the conductivity. On the basis of SEM drawings of CNFs from CT and PAN, it was found that the structure of CNFs after oxidation and carbonization retains the original fibrous structure. It was also found that the diameter of nanofibers decreases from 320.5 - 625.7 nm to 89-449.8 nm. Thus, the proposed method of obtaining CNF is built on the basis of the electrospinning method, which is the most promising method of industrial production.

Study of the Activated Charcoal Structure from Water Hyacinth Based on Carbonization Temperature Variations and Activators

The quality of the carbon material for application of electrodes in the battery is indicated by its ability to intercalate ions, atoms or molecules. Graphite is a carbon material with good intercalation capability. In this research, a carbon material in the form of activated charcoal produced from biomass of water hyacinth has been prepared, which is carbonized at various temperatures of 400, 500, and 600 °C with three different activators of ZnCl2, KOH and H3PO4. The activated charcoal will be used as a cathode composite in lithium sulfur batteries. To determine the quality of the activated charcoal, the structure properties of activated charcoal were characterized using X-ray diffraction (XRD). Several parameters that are determined from XRD data included the degree of crystallinity, and the degree of graphitization (Y). The degree of crystallinity was found in the ranges between 5.56 and 12.6%, where activated charcoal was dominated by amorphous structures. The value of the degree of graphitization was about 36%.

A study on the characteristics of coke in the hearth of a superlarge blast furnace

An in-depth study on the characteristics of coke in the hearths of blast furnaces is of great significance for explaining the mechanism of coke deterioration in blast furnaces. In the present work, the changes in macromorphology, degree of graphitization, and microstructure of the coke taken from different hearth locations of a 5,800 m3 superlarge blast furnace during its intermediate repair period were systematically studied. Significant differences were found between cokes obtained from the edge (“edge coke”) and from the center (“center coke”) of the hearth in terms of properties and degradation mechanisms. Edge coke was severely eroded by liquid metal, and only a small amount of slag was detected in the coke porosity, whereas center coke was basically free from erosion by liquid metal, and a large amount of slag was detected in the coke porosity. The degree of graphitization of edge coke was higher than that of center coke. The carburizing effect of liquid metal was the main cause of the degradation of edge coke and made it smaller or even disappear. Center coke was degraded due to the combination of two factors: slag inserted into micropores on the surface of center coke loosened the surface structure; and graphite-like flakes that appeared on the center coke surface lowered the strength and caused cracks in the surface.