Formation Of Graphite-like Structure Research Articles

Influence of Crystal Structure on the Set of Physicomechanical Characteristics of Composite Materials Based on Ultra-High Molecular Weight Polyethylene

Composite fibers containing boron(III) have been obtained based on solid solutions of cellulose in N-methylmorpholine-N-oxide and orthoboric acid with their subsequent transformation into a viscous-flow state. The rheological behavior of cellulose solutions with different content of orthoboric acid and water studied under conditions of continuous and dynamic shear loading has confirmed the intermolecular interaction between the components. It has been shown that the mechanical characteristics of the composite fibers obtained from a 16% solution in N-methylmorpholine-N-oxide are comparable to these for hydrated cellulose fibers. The process of transformation of the composite fibers of various compositions into carbon fiber has been investigated by means of thermogravimetric analysis and differential scanning calorimetry. Chemical, structural and morphological properties of composite hydrated cellulose fibers and carbon fibers obtained from them have been studied using FTIR-spectroscopy, X-ray diffraction, and scanning electron microscopy. The influence of boron(III) compounds on the carbonization process and the formation of graphite-like structures in carbon fiber has been investigated by Raman-spectroscopy.

Boron(III)-Containing Composite Hydrated Cellulose Fibers As Precursors of Carbon Materials

Composite fibers containing boron(III) have been obtained based on solid solutions of cellulose in N-methylmorpholine-N-oxide and orthoboric acid with their subsequent transformation into a viscous-flow state. The rheological behavior of cellulose solutions with different content of orthoboric acid and water studied under conditions of continuous and dynamic shear loading has confirmed the intermolecular interaction between the components. It has been shown that the mechanical characteristics of the composite fibers obtained from a 16% solution in N-methylmorpholine-N-oxide are comparable to these for hydrated cellulose fibers. The process of transformation of the composite fibers of various compositions into carbon fiber has been investigated by means of thermogravimetric analysis and differential scanning calorimetry. Chemical, structural and morphological properties of composite hydrated cellulose fibers and carbon fibers obtained from them have been studied using FTIR-spectroscopy, X-ray diffraction, and scanning electron microscopy. The influence of boron(III) compounds on the carbonization process and the formation of graphite-like structures in carbon fiber has been investigated by Raman-spectroscopy.

In situ graphitization of small organic molecules on the surface of nano titanium dioxide to construct highly efficient photosynthetic hydrogen peroxide composite catalyst

Hydrogen peroxide (H2O2) is a good strategic choice for developing sustainable energy. In recent years, although many researchers have focused on photocatalytic preparation of H2O2, the progress is still limited for the problems of low efficiency of H2O2 production, complex catalyst preparation, and high cost of catalyst. Here, a novel method to construct a hybrid photocatalyst was developed with one-step graphitization of specific organic small molecules, in which C, N, and O could be introduced simultaneously along with the formation of graphite-like structures within the inner pores of the nano-TiO2 surface. It not only changed the surface defects of TiO2 to successfully reduce its promotion on the photodecomposition of H2O2 but also adjusted the band gap of the catalyst and broadened its visible light absorption range. Besides, it also provided another two-electron oxygen reduction reaction pathway to enhance the catalytic activity of the photosynthesis of H2O2; thus, 11.78 mM/h H2O2, which exceeds all previously reported productivities, was produced under simulated sunlight. The modified catalyst not only has excellent ultraviolet light activity with an apparent quantum efficiency of 34.9% at 365 ± 5 nm but also has very good visible light activity with apparent quantum efficiency of 17.8% at 420 ± 5 nm and more than 1.66% solar-to-chemical conversion (>420 nm), which is very rare for nano-TiO2 and much promising for application. Our present research has proved that the organic molecule tetraethyl 4,4'-(1,4-phenylene)bis(2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate) successfully changed the surface defect modes of TiO2, making the oxygen defect that promotes the decomposition of H2O2 change to the C defect that is conducive to the photocatalytic generation of H2O2, and thus, the photocatalytic performance has been greatly improved. Thus, it is an important instruction for developing highly efficient and low-cost photocatalysts for synthesizing H2O2.

Effect of air annealing on mechanical properties and structure of SiCxNy magnetron sputtered films

Amorphous SiCxNy films (of 2.2–2.7μm) were deposited on Si(111) substrates by reactive DC magnetron sputtering. The SiC target with small excess of carbon was sputtered at various N2/Ar gas flow ratios (0–0.48). The as-deposited films were additionally annealed at temperatures of 700, 900 and 1100°C in the air during 30min and at 900°C in vacuum during 1h. The depth profile of hardness and elastic modulus (nanoindentation), change of the film thickness, film composition and structure (Raman and Infrared spectroscopy) were investigated in dependence on annealing temperature and content of nitrogen.The hardness of the as-deposited films decreases with the growth of N2/Ar flow ratio. Air annealing at 700°C leads to atomic short-range ordering in the amorphous SiCxNy films that significantly increases their hardness and elastic modulus at all used loads (10–100mN). The hardness of the SiCxNy films annealed in air at 900°C reduces when measured at low indenter loads (10–20mN) due to onset of top layer oxidation. Hardness of inner layers, measured at 50–100mN loads, increases approaching values exhibited by the vacuum annealed films. Air annealing at 1100°C leads to intensive surface oxidation and formation of graphite-like structure in carbon clusters of inner layers. The hardness and oxidation resistance of the investigated SiCxNy films reduce with the increase of N2/Ar ratio.

Graphitic structure formation in ion implanted polyetheretherketone

Ion implantation is a technique that is used to change the electrical, optical, hardness and biocompatibility of a wide range of inorganic materials. This technique also imparts similar changes to organic or polymer based materials. With polymers, ion implantation can produce a carbon enriched volume. Knowledge as to the nature of this enrichment and its relative concentration is necessary to produce accurate models of the physical properties of the modified material. One technique that can achieve this is X-ray photoelectron spectroscopy.In this study the formation of graphite like structures in the near surface of polyetheretherketone by ion implantation has been elucidated from detailed analysis of the C 1s and valence band peak structures generated by X-ray photoelectron spectroscopy. Further evidence is given by both Rutherford backscatter spectroscopy and elastic recoil detection.

A theoretical study of carbon chemisorption on nickel surfaces

The effective medium theory is used to calculate chemisorption energies, bond lenghts and vibrational frequencies for carbon chemisorbed on Ni surfaces. The formation of graphite-like structures on Ni(111) is discussed.