Advanced Materials Research Vols. 123-125

Abstract: Beta–D-poly-glucopyranose is widespread class of the natural semi-crystalline polysaccharide known as cellulose. This polymer has complicated multi-level supermolecular structure. It is built from elementary nano-fibrils and their aggregates; moreover, each nano-fibril contains ordered nanocrystallites and low-ordered amorphous nano-domains. Therefore cellulose can be a pronounced and eminent representative of nano-structured matters. Such nano matter has peculiar physico-chemical properties depending on specific surface of nano-scale constituents. In this paper, physico-chemistry of the nano-structured cellulose is discussed. In particular, the ability of nano-scale crystallites to co-crystallization and aggregation, as well as their ability to phase transformation through dissolution, alkalization and chemical modification was a subject of the investigation. Structural characteristics of paracrystalline surface layers of nano-crystallites and their effect on physico-chemical properties of the polysaccharide have been discussed.

Abstract: SDBS modified graphene was prepared by electrochemical method using Sodium dodecylbenzenesulfonate (SDBS) as electrolyte and graphite rod as electrode. The anode graphite rod was corroded and deposited at the bottom of the electrolyte solution. The obtained graphene was characterized by Atomic force microscopy (AFM), Raman and Fourier transform infrared spectra (FT-IR). AFM images indicated that most of the layers had the thickness of less than 2 nm, suggesting the fromation of single layer of graphene. The resulting graphene showed very good dispersion stability both in water and in organic solvents (ethanol, acetone).

Abstract: Onion-like carbon (OLC) was fabricated by annealing nanodiamond at temperatures ranging from 500°C to 1400°C. At 800°C, nanodiamond was completely transformed into amorphous carbon. At 900°C, OLC began appearing. As the annealing temperature increased from 1000°C to 1200°C, OLC particles size became larger and larger and the amorphous carbon coexisted in the center of the OLC particle became less and less. At 1400°C, all the amorphous carbon was transformed into the OLC.

Abstract: Sodium Alginate/bentonite clay composites of different compositions were prepared by solution casting method. The electrical properties (Conductivity, Dielectric constant) of the composites were investigated by standard methods with Impedance Analyzer. The electrical properties were found to improve with the incorporation of bentonite clay. The thermal, physical and mechanical properties of sodium alginate/bentonite clay composite were investigated by Thermo-Mechanical Analyzer (TMA), X-ray Deffraction (XRD), and Universal Testing Machine respectively. . Tensile Strength (TS) and Elongation at break (Eb) of 2% clay containing composite film were found to be 7.6 MPa and 55% respectively. The XRD demonstrates the enhancing crystallinity of sodium alginate/bentonite clay composite with the increasing clay content. TMA results showed a higher thermal stability in the composite. Water absorption properties of the sodium alginate/clay composite were studied and found to decrease with the increase of clay content. . The inter action between sodium alginate and bentonite clay were studied by Fourier transform infrared spectroscopy (FT-IR). All of the results indicate that the developed composite is promising for use in a wide variety of optoelectronic applications.

Abstract: A simple direct synthesis method was used to synthesis SiC/SiO2 core–shell coaxial nanocables by thermal evaporation of the mixture powders of silicon monoxide and active carbon at 1300°C and condensation on Si substrate without assistance of any catalyst. The SiC core typically has diameters of 10-40 nm and is covered by a uniform layer of 2-10nm thick amorphous SiO2. A double vapor–solid growth process is proposed for the formation of this novel structures based on detailed structural characterizations. The cable nanostructures may find applications as building blocks in nanomechanical or nanoelectronic devices.

Abstract: A dense nanostuctured Fe3Al was consolidated by high frequency induction heated sintering method within 2 minutes from mechanically synthesized powders of Fe3Al and milled powders of 3Fe+Al. The consolidation was accomplished under the combined effects of a induced current and mechanical pressure. The grain size, sintering behavior and hardness of Fe3Al sintered from horizontally milled Fe+Al powders and high energy ball milled Fe3Al powder were compared. Keywords: Combustion synthesis; Nanomaterials; Mechanical properties; Rapid sintering

Abstract: As the positive electrodes of Ni/MH batteries, the Ni(OH)2 Electrodes needs some additives to enhance their high power performance. In this paper, two kinds of nanoscale additives were synthesized and added to the Ni(OH)2 electrodes respectively and the high rate discharge capabilities of both electrodes were investigated. Compared with the Ni(OH)2 electrodes with usual CoO, the electrodes with carbon nanotubes and with nanoscale carbon particles modified onto the surface of Ni(OH)2 spheres both presented much better cycling stability and higher specific capacity when discharged at high current rate. It is suggested that when the nanoscale additives were added to the electrodes, more sufficient conductive networks formed among Ni(OH)2 spheres. The results indicate that the nanoscale materials such as carbon nanotubes and nanoscale carbon particles are desirable additives for high power Ni/MH batteries in addition to usual CoO.

Abstract: A short review of recent investigations of the authors on the Ru(II)-based optical oxygen sensors is presented focused on the influence of: (i) type of the supporting matrix (SiO2 or polymethylmetacrylate based), (ii) precursors used (tetraethoxysilane, ormosil-type alkoxosilanes, methylmetacrylate, polymethylmetacrylate), (iii) method applied for the matrix synthesis, (iv) method for films deposition (dip- and spin coating), (v) chromophore leaching as a result of storage of the films in potentially aggressive media (water, diluted acidic and basic solutions) and (vi) working environment nature on the: a) films morphology, b) the analytical characteristics of the sensing component (linearity of the Stern-Volmer dependence, sensitivity of the device, reproducibility of the results), c) admissible parameters (pH, temperature) of the working medium. Special attention is paid on the effect of sol-sonication (as a tool against dye microcrystallization). The results obtained permit optimal precursors, sol preparation conditions and coating procedure to be recommended for gas and for dissolved oxygen measurement, respectively. The sonication of the sol ensures a rather significant improvement of the sensor performance. The strong quenching of the chromophore in the case of in-situ polymerization of the methylmetacrylate is observed.The sensing films are successfully applied for oxygen determination in natural lake waters and beer.

Abstract: During recent years, there have been efforts in developing nanocrystalline bioceramics, to enhance their mechanical and biological properties for use in hard tissue engineering applications. In this work, we study the effects of some sintering additive nanopowders dopants on the properties of the sintered HA structures. Calculated quantities of silica nanopowders are incorporate as dopants into dried HA nanopowder. The mixing powders are uniaxially compacted and then sintered at 1200°C by rate-controlled sintering method in air. Compositional, microstructural, morphological and mechanical characterizations are carried out on sintered HA samples.

Abstract: Polyhedral oligomeric silsesquioxanes (POSS) possessing 7-oxanorbornene-5, 6-dicarboximide (POSS-ONDI) functionalized macromers are synthesised and well characterized using FT-IR, 1H, 13C and 29Si-NMR spectroscopic techniques. The homopolymer of [N-3(trifluoromethyl)phenyl-7-oxanorbornene-5,6-dicarboximide] (TFONDI) and a series of linear copolymers between [N-(POSS)-7-oxanorbornene-5, 6-dicarboximide] POSS-ONDI and TFONDI are prepared through ring opening metathesis polymerisation (ROMP) using Grubbs catalyst. All the polymers are characterized using FT-IR, 1H-NMR, TGA, DSC, AFM, TEM, XRD and GPC techniques.