Solid State Phenomena Vol. 106

Abstract: Thallium sulphide layers of different composition were obtained on the surface of polyethylene when it was sulphurised in a solution of higher polythionic acid, H2S33O6, and then treated with an alkaline solution of thallium(I) sulphate. The stoichiometric composition of the thallium sulphide layers varied between Tl0.3S and Tl2.6S depending on the formation conditions of the layers of TlxSy. A phase composition of the layers obtained was confirmed by X-ray photoelectron spectroscopy. The spectra of Tl 4f7/2, O 1s and S 2p showed the bond of thallium with sulphur in TlS and Tl2S , but Tl2SO4, Tl(OH)3, S8 and Tl2O3 were also found on the surface of the layers. Five thallium sulphide phases TlS, Tl2S, Tl2S2, Tl4S3 and Tl2S5 have also been identified in the layers by X-ray diffraction. The peaks of the TlS phase predominate in the diffractograms.

Abstract: Nanoparticles of carbides, nitrides and carbonitrides can be used to reinforce polymer matrix nanocomposites to obtain the required strength, hardness, corrosion and wear resistance. In order to efficiently achieve the desirable properties the polymer matrix and nanoparticles must be optimised. This paper reports on studies undertaken on TiC reinforced polymer matrix nanocomposites. The TiC nanoparticles were produced by sol-gel method and nanocomposites were obtained in situ, via the reaction and synthesizing of polyether-ester copolymer (PEE). TiC nanoparticles were characterised with a scanning electron microscopy (SEM) and the microstructure of the composites was examined by SEM and atomic force microscopy (AFM). Tensile properties were determined. For comparison, samples of polymer were also studied and composites with submicron size of TiC particles. The results, which are discussed in terms of size of the TiC particles, showed that the particles incorporated in the polymer matrix, influence the strength of the composites.

Abstract: Fullerene-doped liquid crystal compounds have been considered as new nanostructured materials with promising photosensitivity and speed parameters. Self-organization in liquid crystal mesophase based on charge-transfer complexes between an organic donor and fullerene has been investigated. The switch-on time of 50 μs has been obtained. The results are discussed from the viewpoint of increasing the system polarizability and a possible transition from the nematic phase to the smectic one, which is caused by a complex formation.

Abstract: In this work cBN-TiN composites were studied. The composites were prepared by the HPHT technique (p=8 GPa, T=1750 0C). A TiN binding phase was used in two forms: as micro and nanomaterials. Thermodynamic calculations showed that formation of new phases in the cBNTiN composites was not possible in the experimental conditions which was confirmed by XRD investigations carried out. The surface morphology of nanocomposites was studied by scanning electron microscopy. The structure of these composites was compact; a TiN phase was uniformly distributed between cBN grains. Hardness was measured by the Vickers method using an indentation load of 9.81 N. The hardness of the investigated samples was dependent on the volume and grain size of the binding phase. Young's modulus of elasticity was determined, but its value was found to be dependent on the grain size of the TiN phase.

Abstract: Future materials for wear resistant components require a combination of excellent mechanical properties such as hardness and toughness, short processing times and good electrical conductivity to facilitate shaping by electro discharge machining (EDM). In this work, the hardness and fracture toughness of t-ZrO2 based electro conductive composites was optimised, while short processing times below 20 minutes using spark plasma sintering were sufficient to obtain near fully dense materials. The influence of powder processing technique using TiC0.5N0.5 as the starting powder and yttria as a stabiliser on the mechanical properties of ZrO2-TiC0.5N0.5-Al2O3 based composites was investigated. Fully dense Y-TZP based composites possessed an excellent toughness of 9.2 MPa.m1/2 and an increased Vickers hardness of 1397 kg/mm².

Abstract: An Al2O3/Ni-P composite was formed by hot pressing of alumina powder, coated with chemically plated nano Ni-P. The powders were consolidated at room temperature, 600 and 1000oC. The consolidated specimens were studied by SEM, TEM/HRTM, MFM (magnetic force microscopy) and tested or hardness. It was found that the fabrication method results in a structure of interpenetrating phases of high electric conductivity and that samples consolidated at room temperature and sintered at 600oC retain the nanometric grain size of the metallic phase. Hardness measurements are discussed in terms of the fabrication temperature and structure of the composites.