STUDIES ON SYNTHESIS AND PROPERTIES OF NEW TETRATHIFULVALENE DERIVATIVES

Synthesis of three new tetrathiafulvalene(TTF)derivatives-tetrakis(p-halobenzylthio)tetrathiafulvalene and their precursors4,5-bis(p-halobenzylthio)-1.3-dithiole-2-thione is reported Theelectronic spectra of these TTF derivatives show that the energy differences between theirπ-orbitals are smaller than that between BEDT-TTF. The surface pressure-area isotherm fortetrakis(p-chlorobenzylthio)tetrathiafulvalene(TCBT-TTF) indicates that the new TTF derivatives may have good film-forming properties and may be used to prepare Langmuir-Blodgett films.

Effect of annealing treatment on microstructures,mechanical properties and cavitation erosion performance of high velocity oxy-fuel sprayed NiCoCrAlYTa coating

The mechanical parts serving in the marine environment are up against the dual damage of corrosion and cavitation erosion,so the Ni Co Cr Al YTa coating with excellent corrosion resistance is successfully prepared by high velocity oxy-fuel(HVOF)sprayed technology to protect the equipment from deterioration.The chemical composition and mechanical properties as well as the microstructure evolution of the coating before and after annealing treatment are studied.At the same time,the influence of annealing treatment on the corrosion and cavitation erosion behaviors of the coating is investigated,as well.The NiCoCrAlYTa coating mainly containsγ-Ni,β-Ni Al,andγ’-Ni3Al phases.During the deposition,the microcrystals or incomplete crystals generate in the interior of the coating because of the large temperature difference and impact force.Meanwhile,there is twin crystal structure in the as-spayed coating.After annealing treatment,the growth of grains and the segregation of reactive elements improve interface strength and inhibit the formation of micro-defects in the coating.The annealing temperature is of significance to the microstructure,mechanical properties,anti-corrosion and cavitation erosion resistance of the coating.This study provides a combined approach toward improving the corrosion and cavitation erosion resistance of NiCoCrAlYTa coatings.

Fibers reinforced composite hydrogels with improved lubrication and load-bearing capacity

Hydrogels as one kind of soft materials with a typical three-dimensional(3D)hydrophilic network have been getting great attention in the field of biolubrication.However,traditional hydrogels commonly show poor tribology performance under high-load conditions because of their poor mechanical strength and toughness.Herein,pure chemical-crosslinking hydrogels mixed with different types of the micron-scale fibers can meet the requirements of strength and toughness for biolubrication materials,meanwhile the corresponding tribology performance improves significantly.In a typical case,three kinds of reinforcement matrix including needle-punched fibers,alginate fibers,and cottons are separately combined with Poly(n-vinyl pyrrolidone)-poly 2-hydroxyethyl methacrylate(PVP-PHEMA)hydrogels to prepare fibers reinforced composite hydrogels.The experimental results show that the mechanical properties of fibers reinforced composite hydrogels improve greatly comparable with pure PVP-PHEMA hydrogels.Among three kinds of fibers reinforced composite hydrogel,the as-prepared composite hydrogels reinforced with needle-punched fibers possess the best strength,modulus,and anti-tearing properties.Friction tests indicate that the fibers reinforced composite hydrogels demonstrate stable water-lubrication performance comparable with pure PVP-PHEMA hydrogels.Besides,the hydrogel-spunlace fiber samples show the best load-bearing and anti-wear capacities.The improved tribology performance of the composite hydrogels is highly related to mechanical property and the interaction between the fibers and hydrogel network.Finally,spunlace fibers reinforced hydrogel materials with high load-bearing and low friction properties are expected to be used as novel biomimetic lubrication materials.