Applied Mechanics and Materials Vols. 341-342

Abstract: A series of TiC-TiB₂ ceramics were prepared by combustion synthesis in ultra-high gravity field, the microstructure, fracture behavior and toughening mechanism of the composite ceramic are discussed. The maximum fracture toughness of 13.1 MPa · m^0.5 is achieved in TiC-66.7%TiB_2, very close to the values (10~15 MPa · m^0.5) of fiber-reinforced ceramic composite, contributed from the intensive coupled toughening mechanisms of crack deflection, frictionally crack-bridging and pull out by a large number of fine TiB₂ platelets and ductile phase toughing caused by a few Cr-Al metallic phases.

Abstract: Half-Heusler compound YNiBi thin films have been prepared by direct current (DC) magnetron sputtering from an YNiBi target. The film structure and surface morphology of YNiBi thin films were analyzed with X-ray diffraction (XRD) and atomic force microscopy (AFM). The electrical properties of the films were studied by Hall measurements. XRD patterns show that the films prepared at lower sputtering pressure and higher growth temperature exhibit minimum full width at half maximum (FWHM) and maximum diffraction peaks which belong to the same family of crystal planes. Results of AFM reveal that the surface of a variety of fabricated YNiBi films is smooth and keeps good adhesion to the substrate. The increasing of substrate temperature and slightly lowering of sputtering pressure are in favor of reducing the root mean square roughness during magnetron sputtering process. The film with high crystallinity has an electrical conductivity of 938 S/cm and carrier concentration of 2.15×10²¹ cm^-3.

Abstract: Polysulfone modified epoxy resin was chosen as the matrix of composite materials. The epoxy/glass fiber/boron nitride composite materials were prepared by heat press molding. The effect of different size and content of BN on the thermal, mechanical, electrical properties and thermal stability of the composite was investigated. The results showed that thermal conductivity and thermal stability of the composite increased with the content of the BN particles, the thermal conductivity of the composite reached 0.672W/m·K when filled with 1μm BN at 20 wt.%. Impact strength and flexure strength of the composite increased initially and then decreased with the increasing content of BN. The electrical insulating property of the composite remained with the content of 20 wt.% BN.

Abstract: The surface chemistry method is used to produce Zinc Aluminium oxide (ZAO) particle surface which modifying tubular TiO₂ and can produce nanotubes composite material of ZAO/TiO₂. The influence of different atom proportionings, aluminum doping amount as well as the contents of Zn and other conditions on the production of composite material's surface morphology, microstructure and photocatalytic performance were Study with XRDSEMTEM and other characterization means. The experiments indicated when Zn:Ti=1:4(a.t.),it has the best catalytic effect and the methyl orange degradation rate can reach 95% at 50min.

Abstract: A Fe-based composite coating reinforced with in situ synthesized TiC-TiB₂ particles was successfully fabricated on Q235A by laser cladding with mixture powder of TiO₂, Al, B4C, C and Fe55 as precursors. The microstructure and mechanical properties of coating were investigated. The results show that the main phases of coating are TiB₂, TiC, (Fe,Cr)₇C₃ and α-Fe. TiC particles show the shape of block, TiB₂ particles exhibit the shape of strip. Compared with the Q235A, the microhardness of the composite coating improved drastically.

Abstract: Graphite-FeSi absorbents were fabricated by mechanical milling method. The complex permittivity and permeability were measured in frequency 1-4 GHz, and then reflection loss (RL) and shielding effectiveness (SE) were calculated. It was obtained that the graphite was bonded to the surface of FeSi by X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images. The permittivity and permeability could be enlarged as graphite added in the milling process. It was attributed to the excellent conductivity of graphite and interactions of the two particles. The graphite-FeSi composites had a better shielding property (maximum 25.93 dB) in 1-4 GHz as well as the absorbing property at 1GHz than FeSi composites.

Abstract: To improve bonding strength between Ti alloy and bioceramic coating and to eliminate thermal stress during laser cladding, gradient bioceramic coating materials is designed. The bioceramic coating is fabricated by wide band laser cladding technique. And the effect of adding single and multiple rare earth oxide on microstructure is investigated. The samples are soaked with SBF for 14 days, the experimental results indicate that when the content of single rare earth oxide is 0.6wt.%Y₂O₃, a large number of bioactivity phase and chrysanthemum shape microstructure can be observed. When the content of single rare earth oxide is 0.2wt.%Sm₂O₃, a lot of bioactivity phase and coral reef shape microstructure can be observed. When the content of multiple rare earth oxide is 0.3wt.%Sm₂O₃ and 0.4wt.%Y₂O₃, a large amount of bioactivity phase and more homogeneous and dense spherical particles can be observed on coating, which demonstrates the microstructure is of better bioactivity.

Abstract: In this paper, purified multi-walled carbon nanotubes (MWNTs) were obtained by acid treatment and oxidation treatment using the crude MWNTs, then purified MWNTs were filled into acrylate pressure-sensitive adhesive (PSA) to produce electrically conductive adhesives (ECAs). XRD and TEM results showed that the impurities were greatly eliminated after purification treatment. The electrical conductivity of the ECAs increased gradually as the content of the purified MWNTs increased. When the content of the purified MWNTs is 4.0vol%, the properties of ECAs are optimum.

Abstract: The surface of the nanostructured ceramic coatings after grinding appears cracks, these cracks will reduce components intensity, and the cause of these cracks is grinding surface residual stress. The surface residual stress makes the distance change regularly with crystal orientation and stress changing on the cognate crystal plane of different crystal grain, therefore the X ray diffraction line offset, according to the size of the offseted position, the residual stress can be calculated by using σ = K • M.

Abstract: The paper used indentation fracture mechanics model or cutting model to deal with the grinding removal mechanism of nanostructured ceramic coatings, the interaction between the abrasive grains and the workpiece was approximately regarded as ideal small-scale indentation phenomenon, it was used to evaluate the surface quality in ceramic machined processing that formation of grinding crack and its propagation process, the material removed process and the surface defects of the ceramic grinding, the cutting model proved that although the removed material is usually brittle removal, most of the grinding energy consumption was related with plastic deformation.