Advanced Materials Research Vols. 189-193

Abstract: Microstructures, thermal shock resistance and isothermal oxidation resistance of plasma-sprayed nanostructured ceria stabilized zirconia (CSZ) coatings were investigated. The results revealed that the nanostructured CSZ coatings mainly included two kinds of typical microstructures, nanosized CSZ particles embedded in the so-called matrix and micrometer-sized columnar grain structures of CSZ similar to those of the conventional coatings. Compared with the conventional CSZ coatings, the nanostructured CSZ coatings were denser and had finer and fewer porous structures and microcracks. Further study showed that the nanostructured CSZ coatings had higher thermal shock resistance and isothermal oxidation resistance compared with conventional CSZ coatings. The improved properties of the nanostructured CSZ coatings were attributed to the better coating toughness and decreased porosities and microcracks in the coatings.

Abstract: According to the status and service environment of a domestic wharf, the corrosion of reinforced concrete structure was evaluated by multiple detection methods, on the base of which the corresponding repair and anti-corrosion program were adopted, thus good preservative effect was achieved. The research work and demonstration project are expected to provide technical discussion and reference for peer experts, as well as technical basis for the corrosion protection of reinforced concrete structures in similar marine environment.

Abstract: The pure vanadium specimen of 99.65% relative density was prepared by hot isostatic pressing. The initial oxidation characteristics and constructions of pure vanadium at different temperatures were analyzed by thermogravimetric test apparatus (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that the oxidation process and oxygen uptake of pure vanadium follow parabolic kinetics. The activation energy for the oxidation process is 118KJ/mol. With the rising of temperature, the predominant oxide phases are VO_0.03, VO₂ and V₂O₅ in turn. Under 500°C , the specimens’ surface morphology is densely distributed. While at 600°C , the fine fish-scale-shaped morphology is evenly distributed.

Abstract: The MoS₂ powders was coated with Al₂O₃ ratio varying 5wt.% to 50wt.% content. Ni–MoS₂/Al₂O₃ composite coatings were prepared by means of pulse electrodeposition in a nickel-plating bath containing MoS₂/Al₂O₃ powder to be co-deposited. The dependence of surface morphology, microhardness and tribological properties of the composite coatings was investigated in relation to the Al₂O₃ ratio in MoS₂/Al₂O₃ powder. The results demonstrate that the coating co-deposited with MoS₂/50wt.%Al₂O₃ showed a compact and fine granular surface morphology; the highest microhardness and wear resistance. The hardness of Al₂O₃ is responsible for this improvement.

Abstract: Extrusion Freeform Fabrication Process (EFF) is an environmentally friendly solid freeform fabrication method that uses aqueous pastes to fabricate ceramic-based components. The Liquid Phase Migration (LPM) causes variation in liquid content and consequently problems in the paste extrusion. To get uniform ceramics parts with desired composition, the LPM should be avoided in extrusion process. This paper investigated the influence of LPM on extrusion process for aqueous alumina paste in EFF process. It shows that the liquid phase migration occurs in Freeform Extrusion Fabrication process and has a strong impact on extrusion pressure. The LPM can be characterized by the extrusion pressure-ram displacement profiles. The liquid phase migration becomes more serious in intermittent extrusion at low ram velocity.

Abstract: In order to obtain stable and homogeneous diamond-Ni-P composite electroless plating, dispersants were selected by determining the height of emulsion in the colorimetric cylinder after standing different time.The structure,elemental contents and properties of the diamond-Ni-P composite electroless plating coating were investigated by SEM and EDS. Experimental results show that OP-10 of 50mL•L^-1 and softex kw of 1g•L^-1 have better dispersing effect to diamond powder of 1g•L^-1 in water. This composite electroless plating solution can keep stable for more than twelve or eight hours respectively at 85°C. While in the electroless plating solution, Softex kw of 1g•L^-1 has better dispersing effect and can be stable for more than two hours at 85°C. The diamond powder grains in the composite coating are homogeneous and the content of carbon is 2.261 wt% under the certain amount of the selected dispersant. When the content of diamond was 5g•L^-1 in the solution, the diamond powders were dispersed non-homogeneously in plating and cluster phenomena were appeared. The composite electroless plating coating consists of amorphous Ni-P and diamond powder. Its hardness and porosity are similar to those of the electroless plating Ni-P coating. The wear-resisting is improved greatly,which is 2.6 times of electroless plating Ni-P or 2 times of that after heat treatment at 400°C for one hour.

Abstract: Multi-component metal ceramic coating（Ti, Al）C was prepared on the 0.45% carbon steel by electrical discharge coating (EDC) in a hydrocarbon medium. The coating of the samples before and after oxidation was analyzed by different methods including X-ray diffraction (XRD), scanning electron spectroscopy (SEM) and energy disperse spectroscopy (EDS).The thermogravimetric technique was used to approximate the kinetics of oxidation of the coated and the uncoated samples.The results indicated that the thickness of the coating was about 20μm, and the composition of the ceramic coating mainly consisted of (Ti, Al) C and a little Ti₃AlC. An oxide film with compact structure formed after 600°C oxidation for 200h, and it was mainly composed of Al₂O₃ and TiO₂, which inhibited further oxygen diffusion into the coating. The (Ti, Al) C ceramic coating possessed slow oxidation rate and high temperature oxidation resistance.

Abstract: As we know , the materials will swell and contract when it is heated or cooled . A kind of method for mastery the real contractive rate of thermoplastic was bring forward through researching the contractive rate of thermoplastic . Using the method a inspecting testing mould of thermoplastic was designed , and the real contractive rate was masteried by the mould . And this provides the reliable contract date for the design of mould cavity dimension , and reduces the work of mould repair , and also save a lot of money and labor.

Abstract: The effect of Cd and Sb addition on the microstructural and mechanical properties of as-cast AZ31 alloys was investigated and compared. The results indicate that the difference of Sb and Cd in the microstructure and mechanical properties of as-cast AZ31 magnesium alloy is significant. Addition of 0.15%Sb (mass fraction) to AZ31 alloy can refine the matrix and β-Mg₁₇Al₁₂ phase but not form a new phase Mg₃Sb₂. Oppositely, by addition of 0.3-0.7% Cd to AZ31 alloy, Cd was dissolved into the AZ31 alloy, the phase composition did not change but was refined also. Accordingly, the Cd-refined AZ31 alloy exhibits higher tensile and impact toughness and Brinell hardness properties than the Sb- refined one. The difference of Sb and Cd in the mechanical properties is possibly related to the solid solution of Cd into the matrix and formation of Mg₃Sb₂ which has the same close-packed hexagonal structure as α-Mg.

Abstract: The flat compression properties of corrugated sandwich structure are an important factor to evaluate their cushioning properties. At present, more research has been made on the mechanical properties in the cross direction (CD) and machine direction (MD), but less has been made in the flat compression direction. Selecting corrugated paperboards as samples, we analyzed the flat compression properties of the corrugated sandwich structure and explored the critical stress which is a key element for evaluating the cushioning properties based on theory and experiment. It is convenient to evaluate the cushioning properties and optimize the corrugated sandwich structure. Simplifying the corrugated structure into the struts, and referring to the bending theory of the standard beam theory, we explored the evaluating equation of the critical stress for corrugated sandwich structure by the bending moment and Euler formulas. The critical stress is in direct proportion to the elastic modulus and the thickness of the basis material. It is also closely related to the length of the corrugated cell-wall and the pasted width between the corrugated cell-wall and the linerboard. Changing the above parameters, we can change the compression resistance of the corrugated sandwich structure. The theoretical value of the critical stress of the corrugated sandwich structure is higher than the experimental value, since the mechanical properties are lost when the basis material is manufactured into corrugated sandwiches and corrugated boards. Therefore, the lost coefficient is introduced into the theoretic equation which can not only help optimize and design the corrugated sandwich structure, but also find application in optimized design of cushioning pads of corrugated sandwich structure.