FeCo/graphene was synthesized by twostep process, i.e. co-precipitation and then annealing treatment. The phase constituent and morphology of the as-prepared FeCo/graphene were characterized by XRD, FESEM and TEM, respectively. Further, composites of FeCo/graphene-paraffin with different filler amount were prepared and their electromagnetic parameters were measured by microwave vector network analyzer. Then, the reflection loss of the composites was calculated. Results show that the composite of thickness 1.6 mm with the mass ratio of 1:1 for FeCo/graphene to paraffin exhibits the optimal microwave absorption property with an effective bandwidth of 5.0 GHz (12.3~17.3 GHz). The excellent microwave absorption properties of the composite may originate from the combination of dielectric and magnetic loss along with the proper impedance match ratio and attenuation constant.

The effect of section size and solution treatment process on micropore of a nickel-based single crystal superalloy DD33 was investigated by optical microscope (OM) and scanning electron microscope (SEM). The results show that the primary dendrite arm spacing and the volume fraction of eutectics increase with the increasing of section size in the as-cast alloys. Solidification micropores occur at locations near the eutectic. The volume fraction of solidification micropores increases slightly with the increasing of section size. After the same solution treatment for alloys, the volume fractions of residual eutectics and micropores increase with the increasing of section size. Under the condition of the same section size, the volume fraction of micropores increases with the increasing of solution temperature. The formation of internal micropores is due to the Kirkendall effect induced by imbalanced diffusion of the elements during solution treatment. The different section sizes of castings lead to the different segregation degrees, which results in the different volume fractions of the homogenization micropores. According to the evolution of microstructure of the blade, the appropriate solution treatment process was designed and then verified experimentally.

The microstructure evolution and mechanical properties of a cold-rolled Mn-Al transformation-induced plasticity (TRIP) steel with δ ferrite were investigated after annealed at different intercritical annealing temperature for different time. The results show that as the intercritical annealing temperature and time going up, the content of retained austenite (RA) and the product of strength and elongation (PSE) increased first and then decrease. The microstructure of the steel after annealing at 750℃ for 2 min consists of δ ferrite, intercritical ferrite and 24.7% retained austenite, which exhibited a tensile strength of 773 MPa, elongation of 39.4% and the product of strength and elongation of 30.46 GPa%. RA mainly exits at the boundaries between bulky δ ferrite and original martensite, around the recrystallization ferrite from original martensite area, and around the sub-grain boundaries inside δ ferrite.

Creep behavior of the ball grid array (BGA) of lead-free solder joints of Sn-0.7Ag-0.5Cu-3.5Bi-0.05Ni (SACBN) was investigated via nanoindentation by step loading-unloading and single loading-unloading respectively. The results show that: for the two different test modes with the same load 60 mN and holding time 300 s, the creep displacement of solder joints by step loading-unloading is significantly less than that by single loading-unloading. However, the creep hardness for the former case is 1.87 times of that of the later one. The indentation creep decreased at three stages for the case of step loading-unloading, however the creep hardness increased. The creep exponent n was obtained by fitting calculation and found that the n value for the step loading-unloading is 1.31 times of that for single loading-unloading. The creep resistance performance of micro solder joints was improved by strain hardening during the process of step loading-unloading.

In order to study the effect of the form of surface texture on the wettability and tribological performance of materials in oil and water, a theoretical model of hydrodynamic lubrication of textured surface is established to calculate the carrying capacity of the hydrodynamic lubricating film for material with surface texture composed of prism- and cone frustum- like concaves. The calculated results indicate that the carrying capacity of the hydrodynamic lubricating film of the surface with cone frustum-like concaves is 2.4 times larger than that with prism-like ones in case of the area ratio of concaves is 19.6%. According to the above theoretical mode, surface texture composed of prism- and cone frustum-like concaves respectively was established on 5083 Al-alloy via laser processing and then was surface modified with sol-gel SiO₂ coating of low-surface energy. The test result shows that the contact angle of the surface with prism-like concaves is 2°~4° bigger than that with cone frustum-like ones. While with two surface textures plus amphiphobic coating, the tribological performance the 5083 Al-alloy can be significantly enhanced. Besides, the tribological performance of the 5083 Al-alloy with surface texture of cone frustum-like concaves is better than that of prism ones, which is consistent with the calculation results. Finally, the effect of the shape of concaves on the tribological performance is greater than that on the wettability.

The ball bearing steel 8Cr4Mo4V was heat treated by a two step process,i.e. solid solution treatment at temperatures in the range of 1050~1100^oC, and followed with a mesothermal phase transition treatment at 260℃. The microstructure and mechanical property such as hardness and impact toughness of the treated steel were characterized by means of optical microscope scanning electron microscopy and electron probe as well as harness tester and impact tester. Results show that after solution treatment at 1050℃ and 1065℃, certain amount of tinny dot-like carbides still remain in the steel, which hinders the growth of the grains of the steel. However, after solution treatment at 1095℃ and 1110℃, the tinny dot-like carbides all dissolve, thus the average grain size increases. It is noted that the solution treatment only facilitate the solution of the Cr- and V-containing crabide, but not the Mo-containing one. As a result of the high temperature solid solution treatment, the Cr- and V-content of the matrix increase to certain extent, which can reduce the diffusion coefficient of carbon in the matrix and the number of nucleus for bainite formation and the final amount of bainite phase, therewith leading to coarsening of bainite phase. With the increase of solid solution temperature, the hardness of the steel increases, while the impact toughness decreases.

In order to improve the interfacial property of carbon fiber composites, the carbon fiber was pretreated by plasma technique and then coated with polypyrrole (PPy) by chemical oxidation polymerization of pyrrole. The surface modified carbon fiber and composite were characterized by SEM, AFM, XPS, FT-IR and IFSS. Results show that the interfacial shear strength of the modified single fiber increased by 259.3%, which may be ascribed to that the plasma pretreatment can increase the amount of polar groups on the surface of the carbon fiber, and facilitate the formation of hydrogen bonds between the carbon fiber and PPy, thus enhancing the interfacial property of the composite PPy-carbon fiber/epoxy.

TRIP (transformation induced plasticity) 980 high strength steel and SPCC (steel plate cold common) low carbon steel of about 1.5 mm in thickness were welded by resistance spot welding. The optimal welding parameters were acquired according to the test results of the joint shear tensile load. Then the performance and microstructure of the spot welded joint prepared by the optimal process were characterized by means of electronic tensile testing machine, micro-hardness meter, OM, SEM, EBSD and EDS. Results showed that the metallurgical bonding between the two base materials is realized, the molten nuclear of the spot welded joint is oval and has large deviation, molten nuclear of the side of SPCC steel is smaller than that of the TRIP980 one. The interface can obviously be observed in molten core region of spot welded joint. Shear tensile fracture of the spot welded joint is located at the interface, which is close to the edge of fusion zone of the side of SPCC steel, and the fracture is brittle fracture. The microhardness of molten nuclear on the side of the SPCC steel is lower than that of the TRIP980 one, but there existed a peak value of the hardness of nugget zone on the side of the SPCC steel. Elements of C, Mn, Si and Al etc. presented different diffusivity in the molten nuclear, and of which the concentration declines from the side of the TRIP980 steel to that of the SPCC one. The microstructure of the side melting zone of SPCC low carbon steel is quite different. The microstructure near the parent material is soft ferrite. The microstructure near the nugget side is hard martensite. The stress concentration caused by this difference is the main reason that affects the mechanical properties of the joints.

A foam structured catalyst of ZnFe₂O₄-α-Fe₂O₃/SiC was prepared by a slurry-coating method with citric acid-nitrates as binder. Its phase composition, morphology and pore structure were characterized by XRD, SEM and BET. The influence of the concentration of citric acid-nitrates and the deposited amount of slurry on the morphology, pore structure and catalytic performance in the oxidative dehydrogenation of 1-butene of the prepared catalyst were investigated. The result show that the concentration of citric acid-nitrates hardly changed the phase composition; the as-prepared structured catalyst has a compact and neat coating with a wide range distribution of pore size; the concentration of citric acid-nitrates of the slurry or the most probable pore size of the as-prepared catalyst has a little influence on the peformance of the structured catalyst. The BET surface area and the catalytic performance of the structured catalyst gradually increased with the incresing the deposited amount of slurry. In case of gas firing hourly space velocity of bntene of 300 h^-1, the conversion rate of 1-butene and selectivity of butadiene reache ca. 86% and 91%, respectively for the prepared structured catalyst with a deposited amount of 0.2 g/mL slurry, which are much higher than that for particulate catalysts, indicating superior oxidative dehydrogenation performance.

Graphene oxide (GO) nanosheets were prepared via oxidation treatment of graphite and then the dispersion liquid of which was prepared by ultrasound vibration in. The thickness and plane size of GO nanosheets are less than 11.95 nm and within 50~900 nm respectively. There are many chemical groups such as hydroxyl, carbonyl and epoxy groups on GO nanosheets. The prepared composite of graphene oxide/cement composited of ordinary cement and 0.03% GO nanosheets presents the regular micromorphology of ordinary cement, which consists of polyhedron-like cement hydration crystals by interweaving, penetrating and embedding each other. The compressive and flexural strength of the composite of GO/cement after curing for 28 days increase by 76.2% and 86.1% respectively, in comparison to that of the ordinary cement without GO addition, correspondingly the porosity and average pore diameter as well as cracks decrease obviously too.