Abstract:Mn12Ni2MoTi（Al） steels were fabricated by cold rolling with total reductions of 65% and 80%, respectively, and subsequently annealed at 745 ℃ for different times. The microstructures and mechanical properties of samples were investigated using X-ray diffraction（XRD）， scanning electron microscope（SEM）， transmission electron microscope（TEM）， and hardness and tensile tests. The nucleation and coarsening kinetics of Laves phase as well as its influence on grain refinement were also examined. The results show that the fine（Fe，Mn）2（Mo，Ti） Laves phases with hexagonal structure have precipitated during annealing for 5 min. With the increase of annealing time， the Laves particles gradually grow.The volume fraction of Laves particles increases rapidly in the first hour of annealing， and then slowly increases to the maximum value at 8 h. Afterwards，the volume fraction of Laves particles almost keeps unchanged. The Laves phases firstly precipitate at grain boundary，and then pin the grain boundary. The pinning pressure of Laves phase particles first increases and then decreases with the annealing time. When the annealing time is 4 h，the pinning pressure reaches the maximum value. Besides，the larger pre-deformation of cold rolled samples results in the higher coarsening rate of Laves phases. At the same annealing condition， the larger pre-deformation of samples leads to the smaller pinning pressure of Laves phases. Although the long-time annealing or large pre-deformation makes the pinning pressure provided by Laves phase particles to be small， Laves phase particles still can effectively pin the grain boundaries， which greatly improve the thermal stability of the recrystallization grain. For the 65% CR sample， the recrystallization grain still remains at sub-micron level after annealing for 8 h. The Mn12Ni2MoTi（Al） duplex steel with submicron recrystallization grain has both high yield strength and good elongation， which is much higher than that of quenched martensitic samples.

Abstract:The effect of solution time on the solid solution degree， microstructure and mechanical properties of 7050 aluminum alloy was studied by optical microscopy（OM），tensile test at room temperature and scanning electron microscopy（SEM）.The results show that，with the increase of solution time，the degree of recovery and recrystallization increases and the deformation grains change into equiaxed grains.The insoluble phases of Al7Cu2Fe and Al2CuMg in 7050 aluminum alloy are still difficult to dissolve with the prolongation of the solution time. The optimum solution process of 7050 aluminum alloy is solution at 477 ℃ for 1 h. After aging at 121 ℃ for 24 h，the best mechanical properties are measured，in which the tensile strength is 605 MPa，yield strength is 547 MPa，and elongation is 12.8%.

Abstract:The effect of Cu content on the microstructure， fracture and hardenbility of Al-7.6Zn-1.6Mg-XCu alloy was investigated by means of mechanical tensile and jominy end quench testing combined with optical microscopy（OM），scanning electron microscopy（SEM） and transmission electron microscopy（TEM）. The results showed that the strength of the alloys increased first and then decreased with the increase of Cu mass fraction， and the strength of the alloy peaked at Cu mass fraction of 1.70 %. The anisotropic mechanical properties of the alloys decreased first and then increased with the increase of Cu mass fraction， and the alloys had the minimum anisotropy when the Cu mass fraction was 1.45 %. Concomitant with the increase of Cu mass fraction， a transition in fracture mode was observed from predominantly transgranular dimpled rupture to predominantly intergranular dimpled rupture. Compared with the change of the longitudinal elongation of the alloys， the Cu mass fraction had a significant effect on the transverse elongation of the alloys. With the increase of Cu mass fraction and the decrease of quenching rate， obvious precipitation free zone（PFZ） was observed around the equilibrium phases of the alloys after aging， which resulted in significant reduction in hardenability and hardness of the alloys.

Abstract:The repetitive continuous extrusion forming process（R-Conform process）was carried out on the pre-aged 6201 Al alloy produced by continuous casting and rolling.The microstructure characteristic and mechanical property evolution of the R-Conform processed alloy were investigated using electron back-scatter diffraction（EBSD），transmission electron microscopy（TEM），X-ray diffractometer，polarizing metallographic microscopy，and tensile testing. The results show that R-Conform can effectively refine grain size and homogenize alloy microstructure. With the increase of R-Conform pass numbers， the balance of strength-ductility（TS×EL） increased from 2.93 GPa·% to 4.85 GPa·% after fourth passes，and then stabilized.A large number of β″ phases precipitated in the pre-aged 6201 Al alloy after pre-aging. With the increase of R-Conform pass numbers， the grain was effectively refined and the homogenized alloy microstructure was formed， where the average size of the grain was refined from 259 μm to 60 μm.Meanwhile，high density of dislocations formed，gradually tangled with each other，and finally transformed to subgrain boundaries.A part of needle β″ phases dissolved into the Al alloy matrix. The evolution of the mechanical property was mainly attributed to the combined effect of grain refinement and homogenization，the synthetic effect of dislocation increase and the dissolution of β″ phases.

Abstract:In order to elevate the localized corrosion resistance of 2A14 aluminum alloy，the effect of Cu content on the microstructure and corrosion-resistance properties of 2A14 aluminum alloy forgings was investigated by using scanning electron microscopy（SEM），pitting corrosion tests，cyclic anodic polarization curves （Tafel） and electrochemical impedance spectroscopy（EIS）. The results showed that the volume fraction of coarse Al2Cu and AlCuMgSi residual crystalline phase which induced pitting in 2A14 aluminum alloy matrix was reduced with the decrease of Cu content. The pitting density decreased significantly，the resistance to pitting properties and electrochemical corrosion properties was greatly improved due to the reduction of the constituents.

Abstract:The effect of aging treatment on the microstructure and corrosion resistance of Mg-4Zn alloy sheets prepared by high strain rate rolling was investigated by optical microscopy（OM），scanning electron microscopy（SEM）， transmission electron microscope（TEM）， static immersion and electrochemical measurement. The results show that the as-rolled Mg-4Zn alloy is composed of fine homogenous dynamic recrystallization grains with the average grain size of 3 μm and many non-uniformly distributed precipitates. Dislocations are observed in some local regions. After pre-aging treatment， a large number of GP I zones（up to about 3~10 nm in length， 2~3 atomic spacing in width） and ball-like GP II zones（up to about 4~10 nm in diameter） are formed in the grains. Dislocation density is significantly reduced， and precipitates are more uniformly distributed in the Mg-4Zn alloy aged at 70 ℃/10 h + 160 ℃/2 h. A combination of filament corrosion and pitting corrosion is the corrosion mode of as-aged Mg-4Zn alloy in Hank's solution. With the prolonged aging time， its corrosion resistance increases at first and then decreases， and the alloy aged at 70 ℃/10 h + 160 ℃/2 h exhibits the best corrosion resistance due to the reduced dislocation density and the uniform distribution of precipitates. The average corrosion rate，the thickness of corrosion film，corrosion potential and corrosion current density are 0.28 mg·cm-2·d-1，6.3 μm，-1.41 V and 11.8 μA/cm2，respectively.

Abstract:In order to solve the fracture defects in incremental forming， the Oyane criterion was introduced into numerical simulation， and the forming limit of sheet metal in incremental forming was effectively predicted. Firstly， based on DC56D+Z plate and its material constants of the Oyane criterion， the critical value of fracture integral （I=4） was determined by experiment and numerical simulation. Afterwards， by using response surface methodology， a nonlinear model between the process parameters （forming angel α， interlayer spacing Δz and diameter of tool head d） and I was established， and the effectiveness of the model was verified by a parametric analysis. It is found that the value of I can be effectively predicted by the numerical model. The value of I increases with the increase of α， Δz and d. The influence of α， Δz and d on I value gradually decreases in sequence. In addition， the relative large interaction effects of α&Δz and α&d are found.

Abstract:Single pass 316L alloy powder cladding with different thickness has been carried on the surface of 27SiMn hydraulic support column by using YLS-6000 type ytterbium doped fiber laser. The effect of cladding layer thickness on the coating structure， mechanical properties and corrosion resistance was studied by optical microscope （OM），scanning electron microscope（SEM），energy spectrum（EDS） microhardness meter and electrochemical analysis methods.The results show that，with the increase of cladding layer thickness，the cladding layer structure changes from a single columnar crystal to a layer structure including planar crystal，columnar crystal and dendritic crystal，the surface microhardness of the cladding layer decreases，the corrosion potential and polarization resistance rate increase and the corrosion current density decreases；Compared with 0.3 mm and 0.5 mm thick cladding specimens，both the corrosion potential and polarization resistance rate of 1.0 mm thick cladding layer samples show the largest values of 0.053 V and 22.881Ω·cm2，respectively，while the smallest corrosion current density of 1.018 mA·cm-2 occurs. It is concluded that 1.0 mm thick cladding layer exhibits the best corrosion resistance.

Abstract:On-site samples about color difference defect on the surface of hot-rolled low carbon DC04 from steel enterprises were analyzed，and it was determined that the difference of the thickness and the structure of oxide scale between the surfaces in the middle and in the edge was the main reason for the color difference on the surface of hot-rolled strip. The transformation law of microstructure of oxide scale in continuous cooling was simulated and investigated by means of thermogravimetric analysis （TGA） and electron probe microanalysis （EPMA） in order to solve this problem. The results showed that pro-eutectoid Fe3O4 was prior to nucleate at the original Fe3O4 layer. The lamellar eutectoid structure was obtained as the cooling temperature decreased. However， when the cooling rate reached 25 ℃/min， the eutectoid reaction was suppressed in the oxide scale. Industrial trial production was implemented based on the results of laboratory research， the microstructure and thickness of oxide scale were effectively controlled by adjustment of coiling temperature and cooling rate， and the cooling temperature was reduced to the temperature range of eutectoid transformation，and then the color difference defect was basically eliminated.

Abstract:Damping and mechanical properties of bast fiber reinforced composites are important and key issues for their applications in manufacturing vehicle body components of automobile and high-speed train.Therefore，this work experimentally studied the kenaf fiber reinforced polypropylene composites. Investigation on the effect of fiber weight percentage on vibration characteristics and mechanical properties was carried out through mechanical tests and modal analysis.The results indicated that the tensile strain decreased with the increase in fiber content.The tensile modulus and tensile strength showed a rising trend with fiber content increase.Natural frequencies of the composites improved with fiber content increase in both the 1st and 2nd vibration modes.The damping ratio initially increased with the increase of fiber content before 10%，and then decreased after 10%. The highest composite damping ratio was of 0.093 obtained at 10% fiber content，which increased by 20.8% compared with the pure polypropylene.The damping ratio of the 2nd mode was higher than that of the 1st mode for each kenaf/pp composite.This suggests that damping properties of the kenaf/pp composites are related to vibration amplitude.

Abstract:Using AR mesophase pitch as precursor，the foaming process and its kinetic characteristic of mesophase pitch-derived carbon foam were studied by thermogravimetry，viscosity analysis，mass spectroscopy，and Fourier transform infrared spectroscopy. The results suggest that the aliphatic chains of pitch decomposed during foaming process，thus gases such as H2、CH4、H2O and CO were released，and the chemical structures of the pitch were changed，which led to the change of viscosity. In addition，the effect of heating rate and foaming temperature on foaming process of mesophase pitch was investigated based on thermogravimetric analysis，and it was found that mass loss （Δw） at a constant foaming temperature was proportional to a simple fractional exponent of foaming time （tb）. A simple mathematical model was proposed to describe the kinetics of isothermal foaming process for mesophase pitch with respect to heating rate effect by the Arrhenius equation，this research has a theoretical guidance for the controllable preparation of mesophase pitch-derived carbon foams.

Abstract:A new method was presented to exactly solve the anti-plane problem of the interaction between a dislocation and nanoscale crack.Firstly，the problem of straight line crack was turned into an orifice plate problem by using conformal mapping method of the complex function. Secondly，the exact solutions of this problem were obtained by Cauchy integral theorem.Then，the stress field and image force with and without surface effect were formulated.The numerical results show that the stress field near crack tip and image force are decreased due to the surface effect when crack size is reduced to the nanometer level. However the influence of the surface effect can be gradually weakened with the increase of the crack length，and the solutions considering the surface effect approach to the classical elastic theory solutions without the surface effect.

Abstract:The thermodynamic calculation was used to evaluate the possible temperature range for preparing the Mo4.8Si3C0.6 powders by a solid reaction method using molybdenum，silicon and carbon powder as the main raw materials. Influence of temperature on composition，specific surface area，size and microstructure of the obtained materials was investigated by using the X-ray diffraction （XRD），scanning electron microscopy （SEM），BET，et al. The results show that the standard Gibbs free energy for the formation of Mo4.8Si3C0.6 is only -351.3 ~ -338.1 kJ/mol when the temperature range is between 1 400 ~1 900 K. Experimental results show that when the temperature keeps at 1 823 K for 1.5 h，the obtained Mo4.8Si3C0.6 powder possesses high purity，petal-liked shape with a diameter about 4.5 μm，specific surface area of 0.753 3 m2/g and particle size of about 1.23 μm. The reaction mechanism for the formation of Mo4.8Si3C0.6 powder is that，when the reaction temperature keeps at 1 373 K，the main product is Mo2C; when it reaches 1 523 K，the main product is Mo5Si3，and a small amount of Mo4.8Si3C0.6；when it rises to 1 673 K，the main product is Mo4.8Si3C0.6，and minor Mo5Si3；finally，when the temperature reaches 1 823 K，no impurities phase of Mo4.8Si3C0.6 is obtained.

Abstract:The influence of limestone powder on the hydration characteristics and rheological properties of cement was studied from two aspects of content and fineness by micro calorimeter and rotational viscometer. The influence of limestone powder on the system hydration was analyzed through the rate of hydration heat evolution and hydration heat， while the influence of limestone powder on the rheological properties was analyzed from two angles of close packing and particle volume fraction. The results show that limestone powder can promote the system hydration process， and the greater fineness of limestone powder results in the more obvious promoting effect. The addition of limestone powder leads to the decrease of cement content， so the second exothermic peak and total heat of the system decrease with the increase of limestone powder content. With the increase of limestone powder content or fineness， the volume fraction of solid particles increases gradually， the particle size distribution modulus decreases， and the particle size distribution curve of composite system is close to the ideal distribution curve gradually. The yield stress and plastic viscosity of composite systems decrease with the increase of limestone powder content， but increase with the increase of limestone powder fineness.

Abstract:N，N，N，N，N′-Pentakis （2-hydroxyethyl）-1，4，7-triazaheptane was synthesized by diethylenetriamine and 2-chloroethanol as the main raw materials. Single-factor experiments and orthogonal experiments were used to optimize the ratio of raw materials and process conditions. The optimum molar ratio of diethylenetriamine and 2-chloroethanol was 1: 6.5，and the optimum process conditions were as follows: reaction temperature was 85 ℃ and reaction time was 5 h. Under the optimal reaction conditions，the yields can reach 98.76 %. The structure of final product was characterized by determining hydroxyl value and amine value，FT-IR，1H-NMR and ES-MS.

Abstract:Lignosulfonate （Lig）， a by-product of paper processing， is a biomass-derived compound including methoxy and phenolic functional groups， and it can generate pseudo capacitance by the redox reaction. However， it has a poor conductivity，limiting the application directly to supercapacitor electrode material. Herein， the good conductivity Lig/PPy composites were prepared by conducting polymer monomer （Pyrrole） via an in-situ polymerization under the Lig system. The morphology and structure were examined by scanning electron microscopy （SEM） and Fourier transformed infrared（FTIR）. The effect of mass ratio of Rm（Lig : Py） on the electrochemical properties of the compound was reported. When the rational mass ratio of Rm = 1 ∶ 1 was used， LP1 had high capacitance of 346.8 F/g at 1 A/g. Lignosulfonate improved the specific capacitance by 50 F/g and 51.5 % to 60.8 % rate capability from 1 to 10 A/g. LP1 showed a capacitance retention of about 47％ after 1 000 cycles at current density of 10 A/g， which indicated the composite had a good cycle life.

Abstract:Two novel gelators Azo-1 and Azo-2 based on azobenzene were designed and synthesized. The two gelators can form gel in the multiple organic solvents. The SEM images of the xerogels showed the diameter of the gel fibers increased with the increase of polar organic solvents. Further investigation on gelation behavior based on Hansen solubility parameters of solvents revealed that most of solvents could form gels cluster in a certain region in Hansen space， and the value Tgel of gel was influenced by the dispersion parameters. The spectra character of the gelator in gel phase and sol phase was examined by UV-Vis spectra. The azobenzene group of Azo-1 in solution had a much faster trans-cis photoisomerization reaction than that of Azo-2. The azobenzene groups of Azo-1 in the gel in certain solvents performed the expected trans-cis photoisomerization with a gel to sol phase upon irradiation of UV light. An obvious change of morphologies occurred in gel phase and sol phase. The three solvents that could produce photo-induced phase transition lie on the same line in Hansen space.

Abstract:The properties and performance coefficients of thermal storage air conditioning are closely related to the phase change materials. Nano-TiO2 / wax composite emulsion phase change materials （NTWCEPCM） were prepared by using techniques of phase inversion and low energy emulsifying， where the wax and TiO2 nanoparticles were used as dispersion medium and heat carrier， respectively. The effect of nano-TiO2 on the performance of stability，thermal conductivity，and thermal cycling stability of NTWCEPCM was studied. The results show that the thermal conductivity of nano-TiO2 / wax composite emulsion is significantly larger than that of pure wax emulsion; the thermal conductivity of nano-TiO2 / wax composite emulsion increases by 117.95% when the nano-TiO2 particle content is 0.15 %. The phase change platform of nano-TiO2 /wax emulsion in the solid-liquid phase is not obvious during thermal cycling. Moreover，the NTWCEPCM has good thermal cycling stability. The NTWCEPCM is expected to be used in thermal storage air conditioning for improving the performance of thermal storage air conditioning coefficient.

Abstract:Batch experiments were employed to investigate the effect of flocculant and lysozyme treatment on the sludge dewaterability，settling performance and floc characteristics. The results showed that the sludge settling performance was improved in the presence of flocculant and lysozyme alone. When the flocculant and lysozyme worked together, both the sludge settling performance and dewatered speed were further enhanced. The optimum flocculant and lysozyme dosage in the combined system was 2 mL and 0.15 g/g，respectively. And the moisture content of the sludge cake and specific resistance were determined to be 65.7% and 0.08×1012 m, respectively, which were decreased by 25.3% and 75.8% compared with the original mud. The results of extracellular polymeric substance (EPS) and floc shape suggested that lysozyme could change the EPS distribution and crack the floc structure. The absorption and bridge effect of the flocculant improved the sludge dewatering speed. The combination of flocculants and lysozyme increased the number of the two-dimensional fractal dimension of floc, made the floc structure closer and tighter, and improved the moisture ratio that could be dewatered in the sludge. This resulted in the enhanced sludge dewatering performance. This study demonstrated that the combination of flocculant and lysozyme on sludge dewaterbility treatment has a promising application potential.

Abstract:UV/chlorine process was employed to treat polluted water containing alanine（Ala），and the volatile disinfection byproducts（trihalomethanes and haloacetonitriles） generated during the process were determined and analyzed. The effects of chlorine dosage，pH，UV radiation time，concentrations of bromide and ammonia ions on the formation potential of disinfection byproducts （DBPs） were investigated. The results showed that trichloromethane （TCM） and dichloroacetonitrile（DCAN） were produced after UV/chlorine process, and the concentrations of TCM and DCAN reached the highest values of 20.37 μg/L and 34.17 μg/L at 15 min, respectively. Lower [Ala]/[Cl2] molar ratio, longer UV radiation time, and neutral pH can reduce the production of TCM and DCAN, and the optimum conditions in this experiment were as follows: [Ala]/[Cl2] = 1 ∶ 2，UV irradiation for 2 h, and pH= 7. Besides, the presence of bromide ions can form bromochloroacetonitrile (BCAN) during UV/chlorine process, which increased the types and toxicity of DBPs, while the existence of ammonia produced fewer DBPs when compared with the ammonia-free solution. Different processes were also compared, UV irradiation alone did not produce DBPs, and the yield of TCM for chlorine alone was lower than that of UV/chlorine, but the yield of DCAN was greater than that of UV/chlorine. Finally, a possible pathway for UV/chlorine treatment of alanine to generate DBPs was proposed below: first, the hydrogen on the nitrogen atom of alanine was attacked, followed by decarboxylation and deamination to produce acetaldehyde and acetonitrile, and finally a series of substitution and hydrolysis reactions to produce dichloroacetonitrile and trichloromethane were performed. The aforementioned results can provide a theoretical basis for the application and popularization of UV/chlorine process.

Abstract:A method was developed for the determination of AHLs （N-Hexanoyl-DL-homoserine lactone（C6-HSL） and N-Octanoyl-DL-homoserine lactone（C8-HSL） were chosen as the representatives) in activated sludge in MBRs by solid phase extraction（SPE） combined with ultrahigh pressure liquid chromatography-tandem mass spectrometry（UHPLC-MS/MS）. The results showed that C6-HSL and C8-HSL presented good linear relations（R2＞0.998） in the range of 1~200 μg/L. The limit of detection and quantitation were 0.100 μg/L and 1.000 μg/L, respectively. The average recoveries of AHLs at three spiked concentrations were in the range of 80.69%~83.75%, and the relative standard deviations（RSD） were 4.71%~7.25%. The developed method is sensitive, stable and has weak matrix effects, which is applicable to determine the trace AHLs in activated sludge in MBRs.

Abstract:Cationic dye of rhodamine b（RB） was removed by the enhanced precipitation of calcium dodecyl benzene sulfonate（Ca（DBS）2） from aqueous solution and the（Ca（DBS）2） particles were flocculated by microbial flocculant GA1. During this process, the sodium dodecyl benzene sulfonate（SDBS） solubilized the RB molecular, and under the effect of excessive amount of Ca2+, the SDBS micelles and the RB containing calcium dodecyl benzene sulfonate particles（CDBS-RB particles） were precipitated and finally flocculated by microbial flocculant GA1. The response surface methodology（RSM） was applied to optimize the reaction conditions including Ca2+ dosage, SDBS dosage and MBFGA1 dosage to increase the RB removal rate. When the initial concentration of RB was 50 mg/L and pH was 10, the optimal flocculation condition was SDBS dosage（2.67 mmol/L），Ca2+ dosage (5.61 mmol/L) and MBFGA1 dosage（4.34 mL/L）. Under this optimal conditions, the RB and SDBS removal rate were 99.80% and 90.03%, and the effluent value of COD is 89.69mg/L，which was lower than the national emission standard and did not need subsequent processing. The environmental scanning electron microscope (ESEM) analysis was used to explore the RB removal process and the reaction mechanism between Ca2+ and SDBS. In addition, when Ca2+ dosage was enough compared with SDBS dosage, the SDBS micelles containing RB molecular (SDBS-RB micelles) could assemble and shift to the formation of CDBS-RB particles. Finally, the CDBS-RB particles were flocculated by MBFGA1；When SDBS dosage was relatively excessive, the SDBS micelles could form in the solution and CDBS-RB particles could redissolve gradually in order to provide Ca2+ for the SDBS micelles.