Gd thin films with different thickness (about 10 nm and 0.5 nm) were deposited on Si(100) by laser molecular beam epitaxy (LMBE). Thickness dependence of the initial oxidation behaviors of Gd films was studied based on the in situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) analysis under ultra-high vacuum (UHV) condition. When the thin film is around 10 nm, the XPS results show that Gd is extremely reactive with oxygen forming Gd oxides and the oxides of Gd are easily hygroscopic. The UPS results show that the Gd 4f has a double-peak structure and the double-peak structure of Gd 4f evolves into a single-peak feature after exposing to air. When the thickness of the Gd film decreases to about 0.5 nm, the reactivity of Gd film with oxygen is decreased by the diffusion of Si component into Gd layers based on the XPS and UPS results. It is suggested that the silicon atoms segregate at the grain boundaries of Gd film to form a barrier, which block the further diffusion of oxygen and water vapor into the Gd layers.

Amorphous GdTbFeCo magnetic thin films were successfully prepared on glass substrates by RF magnetron sputtering system from a mosaic target. The influences of sputtering parameters on the magnetooptical properties GdTbFeCo thin film were investigated by the variable control method. And the influence mechanism was analyzed in detail. After the sputtering parameters were optimized, it was found that when the distance between target and substrate was 72 mm, the thin film thickness was 120 nm, and the sputtering power, sputtering pressure and sputtering time was 75 W, 0.5 Pa and 613 s, respectively, the coercivity with perpendicular anisotropy could be as high as 6735 Oe, and the squareness ratio of the hysteresis loop was almost equal to 1.

A self-made positively charged nanofiltration(NF) membrane was used to treat textile dye effluent to generate water for reuse, and the factors affecting nanofiltration process such as operating pressure, feed fl ow and membrane cleaning were investigated. With an applied pressure of 1.0 MPa and a feed fl ow of 40 L/h, this NF membrane has a removal of 93.3% for COD_cr and a reduction of approximately 51.0% in TDS, salinity and conductivity achieving the chroma removal of 100%. The permeate obtained through this membrane is suitable for recycling. Moreover, the membrane could be reused after being cleaned with 1% NaOH solution.

The porous TiO₂ film was self-assembled on the surface of electrophoretic-deposited titanate nanoribbon film without the addition of templates by using TiF₄ as the precursor. It was found that the hydrolysis of TiF₄ was accompanied with the self-assembly processes of TiO₂ nanoparticles on the surface of electrophoretic-deposited titanate nanoribbon film, resulting in the formation of porous TiO₂ structures. Titanate nanoribbon film was demonstrated to provide the active sites for the effective self-assembly of porous TiO₂ nanostructures owing to a large amount of hydroxyl groups. Compared with the nonporous TiO₂ film, the prepared porous TiO₂ films obviously showed an enhanced photocatalytic activity, which could be attributed to the rapider diffusion and more efficient transport of various reactants and products during photocatalytic reaction in the porous structures.

Poly[(alanino ethyl ester)_0.67 (glycino ethyl ester)_0.33 phosphazene (PAGP) was synthesized, and morphology and diameter of the electrospun PAGP nanofibers were systematically evaluated by using a cool field emission scanning electron microscope (SEM) with changing the important processing variables such as applied voltage, polymeric concentration, and ambient temperature. The average diameter of PAGP nanofibers was inversely proportional to the applied voltage, but increased with the increase of solution concentration. Lower environmental temperature was unfavorable due to the nanofibers conglutination.

In order to improve the electrochemical performance and thermal stability of Li_1.05Co_1/3Ni_1/3Mn_1/3O₂ materials, Li_1.05Co_0.3 Ni_0.35Mn_0.3M_0.05O₂(M=Ge,Sn) cathode materials were synthesized via co-precipitation method. The structure, electrochemical performance and thermal stability were characterized by X-ray diffraction(XRD), charge/discharge cycling, cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and differential scanning calorimetry(DSC). ESEM showed that Sn-doped and Gedoped slightly increased the size of grains. XRD and CV showed that Sn-doped and Ge-doped powders were homogeneous and had the better layered structure than the bare one. Sn-doped and Ge-doped improved high rate discharge capacity and cycle-life performance. The reason of the better cycling performance of the doped one was the increasing of lithium-ion diffusion rate and charge transfer rate. Sn-doped and Ge-doped also improved the mateials thermal stability.

Cationic nanoparticles (NPs) for gene delivery were successfully prepared by assembling carboxylation poly(lactic-co-glycolic acid) (PLGA), polyethylene glycol (PEG), L-α-Phosphatidylethanolamine (DOPE) and octadecyl quaternized carboxymethyl chitosans (OQCMC). Lactoferrin (Lf) was selected as a targeting ligand conjugated to PLGA via bifunctional PEG, yielding PLGA-PEG-Lf/DOPE NPs to be used for gene vectors. Fourier transform infrared spectroscopy (FTIR), UV and nuclear magnetic resonance (NMR) spectroscopy were performed to evaluate the synthesis of the vectors. The characteristics of the vectors loaded heme oxygenase (HO-1) gene were evaluated by transmission electron microscope (TEM), particle size analyser and fluorescent microscopy. The experimental results showed that the obtained vectors were spherical in shape with average particle size of 142.2 nm and zeta potentials of +16.4 mV. The vectors could protect the loaded gene from the degradation by nuclease. For 293T cells, there is high transfection efficiency of the vectors similar to liposome-2000. It can be concluded that the established cationic PLGA-PEG-Lf/DOPE NPs have potential gene delivery ability for gene therapy.

To explore wear mechanism of stainless steel used in nuclear pump, the wear properties and the worn surface characteristics of unlubricated 304L austenitic stainless steel on itself were investigated in air at room temperature. The experimental results demonstrated that the wear rate of the material decreased with the increase of the wear time. The friction coefficient fluctuated severely when the applied load was 120 N. At 120 N the wear rate was much higher than that of the applied load of 70 N. At 70 N the wear rate did not show much difference from that of 30 N. The wear mechanism was adhesive and abrasive wear under different load at the initial stage of the wear test. Then, the main wear mechanism changed with the wearing time and the applied load.

In order to study the effect of intermaetallics on the corrosion behaviour of 7A52 aluminum alloy, the alloy was characterized by means of SEM-EDS and scanning Kelvin probe force microscopy(SKPFM). The experimental results indicate that there are two different intermetallics:Al-Mn-Fe and Mg₂Si. Both intermetallics exhibite the negative volta potential relative to the matrix indicating an anodic behaviour. Hereby, they are easy to be dissolved and corroded under the erosive environment, and there become the corrosion initiation sites. The Al-Mn-Fe intermetallics show stronger anodic behaviour than those of Mg₂Si intermetalics. It means that Al-Mn-Fe intermetalics are easier to be corroded.

The in situ synthesized NbC particles reinforced Ni-based alloy composite coating was produced by laser cladding a precursor mixture of Ni-based alloy powder, graphite and niobium powders on a steel substrate. The microstructure, phase composition and wear property of the composite coating were investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and dry sliding wear test. The experiment results show that the composite coating is homogeneous and free from cracks, and about 0.8 mm thick. The microstructure of the composite coating is mainly composed of NbC particles, CrB type chromium borides, γ-Ni primary dendrites, and interdendritic eutectics. CrB phases often nucleate and grow on the surface of NbC particles or in their close vicinity. NbC particles are formed via in situ reaction between niobium and graphite in the molten pool during the laser cladding process and they are commonly precipitated in three kinds of morphologies, such as quadrangle, cluster, and flower-like shape. Compared with the pure Ni-based alloy coating, the microhardness of the composite coating is increased about 38%, giving a high average hardness of HV0.21000, and the wear rate of the composite coating is decreased by about 32%, respectively. These are attributed to the presence of in situ synthesized NbC particles and their well distribution in the coating.

Pitting corrosion of 316L stainless steel (316L SS) under various stress was studied by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis in 3.5% NaCl solution. The results of polarization curves show that, with the increase of the stress, the pitting potentials and the passive current density markedly decrease fi rstly (180 MPa), and then increase greatly (200 MPa). The corresponding surface morphologies of the samples after the polarization test well correspond to the results. Mott-Schottky analysis proved the least Cl⁻ adsorbed to the surface of passive fi lm with more positive fl at potential, indicating that a moderate stress could increase the pitting corrosion resistance of 316L SS in 3.5% NaCl solution.

Ni element was introduced to aluminum surface by a simple chemical immersion method, and Al-Ni composite anodic films were obtained by following anodizing. The morphology, structure and composition of the Al-Ni anodic films were examined by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and atomic force microscopy(AFM). The electrochemical behaviors of the films were studied by means of polarization measurement and electrochemical impedance spectroscopy (EIS). The experimental results show that the Al-Ni composite anodic film is more compact with smaller pore diameters than that of the Al anodic film. The introduction of nickel increases the impedances of both the barrier layer and the porous layer of the anodic films. In NaCl solutions, the Al-Ni composite anodic films show higher impedance values and better corrosion resistance.

In order to predict the plate curvature during snake rolling, FE model was constructed based on plane strain assumption. The accuracy of the FE model was verified by the comparison between the plate curvature conducted by FE model and experiment respectively. By using FE model, the effect of offset distance, speed ratio, reduction, roll radius and initial plate thickness on the plate curvature during snake rolling was investigated. The experimental results show that, a proper offsetting distance can efficiently decrease plate curvature, however an excessive offsetting distance will increase plate curvature. A larger speed ratio, reduction will cause a large plate curvature, however a larger roll radius has effect to reduce plate curvature. Plate which undergoes a larger reduction and plate with a larger initial thickness always need a larger offset distance to keep the plate the minimum plate curvature, but for a larger roll radius a smaller offset distance is needed.

The relation between microstructure characteristics and mechanical properties of X80 pipeline steels was investigated using optical microscopy, scanning electron microscopy, etc. It is shown that the structure consists of polygonal ferrite (PF), quasi-polygonal ferrite (QPF), acicular ferrite (AF), and granular bainitic ferrite (GF). With increasing volume fraction of M-A islands (below 3%), the yield strength increases. With increasing content of higher angle grain boundaries(HAGBs), the yield strength, elongation, and DWTT properties at −15° increase, and the volume fraction of M-A islands reaches its highest point in the steel containing the most volume fraction of GF.

Through the comparative analysis of steel plate reinforced, ceramics reinforced and nonreinforced joints under loading condition, the feasibility of strengthening steel joint of architectural structure was studied. By using element birth and death technology simulation of the finite element software ANSYS, it is found that when the reinforced structure is 10 mm in thickness and using steel structure to reinforce the concerned areas, the equivalent stress in concerned regionals reduces by 31.1% compared with that when the structure is not reinforced. When reinforced with ceramics, the equivalent stress in concerned regionals reduces by 24.1% compared with that reinforced with steels; when the reinforced structure is 20 mm in thickness using steels to reinforce the concerned area, the equivalent stress in concerned regionals reduces by 39.4% compared with that when the structure is not reinforced. When using ceramics to reinforce the concerned areas, the equivalent stress only decreases by 3.7% compared with that reinforced with steels.

Cu modified layer was prepared on the surface of AISI304 stainless steel by plasma surface alloying technique. The effects of processing parameters on the thickness, surface topography, microstructure and chemical composition of Cu modified layer were characterized using glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental results show that the surface modified layer is a duplex layer (deposited + diffused layer) with thickness of about 26 μm under the optimum process parameters. The modified layer is mainly composed of a mixture of Cu and expanded austenite phase. The ball-on-disk results show that the modified layer possesses low friction coefficients (0.25) and excellent wear resistance (wear volume 0.005×10⁹ μm³). The Cu modified layer is very effective in killing the bacteria S. aureus. Meanwhile, no viable S. aureus is found after 3 h (100% killed) by contact with the Cu alloyed surface.

A new Precision Extrusion nozzle based ball screw transmission was developed. 3D hierarchical porous PLLA/nano-Hydroxyapatite(PLLA/nHA) scaffolds were fabricated by low-temperature deposition manufacturing. Scaffolds with macropores of 200–500 μm and micropores about 10 μm were fabricated through a thorough study and control of the processing parameters, in which the processing path and speed of material extrusion determine the macropores and there is a suitable temperature zone for fabricating qualified macropores. Micropore morphology can be controlled by adjusting supercooling of solvent crystallization or adding water into the solvent system. The compressive modulus of the scaffolds in air and phosphate buffer solution was measured, which increased with HA addition. In-vitro cell culture results showed a good biocompatibility of PLLA/HA scaffolds with the pre-osteoblastic MC3T3-E1 cells.

The effect of glass ionomer cement and resin-modified glass ionomer cement incorporated with chlorhexidine and bioactive glass on antimicrobial activity and physicochemical properties were investigated. The experimental results showed that groups incorporated with 1% chlorhexidine exhibited a significant reduction of optical density values of the bacterial suspension and increased the degradation of Streptococcus mutans biofilm. However, groups incorporated with 10% bioactive glass did not affect the optical density values and the biofilm formation. The mechanical properties of the materials and the polymerization were not influenced by the addition of chlorhexidine. Nevertheless, the compressive strength was lower when the materials were incorporated with bioactive glass. It can be concluded that glass ionomer cements incorporated with chlorhexidine can maintain its mechanical properties as well as reduce early S mutans biofilm formation. Controlled release/sustained release technology may be required to optimize the antibacterial activity of glass ionomer cements incorporated with bioactive glass.

The effects of five chito-oligomers, from dimer to hexamer (chitobiose, chitotriose, chitotetraose, chitopentaose, chitohexaose) separated from chitosan oligosaccharides, on nuclear factor -kappaB (NF-κB) signaling pathway were investigated by using luciferase assay and laser scanning microscopy. The expression of NF-κB downstream genes (cyclin D1, TNFα and IL-6) were tested by real time PCR. We found that all five chitosan oligosaccharides increased NF-κB-dependent luciferase gene expression and NF-κB downstream genes transcription, and the most significant were chitotetraose and chitohexaose. In addition, laser scanning microscopy experiments showed that chitotetraose and chitohexaose also activated the p65 subunite of NF-κB translocating from cytoplasm to nucleus, which suggested that they were the most potent activators of NF-κB signaling pathway.

A novel poly(N-isopropylacrylamide)-based sandwich-typed hydrogel, which was featured with both ends of linear poly(N-isopropylacrylamide) (PNIPAM) chains being grafted onto cross-linked PNIPAM chains, was successfully prepared in a three-step process by a method of sequential synthesis. The proposed hydrogel displays faster and hydration/dehydration dynamic response to temperature cycling owing to linear PNIPAM chains to form big-pore structure. This work may lead to high attraction for targeting drug delivery systems, polymeric pump, sensors and so on.

Phase transition behavior and influence of ions on the thermo-sensitive polyamide with polyethylene glycol as the main chain were studied in detail. By measuring the light transmission rates of polymer solutions, the change of its lower critical solution temperature (LCST) in the salt solution was investigated. It was found that a reversible phase transition of the polyamide occurred at the LCST and finished in a narrow temperature range. The LCST was associated with species of ions in salt solution. Anions had a great impact on the phase transition performance of the thermo-sensitive polyamide, while the cations had a slight influence on the phase transition. Different anions had different coagulation ability to ‘salt-out’ the polyamide. The order was: CO₃ ²⁻>SiO₃ ²⁻>HPO₄ ²⁻>OH⁻>Cl⁻>HCO³⁻>HSO³⁻>NO²⁻>NO³⁻.

To improve tribological property of MC Nylon6, the glass fiber and fly ash reinforced monomer casting nylon composites (GFFAPA) were prepared by anionic polymerization of ɛ-caprolactam. The friction and wear behaviors of composites under dry condition, water lubrication and oil lubrication were investigated through a ring-black wear tester. Worn surfaces were analyzed using a scanning electron microscope. The experimental results show that the tensile strength and hardness of nylon composites are obviously improved with reinforcement increasing. Compared to MC nylon, the lowest friction coefficient and wear rate of glass fiber reinforced nylon composites (GFPA) with GF30% respectively decrease by 33.1% and 65.3%, of fly ash reinforced nylon composites (FAPA) with FA20% decrease by 5.2% and 68.9% and of GFFAPA composites with GF30% and FA10% decrease by 57.8% and 89.9%. The main wear mechanisms of FAPA composites are adhesive and abrasive wear and of GFPA composites with high proportion are abrasive and fatigue wear. The worn surfaces of GFFAPA composites are much multiplex and the optional distributing glass fiber and fly ash have a synergetic effect on the wear resistance for GFFAPA composites. Compared with dry friction, the friction coefficient and wear rate under oil lubricated conditions decrease sharply while the latter reversely increase under water lubricated conditions. The wear mechanisms under water lubricated condition are principally chemical corrosion wear and abrasive wear and they become boundary friction under oil lubricated condition.

The inorganic-organic hybrid junction was synthesized on ITO glass substrate, which was consisted of an n-type ZnO nanorods (NRs) grown by low-temperature aqueous chemical growth method and a p-type polyfluorene (PF) organic film fabricated by spin-coating. The experimental results indicate that densely and uniformly distributed ZnO nanorods are successfully grown on the PF layer. The thickness of the PF layer plays a dominant role for the current-voltage (I–V) characteristic of the ZnO NRs/PF inorganic-organic hybrid junction device, and a p-n junction with obviously rectifying behavior is achieved with optimal PF layer thickness. The photoluminescence (PL) spectrum covering the broad visible range was obtained from the n-ZnO nanorods/p-polyfluorene (PF) structure, which was originated from the combination of the PF-related blue emission and the ZnO-related deep level emission.

Membrane surfaces modified with poly(N-vinyl-2-pyrrolidone) (PNVP) can be endowed with hydrophilicity, biocompatibility and functionality. In this work, atmospheric pressure dielectric barrier discharge plasma graft polymerization of N-vinyl-2-pyrrolidone (NVP) onto polypropylene (PP) microporous membrane surface was studied. The experimental results reveal that plasma treatment conditions, such as discharge power, treatment time and adsorbed NVP amount, have remarkable effects on the grafting degree of NVP. Structural and morphological changes on the membrane surfaces were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (FT-IR/ATR), X-ray photoelectron spectroscope (XPS) and field emission scanning electron microscopy (FE-SEM). Water contact angles of the membrane surfaces were also measured by the sessile drop method. Water contact angles on the membrane surfaces decrease with the increase of NVP grafting degree, which indicates an enhanced hydrophilicity for the modified membranes. The effects of grafting degrees on pure water fluxes were also measured. It is shown that pure water fluxes increase with grafting degree firstly and then decrease adversely. Finally, filtration of bovine serum albumin (BSA) solution and platelets adhesion of the PNVP modified membranes show good protein resistance and potential biocompatibility due to the enhancement of surface hydrophilicity.

The theory and approach of the surface modified of asphalt fire-retardant with silane coupling agent were introduced. The optimum silane dosage was determined, and the structure and properties of the asphalt fire-retardant before and after the surface modification were characterized by infrared spectrum and thermo gravimetric analysis. The dispersion effect of asphalt fire-retardant was studied. The influence of the surface modification on the hydrophilicity and lipophilicity of the asphalt fire-retardant was analyzed. The experimental results showed that there were physical and chemical interactions between the silane coupling agent and the asphalt fire-retardant, which reduced the surface polarity of the asphalt fire retardant. The optimum silane coupling agent dosage was 0.95% of the asphalt fire retardant. The surface modification improved the thermal stability, dispersibility and lipophilicity of the asphalt fire retardant, which enhanced the compatibility between asphalt fire retardant and asphalt.

In order to investigate the effect of sintering temperature on aging properties and mechanical properties of 3Y-TZP dental ceramic in simulated oral environment, 3Y-TZP nanopowder compacts were pressurelessly sintered at 1 350 °C,1 400 °C, 1 450 °C,1 500 °C, respectively, then were treated by soaking in artificial saliva (65 °C, pH=7) for two months. The treated specimens sintered at 1 350 °C showed there was no phase transformation but whose strength and toughnesswere significantly improved (P<0.05), while those sintered at 1 400 °C–1 500 °C revealed a small amount of phase transformation and insignificant mechanical reinforcement (P>0.05). No micro-cracks were detected but increment in lattice volume was found in all specimens. Lowering sintering temperature favors aging resistance and mechanical reinforcement of 3Y-TZP in a simulated oral environment.

Zr-pillared clays were prepared by heating and ultrasonic methods in intercalation process. The resultants were characterized by XRD, N₂ adsorption-desorption, SEM, and TG/DTA analysis. Ultrasonic technology accelerated the pillaring process effectively and obtained better ordered structure than by heating method. The specific surface area and pore volume of the Zr-pillared clays increased by about 13 and 3 times respectively. Rare earth metal (Ce) was introduced into Zr-pillared clays by co-intercalation and dipping method. The specific surface area was increased by co-intercalation approach, but it was decreased dramatically by dipping method. Thermal stability of Ce modified samples prepared by co-intercalation method was enhanced in comparison with Zr-pillared clays. Modification mechanism and “corrugation-like” structural mode of intercalation process was proposed basing on the double XRD peaks in small-angle range of pillared clays, which was related to the deformation of silicate layer.

Highly boron-doped diamond films were deposited on porous titanium substrates by hot filament chemical vapor deposition technique. The morphology variation of highly boron-doped diamond films grown on porous titanium substrates was investigated, and the effects of carbon concentration on nucleation density and diamond growth were also studied. The continuous change of surface morphology and structure of diamond film were characterized by scanning electron microscopy. The structures of diamond film and interlayer were analyzed by X-ray diffraction. The quality of boron-doped diamond film was confirmed by visible Raman spectroscopy. The experimental results reveal that surface morphology and quality of boron-doped diamond films are various due to the change of carbon concentration. The thickness of intermediate layer decreases with the carbon concentration increasing.

By means of hydration heat, XRD and SEM, effect of phosphorus and fluorine (P₂O₅ and F⁻) in phosphorous slag on hydration process of tricalcium silicate (C₃S) and tricalcium aluminate (C₃A) was explored. The results indicated that the early hydration exothermic rate of C₃S and C₃A was obviously lowered by P₂O₅ and F⁻ in phosphorous slag, the second peak occurring time of C₃A was delayed by 0.9 h, the exothermal output of C₃S was reduced by 25.04% and the time of accelerating stage was postponed by 0.86 h. The early hydration degree of C₃S and C₃A was also decreased. Due to the infl uence of P₂O₅ and F⁻, more pores and thinner crystals can be observed in the microstructure of hardened paste and the chance of cracks was reduced.

Mesoporous chromium aluminophosphate (CrAlPO) was successfully synthesized via solid state reaction (SSR) route at low temperature in the presence of a cationic surfactant cetyltrimethyl ammonium bromide (CTAB) and inorganic sources such as AlCl₃·6H₂O, CrCl₃·6H₂O and NaH₂PO₄·2H₂O. Characterizations by means of powder X-ray diffraction (XRD), N₂ adsorption-desorption, high resolution transmission electron microscopy (HR-TEM), scanning electron micrography (SEM), energy dispersion spectroscopy (EDS), thermo-gravimetry (TG), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet visible light spectroscopy (UV-Vis) were carried out to understand both the pore characteristics and electron transition route of these obtained materials. The experimental results show that the meso-CrAlPO materials with various Cr/Al molar ratios possess a mesostructure and a specifi c surface area of 193 to 310 m²/g corresponding to an average pore size of 5.5 to 2.2 nm, respectively. The maxium content of Cr in meso-CrAlPO materials synthesized via SSR route can achieve 16.7wt%, being significantly higher than that of the meso-CrAlPO prepared via a conventional sol-gel route. Meanwhile, the formation mechanism of the meso-CrAlPO was also proposed.

Feasibility of a wave propagation-based active crack detection technique for nondestructive evaluations (NDE) of concrete structures with surface bonded and embedded piezoelectric-ceramic (PZT) patches was studied. At first, the wave propagation mechanisms in concrete were analyzed. Then, an active sensing system with integrated actuators/sensors was constructed. One PZT patch was used as an actuator to generate high frequency waves, and the other PZT patches were used as sensors to detect the propagating wave. Scattered wave signals from the damage can be obtained by subtracting the baseline signal of the intact structure from the recorded signal of the damaged structure. In the experimental study, progressive cracked damage inflicted artificially on the plain concrete beam is assessed by using both lateral and thickness modes of the PZT patches. The results indicate that with the increasing number and severity of cracks, the magnitude of the sensor output decreases for the surface bonded PZT patches, and increases for the embedded PZT patches.

Simulating the coupling effect brought by freeze-thaw and carbonation environment, we experimentally investigated concrete durability, the variation characteristics of both concrete dynamic elastic modulus, and its neutralization depth. The influences imposed by carbonation on the freeze-thaw damage of concrete was studied as well and vise versa so as to shed light on the influencing mechanism together with the mutual interaction between them. The experimental results show that the damage caused by the coupling effect of freeze-thaw and carbonation on concrete is severer than any single effect of them two could bring. This provides certain theoretical references and paves down foundations for the further study in concrete durability related by the coupling environmental effect.

The microstructure characteristics and meso-defect volume changes of hardened cement paste before and after carbonation were investigated by three-dimensional (3D) X-ray computed tomography (XCT), where three types water-to-cement ratio of 0.53, 0.35 and 0.23 were considered. The high-resolution 3D images of microstructure and filtered defects were reconstructed by an XCT VG Studio MAX 2.0 software. The mesodefect volume fractions and size distribution were analyzed based on 3D images through add-on modules of 3D defect analysis. The 3D meso-defects volume fractions before carbonation were 0.79%, 0.38% and 0.05% corresponding to w/c ratio=0.53, 0.35 and 0.23, respectively. The 3D meso-defects volume fractions after carbonation were 2.44%, 0.91% and 0.14% corresponding to w/c ratio=0.53, 0.35 and 0.23, respectively. The experimental results suggest that 3D meso-defects volume fractions after carbonation for above three w/c ratio increased significantly. At the same time, meso-cracks distribution of the carbonation shrinkage and gray values changes of the different w/c ratio and carbonation reactions were also investigated.

N-layered spherical inclusions model was used to calculate the effective diffusion coefficient of chloride ion in cement-based materials by using multi-scale method and then to investigate the relationship between the diffusivity and the microstructure of cement-basted materials where the microstructure included the interfacial transition zone (ITZ) between the aggregates and the bulk cement pastes as well as the microstructure of the bulk cement paste itself. For the convenience of applications, the mortar and concrete were considered as a four-phase spherical model, consisting of cement continuous phase, dispersed aggregates phase, interface transition zone and their homogenized effective medium phase. A general effective medium equation was established to calculate the diffusion coefficient of the hardened cement paste by considering the microstructure. During calculation, the tortuosity (n) and constrictivity factors (D _s/D ₀) of pore in the hardened pastes are n≈3.2, D _s/D ₀=1.0×10⁻⁴ respectively from the test data. The calculated results using the n-layered spherical inclusions model are in good agreement with the experimental results; The effective diffusion coefficient of ITZ is 12 times that of the bulk cement for mortar and 17 times for concrete due to the difference between particle size distribution and the volume fraction of aggregates in mortar and concrete.

A simple planar multilayer structure was proposed for the observation of acoustic Tamm states. The theoretical and experimental studies show that acoustic Tamm states can be formed at the interface between double one-dimensional phononic crystals with extremely narrow cavity between them. When the width of the cavity increases, the acoustic Tamm states gradually disappear and the cavity resonant states appear instead. By studying the field distribution, we give the physical explanation for the two different acoustic interface states.

The effects of high pressure on structure, elastic and electronic properties of the intermetallic Mg₂Pb were calculated by the first-principles plane wave pseudo-potential method in the scheme of density functional theory (DFT) within the generalized gradient approximation. The elastic constants and Debye temperature obtained at 0 GPa are in good agreement with the available experiment data and other theoretical results. The electronic properties calculated suggest that the electronic density of states (DOS) at the Fermi level decreases under high pressure.

A user-defined three-dimensional (3D) discrete element model was presented to predict the dynamic modulus and phase angle of asphalt concrete (AC). The 3D discrete element method (DEM) model of AC was constructed employing a user-defined computer program developed using the “Fish” language in PFC3D. Important microstructural features of AC were modeled, including aggregate gradation, air voids and mastic. The irregular shape of aggregate particle was modeled using a clump of spheres. The developed model was validated through comparing with experimental measurements and then used to simulate the cyclic uniaxial compression test, based on which the dynamic modulus and phase angle were calculated from the output stressstrain relationship. The effects of air void content, aggregate stiffness and volumetric fraction on AC modulus were further investigated. The experimental results show that the 3D DEM model is able to accurately predict both dynamic modulus and phase angle of AC across a range of temperature and loading frequencies. The userdefined 3D model also demonstrated significant improvement over the general existing two-dimensional models.

In order to prepare heat-resistant inner layer of hot-forging die, plasma spraying, plasma remelting and plasma spray welding were adopted. Cr₃C₂ coatings of Ni-Based were prepared respectively with 10%, 20% and 30% Cr₃C₂ powder and W6Mo5Cr4V2 substrate. The coating microstructure analysis, the micro-hardness test, and the measurement of thermal parameters of coating were conducted. The experimental results show that the coating has the better thermo-physical property by using plasma spray welding method with the powder ratio of 90% Ni60 and 10% Cr₃C₂, and by this way the micro-hardness of coating can achieve 1100 HV.

Vanadium pentoxide, borax, boron carbide and sodium fl uoride were used to grow vanadium carbide coating on surface of Cr12 steel at 950 °C by TD process. The coating of vanadium carbide (VC) extended the serve-life period of Cr12 steel as punching die. Kinetics of vanadium carbide coating growth was brought forward and verified by comparison of the mathematical model with the experimental results. The thickness of coating was illustrated by SEM. The chemical constituent of coating and remnants were tested by X-ray diffraction (XRD) and X-ray energy dispersive spectroscopy (EDS). To increase the thickness, rare earth silicon powder (FeSiRe23) was added to the borax salt bath. The analysis of XRD revealed that FeSiRe23 increased the depth of vanadium car-bide coating as reducing agent and catalysis.