LiFe _xMn_1−xPO₄/C composites were synthesized by a solid-state reaction route using phenolic resin as both reducing agent and carbon source. The effect of Fe doping on the crystallinity and electrochemical performance of LiFe _xMn_1−xPO₄/C was investigated. The experimental results show that the Fe²⁺ substitution for Mn²⁺ will lead to crystal lattice shrinkage of LiFe _xMn_1−xPO₄/C particles due to the smaller ionic radii of Fe²⁺. In the investigated Fe doping range (x = 0 to 0.7), LiFe _xMn_1−xPO₄/C (x = 0.4) composites exhibited a maximum discharge capacity of 148.8 mAh/g at 0.1 C while LiFe _xMn_1−xPO₄/C (x = 0.7) composite showed the best cycle capability with a capacity retention ratio of 99.0% after 30 cycles at 0.2 C. On the contrary, the LiFe _xMn_1−xPO₄/C (x = 0.5) composite performed better trade-off on discharge capacity and capacity retention ratio, 127.2 mAh/g and 94.7% after the first 30 cycles at 0.2 C, respectively, which is more preferred for practical applications.

Ce³⁺, Yb³⁺ co-doped Y₃Al₅O₁₂ films were prepared by pulse laser deposition. X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence spectra were used to characterize their structural and luminescent properties. Near-infrared quantum cutting from the films was observed via a cooperative energy transfer from Ce³⁺ to Yb³⁺ ions. The high quantum efficiency of the films implies that Ce³⁺,Yb³⁺ co-doped Y₃Al₅O₁₂ films have potential application by tuning the solar spectrum to enhance the efficiency of silicon solar cells.

Cu-Ni core-shell nanowires, with an inner Cu core diameter of about 60 nm and varying Ni shell thicknesses (10, 30, 50, 60, and 80 nm), were successfully fabricated in porous polycarbonate (PC) iontrack templates by a two-step etching and electrodeposition method. In our experiment, the thickness of Ni shell can be effectively tuned through the etching time of templates. The core-shell structure was confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The X-ray diffraction (XRD) pattern elucidates the co-existence of characteristic peaks for both Cu and Ni, indicating no other phases were formed during preparation. Magnetic hysteresis loops measured via vibrating sample magnetometry (VSM) revealed that Cu-Ni core-shell nanowires with thinner Ni shell exhibited obviously diamagnetic character and together with a weak ferromagnetic activity, whereas ferromagnetic behavior was primarily measured for the wires with thicker Ni shell. With increasing Ni shell thickness, the squareness and coercivity value became smaller due to the shape anisotropy and the formation of multi-domain structure.

The hydrogenation/dehydrogenation kinetics and thermodynamic behaviors of the MgH₂- WS₂ composites were investigated. The TPD (Temperature-Programmed-Desorption) curves showed that the onset dehydrogenation temperature of the MgH₂ + 20wt% WS₂ composite was 615 K, 58 K lower than that of the pristine MgH₂. The kinetic measurements showed that within 21 min, the MgH₂ + 20wt% WS2 composite could absorb 2.818wt% at 423 K, and release 4.244 wt% of hydrogen at 623 K, while the hydriding/dehydriding capacity of MgH₂ reached only 0.979wt% and 2.319wt% respectively under identical conditions. The improvement of hydrogenation/dehydrogenation performances for the composite was attributed to the cocatalytic effect between the new phases W and MgS which formed during the ball-milling process.

Experiments were designed to investigate the influence of controlling sintering mechanism on electrical properties of multilayer PTCR chip. During the preparation process, heating rate, sintering temperature, high-temperature holding time and cooling method were respectively regulated to prepare multilayer PTCR chip with good performance. After the process of organic casting, the casting PTCR green films were sintered at 1 260-1 280 °C for 0.5 h at reduction atmosphere, which was heated at the rate of 400 °C/h. Then selecting 300 °C/h as the cooling rate, the ceramics were oxidated at 850 °C for 1 h. The prepared multilayer PTCR chips exhibited room temperature resistivity of below 100 Ω·cm, and resistance rising rate more than 104 unit through the Curie temperature.

The pyrolysis behavior of polycarbosilane (PCS) and chemical reaction mechanism during the pyrolysis process were studied by thermogravimetric-mass spectrometry (TG-MS) combined with X-ray diffraction and infrared spectroscopic analysis methods. The experimental results indicate that the main gas phase products generated during pyrolysis of PCS in nitrogen atmosphere include H₂, -CH₃ and CH₄. The heating rate has a large effect on the pyrolysis process of PCS, the lower heating rate releases more small molecule gases and gets bigger rate of pyrolysis mass loss, demonstrating that the lower heating rate is beneficial to fully pyrolysis of PCS and obtain ceramics products with better microstructure.

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co-precipitation method. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel Mn _xZn_1−xFe₂O₄ while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 °C, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 °C is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

In order to improve the healing performance and increase the service life of the polymer matrix composites, microcapsules were prepared by interfacial polymerization process with urea formaldehyde resin and epoxy resin E-51 as the wall material and core material separately. The effects of core/shell mass ratio and emulsifier on the distribution, topography and encapsulation rate of microcapsules were investigated. By optimizing the conditions, microcapsules with little particle size, well dispersion and compact surface were prepared. The distribution, topography, stability and compositions of the microcapsules were characterized using Nano-2s, optical microscope, scanning electron microscopy, thermal analysis and Fourier transform infrared spectroscopy. The osmosis performance of the microcapsules was evaluated. The experimental results showed that the ratio of core/shell materials (1:1) and 1% DBS as emulsifier were optimum preparation conditions and the encapsulation rate was 62.5%. The microcapsules can be synthesized successfully with mean diameter 548.6 nm and exhibit a good chemical stability below 225 °C. The FTIR result indicated that urea-formaldehyde resin was formed and the core materials were successfully encapsulated in urea-formaldehyde shell. Osmosis performance evaluation showed that the microcapsules were well coated and slowly osmosed.

The microstructure and dynamic rheological characteristics of asphalt containing different polymer modifiers (crumb rubber, styrene-butadiene-styrene and crumb rubber mix with styrenebutadiene-styrene) at mid and high service temperature levels were investigated by using scanning electron microscopy(SEM), dynamic shear rheometer(DSR) and repeat creep test. The main objective of the investigation was to rank the modifiers based on their effect on performance characteristics of asphalt under service conditions. To evaluate the effect of different modifiers on the viscoelastic response of asphalt, the temperature and frequency dependences of the dynamic viscoelastic properties were compared. The mid-temperature fatigue resistance and high-temperature rutting resistance of three polymer modified asphalts were evaluated to predict their field performance in roads. Based on the current results, an improved rutting factor was proposed to determine the rutting resistance of asphalt pavements. In addition, the viscous stiffness (Gv), defined as the reciprocal of viscous compliance, was used to evaluate the high-temperature deformation resistance of asphalt mixtures. The experimental results indicate that the asphalt containing crumb rubber only shows superior performance at mid and high service temperatures in all three modified asphalt binders due to the action of the crumb rubber.

Low average temperature, large temperature difference and continual freeze-thaw (F-T) cycles have significant impacts on mechanical property of asphalt pavement. F-T cycles test was applied to illustrate the mixtures’ compressive characteristics. Exponential model was applied to analyze the variation of compressive characteristics with F-T cycles; Loss ratio model and Logistic model were used to present the deterioration trend with the increase of F-T cycles. ANOVA was applied to show the significant impact of F-T cycles and asphalt-aggregate ratio. The experiment results show that the compressive strength and resilient modulus decline with increasing F-T cycles; the degradation is sharp during the initial F-T cycles, after 8 F-T cycles it turns to gentle. ANOVA results show that F-T cycles, and asphalt-aggregate ratio have significant influence on the compressive characteristics. Exponential model, Loss ratio model and Logistic model are significantly fitting the test data from statistics view. These models well reflect the compressive characteristics of asphalt mixture degradation trend with increasing F-T cycles.

An improved multi-step sintering process was used to in-situ prepare TiB₂-TiB-Ti FGMs. According to the sintering temperatures, the functionally graded materials (FGMs) were divided into three sections. After sintering at a proper temperature, the three sections were sintered together in turn. The experimental results showed that there were no obvious pores and cracks in the whole TiB₂-TiB-Ti FGMs, and no delamination was found in the impacting test with good performance features, which indicated that there were no interface effects in FGMs during penetration, so that the TiB₂-TiB-Ti FGMs were an ideal FGM.

Bi-doped MO-B₂O₃ (M=Ca, Sr, Ba) glasses were prepared by melting method. Excitation spectra, visible and infrared luminescence spectra were measured. Near infrared (NIR) emissions located at about 1190 nm with FWHM only 40 nm and at 1300 nm with FWHM about 200 nm can be observed in different samples when excited by 808 nm LD excitation. The two emission bands have different excitation bands. Red emission centered at 660 nm related to Bi²⁺ can be observed in some samples. The NIR emission at 1300 nm band disappears with the increase of optical basicity, while that of the NIR emission at 1190 nm band shows a contrary tendency. We proposed that the NIR emissions located at 1190 nm and 1300 nm originated from different bismuth centers. The infrared emission peak at about 1300 nm derives from low valence Bi ions according to the Duffy’s theory of optical basicity.

The aim of this work was to prepare MgF₂ translucent ceramic by using nanopowders as raw materials and to study its properties.The MgF₂ nanopowders were prepared using chemical precipitation and the translucent ceramics were fabricated by hot-pressing sintering in a vacuum environment. X-ray diffraction analysis showed that the powders were homogeneous with an average particles size about 13 nm. By comparing the results of transmission electron microscopy, it could be concluded that the porous structure of precursor powders could be improved by calcination. The SEM images of MgF₂ indicated that the as-prepared ceramics were well densified at 900 °C. The photo of the ceramic sample showed that high translucence is a main breakthrough in the field of MgF₂ materials preparation. For the translucent ceramic sample sintered at 900 °C, the Vickers hardness and density were 5.55 GPa and 98.74%, respectively, and its highest transmittance with thickness of 1mm reached 87% in the wavelength from 2.5 μm to 10 μm, all which made it advantageous to be a kind of infrared windows and dome materials.

CuO-doped (Ag_0.75Li_0.1Na_0.1K_0.05)NbO₃ (ALNKN-xCuO, x = 0–2mol%) lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2Nb6O16-type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with the grain size of about 1 μm was formed for the ceramics with 0.5mol% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = 1mol% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.

High quality nano-sized zirconium carbide (ZrC) powders were successfully fabricated via a developed chemical active dilution self-propagating high-temperature synthesis (SHS) method assisted by ball milling pretreatment process using traditional cheap zirconium dioxide powder (ZrO₂), magnesium powder (Mg) and sucrose (C₁₂H₂₂O₁₁) as raw materials. FSEM, TEM, HRTEM, SAED, XRD, FTIR and Raman, ICPAES, laser particle size analyzer, oxygen and nitrogen analyzer, carbon/sulfur determinator and TG-DSC were employed for the characterization of the morphology, structure, chemical composition and thermal stability of the as-synthesized ZrC samples. The as-synthesized samples demonstrated high purity, low oxygen content and evenly distributed ZrC nano-powders with an average particle size of 50nm. In addition, the effects of endothermic rate and the possible chemical reaction mechanism were also discussed.

Using the tomography image, a method to characterize the 3D spatial distributions of increased porosity was proposed, and the increased porosity distributions of cement pastes with different leaching degrees were given using the current method. The leaching processes of CH/C-S-H and the contribution of CH/C-S-H leaching to porosity evolution were discussed. The proposed method can be applied to all cement-based materials with any leaching degrees. From the quantitative increased porosity results, we find that the CH leaching finished quickly on the sharp CH leaching front

In order to study the durability of sprayed concrete (shotcrete), effects of different hydration aging and water-binder ratio (w/b) on the microstructure of cement paste and basic mechanical properties of test specimens were investigated. The phase composition, mass percentage of ettringite and portland in hydration production and microstructure were characterized by X-ray diffraction (XRD), thermo gravimetry-differential scanning calorimetry (TG-DSC) and scanning electron microscopy (SEM), respectively. The experimental results showed that changes in phase composition was more significant than those of water-binder ratio. With hydration aging and water-binder ratio increased, the mass percentage of ettringite and portland was decreased from 4.42%, 1.49% to 3.31%, 1.35%, respectively and the microstructure of paste was significantly compacted. Likewise, the mechanical properties including cubic compressive strength and splitting tensile strength were rised obviously.

The impact behaviour of three types of reactive powder concretes (RPC) was studied using the split Hopkinson press bar (SHPB) testing method. These RPC were prepared with steel fiber volume fraction of 0%, 3%, and 4%, respectively. The stress-strain relationship, strain rate sensitivity threshold value, dynamic strength increase factor, modulus of elasticity and failure pattern of these RPC specimens subjected to impact load were investigated. From the tests, the strain rate sensitivity threshold value of 50 s⁻¹ was obtained. The experimental results showed that when the strain rate increased from the threshold value to 95 s⁻¹, the maximum stress of RPC increased by about 20% and the modulus of elasticity of RPC increased by about 30%. The failure pattern of RPC specimens with steel fiber reinforcement was very different from that of the RPC matrix specimen when subjected to impact loading. Under similar impact loading rate, cracks developed in the steel fiber reinforced RPC specimens, whilst the RPC matrix specimens were broken into small pieces.

This study investigated the nature of hydration products of white portland cement (WPC) containing 20 mM malic acid or 1 M calcium chloride hydrated for 11 years. The study identified the hydration products and characterized the chemical composition, morphology, micro/nano structure of C-S-H and the main binding phase in cementitious materials. Calcium hydroxide (CH), ettringite and C-S-H were identified in WPC with 20 mM malic acid paste hydrated for 11 years. WPC with 1 M calcium chloride paste hydrated for 11 years contained the same phases, but with less CH, and the presence of Friedel’s salt (Ca₂Al(OH)₆Cl·2H₂O). There were still small amount of anhydrous cement particles remaining in both pastes after 11 years hydration according to the SEM and ²⁹Si MAS NMR results. The hydration products of paste containing malic acid had a lower porosity than those prepared with calcium chloride upon visual inspection under SEM. The morphology of the outer product (Op) C-S-H was coarse fibrillar and the inner product (Ip) C-S-H had a very fine microstructure in both pastes under TEM. Both Ip and Op C-S-H formed in paste containing malic acid had lower Ca/Si and higher Al/Si than those in paste containing calcium chloride. C-S-H in paste containing calcium chloride had longer MCL and less percentage of bridging tetrahedra occupied by aluminum in silicon/aluminum chains due to relatively less Q ¹ and more Q ². A new type of silicon tetrahedra, Q ^2B, was introduced during deconvolution of ²⁹Si MAS NMR results. Ip and Op C-S-H in both pastes had aluminum substituted tobermorite-type and jennite-type structure, and all the charges caused by aluminum substituting silicon bridging tetrahedra were balanced by Ca²⁺.

The influences of nano-TiO₂ on the setting time, hydration process, hydration productsand morphology of sulphoaluminate cement were studied by Vicat apparatus, isothermal calorimetry, X-raydiffraction (XRD), thermal analysis and scanning electron microscopy (SEM). The experimental results showthat the incorporation of nano-TiO₂ can obviously promote the setting and hardening process of sulphoaluminatecement, and shorten the interval between the initial and final setting time, the hydration induction period ofsulphoaluminate cement is significantly shortened and the acceleration period begins immediately, but thehydration exothermic rate at hydration stationary phase is not obviously impacted. The nano-TiO₂ additives haveinfluence on the formation rate and degree of crystallinity, but do not affect the type of hydration process. Thestructure of hydration products is compact at middle age, but their content and microstructure do not change.

The thermo-dynamics of reactions between carbonatite and sodium silicate solution at ordinary temperature (25 °) were investigated. The calculated results indicate that at ordinary temperature, the reactions between dolomite, calcite, Ca²⁺ and Mg²⁺ in carbonatite and H₄SiO₄, H₃SiO₄ ⁻ and H₂SiO₄ ²⁻ in sodium silicate solution to form the cementitious products of hydrated calcium silicate or hydrated magnesium silicate all possibly happen; among these reactions, the reactions to form gyrolite (2CaO·3SiO₂·2.5H₂O) and serpentine (3MgO·2SiO₂·2H₂O) are the most possible to occur. Further, the dissociation degree of dolomite and calcite and the activity of H₃SiO₄ ⁻, H₂SiO₄ ²⁻ and H₄SiO₄ ions are the key factors to influence the reactions.

The relationship between Pb leaching concentration and the solution’s pH with time was analyzed when cement in its solidified form was leached in an acid medium. The effects of the particle size of the solidified form, the cement adding method, and the hydration degree on Pb solidification were also investigated. The experimental results indicate that cement is quickly dissolved and hydrated in the acid medium, forming a C-S-H gel or silicic acid sol with good adsorption. When cement-Pb solidified form is leached in an acetate solution, the hydrated product erodes with time, so the Pb concentration increases slightly in the beginning. Then, some of the Pb ions are absorbed by the newly generated silicic acid sol, C-S-H. Others produce Pb(OH)₂ precipitation for secondary solidification, leading to a gradual decrease in the Pb concentration in a leaching time of more than two hours. Moreover, the particle size of the solidified form has important effects on the Pb dissolution. When the amount of added cement is low, with a pH of less than 9.5, the solidification affects the sequence of the original cement powder, the cement hydrated powder, and the cement-Pb solidified form. When the added amount of cement increases with a pH of more than 11, the effect of adding methods on solidification decreases, and the solidified form is a little better than others.

The primary objective of this research was to determine optimum dosage of mixing concrete containing plasticizers and fly ash, consistent with desirable structural grade concrete properties. Factorial tests were also conducted to investigate the four main factors: water-cementing materials ratio, water content, content of superplasticizers (SP) and fly ash content. It was found that the requirement for setting time played the dominant role in shrinkage and anti-cracking, and fly ash played a critical role in workability and reducing heat of hydration but showed insignificant effects on slump, early strength and initial setting time of concrete.

The tensile strength of a corroded rebar in a 53-year-old concrete structure was studied. The microstructure of the metallic substrate, the fracture surface, and the corrosion product layers were investigated. Metallographic observation results showed that the carbon steel was constituted of ferrite and some pearlite. The tensile test results indicated that the corroded rebar presented low strength and elongation. In addition, the fracture surface of the rebar in the tensile test displayed dimple fracture behavior. The Raman spectroscopy results indicated that corrosion products at the general corrosion zone were obviously different from those at the localized corrosion zone. The rust layer at the general corrosion zone was composed of goethite (α-FeOOH), magnetite (Fe₃O₄), and hematite (α-Fe₂O₃), while that of the pitting zone was made of feroxyhyte (δ-FeOOH), goethite (α-FeOOH), and hematite (α-Fe₂O₃). However, the general tendencies that the corrosion products were constituted of a mix of oxides and hydroxides, the oxides mainly existed in the internal part and the hydroxides more presented in the external layer were observed.

The corrosion behaviors of a basic type of RE-containing magnesium alloy Mg-15Y processed by different heat treatment methods were studied in 3.5% NaCl solution at room temperature. The amount of Mg₂₄Y₅ phase decreased with the extending of homogenization treatment. The time for achieving dissolving equilibrium of homogenization treatment at 525, 535, and 545 ° was 24, 20, and 8 h, respectively. The corrosion behavior of Mg-15Y alloy was studied using immersion, hydrogen evolution and electrochemical tests. The experimental results revealed that the heat treatment improved the corrosion resistance, and the corrosion resistance became better with increasing the heat treatment time. The corrosion mode of the alloy after heat treatment was microgalvanic corrosion consisting of the cathodic Mg₂₄Y₅ phase and anodic α-Mg matrix, and Mg-15Y exhibited favorable uniform corrosion mode in NaCl solution. The volume and increasing tendency of the homogenization treatment samples were both more than those of the as-cast sample.

Fe-based amorphous and nanocrystalline coatings were fabricated by air plasma spraying. The coatings were further treated by laser remelting process to improve their microstructure and properties. The corrosion resistance of the as-sprayed and laser-remelted coatings in 3.5wt% NaCl and 1 mol/L HCl solutions was evaluated by electrochemical polarization analysis. It was found that laser-remelted coating appeared much denser than the as-sprayed coating. However, laser-remelted coating contains much more nanocrystalline grains than the as-sprayed coatings, resulting from the lower cooling rate in laser remelting process compared with plasma spraying process. Electrochemical polarization results indicated that the laser-remelted coating has great corrosion resistance than the as-sprayed coating because of its dense structure.

The aim of this study was to improve the cyclic oxidation resistance of In718 superalloy by laser peening(LP). Specimens were treated by LP from one to three times, respectively. The cyclic oxidation tests at 900 ° for periods up to 2 h were conducted. Changes of the top surface morphology and microstructure were analyzed by scanning electron microscope (SEM), energy-dispersive spectra (EDS), transmission electron microscope (TEM) and X-ray diffraction technique (XRD), respectively. The weights were measured between the oxidation cycles to assess the oxidation of the specimens. The top surface microstructure after LP was characterized by highly tangled and dense dislocation arrangements and a high amount of twins. Protective oxidation layer was generated more quickly on the surface treated by LP. The average oxidation rate was about 50 % lower. A tiny homogeneous oxidation layer containing (Fe,Cr)₂O₃, NiCrO₃ and Ni(Al,Cr)₂O₄ spinel was generated on the surface. The experimental results of cyclic oxidation tests show that specimens treated by LP have a better high temperature oxidation resistance, and the antistrip performance of the oxidation layer improves. Moreover, the effects of LP are strengthened with the increase of laser peening.

The phosphated and cerium nitrate post-sealed galvanized steel was firstly scratched to expose zinc layer and then placed in neutral salt spray (NSS) chamber for different durations. The microstructure and compositions of the scratches were investigated using SEM and EDS. The phases of the corrosion products were examined through XRD. The self-healing mechanism of the composite coatings was discussed. The experimental results show that the composite coatings have an excellent corrosion resistance. The corrosion products increase with corrosion time and finally cover the whole scratch. They contain phosphorous, cerium, oxygen, chloride and zinc, and are fine needle and exceedingly compact. The composite coatings are favorable self-healing. During corrosion, the self-healing ions such as Ce³⁺, Ce⁴⁺, PO₄ ³⁻, Zn²⁺ in the composite coatings were dissolved, migrated, recombined, and covered the exposed zinc, impeding zinc corrosion. The self-healing process of the scratches on the composite coatings can be divided into three stages, about 2 h, 4 h, and 24 h, respectively.

The dynamic observations of bainitic transformation in a Fe-C-Mn-Si superbainite steel were conducted on a high temperature laser scanning confocal microscope. It is indicated that the mutual intersection of bainite sheaves often occurs during growth of bainite ferrite, resulting in an interlocked bainite microstructure. Moreover, bainite transformation is promoted by higher austenization temperature and the longer and finer bainite platelets are obtained. Further, The average growth rate of bainite after austenization at 1 100 ° is calculated as 5.8 µm·s⁻¹. In situ observation investigation makes it possible to identify bainite transformation in real time during isothermal holding.

The combined microarc oxidation (MAO) and magnetron sputtering deposition process was used to deposit duplex a-C:H/MAO and Ti-a-C:H/MAO coatings on AM80 magnesium alloy. The microstructure, mechanical properties and tribological behavior of the two duplex coatings were investigated. The experimental results showed that the a-C:H and Ti-a-C:H top films on Si substrates were dense and had a low G peak position and ID/IG ratio, compared with the hydrogen-free amorphous carbon films. Numerous micropores were found on the duplex a-C:H/MAO and Ti-a-C:H/MAO coatings together with low values of hardness (H) and elastic modulus (E), which also showed good binding strength with the Mg alloy substrates. Compared to MAO treated substrate used for the protection of the Mg alloy, the duplex a-C:H/MAO and Ti-a-C:H/MAO coatings still had stable and low value of friction coefficient, even though the surface of the duplex coatings was rough and porous. Furthermore, the mechanism of friction reduction of the two duplex coatings on the Mg alloy substrates was discussed.

AerMet100 ultra-high strength steel plates with a thickness of 2 mm were welded using a CO₂ laser welding system. The influences of the welding process parameters on the morphology and microstructure of the welding joints were investigated, and the mechanical property of the welding joints was analyzed. The experimental results showed that the fusion zone of welding joint mainly consisted of columnar grains and a fine dendrite substructure grew epitaxially from the matrix. With the other conditions remaining unchanged, a finer weld microstructure was along with the scanning speed increase. The solidification microstructure gradually transformed from cellular crystal into dendrite crystal and the spaces of dendrite secondary arms rose from the fusion line to the center of the fusion zone. In the fusion zone of the weld, the rapid cooling caused the formation of martensite, which led the microhardness of the fusion zone higher than that of the matrix and the heat affected zone. The tensile strength of the welding joints was tested as 1 700 MPa, which was about 87% of the matrix. However, the tensile strength of the welding joints without defects existed was tested as 1832 MPa, which was about 94% of the matrix.

Mimicking insect flights were used to design and develop new engineering materials. Although extensive research was done to study various aspects of flying insects. Because the detailed mechanics and underlying principles involved in insect flights remain largely unknown. A systematic study was carried on insect flights by using a combination of several advanced techniques to develop new models for the simulation and analysis of the wing membrane and veins of three types of insect wings, namely dragonfly (Pantala flavescens Fabricius), honeybee (Apis cerana cerana Fabricius) and fly (Sarcophaga carnaria Linnaeus). In order to gain insights into the flight mechanics of insects, reverse engineering methods were used to establish three-dimensional geometrical models of the membranous wings, so we can make a comparative analysis. Then nano-mechanical test of the three insect wing membranes was performed to provide experimental parameter values for mechanical models in terms of nano-hardness and elastic modulus. Finally, a computational model was established by using the finite element analysis (ANSYS) to analyze and compare the wings under a variety of simplified load regimes that are concentrated force, uniform line-load and a torque. This work opened up the possibility towards developing an engineering basis for the biomimetic design of thin solid films and 2D advanced engineering composite materials.

Poly(vinyl alcohol)/collagen (PVA/COL) micro-nanofibers were successfully prepared by electrospinning process. Water, green, and non-toxic was used as the solvent. The electrospun mats consisted of micro-nanoscale fibers with mean diameter ranging from approximately 363 nm to 179 nm. It was observed that the mean diameters of PVA/COL electrospun fibers decreased with increasing collagen content. The effects of PVA/COL blending ratio on the rheological behavior of PVA/COL blended solutions were investigated by rotate rheometer. It was found that PVA/COL blended solutions behaved as Non-Newtonian fluids. With increasing collagen content, the Non-Newtonian index (n) of PVA/COL blended solutions decreased. Meanwhile, a linear relationship was found between the Non-Newtonian index (n) and the mean diameters of the PVA/COL micronanofibers. The chemical structures of PVA/COL electrospun fibers were also characterized by FTIR.

Carbon nanotubes (CNTs) were extensively explored for their beneficial use in nervous system tissue engineering. However, an important concern regarding the use of CNTs is their toxicity during the interaction between cells and the nano particles. The rat pheochromocytoma cell line (PC12) was co-cultured with three types of single-walled carbon nanotubes (SWNTs), purified raw SWNTs (C), hydroxyl purified SWNTs (C-OH) and carboxyl purified SWNTs (C-COOH) at 25 µg/mL and 100 µg/ml. The experimental results revealed that SWNTs at the concentration below 100 µg/mL did not affect the cell viability. Notably, powerful antioxidant system in nerous system tissue is able to counteract with the toxicity of CNTs, which is characterized by the prominently enhanced expression of main antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST)). Therefore, we believe that CNTs can be good candidates for the fabrication of biomedical scaffolds for the nerve tissue repair.

A series of novel water soluble chitosan derivatives as gene vectors was synthesized. The delivery systems were tested for their ability to form complexes with plasmid DNA by utilizing agarose gel electrophoresis, particle size analysis, zeta potential measurement and scanning electron microscopy. Furthermore, cytotoxicity of chitosan derivatives and transfection efficiency of polyplexes were evaluated in vitro. The experimental results showed that the novel chitosan derivatives had lower cytotoxicity, good DNA condensation, and higher transfection efficiencies compared to chitosan in both 293T and HeLa cell lines. It was indicated that these chitosan derivatives were promising candidates for non-viral gene vectors

The inclusion complex of β-cyclodextrin (β-CD) and sulfurized isobutylene (T321) was prepared with a co-precipitation method. The tribological properties of the complex with different concentrations were investigated by a four-ball tester in the solution of polyethylene glycol-600 (PEG-600). The experimental results suggest that the complex exhibits better anti-friction and anti-wear properties than β-CD under different load conditions. The tribo-system shows the least friction coefficient when the concentration of the complex is 0.8%. During the friction process, the complex was decomposed into various molecular fragments and the T321 molecules were released onto the friction interface to provide effective lubrication. The XPS analytical results on the worn surfaces reveal that sulfide film formed by the released T321 plays a major role, and the iron alkoxide and carbon deposition films formed by the β-CD fragments have better anti-friction effect on the sulfide film surface. The interactions of different films result in the formation of a mixed boundary lubrication film.

The magnetic susceptibility, high field magnetization, and specific heat of spin-5/2 trigonal prismatic “Fe6” model were investigated in terms of the Heisenberg model by algebraic method. The experimental results showed that the adequate magnetization description of the Heisenberg model were provided. The magnetization curve has four clear plateaus while the susceptibility exhibits typical antiferromagnetic feature. Two board peaks of the specific heat are observed at around 3 K and 15 K, while only a small sharp-peak at low field. Meanwhile, the magnetic susceptibility displays a sharp peak structure at low temperature, which is well consistent with experimental results.