The surface of hollow glass microspheres (HGMs) was roughened by a HCl+NH₄F strategy, which achieved a broken ratio as 16.10%, and then metallized by electroless plating by Co nanoparticles up to 90 wt% (abbreviated as Co-HGMs). The average grain size of Co was measured to range from 0.4 to 0.5 µm. Then Co-HGMs were mixed with liquid silicone rubber and xylene, and cured on a perspex plate applicable for flexible electromagnetic shielding. By attentive parameter optimization, a film about 0.836 mm in thickness was obtained with a density of 0.729 g/cm³, showing a shielding effectiveness of 15.2 dB in the X-band (8.2–12.4 GHz) at room temperature, which was ascribed to the formation of a conductive network of Co-HGMs inside the film. Simultaneously, the tensile strength of 0.89 MPa at an elongation ratio of 194.5% was also obtained, showing good mechanical properties and tensile strength.

The leaching kinetics of magnesium slag in ammonium chloride solutions was investigated. The effects of initial ammonium chloride concentration, liquid-solid ratio and reaction temperature on the leaching rate of calcium were determined. The results showed that the leaching rate increased with the increase in initial ammonium chloride concentration, reaction temperature and liquid-solid ratio. It was determined that the leaching rate fit the Avrami equation, and the leaching process was controlled by diffusion. The activation energy was 13.22 kJ/mol.

The Li₂O-Al₂O₃-SiO₂ (LAS) glass-ceramics with low lithium content were prepared from spodumene mineral by melting method. XRD, DSC, and FTIR were used to study the crystallization process and structure of the samples. The results showed that the addition of Na₂O promoted the precipitation of β-quartz solid solution and its transformation to β-spodumene solid solution. Mechanical performance tests and FESEM indicated that the larger grain size and inhomogeneous grain dispersion caused by the increase of Na₂O content led to lower mechanical properties. In addition, low expansion glass-ceramics were prepared by an appropriate heat treatment according to DSC result, and when Na₂O content was in the range of 1.22 wt% to 2.41 wt%, the average coefficient of thermal expansion (CTE) (30–300 °C) increased from −5.810×10⁻⁷ to 5.322×10⁻⁷°C⁻¹.

Bi₂O₃/BiOI step-scheme(S-scheme) heterojunction photocatalyst was synthesized by green calcination method, its degradation ability of methylene blue was investigated, and the photocatalytic performance of the Bi₂O₃/BiOI heterojunction, Bi₂O₃ and BiOI was compared. The structure and morphology of the samples were characterized by X- ray diffraction(XRD), field emission scanning electron microscopy (FESEM), and UV-vis diffuse reflection spectrum (UV-vis DRS). The degradation rate of methylene blue was analysised by spectrophotometry, and the calculation result showed that the degradation rate of methylene blue was 97.8% in 150 minutes. The first order kinetic rate constant of 10%Bi₂O₃/BiOI is 0.021 8 min⁻¹, which are 2.37 and 2.68 times of BiOI(0.009 18 min⁻¹) and Bi₂O₃ (0.008 03 min⁻¹) respectively. The calculation result shows that the work function of Bi₂O₃ and BiOI are 3.0 eV and 6.0 eV, respectively, by density functional theory(DFT). When this S-scheme heterojunction is used as a photocatalyst, the weaker electrons in the conduction band of BiOI will be combined with the weaker holes in the Bi₂O₃ valence band under combined effect with built-in electric field and band bending, which will retain stronger photoelectrons and holes between Bi₂O₃ and BiOI. This may be the internal reason for the efficient degradation of tetracycline by Bi₂O₃/BiOI S-scheme heterostructures.

We propose a facile facet regulation enabled by nanoarray architecture to achieve a high faradic efficiency of Fe₂O₃ catalyst for NRR. The α-Fe₂O₃ nanorod arrays (NAs) were directly grown on carbon cloth (CC) with specific (104) facet exposure. The highly exposed (104) facets provide abundant unsaturated Fe atoms with dangling bonds as nitrogen reduction reaction catalytically active sites. In addition, the NAs architecture enables the enhanced electrochemical surface area (ECSA) to fully manifest the active sites and maintain the mass diffusion. Thus, the selectively exposed (104) facets coupled with the high ECSA of NAs architecture achieve a high FE of 14.89% and a high yield rate of 17.28 µg h⁻¹ cm⁻². This work presents an effective strategy to develop highly efficient catalytic electrodes for electrochemical NRR via facet regulation and nanoarray architecture.

A pressure swing adsorption (PSA) hydrogen purification model for the four-component gas (H₂/CO₂/CH₄/CO = 73/16/8/3 mol%) in a layered bed packed with Cu-BTC and zeolite 5A was established to achieve better hydrogen purification performance. By comparing its simulation results with the experimental data, the adsorption isotherm model was validated and could be used to accurately describe the adsorption process of the gas mixture on the two adsorbents. The breakthrough curves of the mixed gas on the layered bed were studied to verify the correctness of the established simulation models. Based on the validated model, the performance of the PSA system based on the layered bed was carried out, including the hydrogen purity and recovery. The simulation results show that the hydrogen purification system based on the layered bed model can achieve hydrogen purity of 95.469% and hydrogen recovery of 83.219%. Moreover, a parametric study was carried out and its results show that reductions in feed flow rate and adsorption time result in an increase in hydrogen purity and a decrease in hydrogen recovery. A longer equalization time between the two adsorption beds can simultaneously increase the hydrogen purity and recovery.

The zinc oxide seed film was coated on conductive glass (FTO) substrate by the Czochralski method, Zinc acetate and hexamethylenetetramine were used as raw materials to prepare growth solution, and then ZnO film was prepared by a low-temperature solution method. The effects of annealing temperature on the morphology, structure, stress and optical properties of ZnO films were studied. The thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible absorption spectra (UV — vis), photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The results show that the films are ZnO nanorods. With the increase of annealing temperature, the diameter of the rod increases, and the nanorods tend to be oriented. The band gap of the sample obtained from the light absorption spectra first increases and then decreases with the increase of annealing temperature. When the annealing temperature is 350 °C, the crystallinity of zinc oxide film is the highest, the band gap is close to the theoretical value of pure ZnO.

The spindle-shaped α-Fe₂O₃ was prepared by hydrothermal method, Fe₂O₃/ZnO and Fe₂O₃/ZnO/PANI photocatalytic composite materials were successfully prepared, and their structure and photocatalytic properties were studied. The results show that different amount of PANI has different photocatalytic performance, and the addition of PANI improves the photocatalytic properties of the composite. In addition, Fe₂O₃/ZnO/PANI(10%) exhibits the best photocatalytic performance. After two hours of UV irradiation, the degradation rates of methyl orange and orange II reach 68.1% and 75.4%, respectively.

Multifunctional ceramics of 0.825K_0.5Na_0.5NbO₃-0.175Sr(Yb_0.5Nb_0.5)O₃- x%Er with ferroelectric, transparent and luminescent properties were obtained by doping Er. The effects of Er-doping on the structure, luminescence and electrical properties of the ceramics were studied. After Er doping, the ceramics have luminescent properties and the luminescence intensity reaches the maximum when x=0.75. The ceramics still have good light transmission, but the transmittance decreases with the increase of Er-doping content due to the change of phase structure from pseudo-cubic phase to three-phase orthogonality. The energy storage properties is also greatly improved, and the W _rec and the η of the ceramics reach the maximum value of 0.31 J/cm³ and 94.6% when x=0.25, respectively. At the same time, the maximum electro-induced strain value is 0.031%.

Due to the relatively high density of conventional non-sintered lightweight aggregate(NLA), a low-density core-shell NLA(CNLA) was developed. Moreover, two types of porous lightweight aggregate concrete (PLAC) for wallboard were designed, using both foam and lightweight aggregates. The effects of LA on lightweight concrete workability, compressive strength, dry shrinkage, and thermal conductivity were studied and compared. The bulk density of CNLA can be lowered to 500 kg/m³, and its cylinder crushing strength is 1.6 MPa. PLACs also have compressive strengths ranging from 7.8 to 11.8 MPa, as well as thermal conductivity coefficients ranging from 0.193 to 0.219 W/(m·K⁻¹). The CNLA bonds better to the paste matrix at the interface transition zone, and CNLA concrete has a superior pore structure than SLA concrete, resulting in a 20% improvement in fluidity, a 10% increase in strength, a 6% reduction in heat conductivity, and an 11% decrease in drying shrinkage.

The experimental and modeling approaches were taken to study the deterioration mechanism of concrete under acid rain attack. Concrete specimens were prepared and exposed to the simulated acid rain environment. The neutralization depth of concrete was measured, and the mineralogical composition and microstructure of concrete were analyzed using X-ray diffraction (XRD) and scanning electron microscope (SEM). The experimental results show that the degradation of concrete increases with the corrosion time and the decrease in pH value of acidic solution from 3.5 to 1.5. Concrete was corroded by H⁺ and SO₄ ²⁻ in acid rain, producing gypsum and leading to the neutralization of concrete. The acid rain exposure also resulted in the decomposition of hydration products of cement, such as C-S-H and ettringite, forming the main corrosion products of gypsum and SiO₂·nH₂O. Based on the second Fick diffusion law, a model was developed to describe the deterioration mechanism of concrete exposed to acid rain mathematically, coupling the diffusion of reactive ions and the corrosion reaction. The simulation results and the experimental results were compared and discussed.

Hybrid nanoSiO₂ (HNS) modified cement pastes were explored as a kind of surface protection material (SPM). The carbonation resistance and mechanical properties of SPMs coated samples were tested. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP) were further employed to evaluate the chemical composition and microstructure characteristics of SPM. Besides, thermodynamic modeling was adopted to simulate the changes in the phase assemblages of SPM under the carbonation process. The results showed that SPM with 1 wt% HNS could effectively enhance the carbonation resistance. The incorporation of HNS could densify the microstructure and refine the pore structure. Moreover, the thaumasite can be stable at ambient temperature with the addition of HNS, which is beneficial to maintain alkalinity under the carbonation process.

Phosphogypsum-based materials (PBM) were synthesized with varied phase compositions of phosphogypsum, portland cement and fly ash. Effects of fractal growth characteristics on physicochemical properties, pore structure, compressive strength, as well as the hydration behaviour and mineralogical conversion of mortars were examined by a multitechnological approach, including mercury intrusion porosimetry, rietved phase analysis, thremal analysis, calorimetry and Fourier transforminfrared spectroscopy analysis. Expermental results indicate that the specimens cured with mosite resulted in higher strength and lower porosity compared with those cured in the drying chamber. In addition, a more complicated course of the aluminate and silicate reactions during the hydration process has been published, with the hydration products mainly consisting of calcium silicate hydrate (C-S-H), portlandite, ettringite, hemicarbonate, monocarboaluminate, calcite, quartz, a mixed AFm passed with carbonate, and hydroxide. After all, the nucleation process is a reaction that can be defined as a solid, liquid and gaseous phases that goes through the four stages of materialization mixing and modification, i e, hydration of low calcium content, secondary hydration, high calcium condensation and geoplymensation, respectively. The rupture, recombination, polymerization reactions of Si-O, Ca-O, Al-O bonds contribute to the nucleation mechanism that serves as the formation of C-S-H in hydration products.

In order to study the chemical modification mechanism and rheological properties of polyphosphoric acid (PPA) -modified asphalt, asphalt modified with different PPA contents were characterized by four-component test, atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). In the test, changes in asphalt chemical composition and colloidal structure were analyzed for different PPA contents, and infrared spectra were fitted with a Gaussian function. The reaction mechanism of PPA and matrix asphalt was also discussed. Based on dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test, rheological index G*/sinδ and S/m were used to evaluate the modification effect of PPA on asphalt. The results show that, with an increase in PPA content, both large and small honeycomb structures increased in the three-dimensional topography seen in the atomic force microscope (AFM). In a certain space range, some of the micelles in the asphalt are connected each other to form interlocking skeleton structures, and locally form dense spatial network structures. The added PPA does not chemically react with the functional groups in the functional-group area of the infrared spectra (3 100–2 750 cm⁻¹, 1 800–1 330 cm⁻¹), and the structure is very stable. However, there is an obvious new absorption peak below 1 330 cm⁻¹ in the fingerprint area, that is, the chemical reaction between PPA and the matrix asphalt generates a new compound, inorganic phosphate. Infrared spectra of PPA-modified asphalt with different contents were fitted by a Gaussian function, which makes up for the limitation that the absorption intensity information of each superimposed functional group cannot be obtained directly from the original infrared spectra. Results of this qualitative analysis were further verified by quantitative analysis. The addition of PPA can effectively improve the high and low-temperature performance of asphalt, and the lower the temperature is in the negative temperature zone, the more obvious the improvement is. When PPA content is more than 1%, the improvement of asphalt low-temperature performance is not obvious.

In order to further study the reliability of macro evaluation indexes, molecular dynamics (MD) was applied to the evaluation of asphalt binder. Micro evaluation indexes (potential energy, surface free energy, solubility parameter and diffusion coefficient) of asphalt binder in different service phases (virgin, modified, aged and rejuvenated) were simulated. Combined with the variation characteristics of asphalt binder macro evaluation indexes (permeability, ductility, viscosity and softening point) in different service phases, the cross-scale correlation of macro-micro evaluation indexes was explored. The results show that the macro and micro evaluation indexes of asphalt binder have different characteristics in different service phases. The essence of the variation in the properties of asphalt binders is the difference in micro composition. In addition, there is a certain correlation between macro and micro evaluation indexes, which can be described by the gray relation theory. The cross-scale correlation of macro-micro evaluation indexes can provide a certain theoretical basis for the development of asphalt binder.

The composition of cement raw materials was detected by near-infrared spectroscopy. It was found that the BiPLS-SiPLS method selected the NIR spectral band of cement raw materials, and the partial least squares regression algorithm was adopted to establish a quantitative correction model of cement raw materials with good prediction effect. The root-mean-square errors of SiO₂, Al₂O₃, Fe₂O₃ and CaO calibration were 0.142, 0.072, 0.034 and 0.188 correspondingly. The results show that the NIR spectroscopy method can detect the composition of cement raw meal rapidly and accurately, which provides a new perspective for the composition detection of cement raw meal.

The effects of carbon dioxide (CO₂) curing conditions (temperature, relative humidity and CO₂ curing time) on the physical properties of recycled coarse aggregate (RCA) with varying attached mortar (AM) contents were studied. Before and after CO₂ curing, the physical properties in terms of the apparent density, water absorption and crushing value of RCA were tested and the quality of RCA was determined. Besides, scanning electron microscope was used to observe the microstructure of RCA. Results show that the physical properties variation of RCA with higher AM content are more significant, and the quality of RCA with lower AM content is easier to be upgraded during CO₂ curing. The physical properties of RCA with 40.8% AM content are earlier stable than that with no less than 44.5% AM content during CO₂ curing. The optimal temperature and relative humidity are 50 °C and 55% for CO₂ curing, respectively. CO₂ curing is incapable of upgrading the quality of RCA with AM no less than 50.6%. The quality of RCA with 44.5% AM content can be upgraded only under the optimum CO₂ curing conditions. Under relative humidity higher than 40% and the CO₂ curing time more than 12 h, CO₂ curing upgrades the quality of RCA with 40.8% AM content.

In order to study the influence of highland barley straw ash (HBSA) prepared under certain conditions on the durability of magnesium oxychloride cement mortar (MOCM) under freeze-thaw damage, rapid freeze-thaw cycle tests were carried out firstly. The relative mass evaluation parameters and the relative compressive strength evaluation parameters, which represent the degradation of freeze-thaw resistance, were used as the indices to study the degradation rule of MOCM. Secondly, nuclear magnetic resonance (NMR) tests were carried out on MOCM under different freeze-thaw cycles to analyze the pore diameter changes in the freeze-thaw process. The microstructure of MOCM was tested by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), and then the effect mechanism of HBSA on the anti-freezing performance of MOCM was revealed. Finally, the two-parameter Weibull distribution function was used to analyze the reliability of durability degradation of MOCM added with HBSA under freeze-thaw cycles. The specific conclusions are as follows: With the increase of HBSA’s addition, the freeze-thaw resistance of MOCM increase firstly and then decrease. When the addition of HBSA is 10%, the decay rate of relative mass evaluation parameters and relative compressive strength evaluation parameters is the slowest, and the frost resistance is the best. The proportion of harmful pores and more harmful pores in MOCM added with 10% HBSA decreases by 25.11% and 21.34%, compared with that without HBSA before and after freeze-thaw cycles. A lot of magnesium silicate hydrate (M-S-H) gels are generated in MOCM with HBSA content of 10%, which fills part of the pores, so that the proportion of harmful pores and more harmful pores is the lowest. The Weibull function can be effectively applied to the reliability analysis of the freeze-thaw cycle of MOCM added with HBSA, and the theoretical results are in good agreement with the experimental results.

In this study, the compressive, split tensile, and flexural strengths of concrete with nano-CaCO₃ only were compared with those of concrete with nano-CaCO₃ and basalt fibers through field experiments, and the underlying mechanisms were analyzed by the Scanning Electron Microscope (SEM) techniques. On the mesoscale, a damage model of concrete was established based on the continuum progressive damage theory, which was used to investigate the influence of different lengths and contents of fibers on the mechanical properties of concrete. Then, the experimental and numerical simulation results were compared and analyzed to verify the feasibility of model. The results show that nano-CaCO₃ can enhance the compressive strength of the concrete, with an optimal content of 2.0%. Adding basalt fibers into the nano-CaCO₃ reinforced concrete may further enhance the compressive, split tensile, and flexural strengths of the concrete; however, the higher content of basalt fiber can not lead to higher performance of concrete. The optimal length and content of fiber are 6 mm and 0.20%, respectively. The SEM result shows that the aggregation of basalt fibers is detrimental to the mechanical properties of concrete. The numerical simulation results are in good agreement with the experimental results.

The effect of the content and specific surface area of the ground granulated blast furnace slag (GGBS) on the pore structure of the cement paste was determined through the low-field nuclear magnetic resonance (NMR). The Pearson correlation analysis method was used to calculate the correlation coefficient between the porosity and age of cement paste, the specific surface area of GGBS and the content of GGBS. The test results exhibited that the porosity of the cement paste with different ageing durations gradually decreased on increasing the content and specific surface area of GGBS. The content and specific surface area of GGBS had a negligible effect on the 1–10 nm size gel pores in the cement paste, whereas, had a significant effect on the 10–100 nm size capillary pores. In addition, these parameters did not affect the final most probable pore size of the cement paste. The correlation between age and porosity was the largest, and the correlation between GGBS content and porosity was greater than that between GGBS specific surface area and porosity. Moreover, a modified pore structure model was successfully developed to effectively predict the pore structure of the GGBS based cement paste.

To quantitatively estimate the workability of cement-based grouting material, from the perspective of rheology, the result of the static yield stress evaluated using the rate-controlled and stress-controlled modes, respectively, was compared using the Rheowin rheometer. Also, the correlation of workability and solid concentration of slurry with static yield stress was studied. Results show that the static yield stress of cement-based grouting slurry relates to the established slurry structure, and is the shear stress corresponding to the transformation of elastics to plastics; In rate-controlled mode, the static yield stress of the slurry is related to the shear rate. The higher the shear rate, the greater the yield stress of the slurry. For the stress-controlled mode, the result is more accurate and suitable for testing static yield stress under different water-cement ratios. Since the water-cement ratio has a good correspondence with the static yield stress and the static yield stress has a good correspondence with the slump flow of the slurry, the static yield stress is the minimum stress to be overcome when the slurry begins to flow and it reflects the yield behavior and structural stability of the cement.

The cracking performance of semi-flexible pavement (SFP) was investigated by using the semi-circular bending (SCB) test in this paper. Thirteen grouting slurries were prepared. The compressive strength of these materials ranges from 3 to 100 MPa. The relationship between the compressive strength of the grouting slurry and the cracking property of SFP was obtained at different loading rates and different temperatures. The peak load, fracture energy (E), flexible index (FI), and cracking resistance index (CRI) were calculated to determine the material performance. The results show that the compressive strength of the grout influences the cracking behavior. With a higher comprehensive strength grouting slurry, the FI value of SFP decreased initially and then increased slightly at 25 °C in 50 mm/min. The CRI value decreased at the same time. E values changed just according to the test temperature and loading rate. The damage paths of SFP are different. The damage path of the SFP sample appears as diffuse damage at 1 mm/min at 60 °C or clean damage at 50 mm/min at 25 °C. These findings indicate that there is a correlation between the compressive strength of grouting slurry and SFP cracking behavior. The cracking form is influenced by loading rate and temperature.

Molecular dynamics simulation was utilized to investigate the transport and adsorption of chloride in the nanopore of calcium aluminosilicate hydrate (C-A-S-H) with associated cation types of Ca, Mg, Na and K. The local ionic structure, atomic dynamics and bond stability were analyzed to elucidate the interaction between cations and chloride ions. The results show that interfacial chloride is absorbed through the ion pairing formation in the vicinity of C-A-S-H substrate. Interfacial cations can simultaneously interact aluminosilicate chains, water molecules and Cl⁻ ions, which restrict the motion of interfacial Cl⁻ ions. Pore solution chloride can be immobilized through the solvation effect of cations. Cations along with their hydration shell can connect to neighboring Cl⁻ ions to decrease their mobility. Owing to the varied ionic chemistry, cations show different interaction strength with neighboring water molecules and anions, which determines the chloride transport behavior in the nanopore of C-A-S-H. The chloride immobilization capacity of C-A-S-H nanopore with different associated cations is listed in following order: Mg²⁺<Ca²⁺<Na⁺≈K⁺, which agrees reasonably with previous experiments.

Al-5Cu-4.5Mg-2.5Zn alloy was prepared and the alloy ingots were fabricated by squeeze casting in this work. Considering these negative effects of composition segregation and coarse second phases, some heat treatments were adopted in this research. Microstructures, element distribution, phase constitutions and mechanical properties of Al-5Cu-4.5Mg-2.5Zn alloy ingots before and after heat treatments were investigated. It was discovered that these heat treatments would influence and extremely optimize the microstructures and properties of Al-5Cu-4.5Mg-2.5Zn alloy. Except some residual S (Al₂CuMg) phase and a few of η phase, the precipitate free zone (PFZ) and the Guinier Preston zone (GPZ) formed in the alloy. It was also found that θ″ (Al₂Cu) and η″ (MgZn₂) phases formed and kept a consistent relationship with the aluminum matrix. As the result, these properties of ultimate tensile strength (UTS), percentage of elongation and Brinell hardness (HB) were greatly elevated. The UTS, percent of elongation and HB were 469 MPa, 8.1% and 208 N/mm², respectively.

Five sets of high entropy alloys (HEAs) FeCoNiCu _x (x =0.5, 1.0, 1.5, 2.0, 2.5) were produced by vacuum induction smelting. The effects of Cu content on the microstructure and mechanical properties of the alloys were interrogated by X-ray diffractometer (XRD), field scanning electron microscope (FESEM) and tensile mechanical test. The result shows that the HEAs form single FCC solid solution phase. With the increase of Cu content, the diffraction peak first deviated to the right and then shifted to the left. The alloys changed from equiaxed crystal structure to refined dendritic crystal structure, as Cu content increased. A large number of Cu atoms are isolated in the inter-crystalline region. The tensile mechanical tests show that with the increase of Cu content, the ultimate tensile strength first increased and then decreased. When x is 2.0, the ultimate tensile strength reaches a maximum of 473 MPa, the percent elongation is 43.0%, and the fracture presents ductile behaviour.

The characteristic of near-surface microstructure and its effects on the torsion performance of cold-drawn pearlitic steel wires for bridge cables were investigated by focused ion beam-scanning electron microscope, transmission electron microscopy and differential scanning calorimetry. The samples with similar tensile strength before and after hot-dip galvanizing process are, respectively, characterized as delaminated and non-delaminated in torsion test which indicates that the tensile strength is independent of the toughness value (i e, reduction area and torsion ability). It is interesting to find that there exists submicron granular ferrite on near-surface of the wires, which can be attributed to dislocation rearrangement and sub-grains rotation during cold drawing and hot-dip galvanizing process. And their distribution can suggest homogeneousness of deformation degree to a certain extent: the closer to the surface of their distribution, the more homogeneous deformation of the wires. There is a close relationship between the thermal stability of the cementite layer and distribution of granular ferrite: differential scanning calorimetry (DSC) analysis shows that the sample is accompanied by submicron granular ferrite which is located closer to the surface has higher thermal stability under galvanizing temperature (450 °C). A new mechanism of the torsion delamination of pearlitic steel wires is discussed in terms of the thermal stability of the cementite layer and distribution of granular ferrite.

In order to investigate the influence of natural defect on the fatigue behavior of 5A06/7A05 dissimilar aluminum alloys welding joint, fatigue tests of two types of specimens with and without defects were carried out systematically under stress amplitude control conditions (stress ratio R=0.1) at normal temperature in laboratory air condition. Furthermore, a new parameter, i e, fatigue defect effect factor (FDEF) was introduced to assess the effect of defect on fatigue strength. The fatigue failure analysis was conducted as well to compare the fatigue and fracture behavior of the two types of specimens. The results show that: (1) natural defects have a strong effect on the fatigue lives of welding joint, and the differences between the specimens with and without defects can reach 80 times under a same theoretical net sectional stress; (2) the FDEF parameter introduced is effective to deal with the defect effect, and the FDEF decreases along with the increase of fatigue life. The mean relative error between the experimental data and predicted fatigue strength based on the FDEF is 10.2%; (3) the macro fracture of both types of specimens have three typical zones, i e, fatigue source zone, crack propagation zone and final fracture zone, while there are more than one fatigue sources for specimens with natural defects. The overall pattern of crack propagation zone and fracture zone are quite similar, but the morphologies are different in details.

In order to improve the thermoelectric and mechanical properties of p-type Bi₂Te₃ thermoelectric material, Bi_0.5Sb_1.5Te₃/Ni&Cu core/shell powders were electroless plated with the same content of Ni and different content of Cu, and then reduced by hydrogen, and finally sintered into bulk by spark plasma sintering. After composite electroless plating with Ni&Cu, for the bulk sample with 0.3 wt% Ni and 0.15 wt% Cu, the power factor rises significantly and the highest value increases from 25 to 33 µW·cm⁻¹·K⁻² at room temperature. Meanwhile, the thermal conductivity decreases to about 0.80 W·m⁻¹·K⁻¹ at 623 K. Therefore, the composite electroless plating with Ni&Cu can obviously improve the electrical and thermal transport performance of p-type Bi₂Te₃ based thermoelectric materials. Thus, the ZT value enhances significantly and the highest value increases over 3 times, from 0.35 to 1.16 at 473 K in Bi_0.5Sb_1.5Te₃ with 0.3 wt% Ni and 0.15 wt% Cu bulk sample. At the same time, the mechanical properties have also been improved after composite electroless plating with Ni&Cu.

In order to prepare the polyethylene materials with controlling properties, we developed two kinds of controllable cross-linking polyethylene foaming system. 2, 5-dimethyl-2, 5-bis (tert-butyl peroxy) hexane was used as cross-linking agent and TEMPO as cross-linking inhibitor, azodicarbonamide (AC) was used as foaming agent and citric acid as foaming promoter. The density, expansion ratio, cellular structure and mechanical property of these two kinds of controllable materials were studied. Experimental results show that, properties of these two kinds of materials appear similar trend: cellular size and expansion ratio are enlarged with the amount of cross-linking inhibitor or foaming promoter increasing, while density and mechanical strength appear decreasing trend. Through comparing those two material systems’ properties, cross-linking polyethelene foaming system with citric acid as foaming promoter has better properties.

The effects of the morphologies of liquid crystal (LC) droplets left in polymer network on the performance of polymer dispersed liquid crystal composite films were investigated. By adjusting the relative content range of the crosslinking and diluents, the morphologies of polymer network can be changed. Therefore, the properties of PDLC composite films with imparity polymer morphologies were obtained by experiments and the finite element simulation. Results of the experimental and finite element simulation showed that the electrooptical properties of PDLC composite films were inversely proportional to the domain size of the polymer network and the mechanical properties were proportional to the domain size of the polymer network.

A novel graphene oxide (GO) modified polyurethane thermal conductive insulating adhesive with small addition and excellent insulation properties was prepared by in-situ polymerization using GO as thermal conductive filler. The effects of GO content on the mechanical performance, thermal conductivity, thermal stability and insulation properties of the modified polyurethane adhesive were studied. The results showed that the tensile strength and elongation at break of polyurethane adhesive increased at first and then decreased with the increase of GO content. The thermal conductivity and thermal decomposition temperature of GO/PU composite adhesive can be effectively improved by adding appropriate amount of GO. The tensile strength, thermal conductivity and thermal decomposition temperature of polyurethane adhesive reached the maximum when GO content was 1.5 wt%. The novel GO-modified polyurethane adhesive exhibited good insulation property. The development of GO/PU thermal conductive adhesive will provide a facile method for effectively solving the “trade-off” problem between low filling and high thermal conductivity.