In order to understand the influence of nano-sized B₄C additive on ZA27 alloy, mechanical and physical properties of ZA27-B₄C nanocomposites were investigated in terms of B₄C content. While physical properties were determined in terms of microstructural studies, density and porosity tests, mechanical properties were determined in terms of ultimate tensile strength (UTS) and hardness experiments. Morphological and microstructural studies were carried out with scanning electron microscopy (SEM). The experimental results indicate that nano-sized B₄C can be used to enhance the mechanical properties of ZA27 alloy effectively. The highest mechanical performance can be obtained at ZA27-0.5% B₄C (in weight) nanocomposite with values of tensile strength (247 MPa) and hardness (141,18 BH) and low partial porosity (0.5%). After a pick point, increasing B₄C ratio may cause the formation of agglomeration in grain boundaries, that’s why density, tensile strength, and hardness values are declined.

In order to obtain the suitable phase change material (PCM) with low phase change temperature and improve its heat transfer rate, experimental investigation was conducted. Firstly, different mass ratios of lauric acid (LA) and stearic acid(SA) eutectic mixtures were prepared and characterized by differential scanning calorimetry (DSC). Then, the performance of eutectic mixture during charging process under different fin widths in vertical condition, and performance during charging and discharging processes under different inlet temperature heat transfer fluid (HTF) in horizontal condition were investigated, respectively. The results revealed that the LA-SA eutectic mixture had the suitable phase change temperature and desired latent heat for low-temperature water floor heating system. Wide fins and high inlet temperature HTF significantly enhanced the transfer rate and decreased the melting time.

Silver coatings on the exterior surface of monolithic activated carbon (MAC) with different morphology were prepared by directly immersing MAC into [Ag(NH₃)₂]NO₃ solution. Acid and base treatments were employed to modify the surface oxygenic groups of MAC, respectively. The MACs’ Brunauer-Emmett-Teller (BET) surface area, surface groups, and silver coating morphology were characterized by N₂ adsorption, elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), respectively. The coating morphology was found to be closely related to the surface area and surface functional groups of MAC. For a raw MAC which contained a variety of oxygenic groups, HNO₃ treatment enhanced the relative amount of highly oxidized groups such as carboxyl and carbonates, which disfavored the deposition of silver particles. By contrast, NaOH treatment significantly improved the amount of carbonyl groups, which in turn improved the deposition amount of silver. Importantly, lamella silver was produced on raw MAC while NaOH treatment resulted in granular particles because of the capping effect of carbonyl groups. At appropriate [Ag(NH₃)₂]NO₃ concentrations, silver nanoparticles smaller than 100 nm were homogeneously dispersed on NaOH-treated MAC. The successful tuning of the size and morphology of silver coatings on MAC is promising for novel applications in air purification and for antibacterial or aesthetic purposes.

The dynamic load characteristics of a proton exchange membrane fuel cell (PEMFC) with a dead-ended anode were studied. In a 70 h experiment, the effects of anode pressure, operating temperature, and relative humidity of the cathode on the performances of the fuel cell were investigated. The obtained results show that, with different relative humidity of the cathode at 65 °C, dynamic loading has little effect on the performances of fuel cell and the electrochemically active surface area (ECSA). However, the fuel cell operating under dynamic load is unstable when the relative humidity is 50%, and at 50 °C with 100% relative humidity, applying a dynamic load has a significant influence on the fuel cell performances. Scanning electron microscopy (SEM) showed that both the upstream and middle catalyst layers of the cell were unchanged, whereas the down-stream cathode catalyst layer thinned as a response to dynamic load.

A conjugated polymer of poly(4,4'-bis(thien-2-yl)azobenzene-co-3-hexylthiophene) (PTAB-H), bearing azo group in main chain and soluble in THF, chloroform, was synthesized through FeCl3 oxidation copolymerization with 3-hexylthiophene, and the monomer of 4,4'-bis(thien-2-yl)azobenzene was synthesized by Sandmeyer reaction and Suzuki reaction. The UV-Vis spectra of PTAB-H reveal that azo group in the main chain can extend the absorption and lower the band gap. The fluorescent spectra, photoluminescence (PL) spectra, cyclic voltammetry (CV) of PTAB-H were recorded.The gel permeation chromatography (GPC), thermogravimetry analysis (TGA), and differential scanning calorimetry (DSC) measurements indicated that the molecular weight Mn, Mw and polydispersity indices (PDI) of the polymer are 10 876 g/mol, 22 338 g/mol and 2.05 respectively and the temperature of 5% weight-loss is 224.6 °C. No glass transition and crystallization melting peak was observed in the temperature range from 30 °C to 400 °C.

The interfacial performance of the Fiber Bragg grating (FGB) embedded in the composite was studied and the influence of interface modification on the final profile of the spectra of the FBG sensor was examined. A type of polyamine (Pentaethylenehexamine, PEHA) was proposed to modify the coating of PI on FBG, and the interfacial performance was evaluated by a pull-out test. Sharp improvements of the interfacial shear strength (77%) were obtained by 40 min treatment of PEHA. Compared with untreated specimen, FGB spectra of treated specimen in the tensile tests show improved linearity within the test regime, which proves that the enhanced interface is beneficial for the sensing performance.

The urea-formaldehyde resin/reactive montmorillonite composites were prepared by in situ polymerization. The reactive montmorillonite was prepared firstly by being ion exchanged with organic molecules and secondly by being grafted with silane coupling agent, which could be demonstrated by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) revealed that the morphology of the urea-formaldehyde resin/reactive montmorillonite composites were ellipsoid or columnar particles. Energy dispersive spectrometry (EDS) confirmed that the reactive montmorillonite was encapsulated by urea-formaldehyde resin. Differential scanning calorimetry (DSC) indicated that curing process of the urea-formaldehyde resin/reactive montmorillonite composites consumed more energy than pure urea-formaldehyde resin. Thermogravimetric analysis (TGA) showed that the thermal stability of the urea-formaldehyde resin/reactive montmorillonite composites improved compared to pure urea-formaldehyde resin. Furthermore, the reactive montmorillonites reduced the formaldehyde emission of the composites and increased the water resistance. Finally, the mechanism to prepare the urea-formaldehyde resin/reactive montmorillonite composites was proposed.

Two kinds of 2.5D deep straight-joint structure ultra-high molecular weight polyethylene (UHMWPE) (twisted and original) fibers woven fabric reinforced epoxy resin composites were prepared by the hand lay-up method. Subsequently, the flexural property, microstructures, and failure mechanisms of the composites were also investigated. The average flexural strength of 2.5D deep bend-joint structure twisted fiber and original fiber woven fabric composites were 176.66 MPa and 204.45 MPa, respectively. The results of the characteristics indicated that the twist was the main factor which affected the flexural performance. Flexural property vitally relied on the strength of the fiber itself. Twist decreased the strength of the yarns, which meant that when the mechanical property of woven fabric reinforced composites was improved, the yarns must be kept straight in the woven fabric. The study are extremely valuable to guide the improvement of the mechanical property of the woven fabric reinforced composites.

A bio-inspired layered material of reduced graphene oxide (RGOs) and calcium carbonate was synthesized via a one-pot strategy in DMF/H₂O mixed solvent. The experimental results show that the product is a layered material of wrinkled RGOs networks and micron-sized calcium carbonate particles with uniform granular diameter and homogeneous morphology, which are distributed between the layered gallery of the graphene scaffold. The polymorph and the morphology of the in-situ produced calcium carbonate particles can be manipulated by simply changing the temperature scheme. Besides, the graphene oxide was reduced to a certain extent, and the hierarchical wrinkles were generated in the RGOs layer by the in-situ formation of the calcium carbonate particles. This work provides a facile and controllable strategy for synthesizing layered material of RGOs and carbonates, and also presents a platform for making three-dimensional porous wrinkled RGOs networks.

Hydration mechanism of tabular alumina carbon composites reinforced by Al₄C₃ in situ reaction with Mg and Al was researched in water steam using super automatic thermostatic water bath from 25 °C to 85 °C. It is shown that hydration mechanism of the composites is chemical reaction control at 44.3 °C-84 °C in H₂O(g). The hydration was controlled by diffusion from 24.7 °C to 33 °C. The ratio of added Mg/Al influences the HMOR of the composites.The mechanism of HMOR of the composites with different ratios of Mg/Al can be discovered by means of SEM analysis. The active Mg/Al powder and flake graphite inside give the composites outstanding hot strength resulting from the interlocking structure of Al₄C₃ crystals at high temperature. Besides, the matrix changes into the Al₄C₃ with high refractoriness. The method of preventing the hydration of tabular alumina carbon composites reinforced by Al₄C₃ in situ reaction was immersed in the wax at suitable temperature or storing them below 33 °C in a dry place or storing them with paraffin-coating.

Aiming at the problem of available water conservation in desertification ecological restoration, we prepared the water retention materials with montmorillonite(MMT) modified by Castor Oil Polyoxyethylene Ether(10) (EL-10) emulsifying vegetable waxes. The water retention property was studied in simulated desertification climate, and the materials were analyzed and characterized by UV-Vis, SEM, FTIR and XRD measurements. Moreover, a UV carbon arc lamp was used to test the resistance to aging. The experimental results show that the emulsion has good dispersity. Both the water retention property and the aging resistance performance of the modified clay were excellent. The lamellar structure and chemical composition of MMT had no obvious changes before and after modification. The surfaces of clay particles were coated uniformly with modified MMT, so the loose clay particles were cemented together by vegetable waxes. Meanwhile, the original big hydrophilic pores between the clay particles turned into capillary hydrophobic pores. So the clay particles formed a bonding layer which could inhibit water evaporation. Grass-planting experiment showed that reasonable mass ratio of vegetable waxes and EL-10 was 1:18. The materials not only had great water retention property but also maintained sound air permeability so that the germination rate of grass seed significantly increased from 8% to 52%.

NaCl aqueous solution (15wt%) was used as the quenching medium to prepare amorphous Lithium-Zinc ferrite hollow microspheres (LiZn FHMs) based on self-reactive quenching technology. Investigations by scanning electro microscope, X-ray diffraction, electron diffraction of transmission electron microscope, and differential scanning calorimetry prove that LiZn FHMs are susceptible to amorphization. It is indicated that NaCl aqueous solution (15wt%) has ultra-fast quenching speed, and the growth rate of crystals on LiZn FHMs is so large that the formation and growth of the crystal nucleus are significantly restrained. This is the main reason for the formation of amorphous LiZn FHMs.

The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper (W-Cu) contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microstructure of the W-Cu powders and compacts. The contact resistance, arcing energy, and arcing time were continuously measured by JF04C contact materials test system. Changes in tungsten-copper contact surface were observed by SEM. The test results showed that the arcing time and arcing energy all increase with current and voltage, but the changes of average contact resistance are more complicated. For a short arcing time, the average contact resistance decreases with increasing current due to the vaporization of Cu. However, for a longer arcing time, it slightly increases due to the formation of high resistant films, compound copper tungsten. The formation of compound copper tungsten was confirmed by the increased Rc kept in the range from 1.1 to 1.6 mΩ. The compound copper tungsten is first exposed with a tungsten and copper-rich surface, and then totally exposed due to evaporation of copper from the surface. At last a stabilized surface is created and the crystals decrease from 8 μm to 2 μm caused by the arc erosion.

Titanium phosphonate adsorbent materials with hierarchically porous structure were fabricated using the hydrolysis of tetrabutyl titanate in different organophosphonic acids solutions. Based on the macroporous structure of 100-2000 nm in size, a worm-hole like mesostructure was in the macropore walls, which was supported by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ sorption analysis. Fourier transform infrared spectroscopy (FT-IR) data indicated the organic groups inside the solid materials framework. NH₃ adsorption detection was performed using titanium phosphonate adsorbent materials and some significant results were obtained. The adsorption mechanism was also discussed in this study. Large adsorption amount (75.2 mg/g) was mainly attributed to the acid site via acid-base reactions and the physical adsorption site via Van der Waals forces. Resultant materials could effectively restrain the desorption of adsorbent NH₃ back into air causing secondary pollution, so it could make a promising potential use in decontamination of gas pollutants in the future.

Several action regimes were employed, namely, those exposed to solutions containing single and/or composite chloride and sulfate salts, and under wet-dry cycles and/or flexural loading. The variations in dynamic modulus of elasticity (E _rd values) were monitored, as well as the key factor impacting on the chloride ingress when concrete subjected to multiple action regimes was identified by the method of Grey Relation Analysis (GRA). The changes in micro-structures and mineral products of interior concrete after different action regimes were investigated by means of X-ray diffraction (XRD), mercury intrusion technique (MIP), and scanning electron microscopy (SEM). The test results showed that the cyclic wet-dry accelerated the deterioration of OPC concrete more than the action of 35% flexural loading based on the results of E _rd values and the GEA. The analyses from micro-structures could give certain explanations to the change in E _rd values under different action regimes.

Backscattered electron images (BSE) obtained by scanning electron microscope was used to quantitatively characterize the microstructure of interfacial transition zone (ITZ) in concrete. Influences of aggregate size (5, 10, 20, and 30 mm), water to cement ratio (0.23, 0.35 and 0.53) and curing time (from 3d to 90d) on the microstructure of interfacial transition zone between coarse aggregate and bulk cement matrix were investigated. The volume percentage of detectable porosity and unhydrated cement in ITZ was quantitatively analyzed and compared with that in the matrix of various concretes. Nanoindentation technology was applied to obtain the elastic properties of ITZ and matrix, and the elastic modulus of concrete was then calculated based on the Lu & Torquato model and self-consistence scheme by using the ITZ thickness and elastic modulus obtained from this investigation. The experimental results demonstrated that the microstructure and thickness of ITZ in concrete vary with a variety of factors, like aggregate size, water to cement ratio and curing time. The relative low elastic properties of ITZ should be paid attention to, especially for early age concrete.

The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano-silica (doping Ti⁴⁺) was used as a asphalt modifier. Some physical properties including penetration, ductility, and softening point of asphalt were analyzed with RTFO (Rotating thin film oven) aging and ultraviolet aging. Moreover, the performances of high and low temperature of modified asphalt binders with pressure aging were tested by dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test. These results showed that the penetration decreased, low temperature ductility, and softening point increased when adding mesoporous nano-silica to base asphalt. After ultraviolet radiation aging, the penetration loss and ductility loss of modified asphalt decreased than that of original asphalt, the increase of softening point was also significantly reduced than that of base asphalt. Furthermore, The test results of DSR and BBR showed that the G*sinδ and creep modulus‘s’ of pressure aged asphalt decreased, but the creep rate ‘m’ increased. It can be concluded that the aging resistance and cracking resistance of modified asphalt are improved by adding mesoporous nano-silica, especially the doping of Ti⁴⁺ could improve the aging resistance obviously.

By using oxalate group-modified TiO₂ nanoparticles as the dispersing phase, different kinds of silicone oil with various viscosities and terminal groups (hydroxyl, hydrogen, and methyl) were used as the dispersing media to prepare different electrorheological (ER) fluids. Their zero-field viscosity, yield stress under direct current electric fields, ER efficiency, shear stability, leakage current density, and sedimentation stability were tested to study the effect of carrier liquid on the properties of ER fluids. The results indicate that the zero-field viscosity, the yield stress, and the leakage current density increase with increasing viscosity of the silicone oils. The effects of the viscosity on the ER efficiency, the shear stability, and the sedimentation ratio depend on the competition between the viscous resistance and the aggregation of the particles. Among the three ER fluids prepared with silicone oil with different terminal groups, hydroxyl-terminated oil based sample has the highest zero-field viscosity, the highest field-induced yield stress and ER efficiency, the largest current density, and the best sedimentation stability.

Powder in tube process (PIT) was adopted for the fabrication of single filament Bi-2223 tapes, and a heat treatment process including the first heat treatment (HT1), intermediate rolling (IR), and second heat treatment (HT2) was performed. The phase evolution mechanism and microstructure changes during these heat treatment processes were systematically discussed. The influences of HT1 parameters on the phase evolution process of Bi-2223 tapes were discussed. With the optimized HT1 process, a proper Bi-2223 content of about 90% was achieved. HT2 process was also optimized by adding a post annealing process. An obvious increase of current capacity was obtained due to the enhancement of intergrain connections. Single filament Bi-2223 tapes with the critical current of I _c-90 A were fabricated with the optimized sintering process.

Indium doped ZnO films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of ZnO thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped ZnO thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped ZnO thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10^-4 Ω·cm and the highest carrier concentration of 1.86×10²¹ cm^-3 can be obtained from ZnO thin films with an indium content of 5at% in the target.

Barium ferrite micro/nano fibers were successfully prepared via the electrostatic spinning by using dimethyl formamide (DMF) as the solvent, and poly vinyl pyrrolidone (PVP) as the spinning auxiliaries. Effects of strontium substitution on the structure, morphology, and magnetic properties were investigated by scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and vibration sample magnetometer (VSM). XRD patterns of the samples confirm that pure barium ferrite fibers form, and the Sr substitution makes the main peaks (110), (107), and (114) move to right slightly. Also, the FE-SEM images show that the Sr substituted fibers can keep complete fibrous morphology. Moreover, the VSM results demonstrate that the saturation magnetization can reach 56.7 emu/g when the fibers are calcined at 800°C.

The damage process and corrosion ion distribution in concrete, which was exposed to 60 and 170 drying-immersion cycles of sulfate solution, were systematically investigated. The effects of plain concrete, plain concrete mixed with 4 and 8 kg/m³ modified PP fiber and high-performance concrete (HPC) mixed with 0.8 kg/m³ fine PP fiber on the damage process were also studied. The experimental results showed that thenardite-induced surface scaling, as well as gypsum- and ettringite-induced cracks, were the main degradation forms of concrete under attack of sulfate solution and drying–immersion cycles. The relative dynamic modulus of elasticity of concrete initially increased, then reached stability and finally decreased to failure. The sulfate diffusion coefficients of plain and HPC were 10^-12 and 10^-13 m²/s, respectively. The concentration of sodium ion increased with depth, then maintained stability and finally decreased rapidly with concrete depth. The content of calcium ion on the concrete surface was 110%-150% of that in the interior of specimens. Although fiber worsened the surface scaling of concrete, better resistance capacity of sulfate ion penetration into concrete was observed in plain concrete with 4 kg/m³ modified PP fiber and HPC.

We prepared graphene oxide(GO) saturable absorber (SA) successfully through optical deposition method, which is a simple but effective approach to deposit various materials onto substrate under the effects of light, and investigated several factors that influence the optical deposition result of GO onto optical fiber end, including poly(methyl methacrylate) (PMMA) concentration, light intensity, light mode, and deposition time. The efficient optically deposited GO preserving its nonlinearity guaranteed by GO/PMMA composite formation was also demonstrated. The GO SA prepared by optical deposition shows superior saturable absorption property with modulation depth and nonsaturable loss of 6% and 40%, respectively.

The surface reconstructing of vermicular alpha-alumina exposed under electron-beam irradiation was investigated by a scanning electron microscope with 0.5 keV beam energy and by a transmittance electron microscope at room temperature and 90 K, respectively. The in-situ recorded results showed that the present electron-beam-induced surface reconstructing was both electron dose and temperature dependent and accompanied by bulk shape change. The surface reconstruction was explained by an Auger decay process, in which surface composition constancy was proposed by the equilibrium between electron stmulated reduction of Al₂O₃ and oxidation of aluminum by desorbed oxygen from bulk.

Significant efforts have been made in revealing the mechanism of thaumasite formation in concrete, which continues to be fraught with ambiguities and dissension. Chemical method was employed to synthesize pure C₃S, C₂S, C₃A, ettringite, and thaumasite, and X-ray diffraction (XRD), Raman spectroscopy and infrared spectroscopy (IR) were used to identify thaumasite from other hydrates. To investigate the direct route of thaumasite formation, C₃S, C₂S, gypsum, and calcium carbonate were used to prepare a cement paste so that the interference of ettringite formation can be avoided. The indirect route of thaumasite formation was also studied by considering the effect of C₃A or ettringite content on thaumasite formation. Results show that thaumasite can be definitely generated in the absence of aluminium-bearing minerals or ettringite under appropriate conditions, while the ettringite presence promotes the thaumasite formation. No evidences support the heterogeneous nucleation route in this work. It is concluded that the method mentioned in this work can surely be used to investigate the mechanism of thaumasite formation, and thaumasite can form by both direct and woodfordite routes.

With the application of X-ray computed tomography (CT) technology of C80 high-strength concrete with polypropylene fiber at elevated temperatures, the microscopic damage evolution process observation and image building could be obtained, based on the statistics theory and numerical analysis of the combination of concrete internal defects extension and evolution regularity of microscopic structure. The expermental results show that the defect rate has changed at different temperatures and can determine the concrete degradation threshold temperatures. Also, data analysis can help to establish the evolution equation between the defect rate and the effect of temperature damage, and identify that the addition of polypropylene fibers in the high strength concrete at high temperature can improve cracking resistance.

In order to found new dielectrics ceramics in tungsten bronze structure, unfilled tungsten bronze (TB) ceramics with nominal formula Ba₄PrFe_0.5Nb_9.5O₃₀ were prepared by the solid state reaction method. The microstructure and dielectric properties were studied using powder X-ray diffraction, field emission scanning electron microscope, and variable temperature dielectric test system. The results show that the ceramics have a single phase and belong to the space group of P4bm with the cell of a = b = 12.4839(3) Å, c = 3.9409(5) Å, V = 614.192(2) ų. The frequency dependent dielectrics properties show that the ceramics have a Debye-like relaxation at room temperature, while the temperature dependent dielectrics properties indicate that the ceramics are a relaxor and the relaxation is due to the nanopolars and oxygen vacancies. The ceramics have a potential application in electronic ceramics as temperature-stable multilayer ceramic capacitors.

To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum (CS). The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO₄ completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.

The physical and mechanical properties of unstabilized rammed earth with different clay contents were studied, which could provide a theoretical basis for the understanding of mechanical properties of unstabilized rammed earth and improve the construction design method and specification of RE buildings for sustainable development. The experimental results show that clay content has significant influences on the engineering properties of unstabilized rammed earth. For the fine-grained soil, the liquid limit, plastic limit and plasticity index increase gradually with the increase of the clay content. The influence of clay content on the optimum moisture content compared with the maximum dry density is more significant. The mechanical properties of unstabilized rammed earth are significantly affected by the clay content. There exist good linear relationships, which can be used for the mutual verification or calculation among the mechanical properties. An empirical model of unconfined compression strength with the FA/CA ratio as the main parameter is established, and the UCS may obtain the maximum with a FA/CA ratio of 5.77.

Microstructural evolutions of the railway frog steel solidified under different pressure were studied using OM, FEGSEM, and TEM. The influences of pressure on the solidification, grain sizes, and morphology of carbides of the steel were analyzed. It is found that the melting point of the steel increases with the pressure and the solidified microstructure under high pressure does not vary significantly with the melting temperature. The experimental results show that the solidified microstructure consisting of complete equiaxed dendrites is remarkably refined through the increase of pressure, with the mean dendrite arm spacing of about 24, 18, and 8 μm under 3, 6, and 10 GPa, respectively. It is also revealed by TEM observation that the precipitates change from needle-like and rhombic carbide (M₃C) forms during normal (atmospheric) pressure solidification into nodulized hexagonal precipitate M₇C₃ at 3 GPa, and M₂₃C₆ at 6 GPa and 10 GPa, which is associated with the undercooling and distribution of the trace elements. The diameter of the precipitates is between 80 nm and 200 nm.

The aim of this work was to study the degradation behavior of Ti-6Al-4V alloys for dental applications in acidic artificial saliva with fluoride ion using electrochemical techniques, optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). The experimental results showed that fluoride ion had significant influence on the degradation of Ti-6Al-4V alloys, and there was an obvious critical concentration of fluoride ion (about 0.1wt%). With increasing fluoride ion concentration, the corrosion potential (E _corr) of alloys moved toward negative and the impedance of alloys decreased, meanwhile, noticeable transformation from minimum corrosion to severe pitting corrosion was observed on alloys surface following the dissolution of TiO₂ passive films, leading to the decrease of the corrosion resistance of alloys. The electrochemical dissolution of TiO₂ passive films involved a nucleophilic attack of fluoride atom to the titanium atom of TiO₂. In addition, Ca²⁺ and Na⁺ in acidic saliva may involve the surface reactions and make the reactions more complex.

Hot deformation behavior of as-cast Mn18Cr18N austenitic stainless steel was studied in the temperature range of 950-1200 °C and strain rate range of 0.001-1 s^-1 using isothermal hot compression tests. The true stress-strain curves of the steel were characterized by hardening and subsequent softening and varied with temperatures and strain rates. The hot deformation activation energy of the steel was calculated to be 657.4 kJ/mol, which was higher than that of the corresponding wrought steel due to its as-cast coarse columnar grains and heterogeneous structure. Hot processing maps were developed at different plastic strains, which exhibited two domains with peak power dissipation efficiencies at 1150 °C/0.001 s^-1 and 1200 °C/1 s^-1, respectively. The corresponding microstructures were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). It has been confirmed that dynamic recrystallization (DRX) controlled by dislocation slipping and climbing mechanism occurs in the temperature and strain rate range of 1050-1200 °C and 0.001-0.01 s^-1; And DRX controlled by twinning mechanism occurs in the temperature and strain rate range of 1100-1200 °C, 0.1-1 s^-1. These two DRX domains can serve as the hot working windows of the as-cast steel at lower strain rates and at higher strain rates, respectively. The processing maps at different strains also exhibit that the instability region decreases with increasing strain. The corresponding microstructures and the less tensile ductility in the instability region imply that the flow instability is attributed to flow localization accelerated by a few layers of very fine recrystallized grains along the original grain boundaries.

First-principles calculations within density functional theory have been carried out to investigate α₂ phase in the Ti₃Al based alloy with Zr, Hf, and Sn (6.25at%) elements doped. The lattice constants, total energies and elastic constants were calculated for the supercells. The formation enthalpies, bulk modulus, shear modulus, Young’s modulus, and intrinsic hardness were investigated. The ductility of the doped α₂ phases was analyzed by the Cauchy pressure, G/B and Poisson’s ratio. The results show that the substitution of Ti(6 h) by Zr, Hf, and the substitution of Al(2n) by Sn can make the doped α₂ phase more stable. The inflexibility and hardness of α₂ phase can be enhanced by doping with Zr and Hf, while Sn brings the opposite effect. Sn is more powerful to improve the ductility of the doped α₂ phase than Hf, but Zr can increase the brittleness. The densities of states (DOS and PDOS) and the difference charge density are obtained to reveal the underlying mechanism of the effect of alloying elements.

Two kinds nitride modified layers were obtained on Ti-13Nb-13Zr surface to improve the wear property via magnetron sputtering and plasma nitriding techniques, respectively. The structures of the modified layer and the worn surface after sliding test were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The friction and wear behavior of the modified layer against alumina ball was investigated in the absence of lubricant under different loads (1 N and 2 N). The X-ray diffraction analysis reveals that nitride layer is mainly composed of TiN and Ti2N, while coating film consists of TiN phase. Friction and wear test indicates that both modified layers can improve the wear resistance compared to untreated Ti-13Nb-13Zr. TiN thin film produces very hard surface, but may be easy to cause coating fracture and delamination under high normal load. However, nitride layer exhibits better wear performance. This is attributed to hard compound layer maintained its integrity with the hardened nitrogen diffusion zone during friction and wear process.

Two different morphologies of ZnO (lotus-shaped, rod-shaped) and ZnO/PVDF composite materials were prepared. The morphologies of ZnO and composite materials were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR), thermal gravimetry (TG), and X-ray diffraction (XRD) were also used to characterize the chemical structures and phase composites of ZnO and ZnO/PVDF composite materials. Breakdown voltage, dielectric constant and dielectric loss of ZnO/PVDF composite materials were also tested. Microstructure analysis showed that ZnO nanoparticles dispersed uniformly in the matrix. And the dielectric constant expresses a significantly improvement while the dielectric loss and breakdown voltage expresses no significant change. Moreover, dielectric constant keeps an improvement tendency with increasing content of ZnO.

Superabsorbent hydrogels were prepared successfully from N-succinyl chitosan grafted poly(acrylic acid-co-acrylamide). The potassium persulfate (KPS), N, N’-methylenebisacrylamide (MBA) were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to confirm the porous network structure of superabsorbent hydrogel. The effects of reaction parameters on the swelling behaviors of the superabsorbent hydrogels were investigated. The results indicated that water absorbency increased first, and then decreased gradually with the increase in the contents of monomer (AA+AM), KPS, MBA or acrylamide. The product had excellent water absorbency of 1375 g/g in distilled water and 83 g/g in 0.9wt% NaCl solution. Simultaneously, the superabsorbent hydrogels were pH sensitive. The antibacterial activities of the hydrogels against Escherichia coli (E. coli) were improved effectively because of polyamidoamine (PAMAM) dendrimer absorbed in the hydrogels.

Esterified starch/polylactic acid (ES/PLA) blending composite was prepared by melting extrusion with maleic anhydride esterified starch and PLA as the raw materials. The composite was accelerated aging by using UV aging box, and its properties were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermo gravimetric analysis (TGA) and mechanical testing machine. FT-IR and SEM results show that the infrared absorption peak intensities of C-O, C-H, and C=O in aged samples decrease gradually with increasing aging time. The damage degree of surface and internal of aged samples increases gradually. XRD analysis results show that after aging treatment, the crystalline diffraction peak of thermoplastic esterified starch at 2θ = 21° disappears and the diffraction peaks of PLA at 2θ = 16.5° appear, indicating that the hydrolysis rate of esterified starch is greater than that of PLA. The crystallinity of PLA in aged sample shows an increasing trend at first followed by a decreasing one along with the increasing time of aging treatment, suggesting that the hydrolysis of amorphous regions of PLA is more preferential than its crystalline regions. Because of the influence of crystal structure and the change of composition structure, the initial decomposition temperature of aging test specimen gradually increases with the extension of aging time. The maximum decomposition rate temperature and residual mass increases at first, and then decrease after the aging time extending to 1 600 h. As the aging time increases, the damage degree of combination interface between esterification starch and PLA is exacerbated, resulting in the tensile strength and bending strength of aged specimen decreasing gradually.

A brief review of commonly encountered anions, cations and co-doped HA and Ca-deficient HA was given in the DFT studies. First, the charge compensation mechanism, the preference substitution sites and crystal structure changes of doped HA were described and discussed. And then conclusions were drawn and future challenges were discussed. The review is expected to provide theoretical guidance for the development of bioactive HA with special structures and functions.