A method for acquiring the tensile softening relationship of concrete was presented, which is based on the measurement of flexural crack length using strain gauge and then through fitting the theoretical calculated load and the experimentally determined load for the same cracking length to obtain the tensile softening (s-w) relationship. As long as the s-w relationship is known, the cracking strength, tensile strength, fracture energy and characteristic length of brittleness can be derived. The tension softening relationship of three kinds of fast hardening concretes was obtained using above method. The results show that the cracking strength, tensile strength and fracture energy increase with the increasing compressive strength of concrete, while the characteristic length of brittleness decreases. Therefore, the obtained s-w relationship can be used for fracture analyses of concrete structures.

The microstructure of welding seam was characterized by optical microscope and SEM, and then of which the effect on crack propagation was studied by means of situ tensile test in SEM and EBSD technique for a nuclear grade stainless Z3CN20-09M. The results show that the weld seam composes of lath-shaped and island-like microstructures and different microstructures exhibited different resistance to crack propagation. Island-like microstructure has a strong resistance to the crack propagation, which can induce a deflection of the path way of crack propagation; while lath-shaped structure showed little effect on crack propagation, and the crack passed though the lath-shaped microstructure quickly without any deflection.

SiC foam ceramic/Fe based co-continuous phase composites were prepared by squeeze casting method using oxidized SiC foam ceramic. Then the prepared composites were annealed. The influence of preparation process and SiC volume fraction on microstructures and mechanical properties of the composites were investigated. Results show that a SiO₂ barrier film of 1 mm in thickness on the surfaces of SiC foam can form after oxidizing at 1250°C for 48 h, which then can efficiently prevent the formation of a brittle intermetallic compound Fe₃Si at the interface of Fe matrix and SiC during the preparation of composites. As a result, the flexural strength of composites was increased by 100% and compressive strength by 18%. The thickness of SiO₂ film was increased after oxidizing at 1250°C for 72 h, and a thicker SiO₂ film may induce mismatch of thermal expansion coefficient between SiO₂, Fe and SiC, which thereby resulted in the increase of residual stress. Therefore, the mechanical properties of composites were decreased slightly. The residual stress could be relieved after annealing of composites at 600°C for 4 h, which improved the mechanical properties of composites. The function of bridging and deflecting crack of metal matrix is big for the composite with small SiC volume fraction, which is in turn beneficial to the enhancement of the flexural strength and flexural strain. For the composite with the higher SiC volume fraction, the size of SiC skeleton became bigger and the load-carrying capacity was strengthened, thereby its compressive strength was increased.

A novel magneto-rheological (MR) material, i.e. MR elasticity cement (MREC), was proposed specific for vibration reduction of heavy equipments. High viscosity (≥200 Pas) polysiloxanes based elasticity cement (EC) was used as the carrier of Magneto-rheological fluid (MRF). Three MRECs were prepared from ECs with different viscosities. The prepared EC samples were characterized by an ATR-FTIR spectroscopy. The compressibility of MREC was also tested. The results show that no precipitation could be observed for the prepared MREC after 30 d storage; the MREC exhibited strong MR effect (shear stress of 800 Pas and 60% mass fraction based sample is about 120 kPa in a magnetic field of 0.54T, i.e. 15.4 times the off-state value, and even exceeds the shear stress limit of the rheometer under high magnetic field). Besides, a unique “V-slot MR effect” was first time found. The special helical molecule structure of EC was considered to be responsible for this effect and the unique performance of MRECs.

Plates of 1.5 mm in thickness of a model dual-phase steel 0.16C-1.38Si-3.2Mn was prepared by complex processes of rolling and annealing. The mechanical property and work hardening behavior of the steel after annealing were examined. The microstructure and fracture morphology of the steel were characterized by scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) techniques with emphasis on the strengthen-toughening mechanism of grain refinement of the steel. The results show that the microstructure of the steel annealed at 800℃ consists of ferrite (8.8%) and tempered martensite (91.2%). The annealed steel exhibits good comprehensive performance: the yield strength of 873 MPa with characteristics of continuous yield, tensile strength of 1483 MPa, total elongation of 11% and yield ratio of 0.58. The factors such as the manganese content of the steel, the initial microstructure before annealing, the large deformation of cold rolling and the key parameters of annealing process are all conductive to the grain refining of the steel, as a result the size of ferrite phases is about 1-2 μm and the effective size of martensite bundles is 0.2-1.5 μm. The refined grains may play an important role in blocking the movement of dislocation and increase the resistance to crack propagation thereby enhance the strength, toughness and ductility of the steel sheet.

Conductive epoxy resin based composite coatings were prepared by physical blending process and then applied onto on Q235 carbon steel surface. The results show that there existed lots of micro-blisters in the pure E51 epoxy coating without pigments, which deteriorate the protectiveness of the coatings. In the contrast, the quantity of the micro-blisters of the conductive composite coatings was decreased greatly by adding pigments. The test results of immersion in 3%NaCl solution and salt spray indicated a superior corrosion resistance of the composite coatings. After corrosion test, no bubbling or pickling for the composite coatings could be observed and no corrosion was detected for Q235 carbon steel underneath the coatings. Electrochemical experiments revealed that the impendence of the E51 coating decreased fast, while that of the composite coatings increased with the immersion time in 3.5%NaCl solution. The composite coatings have 'self-healing' ability. The electric resistance and adhesion strength of the composite coatings are in the order of 10³ Ωcm and 9.12 MPa respectively.

Carbon-based iron nitride nanocomposites were prepared by means of preoxidation and then carbonization of a uniformly blended mixture nano-iron powders and liquid polyacrylonitrile. The prepared nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electromagnetic performance of the nanocomposites was evaluated by magnetometer and vector network analyzer, and therewith the effect of the carbonization temperature on microwave absorbing performance could be acquired. The results show that the nanocomposite with the desired phase composition can be prepared after carbonization at 750℃. A 1.5 mm thick coating of the nanocomposite has the maximum reflection loss value -13 dB at 15 GHz, and the absorption bandwidths with reflection loss lower than -10 dB are up to 4.5 GHz.

Bulk composite of mesocarbon microbeads and carbon nanotubes (MCMB/CNTs) was prepared by in-situ thermal polymerization, compression molding and high-temperature sintering. The oxidation resistance of MCMB/CNTs was studied using TG, and isothermal oxidation method. It was found that the oxidation resistance of the composites was enhanced by adding proper amount of CNTs in the matrix. With the increasing amount of CNTs, the interplanar spacing of microcrystall on the carbonized composites decreased and the oxidation resistance became better. An addition of 5% CNTs can induce about 40℃ increase in the initial mass loss temperature of the composite, and the mass loss of the composite was only 8.55% after isothermal oxidation in air for 10 h. But with addition of excessive CNTs, the particle size distribution of the microbeads was broadened and the degree of sphericity of the composite became poor, which led the composite with higher porosity and lower oxidation resistance.

Copolymerized phenolic resin modified bamboo fiber composites(PR-BF) were prepared by a two step process i.e. firstly the bamboo fiber was immersed in an ultrasound irradiated bath of proper water solution of copolymerized phenolic resin and then undergone a heat treatment. The PR-BF composite was characterized by FTIR and its thermal property was examined by means of TG and DTG. The results show that bamboo fiber had excellent absorbability of phenolic resin; the phenolic resin is grafted on to bamboo fiber by copolymerization reaction; the thermal stability of the PR-BF composite increased dramatically with the increasing PR solid content in the solution; and the carbon residue of PR-BF reached a climax of 37.75% for the carburization at 900℃. From the FTIR analysis results it follows that in company with the thermal decomposition of PR-BF, a novel substitution product of benzene might form due to the copolymerization of BF with PR, which results in better thermal stability for PR-BF rather than the merely BF, and better resistance to elevated temperature rather than of the merely phenolic resin. Besides, after carburization the formed fiber-like nano-powders were good dispersed in PR-BF composite.

The thermal stability of Ti₃AlC₂, a kind of ternary laminated machinable ceramic, in hydrogen atmosphere at 1100-1400℃ was investigated. The phase composition and surface morphology of Ti₃AlC₂ before and after hydrogenation were characterized by means of XRD, SEM, SIMS, and Raman. The resulted gaseous products of the hydrogenation process were calculated by Factsage software. Results show that during hydrogenation a small amount of hydrogen dissolves in Ti₃AlC₂; Ti₃AlC₂ decomposes into metastable phase of Ti₃Al_xC₂ by stripping Al atoms. Most of the stripped Al atoms react with the scarce oxygen in the atmosphere to form a homogeneous but not dense Al₂O₃ film, which even spalls off at 1400℃. A gaseous phase of AlH is predicted by the calculation with thermodynamic software. The preliminary results indicate that Ti₃AlC₂ has a good hydrogen resistance at temperatures below 1300℃.

Hollow nanospheres of Ag⁺/Ag-TiO₂ (Ag⁺/Ag-HTS) were synthesized by a two step process i.e. firstly Ag₂S was deposited on the surface of TiO₂/polystyrene composites and subsequently the decorated composites were calcinated in air. The results show that all of the Ag⁺/Ag-HTS have good visible light photocatalytic activities for the photodegradation of methyl orange. It possesses a high efficiency for photodegradation of methyl orange as the solutions with low concentration of methyl orange. The presence of Schottky barrier may facilitate the migration of vacancies to the surface of Ag⁺/Ag-HTS and thereby enhance its photocatalytic efficiency. Ag⁺ in the catalyst is helpful to scavenge photoelectrons to prevent the recombination of electrons and vacancies. The photocatalytic activity of the Ag⁺/Ag-HTS increases with the increase of the amount of deposited Ag₂S in the first step of synthesis process. The degradation of methyl orange by Ag⁺/Ag-modified hollow titania nanosphere photocatalysts fitted the pseudo-first-order kinetics. When the mass ratio of Ag₂S to TiO₂ was 25%, the photodegradation efficiency for methyl orange was up to 70.6% under visible light irradiation for 2 h.

A series (Mg₂₄Ni₁₀Cu₂)_100-xNd_x (x = 0, 5, 10, 15, 20) alloys with a microstructure of nanocrystalline and amorphous structure were prepared by melt spinning technology. The effect of spinning rate and Nd content on the microstructure and the hydrogen storage performance of the alloys was investigated. The results of XRD and TEM examination reveal that all the as-cast alloys exhibit a multiphase microstructure, i.e. Mg₂Ni-type phase is the major component and there exist several secondary phases such as Mg₆Ni, Nd₅Mg₄₁ and NdNi. Furthermore, the as-spun Nd-free alloy shows a microstructure of entire nanocrystallines, whereas the as-spun alloys with Nd addition exhibit a microstructure of nanocrystalline and amorphous structure, meaning that the addition of Nd facilitates the glass forming of the alloys. The measurement of the hydrogen storage kinetics indicates that the melt spinning and the Nd addition can significantly improve the hydrogen storage performance of the alloys either in gaseous atmosphere or by electrochemically charging, and with the increasing spin rate and the amount of Nd addition, the high rate discharge capability (HRD) of the alloys increases firstly and then declines, for which the enhanced hydrogen diffusion coefficient (D) and limiting current density (I_L) and the increased charge transfer resistance (R_ct) resulted from both the melt spinning and the Nd addition are possibly responsible.