Silicon infiltrated silicon carbide (Si-SiC) ceramics, as high hardness materials, are difficult to machine, especially drilling micro-holes. In this study, the interaction of picosecond laser pulses (1 ps at 1 030 nm) with Si-SiC ceramics was investigated. Variations of the diameter and depth of circular holes with the growth of the laser energy density were obtained. The results indicate that the increase of machining depth follows a nonlinear relation with the increasing of laser energy density, while the diameter has little change with that. Moreover, it is found that some debris and particles are deposited around and inside the holes and waviness is in the entrance and at walls of the holes after laser processing.

Er³⁺/Yb³⁺co-doped phosphate are presented, laser glass materials with composition of P₂O₅-A1₂O₃-BaCO₃-KNO₃-Li₂O-ZnO-Er₂O₃-Yb₂O₃ (R-PABKLZ) are presented, in which an optimal molar ratio of 1:4 between Er³⁺ and Yb³⁺ was observed for achieving peak laser gain. Furthermore, due to adding 4.7 mol% Li¹⁺ and 4.6 mol% Zn²⁺ ions into the glass, an optimum composition structure based laser material was demonstrated. On the other hand, since the high temperature melting method with changeable temperature control was used, the emission cross section of fluorescence, excited lifetime, and an effective spectral half width reached 9.70 × 10⁻²¹ cm², 8.20 ms, and 53.16 nm, respectively, so that a laser gain (σ_emi×τ_rad) of 103.05 was obtained, which is significantly higher than previously reported results. The manuscript also argued the mechanism of relevant laser gain improvement.

The waterborne polyurethane/doped TiO₂ nanoparticle hybrid films were prepared. Nd, I doped TiO₂ was prepared with a 50 nm particle size firstly. The hybrid film was prepared by mixing doped TiO₂ with waterborne polyurethane, followed by heat treatment. The presence and nanometric distribution of doped TiO₂ nanoparticles in prepared membranes is evident according to SEM images. The photocatalytic activities of doped TiO₂ were significantly enhanced compared with pure TiO₂ powders. After the hybrid film fabrication, the photocatalytic activities were almost the same as the pure catalysts with k _MB of 0.046. In the antibacterial testing, the hybrid films can inhibit E. coli growth. A significant decrease in membrane fluidity and increase of permeability of E. coli were observed.

Soda-lime glasses were treated by electric field-assisted diffusion (EFAD) process. The mechanical properties and structural evolution on both glass anode and cathode surfaces were investigated, respectively. It was found that the EFAD resulted in the formation of a Na depletion layer on anode surface, which caused the relaxation of the glass anode surface network and the formation of a number of defects. Correspondingly, the hardness and flexural strength declined in anode surface compared to that of the original glass. On the other hand, the EFAD also created a compressive layer on cathode surface, causing the improvement of the hardness and flexural strength on cathode surface. The defected structure could be reconstructed by additional annealing process.

Divalent IIA metals such as Be, Mg, Ca, Sr, Ba and transition IIB metals such as Zn, Cd were investigated as possible n-type dopants into the Cu₂O theoretically by using the first-principles calculations based on density functional theory. By systematical analyses of the lattice parameters, the bond length, the electronic structure, the local density of states and the defect formation energy for various doping systems, it is revealed that Ca, Sr, Ba and Be are more suited for n-type doping into Cu₂O as shallow donors, compared to Mg which introduces a relatively deep donor level in Cu₂O. Meanwhile, Zn and Cd can hardly be doped into Cu₂O due to the positive formation energy of relevant defects.

Cu-Al-O nanofibers are synthesized by an electrospinning method. After electrospinning process, these nanofibers were thermally treated at different temperatures from 900 to 1 100 °C. The morphology and crystal structure of the fibers were analyzed by scanning electron microscopy and X-ray diffraction. Thick film gas sensors were fabricated by spinning the nanofibers on a ceramic substrate with Au-Pt interdigitated electrodes. These sensors exhibited high ozone sensing properties at room temperature. When the sensors were exposed to 100 ppm ozone, the response time was about 2.74 s, and the recovery was about 12.68 s.

The strain effects of the Zn_1−xMg _xO substrate on the bands structure of wurtzite Nb-doped ZnO bulk materials have been investigated using first-principles calculations based on density functional theory. Firstly, the band gap increases gradually with increasing Nb contents in unstrained Nb-doped ZnO, which is consistent with the experimental results. Secondly, the band gap decreases with increasing substrate stress in Nb-doped ZnO/Zn_1−xMg _xO. Splitting energies between HHB (Heavy Hole Band) and LHB (Light Hole Band), HHB and CSB (Crystal Splitting Band) in Zn_0.9167Nb_0.0833O/Zn_1−xMg _xO almost remain unchanged with increasing substrate stress, while decrease slightly in Zn_0.875Nb_0.125O/Zn_1−xMg _xO. In addition, detailed analysis of the strain effects on the effective masses of electron and hole in Nb-doped ZnO/Zn_1−xMg _xO is also given.

C/C composites are the emerging materials of choice for aero-engine hot-end components that will bear impact loading in thermal-oxidizing environments. For the components run for extended periods, the safe operation of components depends on how to evaluate damages under a dynamic load. In this study, Charpy impact tests at a temperature range of 25 to 1 200 °C were carried out on C/C composites to verify the effects of temperature induced thermal expansion and oxidation on their impact performance. Below 800 °C, oxidation was negligible and composites expanding played a leading role, resulting in the remarkable increase in fiber/matrix interface strength and impact energy. However, when the temperature was above 800 °C, the release of CO or CO₂ due to oxidation resulted in a lower impact energy.

The preforms with high SiC volume fraction (>50%) were successfully fabricated by two bonding methods. Moreover, the dimensional change, compressive strength, and microstructure of SiC preforms were investigated, and the bonding mechanism among SiC particulates in preforms was also discussed. Results show that, after heating to 1 100 °C and holding for 2 h, a uniform and interconnected structure in the SiC preforms can be obtained by using starch, stearic acid, and graphite respectively as the pore-forming agents, which benefits the subsequent infiltration by the molten metals. More neck-like-jointing among SiC particulate by using graphite as the pore-forming agent improves the dimensional accuracy and compressive strength of the preform. Besides, the properties of the preforms by the binder bonding are better than those by the oxidation bonding, which is mainly because the mixed neck-like-jointing and binder at high temperature provide effective bonding together.

To understand the quasi-static and dynamic compressive mechanical behavior of two-dimensional SiC fiber-reinforced SiC composites (2D-SiC_f/SiC), their compressive behavior at room temperature was investigated at a strain rate from 10⁻⁴ to 10⁴ /s, and the fracture surfaces and damage morphology were observed. The results show that the dynamic failure strength of 2D-SiC_f/SiC obeys the Weibull distribution, and the Weibull modulus is 5.66. Meanwhile, 2D-SiC_f/SiC presents a transition from brittle to tough with a decrease of strain rate, and 2D-SiC_f/SiC has a more significant strain rate sensitivity compared to the 2D-C/SiC composites. The failure mode of 2D-SiC_f/SiC depends upon the strain rate.

Super-hydrophobic surfaces with water contact angle (WCA) higher than 150° generated a lot of interests both in academic and in industry because of their self-cleaning functionality. Emphasis was given to the effect of pH value on the hydrophobic behavior of the obtained films or powders. At first, SiO₂ sols were prepared by diluted ammonia. We found that following the increase of pH value of sol from 8 to 9, WCAs of the obtained films increased from 121.8° to 131.8°. Following the continued increase of the pH value of sol, precipitates began to appear and smooth film could not be obtained. The WCAs of the obtained powders could reach 121.7°, and through modifying by TMCS could further increase to as high as 165° and the water sliding angle (WSA) was 2°. The results of SEM indicate that the hydrophobic properties of the powders without modifying by TMCS should be originated from the formation of nano/micron binary structure, i e, a micron-scale diameter and a nano-scale surface roughness. In this work we provide a better solution to fabricate super-hydrophobic silica coating surface with a simple method at low cost.

Layered double hydroxides (LDHs)/styrene-butadiene-styrene (SBS) copolymer modified bitumen was prepared by melt blending. The effect of LDHs on the ultraviolet (UV) aging behavior of SBS modified bitumen was investigated. The changes of chemical structures of modified bitumen before and after UV aging were characterized by Fourier transform infrared spectroscopy (FTIR). The results show that LDHs obviously reduce the variation of softening point and low temperature flexibility of SBS modified bitumen under different UV radiation intensities, which indicates that the UV aging resistance performance of SBS modified bitumen is improved effectively by LDHs. Compared with SBS modified bitumen, the changes of carbonyl, sulfoxide and butadienyl of LDHs/SBS modified bitumen decrease significantly after UV aging according to FTIR analysis, demonstrating that the oxidation and degradation reactions of SBS modified bitumen were restrained effectively by adding LDHs.

Double-scale model for three-dimension-4 directional(3D-4d) braided C/SiC composites has been proposed to investigate its elastic properties. The double-scale model involves micro-scale that takes fiber/matrix/porosity in fibers tows into consideration with unit cell which considers the 3D-4d braiding structure. Micro-optical photographs of composites have been taken to study the braided structure. Then a parameterized finite element model that reflects the structure of 3D-4d braided composites is proposed. Double-scale elastic modulus prediction model is developed to predict the elastic properties of 3D-4d braided C/SiC composites. Stiffness and compliance-averaging method and energy method are adopted to predict the elastic properties of composites. Static-tension experiments have been conducted to investigate the elastic modulus of 3D-4d braided C/SiC composites. Finally, the effect of micro-porosity in fibers tows on the elastic modulus of 3D-4d braided C/SiC composites has been studied. According to the conclusion of this thesis, elastic modulus predicted by energy method and stiffness-averaging method both find good agreement with the experimental values, when taking the micro-porosity in fibers tows into consideration. Differences between the theoretical and experimental values become smaller.

IR Li₂Ga₂GeS₆ nonlinear crystals were directly obtained with the composition of 40GeS₂-30Ga₂S₃-30Li₂S, by the conventional melt-quenching method. The high depth digital image indicated that the obtained Li₂Ga₂GeS₆ crystals showed a big size of 0.3 × 0.25 × 0.3 mm³. It was shown that the compound was very susceptive to H₂O with second harmonic observation. Besides, the glass-forming region of GeS₂-Ga₂S₃-Li₂S system was further studied by the conventional melt-quenching method.GeS₂-Ga₂S₃-Li₂S glass-ceramics containing IR Li₂Ga₂GeS₆ nonlinear nanocrystals were obtained at a more carefully controlled heating rate.

Zirconium oxide (ZrO₂) and boron carbide (B₄C) were added to ZrB₂ raw powders to prepare ZrB₂ porous ceramics by reactive spark plasma sintering (RSPS). The reactions between ZrO₂ and B₄C which produce ZrB₂ and gas (such as CO and B₂O₃) result in pore formation. X-Ray Diffraction results indicated that the products phase was ZrB₂ and the reaction was completed after the RSPS process. The porosity could be controlled by changing the ratio of synthesized ZrB₂ to raw ZrB₂ powders. The porosity of porous ceramics with 20 wt% and 40 wt% synthsized ZrB₂ are 0.185 and 0.222, respectivly. And dense ZrB₂-SiC ceramic with a porosity of 0.057 was prepared under the same conditions for comparison. The pores were homogeneously distributed within the microstructure of the porous ceramics. The results indicate a promising method for preparing porous ZrB₂-based ceramics.

Boron-doped hydrogenated microcrystalline Germanium (μc-Ge:H) films were deposited by hot-wire CVD. H₂ diluted GeH₄ and B₂H₆ were used as precursors and the substrate temperature was kept at 300 °C. The properties of the samples were analyzed by XRD, Raman spectroscopy, Fourier transform infrared spectrometer and Hall Effect measurement with Van der Pauw method. It is found that the films are partially crystallized, with crystalline fractions larger than 45% and grain sizes smaller than 50 nm. The B-doping can enhance the crystallization but reduce the grain sizes, and also enhance the preferential growth of Ge (220). The conductivity of the films increases and tends to be saturated with increasing diborane-to-germane ratio $R_{B_2 H_6 } $. All the Hall mobilities of the samples are larger than 3.8 cm²·V⁻¹·s⁻¹. A high conductivity of 41.3 Ω⁻¹·cm⁻¹ is gained at $R_{B_2 H_6 } $=6.7%.

Glass fiber reinforced plastics geogrid has a wide application in the field of soil reinforcement because of its high strength, good toughness, and resistance to environmental stress, creep resistance and strong stability. In order to get high-powered glass fiber reinforced plastics geogrid and its mechanical characteristics, the properties and physical mechanical index of geogrid have been got through the study of its raw material, production process and important quality index. The analysis and study have been made to the geogrid’s mechanical properties with loading speed, three-axial compression, temperature tensile test and FLAC^3D numerical simulation, thus obtain the mechanical parameters of its displacement time curve, breaking strength and elongation at break. Some conclusions can be drawn as follows: (a) Using glass fiber materials, knurling and coated projection process, the fracture strength and corrosion resistance of geogrid are greatly improved and the interlocking bite capability of soil is enhanced. (b) The fracture strength of geogrid is related to temperature and loading rate. When the surrounding rock pressure is fixed, the strength and anti-deformation ability of reinforced soil are significantly enhanced with increasing reinforced layers. (c) The pullout test shows the positive correlation between geogrid displacement and action time. (d) As a new reinforced material, the glass fiber reinforced plastics geogrid is not mature enough in theoretical research and practical experience, so it has become an urgent problem both in theoretical study and practical innovation.

This study aims to introduce an appropriate analytical method for asphalt pavement based upon unified strength theory (UST). The traditional maximum shear stress strength theory (MSST) cannot describe the marked difference between tension strength and compressive strength or variable intermediate principal stress, which significantly affects the geotechnical materials. Our studies try to find a new asphalt pavement failure criterion that considers the influence of both tension-compression strength ratio and intermediate principal stress of asphalt mixture. In order to select a suitable theory on pavement material, the UST is introduced and compared with the traditional theory. Results show that the tension-compression strength ratio of asphalt mixture, which is used as a material parameter, dramatically affects the stress and stress distribution law in pavement; the pavement stress level increases dramatically after considering the intermediate principal stresses. Therefore, the UST which considers both tension-compression strength ratio and intermediate principal stress is more in line with the material characteristics of asphalt pavement.

A self-made 2-acrylamide-2-methyl propylene sulfonic (AMPS)-modified polyacrylic acid superplasticizer and two other commercially available superplasticizers with different molecular structures are used in this study to investigate the effect of an AMPS-modified polyacrylic acid superplasticizer on the properties of concrete materials. In the experiments, initial and 1.5 h slumps over time after admixtion are determined by adding different dosages of three superplasticizers into the premixed concrete to characterize the slump loss resistance of the premixed concrete. The water-reducing rates of three different types of concrete are determined to characterize the water-reducing capacity of the concrete with each superplasticizer. The 3, 7 and 28 d compressive strength is determined to characterize the mechanical properties of the concrete with each superplasticizer. In the meanwhile, 1, 1.5 and 2.0 h slump loss rates over time after admixtion are determined by adding different dosages of the three superplasticizers into the high-performance concrete (HPC) to characterize the slump loss resistance of HPC. The 7, 28, 60 and 90 d compressive strength is determined to characterize the compressive properties of HPC with each superplasticizer. The dry shrinkage rates of three different types of HPC are determined with each superplasticizer. Electric flux after standard curing for 56 d and chloride ion diffusion coefficient after curing for 28 d of HPC are determined to characterize the impermeability of HPC with each superplasticizer. The cross-section was examined using a scanning electron microscopy (SEM) system. Results demonstrate that the AMPS-modified polyacrylic acid superplasticizer has better water-reducing effect and slump than the two commercially available polyacrylic acid superplasticizers. The AMPS-modified polyacrylic acid superplasticizer also shows significant improvement of the compressive strength, especially in comprehensive performance of HPC. In conclusion, the AMPS-modified polyacrylic acid superplasticizer is particularly suitable for the preparation of HPC.

Combined with DTG analysis, X-Ray diffraction analysis (XRD) and field emission scanning electron microscopy analysis (FSEM) affiliated with energy dispersive spectrometer analysis (EDS), the early hydration and carbonation behavior of cement paste compacts incorporated with 30% of dolomite powder at low water to cement ratio (0.15) was investigated. The results showed that early carbonation curing was capable of developing rapid early strength. It is noted that the carbonation duration should be strictly controlled otherwise subsequent hydration might be hindered. Dolomite powder acted as nuclei of crystallization, resulting in acceleration of products formation and refinement of products crystal size. Therefore, as for cement-based material, it was found that early carbonation could reduce cement dosages to a large extent and promote rapid strength gain resulting from rapid formation of products, supplemental enhancement due to water release in the reaction of carbonation, and formation of nanometer CaCO₃ skeleton network at early age.

Three types of pure geopolymer pastes (poly-sialate PS, poly-sialate-siloxo PSS, and poly-sialate-siloxo PSDS) were first prepared by alkali (NaOH and KOH) activated metakaolin. Then a void space network was employed to simulate the 3-D pore-throat distribution across the unit cell of the various hardened geopolymer pastes with reference to their experimental mercury intrusion curves. Based on the simulated 3-D pore-throat structure models, a wide range of pore-level properties such as porosity, connectivity, permeability and tortuosity of various geopolymer pastes were calculated. The 3-D structural model and calculated parameters showed that most of the pores in Na-PS geopolymer paste was very small size pores ranging from 0 to 100 nm. A few very large pores were spread amongst the small pores, resulting in a very high penetration pressure, permeability resistance. Unlike Na-PS geopolymer paste, pore size with medium size of Na-PSS, K-PS and K-PSS geopolymer pastes distributed uniformly across the unit cell, and the size changes of adjacent pores in the 3 geopolymer pastes were little, producing higher penetration pressure, lower permeability, smaller connectivity and larger tortuosity. In contrast, pores in Na-PSDS and K-PSDS geopolymer pastes were relatively large and distributed concentratively, which caused samples to be easily penetrated by mercury, methane and nitrogen etc under relatively low pressures.

Our researches are based on the fact that the systems composed of polyacrylamide and montmorillonite under a kind of shear state often appear in some important practical processes like drilling well etc. The viscosity of polyacrylamide is usually the most important one among the characteristics to decide if the practical processes succeed or not. Therefore, we studied the effect of hydrated montmorillonite on the viscosities of polyacrylamide with temperature and shear rate varying under confined shear by molecular simulation method. Adopting the condition of confined shear in the research could make our simulations and the practical processes as similar as possible. First, the model of one polyacrylamide polymer chain with 20 monomers linearly linking surrounded by water molecules between two of montmorillonite layers was constructed. Then canonical ensemble (NVT) MD simulations were carried out for the built model at different temperatures and shear rates. From the gained simulation results, we calculated the polymer’s structural property-radius of gyration, which was directly related to the viscosity property of polyacrylamide polymer. It was found that the viscosity of the polyacrylamide polymer between hydrated clay layers decreased with the temperature increasing from 298 to 343 K under the condition of confined shear. The variation trend of viscosity from simulation results was also confirmed by our experiments. Besides, the viscosity of the polyacrylamide between hydrated clay layers decreased with the shear rate increasing within the range of higher shear rates.

The present work enhanced the thermal conductivity of poly(p-phenylene sulfide)/expanded graphites and poly(p-phenylene sulfide)/carbon nanotubes, by incorporating composites with hexagonal boron nitride, which simultaneously succeeded in raising the electrical conductivity of the systems. A two-step mechanical processing method which includes rotating solid-state premixing and inner mixing was adopted to improve dispersion of the hybrids, contributing to the formation of an interspered thermal conductive network. Similar synergic effect in thermal conductivity enhancement was discovered in the hybrid systems regardless of the dimension difference between the two carbon fillers. Such is postulated to be the one satisfying advantage generated by the afore-mentioned network; the other is the insulativity of the hybrid systems given by the effective blockage of hexagonal boron nitride as an insulating material in our network.

4,4′-dibromo-2-nitro-biphenyl and 4,4′-dibromo-2,3′-dinitro-biphenyl have been synthesized via nitration reaction with 4,4′-dibromobiphenyl as the raw material. Three novel thiophene derivatives, 4, 4′-di(4-hexyl-thiophen-2-yl)biphenyl, 4,4′-di(4-hexyl-thiophen-2-yl)-2-nitro-biphenyl and 4,4′-di(4-hexyl-thiophen-2-yl)-2,3′-dinitrobiphenyl were synthesized through Stille coupling reaction, followed by polymerization in the presence of FeCl₃, respectively. UV-vis absorption spectra, fluorescence spectra, photoluminescence spectra and electrochemical properties of the polymers were investigated. And the band-gap (E _g), HOMO orbital energy (E _HOMO), and LUMO orbital energy (E _LUMO) of the polymers were calculated. Among the polymers, polymer PBTN and PBTD show lower band-gap (2.67 and 2.63 eV), lower HOMO energy level (−5.38 and −5.4 eV) and broader wavelength (432 and 438 nm) than that of polymer PBTB (2.69 eV, -5.36 eV and 424 nm) with incorporation of one nitro group or two nitro groups in the main chain, respectively.

The effects of boron content in the range of 0–0.0082 wt%, on the inclusion type, microstructure, texture and magnetic properties of non-oriented electrical steels have been studied. After final annealing, the addition of excess boron(w(Bt)〉0.004 1 wt%) led to the formation of Fe₂B particles. As boron content increased, grain size increased and reached a maximum in steel with 0.004 1 wt% boron. Furthermore, steel containing 0.004 1 wt% boron had the strongest {100} fiber texture, Goss texture and the weakest {111} fiber texture among the five tested steels. Flux density firstly rapidly increased and then suddenly decreased with increasing boron content and reached a maximum in steel with 0.004 1 wt% boron. Conversely, core loss first sharply decreased and then abruptly increased with the increase of boron content and reached a minimum in steel containing 0.004 1 wt% boron. Steel containing 0.004 1 wt% boron obtained the best magnetic properties, predominantly through the development of optimum grain size and favorable texture.

An ultrasonic test of spot welding for stainless steel is conducted. Based on wavelet packet decomposition, the ultrasonic echo signal has been analyzed deeply in time - frequency domain, which can easily distinguish the nugget from the corona bond. The 2D C-scan images produced by ultrasonic C scan which contribute to quantitatively calculate the nugget diameter for the computer are further analyzed. The spot welding nugget diameter can be automatically obtained by image enhancement, edge detection and equivalent diameter algorithm procedure. The ultrasonic detection values in this paper show good agreement with the metallographic measured values. The mean value of normal distribution curve is 0.006 67, and the standard deviation is 0.087 11. Ultrasonic C-scan test based on wavelet packet signal analysis is of high accuracy and stability.

The correlation between the microhardness and microstructure features of anodic films on 2024 aluminum alloy formed in the mixed sulfuric acid/oxalic acid electrolyte was studied using micro-hardness tester and scanning electron microscope (SEM). The results show that the microhardness of the anodic film is influenced by the microstructure of the anodic film such as the film porosity, and the order and continuity of the hexagon columnar cells. The film microhardness increases as the porosity of the anodic film decreases and the order and continuity of the film cells increase. With the same current density, as the anodic film thickens with anodizing time, the film microhardness increases because the film porosity decreases and the order and continuity of the cells are also improved. Under the condition of the same anodizing time, as the current density increases, the film microhardness decreases due to the higher film porosity and the poorer order and continuity of the film cells. The film porosity increases because the increased current density can accelerate the oxidation reaction, strengthen the filed-assisted dissolution and the heating effect in the anodic film, resulting in decreased film order and continuity.

Analysis of χ phase precipitation in 2205 duplex stainless steel aged at 700 and 750 °C has been investigated systematically. The experimental results showed that χ phase forms prior to the precipitation of σ phase and disappears once σ phase starts to precipitate. This phenomenon indicates that σ phase nucleated and consumed the χ phase. The σ phase nucleated mainly at ferrite/austenite interface and grew inwards into the ferrite phase. The morphology of σ phase reveals a coral-like structure at the temperature of 700 °C for 120 min followed by quenching in water. The decomposition of ferrite occurs via the following eutectoid reaction: F→σ+γ ₂. The selected area diffraction pattern of zone axes is$[\bar 31\bar 3]_\chi ||[\bar 31\bar 3]_\delta $, indicating a characteristic orientation relationship between χ phase and δ-ferrite.

The novel laminated Ti-TiBw/Ti composites composed of pure Ti layers and TiBw/Ti composite layers have been successfully fabricated by reactive hot pressing. Herein, two-scale structures formed: the pure Ti layer and TiBw/Ti composite layer together constructed a laminated structure at a macro scale. Furthermore, TiBw reinforcement was distributed around Ti particles and then formed a network microstructure in TiBw/Ti composite layer at a micro scale. The laminated Ti-TiBw/Ti composites reveal a superior combination of high strength and high elongation due to two-scale structures compared with the pure Ti, and a further enhancement in ductility compared with the network structured composites. Moreover, the elastic modulus of the laminated composites can be predicted by H-S upper bound, which is consistent with the experimental values.

Nickel-coated 45 steel studs and 6061 aluminum alloy with 4047 Al alloy foil as filler metal were joined by using high frequency induction brazing. The microstructure of Fe/Al brazed joint was studied by means of optical microscopy (OM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD). Results showed that 45 steel stud and 6061 aluminum alloy could be successfully joined by high frequency induction brazing with proper processing parameters. The bonding strength of the joint was of the order of 88 MPa. Ni coating on steel stud successfully avoided the generation of Fe-Al intermetallic compound which is brittle by blocking the contact between Al and Fe. Intermetallic compounds, i e, Al₃Ni₂, Al_1.1Ni_0.9 and Al_0.3Fe₃Si_0.7 presented in Al side, FeNi and Fe-Al-Ni ternary eutectic structure were formed in Fe side. The micro-hardness in intermetallic compound layer was 313 HV. The joint was brittle fractured in the intermetallic compounds layer of Al side, where plenty of Al₃Ni₂ intermetallic compounds were distributed continuously.

RE₁₃Fe₈₄Cr₃(RE=Ce, Pr, Tb, Er) and Pr_13−xFe₈₄Cr₃Ti _x(x=0, 2, 4, 6) alloy powders were prepared by arc smelting method and high energy ball milling technique. The phase structure and the morphology of the alloy powders were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and their microwave absorbing properties were determined by a vector network analyzer. The results show that the alloys with light rare earths (Ce, Pr) have good low frequency absorbing property and those with heavy rare earths (Tb, Er) exhibit an improved high frequency absorbing property. The minimum reflectivity at the absorbing peak frequency of RE₁₃Fe₈₄Cr₃(RE=Ce, Pr, Tb, Er) are −9.49 dB at 5.76 GHz, −22.38 dB at 7.92 GHz, −18.52 dB at 11.68 GHz and −17.59 dB at 10.24 GHz, respectively. The absorbing bandwidth under −10 dB of the Pr₁₃Fe₈₄Cr₃ powder was widened from 1.91 GHz to 3.89 GHz by adding 2% Ti, but the reflectivity of the alloy was increased from −22.38 dB to −14.91 dB.

The true stress-strain relationships of Ti-5Al-2Sn-2Zr-4Mo-4Cr(TC17) alloy with a wide range of strain rates were investigated by uniaxial quasi-static and dynamic compression tests, respectively. Quasistatic compression tests were carried out with Instron 8874 test machine, while dynamic compression tests were performed with the split Hopkinson pressure bar (SHPB) which was installed with heating device and synchroassembly system. The dynamic mechanical behaviors tests of TC17 were carried out from room temperature to 800 °C at intervals of 200 °C and at high strain rates (5 500–1 9200 s⁻¹). The stress-strain curves considering temperature-strain rate coupling actions were obtained. The Johnson-Cook constitutive model was developed through data fitting of the stress-strain curves. The material constants in the developed constitutive model can be determined using isothermal and adiabatic stress-strain curves at different strain rates. The Johnson-Cook constitutive model provided satisfied prediction of the plastic flow stress for TC17 alloy.

Amorphous Ti-Cu-Zr-Ni filler foils with low melting point of 1 133 K were synthesized using a melt-spinning method in argon atmosphere. A Ti₂AlNb based alloy was brazed at 1 153–1 223 K for 600–3 000 s. The effects of brazing temperature (T _b) and time (t _b) on the shear strength of the joints were investigated. The results showed that the joint strength was significantly affected by the reaction layer thickness. The optimum brazing parameters can be determined as follows: T _b=1 173 K, and t _b=600 s. The maximum tensile strength of the joint obtained can reach 260 MPa. Furthermore, the activation energy Q and the growth velocity A ₀ of the reaction layer in the brazed joints were calculated to be 161.742 kJ/mol and 0.213 m²/s, respectively. The growth of the reaction layer (y) could be expressed by the expression: y ² =0.213exp(−19 454/T _b)t _b.

In order to improve the surface performance and increase the lifetime of P110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/element distribution and phase constitution of the Ni-P coating were analyzed using scanning electron microscope (SEM) equipped with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Tribological and electrochemical measurement tests were applied to investigate the wear and corrosion resistance of P110 steel and the Ni-P coating. The results showed that a uniform and compact, high phosphorous Ni-P coating was formed. The obtained Ni-P coating indicated certain friction-reduction effect and lower mass loss during friction-wear tests. The Ni-P coating also exhibited higher corrosion resistance in comparison with bared P110 steel. The obtained Ni-P coating has significantly improved the surface performance of P110 steel.

The effects of yttrium and strontium on the microstructure and mechanical properties of Mg-11Li-3Al magnesium alloy (LA113) are compared and analyzed. Microstructures and phases of the alloys were studied with optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS). Mechanical properties of alloys were measured with tensile tester. The results show that yttrium and/or strontium additions produce a strong grain refining effect in LA113 alloy. Al₂Y and Al₄Sr, etc. phases with different morphologies are verified and exist inside the grain or at the grain boundaries, which directly impact on the mechanical properties of LA113 alloy. The results of tensile tests show that, the as-extruded LA113-1Y-1Sr alloy obtains the optimal tensile property of which the tensile strength and elongation are 253.56 MPa and 18.12%, the tensile strength is increased by almost 25% compared with the asextruded LA113 alloy.

Ti-6Al-4V (TC4) alloys were plasma carbonized at different temperatures (900, 950, and 1 000 °C) for duration of 3 h. Graphite rod was employed as carbon supplier to avoid the hydrogen brittleness which is ubiquitous in traditional gas carbonizing process. Two distinguished structures including a thin compound layer (carbides layer) and a thick layer with the mixed microstructure of TiC and the α-Ti in carburing layer were formed during carburizing. Furthermore, it was found that the microstructure and the properties of TC4 alloy were significantly related to the carbonizing temperature. The specimen plasma carbonized at 950 °C obtained maximum value both in the hardness and wear resistance.

This work demonstrated quantitatively that DSA (dansylamide) and apo CA (dezincified carbon anhydrase) interacted with each other in the presence of Zn²⁺ (zinc ion). The fluorescence emission of DSA in the presence of Zn²⁺ and the intensity of fluorescence, which was proportional to the concentration of Zn²⁺, could be used in the measurement of Zn²⁺ concentration. Considering that Zn²⁺ was the active center of enzymes like CA (carbon anhydrase), two dezincification reagents were compared to ensure the validity of our method. A certain range concentration of Zn²⁺ could be measured by the reaction product of apo CA, DSA and Zn²⁺, where the measurement limitation was about 60 nmol/L. Interaction of CA with DSA was also studied with infrared spectrometry.

To evaluate the effect of restorative materials on stress distribution of endodontically treated teeth, the 3D models of an endodontically treated mandibular first molar, restoration, and cement layer were created. Three different materials (composite resin, ceramage and ceramic) were studied and two loading conditions (vertical and oblique load) were simulated. Mohr-Coulomb failure criterion of enamel, dentine, endocrown and cement were evaluated separately. It is indicated that under both loading conditions, the highest values of Mohr-Coulomb failure criterion were observed in Ceramage-restored group for remaining tooth structure while in ceramic-restored group for the restoration. Compared to composite resin and Ceramage, ceramic endocrown transferred less stress, namely was more protective to the tooth structure.

Bio-ceramsite technology is one of the most effective technologies in the pretreatment of drinking water. In this work, bio-ceramsite was fabricated by Citrobacter freundii (C. freundii) immobilization on the ceramsite. The findings of the current study suggest that the bio-ceramites showed biosorption abilities for Cd(II) and Pb(II) and the removal efficiency for Pb(II) is lower than Cd(II). The adsorption mechanism can be attributed to electrostatic attraction and covalent bond. The morphology of the cells changed after the adsorption of Cd(II) and Pb(II) due to the dissociation of the assembly of peptidoglycan and lipopolysaccharide. The fluorescence polarization has shown a significant decrease in membrane fluidity and an increase of permeability of cell membrane. The spectral profile of C. freundii suggests the alteration of carbonyl, amide and phosphonic groups on the cell membrane.